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Sample records for aden lake victoria

  1. Hazardous thunderstorms over Lake Victoria: climate change and early warnings

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Davin, Edouard L.; Seneviratne, Sonia I.; Bedka, Kristopher; Lhermitte, Stef; van Lipzig, Nicole

    2016-04-01

    Severe thunderstorms and associated high waves represent a constant threat to the 200,000 fishermen operating on Lake Victoria. According to the International Red Cross, presumably 3000 to 5000 fishermen die every year on the lake, thereby substantially contributing to the global death toll from natural disasters. Despite the long-known bad reputation of Lake Victoria, operational early warning systems are lacking and possible future changes of these extreme thunderstorms are unknown. Here we present the first dedicated high-resolution, coupled lake-land-atmosphere climate projection for the African Great Lakes region and analyse it in combination with new satellite data and coarser-scale ensemble projections. Our model projections for the end-of-the-century indicate that Lake Victoria amplifies the future intensification of extreme precipitation seen over the surrounding land. Under a high-emission scenario (RCP8.5), the 1% most extreme over-lake precipitation may intensify up to four times faster compared to surrounding land. Our findings are consistent with an ensemble of coarser-scale climate projections for Africa, but the lower skill of the ensemble over Lake Victoria constrains its applicability. Interestingly, the change in extremes contrasts to the change in average over-lake precipitation, which is projected to decrease by -6% for the same period. By further analyzing the high-resolution output we are able to explain this different response: while mesoscale circulation changes cause the average precipitation decline, the response of extremes is essentially thermodynamic. Finally, the study of the satellite-based detection of severe thunderstorms revealed a strong dependency of the nighttime storm intensity over Lake Victoria on the antecedent daytime land storm activity. This highlights the potential of this new satellite product for predicting intense storms over Lake Victoria. Overall, our results indicate a new major hazard associated with climate

  2. STS-57 Earth observation of Lake Victoria, Africa

    NASA Technical Reports Server (NTRS)

    1993-01-01

    STS-57 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, is of Africa's Lake Victoria, which sits in the middle of the East African Rift Valley System.Lake Victoria is a major resource in eastern Africa, especially to the countries bordering the lake -- Uganda, Kenya and Tanzania. Typical summer indicators in equatorial Africa -- puffy clouds over land mass and clear skies over the lakes -- are in the view. Lake Albert in the western section of the Rift Valley and Lake Turkana in the eastern section can be seen to the west and east of Lake Victoria, respectively. Most of the other features on the right are obscured by clouds. NASA scientists studying the STS-57 Earth photography point out that the wide perspective of this scene gives a sense of the three-dimensional profile of the whole rift system. The scientists cite the way in which the component valleys of the rift system ramp up to Lake Victoria on either side.

  3. Analysis of the water balance of Lake Victoria

    NASA Astrophysics Data System (ADS)

    Nossent, J.; de Brabanter, W.; Bauwens, W.

    2009-04-01

    Lake Victoria is situated within an elevated plateau in the western part of Africa's Great Rift Valley and lies within the territory of three countries: Tanzania, Uganda and Kenya. It is Africa's largest lake and the second widest fresh water lake in the world in terms of surface area. It is also the source of the longest branch of the River Nile, the White Nile. The lake's shallowness, limited river inflow, and large surface area relative to its volume make it vulnerable to climate changes and fluctuations of the water level. This affects the surrounding countries and their people a lot, especially in terms of their food supply and economy. The aim of this study was to get more information on the causes of these fluctuations by analysing the water balance of the lake for the period 1970-1974. It was based both on historical data and measurements and new calculations, and compared with previous studies (e.g. Suttcliffe and Parks, 1999). Precipitation and evaporation over the lake surface were calculated with the Thiessen Polygons method, using measurements from stations around the lake and on the islands. The total inflow of the lake is the sum of the contributions of twelve subbasins. One of these subcatchments, the Nzoia-catchment, was modeled with SWAT (Soil and Water Assessment Tool), a physically based, semi-distributed river basin simulator, as a contribution to the development of a water balance model for Lake Victoria. To calculate the outflow at the Owen Falls Dam in Jinja (Uganda), gauge heights of the lake were used in combination with the "Agreed Curve" (the relationship between water level and flow that was set by the policy makers). As the lake is assumed to be a system with a closed mass balance, the combination of the variations in the above mentioned components resulted in changes of the lake's storage, leading to fluctuations of the water level. For the period 1970-1974 the calculated mean monthly evaporation is 133 mm, with a standard deviation

  4. Origin of the superflock of cichlid fishes from Lake Victoria, East Africa.

    PubMed

    Verheyen, Erik; Salzburger, Walter; Snoeks, Jos; Meyer, Axel

    2003-04-11

    Lake Victoria harbors a unique species-rich flock of more than 500 endemic haplochromine cichlid fishes. The origin, age, and mechanism of diversification of this extraordinary radiation are still debated. Geological evidence suggests that the lake dried out completely about 14,700 years ago. On the basis of phylogenetic analyses of almost 300 DNA sequences of the mitochondrial control region of East African cichlids, we find that the Lake Victoria cichlid flock is derived from the geologically older Lake Kivu. We suggest that the two seeding lineages may have already been lake-adapted when they colonized Lake Victoria. A haplotype analysis further shows that the most recent desiccation of Lake Victoria did not lead to a complete extinction of its endemic cichlid fauna and that the major lineage diversification took place about 100,000 years ago. PMID:12649486

  5. PCBs in fish and their cestode parasites in Lake Victoria.

    PubMed

    Oluoch-Otiego, John; Oyoo-Okoth, Elijah; Kiptoo, Kipkorir Koross Godfrey; Chemoiwa, Emily J; Ngugi, Charles C; Simiyu, Gelas; Omutange, Elijah S; Ngure, Veronica; Opiyo, Mary A

    2016-08-01

    Polychlorinated biphenyls (PCBs) are classified as persistent organic pollutants (POPs) regulated by the Stockholm Convention (2001). Although their production and use was stopped almost three decades ago, PCBs are environmental persistent, toxic, and bioaccumulate in biota. We assessed the levels of 7 PCB congeners (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) in sediment and fish (Oreochromis niloticus, Lates niloticus, and Rastrineobola argentea) and evaluated the potential of cestode fish endoparasite (Monobothrioides sp., Proteocephalaus sp., and Ligula intestinalis) as biomonitors of PCBs in Lake Victoria, Kenya. The median concentration of Σ7PCBs in sediments and fish were 2.2-96.3 μg/kg dw and 300-3,000 μg/kg lw, respectively. At all the sampling sites, CB138, CB153, and CB180 were the dominant PCB congeners in sediment and fish samples. Compared to the muscle of the piscine host, Proteocephalaus sp. (infecting L. niloticus) biomagnified PCBs ×6-14 while Monobothrioides sp. (infecting O. niloticus) biomagnified PCBs ×4-8. Meanwhile, L. intestinalis (infecting R. argentea) biomagnified PCBs ×8-16 compared to the muscle of unparasitized fish. We demonstrate the occurrence of moderate to high levels of PCB in sediments and fish in Lake Victoria. We also provide evidence that fish parasites bioaccumulate higher levels of PCBs than their piscine hosts and therefore provide a promising biomonitor of PCBs. We urge further a long-term study to validate the use of the above cestode fish parasites as biomonitoring tools for PCBs. PMID:27456696

  6. Malaria Vectors in Lake Victoria and Adjacent Habitats in Western Kenya

    PubMed Central

    Minakawa, Noboru; Dida, Gabriel O.; Sonye, George O.; Futami, Kyoko; Njenga, Sammy M.

    2012-01-01

    The prevalence of malaria among the residents of the Lake Victoria basin remains high. The environment associated with the lake may maintain a high number of malaria vectors. Lake habitats including water hyacinths have been suspected to be the source of vectors. This study investigated whether malaria vectors breed in the lake habitats and adjacent backwater pools. Anopheline larvae were collected within the littoral zone of the lake and adjacent pools located along approximately 24.3 km of the lakeshore in western Kenya, and their breeding sites characterized. Three primary vector species, Anopheles arabiensis, Anopheles gambiae s.s. and Anopheles funestus s.s., and three potential vectors, were found in the lake habitats. Unexpectedly, An. arabiensis was the most dominant vector species in the lake sampling sites. Its habitats were uncovered or covered with short grass. A potential secondary malaria vector, Anopheles rivulorum, dominated the water hyacinths in the lake. Most breeding sites in the lake were limited to areas that were surrounded by tall emergent plants, including trees, and those not exposed to waves. Nearly half of adjacent habitats were lagoons that were separated from the lake by sand bars. Lagoons contained a variety of microhabitats. Anopheles arabiensis dominated open habitats, whereas An. funestus s.s. was found mainly in vegetated habitats in lagoons. The current study confirmed that several breeding sites are associated with Lake Victoria. Given that Lake Victoria is the second largest lake in the world, the lake related habitats must be extensive; therefore, making targeted vector control difficult. Further exploration is necessary to estimate the effects of lake associated habitats on malaria transmission so as to inform a rational decision-making process for vector control. PMID:22412913

  7. Characterization of the Ugandan inshore waters of Lake Victoria based on temperature-conductivity diagrams

    NASA Astrophysics Data System (ADS)

    Cózar, AndréS.; Bracchini, Luca; Dattilo, Arduino; Loiselle, Steven; Azza, Nicholas

    2004-12-01

    Temperature-conductivity diagrams are shown as a valid instrument to analyze the hydrographic structure of freshwater ecosystems, even along the surface waters. We put this method in practice in the Ugandan inshore waters of Lake Victoria. A complementary parameter (T-C anomaly) was used to differentiate between upland water intrusions. The relative value of the T-C anomaly provided information about the nature of the water intrusions and showed a considerable correlation with the biological characteristics of the water masses. The results indicated that the connections between catchment attributes, water characteristics, and biological community are quite direct in the inshore waters of Lake Victoria.

  8. Regional nitrogen budget of the Lake Victoria Basin, East Africa: syntheses, uncertainties and perspectives

    NASA Astrophysics Data System (ADS)

    Zhou, Minghua; Brandt, Patric; Pelster, David; Rufino, Mariana C.; Robinson, Timothy; Butterbach-Bahl, Klaus

    2014-10-01

    Using the net anthropogenic nitrogen input (NANI) approach we estimated the N budget for the Lake Victoria Basin in East Africa. The NANI of the basin ranged from 887 to 3008 kg N km-2 yr-1 (mean: 1827 kg N km-2 yr-1) for the period 1995-2000. The net nitrogen release at basin level is due primarily to livestock and human consumption of feed and foods, contributing between 69% and 85%. Atmospheric oxidized N deposition contributed approximately 14% to the NANI of the Lake Victoria Basin, while either synthetic N fertilizer imports or biological N fixations only contributed less than 6% to the regional NANI. Due to the low N imports of feed and food products (<20 kg N km-2 yr-1), nitrogen release to the watershed must be derived from the mining of soil N stocks. The fraction of riverine N export to Lake Victoria accounted for 16%, which is much lower than for watersheds located in Europe and USA (25%). A significant reduction of the uncertainty of our N budget estimate for Lake Victoria Basin would be possible if better data on livestock systems and riverine N export were available. Our study indicates that at present soil N mining is the main source of nitrogen in the Lake Victoria Basin. Thus, sustainable N management requires increasing agricultural N inputs to guarantee food security and rehabilitation and protection of soils to minimize environmental costs. Moreover, to reduce N pollution of the lake, improving management of human and animal wastes needs to be carefully considered in future.

  9. Predator removal: effect on fisheries yields in lake victoria (East Africa).

    PubMed

    Marten, G G

    1979-02-16

    Lake Victoria's artisanal fishery has an overfishing problem. A possible solution is suggested by records showing that fish catches are best where predator populations have been reduced by fishing. It may be possible to remedy overfishing by increasing fishing effort, provided the additional effort is directed toward predators. PMID:17813374

  10. Satellite-Based Assessment of the spatial extent of Aquatic Vegetation in Lake Victoria

    NASA Astrophysics Data System (ADS)

    Clark, W.; Aligeti, N.; Jeyaprakash, T.; Martins, M.; Stodghill, J.; Winstanley, H.

    2011-12-01

    Lake Victoria in Africa is the second largest freshwater lake in the world and is known for its abundance of aquatic wildlife. In particular over 200 different fish species are caught and sold by local fisherman. The lake is a major contributor to the local economy as a corridor of transportation, source of drinking water, and source of hydropower. However, the invasion of aquatic vegetation such as water hyacinth in the lake has disrupted each of these markets. Aquatic vegetation now covers a substantial area of the coastline blocking waterways, disrupting hydropower, hindering the collection of drinking water and decreasing the profitability of fishing. The vegetation serves as a habitat for disease carrying mosquitoes as well as snakes and snails that spread the parasitic disease bilharzia. The current control measures of invasive aquatic vegetation rely on biological, chemical and mechanical control. The objective of this study was to utilize remote sensing to map aquatic vegetation within Lake Victoria from 2000 to 2011. MODIS, Landsat 4-5TM, and Landsat 7-ETM imagery was employed to perform change detections in vegetation and identify the extent of aquatic vegetation throughout the years. The efficiency of containment efforts were evaluated and ideal time for application of such efforts were suggested. A methodology for aquatic vegetation surveillance was created. The results of this project were presented as a workshop to the Lake Victoria Fisheries Organization, SERVIR, and other partner organizations. The workshop provided instruction into the use of NASA and other satellite derived products. Time series animations of the spatial extent of aquatic vegetation within the lake were created. By identifying seasons of decreased aquatic vegetation, ideal times to employ control efforts were identified. SERVIR will subsequently utilize the methodologies and mapping results of this study to develop operational aquatic vegetation surveillance for Lake Victoria.

  11. Water quality management and sustainability: the experience of Lake Victoria Environmental Management Project (LVEMP)??Tanzania

    NASA Astrophysics Data System (ADS)

    Machiwa, Praxeda K.

    Human health and development are threatened in many parts of the world either from lack of water or poor water quality. Human development has partially contributed to water quality deterioration. In Tanzania, for instance, rapid population growth that caused expansion of agricultural activities, livestock keeping, deforestation, biomass burning and human settlement have exerted pressures within the Lake Victoria Basin. These developments have led to land degradation and increased levels of pollution mainly from non-point sources. The Governments of Kenya, Tanzania and Uganda initiated the program of Lake Victoria Environmental Management Project, (LVEMP), in 1994 to rehabilitate the Lake Ecosystem through restoration and conservation of biodiversity in the lake as well as within the catchment. This paper presents the five years (1997-2002) experience of LVEMP in Tanzania on the issues of water quality; focusing on water pollution, water quality monitoring and LVEMP strategies to accomplish water quality management in the Lake Zone (Kagera, Mara and Mwanza regions). The findings show that non-point source pollution from agricultural practices; as well as unplanned urban settlements contribute more to siltation and eutrophication of the of Lake Victoria than that from point source pollution. Recommendations for water quality management and sustainability are presented.

  12. Urban eutrophication and its spurring conditions in the Murchison Bay of Lake Victoria.

    PubMed

    Kabenge, Martin; Wang, Hongtao; Li, Fengting

    2016-01-01

    The efficiency of Lake Victoria in providing its ecosystem services to riparian states, both immediate and along the Nile river basin, is strongly related to its water quality. Over the past few decades, eutrophication has increased in the lake arising from increased inflow of nutrients. This study was carried out in the Murchison Bay area of Lake Victoria with the aims of assessing the progress of eutrophication nutrient enrichment into the lake between 1990 and 2014. Using Landsat satellite floating algae index (FAI) products and data from laboratory analysis of water samples, the study revealed that floating algae reoccurred periodically with coverage varying between 1 and 18 km(2). The findings also indicated that the range of nitrate-nitrogen concentrations increased greatly with maximum concentrations recorded at 31.2 mg l(-1) in 2007 from 0.084 mg l(-1) in 1990. The soluble reactive phosphorus concentration range showed a maximum of 1.45 mg l(-1) in 2007 from 0.043 mg l(-1) in 1990. The chlorophyll levels increased from an average of 17 μg l(-1) in 1992 by threefold in 1996 but had however declined and halved in intensity by 2011. The eutrophication that has occurred in Lake Victoria over the past decades has been due to pollution from industrial, residential, and agricultural areas within the catchment. PMID:26531714

  13. Simulation of pollution buffering capacity of wetlands fringing the Lake Victoria.

    PubMed

    Mwanuzi, F; Aalderink, H; Mdamo, L

    2003-04-01

    Lake Victoria has undergone substantial and most negative changes, especially over the last 30 years. One of the driving factors is nutrient enrichment from human activities in the catchment, which is causing eutrophication. This has been associated with, among others, the rapid proliferation of water hyacinth, alga blooms, and with general disruption of the lake ecosystem. Most of pollution to the lake flow via the natural wetlands. In order to understand how wetlands function within the Lake Victoria ecosystem a wetland model has been developed. The main objective of the model is to establish and simulate the buffering processes and capacity of individual wetlands (that is, their ability to absorb sediments, nutrients and pollutants) within the Lake Victoria basin. It was found that in both seasonal and permanent swamp there is a net export of organic matter produced in the wetlands. Most of the inorganic phosphorous were retained in the wetlands (60% to 90% removal) while there was a negative retention of nitrates probably due to the export of organic matter which associate very much with nitrates. PMID:12605942

  14. High prevalence of non-synonymous substitutions in mtDNA of cichlid fishes from Lake Victoria.

    PubMed

    Shirai, Kazumasa; Inomata, Nobuyuki; Mizoiri, Shinji; Aibara, Mitsuto; Terai, Yohey; Okada, Norihiro; Tachida, Hidenori

    2014-12-01

    When a population size is reduced, genetic drift may fix slightly deleterious mutations, and an increase in nonsynonymous substitution is expected. It has been suggested that past aridity has seriously affected and decreased the populations of cichlid fishes in Lake Victoria, while geographical studies have shown that the water levels in Lake Tanganyika and Lake Malawi have remained fairly constant. The comparably stable environments in the latter two lakes might have kept the populations of cichlid fishes large enough to remove slightly deleterious mutations. The difference in the stability of cichlid fish population sizes between Lake Victoria and the Lakes Tanganyika and Malawi is expected to have caused differences in the nonsynonymous/synonymous ratio, ω (=dN/dS), of the evolutionary rate. Here, we estimated ω and compared it between the cichlids of the three lakes for 13 mitochondrial protein-coding genes using maximum likelihood methods. We found that the lineages of the cichlids in Lake Victoria had a significantly higher ω for several mitochondrial loci. Moreover, positive selection was indicated for several codons in the mtDNA of the Lake Victoria cichlid lineage. Our results indicate that both adaptive and slightly deleterious molecular evolution has taken place in the Lake Victoria cichlids' mtDNA genes, whose nonsynonymous sites are generally conserved. PMID:25241383

  15. Monophyletic origin of Lake Victoria cichlid fishes suggested by mitochondrial DNA sequences.

    PubMed

    Meyer, A; Kocher, T D; Basasibwaki, P; Wilson, A C

    1990-10-11

    Lake Victoria, together with its satellite lakes, harbours roughly 200 endemic forms of cichlid fishes that are classified as 'haplochromines' and yet the lake system is less than a million years old. This 'flock' has attracted attention because of the possibility that it evolved within the lake from one ancestral species and that biologists are thus presented with a case of explosive evolution. Within the past decade, however, morphology has increasingly emphasized the view that the flock may be polyphyletic. We sequenced up to 803 base pairs of mitochondrial DNA from 14 representative Victorian species and 23 additional African species. The flock seems to be monophyletic, and is more akin to that from Lake Malawi than to species from Lake Tanganyika; in addition, it contains less genetic variation than does the human species, and there is virtually no sharing of mitochondrial DNA types among species. These results confirm that the founding event was recent. PMID:2215680

  16. Microbial Fe cycling and mineralization in sediments of an acidic, hypersaline lake (Lake Tyrell, Victoria, Australia)

    NASA Astrophysics Data System (ADS)

    Roden, E. E.; Blöthe, M.; Shelobolina, E.

    2009-12-01

    Lake Tyrrell is a variably acidic, hypersaline, Fe-rich lake located in Victoria, Australia. Terrestrial acid saline lakes like Lake Tyrrell may be analogs for ancient Martian surface environments, as well as possible extant subsurface environments. To investigate the potential for microbial Fe cycling under acidic conditions and high salt concentration, we collected sediment core samples during three field trips between 2006 and 2008 from the southern, acidic edge of the lake. Materials from the cores were used for chemical and mineralogical analyses, as well as for molecular (16S rRNA genes) and culture-based microbiological studies. Near-surface (< 1 m depth) pore fluids contained low but detectable dissolved oxygen (ca. 50 uM), significant dissolved Fe(II) (ca. 500 uM), and nearly constant pH of around 4 - conditions conducive to enzymatic Fe(II) oxidation. High concentrations of Fe(III) oxides begin accumulate at a depth of ca. 10 cm, and may reflect the starting point for formation of massive iron concretions that are evident at and beneath the sediment surface. MPN analyses revealed low (10-100 cells/mL) but detectable populations of aerobic, halophilic Fe(II)-oxidizing organisms on the sediment surface and in the near-surface ground water. With culture-dependent methods at least three different halotolerant lithoautotrophic cultures growing on Fe(II), thiosulfate, or tetrathionate from different acidic sites were obtained. Analysis of 16S rRNA gene sequences revealed that these organisms are similar to previous described gamma proteobacteria Thiobacillus prosperus (95%), Halothiobacillus kellyi (99%), Salinisphaera shabanense (95%) and a Marinobacter species. (98%). 16S rRNA gene pyrosequencing data from two different sites with a pH range between 3 and 4.5 revealed a dominance of gamma proteobacteria. 16S rRNA gene pyrosequencing libraries from both cores were dominated by sequences related to the Ectothiorhodospiraceae family, which includes the taxa

  17. Basin-scale control on the phytoplankton biomass in Lake Victoria, Africa.

    PubMed

    Cózar, Andrés; Bruno, Miguel; Bergamino, Nadia; Ubeda, Bárbara; Bracchini, Luca; Dattilo, Arduino M; Loiselle, Steven A

    2012-01-01

    The relative bio-optical variability within Lake Victoria was analyzed through the spatio-temporal decomposition of a 1997-2004 dataset of remotely-sensed reflectance ratios in the visible spectral range. Results show a regular seasonal pattern with a phase shift (around 2 months) between the south and north parts of the lake. Interannual trends suggested a teleconnection between the lake dynamics and El-Niño phenomena. Both seasonal and interannual patterns were associated to conditions of light limitation for phytoplankton growth and basin-scale hydrodynamics on phytoplankton access to light. Phytoplankton blooms developed during the periods of lake surface warming and water column stability. The temporal shift apparent in the bio-optical seasonal cycles was related to the differential cooling of the lake surface by southeastern monsoon winds. North-south differences in the exposure to trade winds are supported by the orography of the Eastern Great Rift Valley. The result is that surface layer warming begins in the northern part of the lake while the formation of cool and dense water continues in the southern part. The resulting buoyancy field is sufficient to induce a lake-wide convective circulation and the tilting of the isotherms along the north-south axis. Once surface warming spreads over the whole lake, the phytoplankton bloom dynamics are subjected to the internal seiche derived from the relaxation of thermocline tilting. In 1997-98, El-Niño phenomenon weakened the monsoon wind flow which led to an increase in water column stability and a higher phytoplankton optical signal throughout the lake. This suggests that phytoplankton response to expected climate scenarios will be opposite to that proposed for nutrient-limited great lakes. The present analysis of remotely-sensed bio-optical properties in combination with environmental data provides a novel basin-scale framework for research and management strategies in Lake Victoria. PMID:22253837

  18. Environmental impacts of cage culture in Lake Victoria: the case of Shirati Bay-Sota, Tanzania.

    PubMed

    Kashindye, Benedicto Boniphace; Nsinda, P; Kayanda, R; Ngupula, G W; Mashafi, C A; Ezekiel, C N

    2015-01-01

    The experimental cage culture was conducted at Shirati bay, Lake Victoria from February to August 2013, to investigate the impacts of the small scale cage culture on the environment. Three locations along the cages, at the intermediate and one in the offshore (control) were sampled for water quality parameters, phytoplankton and macro invertebrates. A notable increase in nutrient concentration was observed after the set of cages among the stations. However DO, pH, and water transparency showed no major changes and was within the recommended ranges. Cyanophytes an indicator of inorganic pollution dominated before and after the set of cages, an increase in phytoplankton numerical abundance was observed after stocking of fish in cages. In addition there was an increase in the invertebrate community especially bivalves and gastropods. In conclusion we found no consistent environmental change caused by cage culture, and therefore it can be allowed in Lake Victoria, Tanzania part, with close monitoring of its impacts. PMID:26361576

  19. Was Lates Late? A Null Model for the Nile Perch Boom in Lake Victoria

    PubMed Central

    Downing, Andrea S.; Galic, Nika; Goudswaard, Kees P. C.; van Nes, Egbert H.; Scheffer, Marten; Witte, Frans; Mooij, Wolf M.

    2013-01-01

    Nile perch (Lates niloticus) suddenly invaded Lake Victoria between 1979 and 1987, 25 years after its introduction in the Ugandan side of the lake. Nile perch then replaced the native fish diversity and irreversibly altered the ecosystem and its role to lakeshore societies: it is now a prised export product that supports millions of livelihoods. The delay in the Nile perch boom led to a hunt for triggers of the sudden boom and generated several hypotheses regarding its growth at low abundances – all hypotheses having important implications for the management of Nile perch stocks. We use logistic growth as a parsimonious null model to predict when the Nile perch invasion should have been expected, given its growth rate, initial stock size and introduction year. We find the first exponential growth phase can explain the timing of the perch boom at the scale of Lake Victoria, suggesting that complex mechanisms are not necessary to explain the Nile perch invasion or its timing. However, the boom started in Kenya before Uganda, indicating perhaps that Allee effects act at smaller scales than that of the whole Lake. The Nile perch invasion of other lakes indicates that habitat differences may also have an effect on invasion success. Our results suggest there is probably no single management strategy applicable to the whole lake that would lead to both efficient and sustainable exploitation of its resources. PMID:24204684

  20. On the age and origin of the species flock of haplochromine cichlid fishes of Lake Victoria.

    PubMed

    Fryer, G

    2001-06-01

    Recent suggestions concerning the age and origin of the flock of haplochromine cichlid fishes in Lake Victoria (East Africa) are considered. These accept as proven the suggestion that Lake Victoria dried out completely in the Late Pleistocene, was dry for several thousand years, and refilled ca. 12400 years ago. Apart from the fact that other geophysical evidence contradicts this claim, its biological implications, which do likewise, have never been considered by those who have accepted it. Like those of all previous authors who have seized on the presence of the haplochromine flock of perhaps more than 600 species as evidence of extremely rapid evolution since the lake allegedly refilled, the account completely overlooks the fact that any such desiccation must have eliminated not only the haplochromine cichlids but the entire biota of the lake. Nevertheless, its present fauna not only includes the haplochromines but many other endemic organisms that would not be expected, and whose presence and history demand an explanation if the lake did indeed dry out. No such explanation has been offered, nor does such seem possible. The recent interpretation of events is questioned and rejected. PMID:11375102

  1. On the age and origin of the species flock of haplochromine cichlid fishes of Lake Victoria.

    PubMed Central

    Fryer, G.

    2001-01-01

    Recent suggestions concerning the age and origin of the flock of haplochromine cichlid fishes in Lake Victoria (East Africa) are considered. These accept as proven the suggestion that Lake Victoria dried out completely in the Late Pleistocene, was dry for several thousand years, and refilled ca. 12400 years ago. Apart from the fact that other geophysical evidence contradicts this claim, its biological implications, which do likewise, have never been considered by those who have accepted it. Like those of all previous authors who have seized on the presence of the haplochromine flock of perhaps more than 600 species as evidence of extremely rapid evolution since the lake allegedly refilled, the account completely overlooks the fact that any such desiccation must have eliminated not only the haplochromine cichlids but the entire biota of the lake. Nevertheless, its present fauna not only includes the haplochromines but many other endemic organisms that would not be expected, and whose presence and history demand an explanation if the lake did indeed dry out. No such explanation has been offered, nor does such seem possible. The recent interpretation of events is questioned and rejected. PMID:11375102

  2. Nuclear markers reveal unexpected genetic variation and a Congolese-Nilotic origin of the Lake Victoria cichlid species flock.

    PubMed Central

    Seehausen, Ole; Koetsier, Egbert; Schneider, Maria Victoria; Chapman, Lauren J; Chapman, Colin A; Knight, Mairi E; Turner, George F; van Alphen, Jacques J M; Bills, Roger

    2003-01-01

    Phylogenetic analyses based on mitochondrial (mt) DNA have indicated that the cichlid species flock of the Lake Victoria region is derived from a single ancestral species found in East African rivers, closely related to the ancestor of the Lake Malawi cichlid species flock. The Lake Victoria flock contains ten times less mtDNA variation than the Lake Malawi radiation, consistent with current estimates of the ages of the lakes. We present results of a phylogenetic investigation using nuclear (amplified fragment length polymorphism) markers and a wider coverage of riverine haplochromines. We demonstrate that the Lake Victoria-Edward flock is derived from the morphologically and ecologically diverse cichlid genus Thoracochromis from the Congo and Nile, rather than from the phenotypically conservative East African Astatotilapia. This implies that the ability to express much of the morphological diversity found in the species flock may by far pre-date the origin of the flock. Our data indicate that the nuclear diversity of the Lake Victoria-Edward species flock is similar to that of the Lake Malawi flock, indicating that the genetic diversity is considerably older than the 15 000 years that have passed since the lake began to refill. Most of this variation is manifested in trans-species polymorphisms, indicating very recent cladogenesis from a genetically very diverse founder stock. Our data do not confirm strict monophyly of either of the species flocks, but raise the possibility that these flocks have arisen from hybrid swarms. PMID:12590750

  3. Nuclear markers reveal unexpected genetic variation and a Congolese-Nilotic origin of the Lake Victoria cichlid species flock.

    PubMed

    Seehausen, Ole; Koetsier, Egbert; Schneider, Maria Victoria; Chapman, Lauren J; Chapman, Colin A; Knight, Mairi E; Turner, George F; van Alphen, Jacques J M; Bills, Roger

    2003-01-22

    Phylogenetic analyses based on mitochondrial (mt) DNA have indicated that the cichlid species flock of the Lake Victoria region is derived from a single ancestral species found in East African rivers, closely related to the ancestor of the Lake Malawi cichlid species flock. The Lake Victoria flock contains ten times less mtDNA variation than the Lake Malawi radiation, consistent with current estimates of the ages of the lakes. We present results of a phylogenetic investigation using nuclear (amplified fragment length polymorphism) markers and a wider coverage of riverine haplochromines. We demonstrate that the Lake Victoria-Edward flock is derived from the morphologically and ecologically diverse cichlid genus Thoracochromis from the Congo and Nile, rather than from the phenotypically conservative East African Astatotilapia. This implies that the ability to express much of the morphological diversity found in the species flock may by far pre-date the origin of the flock. Our data indicate that the nuclear diversity of the Lake Victoria-Edward species flock is similar to that of the Lake Malawi flock, indicating that the genetic diversity is considerably older than the 15 000 years that have passed since the lake began to refill. Most of this variation is manifested in trans-species polymorphisms, indicating very recent cladogenesis from a genetically very diverse founder stock. Our data do not confirm strict monophyly of either of the species flocks, but raise the possibility that these flocks have arisen from hybrid swarms. PMID:12590750

  4. A review of mercury in Lake Victoria, East Africa: implications for human and ecosystem health.

    PubMed

    Campbell, Linda; Dixon, D G; Hecky, R E

    2003-01-01

    Lake Victoria, East Africa, has been the site of many recent studies measuring mercury (Hg) concentrations in water, fish, sediment, soil, and humans. Most of these studies were motivated by concerns about Hg contamination from processing of gold ore on the southern shores. Total Hg (THg) concentrations in fish were usually below permissible World Health Organization (WHO) concentrations and international marketing limits and do not threaten the lucrative export industry. Nile perch 3-10 kg and most >10 kg had THg concentrations above the WHO threshold concentrations for at-risk groups (200 ng/g). Elevated THg concentrations in large Nile perch are not of major concern because Nile perch are rarely consumed by the people living on Lake Victoria and very large Nile perch are becoming increasingly rare in catches. Water THg concentrations were below Canadian drinking water guidelines but were elevated relative to those in the northern Great Lakes. Sediment and soil THg concentrations were within inter-national guidelines and are comparable to those in northern latitudes but are lower than those in the Amazon basin. Biomass burning and soil erosion are estimated to be the major sources of THg for the lake and probably constitute a larger source of THg than gold mining in Tanzania.THg concentrations in urine and hair from human volunteers indicate that while gold miners and frequent skin-bleaching cream users are at risk of inorganic mercury poisoning, the rest of the population, including fishermen, is not. Human exposure assessments demonstrated that fish consumption and soil geophagy constitute major sources of THg for humans, but the total estimated daily intake of THg was below the Health Canada tolerable daily intake (TDI) limits. The use of beauty creams containing high inorganic Hg concentrations, however, caused the estimated THg exposure to exceed the TDI. The high THg content in the hair of regular cream users supports this assessment. The nutritional

  5. Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS).

    PubMed

    Nyamweya, Chrispine; Desjardins, Christopher; Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

    2016-01-01

    Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria. PMID:27030983

  6. Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS)

    PubMed Central

    Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

    2016-01-01

    Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September–May) and mixing (June–August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore—offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria. PMID:27030983

  7. Metals in Nile perch (Lates niloticus) and suspended particulate matter from Lake Victoria, Tanzania.

    PubMed

    Machiwa, John F

    2005-01-01

    A study was conducted to assess the levels of pollutant metals in suspended particulate matter and Nile perch from Lake Victoria. The metals in particulate matter were determined to ascertain their concentrations at the base of the food chain. Nile perch samples were collected in September 2003 from five major fish processing factories at the shores of Lake Victoria in Mwanza and Musoma. The concentrations of total Hg, Pb, Cd, and Cu were generally low in particulate matter and in most locations were close to or below their limits of detection. The concentrations of Zn were high in suspended particulate matter, the highest being 219.4 +/- 153.0 microg L(-1) found in particulate matter from Nungwe Bay in the southern part of Lake Victoria. Nile perch generally contained low levels of heavy metals; the range for Pb was <0.01-0.08 microg g(-1) ww, Cd was <0.001-0.04 microg g(-1) ww, Cu was 0.01-0.97 microg g(-1) ww, and Zn was <0.01-18.94 microg g(-1) ww. The concentration of total mercury ranged between 31.0 and 684.2 ng g(-1) ww; generally, it was below the Food and Agriculture Organization of the United Nations/World Health Organization (1000 ng total Hg g(-1) ww for piscivorous fish species) maximum allowable level. Indeed, all Nile perch samples that weighed less than 10 kg had less than 200 ng total Hg g(-1) ww and therefore are safe for regular consumption by at-risk groups such as children and pregnant women. Levels of mercury and other heavy metals in Nile perch at present is, therefore, not a severe environmental issue; however, urgent regulatory measures should be taken to minimize metal input into the lake to maintain the current levels in the fish. PMID:16134370

  8. The diversity of male nuptial coloration leads to species diversity in Lake Victoria cichlids.

    PubMed

    Miyagi, Ryutaro; Terai, Yohey

    2013-01-01

    The amazing coloration shown by diverse cichlid fish not only fascinates aquarium keepers, but also receives great attention from biologists interested in speciation because of its recently-revealed role in their adaptive radiation in an African lake. We review the important role of coloration in the speciation and adaptive evolution of Lake Victoria cichlids, which have experienced adaptive radiation during a very short evolutionary period. Mature male cichlids display their colors during mate choice. The color of their skin reflects light, and the reflected light forms a color signal that is received by the visual system of females. The adaptive divergence of visual perceptions shapes and diverges colorations, to match the adapted visual perceptions. The divergence of visual perception and coloration indicates that the divergence of color signals causes reproductive isolation between species, and this process leads to speciation. Differences in color signals among coexisting species act to maintain reproductive isolation by preventing hybridization. Thus, the diversity of coloration has caused speciation and has maintained species diversity in Lake Victoria cichlids. PMID:24025243

  9. Population genetic structure of Anopheles gambiae mosquitoes on Lake Victoria islands, west Kenya

    PubMed Central

    Chen, Hong; Minakawa, Noboru; Beier, John; Yan, Guiyun

    2004-01-01

    Background Understanding the genetic structure of island Anopheles gambiae populations is important for the current tactics in mosquito control and for the proposed strategy using genetically-modified mosquitoes (GMM). Genetically-isolated mosquito populations on islands are a potential site for testing GMM. The objective of this study was to determine the genetic structure of A. gambiae populations on the islands in Lake Victoria, western Kenya. Methods The genetic diversity and the population genetic structures of 13 A. gambiae populations from five islands on Lake Victoria and six villages from the surrounding mainland area in the Suba District were examined using six microsatellite markers. The distance range of sampling sites varied between 2.5 and 35.1 km. Results A similar level of genetic diversity between island mosquito populations and adjacent mainland populations was found. The average number of alleles per locus was 7.3 for the island populations and 6.8 for the mainland populations. The average observed heterozygosity was 0.32 and 0.28 for the island and mainland populations, respectively. A low but statistically significant genetic structure was detected among the island populations (FST = 0.019) and between the island and mainland populations (FST = 0.003). A total of 12 private alleles were found, and nine of them were from the island populations. Conclusion A level of genetic differentiation between the island and mainland populations was found. Large extent of gene flow between the island and mainland mosquito populations may result from wind- or human-assisted dispersal. Should the islands on Lake Victoria be used as a trial site for the release program of GMM, mosquito dispersal between the islands and between the island and the mainland should be vigorously monitored. PMID:15581429

  10. Stable isotope paleoecology of Late Pleistocene Middle Stone Age humans from the Lake Victoria basin, Kenya.

    PubMed

    Garrett, Nicole D; Fox, David L; McNulty, Kieran P; Faith, J Tyler; Peppe, Daniel J; Van Plantinga, Alex; Tryon, Christian A

    2015-05-01

    Paleoanthropologists have long argued that environmental pressures played a key role in human evolution. However, our understanding of how these pressures mediated the behavioral and biological diversity of early modern humans and their migration patterns within and out of Africa is limited by a lack of archaeological evidence associated with detailed paleoenvironmental data. Here, we present the first stable isotopic data from paleosols and fauna associated with Middle Stone Age (MSA) sites in East Africa. Late Pleistocene (∼100-45 ka, thousands of years ago) sediments on Rusinga and Mfangano Islands in eastern Lake Victoria (Kenya) preserve a taxonomically diverse, non-analog faunal community associated with MSA artifacts. We analyzed the stable carbon and oxygen isotope composition of paleosol carbonate and organic matter and fossil mammalian tooth enamel, including the first analyses for several extinct bovids such as Rusingoryx atopocranion, Damaliscus hypsodon, and an unnamed impala species. Both paleosol carbonate and organic matter data suggest that local habitats associated with human activities were primarily riverine woodland ecosystems. However, mammalian tooth enamel data indicate that most large-bodied mammals consumed a predominantly C4 diet, suggesting an extensive C4 grassland surrounding these riverine woodlands in the region at the time. These data are consistent with other lines of paleoenvironmental evidence that imply a substantially reduced Lake Victoria at this time, and demonstrate that C4 grasslands were significantly expanded into equatorial Africa compared with their present distribution, which could have facilitated dispersal of human populations and other biotic communities. Our results indicate that early populations of Homo sapiens from the Lake Victoria region exploited locally wooded and well-watered habitats within a larger grassland ecosystem. PMID:25805041

  11. A pharyngeal jaw evolutionary innovation facilitated extinction in Lake Victoria cichlids.

    PubMed

    McGee, Matthew D; Borstein, Samuel R; Neches, Russell Y; Buescher, Heinz H; Seehausen, Ole; Wainwright, Peter C

    2015-11-27

    Evolutionary innovations, traits that give species access to previously unoccupied niches, may promote speciation and adaptive radiation. Here, we show that such innovations can also result in competitive inferiority and extinction. We present evidence that the modified pharyngeal jaws of cichlid fishes and several marine fish lineages, a classic example of evolutionary innovation, are not universally beneficial. A large-scale analysis of dietary evolution across marine fish lineages reveals that the innovation compromises access to energy-rich predator niches. We show that this competitive inferiority shaped the adaptive radiation of cichlids in Lake Tanganyika and played a pivotal and previously unrecognized role in the mass extinction of cichlid fishes in Lake Victoria after Nile perch invasion. PMID:26612951

  12. Sunspots, El Niño, and the levels of Lake Victoria, East Africa

    NASA Astrophysics Data System (ADS)

    Stager, J. Curt; Ruzmaikin, Alexander; Conway, Declan; Verburg, Piet; Mason, Peter J.

    2007-08-01

    An association of high sunspot numbers with rises in the level of Lake Victoria, East Africa, has been the focus of many investigations and vigorous debate during the last century. In this paper, we show that peaks in the ~11-year sunspot cycle were accompanied by Victoria level maxima throughout the 20th century, due to the occurrence of positive rainfall anomalies ~1 year before solar maxima. Similar patterns also occurred in at least five other East African lakes, which indicates that these sunspot-rainfall relationships were broadly regional in scale. Although irradiance fluctuations associated with the sunspot cycle are weak, their effects on tropical rainfall could be amplified through interactions with sea surface temperatures and atmospheric circulation systems, including ENSO. If this Sun-rainfall relationship persists in the future, then sunspot cycles can be used for long-term prediction of precipitation anomalies and associated outbreaks of insect-borne disease in much of East Africa. In that case, unusually wet rainy seasons and Rift Valley Fever epidemics should occur a year or so before the next solar maximum, which is expected to occur in 2011-2012 AD.

  13. Prevalence of Schistosomes and Soil-Transmitted Helminths among Schoolchildren in Lake Victoria Basin, Tanzania

    PubMed Central

    Siza, Julius E.; Kaatano, Godfrey M.; Chai, Jong-Yil; Eom, Keeseon S.; Rim, Han-Jong; Yong, Tai-Soon; Min, Duk-Young; Chang, Su Young; Ko, Yunsuk; Changalucha, John M.

    2015-01-01

    The objectives of this study was to conduct a survey on schistosomiasis and soil-transmitted helminth (STH) infections in order to come up with feasible control strategies in Lake Victoria basin, Tanzania. Depending on the size of the school, 150-200 schoolchildren were recruited for the study. Duplicate Kato-Katz stool smears were prepared from each child and microscopically examined for Schistosoma mansoni and STHs. Urine specimens were examined for Schistosoma haematobium eggs using the filtration technique. After the survey, mass drug administration was done using praziquantel and albendazole for schistosomiasis and STHs infections, respectively. A total of 5,952 schoolchildren from 36 schools were recruited for the study and had their stool and urine specimens examined. Out of 5,952 schoolchildren, 898 (15.1%) were positive for S. mansoni, 754 (12.6%) for hookworms, 188 (3.2%) for Ascaris lumblicoides, and 5 (0.008%) for Trichuris trichiura. Out of 5,826 schoolchildren who provided urine samples, 519 (8.9%) were positive for S. haematobium eggs. The results revealed that intestinal schistosomiasis, urogenital schistosomiasis, and STH infections are highly prevalent throughought the lake basin. The high prevalence of intestinal and urogenital schistosomisiasis in the study area was a function of the distance from Lake Victoria, the former being more prevalent at localities close to the lake, whilst the latter is more so away from it. Control of schistosomiasis and STHs in the study area requires an integrated strategy that involves provision of health education to communities, regular treatments, and provision of adequate safe water supply and sanitation facilities. PMID:26537030

  14. Impact of Urbanization on Precipitation Distribution and Intensity over Lake Victoria Basin

    NASA Astrophysics Data System (ADS)

    Gudoshava, M.; Semazzi, F. H. M.

    2014-12-01

    In this study, sensitivity simulations on the impact of rapid urbanization over Lake Victoria Basin in East Africa were done using a Regional Climate Model (RegCM4.4-rc29) with the Hostetler lake model activated. The simulations were done for the rainy seasons that is the long rains (March-April-May) and short rains (October-November-December). Africa is projected to have a surge in urbanization with an approximate rate of 590% in 2030 over their 2000 levels. The Northern part of Lake Victoria Basin and some parts of Rwanda and Burundi are amongst the regions with high urbanization projections. Simulations were done with the land cover for 2000 and the projected 2030 urbanization levels. The results showed that increasing the urban fraction over the northern part of the basin modified the physical parameters such as albedo, moisture and surface energy fluxes, aerodynamic roughness and surface emissivity, thereby altering the precipitation distribution, intensity and frequency in the region. The change in the physical parameters gave a response of an average increase in temperature of approximately 2oC over the urbanized region. A strong convergence zone was formed over the urbanized region and thereby accelerating the lake-breeze front towards the urbanized region center. Precipitation in the urbanized region and regions immediate to the area increased by approximately 4mm/day, while drying up the southern (non-urbanized) side of the basin. The drying up of the southern side of the basin could be a result of divergent flow and subsidence that suppresses vertical development of storms.

  15. Prevalence of Schistosomes and Soil-Transmitted Helminths among Schoolchildren in Lake Victoria Basin, Tanzania.

    PubMed

    Siza, Julius E; Kaatano, Godfrey M; Chai, Jong-Yil; Eom, Keeseon S; Rim, Han-Jong; Yong, Tai-Soon; Min, Duk-Young; Chang, Su Young; Ko, Yunsuk; Changalucha, John M

    2015-10-01

    The objectives of this study was to conduct a survey on schistosomiasis and soil-transmitted helminth (STH) infections in order to come up with feasible control strategies in Lake Victoria basin, Tanzania. Depending on the size of the school, 150-200 schoolchildren were recruited for the study. Duplicate Kato-Katz stool smears were prepared from each child and microscopically examined for Schistosoma mansoni and STHs. Urine specimens were examined for Schistosoma haematobium eggs using the filtration technique. After the survey, mass drug administration was done using praziquantel and albendazole for schistosomiasis and STHs infections, respectively. A total of 5,952 schoolchildren from 36 schools were recruited for the study and had their stool and urine specimens examined. Out of 5,952 schoolchildren, 898 (15.1%) were positive for S. mansoni, 754 (12.6%) for hookworms, 188 (3.2%) for Ascaris lumblicoides, and 5 (0.008%) for Trichuris trichiura. Out of 5,826 schoolchildren who provided urine samples, 519 (8.9%) were positive for S. haematobium eggs. The results revealed that intestinal schistosomiasis, urogenital schistosomiasis, and STH infections are highly prevalent throughought the lake basin. The high prevalence of intestinal and urogenital schistosomisiasis in the study area was a function of the distance from Lake Victoria, the former being more prevalent at localities close to the lake, whilst the latter is more so away from it. Control of schistosomiasis and STHs in the study area requires an integrated strategy that involves provision of health education to communities, regular treatments, and provision of adequate safe water supply and sanitation facilities. PMID:26537030

  16. Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

    PubMed Central

    de Zeeuw, Marnix P.; Westbroek, Irene; van Oijen, Martien J.P.; Witte, Frans

    2013-01-01

    Abstract Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania, are described and illustrated. These species closely resemble each other. Their affinities to other zooplanktivorous haplochromines from Lake Victoria are discussed. Haplochromis argens sp. n., which featured under nicknames (mainly Haplochromis “argens”) in more than 50 papers, was caught both in the Mwanza Gulf and the Emin Pasha Gulf, whereas Haplochromis goldschmidti sp. n. was only found in the Emin Pasha Gulf. Of the latter species only males are available, but it seems unlikely that it represents a case of male colour polymorphism as several presumably unrelated characters differ in sympatry between the two species, suggesting that there is no gene flow. Statistical analysis revealed that the overall difference between the two species is greater than that between the populations from the two locations. Body depth of the two species in sympatry in the Emin Pasha Gulf was more similar than that of Haplochromis goldschmidti sp. n. and the allopatric population of Haplochromis argens sp. n. from the Mwanza Gulf,which mayindicate an overall environmental effect. However, several measurements related to the width of snout and mouth differed more between the populations of the two species in sympatry than between the allopatric populations. In contrast to a group of zooplanktivorous species that recovered successfully after environmental changes in the lake, Haplochromis argens sp. n. is among a group that became extremely rare and probably is in danger of extinction; the conservation status of Haplochromis goldschmidti sp. n. is currently unknown. PMID:23717179

  17. Extent and drainage status of organic soils in the Lake Victoria catchment

    NASA Astrophysics Data System (ADS)

    Barthelmes, Reni; Barthelmes, Alexandra; Joosten, Hans

    2016-04-01

    When considering peatlands and organic soils in the tropics, the huge areas in SE Asia prevail in public and scientific perception, whereas Africa has largely been out of focus. However, East Africa contains large areas of organic soils as well. They basically occur in the high altitudes of the uplifted flanks of the East African Rift System, isolated volcanoes and the Ethiopian highlands, in the Zambezian floodplains (e.g. Zambia), and in coastal environments (e.g. Mozambique and Madagascar). We used a mapping approach that integrates old field data and maps, specialized landscape and peatland-related knowledge, and modern RS and GIS techniques to elaborate a comprehensive and rather reliable overview of organic soils (incl. peatlands) in the Lake Victoria catchment. Maps at a scale of 1:25,000 have been prepared for Burundi, Kenya, Rwanda, Tanzania and Uganda. The land use intensity has been estimated for all organic soil areas based on satellite and aerial imagery. Feeding the Nile River, sustaining a fast growing and widely poor population and already facing climatic changes, organic soils of the Lake Victoria neighbouring countries are partially under heavy threat. We mapped 10,645 km2 of organic soils for the entire area of which 8,860 km2 (83.2%) seem to be in near natural condition. We assume slightly drainage and low degradation for 564 km2 (5.3%) and intensive drainage and heavy degradation for 1,222 km2 (11.5%). Degradation hotspot is Burundi with 522 km2 (79.5%) of heavily drained and degrading organic soils. This area assessment has been quite conservative to not overestimate the extent of organic soils. A reserve of 5-7,000 km2 of wetlands in the Lake Victoria catchment may include peatlands too, which needs to be confirmed in field surveys. Considering the key role of peatlands and organic soils for water provision and regulation and their rapid degradation due to drainage and inappropriate use, this inventory might be a step towards organic soil

  18. Tsetse fly (G. f. fuscipes) distribution in the Lake Victoria basin of Uganda.

    PubMed

    Albert, Mugenyi; Wardrop, Nicola A; Atkinson, Peter M; Torr, Steve J; Welburn, Susan C

    2015-04-01

    Tsetse flies transmit trypanosomes, the causative agent of human and animal African trypanosomiasis. The tsetse vector is extensively distributed across sub-Saharan Africa. Trypanosomiasis maintenance is determined by the interrelationship of three elements: vertebrate host, parasite and the vector responsible for transmission. Mapping the distribution and abundance of tsetse flies assists in predicting trypanosomiasis distributions and developing rational strategies for disease and vector control. Given scarce resources to carry out regular full scale field tsetse surveys to up-date existing tsetse maps, there is a need to devise inexpensive means for regularly obtaining dependable area-wide tsetse data to guide control activities. In this study we used spatial epidemiological modelling techniques (logistic regression) involving 5000 field-based tsetse-data (G. f. fuscipes) points over an area of 40,000 km2, with satellite-derived environmental surrogates composed of precipitation, temperature, land cover, normalised difference vegetation index (NDVI) and elevation at the sub-national level. We used these extensive tsetse data to analyse the relationships between presence of tsetse (G. f. fuscipes) and environmental variables. The strength of the results was enhanced through the application of a spatial autologistic regression model (SARM). Using the SARM we showed that the probability of tsetse presence increased with proportion of forest cover and riverine vegetation. The key outputs are a predictive tsetse distribution map for the Lake Victoria basin of Uganda and an improved understanding of the association between tsetse presence and environmental variables. The predicted spatial distribution of tsetse in the Lake Victoria basin of Uganda will provide significant new information to assist with the spatial targeting of tsetse and trypanosomiasis control. PMID:25875201

  19. Tsetse Fly (G.f. fuscipes) Distribution in the Lake Victoria Basin of Uganda

    PubMed Central

    Albert, Mugenyi; Wardrop, Nicola A; Atkinson, Peter M; Torr, Steve J; Welburn, Susan C

    2015-01-01

    Tsetse flies transmit trypanosomes, the causative agent of human and animal African trypanosomiasis. The tsetse vector is extensively distributed across sub-Saharan Africa. Trypanosomiasis maintenance is determined by the interrelationship of three elements: vertebrate host, parasite and the vector responsible for transmission. Mapping the distribution and abundance of tsetse flies assists in predicting trypanosomiasis distributions and developing rational strategies for disease and vector control. Given scarce resources to carry out regular full scale field tsetse surveys to up-date existing tsetse maps, there is a need to devise inexpensive means for regularly obtaining dependable area-wide tsetse data to guide control activities. In this study we used spatial epidemiological modelling techniques (logistic regression) involving 5000 field-based tsetse-data (G. f. fuscipes) points over an area of 40,000 km2, with satellite-derived environmental surrogates composed of precipitation, temperature, land cover, normalised difference vegetation index (NDVI) and elevation at the sub-national level. We used these extensive tsetse data to analyse the relationships between presence of tsetse (G. f. fuscipes) and environmental variables. The strength of the results was enhanced through the application of a spatial autologistic regression model (SARM). Using the SARM we showed that the probability of tsetse presence increased with proportion of forest cover and riverine vegetation. The key outputs are a predictive tsetse distribution map for the Lake Victoria basin of Uganda and an improved understanding of the association between tsetse presence and environmental variables. The predicted spatial distribution of tsetse in the Lake Victoria basin of Uganda will provide significant new information to assist with the spatial targeting of tsetse and trypanosomiasis control. PMID:25875201

  20. Impacts of population growth and economic development on water quality of a lake: case study of Lake Victoria Kenya water.

    PubMed

    Juma, Dauglas Wafula; Wang, Hongtao; Li, Fengting

    2014-04-01

    Anthropogenic-induced water quality pollution is a major environmental problem in freshwater ecosystems today. As a result of this, eutrophication of lakes occurs. Population and economic development are key drivers of water resource pollution. To evaluate how growth in the riparian population and in the gross domestic product (GDP) with unplanned development affects the water quality of the lake, this paper evaluates Lake Victoria Kenyan waters basin. Waters quality data between 1990 and 2012 were analyzed along with reviews of published literature, papers, and reports. The nitrate-nitrogen (NO3-N), soluble phosphorus (PO4-P), chlorophyll a, and Secchi transparencies were evaluated as they are key water quality indicators. The NO3-N increased from 10 μg l(-1) in 1990 to 98 μg 1(-1) in 2008, while PO4-P increased from 4 μg l(-1) in 1990 to 57 μg l(-1) in 2008. The population and economic growth of Kenya are increasing with both having minimums in 1990 of 24.143 million people and 12.18 billion US dollars, to maximums in 2010 of 39.742 million people and 32.163 billion US dollars, respectively. A Secchi transparency is reducing with time, indicating an increasing pollution. This was confirmed by an increase in aquatic vegetation using an analysis of moderate resolution imaging spectroradiometer (MODIS) images of 2000 and 2012 of Kenyan waters. This study found that increasing population and GDP increases pollution discharge thus polluting lakes. One of major factors causing lake water pollution is the unplanned or poor waste management policy and service. PMID:24442964

  1. Hypoxia tolerance of introduced Nile perch: Implications for survival of indigenous fishes in the Lake Victoria basin

    USGS Publications Warehouse

    Schofield, P.J.; Chapman, L.J.

    2000-01-01

    The introduction of predatory Nile perch (Lates niloticus) into the Lake Victoria basin coincided with a dramatic decline in fish diversity. However, remnant populations of indigenous fishes persist in lagoons and satellite lakes separated from the main lakes by extensive areas of swamp, while other indigenous species find refuge in ecotonal areas at edges of marginal swamps in the main lakes. Low-oxygen conditions in these wetlands may physiologically stress Nile perch and therefore minimize its interaction with prey species. This study examined the low-oxygen tolerance of Nile perch collected from Lake Nabugabo, Uganda, by documenting behavioural and physiological strategies that relate to oxygen uptake. In response to hypoxia, Nile perch used aquatic surface respiration (ASR) at the air-water interface, ventilating their gills with water from the surface. However, several lines of evidence suggest that Nile perch in Lake Nabugabo are inefficient at ASR and relatively intolerant of low oxygen conditions. These include high thresholds for ASR relative to other indigenous fishes of the Lake Victoria basin, no decrease in gill ventilation rate with the onset of ASR, a faster time to loss of equilibrium in hypoxic conditions than other species from the region, and a high critical oxygen tension (24 mm Hg).

  2. Urogenital Schistosomiasis in Women of Reproductive Age in Tanzania's Lake Victoria Region

    PubMed Central

    Downs, Jennifer A.; Mguta, Charles; Kaatano, Godfrey M.; Mitchell, Katrina B.; Bang, Heejung; Simplice, Harusha; Kalluvya, Samuel E.; Changalucha, John M.; Johnson, Warren D.; Fitzgerald, Daniel W.

    2011-01-01

    We conducted a community-based study of 457 women aged 18–50 years living in eight rural villages in northwest Tanzania. The prevalence of female urogenital schistosomiasis (FUS) was 5% overall but ranged from 0% to 11%. FUS was associated with human immunodeficiency virus (HIV) infection (odds ratio [OR] = 4.0, 95% confidence interval [CI] = 1.2–13.5) and younger age (OR = 5.5 and 95% CI = 1.2–26.3 for ages < 25 years and OR = 8.2 and 95% CI = 1.7–38.4 for ages 25–29 years compared with age > 35 years). Overall HIV prevalence was 5.9% but was 17% among women with FUS. We observed significant geographical clustering of schistosomiasis: northern villages near Lake Victoria had more Schistosoma mansoni infections (P < 0.0001), and southern villages farther from the lake had more S. haematobium (P = 0.002). Our data support the postulate that FUS may be a risk factor for HIV infection and may contribute to the extremely high rates of HIV among young women in sub-Saharan Africa. PMID:21363971

  3. Environmental epidemiology of intestinal schistosomiasis in Uganda: population dynamics of biomphalaria (gastropoda: planorbidae) in Lake Albert and Lake Victoria with observations on natural infections with digenetic trematodes.

    PubMed

    Rowel, Candia; Fred, Besigye; Betson, Martha; Sousa-Figueiredo, Jose C; Kabatereine, Narcis B; Stothard, J Russell

    2015-01-01

    This study documented the population dynamics of Biomphalaria and associated natural infections with digenetic trematodes, along the shores of Lake Albert and Lake Victoria, recording local physicochemical factors. Over a two-and-a-half-year study period with monthly sampling, physicochemical factors were measured at 12 survey sites and all freshwater snails were collected. Retained Biomphalaria were subsequently monitored in laboratory aquaria for shedding trematode cercariae, which were classified as either human infective (Schistosoma mansoni) or nonhuman infective. The population dynamics of Biomphalaria differed by location and by lake and had positive relationship with pH (P < 0.001) in both lakes and negative relationship with conductivity (P = 0.04) in Lake Albert. Of the Biomphalaria collected in Lake Albert (N = 6,183), 8.9% were infected with digenetic trematodes of which 15.8% were shedding S. mansoni cercariae and 84.2% with nonhuman infective cercariae. In Lake Victoria, 2.1% of collected Biomphalaria (N = 13,172) were infected with digenetic trematodes with 13.9% shedding S. mansoni cercariae, 85.7% shedding nonhuman infective cercariae, and 0.4% of infected snails shedding both types of cercariae. Upon morphological identification, species of Biomphalaria infected included B. sudanica, B. pfeifferi, and B. stanleyi in Lake Albert and B. sudanica, B. pfeifferi, and B. choanomphala in Lake Victoria. The study found the physicochemical factors that influenced Biomphalaria population and infections. The number and extent of snails shedding S. mansoni cercariae illustrate the high risk of transmission within these lake settings. For better control of this disease, greater effort should be placed on reducing environmental contamination by improvement of local water sanitation and hygiene. PMID:25705680

  4. Environmental Epidemiology of Intestinal Schistosomiasis in Uganda: Population Dynamics of Biomphalaria (Gastropoda: Planorbidae) in Lake Albert and Lake Victoria with Observations on Natural Infections with Digenetic Trematodes

    PubMed Central

    Rowel, Candia; Fred, Besigye; Sousa-Figueiredo, Jose C.; Kabatereine, Narcis B.; Stothard, J. Russell

    2015-01-01

    This study documented the population dynamics of Biomphalaria and associated natural infections with digenetic trematodes, along the shores of Lake Albert and Lake Victoria, recording local physicochemical factors. Over a two-and-a-half-year study period with monthly sampling, physicochemical factors were measured at 12 survey sites and all freshwater snails were collected. Retained Biomphalaria were subsequently monitored in laboratory aquaria for shedding trematode cercariae, which were classified as either human infective (Schistosoma mansoni) or nonhuman infective. The population dynamics of Biomphalaria differed by location and by lake and had positive relationship with pH (P < 0.001) in both lakes and negative relationship with conductivity (P = 0.04) in Lake Albert. Of the Biomphalaria collected in Lake Albert (N = 6,183), 8.9% were infected with digenetic trematodes of which 15.8% were shedding S. mansoni cercariae and 84.2% with nonhuman infective cercariae. In Lake Victoria, 2.1% of collected Biomphalaria  (N = 13,172) were infected with digenetic trematodes with 13.9% shedding S. mansoni cercariae, 85.7% shedding nonhuman infective cercariae, and 0.4% of infected snails shedding both types of cercariae. Upon morphological identification, species of Biomphalaria infected included B. sudanica, B. pfeifferi, and B. stanleyi in Lake Albert and B. sudanica, B. pfeifferi, and B. choanomphala in Lake Victoria. The study found the physicochemical factors that influenced Biomphalaria population and infections. The number and extent of snails shedding S. mansoni cercariae illustrate the high risk of transmission within these lake settings. For better control of this disease, greater effort should be placed on reducing environmental contamination by improvement of local water sanitation and hygiene. PMID:25705680

  5. The origin and age of haplochromine fishes in Lake Victoria, east Africa.

    PubMed

    Nagl, S; Tichy, H; Mayer, W E; Takezaki, N; Takahata, N; Klein, J

    2000-05-22

    According to a widely held view, the more than 300 species of haplochromine cichlid fishes in Lake Victoria (LV), East Africa, originated from a single founder species in less than 12,000 years. This view, however, does not follow from the published geological and molecular evidence. The former does indeed suggest that the LV basin dried out less than 15,000 years ago, but it does not provide any information about the species that re-colonized the new lake or that remained in the rivers draining the area. The molecular evidence is inconclusive with respect to the origin of the LV haplochromines because cichlids from critical regions around LV were not adequately sampled; and as far as the age of the LV haplochromines is concerned, it in fact led to an estimate of 250,000-750,000 years old. In the present study, mitochondrial DNA (control region) variation was determined by heteroduplex and sequencing analyses of more than 670 specimens collected at widely distributed East African riverine and lacustrine localities. The analyses revealed the existence of seven haplogroups (I-VII) distinguishable by characteristic substitutions. All endemic LV samples tested fell into one of these haplogroups (V) which, however, was also found to be present at various other localities, both riverine and lacustrine, outside LV. Within this haplogroup, four subgroups (VA through VD) could be distinguished, two of which (VB and VC) were represented in LV and at other localities. The great majority of the LV haplochromine species could be classified as belonging to the VC subgroup, which was found only in LV and in the rivers draining into it. Hence, while the endemic haplochromine species of LV could not have originated from a single founding population, the lake does harbour a large species flock which probably arose in situ. PMID:10874756

  6. The origin and age of haplochromine fishes in Lake Victoria, east Africa.

    PubMed Central

    Nagl, S; Tichy, H; Mayer, W E; Takezaki, N; Takahata, N; Klein, J

    2000-01-01

    According to a widely held view, the more than 300 species of haplochromine cichlid fishes in Lake Victoria (LV), East Africa, originated from a single founder species in less than 12,000 years. This view, however, does not follow from the published geological and molecular evidence. The former does indeed suggest that the LV basin dried out less than 15,000 years ago, but it does not provide any information about the species that re-colonized the new lake or that remained in the rivers draining the area. The molecular evidence is inconclusive with respect to the origin of the LV haplochromines because cichlids from critical regions around LV were not adequately sampled; and as far as the age of the LV haplochromines is concerned, it in fact led to an estimate of 250,000-750,000 years old. In the present study, mitochondrial DNA (control region) variation was determined by heteroduplex and sequencing analyses of more than 670 specimens collected at widely distributed East African riverine and lacustrine localities. The analyses revealed the existence of seven haplogroups (I-VII) distinguishable by characteristic substitutions. All endemic LV samples tested fell into one of these haplogroups (V) which, however, was also found to be present at various other localities, both riverine and lacustrine, outside LV. Within this haplogroup, four subgroups (VA through VD) could be distinguished, two of which (VB and VC) were represented in LV and at other localities. The great majority of the LV haplochromine species could be classified as belonging to the VC subgroup, which was found only in LV and in the rivers draining into it. Hence, while the endemic haplochromine species of LV could not have originated from a single founding population, the lake does harbour a large species flock which probably arose in situ. PMID:10874756

  7. Scenario-based water resources planning for utilities in the Lake Victoria region

    NASA Astrophysics Data System (ADS)

    Mehta, V. K.; Aslam, O.; Dale, L.; Miller, N.; Purkey, D.

    2010-12-01

    Cities in the Lake Victoria (LV) region are experiencing the highest growth rates in Africa, at the same time that their water resource is threatened by domestic waste and industrial pollution. Urban centers use local springs, wetlands and Lake Victoria as source waters. As efforts to meet increasing demand accelerate, integrated water resources management (IWRM) tools provide opportunities for utilities and other stakeholders to develop a planning framework comprehensive enough to include short term (e.g. landuse change), as well as longer term (e.g. climate change) scenarios. This paper presents IWRM models built using the Water Evaluation And Planning (WEAP) decision support system, for three pilot towns in the LV region - Bukoba (Tanzania), Masaka (Uganda), and Kisii (Kenya). Their current populations are 100,000, 70,000 and 200,000 respectively. Demand coverage is ~70% in Masaka and Bukoba, and less than 50% in Kisii. IWRM models for each town were calibrated under current system performance based on site visits, utility reporting and interviews. Projected water supply, demand, revenues and costs were then evaluated against a combination of climate, demographic and infrastructure scenarios upto 2050. In Masaka, flow and climate data were available to calibrate a runoff model to simulate streamflow at water intake. In Masaka, without considering climate change, the system is infrastructure-limited and not water availability (hydrology) limited until 2035, under projected population growth of 2.17%. Under a wet climate scenario as projected by GCM’s for the LV region, the current wetland source could supply all expected demands until 2050. Even under a drought scenario, the wetland could supply all demand until 2032, if the supply infrastructure is updated at an estimated cost of USD 10.8 million. However, demand targets can only be met at the expense of almost no water returning to the wetland downstream of the intake by 2035, unless substantial investments

  8. Impact of immigrant pastoral herds to fringing wetlands of lake Victoria in Magu district Mwanza region, Tanzania

    NASA Astrophysics Data System (ADS)

    Hongo, H.; Masikini, M.

    The assessment of impacts of pastoral herds to the fringing wetlands of Lake Victoria in Magu district in Mwanza region was carried out in 1999/2000. Lamadi village located along Speke Gulf of Lake Victoria was chosen. The main farming systems in the area are agriculture, agro-pastoralism, and pastoralism. The wetlands are heavily used for livestock grazing during the dry season. Since 1990s the area has been experiencing a high influx of immigrant pastoral herds from drought prone districts. The increasing livestock numbers have led into serious degradation of wetlands. The type of damages includes: soil erosion, loss of vegetation cover and deforestation. This lead to pollution of Lake Victoria along the Speke gulf in particular as the wetlands was buffering a lot of pollutants from the catchments. The range condition at Lamadi was rated fair. The carrying capacity of rangelands was estimated at 3.57-6.75 ha/LU and the wetlands were seriously degraded causing heavy soil erosion and environmental pollution during rainy season. It was recommended to raise people’s awareness on conservation of environment and mobilise communities to take responsibility on management of the environmental resources.

  9. Legacy and currently used pesticides in the atmospheric environment of Lake Victoria, East Africa.

    PubMed

    Arinaitwe, Kenneth; Kiremire, Bernard T; Muir, Derek C G; Fellin, Phil; Li, Henrik; Teixeira, Camilla; Mubiru, Drake N

    2016-02-01

    The Lake Victoria watershed has extensive agricultural activity with a long history of pesticide use but there is limited information on historical use or on environmental levels. To address this data gap, high volume air samples were collected from two sites close to the northern shore of Lake Victoria; Kakira (KAK) and Entebbe (EBB). The samples, to be analyzed for pesticides, were collected over various periods between 1999 and 2004 inclusive (KAK 1999-2000, KAK 2003-2004, EBB 2003 and EBB 2004 sample sets) and from 2008 to 2010 inclusive (EBB 2008, EBB 2009 and EBB 2010 sample sets). The latter sample sets (which also included precipitation samples) were also analyzed for currently used pesticides (CUPs) including chlorpyrifos, chlorthalonil, metribuzin, trifluralin, malathion and dacthal. Chlorpyrifos was the predominant CUP in air samples with average concentrations of 93.5, 26.1 and 3.54 ng m(-3) for the EBB 2008, 2009, 2010 sample sets, respectively. Average concentrations of total endosulfan (ΣEndo), total DDT related compounds (ΣDDTs) and hexachlorocyclohexanes (ΣHCHs) ranged from 12.3-282, 22.8-130 and 3.72-81.8 pg m(-3), respectively, for all the sample sets. Atmospheric prevalence of residues of persistent organic pollutants (POPs) increased with fresh emissions of endosulfan, DDT and lindane. Hexachlorobenzene (HCB), pentachlorobenzene (PeCB) and dieldrin were also detected in air samples. Transformation products, pentachloroanisole, 3,4,5-trichloroveratrole and 3,4,5,6-tetrachloroveratrole, were also detected. The five most prevalent compounds in the precipitation samples were in the order chlorpyrifos>chlorothalonil>ΣEndo>ΣDDTs>ΣHCHs with average fluxes of 1123, 396, 130, 41.7 and 41.3 ng m(-2)sample(-1), respectively. PeCB exceeded HCB in precipitation samples. The reverse was true for air samples. Backward air trajectories suggested transboundary and local emission sources of the analytes. The results underscore the need for a concerted

  10. Application of Satellite Observations to Manage Natural Disasters in the Lake Victoria Basin

    NASA Technical Reports Server (NTRS)

    Habib, Shahid; Policelli, F.; Irwin, D.; Korme, Tesfaye; Adler, Bob; Hong, Yang

    2010-01-01

    Lake Victoria, the second largest fresh water lake in the Eastern part of Africa is a vital natural resource for the economic well being and prosperity of over 30 million people located in riparian regions of Uganda, Kenya and Tanzania. It covers a large area of about 68,870 km2 and produces a GDP of about US $30 billion per year. The region is also very much prone to natural disasters such as severe floods during heavy precipitation periods in the Eastern part of Africa. In addition to floods, the precipitation also produces large infestations of mosquito larvae due to the standing water in many areas. This further causes multiple vector borne diseases such as Malaria, Rift Valley Fever and more. These problems are of serious concern and require active and aggressive surveillance and management to minimize the loss of human and animal lives and property damage. Satellite imagery and observations along with the in situ measurements provide a great tool to analyze and study this area and inform the policy makers to make calculated policy decisions which are more beneficial to the environment. Recently, NASA and USAID have joined forces with the Regional Center for Mapping of Resources for Development (RCMRD) located in Nairobi, Kenya to utilize multiple NASA sensors such as TRMM, SRTM and MODIS to develop flood potential maps for the Lake Victoria Basin. The idea is to generate a flood forecasts and "nowcasts" that can be sent to the disaster management organizations of Uganda, Kenya, and Tanzania. Post flood event satellite imagery is becoming a common tool to assess the areas inundated by flooding. However, this work is unique undertaking by utilizing land imaging and atmospheric satellites to build credible flood potential maps. At same time, we are also studying the potential occurrence and spread of Rift Valley Fever disease based on the short term climate records and precipitation data. These activities require multi-nation coordination and agreements and

  11. Pioneering water quality data on the Lake Victoria watershed: effects on human health.

    PubMed

    Jovanelly, Tamie J; Johnson-Pynn, Julie; Okot-Okumu, James; Nyenje, Richard; Namaganda, Emily

    2015-09-01

    Four forest reserves within 50 km of Kampala in Uganda act as a critical buffer to the Lake Victoria watershed and habitat for local populations. Over a 9-month period we capture a pioneering water quality data set that illustrates ecosystem health through the implementation of a water quality index (WQI). The WQI was calculated using field and laboratory data that reflect measured physical and chemical parameters (pH, dissolved oxygen, biological oxygen on demand, nitrates, phosphates, fecal coliform, and temperature turbidity). Overall, the WQI for the four forest reserves reflect poor to medium water quality. Results compared with US Environmental Protection Agency and World Health Organization drinking water standards indicate varying levels of contamination at most sites and all designated drinking water sources, with signatures of elevated nitrates, phosphates, and/or fecal coliforms. As critical health problems are known to arise with elevated exposure to contaminants in drinking water, this data set can be used to communicate necessary improvements within the watershed. PMID:26322777

  12. Fast adaptive responses in the oral jaw of Lake Victoria cichlids.

    PubMed

    van Rijssel, Jacco C; Hoogwater, Ellen S; Kishe-Machumu, Mary A; van Reenen, Elize; Spits, Kevin V; van der Stelt, Ronald C; Wanink, Jan H; Witte, Frans

    2015-01-01

    Rapid morphological changes in response to fluctuating natural environments are a common phenomenon in species that undergo adaptive radiation. The dramatic ecological changes in Lake Victoria provide a unique opportunity to study environmental effects on cichlid morphology. This study shows how four haplochromine cichlids adapted their premaxilla to a changed diet over the past 30 years. Directly after the diet change toward larger and faster prey in the late 1980s, the premaxilla (upper jaw) changed in a way that is in agreement with a more food manipulating feeding style. During the 2000s, two zooplanktivorous species showed a reversal of morphological changes after returning to their original diet, whereas two other species showed no reversal of diet and morphology. These rapid changes indicate a potential for extremely fast adaptive responses to environmental fluctuations, which are likely inflicted by competition release and increase, and might have a bearing on the ability of haplochromines to cope with environmental changes. These responses could be due to rapid genetic change or phenotypic plasticity, for which there is ample evidence in cichlid fish structures associated with food capture and processing. These versatile adaptive responses are likely to have contributed to the fast adaptive radiation of haplochromines. PMID:25403383

  13. Scenario-based water resources planning for utilities in the Lake Victoria region

    NASA Astrophysics Data System (ADS)

    Mehta, Vishal K.; Aslam, Omar; Dale, Larry; Miller, Norman; Purkey, David R.

    Urban areas in the Lake Victoria (LV) region are experiencing the highest growth rates in Africa. As efforts to meet increasing demand accelerate, integrated water resources management (IWRM) tools provide opportunities for utilities and other stakeholders to develop a planning framework comprehensive enough to include short term (e.g. landuse change), as well as longer term (e.g. climate change) scenarios. This paper presents IWRM models built using the Water Evaluation And Planning (WEAP) decision support system, for three towns in the LV region - Bukoba (Tanzania), Masaka (Uganda), and Kisii (Kenya). Each model was calibrated under current system performance based on site visits, utility reporting and interviews. Projected water supply, demand, revenues and costs were then evaluated against a combination of climate, demographic and infrastructure scenarios up to 2050. Our results show that water supply in all three towns is currently infrastructure limited; achieving existing design capacity could meet most projected demand until 2020s in Masaka beyond which new supply and conservation strategies would be needed. In Bukoba, reducing leakages would provide little performance improvement in the short-term, but doubling capacity would meet all demands until 2050. In Kisii, major infrastructure investment is urgently needed. In Masaka, streamflow simulations show that wetland sources could satisfy all demand until 2050, but at the cost of almost no water downstream of the intake. These models demonstrate the value of IWRM tools for developing water management plans that integrate hydroclimatology-driven supply to demand projections on a single platform.

  14. Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa

    NASA Astrophysics Data System (ADS)

    Berke, Melissa A.; Johnson, Thomas C.; Werne, Josef P.; Grice, Kliti; Schouten, Stefan; Sinninghe Damsté, Jaap S.

    2012-11-01

    New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ˜14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ˜10-9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the

  15. Atmospheric concentrations of polycyclic aromatic hydrocarbons in the watershed of Lake Victoria, East Africa.

    PubMed

    Arinaitwe, Kenneth; Kiremire, Bernard T; Muir, Derek C G; Fellin, Phil; Li, Henrik; Teixeira, Camilla; Mubiru, Drake N

    2012-11-01

    In the first study of its kind in Africa, PAHs were measured in high volume (24 h) air samples collected from two sampling stations, at Kakira and Entebbe (KAK and EBB, respectively) within the Lake Victoria watershed in Uganda, to assess source contributions and generate a baseline reference data set for future studies in the East African region. Sampling was conducted over two periods [2000-2004 (KAK and EBB1) and 2008-2010 (EBB2)]. The samples were extracted by accelerated solvent extraction and analyzed for 30 PAHs by GC-MS. The mean total PAH concentrations (ng/m(3)) were found to be 74.3 (range; 19.3-311, N = 39) for KAK, 56.8 (range; 13.3-126, N = 22) for EBB1 and 33.1 (range; 4.91-108, N = 56) for EBB2. The 3-ringed PAHs were the most predominant group with mean concentrations of 35.9 ng/m(3)(EBB1), 30.5 ng/m(3)(KAK) and 23.2 ng/m(3)(EBB2). Naphthalene had an exceptionally high mean concentration (21.9 ng/m(3)) for KAK compared to 0.44 and 0.39 ng/m(3) in EBB1 and EBB2 respectively, likely due to intensive agricultural operations nearby KAK. Principal component and diagnostic ratio analyses showed that the measured levels of PAHs were associated with mixed sources, combustion of petroleum, and biomass being the major sources. PMID:23020709

  16. Identifying Water Insecurity Hotspots in the Lake Victoria Basin of Eastern Africa

    NASA Astrophysics Data System (ADS)

    Pricope, N. G.; Shukla, S.; Linard, C.; Gaughan, A.

    2014-12-01

    The Lake Victoria Basin (LVB), one of Africa's most populated transboundary watersheds and home to more than 30 million inhabitants, is increasingly challenged by both water quality problems and water quantity shortages against a backdrop of climate variability and change; and other environmental challenges. As a result of pollution, droughts, more erratic rainfall, heightened demand for water for both consumption and agricultural needs as well as differences in water allocation among the riverine countries of Uganda, Tanzania, Kenya, Rwanda and Burundi, many parts of this region are already experiencing water scarcity on a recurrent basis. Furthermore, given projected annual population growth rates of 2.5 to 3.5% for the next 20 years, water shortages are likely to be exacerbated in the future. Analyzing historical changes in the water resources of this region is hence important to identify "hot spots" that might be most sensitive to future changes in climate and demography. In this presentation, we report the findings of a comprehensive analysis performed to (i) examine changes in water resources of LVB in recent decades and (ii) identify overlap between regions of significant changes in water resources with land cover changes and high population centers that are also projected to grow the fastest over the coming decades. We first utilize several satellite, stations and model(s) based climatic and hydrologic datasets to assess changes in water resources in this region. We then use a quality-controlled Moderate Resolution Imaging Spectroradiometer (MODIS) land cover product to identify areas of significant land cover changes. Simultaneously we use projections of gridded population density based on differential growth rates for rural and urban population to estimate fastest projected human population growth for 2030 and 2050 relative to 2010 data. Using the outcomes of these change analysis we identify water insecurity hotspots in the LVB.

  17. Intestinal schistosomiasis among preschool children along the shores of Lake Victoria in Uganda.

    PubMed

    Nalugwa, A; Olsen, A; Tukahebwa, M E; Nuwaha, F

    2015-02-01

    Schistosomiasis, a disease caused by Schistosoma trematode parasites, affects hundreds of millions of people and accounts for more than 40% of the global health burden due to neglected tropical diseases. In Uganda, intestinal schistosomiasis is endemic in 73 out of 112 districts and about 55% of the population of 36 million individuals are at risk. There is scanty information on the status and burden of schistosomiasis in preschool children less than six years of age in Uganda. This study aimed to assess the status of Schistosoma mansoni infections in children aged 1-5 years in Uganda. S. mansoni prevalence and intensity of infection were examined in 3058 children from 5 districts along Lake Victoria shoreline, eastern Uganda. For each child one stool sample was collected on three consecutive days. The Kato-Katz technique was used to prepare stool smears on slides for microscopic examination. Short interviews with a standardized pre-tested questionnaire prepared in the local language (Lusoga) were administered to each caregiver to identify risk factors associated with S. mansoni infection. An overall S. mansoni prevalence of 39.3% (95% CI: 38.0-41.1%) was estimated out of the 3058 stool samples examined. The geometric mean intensity of S. mansoni among the infected children was 273 (95% CI: 241-305) eggs per gram of faeces. Both prevalence and intensity of infection increased linearly with age (P<0.0001) and were highest in the age group 49-60 months. Majority (61%) of the children, especially in the age group 12-24 months (84.2%; 95% CI: 75.6-90.1%), were lightly infected. Short interviews with caregivers revealed that preschool children, 1-5 years old, get exposed to S. mansoni infested waters through bathing, playing or swimming. It is important that the Uganda national control programme for schistosomiasis takes preschool children into consideration and that health education on transmission of schistosomiasis is delivered to the endemic communities regularly

  18. Farmer Tree Nursery as a Catalyst for Developing Sustainable Best Management Land Use Practices in Lake Victoria Catchments Ecosystem

    NASA Astrophysics Data System (ADS)

    Shisanya, C. A.; Makokha, M. O.; Kimani, S. K.; Kalumuna, M.; Tenge, A.

    Support to farmer nurseries is classified as either hard referring to material inputs (tree seed, water, tools and fencing) or soft (information, training and backstopping advice). Against a background of poor services for smallholder farmers in the Lake Victoria basin, it was hypothesized that a number of support agents operating at the grassroot level together with farmers themselves provide the different support functions needed in the establishment of farmer tree nurseries. Through financial support from Inter-University Council of East Africa coordinated VicReS Project, a collaborative project involving Kenyatta University (Kenya), Kenya Agricultural Research Institute (KARI) and Mulingano Agricultural Research Institute (Tanzania) has been able to initiate reforestation/afforestation activities in Lake Victoria catchments ecosystems of western Kenya and western Tanzania. Through the initial activities, a total of twenty four farmer groups have been identified in western Kenya and supported through capacity building and supply of basic inputs for tree nursery seed bed preparation and management. The groups have been able to set up tree nurseries and are now managing seed beds with a total of 450,000 agro-forestry seedlings, mainly Grevillea robusta and Casuarina spp. The farmers intend to distribute the seedling among the members for planting on farm boundaries, around homesteads and woodlots within their homesteads and sell the surplus. Preliminary findings show that there is an urgent need to facilitate grassroot level support systems with larger participation from the national extension service for provision of training and backstopping advice. Strengthening the human capital of farmers and service providers emerges as critical in increasing impact. Farmer nurseries are shown to play a number of important and interrelated functions in building natural, human and social capital. Monitoring and evaluating farmer nurseries in catalyzing these three functions

  19. Mini-FLOTAC and Kato-Katz: helminth eggs watching on the shore of lake Victoria

    PubMed Central

    2013-01-01

    Background One of the challenges for monitoring helminth control programmes based on preventive chemotherapy is the lack of a copro-parasitological gold–standard method that combines good sensitivity with quantitative performance, low cost, and easy-to-learn technique. The aim of our study was to evaluate and compare, the WHO recommended quantitative diagnostic technique (Kato-Katz) and the Mini-FLOTAC. Methods Mini-FLOTAC is an innovative method based on floatation of helminths eggs with two different solutions (FS2 and FS7) using a close system (Fill-FLOTAC) with 5% fixative. Kato-Katz was performed following WHO recommendation. The study was carried out in a rural part of Tanzania, close to Lake Victoria, where the laboratory facilities are fairly scarce, and the basic technique used in the local laboratory (direct smear) was taken as reference standard. Results 201 children were screened for intestinal helminths and 91% of them were found to be positive. The agreement among the three techniques was calculated with k Cohen coefficient and was fairly good (k = 0.4), although the Mini-FLOTAC results were more sensitive for hookworm (98%) with FS2, and for S.mansoni (90%) with FS7 followed by Kato-Katz (91% and 60% respectively) and direct smear (30% and 10% respectively). A good agreement was found between Mini-FLOTAC and Kato-Katz (k = 0.81) with FS7 (k = 0.76) for hookworm diagnosis and a fairly good one for S.mansoni diagnosis (k = 0.5). For both infections we had a poor agreement between the two quantitative techniques and the direct smear (k<0.3). Kato-Katz diagnosed a higher number of eggs (calculated by arithmetic mean) both for hookworm (455 vs 424 EPG) and for S.mansoni (71 vs 58 EPG) compared with the Mini-FLOTAC, but the differences were not significant (p = 0.4). Conclusions Mini-FLOTAC is a promising technique, comparable and as sensitive as the Kato-Katz, which is the recommended method in intestinal helminthology for monitoring

  20. Use of Modern Family Planning Methods in Fishing Communities of Lake Victoria, Uganda

    PubMed Central

    Nanvubya, Annet; Ssempiira, Julius; Mpendo, Juliet; Ssetaala, Ali; Nalutaaya, Annet; Wambuzi, Mathias; Kitandwe, Paul; Bagaya, Bernard S.; Welsh, Sabrina; Asiimwe, Stephen; Nielsen, Leslie; Makumbi, Fredrick; Kiwanuka, Noah

    2015-01-01

    Introduction Fishing communities (FCs) in Uganda have high HIV infection rates but poor access to health services including family planning (FP). Although FP is a cost-effective public health intervention, there is a paucity of data on knowledge and use of modern FP in FCs. This study determined knowledge and use of modern FP methods in FCs of Uganda. Methods Data were accrued from a 12-month follow up of 1,688 HIV-uninfected individuals, 18–49 years from 8 FCs along Lake Victoria, between September 2011 and March 2013. Data on knowledge and use of modern FP were collected through a semi-structured questionnaire. Prevalence Risk Ratios with corresponding 95% CIs were used to determine factors associated with Modern FP knowledge and use. Results The mean age was 31.4 years, with nearly half (48.8%) being females while more than half (58.6%) had attained up to primary education level. Knowledge of modern FP was high, 87.5% (1477/1688); significantly higher among females [adj. PRR = 4.84 (95% CI; 3.08, 7.61)], among older respondents (25–29 years) [adj. PRR = 1.83 (95% CI; 1.12, 2.99)] compared to younger ones (18–24 years) and among those conducting business [adj. PRR = 2.42(95% CI; 1.02, 5.74)] relative to those primarily in fishing. Just over a third (35.2%, 595/1688) reported use of at least one modern FP method. Use of modern FP methods was significantly higher among females [adj. PRR = 2.04 (95% CI; 1.56, 2.65, and among those reporting multiple sexual partnerships [adj. PRR = 2.12, 95% CI; 1.63, 2.76)]. Nonuse of modern methods was mostly due to desire for more children (30.6%), fear of side effects (12.2%) and partner refusal (5.2%). Conclusion Despite their high knowledge of FP, FCs have low use of modern FP methods. Key barriers to use of modern FP methods were high fertility desires, fear of perceived side effects and partner refusal of methods. PMID:26512727

  1. Distal tephras of the eastern Lake Victoria basin, equatorial East Africa: correlations, chronology and a context for early modern humans

    NASA Astrophysics Data System (ADS)

    Blegen, Nick; Tryon, Christian A.; Faith, J. Tyler; Peppe, Daniel J.; Beverly, Emily J.; Li, Bo; Jacobs, Zenobia

    2015-08-01

    The tephrostratigraphic framework for Pliocene and Early Pleistocene paleoanthropological sites in East Africa has been well established through nearly 50 years of research, but a similarly comprehensive framework is lacking for the Middle and particularly the Late Pleistocene. We provide the first detailed regional record of Late Pleistocene tephra deposits associated with artifacts or fossils from the Lake Victoria basin of western Kenya. Correlations of Late Pleistocene distal tephra deposits from the Wasiriya beds on Rusinga Island, the Waware beds on Mfangano Island and deposits near Karungu, mainland Kenya, are based on field stratigraphy coupled with 916 electron microprobe analyses of eleven major and minor element oxides from 50 samples. At least eight distinct distal tephra deposits are distinguished, four of which are found at multiple localities spanning >60 km over an approximately north to south transect. New optically stimulated luminescence dates help to constrain the Late Pleistocene depositional ages of these deposits. Our correlation and characterization of volcaniclastic deposits expand and refine the current stratigraphy of the eastern Lake Victoria basin. This provides the basis for relating fossil- and artifact-bearing sediments and a framework for ongoing geological, archaeological and paleontological studies of Late Pleistocene East Africa, a crucial time period for human evolution and dispersal within and out of Africa.

  2. Dioxin-like PCBs and PCDD/Fs in surface sediments near the shore of Winam Gulf, Lake Victoria.

    PubMed

    Omwoma, Solomon; Lalah, Joseph O; Virani, Munir; Schramm, Karl-Werner; Henkelmann, Bernhard

    2015-01-01

    Winam Gulf of Lake Victoria is considered to be contaminated with toxic chemicals emanating from anthropogenic activities, especially near large industrial towns such as Kisumu. This has recently caused concerns about its water quality and impact on aquatic organisms and human beings. This study was justified by the need to generate baseline concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in surface sediment from selected sites in the lake and determine the influence of activities on their concentrations and potential risks to fish-eating birds living near the lake. Surface sediments (<30cm) from three different fish landing beaches, located 200m from the shore of Winam Gulf of Lake Victoria near Kisumu city, Homa Bay and Mbita (control) towns, were analysed. The total mean concentrations (in pgg(-1)drywt) were found to range from 17.4-812 (Σdl-PCBs), 36.6-813 (ΣPCDDs) and 1.45-46.4 (ΣPCDFs). The calculated Toxic Equivalents (TEQWHO(2005)) ranged from 0.001-0.43 (Σdl-PCBs) and 0.09-31 (ΣPCDD/Fs). The fish landing beaches at Kisumu city were found to be contaminated with respect to dl-PCBs and dioxins, followed by Homa Bay and Mbita. The relatively high levels of octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) influenced the TEQ and the ΣPCDFs/ΣPCDDs ratios indicated chemical processes as partial sources of the dioxins. The levels of contaminants obtained in this study showed potential exposure to aquatic organisms and fish eating birds through food chain transfer. PMID:25150826

  3. Construction of chromosome markers from the Lake Victoria cichlid Paralabidochromis chilotes and their application to comparative mapping.

    PubMed

    Kuroiwa, A; Terai, Y; Kobayashi, N; Yoshida, K; Suzuki, M; Nakanishi, A; Matsuda, Y; Watanabe, M; Okada, N

    2014-01-01

    Cichlid fishes in the African Great Lakes are known as a spectacular example of adaptive radiation in vertebrates. Four linkage maps have been constructed to identify the genes responsible for adaptation and speciation, and the genetic linkages of those genes are assumed to play an important role during adaptive evolution. However, it is difficult to analyze such linkages because the linkage groups of one species do not match well with those of the other species. Chromosome markers are a powerful tool for the direct identification of linkage homology between different species. We used information about the linkage map of the Lake Malawi cichlid (Labeotropheus fuelleborni/Metriaclima zebra) to isolate bacterial artificial chromosome (BAC) clones from the BAC library of Paralabidochromis chilotes, Lake Victoria. We identified 18 of 22 P. chilotes chromosomes by single- and multi-color BAC fluorescence in situ hybridization using 19 BAC clones. Comparative mapping with the chromosome markers of P. chilotes in Astatotilapia burtoni (2n = 40) from Lake Tanganyika revealed the chromosome rearrangements that have occurred in this lineage. These chromosome markers will be useful for delineating the process of genome and chromosome evolution in African species. PMID:24217467

  4. Relations between people, relations about things: gendered investment and the case of the Lake Victoria fishery, Tanzania.

    PubMed

    Medard, Modesta

    2012-01-01

    Using the example of one of the African fisheries that has been most significantly transformed from family based to commercialized—that on Lake Victoria in Tanzania—this article considers the social nexus of decision making and focuses on analyzing women’s place. It is true that women have never been more than a minority in fisheries due to traditional inheritance patterns and new market structures, both of which bypass women in questions of ownership and decision making. We look in vain for fishwives, if this means female fish producers acting with a highly visible degree of economic and social autonomy. There is no vernacular term to identify women who work with fish or those rare women who own fishing vessels. And yet the absence of derogatory representation suggests that there have been few attempts to detract from women who are active in the fishery. Should we thus be aiming at more subtlety in our analytical approaches to fishing relations on Lake Victoria? The article unveils the ways in which women’s relations with fishermen are negotiated and how agreements are reached on behalf of their families. It explores for women’s empowerment via the customary social relations and management arrangements that exist in these riparian communities. The lake fishery has a basis for development, but its potential for the kind of growth that will have returns for future generations rests on an appreciation of how fisher-wives conceive of, and respond to, the opportunities, constraints and risks of investing in this fishery. PMID:22545266

  5. Historical deposition of persistent organic pollutants in Lake Victoria and two alpine equatorial lakes from East Africa: Insights into atmospheric deposition from sedimentation profiles.

    PubMed

    Arinaitwe, Kenneth; Rose, Neil L; Muir, Derek C G; Kiremire, Bernard T; Balirwa, John S; Teixeira, Camilla

    2016-02-01

    Information on historical deposition of persistent organic pollutants (POPs) for African lakes is very limited. We investigated historical deposition trends and sources of POPs in sediment cores from Lakes Victoria (SC1), Bujuku (Buju2) and Mahoma (Maho2). The latter two lakes are situated in the Rwenzori mountain range in western Uganda. SC1 was taken from a central depositional area within the Ugandan part of the lake. Profiles in Buju2 and Maho2 were used as a reference for historical atmospheric deposition. For the post-1940 sediment deposits in SC1, average focusing factor-adjusted fluxes (FFFs) of ΣDDTs, polychlorinated biphenyls (ΣPCBs), hexachlorocyclohexanes (ΣHCHs) and chlordanes (ΣCHLs) were 390, 230, 210 and 120 ng m(-2) yr(-1). Higher fluxes of ΣDDTs, ΣPCBs, and ΣCHLs were observed in Buju2 and Maho2. The average FFF of HCB in Buju2 was the highest while the values for Maho2 and SC1 were similar. The endosulfan FFFs in SC1 were lower than in the alpine lake cores. Generally, Buju2 was a better reference for historical atmospheric deposition of POPs than Maho2 probably due to distortion of the latter's profile by Lake Mahoma's forested catchment. Profiles of p,p'-DDE, ΣCHLs and HCB in SC1 were consistent with atmospheric deposition while profiles of PCBs and HCHs were indicative of particle-bound loadings from additional sources. Profiles of endosulfans, DDTs, and chlordanes were consistent with influence of other factors such as anoxia, and dilution. Further studies of spatial resolution of historical deposition, especially in near-shore deposition areas of the lake are recommended. PMID:26539705

  6. A microsatellite-based genetic linkage map and putative sex-determining genomic regions in Lake Victoria cichlids.

    PubMed

    Kudo, Yu; Nikaido, Masato; Kondo, Azusa; Suzuki, Hikoyu; Yoshida, Kohta; Kikuchi, Kiyoshi; Okada, Norihiro

    2015-04-15

    Cichlid fishes in East Africa have undergone extensive adaptive radiation, which has led to spectacular diversity in their morphology and ecology. To date, genetic linkage maps have been constructed for several tilapias (riverine), Astatotilapia burtoni (Lake Tanganyika), and hybrid lines of Lake Malawi cichlids to facilitate genome-wide comparative analyses. In the present study, we constructed a genetic linkage map of the hybrid line of Lake Victoria cichlids, so that maps of cichlids from all the major areas of East Africa will be available. The genetic linkage map shown here is derived from the F2 progeny of an interspecific cross between Haplochromis chilotes and Haplochromis sauvagei and is based on 184 microsatellite and two single-nucleotide polymorphism (SNP) markers. Most of the microsatellite markers used in the present study were originally designed for other genetic linkage maps, allowing us to directly compare each linkage group (LG) among different cichlid groups. We found 25 LGs, the total length of which was 1133.2cM with an average marker spacing of about 6.09cM. Our subsequent linkage mapping analysis identified two putative sex-determining loci in cichlids. Interestingly, one of these two loci is located on cichlid LG5, on which the female heterogametic ZW locus and several quantitative trait loci (QTLs) related to adaptive evolution have been reported in Lake Malawi cichlids. We also found that V1R1 and V1R2, candidate genes for the fish pheromone receptor, are located very close to the recently detected sex-determining locus on cichlid LG5. The genetic linkage map study presented here may provide a valuable foundation for studying the chromosomal evolution of East African cichlids and the possible role of sex chromosomes in generating their genomic diversity. PMID:25639358

  7. Polybrominated diphenyl ethers and alternative flame retardants in air and precipitation samples from the northern Lake Victoria region, East Africa.

    PubMed

    Arinaitwe, Kenneth; Muir, Derek C G; Kiremire, Bernard T; Fellin, Phil; Li, Henrik; Teixeira, Camilla

    2014-01-01

    High volume air and precipitation samples were collected close to the shore of Lake Victoria at Entebbe, Uganda, between October 2008 and July 2010 inclusive. Polybrominated diphenyl ethers (PBDEs) and alternative flame retardants (AFRs) were analyzed by GC-MS. BDEs 47, 99, and 209 were the predominant PBDEs with mean concentrations (in air) of 9.84, 4.38, 8.27 pg m(-3) and mean fluxes in precipitation of 3.40, 6.23, and 7.82 ng m(-2) sample(-1), respectively. 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and hexabromocyclododecane (HBCDD), anti- and syn-Dechlorane plus were detected at levels comparable with those of PBDEs. Both PBDEs and AFRs in air generally increased from 2008 to 2010. Elevated PBDE concentrations in air were associated with slow moving low altitude air masses from the region immediately adjacent to the lake, while low concentrations were mostly associated with fast moving westerly and southwesterly air masses. Analysis of the octa- and nona-BDE profiles suggested photolysis and pyrolytic debromination of BDE-209 in the air samples. The highly halogenated and most abundant PBDEs and AFRs in air also predominated in precipitation samples. This is the first study to report flame retardants in high volume air samples and precipitation in Equatorial Africa. PMID:24400732

  8. SUGAR CANE GROWING AND CATTLE GRAZING AS DRIVERS TO WETLAND DEGRADATION IN UGANDA: A case of upper river Ruizi and Iguluibi catchments Lake Victoria basin

    NASA Astrophysics Data System (ADS)

    Nakiyemba Were, Alice; Isabirye, Moses; Mathijs, Erik; Deckers, Jozef; Poesen, Jean

    2010-05-01

    Introduction: This study was conducted with in the framework of the VLIR-OI project with the aim of making contributions to the Diagnosis and Remediation of Land Degradation Processes in the Riparian Zone of Lake Victoria Uganda in view of reducing sediment pollution of the Lake Waters with a special focus on the upper river Ruiz and Iguluibi catchments. The study seeks to investigate Sugarcane growing and cattle grazing as drivers to wetland degradation in light of the current farming systems and practices and their contributions to land degradation and pollution of the Lake Victoria waters. Vegetation especially wetlands improves the resistance to erosion. The removal of riparian vegetation tends to accelerate surface erosion as a result of human activities. Increased erosion with in the catchments due to clearing of wetlands for sugarcane growing and cattle grazing has caused adverse increased sedimentation, degraded the water quality, and reduced the water productivity of the Lake Victoria Basin. Methods: We conducted a qualitative and quantitative study to investigate Sugarcane growing and cattle grazing as drivers to wetland degradation in Uganda in light of the current farming systems and practices and their socio-economic contributions to wetland degradation and pollution of the Lake Victoria waters. Focus group discussions, key informant interviews, semi structured interviews and observations were undertaken with the relevant stakeholders in the community. Results: Findings reveal that in Iguluibi catchment, sugarcane growing is now a major activity indicating land use change since the 1990s. Community members said when planting sugarcane all vegetations including all trees are cut leaving the land bare to allow the tractor to clear the land for cultivation. This has left the land bare without any natural vegetation with increased erosion hence eventually loss of soil fertility and increased sediment pollution to the Lake Victoria waters. As a result of

  9. Variation in fatty acid composition in muscle and heart tissues among species and populations of tropical fish in Lakes Victoria and Kyoga.

    PubMed

    Kwetegyeka, Justus; Mpango, George; Grahl-Nielsen, Otto

    2008-11-01

    The composition of the fatty acids in muscle and heart tissue of seven fish species, Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus), marbled lungfish (Protopterus aethiopicus), African catfish (Clarias gariepinus), Lake Victoria squeaker (Synodontis victoriae), Bagrus docmas, and Tilapia zilli, from two locations in Lake Kyoga and one location in Lake Victoria was chemometrically determined. The muscle tissue was very lean, with an average of 3.4 mg total fatty acids per g tissue. The lipid level in the heart tissue was approximately five times higher than in the muscle tissue, with an average of 15.5 mg total fatty acids per g tissue. The n-3/n-6 level in the muscles was 1.7 +/- 0.7 and in the heart tissue 1.0 +/- 0.4. The muscle tissue contained an average of 46 mg cholesterol per 100 g, and the heart tissue contained about five times as much. Plasmalogens were detected in 7-8% of the amounts of total fatty acids in both muscle and heart tissue. The seven species had large differences (P < 0.05) in the fatty acid composition for both muscle and heart tissue. Within the species there were differences between fish from the populations in the three locations, although the population differences were smaller than the species differences. These differences appear to be controlled more closely by genetics/transcriptomics than by the diet. PMID:18712426

  10. Capacity Building for Disaster Management in Vulnerable Regions of Africa: Implementing an Operational Flood Warming System in Lake Victoria

    NASA Astrophysics Data System (ADS)

    Hong, Y.; Li, L.; Adler, R.; Policelli, F.

    2008-12-01

    NASA Applied Science program has partnered with USAID and The Regional Centre for Mapping of Resources for Development (RCMRD) in Africa to implement an operational flood warning system for East Africa, SERVIR-Africa project. The project seeks to take advantage of remote sensing information as an alternative and supplemental to ground-based observation in order to preserve the spatial extent of flood hazards. The recently available and virtually uninterrupted supply of satellite-based rainfall estimates is increasingly becoming a cost-effective data source for flood prediction in many under-gauged regions around the world. Our initial focus aims to provide an operational flood warning system for Lake Victoria, a flood-prone region home to 30 million people. The key datasets enabling the development of a distributed hydrological model in Africa include TRMM-based Multi-satellite Precipitation Analysis (TMPA), digital elevation data from the Shuttle Radar Topography Mission (SRTM) mission, HydroSHEDS hydrological products, MODIS Land cover, and soil parameters provided by FAO. This research focuses on evaluation and integration the TMPA Real- Time product into an online operational flood prediction system. We will also identify the optimal calibration strategy for satellite rainfall data into real-time hydrological modeling, one current knowledge gap that has remained relatively unexplored. Early results demonstrate this flood modeling system is useful decision- support tool for governmental officials and international aid organizations to better quantify flood impacts and extent of hazard risk, as well as more expediently respond to flood emergencies.

  11. Environments and trypanosomiasis risks for early herders in the later Holocene of the Lake Victoria basin, Kenya.

    PubMed

    Chritz, Kendra L; Marshall, Fiona B; Zagal, M Esperanza; Kirera, Francis; Cerling, Thure E

    2015-03-24

    Specialized pastoralism developed ∼3 kya among Pastoral Neolithic Elmenteitan herders in eastern Africa. During this time, a mosaic of hunters and herders using diverse economic strategies flourished in southern Kenya. It has been argued that the risk for trypanosomiasis (sleeping sickness), carried by tsetse flies in bushy environments, had a significant influence on pastoral diversification and migration out of eastern Africa toward southern Africa ∼2 kya. Elmenteitan levels at Gogo Falls (ca. 1.9-1.6 kya) preserve a unique faunal record, including wild mammalian herbivores, domestic cattle and caprines, fish, and birds. It has been suggested that a bushy/woodland habitat that harbored tsetse fly constrained production of domestic herds and resulted in subsistence diversification. Stable isotope analysis of herbivore tooth enamel (n = 86) from this site reveals, instead, extensive C4 grazing by both domesticates and the majority of wild herbivores. Integrated with other ecological proxies (pollen and leaf wax biomarkers), these data imply an abundance of C4 grasses in the Lake Victoria basin at this time, and thus little risk for tsetse-related barriers to specialized pastoralism. These data provide empirical evidence for the existence of a grassy corridor through which small groups of herders could have passed to reach southern Africa. PMID:25775535

  12. Environments and trypanosomiasis risks for early herders in the later Holocene of the Lake Victoria basin, Kenya

    PubMed Central

    Chritz, Kendra L.; Marshall, Fiona B.; Zagal, M. Esperanza; Kirera, Francis; Cerling, Thure E.

    2015-01-01

    Specialized pastoralism developed ∼3 kya among Pastoral Neolithic Elmenteitan herders in eastern Africa. During this time, a mosaic of hunters and herders using diverse economic strategies flourished in southern Kenya. It has been argued that the risk for trypanosomiasis (sleeping sickness), carried by tsetse flies in bushy environments, had a significant influence on pastoral diversification and migration out of eastern Africa toward southern Africa ∼2 kya. Elmenteitan levels at Gogo Falls (ca. 1.9–1.6 kya) preserve a unique faunal record, including wild mammalian herbivores, domestic cattle and caprines, fish, and birds. It has been suggested that a bushy/woodland habitat that harbored tsetse fly constrained production of domestic herds and resulted in subsistence diversification. Stable isotope analysis of herbivore tooth enamel (n = 86) from this site reveals, instead, extensive C4 grazing by both domesticates and the majority of wild herbivores. Integrated with other ecological proxies (pollen and leaf wax biomarkers), these data imply an abundance of C4 grasses in the Lake Victoria basin at this time, and thus little risk for tsetse-related barriers to specialized pastoralism. These data provide empirical evidence for the existence of a grassy corridor through which small groups of herders could have passed to reach southern Africa. PMID:25775535

  13. Monitoring Lake Victoria Water Quality from Space: Opportunities for Strengthening Trans-boundary Information Sharing for Effective Resource Management

    NASA Astrophysics Data System (ADS)

    Mugo, R. M.; Korme, T.; Farah, H.; Nyaga, J. W.; Irwin, D.; Flores, A.; Limaye, A. S.; Artis, G.

    2014-12-01

    Lake Victoria (LV) is an important freshwater resource in East Africa, covering 68,800 km2, and a catchment that spans 193,000km2. It is an important source of food, energy, drinking and irrigation water, transport and a repository for agricultural, human and industrial wastes generated from its catchment. For such a lake, and a catchment transcending 5 international boundaries, collecting data to guide informed decision making is a hard task. Remote sensing is currently the only tool capable of providing information on environmental changes at high spatio-temporal scales. To address the problem of information availability for LV, we tackled two objectives; (1) we analyzed water quality parameters retrieved from MODIS data, and (2) assessed land cover changes in the catchment area using Landsat data. We used L1A MODIS-Aqua data to retrieve lake surface temperature (LST), total suspended matter (TSM), chlorophyll-a (CHLa) and diffuse attenuation coefficient (KD490) in four temporal periods i.e. daily, weekly, monthly and seasonal scales. An Empirical Orthogonal Function (EOF) analysis was done on monthly data. An analysis of land cover change was done using Landsat data for 3 epochs in order to assess if land degradation contributes to water quality changes. Our results indicate that MODIS-Aqua data provides synoptic views of water quality changes in LV at different temporal scales. The Winam Gulf in Kenya, the shores of Jinja town in Uganda, as well as the Mwanza region in Tanzania represent water quality hotspots due to their relatively high TSM and CHLa concentrations. High levels of KD490 in these areas would also indicate high turbidity and thus low light penetration due to the presence of suspended matter, algal blooms, and/or submerged vegetation. The EOF analysis underscores the areas where LST and water color variability are more significant. The changes can be associated with corresponding land use changes in the catchment, where for instance wetlands are

  14. Wetland vegetation and nutrient retention in Nakivubo and Kirinya wetlands in the Lake Victoria basin of Uganda

    NASA Astrophysics Data System (ADS)

    Mugisha, P.; Kansiime, F.; Mucunguzi, P.; Kateyo, E.

    Wetlands form an important part of the catchment area of the African Great Lakes and protect water resources therein. One of the most important functions is the retention of nutrients from the inflowing water from the catchment, by wetland plants which store them in their phytomass. An assessment of the capacity in storing nutrients by dominant plants ( Cyeprus papyrus, Miscanthus violaceus, Phragmites mauritianus and Colocasia C. esculenta), of Nakivubo and Kirinya wetlands at the shores of Lake Victoria in Uganda, was studied through the determination of phytomass production and nutrient concentration in the plant parts at different stages of growth. The above ground phytomass production increased rapidly during the exponential growth for C. papyrus and P. mauritianus. In all the dominant plants, nitrogen concentration was highest in juvenile plants and decreased with increasing age. The most pronounced nitrogen level occurred in the young umbels of C. papyrus during the first month of growth with total nitrogen content of 1.95% DW which dropped to 0.62% DW after the fifth month in Nakivubo wetland. Corms (tubers) of yams had the highest nitrogen content in Kirinya and Nakivubo wetlands exhibiting respective values of 4.8% DW and 3.7% DW. There is a close relationship between nutrient content and increase in phytomass. In Nakivubo and Kirinya wetlands, the rapid increase in phytomass during the third and fourth month corresponded with high nutrient levels. Since plants store significant amounts of nitrogen during their growth, periodic harvesting of above ground plant parts can remove significant amounts of nutrients (during the first five months of growth) from the wastewater flowing into the two wetlands. Wetland plant species with high phytomass productivity and well developed root systems and ability to withstand flooding are the best in nutrient removal.

  15. Monitoring basin-scale land cover changes in Kagera Basin of Lake Victoria using ancillary data and remote sensing

    NASA Astrophysics Data System (ADS)

    Wasige, John E.; Groen, Thomas A.; Smaling, Eric; Jetten, Victor

    2013-04-01

    The Kagera Basin is a high value ecosystem in the Lake Victoria watershed because of the hydrological and food services it provides. The basin has faced large scale human induced land use and land cover changes (LUCC), but quantitative data is to date lacking. A combination of ancillary data and satellite imagery were interpreted to construct LUCC dynamics for the last century. This study is an initial step towards assessing the impact of LUCC on sustainable agriculture and water quality in the watershed. The results show that large trends of LUCC have rapidly occurred over the last 100 years. The most dominant LUCC processes were gains in farmland areas (not detectable in 1901 to 60% in 2010) and a net reduction in dense forest (7% to 2.6%), woodlands (51% to 6.9%) and savannas (35% to 19.6%) between 1901 and 2010. Forest degradation rapidly occurred during 1974 and 1995 but the forest re-grew between 1995 and 2010 due to forest conservation efforts. Afforestation efforts have resulted in plantation forest increases between 1995 and 2010. The rates of LUCC observed are higher than those reported in Sub Saharan Africa (SSA) and other parts of the world. This is one of the few studies in SSA at a basin scale that combines multi-source spatio-temporal data on land cover to enable long-term quantification of land cover changes. In the discussion we address future research needs for the area based on the results of this study. These research needs include quantifying the impacts of land cover change on nutrient and sediment dynamics, soil organic carbon stocks, and changes in biodiversity.

  16. Distribution and exploitation of Nile perch Lates niloticus in relation to stratification in Lake Victoria, East Africa

    USGS Publications Warehouse

    Taabu-Munyaho, A.; Kayanda, Robert J.; Everson, Inigo; Grabowski, Timothy B.; Marteinsdóttir, Gudrún

    2013-01-01

    Stratification restricts habitable areas forcing fish to balance between favourable temperature and minimum dissolved oxygen requirements. Acoustic surveys conducted during the stratified and isothermal periods on tropical Lake Victoria indicated that stratification of temperature and dissolved oxygen (DO) affected vertical distribution of Nile perch. There was higher mean temperature (25.6 ± 0.5 °C) and lower DO (6.4 ± 1.8 mg/l) during stratified period compared to the isothermal period (mean temperature 24.9 ± 0.3 °C; mean DO 7.3 ± 0.6 mg/l). Higher mean densities of Nile perch were recorded in the coastal (0.44 ± 0.03) and deep (0.27 ± 0.02 g/m3) strata during the stratified compared to the isothermal season (coastal: 0.24 ± 0.01; deep: 0.12 ± 0.02 g/m3). In addition, Nile perch density in the upper 0–40 m depth layers in the coastal and deep strata increased by over 50% from the isothermal to the stratified season. Daily landings from 65 motorised fishing boats between October 2008 and September 2010 show higher mean catch (26.29 ± 0.17 kg/boat/day) during stratified compared to the isothermal (23.59 ± 0.15) season. Thermal stratification apparently compresses the habitat available to Nile perch and can potentially result in higher exploitation. Managers should evaluate the potential benefits of instituting closed seasons during the stratified period, and stock assessment models should take into account the seasonal niche compression.

  17. Perceptions of HIV and Safe Male Circumcision in High HIV Prevalence Fishing Communities on Lake Victoria, Uganda

    PubMed Central

    Nevin, Paul E.; Pfeiffer, James; Kibira, Simon P. S.; Lubinga, Solomon J.; Mukose, Aggrey; Babigumira, Joseph B.

    2015-01-01

    Background In 2010, the Uganda Ministry of Health introduced its Safe Male Circumcision (SMC) strategy for HIV prevention with the goal of providing 4.2 million voluntary medical male circumcisions by 2015. Fishing communities, where HIV prevalence is approximately 3–5 times higher than the national average, have been identified as a key population needing targeted HIV prevention services by the National HIV Prevention Strategy. This study aimed to understand perceptions of HIV and identify potential barriers and facilitators to SMC in fishing communities along Lake Victoria. Methods We conducted 8 focus group discussions, stratified by sex and age, with 67 purposefully sampled participants in 4 communities in Kalangala District, Uganda. Results There was universal knowledge of the availability of SMC services, but males reported high uptake in the community while females indicated that it is low. Improved hygiene, disease prevention, and improved sexual performance and desirability were reported facilitators. Barriers included a perceived increase in SMC recipients’ physiological libido, post-surgical abstinence, lost income during convalescence, and lengthier recovery due to occupational hazards. Both males and females reported concerns about spousal fidelity during post-SMC abstinence. Reported misconceptions and community-held cultural beliefs include fear that foreskins are sold after their removal, the belief that a SMC recipient’s first sexual partner after the procedure should not be his spouse, and the belief that vaginal fluids aid circumcision wound healing. Conclusions Previous outreach efforts have effectively reached these remote communities, where availability and health benefits of SMC are widely understood. However, community-specific intervention strategies are needed to address the barriers identified in this study. We recommend the development of targeted counseling, outreach, and communication strategies to address barriers

  18. Paleoclimatic and paleoecological reconstruction of early Miocene terrestrial equatorial deposits, Rusinga and Mfangano Islands, Lake Victoria, Kenya

    NASA Astrophysics Data System (ADS)

    Michel, L. A.; Peppe, D. J.; McNulty, K. P.; Driese, S. G.; Lutz, J.; Nightingale, S.; Maxbauer, D. P.; Horner, W. H.; DiPietro, L. M.; Lehmann, T.; Dunsworth, H. M.; Harcourt-Smith, W. E.; Ogondo, J.

    2012-12-01

    Biological responses to climatic shifts are often studied to inform us on future anthropogenic-driven climate change. However, few of these climatic shifts occur over time scales appropriate to modern change and few occur with biota similar to modern. The Miocene Climatic Optimum is an ideal interval to study because of its rapid duration and because it occurred during the rise and proliferation of apes. The sediments on Rusinga and Mfangano Islands, Lake Victoria, Kenya were deposited between 18 and 20 Ma and record a changing equatorial climate just prior to the Miocene Climate Optimum. This location also offers an opportunity to use multiple proxies to constrain climate and landscape, including paleosol geochemistry, paleobotany and paleontology. Additionally, due to the rich fossil preservation on the islands, climatic shifts are framed within the context of early caterrhine evolution. Here, we report a climate shift recorded through three time slices spanning two formations over ~2 myr. The oldest unit, the Wayando Formation, records an arid, probably open ecosystem with pedogenic calcite rhizoliths, a high groundwater table, poorly-formed paleosols and permineralized sedges. The middle time slice, the Grit Member-Fossil Bed Member contact of the Hiwegi Formation, shows evidence of a local saline lake, with desiccation features, satin-spar after gypsum deposits and salt hoppers. Paleobotanical and sedimentological data from roughly contemporaneous strata indicate a warm, highly seasonal environment that supported a mixture of woodland and forested elements across the landscape. The youngest unit, which is within the Kibanga Member of the Hiwegi Formation, displays demonstrable evidence for a closed-canopy multistoried forest with the presence of tree-stump casts and permineralized root systems within a red-brown paleosol. Within the same paleosol horizon, the dental remains of the catarrhines Proconsul and Dendropithecus have been discovered in situ. This

  19. Virus-Host and CRISPR Dynamics in Archaea-Dominated Hypersaline Lake Tyrrell, Victoria, Australia

    DOE PAGESBeta

    Emerson, Joanne B.; Andrade, Karen; Thomas, Brian C.; Norman, Anders; Allen, Eric E.; Heidelberg, Karla B.; Banfield, Jillian F.

    2013-01-01

    The study of natural archaeal assemblages requires community context, namely, a concurrent assessment of the dynamics of archaeal, bacterial, and viral populations. Here, we use filter size-resolved metagenomic analyses to report the dynamics of 101 archaeal and bacterial OTUs and 140 viral populations across 17 samples collected over different timescales from 2007–2010 from Australian hypersaline Lake Tyrrell (LT). All samples were dominated by Archaea (75–95%). Archaeal, bacterial, and viral populations were found to be dynamic on timescales of months to years, and different viral assemblages were present in planktonic, relative to host-associated (active and provirus) size fractions. Analyses of clusteredmore » regularly interspaced short palindromic repeat (CRISPR) regions indicate that both rare and abundant viruses were targeted, primarily by lower abundance hosts. Although very few spacers had hits to the NCBI nr database or to the 140 LT viral populations, 21% had hits to unassembled LT viral concentrate reads. This suggests local adaptation to LT-specific viruses and/or undersampling of haloviral assemblages in public databases, along with successful CRISPR-mediated maintenance of viral populations at abundances low enough to preclude genomic assembly. This is the first metagenomic report evaluating widespread archaeal dynamics at the population level on short timescales in a hypersaline system.« less

  20. Virus-Host and CRISPR Dynamics in Archaea-Dominated Hypersaline Lake Tyrrell, Victoria, Australia

    PubMed Central

    Emerson, Joanne B.; Andrade, Karen; Thomas, Brian C.; Norman, Anders; Allen, Eric E.; Heidelberg, Karla B.; Banfield, Jillian F.

    2013-01-01

    The study of natural archaeal assemblages requires community context, namely, a concurrent assessment of the dynamics of archaeal, bacterial, and viral populations. Here, we use filter size-resolved metagenomic analyses to report the dynamics of 101 archaeal and bacterial OTUs and 140 viral populations across 17 samples collected over different timescales from 2007–2010 from Australian hypersaline Lake Tyrrell (LT). All samples were dominated by Archaea (75–95%). Archaeal, bacterial, and viral populations were found to be dynamic on timescales of months to years, and different viral assemblages were present in planktonic, relative to host-associated (active and provirus) size fractions. Analyses of clustered regularly interspaced short palindromic repeat (CRISPR) regions indicate that both rare and abundant viruses were targeted, primarily by lower abundance hosts. Although very few spacers had hits to the NCBI nr database or to the 140 LT viral populations, 21% had hits to unassembled LT viral concentrate reads. This suggests local adaptation to LT-specific viruses and/or undersampling of haloviral assemblages in public databases, along with successful CRISPR-mediated maintenance of viral populations at abundances low enough to preclude genomic assembly. This is the first metagenomic report evaluating widespread archaeal dynamics at the population level on short timescales in a hypersaline system. PMID:23853523

  1. Virus-host and CRISPR dynamics in Archaea-dominated hypersaline Lake Tyrrell, Victoria, Australia.

    PubMed

    Emerson, Joanne B; Andrade, Karen; Thomas, Brian C; Norman, Anders; Allen, Eric E; Heidelberg, Karla B; Banfield, Jillian F

    2013-01-01

    The study of natural archaeal assemblages requires community context, namely, a concurrent assessment of the dynamics of archaeal, bacterial, and viral populations. Here, we use filter size-resolved metagenomic analyses to report the dynamics of 101 archaeal and bacterial OTUs and 140 viral populations across 17 samples collected over different timescales from 2007-2010 from Australian hypersaline Lake Tyrrell (LT). All samples were dominated by Archaea (75-95%). Archaeal, bacterial, and viral populations were found to be dynamic on timescales of months to years, and different viral assemblages were present in planktonic, relative to host-associated (active and provirus) size fractions. Analyses of clustered regularly interspaced short palindromic repeat (CRISPR) regions indicate that both rare and abundant viruses were targeted, primarily by lower abundance hosts. Although very few spacers had hits to the NCBI nr database or to the 140 LT viral populations, 21% had hits to unassembled LT viral concentrate reads. This suggests local adaptation to LT-specific viruses and/or undersampling of haloviral assemblages in public databases, along with successful CRISPR-mediated maintenance of viral populations at abundances low enough to preclude genomic assembly. This is the first metagenomic report evaluating widespread archaeal dynamics at the population level on short timescales in a hypersaline system. PMID:23853523

  2. High fluoride water in Bondo-Rarieda area of Siaya County, Kenya: a hydro-geological implication on public health in the Lake Victoria Basin

    PubMed Central

    2014-01-01

    Background Only a few studies to evaluate groundwater fluoride in Eastern Africa have been undertaken outside the volcanic belt of the Great Eastern Africa Rift Valley. The extent and impact of water fluoride outside these regions therefore remain unclear. The current study evaluated fluoride levels in household water sources in Bondo-Rarieda Area in the Kenyan part of the Lake Victoria Basin (LVB) and highlighted the risk posed by water fluoride to the resident communities. The results, it was anticipated, will contribute to in-depth understanding of the fluoride problem in the region. Methods A total of 128 water samples were collected from different water sources from the entire study area and analyzed for fluoride content using ion-selective electrodes. Results Lake Victoria was the main water source in the area but dams and open pans (39.5%), boreholes and shallow wells (23.5%), and streams (18.5%) were the principal water sources outside walking distances from the lake. The overall mean fluoride content of the water exceeded recommended limits for drinking water. The mean water fluoride was highest in Uyoma (1.39±0.84 ppm), Nyang’oma (1.00±0.59 ppm) and Asembo (0.92±0.46 ppm) and lowest in Maranda Division (0.69±0.42 ppm). Ponds (1.41±0.82 ppm), springs (1.25±0.43 ppm), dams and open pans (0.96±0.79 ppm), and streams (0.95±0.41 ppm) had highest fluoride levels but lake and river water did not have elevated fluoride levels. Groundwater fluoride decreased with increasing distance from the lake indicating that water fluoride may have hydro-geologically been translocated into the region from geochemical sources outside the area. Conclusions Lake Victoria was the main water source for the residents of Bondo-Rarieda Area. Majority of in-land residents however used water from dams, open pans, boreholes, shallow wells, ponds and streams, which was generally saline and fluoridated. It was estimated that 36% of children living in this area, who

  3. Holistic view to integrated climate change assessment and extreme weather adaptation in the Lake Victoria Basin East Africa

    NASA Astrophysics Data System (ADS)

    Mutua, F.; Koike, T.

    2013-12-01

    Extreme weather events have been the leading cause of disasters and damage all over the world.The primary ingredient to these disasters especially floods is rainfall which over the years, despite advances in modeling, computing power and use of new data and technologies, has proven to be difficult to predict. Also, recent climate projections showed a pattern consistent with increase in the intensity and frequency of extreme events in the East African region.We propose a holistic integrated approach to climate change assessment and extreme event adaptation through coupling of analysis techniques, tools and data. The Lake Victoria Basin (LVB) in East Africa supports over three million livelihoods and is a valuable resource to five East African countries as a source of water and means of transport. However, with a Mesoscale weather regime driven by land and lake dynamics,extreme Mesoscale events have been prevalent and the region has been on the receiving end during anomalously wet years in the region. This has resulted in loss of lives, displacements, and food insecurity. In the LVB, the effects of climate change are increasingly being recognized as a significant contributor to poverty, by its linkage to agriculture, food security and water resources. Of particular importance are the likely impacts of climate change in frequency and intensity of extreme events. To tackle this aspect, this study adopted an integrated regional, mesoscale and basin scale approach to climate change assessment. We investigated the projected changes in mean climate over East Africa, diagnosed the signals of climate change in the atmosphere, and transferred this understanding to mesoscale and basin scale. Changes in rainfall were analyzed and similar to the IPCC AR4 report; the selected three General Circulation Models (GCMs) project a wetter East Africa with intermittent dry periods in June-August. Extreme events in the region are projected to increase; with the number of wet days

  4. Prevalence of Schistosomes and Soil-Transmitted Helminths and Morbidity Associated with Schistosomiasis among Adult Population in Lake Victoria Basin, Tanzania

    PubMed Central

    Siza, Julius E.; Kaatano, Godfrey M.; Chai, Jong-Yil; Eom, Keeseon S.; Rim, Han-Jong; Yong, Tai-Soon; Min, Duk-Young; Chang, Su Young; Ko, Yunsuk; Changalucha, John M.

    2015-01-01

    The objective of this study was to carry out a community survey on schistosomiais and soil-transmitted helminth (STH) infections in order to suggest feasible and effective intervention strategies in Lake Victoria basin, Tanzania. A total of 37 communities selected from 23 districts of the 4 regions in the Lake Victoria basin of Tanzania were involved in the study. From each of the selected locality, 50 adult community members, 25 males and 25 females, were recruited for the study. Each study participant was requested to submit stool and urine specimens. From each stool specimen, duplicate Kato-Katz thick smears were prepared and microscopically examined for Schistosoma mansoni and STH eggs. Urine specimens were processed by the filtration technique and microscopically examined for Schistosoma haematobium eggs. Ultrasound examination for morbidity due to schistosomiasis was performed. Mass treatment was done using praziquantel and albendazole for schistosome and STHs infections, respectively. Out of 1,606 adults who provided stool specimens, 199 (12.4%) were positive for S. mansoni, 349 (21.7%) for hookworms, 133 (8.3%) for Ascaris lumbricoides, and 33 (2.0%) for Trichuris trichiura. Out of 1,400 participants who provided urine specimens, 25 (1.8%) were positive for S. haematobium eggs. Because of the co-endemicity of these afflictions and their impact on vulnerable population groups, the helminthiasis could be simultaneously treated with 2 drugs, praziquantel for schistosomiasis and albendazole for STHs. PMID:26537031

  5. Hydro-climatic trends and water resource management implications based on multi-scale data for the Lake Victoria region, Kenya

    NASA Astrophysics Data System (ADS)

    Koutsouris, A. J.; Destouni, G.; Jarsjö, J.; Lyon, S. W.

    2010-07-01

    Unreliable rainfall may be a main cause of poverty in rural areas, such as the Kisumu district by Lake Victoria in Kenya. Climate change may further increase the negative effects of rainfall uncertainty. These effects could be mitigated to some extent through improved and adaptive water resource management and planning, which relies on our interpretations and projections of the coupled hydro-climatic system behaviour and its development trends. In order to identify and quantify the main differences and consistencies among such hydro-climatic assessments, this study investigates trends and exemplifies their use for important water management decisions for the Lake Victoria drainage basin (LVDB), based on local scale data for the Orongo village in the Kisumu district, and regional scale data for the whole LVDB. Results show low correlation between locally and regionally observed hydro-climatic trends, and large differences, which in turn affects assessments of important water resource management parameters. However, both data scales converge in indicating that observed local and regional hydrological discharge trends are primarily driven by local and regional water use and land use changes.

  6. Male mating preferences pre-date the origin of a female trait polymorphism in an incipient species complex of Lake Victoria cichlids.

    PubMed

    Pierotti, M E R; Seehausen, O

    2007-01-01

    Disruptive sexual selection on colour patterns has been suggested as a major cause of diversification in the cichlid species flock of Lake Victoria. In Neochromis omnicaeruleus, a colour and sex determination polymorphism is associated with a polymorphism in male and female mating preferences. Theoretical work on this incipient species complex found conditions for rapid sympatric speciation by selection on sex determination and sexual selection on male and female colour patterns, under restrictive assumptions. Here we test the biological plausibility of a key assumption of such models, namely, the existence of a male preference against a novel female colour morph before its appearance in the population. We show that most males in a population that lacks the colour polymorphism exhibit a strong mating preference against the novel female colour morph and that reinforcement is not a likely explanation for the origin of such male preferences. Our results show that a specific condition required for the combined action of selection on sex determination and sexual selection to drive sympatric speciation is biologically justified. Finally, we suggest that Lake Victoria cichlids might share an ancestral female recognition scheme, predisposing colour monomorphic populations/species to similar evolutionary pathways leading to divergence of colour morphs in sympatry. PMID:17210017

  7. Prevalence of Schistosomes and Soil-Transmitted Helminths and Morbidity Associated with Schistosomiasis among Adult Population in Lake Victoria Basin, Tanzania.

    PubMed

    Siza, Julius E; Kaatano, Godfrey M; Chai, Jong-Yil; Eom, Keeseon S; Rim, Han-Jong; Yong, Tai-Soon; Min, Duk-Young; Chang, Su Young; Ko, Yunsuk; Changalucha, John M

    2015-10-01

    The objective of this study was to carry out a community survey on schistosomiais and soil-transmitted helminth (STH) infections in order to suggest feasible and effective intervention strategies in Lake Victoria basin, Tanzania. A total of 37 communities selected from 23 districts of the 4 regions in the Lake Victoria basin of Tanzania were involved in the study. From each of the selected locality, 50 adult community members, 25 males and 25 females, were recruited for the study. Each study participant was requested to submit stool and urine specimens. From each stool specimen, duplicate Kato-Katz thick smears were prepared and microscopically examined for Schistosoma mansoni and STH eggs. Urine specimens were processed by the filtration technique and microscopically examined for Schistosoma haematobium eggs. Ultrasound examination for morbidity due to schistosomiasis was performed. Mass treatment was done using praziquantel and albendazole for schistosome and STHs infections, respectively. Out of 1,606 adults who provided stool specimens, 199 (12.4%) were positive for S. mansoni, 349 (21.7%) for hookworms, 133 (8.3%) for Ascaris lumbricoides, and 33 (2.0%) for Trichuris trichiura. Out of 1,400 participants who provided urine specimens, 25 (1.8%) were positive for S. haematobium eggs. Because of the co-endemicity of these afflictions and their impact on vulnerable population groups, the helminthiasis could be simultaneously treated with 2 drugs, praziquantel for schistosomiasis and albendazole for STHs. PMID:26537031

  8. Evolution of the Lake Victoria basin in the context of coeval rift initiation in East Africa: a 3D numerical model approach

    NASA Astrophysics Data System (ADS)

    Wichura, Henry; Quinteros, Javier; Melnick, Daniel; Brune, Sascha; Schwanghart, Wolfgang; Strecker, Manfred R.

    2015-04-01

    Over the last four years sedimentologic and thermochronologic studies in the western and eastern branches of the Cenozoic East African Rift System (EARS) have supported the notion of a broadly contemporaneous onset of normal faulting and rift-basin formation in both segments. These studies support previous interpretations based on geophysical investigations from which an onset of rifting during the Paleogene had been postulated. In light of these studies we explore the evolution of the Lake Victoria basin, a shallow, unfaulted sedimentary basin centered between both branches of the EARS and located in the interior of the East African Plateau (EAP). We quantify the fluvial catchment evolution of the Lake Victoria basin and assess the topographic response of African crust to the onset of rifting in both branches. Furthermore, we evaluate and localize the nature of strain and flexural rift-flank uplift in both branches. We use a 3D numerical forward model that includes nonlinear temperature- and stress-dependent elasto-visco-plastic rheology. The model is able to reproduce the flexural response of variably thick lithosphere to rift-related deformation processes such as lithospheric thinning and asthenospheric upwelling. The model domain covers the entire EAP and integrates extensional processes in a heterogeneous, yet cold and thick cratonic block (Archean Tanzania craton), which is surrounded by mechanically weaker Proterozoic mobile belts, which are characterized by thinner lithosphere ("thin spots"). The lower limits of the craton (170 km) and the mobile belts (120 km) are simulated by different depths of the 1300 °C lithosphere-asthenosphere boundary. We assume a constant extension rate of 4 mm/a throughout the entire simulation of 30 Ma and neglect the effect of dynamic topography and magmatism. Even though the model setup is very simple and the resolution is not high enough to calculate realistic rift-flank uplift, it intriguingly reveals important topographic

  9. Paleoenvironmental context of the Middle Stone Age record from Karungu, Lake Victoria Basin, Kenya, and its implications for human and faunal dispersals in East Africa.

    PubMed

    Faith, J Tyler; Tryon, Christian A; Peppe, Daniel J; Beverly, Emily J; Blegen, Nick; Blumenthal, Scott; Chritz, Kendra L; Driese, Steven G; Patterson, David

    2015-06-01

    The opening and closing of the equatorial East African forest belt during the Quaternary is thought to have influenced the biogeographic histories of early modern humans and fauna, although precise details are scarce due to a lack of archaeological and paleontological records associated with paleoenvironmental data. With this in mind, we provide a description and paleoenvironmental reconstruction of the Late Pleistocene Middle Stone Age (MSA) artifact- and fossil-bearing sediments from Karungu, located along the shores of Lake Victoria in western Kenya. Artifacts recovered from surveys and controlled excavations are typologically MSA and include points, blades, and Levallois flakes and cores, as well as obsidian flakes similar in geochemical composition to documented sources near Lake Naivasha (250 km east). A combination of sedimentological, paleontological, and stable isotopic evidence indicates a semi-arid environment characterized by seasonal precipitation and the dominance of C4 grasslands, likely associated with a substantial reduction in Lake Victoria. The well-preserved fossil assemblage indicates that these conditions are associated with the convergence of historically allopatric ungulates from north and south of the equator, in agreement with predictions from genetic observations. Analysis of the East African MSA record reveals previously unrecognized north-south variation in assemblage composition that is consistent with episodes of population fragmentation during phases of limited dispersal potential. The grassland-associated MSA assemblages from Karungu and nearby Rusinga Island are characterized by a combination of artifact types that is more typical of northern sites. This may reflect the dispersal of behavioral repertoires-and perhaps human populations-during a paleoenvironmental phase dominated by grasslands. PMID:25883052

  10. An Integrated Hydrological and Water Management Study of the Entire Nile River System - Lake Victoria to Nile Delta

    NASA Technical Reports Server (NTRS)

    Habib, Shahid; Zaitchik, Benjamin; Alo, Clement; Ozdogan, Mutlu; Anderson, Martha; Policelli, Fritz

    2011-01-01

    The Nile basin River system spans 3 million km(exp 2) distributed over ten nations. The eight upstream riparian nations, Ethiopia, Eretria, Uganda, Rwanda, Burundi, Congo, Tanzania and Kenya are the source of approximately 86% of the water inputs to the Nile, while the two downstream riparian countries Sudan and Egypt, presently rely on the river's flow for most of the their needs. Both climate and agriculture contribute to the complicated nature of Nile River management: precipitation in the headwaters regions of Ethiopia and Lake Victoria is variable on a seasonal and inter-annual basis, while demand for irrigation water in the arid downstream region is consistently high. The Nile is, perhaps, one of the most difficult trans-boundary water issue in the world, and this study would be the first initiative to combine NASA satellite observations with the hydrologic models study the overall water balance in a to comprehensive manner. The cornerstone application of NASA's Earth Science Research Results under this project are the NASA Land Data Assimilation System (LDAS) and the USDA Atmosphere-land Exchange Inverse (ALEXI) model. These two complementary research results are methodologically independent methods for using NASA observations to support water resource analysis in data poor regions. Where an LDAS uses multiple sources of satellite data to inform prognostic simulations of hydrological process, ALEXI diagnoses evapotranspiration and water stress on the basis of thermal infrared satellite imagery. Specifically, this work integrates NASA Land Data Assimilation systems into the water management decision support systems that member countries of the Nile Basin Initiative (NBI) and Regional Center for Mapping of Resources for Development (RCMRD, located in Nairobi, Kenya) use in water resource analysis, agricultural planning, and acute drought response to support sustainable development of Nile Basin water resources. The project is motivated by the recognition that

  11. Water hyacinth Eichhornia crassipes (Mart.) Solms-Laubach dynamics and succession in the Nyanza Gulf of Lake Victoria (east Africa): implications for water quality and biodiversity conservation.

    PubMed

    Gichuki, John; Omondi, Reuben; Boera, Priscillar; Okorut, Tom; Matano, Ally Said; Jembe, Tsuma; Ofulla, Ayub

    2012-01-01

    This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes, Ipomoea aquatica Forsk., and Enydra fluctuans Lour., during early stages of succession. This is followed by hippo grass Vossia cuspidata (Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities. PMID:22619574

  12. Water Hyacinth Eichhornia crassipes (Mart.) Solms-Laubach Dynamics and Succession in the Nyanza Gulf of Lake Victoria (East Africa): Implications for Water Quality and Biodiversity Conservation

    PubMed Central

    Gichuki, John; Omondi, Reuben; Boera, Priscillar; Okorut, Tom; Matano, Ally Said; Jembe, Tsuma; Ofulla, Ayub

    2012-01-01

    This study, conducted in Nyanza Gulf of Lake Victoria, assessed ecological succession and dynamic status of water hyacinth. Results show that water hyacinth is the genesis of macrophyte succession. On establishment, water hyacinth mats are first invaded by native emergent macrophytes, Ipomoea aquatica Forsk., and Enydra fluctuans Lour., during early stages of succession. This is followed by hippo grass Vossia cuspidata (Roxb.) Griff. in mid- and late stages whose population peaks during climax stages of succession with concomitant decrease in water hyacinth biomass. Hippo grass depends on water hyacinth for buoyancy, anchorage, and nutrients. The study concludes that macrophyte succession alters aquatic biodiversity and that, since water hyacinth infestation and attendant succession are a symptom of broader watershed management and pollution problems, aquatic macrophyte control should include reduction of nutrient loads and implementing multifaceted approach that incorporates biological agents, mechanical/manual control with utilization of harvested weed for cottage industry by local communities. PMID:22619574

  13. YF-17/ADEN system study

    NASA Technical Reports Server (NTRS)

    Gowadia, N. S.; Bard, W. D.; Wooten, W. H.

    1979-01-01

    The YF-17 aircraft was evaluated as a candidate nonaxisymmetric nozzle flight demonstrator. Configuration design modifications, control system design, flight performance assessment, and program plan and cost we are summarized. Two aircraft configurations were studied. The first was modified as required to install only the augmented deflector exhaust nozzle (ADEN). The second one added a canard installation to take advantage of the full (up to 20 deg) nozzle vectoring capability. Results indicate that: (1) the program is feasible and can be accomplished at reasonable cost and low risk; (2) installation of ADEN increases the aircraft weight by 600 kg (1325 lb); (3) the control system can be modified to accomplish direct lift, pointing capability, variable static margin and deceleration modes of operation; (4) unvectored thrust-minus-drag is similar to the baseline YF-17; and (5) vectoring does not improve maneuvering performance. However, some potential benefits in direct lift, aircraft pointing, handling at low dynamic pressure and takeoff/landing ground roll are available. A 27 month program with 12 months of flight test is envisioned, with the cost estimated to be $15.9 million for the canard equipped aircraft and $13.2 million for the version without canard. The feasiblity of adding a thrust reverser to the YF-17/ADEN was investigated.

  14. Excessive Copper(II) and Zinc(II) Levels in Drinkable Water Sources in Areas Along the Lake Victoria Shorelines in Siaya County, Kenya.

    PubMed

    Wambu, Enos W; Omwoyo, Wesley N; Akenga, Teresa

    2016-01-01

    Copper(II) and zinc(II) levels in drinkable water sources in the alluvium areas of the Lake Victoria Basin in Siaya County of Kenya were evaluated to assess the risk posed to resident communities by hydrogeological accumulation of toxic residues in the sedimentary regions of the lake basin. The levels of the metals in water were analyzed by atomic absorption spectroscopy. Metal concentrations ranged from 0.11 to 4.29 mg/L for Cu(II) and 0.03 to 1.62 mg/L for Zn(II), which were both higher than those normally recorded in natural waters. The Cu(II) levels also exceeded WHO guidelines for drinking water in 27% of the samples. The highest prevalence of excessive Cu(II) was found among dams and open pans (38%), piped water (33%) and spring water (25%). It was estimated that 18.2% of the resident communities in the current study area are exposed to potentially toxic levels of Cu(II) through their drinking water. PMID:26615531

  15. Time series analysis of satellite multi-sensors imagery to study the recursive abnormal grow of floating macrophyte in the lake victoria (central Africa)

    NASA Astrophysics Data System (ADS)

    Fusilli, Lorenzo; Cavalli, Rosa Maria; Laneve, Giovanni; Pignatti, Stefano; Santilli, Giancarlo; Santini, Federico

    2010-05-01

    Remote sensing allows multi-temporal mapping and monitoring of large water bodies. The importance of remote sensing for wetland and inland water inventory and monitoring at all scales was emphasized several times by the Ramsar Convention on Wetlands and from EU projects like SALMON and ROSALMA, e.g. by (Finlayson et al., 1999) and (Lowry and Finlayson, 2004). This paper aims at assessing the capability of time series of satellite imagery to provide information suitable for enhancing the understanding of the temporal cycles shown by the macrophytes growing in order to support the monitor and management of the lake Victoria water resources. The lake Victoria coastal areas are facing a number of challenges related to water resource management which include growing population, water scarcity, climate variability and water resource degradation, invasive species, water pollution. The proliferation of invasive plants and aquatic weeds, is of growing concern. In particular, let us recall some of the problems caused by the aquatic weeds growing: Ø interference with human activities such as fishing, and boating; Ø inhibition or interference with a balanced fish population; Ø fish killing due to removal of too much oxygen from the water; Ø production of quiet water areas that are ideal for mosquito breeding. In this context, an integrated use of medium/high resolution images from sensors like MODIS, ASTER, LANDSAT/TM and whenever available CHRIS offers the possibility of creating a congruent time series allowing the analysis of the floating vegetation dynamic on an extended temporal basis. Although MODIS imagery is acquired daily, cloudiness and other sources of noise can greatly reduce the effective temporal resolution, further its spatial resolution can results not always adequate to map the extension of floating plants. Therefore, the integrated use of sensors with different spatial resolution, were used to map across seasons the evolution of the phenomena. The

  16. Petrology, geochronology and emplacement model of the giant 1.37 Ga arcuate Lake Victoria Dyke Swarm on the margin of a large igneous province in eastern Africa

    NASA Astrophysics Data System (ADS)

    Mäkitie, Hannu; Data, Gabriel; Isabirye, Edward; Mänttäri, Irmeli; Huhma, Hannu; Klausen, Martin B.; Pakkanen, Lassi; Virransalo, Petri

    2014-09-01

    A comprehensive description of the petrography, geochemical composition, Sm-Nd data and intrinsic field relationships of a giant arcuate Mesoproterozoic mafic dyke swarm in SW Uganda is presented for the first time. The swarm is ∼100 km wide and mainly hosted in the Palaeoproterozoic Rwenzori Belt between the Mesoproterozoic Karagwe-Ankole Belt and the Archaean Uganda Block. The dykes trend NW-SE across Uganda, but can be correlated across Lake Victoria to another set of arcuate aeromagnetic anomalies that continue southwards into Tanzania, resulting in a remarkably large semi-circular swarm with an outer diameter of ∼500 km. We propose that this unique giant dyke structure be named the Lake Victoria Dyke Swarm (LVDS). The dykes are tholeiites with Mg numbers between 0.69 and 0.44, and with inherited marked negative Nb and P anomalies in spider diagrams. Two dykes provide Sm-Nd mineral ages of 1368 ± 41 Ma and 1374 ± 42 Ma, with initial εNd values of -2.3 and -3.2, and 87Sr/86Sr ratios of ∼0.706-0.709. Geotectonic discrimination diagrams for the swarm exhibit more arc type than within-plate tectonic signatures, but this is in accordance with systematic enrichments in LREE, U and Th in the dolerites, more likely due to the involvement of the continental lithosphere during their petrogenesis. The LVDS is coeval with a regional ∼1375 Ma bimodal magmatic event across nearby Burundi, Rwanda and NW Tanzania, which can collectively be viewed as a large igneous province (LIP). It also indicates that the nearby Karagwe-Ankole Belt sequences - bracketed between 1.78 and 1.37 Ga and assumed by some to have been deposited within intracratonic basins - were capped by flood basalts that have subsequently been removed by erosion. Different geochemical signatures (e.g. LaN/SmN) suggest that most of the arcuate swarm was derived from an enriched SCLM, whereas related intrusions in the centre of this semi-circular segment have more or less enriched asthenospheric mantle

  17. Fatty Acid Composition and Levels of Selected Polyunsaturated Fatty Acids in Four Commercial Important Freshwater Fish Species from Lake Victoria, Tanzania

    PubMed Central

    Robert, Agnes; Mfilinge, Prosper; Limbu, Samwel M.; Mwita, Chacha J.

    2014-01-01

    Fatty acids (FAs) particularly ω3 and ω6 polyunsaturated fatty acids (PUFAs) play important role in human health. This study aimed to investigate the composition and levels of selected ω3 PUFAs in four commercial fish species, Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus), Tilapia zillii, and dagaa (Rastrineobola argentea) from Mwanza Gulf in Lake Victoria. The results indicated that 36 types of FAs with different saturation levels were detected. These FAs were dominated by docosahexaenoic (DHA), eicosapentaenoic (EPA), docosapentaenoic (DPA), and eicosatetraenoic acids. O. niloticus had the highest composition of FAs (34) compared to L. niloticus (27), T. zillii (26), and R. argentea (21). The levels of EPA differed significantly among the four commercial fish species (F = 6.19,  P = 0.001). The highest EPA levels were found in R. argentea followed by L. niloticus and O. niloticus and the lowest in T. zillii. The DPA levels showed no significant difference among the four fish species studied (F = 0.652,  P = 0.583). The study concluded that all four commercial species collected from Mwanza Gulf are good for human health, but R. argentea is the best for consumption because it contains higher levels of ω3 FAs, mainly EPA. PMID:25610654

  18. Socio-Economics of Lake Victoria's Fisheries: An Analysis of the Shifting Roles and Status of Women Fish Traders

    ERIC Educational Resources Information Center

    Craig, Heather

    2007-01-01

    Fishing industries around the world are currently undergoing a process of industrialization and commercialization. A similar story is unfolding in many fishing communities: large-scale industrial fishers who possess enormous capital and advanced technologies are threatening the lives of small-scale fisherfolk. The fishing industry in Lake Victoria…

  19. A Very High Infection Intensity of Schistosoma mansoni in a Ugandan Lake Victoria Fishing Community Is Required for Association with Highly Prevalent Organ Related Morbidity

    PubMed Central

    Tukahebwa, Edridah M.; Magnussen, Pascal; Madsen, Henry; Kabatereine, Narcis B.; Nuwaha, Fred; Wilson, Shona; Vennervald, Birgitte J.

    2013-01-01

    Background In schistosomiasis control programmes using mass chemotherapy, epidemiological and morbidity aspects of the disease need to be studied so as to monitor the impact of treatment, and make recommendations accordingly. These aspects were examined in the community of Musoli village along Lake Victoria in Mayuge district, highly endemic for Schistosoma mansoni infection. Methodology and Principal Findings A cross sectional descriptive study was undertaken in a randomly selected sample of 217 females and 229 males, with a mean age of 26 years (SD ±16, range 7–76 years). The prevalence of S. mansoni was 88.6% (95% CI: 85.6–91.5). The geometric mean intensity (GMI) of S. mansoni was 236.2 (95% CI: 198.5–460.9) eggs per gram (epg) faeces. Males had significantly higher GMI (370.2 epg) than females (132.6 epg) and age was also significantly associated with intensity of infection. Levels of water contact activities significantly influenced intensity of infection and the highest intensity of infection was found among people involved in fishing. However, organomegaly was not significantly associated with S. mansoni except for very heavy infection (>2000 epg). Liver image patterns C and D indicative of fibrosis were found in only 2.2% and 0.2%, respectively. S. mansoni intensity of infection was associated with portal vein dilation and abnormal spleen length. Anaemia was observed in 36.4% of the participants but it was not associated with S. mansoni infection intensity. Considering growth in children as one of the morbidity indicators of schistosomiasis, intensity of S. mansoni was significantly associated with stunting. Conclusion Although organ-related morbidity, with the exception of periportal fibrosis, and S. mansoni infections were highly prevalent, the two were only associated for individuals with very high infection intensities. These results contrast starkly with reports from Ugandan Lake Albert fishing communities in which periportal fibrosis is more

  20. Orbital forcing of glacial/interglacial variations in chemical weathering within the White Nile basin: stable-isotope and biomarker evidence from Lakes Victoria and Edward

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Alayne Street-Perrott, F.; Barker, Philip A.; Leng, Melanie J.; Sloane, Hilary J.; Horstwood, Matthew S. A.; Snelling, Andrea

    2014-05-01

    The continental Si cycle on Quaternary time scales has been largely neglected. Emphasis has been placed on long-term geochemical processes of silicate-rock weathering and the resulting drawdown of atmospheric CO2, rather than on shorter-term biogenic processes occurring along the land-ocean continuum. Si-accumulating plants (notably tropical rainforest hardwoods, savanna and wetland grasses, and Papyrus) and aquatic organisms (such as diatoms and sponges in lakes, rivers and swamps) have the potential to take up, store and recycle significant amounts of Si, thereby modifying the riverine flux of Si to the oceans, the productivity of siliceous marine organisms and the rate of atmospheric CO2 drawdown on an orbital time scale. The main aim of this study was to investigate spatial and temporal patterns of Si cycling along the Nile system during the last 20ka BP. Utilising sediment cores from Lakes Victoria and Edward, coupled measurements of stable Si and O isotopes on cleaned diatom separates were employed to reconstruct millennial-scale variations in biotic Si cycling and palaeohydrology, respectively. Abundance ratios of lipid biomarkers (n-alkanes) were used to track major changes in terrestrial and aquatic ecosystems. The results have been interpreted in the light of multi-isotope analyses (2H,18O,30Si) of modern water samples collected along the courses of the modern White and Blue Niles during both wet- and dry-season conditions. During drier intervals (the Last Glacial Maximum and the late Holocene: high 18Odiatom), Si cycling was greatly reduced. Diminished vegetation cover, reduced biotic rock weathering, a declining soil stock of amorphous silica (ASi) and decreased runoff resulted in reduced dissolved silica (DSi) supply to the lakes in relation to aquatic demand (high 30Sidiatom). In contrast, enhanced monsoon rainfall (low 18Odiatom) during the early to mid-Holocene promoted a substantial increase in terrestrial biomass within the White Nile headwaters

  1. Residue levels and discharge loads of antibiotics in wastewater treatment plants (WWTPs), hospital lagoons, and rivers within Lake Victoria Basin, Kenya.

    PubMed

    Kimosop, Selly Jemutai; Getenga, Z M; Orata, F; Okello, V A; Cheruiyot, J K

    2016-09-01

    The detection of antibiotics in water systems has instigated great environmental concern due to the toxicological effects associated with these compounds. Their discharge into the environment results from the ubiquity of use in medical, veterinary, and agricultural practices. Some of the effects of antibiotics include development of antibiotic-resistant bacteria, making it difficult to treat diseases, variation in natural microbial communities, and enzyme activities. In this study, the first comprehensive survey of some frequently used antibiotics namely ampicillin (AMP), amoxicillin (AMX), sulfamethoxazole (SMX), chloramphenicol (CAP), and ciprofloxacin (CPF) within Lake Victoria Basin of Kenya is presented. Sludge and wastewater samples were collected from wastewater treatment plants (WWTPs) and hospital lagoons within the study area. Samples were extracted and cleaned by solid-phase extraction, and analysis was carried out using high-performance liquid chromatography (HPLC). All wastewater samples and sludge collected contained quantifiable levels of the selected antibiotics. The highest concentrations were recorded for AMP with WWTPs and hospitals having 0.36 ± 0.04 and 0.79 ± 0.07 μg/L, respectively. In sludge samples, SMX recorded the highest concentrations of 276 ± 12 ng/g. The high levels in sludge indicate the preferential partition of antibiotics onto solid phase, posing great danger to consumers of crops grown in biosolid-amended soils. The daily discharge loads of antibiotics from nine WWTPs ranged between 80.75 and 3044.9 mg day(-1) with a total discharge of 6395.85 mg day(-1), signifying a high potential of water resource pollution within the region. This report will aid in the assessment of the risks posed by antibiotics released into the environment. PMID:27553946

  2. Active biomonitoring of trace heavy metals using fish ( Oreochromis niloticus) as bioindicator species. The case of Nakivubo wetland along Lake Victoria

    NASA Astrophysics Data System (ADS)

    Birungi, Z.; Masola, B.; Zaranyika, M. F.; Naigaga, I.; Marshall, B.

    The Nakivubo wetland in Uganda, which feeds Lake Victoria at Murchison bay, has become severely degraded over recent years and is particularly threatened by the expansion of industry, settlement and cultivation on its fertile fringes. The aim of this study was to actively biomonitor selected trace heavy metals using Nile tilapia ( Oreochromis niloticus). Nile tilapia was set in cages at six sampling sites in Murchison bay for a period of six weeks, and sampling was done every 2 weeks for active biomonitoring and weekly for physico-chemical variables. The control (site 7) was at the Aquaculture Research and Development centre, Uganda. Fish tissue was dissected and gills, liver and muscle removed for heavy metal analysis. Water samples and fish tissue from each site were analysed using Atomic Absorption Spectrophotometer (AAS) to determine metal concentrations of zinc, copper, chromium and manganese. Site 4 had the highest average NH 4-N of 14.28 ± 12.73 mg/l which was above effluent standards for Uganda. From the findings, there were significantly higher concentrations of heavy metals in fish than in water ( p > 0.01). Fish kills were recorded highest for sites 4 (55%), 5 (77.5%) and 6 (60%) in less than six weeks indicating high levels of pollution. Gills showed the highest accumulation of copper after a period of six weeks as compared to other metals with a mean ± SE of 11.7 μg/mg wet weight. In general, the order of accumulation of metals in tissue after six weeks was in order; copper > zinc > chromium > manganese and gills > liver > muscle. In conclusion, active biomonitoring was found to be a good tool for monitoring water quality as it integrates responses to combinations of all contaminants thereby indicating overall effects in a water body. To improve the study, there is need to incorporate post mortem studies and biomarker analysis since the later can give early warning of pollution before fish kills are observed.

  3. Orbital forcing of glacial/interglacial variations in chemical weathering and silicon cycling within the upper White Nile basin, East Africa: Stable-isotope and biomarker evidence from Lakes Victoria and Edward

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Street-Perrott, F. Alayne; Barker, Philip A.; Leng, Melanie J.; Sloane, Hilary J.; Ficken, Katherine J.

    2015-12-01

    On Quaternary time scales, the global biogeochemical cycle of silicon is interlocked with the carbon cycle through biotic enhancement of silicate weathering and uptake of dissolved silica by vascular plants and aquatic microalgae (notably diatoms, for which Si is an essential nutrient). Large tropical river systems dominate the export of Si from the continents to the oceans. Here, we investigate variations in Si cycling in the upper White Nile basin over the last 15 ka, using sediment cores from Lakes Victoria and Edward. Coupled measurements of stable O and Si isotopes on diatom separates were used to reconstruct past changes in lake hydrology and Si cycling, while the abundances of lipid biomarkers characteristic of terrestrial/emergent higher plants, submerged/floating aquatic macrophytes and freshwater algae document past ecosystem changes. During the late-glacial to mid-Holocene, 15-5.5 ka BP, orbital forcing greatly enhanced monsoon rainfall, forest cover and chemical weathering. Riverine inputs of dissolved silica from the lake catchments exceeded aquatic demand and may also have had lower Si-isotope values. Since 5.5 ka BP, increasingly dry climates and more open vegetation, reinforced by the spread of agricultural cropland over the last 3-4 ka, have reduced dissolved silica inputs into the lakes. Centennial-to millennial-scale dry episodes are also evident in the isotopic records and merit further investigation.

  4. Petroleum geology of the Gulf of Aden

    SciTech Connect

    Allen, R.B ); Sikander, A.H. ); Abouzakhm, A.G.

    1991-08-01

    Evaluation of eight wells (seven offshore and one onshore) in Yemen and nine wells (two offshore and seven onshore) in Somalia, and a regional interpretation of all geophysical data available from ministry files in Yemen and Somalia has been carried out under the auspices of the World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project. A northwest-southeast pre-Oligocene structural trend affecting the onshore pre-rift Mesozoic and early Tertiary rocks has been overprinted in the offshore by an east-west-trending extensional fault system forming the Gulf of Aden, and segmented by a series of northeast-southwest-trending left-lateral sets of transform faults. Free oil 42-44 API was recovered from Sharmah-1 well from the Eocene Habshiya limestone in Yemen and from the Late Jurassic Wanderer limestone (10-35{degree} API) at Dagah Shabei-1 well in Somalia. Geochemical analyses performed on well cuttings and a review of company data identify oil-sourcing potential in the pre-rift Upper Jurassic, Lower to Upper Cretaceous, and Paleocene to Eocene in Yemen, and Upper Jurassic and Upper Cretaceous in Somalia. The geothermal gradients (3.5C/100m) and maturation data (vitrinite reflectance, thermal alteration index, and T{sub max}) in the Gulf of Aden wells in the Yemen and Somali offshore imply that the oil window is relatively shallow (1,750-3,500 m). Relatively thin Paleogene in the Gulf of Aden area suggests that the Mesozoic and Lower Tertiary sediments which contain multiple source and reservoir sequences are situated within the oil window, and thus are highly prospective for oil and gas.

  5. 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.

  6. 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.

  7. Big Spherules near 'Victoria'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This frame from the microscopic imager on NASA's Mars Exploration Rover Opportunity shows spherules up to about 5 millimeters (one-fifth of an inch) in diameter. The camera took this image during the 924th Martian day, or sol, of Opportunity's Mars-surface mission (Aug. 30, 2006), when the rover was about 200 meters (650 feet) north of 'Victoria Crater.'

    Opportunity discovered spherules like these, nicknamed 'blueberries,' at its landing site in 'Eagle Crater,' and investigations determined them to be iron-rich concretions that formed inside deposits soaked with groundwater. However, such concretions were much smaller or absent at the ground surface along much of the rover's trek of more than 5 kilometers (3 miles) southward to Victoria. The big ones showed up again when Opportunity got to the ring, or annulus, of material excavated and thrown outward by the impact that created Victoria Crater. Researchers hypothesize that some layer beneath the surface in Victoria's vicinity was once soaked with water long enough to form the concretions, that the crater-forming impact dispersed some material from that layer, and that Opportunity might encounter that layer in place if the rover drives down into the crater.

  8. 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…

  9. The tectonic evolution of Red Sea and Gulf of Aden

    SciTech Connect

    Allen, R.B. ); Sikander, A.H. ); Abouzakhm, A.G.

    1991-08-01

    The Red Sea and Gulf of Aden, formed by rifting of the Arabian plate away from Africa, have been the subjects of numerous studies since the 1960s. Geophysical and geological data gathered during hydrocarbon exploration by several companies are being synthesized as part of the World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project. This synthesis provides an opportunity to study the regional variation in tectonic history and structural style within the two basins, particularly toward the basin margins, where data coverage is most complete and a thinner sedimentary cover allows more reliable interpretation of deeper horizons. Based on this data, most of the Red Sea shows a similar tectonic history to that of the Gulf of Suez. Widespread normal faulting developed contemporaneous with deposition of a dominantly clastic sequence of Oligocene( ) to middle Miocene age. The faulting often dies out within or below thick middle to upper Miocene evaporite deposits with only few faults affecting the younger units. The Gulf of Aden, on the other hand, shows a strong contrast between largely west-northwest-east-southeast oriented extensional structures on land, and generally more east-west oriented extensional structures on the continental shelves and slopes. The onshore extensional structures oriented oblique to the coast, and approximately perpendicular to transform fault trends in the oceanic crust of the central Gulf of Aden. This contrast is extensional structure orientations has important implications for the tectonic evolution of the Gulf of Aden.

  10. Partway to 'Victoria'

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows the route that NASA's Mars Exploration Rover Opportunity had driven through its 659th Martian day, or sol, (Dec. 1, 2005) relative to the potential destination of 'Victoria Crater' farther south. The base image is a portion of a mosaic (previously released as PIA07506) combining images from the Mars Observer Camera on NASA's Mars Global Surveyor orbiter, the Thermal Emission Imaging System on NASA's Mars Odyssey orbiter, and Opportunity's own Descent Image Motion Estimation System. The scale bar at lower right is 800 meters (one-half mile).

  11. The Red Sea/Gulf of Aden hydrocarbon potential reassessment

    SciTech Connect

    Beydoun, Z.R. )

    1991-08-01

    Samples from most of the 85 exploration wells drilled in the Red Sea and Gulf of Aden, made available to the UNDP/World Bank Red Sea/Gulf of Aden Regional Hydrocarbon Study Project by the participating states were examined for biostratigraphy and source rock geochemistry. Major tectonic elements segment both basins, but in the Gulf of Aden this is less evident as the drift stage is more advanced; additionally, the Red Sea exhibits asymmetry in crustal composition. All this has influenced the location and development of major sediment depocenters and delta fans. Major Neogeon syn-rift and post-rift (Miocene-Pliocene) lithostratigraphic units are correlatable from the petroliferous Gulf of Suez over the Red Sea: pre-rift (Paleogene and older) and syn-rift/post-rift (Oligocene-Miocene/Pliocene) units correlate well across the Gulf of Aden (middle Oligocene) to the southern Red Sea (upper Oligocene) to the northern Red Sea/Gulf of Suez (lower Miocene). Source-rich intervals are present in the mega-sequence of the pre-rift and syn/post-rift packages. Three undeveloped gas and condensate discoveries and a gas blowout plus numerous oil seepages in the Red Sea, and a black oil discovery in the Gulf of Aden are testimony to hydrocarbon generation and entrapment. Although a higher geothermal gradient is present in the southern Red Sea, modeling of the entire basin (rather than in segments) indicates that, contrary to conventional wisdom, the region is neither too hot nor all gas prone, but it possesses the geological parameters conducive to the generation, expulsion, and trapping of significant amount of oil and gas.

  12. 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…

  13. Topographic Expression of the Gulf of Aden Spreading System and its Tectonics: Hotspots-Ridge Interaction in Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Nakanishi, M.; Tamaki, K.; Fujimoto, H.; Okino, K.; Curewitz, D.; Huchon, P.; Khanbari, K. M.

    2001-12-01

    Gulf of Aden is a young ocean basin formed by the rifting of Arabia away from Somalia (NE Africa). The Arabian plate moves away from Africa in a NE direction, at a rate of about 2 cm/yr. The rifting started from Early Miocene. After the, the Gulf of Aden spreding system is propagating westward into the Arabia-Africa continent (Manighetti et al., 1997). It reached the Afar hotspot area about 10 Ma (Manighetti et al., 1998). The spreading system continues to interact with the hotspot up to the present. Tamsett and Searle (1988) exposed that strike of segmentations of the spreading center in Gulf of Aden is NW-SE, although the trend of the spreading system is ENE. Their survey showed the general topographic features of the spreading system, but more detailed survey is necessary to reveal the tectonics of the Gulf of Aden, especially hotspot-ridge interaction. The bathymetric survey by the SEA BEAM 2120 multi-narrow beam echo sounders aboard the R/V Hakuho-maru was carried out along the spreading system of the Gulf of Aden between 45\\deg30'E and 50° 20'E from December 2000 to January 2001. The interval of the track lines is 4-6 km. The trend of the track lines is N70\\degE. Geomagnetic and gravity fields were measured during the bathymetric. The topographic expression of the spreading centers east of N46° 20'E is an axial rift valley offset by transform faults similar to that observed at slow spreading centers. The trend of the axial rift valley is N65\\degW. The offset of the spreading centers increases in length to the east as Tamsett and Searle (1988) indicated. The axial rift valley west of N46° 20'E, which has an east-west direction, is not offset by any prominent transform faults. N65\\deg$W trending en-echelon basins are situated in the rift valley similar to that of the western Gulf of Aden spreading system (Dauteuil, et al. 2001).

  14. Somalian Gulf of Aden petroleum geology and regional geophysical evaluation

    SciTech Connect

    Behi, M.; Mohamed, S.; Abukar, A.K. )

    1991-08-01

    The World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project was organized to synthesize data on the Red Sea and Gulf of Aden basins. The study of the Somalian Gulf of Aden was based on public-domain exploration data, published information, and data released by operating companies. These included reports, sections and wireline logs from two offshore wells, more limited data from seven onshore wells, and samples from two offshore wells for biostratigraphic and geochemical analysis. Interpretation was carried out on 4,000 line-km of seismic data selected from a grid of 7,369 line-km of data. A series of horizons were identified or a regional basis, including the sea floor, approximate top of Mesozoic and intra-Tertiary unconformities. A bathymetric map, and structure-contour and interval isopach maps were prepared using digitized picks from the interpreted seismic. Examples of each of these interpreted results will be on display. The results show that Upper Jurassic and Upper Cretaceous units, and possibly Oligocene-Miocene units in the offshore, show potential for hydrocarbon generation. Hydrocarbons may have accumulated in largely sub-Oligocene reservoirs in traps related to syn-rift Oligocene and younger or pre-rift structures.

  15. Somali Current rings in the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Fratantoni, David M.; Bower, Amy S.; Johns, William E.; Peters, Hartmut

    2006-09-01

    New satellite-based observations reveal that westward translating anticyclonic rings are generated as a portion of the Somali Current accelerates northward through the Socotra Passage near the mouth of the Gulf of Aden. Rings thus formed exhibit azimuthal geostrophic velocities exceeding 50 cm/s, are comparable in overall diameter to the width of the Gulf of Aden (250 km), and translate westward into the gulf at 5-8 cm/s. Ring generation is most notable in satellite ocean color imagery in November immediately following the transition between southwest (boreal summer) and northeast (winter) monsoon regimes. The observed rings contain anomalous fluid within their core which reflects their origin in the equator-crossing Somali Current system. Estimates of Socotra Passage flow variability derived from satellite altimetry provide evidence for a similar ring generation process in May following the winter-to-summer monsoon transition. Cyclonic recirculation eddies are observed to spin up on the eastern flank of newly formed rings with the resulting vortex pair translating westward together. Recent shipboard and Lagrangian observations indicate that vortices of both sign have substantial vertical extent and may dominate the lateral circulation at all depths in the eastern Gulf of Aden.

  16. 33 CFR 165.837 - Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria, Texas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... regulations in 33 CFR part 165.23, no person or vessel may enter or remain in the zone described in paragraph... Docks, Victoria Barge Canal, Victoria, Texas. 165.837 Section 165.837 Navigation and Navigable Waters... Guard District § 165.837 Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria,...

  17. 33 CFR 165.837 - Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria, Texas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... regulations in 33 CFR part 165.23, no person or vessel may enter or remain in the zone described in paragraph... Docks, Victoria Barge Canal, Victoria, Texas. 165.837 Section 165.837 Navigation and Navigable Waters... Guard District § 165.837 Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria,...

  18. 33 CFR 165.837 - Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria, Texas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... regulations in 33 CFR part 165.23, no person or vessel may enter or remain in the zone described in paragraph... Docks, Victoria Barge Canal, Victoria, Texas. 165.837 Section 165.837 Navigation and Navigable Waters... Guard District § 165.837 Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria,...

  19. 33 CFR 165.837 - Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria, Texas.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... regulations in 33 CFR part 165.23, no person or vessel may enter or remain in the zone described in paragraph... Docks, Victoria Barge Canal, Victoria, Texas. 165.837 Section 165.837 Navigation and Navigable Waters... Guard District § 165.837 Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria,...

  20. 33 CFR 165.837 - Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria, Texas.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... regulations in 33 CFR part 165.23, no person or vessel may enter or remain in the zone described in paragraph... Docks, Victoria Barge Canal, Victoria, Texas. 165.837 Section 165.837 Navigation and Navigable Waters... Guard District § 165.837 Safety Zone; Invista Inc Facility Docks, Victoria Barge Canal, Victoria,...

  1. The Red Sea and Gulf of Aden Basins

    NASA Astrophysics Data System (ADS)

    Bosworth, William; Huchon, Philippe; McClay, Ken

    2005-10-01

    We here summarize the evolution of the greater Red Sea-Gulf of Aden rift system, which includes the Gulfs of Suez and Aqaba, the Red Sea and Gulf of Aden marine basins and their continental margins, and the Afar region. Plume related basaltic trap volcanism began in Ethiopia, NE Sudan (Derudeb), and SW Yemen at ˜31 Ma, followed by rhyolitic volcanism at ˜30 Ma. Volcanism thereafter spread northward to Harrats Sirat, Hadan, Ishara-Khirsat, and Ar Rahat in western Saudi Arabia. This early magmatism occurred without significant extension, and continued to ˜25 Ma. Much of the Red Sea and Gulf of Aden region was at or near sea level at this time. Starting between ˜29.9 and 28.7 Ma, marine syn-tectonic sediments were deposited on continental crust in the central Gulf of Aden. At the same time the Horn of Africa became emergent. By ˜27.5-23.8 Ma a small rift basin was forming in the Eritrean Red Sea. At approximately the same time (˜25 Ma), extension and rifting commenced within Afar itself. At ˜24 Ma, a new phase of volcanism, principally basaltic dikes but also layered gabbro and granophyre bodies, appeared nearly synchronously throughout the entire Red Sea, from Afar and Yemen to northern Egypt. This second phase of magmatism was accompanied in the Red Sea by strong rift-normal extension and deposition of syn-tectonic sediments, mostly of marine and marginal marine affinity. Sedimentary facies were laterally heterogeneous, being comprised of inter-fingering siliciclastics, evaporite, and carbonate. Throughout the Red Sea, the principal phase of rift shoulder uplift and rapid syn-rift subsidence followed shortly thereafter at ˜20 Ma. Water depths increased dramatically and sedimentation changed to predominantly Globigerina-rich marl and deepwater limestone. Within a few million years of its initiation in the mid-Oligocene the Gulf of Aden continental rift linked the Owen fracture zone (oceanic crust) with the Afar plume. The principal driving force for extension

  2. 78 FR 74216 - Aden Solutions, Inc.; Order of Suspension of Trading

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-10

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Aden Solutions, Inc.; Order of Suspension of Trading December 6, 2013. It appears to the... securities of Aden Solutions, Inc. The company has not filed any periodic reports since the period...

  3. Hepatitis E Infections, Victoria, Australia

    PubMed Central

    Adamopoulos, Jim; Carter, Karen; Kelly, Heath

    2005-01-01

    In the first half of 2004, acute hepatitis E virus infections diagnosed in Victoria, Australia, increased 7-fold. Of the interviewed patients with highly reactive serologic results, 90% reported recent clinically compatible illness and overseas travel. The increase is compared with a background of exposure in countries in which hepatitis E is endemic. PMID:15757573

  4. Red Sea/Gulf of Aden source rock geochemical evaluation

    SciTech Connect

    Ducreux, C.; Mathurin, G.; Latreille, M. )

    1991-08-01

    The potential of hydrogen generation in the Red Sea and Gulf of Aden was studied by geochemical analyses of 2,271 samples from 23 wells drilled in 6 countries within the area. Selection of candidate source beds was primarily a function of the sedimentary column penetrated by drilling (i.e., whereas sub-Tertiary sediments are accessible in Somalia and Yemen in the Gulf of Aden, sampling below the thick Neogene evaporitic sequence in the Red Sea could not be achieved due to a general lack of penetration to such levels). Organic matter content and type, maturity levels, petroleum potential of the rock analyzed, and its capacity to have generated liquid or gaseous hydrocarbons are the basic results provided by the analyses. Geochemical well correlations within and between subbasins are presented using the two most representative parameters: total organic carbon (TOC) and Petroleum Potential (PP = S{sub 1} + S{sub 2}), expressed in kilograms of hydrocarbons per ton of rock. In general, results obtained in the two rift basins, with sampling mostly in Neogene sediments in the Red Sea and in sub-Tertiary and Tertiary sediments in the Gulf of Aden, indicate the presence of favorable sources preferentially in this sub-Tertiary succession. It is stressed that geochemical analysis results are from wells whose locations are generally on structural highs and, therefore, are not representative (especially in terms of maturation) of conditions in adjacent depressions, particularly where the difference in structural level is great. Sound simulation modeling makes possible the reconstruction regional thermal and burial history and, thus, identification of maturation kitchens.

  5. Magnetic Anomaly Lineations in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Noguchi, Y.; Nakanishi, M.; Tamaki, K.; Fujimoto, H.; Huchon, P.; Leroy, S. D.; Styles, P.

    2014-12-01

    We present the magnetic anomaly lineations in the Gulf of Aden. The Gulf of Aden has slow spreading ridges between the Arabia Plate and Somalia Plate. The Arabian plate moves away from Somalia Plate in an NE direction, at a rate of about 2 cm/yr. Previous works indicates that seafloor spreading started about 20 Ma in the eastern part of the Gulf of Aden and propagated westward. The spreading axis has a E-W trend west of 46 E and that east of 46 E has a N60 W trend. We examined magnetic data acquired in the cruises by R/V L'Atalante in 1995, R/V Hakuho-maru from 2000 to 2001, R/V Maurice Ewing in 2001, and Shackleton in 1975 and 1979. We also used data obtained from National Geophysical Data Center, NOAA. We calculated magnetic anomalies using the latest Internation Geomagnetic Reference Field. Elongated negative magnetic anomalies, which amplitude are more than 500 nT, observed over the spreading centers. Most of the elongated anomalies are parallel with the spreading centers. The elongated magnetic anomalies west of 46 30'E have an E-W trend around the spreading centers. Several discontinuities in the magnetic anomaly contour map illustrate the position of the fracture zones concealed by sediments. We identified magnetic lineations from 43 E to 52 E. Most of magnetic lineations west and east of 46 30'E have N-E and N60-65 W strikes, respectively. The oldest lineations are C3r (5.48~5.74 Ma) between 43 10'E and 44 E and C5Ar (12.4~12.7 Ma) east of 44 E. Our identification of magnetic anomaly lineations indicates a symmetric seafloor spreading with a spreading rate of about 1.0 cm/yr, although Leroy et al. (2004) showed an asymmetric seafloor spreading of the Sheba Ridge, east of our study area. The kinematics of the Arabia plate changed about 5 Ma, but our results did not show any coeval change in spreading rates of the spreading system in the Gulf of Aden.

  6. sup 3 He and methane in the Gulf of Aden

    SciTech Connect

    Jean-Baptiste, P.; Alaux, G. ); Belviso, S.; Nguyen, B.C.; Mihalopoulos, N. )

    1990-01-01

    During the OCEAT cruise (July, 1987), the vertical and spatial distributions of {sup 3}He and methane were measured at six stations over the West Sheba Ridge (Gulf of Aden). The results show significant {delta}{sup 3}He anomalies (up to 49%). The authors conclude that the origin of this signal is independent from the well known Red Sea hydrothermal {sup 3}He (of the Red Sea Brines). Thus, active hydrothermalism occurs in this extensional basin associated with spreading along an incipient mid-ocean ridge. The {sup 3}He input from the Gulf of Aden accounts for the S-N positive gradient in {sup 3}He concentration observed in the western part of the Indian Ocean. Several methane anomalies are also present (up to 664 nl/l,i.e., 25 times the regional methane background), but the CH{sub 4} and {sup 3}He signals are not systematically correlated, suggesting complex production and consumption mechanisms of methane in these areas. The authors results confirm previous observations in the South West Pacific Ocean.

  7. Sudanese Gulf of Aden petroleum geology and regional geophysical evaluation

    SciTech Connect

    Osman, E.; Rahman, B.A.; Abdella, H.E.M.; Ali, A.O. )

    1991-08-01

    The World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project was organized to synthesize data on the Red Sea and Gulf of Aden basins. The primary objectives were to encourage increased hydrocarbon exploration activity within the project area by applying recent exploration techniques basin wide, and to train national geoscientists in exploration techniques. The study of the Sudanese Red Sea was based on public-domain exploration data, published information, and data released by operating companies. The results show that the Sudanese, Red Sea is similar to the better known, productive Gulf of Suez. In many respects, including the overall tectonic evolution, the structural style,a nd Miocene-to-Holocene stratigraphic sequence. A major difference involves the development of thick depocenters of Pliocene-Holocene super-evaporite sediments, in part controlled by offsets in the topographic rift shoulder of the basin, which result in large paleodrainage basins that supplied sediment to the basin. The sediments in these depocenters are thick enough, and geothermal gradients sufficiently high, to suggest the possibility of significant hydrocarbon generation in the depocenters. This is supported by important super-evaporite hydrocarbon shows in the Tokar Delta area of southern Sudanese Red Sea. Outside of the Pliocene-Holocene depocenters, conditions appear favorable for an attractive hydrocarbon potential in subevaporite units.

  8. Periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome.

    PubMed

    Ali, Nora S; Sartori-Valinotti, Julio C; Bruce, Alison J

    2016-01-01

    Periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome, the most common periodic disorder of childhood, presents with the cardinal symptoms of periodic fever, aphthous stomatitis, pharyngitis, and adenitis typically before age 5. This review presents the recent literature on PFAPA and summarizes key findings in the pathogenesis, evaluation, and treatment of the disease. Theories surrounding the pathogenesis of PFAPA include a faulty innate immunologic response in conjunction with dysregulated T-cell activation. A potential genetic link is also under consideration. Mediterranean fever (MEFV) gene variants have been implicated and appear to modify disease severity. In individuals with the heterozygous variant, PFAPA episodes are milder and shorter in duration. Diagnostic criteria include the traditional clinical signs, in addition to the following biomarkers: elevated C-reactive protein in the absence of elevated procalcitonin, vitamin D, CD64, mean corpuscular volume, and other nonspecific inflammatory mediators in the absence of an infectious explanation for fever. Treatment of PFAPA includes tonsillectomy, a single dose of corticosteroids, and, most recently, interleukin 1 blockers such as anakinra, rilonacept, and canakinumab. Tonsillectomy remains the only permanent treatment modality. PMID:27343963

  9. Degradation of Victoria Crater, Mars

    NASA Technical Reports Server (NTRS)

    Wilson, Sharon A.; Grant, John A.; Cohen, Barbara A.; Golombek, Mathew P.; Geissler, Paul E.; Sullivan, Robert J.; Kirk, Randolph L.; Parker, Timothy J.

    2008-01-01

    The $\\sim$750 m diameter and $\\sim$75 m deep Victoria crater in Meridiani Planum, Mars, presents evidence for significant degradation including a low, serrated, raised rim characterized by alternating alcoves and promontories, a surrounding low relief annulus, and a floor partially covered by dunes. The amount and processes of degradation responsible for the modified appearance of Victoria crater were evaluated using images obtained in situ by the Mars Exploration Rover Opportunity in concert with a digital elevation model created using orbital HiRISE images. Opportunity traversed along the north and northwest rim and annulus, but sufficiently characterized features visible in the DEM to enable detailed measurements of rim relief, ejecta thickness, and wall slopes around the entire degraded, primary impact structure. Victoria retains a 5 m raised rim consisting of 1-2 m of uplifted rocks overlain by 3 m of ejecta at the rim crest. The rim is $\\sim$120 to 220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine craters 500 to 750 m across indicate the original, pristine crater was close to 600 m in diameter. Hence, the crater has been erosionally widened by approximately 150 m and infilled by about 50 m of sediments. Eolian processes are responsible for modification at Victoria, but lesser contributions from mass wasting or other processes cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for $\\sim$50 m widening across a WNW-ESE diameter. The volume of material eroded from the crater walls and rim is $\\sim$20% less than the volume of sediments partially filling the crater, indicating eolian infilling from sources outside the crater over time. The annulus formed when $\\sim$1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped darker, regional

  10. Overview of Approach to 'Victoria'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Figure 1

    This image from the Mars Orbiter Camera aboard NASA's Mars Global Surveyor spacecraft shows an overview of 'Victoria Crater' and a portion of the area NASA's Mars Exploration Rover Opportunity has covered to reach the enormous depression.

    Images such as this one from the Mars Orbiter Camera on NASA's Mars Global Surveyor are helping scientists and engineers decide the best path for NASA's Mars Exploration Rover Opportunity as it approaches 'Victoria Crater.'

    In figure 1, a blue dot indicates 'Cape Verde' and a red dot 'Cabo Frio.' These two points mark the extent of the crater visible from the rover's position on its 945th Martian day, or sol (Sept. 20, 2006), a location it had reached two sols earlier and from which much of this monster depression was still out of sight. The green annotations indicate 'Duck Bay,' a location expected to allow a view to the other side of the crater. A dune, or ripple, is to the left of the crater, right in front of the green dot location. This is where the team initially talked about sending Opportunity for the rover's first view down into the crater. After further consideration, the team opted for a drive to the right of that ripple (south of the green dot) near the rim.

    The yellow lines that surround and intersect Victoria Crater are used to measure the crater and the distance to the far 'bays.' North is up. Victoria Crater is about 800 meters (half a mile) in diameter.

  11. Holocene Full-Vector Secular Variation from African Lakes

    NASA Astrophysics Data System (ADS)

    Lund, S.; Platzman, E. S.; Johnson, T. C.; Scholz, C. A.; Cohen, A. S.; Russell, J. M.

    2014-12-01

    We are developing a regional pattern of Holocene paleomagnetic secular variation (PSV) from four lakes in East Africa - Lake Turkana (3°N), Lake Victoria (1°S), Lake Tanganyika (5°S), and Lake Malawi (10°S). Detailed paleomagnetic and rock magnetic measurements have been made on two cores from Lake Malawi (9m meters in depth, last ~10,000 years), two cores from Lake Victoria (8 m, last ~8,000 years), 11 cores from Lake Turkana (2-9 m, last ~10,000 years), and one core from Lake Tanganyika (5 m, last ~5,000 years). Our rock magnetic studies identify significant intervals of magnetic mineral dissolution in Lakes Victoria and Tanganyika making parts of these cores unsuitable for relative paleointensity studies. On the other hand, rock magnetic variability in the Lake Malawi and Lake Turkana cores are stable and correlatable among cores. We have recovered directional secular variation records from Lakes Malawi, Victoria, and Turkana. Millennial-scale inclination and declination features can be correlated among cores at each lake and between lakes. We have also recovered relative paleointensity records from Lakes Malawi and Turkana. More than 20 radiocarbon dates and detailed seismic stratigraphy (Turkana) provide critical added information for correlating and dating the paleomagnetic records.

  12. Altitude testing of the 2D V/STOL ADEN demonstrator on an F404 engine

    NASA Technical Reports Server (NTRS)

    Blozy, J. T.

    1985-01-01

    The Augmented Deflector Exhaust Nozzle (ADEN) exhaust system was tested in the PSL-3 altitude chamber at the NASA Lewis Research Center in order to evaluate aerodynamic performance, cooling-system effectiveness, and mechanical operation at flight-type conditions. The ADEN, a flight-weight, two-dimensional, thrust-vectoring nozzle, was successfully tested on the F404 engine using a remote engine control system for automatic or manual setting of the throat-area control and available fan air for the nozzle internal cooling system. Throughout the test, the ADEN performed with no adverse effects on the engine or augmentor operation.

  13. Rifting to spreading in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, S.; Razin, P.; Lucazeau, F.; D'Acremont, E.; Autin, J.; Watremez, L.; Robinet, J.; Baurion, C.

    2011-12-01

    The Gulf of Aden margins systems are volcanic to the West, where they are influenced by the Afar hotspot, and non-volcanic East of longitude 46°E. The combined use of magnetics, gravity, seismic reflection, field observations (tectonic and sedimentological) allowed us to obtain better constraints on the timing of continental rifting and seafloor spreading. From the Permo-Triassic to the Oligocene, the Arabian-African plate was subject to distributed extension, probably due, at least from the Cretaceous, to tensile stresses related to the subduction of the Tethysian slab in the north. In Late Eocene, 35 Ma ago, rifting started to localize along the future area of continental breakup. Initially guided by the inherited basins, continental rifting then occurred synchronously over the entire gulf before becoming localized on the northern and southern borders of the inherited grabens, in the direction of the Afar hot-spot. In the areas with non-volcanic margins (in the East), the faults marking the end of rifting trend parallel to the inherited grabens. Only the transfer faults cross-cut the inherited grabens, and some of these faults later developed into transform faults. The most important of these transform faults follow a Precambrian trend. Volcanic margins were formed in the West of the Gulf, up to the Guban graben in the south-east and as far as the southern boundary of the Bahlaf graben in the North-East. Seaward dipping reflectors (SDRs) can be observed on many oil-industry seismic profiles. The influence of the hotspot during rifting was concentrated on the western part of the gulf. Therefore, it seems that the western domain was uplifted and eroded at the onset of rifting, while the eastern domain was characterized by more continuous sedimentation. The phase of distributed deformation was followed by a phase of strain localization during the final rifting stage, just before formation of the Ocean-Continent Transition (OCT), in the most distal graben (DIM

  14. 'Victoria Crater' from 'Duck Bay'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria Crater' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the crater. The rover's navigation camera took the seven exposures combined into this mosaic view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    The far side of the crater is about 800 meters (one-half mile) away. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves, such as Duck Bay. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the crater walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission.

    This view is presented as a cylindrical projection with geometric seam correction.

  15. Hotspot-ridge interaction in the Gulf of Aden, East Africa

    NASA Astrophysics Data System (ADS)

    Tamaki, K.; Fujimoto, H.; Orihashi, Y.; Nakanishi, M.; Huchon, P.

    2001-12-01

    We have conducted a mapping and sampling cruise at the Gulf of Aden along its spreading axis by Aden New Century Cruise (R/V Hakuho-maru, Dec. 2000 - Jan. 2001). The mapping was done by SeaBeam 2120 with gravity and magnetics from 45.5 degree E to 50.5 degree E that occupies the main part of the Gulf of Aden. The obtained data shows the first and clear detailed bathymetry of the spreading system of the Gulf of Aden. The data were jointly analyzed with the bathymetric data at the Tadjoura Rift at the western end of the Gulf of Aden that was obtained by a French Tadjouraden cruise in 1995. The spreading system in the Gulf of Aden is characterized with an oblique and ultraslow spreading system (2.0 cm/y for full rate with N30E direction between Arabia and Africa plates). To the east from 46 deg 20 min E, the spreading system exhibits ridge-transform system with the lengths of each segment with 30 to 60 km. To the west from 46 deg 20 min East, E-W trending Tadjoura Rift is well developed with distinct en-echelon structures in the rift. In the easternmost part of Tadjoura Rift at 45 deg 35 min E we observed shallow peaked twin mountains (Aden New Century Mountains) along the central axis of the rift with the summit depth of 500m. We recovered fresh basaltic lavas from the mountain and the mountains are surrounded by many small volcanic knolls. Based on along-axis bottom rock sampling during the cruise with the compilation of Shilling et al. (1992) data, the Aden New Century Mountains zone shows highly positive anomaly of La/Sm REE anomaly suggesting deep mantle source and we temporarily calls the volcanic zone, the Aden New Century Hotspot. Along-axis profile of bathymetry and La/Sm REE anomaly displays typical pattern of hotspot-ridge interaction with the shallowing of each segment toward the hotspot as well as the increasing geochemical anomalies. Horizontal view of the ridge-transform pattern shows increasing distortion toward the hotspot. The case of hotspot

  16. Degradation of Victoria crater, Mars

    USGS Publications Warehouse

    Grant, J. A.; Wilson, S.A.; Cohen, B. A.; Golombek, M.P.; Geissler, P.E.; Sullivan, R.J.; Kirk, R.L.; Parker, T.J.

    2008-01-01

    The ???750 m diameter and ???75 m deep Victoria crater in Meridiani Planum, Mars, is a degraded primary impact structure retaining a ???5 m raised rim consisting of 1-2 m of uplifted rocks overlain by ???3 m of ejecta at the rim crest. The rim is 120-220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine craters 500-750 m across indicates that the original, pristine crater was close to 600 m in diameter. Hence, the crater has been erosionally widened by ???150 m and infilled by ???50 m of sediments. Eolian processes are responsible for most crater modification, but lesser mass wasting or gully activity contributions cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for ???50 m widening across a WNW-ESE diameter. The volume of material eroded from the crater walls and rim is ???20% less than the volume of sediments partially filling the crater, indicating eolian infilling from sources outside the crater over time. The annulus formed when ???1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped <10-20 cm of darker, regional basaltic sands. Greater relief along the rim enabled meters of erosion. Comparison between Victoria and regional craters leads to definition of a crater degradation sequence dominated by eolian erosion and infilling over time. Copyright 2008 by the American Geophysical Union.

  17. 'Lyell' Panorama inside Victoria Crater

    NASA Technical Reports Server (NTRS)

    2008-01-01

    During four months prior to the fourth anniversary of its landing on Mars, NASA's Mars Exploration Rover Opportunity examined rocks inside an alcove called 'Duck Bay' in the western portion of Victoria Crater. The main body of the crater appears in the upper right of this stereo panorama, with the far side of the crater lying about 800 meters (half a mile) away. Bracketing that part of the view are two promontories on the crater's rim at either side of Duck Bay. They are 'Cape Verde,' about 6 meters (20 feet) tall, on the left, and 'Cabo Frio,' about 15 meters (50 feet) tall, on the right. The rest of the image, other than sky and portions of the rover, is ground within Duck Bay.

    Opportunity's targets of study during the last quarter of 2007 were rock layers within a band exposed around the interior of the crater, about 6 meters (20 feet) from the rim. Bright rocks within the band are visible in the foreground of the panorama. The rover science team assigned informal names to three subdivisions of the band: 'Steno,' 'Smith,' and 'Lyell.'

    This view combines many images taken by Opportunity's panoramic camera (Pancam) from the 1,332nd through 1,379th Martian days, or sols, of the mission (Oct. 23 to Dec. 11, 2007). Images taken through Pancam filters centered on wavelengths of 753 nanometers, 535 nanometers and 432 nanometers were mixed to produce an approximately true-color panorama. Some visible patterns in dark and light tones are the result of combining frames that were affected by dust on the front sapphire window of the rover's camera.

    Opportunity landed on Jan. 25, 2004, Universal Time, (Jan. 24, Pacific Time) inside a much smaller crater about 6 kilometers (4 miles) north of Victoria Crater, to begin a surface mission designed to last 3 months and drive about 600 meters (0.4 mile).

  18. Measles surveillance in Victoria, Australia.

    PubMed Central

    Wang, Yung-Hsuan J.; Andrews, Ross M.; Lambert, Stephen B.

    2006-01-01

    OBJECTIVE: Many countries are implementing measles elimination strategies. In Australia, the State of Victoria has conducted enhanced measles surveillance since 1997 using case interviews and home-based specimen collection for laboratory confirmation. We attempted to identify features of notified cases that would better target surveillance resources. METHODS: We retrospectively classified notifications received from 1998 to 2003 as having been received in an epidemic (one or more laboratory-confirmed cases) or an interepidemic period (no laboratory-confirmed cases). We labelled the first case notified in any epidemic period that was not laboratory-confirmed at the time of notification as a "sentinel case". To maximize detection of sentinel cases while minimizing the follow-up of eventually discarded notifications, we generated algorithms using sentinel cases and interepidemic notifications. FINDINGS: We identified 10 sentinel cases with 422 interepidemic notifications from 1281 Victorian notifications. Sentinel cases were more likely to report fever at rash onset (odds ratio (OR) 15.7, 95% confidence interval (CI) CI: 2.1-688.9), cough (OR 10.4, 95% CI: 1.4-456.7), conjunctivitis (OR 7.9, 95% CI: 1.8-39.1), or year of birth between 1968 and 1981 (OR 31.8, 95% CI: 6.7-162.3). Prospective application of an algorithm consisting of fever at rash onset or born between 1968 and 1981 in the review period would have detected all sentinel cases and avoided the need for enhanced follow-up of 162 of the 422 eventually discarded notifications. CONCLUSION: Elimination strategies should be refined to suit regional and local priorities. The prospective application of an algorithm in Victoria is likely to reduce enhanced measles surveillance resource use in interepidemic periods, while still detecting early cases during measles outbreaks. PMID:16501727

  19. Uppermost mantle velocity from Pn tomography in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Corbeau, Jordane; Rolandone, Frédérique; Leroy, Sylvie; Al-Lazki, Ali; Keir, Derek; Stuart, Graham; Stork, Anna

    2013-04-01

    We present an analysis of Pn traveltimes to determine lateral variations of velocity in the uppermost mantle and crustal thickness beneath the Gulf of Aden and its margins. No detailed tomographic image of the entire Gulf of Aden was available. Previous tomographic studies covered the eastern Gulf of Aden and were thus incomplete or at a large scale with a too low resolution to see the lithospheric structures. From 1990 to 2010, 49206 Pn arrivals were selected from the International Seismological Center catalogue. We also used temporary networks : YOCMAL (Young Conjugate Margins Laboratory) networks with broadband stations located in Oman, Yemen and Socotra from 2003 to 2011, and Djibouti network from 2009 to 2011. From these networks we picked Pn arrivals and selected 4110 rays. Using a least-squares tomographic code (Hearn, 1996), these data were analyzed to solve for velocity variations in the mantle lithosphere. We perform different inversions for shorter and longer ray path data sets in order to separate the shallow and deep structure within the mantle lid. In the upper lid, zones of low velocity (7.7 km/s) around Sanaa, Aden, Afar, and along the Gulf of Aden are related to active volcanism. Off-axis volcanism and a regional melting anomaly in the Gulf of Aden area may be connected to the Afar plume, and explained by the model of channeling material away from the Afar plume along ridge-axis. Our study validates the channeling model and shows that the influence of the Afar hotspot may extend much farther eastwards along the Aden and Sheba ridges into the Gulf of Aden than previously believed. Still in the upper lid, high Pn velocities (>8,2 km/s) are observed in Yemen and may be related to the presence of a magmatic underplating under the volcanic margin of Aden and under the Red Sea margins. In the lower lid, zones of low velocities are spatially located differently than in the upper lid. On the Oman margin, a low velocity zone (7.6 km/s) suggests deep partial

  20. Neutrophilic sebaceous adenitis with intralobular Demodex mites: a case report and review of the literature.

    PubMed

    Liaqat, Maryam; Wilson, Lindsay H; Wada, David; Florell, Scott R; Bowen, Anneli R

    2015-04-01

    A 61-year-old white man presented with a 1-week history of an asymptomatic erythematous, annular plaque with minimal scale limited to the nasal bridge. Histological examination showed a mixed infiltrate of lymphocytes and neutrophils within sebaceous glands. The clinical and histopathological presentation was consistent with a diagnosis of neutrophilic sebaceous adenitis. Several Demodex brevis mites were present deep within the affected sebaceous lobules. Demodex brevis mites are uncommon inhabitants of sebaceous glands of the nose, presenting more commonly on other body sites. The cause of neutrophilic sebaceous adenitis is unknown, but the presence of D. brevis in affected sebaceous glands in this case suggests a possible association. PMID:25229566

  1. Arabia-Somalia plate kinematics, evolution of the Aden-Owen-Carlsberg triple junction, and opening of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Fournier, Marc; Chamot-Rooke, Nicolas; Petit, Carole; Huchon, Philippe; Al-Kathiri, Ali; Audin, Laurence; Beslier, Marie-Odile; D'Acremont, Elia; Fabbri, Olivier; Fleury, Jean-Marc; Khanbari, Khaled; Lepvrier, Claude; Leroy, Sylvie; Maillot, Bertrand; Merkouriev, Serge

    2010-04-01

    New geophysical data collected at the Aden-Owen-Carlsberg (AOC) triple junction between the Arabia, India, and Somalia plates are combined with all available magnetic data across the Gulf of Aden to determine the detailed Arabia-Somalia plate kinematics over the past 20 Myr. We reconstruct the history of opening of the Gulf of Aden, including the penetration of the Sheba Ridge into the African continent and the evolution of the triple junction since its formation. Magnetic data evidence three stages of ridge propagation from east to west. Seafloor spreading initiated ˜20 Myr ago along a 200 km-long ridge portion located immediately west of the Owen fracture zone. A second 500 km-long ridge portion developed westward up to the Alula-Fartak transform fault before Chron 5D (17.5 Ma). Before Chron 5C (16.0 Ma), a third 700 km-long ridge portion was emplaced between the Alula-Fartak transform fault and the western end of the Gulf of Aden (45°E). Between 20 and 16 Ma, the Sheba Ridge propagated over a distance of 1400 km at an extremely fast average rate of 35 cm yr-1. The ridge propagation resulted from the Arabia-Somalia rigid plate rotation about a stationary pole. Since Chron 5C (16.0 Ma), the spreading rate of the Sheba Ridge decreased first rapidly until 10 Ma and then more slowly. The evolution of the AOC triple junction is marked by a change of configuration around 10 Ma, with the formation of a new Arabia-India plate boundary. Part of the Arabian plate was then transferred to the Indian plate.

  2. Scientific Diving Training Course. Red Sea & Gulf of Aden Programme (PERSGA).

    ERIC Educational Resources Information Center

    Arab Organization for Education and Science, Cairo (Egypt).

    This document presents the scientific diving training course organized by the Arab League Educational, Cultural and Scientific Organization (ALECSO) for the Program for Environmental Studies, Red Sea and Gulf of Aden (PERSGA). This course of six weeks duration aims to produce a person who is capable of carrying out scientific diving tasks in the…

  3. Opportunity at Work Inside Victoria Crater

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA Mars Exploration Rover Opportunity used its front hazard-identification camera to capture this wide-angle view of its robotic arm extended to a rock in a bright-toned layer inside Victoria Crater.

    The image was taken during the rover's 1,322nd Martian day, or sol (Oct. 13, 2007).

    Victoria Crater has a scalloped shape of alternating alcoves and promontories around the crater's circumference. Opportunity descended into the crater two weeks earlier, within an alcove called 'Duck Bay.' Counterclockwise around the rim, just to the right of the arm in this image, is a promontory called 'Cabo Frio.'

  4. Yemeni Red Sea and Gulf of Aden petroleum geology and regional geophysical evaluation

    SciTech Connect

    Al-Sanabani, M.; Said, F.M. )

    1991-08-01

    The World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project was organized to synthesize data on the Red Sea and Gulf of Aden basins. The study of Yemeni Red Sea and Gulf of Aden was based on public-domain exploration data, published information, and data released by operating companies. These included reports, sections, and wireline logs from 15 well, samples from 15 wells for biostratigraphic analysis, and samples from 11 wells for geochemical analysis. Interpretation was carried out on 7,419 line-km of seismic data selected from a grid of 21,623 line-km of data. Four horizons were identified on a regional basis in the Red Sea area, including the sea floor, top, and near base of middle to upper Miocene evaporites, and approximate acoustic basement, as well as equivalent series in the Gulf of Aden. Bathymetric, structure-contour, and interval isopach maps were prepared using digitized picks from the interpreted seismic. Examples of each of these interpreted results will be on display. The results show that the Yemeni Red Sea is similar to the better known, productive Gulf of Suez in its tectonic evolution, and in its Miocene to Holocene stratigraphic sequence. Surface shows on the east side of the southern Red Sea in the Yemeni part of the basin suggest that this area contain the necessary elements for several attractive petroleum plays. The Yemeni Red Sea appears to contain the necessary elements for an attractive petroleum potential. The Yemeni Gulf of Aden, on the other hand, shows an attractive potential chiefly in pre-rift Mesozoic to Eocene units, with more limited potential in Oligocene to younger units.

  5. Red Sea and Gulf of Aden petroleum geology and regional geophysical evaluation

    SciTech Connect

    Sikander, A.H. ); Allen, R.B. ); Abouzakhm, A.G.

    1991-08-01

    The World Bank-executed Red Sea/Gulf of Aden Regional Hydrocarbon Study Project was organized to synthesize data on the Red Sea and Gulf of Aden basins. The primary objectives were to encourage increased hydrocarbon exploration activity within the project area by applying recent exploration techniques basin wide, and to train national geoscientists in exploration techniques. The study was based on public-domain exploration data, published information, and data released by operating companies. This included reports, sections, and wireline logs from most of the offshore wells, and samples for biostratigraphic and geochemical analysis. Interpretation was carried out on seismic data selected from basinwide grids. Four horizons were identified on a regional basis in the Red Sea, including the sea floor, top, and near base of middle to upper Miocene evaporite, and approximate acoustic basement, and an equivalent of horizons were identified in the Gulf of Aden. The results of the syntheses show that the hydrocarbon potential of the Red Sea and Gulf of Aden is variable. The Red Sea shows an attractive potential in much of the basin in Miocene to Holocene synrift to post-rift units. This may locally include either lower to middle Miocene sub-evaporite syn-rift units or Pliocene to Holocene superrift units, depending on variations in structural development and sedimentation and thermal history. In addition, sub-rift units of Mesozoic to Paleogene age show an attractive potential in some areas. The primary potential in the Gulf of Aden, on the other hand, may be in Mesozoic to Eocene sub-rift units, with only limited potential in Oligocene and younger units.

  6. 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.

  7. Looking Forward: Community Gateways at Victoria University

    ERIC Educational Resources Information Center

    Mountford, Christine

    2011-01-01

    The mission and values of Victoria University provide the underlying criteria for the development and implementation of the Community Gateways initiative, which aims to transform the lives of those living in the west of Melbourne through the power of further education. Community Gateways takes the university into the community by providing career…

  8. Geography and Geographical Education in Victoria

    ERIC Educational Resources Information Center

    Kriewaldt, Jeana

    2006-01-01

    Victoria has just emerged from 10 years where Geography has been one of three strands in the key learning area of Studies of Society and Environment (SOSE). The overarching framework emerged from an attempt to develop a national curriculum. Whilst the national curriculum was rejected by Australian state and territories who each hold legislative…

  9. Crustal Structure of the Gulf of Aden Continental Margins, from Afar to Oman, by Ambient Noise Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Korostelev, F.; Weemstra, C.; Boschi, L.; Leroy, S. D.; Ren, Y.; Stuart, G. W.; Keir, D.; Rolandone, F.; Ahmed, A.; Al Ganad, I.; Khanbari, K. M.; Doubre, C.; Hammond, J. O. S.; Kendall, J. M.

    2014-12-01

    Continental rupture processes under mantle plume influence are still poorly known although extensively studied. The Gulf of Aden presents volcanic margins to the west, where they are influenced by the Afar hotspot, and non volcanic margins east of longitude 46° E. We imaged the crustal structure of the Gulf of Aden continental margins from Afar to Oman to evaluate the role of the Afar plume on the evolution of the passive margin and its extent towards the East. We use Ambient Noise Seismic Tomography to better understand the architecture and processes along the Gulf of Aden. This recent method, developed in the last decade, allows us to study the seismic signal propagating between two seismic stations. Ambient Noise Seismic Tomography is thus free from artifacts related to the distribution of earthquakes. We collected continuous records from about 200 permanent or temporary stations since 1999 to compute Rayleigh phase velocity maps over the Gulf of Aden.

  10. Arabia-Somalia plate kinematics and the opening of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Fournier, M.; Chamot-Rooke, N.; Patriat, P.; Petit, C.; Huchon, P.

    2009-04-01

    New geophysical data collected at the Aden-Owen-Carlsberg triple junction (AOC survey) between the Arabia, India, and Somalia plates are combined with all available magnetic data across the Gulf of Aden and the NW Arabian Sea to determine the detailed Arabia-Somalia plate kinematics over the past 20 Myr. We reconstruct the history of opening of the Gulf of Aden, including the penetration of the Sheba Ridge into the African continent and the evolution of the triple junction since its formation. Ridge propagation occurred in three stages from east to west. Sea-floor spreading between the Arabia and Somalia plates initiated ca. 20 Myr ago, shortly before Chron 6 (19.7 Ma), along a 200 km long ridge portion located immediately west of the Owen fracture zone and southeast of the Socotra Island. A second 500 km long ridge portion developed westward up to the Alula-Fartak transform fault before Chron 5D (17.2 Ma). About 1 Myr later and before Chron 5C (16.0 Ma), a third 700 km long ridge portion was emplaced between the Alula-Fartak transform fault and the western end of the Gulf of Aden (45°E). Within a short time period bracketed between 20 and 16 Ma, the Sheba Ridge propagated into the Gulf of Aden over a distance of 1400 km at an extremely fast average rate of 35 cm yr 1. The ridge propagation resulted from the Arabia-Somalia rigid plate rotation about a relatively stationary pole located to the northwest of the Gulf of Aden. Since Chron 5C (16.0 Ma), the spreading rate of the Sheba Ridge decreased first rapidly until 10 Ma and then more slowly. Opening rate may still be slightly decreasing, although not as much as recently inferred from geodesy. The evolution of the Arabia-India-Somalia triple junction is marked by a major change of configuration around 10 Ma, with the formation of a new Arabia-India plate boundary including the newly discovered Beautemps-Beaupré Basin. Part of the Arabian plate was then transferred to the Indian plate. Reconstructions of the

  11. Thermocline Regulated Seasonal Evolution of Surface Chlorophyll in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Hoteit, Ibrahim; Yao, Fengchao

    2015-04-01

    The Gulf of Aden, although subject to seasonally reversing monsoonal winds, has been previously reported as an oligotrophic basin during summer, with elevated chlorophyll concentrations only occurring during winter due to convective mixing. However, the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data reveal that the Gulf of Aden also exhibits a prominent summer chlorophyll bloom and sustains elevated chlorophyll concentrations throughout the fall, and is a biophysical province distinct from the adjacent Arabian Sea. Climatological hydrographic data suggest that the thermocline, hence the nutricline, in the entire gulf is markedly shoaled by the southwest monsoon during summer and fall. Under this condition, cyclonic eddies in the gulf can effectively pump deep nutrients to the surface layer and lead to the chlorophyll bloom in late summer, and, after the transition to the northeast monsoon in fall, coastal upwelling driven by the northeasterly winds produces a pronounced increase in surface chlorophyll concentrations along the Somali coast.

  12. Crossing the Gulf of Aden: cutaneous infections in African migrant shipwreck survivors.

    PubMed

    Simon, Fabrice; Gautret, Philippe; Nicolas, Xavier; Ausset, Philippe; De Pina, Jean-Jacques; Demortière, Eric

    2013-01-01

    Skin and soft tissue infections were observed in migrants from Somalia who crossed the Gulf of Aden, crowded on a drifting boat for 14 days. Thirty-three percent of survivors of this hazardous journey had skin infections. Seven were hospitalized for severe Staphylococcus aureus cutaneous infections associated with intracellular dehydration. Migrants face infectious risks during their precarious travel, including severe cutaneous infections that require specific medical and surgical treatment by the emergency services. PMID:23911893

  13. Variations in Shear Wave Splitting Beneath Southern Arabia and the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Gallacher, R. J.; Eakin, C. M.; Keir, D.; Leroy, S. D.; Stuart, G. W.; Harmon, N.; Ahmed, A.

    2015-12-01

    Mantle flow beneath Southern Arabia and the Gulf of Aden remains enigmatic due to a paucity of seismic measurements in the region. Potential processes contributing to mantle flow include northward progression of the African Superplume, radial flow from the Afar plume and vertical flow from small-scale convection along the margins of the Gulf of Aden. These would result in characteristic mantle flow directions, creating mantle anisotropy that can be detected by shear wave splitting. We analyse SKS, SKKS & PKS phases for shear wave splitting at 141 stations deployed throughout Yemen, Oman and Socotra along the margins of the Gulf of Aden. Large numbers of null measurements from a range of back azimuths are found beneath the entire region. These may indicate that vertical anisotropy is present in the upper mantle beneath the region, consistent with models of small-scale convection. The null measurements may also be due to complicated layering of crustal anisotropy interfering destructively and precluding measurement of shear wave splitting. Splitting measurements bordering the Red Sea show North-South orientations that may result from shallow aligned melt along the Red Sea or from variations in lower mantle flow. Fast polarization directions of splitting measurements along the Northern margin of the Gulf of Aden are rift parallel suggesting a shallow source such as rift related faulting might be responsible. These results show that anisotropy beneath the region is not controlled by the northward progression of the African Superplume or radial flow from the Afar plume. Upper mantle flow is likely vertical with splitting occurring either in the crust or the lower mantle.

  14. Seismic structure of the northern margin of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Basuyau, C.; Tiberi, C.; Leroy, S.; Keir, D.; Stuart, G. W.; Ebinger, C. J.; Al-Lazki, A. I.; Al Toubi, K.; Ahmed, H.; Al-Ganad, I.; D'Acremont, E.; Rolandone, F.; Lucazeau, F.

    2009-12-01

    In 2003 and 2005, two temporary seismological networks allowed to image the lithospheric structure of the northern margin of the Gulf of Aden in the Dhofar area (Sultanate of Oman). The most striking result from these studies is certainly the presence of two very low velocity zones between 60 and 200 km depth, where partial melt most probably happens. Even though the margins are expected to be non-volcanic there, some recent works show quaternary volcanic activity in the reagion. Each of these areas is located on the alignment of a main fracture zone: Socotra and Alula-Fartak. Yet, despite good lateral resolution, we are unable to faithfully determine the depth extent of these low velocity zones, their timing and their relation with the Aden ridge and/or the Afar plume. In order to fulfil our understanding of this particularly complex area, we deployed 50 broadband instruments in Yemen in March 2009. The stations are organized in three profiles roughly perpendicular to the main tectonics features, and located in west, central and east Yemen. This new study should help answering key questions: (1) Do similar melting zones extend in the western (volcanic) part of the Gulf of Aden? (2) Is there a difference in the lithospheric structure between the volcanic and non-volcanic part of the Gulf? (3) What is the influence of the Afar plume on the lithosphere of the Arabian Plate and how far can we follow it?

  15. 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.

  16. 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.

  17. Recent off-axis volcanism in the eastern Gulf of Aden: Implications for plume-ridge interaction

    NASA Astrophysics Data System (ADS)

    Leroy, Sylvie; d'Acremont, Elia; Tiberi, Christel; Basuyau, Clémence; Autin, Julia; Lucazeau, Francis; Sloan, Heather

    2010-04-01

    Evidence of anomalous volcanism is readily observed in the Gulf of Aden, although, much of this oceanic basin remains as yet unmapped. In this paper, we investigate the possible connection of the Afar hotspot with a major off-axis volcanic structure and its interpretation as a consequence of a the anomalous presence of melt by integrating several data sets, both published and unpublished, from the Encens-Sheba cruise, the Aden New Century (ANC) cruise and several other onshore and marine surveys. These include bathymetric, gravity, magnetic, magneto-telluric data, and rock samples. Based upon these observations, interpretations were made of seafloor morphology, gravity and magnetic models, seafloor age, geochemical analyses and tectonic setting. We discuss the possible existence of a regional melting anomaly in the Gulf of Aden area and of the probability of its connection to the Afar plume. Several models that might explain the anomalous volcanism are taken into account, such as a local melting anomaly unrelated to the Afar plume, an anomalously large volume of melt associated with seafloor spreading, and interaction of the ridge with the Afar plume. A local melting anomaly and atypical seafloor spreading prove inconsistent with our observations. Two previously proposed models of plume-ridge interactions are examined: the diffuse plume dispersion called pancaked flow and channelized along-axis flow. We conclude that the configuration and structure of this young ocean basin may have the effect of channeling material away from the Afar plume along the Aden and Sheba Ridges to produce the off-axis volcanism observed on the ridge flanks. This interpretation implies that the influence of the Afar hotspot may extend much farther eastwards into the Gulf of Aden than previously believed. The segmentation of the Gulf of Aden and the configuration of the Aden-Sheba system may provide a potential opportunity to study channeled flow of solid plume mantle from the plume along

  18. 'Victoria Crater' from 'Duck Bay' (Stereo)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Figure 1

    [figure removed for brevity, see original site] Figure 2

    NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria Crater' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the crater. The rover's navigation camera took the seven exposures combined into this mosaic view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    The far side of the crater is about 800 meters (one-half mile) away. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves, such as Duck Bay. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the crater walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission.

    The stereo-anaglyph view presented here is a cylindrical projection with geometric seam correction.

  19. 'Victoria Crater' from 'Duck Bay' (Polar Projection)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria Crater' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the crater. The rover's navigation camera took the seven exposures combined into this mosaic view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    The far side of the crater is about 800 meters (one-half mile) away. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves, such as Duck Bay. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the crater walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission.

    This view is presented as a polar projection with geometric seam correction.

  20. 'Victoria Crater' from 'Duck Bay' (Vertical Projection)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity edged 3.7 meters (12 feet) closer to the top of the 'Duck Bay' alcove along the rim of 'Victoria Crater' during the rover's 952nd Martian day, or sol (overnight Sept. 27 to Sept. 28), and gained this vista of the crater. The rover's navigation camera took the seven exposures combined into this mosaic view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    The far side of the crater is about 800 meters (one-half mile) away. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves, such as Duck Bay. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind. The rocky cliffs in the foreground have been informally named 'Cape Verde,' on the left, and 'Cabo Frio,' on the right.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is an expectation that the thick stack of geological layers exposed in the crater walls could reveal the record of past environmental conditions over a much greater span of time than Opportunity has read from rocks examined earlier in the mission.

    This view is presented as a vertical projection with geometric seam correction.

  1. Factors influencing birth control habits in Victoria.

    PubMed

    Selwood, T; Leeton, J

    1981-02-01

    A survey was conducted in March 1978 for the purpose of comparing the contraceptive habits of Melbourne and ex-Melbourne populations in Victoria. Of the 1312 records of sexually active persons collected in 1978, 1254 of those persons were between the ages of 15 and 49. Recorded information included age, sex, marital status, and place of domicile (Melbourne or ex-Melbourne, Victoria). When the Melbourne population was compared with the rest of Victoria, the proportion using each method of contraception was much the same for each group. A marked difference was the proportion using withdrawal in Melbourne; this was over 3 times the proportion among the ex-Melbourne population. Over 35% of persons under age 30 used oral contraceptives (OCs), compared with 24.2 in the over 30 age range. Barrier methods and natural family planning methods and withdrawal were commonly used by the older age groups. A large proportion of the over age 30 group used sterilization and hysterectomy as forms of birth control. Individuals in "de facto" relationships showed a tendency towards more reliable forms of contraception than did other groups. Only 20.3% were not using some form of contraception. Single persons were frequent OC users and users of barrier methods. 28.1% used no form of contraception. The sex of the person interviewed in the survey revealed a bias. Males tended to report male birth control methods and female reported female methods rather than those used by partners of the opposite sex. Marital status influenced birth control choice. The choice of birth control for each marital status was influenced by the confounding factor of mean age of each group. PMID:7247847

  2. 'Victoria' After Sol 950 Drive (Stereo)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Left-eye view of a stereo pair for PIA08778

    [figure removed for brevity, see original site] Right-eye view of a stereo pair for PIA08778 [figure removed for brevity, see original site] Cylindrical view for PIA08778

    A drive of about 30 meters (about 100 feet) on the 950th Martian day, or sol, of Opportunity's exploration of Mars' Meridiani Planum region (Sept. 25, 2006) brought the NASA rover to within about 20 meters (about 66 feet) of the rim of 'Victoria Crater.' From that position, the rover's navigation camera took the exposures combined into this stereo anaglyph, which appears three-dimensional when viewed through red-green glasses. The scalloped shape of the crater is visible on the left edge. Due to a small dune or ripple close to the nearest part of the rim, the scientists and engineers on the rover team planned on sol 951 to drive to the right of the ripple, but not quite all the way to the rim, then to proceed to the rim the following sol. The image is presented in cylindrical projection with geometric seam correction.

    Victoria Crater is about 800 meters (one-half mile) in diameter, about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed. The great lure of Victoria is the expectation that a thick stack of geological layers will be exposed in the crater walls, potentially several times the thickness that was previously studied at Endurance and therefore, potentially preserving several times the historical record.

  3. Ogaden Basin subsidence history: Another key to the Red Sea-Gulf of Aden tectonic puzzle

    SciTech Connect

    Pigott, J.D.; Neese, D.; Carsten, G.

    1995-08-01

    Previous work has attempted to understand the tectonic evolution of the Red Sea-Gulf of Aden region through a focus upon plate kinematics and reconstruction of plate interactions in a two dimensional sense. A significant complement to the three dimensional puzzle can be derived from a critical examination of the vertical component, tectonic subsidence analysis. By removing the isostatic contributions of sediment loading and unloading, and fluctuations in sea level, the remaining thermal-mechanical contribution to a basin`s subsidence can be determined. Such an analysis of several Ogaden Basin wells reveals multiple pulses of tectonic subsidence and uplift which correspond to far-field tectonic activities in the Red Sea and Gulf of Aden. One of the more dramatic is a Jurassic tectonic pulse circa 145-130 m.a., and a later extensional event which correlates to a major subsidence event ubiquitous through-out the Gulf of Aden, related to Gondwana Land breakup activities. Tectonic uplift during the Tertiary coincides with early Red Sea rifting episodes. Such activities suggest the Ogaden Basin has been a relatively stable East African cratonic basin, but with heating-extension events related to nearby plate interactions. In terms of hydrocarbon generation, the use of steady state present day geothermal gradients, coupled with subsidence analysis shows that potential Paleozoic and Mesozoic source rocks initiated generation as early as the Jurassic. The generating potential of Paleozoic source rocks would only be exacerbated by later heating events. Furthermore, cooling and tectonic uplift during the Tertiary would tend to arrest on-going hydrocarbon generation for Jurassic source rocks in the Ogaden area.

  4. Rifting to spreading processes in the eastern Gulf of Aden, the ENCENS project

    NASA Astrophysics Data System (ADS)

    Leroy, S.; D'Acremont, E.; Tiberi, C.; Ebinger, C.

    2004-12-01

    Existing academic and industry data from the eastern Gulf of Aden away from the Afar flood basalt province show that it is an ideal natural laboratory for seismic studies of passive continental margins because 1) the Gulf of Aden margins are largely free of salt deformation structures, and Oligocene-Recent sedimentary strata are relatively thin (< 4 km; Leroy et al. 2004; d'Acremont et al submitted); 2) the onshore and nearshore rift structures are well exposed, and have been mapped in details (e.g., Watchorn, 1998; d'Acremont et al., submitted); 3) Exploratory well data exist for stratigraphic ties; 4) Our study area is more than 1300 km from the proposed centre of the Late Oligocene Afar plume (e.g., Schilling et al., 1992), and isolated intrasedimentary volcanic occurrences should pose no problem to seismic imaging; 5) The Gulf of Aden is one of the few oceanic basins worldwide where the two conjugate passive margins can be reconstructed within relatively little uncertainty. A cruise, ENCENS II in 2006 (R/V L'Atalante), will be dedicated to multichannel seismic profiling and ocean bottom seismometers (OBS) deployment in order to image the crustal structure of the conjugate margins. To complete our view of this area, a detailed broadband seismic survey along continuations of the crustal-scale OBS seismic refraction/wide-angle reflection profiles in ENCENSII will take place onland in the Dhofar area (northern margin) and in the Socotra island (southern margin). This combination of methods will ensure we define crustal and upper mantle seismic velocity variations. We will then be able to constrain both the geometry of the Moho and that of the lithosphere-asthenosphere boundary, and yielding means to evaluate the current continental rifting and breakup models. We will integrate these unique seismic data with existing ENCENS-SHEBA offshore data and Dhofar Seismic Experiment data, bridging the gap between studies of young margins and extended continental rifts.

  5. Extensive cervical lymphadenitis mimicking bacterial adenitis as the first presentation of Kawasaki disease

    PubMed Central

    Rossi, Felipe de Souza; da Silva, Marco Felipe Castro; Kozu, Kátia Tomie; Camargo, Luís Fernando Aranha; Rossi, Flávia Feijó Panico; Silva, Clovis Artur; Campos, Lúcia Maria de Arruda

    2015-01-01

    Cervical adenitis >1.5cm in diameter is the less frequently observed criteria in patients with Kawasaki disease and it is usually found in association with other symptoms during the acute phase. Moreover, the finding of fever and lymphadenitis with intense local signs of inflammation and phlegmon is rarely seen as the initial manifestation of Kawasaki disease. We report the case of a 7-year-old boy who had cervical lymphadenitis with adjacent cellulitis and phlegmon mimicking bacterial adenitis as the first presentation of Kawasaki disease. The patient had fever, cervical lymphadenitis with adjacent cellulitis, and severe headache. Cefadroxil was prescribed based on the clinical diagnosis of bacterial adenitis. Because he remained febrile and phlogistic signs worsened, after 1 day of hospitalization, antibiotics were administrated intravenously (ceftriaxone and oxacillin). The computed tomography of the neck showed primary infectious/inflammatory process. On the fourth day, the patient had dry and scaly lips, and treatment with oxacillin was replaced by clindamycin because the patient was still febrile. On the ninth day, he presented non-exudative bilateral conjunctival injection. On the tenth day of febrile disease, a rash appeared on his trunk, hands and feet. Patient’s symptoms resolved after intravenous administration of immunoglobulin (2g/kg/dose), and he was discharged 2 days later. On the 14th day, the patient had lamellar desquamation of fingers. Kawasaki disease should be considered as a differential diagnosis in children with febrile cervical lymphadenitis unresponsive to empiric antibiotics even if they have adjacent cellulitis and phlegmon. PMID:26132362

  6. Opening of the Aden Gulf Ridge Derived from GPS Constraints and Plate Tectonic Models

    NASA Astrophysics Data System (ADS)

    Fernandes, R. M.; Rolandone, F.; Leroy, S.; Alothman, A.; Al-Aydrus, A.; Khalil, H.; Ahmed, A.; Khanbari, K.; Bos, M. S.; Nicolon, P.; Heydel, L.

    2012-12-01

    The Aden Gulf Ridge forms, together with the Red Sea and the Ethiopian Rift, the only emerged RRR-type (Ridge/Ridge/Ridge) triple junction in the globe: the Afar Triple Junction. The Aden Gulf Ridge defines the boundary between two major tectonic blocks: Arabia and Somalia, being Nubia the third unit in the triple junction (bordering Arabia along the Red Sea and Somalia along the Ethiopian Rift). Although the extensional behaviour of these structures are well known, the present-day magnitudes of their opening rates are still under evaluation, in particular for the opening rate between the Arabia and Somalia plates. This work uses GPS observations acquired in campaign and continuous mode in order to better constrain the opening rates of the three plate boundaries. For the Nubia-Arabia and Nubia-Somalia boundary plates, we use solely the velocity predictions given by our computed angular velocity models using the available continuous stations in Nubia, Somalia and Arabia. The available data set is augmented here with several stations in Saudi Arabia, which allow us to better constrain the angular velocity for the stable part of the Arabia plate. We estimate the angular velocity model with respect to ITRF2008 (the latest realization of the International Terrestrial Reference System) using the value of 2.5 years (although most of the stations have already a significantly longer time-series) as threshold data span for the processed time-series. Temporal correlations are used to properly estimate the uncertainty of the time-series and derived angular velocity model. In addition, to study the near-field in the Aden Gulf, data acquired in denser campaign networks in Yemen and Oman are used to also directly compute the extension rate in the Red Sea. We show that most of the Arabian Peninsula is stable (within the uncertainties) but the southwest part (Yemen) is influenced by the proximity with the Afar Triple Junction.

  7. Anomalous Subsidence at the Ocean Continent Transition of the Gulf of Aden Rifted Continental Margin

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick; Leroy, Sylvie

    2013-04-01

    It has been proposed that some rifted continental margins have anomalous subsidence and that at break-up they were elevated at shallower bathymetries than the isostatic response predicted by classical rift models (McKenzie, 1978). The existence of anomalous syn- or early-post break-up subsidence of this form would have important implications for our understanding of the geodynamics of continental break-up and sea-floor spreading initiation. We have investigated subsidence of the young rifted continental margin of the eastern Gulf of Aden, focussing on the western Oman margin (break-up age 17.6 Ma). Lucazeau et al. (2008) have found that the observed bathymetry here is approximately 1 km shallower than the predicted bathymetry. In order to examine the proposition of an anomalous early post break-up subsidence history of the Omani Gulf of Aden rifted continental margin, we have determined the subsidence of the oldest oceanic crust adjacent to the continent-ocean boundary (COB) using residual depth anomaly (RDA) analysis corrected for sediment loading and oceanic crustal thickness variation. RDAs corrected for sediment loading using flexural backstripping and decompaction have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous subsidence of the Gulf of Aden rifted continental margin. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions of Crosby and McKenzie (2009). Non-zero RDAs at the Omani Gulf of Aden rifted continental margin can be the result of non standard oceanic crustal thickness or the effect of mantle dynamic topography or a non-classical rift and break-up model. Oceanic crustal basement thicknesses from gravity inversion together with Airy isostasy have been used to predict a "synthetic" gravity RDA, in order to determine the RDA contribution from non-standard oceanic crustal thickness. Gravity inversion, used to determine crustal basement thickness

  8. Structural inheritance, segmentation, and rift localization in the Gulf of Aden oblique rift

    NASA Astrophysics Data System (ADS)

    Bellahsen, Nicolas; Leroy, Sylvie; Autin, Julia; d'Acremont, Elia; Razin, Philippe; Husson, Laurent; Pik, Raphael; Watremez, Louise; Baurion, Celine; Beslier, Marie-Odile; Khanbari, Khaled; Ahmed, Abdulhakim

    2013-04-01

    The structural evolution of the Gulf of Aden passive margins was controlled by its oblique divergence kinematics, inherited structures, and the Afar hot spot. The rifting between Arabia and Somalia started at 35 Ma just before the hot spot paroxysm (at 30Ma) and lasted until 18Ma, when oceanic spreading started. Fieldwork suggests that rift parallel normal faults initiated in the (future) distal margins, after a first stage of distributed rifting, and witness the rift localization, as confirmed by 4-layer analogue models. These faults arise either from crust or lithosphere scale buoyancy forces that are strongly controlled by the mantle temperature under the influence of the Afar hot spot. This implies a transition from a distributed mode to a localized one, sharper, both in space and time, in the West (close to the hot spot) than in the East (far away from the hot spot). In this framework, first order transform F.Z. are here (re-) defined by the fact that they deform continental crust. In the Gulf of Aden, as well as in other continental margins, it appears that these F.Z. are often, if not always, located at continental transfer or "transform" fault zones. Our detailed field-study of an offshore transfer fault zone in the southeastern Gulf of Aden (Socotra Island) shows that these structures are long-lived since early rifting until post rift times. During the early rifting, they are inherited structures reactivated as oblique normal faults before accommodating strike-slip motion. During the Ocean-Continent Transition (OCT) formation ("post syn-rift" times), a significant uplift occurred in the transfer fault zone footwall as shown by stratigraphic and LT thermochronology data. Second order transform F.Z. are defined as deforming only the OCT, thus initiated at the moment of its formation. In the western Gulf of Aden, the hot spot provoked a rift localization strongly oblique to the divergence and, as a consequence, several second order transform F.Z. formed (as

  9. Crustal structure of the NE Gulf of Aden continental margin from wide-angle seismic data

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Leroy, S.; Rouzo, S.; D'Acremont, E.; Lucazeau, F.

    2009-04-01

    The Encens survey wide-angle data (Leroy et al., Feb. March 2006, including MCS and gravity) allow us to determine the deep structure of the northeastern Gulf of Aden magma-poor divergent margin. Gulf of Aden is a young oceanic basin, its accretion began at least 17.6 Ma ago (Leroy et al., 2004 ; d'Acremont et al., 2006). The first order segmentation separates the Gulf in three parts: western, central and eastern Gulf of Aden. Northeastern Gulf of Aden margin, between Alula-Fartak (in the West) and Socotra-Hadbeen (in the East) fracture zones, is divided in three second order segments. Our study focus on the westernmost one: the Ashawq-Salalah segment. The studied velocity models show (1) a continental thinning (15-20 km on 50-80 km distance) accommodated by one or two tilted blocks and clearly observed on wide-angle data, (2) a narrow transition from continental to oceanic domain (OCT) showing 5.5 km/s upper-crust velocities comparable to oceanic ones and more than 6.5 km/s lower-crust velocities comparable to continental ones, (3) a diminution of oceanic crust thicknesses from 10 km in the centre of the Ashawq-Salalah segment to 5.5 km near to the second order segmentation discontinuity, probably linked to a diminution of magma supply eastward the discontinuity of paleo-spreading ridge axis, and (4) a 5 km thick intermediate velocity/density body at the crust-mantle interface, with P-wave velocities ranging from 7.6 to 7.8 km/s and densities of 2.9 to 3, and interpreted as post-rift underplated material that may be linked to the presence of a volcano evidenced by heat flow measurement (Lucazeau et al., subm) and multichannel seismic reflection (Autin et al., subm). Furthermore, a persistent thermal activity has been evidenced in the adjoining eastern Mirbat segment (Lucazeau et al., 2008). These results show an abrupt thinning of the continental crust, a narrow OCT and a post-rift volcanism inducing magmatic underplating affecting this magma-poor margin. This

  10. [Langerhans cell histiocytosis presenting as isolated adenitis in an infant: case report].

    PubMed

    Soriano-Ramos, María; Salcedo Lobato, Enrique; Baro Fernández, María; Blázquez-Gamero, Daniel

    2016-08-01

    Langerhans cell histiocytosis in infants is a rare condition, and presentation as an isolated cervical adenitis is exceptional at this age. We describe the case of a 3-month-old female infant presenting with a neck mass in the right mandibular angle with poor response to antibiotic treatment. Fine needle aspiration was performed and confirmed the diagnosis of Langerhans cell histiocytosis with complementary tests showing no features of systemic involvement. Langerhans cell histiocytosis should be considered in the differential diagnosis of subacute neck masses with poor outcome in infants and physicians should consider performing a fine needle aspiration to establish the diagnosis. PMID:27399030

  11. Uranium mineralization in southern Victoria Land, Antarctica

    SciTech Connect

    Dreschhoff, G.A.M.; Zeller, E.J.

    1986-01-01

    For the past 10 antarctic field seasons, an airborne gamma-ray spectrometric survey has been conducted over widely separated parts of the continent. Localized accumulations of both primary and secondary uranium minerals have been discovered at several localities scattered along the Transantarctic Mountains from the Scott Glacier to northern Victoria Land. A number of highly significant radiation anomalies have been discovered in the area between the Koettlitz Glacier and the Pyramid Trough. The occurrences consist of pegmatite vein complexes which contain an association of primary uranium and thorium minerals. Of still greater significance is the fact that abundant secondary uranium minerals were found in association with the primary deposits, and they indicate clearly that uranium is geochemically mobile under the conditions imposed by the arid polar climate that now exists in southern Victoria Land. Preliminary results of a uranium analysis performed by neutron activation indicate a concentration of 0.12% uranium in a composite sample from the two veins. Even higher levels of thorium are present. The nature of the primary uranium mineralization is currently under investigation. Preliminary results are discussed.

  12. On the Rim of 'Victoria Crater'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity reached the rim of 'Victoria Crater' in Mars' Meridiani Planum region with a 26-meter (85-foot) drive during the rover's 951st Martian day, or sol (Sept. 26, 2006). After the drive, the rover's navigation camera took the three exposures combined into this view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    A half mile in the distance one can see about 20 percent of the far side of the crater framed by the rocky cliffs in the foreground to the left and right of the image. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind.

    The position at the end of the sol 951 drive is about six meters from the lip of an alcove called 'Duck Bay.' The rover team planned a drive for sol 952 that would move a few more meters forward, plus more imaging of the near and far walls of the crater.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed.

    This view is presented as a cylindrical projection with geometric seam correction.

  13. At Bright Band Inside Victoria Crater

    NASA Technical Reports Server (NTRS)

    2007-01-01

    A layer of light-toned rock exposed inside Victoria Crater in the Meridiani Planum region of Mars appears to mark where the surface was at the time, many millions of years ago, when an impact excavated the crater. NASA's Mars Exploration Rover Opportunity drove to this bright band as the science team's first destination for the rover during investigations inside the crater.

    Opportunity's left front hazard-identification camera took this image just after the rover finished a drive of 2.25 meters (7 feet, 5 inches) during the rover's 1,305th Martian day, or sol, (Sept. 25, 2007). The rocks beneath the rover and its extended robotic arm are part of the bright band.

    Victoria Crater has a scalloped shape of alternating alcoves and promontories around the crater's circumference. Opportunity descended into the crater two weeks earlier, within an alcove called 'Duck Bay.' Counterclockwise around the rim, just to the right of the arm in this image, is a promontory called 'Cabo Frio.'

  14. Does Water Hyacinth on East African Lakes Promote Cholera Outbreaks?

    PubMed Central

    Feikin, Daniel R.; Tabu, Collins W.; Gichuki, John

    2010-01-01

    Cholera outbreaks continue to occur regularly in Africa. Cholera has been associated with proximity to lakes in East Africa, and Vibrio cholerae has been found experimentally to concentrate on the floating aquatic plant, water hyacinth, which is periodically widespread in East African lakes since the late 1980s. From 1994 to 2008, Nyanza Province, which is the Kenyan province bordering Lake Victoria, accounted for a larger proportion of cholera cases than expected by its population size (38.7% of cholera cases versus 15.3% of national population). Yearly water-hyacinth coverage on the Kenyan section of Lake Victoria was positively associated with the number of cholera cases reported in Nyanza Province (r = 0.83; P = 0.0010). Water hyacinth on freshwater lakes might play a role in initiating cholera outbreaks and causing sporadic disease in East Africa. PMID:20682884

  15. Degradation of Victoria Crater, Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Grant, J. A.; Wilson, S. A.; Cohen, B. A.; Golombek, M. P.; Geissler, P. E.; Sullivan, R. J.

    2007-12-01

    Victoria crater (2.05N, 354.51E) is ~750 m in diameter and the largest crater on Mars observed in situ. The Mars Exploration Rover Opportunity traversed NW to SE across a broad annulus dominated by dark sand that at least partially surrounds the crater before navigating the northern crater rim. Rover observations of the crater and ejecta deposits are complemented by images with 26-52 cm/pixel scales from the High Resolution Imaging Science Experiment (HiRISE) on Mars Reconnaissance Orbiter and enable assessment of degradation state. The present depth/diameter ratio for Victoria is 0.1, less than the 0.2 expected for a pristine primary impact structure. Together with the eroded, serrated rim, this implies an originally smaller crater diameter and/or considerable infilling consistent with occurrence of a large dune field and few exposed rocks on the crater floor. The height and width of the raised rim is generally 4-5 m and 150-225 m, respectively, less than the 30 m and 500-600 m, respectively, expected for a pristine 750 m diameter crater. Ejecta thicknesses around the rim were derived using rover-based and HiRISE images and yield consistent estimates averaging ~3 m. The serrated rim plan creates a series of promontories extending up to 50 m into the crater and generally fronted by 30-60 degree slopes that are locally vertical and are separated by bays whose floors typically slope 15-25 degrees. A crater originally on order of 600-650 m in diameter and subsequently enlarged by mass wasting and aeolian erosion may yield a structure resembling Victoria today. The steep expression of the promontories and local outcroppings of rocks in the ejecta blanket points to some ongoing mass wasting, but the relative paucity of associated flanking talus indicates derived blocks of sulfate sandstone are not resistant to saltating sand and are rapidly broken down by the wind or are completely covered/filled in by aeolian drift. At Cape St. Vincent, the promontory appears undercut

  16. Thermocline Regulated Seasonal Evolution of Surface Chlorophyll in the Gulf of Aden

    PubMed Central

    Yao, Fengchao; Hoteit, Ibrahim

    2015-01-01

    The Gulf of Aden, although subject to seasonally reversing monsoonal winds, has been previously reported as an oligotrophic basin during summer, with elevated chlorophyll concentrations only occurring during winter due to convective mixing. However, the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data reveal that the Gulf of Aden also exhibits a prominent summer chlorophyll bloom and sustains elevated chlorophyll concentrations throughout the fall, and is a biophysical province distinct from the adjacent Arabian Sea. Climatological hydrographic data suggest that the thermocline, hence the nutricline, in the entire gulf is markedly shoaled by the southwest monsoon during summer and fall. Under this condition, cyclonic eddies in the gulf can effectively pump deep nutrients to the surface layer and lead to the chlorophyll bloom in late summer, and, after the transition to the northeast monsoon in fall, coastal upwelling driven by the northeasterly winds produces a pronounced increase in surface chlorophyll concentrations along the Somali coast. PMID:25789465

  17. Monsoon-modulated ring generation in the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Fratantoni, D. M.

    2009-04-01

    The Somali Current is unique among major western boundary currents in its propensity to reverse direction in response to semi-annual monsoon wind forcing. As a consequence, the western tropical Indian Ocean is rife with eddy variability spanning a range of temporal and spatial scales, much of it carefully documented by Fritz Schott and colleagues. We report here on in-situ and remote observations of westward-translating anticyclonic rings generated as a portion of the Somali Current accelerates northward through the Socotra Passage following the October and April monsoon transitions. The observed rings exhibit strong azimuthal velocities exceeding 50 cm/s, are comparable in overall diameter to the width of the Gulf of Aden (250 km), and translate westward at 5-8 cm/s. We combine unique transport measurements obtained by Schott and colleagues during 1995-1996 with recent satellite altimetry and ocean color imagery to demonstrate that Socotra Passage transport extrema associated with the monsoon transitions are strongly correlated with ring generation events. This distinct and predictable formation process distinguishes these rings from the spectrum of eddies which propagate into the Gulf of Aden from the Arabian Sea and the interior Indian Ocean.

  18. Physical abuse in basic-education schools in Aden governorate, Yemen: a cross-sectional study.

    PubMed

    Ba-Saddik, A S; Hattab, A S

    2013-04-01

    Physical abuse in school has lifelong consequences affecting child health and educational achievements. A study was designed to assess the prevalence of physical abuse experienced by pupils in basic-education schools in Aden, Yemen, and to examine the risk factors associated with it. A cross-sectional study covering 1066 pupils in 7th-9th grades from 8 schools in different districts of Aden governorate were randomly selected. Answering an anonymous self-administered questionnaire, 55.7% of pupils reported physical abuse at least once in their school lifetime (73.2% of males versus 26.6% of females). Teachers were the main perpetrators (45.4%). A statistically significant association was found between physical abuse and sex, age group, family type and father's education. Significant predictors of physical abuse on multivariate regression were male sex (OR=7.89) and extended family type (OR=1.36). Physical abuse in basic-education schools requires serious consideration by educational authorities, families and the community at large. PMID:23882958

  19. Hematological Parameters in Severe Complicated Plasmodium falciparum Malaria among Adults in Aden

    PubMed Central

    Bakhubaira, Sawsan

    2013-01-01

    Objective: To study some hematological parameters in adult patients with complicated severe malaria and their relations to clinical outcome. Materials and Methods: This was a prospective study, including 77 patients from Aden Governorate with complicated severe malaria over the course of 2 years (2010-2011). Results: The common form of severe malaria in Aden was cerebral malaria (25.9%), followed by renal failure (18.2%), severe anemia (16.9%), and hepatitis (14.3%), with a case fatality rate of 7.8%. Hemoglobin concentration was significantly different among the various complications of severe malaria, while platelet and white blood cell counts did not show such differences. The mean age was older among patients that died. Hematological parameters did not significantly differ among dead or surviving patients. Thrombocytopenia was seen in 42.9% of patients and 18.2% of these had platelet counts of <50.0x109/L. However, none of them developed bleeding. Conclusion: This study concluded that hematological changes are common complications encountered in severe malaria, but they are not related to the clinical outcome. Conflict of interest:None declared. PMID:24385830

  20. Thermocline regulated seasonal evolution of surface chlorophyll in the Gulf of Aden.

    PubMed

    Yao, Fengchao; Hoteit, Ibrahim

    2015-01-01

    The Gulf of Aden, although subject to seasonally reversing monsoonal winds, has been previously reported as an oligotrophic basin during summer, with elevated chlorophyll concentrations only occurring during winter due to convective mixing. However, the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data reveal that the Gulf of Aden also exhibits a prominent summer chlorophyll bloom and sustains elevated chlorophyll concentrations throughout the fall, and is a biophysical province distinct from the adjacent Arabian Sea. Climatological hydrographic data suggest that the thermocline, hence the nutricline, in the entire gulf is markedly shoaled by the southwest monsoon during summer and fall. Under this condition, cyclonic eddies in the gulf can effectively pump deep nutrients to the surface layer and lead to the chlorophyll bloom in late summer, and, after the transition to the northeast monsoon in fall, coastal upwelling driven by the northeasterly winds produces a pronounced increase in surface chlorophyll concentrations along the Somali coast. PMID:25789465

  1. Emotional abuse towards children by schoolteachers in Aden Governorate, Yemen: A cross-sectional study

    PubMed Central

    2012-01-01

    Background Emotional abuse is central to other forms of abuse. The primary objective of this paper was to estimate the prevalence of emotional abuse among pupils in basic education schools and the risk factors associated with it in Aden governorate, Yemen. Methods Four districts were randomly selected from across the governorate of Aden, 2 schools were selected at random in each district, and then 1066 pupils were randomly selected from the 8 schools. An anonymous self-administered questionnaire was used for data collection. Data were analyzed using Statistical Package for Social Sciences ver.15. Mean, standard deviation and chi square were used for descriptive statistics. Univariate and Multivariate logistic regression analysis was used to examine the associations between emotional abuse with pupils/parents characteristics. Results Pupils reported high rates of emotional abuse 55.2% at least once in their school lifetime. Male pupils had higher prevalence of emotional abuse 72.6% than females 26.1%. Teachers constituted the highest proportion of perpetrators 45.6%. Odds Ratio (95% confidence interval) showed statistically significant association between emotional abuse and pupils' gender, family type and father education: 9.94 (7.19-13.74), 1.40 (1.02-1.91), .58 (.39-.86) respectively. Conclusion Emotional child abuse was highly prevalent in pupils in basic school education. Pupils' gender, family type and father education were the main risk factors associated with emotional abuse. PMID:22888950

  2. The Bands Culture in Victoria, Australia: Live Music Benefits Career Paths, Employment and Community

    ERIC Educational Resources Information Center

    Watson, Amanda; Forrest, David

    2012-01-01

    This study explores the career paths, employment, business opportunities and community contributions made available through the provision and development of the contemporary performance bands' culture in the State of Victoria. It is framed with the support given to live music performers by Arts Victoria, Small Business Victoria and Music Victoria.…

  3. Structural style and tectonic evolution of the easternmost Gulf of Aden conjugate margins (Socotra - Southern Oman)

    NASA Astrophysics Data System (ADS)

    Nonn, Chloe; Leroy, Sylvie; Castilla, Raymi; de Clarens, Philippe; Lescanne, Marc

    2016-04-01

    Observations from distal rifted margins in present day magma-poor rifted margins led to the discovery of hyperextended crust and exhumed sub-continental mantle. This finding allowed to better figure out how thinning process are accommodate by tectonic structures, forming various crustal domains, as the deformation localized towards the future area of breakup. However, some of the current challenges are about clarifying how factors as oblique kinematic, pre-existing structures and volcanism can control the 3D geometry and crustal architecture of the passive margins? A key to better understand the rifting evolution in its entirety is to study conjugate margins. The gulf of Aden is a young oceanic basin (with a global trend about N75°E) oblique to the divergence (about 30°N), separating Arabia from Somalia of less than 800 km. Thanks to its immerged margins and its thin post-rift sediment cover, the gulf of Aden basin is a natural laboratory to investigate conjugate margins and strain localisation throughout the rift history. In this contribution, we focus our interest on offshore Socotra Island (Yemen) and its conjugate in Southeastern Oman. This area extends from Socotra-Hadbeen (SHFZ) and the eastern Gulf of Aden fault zones (EGAFZ). In the easternmost part of the gulf of Aden, we provide new insights into crustal deformation and emplacement of the new oceanic crust thanks to bathymetric, magnetic, gravimetric data and single-, multi-channel, high speed seismic reflection data collected during Encens-Sheba (2000), Encens (2006) and the more recent Marges-Aden (2012) cruises respectively. The results obtained after compilation of these data, previous geological (field works) and geophysical (receiver functions, Pn-tomography, magnetic anomalies, heat flow) studies on the focused area, allowed us to provide new structural mapping and stratigraphic correlation between onshore and offshore parts of Socotra and Oman margins. We precisely defined and map crustal

  4. Correlation of Pliocene and Pleistocene tephra layers between the Turkana Basin of East Africa and the Gulf of Aden

    USGS Publications Warehouse

    Brown, F.H.; Sarna-Wojcicki, A. M.; Meyer, C.E.; Haileab, B.

    1992-01-01

    Electron-microprobe analyses of glass shards from volcanic ash in Pliocene and Pleistocene deep-sea sediments in the Gulf of Aden and the Somali Basin demonstrate that most of the tephra layers correlate with tephra layers known on land in the Turkana Basin of northern Kenya and southern Ethiopia. Previous correlations are reviewed, and new correlations proposed. Together these data provide correlations between the deep-sea cores, and to the land-based sections at eight levels ranging in age from about 4 to 0.7 Ma. Specifically, we correlate the Moiti Tuff (???4.1 Ma) with a tephra layer at 188.6 m depth in DSDP hole 231 and with a tephra layer at 150 m depth in DSDP hole 241, the Wargolo Tuff with a tephra layer at 179.7 m in DSDP Hole 231 and with a tephra layer at 155.3 m depth in DSDP Hole 232, the Lomogol Tuff (defined here) with a tephra layer at 165 m in DSDP Hole 232A, the Lokochot Tuff with a tephra layer at 140.1 m depth in DSDP Hole 232, the Tulu Bor Tuff with a tephra layer at 160.8 m depth in DSDP Hole 231, the Kokiselei Tuff with a tephra layer at 120 m depth in DSDP Hole 231 and with a tephra layer at 90.3 m depth in DSDP Hole 232, the Silbo Tuff (0.74 Ma) with a tephra layer at 35.5 m depth in DSDP Hole 231 and possibly with a tephra layer at 10.9 m depth in DSDP Hole 241. We also present analyses of other tephra from the deep sea cores for which correlative units on land are not yet known. The correlated tephra layers provide eight chronostratigraphic horizons that make it possible to temporally correlate paleoecological and paleoclimatic data between the terrestrial and deep-sea sites. Such correlations may make it possible to interpret faunal evolution in the Lake Turkana basin and other sites in East Africa within a broader regional or global paleoclimatic context. ?? 1992.

  5. Training Course on the Marine Ecology of the Red Sea. Red Sea & Gulf of Aden Programme (PERSGA).

    ERIC Educational Resources Information Center

    Arab Organization for Education and Science, Cairo (Egypt).

    This document presents a training course on the marine ecology of the Red Sea designed by the Arab League Educational, Cultural and Scientific Organization (ALECSO) in collaboration with the Marine Science Department of UNESCO for the Program for Environmental Studies, Red Sea and Gulf of Aden (PERSGA). It was hosted by the Marine Science Station,…

  6. Programme for Environmental Studies, Red Sea and Gulf of Aden, Jeddah II Conference, 12-18 January 1976. Provisional Report.

    ERIC Educational Resources Information Center

    Arab Organization for Education and Science, Cairo (Egypt).

    This publication presents the report of Jeddah II Conference of the Program for Environmental Studies, Red Sea and Gulf of Aden (PERSGA) hosted by King Abdul Aziz University in Jeddah in January 1976. The Arab League Educational, Cultural and Scientific Organization (ALECSO) initiated the conference to study the issues of scientific research on,…

  7. Analyzing the Modeled Tidal Signal in the Bab El Mandeb Strait and Adjacent Red Sea and Gulf of Aden Waters

    NASA Astrophysics Data System (ADS)

    Guillory, R. N. B.

    2014-12-01

    The tidal forces that dominate the Bab el Mandeb region are influenced by both the generally semi-diurnal tides in the Red Sea and mixed tides in the Gulf of Aden. Also, the tidal ranges are much greater in the Gulf of Aden (~ 2 m) than in the Red Sea (< 1m), which further complicates the tidal signal in Bab el Mandeb Strait. The Red Sea Regional Navy Coastal Model (NCOM), which includes the entire Red Sea, and the western part of the Gulf of Aden at a 1 km resolution, will be evaluated on how well it replicates the tidal signal described in literature and historical observations. In addition, the model will be compared to available temperature/salinity in situ profiles. NCOM incorporates the Oregon State University Tide Model, which should allow the ocean model to accurately reflect the transitional tides in the Bab el Mandeb Strait. Preliminary estimates indicate that the model replicates the overall circulation pattern seen in literature and the fact that there are higher tidal amplitudes in the Gulf of Aden than in the Red Sea. Approved for Public Release, Distribution Unlimited

  8. Layers of 'Cape Verde' in 'Victoria Crater'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of Victoria crater is looking north from 'Duck Bay' towards the dramatic promontory called 'Cape Verde.' The dramatic cliff of layered rocks is about 50 meters (about 165 feet) away from the rover and is about 6 meters (about 20 feet) tall. The taller promontory beyond that is about 100 meters (about 325 feet) away, and the vista beyond that extends away for more than 400 meters (about 1300 feet) into the distance. This is an approximately true color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  9. Layers of 'Cabo Frio' in 'Victoria Crater'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is an approximately true color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  10. Forty Meters from Entry to Victoria Crater

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera during the rover's 1,278th Martian day, or sol, (Aug. 28, 2007) to take the images combined into this view. The rover was perched at the lip of Victoria Crater, which is about 800 meters (one-half mile) in diameter.

    After assessment of possible routes for Opportunity to descend into the crater, the rover team selected a site farther to the right along the rim. That selected entry point lies near the ripple of bright soil visible just outside the crater near the top center of this scene. The driving distance for Opportunity from the Sol 1,278 viewpoint to the selected entry point is about 40 meters (about 130 feet).

    This view is presented as a cylindrical projection with geometric seam correction.

  11. Space Radar Image of Victoria, Canada

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This three-frequency spaceborne radar image shows the southern end of Vancouver Island on the west coast of Canada. The white area in the lower right is the city of Victoria, the capital of the province of British Columbia. The three radar frequencies help to distinguish different land use patterns. The bright pink areas are suburban regions, the brownish areas are forested regions, and blue areas are agricultural fields or forest clear-cuts. Founded in 1843 as a fur trading post, Victoria has grown to become one of western Canada's largest commercial centers. In the upper right is San Juan Island, in the state of Washington. The Canada/U.S. border runs through Haro Strait, on the right side of the image, between San Juan Island and Vancouver Island. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on October 6, 1994, onboard the space shuttle Endeavour. The area shown is 37 kilometers by 42 kilometers (23 miles by 26 miles) and is centered at 48.5 degrees north latitude, 123.3 degrees west longitude. North is toward the upper left. The colors are assigned to different radar frequencies and polarizations as follows: red is L-band horizontally transmitted and received; green is C-band, vertically transmitted and received; and blue is X-band, vertically transmitted and received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to Planet Earth program.

  12. On the Rim of 'Victoria Crater' (Stereo)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Left-eye view of a stereo pair for PIA08780

    [figure removed for brevity, see original site] Right-eye view of a stereo pair for PIA08780

    NASA's Mars rover Opportunity reached the rim of 'Victoria Crater' in Mars' Meridiani Planum region with a 26-meter (85-foot) drive during the rover's 951st Martian day, or sol (Sept. 26, 2006). After the drive, the rover's navigation camera took the three exposures combined into this view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    A half mile in the distance one can see about 20 percent of the far side of the crater framed by the rocky cliffs in the foreground to the left and right of the image. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind.

    The position at the end of the sol 951 drive is about six meters from the lip of an alcove called 'Duck Bay.' The rover team planned a drive for sol 952 that would move a few more meters forward, plus more imaging of the near and far walls of the crater.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed.

    This view is presented as a cylindrical-perspective projection with geometric seam correction.

  13. 'Lyell' Panorama inside Victoria Crater (Stereo)

    NASA Technical Reports Server (NTRS)

    2008-01-01

    During four months prior to the fourth anniversary of its landing on Mars, NASA's Mars Exploration Rover Opportunity examined rocks inside an alcove called 'Duck Bay' in the western portion of Victoria Crater. The main body of the crater appears in the upper right of this stereo panorama, with the far side of the crater lying about 800 meters (half a mile) away. Bracketing that part of the view are two promontories on the crater's rim at either side of Duck Bay. They are 'Cape Verde,' about 6 meters (20 feet) tall, on the left, and 'Cabo Frio,' about 15 meters (50 feet) tall, on the right. The rest of the image, other than sky and portions of the rover, is ground within Duck Bay.

    Opportunity's targets of study during the last quarter of 2007 were rock layers within a band exposed around the interior of the crater, about 6 meters (20 feet) from the rim. Bright rocks within the band are visible in the foreground of the panorama. The rover science team assigned informal names to three subdivisions of the band: 'Steno,' 'Smith,' and 'Lyell.'

    This view incorporates many images taken by Opportunity's panoramic camera (Pancam) from the 1,332nd through 1,379th Martian days, or sols, of the mission (Oct. 23 to Dec. 11, 2007). It combines a stereo pair so that it appears three-dimensional when seen through blue-red glasses. Some visible patterns in dark and light tones are the result of combining frames that were affected by dust on the front sapphire window of the rover's camera.

    Opportunity landed on Jan. 25, 2004, Universal Time, (Jan. 24, Pacific Time) inside a much smaller crater about 6 kilometers (4 miles) north of Victoria Crater, to begin a surface mission designed to last 3 months and drive about 600 meters (0.4 mile).

  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. Gulf of Aden: Structure and evolution of a young ocean basin and continental margin

    SciTech Connect

    Cochran, J.R.

    1981-01-10

    New marine geophysical data are used to describe the structure and history of the Gulf of Aden. Magnetic anomaly data shows seafloor spreading magnetic anomalies of Sheba Ridge from the axial anomaly to anomaly 5 (10 m.y. B.P.) between the Owen fracture zone and 45 /sup 0/E and to anomaly 2' (3 m.y. B.P.) or anomaly 3 (4 m.y. B.P.) west of 45 /sup 0/E. The data does not support the two episodes of seafloor spreading recently proposed. Landward of the seafloor spreading magnetic anomalies is a magnetic quiet zone of uncorrelatable anomalies. The magnetic quiet zone boundary is also a structural boundary effectively marking the edge of Sheba Ridge, with deeper basement lacking a significant topographic gradient found on the landward side. A magnetic quiet zone is found not only where Sheba Ridge splits continental lithosphere but also on East Sheba Ridge where the ridge splits the old oceanic lithosphre of the Owen and Somali basins. There the position occupied by the continental margin within the gulf is marked by nonmagnetic ridge complexes that stretch from the continents to the Owen fracture zone. The magnetic quiet zone boundary is not an isochron in either the Gulf of Aden or the Red Sea, suggesting that significant horizontal motions can occur prior to the initiation of seafloor spreading. The offset on the Dead Sea Rift is used to estimate that from 80 to 160 km of opening, amounting to between 65% and 200% extension of the initial rift valley, occurred in the Gulf of Aden and Red Sea prior to the establishment of a mid-ocean ridge. It is suggested that the development of a new ocean basin occurs in two stages. The first involves diffuse extension over an area perhaps 10 km wide in a rift valley environment without an organized spreading center. This is followed by concentration of the extension at a single axis and the beginning of true seafloor spreading.

  16. Evidence of a thermal anomaly in the eastern gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, S.; D'Acremont, E.; Patriat, P.; Maia, M.; Gente, P.; Burov, E.; Toh, H.

    2003-04-01

    The data set of the Encens-Sheba and Aden New Century cruises allows to evidence a thermal anomaly into the young oceanic crust of the eastern Gulf of Aden, between the Alula-Fartak and Socotra transform faults. Thanks to bathymetric and gravity data, the oceanic domain of the Encens-Sheba area is divided in two distinct areas trending NE-SW perpendicular to the Sheba ridge. (1) The Eastern area is characterised by a shorter wavelength variation of the axial segmentation with spreading segments ranging in length from 30 to 40 km, and by a thin crust particularly on the northern and southern ends of its flanks. (2) The Western zone associated with a long axial segment greater than 120 km is characterised by a thick crust and/or a hot mantle. This abnormal activity for a slow spreading ridge is emphasised by bathymetric highs with volcanic edifices of 5-10 km in diameter, by an electric conductivity body (2D electric section), and by a negative anomaly of the MBA. These different methods support the presence of a recent thermal anomaly which is shallow and centred in the southern flank of the Sheba ridge. Surface anomaly track obtains using absolute motion of afro-arabia plates, reveals that this thermal anomaly should be relatively recent (<5 Ma). In this specific context, the thermomechanical processes of the plume head-lithosphere interaction have been modelised by using the numerical code Parovoz. The lava flows and the magmatic intrusions are induced by the thermal and density anomaly which generates a topographic elevation in turn producing an extension above the plumes. The experiments predict that the first surface elevation occurs in less than 0.2 Ma after plume initiation at 400 km depth, before the plume spreading at the base of the lithosphere. Regarding the Afar hot-spot, this upheaval is centred on the Afar triangle, associated with the outflow of lava flows and with the outcrop of the basement. A wider 1500 km diameter circle could be proposed to

  17. Young Conjugate Margins Laboratory in the Gulf of Aden : the YOCMAL project

    NASA Astrophysics Data System (ADS)

    Leroy, S.; Lucazeau, F.; Razin, P.; Manatschal, G.; YOCMAL Team

    2007-12-01

    A comprehensive multi-disciplinary study of the eastern part of the Gulf of Aden has been undertaken recently in the framework of the French margins program (Encens project), with the long-term objective to integrate in a consistent model of evolution field observations where the margin crops out, results of marine geophysical survey where the margins are submerged, seismological observations of deep interior structure and geodetic measurements. First results show the potentiality of such an approach in this area to understand the relationships between the dynamics of rifting and spreading, the observed structures and the vertical motions of a margin in its early stages. Among the main results, we evidence the structural and sedimentologic characteristics of the continental and oceanic domain of the margin, especially their segmentation, related to the opening obliquity, and their consequences on the oceanic spreading, the importance of the structural inheritance at both lithospheric and crustal scale. We also describe the presence of a ocean-continent transition zone with high heat flow values, of a deep thermal anomaly (170 km) and of a sub-active volcano in the deep margin, that relaunch debate on the importance of the volcanism in the margins formation. The results also emphasize that both the area of investigation and the methods should be extended to be able to describe and understand the variability and the evolution in space and time of the studied structures, notably related to the Afar hotspot. This project intends therefore to study the Gulf of Aden as a natural laboratory for the study of rifting and oceanic spreading onset processes. The extended further ongoing investigations onland in the eastern area (Oman) and its conjugate margins in the South (Socotra island) and in the volcanic margin in the West (Yemen) allow to reach the objectives concerning: - The deep structure and thermal regime (seismic tomography, OBS, heat-flow). - The crustal structure

  18. Deep Structure of the Northeastern Gulf of Aden Margin From Wide-Angle Seismic Network

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Leroy, S.; Rouzo, S.; D'Acremont, E.; Tiberi, C.; Burov, E.; Al-Lazki, A.

    2007-12-01

    The Gulf of Aden is an oblique rift system with spreading segments connected by several transform faults. Rifting in the gulf began ca. 35 Ma ago when the Afar hotspot activity takes place. Onset of spreading recorded by the first magnetic anomaly (A5d) is dated at least 17.6 Ma. We describe first results from the Encens seismic experiment in the northeastern Gulf of Aden and present crustal-scale images across three second-order segments between Alula-Fartak and Socotra fracture zones. Each of these segments was instrumented with 10-15 km, evenly spaced ocean-bottom seismometers complemented onshore by an array of seismometers. 8000 shots from the 8410 in3 ( ~ 138 l) source on board R/V L"Atalante (Ifremer) have been recorded, providing an extensive dataset, with offsets up to 180 km. Excellent-quality data from this dense source and receiver coverage enable the modeling of the P-waves across and along the strike of the ocean-continent transition (OCT) and continental margin for the different rift segments. Coincident multichannel seismic data is used to better constrain the structure down to the basement, and the crustal structure is eventually validated through the modeling of synthetic gravity anomalies. Our results indicate that a single morphology and geometry of the continental margins does not exist in the eastern Gulf of Aden. Indeed, distinct styles of rifting occur within the first-order segmentation of the gulf, which may be related to pre-rift history and to the syn or post-rift magmatism. The continental crust has a maximum of 35 km thickness in the west and 32 km in the east, with velocities ranging from 6 to 7.3 km/s. The base of the oceanic crust has relatively low P-wave velocities ranging from 6.6 to 7.5 km/s, and a thickness of about 5 km in the west and 7 km in the east. A 130 km long gradual thinning of the crust is observed while the OCT width ranges from 20 to 30 km. The transitional crust is around 8 km thick and the P-wave velocities are

  19. POST-RIFT UPLIFT OF THE RIFTED MARGIN OF THE GULF OF ADEN

    NASA Astrophysics Data System (ADS)

    Bache, F.; Leroy, S.; Baurion, C.; Gorini, C.; Lucazeau, F.; Razin, P.; Robinet, J.; D'Acremont, E.; Autin, J.

    2009-12-01

    The Gulf of Aden is a young and narrow oceanic basin formed in Oligo-Miocene time between the rifted margins of the Arabian and Somalian plates. The distal margin and particularly the Ocean-Continent Transition (OCT) domain were previously studied considering a large set of data (Leroy et al., 2004; d'Acremont et al., 2005; d'Acremont et al., 2006; Autin, et al accepted). This study focus on the sedimentary cover identified on seismic reflection profiles collected during Encens-Sheba (2000) and Encens (2006) cruises. Sedimentary stratal pattern and seismic facies succession permit us to highlight a late tectonic event affecting the Dhofar margin. The understanding of facies and depositional sequences is a major challenge for the knowledge of the post-rift tectono-sedimentological evolution of the Gulf of Aden during the spreading. This study let us to distinguish three domains, which match to the structural segmentation inherited from the rifting episode of this margin. The sedimentary record is strongly controlled by a recent (quaternary to now) tectonic phase. Vertical movements lead to the formation of numerous instabilities on the continental slope and Mass-transport deposits (MTDs) on the lower slope and deep basin. The quaternary uplift rate increases eastward, toward the Socotra Hadbeen transform fault zone. The recurrence of the gravitational events shows that the margin history can be divided into active and passive periods since the beginning of the post-rifting evolution of North Aden (17-6 Ma). There is a main sedimentological switch in the studied zone around 7- 10 Ma. This major changes of sedimentation rate and facies types (slope-wash detritus, Mass-transport deposits MTDs, first occurrence of deep sea fans) is probably due to the uplift of the margin and climatic change (first occurrence of the Monsoon in this region). All the incision/erosion stages of continental slope (from slope instabilities set up to the formation of mature canyon) observed

  20. Oblique rifting and segmentation of the NE Gulf of Aden passive margin

    NASA Astrophysics Data System (ADS)

    Fournier, Marc; Bellahsen, Nicolas; Fabbri, Olivier; Gunnell, Yanni

    2004-11-01

    The Gulf of Aden is a young, obliquely opening, oceanic basin where tectonic structures can easily be followed and correlated from the passive margins to the active mid-oceanic ridge. It is an ideal laboratory for studies of continental lithosphere breakup from rifting to spreading. The northeastern margin of the Gulf of Aden offers the opportunity to study on land the deformation associated with oblique rifting over a wide area encompassing two segments of the passive margin, on either side of the Socotra fracture zone, exhibiting distinct morphologic, stratigraphic, and structural features. The western segment is characterized by an elevated rift shoulder and large grabens filled with thick synrift series, whereas the eastern segment exhibits low elevation and is devoid of major extensional structures and typical synrift deposits. Though the morphostructural features of the margin segments are different, the stress field analysis provides coherent results all along the margin. Four directions of extension have been recognized and are considered to be representative of two tensional stress fields with permutations of the horizontal principal stresses σ2 and σ3. The two dominant directions of extension, N150°E and N20°E, are perpendicular to the mean trend of the Gulf of Aden (N75°E) and parallel to its opening direction (N20°E-N30°E), respectively. Unlike another study in the western part of the gulf, our data suggest that the N150°E extension stage is older than the N20°E extension stage. These conflicting chronologies, which are nowhere unambiguously established, suggest that the two extensions coexisted during the rifting. On-land data are compared with offshore data and are interpreted with reference to oblique rifting. The passive margin segmentation represents a local accommodation of the extensional deformation in a homogeneous regional stress field, which reveals the asymmetry of the rifting process. The first-order segmentation of the Sheba Ridge

  1. Victoria Land, Ross Sea, and Ross Ice Shelf, Antarctica

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On December 19, 2001, MODIS acquired data that produced this image of Antarctica's Victoria Land, Ross Ice Shelf, and the Ross Sea. The coastline that runs up and down along the left side of the image denotes where Victoria Land (left) meets the Ross Ice Shelf (right). The Ross Ice Shelf is the world's largest floating body of ice, approximately the same size as France. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  2. Recent plant studies using Victoria 2.0

    SciTech Connect

    BIXLER,NATHAN E.; GASSER,RONALD D.

    2000-03-08

    VICTORIA 2.0 is a mechanistic computer code designed to analyze fission product behavior within the reactor coolant system (RCS) during a severe nuclear reactor accident. It provides detailed predictions of the release of radioactive and nonradioactive materials from the reactor core and transport and deposition of these materials within the RCS and secondary circuits. These predictions account for the chemical and aerosol processes that affect radionuclide behavior. VICTORIA 2.0 was released in early 1999; a new version VICTORIA 2.1, is now under development. The largest improvements in VICTORIA 2.1 are connected with the thermochemical database, which is being revised and expanded following the recommendations of a peer review. Three risk-significant severe accident sequences have recently been investigated using the VICTORIA 2.0 code. The focus here is on how various chemistry options affect the predictions. Additionally, the VICTORIA predictions are compared with ones made using the MELCOR code. The three sequences are a station blackout in a GE BWR and steam generator tube rupture (SGTR) and pump-seal LOCA sequences in a 3-loop Westinghouse PWR. These sequences cover a range of system pressures, from fully depressurized to full system pressure. The chief results of this study are the fission product fractions that are retained in the core, RCS, secondary, and containment and the fractions that are released into the environment.

  3. Style of extensional tectonism during rifting, Red Sea and Gulf of Aden

    USGS Publications Warehouse

    Bohannon, R.G.

    1989-01-01

    Geologic and geophysical studies from the Arabian continental margin in the southern Red Sea and LANDSAT analysis of the northern Somalia margin in the Gulf of Aden suggest that the early continental rifts were long narrow features that formed by extension on closely spaced normal faults above moderate- to shallow-dipping detachments with break-away zones defining one rift flank and root zones under the opposing rift flank. The rift flanks presently form the opposing continental margins across each ocean basin. The detachment on the Arabian margin dips gently to the west, with a breakaway zone now eroded above the deeply dissected terrain of the Arabian escarpment. A model is proposed in which upper crustal breakup occurs on large detachment faults that have a distinct polarity. -from Author

  4. Propagation of rifting along the Arabia-Somalia Plate Boundary: The Gulfs of Aden and Tadjoura

    NASA Astrophysics Data System (ADS)

    Manighetti, Isabelle; Tapponnier, Paul; Courtillot, Vincent; Gruszow, Sylvie; Gillot, Pierre-Yves

    1997-02-01

    The localization and propagation of rifting between Arabia and Somalia are investigated by assessing the deformation geometry and kinematics at different scales between the eastern Gulf of Aden and the Gulf of Tadjoura, using bathymetric, magnetic, seismological, and structural evidence. Large-scale, southwestward propagation of the Aden ridge, markedly oblique to the Arabia-Somalia relative motion vector, began about 30 Myr ago between the Error and Sharbithat ridges. It was an episodic process, with stages of rapid propagation, mostly at rates >10 cm/yr, interrupted by million year pauses on transverse discontinuities coinciding with rheological boundaries between different crustal provinces of the Arabia-Somalia plate. The longest pause was at the Shukra-El Sheik discontinuity (≈45°E), where the ridge tip stalled for ≈13 Myr, between ≈17 and ≈4 Ma. West of that discontinuity, rifting and spreading took place at an azimuth (≈N25°±10°E) and rate (1.2±0.3 cm/yr) different from those of the global Arabia-Somalia motion vector (≈N39°, ≈1.73 cm/yr), implying an additional component of movement (N65°±10°E, 0.7±0.2 cm/yr) due to rotation of the Danakil microplate. At Shukra-El Sheik, the typical oceanic ridge gives way to a narrow, WSW trending axial trough, resembling a large fissure across a shallow shelf. This trough is composed of about eight rift segments, which result from normal faulting and fissuring along N110°-N130°E trends. All the segments step to the left southwestward, mostly through oblique transfer zones with en échelon normal faults. Only two segments show clear, significant overlap. There is one clear transform, the Maskali fault, between the Obock and Tadjoura segments. The latter segment, which encroaches onland, is composed of two parallel subrifts (Iboli, Ambabbo) that propagated northwestward and formed in succession. The most recent, southwestern subrift (Ambabbo) represents the current tip of the Aden ridge. We propose

  5. 'Lyell' Panorama inside Victoria Crater (False Color)

    NASA Technical Reports Server (NTRS)

    2008-01-01

    During four months prior to the fourth anniversary of its landing on Mars, NASA's Mars Exploration Rover Opportunity examined rocks inside an alcove called 'Duck Bay' in the western portion of Victoria Crater. The main body of the crater appears in the upper right of this stereo panorama, with the far side of the crater lying about 800 meters (half a mile) away. Bracketing that part of the view are two promontories on the crater's rim at either side of Duck Bay. They are 'Cape Verde,' about 6 meters (20 feet) tall, on the left, and 'Cabo Frio,' about 15 meters (50 feet) tall, on the right. The rest of the image, other than sky and portions of the rover, is ground within Duck Bay.

    Opportunity's targets of study during the last quarter of 2007 were rock layers within a band exposed around the interior of the crater, about 6 meters (20 feet) from the rim. Bright rocks within the band are visible in the foreground of the panorama. The rover science team assigned informal names to three subdivisions of the band: 'Steno,' 'Smith,' and 'Lyell.'

    This view combines many images taken by Opportunity's panoramic camera (Pancam) from the 1,332nd through 1,379th Martian days, or sols, of the mission (Oct. 23 to Dec. 11, 2007). Images taken through Pancam filters centered on wavelengths of 753 nanometers, 535 nanometers and 432 nanometers were mixed to produce this view, which is presented in a false-color stretch to bring out subtle color differences in the scene. Some visible patterns in dark and light tones are the result of combining frames that were affected by dust on the front sapphire window of the rover's camera.

  6. View of portion of Murray River Basin of State of Victoria, Australia

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A near vertical view of a portion of the Murray River Basin area in the northwest corner of the State of Victoria, Australia (35.5S, 142,0E), as seen from the Skylab space station in Earth orbit. Dry Lake Tyrrell appears as pink and white. The Murray River is in the lower right corner of the photograph. A mass of clouds (white) covers a large portion of the left side of the picture. Rectangular fields of varying sizes indicate an area of major agriculture. A difference in soil color (from pink near the river to buff extending outward) is evident. Large uncultivated areas (dark) are either areas of recent burning or areas unsuitable for growing crops.

  7. Opportunity's First Dip into Victoria Crater

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Opportunity entered Victoria Crater during the rover's 1,291st Martian day, or sol, (Sept. 11, 2007). The rover team commanded Opportunity to drive just far enough into the crater to get all six wheels onto the inner slope, and then to back out again and assess how much the wheels slipped on the slope. The driving commands for the day included a precaution for the rover to stop driving if the wheels were slipping more than 40 percent. Slippage exceeded that amount on the last step of the drive, so Opportunity stopped with its front pair of wheels still inside the crater. The rover team planned to assess results of the drive, then start Opportunity on an extended exploration inside the crater.

    This wide-angle view taken by Opportunity's front hazard-identification camera at the end of the day's driving shows the wheel tracks created by the short dip into the crater. The left half of the image looks across an alcove informally named 'Duck Bay' toward a promontory called 'Cape Verde' clockwise around the crater wall. The right half of the image looks across the main body of the crater, which is 800 meters (half a mile) in diameter.

  8. Late differentiation of proximal and distal margins in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Bache, F.; Leroy, S.; D'Acremont, E.; Autin, J.; Watremez, L.; Rouzo, S.

    2009-04-01

    Non-volcanic passive margins are usually described in three different domains (Boillot et al., 1988), namely (1) the continental domain, where the basement is structured in a series of basins and basement rises, (2) the true oceanic domain, where the bathymetry is relatively smooth, and (3) in between them, a transitional domain referred to as the oceanic-continental transition (OCT), where the basement is partly composed of exhumed mantle. The Gulf of Aden is a young and narrow oceanic basin formed in Oligo-Miocene time between the rifted margins of the Arabian and Somalian plates. The distal margin and particularly the OCT domain were previously studied considering a large set of data (Leroy et al., 2004; d'Acremont et al., 2005; d'Acremont et al., 2006; Autin, 2008). This study focalises on the sedimentary cover identified on seismic reflexion profiles acquired during Encens-Sheba (2000) and Encens (2006) cruises. Sedimentary stratal pattern and seismic facies succession suggest that the differentiation between the proximal and the distal margins occurred very late in the formation of the margin, after the deposition of ~2 km of "syn-OCT" sediments which filled the distal margin grabens. A high position of the proximal and distal margins during rifting and "syn-OCT" sediments deposition could be proposed. The major implication of this evolution should be a shallow nature of "syn-OCT" deposits. The lack of boreholes doesn't permit to affirm this last point. Comparable observations have been described on other passive margins (Moulin, 2003; Moulin et al., 2005; Labails, 2007; Aslanian et al., 2008; Bache, 2008). For some authors, it shows the persistence of a deep thermal anomaly during the early history of the margin (Steckler et al., 1988; Dupré et al., 2007). These observations could be a common characteristic of passive margins evolution and are of major interest for petroleum exploration. Aslanian, D., M. Moulin, O. J.L., P. Unternehr, F. Bache, I. Contrucci

  9. Buoyancy and localizing properties of continental mantle lithosphere: Insights from thermomechanical models of the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Burov, E.; d'Acremont, E.; Leroy, S.; Huet, B.; Pourhiet, L.; Bellahsen, N.

    2013-08-01

    Physical properties of the mantle lithosphere have a strong influence on the rifting processes and rifted structures. In particular, in context of rifting, two of these properties have been overlooked: (1) Mohr-Coulomb plasticity (localizing pressure dependent) may not be valid at mantle depths as opposed to nonlocalizing pressure-independent plasticity (hereafter, perfect plasticity), and (2) lithosphere buoyancy can vary, depending on the petrological composition of the mantle. Focussing on the Arabian plate, we show that the lithosphere may be negatively buoyant. We use thermomechanical modeling to investigate the importance of mantle rheology and composition on the formation of a passive margin, ocean-continent transition (OCT) and oceanic basin. We compare the results of this parametric study to observations in the eastern Gulf of Aden (heat flow, refraction seismics and topography) and show that (1) mantle lithosphere rheology controls the margin geometry and timing of the rifting; (2) lithosphere buoyancy has a large impact on the seafloor depth and the timing of partial melting; and (3) a perfectly plastic mantle lithosphere 20 kg m-3 denser than the asthenosphere best fits with observed elevation in the Gulf of Aden. Finally, thermomechanical models suggest that partial melting can occur in the mantle during the Arabian crustal breakup. We postulate that the produced melt could then infiltrate through the remnant continental mantle lithosphere, reach the surface and generate oceanic crust. This is in agreement with the observed narrow OCT composed of exhumed continental mantle intruded by volcanic rocks in the eastern Gulf of Aden.

  10. Proterozoic inheritance in the Gulf of Aden: the example of the Socotra island (Yemen)

    NASA Astrophysics Data System (ADS)

    Yoann, D.; Leroy, S.; Champanhet, J.; Bellahsen, N.; Pik, R.

    2009-12-01

    Numerous field studies highlighted the necessity of integrating the inheritance phenomena in models of passive margin formation. For instance, the continental break-up in the Gulf of Aden is clearly influenced by the location of the Mesozoic basins. However, the inheritance phenomena linked to the Proterozoïc basement are still poorly understood. We realized a petrostructural study of the basement of the Socotra Island located on the southern passive margin of the Gulf of Aden. This island is characterized by two Tertiary structural domains separated by a north-west dipping tranfer zone trending N45°E. In the hanging wall of the transfer zone, the relief is structured by several tilted blocks trending N110°E and dipping to N200°E. By contrast, the footwall corresponds to a single mega tilted block. The basement of the western structural domain is constituted by more or less migmatitic ortho-amphibolite, quartzite and paragneiss.This metamorphic series is intruded by several calc-alkaline plutons. Field structural studies in metamorphic rocks show that these formations were strongly foliated and folded along N120°E direction with a sub-vertical attitude. Anisotropy of Susceptibility Magnetic (ASM) data in calc-alkaline plutons show that these plutons are equally foliated in a N120°E direction. The basement of the eastern structural domain displays different petrostructural characteristics. It was constituted by a pluri-kilometric per-alkaline pluton associated at the periphery with dykes of per-alkaline microgranites and at the roof with a complex of mafic and acid volcanic dykes and sills. Structural study points out that the orientation of volcanics and per-alkaline plutonic dykes are homogeneously striking around a N45°E direction and are steeply dipping. The comparison between the structure developped during the Tertiary formation of the Gulf of Aden and the Proterozoïc petrostructural characteristic underlines unambiguously inheritance phenomena. In the

  11. Geologic map and structural analysis of the Victoria quadrangle, Mercury

    NASA Astrophysics Data System (ADS)

    Galluzzi, Valentina; Di Achille, Gaetano; Ferranti, Luigi; Rothery, David A.; Palumbo, Pasquale

    2015-04-01

    In this work we present a new geologic map and structural analysis of the Victoria quadrangle (H2) of Mercury, along with a reconnaissance study of the geometry and kinematics of lobate scarps in this area. To this end, we produced a 1:3,000,000 geologic map of the area using the images provided by the NASA spacecraft MESSENGER, which has been orbiting the planet since March, 2011. The geologic map shows the distribution of smooth plains, intermediate plains, intercrater plains units and a classification of crater materials based on an empirical distinction among three stages of degradation. Structural mapping shows that the H2 quadrangle is dominated by N-S faults (here grouped into the Victoria system) to the east and NE-SW faults (Larrocha system) to the west, with the secondary existence of NW-SE-trending faults (Carnegie system) in the north-western area of the quadrangle. A systematic analysis of these systems has led to the following results. 1) the Victoria system is characterized by a main array of faults located along Victoria Rupes - Endeavour Rupes - Antoniadi Dorsum. The segmentation of this array into three different sectors changes from north to south and is spatially linked to the presence of three volcanic vents located at the boundaries between each sector and at the northern end of the Victoria Rupes sector , suggesting that volcanism and faulting are interrelated 2) The main array of Carnegie system is kinematically linked and antithetical to the Victoria system. Both systems have arguably controlled the growth of a longitudinal, fault-free, crustal and gravimetric bulge in the central area of the Victoria quadrangle, which is interpreted as a regional contractional pop-up. 3) The Larrocha system is interrupted against the central bulge and thus is probably older than the Victoria and Carnegie systems. Buffered crater counting performed on the Victoria system confirms the young relative age of its fault segments with respect to the map units

  12. Propagation of an oblique spreading centre: the western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Dauteuil, O.; Huchon, P.; Quemeneur, F.; Souriot, T.

    2001-03-01

    The east-west trending Gulf of Aden rift, between Arabia and Somalia, is spreading along a N35°E direction. It propagates westward inside the African continent, toward the Afar triple junction, oblique to the spreading direction. These combined propagation and oblique rifting generate a special faulting pattern associated with an irregular distribution of volcanism. We analyse this pattern using a structural map derived from the analysis of multibeam bathymetric data and backscattering images from the 1995 TADJOURADEN cruise in the western Gulf of Aden. The rift valley is bounded by faults trending from N110°E to N130°E in the eastern part of the surveyed area where the valley trends N90°E and by large faults in the central-western part where the valley is oriented N70°E. The direction of extension deduced from the fault histogram is N37°E±10° over the whole area, whatever the rift trend. Therefore, this bend of the plate boundary does not result from a change in the stretching direction. This bending increases the rifting obliquity westward and therefore modifies the faulting pattern. Faults display two distinct patterns, either en-échelon on the walls, indicating a right-lateral component of shear, or purely normal and parallel to the rift trend inside the valley. Volcanoes are mostly located in the eastern part of the rift where they are aligned into swarms trending roughly perpendicular to the extension direction deduced from fault directions. Backscattering images show that recent lava flows fill the axial valley of the eastern part; whereas in the central and western parts, volcanoes are scattered in the middle part of the valley. This distribution is interpreted as a westward propagation of the volcanism, and as the direction of deformation migration. The thickness of the upper brittle layer of the lithosphere is estimated from the width if the inner graben is inside the rift. It indicates a deepening of the brittle/ductile transition from east (6

  13. Magnetic and gravity anomalies of the slow-spreading system in the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Nakanishi, M.; Fujimoto, H.; Tamaki, K.; Okino, K.

    2002-12-01

    The spreading system in the Gulf of Aden between Somalia, NE Africa, and Arabia has an ENE-WSW trend and its half spreading rate is about 1.0 cm/yr (e.g., Jestin et al., 1994). Previous studies (e.g., Tamsett and Searle, 1988) provided the general morphology of the spreading system. To reveal detailed morphology and tectonics of the spreading system in the Gulf of Aden, geophysical investigation was conducted along the spreading system between 45°30OE and 50°20OE by the R/V Hakuho-maru from December 2000 to January 2001. Bathymetric data were collected using an echo sounder SEA BEAM 2120 aboard R/V Hakuho-maru. Magnetic and gravity data were collected by towed proton magnetometer and shipboard gravimeter, respectively. The strike of the spreading centers east of 46°30OE is N65°W. The topographic expression of the spreading centers east of N46°30OE is an axial rift valley offset by transform faults siilar to that observed at slow spreading centers in other areas. The bathymetric feature of the spreading centers between 45°50OE and 46°30OE with a strike N80°E is N65°W trending en-echelon basins. The spreading center west of 45°50OE with a strike E-W is bouned by linear ridges and its bathymetric expression is N65°W trending en-echelon ridges. The axial rift valley west of N46°30OE is not offset by any prominent transform faults. Negative magnetic anomaly is dominant over the axial valleys. Its amplitude is about 500 nT and the wavelength is about 30 km. Prominent linear negative magnetic anomaly, which is more than 1000 nT, exists west of N46°30OE. The strike of the linear magnetic anomaly correlates with that of axial valleys west of N46°30OE. Mantle Bouguer gravity anomaly of the spreading centers increases eastward. This trend correlates with the eastward deepening of spreading centers.

  14. Seismic constraints on a large dyking event in Western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Ahmed, A.; Doubre, C.; Leroy, S.; Perrot, J.; Audin, L.; Rolandone, F.; Keir, D.; Al-Ganad, I.; Khanbari, K.; Mohamed, K.; Vergne, J.; Jacques, E.; Nercessian, A.

    2012-04-01

    In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik transform zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the thermal anomaly of the Afar Hot Spot. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115°-trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ~ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift

  15. Break-up processes for the Red Sea and the Gulf of Aden from a receiver function analysis

    NASA Astrophysics Data System (ADS)

    Ahmed, A. A.; Tiberi, C.; Leroy, S.; Stuart, G. W.; Keir, D.; Sholan, J.; Kanbari, K.; Al-Ganad, I.; Rolandone, F.

    2010-12-01

    The influence of the Afar hotspot on the break-up and incipient spreading of Red sea and Gulf of Aden is still not well understood. The presence of thick pre-rift volcanic strata (on the Ethiopian Plateau and on the western part of the northern margin of the Gulf of Aden) and its lack on the eastern part suggests hotspot tectonism may be spatially restricted. However, lithospheric low velocity zones have been recently evidenced in the Dhofar area of the eastern Gulf of Aden, which could question this thought. In order to quantify the influence of anomalously warm mantle beneath the northern margin of the Gulf of Aden on the lithospheric break-up and structure, we use a temporary seismological network deployed in 2009 on the southern part of continental Yemen to study crustal structure using teleseismic receiver functions. About 50 broadband stations were deployed from March 2009 to February 2010 on continental Yemen to record local and teleseismic events to provide an insight of the crustal and mantle structures of the east and north margin of Red Sea rift and Gulf of Aden, respectively (YOCMAL experiment). The stations were organized in 3 profiles roughly perpendicular to the main tectonic features, in order to study the lateral evolution of the structures accordingly to the Afar hotspot distance. We present here the first receiver function study from recordings on the YOCMAL network. The results first show the crust to thin from about 37 km on the northern plateau to 23 km near the coast for the western profile. As previously seen in other part of passive margins, the most extreme crustal thinning is probably located off-shore. A number of the receiver functions exhibit a typical signal coming from anisotropy, dipping interfaces, sedimentary basins and underplating. The presence of these features sometimes altogether interacts to produce a complex signal we treated with various methods in order to distinguish the different effects and to clearly identify them. We

  16. 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)…

  17. IDEAL Symposium on the East African Lakes

    NASA Astrophysics Data System (ADS)

    Johnson, T. C.; Kelts, K.; Lehman, J. T.; Wuest, A.

    A vast array of interdisciplinary problems presented by the African Great Lakes were highlighted at the International Symposium on the Limnology, Climatology and Paleoclimatology of the East African Lakes, organized by the International Decade for the East African Lakes (IDEAL) February 17-21 in Jinja, Uganda. Approximately 125 scientists attended from North America, Europe, Africa, and New Zealand. Jinja is located on the northern shore of Lake Victoria at the head-waters of the Nile and is the site of the host institution for the symposium, the Uganda Freshwater Fisheries Research Organization (UFFRO). The conveners of the symposium were Tom Johnson of Duke University, George Kitaka of UNESCO-ROSTA, and Eric Odada of the University of Nairobi.

  18. Young rift kinematics in the Tadjoura rift, western Gulf of Aden, Republic of Djibouti

    NASA Astrophysics Data System (ADS)

    Daoud, Mohamed A.; Le Gall, Bernard; Maury, René C.; Rolet, JoëL.; Huchon, Philippe; Guillou, Hervé

    2011-02-01

    The Tadjoura rift forms the westernmost edge of the westerly propagating Sheba ridge, between Arabia and Somalia, as it enters into the Afar depression. From structural and remote sensing data sets, the Tadjoura rift is interpreted as an asymmetrical south facing half-graben, about 40 km wide, dominated by a large boundary fault zone to the north. It is partially filled up by the 1-3 Myr old Gulf Basalts which onlapped the older Somali Basalts along its shallower southern flexural margin. The major and trace element analysis of 78 young onshore lavas allows us to distinguish and map four distinct basaltic types, namely the Gulf, Somali, Goumarre, and Hayyabley Basalts. These results, together with radiometric age data, lead us to propose a revised volcano-stratigraphic sketch of the two exposed Tadjoura rift margins and to discriminate and date several distinct fault networks of this oblique rift. Morphological and statistical analyses of onshore extensional fault populations show marked changes in structural styles along-strike, in a direction parallel to the rift axis. These major fault disturbances are assigned to the arrest of axial fault tip propagation against preexisting discontinuities in the NS-oriented Arta transverse zone. According to our model, the sinistral jump of rifting into the Asal-Ghoubbet rift segment results from structural inheritance, in contrast with the en échelon or transform mechanism of propagation that prevailed along the entire length of the Gulf of Aden extensional system.

  19. Tonsillar microbiota in children with PFAPA (periodic fever, aphthous stomatitis, pharyngitis, and adenitis) syndrome.

    PubMed

    Tejesvi, M V; Uhari, M; Tapiainen, T; Pirttilä, A M; Suokas, M; Lantto, U; Koivunen, P; Renko, M

    2016-06-01

    Periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) is a childhood febrile syndrome of unknown origin that is often cured with tonsillectomy. We aimed to compare the bacterial microbiota of the tonsils removed from PFAPA patients with those of controls. We used next-generation sequencing technology to investigate the bacterial microbiota of the tonsils of 30 PFAPA patients and 24 controls. We found significant differences in the presence and relative abundance of many bacteria between PFAPA cases and controls. For example, cyanobacteria, potential producers of microcystins and other toxins, were more common in the case samples (14/30, 47 %) than in the controls (4/24, 17 %, p = 0.02), and the mean relative abundance of cyanobacteria was higher in the case samples (0.2 %) than in the controls (0.01 %, p = 0.01). Streptococci were present in all samples in both groups, but their mean relative abundance was lower in the case samples (3.7 %) than in the controls (9.6 %, p = 0.01). Typical nasopharyngeal microbes such as fusobacteria, Prevotella, Tannerella, Porphyromonas, and Parvimonas dominated the microbiota of the tonsils in both groups. The microbiota of the tonsils removed from PFAPA patients differed significantly from those of the controls. Tonsillar microbiota may play a role in triggering the inflammatory processes that lead to symptoms of PFAPA. PMID:27025724

  20. Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis (PFAPA) Syndrome: a Review of the Pathogenesis.

    PubMed

    Theodoropoulou, Katerina; Vanoni, Federica; Hofer, Michaël

    2016-04-01

    PFAPA syndrome represents the most common cause of recurrent fever in children in European populations, and it is characterized by recurrent episodes of high fever, pharyngitis, cervical adenitis, and aphthous stomatitis. Many possible causative factors have been explored so far, including infectious agents, immunologic mechanisms and genetic predisposition, but the exact etiology remains unclear. Recent findings demonstrate a dysregulation of different components of innate immunity during PFAPA flares, such as monocytes, neutrophils, complement, and pro-inflammatory cytokines, especially IL-1β, suggesting an inflammasome-mediated innate immune system activation and supporting the hypothesis of an autoinflammatory disease. Moreover, in contrast with previous considerations, the strong familial clustering suggests a potential genetic origin rather than a sporadic disease. In addition, the presence of variants in inflammasome-related genes, mostly in NLRP3 and MEFV, suggests a possible role of inflammasome-composing genes in PFAPA pathogenesis. However, none of these variants seem to be relevant, alone, to its etiology, indicating a high genetic heterogeneity as well as an oligogenic or polygenic genetic background. PMID:26984802

  1. Evaluation of the performance of the WRF 1-Dimensional Lake model over the East Africa Great Lakes

    NASA Astrophysics Data System (ADS)

    Gudoshava, M.; Semazzi, F. H. M.

    2015-12-01

    This study seeks to investigate the performance of the 1-Dimensional lake model coupled to WRF over East Africa. The Africa Great lakes exert a great influence on the climate of the region and a number of studies have shown how the lake influences the circulation and the total precipitation over the region. The lakes have highly variable depths, with Lake Victoria having an average depth of 40m and Lake Tanganyika a depth of 450m. The Lake model for WRF was tested and calibrated for the Great lakes, however it was not tested for tropical lakes. We hypothesize that the inclusion of a 1-dimensional lake will reduce the precipitation bias as compared to the WRF model without the lake model. In addition initializing the lake temperature using a vertical temperature profile that closes resembles the one over these lakes will greatly reduce the spin up time. The simulations utilized three nested domains at 36, 12 and 4km. The 4km domain is centered over Lake Victoria Basin, while the 12 km domain includes all the lakes in East Africa. The Tropical Rainfall Measuring Mission (TRMM) datasets are used in evaluating the precipitation, and the following statistics were calculated: root mean square error, standard deviation of the model and observations and mean bias. The results show that the use of the 1-dimensional lake model improves the precipitation over the region considerably compared to an uncoupled model. The asymmetrical rainfall pattern is evident in the simulations. However using the default vertical temperature profile with a three-month spin up is not adequate to transfer heat to the bottom of the lake. Hence the temperatures are still very cold at the bottom. A nine-month spin up improves the lake surface temperatures and lake temperatures at the bottom. A two year spin up greatly improves the lake surface temperatures and hence the total precipitation over the lake. Thus longer spin up time allows for adequate heat transfer in the lake. Initializing the

  2. Aboriginal Students in Victoria. ACER Research Monograph No. 3.

    ERIC Educational Resources Information Center

    de Lemos, Marion M.

    An estimated 80%-90% of all Aboriginal students enrolled in the primary and secondary schools of Victoria, Australia, were tested and surveyed to determine their numbers, distribution, attendance, achievement, attitudes, and school leaving patterns. Most of the 1244 Aboriginals surveyed attended state schools and 75% were schooled in rural areas.…

  3. Information Brokers in Victoria: Doing What, for Whom and How.

    ERIC Educational Resources Information Center

    Broadbent, Marianne; Kelson, Deborah

    1984-01-01

    Reports findings of study of information brokers in Victoria, Australia, which identified services offered by individual brokers and information brokerage businesses, resources used to provide those services, their clientele and pricing strategies, the attributes needed for a successful broker, and relationships between brokers and traditional…

  4. Reaching Year 12 in Victoria, Australia: Student and School Influences

    ERIC Educational Resources Information Center

    Marks, Gary

    2014-01-01

    This paper examines student and school influences on reaching Year 12, the final year of schooling in Victoria, Australia. It analyses data from the population of students who were in Year 9 in 2008. Male, English-speaking background, government school, and especially Indigenous students were less likely to reach Year 12 than comparison groups.…

  5. Vocabulary Size Research at Victoria University of Wellington, New Zealand

    ERIC Educational Resources Information Center

    Nation, Paul; Coxhead, Averil

    2014-01-01

    The English Language Institute (now the School of Linguistics and Applied Language Studies) at Victoria University of Wellington has a long history of corpus-based vocabulary research, especially after the arrival of the second director of the institute, H. V. George, and the appointment of Helen Barnard, whom George knew in India. George's…

  6. Catalogue Use at the State Library of Victoria

    ERIC Educational Resources Information Center

    Hider, Philip

    2008-01-01

    A questionnaire survey conducted at the State Library of Victoria indicates that users in general, and not just scholars, value the standard elements of bibliographic data found in the Library's catalogues, and consider all these elements useful for finding, identifying and selecting items. Rather than making do with less, users wanted more…

  7. Epilithic lichens in the Beacon sandstone formation, Victoria Land, Antarctica

    NASA Technical Reports Server (NTRS)

    Hale, M. E.; Friedmann, E. I. (Principal Investigator)

    1987-01-01

    The epilithic lichen flora on the Beacon sandstone formation in Victoria Land consists of seven species: Acarospora gwynnii Dodge & Rudolph, Buellia grisea Dodge & Baker, B. pallida Dodge & Baker, Carbonea capsulata (Dodge & Baker) Hale comb. nov., Lecanora fuscobrunnea Dodge & Baker, Lecidea cancriformis Dodge & Baker, and L. siplei Dodge & Baker. The typification of the species is given along with descriptions and distribution in Antarctica.

  8. Sensitivity of the East African rift lakes to climate variability

    NASA Astrophysics Data System (ADS)

    Olaka, L.; Trauth, M. H.

    2009-04-01

    Lakes in the East African Rift have provided excellent proxies to reconstruct past climate changes in the low latitudes. The lakes occupy volcano-tectonic depressions with highly variable climate and hydrological setting, that present a good opportunity to study the climatic and hydrogeological influences on the lake water budget. Previous studies have used lake floor sediments to establish the sensitivity of the East African rift lakes. This study focuses on geomorphology and climate to offer additional or alternative record of lake history that are key to quantifying sensitivity of these lakes as archives to external and internal climatic forcings. By using the published Holocene lake areas and levels, we analyze twelve lakes on the eastern arm of the East African rift; Ziway, Awassa, Turkana, Suguta, Baringo, Nakuru, Elmenteita, Naivasha, Natron, Manyara and compare with Lake Victoria, that occupies the plateau between the east and the western arms of the rift. Using the SRTM data, Hypsometric (area-altitude) analysis has been used to compare the lake basins between latitude 80 North and 30 South. The mean elevation for the lakes, is between 524 and 2262 meters above sea level, the lakes' hypsometric integrals (HI), a measure of landmass volume above the reference plane, vary from 0.31 to 0.76. The aridity index (Ai), defined as Precipitation/ Evapotranspiration, quantifies the water available to a lake, it encompasses land cover and climatic effects. It is lowest (arid) in the basin between the Ethiopian rift and the Kenyan rift and at the southern termination of the Kenyan Rift in the catchments of lake Turkana, Suguta, Baringo and Manyara with values of 0.55, 0.43, 0.43 and 0.5 respectively. And it is highest (wet) in the catchments of, Ziway, Awassa, Nakuru and Naivasha as 1.33,1.03 and 1.2 respectively, which occupy the highest points of the rift. Lake Victoria has an index of 1.42 the highest of these lakes and receives a high precipitation. We use a

  9. Glacial and pluvial periods: their relationship revealed by pleistocene sediments of the red sea and gulf of aden.

    PubMed

    Deuser, W G; Ross, E H; Waterman, L S

    1976-03-19

    Oxygen isotope analyses of planktonic foraminifera from the Red Sea and Gulf of Aden indicate that during periods of maximum continental and polar glaciation in the late Pleistocene, the Red Sea was subject to strong evaporation. Between glacial maximums the salinity of the Red Sea was equal to or below that of the open ocean. This suggests that high-latitude glacial periods corresponded in time to interpluvial stages in the present-day desert belt of northern Africa, whereas high-latitude interglacial periods coincided with pluvial stages. PMID:17781646

  10. Spatial distribution of fifty ornamental fish species on coral reefs in the Red Sea and Gulf of Aden.

    PubMed

    Khalaf, Maroof A; Abdallah, Mohamed

    2014-01-01

    The spatial distribution of 50 ornamental fish species from shallow water habitats on coral reefs were investigated using visual census techniques, between latitudes 11-29°N in the Red Sea, in Jordan, Egypt, Saudi Arabia, and Yemen, and in the adjacent Gulf of Aden in Djibouti. One hundred eighteen transects (each 100×5 m) were examined in 29 sites (3-8 sites per country). A total of 522,523 fish individuals were counted during this survey, with mean abundance of 4428.2 ± 87.26 individual per 500 m² transect. In terms of relative abundance (RA), the most abundant species were Blue green damselfish, Chromis viridis (RA=54.4%),followed bySea goldie, Pseudanthias squamipinnis (RA= 34.7), Whitetail dascyllus, Dascyllus aruanus (RA= 2.6%), Marginate dascyllus, Dascyllus marginatus (RA= 2.0),Red Sea eightline flasher Paracheilinus octotaenia (RA=1.0),andKlunzinger's wrasse, Thalassoma rueppellii (0.7%). The highest number of species (S) per 500 m² transect was found on reefs at the latitude 20° in Saudi Arabia (S=21.8), and the lowest number of species was found at the latitude 15° in Djibouti (S=11.11). The highest mean abundance (8565.8) was found on reefs at latitude 20° in Saudi Arabia and the lowest mean abundance (230) was found on reefs at latitude 22°, also in Saudi Arabia. Whereas, the highest Shannon-Wiener Diversity Index was found in reefs at the latitude 22° (H`=2.4) and the lowest was found in reefs at the latitude 20° (H`=0.6). This study revealed marked differences in the structure of ornamental fish assemblages with latitudinal distribution. The data support the presence of two major biogeographic groups of fishes in the Red Sea and Gulf of Aden: the southern Red Sea and Gulf of Aden group and the group in the northern and central Red Sea. Strong correlations were found between live coral cover and the number of fish species, abundance and Shannon-Wiener Diversity indices, and the strength of these correlations varied among the reefs. A

  11. Spatial distribution of fifty ornamental fish species on coral reefs in the Red Sea and Gulf of Aden

    PubMed Central

    Khalaf, Maroof A.; Abdallah, Mohamed

    2014-01-01

    Abstract The spatial distribution of 50 ornamental fish species from shallow water habitats on coral reefs were investigated using visual census techniques, between latitudes 11−29°N in the Red Sea, in Jordan, Egypt, Saudi Arabia, and Yemen, and in the adjacent Gulf of Aden in Djibouti. One hundred eighteen transects (each 100×5 m) were examined in 29 sites (3−8 sites per country). A total of 522,523 fish individuals were counted during this survey, with mean abundance of 4428.2 ± 87.26 individual per 500 m² transect. In terms of relative abundance (RA), the most abundant species were Blue green damselfish, Chromis viridis (RA=54.4%),followed bySea goldie, Pseudanthias squamipinnis (RA= 34.7), Whitetail dascyllus, Dascyllus aruanus (RA= 2.6%), Marginate dascyllus, Dascyllus marginatus (RA= 2.0),Red Sea eightline flasher Paracheilinus octotaenia (RA=1.0),andKlunzinger’s wrasse, Thalassoma rueppellii (0.7%). The highest number of species (S) per 500 m² transect was found on reefs at the latitude 20° in Saudi Arabia (S=21.8), and the lowest number of species was found at the latitude 15° in Djibouti (S=11.11). The highest mean abundance (8565.8) was found on reefs at latitude 20° in Saudi Arabia and the lowest mean abundance (230) was found on reefs at latitude 22°, also in Saudi Arabia. Whereas, the highest Shannon-Wiener Diversity Index was found in reefs at the latitude 22° (H`=2.4) and the lowest was found in reefs at the latitude 20° (H`=0.6). This study revealed marked differences in the structure of ornamental fish assemblages with latitudinal distribution. The data support the presence of two major biogeographic groups of fishes in the Red Sea and Gulf of Aden: the southern Red Sea and Gulf of Aden group and the group in the northern and central Red Sea. Strong correlations were found between live coral cover and the number of fish species, abundance and Shannon-Wiener Diversity indices, and the strength of these correlations varied among the

  12. Five years cancer incidence in Aden Cancer Registry, Yemen (2002-2006).

    PubMed

    Ba Saleem, Huda Omer; Bawazir, Amin Ahmed; Moore, Malcolm; Al-Sakkaf, Khaled Abdulla

    2010-01-01

    The population-based Aden Cancer Registry (ACR) started its activities in 1997. The objective of the registry is to establish a reliable magnitude of cancer in the area covered and the first report was published in 2003. The present article describes data from the second report of cancer incidence over a five year period (2002-2006). Internationally accepted standardized cancer registration methodologies described by IACR and IARC were used. CanReg-4 using ICDO-3 and ICD-10 were applied in the data processing and analysis. Results showed no difference in the overall incidence between the males and females (ratio was 0.83:1) and age standardized rate s(ASR) per 100,000 inhabitants were 30.2 and 31.1. The five most common cancers were breast cancer, leukemia, non-Hodgkin's lymphomas (NH lymphoma), brain cancer and Hodgkin's disease (16.6%, 12.6%, 7.8%, 5.2% and 4.4%, respectively). Among males, leukemia was the first followed by NH lymphoma, Hodgkin's disease, brain and liver. In females, breast was the first, then leukemia, NH lymphoma, thyroid and brain cancer. The highest ASR for males (145 per 100,00 inhabitants) was observed at age 70-74 years whereas for females, two peaks (each 105 per 100,000 inhabitants) were equally noticed at age 60-64 and 70-74 years. Generally, females showed equal or higher incidence compared to males until age 55-59 where males reported higher incidence. The overall pattern of cancer incidence in this report is not much different from that in the previous report. Furthermore, the report generally indicates that the pattern of the most common registered cancer bears some similarities with the adjacent Gulf Cooperation Council States with which we share many characteristics, despite differences that warrant further investigation. PMID:20843142

  13. Westward movement of eddies into the Gulf of Aden from the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Al Saafani, M. A.; Shenoi, S. S. C.; Shankar, D.; Aparna, M.; Kurian, J.; Durand, F.; Vinayachandran, P. N.

    2007-11-01

    Sea level anomalies (SLA) from satellite altimetry (1993-2003) reveal the westward movement of mesoscale eddies in the Gulf of Aden. Inside the gulf the eddies move at a speed of ˜6.0-8.5 cm s-1, comparable to the first-mode baroclinic Rossby wave speed of 7.2 cm s-1. We show that the eddies, which enter the gulf from the Arabian Sea, owe their existence to more than one mechanism. Local Ekman pumping in the western Arabian Sea is important during the summer monsoon (June-September). In May and during the latter half of the summer monsoon (late July to September) and the fall intermonsoon (October), the dominant mechanism is the generation of eddies by the instabilities in the Somali Current and the large eddies associated with it (Great Whirl and Socotra eddy). During the winter monsoon (November-April) the dominant mechanism involves the westward propagating Rossby waves generated either in the Arabian Sea by Ekman pumping or along the west coast of India by poleward propagating Kelvin waves. These Rossby waves from the Arabian Sea propagate slower on entering the gulf because of a shallower thermocline in the gulf. Analysis shows that the SLA signal consists of low (annual and subannual) and high (˜100-180 d) frequencies. The low-frequency signal (mainly annual) shows a discontinuity between 52°E and 60°E. Though the high-frequency signal is seen at all longitudes, a wavelet analysis shows that it was significant only west of 60°E. An energy analysis, based on model simulations, suggests that barotropic instabilities are important during the entire year and that baroclinic instabilities are also important during the summer monsoon.

  14. New Observations of the Gulf of Aden Intermediate Water Intrusion into the Red Sea.

    NASA Astrophysics Data System (ADS)

    Bower, A.; Abualnaja, Y.

    2012-04-01

    The three-layer exchange flow between the Red Sea and the Indian Ocean during summer is characterized by a thick, northward intrusion of relatively cold, low-salinity and low in dissolved oxygen (< 0.5 ml/l); Gulf of Aden Intermediate Water (GAIW), sandwiched between two thin layers of outflow water. The flux of GAIW into the Red Sea is important in the heat, freshwater and nutrient budgets of the Red Sea, but the structure and pathways of the intrusion are not well-known due to a paucity of hydrographic and direct velocity observations. A research cruise was executed at the eastern side of the Red Sea during September-October 2011 to conduct the first large-scale survey of the intrusion. This mission is part of a series of expeditions in the Red Sea designed to investigate the seasonal Red Sea circulation. Surprisingly, the GAIW intrusion was observed to stretch nearly the entire length of the Red Sea (~1500 km) as a narrow eastern boundary current with subsurface velocity maximum of 0.1-0.3 m/s in the depth range 50-100 m. The intruding layer is weakly stratified compared to the background, possibly an indication of strong vertical mixing as it flows through the strait. Some GAIW was observed to enter deep channels in a coral reef bank (Farasan Banks) located in the southeastern Red Sea, and to enter the Red Sea interior, the latter possibly due to interactions between the boundary current and mesoscale eddies. The pathways and erosion of the GAIW intrusion will likely have major implications for the spatial distribution of biological productivity.

  15. Model for heat-up of structures in VICTORIA

    SciTech Connect

    Bixler, N.E.

    1993-12-01

    VICTORIA is a mechanistic computer code that treats fission product behavior in the reactor coolant system during a severe accident. During an accident, fission products that deposit on structural surfaces produce heat loads that can cause fission products to revaporize and possibly cause structures, such as a pipe, to fail. This mechanism had been lacking from the VICTORIA model. This report describes the structural heat-up model that has recently been implemented in the code. A sample problem shows that revaporization of fission products can occur as structures heat up due to radioactive decay. In the sample problem, the mass of deposited fission products reaches a maximum, then diminishes. Similarly, temperatures of the deposited film and adjoining structure reach a maximum, then diminish.

  16. View of 'Bottomless Bay' on Rim of 'Victoria'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    As part of its investigation of 'Victoria Crater,' NASA's Mars Exploration Rover Opportunity examined a section of the scalloped rim called 'Bottomless Bay' (or 'Bahia sin Fondo'). This view shows the northeastern side of Bottomless Bay as seen from the southwest. The exposures combined into this mosaic were taken by the rover's panoramic camera through a 750-nanometer filter during the 1,019th Martian day, or sol, of Opportunity's Mars-surface mission (Dec. 5, 2006).

  17. Thickness of ice on perennially frozen lakes.

    PubMed

    McKay, C P; Clow, G D; Wharton, R A; Squyres, S W

    1985-02-14

    The dry valleys of southern Victoria Land, constituting the largest ice-free expanse in the Antarctic, contain numerous lakes whose perennial ice cover is the cause of some unique physical and biological properties. Although the depth, temperature and salinity of the liquid water varies considerably from lake to lake, the thickness of the ice cover is remarkably consistent, ranging from 3.5 to 6 m, which is determined primarily by the balance between conduction of energy out of the ice and the release of latent heat at the ice-water interface and is also affected by the transmission and absorption of sunlight. In the steady state, the release of latent heat at the ice bottom is controlled by ablation from the ice surface. Here we present a simple energy-balance model, using the measured ablation rate of 30 cm yr-1, which can explain the observed ice thickness. PMID:11539028

  18. Thickness of ice on perennially frozen lakes

    USGS Publications Warehouse

    McKay, C.P.; Clow, G.D.; Wharton, R.A., Jr.; Squyres, S. W.

    1985-01-01

    The dry valleys of southern Victoria Land, constituting the largest ice-free expanse in the Antarctic, contain numerous lakes whose perennial ice cover is the cause of some unique physical and biological properties 1-3. Although the depth, temperature and salinity of the liquid water varies considerably from lake to lake, the thickness of the ice cover is remarkably consistent1, ranging from 3.5 to 6m, which is determined primarily by the balance between conduction of energy out of the ice and the release of latent heat at the ice-water interface and is also affected by the transmission and absorption of sunlight. In the steady state, the release of latent heat at the ice bottom is controlled by ablation from the ice surface. Here we present a simple energy-balance model, using the measured ablation rate of 30 cm yr-1, which can explain the observed ice thickness. ?? 1985 Nature Publishing Group.

  19. Epinephelus geoffroyi (Klunzinger, 1870) (Pisces: Serranidae), a valid species of grouper endemic to the Red Sea and Gulf of Aden.

    PubMed

    Randall, John E; Bogorodsky, Sergey V; Krupp, Friedhelm; Rose, Jean Michel; Fricke, Ronald

    2013-01-01

    The grouper Epinephelus geoffioyi (Klunzinger), type locality Red Sea, previously regarded as a synonym of E. chlorostigma (Valenciennes) is recognized as a valid species. It is differentiated from E. chlorostigma by having 25-29 (modally 27) gill rakers vs. 23-26 (modally 24), a more angular anal fin, the dark spots on the abdomen more widely separated, and lacking a clear white margin posteriorly on the caudal fin. The missing holotype of E. geoffroyi was found at the Staatliches Museum für Naturkunde Stuttgart (SMNS 233, 191 mm). Epinephelits chlorostigma is wide-ranging from the Gulf of Aden and east coast of Africa to Samoa; it is reported from the depth range of 32-280 m. Epinephelus geoffroyi is presently known only from the Red Sea and Gulf of Aden at depths of 3-32 m. Illustrations are provided for three other species of groupers with numerous small dark spots, E. areolatus (Forsskål), E. gabriellae Randall & Heemstra, and E. polylepis Randall & Heemstra, that are, or might be, sympatric with E. geoffroyi. PMID:26287104

  20. Distribution and relationships of selected trace metals in molluscs and associated sediments from the Gulf of Aden, Yemen.

    PubMed

    Szefer, P; Ali, A A; Ba-Haroon, A A; Rajeh, A A; Gełdon, J; Nabrzyski, M

    1999-09-01

    Concentrations of Cd, Pb, Zn, Cu, Ni, Co, Cr, Mn and Fe in the soft tissue of Turbo coronatus, Acanthopleura haddoni, Ostrea cucullata and Pitar sp., as well as in associated surface sediments (bulk and bioavailable metal concentrations) from the Gulf of Aden, Yemen, were determined by atomic absorption spectrophotometry method. Large differences between size-classes of molluscs in metal concentrations were recorded. Significant spatial differences in metal concentrations in both the soft tissue of the molluscs and associated sediments studied were mostly identified. Statistically significant correlations (p<0.01) between concentrations of selected metals were observed. A slope of the linear regression is significantly higher than unity for Fe (9.91) and Cd (3.45) in A. haddoni and for Ni (4.15) in T. coronatus, suggesting that the bioavailability of these metals is disproportionally increased with a degree of enrichment of the sediments in Fe, Cd and Ni, respectively. A slope constant approximating to unity (1.14) for Cu in A. haddoni relative to its concentration in sediment extract implies that bioavailability of this metal proportionally increased with growing concentrations of its labile forms in the associated sediment. The degree of contamination of Gulf of Aden waters by the metals studied is discussed and the potential ability of molluscs, especially A. haddoni and T. coronatus, as biomonitors of metallic pollutants is postulated. PMID:15093026

  1. Status of VICTORIA: NRC peer review and recent code applications

    SciTech Connect

    Bixler, N.E.; Schaperow, J.H.

    1997-12-01

    VICTORIA is a mechanistic computer code designed to analyze fission product behavior within a nuclear reactor coolant system (RCS) during a severe accident. It provides detailed predictions of the release of radioactive and nonradioactive materials from the reactor core and transport and deposition of these materials within the RCS. A summary of the results and recommendations of an independent peer review of VICTORIA by the US Nuclear Regulatory Commission (NRC) is presented, along with recent applications of the code. The latter include analyses of a temperature-induced steam generator tube rupture sequence and post-test analyses of the Phebus FPT-1 test. The next planned Phebus test, FTP-4, will focus on fission product releases from a rubble bed, especially those of the less-volatile elements, and on the speciation of the released elements. Pretest analyses using VICTORIA to estimate the magnitude and timing of releases are presented. The predicted release of uranium is a matter of particular importance because of concern about filter plugging during the test.

  2. Transcriptome pyrosequencing of the Antarctic brittle star Ophionotus victoriae.

    PubMed

    Burns, Gavin; Thorndyke, Michael C; Peck, Lloyd S; Clark, Melody S

    2013-03-01

    Brittle stars are included within a whole range of species, which contribute to knowledge in the medically important area of tissue regeneration. All brittle stars regenerate lose limbs, but the rate at which this occurs is highly variable and species-specific. One of the slowest rates of arm regeneration reported so far is that of the Antarctic Ophionotus victoriae. Additionally, O. victoriae also has an unusual delay in the onset of regeneration of about 5months. Both processes are of interest for the areas of regeneration biology and adaptation to cold environments. One method of understanding the details of regeneration events in brittle stars is to characterise the genes involved. In the largest transcriptome study of any ophiuroid to date, we describe the results of mRNA pyrosequencing from pooled samples of regenerating arms of O. victoriae. The sequencing reads resulted in 18,000 assembled contiguous sequences of which 19% were putatively annotated by blast sequence similarity searching. We focus on the identification of major gene families and pathways with potential relevance to the regenerative processes including the Wnt/β-catenin pathway, Hox genes, the SOX gene family and the TGF beta signalling pathways. These data significantly increase the amount of ophiuroid sequences publicly available and provide candidate transcripts for the further investigation of the unusual regenerative process in this Antarctic ophiuroid. PMID:23904059

  3. Anomalous Subsidence of the Ocean Continent Transition at Rifted Continental Margins: Observations from the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Cowie, L.; Kusznir, N. J.

    2011-12-01

    It has been proposed that some continental rifted margins have anomalous early subsidence histories and that at break-up they were elevated at shallower bathymetries than the isostatic response of classical rift models (McKenzie 1978) would predict. The existence of anomalous syn- or early post-breakup subsidence, of this form, would have important implications for our understanding of the geodynamics of continental breakup and sea-floor spreading initiation and important consequences for syn- and post-breakup depositional systems. Possible explanations for anomalous subsidence during continental breakup could include transient effects as the continental geotherm evolves towards an oceanic form, or small scale convection. Lucazeau et al. (2008) have reported anomalously high heat-flows in the ocean continent transition (OCT) of the young rifted margin of the Eastern Gulf of Aden which would have implications for its subsidence history. In order to verify (or otherwise) the proposition of an anomalous early post-breakup subsidence history in the Eastern Gulf of Aden, we have determined anomalous oceanic subsidence using residual depth anomaly (RDA) analysis and have compared lithosphere thinning across the OCT measured using subsidence analysis with continental crustal basement thinning from gravity inversion. Both 3D regional and localised 2D analyses have been carried out. The localised studies focus on published seismic reflection lines (Autin et al, 2010; D'Acremont et al, 2005; Fournier et al, 2007; Leroy et al, 2004; Leroy et al, 2010; Lucazeau et al 2008; Lucazeau et al 2010). RDAs have been calculated by comparing observed and predicted oceanic bathymetries. Regional 3D RDAs for the Gulf of Aden, without a sediment correction, show positive RDAs between 3km and 4km at the rifted margins decreasing to 0.5km at the ocean ridge axis. Localised 2D sediment corrected RDA profiles determined within and adjacent to the OCT of the Eastern Gulf of Aden are also

  4. 27 m of lake ice on an Antarctic lake reveals past hydrologic variability

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo Dry Valleys. Unlike other lakes in the region, the surface ice extends at least 27 m, which has created an extreme and unique habitat by isolating a liquid-brine with salinity of 195 g L-1. 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 abundances of 18O and 2H, ground penetrating radar profiles, and mineralogy, we conclude that the entire 27 m of ice formed from surface runoff, and the sediment layers represent the accumulation of fluvial and aeolian 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 climatic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an excellent Mars analog for understanding the preservation of subsurface brine, ice and sediment in a cold desert environment.

  5. Structure and evolution of the eastern Gulf of Aden conjugate margins from seismic reflection data

    NASA Astrophysics Data System (ADS)

    d'Acremont, Elia; Leroy, Sylvie; Beslier, Marie-Odile; Bellahsen, Nicolas; Fournier, Marc; Robin, Cécile; Maia, Marcia; Gente, Pascal

    2005-03-01

    The Gulf of Aden is a young and narrow oceanic basin formed in Oligo-Miocene time between the rifted margins of the Arabian and Somalian plates. Its mean orientation, N75°E, strikes obliquely (50°) to the N25°E opening direction. The western conjugate margins are masked by Oligo-Miocene lavas from the Afar Plume. This paper concerns the eastern margins, where the 19-35 Ma breakup structures are well exposed onshore and within the sediment-starved marine shelf. Those passive margins, about 200 km distant, are non-volcanic. Offshore, during the Encens-Sheba cruise we gathered swath bathymetry, single-channel seismic reflection, gravity and magnetism data, in order to compare the structure of the two conjugate margins and to reconstruct the evolution of the thinned continental crust from rifting to the onset of oceanic spreading. Between the Alula-Fartak and Socotra major fracture zones, two accommodation zones trending N25°E separate the margins into three N110°E-trending segments. The margins are asymmetric: offshore, the northern margin is narrower and steeper than the southern one. Including the onshore domain, the southern rifted margin is about twice the breadth of the northern one. We relate this asymmetry to inherited Jurassic/Cretaceous rifts. The rifting obliquity also influenced the syn-rift structural pattern responsible for the normal faults trending from N70°E to N110°E. The N110°E fault pattern could be explained by the decrease of the influence of rift obliquity towards the central rift, and/or by structural inheritance. The transition between the thinned continental crust and the oceanic crust is characterized by a 40 km wide zone. Our data suggest that its basement is made up of thinned continental crust along the southern margin and of thinned continental crust or exhumed mantle, more or less intruded by magmatic rocks, along the northern margin.

  6. The conjugate passive margins of the eastern gulf of Aden : structure and oceanic initiation

    NASA Astrophysics Data System (ADS)

    D'Acremont, E.; Leroy, S.; Beslier, M. O.; Fournier, M.; Bellahsen, N.; Patriat, P.; Maia, M.

    2003-04-01

    The geophysical data set of the Encens-Sheba cruise in the eastern gulf of Aden allows us to define and compare the structure of the conjugate passive margins and to locate the continental ocean transition zone (COT). Between the Alula-Fartak and Socotra transform faults, the non-volcanic margins are segmented by two transfer fault zones trending N027°E. These transfer zones with left-lateral offsets define three N110°E trending segments. The two margins display titled blocks, horsts and grabens bounded by landward and seaward dipping faults, responsible for two syn-rift antithetic sequences observed on the seismic profile. Normal faulting prevails on the northern margin, with prominent basement rises and basins, and is less important on the southern margin. The latter being characterised by a deep basin at the toe of the continental slope in the vicinity of the continent-ocean transition. Moreover, the offsets along the transfer zones are greater on the northern margin than on the southern one. The conjugate margins are asymmetrical: the southern rifted domain is about twice as large as the northern one. This asymmetry could be due to reactivation of inherited faults. Indeed, the Jurassic rifting has affected the southern margin and not the northern one. The segmentation of the first oceanic spreading centre which is dated at least at 17.6 Ma by the magnetic anomaly An-5d identification seems to be directly related to the segmentation of the margins. The segmentation of the oceanic crust between the Alula-Fartak and Socotra transform faults evolves from three segments (an5d to an5) to two segments (an5 to an1). At the onset of the accretion process, the western segment propagated eastward at the expense of the eastern segment. Reconstruction of the oceanisation process suggests a complex non-uniform opening along the COT by punctiform initiation of seafloor spreading. Several arguments lead to propose a rifting model by mantle exhumation in the COT. The gravity

  7. Sebaceous adenitis in Swedish dogs, a retrospective study of 104 cases

    PubMed Central

    Hernblad Tevell, Elisabeth; Bergvall, Kerstin; Egenvall, Agneta

    2008-01-01

    Background Sebaceous adenitis (SA) is an uncommon, immune mediated skin disease in dogs. The aim was to retrospectively investigate SA in dogs in Sweden with respect to breed, sex and age distribution. A second aim was to retrospectively compare clinical signs in dogs with generalized SA and to estimate the survival after diagnosis in the English springer spaniel, standard poodle and the akita. Methods In total 34 Swedish veterinarians contributed with 104 clinically and histologically verified SA cases. Breed, gender and age at diagnosis were registered for each case. The degree of clinical signs at time for diagnosis and at follow-up and information about treatments, concurrent diseases and euthanasia were recorded for the springer spaniels, standard poodles and akitas using a standardized questionnaire. Results A total of 104 cases of SA were included; most cases were recorded for the springer spaniel (n = 25), standard poodle (n = 21) and the akita (n = 10). These three breeds, together with the lhasa apso and the chow-chow, were the most common when national registry data from the Swedish Board of Agriculture and Swedish Kennel Club were considered. The mean age at diagnosis was 4.8 years. The proportion of males was 61%. When the springer spaniels, standard poodles and the akitas with generalized signs were compared (n = 51), the spaniels showed significantly more severe clinical signs than the poodles at diagnosis regarding alopecia, seborrhoea, pyoderma and the overall severity of clinical signs. At follow-up, the degree of clinical signs for otitis externa and pyoderma differed significantly between the breeds. The estimated median survival time was 42 months. In dogs where data regarding survival was available at the end of the study (n = 44), SA was reported to be the reason for euthanasia in 14 dogs, whereof 7 within 24 months after diagnosis. Conclusion The result of this study implicates that the English springer spaniel is a breed predisposed to SA

  8. A note on the flow of Gulf of Aden Intermediate Water in the Red Sea

    NASA Astrophysics Data System (ADS)

    Wafar, Mohideen

    2016-11-01

    In this short communication, we compare our results with an earlier study by Churchill et al. (2014) who arrived at similar findings. Recently we published a paper (Wafar et al., 2016) on the spread of Gulf of Aden Intermediate Water (GAIW) in the Red Sea in Journal of Marine Systems. Churchill et al. (2014) published findings similar to ours earlier than we did but by unfortunate oversight we failed to cite their paper when we wrote ours. We sincerely regret this negligence. The important findings from the study of Churchill et al. (2014) are that the GAIW: flows as a coastal current along Saudi coast, is traceable up to about 24°N, constitutes a source of new N to the coastal reef ecosystems, and is transported across the basin in an anticyclonic eddy circulation. Our findings agree with these. Our results also demonstrate the presence of GAIW still further north, as far as 26°N, by using a multiple tracer analysis, and the entrainment of GAIW in more than one anticyclonic eddy circulation. Regardless of the precedence, the results from the study of Churchill et al. (2014) and subsequently ours together add definite proof of GAIW flowing as an eastern boundary current which was only surmised before. While we have not examined the importance of GAIW as a source of new N to coral reefs, our demonstration that the GAIW is entrained across the basin in several eddy circulations, besides being consistent with the findings of Churchill et al. (2014), strongly supports the possibility that this is a mechanism of determining the extents of basin-wide biological production. Red Sea is a sea area that remains even now less intensively sampled and it is extremely unfortunate that a recent paper like that of Churchill et al. (2014) escaped our attention. However, we are happy that our findings are consistent with theirs and build more on what they deduced on the flow of GAIW and its role on nutrient enrichment of the Red Sea waters.

  9. Recent MELCOR and VICTORIA Fission Product Research at the NRC

    SciTech Connect

    Bixler, N.E.; Cole, R.K.; Gauntt, R.O.; Schaperow, J.H.; Young, M.F.

    1999-01-21

    The MELCOR and VICTORIA severe accident analysis codes, which were developed at Sandia National Laboratories for the U. S. Nuclear Regulatory Commission, are designed to estimate fission product releases during nuclear reactor accidents in light water reactors. MELCOR is an integrated plant-assessment code that models the key phenomena in adequate detail for risk-assessment purposes. VICTORIA is a more specialized fission- product code that provides detailed modeling of chemical reactions and aerosol processes under the high-temperature conditions encountered in the reactor coolant system during a severe reactor accident. This paper focuses on recent enhancements and assessments of the two codes in the area of fission product chemistry modeling. Recently, a model for iodine chemistry in aqueous pools in the containment building was incorporated into the MELCOR code. The model calculates dissolution of iodine into the pool and releases of organic and inorganic iodine vapors from the pool into the containment atmosphere. The main purpose of this model is to evaluate the effect of long-term revolatilization of dissolved iodine. Inputs to the model include dose rate in the pool, the amount of chloride-containing polymer, such as Hypalon, and the amount of buffering agents in the containment. Model predictions are compared against the Radioiodine Test Facility (RTF) experiments conduced by Atomic Energy of Canada Limited (AECL), specifically International Standard Problem 41. Improvements to VICTORIA's chemical reactions models were implemented as a result of recommendations from a peer review of VICTORIA that was completed last year. Specifically, an option is now included to model aerosols and deposited fission products as three condensed phases in addition to the original option of a single condensed phase. The three-condensed-phase model results in somewhat higher predicted fission product volatilities than does the single-condensed-phase model. Modeling of U02

  10. Lake evaporation estimates in tropical Africa (Lake Ziway, Ethiopia)

    NASA Astrophysics Data System (ADS)

    Vallet-Coulomb, Christine; Legesse, Dagnachew; Gasse, Françoise; Travi, Yves; Chernet, Tesfaye

    2001-05-01

    Estimates of evaporation from an open shallow lake in tropical Africa (Lake Ziway, Main Ethiopian Rift) are made by using monthly hydrometeorological data available for the past three decades. On the one hand, annual average estimates are inferred from three climatic approaches, which can be applied in areas with limited meteorological data. The lake energy balance yields an evaporation rate of 1780 mm yr -1, assuming a Bowen ratio of 0.15 (that of Lake Victoria). The Penman method gives an annual evaporation rate of 1870 mm. The complementary relationship lake evaporation model (CRLE) applied on monthly averaged values of air temperature, air humidity and sunshine duration gives 1730 mm yr -1. The sensitivity of each method to changes in input variables is analyzed in order to test the stability of the resulting estimates. This helps discuss uncertainties and possible inter-annual variations of the evaporation rate. On the other hand, the monthly lake level records together with precipitation and river discharge data between 1969 and 1990, allow us to estimate the water balance, providing an annual rate of 1937 mm for the combined evaporation and groundwater losses. The chloride budget is used to discriminate the groundwater from the evaporation loss. It gives us an annual evaporation rate of 1740 mm and a corresponding groundwater loss of 200 mm yr -1. The groundwater loss estimate is of the same order of magnitude as the surface outflow, but the associated error in the former is significant because the result is sensitive to the poorly known chloride content of river inflows. Our results can be used to forecast the impact of increased water consumption in the basin.

  11. Reprint of: Revised magnetostratigraphic chronologies for New Harbour drill cores, southern Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Ohneiser, Christian; Wilson, Gary

    2012-10-01

    The Taylor Valley (DVDP-10, -11) and Ferrar Fiord (CIROS-2) drill cores offer a window into the evolution of southern Victoria Land glaciers and the Antarctic climate system during the late-Neogene. Here we present new magnetostratigraphic chronologies, which we use to correlate the drill core successions with onshore dry-valleys geomorphic records and offshore deep-ocean records. Magnetostratigraphies were constructed using stepwise AF and/or thermal demagnetisation of discrete specimens from the drill cores. Correlation of magnetostratigraphies with the magnetic polarity timescale was guided by biostratigraphic and radiometric constraints. We recognise five styles of sedimentation in the Taylor/Ferrar fiords, which we correlate with discrete climate phases. During the latest Miocene-early Pliocene, wet based glaciers filled the Taylor and Ferrar fiords with active sedimentation in the Taylor Fiord and erosion of basement rocks in the Ferrar Fiord. Glaciers retreated during the Pliocene warm period leaving open marine conditions and deep fiords (> 300 m) at a time when the Ross Sea was free of ice and sea surface temperatures around Antarctica were at least 5 °C warmer than today. We recognise the first significant cooling in DVDP-11 post 2.6 Ma by a shift to current winnowed sediments sourced from the Ross Sea rather than from East Antarctic glaciers. Post 1.7 Ma, lacustrine sediments were deposited behind ice-dammed lakes, which formed when West Antarctic ice expanded and grounded across the Ross Embayment and abutted the Transantarctic Mountains.

  12. Revised magnetostratigraphic chronologies for New Harbour drill cores, southern Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Ohneiser, Christian; Wilson, Gary

    2012-02-01

    The Taylor Valley (DVDP-10, -11) and Ferrar Fiord (CIROS-2) drill cores offer a window into the evolution of southern Victoria Land glaciers and the Antarctic climate system during the late-Neogene. Here we present new magnetostratigraphic chronologies, which we use to correlate the drill core successions with onshore dry-valleys geomorphic records and offshore deep-ocean records. Magnetostratigraphies were constructed using stepwise AF and/or thermal demagnetisation of discrete specimens from the drill cores. Correlation of magnetostratigraphies with the magnetic polarity timescale was guided by biostratigraphic and radiometric constraints. We recognise five styles of sedimentation in the Taylor/Ferrar fiords, which we correlate with discrete climate phases. During the latest Miocene-early Pliocene, wet based glaciers filled the Taylor and Ferrar fiords with active sedimentation in the Taylor Fiord and erosion of basement rocks in the Ferrar Fiord. Glaciers retreated during the Pliocene warm period leaving open marine conditions and deep fiords (> 300 m) at a time when the Ross Sea was free of ice and sea surface temperatures around Antarctica were at least 5 °C warmer than today. We recognise the first significant cooling in DVDP-11 post 2.6 Ma by a shift to current winnowed sediments sourced from the Ross Sea rather than from East Antarctic glaciers. Post 1.7 Ma, lacustrine sediments were deposited behind ice-dammed lakes, which formed when West Antarctic ice expanded and grounded across the Ross Embayment and abutted the Transantarctic Mountains.

  13. Evidence for a Drought-driven (pre-industrial) Regime Shift in an Australian Shallow Lake

    NASA Astrophysics Data System (ADS)

    Mills, K.; Gell, P.; Doan, P.; Kershaw, P.; McKenzie, M.; Lewis, T.; Tyler, J. J.

    2015-12-01

    We present a 750-year record of ecosystem response to long-term drought history from Lake Colac, Victoria. Using multiple lines of evidence, we test the sensitivity and resilience of Lake Colac to independently reconstructed drought history. The sedimentary archive shows that Lake Colac appears to be sensitive to periods of drought. Following drought conditions c. CE 1390, the lake ecosystem indicates signs of recovery. A succession of droughts in the early 1500s initiates a change in the diatom flora, with freshwater species declining and replaced by saline tolerant species, though there is little interpretable change in aquatic palynomorphs. An inferred drought, around CE 1720 appears to precede a major switch in the lake's ecosystem. The lake became increasingly turbid and saline and there is a distinct switch from a macrophyte-dominated system to an algal-dominated system. The arrival of Europeans in Victoria (CE1840) appears to have little effect on the lake's ecosystem, but the terrestrial vegetation indicates regionally established changes including declines in native trees, especially Casuarina, and arrival and expansion of exotic shade or plantation trees Pinus and Cupressus as well as native and introduced weeds. As European impact in the catchment increases, nutrients appear to play a role in the modification of the lake's ecosystem. A long-term drying trend from c. CE 1975 is evident, culminating in the Millennium Drought, which suggests unprecedented conditions in the ecological history of the Lake.

  14. Initiation and evolution processes of submarine instabilities and canyons: Insights from the Northern margin of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Céline, B.; Christian, G.; Leroy, S.; Francis, L.; François, B.; Al-Toubi, K. I.

    2010-12-01

    The study of turbiditic systems and their interactions (climate, tectonic) are not well known in monsoon-influenced areas and on young margins. The Gulf of Aden is a good example of young stretched margin (35-18 Ma), where post-rift sediments are recording the intensification of the Asian monsoon (~7-8 Ma). Therefore the understanding of facies and depositional sequences on this margin is a major challenge for the knowledge of the interactions between sedimentological processes and the dynamic of a young stretched margin. In this paper, the Northern margin of the Gulf of Aden (South Sultanate of Oman; Dhofar) has been studied by both a stratigraphic (seismic reflection data) and a semi-quantitative geomorphologic approach (acoustic imagery, bathymetry and ground DEM) leading firstly to a morphology classification. Three morphological domains have been defined, which match to the structural segmentation inherited from the Oligocene-Miocene margin formation in an oblique rifting context. On the eastern part of the margin, the quaternary to current sedimentary record is strongly controlled by a late uplift. Vertical movements lead to the formation of numerous gravitational instabilities on the continental slope and Mass-Transport Complexes (MTCs) on the lower slope and deep basin. All the incision/erosion stages of the continental slope, from slope instabilities to the formation of mature canyon, are observed on the eastern part of the margin and lead to an incision shaping model on a tectonically controlled steep slope. A main sedimentological switch at least 10 Ma affects the eastern basin of the Gulf of Aden and is characterized by the first occurrence and evolution of deep sea fans and associated MTCs. This supersequence can be divided in two sequences: the first occurrences of MTCs and deep sea fans on the whole margin in the sedimentological record, and only on the eastern part of the margin, the second MTCs event linked to the rising mean slope value. Two

  15. Tectonics and Evolution of the Conjugate Passive Margins of the Eastern Gulf of Aden (Encens-Sheba cruise)

    NASA Astrophysics Data System (ADS)

    D'Acremont, E.; Leroy, S.; Ruellan, P.; Bellahsen, N.; Beslier, M.; Fournier, M.; Gente, P.; Patriat, P.

    2001-12-01

    The gulf of Aden is one of the few oceanic basins in the world where the two conjugate passive margins are preserved beneath a thin post-rift sedimentary cover and can be correlated within a lateral error smaller than 10 km. It is also one of the few basins where the structures can be followed from the oceanic ridge to the margins. It is therefore an adequate site to compare conjugate margins and to study the oceanisation process from the continental break-up to the emplacement of an active spreading ridge. The geophysical data set of the Encens-Sheba cruise in the eastern Gulf of Aden and previous experiment, allow us to define the structure of the two conjugate passive margin in this area. These data show that the basement can be divided into three domains from east to west, with distinct morphologic and sedimentary character. (1) an area of rifted continental crust exhibiting one or two parallel horst blocks trending N110{ ~}E (2) a 20-30km long continent-ocean transition and (3) an oceanic crust with rough basement but smoother relief than the rifted crust. The two conjugate margins are narrow and asymmetrical. The northern margin (southern Yemen and Oman) is steep whereas the southern one (northern and western of Socotra island) is broad. Titled blocks, horsts and grabens bounded by faults dipping towards the ocean or the continent compose the northern margin, whereas a deep basin near the continental slope in the vicinity of the continent-ocean transition characterizes the southern margin. The continent-ocean transition is marked by a negative gradient of the free-air gravity anomalies. The two conjugate margins are divided by transfer faults in 3 major segments. This segmentation that occurs during the continental rifting seems to be directly correlated to the segmentation of the inception oceanic spreading center. The first identifiable magnetic anomalies is the An 5C-An 5D that gives an age of opening of the Gulf of Aden as 16-17Ma ago.

  16. Details of Layers in Victoria Crater's Cape St. Vincent

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Opportunity rover spent about 300 sols (Martian days) during 2006 and 2007 traversing the rim of Victoria Crater. Besides looking for a good place to enter the crater, the rover obtained images of rock outcrops exposed at several cliffs along the way.

    The cliff in this image from Opportunity's panoramic camera (Pancam) is informally named Cape St. Vincent. It is a promontory approximately 12 meters (39 feet) tall on the northern rim of Victoria crater, near the farthest point along the rover's traverse around the rim. Layers seen in Cape St. Vincent have proven to be among the best examples of meter scale cross-bedding observed on Mars to date. Cross-bedding is a geologic term for rock layers which are inclined relative to the horizontal and which are indicative of ancient sand dune deposits. In order to get a better look at these outcrops, Pancam 'super-resolution' imaging techniques were utilized. Super-resolution is a type of imaging mode which acquires many pictures of the same target to reconstruct a digital image at a higher resolution than is native to the camera. These super-resolution images have allowed scientists to discern that the rocks at Victoria Crater once represented a large dune field, not unlike the Sahara desert on Earth, and that this dune field migrated with an ancient wind flowing from the north to the south across the region. Other rover chemical and mineral measurements have shown that many of the ancient sand dunes studied in Meridiani Planum were modified by surface and subsurface liquid water long ago.

    This is a Mars Exploration Rover Opportunity Panoramic Camera image acquired on sol 1167 (May 7, 2007), and was constructed from a mathematical combination of 16 different blue filter (480 nm) images.

  17. Exploration of Victoria crater by the mars rover opportunity

    USGS Publications Warehouse

    Squyres, S. W.; Knoll, A.H.; Arvidson, R. E.; Ashley, James W.; Bell, J.F., III; Calvin, W.M.; Christensen, P.R.; Clark, B. C.; Cohen, B. A.; De Souza, P.A., Jr.; Edgar, L.; Farrand, W. H.; Fleischer, I.; Gellert, Ralf; Golombek, M.P.; Grant, J.; Grotzinger, J.; Hayes, A.; Herkenhoff, K. E.; Johnson, J. R.; Jolliff, B.; Klingelhofer, G.; Knudson, A.; Li, R.; McCoy, T.J.; McLennan, S.M.; Ming, D. W.; Mittlefehldt, D. W.; Morris, R.V.; Rice, J. W., Jr.; Schroder, C.; Sullivan, R.J.; Yen, A.; Yingst, R.A.

    2009-01-01

    The Mars rover Opportunity has explored Victoria crater, a ???750-meter eroded impact crater formed in sulfate-rich sedimentary rocks. Impact-related stratigraphy is preserved in the crater walls, and meteoritic debris is present near the crater rim. The size of hematite-rich concretions decreases up-section, documenting variation in the intensity of groundwater processes. Layering in the crater walls preserves evidence of ancient wind-blown dunes. Compositional variations with depth mimic those ???6 kilometers to the north and demonstrate that water-induced alteration at Meridiani Planum was regional in scope.

  18. View of 'Bottomless Bay' on Rim of 'Victoria' (Altered Contrast)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    As part of its investigation of 'Victoria Crater,' NASA's Mars Exploration Rover Opportunity examined a section of the scalloped rim called 'Bottomless Bay' (or 'Bahia sin Fondo'). This view shows the northeastern side of Bottomless Bay as seen from the southwest. The exposures combined into this mosaic were taken by the rover's panoramic camera through a 750-nanometer filter during the 1,019th Martian day, or sol, of Opportunity's Mars-surface mission (Dec. 5, 2006). Contrast has been altered to improve the visibility of details in shadowed areas.

  19. Bigger Crater Farther South of 'Victoria' on Mars

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Annotated version

    The team operating NASA's Mars Exploration Rover Opportunity has chosen southeast as the direction for the rover's next extended journey, toward a crater more than 20 times wider than 'Victoria Crater.' Opportunity exited Victoria Crater on Aug. 28, 2008, after nearly a year investigating the interior.

    The crater to the southeast is about 22 kilometers (13.7 miles) in diameter and about 300 meters (1,000 feet) deep, exposing a much thicker stack of rock layers than those examined in Victoria Crater.

    The rover team informally calls the bigger crater 'Endeavour' and emphasizes that Opportunity may well never reach it. The rover has already operated more than 18 times longer than originally planned, and the distance to the big crater, about 12 kilometers (7 miles) matches the total distance Opportunity has driven since landing in early 2004. Driving southeastward is expected to take Opportunity to exposures of younger rock layers than is has previously seen and to provide access to rocks on the plain that were thrown long distances by impacts that excavated even deeper, more distant craters.

    The crater that Opportunity will drive toward dominates this orbital view from the Thermal Emission Imaging System (THEMIS) camera on NASA's Mars Odyssey orbiter. The much smaller Victoria Crater is the most prominent circle near the upper left corner of the image. This view is a mosaic of about 50 separate visible-light images taken by THEMIS.

    NASA's Jet Propulsion Laboratory manages the Mars Odyssey and Mars Exploration Rover missions for the NASA Science Mission Directorate, Washington, D.C. THEMIS was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the

  20. Injury surveillance in Victoria, Australia: developing comprehensive injury incidence estimates.

    PubMed

    Watson, W L; Ozanne-Smith, J

    2000-03-01

    This study aimed to develop an estimate of the incidence of all medically-treated injury by level of severity and to broadly describe the epidemiology of injury in the Australian State of Victoria in a given year. Victoria has developed a relatively comprehensive injury surveillance system. Data is currently collected by various agencies on injury deaths, hospitalisations and emergency department attendances. The method used to establish the incidence of both unintentional and intentional injury is described. Incidence figures were directly derived, or estimated from, the available Victorian health sector and Coronial data bases for three level of severity (deaths, hospitalisations and medical treatment only) and for causes of injury, age and gender groups, location of the injury event and activity at the time of injury. In 1993/1994, injuries resulted in at least 1487 deaths, 67,402 persons hospitalised and an estimated 397,160 medically-treated, non-hospitalised injured persons in Victoria. In total, over 466,000 people were injured or 10.5 persons per year for every 100 residents. Males sustain 62% of all injuries yet represent 49.5% of the population. Almost three-quarters of injury fatalities and over 60% of non-fatal injuries occur among males. Young people aged 15-24 years account for 22% of all injuries yet represent only about 16% of the Victorian population. Children (0-14 years) also suffer relatively high injury rates, although mainly less severe, while the elderly are at risk of more severe injuries. The leading cause of injury death in Victoria is suicide, followed by motor vehicle accidents, whereas falls are the leading cause of all non-fatal injury. Most injuries occur in the home (36%), areas of sport and recreation (12.5%) and transport (11.7%). They are mainly associated with leisure activities (33.1%), work (11%) and transportation (10.8%). This study demonstrates a method for the development of comprehensive injury incidence estimates. The

  1. Exploration of Victoria Crater by the Mars Rover Opportunity

    NASA Astrophysics Data System (ADS)

    Squyres, S. W.; Knoll, A. H.; Arvidson, R. E.; Ashley, J. W.; Bell, J. F.; Calvin, W. M.; Christensen, P. R.; Clark, B. C.; Cohen, B. A.; de Souza, P. A.; Edgar, L.; Farrand, W. H.; Fleischer, I.; Gellert, R.; Golombek, M. P.; Grant, J.; Grotzinger, J.; Hayes, A.; Herkenhoff, K. E.; Johnson, J. R.; Jolliff, B.; Klingelhöfer, G.; Knudson, A.; Li, R.; McCoy, T. J.; McLennan, S. M.; Ming, D. W.; Mittlefehldt, D. W.; Morris, R. V.; Rice, J. W.; Schröder, C.; Sullivan, R. J.; Yen, A.; Yingst, R. A.

    2009-05-01

    The Mars rover Opportunity has explored Victoria crater, a ~750-meter eroded impact crater formed in sulfate-rich sedimentary rocks. Impact-related stratigraphy is preserved in the crater walls, and meteoritic debris is present near the crater rim. The size of hematite-rich concretions decreases up-section, documenting variation in the intensity of groundwater processes. Layering in the crater walls preserves evidence of ancient wind-blown dunes. Compositional variations with depth mimic those ~6 kilometers to the north and demonstrate that water-induced alteration at Meridiani Planum was regional in scope.

  2. Apristurus breviventralis, a new species of deep-water catshark (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from the Gulf of Aden.

    PubMed

    Kawauchi, Junro; Weigmann, Simon; Nakaya, Kazuhiro

    2014-01-01

    A new deep-water catshark of the genus Apristurus Garman, 1913 is described based on nine specimens from the Gulf of Aden in the northwestern Indian Ocean. Apristurus breviventralis sp. nov. belongs to the 'brunneus group' of the genus and is characterized by having pectoral-fin tips reaching beyond the midpoint between the paired fin bases, a much shorter pectoral-pelvic space than the anal-fin base, a low and long-based anal fin, and a first dorsal fin located behind pelvic-fin insertion. The new species most closely resembles the western Atlantic species Apristurus canutus, but is distinguishable in having greater nostril length than internarial width and longer claspers in adult males. Apristurus breviventralis sp. nov. represents the sixth species of Apristurus from the western Indian Ocean and the 38th species globally.  PMID:25543616

  3. The role of structural inheritance in oblique rifting: Insights from analogue models and application to the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Autin, Julia; Bellahsen, Nicolas; Leroy, Sylvie; Husson, Laurent; Beslier, Marie-Odile; d'Acremont, Elia

    2013-11-01

    The geometry and kinematics of rifts are strongly controlled by pre-existing structures that may be present in both the crust and the mantle lithosphere. In the Gulf of Aden, the Tertiary oblique rift developed through inherited Mesozoic extensional basins that trend orthogonal to the direction of Oligo-Miocene divergence. Such inheritance may produce lateral variations in crustal thickness and thus in rheology of the crust and mantle lithosphere. How can such variations influence the present-day geometry of oblique rifts? May they locally overcome the impact of the oblique rheological weaknesses that in certain cases control the overall trend of the rift system? Moreover, we observe that major fracture zones systematically crosscut the inherited basins: may such inheritance influence the localization of major fracture zones by shifting the initial spreading centers?

  4. Ages of tuff beds at East African early hominid sites and sediments in the Gulf of Aden

    USGS Publications Warehouse

    Sarna-Wojcicki, A. M.; Meyer, C.E.; Roth, P.H.; Brown, F.H.

    1985-01-01

    The early hominids of East Africa were dated by determining the ages of tuff beds at the sites. Despite much research using palaeomagnetic and K/Ar-dating techniques, some of those ages are still controversial 1,2. To obtain independent age estimates for these tephra layers, we have examined cores from DSDP Sites 231 and 232 in the Gulf of Aden (Fig. 1a) which consist mainly of calcareous nannofossil ooze, but also contain rare tephra horizons3 dated by interpolation from the established nannofossil stratigraphy (Fig. 1b). Chemical analysis confirms that the identity and sequence of these horizons is the same as that at the East African sites. We conclude that the age of the Tulu Bor Tuff is <3.4 Myr and hence that the Hadar hominid specimens are also

  5. Cenozoic evolution of the Socotra Island: opening of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Razin, P.; Robin, C.; Serra Kiel, J.; Leroy, S.; Bellahsen, N.; Khanbari, K.

    2009-12-01

    A complete stratigraphic and geological map revision of the Tertiary of Socotra Island is undertaken in order to better characterize the geometry and the tecto-sedimentary evolution of the southern margin of the Gulf of Aden, and compare them with those of the conjugate northern margin in Oman. An increase of the rate of subsidence is recorded during the Late Eocene and is associated with a transgressive peak within carbonate platform deposits (Aydim Fm.). At the scale of the Arabian plate, the extent of this platform is reduced to the future rift area. This evolution of the platform system shows a modification of the sedimentary profiles, controlled by the beginning of the rifting. The syn-rift deposits of the Early Oligocene correspond to sub-reef carbonate platform facies (Ashawq Fm.). First, the throw of synsedimentary faults and the movements linked with differential subsidence are widely compensated by carbonate production which manages to maintain a platform profile. These movements are recorded by thickness variations, significant lateral variations in the platform facies and by a local inversion of sedimentary polarities controlled by the tilting of faulted blocks. Like on the northern margin, an acceleration of the extension process leads, during the Late Oligocene, to a collapse of the platform and to the creation of deep sub-basins with carbonate gravity-flow sedimentation. Marginal reef platforms keep growing at this stage on the structural highs and feed gravity-flow sedimentary systems. The sedimentation rate stays then relatively low in the basin, forming a complex topography of the margin, marked by a segmentation into numerous sub-basins more or less connected and separated by submarine escarpments marked by wedges of breccia deposits along active normal faults. In different points, these faults are sealed by sedimentary deposits characterized by progressive unconformities and onlap geometries on the fault escarpments. These geometries show the

  6. Turbidite system architecture and recent sedimentary processes along the Nothern margin of the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Baurion, C.; Zaragosi, S.; Gorini, C.; Leroy, S.; Lucazeau, F.; Migeon, S.

    2012-04-01

    The depositional architecture across a stretched and segmented margin is composed of several turbidite systems and mass-transport deposits, which constitute the record of tectonic, climate and high-resolution eustatic events. The characterisation of turbidite system architecture is a main challenge in order to clarify which of these parameters controls the margin dynamics. In the Eastern part of the Northern margin of the Gulf of Aden, the main turbidite systems are localised in the western part of the basin and the mass-transport deposits are mainly concentrated along the part of the margin affected by a late post-rift uplift. Using bathymetric data, backscatter imagery, Chirp profiles, and sediment cores, we show that these deep-water turbidite systems highlight the importance of flooding of wadis (streambed that remains dry except during the rainy season), under the influence of the Asian monsoon-climate, on the sediment transfer from onshore to the deep basin. Although previous studies revealed the importance of coarse-grained carbonate turbidites on the sedimentation of the basin, our cores underline the predominance of fine-grained turbidites in our study area. This second type of turbidites seems to be related to the onshore sedimentary cover, which is mainly composed of carbonate rocks. These rocks are incised by a drainage system, which is characterised by a watershed localised only a few kilometres from the coastline. This morphology implies that the drainage network is not mature on this starved margin, affected by post-rift uplift. To conclude, the recent sediment architecture of the northern margin of the Gulf of Aden appears to be primarily controlled by the strong climatic and tectonic forcing parameters.

  7. Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden

    NASA Astrophysics Data System (ADS)

    Lucazeau, Francis; Leroy, Sylvie; Rolandone, Frédérique; d'Acremont, Elia; Watremez, Louise; Bonneville, Alain; Goutorbe, Bruno; Düsünur, Doga

    2010-07-01

    In order to investigate the importance of fluid circulation associated with the formation of ocean-continent transitions (OCT), we examine 162 new heat-flow (HF) measurements in the eastern Gulf of Aden, obtained at close locations along eight seismic profiles and with multi-beam bathymetry. The average HF values in the OCT and in the oceanic domain (~ 18 m.y.) are very close to the predictions of cooling models, showing that the overall importance of fluids remains small at the present time compared to oceanic ridge flanks of the same age. However, local HF anomalies are observed, although not systematically, in the vicinity of the unsedimented basement and are interpreted by the thermal effect of meteoric fluids flowing laterally. We propose a possible interpretation of hydrothermal paths based on the shape of HF anomalies and on the surface morphology: fluids can circulate either along-dip or along-strike, but are apparently focussed in narrow "pipes". In several locations in the OCT, there is no detectable HF anomaly while the seismic velocity structure suggests serpentinization and therefore past circulation. We relate the existence of the present day fluid circulation in the eastern Gulf of Aden to the presence of unsedimented basement and to the local extensional stress in the vicinity of the Socotra-Hadbeen fault zone. At the scale of rifted-margins, fluid circulation is probably not as important as in the oceanic domain because it can be inhibited rapidly with high sedimentation rates, serpentinization and stress release after the break-up.

  8. Structure of a Young Oceanic Basin: Results of the Encens-Sheba Cruise in the Eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, S.; Fournier, M.; Gente, P.; Al-Kathiri, A.; Bellahsen, N.; Beslier, M.; Blais, A.; d'Acremont, E.; Mercouriev, S.; Patriat, P.; Perrot, J.

    2001-12-01

    The Encens-Sheba cruise was carried out in July 2000 aboard R/V Marion Dufresne in the eastern part of the Gulf of Aden. It produced a complete swath bathymetry, gravity and magnetic data set between southern Oman (Dhofar) and Yemen in the north and Socotra island in the south, and between Alula-Fartak fracture zone in the west and the Socotra fracture zone in the east. The new data set shows a complete section of a young oceanic basin from conjugate passive continental margins up to the oceanic spreading center. On the conjugate passive margins, single channel seismic data have been also collected. The two conjugate margins are steep, narrow and asymmetric. Titled blocks, horsts and grabens bounded by faults dipping towards the ocean or the continent compose the northern margin, whereas a deep basin near the continental slope in the vicinity of the continent-ocean transition characterizes the southern margin. The two margins are divided by transfer faults in 3 major segments. The continent-ocean transition is marked by a negative gradient of the free-air gravity anomalies. The present Sheba ridge is divided by discontinuities in 3 segments from 20 to 100 km long. The central part of the 100-km-long western segment is characterized by an axial uplift reflecting a large magmatic activity. The two other shorter segments display axial valley more classical for a slow spreading ridge (1.1cm/a). Although the magnetic anomalies show a complex history of oceanic accretion, the evolution of the segmentation can be followed. Indeed, the segmentation of the conjugate passive margins seems to be correlated with the location of early traces of identifiable Sheba ridge offset. The oldest anomalies are identified as an5C-an5D. The Gulf of Aden in this area thus opened 16-17Ma ago, which is significantly older than the 12-13 Ma suggested by previous studies.

  9. Nature of deep crustal structures of the northeastern Gulf of Aden margin inferred from S-wave modeling

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Leroy, S.; D'Acremont, E.

    2011-12-01

    The Encens cruise (Feb.-March 2006, Leroy et al., 2010) allowed for the acquisition of a large refraction/wide-angle reflection dataset along the northeastern Gulf of Aden margin, between the first order segmentation of the gulf defined by Alula-Fartak and Socotra-Hadbeen fracture zones. A second order segmentation divides this margin into three parts, from west to east: Ashawq-Salalah, Taqah and Mirbat segments. P-wave velocity modeling already allows us to image crustal thinning and structures from the continental to the oceanic crust, and to identify a lower crustal intermediate body on the Ashawq-Salalah segment at the base of the transitional and oceanic crusts. This intermediate body has been interpreted as mafic , and linked to a post-rift thermal anomaly. The instruments, which have been deployed on the Ashawq-Salalah segment, were recording shots on 4-components. Data show good quality S-wave converted arrivals in the transitional and oceanic crust. After picking and modeling of these arrivals, we have identified two families of converted waves:: (1) P-waves converted to S-waves at the basement interface on the way up, and (2) P-waves converted to S-waves at the basement on the way down and traveling through deep structures as shear-waves. The first family provides constraints on the S-wave velocities in the sediment layer while the second family constrains S-wave velocities in the transitional and oceanic crust. The Poisson ratio in the intermediate body (0.285) together with the P-wave velocity (7.7 km/s) and density (3.1 kg/m3) confirms its mafic nature. Furthermore, this study provides more information on the nature of the ocean-continent transition crust and its variations along the northeastern Gulf of Aden margin from a thermally affected segment to a tectonically influenced one.

  10. The crustal structure of the north-eastern Gulf of Aden continental margin: insights from wide-angle seismic data

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Leroy, S.; Rouzo, S.; D'Acremont, E.; Unternehr, P.; Ebinger, C.; Lucazeau, F.; Al-Lazki, A.

    2011-02-01

    The wide-angle seismic (WAS) and gravity data of the Encens survey allow us to determine the deep crustal structure of the north-eastern Gulf of Aden non-volcanic passive margin. The Gulf of Aden is a young oceanic basin that began to open at least 17.6 Ma ago. Its current geometry shows first- and second-order segmentation: our study focusses on the Ashawq-Salalah second-order segment, between Alula-Fartak and Socotra-Hadbeen fracture zones. Modelling of the WAS and gravity data (three profiles across and three along the margin) gives insights into the first- and second-order structures. (1) Continental thinning is abrupt (15-20 km thinning across 50-100 km distance). It is accommodated by several tilted blocks. (2) The ocean-continent transition (OCT) is narrow (15 km wide). The velocity modelling provides indications on its geometry: oceanic-type upper-crust (4.5 km s-1) and continental-type lower crust (>6.5 km s-1). (3) The thickness of the oceanic crust decreases from West (10 km) to the East (5.5 km). This pattern is probably linked to a variation of magma supply along the nascent slow-spreading ridge axis. (4) A 5 km thick intermediate velocity body (7.6 to 7.8 km s-1) exists at the crust-mantle interface below the thinned margin, the OCT and the oceanic crust. We interpret it as an underplated mafic body, or partly intruded mafic material emplaced during a `post-rift' event, according to the presence of a young volcano evidenced by heat-flow measurement (Encens-Flux survey) and multichannel seismic reflection (Encens survey). We propose that the non-volcanic passive margin is affected by post-rift volcanism suggesting that post-rift melting anomalies may influence the late evolution of non-volcanic passive margins.

  11. Formula-Based Public School Funding System in Victoria: An Empirical Analysis of Equity

    ERIC Educational Resources Information Center

    Bandaranayake, Bandara

    2013-01-01

    This article explores the formula-based school funding system in the state of Victoria, Australia, where state funds are directly allocated to schools based on a range of equity measures. The impact of Victoria' funding system for education in terms of alleviating inequality and disadvantage is contentious, to say the least. It is difficult…

  12. A Snapshot: Multicultural Music Teaching in Schools in Victoria, Australia, Portrayed by School Teachers

    ERIC Educational Resources Information Center

    Nethsinghe, Rohan Nishantha

    2012-01-01

    Due to the changing demographic factors and as demanded by the governmental policies and regulations, schools in Victoria, Australia, are expected to foster multicultural educational programs that address the diverse needs of students. Research has found that school teachers in Victoria struggle to provide the aspired to multicultural education…

  13. Events Management Education through CD-ROM Simulation at Victoria University of Technology.

    ERIC Educational Resources Information Center

    Perry, Marcia; And Others

    There has been a rapid growth in the events industry in Victoria and Australia over the past five years with an increase in large scale events--resulting in substantive economic impact. The growth in events in Australia is projected to continue to beyond 2001. The Department of Management at Victoria University of Technology (VU) received a…

  14. Rock Glaciers in the Upper Basin of Bermejo River, Santa Victoria, Argentina

    NASA Astrophysics Data System (ADS)

    Ahumada, A. L.; Íbáñez Palacios, G. P.; Toledo, M. A.; Páez, S. V.

    2013-05-01

    The Bermejo River is an international basin in the Tropical Andes, Santa Victoria range. The Santa Victoria range extend in N-S sense (22°08' and 23°00' South latitude between 65° and 65°30' West longitude). It maxim height is about 5.055 m s.n.m. and it average height is 3000 m s.n.m. There have been localize intact rock glaciers (active and inactive) and relict. The rock glaciers are frozen water reservoir and regulate the water regime in the high mountain over the world. The global warming effects have been express in this region with average annual air temperatures in increase: The series of temperatures of La Quiaca weather station, years 1911-2010, shows an increase about 1° C (from 9,14° C to 10,08° C) since 70' decade to actuality. This study aims to contribute to the survey of intact rock glaciers and the suite of accompanying landforms. The geographic identification and location of rock glaciers have made through the interpretation of aerial photographs and LandSat 7 and Aster Images in comparison with Google Earth using GIS and visual interpretation technics. This information has controlled with fieldwork in several campaigns. The rock glaciers are classified (in base of it activity) in actives, inactives and relict. The first and the second class were grouped in a category called intact rock glaciers for simplify it identification. The unified categories are water-storing. In the fieldwork have determinated the following aspects: 1- Active processes determination (needle ice, lenticular ice formation, etc.) and its sedimentary products: sucrose structure, inverted gradation, extrusion, open work gravels. 2- Location and geomorphologic measurement of rock glaciers and periglacial forms. There are identified 318 intact rock glaciers in high basin of Bermejo river, Sub-basins Condado river, Los Toldos-Lipeo river and Iruya river, Santa Victoria range. The actives rock glaciers, indicators of discontinuous permafrost, are installed from 4300 m s

  15. On the Rim of 'Victoria Crater' (Vertical Projection)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity reached the rim of 'Victoria Crater' in Mars' Meridiani Planum region with a 26-meter (85-foot) drive during the rover's 951st Martian day, or sol (Sept. 26, 2006). After the drive, the rover's navigation camera took the three exposures combined into this view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    A half mile in the distance one can see about 20 percent of the far side of the crater framed by the rocky cliffs in the foreground to the left and right of the image. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind.

    The position at the end of the sol 951 drive is about six meters from the lip of an alcove called 'Duck Bay.' The rover team planned a drive for sol 952 that would move a few more meters forward, plus more imaging of the near and far walls of the crater.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed.

    This view is presented as a vertical projection with geometric seam correction.

  16. On the Rim of 'Victoria Crater' (Polar Projection)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA's Mars rover Opportunity reached the rim of 'Victoria Crater' in Mars' Meridiani Planum region with a 26-meter (85-foot) drive during the rover's 951st Martian day, or sol (Sept. 26, 2006). After the drive, the rover's navigation camera took the three exposures combined into this view of the crater's interior. This crater has been the mission's long-term destination for the past 21 Earth months.

    A half mile in the distance one can see about 20 percent of the far side of the crater framed by the rocky cliffs in the foreground to the left and right of the image. The rim of the crater is composed of alternating promontories, rocky points towering approximately 70 meters (230 feet) above the crater floor, and recessed alcoves. The bottom of the crater is covered by sand that has been shaped into ripples by the Martian wind.

    The position at the end of the sol 951 drive is about six meters from the lip of an alcove called 'Duck Bay.' The rover team planned a drive for sol 952 that would move a few more meters forward, plus more imaging of the near and far walls of the crater.

    Victoria Crater is about five times wider than 'Endurance Crater,' which Opportunity spent six months examining in 2004, and about 40 times wider than 'Eagle Crater,' where Opportunity first landed.

    This view is presented as a polar projection with geometric seam correction.

  17. Analysis of continuous GPS measurements from southern Victoria Land, Antarctica

    USGS Publications Warehouse

    Willis, Michael J.

    2007-01-01

    Several years of continuous data have been collected at remote bedrock Global Positioning System (GPS) sites in southern Victoria Land, Antarctica. Annual to sub-annual variations are observed in the position time-series. An atmospheric pressure loading (APL) effect is calculated from pressure field anomalies supplied by the European Centre for Medium-Range Weather Forecasts (ECMWF) model loading an elastic Earth model. The predicted APL signal has a moderate correlation with the vertical position time-series at McMurdo, Ross Island (International Global Navigation Satellite System Service (IGS) station MCM4), produced using a global solution. In contrast, a local solution in which MCM4 is the fiducial site generates a vertical time series for a remote site in Victoria Land (Cape Roberts, ROB4) which exhibits a low, inverse correlation with the predicted atmospheric pressure loading signal. If, in the future, known and well modeled geophysical loads can be separated from the time-series, then local hydrological loading, of interest for glaciological and climate applications, can potentially be extracted from the GPS time-series.

  18. VICTORIA-92 pretest analyses of PHEBUS-FPT0

    SciTech Connect

    Bixler, N.E.; Erickson, C.M.

    1994-01-01

    FPT0 is the first of six tests that are scheduled to be conducted in an experimental reactor in Cadarache, France. The test apparatus consists of an in-pile fuel bundle, an upper plenum, a hot leg, a steam generator, a cold leg, and a small containment. Thus, the test is integral in the sense that it attempts to simulate all of the processes that would be operative in a severe nuclear accident. In FPT0, the fuel will be trace irradiated; in subsequent tests high burn-up fuel will be used. This report discusses separate pretest analyses of the FPT0 fuel bundle and primary circuit have been conducted using the USNRC`s source term code, VICTORIA-92. Predictions for release of fission product, control rod, and structural elements from the test section are compared with those given by CORSOR-M. In general, the releases predicted by VICTORIA-92 occur earlier than those predicted by CORSOR-M. The other notable difference is that U release is predicted to be on a par with that of the control rod elements; CORSOR-M predicts U release to be about 2 orders of magnitude greater.

  19. 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 ...

  20. 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...

  1. 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 ...

  2. Cationic Triarylmethane Photosensitizers For Selective Photochemotherapy: Victoria Blue-Bo, Victoria Blue-R And Malachite Green

    NASA Astrophysics Data System (ADS)

    Wadwa, K.; Smith, S.; Oseroff, A. R.

    1989-03-01

    We have investigated the malignant cell selective phototoxicity of some triarylmethane dyes including Victoria Blue BO (VB-BO), Victoria Blue R (VB-R), and Malachite Green (MG). Phototoxicity was studied in human squamous (FaDu) and colon (CX-1) carcinoma, and in human and murine melanoma (NEL, B-16) cell lines, as well as in non-malignant monkey kidney cells (CV-1). Cultured cells were exposed to varying concentrations of the dyes for 60 min, washed with PBS, irradiated after an efflux time of 90 min in culture media, and placed in a colony forming assay. VB-BO was the most effective photosensitizer, giving 90% killing of malignant cells such as B-16 when treated with 5x10-8 M dye and 13 J/cm2 light. CV-1 cells were unaffected under these conditions. VB-R was about 10 fold less effective, while MG had minimal phototoxicity in this assay. VB-BO was studied in vivo, using subcutaneous FaDu tumors in nude mice. At a dose of 3 mg/kg followed 4 hrs later by dye laser irradiation under conditions which did not produce hyperthermia, there was an 80% complete remission rate without significant phototoxicity to overlying or adjacent normal skin. The triarylmethanes are a novel class of photosensitizers which may have promise in vitro and in vivo.

  3. The Paleogene pre-rift to syn-rift succession in the Dhofar margin (northeastern Gulf of Aden): Stratigraphy and depositional environments

    NASA Astrophysics Data System (ADS)

    Robinet, J.; Razin, P.; Serra-Kiel, J.; Gallardo-Garcia, A.; Leroy, S.; Roger, J.; Grelaud, C.

    2013-11-01

    The Paleogene deposits on the northern passive margin of the Gulf of Aden record the transition from the pre-rift to the syn-rift stages of the southern Arabian plate margin. In southern Oman (Dhofar Region), the relative continuity of the sedimentary record offers the possibility to investigate the early deformation phases of the Aden rift system. A new detailed sedimentological and biostratigraphic analysis of the Cuisian to Rupelian deposits of the Dhofar region allows to define a second-order transgressive-regressive cycle, that can be further subdivided into four third-order sequences between the Late Cuisian and the Early Rupelian time. The sequence stratigraphy established in this study has major implications for the understanding of the time equivalent deposits described in the eastern Arabian plate and illustrates the polyphased history of the initiation of the Aden Gulf rift system. The first two depositional sequences are controlled by a phase of deformation that only affects the eastern Oman margin, in relation with the tectonic activity at the Arabian-Indian plate boundary, during the Late Cuisian-Middle Lutetian. The last two depositional sequences record a westward migration of the deformation within the eastern realm of the proto-Gulf of Aden from the Bartonian. Priabonian uplift resulted in the basinward shift of the depositional system followed by a phase of tectonic subsidence that is recorded by the aggradation of lacustrine deposits in localized fault bounded basins. A subsequent major regional relative sea level fall related to domal uplift is recorded by terrigenous deposits (lower part of the Ashawq Formation) prior to the main phase of syn-rift tectonic subsidence (upper part of the Ashawq and Mughsayl formations) in Rupelian-Chattian times.

  4. 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.

  5. VENUS - The Victoria Experimental Network Under the Sea: First Light

    NASA Astrophysics Data System (ADS)

    Dewey, R. K.; Tunnicliffe, V.; Round, A.

    2006-05-01

    The Victoria Experimental Network Under the Sea (VENUS) is a recently installed cabled ocean observatory representing the next generation of infrastructure technology. VENUS is scheduled to consist of two major segments, one in Saanich Inlet (installed in February 2006), and a second in the Strait of Georgia (planned for October 2006). The technologies associated with both the hardware and software that will deliver data from instruments to scientists is being developed in collaboration with both the NEPTUNE Canada and MARS observatories. The presentation will provide an overview of the science projects planned for stage one of the installed instruments, the engineering design of the infrastructure, the preliminary design of the Data Management and Archive System (DMAS), lessons learned so far, and preliminary results from the first few months of data from Saanich Inlet.

  6. Layers of 'Cape Verde' in 'Victoria Crater' (Stereo)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of Victoria crater is looking north from 'Duck Bay' towards the dramatic promontory called 'Cape Verde.' The dramatic cliff of layered rocks is about 50 meters (about 165 feet) away from the rover and is about 6 meters (about 20 feet) tall. The taller promontory beyond that is about 100 meters (about 325 feet) away, and the vista beyond that extends away for more than 400 meters (about 1300 feet) into the distance. This is a red-blue stereo anaglyph generated from images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 430-nanometer filters.

  7. Layers of 'Cape Verde' in 'Victoria Crater' (Enhanced)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of Victoria crater is looking north from 'Duck Bay' towards the dramatic promontory called 'Cape Verde.' The dramatic cliff of layered rocks is about 50 meters (about 165 feet) away from the rover and is about 6 meters (about 20 feet) tall. The taller promontory beyond that is about 100 meters (about 325 feet) away, and the vista beyond that extends away for more than 400 meters (about 1300 feet) into the distance. This is a false color rendering (enhanced to bring out details from within the shadowed regions of the scene) of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  8. Layers of 'Cape Verde' in 'Victoria Crater' (False Color)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of Victoria crater is looking north from 'Duck Bay' towards the dramatic promontory called 'Cape Verde.' The dramatic cliff of layered rocks is about 50 meters (about 165 feet) away from the rover and is about 6 meters (about 20 feet) tall. The taller promontory beyond that is about 100 meters (about 325 feet) away, and the vista beyond that extends away for more than 400 meters (about 1300 feet) into the distance. This is an enhanced false color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  9. Layers of 'Cabo Frio' in 'Victoria Crater' (False Color)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is an enhanced false color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  10. Layers of 'Cabo Frio' in 'Victoria Crater' (Stereo)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is a red-blue stereo anaglyph generated from images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 430-nanometer filters.

  11. Forty Meters from Entry to Victoria Crater (Polar)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera during the rover's 1,278th Martian day, or sol, (Aug. 28, 2007) to take the images combined into this view. The rover was perched at the lip of Victoria Crater, which is about 800 meters (one-half mile) in diameter.

    After assessment of possible routes for Opportunity to descend into the crater, the rover team selected a site farther to the right along the rim. That selected entry point lies near the ripple of bright soil visible just outside the crater near the top center of this scene. The driving distance for Opportunity from the Sol 1,278 viewpoint to the selected entry point is about 40 meters (about 130 feet).

    This view is presented as a polar projection with geometric seam correction.

  12. Forty Meters from Entry to Victoria Crater (Vertical)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Opportunity used its navigation camera during the rover's 1,278th Martian day, or sol, (Aug. 28, 2007) to take the images combined into this view. The rover was perched at the lip of Victoria Crater, which is about 800 meters (one-half mile) in diameter.

    After assessment of possible routes for Opportunity to descend into the crater, the rover team selected a site farther to the right along the rim. That selected entry point lies near the ripple of bright soil visible just outside the crater near the top center of this scene. The driving distance for Opportunity from the Sol 1,278 viewpoint to the selected entry point is about 40 meters (about 130 feet).

    This view is presented as a vertical projection with geometric seam correction.

  13. Impact of Land Use on Soil Respiration in Southwestern Victoria

    NASA Astrophysics Data System (ADS)

    Teodosio, B.; Daly, E.; Pauwels, V. R. N.

    2015-12-01

    Land use management is one of the key contributors to the global environmental change. Considerable changes in landscapes have been experienced in Southwestern Victoria, Australia in the past two decades. Eucalyptus globulus (blue gum) plantations have expanded, resulting in possible changes in the water and carbon balances of catchments. The shift from pastures to plantations could have a significant impact on the local carbon balance with possible effects on atmospheric CO2 concentration and vegetation productivity. We present preliminary measurements from a field study comparing soil respiration in a plantation and a pasture. Adjacent catchments in Southwestern Victoria, near Gatum, were used as study areas; the prominent difference between the two catchments is the land use, with one catchment being used as a pasture for livestock grazing and the other catchment being mainly planted with blue gums. The variability of soil respiration in the pasture is governed by differences in soil moisture and substrate content due to local features of the topography and livestock grazing. Soil respiration measurements in the plantation were taken on mounds, access tracks, and open spaces. Most observations on mounds had higher soil respiration possibly due to root and mycorrhizal respiration. The measurements in open spaces had comparable values with mound measurements; this might be due to a less limited radiation. The soil respiration between trees had lower values, possibly because of radiation limitation due to the canopy cover. These preliminary measurements allow us to compare soil respiration variability across catchments with different land uses. This is important to estimate CO2 fluxes from soil to the atmosphere in large areas and will be valuable in estimating gross primary production from measurements of net ecosystem exchange.

  14. Color variations on Victoria quadrangle: support for the geological mapping

    NASA Astrophysics Data System (ADS)

    Zambon, F.; Galluzzi, V.; Carli, C.; Giacomini, L.; Massironi, M.; Palumbo, P.; Guzzetta, L.; Mancinelli, P.; Vivaldi, V.; Ferranti, L.; Pauselli, C.; Frigeri, A.; Zusi, M.; Pozzobon, R.; Cremonese, G.; Ferrari, S.; Capaccioni, F.

    2015-10-01

    Mercury is the closest planet to the Sun. Its extreme thermal environment makes it difficult to explore onsite. In 1974, Mariner 10, the first mission dedicated to Mercury, covered 45% of the surface during of the three Hermean flybys [1]. For about 30 years after Mariner 10, no other mission has flownto Mercury. Many unresolved issues need an answer, and in recent years the interest about Mercury has increased. MESSENGER mission contributed to understand Mercury's origin, its surface structure, and the nature of its magnetic field, exosphere, and magnetosphere [1]. The Mercury Dual Imaging System (MDIS) provided a global coverage of Mercury surface with variable spatial resolution. MDIS is equipped with a narrow angle camera (NAC), dedicated to the study of the geology and a wide angle camera (WAC) with 12 filters useful to investigate the surface composition[2]. Mercury has been divided into 15 quadrangles for mapping purposes [3]. The mapping process permits integration of different geological surface information to better understand the planet crust formation and evolution. Merging spectroscopically data is a poorly followed approach in planetary mapping, but it gives additional information about lithological composition, contributing to the construction of a more complete geological map [e.g. 4]. Recently, [5] proposed a first detailed map of all the Victoria quadrangle (H2). Victoria quadrangle is located in a longitude range between 270°E and 360°E and a latitude range of 22.5°N and 65°N,and itwas only partially mapped by Mariner 10 data[3]. Here we investigate the lithological variation by using the MDIS-WAC data to produce a set of color map products which could be asupport to the geological mapping [5]. The future ESA-JAXA mission to Mercury, BepiColombo, will soon contribute to improve the knowledge of Mercury surface composition and geology thanks to the Spectrometer and Imagers for MPO BepiColombo-Integrated Observatory SYStem (SIMBIO-SYS)[6].

  15. Offshore investigations on Wilkes land-Victoria land margin, Antarctica

    SciTech Connect

    Eittreim, S.L.

    1984-04-01

    In January 1984, the US Geological Survey research vessel S. P. Lee carried out investigations of the Antarctic continental margin in the Wilkes Land Victoria Land areas, using 24-channel and high-resolution seismic, sonobuoy refraction, gravity, magnetic, and bottom-sampling methods. This investigation augmented previous surveys of the Dumont d'Urville area by the French Petroleum Institute and explored new areas west and east to the boundary between the onshore Wilkes basin and the Victoria Land highlands. These surveys defined sediment thickness distribution and seismic stratigraphy in this frontier area. The tectonic style of the boundary between the East Antarctic craton and the younger crust of West Antarctica in the Ross Sea is revealed by one multichannel seismic line across this important boundary. The initial breakup of Antarctical from Australia occurred as a slowly spreading phase during the middle Cretaceous. According to Deep Sea Drilling Project results on the Tasman Rise, conditions of restricted circulation existed in the growing basin between the continents before the late Eocene. After the late Eocene, the major oceanic circulation pattern was established. Before that time, conditions were favorable for preservation of organic-carbon deposits on the sea floor. Among the questions to be addressed with this data are the following. How do apparent subsidence rates of this passive margin compare with others around the world. Does the onshore subglacial Wilkes basins to the Otway and Ceduna basins of Australia exists. What is the effect of the ice cap on the stratigraphy of this margin. Do the two major Tertiary ice advances have conspicuous seismic-stratigraphic signatures.

  16. The effect of thermal weakening and buoyancy forces on rift localization: Field evidences from the Gulf of Aden oblique rifting

    NASA Astrophysics Data System (ADS)

    Bellahsen, N.; Husson, L.; Autin, J.; Leroy, S.; d'Acremont, E.

    2013-11-01

    On the basis of field and geophysical data, analog and numerical models, we here discuss the role of buoyancy forces arising from thickness variations in the lithosphere during rifting. In the Gulf of Aden, an oceanized Tertiary oblique rift, several successive directions of extension and associated normal faults suggest that transient stress rotations occurred during rifting. Especially, rift-parallel faults (070°E) overprinted the early divergence-perpendicular normal faults (110°E). Moreover, some first-order differences are noticeable between the western part of the Gulf, which deformed under the Afar hot spot influence, and the eastern part. In the western Gulf of Aden, the ocean-continent transition (OCT) and the oceanic ridge have cut obliquely through the inherited and reactivated Mesozoic basins (100°E to 140°E). The OCT trend is parallel to the overall Gulf trend (070°E). In the eastern part, the oceanization occurred within few syn-rift 110°E-trending basins and the OCT trends mostly perpendicular to the divergence direction. Here, we propose that this contrast is strongly controlled by the Afar hot spot: during rifting times, the hot spot likely induced a hot thermal anomaly in the western asthenosphere. This may have triggered both thermal buoyancy forces and thermal weakening of the lithosphere that helped localizing the rift obliquely. In such localized rift, rift-perpendicular trending crustal buoyancy forces (i.e. around 160°E) have enhanced rift-parallel normal faults (070°E) during final rift localization into a narrow zone strongly oblique to the early syn-rift basins. As a consequence of the Afar hot spot, in the west, the ridge is long and straight; in the east, the ridge segments are rather long too (although less than in the west) as the ridge initiated parallel to the OCT; in between, the ridge is more segmented as both the hot spot influence gradually decreases eastward and the ridge initiated obliquely to the OCT.

  17. Electrical 2D Section of a Continental Break-up Region, Gulf of Aden - Results From the ANC Cruise

    NASA Astrophysics Data System (ADS)

    Toh, H.; Goto, T.; d'Acremont, E.; Leroy, S.

    2001-12-01

    Seafloor magnetotelluric (MT) array study was conducted in the western part of Sheba Ridge, Gulf of Aden. Five ocean bottom electromagnetometers were deployed along a 200 km long profile perpendicular to a mature ridge segment over the continental break-up region. All these instruments were successfully recovered during the Aden New Century Cruise (ANCC). Temporal EM variations were measured for about three weeks at a sampling rate of 0.1 Hz in order to delineate the electrical structure beneath the continental break-up region. The magnetic and electric resolutions were 10 pT and 60 nV/m, respectively. The time- and tilt-corrected EM time series were processed by the robust remote reference method (Chave et al., 1987) to yield MT impedance tensors at each site for 12 periods ranging from 480s to 40960s. The MT tensors were then rotated toward a direction perpendicular to the mean geological strike of the ridge segment (N27E). The ridge-parallel and ridge-perpendicular components of the tensors were used as TM and TE modes in subsequent two-dimensional (2D) MT inversions (Uchida, 1993) using Akaike's Bayesian Information Criterion (ABIC). A joint 2D ABIC inversion using both modes and incorporating the 2D bathymetry along the profile yielded a model that showed a shallow conductor in the south of the ridge crest centered at a depth of approximately 30 km. The joint model also implies the presence of deeper (>125 km) conductor in the northern side. The bathymetry and the mantle bougurer anomly across the ridge segment are known to show asymmetry (Leroy et al., 2000). Volcanic seamounts seem to be abundant in the south of the ridge crest and the mean depth close to each margin is deeper in the north. The mantle bouguer anomaly extends more in the south-southwest direction as well. These features can be explained by the presence of shallow conductor in the south. It is possible that a hot melt body in the southern conductor supports the relatively intensive volcanic

  18. Volcanism, jump and propagation on the Sheba ridge, eastern Gulf of Aden: segmentation evolution and implications for oceanic accretion processes

    NASA Astrophysics Data System (ADS)

    d'Acremont, Elia; Leroy, Sylvie; Maia, Marcia; Gente, Pascal; Autin, Julia

    2010-02-01

    The rifting between Arabia and Somalia, which started around 35 Ma, was followed by oceanic accretion from at least 17.6 Ma leading to the formation of the present-day Gulf of Aden. Bathymetric, gravity and magnetic data from the Encens-Sheba cruise are used to constrain the structure and segmentation of the oceanic basin separating the conjugate continental margins in the eastern part of the Gulf of Aden between 51°E and 55.5°E. Data analysis reveals that the oceanic domain along this ridge section is divided into two distinct areas. The Eastern area is characterized by a shorter wavelength variation of the axial segmentation and an extremely thin oceanic crust. In the western segment, a thicker oceanic crust suggests a high melt supply. This supply is probably due to an off-axis melting anomaly located below the southern flank of the Sheba ridge, 75 km east of the major Alula-Fartak transform fault. This suggests that the axial morphology is produced by a combination of factors, including spreading rate, melt supply and the edge effect of the Alula-Fartak transform fault, as well as the proximity of the continental margin. The oceanic domains have undergone two distinct phases of accretion since the onset of seafloor spreading, with a shift around 11 Ma. At that time, the ridge jumped southwards, in response to the melting anomaly. Propagating ridges were triggered by the melting activity, and propagated both eastward and westward. The influence of the melting anomaly on the ridges decreased, stopping their propagation since less than 9 Ma. From that time up to the present, the N025°E-trending Socotra transform fault developed in association with the formation of the N115°E-trending segment #2. In recent times, a counter-clockwise rotation of the stress field associated with kinematic changes could explain the structural morphology of the Alula-Fartak and Socotra-Hadbeen fracture zones.

  19. Crustal Geometry of a First Order Segment in the Northeastern Gulf of Aden Margin From Seismic Reflection (Offshore Oman)

    NASA Astrophysics Data System (ADS)

    Autin, J.; Leroy, S.; D'Acremont, E.; Beslier, M.; Ribodeti, A.; Bellahsen, N.; Razin, P.; Robin, C.; Grelaud, C.; Al-Tobi, K.

    2007-12-01

    The Gulf of Aden is an oceanic basin separating Arabia from Somalia. The rifting started 35 Ma ago followed by oceanic spreading from 17.6 Ma. The gulf orientation (N75°E) and the kinematics (about N30°E divergence) mark an oblique rifting where normal faults striking between N70°E (rift axis parallel) and N110°E (perpendicular to the divergence), are due to an extension direction probably evolving from N20°E to N160°E. The accurate 3D structure of the margins and the influence of structural inheritance or thermal and rheological evolution need to be better constrained. In order to answer this question, we mapped the 3D architecture of sedimentary units and tectonic features in the first-order segment between Alula-Fartak and Socotra Fracture Zones of the eastern Gulf of Aden continental margin. During the Encens cruise (Leroy et al., 2006) conducted in this area where the syn-rift structures are well exposed and covered by thin post-rift sediments onshore, multibeam bathymetry, 360 channels seismic reflection (10 km spaced profiles), gravity and magnetism data were gathered. Furthermore two reflection seismic profiles were processed with a pre-stack migration method. This excellent-quality dataset will permit us to image the structure of the margin and to reconstruct the 3D evolution from rifting to the onset of oceanic spreading. These results complement the field work realized onshore on conjugate margins (Oman and Socotra). The style of deposit seems completely different in the proximal and in distal parts of the margin. Indeed fault controlled syn-rift carbonate systems, well developed onshore, are not really well expressed offshore. The paleohigh seems to be preserved at the end of the rifting and filled by a thick syn-OCT and/or post-rift series. A late rifting or coeval to the OCT uplift seemingly sets going on the margin edge. Several seaward dipping normal faults cut the main escarpment of the last continental block, filled by small sedimentary

  20. Initiation and evolution processes of submarine instabilities and canyons: insights from the Northern margin of the Gulf of Aden.

    NASA Astrophysics Data System (ADS)

    Baurion, Céline; Gorini, Christian; Leroy, Sylvie; Lucazeau, Francis; Bache, François; Al-Toubi, Khalfan

    2010-05-01

    The study of turbiditic systems and their interactions (sea-level falls, floods, earthquakes) are not well known and require the comparison of observations in various geological contexts. On young continental margins, it provides informations on sedimentological processes during early phases of rifting, for which vertical movements (subsidence, uplift) can be more important. The understanding of facies and depositional sequences is a major challenge for the knowledge of the post-rift tectono-sedimentological evolution of the Gulf of Aden, rare current example of young passive margin. The data were acquired during oceanographic cruises (ENCENS-SHEBA (Leroy et al 2004; and ENCENS; Leroy et al 2006). The Northern margin has been studied by both a stratigraphic (seismic reflection data) and a semi-quantitative geomorphologic approach (acoustic imagery, bathymetry and ground DEM) leading firstly to a morphologies classification. This "seismic geomorphology" study let us to distinguish three sedimentological domains, which match to the structural segmentation inherited from the formation of margin in oblique rifting context. All the incision/erosion stages of continental slope (from slope instabilities set up to the formation of mature canyon) observed on the eastern part of the margin lead to an incision shaping model on a steep continental slope. The sedimentary record is strongly controlled by a recent tectonic phase. Vertical movements lead to the formation of numerous instabilities on the continental slope and Mass-Transport Deposits (MTDs) on the lower slope and deep basin. The drainage network extraction shows the sporadic connexion between some of rivers and noticed deep sea fans (which extending canyons with axial incision). Links with the continental drainage network are probably interfered with the recent vertical movements. The quaternary uplift rate increase eastward, toward the Socotra-Hadbeen transform fault zone. The recurrence of the gravitational events

  1. Structure and Evolution of The Conjugate Passive Margins of The Eastern Gulf of Aden: The Oceanisation Process

    NASA Astrophysics Data System (ADS)

    D'Acremont, E.; Leroy, S.; Bellahsen, N.; Beslier, M. O.; Fournier, M.; Gente, P.; Patriat, P.; Fleury, J. M.

    The geophysical data set of the Encens-Sheba cruise recorded in the eastern Gulf of Aden and previous experiment, allow us to define the structure of the two conjugate margins, to localise the position of the ocean-continent transition zone (OCT), and fi- nally to study the oceanisation process from the continental break-up to the emplace- ment of an active spreading ridge, the Sheba ridge. Through the two margins, the base- ment, observed by seismic reflection, can be individualised into three domains from continental area to oceanic area, with distinct morphology and sedimentary charac- ters: (1) an area of rifted continental crust composed by a series of titled blocks, horsts and grabens bounded by faults N110E trending which can be related with onshore structures (2) a 20-30km wide ocean-continent transition and (3) an oceanic crust with a smoother relief than the rifted crust. The two conjugate margins are characterised by three major segments bounded from west to east respectively by the Alula-Fartak and the Socotra fracture zones, divided by two transfer faults N027E trending. The ocean- continent transition is marked by a negative gradient of the free-air gravity anomalies; by a seismic reflection pattern of the top acoustic basement that becomes rough in the oceanic domain; by the last presence of syn-rift sediment before the oceanic crust; and finally by the lack of well-constrained oceanic magnetic anomalies. The first identi- fiable magnetic anomaly is the An5d that gives 17Ma as opening age for the oriental Gulf of Aden. The crustal section of the margins constrained by gravity model and seismic profiles, shows that the steep and starved northern margin and the broad and thickly sedimented southern margin are asymmetric. On the northern side, the crust is slightly less thick than on the southern side. The width of the rifted continental crust varies between the two margins and from west to east, testifying an asymme- try during the continental break

  2. Seismic constraints on a large dyking event and initiation of a transform fault zone in Western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Ahmed, AbdulHakim; Doubre, Cecile; Leroy, Sylvie; Perrot, Julie; Audin, Laurence; Rolandone, Frederique; Keir, Derek; Al-Ganad, Ismael; Sholan, Jamal; Khanbari, Khaled; Mohamed, Kassim; Vergne, Jerome; Jacques, Eric; Nercessian, Alex

    2013-04-01

    In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik fracture zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the Afar plume. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115° -trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ˜ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift zone. Taking into account

  3. Conditions for initiating Lake Victoria haplochromine (Oreochromis esculentus) primary cell cultures from caudal fin biopsies.

    PubMed

    Filice, Melissa; Lee, C; Mastromonaco, Gabriela F

    2014-10-01

    The global decline of freshwater fishes has created a need to cryopreserve biological materials from endangered species in an effort to conserve the biodiversity within this taxon. Since maternal gametes and embryos from fish are difficult to cryopreserve, somatic cells obtained from caudal fins have become an increasingly popular resource as they contain both maternal and paternal DNA ensuring valuable traits are not lost from the population. Somatic cells stored in cryobanks can be used to supplement endangered populations with genetically valuable offspring with the use of assisted reproductive technologies. However, initiating primary cell cultures from caudal fin biopsies of endangered species can be challenging as standardized protocols have not yet been developed. The objective of this study was to identify culture conditions, including antibiotic supplementation, biopsy size, and culture temperature, suitable for establishing primary cell cultures of ngege (Oreochromis esculentus), a critically endangered African cichlid. Six-millimeter caudal fin biopsies provided sufficient material to develop a primary cell culture when incubated at 25°C using standard fish cell culture medium containing 1× Primocin. Further investigation and application of these culture conditions for other endangered freshwater fishes is necessary. PMID:24985486

  4. Schistosoma mansoni infection along the coast of Lake Victoria in Mwanza region, Tanzania.

    PubMed

    Olsen, Annette; Kinung'hi, Safari; Magnussen, Pascal

    2015-06-01

    Prevalence and intensity of Schistosoma mansoni infection according to age, sex, and occupation were investigated in 100 first-year students (aged 7-8 years), 100 schoolchildren (aged 9-12 years), and 50 adults (aged 20-55 years) from 149 villages. The schoolchildren provided three stool specimens while the rest provided only one specimen. A total of 31,865 individuals provided at least one specimen with an overall prevalence of 38.5% and geometric mean intensity of positives of 107.0 eggs per gram of feces. With the exception of first-year students, males had higher prevalence than females (P < 0.0005). Schoolchildren had higher prevalence than first-year students that again had higher prevalence than adults. There was no sex difference in intensities among the children, but adult males had higher intensities than adult females. Intensity among the children was higher than that of the adults (P < 0.0005). Prevalence was significantly higher in those having fishing as their main occupation. Three stools samples were obtained from 13,119 schoolchildren, resulting in a prevalence of 38.1% if only one sample was included, 47.5% including two samples, and 52.6% if all three samples were included. PMID:25825388

  5. Spatial modelling of arsenic distribution and human health effects in Lake Victoria basin, Tanzania

    NASA Astrophysics Data System (ADS)

    Ijumulana, Julian; Mtalo, Felix; Bhattacharya, Prosun

    2016-04-01

    Increasing incidences of naturally occurring geogenic pollutants in drinking water sources and associated human health risks are the two major challenges requiring detailed knowledge to support decision making process at various levels. The presence, location and extent of environmental contamination is needed towards developing mitigation measures to achieve required standards. In this study we are developing a GIS-based model to detect and predict drinking water pollutants at the identified hotspots and monitor its variation in space. In addition, the mobility of pollutants within the affected region needs to be evaluated using topographic and hydrogeological data. Based on these geospatial data on contaminant distribution, spatial relationship of As and F contamination and reported human health effects such as dental caries, dental fluorosis, skeletal fluorosis and bone crippling, skin and other cancers etc. can be modeled for potential interventions for safe drinking water supplies.

  6. The rift to break-up evolution of the Gulf of Aden: Insights from 3D numerical lithospheric-scale modelling

    NASA Astrophysics Data System (ADS)

    Brune, Sascha; Autin, Julia

    2013-11-01

    The Gulf of Aden provides an ideal setting to study oblique rifting since numerous structural data are available onshore and offshore. Recent surveys showed that the spatio-temporal evolution of the Gulf of Aden rift system is dominated by three fault orientations: displacement-orthogonal (WSW), rift-parallel (WNW) and an intermediate E-W trend. The oldest parts of the rift that are exposed onshore feature displacement-orthogonal and intermediate directions, whereas the subsequently active necking zone involves mainly rift-parallel faults. The final rift phase recorded at the distal margin is characterised by displacement-orthogonal and intermediate fault orientations. We investigate the evolution of the Gulf of Aden from rift initiation to break-up by means of 3D numerical experiments on lithospheric scale. We apply the finite element model SLIM3D which includes realistic, elasto-visco-plastic rheology and a free surface. Despite recent advances, 3D numerical experiments still require relatively coarse resolution so that individual faults are poorly resolved. We address this issue by proposing a simple post-processing method that uses the surface stress-tensor to evaluate stress regime (extensional, strike-slip, compressional) and preferred fault azimuth. The described method is applicable to any geodynamic model and easy to introduce. Our model reproduces the observed fault pattern of the Gulf of Aden and illustrates how multiple fault directions arise from the interaction of local and far-field tectonic stresses in an evolving rift system. The numerical simulations robustly feature intermediate faults during the initial rift phase, followed by rift-parallel normal faulting at the rift flanks and strike-slip faults in the central part of the rift system. Upon break-up, displacement-orthogonal as well as intermediate faults occur. This study corroborates and extends findings from previous analogue experiments of oblique rifting on lithospheric scale and allows new

  7. End‐of‐life decisions in medical practice: a survey of doctors in Victoria (Australia)

    PubMed Central

    Neil, D A; Coady, C A J; Thompson, J; Kuhse, H

    2007-01-01

    Objectives To discover the current state of opinion and practice among doctors in Victoria, Australia, regarding end‐of‐life decisions and the legalisation of voluntary euthanasia. Longitudinal comparison with similar 1987 and 1993 studies. Design and participants Cross‐sectional postal survey of doctors in Victoria. Results 53% of doctors in Victoria support the legalisation of voluntary euthanasia. Of doctors who have experienced requests from patients to hasten death, 35% have administered drugs with the intention of hastening death. There is substantial disagreement among doctors concerning the definition of euthanasia. Conclusions Disagreement among doctors concerning the meaning of the term euthanasia may contribute to misunderstanding in the debate over voluntary euthanasia. Among doctors in Victoria, support for the legalisation of voluntary euthanasia appears to have weakened slightly over the past 17 years. Opinion on this issue is sharply polarised. PMID:18055904

  8. VICTORIA: A mechanistic model of radionuclide behavior in the reactor coolant system under severe accident conditions

    SciTech Connect

    Heames, T.J. ); Williams, D.A.; Johns, N.A.; Chown, N.M. ); Bixler, N.E.; Grimley, A.J. ); Wheatley, C.J. )

    1990-10-01

    This document provides a description of a model of the radionuclide behavior in the reactor coolant system (RCS) of a light water reactor during a severe accident. This document serves as the user's manual for the computer code called VICTORIA, based upon the model. The VICTORIA code predicts fission product release from the fuel, chemical reactions between fission products and structural materials, vapor and aerosol behavior, and fission product decay heating. This document provides a detailed description of each part of the implementation of the model into VICTORIA, the numerical algorithms used, and the correlations and thermochemical data necessary for determining a solution. A description of the code structure, input and output, and a sample problem are provided. The VICTORIA code was developed upon a CRAY-XMP at Sandia National Laboratories in the USA and a CRAY-2 and various SUN workstations at the Winfrith Technology Centre in England. 60 refs.

  9. Propagation of Gulf of Aden Intermediate Water (GAIW) in the Red Sea during autumn and its importance to biological production

    NASA Astrophysics Data System (ADS)

    Wafar, Mohideen; Ashraf, Mohamed; Manikandan, K. P.; Qurban, Mohammad Ali; Kattan, Yasser

    2016-02-01

    Analysis of high-resolution CTD data acquired at closely spaced stations during two cruises in the Saudi Arabian waters of the Red Sea (17 to 27°N), supported by the multiple tracer analysis (Mackas et al., 1987), showed that the Gulf of Aden Intermediate Water (GAIW) is clearly detectable as far as north as 26°N in the Red Sea basin albeit at a fraction less than 10%. Continuity of core salinity minima of the GAIW layer also showed that the northward propagation of GAIW north of 20°N happens mainly along the Saudi Arabian coast. The discontinuity of core minima of GAIW properties in a section along the axis, coincidence of these with alternating directions of zonal currents, the good relationships between concentrations of nutrients and salinity in the GAIW layer, and the cores of high nutrient concentrations in this section led to the conclusions that the GAIW is entrained in eddy circulations across the basin and that it is a significant source of nutrients to the entire Red Sea basin. However, the addition of nutrients with GAIW could account for only a small fraction of the nutrients (as nitrogen) needed for primary production, suggesting that recycling within the Red Sea and input from other sources will have to be significant enough to sustain the current levels of primary production measured in Red Sea waters.

  10. Evidence of partial melting beneath a continental margin: case of Dhofar, in the Northeast Gulf of Aden (Sultanate of Oman)

    NASA Astrophysics Data System (ADS)

    Basuyau, C.; Tiberi, C.; Leroy, S.; Stuart, G.; Al-Lazki, A.; Al-Toubi, K.; Ebinger, C.

    2010-02-01

    Gravity data and P-wave teleseismic traveltime residuals from 29 temporary broad-band stations spread over the northern margin of the Gulf of Aden (Dhofar region, Oman) were used to image lithospheric structure. We apply a linear relationship between density and velocity to provide consistent density and velocity models from mid-crust down to about 250 km depth. The accuracy of the resulting models is investigated through a series of synthetic tests. The analysis of our resulting models shows: (1) crustal heterogeneities that match the main geological features at the surface; (2) the gravity edge effect and disparity in anomaly depth locations for layers at 20 and 50 km; (3) two low-velocity anomalies along the continuation of Socotra-Hadbeen and Alula-Fartak fracture zones between 60 and 200 km depth; and (4) evidence for partial melting (3-6 per cent) within these two negative anomalies. We discuss the presence of partial melting in terms of interaction between the Sheba ridge melts and its along-axis segmentation.

  11. Heavy metal concentrations in marine green, brown, and red seaweeds from coastal waters of Yemen, the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Al-Shwafi, Nabil A.; Rushdi, Ahmed I.

    2008-08-01

    The purpose of this study was to investigate the concentration levels of heavy metals in different species of the main three marine algal divisions from the Gulf of Aden coastal waters, Yemen. The divisions included Chlorophyta—green plants ( Halimeda tuna, Rhizoclonium kochiamum, Caldophora koiei, Enteromorpha compressa, and Caulerpa racemosa species), Phaeophyta—brown seaweeds ( Padina boryana, Turbinaria elatensis, Sargassum binderi, Cystoseira myrica, and Sargassum boveanum species), and Rhodophyta—red seaweeds ( Hypnea cornuta, Champia parvula, Galaxaura marginate, Laurencia paniculata, Gracilaria foliifere, and species). The heavy metals, which included cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), Iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn), and vanadium (V) were measured by Atomic Absorption Spectrophotometer (AAs). The concentrations of heavy metals in all algal species are in the order of Fe >> Cu > Mn > Cr > Zn > Ni > Pb > Cd > V > Co. The results also showed that the uptake of heavy metals by different marine algal divisions was in the order of Chlorophyta > Phaeophyta > Rhodophyta. These heavy metals were several order of magnitude higher than the concentrations of the same metals in seawater. This indicates that marine alga progressively uptake heavy metals from seawater.

  12. Integration of altimetric lake levels and GRACE gravimetry over Africa: Inferences for terrestrial water storage change 2003-2011

    NASA Astrophysics Data System (ADS)

    Moore, P.; Williams, S. D. P.

    2014-12-01

    Terrestrial water storage (TWS) change for 2003-2011 is estimated over Africa from GRACE gravimetric data. The signatures from change in water of the major lakes are removed by utilizing kernel functions with lake heights recovered from retracked ENVISAT satellite altimetry. In addition, the contribution of gravimetric change due to soil moisture and biomass is removed from the total GRACE signal by utilizing the GLDAS land surface model. The residual TWS time series, namely groundwater and the surface waters in rivers, wetlands, and small lakes, are investigated for trends and the seasonal cycle using linear regression. Typically, such analyses assume that the data are temporally uncorrelated but this has been shown to lead to erroneous inferences in related studies concerning the linear rate and acceleration. In this study, we utilize autocorrelation and investigate the appropriate stochastic model. The results show the proper distribution of TWS change and identify the spatial distribution of significant rates and accelerations. The effect of surface water in the major lakes is shown to contribute significantly to the trend and seasonal variation in TWS in the lake basin. Lake Volta, a managed reservoir in Ghana, is seen to have a contribution to the linear trend that is a factor of three greater than that of Lake Victoria despite having a surface area one-eighth of that of Lake Victoria. Analysis also shows the confidence levels of the deterministic trend and acceleration identifying areas where the signatures are most likely due to a physical deterministic cause and not simply stochastic variations.

  13. A critical review of the development, current hotspots, and future directions of Lake Taihu research from the bibliometrics perspective.

    PubMed

    Zhang, Yunlin; Yao, Xiaolong; Qin, Boqiang

    2016-07-01

    Lake Taihu, as the important drinking water source of the Yangtze River Delta urban agglomeration and the third largest freshwater lake in China, has experienced serious lake eutrophication and water quality deterioration in the past three decades. Growing scientific, political, and public attention has been given to the water quality of Lake Taihu. This study aimed to conduct a comparative quantitative and qualitative analysis of the development, current hotspots, and future directions of Lake Taihu research using a bibliometric analysis of eight well-studied lakes (Lake Taihu, Lake Baikal, Lake Biwa, Lake Erie, Lake Michigan, Lake Ontario, Lake Superior and Lake Victoria) around the world based on the Science Citation Index (SCI) database. A total of 1582 papers discussing Lake Taihu research were published in 322 journals in the past three decades. However, the first paper about Lake Taihu research was not found in the SCI database until 1989, and there were only zero, one, or two papers each year from 1989 to 1995. There had been rapid development in Lake Taihu research since 1996 and a sharp increase in papers since 2005. A keyword analysis showed that "sediment," "eutrophication", "Microcystis aeruginosa", "cyanobacterial blooms", and "remote sensing" were the most frequently used keywords of the study subject. Owing to its significant impact on aquatic ecosystems, a crucial emphasis has been placed on climate change recently. In addition, the future focuses of research directions, including (1) environmental effects of physical processes; (2) nutrient cycles and control and ecosystem responses; (3) cyanobacteria bloom monitoring, causes, forecast and management; (4) eutrophication and climate change interactions; and (5) ecosystem degradation mechanism and ecological practice of lake restoration, are presented based on the keyword analysis. Through multidisciplinary fields (physics, chemistry, and biology) cross and synthesis study of Lake Taihu, the

  14. Sensitivity analysis of the GNSS derived Victoria plate motion

    NASA Astrophysics Data System (ADS)

    Apolinário, João; Fernandes, Rui; Bos, Machiel

    2014-05-01

    Fernandes et al. (2013) estimated the angular velocity of the Victoria tectonic block from geodetic data (GNSS derived velocities) only.. GNSS observations are sparse in this region and it is therefore of the utmost importance to use the available data (5 sites) in the most optimal way. Unfortunately, the existing time-series were/are affected by missing data and offsets. In addition, some time-series were close to the considered minimal threshold value to compute one reliable velocity solution: 2.5-3.0 years. In this research, we focus on the sensitivity of the derived angular velocity to changes in the data (longer data-span for some stations) by extending the used data-span: Fernandes et al. (2013) used data until September 2011. We also investigate the effect of adding other stations to the solution, which is now possible since more stations became available in the region. In addition, we study if the conventional power-law plus white noise model is indeed the best stochastic model. In this respect, we apply different noise models using HECTOR (Bos et al. (2013), which can use different noise models and estimate offsets and seasonal signals simultaneously. The seasonal signal estimation is also other important parameter, since the time-series are rather short or have large data spans at some stations, which implies that the seasonal signals still can have some effect on the estimated trends as shown by Blewitt and Lavellee (2002) and Bos et al. (2010). We also quantify the magnitude of such differences in the estimation of the secular velocity and their effect in the derived angular velocity. Concerning the offsets, we investigate how they can, detected and undetected, influence the estimated plate motion. The time of offsets has been determined by visual inspection of the time-series. The influence of undetected offsets has been done by adding small synthetic random walk signals that are too small to be detected visually but might have an effect on the

  15. 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.

  16. 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 ...

  17. 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...

  18. Fish faunal resurgence in Lake Nabugabo, East Africa

    USGS Publications Warehouse

    Chapman, L.J.; Chapman, Colin A.; Schofield, P.J.; Olowo, J.P.; Kaufman, L.S.; Seehausen, O.; Ogutu-Ohwayo., R.

    2003-01-01

     In Lake Nabugabo, Uganda, a small satellite of the equatorial Lake Victoria, approximately 50% of the indigenous fish species disappeared from the open waters subsequent to establishment of the introduced predatory Nile perch (   Lates niloticus ). However, several of these species persisted in wetland refugia. Over the past decade, Nile perch in Lake Nabugabo have been intensively fished. Herein we report a resurgence of some indigenous species in open waters. In a multiyear study, we used annual transects in inshore and offshore waters of exposed ( no wetland ) and wetland habitats to document the pattern of resurgence. In 1995, haplochromine cichlids were largely confined to inshore areas, particularly wetland ecotones, and were rare in Nile perch stomachs, as were most other indigenous species. By 2000 haplochromine cichlids were abundant in inshore and offshore areas of both exposed and wetland transects. Several indigenous noncichlids also reappeared in the main lake, including three of the four original mormyrid species. Between 1995 and 1999, there was a dramatic increase in the proportion of haplochromines in the diet of Nile perch. When haplochromines were rare ( 1995 ), Nile perch switched from an invertebrate-dominated diet to piscivory at a large size ( 30 cm total length ). In 2000, however, Nile perch were strongly piscivorous by 5–10 cm total length. The pattern of faunal loss and recovery in Lake Nabugabo demonstrates the importance of refugia in providing the seeds of resurgence and provides a model with which to understand some changes in Lake Victoria.

  19. 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.

  20. Forty Meters from Entry to Victoria Crater (Stereo)

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Left-eye view of a color stereo pair for PIA09972 [figure removed for brevity, see original site] Right-eye view of a color stereo pair for PIA09972

    NASA's Mars Exploration Rover Opportunity used its navigation camera during the rover's 1,278th Martian day, or sol, (Aug. 28, 2007) to take the images combined into this stereo view. The rover was perched at the lip of Victoria Crater, which is about 800 meters (one-half mile) in diameter.

    After assessment of possible routes for Opportunity to descend into the crater, the rover team selected a site farther to the right along the rim. That selected entry point lies near the ripple of bright soil visible just outside the crater near the top center of this scene. The driving distance for Opportunity from the Sol 1,278 viewpoint to the selected entry point is about 40 meters (about 130 feet).

    This view combines a stereo pair and appears three-dimensional when seen through blue-red glasses. It is presented as a cylindrical-perspective projection with geometric seam correction.

  1. Victorias energy efficiency and cogeneration project. Final report

    SciTech Connect

    1998-10-31

    This report describes a two-phase energy project currently contemplated for joint implementation at the Victorias Milling Company, a large sugar mill and refinery on the island of Negros in the Visayas region of the Philippines. The Energy Efficiency (EE) phase is expected to reduce of eliminate VMC`s fossil fuel consumption, which will have a direct and substantial impact on carbon emissions. Phase I is an EE project which involves the installation of equipment to reduce steam and electricity demand in the factories. Phase II, will involve retrofitting and increasing the capacity of the steam and power generation systems, and selling power to the grid. By increasing efficiency and output, the cogeneration project will allow the factory to use only bagasse sugar cane fiber waste as fuel for energy needs. The cogeneration project will also eliminate VMC`s electricity purchases and supply additional power for the island, which will offset generation capacity expansion on the island and the Visayas region.

  2. Diversity of soil yeasts isolated from South Victoria Land, Antarctica

    USGS Publications Warehouse

    Connell, L.; Redman, R.; Craig, S.; Scorzetti, G.; Iszard, M.; Rodriguez, R.

    2008-01-01

    Unicellular fungi, commonly referred to as yeasts, were found to be components of the culturable soil fungal population in Taylor Valley, Mt. Discovery, Wright Valley, and two mountain peaks of South Victoria Land, Antarctica. Samples were taken from sites spanning a diversity of soil habitats that were not directly associated with vertebrate activity. A large proportion of yeasts isolated in this study were basidiomycetous species (89%), of which 43% may represent undescribed species, demonstrating that culturable yeasts remain incompletely described in these polar desert soils. Cryptococcus species represented the most often isolated genus (33%) followed by Leucosporidium (22%). Principle component analysis and multiple linear regression using stepwise selection was used to model the relation between abiotic variables (principle component 1 and principle component 2 scores) and yeast biodiversity (the number of species present at a given site). These analyses identified soil pH and electrical conductivity as significant predictors of yeast biodiversity. Species-specific PCR primers were designed to rapidly discriminate among the Dioszegia and Leucosporidium species collected in this study. ?? 2008 Springer Science+Business Media, LLC.

  3. Work-related suicide in Victoria, Australia: a broad perspective.

    PubMed

    Routley, Virginia Hazel; Ozanne-Smith, Joan E

    2012-01-01

    While unintentional work-related injury is increasingly recognised as important and preventable, population studies of the full range of work related suicides have received less attention. The objective of this study is to investigate the epidemiology of work-related suicide in Victoria, July 2000-December 2007. The study draws on a database of all work-related deaths reported to the Victorian Coroner, inclusive of broadly defined work-relatedness. Inclusion criteria for work-related suicide were at least one of: suicide means was work related, work stressors were identified in police reports to the Coroners or the Coroner's finding, the suicide method involved another person's work (e.g. rail suicide, heavy vehicle) or the suicide location was a workplace. Cases still open for investigation were excluded. Of 642 work-related suicides, 55% had an association with work stressors; 32% jumped or lay in front of a train or heavy vehicle; 7% involved a work location and 6% involved work agents. Work stressor cases identified included business difficulties, recent or previous work injury, unemployment/redundancy or conflict with supervisors/colleagues (including workplace bullying). Work-related suicide is a substantial problem, for which few detailed population wide studies are available. Further research is required to understand the contribution of work stressors and effective interventions. PMID:22132703

  4. Evolution of post-rift sediment transport on a young rifted margin : Insights from the eastern part of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Baurion, C.; Gorini, C.; Leroy, S.; Lucazeau, F.; Migeon, S.

    2012-04-01

    The formation of gravity-driven sedimentary systems on continental rifted margins results from the interaction between climate, ocean currents and tectonic activity. During the early stages of margin evolution, the tectonic processes are probably as important as climate for the sedimentary architecture. Therefore, the young margins (ca. 35 Ma) of the Gulf of Aden provide the opportunity to evaluate the respective roles of monsoon and tectonic uplift in the formation and evolution through the post-rift period of gravity-driven deposits (Mass Transport Complexes (MTCs) and deep-sea systems) on the continental slopes and in the oceanic basin respectively. Here we present a combined geomorphologic and stratigraphic study of the northern margin (Oman and Yemen) and the southern margin (Socotra island), in which we classified and interpreted the gravity-driven processes, their formation and their evolution during the post-rift period. The interpretation of seismic lines reveals the presence of bottom currents since the drift phase, suggesting that the Gulf of Aden was connected to the world oceans at that time. An abrupt depositional change affected the eastern basin of the Gulf of Aden around 10 Ma or thereafter (Chron 5), characterised by the first occurrence of deep sea fans and an increase in the number of MTCs. The first occurrence of MTCs may be explained by the combined 2nd-3rd order fall of the relative sea-level (Serravalian/Tortonian transition). This variation of relative sea level combined with a climatic switch (Asian monsoon onset around 15 Ma and its intensification around 7-8 Ma) control the sediment flux. The youngest unit of the post-rift supersequence is characterised by a second important MTC occurrence that is restricted to the eastern part of the deep basin. This is caused by a late uplift of the northern and southern margins witnessed onshore by the presence of young stepped marine terraces.

  5. Role of Needle Aspiration in Diagnosis and Management of Suppurative Bacille Calmette–Guerin Adenitis: An Institutional Study of 30 Cases

    PubMed Central

    Pal, Subrata; Chakarabarti, Srabani; Phukan, Jyoti Prakash; Biswas, Sudhanya; Sinha, Anuradha; Sinha, Rajani

    2015-01-01

    Context: Regional lymphadenitis is the most common complication of bacille Calmette–Guerin (BCG) vaccination. Most of the BCG lymphadenitis cases are nonsuppurative, but some suppurate and follow abscess formation, rupture, ulceration and cicatrization. Needle aspiration is the rapid, safe and cost-effective method for diagnosis as well as management of suppurative BCG adenitis. Aims: The aims of the present study were to assess the clinical and cytological spectrum of BCG lymphadenitis and to evaluate the role of needle aspiration in the management of suppurative BCG lymphadenitis. Settings and Design: We have approached every cases of ipsilateral axillary lymphadenopathy having history of BCG vaccination. We designed to aspirate the suppurative axillary lymph nodes and follow-up of nonsuppurative cases. Subjects and Methods: 30 cases of BCG adenitis were studied during a period of 2 years. 12 cases of suppurative lymphadenitis were approached by needle aspiration and cytologically evaluated, and all the cases were followed-up for 12 weeks after diagnosis. Anti-tubercular drugs were not applied, and surgical excision was reserved for nonhealing lesions. Statistical Analysis Used: Data tables. Results: Ipsilateral axillary lymph nodes were commonest site and none had constitutional symptoms. Acid-fast bacilli were detected in 11 (91.67%) cases of suppurative BCG lymphadenitis. On follow-up all nonsuppurative adenitis were resolved spontaneously, and 8 suppurative lymphadenitis cases were resolved after 4 weeks of needle aspiration. Four cases needed repeat aspiration among which 3 resolved in 8 weeks, and one needed surgical excision. Conclusions: We recommend needle aspiration as a simple, safe, chief and effective modality, which helps in diagnosis as well as in management of suppurative BCG lymphadenitis. PMID:25949055

  6. Complete mitochondrial DNA sequences of the Victoria tilapia (Oreochromis variabilis) and Redbelly Tilapia (Tilapia zilli): genome characterization and phylogeny analysis.

    PubMed

    Kinaro, Zachary Omambia; Xue, Liangyi; Volatiana, Josies Ancella

    2016-07-01

    The Cichlid fishes have played an important role in evolutionary biology, population studies and aquaculture industry with East African species representing a model suited for studying adaptive radiation and speciation for cichlid genome projects in which closely related genomes are fast emerging presenting questions on phenotype-genotype relations. The complete mitochondrial genomes presented here are for two closely related but eco-morphologically distinct Lake Victoria basin cichlids, Oreochromis variabilis, an endangered native species and Tilapia zilli, an invasive species, both of which are important economic fishes in local areas. The complete mitochondrial genomes determined for O. variabilis and T. zilli are 16 626 and 16,619 bp, respectively. Both the mitogenomes contain 13 protein-coding genes, 22 tRNAs, 2 rRNAs and a non-coding control region, which are typical of vertebrate mitogenomes. Phylogenetic analyses of the two species revealed that though both lie within family Cichlidae, they are remotely related. PMID:27158785

  7. Continental break-up history of conjugate poor magmatic margins from seismic reflection and analogue modelling (oriental Gulf of Aden)

    NASA Astrophysics Data System (ADS)

    Autin, J.; Leroy, S.; D'Acremont, E.; Beslier, M.; Bellahsen, N.; Husson, L.; Ribodetti, A.; Razin, P.; Robin, C.; Al Toubi, K.

    2009-12-01

    The Gulf of Aden is a young oceanic basin (~20 Ma), separating Arabia from Somalia. The gulf orientation (N75°E) and the kinematics (about N30°E divergence) mark an oblique rifting where normal faults striking between N70°E (rift axis parallel) and N110°E (perpendicular to the divergence), are due to an extension direction probably evolving from N20°E to N160°E. The accurate 3D structure of the margins and the influence of structural inheritance or thermal and rheological evolution need to be better constrained. In order to answer this question, we mapped the tectonic features of the first-order segment between Alula-Fartak and Socotra Fracture Zones of the eastern Gulf of Aden continental margin. The Encens cruise (Leroy et al., 2006) takes place in this area where the syn-rift structures are well exposed. Multibeam bathymetry, 360 channels seismic reflection (10 km spaced lines), gravity and magnetism data were gathered. Furthermore one reflection seismic profile was processed with a pre-stack depth migration method. This excellent-quality dataset will permit us to image the structure of the margin and to propose an evolution from rifting to the onset of oceanic spreading. These results complement the field work realized onshore on conjugate margins (Oman and Socotra). Thus the land evolution can be correlated to the distal evolution. The style of deposit seems completely different in the proximal and in distal parts of the margin. Indeed fault controlled syn-rift carbonate systems, well developed onshore, are not really well expressed offshore. After the major syn-rift structuration in grabens and horsts, the deformation localised where the crust is the thinnest. This occurred in the distal margin graben (DIM) at the northern boundary of the Ocean-Continent Transition (OCT) represented by the OCT ridge. At the onset of the OCT formation, a differential uplift induces a landslide on the top of the deepest tilted block and the crustal deformation is

  8. Continental break-up history of conjugate poor magmatic margins from seismic reflection (oriental Gulf of Aden)

    NASA Astrophysics Data System (ADS)

    Autin, J.; Leroy, S.; D'Acremont, E.; Beslier, M.-O.; Ribodetti, A.; Bellahsen, N.; Razin, Ph.; Robin, C.

    2009-04-01

    The Gulf of Aden is an oceanic basin separating Arabia from Somalia. The rifting started 35 Ma ago followed by oceanic spreading from 17.6 Ma. The gulf orientation (N75°E) and the kinematics (about N30°E divergence) mark an oblique rifting where normal faults striking between N70°E (rift axis parallel) and N110°E (perpendicular to the divergence), are due to an extension direction probably evolving from N20°E to N160°E. The accurate 3D structure of the margins and the influence of structural inheritance or thermal and rheological evolution need to be better constrained. In order to answer this question, we mapped the tectonic features of the first-order segment between Alula-Fartak and Socotra Fracture Zones of the eastern Gulf of Aden continental margin. The Encens cruise (Leroy et al., 2006) take place in this area where the syn-rift structures are well exposed. Multibeam bathymetry, 360 channels seismic reflection (10 km spaced profiles), gravity and magnetism data were gathered. Furthermore one reflection seismic profile was processed with a pre-stack depth migration method. This excellent-quality dataset will permit us to image the structure of the margin and to propose an evolution from rifting to the onset of oceanic spreading. These results complement the field work realized onshore on conjugate margins (Oman and Socotra). Thus the land evolution can be correlated to the distal evolution. The style of deposit seems completely different in the proximal and in distal parts of the margin. Indeed fault controlled syn-rift carbonate systems, well developed onshore, are not really well expressed offshore. After the major syn-rift structuration in grabens and horsts, the deformation localised where the crust is the thinnest. This occurred in the distal margin graben (DIM) at the northern boundary of the Ocean-Continent Transition (OCT) represented by the OCT ridge. At the onset of the OCT formation, a differential uplift induces a landslide on the top of the

  9. Mesoscale eddies in the Gulf of Aden and their impact on the spreading of Red Sea Outflow Water

    NASA Astrophysics Data System (ADS)

    Bower, Amy S.; Furey, Heather H.

    2012-04-01

    The Gulf of Aden (GOA) in the northwestern Indian Ocean is the receiving basin for Red Sea Outflow Water (RSOW), one of the World’s few high-salinity dense overflows, but relatively little is known about spreading pathways and transformation of RSOW through the gulf. Here we combine historical data, satellite altimetry, new synoptic hydrographic surveys and the first in situ direct observations of subsurface currents in the GOA to identify the most important processes in the spreading of RSOW. The new in situ data sets were collected in 2001-2003 as part of the Red Sea Outflow Experiment (REDSOX) and consist of two CTD/LADCP Surveys and 49 one-year trajectories from acoustically tracked floats released at the depth of RSOW. The results indicate that the prominent positive and negative sea level anomalies frequently observed in the GOA with satellite altimetry are associated with anticyclonic and cyclonic eddies that often reach to at least 1000 m depth, i.e., through the depth range of equilibrated RSOW. The eddies dominate RSOW spreading pathways and help to rapidly mix the outflow water with the background. Eddies in the central and eastern gulf are basin-scale (∼250-km diameter) and have maximum azimuthal speeds of about 30 cm/s at the RSOW level. In the western gulf, smaller eddies not detectable with satellite altimetry appear to form as the larger westward-propagating eddies impale themselves on the high ridges flanking the Tadjura Rift. Both the hydrographic and Lagrangian observations show that eddies originating outside the gulf often transport a core of much cooler, fresher water from the Arabian Sea all the way to the western end of the GOA, where the highest-salinity outflow water is found. This generates large vertical and horizontal gradients of temperature and salinity, setting up favorable conditions for salt fingering and diffusive convection. Both of these mixing processes were observed to be active in the gulf. Two new annually appearing

  10. High-resolution estimates of Nubia-Somalia plate motion since 20 Ma from reconstructions of the Southwest Indian Ridge, Red Sea, and Gulf of Aden

    NASA Astrophysics Data System (ADS)

    DeMets, C.; Merkuryev, S. A.

    2015-12-01

    We estimate Nubia-Somalia rotations at ~1-Myr intervals for the past 20 Myr from newly available, high-resolution reconstructions of the Southwest Indian Ridge and reconstructions of the Red Sea and Gulf of Aden. The former rotations are based on many more data, extend farther back in time, and have more temporal resolution than has previously been the case. Nubia-Somalia plate motion has remained remarkably steady since 5.2 Ma. For example, at the northern end of the East Africa rift, our Nubia-Somalia plate motion estimates at six different times between 0.78 Ma and 5.2 Ma agree to within 3% with the rift-normal component of motion that is extrapolated from the recently estimated Saria et al. (2014) GPS angular velocity. Over the past 10.6 Myr, the Nubia-Somalia rotations predict 42±4 km of rift-normal extension across the northern segment of the Main Ethiopian Rift. This agrees with approximate minimum and maximum estimates of 40 km and 53 km for post-10.6-Myr extension from seismological surveys of this narrow part of the plate boundary and is also close to 55-km and 48±3 km estimates from published and our own reconstructions of the Nubia-Arabia and Somalia-Arabia seafloorspreading histories for the Red Sea and Gulf of Aden. Our new rotations exclude at high confidence level two previously published estimates of Nubia-Somalia motion based on inversions of Chron 5n.2 along the Southwest Indian Ridge, which predict rift-normal extensions of 13±14 km and 129±16 km across the Main Ethiopian Rift since 11 Ma. Constraints on Nubia-Somalia motion before ~15 Ma are weaker due to sparse coverage of pre-15-Myr magnetic reversals along the Nubia-Antarctic plate boundary, but appear to require motion before 15 Ma. Nubia-Somalia rotations that we estimate from a probabilistic analysis of geometric and age constraints from the Red Sea and Gulf of Aden are consistent with those determined from Southwest Indian Ridge data, particularly for the past 11 Myr. Nubia

  11. False-Positive Axillary Lymph Nodes Due to Silicone Adenitis on (18)F-FDG PET/CT in an Oncological Setting.

    PubMed

    D'hulst, Ludovic; Nicolaij, Daniël; Beels, Laurence; Gheysens, Olivier; Alaerts, Herwig; Van de Wiele, Christophe; Maes, Alex

    2016-06-01

    The case of a 49-year-old transgender individual with a history of bilateral silicone breast implants and a right lung mass proven by biopsy to be a non-small cell lung cancer is presented. In addition to the primary malignancy, a positron emission tomography/computed tomography scan showed contralateral hypermetabolic adenopathy in the left axilla that was suggestive of nodal metastatic disease. Additional imaging and histological examination of the lymph nodes indicated silicone breast implant leakage and silicone adenitis as the underlying cause of the hypermetabolic axillary lymph node. PMID:26776866

  12. Crustal structure of the Gulf of Aden southern margin: Evidence from receiver functions on Socotra Island (Yemen)

    NASA Astrophysics Data System (ADS)

    Ahmed, Abdulhakim; Leroy, Sylvie; Keir, Derek; Korostelev, Félicie; Khanbari, Khaled; Rolandone, Frédérique; Stuart, Graham; Obrebski, Mathias

    2014-12-01

    Breakup of continents in magma-poor setting occurs primarily by faulting and plate thinning. Spatial and temporal variations in these processes can be influenced by the pre-rift basement structure as well as by early syn-rift segmentation of the rift. In order to better understand crustal deformation and influence of pre-rift architecture on breakup we use receiver functions from teleseismic recordings from Socotra which is part of the subaerial Oligo-Miocene age southern margin of the Gulf of Aden. We determine variations in crustal thickness and elastic properties, from which we interpret the degree of extension related thinning and crustal composition. Our computed receiver functions show an average crustal thickness of ~ 28 km for central Socotra, which decreases westward along the margin to an average of ~ 21 km. In addition, the crust thins with proximity to the continent-ocean transition to ~ 16 km in the northwest. Assuming an initial pre-rift crustal thickness of 35 km (undeformed Arabian plate), we estimate a stretching factor in the range of ~ 2.1-2.4 beneath Socotra. Our results show considerable differences between the crustal structure of Socotra's eastern and western sides on either side of the Hadibo transfer zone; the east displays a clear intracrustal conversion phase and thick crust when compared with the western part. The majority of measurements across Socotra show Vp/Vs ratios of between 1.70 and 1.77 and are broadly consistent with the Vp/Vs values expected from the granitic and carbonate rock type exposed at the surface. Our results strongly suggest that intrusion of mafic rock is absent or minimal, providing evidence that mechanical thinning accommodated the majority of crustal extension. From our observations we interpret that the western part of Socotra corresponds to the necking zone of a classic magma-poor continental margin, while the eastern part corresponds to the proximal domain.

  13. Comparative Epidemiology of Influenza B Yamagata- and Victoria-Lineage Viruses in Households.

    PubMed

    Xu, Cuiling; Chan, Kwok-Hung; Tsang, Tim K; Fang, Vicky J; Fung, Rita O P; Ip, Dennis K M; Cauchemez, Simon; Leung, Gabriel M; Peiris, J S Malik; Cowling, Benjamin J

    2015-10-15

    Influenza B viruses split into 2 distinct lineages in the early 1980s, commonly named the Victoria and Yamagata lineages. There are few data on the comparative epidemiology of Victoria- and Yamagata-lineage viruses. In 2007-2011, we enrolled 75 and 34 households containing index patients with acute respiratory illness who tested positive for Yamagata- and Victoria-lineage viruses, respectively, from outpatient clinics in Hong Kong, China. These index patients and their household contacts were followed up for 7-10 days. We examined overall risk of polymerase chain reaction-confirmed infection among household contacts and the risk of secondary infection within households using an individual-based hazard model that accounted for tertiary transmission and infections occurring outside the household. We found that for Victoria-lineage viruses, the risk of within-household infection among household contacts aged ≤15 years was significantly higher (risk ratio = 12.9, 95% credibility interval: 4.2, 43.6) than that for older household contacts, while for Yamagata-lineage viruses, the risk of within-household infection for household contacts did not differ by age. Influenza B Yamagata- and Victoria-lineage viruses have similar characteristics in terms of viral shedding and clinical illness. The mechanisms underlying these epidemiologic differences deserve further investigation. PMID:26400854

  14. Characterising groundwater dynamics in Western Victoria, Australia using Menyanthes software

    NASA Astrophysics Data System (ADS)

    Woldeyohannes, Yohannes; Webb, John

    2010-05-01

    Water table across much of the western Victoria, Australia have been declining for at least the last 10-15 years, and this is attributed to the consistently low rainfall for these years, but over the same period of time there has been substantial change in land use, with grazing land replaced by cropping and tree plantations appearing in some areas. Hence, it is important to determine the relative effect the climate and land use factors on the water table changes. Monitoring changes in groundwater levels to climate variables and/or land use change is helpful in indicating the degree of threat faced to agricultural and public assets. The dynamics of the groundwater system in the western Victoria, mainly on the basalt plain, have been modelled to determine the climatic influence in water table fluctuations. In this study, a standardized computer package Menyanthes was used for quantifying the influence of climatic variables on the groundwater level, statistically estimating trends in groundwater levels and identify the properties that determine the dynamics of groundwater system. This method is optimized for use on hydrological problems and is based on the use of continuous time transfer function noise model, which estimates the Impulse response function of the system from the temporal correlation between time series of groundwater level and precipitation surplus. In this approach, the spatial differences in the groundwater system are determined by the system properties, while temporal variation is driven by the dynamics of the input into the system. 80 time series models are analysed and the model output parameter values characterized by their moments. The zero-order moment Mo of a distribution function is its area and M1 is related to the mean of the impulse response function. The relation is M1/Mo. It is a measure of the system's memory. It takes approximately 3 times the mean time (M1/Mo) for the effect of a shower to disappear completely from the system. Overall

  15. Evaluation of vehicle side airbag effectiveness in Victoria, Australia.

    PubMed

    D'Elia, Angelo; Newstead, Stuart; Scully, Jim

    2013-05-01

    Side airbag systems were first introduced into vehicles around 1995 to help protect occupants from injury in side impact crashes. International studies have shown that side airbags are effective in reducing the risk of death and injury, however, serious injuries can still occur even when side airbags deploy. The objective of this study was to use detailed injury information from insurance injury compensation claims data linked to Police reported crash data to determine the effectiveness of side airbags in reducing the risk of death or injury for occupants involved in side impact crashes in Victoria, Australia based on the specific body regions that side airbag systems are designed to protect. It was found that head and torso-protecting dual airbag systems designed to protect the head, neck, face, chest and abdomen are highly effective in reducing driver death or injury due to near side crashes. They were associated with a statistically significant reduction of 41.1% (25.9%, 53.2%) in the odds of death or injury across all body regions; and a 48.0% (28.0%, 62.4%) reduction in the odds of death or injury to the head, neck, face, chest and abdomen. The study did not find any evidence that torso-protecting airbags alone are effective in reducing death or injury. Analysis results indicate that head and torso-protecting side airbag systems in vehicles are a highly effective technology for reducing the risk of death or injury to vehicle occupants in near side crashes. The magnitude of the injury reduction benefits estimated indicate that fitment of this technology to all vehicles should be a high priority and will yield significant savings in overall road trauma. PMID:23499979

  16. Impact of cruise ship emissions in Victoria, BC, Canada

    NASA Astrophysics Data System (ADS)

    Poplawski, Karla; Setton, Eleanor; McEwen, Bryan; Hrebenyk, Dan; Graham, Mark; Keller, Peter

    2011-02-01

    Characterization of the effects of cruise ship emissions on local air quality is scarce. Our objective was to investigate community level concentrations of fine particulate matter (PM 2.5), nitrogen dioxide (NO 2) and sulphur dioxide (SO 2) associated with cruise ships in James Bay, Victoria, British Columbia (BC), Canada. Data obtained over four years (2005-2008) at the nearest air quality network site located 3.5 km from the study area, a CALPUFF modeling exercise (2007), and continuous measurements taken in the James Bay community over a three-month period during the 2009 cruise ship season were examined. Concentrations of PM 2.5 and nitrogen oxide (NO) were elevated on weekends with ships present with winds from the direction of the terminal to the monitoring station. SO 2 displayed the greatest impact from the presence of cruise ships in the area. Network data showed peaks in hourly SO 2 when ships were in port during all years. The CALPUFF modeling analysis found predicted 24-hour SO 2 levels to exceed World Health Organization (WHO) guidelines of 20 μg m -3 for approximately 3% of 24-hour periods, with a maximum 24-hour concentration in the community of 41 μg m -3; however, the CALPUFF model underestimated concentrations when predicted and measured concentrations were compared at the network site. Continuous monitoring at the location in the community predicted to experience highest SO 2 concentrations measured a maximum 24-hour concentration of 122 μg m -3 and 16% of 24-hour periods were above the WHO standard. The 10-minute concentrations of SO 2 reached up to 599 μg m -3 and exceeded the WHO 10-minute SO 2 guideline (500 μg m -3) for 0.03% of 10-minute periods. No exceedences of BC Provincial or Canadian guidelines or standards were observed.

  17. Evidence of partial melting beneath the passive margin of the Gulf of Aden from a joint analysis of gravity and seismology

    NASA Astrophysics Data System (ADS)

    Basuyau, C.; Tiberi, C.; Leroy, S.; Ebinger, C.; Al-Lazki, A.; Al-Tobi, K.

    2007-12-01

    Rifting processes though extensively studied are still not well known. Nevertheless geophysical studies can provide new insight into the mechanisms of continental opening. The Gulf of Aden is a young narrow and obliquely opening oceanic basin formed during the Olig-Miocene. Its conjugate margins are well preserved beneath a thin post-rift sedimentary cover.It thus makes it an ideal region to study the processes of rifting and continental lithospheric break-up. In 2003 and 2005, numerous teleseismic earthquakes were recorded at twenty-nine broadband seismic stations in Dhofar (Oman) in order to study the northern margin of the Gulf of Aden. In this work, we used a joint inversion of teleseismic P-wave delay times and Bouguer anomaly. We obtain velocity ans density models that shows (1) crustal heterogeneities that match to the main geological features at the surface, (2) the presence of two low velocity anomalies in the continuation of Socotra and Alula Fartak fracture zones that appear at 60 km depth and may extend to at least 200 km, (3) gravity edge effect on the margin. The S wave tomography results are consistent with the joint inversion ones, and evidence partial melting within the two deep velocity anomalies. These results which suggest that the Afar hotspot has an influence up to the Dhofar will be discussed.

  18. Segmentation and along-strike asymmetry of the passive margin in Socotra, eastern Gulf of Aden: Are they controlled by detachment faults?

    NASA Astrophysics Data System (ADS)

    Fournier, Marc; Huchon, Philippe; Khanbari, Khaled; Leroy, Sylvie

    2007-03-01

    On the island of Socotra, the southern passive margin of the Gulf of Aden displays along its strike two different types of asymmetric structures. Western Socotra is made up of a series of southward tilted blocks bounded by consistently northward dipping normal faults. Eastern Socotra consists of a broad asymmetric anticline with a steep northern limb and a gently dipping southern limb. A zone of NE-SW striking strike-slip and normal faults separates the two areas. The overall structure is interpreted as representing two rift segments separated by a transfer zone. The along-strike juxtaposition of crustal-scale asymmetric structures on the southern margin of the Gulf of Aden is complemented by the asymmetry of the conjugate margins on either side of the gulf. Whereas the western Socotra margin is narrow and characterized by oceanward dipping normal faults, the conjugate Oman margin is broader and dominated by horsts and graben. Considering that asymmetric structures in the upper crust are often associated with synthetic shear zones at deeper ductile levels, we propose that the western and eastern Socotra margin segments were controlled at depth by two detachment faults with opposite dips and senses of shear. The normal faults of western Socotra would sole out into a top-to-the-north ductile shear zone, whereas the asymmetric anticline of eastern Socotra would be associated with a top-to-the-south detachment fault.

  19. Reactivated tectonic boundaries and implications for the reconstruction of southeastern Australia and northern Victoria Land, Antarctica

    SciTech Connect

    Foster, D.A.; Gleadow, A.J.W. )

    1992-03-01

    Rifted continental margins are strongly influenced by the location of zones of preexisting crustal weakness. Apatite fission track thermochronological data indicate that the Paleozoic lithospheric boundary between the Kanmantoo and Lachlan fold belts in western Victoria, Australia, was reactivated during Mesozoic rifting as a transfer fault. To the east of this boundary, 1-2 km of material was denuded during extension, while essentially no denudation took place during rifting to the west. The correlated tectonic boundary within the Bowers terrane of northern Victoria Land, Antarctica, was also reactivated upon rifting. During fragmentation of Gondwana, movement on this zone perpendicular to the direction of rifting probably determined the location of the Tasman Fracture Zone. When Australia and Antarctica are reconstructed along the trace of the Tasman Fracture Zone, the tectonic boundary in Victoria falls into precise alignment with the Bowers terrane.

  20. Institutional responses to communicable diseases at Victoria College, University of Toronto, 1900-1940.

    PubMed

    Gidney, Catherine

    2007-01-01

    Between 1900 and 1940 students and staff risked their lives to attend, and teach at, Victoria College. Not only did Victoria experience three major epidemics--diphtheria in 1911, influenza from 1918 to 1920, and smallpox in 1927--but almost yearly one or two students contracted diseases such as scarlet fever, measles, and mumps. Yet at a time when there was no health insurance and few hospital facilities, how did the university cope with the problem? This paper examines the care provided to Victoria's residential students. In the process the paper illustrates not only the upheaval endured by individual students but also the enormous financial and emotional toll paid by the institution, especially by members of its female staff. PMID:18447307

  1. 78 FR 35604 - Foreign-Trade Zone (FTZ) 155-Calhoun/Victoria Counties, Texas; Notification of Proposed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-13

    ... Proposed Production Activity; Caterpillar, Inc.; (Excavator and Frame Assembly Production), Victoria, Texas... proposed production activity to the FTZ Board on behalf of Caterpillar, Inc. (Caterpillar), located in..., at 7300 Lone Tree Road, Victoria, Texas. The facility is used for the production of excavators...

  2. Identifying coherent patterns of environmental change between multiple, multivariate records: an application to four 1000-year diatom records from Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Tyler, Jonathan J.; Mills, Keely; Barr, Cameron; Sniderman, J. M. Kale; Gell, Peter A.; Karoly, David J.

    2015-07-01

    Empirical orthogonal functions (EOFs) of indirect archives of environmental change are increasingly used to identify coherent trends between palaeoclimate records, to separate externally forced patterns from locally driven idiosyncrasies. Lake sediments are particularly suited to such syntheses: they are abundant in most landscapes and record a wide array of information, yet local complexities often conceal or confuse the climate signal recorded at individual sites. Lake sediment parameters usually exhibit non-linear, multivariate and indirect responses to climate, therefore identifying coherent patterns between two or more lake records presents a complex challenge. Ideally, the selection of representative variables should be non-subjective and inclusive of as many different variables as possible, allowing for unexpected correlations between sites. In order to meet such demands, we propose a two-tier ordination procedure whereby site-specific (local) ordinations, obtained using Detrended Correspondence Analysis (DCA), are nested within a second, regional EOF. Using the local DCAs as representative variables allows the retention of a larger fraction of variance from each site, removes any subjectivity from variable selection and retains the potential for observing multiple, coherent signals from within and between each dataset. We explore this potential using four decadally resolved diatom records from volcanic lakes in Western Victoria, Australia. The records span the 1000 years prior to European settlement in CE 1803. Our analyses reveal at least two coherent patterns of ecological change that are manifest in each of the four datasets, patterns which may have been overlooked by a single-variable, empirical orthogonal function approach. This intra-site coherency provides a valuable step towards understanding multi-decadal hydroclimate variability in southeastern Australia.

  3. 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.

  4. Differential age susceptibility to influenza B/Victoria lineage viruses in the 2015 Australian influenza season.

    PubMed

    Barr, Ian G; Vijaykrishna, Dhanasekaran; Sullivan, Sheena G

    2016-01-01

    Influenza B viruses make up an important part of the burden from seasonal influenza globally. The 2015 season in Australia saw an unusual predominance of influenza B with a distinctive switch during the season from B/Yamagata/16/88 lineage viruses to B/Victoria/2/87 lineage viruses. We also noted significant differences in the age groups infected by the different B lineages, with B/Victoria infecting a younger population than B/Yamagata, that could not be explained by potential prior exposure. PMID:26848118

  5. Stratigraphic architecture of bedrock reference section, Victoria Crater, Meridiani Planum, Mars

    USGS Publications Warehouse

    Edgar, Lauren A.; Grotzinger, John P.; Hayes, Alex G.; Rubin, David M.; Squyres, Steve W.; Bell, James F.; Herkenhoff, Ken E.

    2012-01-01

    The Mars Exploration Rover Opportunity has investigated bedrock outcrops exposed in several craters at Meridiani Planum, Mars, in an effort to better understand the role of surface processes in its geologic history. Opportunity has recently completed its observations of Victoria crater, which is 750 m in diameter and exposes cliffs up to ~15 m high. The plains surrounding Victoria crater are ~10 m higher in elevation than those surrounding the previously explored Endurance crater, indicating that the Victoria crater exposes a stratigraphically higher section than does the Endurance crater; however, Victoria strata overlap in elevation with the rocks exposed at the Erebus crater. Victoria crater has a well-developed geomorphic pattern of promontories and embayments that define the crater wall and that reveal thick bedsets (3–7m) of large-scale cross-bedding, interpreted as fossil eolian dunes. Opportunity was able to drive into the crater at Duck Bay, located on the western margin of Victoria crater. Data from the Microscopic Imager and Panoramic Camera reveal details about the structures, textures, and depositional and diagenetic events that influenced the Victoria bedrock. A lithostratigraphic subdivision of bedrock units was enabled by the presence of a light-toned band that lines much of the upper rim of the crater. In ascending order, three stratigraphic units are named Lyell, Smith, and Steno; Smith is the light-toned band. In the Reference Section exposed along the ingress path at Duck Bay, Smith is interpreted to represent a zone of diagenetic recrystallization; however, its upper contact also coincides with a primary erosional surface. Elsewhere in the crater the diagenetic band crosscuts the physical stratigraphy. Correlation with strata present at nearby promontory Cape Verde indicates that there is an erosional surface at the base of the cliff face that corresponds to the erosional contact below Steno. The erosional contact at the base of Cape Verde

  6. Ocean-continent-transition and oceanic ridge structural evolution (eastern Gulf of Aden): Implications for rift to seafloor spreading processes

    NASA Astrophysics Data System (ADS)

    D'Acremont, E.; Leroy, S. D.; Beslier, M.; Autin, J.; Watremez, L.; Maia, M. A.; Gente, P.

    2009-12-01

    The rifting between Arabia and Somalia, which started around 35 Ma ago, is followed by oceanic accretion from at least 17.6 Ma leading to the present Gulf of Aden. The transition between the thinned continental and the oceanic crusts is characterized, in space and time, by an ocean-continent transition (OCT). Here, we use bathymetry, gravity, seismic reflection and magnetism from the Encens-Sheba and Encens cruises in order to constrain the structure and segmentation of the conjugate OCT as well as the oceanic ridge between two main fracture zones (Alula-Fartak and Socotra-Hadbeen). The segmentation of the initial oceanic spreading centers seem directly related to the margin structure. Then, magmatic processes and kinematics change strongly influenced the evolution of the segmentation. The OCT and the oceanic domain can be divided into two distinct areas in the study area. The Eastern area is characterized by an extremely thin OCT and oceanic crusts (< 4km), a ~30 km wide and tectonized OCT with isolated continental blocks and short axial segments. In the western area, thicker OCT and oceanic crusts (>5km), a ~15 km wide OCT with a volcanic ridge, and a 6 km thick underplated mafic body in the northern margin suggest a high melt supply. The magmatic supply observed in the western domain is probably due to an off-axis thermal anomaly located below the southern flank of the Sheba ridge, at 75 km east of the major Alula-Fartak transform fault. This suggests that the OCT and the axial ridge morphology of this domain are perturbed by post-rift volcanism, which is due to a combination of the spreading rate, a thermal anomaly, and the cold edge effect of the Alula-Fartak transform fault. The presence of the inherited Mesozoic basins (Jezar-Qamar-Gardafui basin) located on this western domain can also explain, the difference in both the structure and the nature of the OCT between the two domains. The nature of the OCT could be either (or both) exhumed lower crust or

  7. Structural Analysis of the Victoria Quadrangle (H2) of Mercury based on NASA MESSENGER Data

    NASA Astrophysics Data System (ADS)

    Galluzzi, Valentina

    2015-04-01

    Objective of this thesis is the mapping and structural analysis of the H2 quadrangle, “Victoria”, and a reconnaissance study of the geometry and kinematics of lobate scarps on Mercury. To this end, I produced a 1:3,000,000 geologic map of the area using the images provided by the NASA spacecraft MESSENGER, which has been orbiting the planet since March, 2011. The geologic map shows the distribution of smooth plains, intermediate plains, intercrater plains units and a classification of crater materials based on an empirical distinction among three stages of degradation. Structural mapping shows that the H2 quadrangle is dominated by N-S faults (here grouped into the Victoria system) to the east and NE-SW faults (Larrocha system) to the west, with the secondary existence of NW-SE-trending faults (Carnegie system) in the north-western area of the quadrangle. A systematic analysis of these systems has led to the following results. 1) The Victoria system is characterized by a main array of faults located along Victoria Rupes – Endeavour Rupes – Antoniadi Dorsum. The segmentation of this array into three different sectors changes from north to south and is spatially linked to the presence of three volcanic vents located at the boundaries between each sector and at the northern end of the Victoria Rupes sector, suggesting that volcanism and faulting are interrelated. 2) The main array of Carnegie system is kinematically linked and antithetical to the Victoria system. Both systems have arguably controlled the growth of a longitudinal, fault-free, crustal and gravimetric bulge in the central area of the Victoria quadrangle, which is interpreted as a regional contractional pop-up. 3) The Larrocha system is interrupted against the central bulge and thus is probably older than the Victoria and Carnegie systems. Buffered crater counting performed on the Victoria system confirms the young relative age of its fault segments with respect to the map units. The faults of the

  8. Which Fault Orientations Occur during Oblique Rifting? Combining Analog and Numerical 3d Models with Observations from the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Autin, J.; Brune, S.

    2013-12-01

    Oblique rift systems like the Gulf of Aden are intrinsically three-dimensional. In order to understand the evolution of these systems, one has to decode the fundamental mechanical similarities of oblique rifts. One way to accomplish this, is to strip away the complexity that is generated by inherited fault structures. In doing so, we assume a laterally homogeneous segment of Earth's lithosphere and ask how many different fault populations are generated during oblique extension inbetween initial deformation and final break-up. We combine results of an analog and a numerical model that feature a 3D segment of a layered lithosphere. In both cases, rift evolution is recorded quantitatively in terms of crustal fault geometries. For the numerical model, we adopt a novel post-processing method that allows to infer small-scale crustal fault orientation from the surface stress tensor. Both models involve an angle of 40 degrees between the rift normal and the extensional direction which allows comparison to the Gulf of Aden rift system. The resulting spatio-temporal fault pattern of our models shows three normal fault orientations: rift-parallel, extension-orthogonal, and intermediate, i.e. with a direction inbetween the two previous orientations. The rift evolution involves three distinct phases: (i) During the initial rift phase, wide-spread faulting with intermediate orientation occurs. (ii) Advanced lithospheric necking enables rift-parallel normal faulting at the rift flanks, while strike-slip faulting in the central part of the rift system indicates strain partitioning. (iii) During continental break-up, displacement-orthogonal as well as intermediate faults occur. We compare our results to the structural evolution of the Eastern Gulf of Aden. External parts of the rift exhibit intermediate and displacement-orthogonal faults while rift-parallel faults are present at the rift borders. The ocean-continent transition mainly features intermediate and displacement

  9. 78 FR 48318 - Approval and Promulgation of Air Quality Implementation Plans; Texas; Victoria County, 1997 8...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-08

    ... Quality Standards (NAAQS) for 1- hour ozone (43 FR 8962). As required by the CAA, the state of Texas... in March 25, 1980 (45 FR 19231) and another in August 13, 1984 (49 FR 32180). An additional SIP..., 1995 (60 FR 12438). On July 27, 1994, Texas submitted a request to redesignate Victoria County...

  10. Supervision and Satisfaction among School Psychologists: An Empirical Study of Professionals in Victoria, Australia

    ERIC Educational Resources Information Center

    Thielking, Monica; Moore, Susan; Jimerson, Shane R.

    2006-01-01

    This study examined the supervision arrangements and job satisfaction among school psychologists in Victoria, Australia. Participation in professional supervision was explored in relation to the type of employment and job satisfaction. The results revealed that the frequency of participation in supervision activities was less than optimal, with…

  11. The Killing of the Workers' Educational Association of Victoria: A Myth Challenged

    ERIC Educational Resources Information Center

    Dadswell, Gordon

    2004-01-01

    On 21 March 1941, the Council of the Workers' Educational Association of Victoria, Australia, (the Association) voted the organisation out of existence. The demise was in no way contemplated, and there was no practical reason why the Council acted in the way it did. This paper is the story of the destruction of a successful adult education…

  12. Communicating Risk with Parents: Exploring the Methods and Beliefs of Outdoor Education Coordinators in Victoria, Australia

    ERIC Educational Resources Information Center

    Dallat, Clare

    2009-01-01

    This paper examines the risk communication strategies currently being employed by seven outdoor education co-ordinators in Government schools in Victoria, Australia. Of particular interest are the beliefs and assumptions held by these co-ordinators in relation to communicating risk with parents. Current policy stipulates that parents must be…

  13. 40 CFR 81.136 - Corpus Christi-Victoria Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 17 2010-07-01 2010-07-01 false Corpus Christi-Victoria Intrastate Air Quality Control Region. 81.136 Section 81.136 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... County, Jackson County, Jim Wells County, Kenedy County, Kleberg County, Lavaca County, Live Oak...

  14. Rhetoric, Reality and Resources: The New 3R's for Victoria's "Schools of the Future."

    ERIC Educational Resources Information Center

    Townsend, Tony

    The new government of the state of Victoria (Australia) announced its "Schools of the Future" program in 1993. The emphasis on the role of the community in education and self-management by schools seemed promising for the quality of education in the state, but after 3 years of implementation, the reality does not match the rhetoric of this reform.…

  15. Perception of Aquaculture Education to Support Further Growth of Aquaculture Industry in Victoria, Australia

    ERIC Educational Resources Information Center

    Awal, Sadiqul; Christie, Andrew; Watson, Matthew; Hannadige, Asanka G. T.

    2012-01-01

    Purpose: The central aim of this study was to determine the perception of aquaculture educational provisions in the state of Victoria, and whether they are sufficient to ultimately support further growth of the industry. Design/methodology/approach: Questionnaires were formulated and distributed to participants in a variety of ways, including via…

  16. Chlamydia pecorum Infection in Free-ranging Koalas ( Phascolarctos cinereus ) on French Island, Victoria, Australia.

    PubMed

    Legione, Alistair R; Amery-Gale, Jemima; Lynch, Michael; Haynes, Leesa; Gilkerson, James R; Sansom, Fiona M; Devlin, Joanne M

    2016-04-28

    We detected Chlamydia pecorum in two koalas ( Phascolarctos cinereus ) from a closed island population in Victoria, Australia, previously free of Chlamydia infection. The ompA and multilocus sequence type were most closely related to published isolates of livestock rather than koala origin, suggesting potential cross-species transmission of C. pecorum . PMID:26981690

  17. Vulnerability to Bushfires in Rural Australia: A Case Study from East Gippsland, Victoria

    ERIC Educational Resources Information Center

    Whittaker, Joshua; Handmer, John; Mercer, David

    2012-01-01

    This paper investigates the nature and causes of vulnerability to bushfires in the Wulgulmerang district of East Gippsland, Victoria, in south-eastern Australia. In 2003 bushfires devastated the small population of this isolated farming district, destroying homes, agricultural assets and public infrastructure. The fires also adversely affected the…

  18. Connections '96. Proceedings of a Faculty Conference (2nd, Victoria, British Columbia, Canada, May 1996).

    ERIC Educational Resources Information Center

    Dayton-Sakari, Mary, Ed.; Miller, Carole S., Ed.; Liedtke, Werner, Ed.

    This proceedings contains 19 papers presented at the second annual faculty conference at the University of Victoria (British Columbia, Canada). Papers cover a wide variety of disciplines, including preschool education, classroom communication, mathematics instruction, theater, attention deficit disorders, distance learning by rural home schoolers,…

  19. Educational Enrolment of Students with a Disability in New South Wales and Victoria.

    ERIC Educational Resources Information Center

    Dempsey, Ian; Foreman, Phil; Jenkinson, Josephine

    2002-01-01

    This article discusses the impact of legislative and special education policy on the educational enrollment of students with a disability across Australia. Enrollment trends in New South Wales and Victoria are examined and discussed within the context of their respective special education policies, disability discrimination legislation, and…

  20. Equity Indicators: Measures of Socio-Economic Status at Victoria University.

    ERIC Educational Resources Information Center

    Sinclair, Genevieve; Doughney, James; Palermo, Josephine

    After a review of relevant literature on socioeconomic status (SES) and the ways in which is used for higher education institutional research and policy, a detailed data analysis of Victoria University (VU), Australia student data was undertaken. Between 10,000 and 15,000 domestic student addresses were geocoded to Australian Bureau of Statistics…

  1. A Vision for Training and Further Education in Victoria. Vision Statement.

    ERIC Educational Resources Information Center

    Victoria Training Board, Melbourne (Australia).

    The state of Victoria (Australia) needs a well-educated, adaptable work force to face the numerous challenges stemming from the following: shifts in employment toward "knowledge workers"; the impact of competition, technological change, and microeconomic reform; aging of the population; disparate views regarding the purpose of education; and the…

  2. People Management Practices in the Public Health Sector: Developments from Victoria, Australia

    ERIC Educational Resources Information Center

    Stanton, Pauline; Bartram, Timothy; Harbridge, Raymond

    2004-01-01

    This study investigates the impact on human resource management (HRM) practices in the public health sector in Victoria, Australia of two different government policy environments. First, it explores the Liberal Coalition Government's decentralisation of public health sector management, from 1992-1999 and second, the Labor Government's…

  3. Establishing an Online Community of Inquiry at the Distance Education Centre, Victoria

    ERIC Educational Resources Information Center

    Jackson, Luke C.; Jackson, Alun C.; Chambers, Dianne

    2013-01-01

    This pilot intervention focused on three courses that were redesigned to utilize the online environment to establish an online community of inquiry (CoI). The setting for this research study was the Distance Education Centre, Victoria (DECV), an Australian co-educational school with approximately 3000 students who, for a variety of reasons, are…

  4. What Do the Public Search for on the Catalogue of the State Library of Victoria?

    ERIC Educational Resources Information Center

    Waller, Vivienne

    2009-01-01

    This study examines what the public search for in the catalogue of the State Library of Victoria (SLV). As well as indicating the type of content being accessed, this gives an indication of what catalogue users expect of the State Library collection. A content analysis was undertaken of a random, stratified sample of 4,000 search queries typed in…

  5. Connections '99. Proceedings of a Faculty Conference (5th, Victoria, British Columbia, Canada, May 1999).

    ERIC Educational Resources Information Center

    Gibbons, Sandra L., Ed.; Liedtke, Werner W., Ed.

    This proceedings contains 13 papers from the 1999 annual conference of the Faculty of Education, University of Victoria (British Columbia). The papers are: (1) "Sacred and the Profane in Advertising Art" (Bill Zuk, Robert Dalton); (2) "Finding the Fund$ in Fun Run: Evaluating the Effectiveness and Efficiency of Physical Activity Events as…

  6. Connections '98. Proceedings of a Faculty Conference (4th, Victoria, British Columbia, Canada, May 1998).

    ERIC Educational Resources Information Center

    Gibbons, Sandra L., Ed.; Anderson, John O., Ed.

    This proceedings contains 13 papers from the 1998 annual Faculty of Education conference at the University of Victoria, British Columbia (Canada). The papers are: (1) "Struggling with Re-Presentation, Voice, and Self in Narrative Research" (Marla Arvay); (2) "Women's Soccer in Canada: A Slow Road to Equity" (Meredith Bogle, Bruce Howe); (3)…

  7. Connections '97. Proceedings of a Faculty Conference (3rd, Victoria, British Columbia, Canada, May 1997).

    ERIC Educational Resources Information Center

    Liedtke, Werner, Ed.

    This proceedings contains 17 papers presented at the third annual faculty conference at the University of Victoria (British Columbia, Canada). Papers cover a wide variety of disciplines and topics, including student teaching, athletics, researcher-teacher collaboration, hands-on science instruction, violence prevention, youth violence, counseling,…

  8. Ground ice recharge via brine transport in frozen soils of Victoria Valley, Antarctica: Insights from modeling δ 18O and δD profiles

    NASA Astrophysics Data System (ADS)

    Hagedorn, Birgit; Sletten, Ronald S.; Hallet, Bernard; McTigue, David F.; Steig, Eric J.

    2010-01-01

    Soils in the McMurdo Dry Valleys, Antarctica contain ice and considerable amounts of salt. Ice often occurs at shallow depth throughout the Dry Valleys and other areas of hyperarid permafrost, notably on Mars. This common occurrence of shallow ice is enigmatic; however, since according to published sublimation models it should disappear relatively quickly (at rates of order 0.1 mm a -1) due to vapor loss to the atmosphere. This loss may be offset by recharge from snowmelt infiltrating and freezing in the soil. Herein, we present a first quantitative estimate of this recharge based on measured vertical profiles of δD and δ 18O that reveal considerable detail about the sources and sinks of ice. We model these profiles, taking into account the salt content and a soil temperature record along a 1.6 m depth profile of ˜10 ka old ice-cemented soils in Victoria Valley, Antarctica. The stable isotopes of ice are enriched in heavy isotopes at the top of the ice cement (20 cm depth); both δD and δ 18O values plotted against depth exhibit a concave upward curve. At depth, the isotope composition is similar to that of Lake Victoria and modern meteoric water. The concave shape of the isotope profile is suggestive of downward advection-dispersion of snowmelt water enriched in heavy isotopes into the ice cement. Our advection-dispersion model, coupled with field data, enables us to quantify the advective flux and dispersion of melt water into the ice. The advective velocity and dispersion coefficient depend on the time since advection began and the ice-to-brine ratio; they are, respectively, of the order of 10 -11-10 -10 m s -1 and 10 -12-10 -11 m 2 s -1. These values suggest that over the ˜10 ka time period, a total of 190 mm water infiltrated into the ice-cemented ground. The isotope composition and deuterium excess values of the uppermost ice cement can be modeled from snowmelt water enriched in salts using open system-Rayleigh fractionation. To develop the isotopic

  9. 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.

  10. Mitochondrial phylogeography of rock-dwelling cichlid fishes reveals evolutionary influence of historical lake level fluctuations of Lake Tanganyika, Africa.

    PubMed

    Verheyen, E; Rüber, L; Snoeks, J; Meyer, A

    1996-06-29

    The East African Lakes Tanganyika, Malawi and Victoria each harbour hundreds of endemic invertebrate and vertebrate species. Inferences about the ecological and evolutionary processes responsible for the origin of these species flocks will only be possible when they are made within historical and comparative frameworks. Specifically, the relative importance of intrinsic characteristics and extrinsic factors may offer information about the processes that drive diversification and speciation in these species. We investigated the sequence variation of a segment of the mitochondrial DNA control region of 32 populations representing all four nominal species in the three genera of eretmodine cichlids from Lake Tanganyika. Based on a phylogenetic analysis of these data we attempted to evaluate the importance of major lake level fluctuations on patterns of intralacustrine speciation. The geography of genetic variation reveals a high degree of within-lake endemism among genetically well-separated lineages distributed along the inferred shore lines of three historically intermittent lake basins. Seismic data indicate that extreme lowering of water levels in the Pleistocene caused the single Lake Tanganyika basin to split into three isolated ones. The strong phylogeographic structure of the Eretmodini, and the observation that some closely related populations occur on opposite shores of the lake, agree with this geological scenario. The three-clade-three-basin phylogeographic pattern was repeated twice within this tribe of cichlids. The phylogeographic pattern of eretmodine cichlids suggests that major fluctuations in the level of the lake have been important in shaping their adaptive radiation and speciation. The mitochondrially defined clades are in conflict with the current taxonomy of the group and suggest that there has been convergent evolution in trophic morphology, particularly in the shapes of oral teeth, taxonomically the most diagnostic characters of the three

  11. Terrestrial environmental changes around the Gulf of Aden over the last 210 kyr deduced from the sediment n-alkane record: Implications for the dispersal of Homo sapiens

    NASA Astrophysics Data System (ADS)

    Isaji, Yuta; Kawahata, Hodaka; Ohkouchi, Naohiko; Murayama, Masafumi; Tamaki, Kensaku

    2015-03-01

    We analyzed long-chain (C25-C36) n-alkanes and pollen grains in sediments from the Gulf of Aden covering the last 212 kyr to reconstruct the surrounding terrestrial environment, a critical region for the dispersal of Homo sapiens. Substantial increases in the flux of n-alkanes during 200-185, 120-95, and 70-50 ka were interpreted to indicate enhanced vegetation biomass in the Arabian Peninsula and the northern part of the Horn of Africa or increase in lithogenic material inputs. Periods of enhanced n-alkane flux occurred during or immediately after pluvial episodes, indicating that the increased precipitation may have induced substantially enhanced vegetation biomass, creating favorable conditions for Homo sapiens. Additionally, vegetation may have increased due to moderate precipitation unrecorded by speleothems or in accordance with the lowering of sea level, indicating that the dispersal might have been possible even after the shift to an arid environment indicated by the speleothems.

  12. Varying responses to Indian monsoons during the past 220 kyr recorded in deep-sea sediments in inner and outer regions of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Isaji, Yuta; Kawahata, Hodaka; Ohkouchi, Naohiko; Ogawa, Nanako O.; Murayama, Masafumi; Inoue, Kazuki; Tamaki, Kensaku

    2015-11-01

    Although the climate in the Arabian Sea is controlled primarily by the southwest monsoon, the southwest monsoon has little influence in the Gulf of Aden. To examine the different responses to monsoons between the Gulf of Aden and areas outside the gulf, a comprehensive data set of bulk organic and inorganic geochemistry, sea surface temperature, and δ15N of pheopigments was obtained from deep-sea sediment cores recovered from inner and outer regions of the gulf. The results indicated that during the past 220 kyr, the influence of the southwest monsoon was stronger in the outer region of the gulf than in the inner region, which implies that the southwest monsoon trajectory has not changed substantially during that time period. Furthermore, influxes of O2-depleted water from the Southern Ocean and the lateral advection of upwelled seawater also had limited influence in the inner region. In contrast, concentrations of lithogenic materials transported by the southwest monsoon were similar in the two regions. δ15N of pheopigments indicated that during the last glacial maximum, the southwest monsoon was weaker and the northeast monsoon was stronger than at present. A stronger southwest monsoon during interglacials enhanced primary productivity and may have caused anoxic conditions to develop in the Arabian Sea, as indicated by redox proxies in the outer region. Anoxic conditions also formed during MIS 3, but no increase in the primary productivity is indicated; therefore, another mechanism, such as an influx of O2-depleted water from the Southern Ocean, may have been the cause.

  13. The onshore-offshore ENCENS project: Imaging the stretching of the continental lithosphere and inception of oceanic spreading in the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, S.; Ebinger, C.; D'Acremont, E.; Stuart, G.; Al-Lazki, A.; Tiberi, C.; Autin, J.; Watremez, L.; Beslier, M.; Bellahsen, N.; Lucazeau, F.; Perrot, J.; Mouthereau, F.; Courrèges, E.; Huchon, P.; Rouzo, S.; Balahaf, S.; Sholan, J.; Unternehr, P.; Hello, Y.; Anglade, A.; Desprez, O.; Beguery, L.; Aouji, O.; Daniel, R.; Al Toubi, K.

    2006-12-01

    The eastern Gulf of Aden exemplifies several extensional processes that began 35 Ma ago from continental rifting to seafloor spreading at 2 cm/yr. Thin post-breakup sediment cover reveals the syn- and pre-rift basement fabric and the variable styles of conjugate margins along and across strike. A comprehensive multi- disciplinary study of the eastern part of the northern margin of the Gulf of Aden has been undertaken recently in the framework of the French margins program (GDR Marges) and the NERC with the long term objective to integrate in a consistent model of evolution, field observations where the margins crop out, results of marine geophysical survey where the margins are submerged and seismological observations of deep interior structure. A deep onshore-offshore seismic survey operated by IFREMER-GENAVIR was conducted between February, 3rd and March 14th 2006 off the Dhofar coast (southern Oman). We collect 67 multichannel seismic reflection profiles and 15 seismic refraction profiles acquired thanks to 60 stations. The shots have been recorded by 35 Ocean Bottom Seismometers (15 from IRD-Villefranche sur Mer and 20 from INSU Paris) and 25 seismological stations deployed onland in Southern Oman (18 stations from Encens-UK project funded by NERC and managed by RHUL ; 2 temporary and 4 permanent stations from Sultan Qaboos University ; 1 from ENS Paris). The network has been extended to the southern conjugate margin with 2 broadband stations deployed in Socotra island. The preliminary results show the evolution of the thickness of the crust from 35 km in the upper part of the margin to about 5 km in the ocean-continent transition. From our observations (low angle faults dipping toward the ocean or the continent imaged) we will propose rifting models responsible for the lithospheric stretching. The segmentation of the margins should be also precisely defined thanks to the multibeam bathymetry, the magnetism and the gravity acquired during the cruise.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Stromatolites and thrombolites are microbially-mediated, sedimentary structures of various size and morphology, found throughout the rock record. Although they do not always contain fossils of microbial cells, ancient stromatolitic structures are considered biogenic in origin and, therefore, evidence of early life. Modern, living stromatolites are found in lacustrine and marine environments and can provide a window in which to observe some of Earth's earliest biological processes. However, secular variation in marine chemistry over geological time means that modern marine settings are not always the best analogues for ancient carbonates. This study describes the occurrence of modern stromatolites in a saline, alkaline maar in Victoria, Australia. Dolomite is a principle carbonate mineral precipitating from this lake, an unusual and poorly understood occurrence in modern environments, but one that was common in the Precambrian. The peculiar lacustrine chemistry in this volcanic region may, therefore, provide a better analogue for Precambrian marine carbonates than modern marine environments. Several types of stromatolites/thrombolites are observed occurring around this maar. Living thrombolites grow just below the shoreline to ~60 cm below the surface of the water. They are nucleating on the cemented surfaces of older lake carbonates, as well as cattle skulls and fence wires that have become submerged. Distinct microbial mats are observed, the uppermost being cyanobacteria, followed by purple sulfur bacteria, and underlain by sulfate reducing bacteria. Older exposed stromatolites are more consolidated and have a more clearly defined laminated and columnar morphology. The thickness ranges from a few to 15 cm and each column is up to a centimeter in diameter. Together these give the surface of the rock a "bubbly" appearance. Along the shore, a sandy-gravel composed of stromatolite remnants has formed, indicating that wind-generated surface waves of substantial

  15. The Cambrian Ross Orogeny in northern Victoria Land (Antarctica) and New Zealand: A synthesis

    USGS Publications Warehouse

    Federico, L.; Capponi, G.; Crispini, L.; Bradshaw, J.D.

    2007-01-01

    In the Cambrian, the paleo-Pacific margin of the Gondwana supercontinent included East Antarctica, Australia, Tasmania and New Zealand and was affected by themajor Ross-Delamerian Orogeny. In Antarctica, evidence suggests that this resulted from oblique subduction and that in northern Victoria Land it was accompanied by the opening and subsequent closure of a back-arc basin. Comparison of the type and timing of sedimentary, magmatic and metamorphic events in areas noted above shows strong similarities between northern Victoria Land and New Zealand. In both regions Middle Cambrian volcanites are interpreted as arc/back-arc assemblages produced by west-directed subduction; sediments interbedded with the volcanites show provenance both from the arc and from the Gondwana margin and therefore place the basin close to the continent. Back-arc closure in the Late Cambrian was likely accomplished through a second subduction system

  16. Episodic rifting of phanerozoic rocks in the victoria land basin, Western ross sea, antarctica.

    PubMed

    Cooper, A K; Davey, F J

    1985-09-13

    Multichannel seismic-reflection data show that the Victoria Land-basin, unlike other sedimentary basins in the Ross Sea, includes a rift-depression 15 to 25 kilometers wide that parallels the Transantarctic Mountains and contains up to 12 kilometers of possible Paleozoic to Holocene age sedimentary rocks. An unconformity separates the previously identified Cenozoic sedimentary section from the underlying strata of possible Mesozoic and Paleozoic age. Late Cenozoic volcanic rocks intrude into the entire section along the eastern flank of the basin. The Victoria Land basin is probably part of a more extensive rift system that has been active episodically since Paleozoic time. Inferred rifting and basin subsidence during Mesozoic and Cenozoic time may be associated with regional crustal extension and uplift of the nearby Transantarctic Mountains. PMID:17753283

  17. Modes of climate variability and heat waves in Victoria, southeastern Australia

    NASA Astrophysics Data System (ADS)

    Parker, Teresa J.; Berry, Gareth J.; Reeder, Michael J.; Nicholls, Neville

    2014-10-01

    Summertime heat waves in the southeastern state of Victoria, Australia, are associated with broad anticyclonic upper level potential vorticity (PV) anomalies. The current research establishes the relationship between heat waves, precipitation, and three modes of climate variability of importance for rainfall in Australia: the El Niño-Southern Oscillation (ENSO), Madden-Julian Oscillation (MJO), and Southern Annular Mode (SAM). Heat waves in Victoria in summer are more common during phases 3-6 of the MJO (when convection is enhanced over the eastern Indian Ocean, Maritime Continent, and western Pacific Ocean) and La Niña phases of ENSO. The PV-Theta (Θ) structure of the heat wave and pattern of convection varies with the phase of each mode of variability. Enhanced tropical convection results in a heat wave characterized by a monopole of anticyclonic PV, whereas suppressed convection is associated with a dipole of anticyclonic and cyclonic PV.

  18. VLUIS, a land use data product for Victoria, Australia, covering 2006 to 2013.

    PubMed

    Morse-McNabb, Elizabeth; Sheffield, Kathryn; Clark, Rob; Lewis, Hayden; Robson, Susan; Cherry, Don; Williams, Steve

    2015-01-01

    Land Use Information is a key dataset required to enable an understanding of the changing nature of our landscapes and the associated influences on natural resources and regional communities. The Victorian Land Use Information System (VLUIS) data product has been created within the State Government of Victoria to support land use assessments. The project began in 2007 using stakeholder engagement to establish product requirements such as format, classification, frequency and spatial resolution. Its genesis is significantly different to traditional methods, incorporating data from a range of jurisdictions to develop land use information designed for regular on-going creation and consistency. Covering the entire landmass of Victoria, the dataset separately describes land tenure, land use and land cover. These variables are co-registered to a common spatial base (cadastral parcels) across the state for the period 2006 to 2013; biennially for land tenure and land use, and annually for land cover. Data is produced as a spatial GIS feature class. PMID:26602150

  19. Episodic rifting of phanerozoic rocks in the Victoria Land basin, Western Ross Sea, Antarctica

    USGS Publications Warehouse

    Cooper, A. K.; Davey, F.J.

    1985-01-01

    Multichannel seismic-reflection data show that the Victoria Land basin, unlike other sedimentary basins in the Ross Sea, includes a rift-depression 15 to 25 kilometers wide that parallels the Transantarctic Mountains and contains up to 12 kilometers of possible Paleozoic to Holocene age sedimentary rocks. An unconformity separates the previously identified Cenozoic sedimentary section from the underlying strata of possible Mesozoic and Paleozoic age. Late Cenozoic volcanic rocks intrude into the entire section along the eastern flank of the basin. The Victoria Land basin is probably part of a more extensive rift system that has been active episodically since Paleozoic time. Inferred rifting and basin subsidence during Mesozoic and Cenozoic time may be associated with regional crustal extension and uplift of the nearby Transantarctic Mountains.

  20. VLUIS, a land use data product for Victoria, Australia, covering 2006 to 2013

    PubMed Central

    Morse-McNabb, Elizabeth; Sheffield, Kathryn; Clark, Rob; Lewis, Hayden; Robson, Susan; Cherry, Don; Williams, Steve

    2015-01-01

    Land Use Information is a key dataset required to enable an understanding of the changing nature of our landscapes and the associated influences on natural resources and regional communities. The Victorian Land Use Information System (VLUIS) data product has been created within the State Government of Victoria to support land use assessments. The project began in 2007 using stakeholder engagement to establish product requirements such as format, classification, frequency and spatial resolution. Its genesis is significantly different to traditional methods, incorporating data from a range of jurisdictions to develop land use information designed for regular on-going creation and consistency. Covering the entire landmass of Victoria, the dataset separately describes land tenure, land use and land cover. These variables are co-registered to a common spatial base (cadastral parcels) across the state for the period 2006 to 2013; biennially for land tenure and land use, and annually for land cover. Data is produced as a spatial GIS feature class. PMID:26602150

  1. Levels and patterns of persistent organic pollutants (POPs) in tilapia (Oreochromis sp.) from four different lakes in Tanzania: geographical differences and implications for human health.

    PubMed

    Polder, A; Müller, M B; Lyche, J L; Mdegela, R H; Nonga, H E; Mabiki, F P; Mbise, T J; Skaare, J U; Sandvik, M; Skjerve, E; Lie, E

    2014-08-01

    In Tanzania fish is one of the most important protein sources for the rapidly increasing population. Wild fish is threatened by overfishing and pollution from agriculture, industries, mining, household effluents and vector control. To monitor possible implications for public health, the geographical differences of the occurrence and levels of persistent organic pollutants (POPs) in tilapia fish (Oreochromis sp.) from four different Tanzanian lakes were investigated in 2011. Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyls (PBDEs) and hexabromocyclododecane (HBCDD) were determined in pooled samples of tilapia muscle from Lake (L) Victoria, L. Tanganyika, L. Nyasa (also called L. Malawi) and L. Babati in Tanzania in 2011. Levels of Σ-DDTs (274 ng/g lipid weight (lw)) and sum of 7 indicator PCBs (Σ-7PCBs) (17 ng/g lw) were significantly higher in tilapia from L. Tanganyika compared to the other lakes. The highest levels of Σ-endosulfan (94 ng/g lw) were detected in tilapia from L. Victoria. Toxaphenes were detected in low levels in fish from L. Tanganyika and L. Babati. Results revealed a geographic difference in the use of DDT and endosulfan between L. Victoria and L. Tanganyika. Low ratios of DDE/DDT in tilapia from L. Tanganyika indicated an on-going use of DDT in the area. Median levels of ΣBDEs, including BDE-209, were highest in L. Victoria (19.4 ng/g lw) and BDE-209 was present in 68% of the samples from this lake. The presence of BDE-209 indicates increasing influence of imported products from heavy industrialized countries. The measured POP levels in the studied tilapia were all below MRLs of EU or were lower than recommended levels, and thus the fish is considered as safe for human consumption. They may, however, pose a risk to the fish species and threaten biodiversity. PMID:24836134

  2. The minimal response to contact metamorphism by the Devonian Buchan Caves Limestone, Buchan Rift, Victoria, Australia

    USGS Publications Warehouse

    Barker, C.E.; Bone, Y.

    1995-01-01

    A 2.2 m thick, Late Eocene (?) dike that intruded the Devonian Buchan Caves Limestone, near Murrindal, Victoria, has produced a narrow contact aureole only centimeters wide in the adjacent host rock. The lack of response of the Buchan Caves Limestone to contact metamorphism is attributed to: 1) prior heating to near 200??C; and 2) the fact that the dike intruded into cool, near surface, low-porosity rocks which may have been in the vadose zone. -from Authors

  3. STUDIES IN ATYPICAL FORMS OF TUBERCLE BACILLI ISOLATED DIRECTLY FROM THE HUMAN TISSUES IN CASES OF PRIMARY CERVICAL ADENITIS

    PubMed Central

    Duval, Charles W.

    1909-01-01

    The four cultures which form the basis of this communication were recovered from peculiar cases of primary cervical adenitis in man, three of which terminated fatally of disseminated acute miliary tuberculosis in four to six weeks. A careful comparative study shows that Culture II corresponds closely with the "human" and Culture IV with the "bovine" type of tubercle bacilli; while Cultures I and III present variations from the standard types and are to be retarded as "intermediate" or "atypical" forms. Culture I is of unusual interest because of its remarkable variations. The clinical picture of the case, the rapid course of the infection, the enormous number of the bacilli in the tissue, their tendency to occur in "heaps" like the leprosy bacillus, the high degree of virulence alike for rabbits and guinea-pigs, the production of lesions in chickens, the case of cultivation and the prolonged viability under unfavorable conditions, all mark the organism as a decided atypical form of tubercle bacillus in man. The prolonged viability, the production of lesions in the chicken and the great profusion of bacillary growth in the tissues would indicate an avian type. Though for years the reaction curve was atypical it has since changed completely to the "avian" curve. In this connection it is of interest to note that L. Rabinowitsch (3) states that she has isolated avian tubercle bacilli from two cases of tuberculosis in man. Cultures II and III undoubtedly belong to the human type of the tubercle family though they were under cultivation and were repeatedly tested upon glycerine broth over a period of months before their identity was definitely established. Culture IV completely corresponds in growth and reaction in glycerine bouillon to the bovine strain; however, it manifests a low degree of virulence for rabbits which is exceptional for bovine cultures. The old belief that bovine bacilli are more slender and beaded in the tissues and are thicker and shorter in culture

  4. Mapping dominant annual land cover from 2009 to 2013 across Victoria, Australia using satellite imagery.

    PubMed

    Sheffield, Kathryn; Morse-McNabb, Elizabeth; Clark, Rob; Robson, Susan; Lewis, Hayden

    2015-01-01

    There is a demand for regularly updated, broad-scale, accurate land cover information in Victoria from multiple stakeholders. This paper documents the methods used to generate an annual dominant land cover (DLC) map for Victoria, Australia from 2009 to 2013. Vegetation phenology parameters derived from an annual time series of the Moderate Resolution Imaging Spectroradiometer Vegetation Indices 16-day 250 m (MOD13Q1) product were used to generate annual DLC maps, using a three-tiered hierarchical classification scheme. Classification accuracy at the broadest (primary) class level was over 91% for all years, while it ranged from 72 to 81% at the secondary class level. The most detailed class level (tertiary) had accuracy levels ranging from 61 to 68%. The approach used was able to accommodate variable climatic conditions, which had substantial impacts on vegetation growth patterns and agricultural production across the state between both regions and years. The production of an annual dataset with complete spatial coverage for Victoria provides a reliable base data set with an accuracy that is fit-for-purpose for many applications. PMID:26602009

  5. Mapping dominant annual land cover from 2009 to 2013 across Victoria, Australia using satellite imagery

    PubMed Central

    Sheffield, Kathryn; Morse-McNabb, Elizabeth; Clark, Rob; Robson, Susan; Lewis, Hayden

    2015-01-01

    There is a demand for regularly updated, broad-scale, accurate land cover information in Victoria from multiple stakeholders. This paper documents the methods used to generate an annual dominant land cover (DLC) map for Victoria, Australia from 2009 to 2013. Vegetation phenology parameters derived from an annual time series of the Moderate Resolution Imaging Spectroradiometer Vegetation Indices 16-day 250 m (MOD13Q1) product were used to generate annual DLC maps, using a three-tiered hierarchical classification scheme. Classification accuracy at the broadest (primary) class level was over 91% for all years, while it ranged from 72 to 81% at the secondary class level. The most detailed class level (tertiary) had accuracy levels ranging from 61 to 68%. The approach used was able to accommodate variable climatic conditions, which had substantial impacts on vegetation growth patterns and agricultural production across the state between both regions and years. The production of an annual dataset with complete spatial coverage for Victoria provides a reliable base data set with an accuracy that is fit-for-purpose for many applications. PMID:26602009

  6. Characterization of bacterial communities in lithobionts and soil niches from Victoria Valley, Antarctica.

    PubMed

    Van Goethem, Marc W; Makhalanyane, Thulani P; Valverde, Angel; Cary, Stephen C; Cowan, Don A

    2016-04-01

    Here we provide the first exploration of microbial diversity from three distinct Victoria Valley edaphic habitats, namely lithobionts (hypoliths, endoliths) and surface soils. Using a combination of terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene amplicon pyrosequencing we assess community structure and diversity patterns, respectively. Our analysis revealed that habitat type (endolithic versus hypolithic versus surface soils) significantly influenced bacterial community composition, even though dominant phyla such as Actinobacteria (41% of total reads) were common to all samples. Consistent with previous surveys in other Dry Valley ecosystems, we found that lithobionts were colonized by a few highly dominant phylotypes (such asGemmatimonasandLeptolyngbya). Our analyses also show that soil bacteria were more diverse and evenly distributed than initially expected based on previous evidence. In contrast to total bacteria, the distribution of Cyanobacteria was not strongly influenced by habitat type, although soil- and endolith-specific cyanobacterial lineages were found. The detection of cyanobacterial lineages in these habitats appears to be influenced by the dispersal of aquatic inocula from lacustrine communities or benthic mats which are abundant in Victoria Valley. Together, our results provide insights into the phylogenetic variation and community structure across niche habitats in Victoria Valley. PMID:26946500

  7. Pervasive, tholeiitic refertilisation and heterogeneous metasomatism in Northern Victoria Land lithospheric mantle (Antarctica)

    NASA Astrophysics Data System (ADS)

    Pelorosso, Beatrice; Bonadiman, Costanza; Coltorti, Massimo; Faccini, Barbara; Melchiorre, Massimiliano; Ntaflos, Theodoros; Gregoire, Michel

    2016-04-01

    The petrology of peridotite xenoliths in the Cenozoic volcanics from Greene Point (Northern Victoria Land, Antarctica) provides new constraints on the characterisation of the lithospheric mantle beneath the West Antarctic Rift. Based on mineral major and trace element models, this mantle domain is proposed to represent a residuum after 10% and 20% partial melting. Moreover, melting models and isotopic results for Sr and Nd systematics highlight the substantial contribution of tholeiitic melts percolating through peridotites. Close correlation with trace element contents in clinopyroxene phenocrysts from Ferrar and Karoo tholeiites allows us to ascribe this refertilisation event to the Jurassic. This asthenospheric melt was also able to transfer a garnet signature to the Northern Victoria Land mantle segment. The rare presence of glass and secondary phases indicate that Greene Point xenoliths were heterogeneously affected by alkaline metasomatism, probably related to the West Antarctic Rift System opening; this has also been widely observed in other Northern Victoria Land localities (i.e., Baker Rocks). Temperature and fO2 were calculated (950 °C; Δlog fO2 (QFM), - 1.70 to - 0.39) at a fixed pressure of 15 kbar, confirming the tendency of the anhydrous Greene Point xenolith population to have higher equilibration temperatures and comparable redox conditions, compared to the nearby amphibole-bearing peridotites from Baker Rocks.

  8. 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.

  9. Comparison of Mortality Following Hospitalisation for Isolated Head Injury in England and Wales, and Victoria, Australia

    PubMed Central

    Gabbe, Belinda J.; Lyons, Ronan A.; Lecky, Fiona E.; Bouamra, Omar; Woodford, Maralyn; Coats, Timothy J.; Cameron, Peter A.

    2011-01-01

    Background Traumatic brain injury (TBI) remains a leading cause of death and disability. The National Institute for Health and Clinical Excellence (NICE) guidelines recommend transfer of severe TBI cases to neurosurgical centres, irrespective of the need for neurosurgery. This observational study investigated the risk-adjusted mortality of isolated TBI admissions in England/Wales, and Victoria, Australia, and the impact of neurosurgical centre management on outcomes. Methods Isolated TBI admissions (>15 years, July 2005–June 2006) were extracted from the hospital discharge datasets for both jurisdictions. Severe isolated TBI (AIS severity >3) admissions were provided by the Trauma Audit and Research Network (TARN) and Victorian State Trauma Registry (VSTR) for England/Wales, and Victoria, respectively. Multivariable logistic regression was used to compare risk-adjusted mortality between jurisdictions. Findings Mortality was 12% (749/6256) in England/Wales and 9% (91/1048) in Victoria for isolated TBI admissions. Adjusted odds of death in England/Wales were higher compared to Victoria overall (OR 2.0, 95% CI: 1.6, 2.5), and for cases <65 years (OR 2.36, 95% CI: 1.51, 3.69). For severe TBI, mortality was 23% (133/575) for TARN and 20% (68/346) for VSTR, with 72% of TARN and 86% of VSTR cases managed at a neurosurgical centre. The adjusted mortality odds for severe TBI cases in TARN were higher compared to the VSTR (OR 1.45, 95% CI: 0.96, 2.19), but particularly for cases <65 years (OR 2.04, 95% CI: 1.07, 3.90). Neurosurgical centre management modified the effect overall (OR 1.12, 95% CI: 0.73, 1.74) and for cases <65 years (OR 1.53, 95% CI: 0.77, 3.03). Conclusion The risk-adjusted odds of mortality for all isolated TBI admissions, and severe TBI cases, were higher in England/Wales when compared to Victoria. The lower percentage of cases managed at neurosurgical centres in England and Wales was an explanatory factor, supporting the changes made to the NICE

  10. 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

  11. Hydrothermal plumes in the Gulf of Aden, as characterized by light transmission, Mn, Fe, CH4 and δ13C-CH4 anomalies

    NASA Astrophysics Data System (ADS)

    Gamo, Toshitaka; Okamura, Kei; Hatanaka, Hiroshi; Hasumoto, Hiroshi; Komatsu, Daisuke; Chinen, Masakazu; Mori, Mutsumi; Tanaka, Junya; Hirota, Akinari; Tsunogai, Urumu; Tamaki, Kensaku

    2015-11-01

    We conducted water column surveys to search for hydrothermal plumes over the spreading axes in the Gulf of Aden between 45°35‧E and 52°42‧E. We measured light transmission and chemical tracers Mn, Fe, CH4 and δ13C of CH4 in seawater taken using a CTD-Carrousel multi-sampling system at 12 locations including a control station in the Arabian Sea. We recognized three types of hydrothermal plumes at depths of ~650 to ~900 m (shallow plumes), ~1000 to ~1200 m (intermediate plumes), and >1500 m (deep plumes). The shallow plumes were apparently originated from newly discovered twin seamounts (12°03-06‧N and 45°35-41‧E) at the westernmost survey area, where two-dimensional distributions of light transmission and Mn were mapped by tow-yo observations of the CTD-sampling system with an in situ auto-analyzer GAMOS. The maximum concentrations of Mn, Fe, and CH4 of 46 nM, 251 nM, and 15 nM, respectively, were observed for collected seawater within the shallow plumes. The intermediate plumes were characterized by anomalies of light transmission, Mn, Fe, and δ13C of CH4, but by little CH4 anomalies, suggesting that CH4 had been consumed down to the background level during the aging of the plumes. Anomalies of δ3He already reported by the World Ocean Circulation Experiment (WOCE) program exhibited a hydrothermal plume-like peak at ~2000 m depth in the Gulf of Aden, which seems to coincide with the deep plumes observed in this study. The endmember δ13C-CH4 values for the shallow and the deep plumes were estimated to be in a range between -10‰ and -15‰, demonstrating that the sources of CH4 are not biogenic but magmatic as similarly observed at sediment-starved mid-oceanic ridges.

  12. Determining OCT structure and COB Location of the Omani Gulf of Aden Continental Margin from Gravity Inversion, Residual Depth Anomaly and Subsidence Analysis.

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick; Leroy, Sylvie; Manatshal, Gianreto

    2013-04-01

    Knowledge and understanding of the ocean-continent transition (OCT) structure and continent-ocean boundary (COB) location, the distribution of thinned continental crust and lithosphere, its distal extent and the start of unequivocal oceanic crust are of critical importance in evaluating rifted continental margin formation and evolution. In order to determine the OCT structure and COB location for the eastern Gulf of Aden, along the Oman margin, we use a combination of gravity inversion, subsidence analysis and residual depth anomaly (RDA) analysis. Gravity inversion has been used to determine Moho depth, crustal basement thickness and continental lithosphere thinning; subsidence analysis has been used to determine the distribution of continental lithosphere thinning; and RDAs have been used to investigate the OCT bathymetric anomalies with respect to expected oceanic bathymetries at rifted margins. The gravity inversion method, which is carried out in the 3D spectral domain, incorporates a lithosphere thermal gravity anomaly and includes a correction for volcanic addition due to decompression melting. Reference Moho depths used in the gravity inversion have been calibrated against seismic refraction Moho depths. RDAs have been calculated by comparing observed and age predicted oceanic bathymetries, using the thermal plate model predictions from Crosby and McKenzie (2009). RDAs have been computed along profiles and have been corrected for sediment loading using flexural back-stripping and decompaction. In addition, gravity inversion crustal basement thicknesses together with Airy isostasy have been used to predict a synthetic RDA. The RDA results show a change in RDA signature and may be used to estimate the distal extent of thinned continental crust and where oceanic crust begins. Continental lithosphere thinning has been determined using flexural back-stripping and subsidence analysis assuming the classical rift model of McKenzie (1978) with a correction for

  13. How and when did a strong thinning occur in the Gulf of Aden? A discussion from field, geophysical data and analogue models

    NASA Astrophysics Data System (ADS)

    Bellahsen, N.; Autin, J.; Leroy, S. D.; D'Acremont, E.; Beslier, M.; Husson, L.; Al-Toubi, K. I.

    2009-12-01

    In the complex evolution of modern scenario of continental rifting, questions about transitions between stages of extension (distributed vs. localized extension, mantle exhumation …) may arise. How and why extension localizes is still a matter of debate. Thus, the parameters controlling the triggering of localized extension must be discussed. Here, we study the effect of local stresses arising from thickness variations in the crust. Here, we use the Gulf of Aden as a natural laboratory to better constrain the evolution of the modes of extension. The Gulf of Aden, at the boundary between Arabian and Somalian plates, offers many advantages, among which its obliquity: the Gulf (075°E) trends obliquely to the plate displacement (025°E). Thus, many fault populations were initiated with different strike through time. Those different fault populations were due to different processes and different stress regimes. From field data in southern Sultanate of Oman and Yemen (Socotra Island), we show that a complex space and time distribution of fault initiation occurred. A counter-clockwise rotation of extension (from 020°E to 160°E, becoming orthogonal to the rift) might have happened during rifting. We suggest that this may be due to local stresses arising from crust thickness variations. However, the question is whether or not those local stresses strongly influenced the rift localization. On seismic profiles, constrained by bathymetric, gravity data and seismic refraction, shallow and deep structure were imaged. Several faults are observed, some of them clearly accommodating much of the far-field early and late extension. A detailed mapping, in map view, of those faults shows that many of them strike at a significant angle from the perpendicular to the divergence. Thus, one can wonder that those faults may be due to local stresses oblique to the rift trend. Finally, we present an analogue model of oblique rifting that allows observing the fault evolution through time

  14. Preliminary insight into the age and origin of the Labeobarbus fish species flock from Lake Tana (Ethiopia) using the mtDNA cytochrome b gene.

    PubMed

    de Graaf, Martin; Megens, Hendrik-Jan; Samallo, Johannis; Sibbing, Ferdinand

    2010-02-01

    The high diversity of Cyprinid fish in Ethiopia's Lake Tana appears to be an example of ecological differentiation and assortative mating leading to rapid sympatric speciation. Lake Tana's Labeobarbus species flock consists of 15 morphological and ecological distinct species. This is the first attempt to determine the age and origin and inter-species relationships of Lake Tana's Labeobarbus species using the mtDNA cytochrome b gene. Analysis of cytchrome b sequences shows that Lake Tana's species flock appears to be young but the present dataset did not unequivocally support monophyly of Lake Tana's species. Additional markers are needed to determine whether Lake Tana's labeobarbs originated from a single or multiple incursion(s) of ancestral L. intermedius in the Lake Tana drainage basin, or the disruption of an ancient continuous riverine population by the emergence of the Tissisat waterfalls. Adaptive radiation and speciation within Lake Tana's Labeobarbus species flock may have occurred in the last 10,000-25,000years, following the desiccation of Lake Tana around 17,000years ago, at the same time as Lake Victoria, however, obtaining more data using other (nuclear) markers is urgently required. PMID:19878730

  15. 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.

  16. Predictors of Extra-Marital Partnerships among Women Married to Fishermen along Lake Victoria in Kisumu County, Kenya

    PubMed Central

    Kwena, Zachary; Mwanzo, Isaac; Shisanya, Chris; Camlin, Carol; Turan, Janet; Achiro, Lilian; Bukusi, Elizabeth

    2014-01-01

    Background The vulnerability of women to HIV infection makes establishing predictors of women's involvement in extra-marital partnerships critical. We investigated the predictors of extra-marital partnerships among women married to fishermen. Methods The current analyses are part of a mixed methods cross-sectional survey of 1090 gender-matched interviews with 545 couples and 12 focus group discussions (FGDs) with 59 couples. Using a proportional to size simple random sample of fishermen as our index participants, we asked them to enrol in the study with their spouses. The consenting couples were interviewed simultaneously in separate private rooms. In addition to socio-economic and demographic data, we collected information on sexual behaviour including extra-marital sexual partnerships. We analysed these data using descriptive statistics and multivariate logistic regression. For FGDs, couples willing to participate were invited, consented and separated for simultaneous FGDs by gender-matched moderators. The resultant audiofiles were transcribed verbatim and translated into English for coding and thematic content analysis using NVivo 9. Results The prevalence of extra-marital partnerships among women was 6.2% within a reference time of six months. Factors that were independently associated with increased likelihood of extra-marital partnerships were domestic violence (aOR, 1.45; 95% CI 1.09–1.92), women reporting being denied a preferred sex position (aOR, 3.34; 95% CI 1.26–8.84) and spouse longer erect penis (aOR, 1.34; 95% CI 1.00–1.78). Conversely, women's age – more than 24years (aOR, 0.33; 95% CI 0.14–0.78) and women's increased sexual satisfaction (aOR, 0.92; 95% CI 0.87–0.96) were associated with reduced likelihood of extra-marital partnerships. Conclusion Domestic violence, denial of a preferred sex positions, longer erect penis, younger age and increased sexual satisfaction were the main predictors of women's involvement in extra-marital partnerships. Integration of sex education, counselling and life skills training in couple HIV prevention programs might help in risk reduction. PMID:24747951

  17. Petrology and geochemistry of granites from the Archæan terrain north of Lake Victoria, western Kenya

    NASA Astrophysics Data System (ADS)

    Opiyo-Akech, Norbert; Tarney, John; Hoshino, M.

    1999-08-01

    The Neoarchæan greenstone belt of western Kenya forms part of the Tanzania Craton of East Africa. Two groups of supracrustal rock sequences are recognised in this greenstone belt, namely a dominantly volcanic supergroup (the Nyanzian) and a dominantly sedimentary one (the Kavirondian); this is typical of many other Neoarchæan greenstone belts. The Nyanzian volcanics include mafic lavas (rarely ultramafic) which could be part of an original oceanic plateau sequence, but comprising an 'island-arc' sequence of basaltic andesites, dacites and rhyolites. These supracrustal rocks are intruded by later granites, and it is the petrogenesis of the granitoids that is the focus of this paper. Geochemical studies indicate that the granites are all I-type, having calc-alkaline affinity, compositionally varying between monzodiorite, through granodiorite and quartz monzonite, and having chemical trends comparable to those of granites found in present day Andean-type continental arc environments. The granitoids are very primitive in terms of isotropic ratios, and most have high Ba and Sr contents and low Y and HREE typical of many trondhjemite-tonalite-granodiorite (TTG) plutonic suites that dominate the Archæan, but are more potash-rich than most such suites. They carry a high proportion of mafic enclaves. There is little doubt that the rocks are related in their petrogenesis, but are not crustal melts. While major element modelling is superficially compatible with the calc-alkaline trends being derived by crystal fractionation, it is more likely they are derived through melting of a mafic source with residual garnet (to account for the HREE and Y depletion). This paper also speculates on how the granitoids could be related to the calc-alkaline volcanics and to the mafic volcanic sequence.

  18. Fault propagation and climatic control of sedimentation on the Ghoubbet Rift Floor: insights from the Tadjouraden cruise in the western Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Audin, L.; Manighetti, I.; Tapponnier, P.; Métivier, F.; Jacques, E.; Huchon, P.

    2001-02-01

    A detailed geophysical survey of the Ghoubbet Al Kharab (Djibouti) clarifies the small-scale morphology of the last submerged rift segment of the propagating Aden ridge before it enters the Afar depression. The bathymetry reveals a system of antithetic normal faults striking N130°E, roughly aligned with those active along the Asal rift. The 3.5kHz sub-bottom profiler shows how the faults cut distinct layers within the recent, up to 60m thick, sediment cover on the floor of the basin. A large volcanic structure, in the centre of the basin, the `Ghoubbet' volcano, separates two sedimentary flats. The organization of volcanism and the planform of faulting, with en echelon subrifts along the entire Asal-Ghoubbet rift, appear to confirm the westward propagation of this segment of the plate boundary. Faults throughout the rift have been active continuously for the last 8400yr, but certain sediment layers show different offsets. The varying offsets of these layers, dated from cores previously retrieved in the southern basin, imply Holocene vertical slip rates of 0.3-1.4mmyr-1 and indicate a major decrease in sedimentation rate after about 6000yr BP, and a redistribution of sediments in the deepest troughs during the period that preceded that change.

  19. How does continental crust thin in a young continental margin? Insights from Oman/Socotra conjugate margins in the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Leroy, Sylvie; d'Acremont, Elia; Lucazeau, Francis; Poort, Jeffrey; Ahmed, Abdulhakim; Keir, Derek; Stuart, Graham; Khanbari, Khaled; Bellahsen, Nicolas; Nonn, Chloé

    2013-04-01

    The discovery of hyper-thinned continental crust and exhumed mantle on continental margins has raised several key questions, such as how the crust thins until the breakup or what controls the locus of extreme crustal thinning, exhumation and final oceanic spreading. Reflection seismic lines (ENCENS-Sheba, Encens, Marges-Aden cruises) and seismological investigations (YOCMAL ANR project) across conjugate margins of the Oman/Socotra margins allow a detailed study of the crustal and sedimentary structure and a discussion on the structures and the age of the deformation. Structural analysis of new dataset enables mapping the area where the continental extension seems to be coupled to the mantle illustrating the exhumation phase. The crustal thinning is abrupt occurring mostly at the shoreline on both margins and shows along-margin variations.The thinning progressively migrates towards the locus of final breakup, which is interpreted by a progressive weakening of the mantle by lithospheric thinning and serpentinization. Then, a stage of uplift and erosion is observed in the proximal margins after the thinning phase. Uplift is usually higher where crustal thinning is more important in the deep basin, which could be interpreted by the onset of small-scale convection driven by the lateral temperature gradients at the necking zone.

  20. Pre-existing oblique transfer zones and transfer/transform relationships in continental margins: New insights from the southeastern Gulf of Aden, Socotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    Bellahsen, N.; Leroy, S.; Autin, J.; Razin, P.; d'Acremont, E.; Sloan, H.; Pik, R.; Ahmed, A.; Khanbari, K.

    2013-11-01

    Transfer zones are ubiquitous features in continental rifts and margins, as are transform faults in oceanic lithosphere. Here, we present a structural study of the Hadibo Transfer Zone (HTZ), located in Socotra Island (Yemen) in the southeastern Gulf of Aden. There, we interpret this continental transfer fault zone to represent a reactivated pre-existing structure. Its trend is oblique to the direction of divergence and it has been active from the early up to the latest stages of rifting. One of the main oceanic fracture zones (FZ), the Hadibo-Sharbithat FZ, is aligned with and appears to be an extension of the HTZ and is probably genetically linked to it. Comparing this setting with observations from other Afro-Arabian rifts as well as with passive margins worldwide, it appears that many continental transfer zones are reactivated pre-existing structures, oblique to divergence. We therefore establish a classification system for oceanic FZ based upon their relationship with syn-rift structures. Type 1 FZ form at syn-rift structures and are late syn-rift to early syn-OCT. Type 2 FZ form during the OCT formation and Type 3 FZ form within the oceanic domain, after the oceanic spreading onset. The latter are controlled by far-field forces, magmatic processes, spreading rates, and oceanic crust rheology.

  1. Lake Nasser and Toshka Lakes, Egypt

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Lake Nasser (center) and the Toshka Lakes (center left) glow emerald green and black in this MODIS true-color image acquired March 8, 2002. Located on and near the border of Egypt and Norther Sudan, these lakes are an oasis of water in between the Nubian (lower right) and Libyan Deserts (upper left). Also visible are the Red Sea (in the upper right) and the Nile River (running north from Lake Nasser). Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  2. Irrigator responses to groundwater resource management in northern Victoria, southeastern Australia

    NASA Astrophysics Data System (ADS)

    Gill, Bruce C.; Webb, John; Wilkinson, Roger; Cherry, Don

    2014-10-01

    In northern Victoria, farmers are the biggest users of groundwater and therefore the main stakeholders in plans that seek to sustainably manage the resource. Interviews with 30 irrigation farmers in two study areas, analysed using qualitative social research methods, showed that the overwhelming majority of groundwater users agreed with the need for groundwater management and thought that the current plans had achieved sustainable resource use. The farmers also expressed a strong need for clear technical explanations for management decisions, in particular easily understood water level data. The social licence to implement the management plans arose through effective consultation with the community during plan development. Several additional factors combined to gain acceptance for the plans: good data on groundwater usage and aquifer levels is available; irrigation farmers had been exposed to usage restrictions since the late 1990s; an ‘adaptive’ management approach is in use which allowed refinements to be readily incorporated and fortuitously, plan development coincided with the 1998-2009 drought, when declines in groundwater levels reinforced the usefulness of the plans. The imposition of a nation-wide water use reduction plan in 2012 had relatively little impact in Victoria because of the early implementation of effective groundwater management plans. However, economic difficulties that reduce groundwater users’ capacity to pay groundwater management charges mean that the future of the plans in Victoria is not assured. Nevertheless, the high level of trust that exists between Victorian irrigation farmers and the management agencies suggests that the continued use of a consultative approach will continue to produce workable outcomes. Lessons from the Victorian experience may be difficult to apply in other areas of groundwater use in Australia and overseas, where there may be a quite different history of development and culture of groundwater management.

  3. Reconstruction of Eolian Bedforms from Cross-Bedded Strata at Victoria Crater, Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Hayes, A. G.; Grotzinger, J. P.; Squyres, S. W.; Lewis, K.; Metz, J.; Bell, J. F.; Athena Science Team

    2007-12-01

    Outcrop exposures imaged by the Opportunity rover at Meridiani Planum have depicted cross-bedded strata with geometries and scales similar to eolian and subaqeous deposits on Earth. On Earth preserved cross-strata are rich in geologic information, providing insight into the depositional environment and sediment transport directions. The high-resolution stratigraphy of these cross-bedded strata can be used to reconstruct sedimentary bedforms on Mars to infer formation process and describe the depositional environment. Meter-scale cross bedding at Victoria Crater is similar to terrestrial eolian deposits and is interpreted as a dry dune field. Sets of cross-strata in the Cape St. Vincent and Cape St. Mary sections of Victoria Crater are comparable to Jurassic-age eolian deposits of the western US. The Opportunity Rover has spent ~300 sols traversing 90 degrees of the rim of Victoria crater, obtaining images of rock outcrops exposed by several promontories along the way. The outcrops at the Cape St. Mary and Cape St. Vincent promontories, which are located at opposite ends of the traverse, have proven to be the best examples of meter scale cross-bedding observed on Mars to date. Super-resolution imaging techniques and long baseline stereo observations were utilized during an extended imaging campaign of both outcrop faces. Cape St. Mary is characterized by meter-scale trough-style cross bedding, suggesting sinuous crested dunes with scour pits migrating perpendicular to the outcrop face. Cape St. Vincent, which is striking 110° away from Cape St. Mary, has layering indicative of a single climbing bedform with dune heights of several meters. The findings at Cape St. Mary and Cape St. Vincent are combined with other bedding faces to produce an eolian deposition model for layering exposed at Victoria Crater. Any depositional model used to explain the bedding must conform to an observed N-S paleo-flow direction. In addition to bedded layering, a bright band is observed

  4. A new species of Anabarhynchus (Diptera: Therevidae) from an ocean beach in south east Victoria.

    PubMed

    Ferguson, David J; Yeates, David K

    2014-01-01

    Anabarhynchus Macquart 1848 is a large genus of the Therevidae (Diptera) that are endemic to Australasia with a couple of described species from Melanesia. We describe and illustrate Anabarhynchusoceanus sp. n., a species found on ocean beaches in eastern Victoria, Australia. The species shares most characters with the monobasic Anabarhynchuskampmeierae species group of Lyneborg (2001), but also shares a unique feature of the male genitalia with the endemic New Zealand genus Megathereva Lyneborg, 1992. This new species brings the total number of described Australian species in the genus to 113. PMID:25349526

  5. A new species of Anabarhynchus (Diptera: Therevidae) from an ocean beach in south east Victoria

    PubMed Central

    Yeates, David K.

    2014-01-01

    Abstract Anabarhynchus Macquart 1848 is a large genus of the Therevidae (Diptera) that are endemic to Australasia with a couple of described species from Melanesia. We describe and illustrate Anabarhynchus oceanus sp. n., a species found on ocean beaches in eastern Victoria, Australia. The species shares most characters with the monobasic Anabarhynchus kampmeierae species group of Lyneborg (2001), but also shares a unique feature of the male genitalia with the endemic New Zealand genus Megathereva Lyneborg, 1992. This new species brings the total number of described Australian species in the genus to 113. PMID:25349526

  6. Gambling revenues as a public administration issue: electronic gaming machines in Victoria.

    PubMed

    Pickernell, David; Keast, Robyn; Brown, Kerry; Yousefpour, Nina; Miller, Chris

    2013-12-01

    Gambling activities and the revenues derived have been seen as a way to increase economic development in deprived areas. There are also, however, concerns about the effects of gambling in general and electronic gaming machines (EGMs) in particular, on the resources available to the localities in which they are situated. This paper focuses on the factors that determine the extent and spending of community benefit-related EGM-generated resources within Victoria, Australia, focusing in particular on the relationships between EGM activity and socio-economic and social capital indicators, and how this relates to the community benefit resources generated by gaming. PMID:23065238

  7. Researches on Türkoğlu Gavur Lake in Kahramanmaraş-Turkey and some projections from past to future.

    PubMed

    Inac, Selcuk; Gorucu, Ozden

    2002-04-01

    Gavur Lake, takes place on the Saghk Plain in the south of Turkoglu subprovince in Kahramanmaras, was one of the most important places, that was available in the past time, south of our homeland. Gavur Lake represents the northest point of the bird immigration route that extends to Victoria Lake in Africa together with Emen and Amik Lakes dried locate on more south. Gavur Lake had been dried because of the some reasons those were being the marsh inn time by without oxygen cycle and emerging the situation of the microorganisms those were big threat for human health and to provide land in 1950's for the people of immigrants in Turkoglu. Presently, the big part of the Gavur Lake has dried. Drying activities are continuing. Whereas, Gavur Lake have all the conditions of the Ramsar Accord. With the improving of the Turkoglu reed bed the local people will earn more money by tourism than agricultural. Otherwise, the future of the Gavur Lake is going to be like Amik Lake. PMID:12602854

  8. VICTORIA: A mechanistic model of radionuclide behavior in the reactor coolant system under severe accident conditions. Revision 1

    SciTech Connect

    Heams, T J; Williams, D A; Johns, N A; Mason, A; Bixler, N E; Grimley, A J; Wheatley, C J; Dickson, L W; Osborn-Lee, I; Domagala, P; Zawadzki, S; Rest, J; Alexander, C A; Lee, R Y

    1992-12-01

    The VICTORIA model of radionuclide behavior in the reactor coolant system (RCS) of a light water reactor during a severe accident is described. It has been developed by the USNRC to define the radionuclide phenomena and processes that must be considered in systems-level models used for integrated analyses of severe accident source terms. The VICTORIA code, based upon this model, predicts fission product release from the fuel, chemical reactions involving fission products, vapor and aerosol behavior, and fission product decay heating. Also included is a detailed description of how the model is implemented in VICTORIA, the numerical algorithms used, and the correlations and thermochemical data necessary for determining a solution. A description of the code structure, input and output, and a sample problem are provided.

  9. Lakes Ecosystem Services Online

    EPA Science Inventory

    Northeastern lakes provide valuable ecosystem services that benefit residents and visitors and are increasingly important for provisioning of recreational opportunities and amenities. Concurrently, however, population growth threatens lakes by, for instance, increasing nutrient ...

  10. Utah: Salt Lake Region

    Atmospheric Science Data Center

    2014-05-15

    article title:  Winter and Summer Views of the Salt Lake Region     View Larger Image Magnificent views of the region surrounding Salt Lake City, Utah are captured in these winter and summer images from the ...

  11. Lake trout rehabilitation in Lake Ontario

    USGS Publications Warehouse

    Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.; Eckert, Thomas H.; Schaner, Ted; Bowlby, James N.; Schleen, Larry P.

    1995-01-01

    Attempts to maintain the native lake trout (Salvelinus namaycush) population in Lake Ontario by stocking fry failed and the species was extirpated by the 1950s. Hatchery fish stocked in the 1960s did not live to maturity because of sea lamprey (Petromyzon marinus) predation and incidental commercial harvest. Suppression of sea lampreys began with larvicide treatments of Lake Ontario tributaries in 1971 and was enhanced when the tributaries of Oneida Lake and Lake Erie were treated in the 1980s. Annual stocking of hatchery fish was resumed with the 1972 year class and peaked at about 1.8 million yearlings and 0.3 million fingerlings from the 1985–1990 year classes. Survival of stocked yearlings declined over 50% in the 1980 s and was negatively correlated with the abundance of lake trout > 550 mm long (r = −0.91, P < 0.01, n = 12). A slot length limit imposed by the State of New York for the 1988 fishing season reduced angler harvest. Angler harvest in Canadian waters was 3 times higher in eastern Lake Ontario than in western Lake Ontario. For the 1977–1984 year classes, mean annual survival rate of lake trout age 6 and older was 0.45 (range: 0.35–0.56). In U.S. waters during 1985–1992, the total number of lake trout harvested by anglers was about 2.4 times greater than that killed by sea lampreys. The number of unmarked lake trout < 250 mm long in trawl catches in 1978–1992 was not different from that expected due to loss of marks and failure to apply marks at the hatchery, and suggested that recruitment of naturally-produced fish was nil. However, many of the obstacles which may have impeded lake trout rehabilitation in Lake Ontario during the 1980s are slowly being removed, and there are signs of a general ecosystem recovery. Significant recruitment of naturally produced lake trout by the year 2000, one interim objective of the rehabilitation plan for the Lake, may be achieved.

  12. Lake Layers: Stratification.

    ERIC Educational Resources Information Center

    Brothers, Chris; And Others

    This teacher guide and student workbook set contains two learning activities, designed for fifth through ninth grade students, that concentrate on lake stratification and water quality. In the activities students model the seasonal temperature changes that occur in temperate lakes and observe the resulting stratification of lake waters. Students…

  13. Great Lakes: Chemical Monitoring

    ERIC Educational Resources Information Center

    Delfino, Joseph J.

    1976-01-01

    The Tenth Great Lakes Regional Meeting of the American Chemical Society met to assess current Chemical Research activity in the Great Lakes Basin, and addressed to the various aspects of the theme, Chemistry of the Great Lakes. Research areas reviewed included watershed studies, atmospheric and aquatic studies, and sediment studies. (BT)

  14. Great Minds? Great Lakes!

    ERIC Educational Resources Information Center

    Environmental Protection Agency, Chicago, IL. Great Lakes National Program Office.

    This book contains lesson plans that provide an integrated approach to incorporating Great Lakes environmental issues into elementary subjects. The book is divided into three subject areas: (1) History, which includes the origins of the Great Lakes, Great Lakes people, and shipwrecks; (2) Social Studies, which covers government, acid rain as a…

  15. A Killer Lake

    ERIC Educational Resources Information Center

    Horvath, Thomas

    2005-01-01

    In 1986, Lake Nyos, a volcanic lake in Cameroon, released a huge amount of carbon dioxide gas, killing over 1,700 people in the surrounding area. This case study, developed for use in a limnology or aquatic biology course, explores that event, introducing students to concepts relating to lake formation, thermal stratification, and dissolved gases.…

  16. Round the bend: a brief history of mental health nursing in Victoria, Australia 1848 to 1950's.

    PubMed

    Sands, Natisha Marina

    2009-06-01

    This paper presents a history of mental health nursing in Victoria, Australia from 1848 to the 1950's, or the asylum years to the era of the mental hospital. The research for this historical overview was conducted as part of a literature review for a mental health nursing doctoral thesis, which included an account of the evolution of the profession from asylum attendant to the present time. The literature reviewed for this project revealed a distinct lack of a coherent, chronological account of the historical development of mental health nursing in Victoria, and this paper seeks to address that knowledge gap. PMID:19499436

  17. Three Licentiates of the Royal College of Surgeons of Edinburgh who were decorated with the Victoria Cross.

    PubMed

    Kaufman, M H

    2011-08-01

    Since the Victoria Cross was introduced in January 1856 by Queen Victoria to reward acts of valour in the face of the enemy, initially during the Crimean War, over 1350 medals have been awarded. Of these, three were awarded to medical officers who had previously gained the Licentiate Diploma of the Royal College of Surgeons of Edinburgh (LRCS Edin) - Valentine Munbee McMaster on 25 September 1857, Henry Thomas Sylvester on 20 November 1857 (although the acts of valour for which he was awarded his VC occurred on two occasions in September 1855) and Campbell Mellis (or Millis) Douglas on 7 May 1867. PMID:21810849

  18. Lake Effects: The Lake Superior Curriculum Guide.

    ERIC Educational Resources Information Center

    Beery, Tom; And Others

    This curriculum guide was launched in response to a need for Lake Superior-specific educational materials and contains lessons and activities that can be used to teach about Lake Superior. The lessons in this book are divided into four sections. Each of the first three sections has a background section that provides basic information about Lake…

  19. Risk factors for severe injury in cyclists involved in traffic crashes in Victoria, Australia.

    PubMed

    Boufous, Soufiane; de Rome, Liz; Senserrick, Teresa; Ivers, Rebecca

    2012-11-01

    This study examines the impact of cyclist, road and crash characteristics on the injury severity of cyclists involved in traffic crashes reported to the police in Victoria, Australia between 2004 and 2008. Logistic regression analysis was carried out to identify predictors of severe injury (serious injury and fatality) in cyclist crashes reported to the police. There were 6432 cyclist crashes reported to the police in Victoria between 2004 and 2008 with 2181 (33.9%) resulting in severe injury of the cyclist involved. The multivariate analysis found that factors that increase the risk of severe injury in cyclists involved in traffic crashes were age (50 years and older), not wearing a helmet, riding in the dark on unlit roads, riding on roads zoned 70 km/h or above, on curved sections of the road, in rural locations and being involved in head-on collisions as well as off path crashes, which include losing control of vehicle, and on path crashes which include striking the door of a parked vehicle. While this study did not test effectiveness of preventative measures, policy makers should consider implementation of programs that address these risk factors including helmet programs and environmental modifications such as speed reduction on roads that are frequented by cyclists. PMID:23036419

  20. Pb isotope record over one century in snow from Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Van de Velde, K.; Vallelonga, P.; Candelone, J.-P.; Rosman, K. J. R.; Gaspari, V.; Cozzi, G.; Barbante, C.; Udisti, R.; Cescon, P.; Boutron, C. F.

    2005-03-01

    Pb and Ba concentrations and Pb isotopic compositions are reported for firn core and snow pit samples from Victoria Land, Antarctica, dating from 1872 AD to 1994 AD. From variations in Pb/Ba ratios and Pb isotopic compositions, two periods of major Pb enhancements were identified, from 1891 to 1908 AD and from 1948 to 1994 AD. The earlier pollution event is attributed to Pb emissions from non-ferrous metal production and coal combustion in the Southern Hemisphere and is in excellent agreement with coincident pollution inputs reported in firn/ice cores from two other regions of Antarctica, at Coats Land and Law Dome. Using Pb isotopic systematics, it was calculated that ˜50% of Pb deposited in Victoria Land in 1897 originated from anthropogenic emission sources. The more recent period of Pb enhancements, from 1948 to 1994 AD, corresponds to the introduction and widespread use of gasoline alkyl Pb additives in automobiles in the Southern Hemisphere, with anthropogenic Pb inputs averaging 60% of total Pb but with large uncertainty. Intra- and inter-annual variations in Pb concentrations and isotopic compositions were evaluated in snow pits samples corresponding to the period 1991-1994. Substantial variations in Pb/Ba and 206Pb/ 207Pb ratios were detected but the absence of a regular seasonal pattern for these parameters suggests that the transport and deposition of aerosols to the Antarctic ice sheet are complex and vary from year to year.

  1. Stretching out the Australasian microtektite strewn field in Victoria Land Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Folco, Luigi; D'Orazio, Massimo; Gemelli, Maurizio; Rochette, Pierre

    2016-06-01

    Petrographic and geochemical studies of microtektites collected in newly explored summit plateaus of the Transantarctic Mountains (i.e., Schroeder Spur, Killer Nunatak, Miller Butte in the inland catchment of the Rennick Glacier, and Allan Hills, in the inland catchment of the Mackay-David Glaciers) document a regional distribution of Australasian microtektites in Victoria Land. A geochemical comparison with Australasian microtektites from deep sea sediments at lower latitudes identifies a possible projectile geochemical signature for the first time, and confirms that Transantarctic Mountains microtektites experienced higher thermal regimes. Ballistic calculations reveal that the extraordinary distance of the Transantarctic Mountains microtektites from the hypothetical impact location in Indochina (∼11,000 km) could be more efficiently attained at relatively low ejection angles (20°-40°). Finally, the occurrence of Australasian microtektites (∼0.8 Ma old) on specific glacial surfaces of the Antarctic bedrock constrains the glacial history of the East Antarctic Ice Sheet in Victoria Land. In particular, data from Allan Hills supports a glaciological scenario envisaging an extremely stable East Antarctic Ice Sheet over at least the last ∼1 Ma in the inland catchment of the Mackay/David glaciers. This is consistent with the large accumulation of meteorites in the adjacent blue ice fields.

  2. Rural Health and Spiritual Care Development: A Review of Programs across Rural Victoria, Australia.

    PubMed

    Carey, Lindsay B; Hennequin, Christine; Krikheli, Lillian; O'Brien, Annette; Sanchez, Erin; Marsden, Candace R

    2016-06-01

    Given declining populations in rural areas and diminishing traditional religious support, this research explores whether spiritual care education programs would be beneficial for and appreciated by those working in rural health and/or community organizations. An overview of literature identified three dominant rural health issues affecting the provision of spiritual care in rural areas, namely the disparity between rural and urban areas in terms of resources, the lack of access to services, plus the need for education and training within rural areas. Spiritual Health Victoria Incorporated (Victoria, Australia) sought to address these issues with the implementation of a variety of spiritual education programs within rural areas. Results of an evaluation of these programs are presented specifying participant demographics, reasons why participants attended, their evaluation of the program and any recommendations for future programs. In overall terms, the results indicated that at least 90 % of participants favorably rated their attended program as either 'very good' or 'good' and indicated that the main reason for their attendance was to develop their own education and/or practice of spiritual care within their rural context for the benefit of local constituents. Several recommendations are made for future programs. PMID:26350290

  3. The Influence of Subsurface Karst Terrain on Hydrology and Hydrogeology in Southwestern Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Perveen, F.; Webb, J.; Dresel, E.; Hekmeijer, P.; Zydor, H.

    2012-12-01

    A detailed study, in collaboration with Department of Primary Industries (DPI), Victoria, has been carried out in three small subcatchments of southwestern Victoria (total area 8.4 km2), which are characterised by varying degrees of influence of a subsurface karst terrain. Lithological logs and downhole geophysics (gamma and bulk conductivity - EM39) on 15 bores within the catchments were supplemented by 2D electrical resistivity vertical profiling, and showed that the middle to late Miocene Port Campbell Limestone is present at shallow depths (~5 m) in two catchments, and somewhat deeper (>70 m) in the third catchment. The limestone is overlain by early Pliocene clay-rich Dorodong Sands. The topography of the third catchment is characterised by shallow closed depressions. Detailed hydrogeological cross-sections using groundwater levels in the bores show closed depressions within the potentiometric surface, that are attributed to the presence of subsurface conduits within the highly permeable limestone, verified by the variable hydraulic conductivity values ( 0.005 - 0.545m/day) obtained from single borehole recovery tests. Stream hydrographs reveal that there is virtually no surface runoff from one subcatchment, due to leakage into a conduit in the underlying limestone. A perched water table is also found in the same area. Thus the study area shows the typical karst features of a highly heterogeneous terrain with massive connectivity between surface water and groundwater regimes, despite the fact that the limestone is overlain by the clay-rich Dorodong Sands.

  4. Oligo-Miocene syn-rift and Miocene post-rift sedimentary records: the tectono-stratigraphic development of the northern proximal margin of the Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Robinet, J.; Razin, P.; Serra Kiel, J.; Gallardo Garcia, A.; Grelaud, C.; Roger, J.; Leroy, S.; Malaval, M.

    2012-04-01

    The northern margin of the Gulf of Aden results from the Oligo-Miocene rifting (34Ma) leading to continental break-up and the oceanic spreading since the Burdigalian (17.6 Ma). We, here, investigate in detail the tectono-stratigraphy development of the Ashawq Graben belonging to the proximal part of northern margin (southern Oman, Dhofar). This graben exhibits sedimentary records of syn-rift and post-rift sequences, so-called Dhofar (Rupelian-Burdigalian) and Fars (middle Miocene-Pliocene) Groups respectively. Analyzing the deposit conditions and sequences geometries provide fundamental inputs for the whole margin understanding. An accurate sedimentological and biostratigraphical analysis evidences two second-order sea level cycles corresponding to the syn-rift and the post-rift units separated by an erosive surface with paleo-karst cavities. The first stage of the rifting expresses as a regional uplift which led to set up of an early Oligocene mix platform system (Ashawq Fm., Shizar Mb.) overlying the proximal platform (Aydim Fm.) and continental (Zalumah Fm.) system deposit of the late Eocene to earliest Oligocene time. Then, the rift extension process during early Oligocene leads to verticals movements along normal faults and increase of the accommodation rate in the Ashawq graben. Such increase of accommodation is fully compensated by an important carbonate production leading to the aggradation of a thick reefal carbonate platform (Ashawq Fm., Nakhlit Mb.). An acceleration of the extension processes during late Oligocene time reaches an increase of the tectonic subsidence associated to the partial drowning and collapsing of the platform and to the set up of carbonate gravity-flow deposits in a deep basin (Mughsayl Fm.). In the most proximal realm, the sedimentation rate attempts to compensate the accommodation rate resulting in a differential aggradation of the reefal carbonate platform, sometimes in the form of patch reef. At the early Miocene time, the

  5. Food of lake trout in Lake Superior

    USGS Publications Warehouse

    Dryer, William R.; Erkkila, Leo F.; Tetzloff, Clifford L.

    1965-01-01

    Stomachs were examined from 1,492 lake trout and 83 siscowets collected from Lake Superior. Data are given on the food of lake trout of legal size (17 inches or longer) by year, season, and depth of water, and on the relation between food and size among smaller lake trout. Fish contributed 96.7 to 99.9 per cent of the total volume of food in the annual samples. Ciscoes (Coregonus spp.) were most common (52.2 to 87.5 per cent of the volume) in 1950 to 1953 and American smelt ranked first (65.6 per cent of the volume) in 1963. Cottids were in 8.9 to 12.3 per cent of the stomachs in 1950 to 1953 but in only 4.3 per cent in 1963. Insects ranked second to fish in occurrence (9.6 per cent for the combined samples) and crustaceans followed at 3.9 per cent. The greatest seasonal changes in the food of lake trout were among fish caught at 35 fathoms and shallower. The occurrence of Coregonus increased from 34.6 per cent in February-March to 71.1 per cent in October-December. Smelt were in 76.9 per cent of the stomachs in February-March but in only 2.2 per cent in October-December. Cottids, Mysis relicta, and insects were most common in the July-September collections. Lake trout taken at depths greater than 35 fathoms had eaten a higher percentage of Cottidae and Coregonus than had those captured in shallower water. Smelt, ninespine sticklebacks, Mysis, and insects were more frequent in stomachs of lake trout from less than 35 fathoms. Crustaceans comprised more than 70 per cent of the total volume of food for 4.0- to 7.9-inch lake trout but their importance decreased as the lake trout grew larger. Pontoporeia affinis was the most common in the stomachs of 4.0- to 6.9-inch lake trout and Mysis held first rank at 7.0 to 12.9 inches. Ostracods were important only to 4.0- to 4.9-inch lake trout. As the lake trout became larger, the importance of fish grew from 4.4-per cent occurrence at 5.0 to 5.9 inches to 93.9 per cent at 16.0 to 16.9 inches. Smelt were most commonly eaten by

  6. The eastern Gulf of Aden: A case study for the setting up of the deep-sea gravity sedimentation on a young continental margin

    NASA Astrophysics Data System (ADS)

    Baurion, Celine; Zaragosi, Sebastien; Leroy, Sylvie; Gorini, Christian; Lucazeau, Francis; Migeon, Sebastien; Garlan, Thierry

    2013-04-01

    The study of sedimentary processes across a young and segmented passive margin under the influence of the Asian monsoon-climate, provide a potential record of tectonic, climatic and high-resolution eustatic events. The northern margin of the eastern Gulf of Aden is one of the world rare examples to study the setting up of gravity sedimentation in a deep basin and the related control parameters. Using multibeam data, Chirp profiles, and sediment cores, we show that this gravity sedimentation highlights the importance of flooding of wadis on the sediment transfer from onshore to the deep basin. The drainage network is not mature on this starved margin, which is affected by post-rift uplift. The main channelized turbidite systems are localized in the western part of the margin, while mass-transport deposits and sheet turbidite deposits are concentrated along the eastern part of the margin affected by a late post-rift uplift. The deep-basin sedimentation is composed of many coarse-grained carbonate turbidites that are related to the lithology of the onshore sedimentary cover. The central part of the uplifted margin does not exhibit coarse-grained turbidites since about 70 ka BP, while the eastern part displays turbidites until recently. This monsoon-influenced margin is characterized by strong along-strike variability in tectonics and fluvial input distribution that might directly influence and segment the gravity sedimentation: (i) the western channelized turbidite system formation depend mainly of the wide catchment area onshore in combination with the geometry of the deep basin; (ii) the starved part of the margin, characterized by mass-transport deposits is mainly controlled by the post-rift uplift; (iii) along the eastern part of the uplifted margin, the unchannelized turbidite deposits seem to be primarily controlled by the presence of a well-developed continental shelf combined to the late uplift impact on the sedimentary supply.

  7. Trace metals in the brown mussel Perna perna from the coastal waters off Yemen (Gulf of Aden): how concentrations are affected by weight, sex, and seasonal cycle.

    PubMed

    Sokolowski, A; Bawazir, A S; Wolowicz, M

    2004-01-01

    The effects of seasonal cycle, sex of individuals, and changes of soft tissues weight on accumulated trace metal concentrations (Cd, Cu, Fe, Mn, Pb, Zn) were examined in the brown mussel Perna perna collected monthly from a natural rocky habitat in the coastal waters off Yemen, the Gulf of Aden, for a period of ten months. Basic hydrological parameters were recorded simultaneously. All metals analyzed displayed seasonal fluctuations with different temporal patterns and variable amplitudes. Similar seasonal cycles were observed for Cu, Mn, and Pb with an increase in accumulated concentration during the rainy period (NE monsoon), and a decrease thereafter. The concentrations of Cu, Mn, and partially Pb appeared to be related to environmental changes, the concentration of Pb possibly also being related to changes in body weight. Accumulated concentrations of Cu and Mn thus seem to reflect actual metal bioavailability in the ecosystem quite efficiently. The tissue levels of Fe and Cd changed inversely to fluctuations in body weight with additional variation due to monsoon-related environmental changes. The behaviors of Fe and Cd are therefore driven by seasonally changing body weight with a considerable contribution of external factors including fluctuations in hydrological conditions and metal exposure. The Zn concentrations tended to increase gradually throughout most of the year regardless of its concentration in the environment. Zinc is considered to be mainly regulated by physiological mechanisms in the mussel, making its accumulated metal concentration independent to some degree of environmental levels. Significant differences in trace metal concentrations between sexes (in favour of females) might have resulted from more intense formation of reproductive tissues and metal accumulation in sexual products of females during the prespawning and spawning periods. PMID:15025166

  8. Measurement of sediment and crustal thickness corrected RDA for 2D profiles at rifted continental margins: Applications to the Iberian, Gulf of Aden and S Angolan margins

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick

    2014-05-01

    Subsidence analysis of sedimentary basins and rifted continental margins requires a correction for the anomalous uplift or subsidence arising from mantle dynamic topography. Whilst different global model predictions of mantle dynamic topography may give a broadly similar pattern at long wavelengths, they differ substantially in the predicted amplitude and at shorter wavelengths. As a consequence the accuracy of predicted mantle dynamic topography is not sufficiently good to provide corrections for subsidence analysis. Measurements of present day anomalous subsidence, which we attribute to mantle dynamic topography, have been made for three rifted continental margins; offshore Iberia, the Gulf of Aden and southern Angola. We determine residual depth anomaly (RDA), corrected for sediment loading and crustal thickness variation for 2D profiles running from unequivocal oceanic crust across the continental ocean boundary onto thinned continental crust. Residual depth anomalies (RDA), corrected for sediment loading using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average or from anomalous uplift or subsidence. Gravity anomaly inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic reflection data has been used to determine Moho depth, calibrated using seismic refraction, and oceanic crustal basement thickness. Crustal basement thicknesses derived from gravity inversion together with Airy isostasy have been used to correct for variations of crustal thickness from a standard oceanic thickness of 7km. The 2D profiles of RDA corrected for both sediment loading and non-standard crustal

  9. Impact of gravity processes on the initial post-rift stages of construction and evolution of a continental margin: Insights from the eastern Gulf of Aden

    NASA Astrophysics Data System (ADS)

    Baurion, Celine; Gorini, Christian; Leroy, Sylvie; Migeon, Sebastien; Lucazeau, Francis; Bache, Francois; Zaragosi, Sebastien; Smit, Jeroen; Al-Toubi, Khalfan; dos Reis, Antonio

    2013-04-01

    The study of the post-rift sediment architecture and continental slope morphology leads to a reconstruction of the initial stages of formation and evolution of gravity-driven processes on the northern margin of the eastern Gulf of Aden. The slope-related features and associated deposits in the deep basin along this young passive margin are investigated through the analysis of a set of seismic-reflection and multibeam bathymetry data. This study demonstrates how preconditioning and triggering factors (tectonics, climate and eustatic variations) can interact and control the margin morphology and post-rift sediment architecture in a source-to-sink perspective. The combined geomorphological and stratigraphic study of this margin allows us to identify three morphological domains inherited from the structural segmentation. The monsoon climate combined with a major eustatic lowstand is proposed as the most likely set of factors preconditioning slope destabilisation on the whole margin. These factors also enhance the effect of the late post-rift uplift of the eastern morphological domain of the studied margin. The formation and distribution of the slope-related features are thus mainly controlled by active faults on the continental slope and the potential effect of bottom currents at the base of the continental slope. The oversteepening of the continental slope in the eastern domain of the studied margin is probably the main triggering factor controlling the generation of failure processes and subsequent canyon formation by upslope erosion. The analysis of canyon location and morphology along the uplifted part of the continental slope reveals the long-term influence of secondary slope-related features, contour currents and turbidite flows on the development of canyons. As a consequence of the late post-rift uplift that only affected the eastern part of the studied margin, huge volumes of sediment were accumulated in mass-transport complexes at the foot of numerous slope

  10. Structure and evolution of the eastern Gulf of Aden: insights from magnetic and gravity data (Encens-Sheba MD117 cruise)

    NASA Astrophysics Data System (ADS)

    d'Acremont, Elia; Leroy, Sylvie; Maia, Marcia; Patriat, Philippe; Beslier, Marie-Odile; Bellahsen, Nicolas; Fournier, Marc; Gente, Pascal

    2006-06-01

    Magnetic and gravity data gathered during the Encens-Sheba cruise (2000 June) in the eastern Gulf of Aden provide insights on the structural evolution of segmentation from rifted margins to incipient seafloor spreading. In this study, we document the conjugate margins asymmetry, confirm the location of the ocean-continent transition (OCT) previously proposed by seismic data, and describe its deep structure and segmentation. In the OCT, gravity models indicate highly thinned crust while magnetic data indicate presence of non-oceanic high-amplitude magnetic anomalies where syn-rift sediments are not observed. Thus, the OCT could be made of ultra-stretched continental crust intruded by magmatic bodies. However, locally in the north, the nature of the OCT could be either an area of ultra-slow spreading oceanic crust or exhumed serpentinized mantle. Between the Alula-Fartak and Socotra fracture zones, the non-volcanic margins and the OCT are segmented by two N027°E-trending transfer fault zones. These transfer zones define three N110°E-trending segments that evolve through time. The first evidence of oceanic spreading corresponds to the magnetic anomaly A5d and is thus dated back to 17.6 Ma at least. Reconstruction of the spreading process suggests a complex non-uniform opening by an arc-like initiation of seafloor spreading in the OCT. The early segmentation appears to be directly related to the continental margin segmentation. The spreading axis segmentation evolved from three segments (17.6 to 10.95 Ma) to two segments (10.95 Ma to present). At the onset of the spreading process, the western segment propagated eastwards, thus reducing the size of the central segment. The presence of a propagator could explain the observed spreading asymmetry with the northern flank of the Sheba ridge being wider than the southern one.

  11. Continental break-up history of a deep magma-poor margin based on seismic reflection data (northeastern Gulf of Aden margin, offshore Oman)

    NASA Astrophysics Data System (ADS)

    Autin, Julia; Leroy, Sylvie; Beslier, Marie-Odile; d'Acremont, Elia; Razin, Philippe; Ribodetti, Alessandra; Bellahsen, Nicolas; Robin, Cécile; Al Toubi, Khalfan

    2010-02-01

    Rifting between Arabia and Somalia started around 35 Ma followed by spreading at 17.6 Ma in the eastern part of the Gulf of Aden. The first-order segment between Alula-Fartak and Socotra-Hadbeen fracture zones is divided into three second-order segments with different structure and morphology. Seismic reflection data were collected during the Encens Cruise in 2006 on the northeastern margin. In this study, we present the results of Pre-Stack Depth Migration of the multichannel seismic data from the western segment, which allows us to propose a tectono-stratigraphic model of the evolution of this segment of the margin from rifting to the present day. The chronological interpretation of the sedimentary sequences is mapped out within relation to the onshore observations and existing dating. After a major development of syn-rift grabens and horsts, the deformation localized where the crust is the thinnest. This deformation occurred in the distal margin graben (DIM) at the northern boundary of the ocean-continent transition (OCT) represented by the OCT ridge. At the onset of the OCT formation differential uplift induced a submarine landslide on top of the deepest tilted block and the crustal deformation was restricted to the southern part of the DIM graben, where the continental break-up finally occurred. Initial seafloor spreading was followed by post-rift magmatic events (flows, sills and volcano-sedimentary wedge), whose timing is constrained by the analysis of the sedimentary cover of the OCT ridge, correlated with onshore stratigraphy. The OCT ridge may represent exhumed serpentinized mantle intruded by post-rift magmatic material, which modified the OCT after its emplacement.

  12. The coralline red alga Lithophyllum kotschyanum f. affine as proxy of climate variability in the Yemen coast, Gulf of Aden (NW Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Caragnano, A.; Basso, D.; Jacob, D. E.; Storz, D.; Rodondi, G.; Benzoni, F.; Dutrieux, E.

    2014-01-01

    Recent investigations have shown the potential of red coralline algae as paleoclimatic archive. A previously unexplored subfamily of coralline algae, the Lithophylloideae, was investigated from the Gulf of Aden (Balhaf, Yemen). Seasonal changes in Mg/Ca, Li/Ca and Ba/Ca composition of Lithophyllum kotschyanum f. affine were investigated by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). For the first time in coralline algae, the Li/Ca composition was analyzed and showed a highly significant and positive correlation with Mg/Ca and SST. Monthly algal Mg/Ca and Li/Ca variations indicate a positive correlation with sea surface temperature (SST), and sea surface salinity (SSS), although low growth rates decrease the resolution of the algal record. Albeit no or weak positive correlation between monthly algal Ba/Ca and local SST was found, fluctuations in Ba/Ca suggest the seasonal influence of nutrient-rich deep waters introduced by upwelling, and record an increase of sedimentation at the sampling site likely due to an intensified land use in the area. The Mg/Ca age model shows an average algal extension rate of 1.15 mm yr-1, and reveals multiple intra-annual banding (previously unreported in the genus Lithophyllum) together with carposporangia formation in late February-early March, when temperature begins to increase. The concentration of MgCO3 in the thallus of L. kotschyanum f. affine is 20 mol% (1 SE), confirming that within the genus, the species sampled in warmer regions contain higher mol% MgCO3. The concentrations of LiCO3 and BaCO3 are 8 μmol% (0.7 SE) and 0.5 μmol% (0.03 SE), respectively. Despite the limitations from low-growth rate and species-specific vital effect, coralline algae confirm their utility in climate and oceanographic reconstruction.

  13. Influence of the Afar plume on the deep structure of Aden and Red Sea margins - Insight from teleseismic tomography in western Yemen

    NASA Astrophysics Data System (ADS)

    Korostelev, Félicie; Basuyau, Clémence; Leroy, Sylvie; Ahmed, Abdulhakim; Keir, Derek; Stuart, Graham; Rolandone, Frédérique; Ganad, Ismail Al; Khanbari, Khaled

    2013-04-01

    Continental rupture processes under mantle plume influence are still poorly known although extensively studied. The Afar plume has been largely investigated in Ethiopia to study early stages of continental break-up. Here we imaged the lithospheric structure of western continental Yemen to evaluate the role of the Afar plume on the evolution of the continental margin and its extent towards the East. A part of the YOCMAL project (YOung Conjugate MArgins Laboratory) permitted the deployment of twenty-three broadband stations in Yemen (from 2009 to 2010). Using a classical teleseismic tomography (Aki et al., 1974) on these stations together with a permanent GFZ station, we image the relative velocity variations of P-waves in the crust and lithosphere down to 300 km depth, with a maximum lateral resolution of about ~20 km. The model thus obtained shows (1) a dramatic and localized thinning of the crust in the vicinity of the Red Sea and the Gulf of Aden (2) the presence of magmatic underplating related to seaward dipping reflectors under those two volcanic margins (3) two granitic syn-rift intrusions on the border of the great escarpment (4) a low velocity anomaly in which with evidence of partial melting, just below thick Oligocene trapps series and other volcanic events (from 15 Ma to present). This low velocity anomaly could correspond to an abnormally hot mantle and could be responsible for dynamic topography and recent magmatism in western Yemen. (5) Finally, we infer the presence of hot material under the Southwestern corner of Yemen that could be related to Miocene volcanism in Jabal an Nar.

  14. Geophysical imaging reveals brine system beneath an ice-sealed Antarctic lake

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The habitability of polar desert environments on Earth, and other neighboring planets, is dependent on the availability of liquid water. In areas where the surface is frozen, lenses of water present in the subsurface may act as microbial refugia. In the McMurdo Dry Valleys of Antarctica, the presence of highly saline brine in valley lakes raises the potential for the existence of a deep groundwater network. We report on a geophysical study that shows Lake Vida, in Victoria Valley, is nearly frozen, and the remaining brine is confined beneath thick ice. Near surface, bathymetric mapping of grounded lake ice was accomplished from a series of ground penetrating radar surveys. Radar penetration was limited to 20 m. An airborne transient electromagnetic survey (AEM) revealed a low resistivity zone at 30-100 m depth beneath the surface of the lake. Based on previous knowledge of brine chemistry and local geology, this zone is interpreted as brine saturated unconsolidated sediments with a porosity of 23-42%. Brine volume is calculated at 15 to 32 million cubic meters, which is of similar magnitude to the brine volume in nearby saline lakes. The AEM survey provided a means of quantifying the spatial extent of deep subsurface brine in this remote environment, and has provided a new perspective on the potential for subsurface habitats in areas often considered devoid of life.

  15. A Revised Holocene History of Lake Kivu, East Africa

    NASA Astrophysics Data System (ADS)

    Votava, J. E.; Johnson, T. C.; Hecky, R. E.

    2013-12-01

    The great lakes of the East African Rift valley are a vast chain of lakes formed in a region of active tectonics. These large, deep lakes are relatively old and many (e.g. Tanganyika, Malawi, and Turkana) have greatly influenced our understanding of terrestrial, tropical East African paleoclimate. Lake Kivu (max depth, 485m) sits at the heart of these rift lakes, north of Lake Tanganyika between the Democratic Republic of the Congo and Rwanda (roughly 250 km west of Lake Victoria). At over 1,400 meters in elevation, this 2,060 km2 mesotrophic lake has a complex stratification regime imposed by hydrothermal springs and deep waters supersaturated at STP in CO2 and CH4 gasses. The active Virunga Volcanoes to the north of the lake supply heated, high-salinity waters below 280 meters water depth maintaining the modern crenogenic meromixis. Based on detailed studies of diatom assemblages and bulk sedimentology, previous workers have suggested this hydrothermal activity began roughly 5,000 years BP. Unfortunately, dating and stratigraphic correlations of these original cores from the 1970 Woods Hole Oceanographic Institution's expedition have been problematic. Here we offer an improved chronology and new carbonate analyses from cores recovered in 2012 and 2013. Our AMS radiocarbon ages come from six terrigeneous macrofossils spanning the last 9,100 years (cal BP). These ages suggest a rather high sedimentation rate on the order of 70cm/kyr, and hence, our 8 m-long core provides us with a high-resolution lake history for the past 10,000 years. Most notable over the past 5,000 years in the lake history is the repeated onset and cessation of carbonate deposition, punctuated by organic-rich intervals. Earlier studies of the Woods Hole cores placed the onset of carbonate deposition at ca. 11,000 years BP suggesting changes in lake hydrology (i.e. closed to open), while the abrupt cessation of carbonate was dated at ca. 5,000 years BP and attributed to the beginning of

  16. Water quality of Lake Austin and Town Lake, Austin, Texas

    SciTech Connect

    Andrews, F.L.; Wells, F.C.; Shelby, W.J.; McPherson, E.M.

    1988-01-01

    Lake Austin and Town Lake are impoundments on the Colorado River in Travis County, central Texas, and are a source of water for municipal industrial water supplies, electrical-power generation, and recreation for more than 500,000 people in the Austin metropolitan area. Small vertical temperature variations in both lakes were attributed to shallow depths in the lakes and short retention times of water in the lakes during the summer months. The largest areal variations in dissolved oxygen generally occur in Lake Austin during the summer as a result of releases of water from below the thermocline in Lake Travis. Except for iron, manganese, and mercury, dissolved concentrations of trace elements in water collected from Lake Austin and Town Lake did not exceed the primary or secondary drinking water standards set by the US Environmental Protection Agency. Little or no effect of stormwater runoff on temperature, dissolved oxygen, or minor elements could be detected in either Lake Austin or Town Lake. Little seasonal or areal variation was noted in nitrogen concentrations in Lake Austin or Town lake. Total phosphorus concentrations generally were small in both lakes. Increased concentrations of nitrogen and phosphorus were detected after storm runoff inflow in Town Lake, but not in Lake Austin; densities of fecal-coliform bacteria increased in Lake Austin and Town Lake, but were substantially greater in Town Lake than in Lake Austin. 18 refs., 38 figs., 59 tabs.

  17. Lake trout rehabilitation in Lake Huron

    USGS Publications Warehouse

    Eshenroder, Randy L.; Payne, N. Robert; Johnson, James E.; Bowen, Charles, II; Ebener, Mark P.

    1995-01-01

    Efforts to restore lake trout (Salvelinus namaycush) in Lake Huron after their collapse in the 1940s were underway in the early 1970s with completion of the first round of lampricide applications in tributary streams and the stocking of several genotypes. We assess results of rehabilitation and establish a historical basis for comparison by quantifying the catch of spawning lake trout from Michigan waters in 1929-1932. Sixty-eight percent of this catch occurred in northern waters (MH-1) and most of the rest (15%) was from remote reefs in the middle of the main basin. Sea lampreys (Petromyzon marinus) increased in the early 1980s in the main basin and depressed spawning populations of lake trout. This increase was especially severe in northern waters and appeared to be associated with untreated populations in the St. Marys River. Excessive commercial fishing stemming from unresolved treaty rights also contributed to loss of spawning fish in northern Michigan waters. Seneca-strain lake trout did not appear to be attacked by sea lampreys until they reached a size > 532 mm. At sizes > 632 mm, Seneca trout were 40-fold more abundant than the Marquette strain in matched-planting experiments. Natural reproduction past the fry stage has occurred in Thunder Bay and South Bay, but prospects for self-sustaining populations of lake trout in the main basin are poor because sea lampreys are too abundant, only one side of the basin is stocked, and stocking is deferred to allow commercial gillnetting in areas where most of the spawning occurred historically. Backcross lake trout, a lake trout x splake (s. Fontinalis x s. Namaycush) hybrid, did not reproduce in Georgian Bay, but this genotype is being replaced with pure-strain lake trout, whose early performance appears promising.

  18. Profile of BC College Transfer Students Admitted to the University of Victoria 2003/04 to 2007/08

    ERIC Educational Resources Information Center

    Martell, Jim; Wilson, Alan

    2009-01-01

    This report examines the population of college transfer students who entered the University of Victoria (UVic) from 2003/04 to 2007/08, updating a June 2004 report. Section A provides a general profile of the 6,917 British Columbia (BC) college transfer students who first registered and commenced studies at UVic in any session between summer 2003…

  19. Appendices. Impact and Adequacy; a Report of an Evaluation of Government Post-Primary School Libraries in Victoria.

    ERIC Educational Resources Information Center

    Balson, M.; And Others

    The appendixes to the evaluation of Victoria, Australia's secondary school libraries include lists of the 33 schools visited to gather information and of the interviewees. The names of the 132 high schools with Commonwealth libraries are given with the dates of their openings and maps showing their locations. Copies of survey instruments used to…

  20. Complete Genome Sequence of Cryobacterium arcticum Strain PAMC 27867, Isolated from a Sedimentary Rock Sample in Northern Victoria Land, Antarctica.

    PubMed

    Lee, Jaejin; Cho, Ahnna; Yang, Jae Young; Woo, Jusun; Lee, Hong Kum; Hong, Soon Gyu; Kim, Ok-Sun

    2016-01-01

    Cryobacterium arcticum PAMC 27867, a psychrotolerant, Gram-positive bacterium, was isolated from a sedimentary rock sample collected at Eureka Spurs in northern Victoria Land, Antarctica. Here, we report the genome sequence of C. arcticum PAMC 27867. PMID:27587812

  1. Three Decades of Implementation of School-Based Management in the Australian Capital Territory and Victoria in Australia

    ERIC Educational Resources Information Center

    Gammage, David T.

    2008-01-01

    Purpose: The purpose of this paper is to explore how the process of implementation of school-based management (SBM) has worked within the public school systems in the Australian Capital Territory (ACT) and Victoria in Australia. The period covered was 1976-2006. Design/methodology/approach: The approach adopted was the mixed methodology which…

  2. "Why Didn't They Teach Us Any of This before?": Youth Appraisal of Turkish Provision in Victoria

    ERIC Educational Resources Information Center

    Beykont, Zeynep F.

    2012-01-01

    This article examines youth assessment of the quality and success of languages provision. The discussion draws on data collected from students and graduates of Victoria's 16 secondary Turkish programs in large-scale surveys (n=858) and follow-up interviews (n=177). Surveys revealed that upper secondary Turkish classrooms serve predominantly…

  3. "Why Has It Only become an Issue Now?": Young Drug Users' Perceptions of Drug Driving in Melbourne, Victoria

    ERIC Educational Resources Information Center

    Wilson, Laura Ann; Wilson, Dean

    2010-01-01

    Preliminary research into drug-user perceptions of drug driving was undertaken with a sample group of drug users aged 18 to 24 from Melbourne, Victoria. Eleven males and nine females participated in semi-structured interviews and completed self-report surveys. Participants discussed their drug driving and their perceptions of the likelihood of…

  4. The Discourse of Public Education: An Urban Campaign for a Local Public High School in Melbourne, Victoria

    ERIC Educational Resources Information Center

    Rowe, Emma E.

    2014-01-01

    This paper explores the metonymic slippage surrounding the discourse of public education, through observations and interviews with Lawson High School active campaigners in the state of Victoria, Australia. The notion of campaigning for public education has become an ever-present issue on an international scale, and this article aims to contribute…

  5. University of Victoria Genome British Columbia Proteomics Centre Partners with CPTAC - Office of Cancer Clinical Proteomics Research

    Cancer.gov

    University of Victoria Genome British Columbia Proteomics Centre, a leader in proteomic technology development, has partnered with the U.S. National Cancer Institute (NCI) to make targeted proteomic assays accessible to the community through NCI’s CPTAC Assay Portal.

  6. The Development and Use of Individual Learning Plans for Deaf and Hard of Hearing Students in Victoria, Australia

    ERIC Educational Resources Information Center

    Brown, P. Margaret; Byrnes, Linda J.

    2014-01-01

    This study investigated the Individual Learning Plans of eighty-eight students who were deaf and hard of hearing attending facilities and schools for the deaf in Victoria Australia. The students' assessment and planning portfolios were scrutinised for evidence of formal and informal assessment used to generate goals for the Individual…

  7. "Comfortably British" to "Fundamentally Economic"? The Effects of Language Policies on Year 12 Language Candidature in Victoria

    ERIC Educational Resources Information Center

    Baldwin, Jennifer

    2011-01-01

    This article seeks to explore how various language policies may have impacted Year 12 language candidature in Victoria. Australian Federal and Victorian State Government language policies are but one of the influences yet, it may be argued, the most significant influence. These stand alongside waves of immigration, global events and conflicts, and…

  8. Rips, Currents and Snags: Investigating the Delivery of Educational Goals for Young Australians in the Region of Gippsland, Victoria

    ERIC Educational Resources Information Center

    Lynch, Timothy

    2012-01-01

    Monash University (Gippsland campus) is situated in Churchill, Latrobe Valley, located in central Gippsland, eastern Victoria. A large percentage of the Gippsland region comprises of a socio-economically disadvantaged population (Figure 1). In Semester One, 2011 as part of the Bachelor of Primary Education course at Monash, it was decided that a…

  9. Biogenesis, structure, and immune-suppressive effects of virus-like particles of a Drosophila parasitoid, Leptopilina victoriae.

    PubMed

    Morales, Jorge; Chiu, Hsiling; Oo, Thiri; Plaza, Rosemary; Hoskins, Sally; Govind, Shubha

    2005-02-01

    Drosophila melanogaster larvae are attacked by virulent strains of parasitoid wasps. Females of Leptopilina heterotoma produce virus-like particles (VLPs) that efficiently destroy lamellocytes, a major larval immune effector cell type. We report here that L. victoriae, a closely related wasp species, also produces VLPs that trigger immune suppression responses in fly hosts. We compare the ability of immune suppression of the two parasitoids using a mutant host strain hopscotch(Tumorous-lethal) (hop(Tum-l)). hop(Tum-l) larvae have two defects of hematopoietic origin: overproliferation of hemocytes and constitutive encapsulation of self-tissue by lamellocytes. The encapsulation phenotype is suppressed weakly by L. victoriae and strongly by L. heterotoma. In vitro studies on hop(Tum-l) lamellocytes show that VLP-containing fluid from either wasp species induces lamellocyte lysis, but with different kinetics. Previously undocumented precursors of L. victoriae VLPs are synthesized in the long gland and are first visible within canals connecting secretory cells to the long gland lumen. VLP assembly occurs in the lumen. VLPs show multiple electron-dense projections surrounding a central core. Maturing particles appear segmented, singly or in arrays, embedded in the reservoir matrix. In sections, mature particles are pentagonal or hexagonal; the polygon vertices extending into spikes. Our results suggest that L. victoriae is likely to promote immune suppression by an active mechanism that is mediated by VLPs, similar to that used by L. heterotoma. PMID:15749103

  10. Language in the Workplace Project and Workplace Communication for Skilled Migrants Course at Victoria University of Wellington, New Zealand

    ERIC Educational Resources Information Center

    de Bres, Julia; Holmes, Janet; Joe, Angela; Marra, Meredith; Newton, Jonathan; Riddiford Nicky; Vine, Bernadette

    2009-01-01

    The School of Linguistics and Applied Language Studies (LALS) at Victoria University of Wellington conducts research and teaching in Linguistics, Applied Linguistics, Writing and Deaf Studies. It incorporates a Deaf Studies Research Unit, which undertakes research on topics relating to deaf people and their language in New Zealand, and the New…

  11. 75 FR 43579 - Exelon Generation Company, LLC; Victoria County Station, Units 1 and 2; Notice of Withdrawal of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-26

    ... receipt and availability of this application was published in the Federal Register (73 FR 56867) on September 30, 2008. On November 6, 2008, a subsequent notice was published in the Federal Register (73 FR... COMMISSION Exelon Generation Company, LLC; Victoria County Station, Units 1 and 2; Notice of Withdrawal...

  12. 78 FR 60826 - Foreign-Trade Zone 155-Calhoun/Victoria Counties, Texas; Authorization of Production Activity...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-02

    ... (78 FR 35604, 06/13/2013). The FTZ Board has determined that no further review of the activity is... Production Activity; Caterpillar, Inc. (Excavator and Frame Assembly Production); Victoria, Texas On May 29... proposed production activity to the Foreign-Trade Zones (FTZ) Board on behalf of Caterpillar, Inc.,...

  13. Rates of Student-Reported Antisocial Behavior, School Suspensions, and Arrests in Victoria, Australia and Washington State, United States

    ERIC Educational Resources Information Center

    Hemphill, Sheryl A.; McMorris, Barbara J.; Toumbourou, John W.; Herrenkohl, Todd I.; Catalano, Richard F.; Mathers, Megan

    2007-01-01

    Background: Few methodologically rigorous international comparisons of student-reported antisocial behavior have been conducted. This paper examines whether there are differences in the frequency of both antisocial behavior and societal responses to antisocial behavior in Victoria, Australia and Washington State, United States. These 2 states were…

  14. Complete Genome Sequence of Cryobacterium arcticum Strain PAMC 27867, Isolated from a Sedimentary Rock Sample in Northern Victoria Land, Antarctica

    PubMed Central

    Lee, Jaejin; Cho, Ahnna; Yang, Jae Young; Woo, Jusun; Lee, Hong Kum; Hong, Soon Gyu

    2016-01-01

    Cryobacterium arcticum PAMC 27867, a psychrotolerant, Gram-positive bacterium, was isolated from a sedimentary rock sample collected at Eureka Spurs in northern Victoria Land, Antarctica. Here, we report the genome sequence of C. arcticum PAMC 27867. PMID:27587812

  15. Marching Backwards into the Future: The Introduction of the English Creative Music Movement in State Secondary Schools in Victoria, Australia

    ERIC Educational Resources Information Center

    Burke, Harry

    2014-01-01

    In 1910, Victoria established an elite form of state secondary education that remained essentially unchanged until the introduction of a progressive curriculum during the late 1960s. This radical and voluntary curriculum introduced child-centred learning and personal development skills to state secondary schools. Many state secondary music…

  16. Supporting breastfeeding In Local Communities (SILC) in Victoria, Australia: a cluster randomised controlled trial

    PubMed Central

    McLachlan, Helen L; Forster, Della A; Amir, Lisa H; Cullinane, Meabh; Shafiei, Touran; Watson, Lyndsey F; Ridgway, Lael; Cramer, Rhian L; Small, Rhonda

    2016-01-01

    Objectives Breastfeeding has significant health benefits for mothers and infants. Despite recommendations from the WHO, by 6 months of age 40% of Australian infants are receiving no breast milk. Increased early postpartum breastfeeding support may improve breastfeeding maintenance. 2 community-based interventions to increase breastfeeding duration in local government areas (LGAs) in Victoria, Australia, were implemented and evaluated. Design 3-arm cluster randomised trial. Setting LGAs in Victoria, Australia. Participants LGAs across Victoria with breastfeeding initiation rates below the state average and > 450 births/year were eligible for inclusion. The LGA was the unit of randomisation, and maternal and child health centres in the LGAs comprised the clusters. Interventions Early home-based breastfeeding support by a maternal and child health nurse (home visit, HV) with or without access to a community-based breastfeeding drop-in centre (HV+drop-in). Main outcome measures The proportion of infants receiving ‘any’ breast milk at 3, 4 and 6 months (women's self-report). Findings 4 LGAs were randomised to the comparison arm and provided usual care (n=41 clusters; n=2414 women); 3 to HV (n=32 clusters; n=2281 women); and 3 to HV+drop-in (n=26 clusters; 2344 women). There was no difference in breastfeeding at 4 months in either HV (adjusted OR 1.04; 95% CI 0.84 to 1.29) or HV+drop-in (adjusted OR 0.92; 95% CI 0.78 to 1.08) compared with the comparison arm, no difference at 3 or 6 months, nor in any LGA in breastfeeding before and after the intervention. Some issues were experienced with intervention protocol fidelity. Conclusions Early home-based and community-based support proved difficult to implement. Interventions to increase breastfeeding in complex community settings require sufficient time and partnership building for successful implementation. We cannot conclude that additional community-based support is ineffective in improving breastfeeding

  17. Risk factors for maternal morbidity in Victoria, Australia: a population-based study

    PubMed Central

    Lindquist, Anthea C; Kurinczuk, Jennifer J; Wallace, Euan M; Oats, Jeremy; Knight, Marian

    2015-01-01

    Objectives The aim of this analysis was to quantify the risk factors associated with maternal morbidity among women in Victoria, Australia, focusing particularly on sociodemographic factors. Design Case–control analysis. Participants Data on all maternities in Victoria from 1 January 2006 to 31 December 2008. Methods A case–control analysis was conducted using unconditional logistic regression to calculate adjusted ORs (aORs). Cases were defined as all women noted to have had a severe complication during the index pregnancy. Severe maternal morbidity was defined by the validated, composite Australian Maternal Morbidity Outcome Indicator. Socioeconomic position was defined by Socio-Economic Indices for Areas (SEIFA), specifically the Index of Relative Socioeconomic Disadvantage (IRSD), and other variables analysed were age, parity, Indigenous background, multiple pregnancy, country of birth, coexisting medical condition, previous caesarean section, spontaneous abortion or ectopic pregnancy. Results The study population comprised 211 060 women, including 1119 cases of severe maternal morbidity (0.53%). Compared with the highest IRSD quintile, the aOR for the 2nd quintile was 1.23 (95% CI 1.03 to 1.49), 0.98 (95% CI 0.79 to 1.21) for the 3rd quintile, 1.55 (95% CI 1.28 to 1.87) for the 4th and 1.21 (95% CI 1.00 to 1.47) for the lowest (most deprived) quintile. Indigenous status was associated with twice (aOR 2.02; 95% CI 1.32 to 3.09) the odds of being a case. Other risk factors for severe maternal morbidity were age ≥35 years (aOR 1.22; 95% CI 1.04 to 1.44), coexisting medical condition (aOR 1.39; 95% CI 1.16 to 1.65), multiple pregnancy (aOR 2.30; 95% CI 1.71 to 3.10), primiparity (aOR 1.36; 95% CI 1.18 to 1.57), previous caesarean section (aOR 1.79; 95% CI 1.53 to 2.10) and previous spontaneous miscarriage (aOR 1.25; 95% CI 1.08 to 1.44). Conclusions The findings from Victoria strongly suggest that social disadvantage needs to be acknowledged and further

  18. Deeply Frozen Lakes in a Terrestrial Peri-Glacial Environment

    NASA Astrophysics Data System (ADS)

    Doran, P. T.; Fritsen, C. H.

    1998-01-01

    , which is indicative of prolonged exposure to a thermal gradient. At 15.8 m in the profile, wet saline ice was encountered at -11.6C (logged upon collection). The brine was later determined to be NaCl with an inferred concentration of 600 ppt, or about 17x seawater. Based on the GPR survey this brine would have been 3-4 in from the ice/liquid water interface. The GPR results show parabolic reflections in the ice starting at 16 m, which we now interpret as the start of the briny ice. A meteorological station at the west end of the lake recorded a mean annual temperature at Lake Vida of -26C. This is about 9'C colder than annual averages in Taylor and Wright Valleys during the same period. The difference occurs entirely during the winter, with the summers being very similar. The reason for the cold Victoria Valley winters appears to be a lack of foehn winds. Since local topography does not seem to be blocking these winds, we suggest that a strong winter temperature inversion in the valley forces the foehn winds to stay off the valley floor. The meteorological record thus shows that the environment at Lake Vida provides greater freezing potential than the environment of other dry valley lakes. We used these meteorological data to model the annual thermal wave in Lake Vida ice without considering the influence of the underlying water body. The modeled temperatures are compared against the actual first year's data. From this comparison it is clear that the actual temperature profile gets warmer toward the bottom, suggesting a heat source at depth. There are three probable, not mutually exclusive, candidates for this heat source: (1) localized geothermal heating, (2) ice growth at the base of the ice cover with the resultant release of latent heat, and (3) additional cooling of the water column and the release of specific heat associated with ice growth and concomitant rejection of salts, which would depress the freezing temperature of the solution in front of the advancing

  19. View of Lake Sabrina Dam and Lake Sabrina from east ...

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

    View of Lake Sabrina Dam and Lake Sabrina from east ridge showing spillway at photo center, view southwest - Bishop Creek Hydroelectric System, Plant 2, Lake Sabrina Dam, Bishop Creek, Bishop, Inyo County, CA

  20. Origin and speciation of haplochromine fishes in East African crater lakes investigated by the analysis of their mtDNA, Mhc genes, and SINEs.

    PubMed

    Sato, Akie; Takezaki, Naoko; Tichy, Herbert; Figueroa, Felipe; Mayer, Werner E; Klein, Jan

    2003-09-01

    The Western Branch of the East African Great Rift Valley is pocketed with craters of extinct or dormant volcanoes. Many of the craters are filled with water, and the lakes are inhabited by fishes. The objective of the present study was to determine the amount and nature of genetic variation in haplochromine fishes inhabiting two of these crater lakes, Lake Lutoto and Lake Nshere, and to use this information to infer the origin and history of the two populations. To this end, sequences of mitochondrial (mt) DNA control region, exon 2 of major histocompatibility complex (Mhc) class II B genes, and short interspersed elements (SINEs) were analyzed. The results indicate that the Lake Nshere and Lake Lutoto fishes originated from different but related large founding populations derived from the Kazinga Channel, which connects Lake Edward and Lake George. Some of the genetic polymorphism that existed in the ancestral populations was lost in the populations of the two lakes. The polymorphism that has been retained has persisted for some 50000 generations (years). During this time, new mutations arose and became fixed in each of the two populations in the mtDNA, giving rise to sets of diagnostic substitutions. Each population evolved in isolation after the colonization of the lakes less than 50000 years ago. There appears to be no population structure within the crater lake fishes, and their present effective population sizes are in the order of 104 to 105 individuals. Comparisons with the endemic haplochromine species of Lake Victoria reveal interesting parallels, as well as differences, which may help to understand the nature of the speciation process. PMID:12777512

  1. Recruiting and retaining competent clinical nurses. The Clinical Promotion Project Victoria General Hospital, Halifax, Nova Scotia.

    PubMed

    Grantham, M; Ross, S E; MacKay, R; Banfield, V; Brown, J; Beanlands, H

    1989-06-01

    A career advancement program for nurses has been developed and implemented at the Victoria General Hospital, Halifax, as part of a manpower planning strategy for recruitment and retention of clinical nurses. A competency based performance appraisal system was developed and implemented as part of the program. This system identifies four levels of clinical expertise. Progression through each level indicates that a nurse has achieved a certain level of skill, knowledge and abilities. Demonstrated competence in one level is a prerequisite to promotion to the next level of practice. Implementation of this system provides clinical career opportunities for nurses in direct patient care. This article will provide the nurse administrator with an insight into the development and implementation of a clinical career advancement program. Future articles will described the research evaluation of the Clinical Performance Appraisal System and clinical nurses' reactions to the new system. PMID:2486680

  2. A new resonance Rayleigh scattering spectral method for determination of O3 with victoria blue B

    NASA Astrophysics Data System (ADS)

    Wen, Guiqing; Yang, Duo; Jiang, Zhiliang

    2014-01-01

    Ozone (O3) could be absorbed by boric acid-potassium iodide (BKI) absorbent solution to produce tri-iodine ion (I3-) that react with victoria blue B (VBB) to form the associated particle (VBB-I3)n and exhibited a strong resonance Rayleigh scattering (RRS) peak at 722 nm. Under the chosen conditions, the RRS peak intensity was linear with O3 concentration in the range of 0.2-50 μmol/L, with a linear regression equation of ΔI722 = 17.9c - 45.4 and detection limit of 0.057 μmol/L. Accordingly, a simple, rapid and sensitive RRS spectral method was set up for determination of trace O3 in air, with satisfactory results.

  3. Chemostratigraphy and Fe Mineralogy of the Victoria Crater Duck Bay Section: Opportunity APXS and Moessbauer Results

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, D. W.; Schroeder, C.; Gellert, R.; Klingelhoefer, G.; Jolliff, B. L.; Morris, R. V.

    2008-01-01

    Meridiani Planum is a vast plain of approximately horizontally bedded sedimentary rocks composed of mixed and reworked basaltic and evaporitic sands containing secondary, diagenetic minerals [e.g., 1-5]. Because bedding planes are subparallel to topography, investigation of contiguous stratigraphy requires examining exposures in impact craters. Early in the mission (sols 130-317), Opportunity was commanded to do detailed study of exposed outcrops in Endurance crater, including the contiguous Karatepe section at the point of ingress. Just over 1000 sols later and roughly 7 km to the south, the rover is being commanded to do a similar study of the Duck Bay section of Victoria crater. Here we report on the preliminary results from the Alpha Particle X-ray Spectrometer (APXS) and Moessbauer instruments.

  4. Suffering by comparison: Twitter users' reactions to the Victoria's Secret Fashion Show.

    PubMed

    Chrisler, Joan C; Fung, Kaitlin T; Lopez, Alexandra M; Gorman, Jennifer A

    2013-09-01

    Social comparison theory suggests that evaluating the self in comparison with others (e.g., peers, celebrities, models) can influence body image. Experimental studies that have tested effects of viewing idealized images in the media often show that women feel worse about themselves after seeing images that illustrate the beauty ideal. Twitter presents a naturally occurring opportunity to study viewers' reactions. An analysis was conducted of 977 tweets sent immediately before and during the 2011 Victoria's Secret Fashion Show that reference the show. Although the majority were idiosyncratic remarks, many tweets contain evidence of upward social comparisons to the fashion models. There were tweets about body image, eating disorders, weight, desires for food or alcohol, and thoughts about self-harm. The results support social comparison theory, and suggest that vulnerable viewers could experience negative affect, or even engage in harmful behaviors, during or after viewing the show or others like it. PMID:23769929

  5. Seismicity and arrival-time residuals from the Victoria Earthquake of June 9, 1980

    SciTech Connect

    Wong, V.; Frez, J.

    1981-01-01

    Hypocenter distribution in space and time of the aftershock activity from the Victoria Earthquake of June 9, 1980 was studied. It was concluded that the main event excited aftershocks in several pre-existing nests at the northwest end of the Cerro Prieto Fault, but no significant activity occurred at the immediate neighborhood of the main event. The depth of the aftershocks increases with the distance from the northwest end of the fault and this feature might be related with the higher temperatures and the spreading center located between the ends of the Imperial and Cerro Prieto Faults. The significance of the arrival-times residuals for local and regional stations is discussed both for P and S-waves and the importance of obtaining station corrections is emphasized. The non-uniqueness in determining a structure which minimizes the residuals is illustrated. Two different structures which satisfy the local data are presented.

  6. Sir James Mouat, VC KCB FRCS (1815-1899): winner of the first medical Victoria Cross.

    PubMed

    Lawrenson, Ross

    2004-11-01

    Sir James Mouat was the first of 36 doctors to win the Victoria Cross. Born in Kent in 1815, he was educated at University College London before joining the army. After service in India and Ireland he joined the 6th Dragoon Guards as regimental surgeon and served with them throughout the Crimean War. He won his VC at the Battle of Balaclava. After the Crimean War he was appointed principal medical officer to the British troops in the New Zealand Wars. After serving in New Zealand he returned to England and became Inspector General of Hospitals. Surgeon General Mouat retired on 28 April 1876. He was appointed an honorary surgeon to the Queen in 1888, and a Knight Commander of the Order of the Bath in 1894. He died of a stroke on 4 January 1899 at the age of 83. PMID:15486614

  7. Steranes and triterpanes in the Beacon Supergroup samples from southern Victoria Land in Antarctica

    SciTech Connect

    Matsumoto, Genki I.; Watanuki, Kunihiko ); Machihara, Tsutomu ); Suzuki, Noriyuki ); Funaki, Minoru )

    1987-10-01

    Steranes and triterpanes in Beacon Supergroup samples (sedimentary rock and silicified wood) from Allan Hills and Carapace Nunatak of southern Victoria Land in Antarctica were studied to elucidate sources of organic materials, sedimentary paleoenvironment and thermal history after deposition. Relative abundances of C{sub 27}, C{sub 28} and C{sub 29} steranes and visual kerogen results of Beacon Supergroup samples from Allan Hills imply that organic materials in the sedimentary paleoenvironments are contributed mainly by vascular plants with some influence of microorganisms, while those of the Carapace Nunatak sample may be largely due to fern spores. The pristane/phytane and pristane/heptadecane ratios of the samples were generally close to unity and between 0.50 and 0.99, respectively, suggesting that the sedimentary paleoenvironment was shallow lacustrine with alternating oxic and anoxic conditions.

  8. Basal Adare volcanics, Robertson Bay, North Victoria Land, Antarctica: Late Miocene intraplate basalts of subaqueous origin

    USGS Publications Warehouse

    Mortimer, N.; Dunlap, W.J.; Isaac, M.J.; Sutherland, R.P.; Faure, K.

    2007-01-01

    Late Cenozoic lavas and associated hyaloclastite breccias of the Adare volcanics (Hallett volcanic province) in Robertson Bay, North Victoria Land rest unconformably on Paleozoic greywackes. Abundant hyaloclastite breccias are confined to a paleovalley; their primary geological features, and the stable isotope ratios of secondary minerals, are consistent with eruption in a subaqueous environment with calcite formation probably involving seawater. In contrast, the lavas which stratigraphically overlie the hyaloclastites on Mayr Spur probably were erupted subaerially. K-Ar dating of eight samples from this basal sequence confirms the known older age limit (Late Miocene) of the Hallett volcanic province. Geochemical data reveal an ocean island basalt-like affinity, similar to other Cenozoic igneous rocks of the Hallett volcanic province. If a submarine eruptive paleoenvironment is accepted then there has been net tectonic or isostatic post-Late Miocene uplift of a few hundred metres in the Robertson Bay-Adare Peninsula area

  9. Origins of rainbow smelt in Lake Ontario

    USGS Publications Warehouse

    Bergstedt, Roger A.

    1983-01-01

    The first rainbow smelt (Osmerus mordax) to enter Lake Ontario were probably migrants from an anadromous strain introduced into New York's Finger Lakes. Since the upper Great Lakes were originally stocked with a landlocked strain from Green Lake, Maine, subsequent migration to Lake Ontario from Lake Erie makes Lake Ontario unique among the Great Lakes in probably having received introductions from two distinct populations.

  10. Mineralogy and Geochemistry of Granitic rocks within Lichen Hills, Outback Nunatak, Northern Victoria Land, Antarctica

    NASA Astrophysics Data System (ADS)

    KIM, T.; KIM, Y.; Lee, I.; Lee, J.; Woo, J.

    2015-12-01

    The study areas, Lichen Hills and Outback Nunatak are located in the Northern Victoria Land which is close to Pacific Ocean side of Transantarctic Mountain (TAM), Antarctica. According to the study of Zeller and Dreschoff (1990), the radioactivity values of Lichen hills and Frontier Mt. area in the Victoria Land were very high. To identify the geochemical characteristics of granitic rocks in these areas, 13 samples of Lichen Hills rocks and 4 samples of Outback Nunatak rocks are analyzed. For mineralogical study, samples were observed in macroscale as well as microscale including microscope electron probe analysis. Rock samples of Lichen Hills, Outback Nunatak are mainly leucogranite and granitic pegmatite. These rock samples are composed of quartz, k-feldspar, plagioclase, muscovite, garnet, tourmaline like granite. In SEM-EDS analysis, the observed light colored minerals show relatively high Th, U, Dy, Ce, Nb concentration. This suggests that rock samples may contain minerals such as fergusonite, monazite, thorite, allanite, karnasurtite which are considered to be REE-bearing minerals. Samples of related rocks have been analyzed in terms of major, trace and rare earth element (REE) concentrations using X-ray fluorescence (XRF) spectrometer and Inductively Coupled Plasma Mass Spectrometer (ICP-MS). As concentration of SiO2 increase, Al2O3, TiO2, Fe2O3, MgO, P2O5 concentration decrease and Na2O, K2O, MnO concentration increase. Analyzed trace elements and REE are normalized using CI Chondrite, Primitive mantle. The normalized data show that LREE are enriched compared to HREE. The distinct negative anomalies of Eu, Sr are observed, indicating that rock-forming melts are fairly processed state of fractional crystallization. It means that Th, U, Nb, Ta are much enriched in the melts.

  11. Geology and petrogenesis of the Kirkpatrick Basalt, Pain Mesa and Solo Nunatak, northern Victoria Land, Antarctica

    SciTech Connect

    Mensing, T.M.

    1987-01-01

    The flows on Pain Mesa were divided into a Lower Suite and an Upper Suite based on differences in their chemical compositions. The Upper Suite has higher concentrations of SiO/sub 2/, alkalies, total Fe, MnO, TiO/sub 2/, and P/sub 2/O/sub 5/ than the Lower Suite. In addition, the flows of the Upper Suite are homogeneous in chemical composition compared to the Lower Suite which is differentiated. The isotope compositions of Sr and O of the Lower Suite are positively correlated which indicates that the magma was contaminated by crustal material. The isotopic and chemical compositions of the flows of the Lower Suite were explained by fractional crystallization and simultaneous assimilation of a crustal contaminant. The initial Sr isotope ratios of the Upper Suite, calculated for an assumed age of 175 Ma, were lower than those of the Lower Suite, and are not constant. However, by lowering the assumed age of the Upper Suite to 92 Ma the range of the initial Sr-isotope ratios was greatly reduced. Paleomagnetic results and K-Ar dating of Ferrar rocks at the Litell Rocks Nunatak in northern Victoria Land also support the hypothesis that the Upper Suite is Cretaceous in age. The magma source of both suites has elevated /sup 87/Sr//sup 86/Sr ratios compared to normal mantle values because of prior enrichment in Rb. The magma source was enriched in Rb about 475 Ma years ago. This data coincides with the Ross Orogeny which may reflect a causal relationship between these events. The occurrence of igneous activity in northern Victoria Land and Marie Byrd Land were juxtaposed during the Mesozoic Era but were later separated as a result of major right lateral displacement along the Transantarctic rift system.

  12. Impact of an outright ban on the availability of commercial tanning services in Victoria, Australia.

    PubMed

    Sinclair, C; Cleaves, N; Dunstone, K; Makin, J; Zouzounis, S

    2016-08-01

    Australian states have introduced an outright ban on commercial artificial tanning sunbeds. This was based on evidence from systematic reviews affirming a strong association between tanning bed use and increased risk of melanoma. The implementation of the ban provides an opportunity to assess the effectiveness of the legislation in preventing access to artificial UV radiation. Compliance with the ban has been enforced and monitored by government departments. We additionally monitored online tanning bed advertisements before and after the ban, showing a decline over time in the number of sunbeds advertised for sale on gumtree.com.au and ebay.com.au, from a peak of 115 advertisements in May 2014 to 50 or fewer per month from February 2015. There was also an increase in advertised price, with the percentage of sunbeds offered in Victoria on gumtree.com.au at higher than $2 000 increasing from around 25% between January and June 2014 to 65% in the quarter following the introduction of the ban. Advertisements on gumtree.com.au from individuals wishing to access a sunbed in a private home in Victoria increased from only isolated instances in the months immediately prior to the ban, to between 25 and 77 advertisements per month in the quarter following the ban. In summary, the introduction of an outright ban of commercial sunbeds has achieved a dramatic reduction in the availability of harmful artificial UV radiation sources in Australia. Long-term benefits to the health of the population and a reduction in costs to the health system are expected to result. PMID:27535604

  13. Long-term groundwater storage change in Victoria, Australia from satellite gravity and in situ observations

    NASA Astrophysics Data System (ADS)

    Chen, J. L.; Wilson, C. R.; Tapley, B. D.; Scanlon, Bridget; Güntner, Andreas

    2016-04-01

    Analysis based on satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and land surface models indicates that groundwater storage in Victoria, Australia had been declining steadily, until a trend reversal around early 2010, attributed to two wetter seasons in 2010 and 2011. In situ groundwater level measurements (from a network of 1395 bores in Victoria) also indicate a steady groundwater depletion since the early 1990's, and show remarkable agreement with GRACE estimates for the 10-year period (2003-2012) in common with the GRACE mission. Groundwater depletion rates for 2005 to 2009 are relatively large as indicated by both GRACE estimates (8.0 ± 1.7 km3/yr) and in situ measurements (8.3 ± 3.4 km3/yr). Over the same period (2005-2009), GRACE measurements capture significant groundwater depletion in a wider region covering much of the southern Murray-Darling Basin, and the total groundwater depletion rate in this region is about 17.2 ± 4.7 km3/yr. Annual groundwater storage changes are strongly correlated with precipitation anomalies, but only about one-fifth of anomalous precipitation contributes to groundwater recharge. The strong correlation suggests that this groundwater depletion is primarily related to drought with related groundwater pumping for agricultural and domestic consumption. The remarkable agreement between GRACE estimates and in situ measurements demonstrates the great potential of satellite gravity observations in combination with land surface model estimates to quantify changes in regional groundwater resources, especially when in situ measurements are limited or unavailable. This study shows the importance of reducing leakage bias in GRACE observations and the effectiveness of the forward modeling iterative method used.

  14. Perceptions of Prescribed Burning in a Local Forest Community in Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Bell, Tina; Oliveras, Immaculada

    2006-11-01

    The general perceptions of prescribed burning were elicited from forest users for an area that has been subject to this form of land management for at least 20 years. The largest group consisted of local residents living in and around the Wombat State Forest with two smaller groups of students from a nearby university campus and local professional land managers. A questionnaire was given to each participant in order to explore how the forest was used, to determine the level of knowledge of burning in the targeted forest and Victoria and the perception of the appearance, effectiveness of protection, and accessibility to the forest after prescribed burning. Generally all groups had similar responses with community members having stronger views on the effectiveness and practicalities of prescribed burning, whereas students were more neutral in their opinions. All participants claimed knowledge of prescribed burning activities within Victoria, but fewer had experience of planned fires in the Wombat State Forest. All groups agreed that areas that had not been recently burned had a better appearance than those that had, but this result may have included a range of value judgments. Land managers had a greater understanding of the ecological importance of season and timing of burning; however, some students and community members were equally knowledgeable. Prescribed burning did not impede access to the forest, nor did smoke from prescribed burns pose any great problem. The majority of the participants felt that the amount of prescribed burning done in the forest was adequate for engendering a feeling of protection to life and property, yet many were still suspicious of this management practice. These initial findings indicate several areas in which further research would be useful including the efficacy of education programs for community members and improved communication of burn plans by land managers.

  15. Perceptions of prescribed burning in a local forest community in Victoria, Australia.

    PubMed

    Bell, Tina; Oliveras, Immaculada

    2006-11-01

    The general perceptions of prescribed burning were elicited from forest users for an area that has been subject to this form of land management for at least 20 years. The largest group consisted of local residents living in and around the Wombat State Forest with two smaller groups of students from a nearby university campus and local professional land managers. A questionnaire was given to each participant in order to explore how the forest was used, to determine the level of knowledge of burning in the targeted forest and Victoria and the perception of the appearance, effectiveness of protection, and accessibility to the forest after prescribed burning. Generally all groups had similar responses with community members having stronger views on the effectiveness and practicalities of prescribed burning, whereas students were more neutral in their opinions. All participants claimed knowledge of prescribed burning activities within Victoria, but fewer had experience of planned fires in the Wombat State Forest. All groups agreed that areas that had not been recently burned had a better appearance than those that had, but this result may have included a range of value judgments. Land managers had a greater understanding of the ecological importance of season and timing of burning; however, some students and community members were equally knowledgeable. Prescribed burning did not impede access to the forest, nor did smoke from prescribed burns pose any great problem. The majority of the participants felt that the amount of prescribed burning done in the forest was adequate for engendering a feeling of protection to life and property, yet many were still suspicious of this management practice. These initial findings indicate several areas in which further research would be useful including the efficacy of education programs for community members and improved communication of burn plans by land managers. PMID:17001507

  16. Detailed glaciochemical investigations in southern Victoria Land - a proxy climatic record

    SciTech Connect

    Mayewski, P.A.

    1987-09-01

    Local accumulation-basins in the Transantarctic Mountains possess sites suitable for recovering ice-core records that are valuable for studying climate change. These sites are also unique, because they are close to the sites of other ice-core studies and to areas with established terrestrial records. The objective is to study a snowpit in detail and collect ice cores in southern Victoria Land; this work will be similar to the investigations that the authors has conducted in south Greenland and in the Dominion Range near the Beardmore Glacier. The proposed sites are in Convoy, Asgard, and Royal Society ranges. The authors will select one site at which he will recover two ice cores, each approximately 200 to 300 meters in depth. Samples will be analyzed for major anions (chloride, sulfate, nitrate, fluoride) and cations (sodium, potassium, magnesium, ammonium, silicate), total acidity, conductivity, density, and core stratigraphy with dating provided by cross-calibration of all of the preceding plus total beta-activity, lead-210, oxygen isotopes, and microparticles. This investigation will yield a detailed record of several thousand years of glacial history, climate change, and volcanic activity for southern Victoria Land. This record will be compared to existing terrestrial records to add necessary detail and to other global ice-core records to assess global climatic change. It will also help to document volcanic activity for Mount Erebus as well as other volcanos in the Southern Hemisphere and possibly some in the Northern Hemisphere. With this record, the author will be able to evaluate the influence of volcanic and solar activity on climate as well as add greatly to the understanding of the chemistry of the global atmosphere.

  17. Elevated East Antarctic outlet glaciers during warmer-than-present climates in southern Victoria Land

    NASA Astrophysics Data System (ADS)

    Swanger, K.; Marchant, D. R.; Schaefer, J. M.; Winckler, G.; Head, J. W.

    2010-12-01

    We document Plio-Pleistocene changes in the level of Taylor Glacier, an outlet glacier in southern Victoria Land that drains Taylor Dome on the periphery of the East Antarctic Ice Sheet (EAIS). Chronologic control comes from 3He cosmogenic-nuclide analyses of 27 boulders sampled from drifts and moraines in Kennar Valley, a small hanging valley that opens onto a peripheral lobe of Taylor Glacier in the Quartermain Mountains. Assuming a constant boulder-erosion rate of 10 cm Myr-1, our preferred age model spans the last 3.1 Myr and calls for stepped ice recession from a local highstand ~200 m above the present Taylor Glacier at the mouth of Kennar Valley. The texture and sedimentology of all mapped moraines and drifts indicate deposition from cold-based ice, analogous with the situation for the modern Taylor Glacier. Correlation of our moraine record with published reports for fluctuations of Taylor Glacier elsewhere in the Quartermain Mountains, and with a dated moraine record for Ferrar Glacier (a second outlet for Taylor Dome) in the nearby Wilkness Mountains, reveals consistent ice-surface changes, highlighting minor, but widespread ice recession in southern Victoria Land since the mid to late Pliocene. The combined records show an atypical relationship with average global temperatures, with higher-than-present ice levels occurring during globally warm periods, including the Pliocene climatic optimum (˜3.1 Ma), Marine Oxygen Isotope Stage (MIS) 31 (~1.1 Ma), and the penultimate interglacial, MIS 5.5 (~120 ka). The combined records also suggest that the rate of ice-surface lowering for both outlet glaciers accelerated after the Mid-Pleistocene transition at ~0.9 Myr.

  18. 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...

  19. Lake Mead, NV

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Lake Mead, Nevada, (36.0N, 114.5E) where the water from the Colorado River empties after it's 273 mile journey through the Grand Canyon of Arizona is the subject of this photo. Other features of interest are Hoover Dam on the south shore of Lake Mead where cheap hydroelectric power is secondary to the water resources made available in this northern desert region and the resort city of Las Vegas, just to the west of Lake Mead.

  20. The impact of the African Great Lakes on the regional climate in a dynamically downscaled CORDEX simulation

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Panitz, Hans-Jürgen; Davin, Edouard; van Lipzig, Nicole

    2014-05-01

    stability, increased downwind precipitation, stronger winds, and the formation of local circulation patterns. Particular attention is payed to the impact of lakes on extreme night-time convection over Lake Victoria. This is achieved through comparison to a model integration excluding lake effects.

  1. Great Lakes Literacy Principles

    NASA Astrophysics Data System (ADS)

    Fortner, Rosanne W.; Manzo, Lyndsey

    2011-03-01

    Lakes Superior, Huron, Michigan, Ontario, and Erie together form North America's Great Lakes, a region that contains 20% of the world's fresh surface water and is home to roughly one quarter of the U.S. population (Figure 1). Supporting a $4 billion sport fishing industry, plus $16 billion annually in boating, 1.5 million U.S. jobs, and $62 billion in annual wages directly, the Great Lakes form the backbone of a regional economy that is vital to the United States as a whole (see http://www.miseagrant.umich.edu/downloads/economy/11-708-Great-Lakes-Jobs.pdf). Yet the grandeur and importance of this freshwater resource are little understood, not only by people in the rest of the country but also by many in the region itself. To help address this lack of knowledge, the Centers for Ocean Sciences Education Excellence (COSEE) Great Lakes, supported by the U.S. National Science Foundation and the National Oceanic and Atmospheric Administration, developed literacy principles for the Great Lakes to serve as a guide for education of students and the public. These “Great Lakes Literacy Principles” represent an understanding of the Great Lakes' influences on society and society's influences on the Great Lakes.

  2. A late Holocene paleoclimatic history of Lake Tanganyika, East Africa

    NASA Astrophysics Data System (ADS)

    Stager, J. Curt; Cocquyt, Christine; Bonnefille, Raymonde; Weyhenmeyer, Constanze; Bowerman, Nicole

    2009-07-01

    A nearshore core (LT03-05) from the north basin of Lake Tanganyika provides diatom, pollen, and sedimentary time series covering the last ca. 3800 yr at 15-36 yr resolution. A chronology supported by 21 AMS dates on terrestrial and lacustrine materials allows us to account for ancient carbon effects on 14C ages and to propose refinements of the region's climatic history. Conditions drier than those of today were followed after ca. 3.30 ka by an overall wetting trend. Several century-scale climate variations were superimposed upon that trend, with exceptionally rainy conditions occurring 1.70-1.40 ka, 1.15-0.90 ka, 0.70-0.55 ka, and 0.35-0.20 ka. Around 0.55-0.35 ka, during the Spörer sunspot minimum, drier conditions developed in the northern Tanganyika basin while more humid conditions were registered at Lakes Victoria and Naivasha. This indicates significant variability in the nature and distribution of near-equatorial rainfall anomalies during much of the Little Ice Age.

  3. Large geodetic time series constraining the spatial distribution and the time evolution of the velocity field at the western tip of the Aden Ridge in Afar

    NASA Astrophysics Data System (ADS)

    Doubre, C.; Deprez, A.; Masson, F.; Socquet, A.; Ulrich, P.; Ibrahim Ahmed, S.; de Chabalier, J. B.; Ahmadine Omar, A.; Vigny, C.; Ruegg, J. C.

    2014-12-01

    We present the results of the last GPS campaign conducted over the Djiboutian part of Eastern Afar. A large and dense geodetic network has been measured regularly since the 90's, and allows an accurate determination of the velocity field associated with the western tip of the Arabia-Somalia divergent plate boundary. Within the Tadjoura Gulf, the Aden ridge consists of a series of 3 en échelon, submerged spreading segments, except for the Asal segment, which is partly above water. The repetition of 6 to 7 measurements together with 6 permanent continuous GNSS stations allow an opportunity to study the spatial distribution of the active extension in relation to these 3 segments, but also to study time variations of the displacements, which are greatly expected to be transitory because of the occurrence of dyking events, small to intermediate seismic events, and volcanic activity. The divergent motion of the two margins of the Gulf occurs at ~15 mm/yr, which is consistent with the long-term estimates of the Arabia-Somalia motion. Across the Asal segment, this value confirms that the effect of the dyking event in 1978 has ended. The velocity gradients show that the deformation is distributed from the southern to the northern rift shoulder. As revealed by the InSAR data however, the along-axis variations of the deformation pattern, i.e. clear superficial active faults in the SE part of the rift and deep opening in the NW part, suggests the remaining influence of the previous dyke intrusions within the segment inner floor. The time series show that the velocity field was more heterogeneous before 2003, when the micro-seismic activity was significant, particularly around the volcanic center. The striking feature of the time evolution of the velocity field consists in the transition from an extension mainly localized across the Asal segment before 2003 to an extension more distributed, implying the influence of the southern Quaternary structures forming the Gaggade and

  4. Structure and segmentation of the eastern Gulf of Aden basin and the Sheba ridge from gravity, bathymetric and magnetic anomalies: implications for accretion processes

    NASA Astrophysics Data System (ADS)

    D'Acremont, E.; Leroy, S.; Maia, M.; Gente, P.; Autin, J.

    2007-12-01

    The eastern Gulf of Aden is a key place for investigating seafloor spreading processes and the evolution in space and time of the margin and ridge segmentation. The rifting of the Gulf that separated Arabia from Somalia started around 35 Ma ago followed by oceanic accretion from at least17.6 Ma. Bathymetric, gravity and magnetic data from the Encens-Sheba cruise are used to study the structure and segmentation of the eastern part of the basin and ridge, which have strong implications for accretion processes. The segmentation of the first oceanic spreading centre, which is dated at least 17.6 Ma by the magnetic anomaly (A5d) identification, seems to be directly related to the structural geometry of the margins. Then, magmatic processes governed the evolution of the segmentation. The segmentation of the oceanic crust evolved, by eastward propagation of the western segment, from three segments (from an5d to an5) to two segments (from an5). At 6 Ma (an3a) a third segment appeared by duplication of the Socotra transform fault, maybe due to a regional kinematics change. The Encens-Sheba oceanic domain is divided in two distinct areas trending NE-SW perpendicular to the Sheba ridge. (1) The Eastern area is characterized by a shorter wavelength variation of the axial segmentation with two spreading segments 30 to 40 km long, and by a thin crust particularly on the northern and southern ends of its flanks. (2) The Western zone, whose axial segment is more than 120 km long, is characterized by a thick crust and/or a hot mantle and no axial rift valley. This abnormal volcanic activity for a slow spreading ridge is emphasized by bathymetric highs with 5-10 km wide volcanic edifices, and by a negative anomaly of the MBA. These different results support the presence of an off-axis thermal anomaly located below the southern flank of the Sheba ridge. The magnetic anomalies and spreading asymmetry reveal that the location of this thermal anomaly might be relatively recent (~ 10 Ma

  5. High-resolution estimates of Nubia-Somalia plate motion since 20 Ma from reconstructions of the Southwest Indian Ridge, Red Sea, and Gulf of Aden

    NASA Astrophysics Data System (ADS)

    DeMets, C.; Merkouriev, S.

    2016-07-01

    Large gaps and inconsistencies remain in published estimates of Nubia-Somalia plate motion based on reconstructions of seafloor spreading data around Africa. Herein, we use newly available reconstructions of the Southwest Indian Ridge at ˜1-Myr intervals since 20 Ma to estimate Nubia-Somalia plate motion farther back in time than previously achieved and with an unprecedented degree of temporal resolution. At the northern end of the East African rift, our new estimates of Nubia-Somalia motion for six times from 0.78 Ma to 5.2 Ma differ by only 2% from the rift-normal component of motion that is extrapolated from a recently estimated GPS angular velocity. The rate of rift-normal extension thus appears to have remained steady since at least 5.2 Ma. Our new rotations indicate that the two plates have moved relative to each other since at least 16 Ma and possibly longer. Motion has either been steady since at least 16 Ma or accelerated modestly between 6 and 5.2 Ma. Our Nubia-Somalia rotations predict 42.5±3.8 km of rift-normal extension since 10.6 Ma across the well-studied, northern segment of the Main Ethiopian Rift, consistent with 40-50 km estimates for extension since 10.6 Myr based on seismological surveys of this narrow part of the plate boundary. Nubia-Somalia rotations are also derived by combining newly estimated Somalia-Arabia rotations that reconstruct the post-20-Ma opening of the Gulf of Aden with Nubia-Arabia rotations estimated via a probabilistic analysis of plausible opening scenarios for the Red Sea. These rotations predict Nubia-Somalia motion since 5.2 Myr that is consistent with that determined from Southwest Indian Ridge data and also predict 40±3 km of rift-normal extension since 10.6 Ma across the Main Ethiopian Rift, consistent with our 42.5±3.8 km Southwest Indian Ridge estimate. Our new rotations exclude at high confidence level previous estimates of 12±13 km and 123±14 km for rift-normal extensions across the Main Ethiopian Rift since

  6. Lake level change and total water discharge in East Africa Rift Valley from satellite-based observations

    NASA Astrophysics Data System (ADS)

    Hassan, Ayman A.; Jin, Shuanggen

    2014-06-01

    The measurement of total basin water discharge is important for understanding the hydrological and climatologic issues related to the water and energy cycles. Climatic extreme events are normal climatic occurrences in Africa. For example, extensive droughts are regular features in the last few decades in parts of East Africa, which suffers from a lack of in situ observations as well as a lack of regional hydrological models. In this study, multi-disciplinary different types of space-borne observations and global hydrological models are used to study total water discharge in the Great Rift Valley of East Africa (i.e. Lakes Victoria, Tanganyika, and Malawi) from January 2003 to December 2012. The data include the following: (1) total water storage (TWS) variations from Gravity Recovery and Climate Experiment (GRACE), (2) the lake level variations from Satellite Alimetric data, (3) rainfall from Tropical Rainfall Measurement Mission (TRMM) products, (4) soil moisture from WaterGAP Global Hydrology Model (WGHM), and (5) water fluxes from Global Land Data Assimilation System (GLDAS). Results show that a significant decline in the average lake level is found for all of the three lakes between 2003 and 2006. GRACE TWS variations of the whole basin area show the same pattern of variation as the average lake level variations estimated from Altimetric data. The TWS in the basin area of Lakes Victoria and Malawi is governed by the surface water stored in each lake itself, while for Lake Tanganyika, it is governed by both surface water and the soil moisture content in the basin area. Furthermore, the effect of rainfall on TWS is also studied. A phase lag of ~ 2 months is found between TRMM rainfall and GRACE TWS (generally, rainfall precedes the GRACE TWS) for the three lakes. In addition, the regional evapotranspiration ET is estimated from the water balance equation using GRACE land-water solutions, rainfall data from TRMM and runoff values obtained as a fraction of rainfall

  7. Lakes, Lagerstaetten, and Evolution

    NASA Astrophysics Data System (ADS)

    Kordesch, E. G.; Park, L. E.

    2001-12-01

    The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of

  8. Lessons from a Lake.

    ERIC Educational Resources Information Center

    Goethals, Susan

    1997-01-01

    Describes a study that included classroom lessons on hydroelectric power, the history and construction of a nearby lake, data recording, the use of field guides, and methods of counting natural populations. The study culmin