WorldWideScience

Sample records for aegean island arc

  1. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece

    Science.gov (United States)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos

    2014-05-01

    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  2. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NARCIS (Netherlands)

    Klaver, M.; Djuly, T.; de Graaf, S.; Sakes, A.; Wijbrans, J.R.; Davies, G.R.; Vroon, P.Z.

    2015-01-01

    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by

  3. Hydrothermal influence on nearshore sediments of Kos Island, Aegean Sea

    Science.gov (United States)

    Megalovasilis, Pavlos; Godelitsas, Athanasios

    2015-04-01

    The Kos-Nisyros volcanic centre is a long-active, Plio-Pleistocene magmatic system in the subduction zone along the easternmost edge of the active Hellenic volcanic arc in the Aegean Sea. Although today there are signs of relative quiescence in volcanic activity, active onshore fumaroles and shallow-sea hydrothermal vents persist on, amongst others, the island of Kos. The present study explores the large-scale imprint of hydrothermally sourced heavy metals and nutrients on the island's coastal marine environment, based on geochemical data collected in September 2007 from hydrothermal waters and surficial nearshore sediments (Kos is severely influenced by ongoing submarine hydrothermal activity, and confirm that shallow-water sediment Fe, Mn, Zn and Pb levels are substantially higher than those of other islands along the Hellenic volcanic arc, and even exceed those of some deep-water hydrothermal vents in other world regions. Evidently, there may be significant metallic sulphide deposits of hydrothermal origin at depth beneath Kos.

  4. A geochemical study of Nea-Kameni hyalodacites (Santorini Volcano, Aegean island arc). Inferences concerning the origin and effects of solfataras and magmatic evolution

    Science.gov (United States)

    Briqueu, Louis; Lancelot, Joël R.

    1984-03-01

    Since the Santorini Volcano (Aegean arc, eastern Mediterranean Sea) collapsed, volcanic activity has been located at the center of the flooded caldera. Over the past 800 years, five lava flows have formed one of the central islets (Nea-Kameni). Since 1951, when the last eruption occurred, a permanent fumarolic activity has remained. We present chemical analyses (major elements, trace-elements and Sr isotopic ratios) of ten samples from the five hyalodacitic lava flows, showing different stages of alteration, from a completely fresh lava up to one bearing native sulfur and other sublimates. Only the macroscopic aspect of these hyalodacites is affected by fumarolic activity. The elements that are mobile as a result of hydrothermal processes, such as the alkaline (K, Rb) or the chalcophile elements (Zn, Pb), show great homogeneity; the same can be said for the Sr isotopic compositions which range from 0.7046 to 0.7049. None of the analyzed samples has an Sr isotopic composition as high as those reported by Puchelt and Hoefs (1971) for rock samples collected in the same lava flows. If we take into account the marine surroundings of Nea-Kameni islet, these observations put severe restraints on the different hypotheses regarding the origin of the halogens (seawater or meteoric water). The contamination processes of these dacitic lavas are clearly less important than assumed by other authors according to previous Sr isotopic data. Finally, the homogeneity of the elements with low partition coefficients is sufficient to show that the magma has not undergone any perceptible evolution during the last 300 years.

  5. Island dynamics and Minoan expansion in the Aegean: the Kythera Island Project

    Directory of Open Access Journals (Sweden)

    Cyprian Broodbank

    1999-11-01

    Full Text Available In recent years archaeologists have become increasingly interested in the investigation of island societies. At a global level, discoveries in the Pacific, Caribbean, Mediterranean and elsewhere have greatly improved our understanding of the antiquity and dynamics of island life. Now archaeologists at the Institute, together with other colleagues, have embarked on a long-term interdisciplinary study of the island of Kythera in the Aegean.

  6. North Aegean island landscapes as ecomuseums: the case of Lesvos Island

    Directory of Open Access Journals (Sweden)

    Evangelos Pavlis

    2017-05-01

    Full Text Available The main advantage of the Aegean islands, in generating national, regional, or international competitiveness, compared to the areas on the continental mainland, is their natural and cultural assets, their cultural landscapes. Consequently, the organized utilization of cultural heritage, rich biodiversity, and the unique Aegean landscape, could make the islands attractive as places to live or work and help them fulfill their sustainability goals. Ecomuseums are ‘in situ’ museums, aimed at local communities and managed by them, aiming at the interpretation, protection, utilization, and promotion of natural and cultural assets of a place, and at the economic revival of marginal regions through the combinational development of small-scale tourism, local manufacturing, and primary production sectors. They could function as laboratories of sustainable development. The island of Lesvos has been selected as a case study for such a potential ecomuseum.

  7. Anthropogenic transformation of the relief of the Aegean Islands

    Directory of Open Access Journals (Sweden)

    Tsermegas Irena

    2015-06-01

    Full Text Available The purpose of this article is to present the role of human impact in the forming and transformation of the relief of the Aegean Islands. The most significant changes (with a displacement of more than 10 bln m3 of rock material are related to the creation of road infrastructure and the construction of agricultural terraces. In order to create stone buildings, 20 mln m3 of rock material was used; for the purposes of air transport a surface area of nearly 2.5 km2 was levelled; many kilometres of artificial shorelines were created and at least 4.5 mln m3 of material was displaced for the purposes of the construction of artificial reservoirs of a total capacity of more than 25 mln m3. A huge amount of material was removed as a result of mining activities. The indirect impact of economic activities on the relief of the discussed area includes mainly slope, fluvial and coastal processes.

  8. Natural tracers for identifying the origin of the thermal fluids emerging along the Aegean Volcanic arc (Greece): Evidence of Arc-Type Magmatic Water (ATMW) participation

    Science.gov (United States)

    Dotsika, E.; Poutoukis, D.; Michelot, J. L.; Raco, B.

    2009-01-01

    The Aegean volcanic arc is the result of a lithosphere subduction process during the Quaternary time. Starting from the Soussaki area, from west to east, the arc proceeds through the islands of Egina, Methana, Milos, Santorini, the Columbus Bank, Kos and Nisyros. Volcano-tectonic activities are still pronounced at Santorini and Nisyros in form of seismic activity, craters of hydrothermal explosions, hot fumaroles and thermal springs. A significant number of cold water springs emerge in the vicinity of hot waters on these islands. Chemical and isotopic analyses were applied on water and fumaroles samples collected in different areas of the volcanic arc in order to attempt the assessment of these fluids. Stable isotopes of water and carbon have been used to evaluate the origin of cold and thermal water and CO 2. Chemical solute concentrations and isotopic contents of waters show that the fluids emerging in Egina, Soussaki, Methana and Kos areas represent geothermal systems in their waning stage, while the fluids from Milos, Santorini and Nisyros proceed from active geothermal systems. The δ 2H-δ 18O-Cl - relationships suggest that the parent hydrothermal liquids of Nisyros and Milos are produced through mixing of seawater and Arc-Type Magmatic Water (ATMW), with negligible to nil contribution of local ground waters and with very high participation of the magmatic component, which is close to 70% in both sites. A very high magmatic contribution to the deep geothermal system could occur at Santorini as well, perhaps with a percentage similar to Nisyros and Milos, but it cannot be calculated because of steam condensation heavily affecting the fumarolic fluids of Nea Kameni before the surface discharge. The parent hydrothermal liquid at Methana originates through mixing of local groundwaters, seawater and ATMW, with a magmatic participation close to 19%. All in all, the contribution of ATMW is higher in the central-eastern part of the Aegean volcanic arc than in the

  9. Plant speciation in continental island floras as exemplified by Nigella in the Aegean Archipelago

    OpenAIRE

    Comes, Hans Peter; Tribsch, Andreas; Bittkau, Christiane

    2008-01-01

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of geographical isolation on non-adaptive radiation and allopatric speciation brought about by genetic drift. The Aegean Archipelago forms a highly fragmented complex of mostly continental shelf islands that have become disconnected from each other and the mainland in relatively recent geological times (ca

  10. Magma evolution in the Pliocene Pleistocene succession of Kos, South Aegean arc (Greece)

    Science.gov (United States)

    Pe-Piper, Georgia; Moulton, Ben

    2008-11-01

    This study investigates the petrogenesis of Pliocene-Quaternary andesites, dacites and rhyolites of the island of Kos. These volcanic rocks differ from other volcanic centres in the South Aegean arc in the narrow range of Pliocene volcanic products, the abundance of high-silica rhyolite, the lower ɛNd for a given Sr isotope composition, and greater depth to the subducting slab. Pliocene and early Pleistocene dacite stocks and rhyolite domes are succeeded by younger tuffs, notably the 0.16 Ma Kos Plateau Tuff derived from a super-eruption of an andesite stratocone now subsided beneath the sea south of Kos. Volcanic products in tuffs have been sampled from lithic clasts. Andesite, dacite and rhyolite all have ɛNd ˜+ 1.5 to -1.5 and 86Sr/ 87Sr ˜ 0.7042; this unusual composition is argued to be the result of subduction of sediments derived from the River Nile. All rock types show structures indicative of widespread magma mixing, including complexly zoned plagioclase, clinopyroxene and amphibole containing glass inclusions of trachyte and rhyolite compositions. The observed rocks result from fractionation and mixing of three principal magma types: (a) calc-alkaline high-Al basalt that fractionated to andesite at the base of crust; (b) partially melted metabasaltic amphibolite underplated at the base of crust, that fractionated to produce high-SiO 2 rhyolite; and (c) a minor component of trachytic magma from partial melting of enriched subcontinental lithospheric mantle. The complexly zoned phenocrysts with glass inclusions provide specific evidence for mixing of these three components. Specifically, it was the emplacement of the andesite into a voluminous rhyolite magma in a mid-crustal magma chamber that led to the explosive Kos Plateau Tuff super-eruption.

  11. The large 1956 earthquake in the South Aegean: Macroseismic field configuration, faulting, and neotectonics of Amorgos Island

    Science.gov (United States)

    Papadopoulos, Gerassimos A.; Pavlides, Spyros B.

    1992-10-01

    New field observations of the seismic intensity distribution of the large (M s = 7.4) South Aegean (Amorgos) earthquake of 9 July 1956 are presented. Interpretations based on local ground conditions, structural properties of buildings and peculiarities of the rupture process lead to a re-evaluation of the macroseismic field configuration. This, together with the aftershock epicentral distribution, quite well defines the earthquake rupture zone, which trends NE-SW and coincides with the Amorgos Astypalea trough. The lateral extent of the rupture zone, however, is about 40% smaller than that predicted for Aegean earthquakes of M s = 7.4. This discrepancy could be attributed to sea-bottom topography changes, which seem to control the rupture terminations, and to relatively high stressdrop with respect to other Aegean earthquakes. Fault plane solutions obtained by several authors indicate either mainly normal faulting with a significant right-lateral strike-slip component or predominantly strike-slip motion. The neotectonism of Amorgos Island, based on new field observations, aerial photograph analysis and fault mechanisms, is consistent with the dip-slip interpretation. The neotectonic master fault of Amorgos and the 1956 seismic faulting appear to belong to the same tectonic phase (NE-SW strike and a southeasterly dip). However, the significant right-lateral strike-slip component supports the idea that the Amorgos region deviates from the simple description for pure extension in back-arc conditions.

  12. Zircon crytallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Science.gov (United States)

    Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.

    2007-01-01

    In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Miff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ??? 60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction). ?? 2007 Geological Society of America.

  13. Zircon crystallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Science.gov (United States)

    Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.

    2007-01-01

    In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Tuff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ~60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction).

  14. Car-borne and on foot scintillometer survey of the Aegean Sea Islands (Greece). Pt. A

    International Nuclear Information System (INIS)

    Pippos, H.S.

    1984-10-01

    The present report deals with the geological, technical and statistical data of the car-borne scintillometer survey (4,750.7 km) of 38 islands and of the on foot radiometry (87.5 km) of 13 islands of the Aegean Sea. Sixty-nine map sheets (scale 1:50,000) have been covered, corresponding to the total surveyed area of 9,464 km 2 . (author)

  15. Magma differentiation fractionates Mo isotope ratios: Evidence from the Kos Plateau Tuff (Aegean Arc)

    Science.gov (United States)

    Voegelin, Andrea R.; Pettke, Thomas; Greber, Nicolas D.; von Niederhäusern, Brigitte; Nägler, Thomas F.

    2014-03-01

    We investigated high temperature Mo isotope fractionation in a hydrous supra-subduction volcano-plutonic system (Kos, Aegean Arc, Greece) in order to address the debate on the δ98/95Mo variability of the continental crust. In this igneous system, where differentiation is interpreted to be dominated by fractional crystallization, bulk rock data from olivine basalt to dacite show δ98/95Mo ratios increasing from + 0.3 to + 0.6‰ along with Mo concentrations increasing from 0.8 to 4.1 μg g- 1. Data for hornblende and biotite mineral separates reveal the extraction of light Mo into crystallizing silicates, with minimum partition coefficients between hornblende-silicate melt and biotite-silicate melt of 0.6 and 0.4 δ98/95Mo, respectively.

  16. Diversification in continental island archipelagos: new evidence on the roles of fragmentation, colonization and gene flow on the genetic divergence of Aegean Nigella (Ranunculaceae).

    Science.gov (United States)

    Jaros, Ursula; Tribsch, Andreas; Comes, Hans Peter

    2018-02-12

    Disentangling the relative roles of past fragmentation (vicariance), colonization (dispersal) and post-divergence gene flow in the genetic divergence of continental island organisms remains a formidable challenge. Amplified fragment length polymorphisms (AFLPs) were used to (1) gain further insights into the biogeographical processes underlying the Pleistocene diversification of the Aegean Nigella arvensis complex; (2) evaluate the role of potential key factors driving patterns of population genetic variability (mating system, geographical isolation and historical contingencies); and (3) test the robustness of conclusions previously drawn from chloroplast (cp) DNA. Genetic diversity was analysed for 235 AFLP markers from 48 populations (497 individuals) representing 11 taxa of the complex using population genetic methods and Bayesian assignment tests. Most designated taxa are identifiable as genetically distinct units. Both fragmentation and dispersal-driven diversification processes occurred at different geological time scales, from Early to Late Pleistocene, specifically (1) sea barrier-induced vicariant speciation in the Cyclades, the Western Cretan Strait and Ikaria; and (2) bi-regional colonizations of the 'Southern Aegean Island Arc' from the Western vs. Eastern Aegean mainland, followed by allopatric divergences in Crete vs. Rhodos and Karpathos/Kasos. Outcrossing island taxa experienced drift-related demographic processes that are magnified in the two insular selfing species. Population genetic differentiation on the mainland seems largely driven by dispersal limitation, while in the Central Aegean it may still be influenced by historical events (island fragmentation and sporadic long-distance colonization). The biogeographical history of Aegean Nigella is more complex than expected for a strictly allopatric vicariant model of divergence. Nonetheless, the major phylogeographical boundaries of this radiation are largely congruent with the geography and

  17. Natural radioactivity in environmental samples from an island of volcanic origin (Milos, Aegean Sea)

    International Nuclear Information System (INIS)

    Florou, H.; Kritidis, P.

    1991-01-01

    Enhanced concentrations of natural radionuclides occur in volcanic islands such as Milos in the Aegean Sea. The natural gamma radiation status of the entire environment in Milos were studied using gamma radiometry. Gamma spectrometry was used to analyse ore samples, sediments and marine biota. While non-living materials showed enhanced levels of natural radioactivity, most of the marine organisms examined did not seem to reflect this radiological status. (UK)

  18. Present situation and future prospects of electricity generation in Aegean Archipelago islands

    International Nuclear Information System (INIS)

    Kaldellis, J.K.; Zafirakis, D.

    2007-01-01

    The Aegean Archipelago is a remote Hellenic area, including several hundreds of scattered islands of various sizes. In these islands more than 600,000 people are living mainly in small remote communities. The main economical activities of the islanders are apart from tourism, seafaring, fishery, agriculture and stock farming. One of the major problems of the area is the insufficient infrastructure, strongly related with the absence of an integrated and cost-effective electrification plan. In this context, the present work is concentrated on analyzing the present situation and demonstrating the future prospects of electricity generation in the Aegean Archipelago islands. For this purpose, one should first investigate the time evolution of the corresponding electricity generation parameters (i.e. annual electricity consumption, peak power demand, capacity factor, specific fuel consumption) for the last 30 years. Subsequently, the corresponding diesel and heavy-oil consumption along with the electricity production cost for every specific autonomous power station of the area are investigated. Special attention is paid in order to estimate the contribution of renewable energy sources (RES) in the energy balance of each island. Finally, an attempt is made to describe in brief the most realistic electricity production solutions available, including the operation of hybrid RES-based power plants in collaboration with appropriate energy storage facilities. Additionally, the idea of connecting the islands of the area with the mainland and interconnecting them is also taken into consideration

  19. Phlebotomine sand flies (Diptera: Psychodidae in the Greek Aegean Islands: ecological approaches

    Directory of Open Access Journals (Sweden)

    Nikolaos Tsirigotakis

    2018-02-01

    Full Text Available Abstract Background Blood-sucking phlebotomine sand flies are the vectors of the protozoan parasites Leishmania spp. Different Phlebotomus species transmit different Leishmania species causing leishmaniases which are neglected diseases emerging/reemerging in new regions. Thirteen sand fly species, ten belonging to the medically important genus Phlebotomus and three belonging to Sergentomyia are known in Greece. An increasing number of human and dog cases are reported each year from all parts of the country including the Aegean Islands. However, no previous study has been conducted on the sand fly fauna on the islands, except for Rhodes and Samos. The aim of this study was to investigate sand fly species in eleven small Aegean islands; to understand species-specific relationships with environmental and climatic factors and to compare sand fly community parameters among islands. A risk analysis was carried out for each species using climatic and environmental variables. Results Nine sand fly species: Phlebotomus neglectus, P. tobbi, P. similis, P. simici, P. perfiliewi, P. alexandri, P. papatasi, Sergentomyia minuta and S. dentata, were collected from the islands studied. Phlebotomus (Adlerius sp. and Sergentomyia sp. specimens were also collected but not identified to the species level. There was a positive effect of distance from the sea on the abundance of P. neglectus, S. minuta and S. dentata, and a negative effect on the abundance of P. tobbi, P. simici and P. similis. In general, temperature preferences of sand fly populations were between 21 and 29 °C. Nevertheless, there were significant differences in terms of temperature and relative humidity preference ranges among species. The most important species found, P. neglectus, was indisputably the most adapted species in the study area with a very high reaction norm, favoring even the lower temperature and humidity ranges. Overall, the sand fly fauna in the islands was very rich but there

  20. The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)

    Science.gov (United States)

    Bachmann, Olivier

    2010-09-01

    The Kos Plateau Tuff is a large (>60 km3) and young (160 k.y.) calc-alkaline, high-SiO2 rhyolitic ignimbrite from the active Kos-Nisyros volcanic center in the Aegean arc (Greece). Combined textural, petrological and geochemical information suggest that (1) the system evolved dominantly by crystal fractionation from (mostly unerupted) more mafic parents, (2) the magma chamber grew over ≥ 250 000 years at shallow depth (˜1.5-2.5 kb) and was stored as a H2O-rich crystalline mush close to its solidus (˜670-750°C), (3) the eruption occurred after a reheating event triggered by the intrusion of hydrous mafic magma at the base of the rhyolitic mush. Rare banded pumices indicate that the mafic magma only mingled with a trivial portion of resident crystal-rich rhyolite; most of the mush was remobilized following partial melting of quartz and feldspars induced by advection of heat and volatiles from the underplated, hotter mafic influx.

  1. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf, and O isotopic ratios in the lavas of Milos and Santorini-geodynamic implications

    Science.gov (United States)

    Briqueu, L.; Javoy, M.; Lancelot, J.R.; Tatsumoto, M.

    1986-01-01

    In this comparative study of variations in the isotopic compositions (Sr, Nd, O and Hf) of the calc-alkaline magmas of the largest two volcanoes, Milos and Santorini, of the Aegean arc (eastern Mediterranean) we demonstrate the complexity of the processes governing the evolution of the magmas on the scale both of the arc and of each volcano. On Santorini, the crustal contamination processes have been limited, effecting the magma gradually during its differentiation. The most differentiated lavas (rhyodacite and pumice) are also the most contaminated. On Milos, by contrast, these processes are very extensive. They are expressed in the 143Nd/144Nd vs. 87Sr/86Sr diagram as a continuous mixing curve between a mantle and a crustal end member pole defined by schists and metavolcanic rocks outcropping on these volcanoes. In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. These isotopic singularities can be correlated with the geodynamic evolution of the Aegean subduction zone, consisting of alternating tectonic phases of distension and compression. The genesis of rhyolitic magmas can be linked to the two phases of distension, and the contamination of the calc-alkaline mantle-derived magmas with the intermediate compressive phase. The isotopic characteristics of uncontaminated calc-alkaline primitive magmas of Milos and Santorini are directly comparable to those of magmas generated in subduction zones for which a contribution of subducted sediments to partial melts from the mantle is suggested, such as in the Aleutian, Sunda, and lesser Antilles island arcs. However, in spite of the importance of the sediment pile in the eastern Mediterranen oceanic crust (6-10 km), the contribution of the subducted terrigenous materials remains of limited amplitude. ?? 1986.

  2. Neogene displacements in the Solomon Islands Arc

    Science.gov (United States)

    Ridgway, J.

    1987-02-01

    The geology and present configuration of the Solomon Island arc can be explained in terms of the Neogene displacement of a single linear chain of islands. The central part of an original arc consisting of Bougainville, Choiseul, Santa Ysabel, Guadalcanal and San Cristobal was displaced to the northeast as a consequence of the attempted subduction of the Woodlark spreading system. Malaita arose on the northeastern side of the arc as a result of interaction between the arc and the Pacific Ocean floor and the volcanic islands of the New Georgia group formed to the southwest in response to the subduction of a spreading ridge, thus giving rise to the present double chain structure of the arc.

  3. Ductile nappe stacking and refolding in the Cycladic Blueschist Unit: insights from Sifnos Island (south Aegean Sea)

    NARCIS (Netherlands)

    Aravadinou, E.; Xypolias, P.; Chatzaras, V.; Iliopoulos, I.; Gerogiannis, N.

    2016-01-01

    New geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the Cycladic Blueschist Unit (CBU) on Sifnos Island (Cyclades, Aegean Sea). We concentrate on north Sifnos, an area characterized by exceptionally

  4. Earthquake location in island arcs

    Science.gov (United States)

    Engdahl, E.R.; Dewey, J.W.; Fujita, K.

    1982-01-01

    A comprehensive data set of selected teleseismic P-wave arrivals and local-network P- and S-wave arrivals from large earthquakes occurring at all depths within a small section of the central Aleutians is used to examine the general problem of earthquake location in island arcs. Reference hypocenters for this special data set are determined for shallow earthquakes from local-network data and for deep earthquakes from combined local and teleseismic data by joint inversion for structure and location. The high-velocity lithospheric slab beneath the central Aleutians may displace hypocenters that are located using spherically symmetric Earth models; the amount of displacement depends on the position of the earthquakes with respect to the slab and on whether local or teleseismic data are used to locate the earthquakes. Hypocenters for trench and intermediate-depth events appear to be minimally biased by the effects of slab structure on rays to teleseismic stations. However, locations of intermediate-depth events based on only local data are systematically displaced southwards, the magnitude of the displacement being proportional to depth. Shallow-focus events along the main thrust zone, although well located using only local-network data, are severely shifted northwards and deeper, with displacements as large as 50 km, by slab effects on teleseismic travel times. Hypocenters determined by a method that utilizes seismic ray tracing through a three-dimensional velocity model of the subduction zone, derived by thermal modeling, are compared to results obtained by the method of joint hypocenter determination (JHD) that formally assumes a laterally homogeneous velocity model over the source region and treats all raypath anomalies as constant station corrections to the travel-time curve. The ray-tracing method has the theoretical advantage that it accounts for variations in travel-time anomalies within a group of events distributed over a sizable region of a dipping, high

  5. On magma fragmentation by conduit shear stress: Evidence from the Kos Plateau Tuff, Aegean Volcanic Arc

    Science.gov (United States)

    Palladino, Danilo M.; Simei, Silvia; Kyriakopoulos, Konstantinos

    2008-12-01

    Large silicic explosive eruptions are the most catastrophic volcanic events. Yet, the intratelluric mechanisms underlying are not fully understood. Here we report a field and laboratory study of the Kos Plateau Tuff (KPT, 161 ka, Aegean Volcanic Arc), which provides an excellent geological example of conduit processes that control magma vesiculation and fragmentation during intermediate- to large-scale caldera-forming eruptions. A prominent feature of the KPT is the occurrence of quite unusual platy-shaped tube pumice clasts in pyroclastic fall and current deposits from the early eruption phases preceding caldera collapse. On macroscopic and SEM observations, flat clast faces are elongated parallel to tube vesicles, while transverse surfaces often occur at ~ 45° to vesicle elongation. This peculiar pumice texture provides evidence of high shear stresses related to strong velocity gradients normal to conduit walls, which induced vesiculation and fragmentation of the ascending magma. Either an increasing mass discharge rate without adequate enlargement of a narrow central feeder conduit or a developing fissure-like feeder system related to incipient caldera collapse provided suitable conditions for the generation of plate tube pumice within magma volumes under high shear during the pre-climactic KPT eruption phases. This mechanism implies that the closer to the conduit walls (where the stronger are the velocity gradients) the larger was the proportion of plate vs. conventional (lensoid) juvenile fragments in the ascending gas-pyroclast mixture. Consequently, plate pumice clasts were mainly entrained in the outer portions of the jet and convecting regions of a sustained, Plinian-type, eruption column, as well as in occasional lateral blast currents generated at the vent. As a whole, plate pumice clasts in the peripheral portions of the column were transported at lower altitudes and deposited by fallout or partial collapse closer to the vent relative to lensoid ones

  6. Creating the electric energy mix of a non-connected Aegean island

    Science.gov (United States)

    Stamou, Paraskevi; Karali, Sophia; Chalakatevaki, Maria; Daniil, Vasiliki; Tzouka, Katerina; Dimitriadis, Panayiotis; Iliopoulou, Theano; Papanicolaou, Panos; Koutsoyiannis, Demetris; Mamasis, Nikos

    2017-04-01

    As the electric energy in the non-connected islands is mainly produced by oil-fueled power plants, the unit cost is extremely high. Here the various energy sources are examined in order to create the appropriate electric energy mix for a non-connected Aegean island. All energy sources (renewable and fossil fuels) are examined and each one is evaluated using technical, environmental and economic criteria. Finally the most appropriate energy sources are simulated considering the corresponding energy works. Special emphasis is given to the use of biomass and the possibility of replacing (even partially) the existing oil-fueled power plant. Finally, a synthesis of various energy sources is presented that satisfies the electric energy demand taking into account the base and peak electric loads of the island. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  7. Geochemical studies on island arc volcanoes

    International Nuclear Information System (INIS)

    Notsu, Kenji

    1998-01-01

    This paper summarizes advances in three topics of geochemical studies on island arc volcanoes, which I and my colleagues have been investigating. First one is strontium isotope studies of arc volcanic rocks mainly from Japanese island arcs. We have shown that the precise spatial distribution of the 87 Sr/ 86 Sr ratio reflects natures of the subduction structure and slab-mantle interaction. Based on the 87 Sr/ 86 Sr ratio of volcanic rocks in the northern Kanto district, where two plates subduct concurrently with different directions, the existence of an aseismic portion of the Philippine Sea plate ahead of the seismic one was suggested. Second one is geochemical monitoring of active arc volcanoes. 3 He/ 4 He ratio of volcanic volatiles was shown to be a good indicator to monitor the behavior of magma: ascent and drain-back of magma result in increase and decrease in the ratio, respectively. In the case of 1986 eruptions of Izu-Oshima volcano, the ratio began to increase two months after big eruptions, reaching the maximum and decreased. Such delayed response is explained in terms of travelling time of magmatic helium from the vent area to the observation site along the underground steam flow. Third one is remote observation of volcanic gas chemistry of arc volcanoes, using an infrared absorption spectroscopy. During Unzen eruptions starting in 1990, absorption features of SO 2 and HCl of volcanic gas were detected from the observation station at 1.3 km distance. This was the first ground-based remote detection of HCl in volcanic gas. In the recent work at Aso volcano, we could identify 5 species (CO, COS, CO 2 , SO 2 and HCl) simultaneously in the volcanic plume spectra. (author)

  8. Lifestyle and health determinants of cardiovascular disease among Greek older adults living in Eastern Aegean Islands: An adventure within the MEDIS study

    Directory of Open Access Journals (Sweden)

    Alexandra Foscolou

    2016-11-01

    Conclusions: Overall, CVD risk seems to be low among Eastern Aegean Islanders; certain differences in CVD risk factors exist between Greek islanders and their counterparts living in Gökçeada, and those differences may be attributed to various environmental, cultural and lifestyle factors.

  9. Decapod crustaceans on the Gökçeada (Imbros island continental shelf (north-eastern Aegean Sea

    Directory of Open Access Journals (Sweden)

    A.S. ATES

    2006-12-01

    Full Text Available The present composition of decapod crustaceans found at the sublittoral depths (5-104 m off the coast of the island of Gökçeada (north-eastern Aegean Sea is presented. A total of 28 species (11 caridean shrimps, 1 thalassinid ghost crab, 7 anomurans and 9 brachyuran crabs and 277 specimens were recorded. The caridean shrimp, Athanas nitescens had the highest abundance with a dominance value of 20.94% in samples. The dominant group is caridean, represented by a total of 11 species and an occurrence frequency of 39.29%.

  10. Controls on magma permeability in the volcanic conduit during the climactic phase of the Kos Plateau Tuff eruption (Aegean Arc)

    Science.gov (United States)

    Degruyter, W.; Bachmann, O.; Burgisser, A.

    2010-01-01

    X-ray computed microtomography (µCT) was applied to pumices from the largest Quaternary explosive eruption of the active South Aegean Arc (the Kos Plateau Tuff; KPT) in order to better understand magma permeability within volcanic conduits. Two different types of pumices (one with highly elongated bubbles, tube pumice; and the other with near spherical bubbles, frothy pumice) produced synchronously and with identical chemical composition were selected for µCT imaging to obtain porosity, tortuosity, bubble size and throat size distributions. Tortuosity drops on average from 2.2 in frothy pumice to 1.5 in tube pumice. Bubble size and throat size distributions provide estimates for mean bubble size (~93-98 μm) and mean throat size (~23-29 μm). Using a modified Kozeny-Carman equation, variations in porosity, tortuosity, and throat size observed in KPT pumices explain the spread found in laboratory measurements of the Darcian permeability. Measured difference in inertial permeability between tube and frothy pumices can also be partly explained by the same variables but require an additional parameter related to the internal roughness of the porous medium (friction factor f 0 ). Constitutive equations for both types of permeability allow the quantification of laminar and turbulent gas escape during ascent of rhyolitic magma in volcanic conduits.

  11. Assessment of island beach erosion due to sea level rise: the case of the Aegean archipelago (Eastern Mediterranean)

    Science.gov (United States)

    Monioudi, Isavela N.; Velegrakis, Adonis F.; Chatzipavlis, Antonis E.; Rigos, Anastasios; Karambas, Theophanis; Vousdoukas, Michalis I.; Hasiotis, Thomas; Koukourouvli, Nikoletta; Peduzzi, Pascal; Manoutsoglou, Eva; Poulos, Serafim E.; Collins, Michael B.

    2017-03-01

    The present contribution constitutes the first comprehensive attempt to (a) record the spatial characteristics of the beaches of the Aegean archipelago (Greece), a critical resource for both the local and national economy, and (b) provide a rapid assessment of the impacts of the long-term and episodic sea level rise (SLR) under different scenarios. Spatial information and other attributes (e.g., presence of coastal protection works and backshore development) of the beaches of the 58 largest islands of the archipelago were obtained on the basis of remote-sensed images available on the web. Ranges of SLR-induced beach retreats under different morphological, sedimentological and hydrodynamic forcing, and SLR scenarios were estimated using suitable ensembles of cross-shore (1-D) morphodynamic models. These ranges, combined with empirically derived estimations of wave run-up induced flooding, were then compared with the recorded maximum beach widths to provide ranges of retreat/erosion and flooding at the archipelago scale. The spatial information shows that the Aegean pocket beaches may be particularly vulnerable to mean sea level rise (MSLR) and episodic SLRs due to (i) their narrow widths (about 59 % of the beaches have maximum widths Report (AR5) of the Intergovernmental Panel on Climate change (IPCC) - a storm-induced sea level rise of 0.6 m is projected to result in a complete erosion of between 31 and 88 % of all beaches (29-87 % of beaches are currently fronting coastal infrastructure and assets), at least temporarily. Our results suggest a very considerable risk which will require significant effort, financial resources and policies/regulation in order to protect/maintain the critical economic resource of the Aegean archipelago.

  12. Macrophthalmus graeffei A. Milne Edwards, 1873 (Crustacea: Brachyura: Macrophthalmidae: a new Indo-Pacific guest off Rhodes Island (SE Aegean Sea, Greece

    Directory of Open Access Journals (Sweden)

    M.A. PANCUCCI-PAPADOPOULOU

    2010-05-01

    Full Text Available A new alien crab, the macrophthalmid Macrophthalmus graeffei, is reported from the eastern coastline of Rhodes Island. The species, of Indo-West Pacific origin, is known from muddy sediments up to about 80 m depth. In the Mediterranean, its presence has been observed along Levantine coasts as well as along the Turkish coast of the Aegean Sea.Macrophthalmus graeffei increases to twelve the number of alien brachyurans present in the Hellenic SE Aegean Sea, ten of them having Indo-Pacific origin.

  13. Source parameters of the M 6.5 Skyros Island (North Aegean Sea earthquake of July 26, 2001

    Directory of Open Access Journals (Sweden)

    A. Kiratzi

    2002-06-01

    Full Text Available Teleseismic body wave modelling, time domain moment tensor inversion of regional waveforms and spectral analysis of the far-field P-wave pulses are used to derive the source parameters of the July 26, 2001 Skyros earthquake (M 6.5. Its epicentre is located south of the Sporades Islands in the North Aegean Sea (Greece. Previous focal mechanism solutions indicate motion on strike-slip faults. The time domain moment tensor inversion is applied for the first time to the regional waveforms of the recently established broadband network in Greece. Its application gave results which are highly consistent with teleseismic waveform modelling. The results of this study, in combination with the distribution of aftershocks, indicate left-lateral strike slip motion on a NW-SE striking fault with parameters: fault plane (strike = 151°, dip = 83°, rake = 7° and auxiliary plane (strike = 60°, dip = 84°, rake = 173°, depth 12 km and M 0 = 5.98e18 N m. Moreover, the time domain moment tensor inversion technique yielded a pure double couple source with negligible CLVD. The spectral analysis of the far-field P-wave pulses resulted in a fault length L ~ 32 km, stress drop ~ 9 bars and average displacement u ~ 30 cm.These values are in very good agreement with those estimated from empirical scaling relations applicable to the Aegean area.

  14. The melt inclusion record from the rhyolitic Kos Plateau Tuff (Aegean Arc)

    Science.gov (United States)

    Bachmann, Olivier; Wallace, Paul J.; Bourquin, Julie

    2010-02-01

    The >60 km3 rhyolitic Kos Plateau Tuff provides an exceptional probe into the behavior of volatile components in highly evolved arc magmas: it is crystal-rich (30-40 vol% crystals), was rapidly quenched by the explosive eruptive process, and contains abundant homogeneous melt inclusions in large quartz crystals. Several methods for measuring major, trace and volatile element concentrations (SIMS, FTIR, Raman spectroscopy, electron microprobe, LA-ICPMS) were applied to these melt inclusions. We found a ~2 wt% range of H2O contents (4.5-6.5 wt% H2O, measured independently by SIMS, FTIR, and Raman spectroscopy) and relatively low CO2 concentrations (15-140 ppm measured by FTIR, with most analyses <100 ppm). No obvious correlations between H2O, CO2, major and trace elements are observed. These observations require a complex, protracted magma evolution in the upper crust that included: (1) vapor-saturated crystallization in a chamber located between 1.5 and 2.5 kb pressure, (2) closed-system degassing (with up to 10 vol% exsolved gas) as melts percolated upwards through a vertically extensive mush zone (2-4 km thick), and (3) periodic gas fluxing from subjacent, more mafic and more CO2-rich magma, which is preserved as andesite bands in pumices. These processes can account for the range of observed H2O and CO2 values and the lack of correlation between volatiles and trace elements in the melt inclusions.

  15. Increased diversity of sessile epibenthos at subtidal hydrothermal vents: seven hypotheses based on observations at Milos Island, Aegean Sea

    Directory of Open Access Journals (Sweden)

    Carlo Nike Bianchi

    2011-06-01

    Full Text Available Research on subtidal hydrothermal vent ecosystems at Milos, Hellenic Volcanic Arc (Aegean Sea, suggested that vent activity increased the species richness of sessile epibenthic assemblages. Based on 303 species found in 6 sites (3 close to vents, 3 farther away, the present paper uses correspondence analysis and species/samples curves to examine the species composition and richness of these assemblages. Differences due to vent proximity were more important than those due to bottom depth and distance from the shore. Diversity was confirmed to be higher near the vents, although none of the 266 species found at the vent sites can be considered as obligate vent-associated species. Seven different, although not mutually exclusive, hypotheses are discussed to explain the pattern of increased epibenthic species diversity at the vent sites, namely: (i vents represent an intermediate disturbance, inducing mortality by the emission of toxic fluids; (ii higher winter temperature allows for the occurrence of warm-water species, which add to the regional background; (iii venting disrupts the homogeneity of the water bottom layer, increasing bottom roughness and hence habitat heterogeneity; (iv deposition of minerals and enhanced bioconstruction by Ca enrichment increment habitat provision; (v fluid emission induces advective mechanisms that favour recruitment; (vi vents emit CO2, nutrients and trace elements that enhance primary productivity; and (vii bacterial chemosynthesis add to photosynthesis to provide a diversity of food sources for the fauna.

  16. Tomographic imaging of subducted lithosphere below northwest Pacific island arcs

    Science.gov (United States)

    Van Der Hilst, R.; Engdahl, R.; Spakman, W.; Nolet, G.

    1991-01-01

    The seismic tomography problem does not have a unique solution, and published tomographic images have been equivocal with regard to the deep structure of subducting slabs. An improved tomographic method, using a more realistic background Earth model and surf ace-reflected as well as direct seismic phases, shows that slabs beneath the Japan and Izu Bonin island arcs are deflected at the boundary between upper and lower mantle, whereas those beneath the northern Kuril and Mariana arcs sink into the lower mantle.

  17. A new species of Berinda (Araneae, Gnaphosidae from the eastern Aegean Islands, Greece

    Directory of Open Access Journals (Sweden)

    Lissner, Jørgen

    2016-04-01

    Full Text Available A new ground spider, Berinda idae Lissner spec. nov. is described from material collected in Kalymnos and Nisyros of the Dodecanese Islands, as well as Santorini and Christiani of the Thira island complex, Cyclades, Greece. The affinity of this species to ist congeners is briefly discussed.

  18. A Spatial Analysis and Game Theoretical Approach Over the Disputed Islands in the Aegean Sea

    Science.gov (United States)

    2016-06-01

    sovereignty of the “Gray Zone Islands” comes forth as the basic conflict between the two countries. This thesis proposes an approach to reconcile this...Thrace. It holds a very important position providing one of the major trade routes between the Eastern and Western worlds. It is the only way to the...disputed islands (Gray Zone Islands) During the 20th century, tensions between both countries have been strained by these issues. Furthermore, the two

  19. Formation of heterogeneous magmatic series beneath North Santorini, South Aegean island arc

    DEFF Research Database (Denmark)

    Bailey, John C; Jensen, E.S.; Hansen, A.

    2008-01-01

    magma formation beneath North Santorini throughout its 500 ka history is attributed to variable transfer of sedimentary components - either terrigenous or pelagic, as bulk sediments or high-temperature partial melts rather than fluids or low-temperature partial melts - from a rupture zone...... in the subducted slab to the overlying mantle. The three main magmatic series followed independent paths of assimilation of upper crustal materials during fractional crystallization. Assimilation was more pronounced at the basaltic stage. The long-lived histories of the three main magmatic series imply repetitive...... melting of isolated mantle regions, ascent of magmas through independent feeder systems, and their residence in separate crustal magma chambers....

  20. Investigation of the stochastic nature of wave processes for renewable resources management: a pilot application in a remote island in the Aegean sea

    Science.gov (United States)

    Moschos, Evangelos; Manou, Georgia; Georganta, Xristina; Dimitriadis, Panayiotis; Iliopoulou, Theano; Tyralis, Hristos; Koutsoyiannis, Demetris; Tsoukala, Vicky

    2017-04-01

    The large energy potential of ocean dynamics is not yet being efficiently harvested mostly due to several technological and financial drawbacks. Nevertheless, modern renewable energy systems include wave and tidal energy in cases of nearshore locations. Although the variability of tidal waves can be adequately predictable, wind-generated waves entail a much larger uncertainty due to their dependence to the wind process. Recent research has shown, through estimation of the wave energy potential in coastal areas of the Aegean Sea, that installation of wave energy converters in nearshore locations could be an applicable scenario, assisting the electrical network of Greek islands. In this context, we analyze numerous of observations and we investigate the long-term behaviour of wave height and wave period processes. Additionally, we examine the case of a remote island in the Aegean sea, by estimating the local wave climate through past analysis data and numerical methods, and subsequently applying a parsimonious stochastic model to a theoretical scenario of wave energy production. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  1. Volcanism in slab tear faults is larger than in island-arcs and back-arcs.

    Science.gov (United States)

    Cocchi, Luca; Passaro, Salvatore; Tontini, Fabio Caratori; Ventura, Guido

    2017-11-13

    Subduction-transform edge propagators are lithospheric tears bounding slabs and back-arc basins. The volcanism at these edges is enigmatic because it is lacking comprehensive geological and geophysical data. Here we present bathymetric, potential-field data, and direct observations of the seafloor on the 90 km long Palinuro volcanic chain overlapping the E-W striking tear of the roll-backing Ionian slab in Southern Tyrrhenian Sea. The volcanic chain includes arc-type central volcanoes and fissural, spreading-type centers emplaced along second-order shears. The volume of the volcanic chain is larger than that of the neighbor island-arc edifices and back-arc spreading center. Such large volume of magma is associated to an upwelling of the isotherms due to mantle melts upraising from the rear of the slab along the tear fault. The subduction-transform edge volcanism focuses localized spreading processes and its magnitude is underestimated. This volcanism characterizes the subduction settings associated to volcanic arcs and back-arc spreading centers.

  2. A Late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean arc

    NARCIS (Netherlands)

    Duermeijer, C.E.; Krijgsman, W.; Langereis, C.G.; Meulenkamp, J.E.; Triantaphyllou, M.V.; Zachariasse, W.J.

    1999-01-01

    Palaeomagnetic measurements have been carried out on Eocene to Pleistocene sediments on the Ionian island of Zakynthos, NW Greece. Magnetostratigraphic constraints, biostratigraphic analyses of planktonic foraminifera and calcareous nannofossils provide a reliable time frame for these deposits.

  3. An extending island arc: The case of Kamchatka

    Science.gov (United States)

    Kozhurin, Andrey; Zelenin, Egor

    2017-06-01

    We report a first estimate of the extension rate of the onshore Kamchatka island arc, it central wider part. This average rate is 17 ± 3 mm/yr over mid-late Quaternary time. The extension is absorbed by slip on major normal active faults of Central Kamchatka, and graben-producing faulting in its volcanic belt. Probable extension of the underwater portion of the arc, its rate remaining unknown, may add up to the total value. The onshore extension rate, established by remote fault scarp measurements on DEMs resembles the numerical modelling estimate of Schellart et al. (2007), suggesting that the primary driving force responsible for the extension at Kamchatka is slab and trench retreat.

  4. Geometry of the Aegean Benioff zones

    Directory of Open Access Journals (Sweden)

    M. Knapmeyer

    1999-06-01

    Full Text Available The morphology of the Aegean Benioff zone was reconstructed using 1366 hypocentres from the PDE catalogue 1973-1997. Two such zones are identified under the Aegean area, a large one (Main Aegean Subduction, MAS spanning the whole Hellenic arc and a smaller and younger one under the Western Peloponnesus. The geometry of the MAS suggests that it blocks its own subduction and, therefore, causes the development of the smaller western zone as a result of a step back process in the Pliocene.

  5. Magma genesis and slab-wedge interaction across an island arc-continent collision zone, East Sunda Arc, Indonesia

    NARCIS (Netherlands)

    Hoogewerff, J.A.

    1999-01-01

    This thesis presents the results of a detailed trace element and isotope geochemistry study into the magma-genesis ofvolcanoes in the Adonara-Pantar Section (APS) ofthe East Sunda Arc in Indonesia, a setting where an oceanic island arc is colliding with a passive continental margin. Sr, Nd, Pb, Ra,

  6. Magma genesis and slab-wedge interaction across an island arc-continent collision zone, East Sunda Arc, Indonesia

    NARCIS (Netherlands)

    Hoogewerff, J.A.

    1999-01-01

    This thesis presents the results of a detailed trace element and isotope geochemistry study into the magma-genesis ofvolcanoes in the Adonara-Pantar Section (APS) ofthe East Sunda Arc in Indonesia, a setting where an oceanic island arc is colliding with a passive continental margin. Sr, Nd, Pb,

  7. The importance of shallow hydrothermal island arc systems in ocean biogeochemistry

    NARCIS (Netherlands)

    Hawkes, J.A.; Connelly, D.P.; Rijkenberg, M.J.A.; Achterberg, E.P.

    2014-01-01

    Hydrothermal venting often occurs at submarine volcanic calderas on island arc chains, typically at shallower depths than mid-ocean ridges. The effect of these systems on ocean biogeochemistry has been under-investigated to date. Here we show that hydrothermal effluent from an island arc caldera was

  8. Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

    Science.gov (United States)

    Bouvet de Maisonneuve, Caroline; Bachmann, Olivier; Burgisser, Alain

    2009-08-01

    Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy” pumice (highly porous with large, sub-rounded vesicles), which form 5-10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly “microvesicular” and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (<50 μm in diameter) vesicles and few mm-sized, irregular voids, (3) grey or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore, record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular, crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in

  9. Tales of some ancient harbors in the Aegean back-arc region: Earthquakes, coastal changes, historical impacts

    Science.gov (United States)

    Stiros, Stathis; Saltogianni, Vasso

    2017-04-01

    Tectonically active terrains are characterized by seismic transient ground motions (shaking) and by permanent ground motions in the vicinity of activated faults, with both effects occasionally leaving their signature on human constructions and the landscape. Especially in coastal areas marked by small tidal ranges and normal water salinity, as is the case with most parts of the Eastern Mediterranean, even small-amplitude tectonic motions can be derived from observations on coastal constructions, mainly harbors, but also on spring chambers in nearly arid environments, sewers, etc. Such observations, if coupled with well-dated observations of destructions and repairs and of changes in the occupation style of ancient sites can permit precious information conveyed from archaeology to tectonics/seismology and vice versa. A transect with harbor remains from Rhodes to the Gulf of Corinth and then till the Ionian Islands provides some excellent examples. The military harbor of Rhodes, in an area of long term uplift, a coded report of which seems to be provided by ancient poet Pindar, was subject to seismic subsidence and destruction, but with major international support, it was repaired, till renewed uplift brought it several meters above the water. In the Corinth area, the Kenchreai harbor was abruptly submerged during a major repair of a temple, as revealed by precious stained glass panels, ready to use but abandoned in shallow water beneath ruins, while radiometric dating of the uplift in the western Lechaion harbor, constrains its excavation in swampy environment not in Roman times, but to the period of flourishing of Corinth in circa 600BC and the colonization of Italy. Farther west, the sea-level mark of the harbor of Aigeira, at Mavra Litharia (Derveni/Akrata) indicates 4m uplift since the Roman period, at least partly seismic, correlating with an exposed reef and the abandonment of the repairs of the theatre of Aigeira. Seismic land uplift explains the demise of

  10. Petrology and tectonics of Phanerozoic continent formation: From island arcs to accretion and continental arc magmatism

    Science.gov (United States)

    Lee, C.-T.A.; Morton, D.M.; Kistler, R.W.; Baird, A.K.

    2007-01-01

    Mesozoic continental arcs in the North American Cordillera were examined here to establish a baseline model for Phanerozoic continent formation. We combine new trace-element data on lower crustal xenoliths from the Mesozoic Sierra Nevada Batholith with an extensive grid-based geochemical map of the Peninsular Ranges Batholith, the southern equivalent of the Sierras. Collectively, these observations give a three-dimensional view of the crust, which permits the petrogenesis and tectonics of Phanerozoic crust formation to be linked in space and time. Subduction of the Farallon plate beneath North America during the Triassic to early Cretaceous was characterized by trench retreat and slab rollback because old and cold oceanic lithosphere was being subducted. This generated an extensional subduction zone, which created fringing island arcs just off the Paleozoic continental margin. However, as the age of the Farallon plate at the time of subduction decreased, the extensional environment waned, allowing the fringing island arc to accrete onto the continental margin. With continued subduction, a continental arc was born and a progressively more compressional environment developed as the age of subducting slab continued to young. Refinement into a felsic crust occurred after accretion, that is, during the continental arc stage, wherein a thickened crustal and lithospheric column permitted a longer differentiation column. New basaltic arc magmas underplate and intrude the accreted terrane, suture, and former continental margin. Interaction of these basaltic magmas with pre-existing crust and lithospheric mantle created garnet pyroxenitic mafic cumulates by fractional crystallization at depth as well as gabbroic and garnet pyroxenitic restites at shallower levels by melting of pre-existing lower crust. The complementary felsic plutons formed by these deep-seated differentiation processes rose into the upper crust, stitching together the accreted terrane, suture and former

  11. Estimation of critical CO2 values when planning the power source in water desalination: The case of the small Aegean islands

    International Nuclear Information System (INIS)

    Karagiannis, Ioannis C.; Soldatos, Peter G.

    2010-01-01

    Climate change is one of the most important issues our world faces today and it is responsible for a number of natural disasters that threaten human life and existence. Carbon dioxide, produced from almost every energy consuming activity, is the dominant greenhouse gas responsible for global warming. Water desalination is an energy intensive activity, and when it is powered by conventional energy sources, significant amounts of CO 2 are released. For every cubic metre of fresh water produced, there is a 2 kg of CO 2 reduction if renewable energy sources (RES) are used instead of electricity from the local grid. On the other hand, the cost of fresh water produced by desalination is much less if conventional sources of energy are used. Making appropriate policy choices require information on both costs and benefits. So here we estimate the critical CO 2 cost, above which desalination units should use renewable energy instead of conventional energy sources. It was found that the critical CO 2 emissions cost can be close to the CO 2 capture cost and in many cases less than the penalties imposed by the European Commission. Several case studies of water desalination in the Aegean islands verify the conclusions.

  12. Setting an ecological baseline prior to the bottom-up establishment of a marine protected area in Santorini island, Aegean Sea

    Directory of Open Access Journals (Sweden)

    M. SALOMIDI

    2016-08-01

    Full Text Available Since 2010, a bottom-up initiative has been launched in Santorini Island (Aegean Sea, Eastern Mediterranean for the establishment of the first fully-protected marine protected area in the Cyclades, aiming at improving fisheries and enhancing responsible recreational uses at sea. Following discussions with local small-scale fishers and divers, two sites along the southern and southeastern coasts of the island were suggested as suitable to this end. In 2012, a baseline study was conducted at these areas to assess their state and provide an ecological snapshot that would enable sound designation and monitoring. Several ad hoc indices and metrics were applied, taking into account structural and functional features of the upper infralittoral algae and Posidonia oceanica beds. An integrated assessment of the infralittoral fish assemblages and their associated benthic communities was also performed. Our most important findings were: (i the low total fish biomass and the absence of adult top predators, indicating overfishing; (ii the overgrazing effects of the overabundant alien herbivore spinefoot fishes (Siganus spp., as reflected by the abnormal structure of the algal communities; (iii the scarcity of signs of pollution or other direct anthropogenic pressures, as indicated by the good environmental status of the P. oceanica meadows and the upper infralittoral vegetation; and (iv the presence of a rich diversity of species and habitats, especially along the Akrotiri Peninsula and the wider volcanic Caldera. These findings provide useful insights on strengths and weaknesses of the study area and are discussed together with their implications for protection and management.

  13. The 40Ar/39Ar and U/Pb dating of young rhyolites in the Kos-Nisyros volcanic complex, Eastern Aegean Arc, Greece: Age discordance due to excess 40Ar in biotite

    Science.gov (United States)

    Bachmann, O.; Schoene, B.; Schnyder, C.; Spikings, R.

    2010-08-01

    High-precision dating of Quaternary silicic magmas in the active Kos-Nisyros volcanic center (Aegean Arc, Greece) by both 40Ar/39Ar on biotite and U/Pb on zircon reveals a complex geochronological story. U/Pb ID-TIMS multi and single-grain zircon analyses from 3 different units (Agios Mammas and Zini domes, Kefalos Serie pyroclasts) range in age from 0.3 to 0.5 to 10-20 Ma. The youngest dates provide the maximum eruption age, while the oldest zircons indicate inheritance from local continental crust (Miocene and older). Step-heating 40Ar/39Ar experiments on 1-3 crystals of fresh biotite yielded highly disturbed Ar-release patterns with plateau ages typically older than most U/Pb ages. These old plateau ages are probably not a consequence of inheritance from xenocrystic biotites because Ar diffuses extremely fast at magmatic temperatures and ratios are reset within a few days. On the basis of (1) elevated and/or imprecise 40Ar/36Ar ratios, (2) shapes of the Ar release spectra, and (3) a high mantle 3He flux in the Kos-Nisyros area, we suggest that biotite crystals retained some mantle 40Ar that led to the observed, anomalously old ages. In contrast, sanidine crystals from the only sanidine-bearing unit in the Kos-Nisyros volcanic center (the caldera-forming Kos Plateau Tuff) do not appear to store any excess 40Ar relative to atmospheric composition. The eastern edge of the Aegean Arc is tectonically complex, undergoing rapid extension and located close to a major structural boundary. In such regions, which are characterized by high fluxes of mantle volatiles, 40Ar/39Ar geochronology on biotite can lead to erroneous results due to the presence of excess 40Ar and should be checked either against 40Ar/39Ar sanidine or U/Pb zircon ages.

  14. A geochemical and geochronological section through the Eastern Aegean

    Science.gov (United States)

    Boehm, Katharina; Kuiper, Klaudia; Vroon, Pieter; Wijbrans, Jan

    2017-04-01

    The convergence of Africa and Eurasia and the subduction of a oceanic lithosphere of narrow basins between Gondwana terranes has controlled the geological evolution of the Eastern Mediterranean region since the Cretaceous. This resulted in back-arc extension and lithospheric thinning caused by slab roll-back together with the westward extrusion of Anatolia, in the southwards retreat and stepwise development of the subduction system and also in a low velocity seismic anomaly gap between the Cyprus and Hellenic slab and other slab segments. However, the exact timing of all these events in the Eastern Mediterranean region is still a matter of debate, and the purpose of this study is therefore to disentangle when terrains collided and slab detached in the last 30Ma. In a N-S transect magmatic rocks of the Aegean plate are studied, including volcanics from the islands Nisyros, Kos, Patmos, Chios, Lesbos and Samothraki. Major- and trace elements as well as Sr-Nd-Hf-Pb-O isotopes are used to interpret the different features of the Aegean subduction zone. With this geochemical approach the extend of upwelling hot asthenospheric material from the slab tear can be traced in the recent to Eocene volcanic rocks. The volcanic rocks give a wide scatter in classification diagrams and pose for example the question how the sodium rich volcanic products of Patmos can be explained. On the other hand Chios seems to play a key role around 15 Ma years in a phase of relatively low volcanic activity. To get a reliable timeline of the subduction in the Aegean since the Eocene we are aiming to tie our chemical and isotopic data to parallel obtained geochronological ages. New 40Ar/39Ar data will allow us to get the needed resolution for this time span and material.

  15. Seismic activity around and under Krakatau volcano, Sunda Arc: constraints to the source region of island arc volcanics

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

    2002-01-01

    Roč. 46, č. 3 (2002), s. 545-565 ISSN 0039-3169 R&D Projects: GA ČR GA205/97/0898; GA AV ČR IAA3012002 Institutional research plan: CEZ:AV0Z3012916 Keywords : Krakatau * Sunda Strait seismicity * island arc volcanism * subduction * Wadati-Benioff zone Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.571, year: 2002

  16. Costs of Low-Scale Distance Learning Programs: A Case of Distance Learning Courses in the Aegean Islands.

    Directory of Open Access Journals (Sweden)

    Costas Tsolakidis

    2010-03-01

    Full Text Available The advance of Information and Communication Technology (ICT and the reduction of cost in digital applications motivate course designers to develop new application of distance learning programs so as to meet the increasing educational needs in the knowledge-based society. As a consequence, distance learning courses are increasing in number, credibility and acceptability all over the world. The question is whether these programs are efficient in terms of costs. The main theme of this work is to investigate cost behaviour and estimate cost efficiency of distance learning courses applied in low-inhabited, remote islands. The target group consists of high school students of Grade I. The distance learning course that is designed uses several scenarios of the “what-if form” and reaches the conclusion that cost of such solutions is far lower than that of any traditional course, even at the absence of scale economies.

  17. Bivergent thrust wedges surrounding oceanic island arcs: Insight from observations and sandbox models of the northeastern caribbean plate

    Science.gov (United States)

    ten Brink, Uri S.; Marshak, S.; Granja, Bruna J.L.

    2009-01-01

    At several localities around the world, thrust belts have developed on both sides of oceanic island arcs (e.g., Java-Timor, Panama, Vanuatu, and the northeastern Caribbean). In these localities, the overall vergence of the backarc thrust belt is opposite to that of the forearc thrust belt. For example, in the northeastern Caribbean, a north-verging accretionary prism lies to the north of the Eastern Greater Antilles arc (Hispaniola and Puerto Rico), whereas a south-verging thrust belt called the Muertos thrust belt lies to the south. Researchers have attributed such bivergent geometry to several processes, including: reversal of subduction polarity; subduction-driven mantle flow; stress transmission across the arc; gravitational spreading of the arc; and magmatic inflation within the arc. New observations of deformational features in the Muertos thrust belt and of fault geometries produced in sandbox kinematic models, along with examination of published studies of island arcs, lead to the conclusion that the bivergence of thrusting in island arcs can develop without reversal of subduction polarity, without subarc mantle flow, and without magmatic inflation. We suggest that the Eastern Greater Antilles arc and comparable arcs are simply crustalscale bivergent (or "doubly vergent") thrust wedges formed during unidirectional subduction. Sandbox kinematic modeling suggests, in addition, that a broad retrowedge containing an imbricate fan of thrusts develops only where the arc behaves relatively rigidly. In such cases, the arc acts as a backstop that transmits compressive stress into the backarc region. Further, modeling shows that when arcs behave as rigid blocks, the strike-slip component of oblique convergence is accommodated entirely within the prowedge and the arc-the retrowedge hosts only dip-slip faulting ("frontal thrusting"). The existence of large retrowedges and the distribution of faulting in an island arc may, therefore, be evidence that the arc is

  18. Aseismic blocks and destructive earthquakes in the Aegean

    Science.gov (United States)

    Stiros, Stathis

    2017-04-01

    Aseismic areas are not identified only in vast, geologically stable regions, but also within regions of active, intense, distributed deformation such as the Aegean. In the latter, "aseismic blocks" about 200m wide were recognized in the 1990's on the basis of the absence of instrumentally-derived earthquake foci, in contrast to surrounding areas. This pattern was supported by the available historical seismicity data, as well as by geologic evidence. Interestingly, GPS evidence indicates that such blocks are among the areas characterized by small deformation rates relatively to surrounding areas of higher deformation. Still, the largest and most destructive earthquake of the 1990's, the 1995 M6.6 earthquake occurred at the center of one of these "aseismic" zones at the northern part of Greece, found unprotected against seismic hazard. This case was indeed a repeat of the case of the tsunami-associated 1956 Amorgos Island M7.4 earthquake, the largest 20th century event in the Aegean back-arc region: the 1956 earthquake occurred at the center of a geologically distinct region (Cyclades Massif in Central Aegean), till then assumed aseismic. Interestingly, after 1956, the overall idea of aseismic regions remained valid, though a "promontory" of earthquake prone-areas intruding into the aseismic central Aegean was assumed. Exploitation of the archaeological excavation evidence and careful, combined analysis of historical and archaeological data and other palaeoseismic, mostly coastal data, indicated that destructive and major earthquakes have left their traces in previously assumed aseismic blocks. In the latter earthquakes typically occur with relatively low recurrence intervals, >200-300 years, much smaller than in adjacent active areas. Interestingly, areas assumed a-seismic in antiquity are among the most active in the last centuries, while areas hit by major earthquakes in the past are usually classified as areas of low seismic risk in official maps. Some reasons

  19. Temporal geochemical trends in northern Luzon arc lavas (Philippines): implications on metasomatic processes in the island arc mantle

    International Nuclear Information System (INIS)

    Maury, R.C.; Bellon, H.; Jacques, D.; Defant, J.; Joron, J.L.; Mcdermott, F.; Vidal, Ph.

    1998-01-01

    Neogene and Quaternary lavas from Batan, Babuyan de Claro, Camiguin and Calayan islands (northern Luzon arc) display temporal increases in incompatible elements including Cs, Rb, Ba, K, La, Ce, Th, U, Ta, Hf and Zr from volcanoes older than 3 Ma to younger ones. These enrichments occur either within a single island (Batan) or within an island group (from Calayan to Camiguin and Babuyan). We show that these enrichments result from incompatible element input into the mantle wedge rather than from partial melting or fractionation effects. The fact that highly incompatible elements display temporal enrichment patterns in Batan lavas whatever their chemical properties indicates that hydrous fluids are not the only metasomatic agents operating in the mantle wedge and that slab-derived melts (adakitic magmas) may also be involved. The coupled temporal variation patterns of large ion lithophile elements and Sr-Nd isotopes suggest that the metasomatic budgets beneath the southern group of islands are mainly controlled by hydrous fluids inputs. In contrast, young Batan lavas likely derive from a mantle source mostly metasomatized by adakitic magmas. (authors)

  20. Fundamental structure model of island arcs and subducted plates in and around Japan

    Science.gov (United States)

    Iwasaki, T.; Sato, H.; Ishiyama, T.; Shinohara, M.; Hashima, A.

    2015-12-01

    The eastern margin of the Asian continent is a well-known subduction zone, where the Pacific (PAC) and Philippine Sea (PHS) plates are being subducted. In this region, several island arcs (Kuril, Northeast Japan, Southwest Japan, Izu-Bonin and Ryukyu arcs) meet one another to form a very complicated tectonic environment. At 2014, we started to construct fundamental structure models for island arcs and subducted plates in and around Japan. Our research is composed of 6 items of (1) topography, (2) plate geometry, (3) fault models, (4) the Moho and brittle-ductile transition zone, (5) the lithosphere-asthenosphere boundary, and (6) petrological/rheological models. Such information is basic but inevitably important in qualitative understanding not only for short-term crustal activities in the subduction zone (particularly caused by megathrust earthquakes) but also for long-term cumulative deformation of the arcs as a result of strong plate-arc/arc-arc interactions. This paper is the first presentation of our research, mainly presenting the results of items (1) and (2). The area of our modelling is 12o-54o N and 118o-164o E to cover almost the entire part of Japanese Islands together with Kuril, Ryukyu and Izu-Bonin trenches. The topography model was constructed from the 500-m mesh data provided from GSJ, JODC, GINA and Alaska University. Plate geometry models are being constructed through the two steps. In the first step, we modelled very smooth plate boundaries of the Pacific and Philippine Sea plates in our whole model area using 42,000 earthquake data from JMA, USGS and ISC. For 7,800 cross sections taken with several directions to the trench axes, 2D plate boundaries were defined by fitting to the earthquake distribution (the Wadati-Benioff zone), from which we obtained equi-depth points of the plate boundary. These equi-depth points were then approximated by spline interpolation technique to eliminate shorter wave length undulation (75-150 km), but provide a

  1. Eocene to Miocene back-arc basin basalts and associated island arc tholeiites from northern Sulawesi (Indonesia): Implications for the geodynamic evolution of the Celebes basin

    International Nuclear Information System (INIS)

    Rangin, C.; Maury, R.C.; Bellon, H.; Cotten, J.; Polve, M.; Priadi, B.; Soeria-Atmadja, R.; Joron, J.L.

    1997-01-01

    Eocene BABB basalts intruded by tholeiitic and calk-alkalic island arc magmatic rocks are reported from the north arm of Sulawesi (Indonesia). Age and geochemical similarities between these basalts and those drilled in the Celebes Sea indicate this North Sulawesi volcanic arc was built on the same oceanic crust. The 25 deg late Neogene clockwise rotation of the north arm of Sulawesi following its collision with fragments of Australia (Sula, Buton) is not sufficient to explain the asymmetrical magnetic anomalies in the Celebes basin. The North Sulawesi island arc could be interpreted as having progressively retreated northward on its own Celebes sea back arc basin, during an episode of Palaeogene-early Neogene tectonic erosion along the trench. (authors)

  2. Lead isotopic compositions of South Sandwich Island volcanic rocks and their bearing on magmagenesis in intra-oceanic island arcs

    International Nuclear Information System (INIS)

    Barreiro, B.

    1983-01-01

    Pb isotope ratios have been measured in 12 volcanic rocks from the South Sandwich Islands. The results are reported. In 207 Pb/ 204 Pb- 206 Pb/ 204 Pb and 208 Pb/ 204 Pb- 206 Pb/ 204 Pb correlation diagrams, the South Sandwich data plot distinctly above the fields for ocean ridge basalts, and yield trends showing apparent mixing with a sedimentary end member similar to South Atlantic pelagic sediments as reported by Chow and Patterson (1962) and this study. Armstrong and Cooper (1971) have likewise shown that volcanics from the Lesser Antilles show mixing trends with North Atlantic sediments in Pb isotope correlation diagrams. The North Atlantic sediments have distinctly higher 206 Pb/ 204 Pb and 208 Pb/ 204 Pb ratios compared to the South Atlantic sediments. The parallel relationships between sediments and volcanic island arc rocks of the North and South Atlantic provide strong evidence for a component of Pb from subducted sediments in the lavas of the west Atlantic basin. In contrast to these data, lavas from the Mariana Arc in the western Pacific show little or no component of Pb from pelagic sediments. The reason for the different behaviors in the two settings is speculative. (author)

  3. K-Ar geochronology and palaeomagnetism of volcanic rocks in the lesser Antilles island arc

    International Nuclear Information System (INIS)

    Briden, J.C.; Rex, D.C.; Faller, A.M.; Tomblin, J.F.

    1979-01-01

    K-Ar age determinations on rocks and minerals from 95 locations in the Lesser Antilles. An age range of 38 - 10 million years was found for the outer arc (Limestone Caribbees) but less than 7.7 million years in the inner arc (Volcanic Caribbees). From Martinique southwards the two arcs are superimposed. These age ranges fit between discontinuities in sea floor spreading in the North Atlantic at about 38 and 9 million years and a causal connection between spreading change and relocation of arc volcanicity is suggested. Paleomagnetic directions at 108 localities in 10 islands fall into normal and reversed groups with 6 sites intermediate and 5 indeterminate. The mean dipole axis is within 2% of the present rotation axis. The data generally agrees with the established geomagnetic polarity time scale but there is some suggestion of a normal polarity event at about 1.18 million years. The paleomagnetic data suggest that in the past 10 million years the Lesser Antilles have not changed their latitude or geographical orientation and the geomagnetic field has averaged that of a central axial dipole. (author)

  4. The geochemistry of marine sediments, island arc magma genesis, and crust-mantle recycling

    International Nuclear Information System (INIS)

    Ben Othman, D.; Paris-6 Univ., 75; White, W.M.; Cornell Univ., Ithaca, NY; Patchett, J.; Arizona Univ., Tucson

    1989-01-01

    To assess the role of sediment subduction and recycling in island arc magma genesis and mantle evolution, we have determined Sr, Nd, and Pb isotope ratios and the concentrations of K, Rb, Cs, Ba, Sr, U, Th, Pb and rare earth elements in 36 modern marine sediments, including Mn nodules, biogenic oozes, and pelagic and hemipelagic clays from the Pacific, Antlantic and Indian Oceans. Sr and Nd isotope ratios and the Sr/Nd concentration ratios in sediments are such that mixing between subducted sediment on the one hand and depleted mantle or subducted oceanic crust on the other can produce mixing arrays which may pass either through or outside of the oceanic basalt Sr-Nd isotope 'mantle array'. Thus whether isotope compositions of island arc volcanics (IAV) plot inside our outside of the mantle array is not a good indication of whether or not their sources contain a subducted sediment component. The presence of subducted sediment in the sources of IAV should lead to Cs/Rb and Pb/Ce ratios which are higher than those in oceanic basalts, and Ba/Rb ratios which may be either higher or lower than oceanic basalts. Simple mixing calculations suggest that as little as a percent or so sediment in island arc magma sources can account for the observed Cs/Rb, Pb/Ce, and Ba/Rb ratios in IAV. However, it does not appear that high Ba/La ratios and negative Ce anomalies in IAV are inherited from sediment in IAV magma sources. It is more likely these features reflect fractionation of alkalis and alkaline earths from rare earths during slab dehydration and metasomatism. Pb isotope ratios in sediments from the Warton Basin south of the Sunda Arc are collinear in 208 Pb/ 204 Pb- 207 Pb/ 204 Pb- 206 Bp/ 204 Pb space with volcanics from West Sunda, but not with volcanics from the East Sunda. This collinearity is consistent with the hypothesis that sediments similar to these are being subducted to the magma genesis zone of the West Sunda Arc. (orig./WB)

  5. Geochemistry of southern Pagan Island lavas, Mariana arc: The role of subduction zone processes

    Science.gov (United States)

    Marske, J.P.; Pietruszka, A.J.; Trusdell, F.A.; Garcia, M.O.

    2011-01-01

    New major and trace element abundances, and Pb, Sr, and Nd isotopic ratios of Quaternary lavas from two adjacent volcanoes (South Pagan and the Central Volcanic Region, or CVR) located on Pagan Island allow us to investigate the mantle source (i.e., slab components) and melting dynamics within the Mariana intra-oceanic arc. Geologic mapping reveals a pre-caldera (780-9.4ka) and post-caldera (<9.4ka) eruptive stage for South Pagan, whereas the eruptive history of the older CVR is poorly constrained. Crystal fractionation and magma mixing were important crustal processes for lavas from both volcanoes. Geochemical and isotopic variations indicate that South Pagan and CVR lavas, and lavas from the northern volcano on the island, Mt. Pagan, originated from compositionally distinct parental magmas due to variations in slab contributions (sediment and aqueous fluid) to the mantle wedge and the extent of mantle partial melting. A mixing model based on Pb and Nd isotopic ratios suggests that the average amount of sediment in the source of CVR (~2.1%) and South Pagan (~1.8%) lavas is slightly higher than Mt. Pagan (~1.4%) lavas. These estimates span the range of sediment-poor Guguan (~1.3%) and sediment-rich Agrigan (~2.0%) lavas for the Mariana arc. Melt modeling demonstrates that the saucer-shaped normalized rare earth element (REE) patterns observed in Pagan lavas can arise from partial melting of a mixed source of depleted mantle and enriched sediment, and do not require amphibole interaction or fractionation to depress the middle REE abundances of the lavas. The modeled degree of mantle partial melting for Agrigan (2-5%), Pagan (3-7%), and Guguan (9-15%) lavas correlates with indicators of fluid addition (e.g., Ba/Th). This relationship suggests that the fluid flux to the mantle wedge is the dominant control on the extent of partial melting beneath Mariana arc volcanoes. A decrease in the amount of fluid addition (lower Ba/Th) and extent of melting (higher Sm/Yb), and

  6. Focal mechanisms in the southern Aegean from temporary seismic networks - implications for the regional stress field and ongoing deformation processes

    Science.gov (United States)

    Friederich, W.; Brüstle, A.; Küperkoch, L.; Meier, T.; Lamara, S.; Egelados Working Group

    2014-05-01

    The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini-Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW-SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE-SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east-west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW-SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except in volcanic areas, where both

  7. THE NEOPROTEROZOIC ISLAND-ARC ASSOCIATION OF THE MUKODEK GOLD-ORE FIELD, NORTHERN BAIKAL AREA

    Directory of Open Access Journals (Sweden)

    V. A. Vanin

    2014-01-01

    Full Text Available Metamorphosed volcanic rocks of the Ushmukan suite were studied in the Mukodek gold-ore field located in the Baikal-Muya belt in the Northern Baikal area, Russia. The Ushmukan suite shows interleaving of ortoschists which compositions are widely variable. Basalt-andesite-dacite series of normal alkalinity are the substrate of the studied metavolcanic rocks. Based on the set of geochemical characteristics, it is concluded that the rocks were formed in suprasubduction geodynamic conditions corresponding to a mature island arc. The proximity of the geological locations and the similarity of the geochemical characteristics of the volcanic rocks of the Ushmukan suite and rocks of the Kelyan suite (Neoproterozoic, 823 Ma, which have similar compositions, give grounds to consider these two rock suites as age peers. Specific features of gold distribution through the Mukodek gold-ore field are analyzed. Industrial gold contents are recorded only in berezite-listvenite metasomatic rocks of the gold-quartz-sulfide formation which were formed on metavolcanic rocks of the Ushmukan suite. It is concluded that the volcanic rocks, which are specific of the island-arc setting, could be a source of gold for deposits in the Mukodek gold-ore field. 

  8. Seismological Imaging of Melt Production Regions Beneath the Backarc Spreading Center and Volcanic Arc, Mariana Islands

    Science.gov (United States)

    Wiens, Douglas; Pozgay, Sara; Barklage, Mitchell; Pyle, Moira; Shiobara, Hajime; Sugioka, Hiroko

    2010-05-01

    We image the seismic velocity and attenuation structure of the mantle melt production regions associated with the Mariana Backarc Spreading Center and Mariana Volcanic Arc using data from the Mariana Subduction Factory Imaging Experiment. The passive component of this experiment consisted of 20 broadband seismographs deployed on the island chain and 58 ocean-bottom seismographs from June, 2003 until April, 2004. We obtained the 3D P and S wave velocity structure of the Mariana mantle wedge from a tomographic inversion of body wave arrivals from local earthquakes as well as P and S arrival times from large teleseismic earthquakes determined by multi-channel cross correlation. We also determine the 2-D attenuation structure of the mantle wedge using attenuation tomography based on local and regional earthquake spectra, and a broader-scale, lower resolution 3-D shear velocity structure from inversion of Rayleigh wave phase velocities using a two plane wave array analysis approach. We observe low velocity, high attenuation anomalies in the upper mantle beneath both the arc and backarc spreading center. These anomalies are separated by a higher velocity, lower attenuation region at shallow depths (< 80 km), implying distinct magma production regions for the arc and backarc in the uppermost mantle. The largest magnitude anomaly beneath the backarc spreading center is found at shallower depth (25-50 km) compared to the arc (50-100 km), consistent with melting depths estimated from the geochemistry of arc and backarc basalts (K. Kelley, pers. communication). The velocity and attenuation signature of the backarc spreading center is narrower than the corresponding anomaly found beneath the East Pacific Rise by the MELT experiment, perhaps implying a component of focused upwelling beneath the spreading center. The strong velocity and attenuation anomaly beneath the spreading center contrasts strongly with preliminary MT inversion results showing no conductivity anomaly in the

  9. Magmatic versus tectonic influence in the Eolian arc: the case of Vulcano and Lipari islands revisited

    Science.gov (United States)

    Ruch, Joel; Di Lorenzo, Riccardo; Vezzoli, Luigina Maria; De Rosa, Rosanna; Acocella, Valerio; Catalano, Stefano; Romagnoli, Gino

    2014-05-01

    The prevalent influence of magma versus tectonics for the edification and the evolution of volcanic zones is matter of debate. Here we focus on Vulcano and Lipari, two active volcanic islands located in the central sector of the Eolian arc (North of Sicily). Both systems are influenced by regional tectonics and affected by historical magmatic events taking place along a NS oriented structure, connecting both islands. We revisit and implement previous structural studies performed during the 1980's considering several new geophysical, geochemical and geodynamical findings. Four extensive structural campaigns have been performed on both islands and along the shorelines in 2012-2013 covering about 80% of the possible accessible outcrops. We collected ~500 measurements (e.g. faults, fractures and dikes) at 40 sites. Overall, most of the observed structures are oriented N-S and NNW-SSE, confirming previous studies, however, almost all features are strikingly dominated by an EW-oriented extensive regime, which is a novelty. These findings are supported by kinematic indicators and suggest a predominant dip-slip component (pitch from 80 and 130°) with alternating left and right kinematics. Marginal faulting in most recent formations have been observed, suggesting that the deformation may occur preferentially during transient deformation related to periods of magmatic activity, instead of resulting from continuous regional tectonic processes. Overall, fault and dike planes are characterized by a dominant eastward immersion, suggesting an asymmetric graben-like structure of the entire area. This may be explained by the presence of a topographic gradient connecting both islands to the deep Gioia basin to the East, leading to a preferential ample gravitational collapse. Finally, we propose a model in which the stress field rotates northward. It transits from a pure right lateral strike-slip regime along the Tindari fault zone (tectonic-dominant) to an extensive regime

  10. Bimodal volcanism in northeast Puerto Rico and the Virgin Islands (Greater Antilles Island Arc): Genetic links with Cretaceous subduction of the mid-Atlantic ridge Caribbean spur

    Science.gov (United States)

    Jolly, Wayne T.; Lidiak, Edward G.; Dickin, Alan P.

    2008-07-01

    Bimodal extrusive volcanic rocks in the northeast Greater Antilles Arc consist of two interlayered suites, including (1) a predominantly basaltic suite, dominated by island arc basalts with small proportions of andesite, and (2) a silicic suite, similar in composition to small volume intrusive veins of oceanic plagiogranite commonly recognized in oceanic crustal sequences. The basaltic suite is geochemically characterized by variable enrichment in the more incompatible elements and negative chondrite-normalized HFSE anomalies. Trace element melting and mixing models indicate the magnitude of the subducted sediment component in Antilles arc basalts is highly variable and decreases dramatically from east to west along the arc. In the Virgin Islands, the sediment component ranges between 4% during the Cenomanian-Campanian interval. The silicic suite, consisting predominantly of rhyolites, is characterized by depleted Al 2O 3 (average Virgin Islands on the east, rhyolites comprise up to 80% of Lower Albian strata (112 to 105 Ma), and about 20% in post-Albian strata (105 to 100 Ma). Farther west, in Puerto Rico, more limited proportions (Atlantic Ridge, which was located approximately midway between North and South America until Campanian times. Within this hypothetical setting the centrally positioned Virgin Islands terrain remained approximately fixed above the subducting ridge as the Antilles arc platform swept northeastward into the slot between the Americas. Accordingly, heat flow in the Virgin Islands was elevated throughout the Cretaceous, giving rise to widespread crustal melting, whereas the subducted sediment flux was limited. Conversely, toward the west in central Puerto Rico, which was consistently more remote from the subducting ridge, heat flow was relatively low and produced limited crustal melting, while the sediment flux was comparatively elevated.

  11. 230Th/234U activity ratio in the products from Izu-Bonin island-arc volcanoes

    International Nuclear Information System (INIS)

    Kurihara, Y.; Takahashi, M.; Sato, J.

    2006-01-01

    Magma genesis at subduction zone is generally inferred to be induced by the partial melting of the mantle wedge by the addition of fluid derived from the subducting slab. Uranium-series disequilibria in the volcanic products are a useful tracer to understand various magma processes. Young island-arc volcanic rocks showed the characteristic feature of excess 234 U over 230 Th. Observation was carried out on the radioactive disequilibrium between 234 U and 230 Th in the volcanic products from Asama volcano and Izu-Mariana island-arc volcanoes. Thorium and Uranium in the volcanic rock samples were separated by anion-exchange resin and purified by TEVA·Spec. and UTEVA·Spec. resins, respectively. Purified Th and U were electrodeposited onto a stainless steel planchet for α-ray counting. U-234 and 230 Th in volcanic rock samples were determined by isotope dilution method coupled with α-ray spectrometry. 230 Th/ 234 U activity ratio in the volcanic products from Asama volcano and Izu-Bonin island-arc volcanoes were in radioactive disequilibrium, enriched in 234 U relative to 230 Th, which is often observed for volcanic products from young island-arc volcanic products. (author)

  12. On the time-scales of magmatism at island-arc volcanoes.

    Science.gov (United States)

    Turner, S P

    2002-12-15

    Precise information on time-scales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the Earth sciences. U-series isotope studies are revolutionizing this field by providing time information in the range 10(2)-10(4) years, which is similar to that of many modern Earth processes. I review how the application of U-series isotopes has been used to constrain the time-scales of magma formation, ascent and storage beneath island-arc volcanoes. Different elements are distilled-off the subducting plate at different times and in different places. Contributions from subducted sediments to island-arc lava sources appear to occur some 350 kyr to 4 Myr prior to eruption. Fluid release from the subducting oceanic crust into the mantle wedge may be a multi-stage process and occurs over a period ranging from a few hundred kyr to less than one kyr prior to eruption. This implies that dehydration commences prior to the initiation of partial melting within the mantle wedge, which is consistent with recent evidence that the onset of melting is controlled by an isotherm and thus the thermal structure within the wedge. U-Pa disequilibria appear to require a component of decompression melting, possibly due to the development of gravitational instabilities. The preservation of large (226)Ra disequilibria permits only a short period of time between fluid addition and eruption. This requires rapid melt segregation, magma ascent by channelled flow and minimal residence time within the lithosphere. The evolution from basalt to basaltic andesite probably occurs rapidly during ascent or in magma reservoirs inferred from some geophysical data to lie within the lithospheric mantle. The flux across the Moho is broadly andesitic, and some magmas subsequently stall in more shallow crustal-level magma chambers, where they evolve to more differentiated compositions on time-scales of a few thousand years or less.

  13. Using experimental petrology to constrain genesis of wet, silicic magmas in the Tonga-Kermadec island arc

    Science.gov (United States)

    Brens, R.; Rushmer, T. A.; Turner, S.; Adam, J.

    2012-12-01

    The Tongan arc system is comprised of a pair of island chains, where the western chain is the active volcanic arc. A range of rock suites, from basaltic andesites (53-56% SiO2) to dacites (64-66% SiO2), has been recovered from Late, Tofua and Fonualei in the Tonga-Kermadec primitive island arc system. For which the question arises: What is the mechanism that allows for silicic magmas to develop in a primitive island arc system? Caufield et al. (2012) suggest that fractional crystallization of a multi magma chamber process, with varying depth, is responsible for the silicic magma generation in this arc. Models such as this one have been proposed and experimentally tested in other systems (Novarupta, Alaska) to explain the origin of these silicic rocks. Our Tongan suite of rocks has had a full geochemical analysis for majors, traces and isotopes. The lavas from Tofua and Late are Fe-rich and have low concentrations of K, Rb, Ba, Zr, REE, Pb and U. However, experimental studies are needed to complement the extensive geochemical analysis done on the Tongan arc. Former geochemical work done on the igneous rocks from both of these volcanic suites from this arc suggests that the source of these rocks extend from 1.5-5.5 km in depth (Caulfield et al., 2012). Here, we present an experimental study of the phase equilibria on a natural andesitic sample (Late 1, from Ewart et al., 1975) from the island of Late. Experiments were run using the temperature constraints between 900 to 1220oC, pressure from 5 to 25 kbars and H2O addition of mostly 5wt% (but some results were obtained at 2wt% in the rocks). In the presence of 5 wt% water, phase equilibria of these experiments show the garnet stability field at >10 kb for 900 oC and increases with increasing temperature, while plagioclase enters at lower pressures when garnet exits. Experimental results currently suggests, at lower temperatures (900-950oC), a fractional crystallization relationship due to shallow level pressures of

  14. Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes

    Directory of Open Access Journals (Sweden)

    W. Friederich

    2014-05-01

    Full Text Available The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earthquakes fall into 16 distinct spatial clusters distributed over the southern Aegean region. For each cluster, a stress inversion could be carried out yielding consistent estimates of the stress field and its spatial variation. At crustal levels, the stress field is generally dominated by a steeply dipping compressional principal stress direction except in places where coupling of the subducting slab and overlying plate come into play. Tensional principal stresses are generally subhorizontal. Just behind the forearc, the crust is under arc-parallel tension whereas in the volcanic areas around Kos, Columbo and Astypalea tensional and intermediate stresses are nearly degenerate. Further west and north, in the Santorini–Amorgos graben and in the area of the islands of Mykonos, Andros and Tinos, tensional stresses are significant and point around the NW–SE direction. Very similar stress fields are observed in western Turkey with the tensional axis rotated to NNE–SSW. Intermediate-depth earthquakes below 100 km in the Nisyros region indicate that the Hellenic slab experiences slab-parallel tension at these depths. The direction of tension is close to east–west and thus deviates from the local NW-oriented slab dip presumably owing to the segmentation of the slab. Beneath the Cretan sea, at shallower levels, the slab is under NW–SE compression. Tensional principal stresses in the crust exhibit very good alignment with extensional strain rate principal axes derived from GPS velocities except

  15. THE SOUTHERN AEGEAN SYSTEM

    Directory of Open Access Journals (Sweden)

    Ina Berg

    2015-08-01

    Full Text Available Although world-systems theory was originally formulated with our modern economic system in mind (Wallerstein 1974, it was not long before archaeologists began to apply it to ancient societies. Archaeologists and world-system theorists alike both argued that Wallerstein had disregarded evidence of interconnected, hierarchical systems in prehistoric times (Schneider 1977; Chase-Dunn & Hall 1991, 1997; Kardulias 1999a. Pailes and Whitecotton (1979 were among the first to modify world-systems theory for use in pre-capitalist settings. Since then many archaeologists have looked at data and regions with a world-systems perspective in mind (e.g. Champion 1989; Bilde et al. 1993; Rowlands & Larsen 1987; Kardulias 1999a. Some have attempted to map Wallerstein's theory directly onto prehistory (Kohl 1979; Whitecotton & Pailes 1986; Ekholm & Friedman 1982. Others have found the world systems model heuristically useful but lacking the analytical power needed for their prehistoric cases (Blanton et al. 1981; Upham 1982; Plog 1983; Alcock 1993. Building on the assumption that ancient societies were not qualitatively, but only quantitatively, different from modern capitalist ones (Schneider 1977; Sherratt & Sherratt 1991, this study applies world systems theory to the Southern Aegean during the Middle and Late Bronze Age (ca. 2000-1550 BC.

  16. Temporal evolution of the Western and Central volcanism of the Aeolian Island Arc (Italy, southern Tyrhhenian Sea)

    Science.gov (United States)

    Leocat, E.; Gillot, P.-Y.; Peccerillo, A.

    2009-04-01

    The Aeolian Archipelago is a volcanic arc in the Southern Tyrrhenian Sea located on the continental margin of the Calabro-Peloritan basement. The Aeolian volcanism occurs in a very complex geodynamic setting linked to the convergence of the European and African plates. For that reason, it is strongly related to regional tectonic lineaments, such as the NW-SE trending Tindari-Letojani (TL) fault. The archipelago consists of seven main islands and several seamounts, which extend around the Marsili Basin, forming a ring-like shape, typical for an island arc. While the seamounts began their activities around 1 Ma , the emerged part is active since about 400 ka. The magmatic products of the whole arc range from typical island arc calc-alkaline (CA) and shoshonitic series, to slightly silica undersaturated potassic alkaline series that are typical of post-collisional settings. Furthermore, the TL fault, along which the Lipari and Vulcano islands are developed, separates a calc-alkaline western sector (Alicudi, Filicudi and Salina islands) from the calc-alkaline to potassic eastern system (Panarea and Stromboli islands) (Peccerillo,1999). This makes of the Aeolian Islands a complex volcanism, with a still controversial origin. In this context, the aim of this work is to constrain the sources and spatio-temporal evolution of this magmatism. We present here new K-Ar ages based on the accurate Cassignol-Gillot technique devoted to the dating of very young rocks (Gillot et Cornette, 1986). These geochronological data were used together with new geochemical data on the same samples. In this study, we attempt to understand the origin of those magmatic events and the relationship between the deep processes and the shallow structures. Our results allow us to define specific periods of very quick geomechemical changes. In the case of Filicudi island, the first rocks range in composition from CA basalts to andesites. This period ended with the edification of the Mte Guardia at 189

  17. CRED 40 m Gridded bathymetry of Howland Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (40 m cell size) bathymetry of the shelf and slope environments of Howland Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  18. CRED 5 m Gridded bathymetry of Jarvis Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the shelf and slope environments of Jarvis Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  19. CRED 40 m Gridded bathymetry of Baker Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (40 m cell size) bathymetry of the shelf and slope environments of Baker Island, Pacific Remote Island Areas, Central Pacific. Almost complete bottom...

  20. Paleozoic subduction complex and Paleozoic-Mesozoic island-arc volcano-plutonic assemblages in the northern Sierra terrane

    Science.gov (United States)

    Hanson, Richard E.; Girty, Gary H.; Harwood, David S.; Schweickert, Richard A.

    2000-01-01

    This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly Complex) overlain by submarine arc-related deposits that record the evolution of three separate island-arc systems in the Late Sevonian-Early Mississippian, Permian, and Late Triassic-Jurassic. The two Paleozoic are packages and the underlying Shoo Fly Complex have an important bearing on plate-tectonic processes affecting the convergent margin outboard of the Paleozoic Cordilleran miogeocline, although their original paleogeographic relations to North America are controversial. The third arc package represents an overlap assemblage that ties the terrane to North America by the Late Triassic and helps constrain the nature and timing of Mesozoic orogenesis. Several of the field-trip stops examine the record of pre-Late Devonian subduction contained in the Shoo Fly Complex, as well as the paleovolcanology of the overlying Devonian to Jurassic arc rocks. Excellent glaciated exposures provide the opportunity to study a cross section through a tilted Devonian volcano-plutonic association. Additional stops focus on plutonic rocks emplaced during the Middle Jurassic arc magmatism in the terrane, and during the main pulse of Cretaceous magmatism in the Sierra Nevada batholith to the east.

  1. North Aegean core complexes, the gravity spreading of a thrust wedge

    NARCIS (Netherlands)

    Kydonakis, Konstantinos; Brun, Jean Pierre; Sokoutis, Dimitrios

    2015-01-01

    The North Aegean core complexes developed in middle Eocene soon after the end of continental block convergence and piling up of the Hellenic Thrust Wedge. They formed during back-arc extension, driven by the Hellenic slab rollback, at the back of the thrust wedge. A series of scaled laboratory

  2. Volcano-Hydrothermal Systems of the Kuril Island Arc (Russia): Geochemistry of the Thermal Waters and Gases.

    Science.gov (United States)

    Kalacheva, E.; Taran, Y.; Voloshina, E.; Kotenko, T.; Tarasov, K.

    2017-12-01

    More than 30 active volcanoes with historical eruptions are known on 20 main islands composing the Kuril Arc. Eight islands - Paramushir, Shiashkotan, Rasshua, Ushishir, Ketoy, Urup, Iturup and Kunashir - are characterized by hydrothermal activity, complementary to the fumarole activity in the craters and volcano slopes. At Paramushir, Shiashkotan, Iturup and Kunashir most of thermal manifestations are acidic to ultra-acidic hot springs associated with hydrothermal aquifers inside volcano edifices. The most powerful of them is the ultra-acid hydrothermal system of Ebeko volcano (Paramushir island) with more than 80 t/day of the chloride output and pH of springs of 1.5. At the summit part of the Ebeko volcano there are 12 thermal fields with the total thermal area exceeding 1 km2. The measured temperatures of fumaroles are from 98º C to 500ºC. Another type of hydrothermal activity are the wide spread coastal hot and neutral springs situated as a rule within the tide zone. Four groups of this type of thermal manifestation were found on the western shore of Shiashkotan island. It have Na-Ca-Cl-SO4 composition with temperatures 50-80°C and TDS 7-8 g/L. Coastal neutral springs were found also on Russhua, Uturup and Kunashir islands. Ushishir volcano-hydrothermal system in the middle of the arc is formed by the absorption of magmatic gases by seawater. In the crater of the Pallas cone (Ketoy island) there is a small Glazok lake with acid SO4 water and pH=2.4, TDS=2g/L, T=12oC. Ketoy volcano on the same island hosts a high temperature hydrothermal system with unusual boiling Ca-Na-SO4 neutral springs and steam vents. Mendeleev and Golovnin volcanoes on Kunashir Island are the southernmost of the Kuril arc. Mendeleev edifice is a centre of a large thermal area with many manifestations of different types including steam vents, acid springs and neutral coastal springs. In a 4.2x4 km wide caldera of Golovnin volcano there are two lakes with acid Cl-SO4 water and numerous

  3. Eocene to Miocene back-arc basin basalts and associated island arc tholeiites from northern Sulawesi (Indonesia): Implications for the geodynamic evolution of the Celebes basin; Basaltes de bassin arriere-arc de l`Eocene-Miocene et tholeiites d`arc insulaire associees du nord Sulawesi (Indonesie): implications pour l`evolution geodynamique du bassin des Celebes

    Energy Technology Data Exchange (ETDEWEB)

    Rangin, C. [Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France); Maury, R.C.; Bellon, H.; Cotten, J. [Universite de Bretagne Occidentale, 29 - Brest (France); Polve, M. [Universite Paul Sabatier, 31 - Toulouse (France); Priadi, B.; Soeria-Atmadja, R. [Department of Geology, ITB, Bandung (Indonesia); Joron, J.L. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Recherche sur l`Etat Condense, les Atomes et les Molecules

    1997-12-31

    Eocene BABB basalts intruded by tholeiitic and calk-alkalic island arc magmatic rocks are reported from the north arm of Sulawesi (Indonesia). Age and geochemical similarities between these basalts and those drilled in the Celebes Sea indicate this North Sulawesi volcanic arc was built on the same oceanic crust. The 25 deg late Neogene clockwise rotation of the north arm of Sulawesi following its collision with fragments of Australia (Sula, Buton) is not sufficient to explain the asymmetrical magnetic anomalies in the Celebes basin. The North Sulawesi island arc could be interpreted as having progressively retreated northward on its own Celebes sea back arc basin, during an episode of Palaeogene-early Neogene tectonic erosion along the trench. (authors) 37 refs.

  4. K, Rb and Sr abundances and Sr isotopic composition of the Tanzawa granitic and associated gabbroic rocks, Japan: low-potash island arc plutonic complex

    International Nuclear Information System (INIS)

    Ishizaka, K.; Yanagi, T.

    1977-01-01

    The granitic and associated gabbroic rocks of the Tanzawa plutonic complex of Miocene age occurring in the northern part of the Izu-Bonin arc are characterized by low abundances of K (229-6790 ppm) and Rb (0.414-12.1 ppm), low K 2 O/Na 2 O ratios (0.037-0.21), moderately high K/Rb ratios (541-630), low Rb/Sr ratios (0.00137-0.0579) and low initial 87 Sr/ 86 Sr ratios (0.70332-0.70372). This indicates that acid to intermediate plutonic rocks with these geochemical characteristics also occur in island arc environments besides mid-oceanic ridge environments. They represent, together with associated gabbroic rocks, a low-potash island arc plutonic complex and are expected to occur beneath young island arcs, although now unexposed. The Tanzawa plutonic complex may have been formed by differentiation of low-K calc-alkaline magma. (Auth.)

  5. An alternative approach to probabilistic seismic hazard analysis in the Aegean region using Monte Carlo simulation

    Science.gov (United States)

    Weatherill, Graeme; Burton, Paul W.

    2010-09-01

    mapping calculations. These hazard maps are in general agreement with previous maps for the Aegean, recognising the highest hazard in the Ionian Islands, Gulf of Corinth and Hellenic Arc. Peak Ground Accelerations for some sites in these regions reach as high as 500-600 cm s -2 using European/NGA attenuation models, and 400-500 cm s -2 using Greek attenuation models.

  6. Magnetization strucrure of thermal vent on island arc from vector magnetic anomlies using AUV

    Science.gov (United States)

    Isezaki, N.; Matsuo, J.; Sayanagi, K.

    2012-04-01

    The geomagnetic anomaly measured by a scalar magnetometer,such as a proton precession magnetometer cannot be defined its direction, then it does not satisfy the Laplace's equation. Therefore physical formula describing the relation between magnetic field and magnetization cannot be established.Because the difference between results obtained from scalar data and from vector data is very significant, we must use vector magnetic field data for magnetization analyses to get the more reliable and exact solutions. The development program of fundamental tools for exploration of deep seabed resources started with the financial support of the Ministry of Education, Culture, Sports, Science & Technology (MEXT) in 2008 and will end in 2012. In this project, we are developing magnetic exploration tools for seabed resources using AUV (Autonomous Underwater Vehicle) and other deep-towed vehicles to measure not the scalar magnetic field but the vector magnetic field in order to estimate magnetization structure below the sea-floor exactly and precisely. We conducted AUV magnetic survey in 2010 at the thermal area called Hakurei deposit in the Bayonnaise submarine caldera at the southern end of Izu island arc, about 400km south of Tokyo. We analyzed the observed vector magnetic fields to get the vector magnetic anomaly Fields using the method of Isezaki(1984). We inverted these vector magnetic anomaly fields to magnetization structure. CONCLUSIONS 1.The scalar magnetic field TIA (Total Intensity Anomaly) has no physical formula describing the relation between M (Magnetization) and TIA because TIA does not satisfy the Laplace's equation. Then it is impossible to estimate M from TIA. 2.Anlyses of M using TIA have been done so far under assumption TIA=PTA (Projected Total Anomay on MF (Main Geomagnetic Field)), however, which caused the analysis error due to ɛT= TIA - PTA . 3.We succeeded to measure the vector magnetic anomaly fields using AUV despite the severe magnetic noises

  7. Microseismicity in the SE Aegean using data of he temporary EGELADOS network

    Science.gov (United States)

    Brüstle, Andrea; Küperkoch, Ludger; Meier, Thomas; Friederich, Wolfgang; Egelados Working Group

    2010-05-01

    The temporary broadband EGELADOS network covered the entire Hellenic Subduction Zone from October 2005 to April 2007. Seismic events are detected and identified by an STA/LTA-trigger and a grid-search algorithm, where relative travel times of pre-defined masterevents are compared to observed differential trigger times. Because of the high seismicity, we will focus on this poster on the south-eastern part of the Hellenic Subduction Zone including the forearc around Rhodes, Karpathos and Kassos and the volcanic arc around Nisyros. In addition, the considered region covers the transition zone from the Aegean to the Anatolian microplates at the west coast of Turkey. In this region we have located more than 3500 local earthquakes in 13 months of the network. Microseismicity down to a magnitude of about ML 1.8 is detected completely. In regions with an increased station density, microseismicity may be observed completely down to magnitudes of ML 1. High shallow microseismicity is observed in the forearc with clusters southeast of Crete (Ptolemy trench), south of Karpathos and southwest of Amorgos within the volcanic arc. A continuous seismically active zone strikes along the EW trending rift of the Gulf of Goekova to western Kos and changes its direction to NS by crossing the volcanic island Nisyros and extruding into the forearc near Kassos. Intermediate depth seismicity of the subducting slab is located in the volcanic arc between Astypalea and Tilos. The strong attenuation of the S-waves of intermediate depth events points to low Q in the mantle wedge above the subducting African lithosphere. In contrast, S-waves propagating within the slab from the source to the stations in the forearc are much less attenuated.

  8. Microseismicity in the southeastern Aegean using data of the temporary EGELADOS network

    Science.gov (United States)

    Brüstle, A.; Küperkoch, L.; Meier, T.; Friederich, W.; Egelados Working Group

    2009-04-01

    The temporary broadband EGELADOS network covered the entire Hellenic Subduction Zone from October 2005 to April 2007. Seismic events are detected and identified by an STA/LTA-trigger and a grid-search algorithm, where relative travel times of pre-defined masterevents are compared to observed differential trigger times. Because of the high seismicity, we focus on the south-eastern part of the Hellenic Subduction Zone including the forearc around Rhodes, Karpathos and Kassos and the volcanic arc around Nisyros. In addition, the considered region covers the transition zone from the Aegean to the Anatolian microplates at the west coast of Turkey. For this region more than 1800 of the 2646 events, triggered during the first 6 months of the experiment, were identified as local earthquakes and localised. The other triggers represent earthquakes outside the working region, multiply triggered events, teleseismic events or noise, respectively. Microseismicity down to a magnitude of about ML 1.8 is detected completely. In regions with an increased station density, microseismicity may be observed completely down to magnitudes of ML 1. High shallow microseismicity is observed in the forearc with clusters southeast of Crete (Ptolemy trench), south of Karpathos and southwest of Amorgos within the volcanic arc. A continuous seismically active zone strikes along the EW trending rift of the Gulf of Gökova to western Kos and changes its direction to NS by crossing the volcanic island Nisyros and extruding into the forearc near Kassos. Intermediate depth seismicity of the subducting slab is located in the volcanic arc between Astypalea and Tilos. The strong attenuation of the S-waves of intermediate depth events points to low Q in the mantle wedge above the subducting African lithosphere. In contrast, S-waves propagating within the slab from the source to the stations in the forearc are much less attenuated.

  9. CRED 20m Gridded bathymetry of Necker Island, Hawaii, USA (Arc ASCII format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry of the shelf and slope environments of Necker Island, Northwestern Hawaiian Islands, Hawaii, USA. This ASCII includes multibeam bathymetry from...

  10. Silica-enriched mantle sources of subalkaline picrite-boninite-andesite island arc magmas

    Science.gov (United States)

    Bénard, A.; Arculus, R. J.; Nebel, O.; Ionov, D. A.; McAlpine, S. R. B.

    2017-02-01

    Primary arc melts may form through fluxed or adiabatic decompression melting in the mantle wedge, or via a combination of both processes. Major limitations to our understanding of the formation of primary arc melts stem from the fact that most arc lavas are aggregated blends of individual magma batches, further modified by differentiation processes in the sub-arc mantle lithosphere and overlying crust. Primary melt generation is thus masked by these types of second-stage processes. Magma-hosted peridotites sampled as xenoliths in subduction zone magmas are possible remnants of sub-arc mantle and magma generation processes, but are rarely sampled in active arcs. Published studies have emphasised the predominantly harzburgitic lithologies with particularly high modal orthopyroxene in these xenoliths; the former characteristic reflects the refractory nature of these materials consequent to extensive melt depletion of a lherzolitic protolith whereas the latter feature requires additional explanation. Here we present major and minor element data for pristine, mantle-derived, lava-hosted spinel-bearing harzburgite and dunite xenoliths and associated primitive melts from the active Kamchatka and Bismarck arcs. We show that these peridotite suites, and other mantle xenoliths sampled in circum-Pacific arcs, are a distinctive peridotite type not found in other tectonic settings, and are melting residues from hydrous melting of silica-enriched mantle sources. We explore the ability of experimental studies allied with mantle melting parameterisations (pMELTS, Petrolog3) to reproduce the compositions of these arc peridotites, and present a protolith ('hybrid mantle wedge') composition that satisfies the available constraints. The composition of peridotite xenoliths recovered from erupted arc magmas plausibly requires their formation initially via interaction of slab-derived components with refractory mantle prior to or during the formation of primary arc melts. The liquid

  11. Constraints on the source of Cu in a submarine magmatic-hydrothermal system, Brothers volcano, Kermadec island arc

    Science.gov (United States)

    Keith, Manuel; Haase, Karsten M.; Klemd, Reiner; Smith, Daniel J.; Schwarz-Schampera, Ulrich; Bach, Wolfgang

    2018-05-01

    Most magmatic-hydrothermal Cu deposits are genetically linked to arc magmas. However, most continental or oceanic arc magmas are barren, and hence new methods have to be developed to distinguish between barren and mineralised arc systems. Source composition, melting conditions, the timing of S saturation and an initial chalcophile element-enrichment represent important parameters that control the potential of a subduction setting to host an economically valuable deposit. Brothers volcano in the Kermadec island arc is one of the best-studied examples of arc-related submarine magmatic-hydrothermal activity. This study, for the first time, compares the chemical and mineralogical composition of the Brothers seafloor massive sulphides and the associated dacitic to rhyolitic lavas that host the hydrothermal system. Incompatible trace element ratios, such as La/Sm and Ce/Pb, indicate that the basaltic melts from L'Esperance volcano may represent a parental analogue to the more evolved Brothers lavas. Copper-rich magmatic sulphides (Cu > 2 wt%) identified in fresh volcanic glass and phenocryst phases, such as clinopyroxene, plagioclase and Fe-Ti oxide suggest that the surrounding lavas that host the Brothers hydrothermal system represent a potential Cu source for the sulphide ores at the seafloor. Thermodynamic calculations reveal that the Brothers melts reached volatile saturation during their evolution. Melt inclusion data and the occurrence of sulphides along vesicle margins indicate that an exsolving volatile phase extracted Cu from the silicate melt and probably contributed it to the overlying hydrothermal system. Hence, the formation of the Cu-rich seafloor massive sulphides (up to 35.6 wt%) is probably due to the contribution of Cu from a bimodal source including wall rock leaching and magmatic degassing, in a mineralisation style that is hybrid between Cyprus-type volcanic-hosted massive sulphide and subaerial epithermal-porphyry deposits.

  12. CRED 5 m Gridded bathymetry of Baker Island, Pacific Remote Island Areas, Central Pacific (Arc ASCII Format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded (5 m cell size) bathymetry of the shelf and slope environments of Baker Island, Pacific Remote Isand Areas, Central Pacific. Almost complete bottom coverage...

  13. The mantle source of island arc magmatism during early subduction: Evidence from Hf isotopes in rutile from the Jijal Complex (Kohistan arc, Pakistan)

    Science.gov (United States)

    Ewing, Tanya A.; Müntener, Othmar

    2018-05-01

    The Cretaceous-Paleogene Kohistan arc complex, northern Pakistan, is renowned as one of the most complete sections through a preserved paleo-island arc. The Jijal Complex represents a fragment of the plutonic roots of the Kohistan arc, formed during its early intraoceanic history. We present the first Hf isotope determinations for the Jijal Complex, made on rutile from garnet gabbros. These lithologies are zircon-free, but contain rutile that formed as an early phase. Recent developments in analytical capabilities coupled with a careful analytical and data reduction protocol allow the accurate determination of Hf isotope composition for rutile with <30 ppm Hf for the first time. Rutile from the analysed samples contains 5-35 ppm Hf, with sample averages of 13-17 ppm. Rutile from five samples from the Jijal Complex mafic section, sampling 2 km of former crustal thickness, gave indistinguishable Hf isotope compositions with εHf(i) ranging from 11.4 ± 3.2 to 20.1 ± 5.7. These values are within error of or only slightly more enriched than modern depleted mantle. The analysed samples record variable degrees of interaction with late-stage melt segregations, which produced symplectitic overprints on the main mineral assemblage as well as pegmatitic segregations of hydrous minerals. The indistinguishable εHf(i) across this range of lithologies demonstrates the robust preservation of the Hf isotope composition of rutile. The Hf isotope data, combined with previously published Nd isotope data for the Jijal Complex garnet gabbros, favour derivation from an inherently enriched, Indian Ocean type mantle. This implies a smaller contribution from subducted sediments than if the source was a normal (Pacific-type) depleted mantle. The Jijal Complex thus had only a limited recycled continental crustal component in its source, and represents a largely juvenile addition of new continental crust during the early phases of intraoceanic magmatism. The ability to determine the Hf

  14. Diagenesis of arc-derived sandstones of Cretaceous formations in the Queen Charlotte Islands, British Columbia, Canada(MEMORIAL VOLUME TO THE LATE PROFESSOR TERUHIKO SAMESHIMA)

    OpenAIRE

    Yagishita, Koji

    1994-01-01

    Diagenesis of sediments derived from a magmatic arc provenance may greatly differ from that of sediments derived from an intracratonic- or foreland-type provenance. Sediments from the magmatic arc are compositionally immature and rich in volcanic and sedimentary rock fragments. Sandstone samples of mid- to Upper Cretaceous formations in the Queen Charlotte Islands, British Columbia, Canada, contain either large amounts of pseudomatrix or authigenic cements. An inverse relationship between the...

  15. AegeanMarTech project: General Introduction

    Science.gov (United States)

    Psarra, S.; Zervakis, V.; Karageorgis, A. P.

    2017-10-01

    This issue of "Continental Shelf Research" is dedicated to the study of processes potentially responsible for the relatively high productivity of the North Aegean Sea in comparison to other regions of the Eastern Mediterranean. This region, one of the most important fishing grounds in the eastern Mediterranean, is characterized by: i) the inflow of mesotrophic waters of Black Sea (BSW) origin into the North Aegean and their interaction with the more saline Levantine waters (LW); and ii) the wind-generated coastal upwelling occurring every summer in the eastern Aegean. The study of these two natural fertilization mechanisms has been the major aim of the AegeanMarTech project ("Technological and oceanographic cooperation Network for the Study of mechanisms fertilizing the North-East Aegean Sea").

  16. Magmatic dyke swarms of the south shetland islands volcanic arc, west-antarctica - tracers of geodynamic history

    Science.gov (United States)

    Kraus, St.; Miller, H.

    2003-04-01

    Magmatic dykes are essential components of volcanic arcs, following joint systems and fracture zones. This work aims to reconstruct the deformational and intrusive history of the northern part of the Antarctic Peninsula by combining structural information with the geochemistry, isotopy and age of the dykes. On the South Shetland Islands volcanic activity began about 130 Ma ago. From Mid to Late Eocene (49-34 Ma) the northern Antarctic Peninsula and southern South America underwent extensional tectonics, which led to sea-floor spreading in the Drake Passage 28 Ma ago. Subsequent slab-rollback caused arc-extension and the opening of the Bransfield Rift as a backarc-basin between 4 and 1.3 Ma ago. Very slow subduction (1mm/a) at the South Shetland trench continues until the present day. Several changes of subduction direction caused crucial variations regarding the tectonic regime in the overlying South Shetland block, being the reason for the shifting strike of the dykes. Several dyke systems were mapped in areas of up to 100000m2, with the outcrop situation being good enough to observe plenty of relative age relationships. ICP-MS geochemical analysis on 132 dykes shows, as expected, that the majority of them correspond to a typical subduction-related calcalcalic suite, ranging from basalts to rhyolites. Nevertheless, some dykes show shoshonitic characteristics and are maybe related to an early stage extensional crustal regime. This is supported by the relative ages observed in the field, indicating, that these dykes belong to the oldest ones outcropping in the investigated area. In one case, the geochemical behaviour of the dyke corresponds clearly to adacitic conditions, being a hint on partially molten subducted oceanic crust. In several areas (e.g. Potter Peninsula, King George Island, and Hurd Peninsula, Livingston Island) a strong correlation between chemism and strike of the dykes - and therefore the tectonic regime at the time of intrusion - is observed. Ce

  17. Evolution of an intra-oceanic island arc during the late Silurian to late Devonian, New England fold belt

    International Nuclear Information System (INIS)

    Offler, R.; Gamble, J.

    2002-01-01

    Geochemical studies of volcanic rocks in the Gamilaroi terrane and Calliope Volcanic Assemblage, New England Fold Belt, eastern Australia, indicate that the setting in which these rocks formed changed in both space and time. The Upper Silurian to Middle Devonian basalts of the Gamilaroi terrane show flat to slightly light rare-earth element (LREE) depleted chondrite normalised patterns, depletion of high field strength elements (HFSE) relative to N-MORB, low Ti/V and high Ti/Zr ratios, high Ni, Cr and large-ion lithophile element (LILE) contents, features characteristic of intra-oceanic island arc basaltic magmas. They are associated with low-K, less mafic volcanics, showing moderate LREE enrichment, low Nb and Y contents and Rb/Zr ratios. The depletion of HFSE in the basalts indicates that the magmas were derived from a refractory source in a supra-subduction zone setting. The presence of such a zone implies that the arc was associated with a backarc basin, the location of which was to the west where a wide backarc region existed from the Middle Silurian. This polarity of arc and backarc basin suggests that the subduction zone dipped to the west. In contrast to their older counterparts, Middle to Upper Devonian basalts of the Gamilaroi terrane have MORB-like chondrite normalised patterns and higher Ti and lower LILE contents. Moreover, they have low Ti/Zr ratios and MORB-like Ti/V ratios and HFSE contents, features typical of backarc basins. Dolerites of the Gamilaroi terrane also have predominantly backarc basin signatures. These features suggest that both the basalts and dolerites have been emplaced in an extensional environment produced during the rifting of the intra-oceanic island arc lithosphere. A progressive increase in Ti/V ratios, and TiO 2 and Fe 2 O 3 contents at constant MgO, of stratigraphically equivalent basalts, towards the north-northwest part of the belt, is consistent with either greater extension to the north or melting of a more fertile magma

  18. U-Series disequilibria, magma petrogenesis and flux rates along the depleted Tonga-Kermadec Island Arc

    International Nuclear Information System (INIS)

    Turner, S.; Hawkesworth, C.; Rogers, N.; Bartlett, J.; Smith, I.; Worthington, T.; Smith, I.; Worthington, T.

    1997-01-01

    The fluid contribution to the lava source has been calculated as -1 ppm Rb, 10 ppm Ba, 0.02 ppm U, 600 ppm K 0.2 ppm Pb and 30 ppm Sr. It has 87 Sr/ 86 Sr = 0.7035 and 206 Pb/ 204 Pb = 18.5 and thus is inferred to be derived from dehydration of the subducting altered oceanic crust. U-Th isotope disequilibria reflect the time since fluid release from the subducting slab and a pseudo-isochron through the lowest ( 230 Th/ 232 Th) lavas constrains this to be ∼ 50 000 yr. Significantly, U-Th isotope data record similar timescales in the Lesser Antilles (∼40 000 yr, Turner et al., 1996) and in the Marianas (30 000 yr, Elliott et al., 1996) which provides encouragement that these data reflect some general aspect of the flux rates beneath island arcs. Large 226 Ra excesses have also been reported from Tonga-Kermadec (( 226 Ra/ 230 Th) = 1.5-3.0, Gill and Williams, 1990). Since 226 Ra will return to secular equilibrium with 230 Th (( 226 Ra/ 230 Th) = 1) within 7500 yr of Ra/Th fractionation the 238 U/ 230 Th and 226 Ra/ 230 Th disequilibria are clearly decoupled (see also Turner et al., 1996). This is an unexpected result and clearly the 226 Ra/ 230 Th disequilibria must have developed after the process responsible for the major U/Th fractionation. It is suggested that Th-Ra isotope disequilibria record the time since partial melting and thus indicate rapid channelled magma ascent. Olivine gabbro xenoliths from Raoul are interpreted as cumulates to their host lavas with which they form zero age U-Th isochrons indicating that minimal time was spent in magma chambers. The subduction signature is not observed in lavas from the back arc island of Niuafo'ou and thus does not penetrate as far 200 km beyond the arc front volcanoes. These were derived from partial melting of fertile peridotite at 130-160 km depth with melt rates around 2 x 10 -4 kg m -3 yr -1 , possibly due to volatiles released from the breakdown of phengite and lawsonite in the underlying slab at 200 km

  19. Ancient xenocrystic zircon in young volcanic rocks of the southern Lesser Antilles island arc

    Science.gov (United States)

    Rojas-Agramonte, Yamirka; Williams, Ian S.; Arculus, Richard; Kröner, Alfred; García-Casco, Antonio; Lázaro, Concepción; Buhre, Stephan; Wong, Jean; Geng, Helen; Echeverría, Carlos Morales; Jeffries, Teresa; Xie, Hangqian; Mertz-Kraus, Regina

    2017-10-01

    The Lesser Antilles arc is one of the best global examples in which to examine the effects of the involvement of subducted sediment and crustal assimilation in the generation of arc crust. Most of the zircon recovered in our study of igneous and volcaniclastic rocks from Grenada and Carriacou (part of the Grenadines chain) is younger than 2 Ma. Within some late Paleogene to Neogene ( 34-0.2 Ma) lavas and volcaniclastic sediments however, there are Paleozoic to Paleoarchean ( 250-3469 Ma) xenocrysts, and Late Jurassic to Precambrian zircon ( 158-2667 Ma) are found in beach and river sands. The trace element characteristics of zircon clearly differentiate between different types of magmas generated in the southern Lesser Antilles through time. The zircon population from the younger arc (Miocene, 22-19 Ma, to Present) has minor negative Eu anomalies, well-defined positive Ce anomalies, and a marked enrichment in heavy rare earth elements (HREE), consistent with crystallization from very oxidized magmas in which Eu2 + was in low abundance. In contrast, zircon from the older arc (Eocene to mid-Oligocene, 30-28 Ma) has two different REE patterns: 1) slight enrichment in the light (L)REE, small to absent Ce anomalies, and negative Eu anomalies and 2) enriched High (H)REE, positive Ce anomalies and negative Eu anomalies (a similar pattern is observed in the xenocrystic zircon population). The combination of positive Ce and negative Eu anomalies in the zircon population of the older arc indicates crystallization from magmas that were variably, but considerably less oxidized than those of the younger arc. All the igneous zircon has positive εHf(t), reflecting derivation from a predominantly juvenile mantle source. However, the εHf(t) values vary significantly within samples, reflecting considerable Hf isotopic heterogeneity in the source. The presence of xenocrystic zircon in the southern Lesser Antilles is evidence for the assimilation of intra-arc crustal sediments and

  20. Geophysical characteristics of the Ninetyeast Ridge–Andaman island arc/trench convergent zone

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, C.; Gireesh, R.; Chand, S.; KameshRaju, K.A.; Rao, D.G.

    ] N. Furus, Y. Kono, Slab residual gravity anomaly: gravity reduction due to subducting plates beneath the Japanese Islands, J. Geodyn. 36 (2003) 497-514. 19 [15] S Dasgupta, M. Mukhopadhyay, A. Bhattacharya, T. K. Jana, The geometry...

  1. CRED 20m Gridded bathymetry of Nihoa Island, Hawaii, USA (Arc ASCII format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (20m) of the shelf and slope environments of Nihoa Island, Hawaii, USA. The ASCII includes multibeam bathymetry from the Simrad EM120, Simrad...

  2. Effects of relative plate motion on the deep structure and penetration depth of slabs below the Izu-Bonin and Mariana island arcs

    NARCIS (Netherlands)

    Hilst, R.D. van der; Seno, Tetsuzo

    1993-01-01

    An increasing number of seismological studies indicate that slabs of subducted lithosphere penetrate the Earth's lower mantle below some island arcs but are deflected, or, rather, laid down, in the transition zone below others. Recent numerical simulations of mantle flow also advocate a hybrid form

  3. Ankaramite: A New Type of High-Magnesium and High-Calcium Primitive Melt in the Magnitogorsk Island-Arc Zone (Southern Urals)

    Science.gov (United States)

    Pushkarev, E. V.; Ryazancev, A. V.; Gottman, I. A.; Degtyarev, K. E.; Kamenetsky, V. S.

    2018-04-01

    This work describes the geological position, mineral and chemical composition of high-Mg effusive ankaramites occurring as dykes and lava flows. They were found in the mélange zone of the western margin of the Magnitogorsk island arc zone in the Southern Urals. Data on the liquidus association of phenocrysts and on the composition of the matrix of effusives are given. According to the data obtained, the conclusion was drawn that the ankaramites studied can be attributed to the primary island arc melts, which were not subject to essential differentiation. This type of effusives has not been distinguished previously among island arc volcanogenic formations of the Urals. It is shown that ankaramites can be considered to be primary melts parental for dunite-clinopyroxenites-gabbro complexes of Ural-Alaskan type. The occurrence of ankaramites in the Paleozoic island arc formations of the Urals indicates the wehrlite composition of the mantle as the reason for the extremely wide development of wehrlites and clinopyroxenites in different mafic-ultramafic complexes of the Urals.

  4. Comparison of hypocentre parameters of earthquakes in the Aegean region

    Science.gov (United States)

    Özel, Nurcan M.; Shapira, Avi; Harris, James

    2007-06-01

    The Aegean Sea is one of the more seismically active areas in the Euro-Mediterranean region. The seismic activity in the Aegean Sea is monitored by a number of local agencies that contribute their data to the International Seismological Centre (ISC). Consequently, the ISC Bulletin may serve as a reliable reference for assessing the capabilities of local agencies to monitor moderate and low magnitude earthquakes. We have compared bulletins of the Kandilli Observatory and Earthquake Research Institute (KOERI) and the ISC, for the period 1976-2003 that comprises the most complete data sets for both KOERI and ISC. The selected study area is the East Aegean Sea and West Turkey, bounded by latitude 35-41°N and by longitude 24-29°E. The total number of events known to occur in this area, during 1976-2003 is about 41,638. Seventy-two percent of those earthquakes were located by ISC and 75% were located by KOERI. As expected, epicentre location discrepancy between ISC and KOERI solutions are larger as we move away from the KOERI seismic network. Out of the 22,066 earthquakes located by both ISC and KOERI, only 4% show a difference of 50 km or more. About 140 earthquakes show a discrepancy of more than 100 km. Focal Depth determinations differ mainly in the subduction zone along the Hellenic arc. Less than 2% of the events differ in their focal depth by more than 25 km. Yet, the location solutions of about 30 events differ by more than 100 km. Almost a quarter of the events listed in the ISC Bulletin are missed by KOERI, most of them occurring off the coast of Turkey, in the East Aegean. Based on the frequency-magnitude distributions, the KOERI Bulletin is complete for earthquakes with duration magnitudes Md > 2.7 (both located and assigned magnitudes) where as the threshold magnitude for events with location and magnitude determinations by ISC is mb > 4.0. KOERI magnitudes seem to be poorly correlated with ISC magnitudes suggesting relatively high uncertainty in the

  5. Field {gamma}-ray spectrometry on the Vulcano island (Aeolian Arc, Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Chiozzi, P.; Pasquale, V.; Russo, D.; Verdoya, M. [Dipartimento di Scienze della Terra, Universita di Genova, Genoa (Italy); De Felice, P. [Istituto Nazionale di Metrologica delle Radiazioni Ionizzanti ENEA, Dipartimento Ambiente, Centro Ricerche Casaccia, Rome (Italy)

    1999-08-01

    In situ NaI(Tl) {gamma}-ray spectrometric measurements on the Vulcano island show that the magmatic evolution of the main structural units is reflected by the uranium, thorium and potassium concentrations. The results allowed us to delineate two temporal and radiometric districts. The older district comprises lava flows and pyroclastics of mafic composition forming the whole southern part of the island, with an equivalent uranium concentration and an eTh/eU ratio ranging, on average, from 2.9 to 3.4 ppm and from 2.4 to 4.1, respectively. Rocks of the younger district, ranging from leucitic tephritic and trachytic to rhyolitic composition, show higher K contents (about 6%) and more variable eTh/eU ratios (2.4-6.1)

  6. Field γ-ray spectrometry on the Vulcano island (Aeolian Arc, Italy)

    International Nuclear Information System (INIS)

    Chiozzi, P.; Pasquale, V.; Russo, D.; Verdoya, M.; De Felice, P.

    1999-01-01

    In situ NaI(Tl) γ-ray spectrometric measurements on the Vulcano island show that the magmatic evolution of the main structural units is reflected by the uranium, thorium and potassium concentrations. The results allowed us to delineate two temporal and radiometric districts. The older district comprises lava flows and pyroclastics of mafic composition forming the whole southern part of the island, with an equivalent uranium concentration and an eTh/eU ratio ranging, on average, from 2.9 to 3.4 ppm and from 2.4 to 4.1, respectively. Rocks of the younger district, ranging from leucitic tephritic and trachytic to rhyolitic composition, show higher K contents (about 6%) and more variable eTh/eU ratios (2.4-6.1)

  7. Structural, Geochemical, and Isotopic Studies on Magmatic Dyke Swarms of the South Shetland Islands Volcanic Arc, West Antarctica - Revealing the Geodynamic History

    Science.gov (United States)

    Kraus, S.; Miller, H.

    2003-12-01

    Between 2000 and 2002 areas of up to 100,000 m2 have been mapped at several locations of the South Shetland Islands, mainly on King George and Livingston Islands. A structural analysis of the dykes and the host rocks was undertaken, and about 250 dykes were sampled for geochemical studies. On Livingston Island six different strike directions were identified, yielding a reliable relative time sequence as deduced from field-relationships. Geochemically, these dykes can be separated into five different groups, correlating with the different strike directions, one of those groups comprising two directions. Analysis of the structural data shows, that at least on Livingston Island only minor changes of the tensional situation occurred. Geochemical data reveal that all dykes of the South Shetland Islands belong to a calc-alkaline, arc-related suite, ranging from primitive basalts to highly differentiated rhyolites. Interpretation of Sr isotopic data of the dykes proves difficult, as there are indications for sea-water induced Sr-alteration. Nd isotopic analysis yield better results, revealing a three-stage development from the oldest dykes (ɛ Nd -0.2 to 0.6) on Livingston Island towards a second, younger group (ɛ Nd 2.8 to 4.2, also Livingston), terminating with a third one (ɛ Nd 5.2 to 7.6), which includes the youngest dykes on Livingston and all dykes on King George and also Penguin Island. Either two mantle sources were involved, or the amount of crustal contamination changed considerately with time. It may have been high during initial arc volcanism, because of a still unstretched crust, then decreasing continually with progressing volcanism. In any case, the pattern reflects a chronological sequence corresponding with other authors' hypothesis of a migrating arc volcanism from SW to NE, i.e. from Livingston (older dykes) towards King George Island (younger dykes). Pb isotopic data, plottet together with MORB- and sediment-samples dredged from the Drake Passage

  8. K-U-Th systematics of terrestrial igneous rocks for planetological comparisons: volcanic rocks of the Earth oceanic island arc and Venus surface material

    International Nuclear Information System (INIS)

    Nikolaeva, O.V.

    1997-01-01

    Principles of the formation o data base for 339 samples of oceanic island arc (OIA) igneous rocks of the Earth available in literature are described as well as of the formation of fresh rock sample, characteristics of this sample, and K-U-Th-systematics of the fresh igneous rocks of Earth OIA. Results of comparison of the Venus measured rocks and Earth OIA rocks by K, U, Th

  9. Erosive effects of the storms HELENA (1963) and HUGO (1989) on Basse-Terre island (Guadeloupe - Lesser Antilles Arc).

    Science.gov (United States)

    Le Bivic, Rejanne; Allemand, Pascal; Delacourt, Christophe; Quiquerez, Amélie

    2014-05-01

    Basse-Terre is a volcanic island which belongs to the archipelago of Guadeloupe located in the Lesser Antilles Arc (Caribbean Sea). As a mountainous region in the tropical belt, Basse-Terre is affected by intense sediment transport due to extreme meteorological events. During the last fifty years, eight major tropical storms and hurricanes with intense rainfalls induced landslides and scars in the weathered layers. The purpose of this study is to compare two major meteorological events within a period of 26 years (HELENA in 10/1963 and HUGO in 09/1989) in order to qualify the parameters responsible of the spatial distribution of landslides and scars. The storm HELENA affected Basse-Terre between the 23rd and the 25th of October, 1963. The maximal daily rainfall reached 300 mm in Baillif which is located on the leeward coast at the altitude of 650 m while the maximum wind velocity reached 50 km/h. A similar exceptional event happened when the hurricane HUGO slammed the island in September 17, 1989. The maximum daily rainfall recorded in Sainte-Rose (on the northern coast) was 250 mm while it reached 208 mm in Petit-Bourg and the maximum wind speed was 60 km/h. Aerial images were acquired by the IGN (French Geographical Institute) before and a few weeks after the extreme events: less than three months after the event HELENA and less than a month after the event HUGO. Those images have been orthorectified at a metric resolution and combined in a GIS with a 10 m resolution DEM. Scars and landslides were digitalized and their surface area and mean slope were measured for both HELENA and HUGO. This work confirms several results proposed by a previous study related to the HELENA event: (1) the landslides occurred mainly in the center of the island and (2) the slope is the main parameter for the initiation of landslides, since all of them occurred with a slope superior to 30°. Furthermore, the resiliency of the surface affected by the landslides induced by HELENA was

  10. Application of Satellite Geodesy in Analyzing the Accelerated Movement of the Back-arc Rifting in the Izu Bonin Islands, Japan

    Science.gov (United States)

    Arisa, D.; Heki, K.

    2014-12-01

    The Izu-Bonin islands lies along the convergent boundary between the subducting Pacific plate (PA) and the overriding Philippine Sea plate (PH) in the western Pacific. Nishimura (2011) found that the back-arc rifting goes on behind the Izu arc by studying the horizontal velocities of GNSS stations on the Izu islands. Here we show that this rifting has accelerated in 2004 using GNSS data at Aogashima, Hachijoujima, and Mikurajima stations. The back-arc rifting behind the Izu islands can be seen as the increasing distance between stations in the Izu-Bonin islands and stations located in the stable part of PH. We found that their movement showed clear acceleration around the third quarter of 2004. Obtaining the Euler vector of the PH is necessary to analyzed the movement of each stations relative to the other stations on the same plate. The analyzing of GPS timeseries leads us to one initial conclusion that some accelerated movement started to occur in the third quarter of 2004. This event was closely related to the earthquake on May 29, 2004 in Nankai Trough and September 5, 2004 earthquake near the triple junction of Sagami Trough. The analyzing process help us to understand that this accelerated movement was not the afterslip of any of these earthquakes, but it was triggering these area to move faster and further than it was. We first rule out the best possible cause by constraining the onset time of the accelerated movement, and correlating it with the earthquakes. May 29, 2004 earthquake (M6.5) at the PA-PH boundary clearly lacked the jump which should mark the onset of the eastward slow movement. Moreover, additional velocity vectors do not converge to the epicenter, and onset time that minimizes the post-fit residual is significantly later than May. We therefore conclude that accelerated movement started in 2004 was not due to the afterslip of interplate earthquake in May 29. On the next step we found that the onset time coincides with the occurrence of

  11. Palaeomagnetic and geochronological evidence for a major middle miocene unconformity in Söke Basin (western Anatolia) and its tectonic implications for the Aegean region

    NARCIS (Netherlands)

    Uzel, Bora; Sümer, Ökmen; Özkaptan, Murat; Özkaymak, Çağlar; Kuiper, Klaudia; Sözbilir, Hasan; Kaymakci, Nuretdin; İnci, Uğur; Langereis, Cornelis G.

    2017-01-01

    Cenozoic convergence between the Eurasian and African plates and concurrent slab roll-back processes have produced a progressive extension in back-arc areas, such as the Aegean region andwestern Anatolia. There is still a long-standing controversy as to whether this was a continuous or stepwise

  12. Source of Aegean Sea harbour porpoises

    DEFF Research Database (Denmark)

    Lockyer, Christina; Rosel, P. E.; Frantzis, A.

    2003-01-01

    Documented sightings of harbour porpoises in the Mediterranean are rare, although the species is common in the neighbouring North Atlantic and Black Sea. However, in the past 2 decades, 4 harbour porpoises Phocoena phocoena have been recorded in the northern Aegean Sea in the eastern Mediterranea...

  13. Segmented Coastal Uplift Along an Erosional Subduction Margin, Northern Hikurangi Fore Arc, North Island, New Zealand

    Science.gov (United States)

    Marshall, J. S.; Litchfield, N. J.; Berryman, K. R.; Clark, K.; Cochran, U. A.

    2013-12-01

    The Hikurangi subduction margin along North Island, New Zealand accommodates oblique convergence of the Pacific plate westward beneath the Australian plate at 45 mm/yr. Along the southern margin, frontal accretion and pronounced forearc uplift occur inboard of the subducting Hikurangi plateau. In the north, subduction erosion and segmented uplift occur inboard of subducting seamounts along the plateau flank. Prior workers have established a robust foundation for coastal terrace studies along the northern Hikurangi margin (e.g., Berryman et al., 1989; Ota et al., 1992; Berryman, 1993; Wilson et al., 2006, 2007; Clark et al., 2010; Litchfield et al, 2007, 2010). New field observations presented here provide additional constraints on terrace uplift along this erosional subduction margin. Along Raukumara Peninsula (north of Poverty Bay), multiple Holocene to late Pleistocene marine and fluvial terraces occur at varying elevations, recording differential uplift across six coastal segments from Gisborne to East Cape (Ota et al., 1992; Wilson et al., 2007). In this study, two to three late Pleistocene terraces were observed on rocky headlands within the first segment (Gisborne to Whangara) at elevations of 80-185 m above msl. Preliminary correlation with OIS 5a-e sea level high stands (80-125 ka) indicates net uplift at 1.2-1.5 m/ky. Uplifted Holocene wavecut platforms occur in steps along the seaward edge of these terraces, consistent with coseismic uplift. At Makorori Point, an uplifted bench occurs along the modern seacliff at 2.3 m above the cliff base. A fossil gastropod shell from paleo-beach gravels on the platform inner edge yielded a calibrated radiocarbon age of 1680 ×110 ybp. At Turihaua Point, a ≥1 m thick deposit of Holocene beach sands overlies an uplifted wavecut platform at ≥1.5 m above mean sea level. Carbonate-cemented beachrock at the base of the sand deposit yields a calibrated radiocarbon age of 2990 ×70 ybp. At Mahia Peninsula (between Poverty

  14. Scenario based tsunami wave height estimation towards hazard evaluation for the Hellenic coastline and examples of extreme inundation zones in South Aegean

    Science.gov (United States)

    Melis, Nikolaos S.; Barberopoulou, Aggeliki; Frentzos, Elias; Krassanakis, Vassilios

    2016-04-01

    A scenario based methodology for tsunami hazard assessment is used, by incorporating earthquake sources with the potential to produce extreme tsunamis (measured through their capacity to cause maximum wave height and inundation extent). In the present study we follow a two phase approach. In the first phase, existing earthquake hazard zoning in the greater Aegean region is used to derive representative maximum expected earthquake magnitude events, with realistic seismotectonic source characteristics, and of greatest tsunamigenic potential within each zone. By stacking the scenario produced maximum wave heights a global maximum map is constructed for the entire Hellenic coastline, corresponding to all expected extreme offshore earthquake sources. Further evaluation of the produced coastline categories based on the maximum expected wave heights emphasizes the tsunami hazard in selected coastal zones with important functions (i.e. touristic crowded zones, industrial zones, airports, power plants etc). Owing to its proximity to the Hellenic Arc, many urban centres and being a popular tourist destination, Crete Island and the South Aegean region are given a top priority to define extreme inundation zoning. In the second phase, a set of four large coastal cities (Kalamata, Chania, Heraklion and Rethymno), important for tsunami hazard, due i.e. to the crowded beaches during the summer season or industrial facilities, are explored towards preparedness and resilience for tsunami hazard in Greece. To simulate tsunamis in the Aegean region (generation, propagation and runup) the MOST - ComMIT NOAA code was used. High resolution DEMs for bathymetry and topography were joined via an interface, specifically developed for the inundation maps in this study and with similar products in mind. For the examples explored in the present study, we used 5m resolution for the topography and 30m resolution for the bathymetry, respectively. Although this study can be considered as

  15. CRED 20 m Gridded bathymetry and IKONOS estimated depths of Northampton Seamounts to Laysan Island, Northwestern Hawaiian Islands, USA (Arc ASCII format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of Northampton Seamounts to Laysan Island, Northwestern Hawaiian Islands, Hawaii,...

  16. Homogenous stretching or detachment faulting? Which process is primarily extending the Aegean crust

    Science.gov (United States)

    Kumerics, C.; Ring, U.

    2003-04-01

    In extending orogens like the Aegean Sea of Greece and the Basin-and-Range province of the western United States, knowledge of rates of tectonic processes are important for understanding which process is primarily extending the crust. Platt et al. (1998) proposed that homogeneous stretching of the lithosphere (i.e. vertical ductile thinning associated with a subhorizontal foliation) at rates of 4-5 km Myr-1 is the dominant process that formed the Alboran Sea in the western Mediterranean. The Aegean Sea in the eastern Mediterranean is well-known for its low-angle normal faults (detachments) (Lister et al., 1984; Lister &Forster, 1996) suggesting that detachment faulting may have been the primary agent achieving ~>250 km (McKenzie, 1978) of extension since the Miocene. Ring et al. (2003) provided evidence for a very fast-slipping detachment on the islands of Syros and Tinos in the western Cyclades, which suggests that normal faulting was the dominant tectonic process that formed the Aegean Sea. However, most extensional detachments in the Aegean do not allow to quantify the amount of vertical ductile thinning associated with extension and therefore a full evaluation of the significance of vertical ductile thinning is not possible. On the Island of Ikaria in the eastern Aegean Sea, a subhorizontal extensional ductile shear zone is well exposed. We studied this shear zone in detail to quantify the amount of vertical ductile thinning associated with extension. Numerous studies have shown that natural shear zones usually deviate significantly from progressive simple shear and are characterized by pronounced shortening perpendicular to the shear zone. Numerous deformed pegmatitic veins in this shear zone on Ikaria allow the reconstruction of deformation and flow parameters (Passchier, 1990), which are necessary for quantifying the amount of vertical ductile thinning in the shear zone. Furthermore, a flow-path and finite-strain study in a syn-tectonic granite, which

  17. Cold-front driven storm erosion and overwash in the central part of the Isles Dernieres, a Louisiana barrier-island arc

    Science.gov (United States)

    Dingler, J.R.; Reiss, T.E.

    1990-01-01

    Tropical and extratropical storms produce significant erosion on the barrier islands of Louisiana. Over the past 100 years, such storms have produced at least 2 km of northward beach-face retreat and the loss of 63% of the surface area of the Isles Dernieres, a low-lying barrier-island arc along the central Louisiana coast. Elevations on the islands within the arc are typically less than 2 m above mean sea level. The islands typically have a washover-flat topography with occasional, poorly developed, dune-terrace topography consisting of low-lying and broken dunes. The central part of the arc consists of salt-marsh deposits overlain by washover sands along the Gulf of Mexico shoreline. Sand thicknesses range from zero behind the beach, to less than 2 m under the berm crest, and back to zero in the first nearshore trough. The sand veneer is sufficiently thin that storms can strip all the sand from the beach face, exposing the underlying marsh deposits. The geomorphic changes produced by cold fronts, a type of extratropical storm that commonly affect the Isles Dernieres between late fall and early spring are described. Between August 1986 and September 1987, repeated surveys along eleven shore-normal transects that covered 400 m of shoreline revealed the timing and extent of cold-front-produced beach change along a typical section of the central Isles Dernieres. During the study period, the beach face retreated approximately 20 m during the cold-front season but did not rebuild during the subsequent summer. Because the volume of sand deposited on the backshore (5600 m3) was less than the volume of material lost from the beach face (19,200 m3), approximately 13,600 m3 of material disappeared. Assuming that underlying marsh deposits decrease in volume in direct proportion to the amount of beach-face retreat, an estimate of the mud loss during the study period is 14,000 m3. Thus, the decrease in volume along the profiles can be accounted for without removing any sand

  18. Trace-element and isotopic constraints on the source of magmas in the active volcano and Mariana island arcs, Western Pacific

    Science.gov (United States)

    Stern, Robert James; Ito, Emi

    1983-10-01

    Analytical results of the relative and absolute abundance of LIL-incompatible trace elements (K, Rb, Cs, Sr, and Ba) and isotopic compositions ( {18O}/{16O}, {87Sr}/{86Sr}, and {143Nd}/{144Nd}) are summarized for fresh samples from active and dormant volcanoes of the Volcano and Mariana island arcs. The presence of thickened oceanic crust ( T ˜ 15-20 km) beneath the arc indicates that while hybridization processes resulting in the modification of primitive magmas by anatectic mixing at shallow crustal levels cannot be neglected, the extent and effects of these processes on this arc's magmas are minimized. All components of the subducted plate disappear at the trench. This observation is used to reconstruct the composition of the crust in the Wadati-Benioff zone by estimating proportions of various lithologies in the crust of the subducted plate coupled with analyses from DSDP sites. Over 90% of the mass of the subducted crust consists of basaltic Layers II and III. Sediments and seamounts, containing the bulk of the incompatible elements, make up the rest. Bulk Western Pacific seafloor has {87Sr}/{86Sr} ˜ 0.7032 , δ 18O ˜ +7.2 , K/Rb ˜ 510, K/Ba ˜ 46, and K/Cs ˜ 13,500. Consideration of trace-element data and combined δ 18O - {87Sr}/{86Sr} systematics limits the participation of sediments in magmagenesis to less than 1%, in accord with the earlier results of Pb-isotopic studies. Combined {143Nd}/{144Nd} - {87Sr}/{86Sr} data indicate little, if any, involvement of altered basaltic seafloor in magmagenesis. Perhaps more important than mean isotopic and LIL-element ratios is the restricted range for lavas from along over 1000 km of this arc. Mixtures of mantle with either the subducted crust or derivative fluids should result in strong heterogeneities in the sources of individual volcanoes along the arc. Such heterogeneities would be due to: (1) gross variations of crustal materials supplied to the subduction zone; and (2) lesser efficiency of mixing processes

  19. Characterising the continental crust factory: new insights into the roots of an island arc from Hf isotopes in rutile (Kohistan complex, Pakistan)

    Science.gov (United States)

    Ewing, Tanya; Müntener, Othmar; Schaltegger, Urs

    2017-04-01

    Island arcs are one of the primary sites of generation of new continental crust. As such, a question of fundamental importance to models of continental growth is to what extent island arc magmas are strictly juvenile melts derived directly from the mantle, versus potentially incorporating a significant recycled continental component, for example from subducted sediment. The Kohistan complex (northeastern Pakistan) preserves a remarkably complete ˜50 km thick cross-section through an exhumed Jurassic-Cretaceous island arc. It affords a rare opportunity to study the evolution of island arc magmatism from subduction initiation, through intra-oceanic subduction, to arc-continent collision. In this study, we investigate the ultramafic-mafic Jijal Complex, which preserves part of the plutonic roots of the Kohistan complex formed over ˜20 Ma of intra-oceanic subduction. The Jijal Complex is volumetrically dominated by ultramafic rocks and garnet-bearing gabbros whose petrogenesis is controversial. Garnet formation has variously been attributed a prograde metamorphic origin1, a magmatic origin recording crystallisation at high pressures2,3, or a restitic origin following partial melting4. We have characterised the source of the Jijal Complex using in situ LA-MC-ICPMS determination of the Hf isotope composition of rutile from garnet gabbros, which are zircon-free. This work exploits the superior sensitivity of the Neptune Plus, coupled with an improved analytical protocol, to improve precision of this novel technique and permit in situ analysis of rutile with only ˜10-30 ppm Hf. Rutile occurs included in early-formed minerals such as clinopyroxene and garnet, indicating crystallisation at high pressures and temperatures. Rutile from all samples, collected across ˜3 km of former crustal depth, has indistinguishable Hf isotope compositions close to depleted mantle values. Integrating the new Hf isotope data for rutile with previously published whole rock Nd-Sr isotope

  20. Neogene volcanism and extension in Western Anatolian-Aegean area: A new geodynamic model

    Energy Technology Data Exchange (ETDEWEB)

    Agostini, S; Tonarini, S [Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via G. Moruzzi 1, 56124 Pisa (Italy); Doglioni, C [Dipartimento di Scienze della Terra, Universita La Sapienza, Roma (Italy); Innocenti, F [Dipartimento di Scienze della Terra, Universita di Pisa, Pisa (Italy); Manetti, P [Dipartimento di Scienze della Terra, Universita di Firenze, Firenze (Italy)], E-mail: s.agostini@igg.cnr.it

    2008-07-01

    The widespread Western Anatolian-Aegean Neogene volcanism presents a complex geochemical evolution reflecting the uncommon space-time variability of the geodynamic setting of the region. In the Western Anatolian and Central Aegean, a widespread supra-subduction magmatism, with calc-alkaline to shoshonitic affinity, took place from Early to Middle Miocene; this phase of activity ends with spots of ultra-K lavas and dykes. From Late Miocene onwards scattered alkali basaltic lavas with intraplate affinity were emitted, while calc-alkaline activity occurred in the South Aegean arc. Since Late Oligocene-Early Miocene, the region was, and still is, affected by extensional tectonics generally ascribed to a backarc rift. However the Aegean region should rather be considered as an unconventional backarc since its characteristics rather differ from 'typical' backarcs. In fact, in spite of a long lasting(>40Ma) active NE-directed subduction of Africa, the backarc area still maintains a relatively thick continental crust (>20-25 km). Moreover, the upper Eurasian plate is overriding the lower Africa plate with separate segments, with Greece moving faster, and Turkey moving slower. The differential velocity between Greece and Turkey determines extension in the upper plate, unrelated to the loss of subducted retreating lithosphere, which is the usual setting for the origin of 'classic' backarc settings. The geodynamic framework is supported by the geochemical and isotopic features of the supra-subduction magmas revealing the occurrence of a trapped, drying slab, with progressive decreasing of Fluid Mobile Elements/Fluid Immobile Elements ratios, {delta}{sup 11}B and {delta}{sup 7}Li, coupled with scarce variations of Sr and Nd isotopes. Moreover, the differential motion between the Greek and Anatolian micro-plates creates tear zones with the formation of slab ruptures or vertical slab windows. The occurrence of such windows is, in fact, outlined by the

  1. Alaska Open-file Report 144 Assessment of Thermal Springs Sites Aleutian Arc, Atka Island to Becherof Lake -- Preliminary Results and Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Motyka, R.J.; Moorman, M.A.; Liss, S.A.

    1981-12-01

    Twenty of more than 30 thermal spring areas reported to exist in the Aleutian arc extending from Atka Island to Becherof Lake were investigated during July and August, 1980. Thermal activity of three of these sites had diminished substantially or no longer existed. At least seven more sites where thermal-spring activity is probable or certain were not visited because of their remoteness or because of time constraints. The existence of several other reported thermal spring sites could not be verified; these sites are considered questionable. On the basis of geothermometry, subsurface reservoir temperatures in excess of 150 C are estimated for 10 of the thermal spring sites investigated. These sites all occur in or near regions of Recent volcanism. Five of the sites are characterized by fumaroles and steaming ground, indicating the presence of at least a shallow vapor-dominated zone. Two, the Makushin Valley and Glacier Valley thermal areas, occur on the flanks of active Mukushin Volcano located on Unalaska Island, and may be connected to a common source of heat. Gas geothermometry suggests that the reservoir feeding the Kliuchef thermal field, located on the flanks of Kliuchef volcano of northeast Atka Island, may be as high as 239 C.

  2. Seismically active column and volcanic plumbing system beneath the island arc of the Izu-Bonin subduction zone

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš; Vaněk, Jiří; Hanuš, Václav

    2009-01-01

    Roč. 179, č. 3 (2009), s. 1301-1312 ISSN 0956-540X Institutional research plan: CEZ:AV0Z30120515 Keywords : seismicity and tectonics * volcano seismology * subduction zone processes * volcanic arc processes * magma migration and fragmentation * Pacific Ocean Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.435, year: 2009

  3. Offshore wind power in the Aegean Sea

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Hahmann, Andrea N.

    hub heights at around 100 m using a combination of satellite wind fields and the long-term climate of atmospheric stability from the mesoscale model (Badger et al. 2016). The result of the mean wind speed at hub-height for the Aegean Sea is shown in Figure 1. The map shows the stability dependent......, where the spatial variations in wind speed are very high, accurate resource mapping is of great importance as the produced wind power is proportional to the cubed wind speed. It is challenging to model the wind resource and it is costly to measure from the ground at every place of interest. Maps based...

  4. CRED 60 m Gridded bathymetry and IKONOS estimated depths of UTM Zone 2, Northwestern Hawaiian Islands, USA (Arc ASCII format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of the Northwestern Hawaiian Islands, USA within UTM Zone 2. Bottom coverage was...

  5. CRED 60m Gridded bathymetry and IKONOS estimated depths of UTM Zone 3, Northwestern Hawaiian Islands, USA (Arc ASCII format)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry and IKONOS estimated depths of the shelf and slope environments of the Northwestern Hawaiian Islands, USA within UTM Zone 3. Bottom coverage was...

  6. Melt inclusion: methods, applications and problem: Silica-rich melts in quartz xenoliths from Vulcano islands and their bearing on processes of crustal melting and crust-magma interaction in the Aeolian Arc, Italy

    NARCIS (Netherlands)

    Frezzotti, M.L.; Zavon, V.; Peccerillo, A.; Nikogosian, I.

    2002-01-01

    Silica-rich melts in quartz xenoliths from Vulcano islands and their bearing on processes of crustal melting and crust-magma interaction in the Aeolian Arc, Italy Proceedings of workshop Melt inclusion: methods, applications and problem. Napoli, Italy, September 2002, p. 71-73

  7. Anelastic attenuation structure of the southern Aegean subduction area

    Science.gov (United States)

    Ventouzi, Chrisanthi; Papazachos, Constantinos; Papaioannou, Christos; Hatzidimitriou, Panagiotis

    2014-05-01

    The study of the anelastic attenuation structure plays a very important role for seismic wave propagation and provides not only valuable constraints for the Earth's interior (temperature, relative viscosity, slab dehydration and melt transport) but also significant information for the simulation of strong ground motions. In order to investigate the attenuation structure of the broader Southern Aegean subduction area, acceleration spectra of intermediate depth earthquakes produced from data provided by two local networks which operated in the area were used. More specifically, we employed data from approximately 400 intermediate-depth earthquakes, as these were recorded from the EGELADOS seismic monitoring project which consisted of 65 land stations and 24 OBS recorders and operated during 2005-2007, as well as data from the earlier installed CYCNET local network, which operated during 2002-2005. A frequency-independent path attenuation operator t* was computed for both P and S arrivals for each waveform, using amplitude spectra generated by the recorded data of the aforementioned networks. Initially, estimated P and S traveltimes were examined and modeled as a function of epicentral distance for different groups of focal depths, using data from the CYCNET network in order to obtain the expected arrival information when original arrival times were not available. Two approaches to assess the spectral-decay were adopted for t* determination. Initially, an automated approach was used, where t* was automatically calculated from the slope of the acceleration spectrum, assuming an ω2 source model for frequencies above the corner frequency, fc. Estimation of t* was performed in the frequency band of 0.2 to 25 Hz, using only spectra with a signal-to-noise ratio larger than 3 for a frequency range of at least 4Hz for P-waves and 1Hz for S-waves, respectively. In the second approach, the selection of the linearly-decaying part of the spectra where t* was calculated, was

  8. Late Proterozoic island-arc complexes and tectonic belts in the southern part of the Arabian Shield, Kingdom of Saudi Arabia

    Science.gov (United States)

    Greenwood, William R.; Stoeser, D.B.; Fleck, R.J.; Stacey, J.S.

    1983-01-01

    Sr ratios are not included in the appendix, but all rocks more than 660 m.y. old have initial ratios in the range 0.7021-0.7035, with only two greater than 0.7030. Thus, nothing in the Rb-Sr data suggests involvement of an older continental crust during the evolution of the southern Shield. A lead isotope study of ore minerals and potassium feldspars of the Arabian Shield by Stacey and others (1980) also suggests that no older (Archean to early Proterozoic) evolved continental-type crust underlies the southern Shield. An early summary of mapping (Schmidt and others, 1973) suggests that older sialic basement underlies the late Proterozoic layered rocks in the southern Shield. However, subsequent-mapping and the isotopic studies cited above have established that all of these rocks are of late Proterozoic age and that all rocks of the southern Shield that are more than 660 m.y. old have ensimatic or mantle isotopic characteristics. Figure 2 shows, with only two exceptions, that rocks more than 800 m.y. old are present west of the boundary separating the Tayyah and Khadra belts. The exceptions are two poorly controlled Rb-Sr ages obtained by Fleck (1980) on two quartz diorite plutons in the Malahah region (appendix 1, localities 26 and 27). Preliminary uranium-thorium zircon data of Stacey now suggest that one of these quartz diorite plutons (locality 26) has an age of approximately 640 m.y. Therefore, we prefer to discount the two dates of Fleck until further information is available. As noted earlier and as described below, most of the rocks of the southern Arabian Shield have characteristics typical of those formed in the island-arc environment by subduction-related processes. We shall refer to the group of rocks in the western part of the southern Shield, which formed from 1100 to 800 m.y. ago, as the 'older ensimatic-arc complex' and those in the eastern and northwestern parts, which formed from 800 to 690 m.y. ago, as the 'younger marginal-arc compl

  9. 143Nd/144Nd and 87Sr/86Sr isotope ratio variations in magmatic rocks of Aleutian island arc as regard to the problem of their petrogenesis

    International Nuclear Information System (INIS)

    Zhuravlev, D.Z.; Chernyshev, I.V.; Tsvetkov, A.A.; Borsuk, A.M.; Agapova, A.A.; Serdyuk, N.I.

    1983-01-01

    The results of precision measurement of isotope composition of neodymium in rocks of Pre-Quaternary magmatic formations of the Aleutian island arc (AIA) (Commander Islands). It has been found summing the Nd and Sr analysis results in AIA magmatic rocks that AIA magmatic melts are of mantle origin. The AIA magma source the full its length off and for all the history of geological development remained isotopically homogeneousm Crust contamination of magmatic melts played a significant role only in the initial and early stages of the AIA development, in the later and conclusive stages this process has been sharply reduced. Sedimentary material practically did not take part in the magmaproduction process at the initial stage of the AIA development, it is hardly probable that its role increased at the later stages. The cause of important 87 Sr/ 86 Sr ratio variations in the rocks of one AIA petrographic type is the propylitization process with participation of sea water. Variance of 87 Sr/ 86 Sr ratios without taking into account other isotope systems data is not an indisputable proof of magma source heterogeneity

  10. Social factors associated with pulmonary hydatid cyst in Aegean ...

    African Journals Online (AJOL)

    Social factors associated with pulmonary hydatid cyst in Aegean, Turkey. ... where there are insufficient environmental health and preventive medicine services. ... The offices of the public administration have a responsibility to inform citizens ...

  11. Evidence for Prehistoric Astronomy in the Aegean

    Science.gov (United States)

    Banos, G.

    In this study an effort is made to find evidence, based on literary and archaeological sources, for the astronomical knowledge of the people in and around the Aegean in prehistoric times. The main conclusions are: 1) The Minoans, as well as the Mycenaeans, had a calendar, not necessarily the same. The existence of a Mycenaean calendar is well known from the Knossos and Pylos tablets containing a number of months. 2) The Minoans had a luni-solar calendar and a time record system. They used as a basic time unit the time of rise of the solar disc, measured probably through a clepsydre, and the well known gaming board (zatrikion) of the Heraclion Museum as a time-keeper. Bigger units were the day, the lunar months, the year and the octaetiris. 3) The necessary observations were probably made from sites such as the peak sanctuaries in Crete.

  12. Geological Structures Appearances and Its Relation to Mechanism of Arc-Continent Collision Northen Alor-Wetar Islands

    Directory of Open Access Journals (Sweden)

    Subarsyah Subarsyah

    2017-02-01

    Full Text Available Study area is located in South Banda Basin near the triple junction between Eurasian, Pacific and Indo-Australian Plates. This area is part of back-arc thrusting zone that evolved to compensate convergence between Australia Continent and Banda Arc. Based on seismic section in this area, geological structure analysis is characterized into three distinctive zones. There are Thrust Zone (TZ, Proto Thrust Zone (PTZ and Normal Fault Zone (NFZ. TZ is defined by distribution of numerous of thrust fault, PTZ contains a blind zone or folds instead of thrust fault, and NFZ defined by distribution of numerous normal fault in the upper portion of seismic section. PTZ identified at several seismic section along the bending zone of oceanic crust. The appearances of bending zone will be easily understood by comprehend the driving mechanism of Australia Continent to the Northeast. The bending zone also related to geometry and tectonic stress of collision. Based on this mechanism it was clearly understood why the western end of study area was not identified the bending zone but it probably the initial process of bending. Contradictive to the western end, the eastern part was clearly shown the bending zone that assumed to have the biggest tectonic stress at this moment. Map of structural analysis also explain that PTZ getting narrow towards the west as the indicator of less of tectonic stress.

  13. Cephalopods distribution in the southern Aegean Sea

    Directory of Open Access Journals (Sweden)

    E. LEFKADITOU

    2003-06-01

    Full Text Available The present study concerns faunal composition and distribution of cephalopods in the southern Aegean Sea (35Ζ 13’ 19’’- 37Ζ 55’ 25’’ N, 23Ζ 00’ 15’’ - 28Ζ 15’ 37’’ E. Samples were collected from 708 hauls, obtained by an experimental bottom trawl net during eight surveys carried out in the summers of the years 1994-2001, as well as by commercial trawl net during four surveys carried out in September 1995, December 1995, May and September 1996. The hauls were performed at depths ranging from 16 to 778 m. A total of 34 species of cephalopod in 12 families were identified, including 11 oegopsid squid, 3 myopsid squid, 7 octopod, 3 cuttlefish and 10 sepiolid. Trawling with the experimental net resulted in the capturing of some uncommon pelagic species, such as Ctenopteryx siculaand Octopoteuthis sicula, which were recorded for the first time in the Aegean Sea. Most of the species showed a wide depth and geographical range. The species: Sepia officinalis, Sepietta neglecta, Sepietta obscuraand Sepiola rondeletiwere caught only on the continental shelf, whereas the Ancistroteuthis lichtensteini, Bathypolypous sponsalis, Brachioteuthis riisei, Chiroteuthis veranyi, Ctenopteryx sicula, Heteroteuthis dispar, Histioteuthis reversa, Neorossia caroli and Pyroteuthis margaritiferawere found only on the slope. The rest of the species extended in both continental shelf and slope. The spatial distribution of different species groups is discussed in relation to the hydrology and topography of the study area and the species ecology.

  14. Sr-Pb-Nd isotopic evidence that both MORB and OIB sources contribute to oceanic island arc magmas in Fiji

    International Nuclear Information System (INIS)

    Gill, J.B.

    1984-01-01

    Twenty-eight new Pb, 20 Sr, and 9 Nd isotopic compositions are presented for 32 rocks and one galena from Fiji and the South Fiji (back-arc) Basin. The Fijian rocks range in age from 35 to 143 Nd/ 144 Nd and low 206 Pb/ 204 Pb). Nearly constant 207 Pb/ 204 Pb, and an OIB source component lying within the conventional Sr-Nd-Pb mantle array. In later calc-alkaline and shoshonitic series rocks, these same trace element and isotopic ratios are more like those of OIB. The change was not accompanied by an increase in 207 Pb/ 204 Pb or Cs/K, indeed, 207 Pb/ 204 Pb is closer to the mantle array in these later series. Consequently, the change indicates a greater contribution from OIB sources, rather than from recycled ocean crust. These interpretations require that both MORB and OIB sources coexist in the uppermost mantle above subducted lithosphere. (orig./WB)

  15. Cesium-137 concentrations in marine macroalgae from different biotopes in the Aegean Sea (Greece).

    Science.gov (United States)

    Sawidis, Thomas; Heinrich, Gerorg; Brown, Murray-T

    2003-03-01

    The commonest species of red, brown, and green macroalgae were sampled from a range of biotopes in the Aegean Sea during 1998 for their 137Cs content. Significant differences in 137Cs concentrations were found among different species growing under similar environmental conditions, suggesting that uptake does not follow physical levels but is influenced by allometric parameters and physiological mechanisms. 137Cs content in collected seaweeds were in the descending order: Ulva lactuca>Enteromorpha linza>Gracilaria verrucosa>Ceramium rubrum>Cystoseira barbata. A comparison of the stations studied indicated that the degree of accumulation is also dependent on the geomorphology of the specific area. The west side of Thermaikos Gulf, where the rivers Axios, Aliakmon, and Pinios flow, was highly contaminated as was the Strymonicos Gulf where the river Strymon flows. High cesium concentrations were also observed in algae from Lemnos Island near the mouth of the Dardanelles Channel, most likely due to the horizontal circulation of water masses from the Marmaras Sea to the Aegean Sea resulting in the discharge of 137Cs during the purification process in the Black Sea through the Dardanelles Straits. It is concluded that the general dispersion of 137Cs results from the water circulation regime within the Aegean Sea. Higher levels are present in the northern part of the basin due to current circulation originating from the Black Sea and from outflow of rivers. Levels decrease to the south and east, but increase again to the west of Crete where the Black Sea water mass can be periodically traced.

  16. Quaternary volcanism in Deception Island (Antarctica): South Shetland Trench subduction-related signature in the Bransfield Basin back arc domain

    International Nuclear Information System (INIS)

    Gale, C.; Ubide, T.; Lago, M.; Gil-Imaz, A.; Gil-Pena, I.; Galindo-Zaldivar, J.; Rey, J.; Maestro, A.; Lopez-Martinez, J.

    2014-01-01

    Deception Island shows a volcanism related to the Phoenix Plate subduction and roll-back under South Shetland Block in the present times. The development of the island is related to the evolution and collapse of a volcanic caldera, and this study is focused on the petrology, mineralogy and geochemistry of the post-caldera rocks. We have made a study of the lava flows, dikes and the youngest historic eruption in 1970. These rocks range from dacite to rhyolite and have a microporphyritic texture with olivine and minor clinopyroxene. A pre-caldera basaltic andesite has also been studied. It has a microporphyritic texture with clinopyroxene. The intermediate and acid compositions alternating in the volcanostratigraphic sequence suggest either mafic recharge events or melt extraction from different levels in the deep magmatic system. All the studied compositions share a subduction-related signature similar to other magmatics from the Bransfield Basin. However, compositional differences between pre-caldera and post-caldera rocks indicate a different magma source and depth of crystallisation. According to the geothermobarometric calculations the pre-caldera magmas started to crystallise at deeper levels (13.5-15 km) than the post-caldera magmas (6.2-7.8 km). Specifically, the postcaldera magmas indicate a smaller influence of the subducting slab in the southwestern part of the Bransfield Basin in respect to the available data from other sectors as well as the involvement of crustal contamination in the genesis of the magmas. (Author)

  17. Surveillance at sea: The transactional politics of border control in the Aegean.

    Science.gov (United States)

    Dijstelbloem, Huub; van Reekum, Rogier; Schinkel, Willem

    2017-06-01

    The relationship between vision and action is a key element of both practices and conceptualizations of border surveillance in Europe. This article engages with what we call the 'operative vision' of surveillance at sea, specifically as performed by the border control apparatus in the Aegean. We analyse the political consequences of this operative vision by elaborating on three examples of fieldwork conducted in the Aegean and on the islands of Chios and Lesbos. One of the main aims is to bring the figure of the migrant back into the study of border technologies. By combining insights from science and technology studies with border, mobility and security studies, the article distinguishes between processes of intervention, mobilization and realization and emphasizes the role of migrants in their encounter with surveillance operations. Two claims are brought forward. First, engaging with recent scholarly work on the visual politics of border surveillance, we circumscribe an ongoing 'transactional politics'. Second, the dynamic interplay between vision and action brings about a situation of 'recalcitrance', in which mobile objects and subjects of various kinds are drawn into securitized relations, for instance in encounters between coast guard boats and migrant boats at sea. Without reducing migrants to epiphenomena of those relations, this recalcitrance typifies the objects of surveillance as both relatable as well as resistant, particularly in the tensions between border control and search and rescue.

  18. Trace metal concentrations in marine organisms from the Eastern Aegean, Turkey

    International Nuclear Information System (INIS)

    Kucuksezgin, F.

    1999-01-01

    Monitoring of mercury, cadmium and lead levels in striped mullet (Mullus barbatus) was conducted in the Eastern Aegean over 3 year period and in some other species during 1996 in the framework of a National Marine Measurement Program and MED-POL II Project for the Aegean Sea. Of all the research on the concentrations of trace metals in the Aegean environment only a little has been carried out in that part of the Eastern Aegean

  19. Climatological Factors Affecting Electromagnetic Surface Ducting in the Aegean Sea Region

    Science.gov (United States)

    2012-03-01

    low precipitation, and northeasterly winds, all due to changes in large scale circulations and a northward shift in extratropical storm tracks. The...differences over the Aegean region, that are governed by large-scale climate factors. a. Winter During winter, the Aegean area is subject to extratropical ... extratropical cyclones from entering the Aegean region, while opposite shifts can 18 allow extratropical cyclones to more frequently enter the Aegean

  20. Frictional properties of relic fore arc metasediments from Kodiak Island, AK: Implications for slip in the upper accretionary prism

    Science.gov (United States)

    Miller, P.; Rabinowitz, H. S.; Saffer, D. M.; Savage, H. M.

    2017-12-01

    The slip behavior of subduction megathrusts is controlled by the mechanical and frictional properties of the material entrained along the plate interface. The shallow reaches of subduction thrusts (i.e. Events (SSE's), tremor, and very low frequency earthquakes (VLFE). However, there remain few detailed experimental studies of relevant fault materials under in situ conditions to probe the connections between rock frictional properties and fault slip behavior. To quantitatively understand the evolution of frictional properties along the upper part of the megathrust, we conducted a suite of shearing experiments at pressures and temperatures similar to in situ conditions, using exhumed subduction zone fault rocks composed of metamorphosed clay-rich sediments from Kodiak Island, Alaska. The metasediments we tested have experienced maximum burial depths ranging from 4-6 to 10-15 km, and peak temperatures ranging from 100-125 to 280 oC, making them ideal analogs for investigating the evolution of friction across the stability transition and into the seismogenic zone. These samples were powdered and sheared in a triaxial deformation apparatus at conditions ranging from 25 MPa and 20 oC, to 195 MPa and 200 oC. Preliminary results at room temperature show steady state friction values of 0.56 and rate strengthening behavior (a-b 0.002) with Dc of 19 mm. Ongoing work is characterizing the frictional properties across the stability transition in greater detail.

  1. Seismically active column and volcanic plumbing system beneath the island arc of the Izu-Bonin subduction zone

    Science.gov (United States)

    Špičák, Aleš; Vaněk, Jiří; Hanuš, Václav

    2009-12-01

    A detailed spatio-temporal analysis of teleseismic earthquake occurrence (mb > 4.0) along the convergent margin of the Izu-Bonin-Mariana arc system reveals an anomalously high concentration of events between 27° and 30.5°N, beneath a chain of seamounts between Tori-shima and Nishino-shima volcanoes. This seismicity is dominated by the 1985/1986 earthquake swarm represented in the Engdahl-van der Hilst-Buland database by 146 earthquakes in the body wave magnitude range 4.3-5.8 and focal depth range 1-100 km. The epicentral cluster of the swarm is elongated parallel to the volcanic chain. Available focal mechanisms are consistent with an extensional tectonic regime and reveal nodal planes with azimuths close to that of the epicentral cluster. Earthquakes of the 1985/1986 swarm occurred in seven time phases. Seismic activity migrated in space from one phase to the other. Earthquake foci belonging to individual phases of the swarm aligned in vertically disposed seismically active columns. The epicentral zones of the columns are located in the immediate vicinity of seamounts Suiyo and Mokuyo, recently reported by the Japanese Meteorological Agency as volcanically active. The three observations-episodic character of earthquake occurrence, column-like vertically arranged seismicity pattern, and existence of volcanic seamounts at the seafloor above the earthquake foci-led us to interpret the 1985/1986 swarm as a consequence of subduction-related magmatic and/or fluid activity. A modification of the shallow earthquake swarm magmatic model of D. Hill fits earthquake foci distribution, tectonic stress orientation and fault plane solutions. The 1985/1986 deep-rooted earthquake swarm in the Izu-Bonin region represents an uncommon phenomenon of plate tectonics. The portion of the lithospheric wedge that was affected by the swarm should be composed of fractured rigid, brittle material so that the source of magma and/or fluids which might induce the swarm should be situated at a

  2. Absolute dating of the Aegean Late Bronze Age

    International Nuclear Information System (INIS)

    Warren, P.M.

    1987-01-01

    A recent argument for raising the absolute date of the beginning of the Aegean Late Bronze (LB) Age to about 1700 B.C. is critically examined. It is argued here that: (1) the alabaster lid from Knossos did have the stratigraphical context assigned to it by Evans, in all probability Middle Minoan IIIA, c. 1650 B.C.; (2) the attempt to date the alabastron found in an early Eighteenth Dynasty context at Aniba to Late Minoan IIIA:1 is open to objections; (3) radiocarbon dates from Aegean LB I contexts are too wide in their calibrated ranges and too inconsistent both within and between site sets to offer any reliable grounds at present for raising Aegean LB I absolute chronology to 1700 B.C. Other evidence, however, suggests this period began about 1600 B.C., i.e. some fifty years earlier than the conventional date of 1550 B.C. (author)

  3. Tsunami recurrence in the eastern Alaska-Aleutian arc: A Holocene stratigraphic record from Chirikof Island, Alaska

    Science.gov (United States)

    Nelson, Alan R.; Briggs, Richard; Dura, Tina; Engelhart, Simon E.; Gelfenbaum, Guy; Bradley, Lee-Ann; Forman, S.L.; Vane, Christopher H.; Kelley, K.A.

    2015-01-01

    cannot estimate source earthquake locations or magnitudes for most tsunami-deposited beds. We infer that no more than 3 of the 23 possible tsunamis beds at both sites were deposited following upper plate faulting or submarine landslides independent of megathrust earthquakes. If so, the Semidi segment of the Alaska-Aleutian megathrust near Chirikof Island probably sent high tsunamis southward every 180–270 yr for at least the past 3500 yr.                   

  4. Paleozoic tectonic evolution of the Dananhu-Tousuquan island arc belt, Eastern Tianshan: Constraints from the magmatism of the Yuhai porphyry Cu deposit, Xinjiang, NW China

    Science.gov (United States)

    Wang, Yunfeng; Chen, Huayong; Han, Jinsheng; Chen, Shoubo; Huang, Baoqiang; Li, Chen; Tian, Qinglei; Wang, Chao; Wu, Jianxin; Chen, Mingxia

    2018-03-01

    The Yuhai intrusions (quartz diorite, granite and pyroxene diorite) are located in the eastern part of the Dananhu-Tousuquan island arc belt of the Eastern Tianshan, and associated with the early Paleozoic porphyry Cu mineralization. LA-ICP-MS zircon U-Pb dating yielded emplacement ages of 443.5 ± 4.1 Ma for the quartz diorite, 325.4 ± 2.5 Ma for the granite, and 291 ± 3.0 Ma for the pyroxene diorite. These rocks are tholeiitic to calc-alkaline and metaluminous, with A/CNK values ranging from 0.66 to 1.10. The Silurian ore-bearing Yuhai quartz diorite is rich in LREEs and LILEs (e.g., K, Ba, Pb and Sr), and depleted in HREEs and HFSEs (e.g., Nb, Ta and Ti). These rocks are MgO-rich (1.90-3.80 wt.%; Mg# = 37-72), with high Sr/Y, La/Yb and Ba/Th ratios, positive εNd(t) (6.31-6.84) and εHf(t) (13.26-16.40), low (87Sr/86Sr)i (0.7037-0.7039), and low Nb/U and Ta/U ratios. The data suggest that the quartz diorite was generated by the partial melting of subducted juvenile oceanic slab. The oxygen fugacity (ƒO2) of the quartz diorite, calculated by zircon Ce4+/Ce3+ ratios, is higher than that of the granite and pyroxene diorite, implying that the quartz diorite was more favorable to porphyry Cu mineralization. The Carboniferous Yuhai granite reveals similar geochemical features with the quartz diorite, except for the lower Mg# (27-33), and the more elevated Th/U and Th/La ratios. Furthermore, these rocks also show high εNd(t) (5.2-5.8) and εHf(t) (11.03-14.85) values, and low (87Sr/86Sr)i (0.7036-0.7037). These features indicate that the parental magma of the granite was probably derived from a juvenile lower crust with no significant mantle component involvement. Different from the Yuhai quartz diorite and granite, the early Permian Yuhai pyroxene diorite contains low SiO2 (50.76-55.74 wt.%) and high MgO (3.96-4.33 wt.%; Mg# = 40-44). The εNd(t), εHf(t) and (87Sr/86Sr)i values of the pyroxene diorite are 5.77-6.42, 7.99-12.10 and 0.7035-0.7040, respectively. The

  5. Seismicity of the 24 May 2014 Mw 7.0 Aegean Sea earthquake sequence along the North Aegean Trough

    Science.gov (United States)

    Görgün, Ethem; Görgün, Burçak

    2015-11-01

    The northern Aegean Sea was hit by a large size (Mw = 7.0) earthquake on 2014 May 24. Centroid moment tensor solutions for 40 events with moment magnitudes (Mw) between 3.3 and 7.0 are computed by applying a waveform inversion method on data from the Turkish and Greek broadband seismic networks. The time span of data covers the period between 2014 May 24 and 2014 June 26. The mainshock is a shallow focus strike-slip event at a depth of 15 km. Focal depths of aftershocks range from 6 to 30 km. The seismic moment (Mo) of the mainshock is estimated as 4.60 × 1019 Nm. The calculated rupture duration of the North Aegean Sea mainshock is 40 s. The focal mechanisms of the aftershocks are mainly strike-slip faulting with a minor normal component. The geometry of focal mechanisms reveals a strike-slip faulting regime with NE-SW trending direction of T-axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to acquire a more accurate picture of the northern Aegean Sea stress field along the North Aegean Trough. The stress tensor inversion results indicate a predominant strike-slip stress regime with a NW-SE oriented maximum principal compressive stress (σ1). In the development of the North Aegean Trough in Aegean Sea is in good agreement with the resolved stress tensors. With respect the newly determined focal mechanisms, the effect of the propagating of the North Anatolian Fault into Aegean Sea is very clearly pronounced. According to high-resolution hypocenter relocation of the North Aegean Sea seismic sequence, three main clusters are revealed. The aftershock activity in the observation period between 2014 May 24 and 2014 July 31 extends from the mainshock cluster from NE to the SW direction. Seismic cross-sections indicate that a complex pattern of the hypocenter distribution with the activation of seventeen segments. The eastern cluster is associated with a fault plane trending mainly ENE-WSW and dipping vertical, while the

  6. Ambient noise levels and characterization in Aegean region, Turkey

    Science.gov (United States)

    Sevim, Fatih; Zor, Ekrem; Açıkgöz, Cem; Tarancıoğlu, Adil

    2018-03-01

    We assessed the ambient noise level in the Aegean region and analyzed its diurnal variation and its relation to the earthquake detection capability of the Aegean Region Seismic Network (ARSN). We prepared probability density functions (PDFs) for 19 broadband stations in the Aegean region operated by the Earth and Marine Sciences Institute (EMSI) of the Marmara Research Center (MRC) of the Turkish Scientific Research Council (TÜBİTAK). The power spectral densities (PSDs) used to construct PDFs for each station were computed for the periods between 0.02 and 180 s. In addition, we generated noise map of the Aegean region for different periods using the PDFs to assess the origin of the noise. We analyzed earthquake activity in the region and found that there are more local events recorded at night than during the day for each station. This difference is strongly related to diurnal variation of background noise level for the period range mostly covering the frequency range for the local events. We observed daytime noise level 15 to 20 dB higher than that at the nighttime in high frequencies for almost all stations caused by its proximity to settled areas and roads. Additionally, we observed a splitting peak within the Double Frequency (DF) microseism band; it showed a clear noise increase around the short period DF band at all the stations, decreasing inland. This peak may be related to sea waves locally generated in the Aegean Sea. We also identified a prominent increase related to marble saw companies in some stations' noise PDFs.

  7. Physical and chemical processes of air masses in the Aegean Sea during Etesians: Aegean-GAME airborne campaign

    Czech Academy of Sciences Publication Activity Database

    Tombrou, M.; Bossioli, E.; Kalogiros, J.; Allan, J. D.; Bacak, A.; Biskos, J.G.; Coe, H.; Dandou, A.; Kouvarakis, G.; Mihalopoulos, N.; Percival, C. J.; Protonotariou, A. P.; Szabó-Takács, Beáta

    2015-01-01

    Roč. 506, feb (2015), s. 201-216 ISSN 0048-9697 Institutional support: RVO:67179843 Keywords : Aegean-GAME campaign * Air borne measurements * Marine Atmospheric Boundary Layer * Turbulent fluxes * Gas and aerosol composition * Etesian winds Subject RIV: EH - Ecology, Behaviour Impact factor: 3.976, year: 2015

  8. KALMAR - "Kurile-Kamchatka and Aleutean Marginal Sea-Island Arc Systems: Geodynamic and Climate Interaction in Space and Time" - an integrated science approach between Russia and Germany

    Science.gov (United States)

    Dullo, Wolf-Christian; Baranov, Boris; van den Bogaard, Christel

    2010-05-01

    The exploration of the arctic seas require an integrated approach applying different infrastructures. In Fall 2009 German and Russian scientists performed a geo marine cruise off Kamchatka and in the western Bering Sea within the frame of the KALMAR-Project. Two main research subjects formed the scientific backbone of the cruise: The first objective focuses on the geodynamic and volcanological-magmatic development of the Kuril-Kamchatka island arc system and the Kamchatka Aleutean Islands Triple-Junction. Very little is known about the composition of the mantle and the oceanic crust as well as of the seamounts including their ages. The best studied site is the Volcanologist's Massif located between the Bering- and the Alpha Fracture Zone (Tsvetkov 1990, Volynets et al. 1992, Yogodzinsky et al. 1994), which structurally belongs to the Komandorsky Basin. The oldest rocks of the Volcanologist's Massif show very similar trace element and isotope signatures like those rocks cropping out in the volcanoes on Kamchatka in the prolongation of the Alpha Fracture Zone (Portnyagin et al. 2005a), indicating similar conditions of magma formation. The top of the Volcanologist's Massif is characterized by the young (Emperor-Seamount chain, having an age of probably > 85 Ma. The only existing basement rocks from this seamount were gained during DSDP Leg 19. These are basalts with MORB like trace element and isotope signatures (Keller et al. 2000, Regelous et al. 2003). These data indicate that the Hawaii-Hotspot was at a MOR in Cretaceous time and that large volumes of depleted mantle material played a role during the magma formation. The second objective focuses on paleo-oceanographic investigations concentrating on the sediments along the eastern continental slope of Kamchatka, in the Komandorsky Basin, and on the Shirshov Ridge in order to explore paleoclimate archives to better understand the subpolar water mass transfer and the oceanographic and climatic development in the

  9. Modeling the buoyancy-driven Black Sea Water outflow into the North Aegean Sea

    Directory of Open Access Journals (Sweden)

    Nikolaos Kokkos

    2016-04-01

    Full Text Available A three-dimensional numerical model was applied to simulate the Black Sea Water (BSW outflux and spreading over the North Aegean Sea, and its impact on circulation and stratification–mixing dynamics. Model results were validated against satellite-derived sea surface temperature and in-situ temperature and salinity profiles. Further, the model results were post-processed in terms of the potential energy anomaly, ϕ, analyzing the factors contributing to its change. It occurs that BSW contributes significantly on the Thracian Sea water column stratification, but its signal reduces in the rest of the North Aegean Sea. The BSW buoyancy flux contributed to the change of ϕ in the Thracian Sea by 1.23 × 10−3 W m−3 in the winter and 7.9 × 10−4 W m−3 in the summer, significantly higher than the corresponding solar heat flux contribution (1.41 × 10−5 W m−3 and 7.4 × 10−5 W m−3, respectively. Quantification of the ϕ-advective term crossing the north-western BSW branch (to the north of Lemnos Island, depicted a strong non-linear relation to the relative vorticity of Samothraki Anticyclone. Similar analysis for the south-western branch illustrated a relationship between the ϕ-advective term sign and the relative vorticity in the Sporades system. The ϕ-mixing term increases its significance under strong winds (>15 m s−1, tending to destroy surface meso-scale eddies.

  10. Early Neolithic settlement patterns and exchange networks in the Aegean

    Directory of Open Access Journals (Sweden)

    Agathe Reingruber

    2011-12-01

    Full Text Available The Neolithisation process is one of the major issues under debate in Aegean archaeology, since the description of the basal layers of Thessalian tell-settlements some fifty years ago. The pottery, figurines or stamps seemed to be of Anatolian origin, and were presumably brought to the region by colonists. The direct linking of the so-called ‘Neolithic Package’ with groups of people leaving Central Anatolia after the collapse of the Pre-Pottery Neolithic B resulted in the colonisation model of the Aegean. This view is not supported by results obtained from natural sciences such as archaeobotany, radiocarbon analyses, and neutron activation on obsidian. When theories of social networks are brought into the discussion, the picture that emerges becomes much more differentiated and complex.

  11. Wind Atlas of Aegean Sea with SAR data

    DEFF Research Database (Denmark)

    Bingöl, Ferhat; Hasager, Charlotte Bay; Badger, Merete

    2013-01-01

    The Global Wind Atlas project is established to create a “free-to-use” wind atlas of the whole globe. The modelling chain of the project includes micro-scale models and new reanalysis datasets. Local measurements are planed to be use for test and validation. Unfortunately, it is not always possible...... to find long term offshore measurement to make wind statistics. The main reason is the cost of setup and maintenance of an offshore mast. One of the regions which has high potential in wind resources but so far is without any long term offshore measurement is the Aegean sea. Recent developments...... in satellite radar technologies made it possible to use Synthetic Aperture Radars (SAR) for wind speed and direction measurements at offshore locations. In this study, a new technique of making wind atlases is applied to the region of Aegean Sea is presented. The method has been tested and validated...

  12. Precursory accelerated Benioff strain in the Aegean area

    Energy Technology Data Exchange (ETDEWEB)

    Papazachos, C.; Papazachos, B. [Thessaloniki Univ., Thessaloniki (Greece). Geophysical Laboratory

    2001-04-01

    Accelerating seismic crustal information due to the occurrence of intermediate magnitude earthquakes leading to the generation of a main shock has recently been considered a critical phenomenon. This hypothesis is tested by the use of a large sample concerning the Aegean area. Elliptical critical regions for fifty-two strong main shocks, which have occurred in the Aegean area since 1930, have been identified by applying a power-law relation between the cumulative Benioff strain and the time to the main rupture. Empirical relations between the parameters of this model have been further improved by the use of a large data sample. The spatial distribution of pre shocks with respect to the main shock is examined and its tectonic significance is pointed out. The possibility of using the results of this work to predict the epicentre, magnitude and time of ensuing main shocks are discussed and further work towards this goal is suggested.

  13. The Contacts of the Hittites with the Aegean Peoples

    Directory of Open Access Journals (Sweden)

    Mladen Horvat

    2003-07-01

    defeated and its prince probably handed over to the Hittites by the Ahhiyawa king. In the time of the next Hittite king, Muwatalli 11., there occurs a reference to the country of Wilusa and its ruler Alaksandu, which were identified by some scholars with Troy and its prince Paris-Alexandros. While the identity of the latter is somewhat questionable, the identification of the former is probably confirmed by another document. It deals with the attack of the Hittite renegade Piyamaradu on a place called Lazpa (the classical island of Lesbos and mentions Wilusa as well. Probably the most important, and certainly the longest, Hittite text regarding Ahhiyawa is the so-called Tawagalawa Letter. It is the letter of a Hittite king, most likely Hatusilli III., to the king of Ahhiyawa, whose name is unfortunately not preserved. The letter is named after the first person mentioned in it, which is Tawagalawa, brother of the Ahhiyawa king. A more suitable label, however, would be "the Piyamaradu Letter", because it is a complaint of the Hittite king to his fellow sovereign in Ahhiyawa about the depredations of Piyamaradu on Hittite territory, apparently committed with the tacit approval of the Ahhiyawa king. The most prominent feature of the letter is the apologetic and conciliatory tone used by the Hittite king to address the king of Ahhiyawa, probably a proof that the country of the latter was a respectable military power beyond Hittite reach. All this is compatible with the facts known to us about the Mycenaeans of that age. The Hittites remained active in the Aegean area even close to the end of their empire, as is proved by the texts from the time of Tudhalija IV. He not only successfully suppressed the revolts in the west - namely the land around the Seha River -, and the southwest - Lycia and Caria -, but even managed to establish control over Millawanda-Miletus. The relations with Ahhiyawa remained tense, as can be seen from the trade embargo imposed on a Hittite vassal in

  14. Stochastic strong ground motion simulations for the intermediate-depth earthquakes of the south Aegean subduction zone

    Science.gov (United States)

    Kkallas, Harris; Papazachos, Konstantinos; Boore, David; Margaris, Vasilis

    2015-04-01

    We have employed the stochastic finite-fault modelling approach of Motazedian and Atkinson (2005), as described by Boore (2009), for the simulation of Fourier spectra of the Intermediate-depth earthquakes of the south Aegean subduction zone. The stochastic finite-fault method is a practical tool for simulating ground motions of future earthquakes which requires region-specific source, path and site characterizations as input model parameters. For this reason we have used data from both acceleration-sensor and broadband velocity-sensor instruments from intermediate-depth earthquakes with magnitude of M 4.5-6.7 that occurred in the south Aegean subduction zone. Source mechanisms for intermediate-depth events of north Aegean subduction zone are either collected from published information or are constrained using the main faulting types from Kkallas et al. (2013). The attenuation parameters for simulations were adopted from Skarladoudis et al. (2013) and are based on regression analysis of a response spectra database. The site amplification functions for each soil class were adopted from Klimis et al., (1999), while the kappa values were constrained from the analysis of the EGELADOS network data from Ventouzi et al., (2013). The investigation of stress-drop values was based on simulations performed with the EXSIM code for several ranges of stress drop values and by comparing the results with the available Fourier spectra of intermediate-depth earthquakes. Significant differences regarding the strong-motion duration, which is determined from Husid plots (Husid, 1969), have been identified between the for-arc and along-arc stations due to the effect of the low-velocity/low-Q mantle wedge on the seismic wave propagation. In order to estimate appropriate values for the duration of P-waves, we have automatically picked P-S durations on the available seismograms. For the S-wave durations we have used the part of the seismograms starting from the S-arrivals and ending at the

  15. ARC Operations

    Science.gov (United States)

    coordination on a regular basis. The overall ARC organizational structure is shown below. Organizational Structure Dynamics and Control of Vehicles Human Centered Modeling and Simulation High Performance

  16. The Aegean/Cycladic and the Basin and Range Extensional Provinces - A Tectonic and Geochronologic Perspective

    Science.gov (United States)

    Stockli, D. F.

    2017-12-01

    The Aegean/Cycladic region (AC) and the Basin and Range Province (B&R) are two of the most famous Cenozoic extensional provinces and have greatly influenced our thinking about syn-convergent back-arc extension, core complex formation, syn-extensional magmatism, and kinematic transitions. They share numerous tectonic and structural similarities, such as a syn-convergent setting, previous contractional deformation, and core complex formation, but fundamental geological ambiguities remain, mainly centering around timing. The B&R affected a previously contractional belt (Sevier) and voluminous continental magmatic arc that created a pre-extensional orogenic highland. Extension was long-lived and complex, driven by both gravitational collapse and temporally distinct kinematic boundary condition changes. The B&R was also affected by massive, largely pre-extensional regional magmatic flare-ups that modified both the thermal and crustal composition. As the B&R occupies an elevated interior plateau, syn-extensional basin deposits are exclusively continental in character. In contrast, the AC is a classic marine back-arc extensional province that affected an active subduction margin with numerous accreted oceanic and continental ribbons, exhuming an early Cenozoic HP-LT subduction complex. Exhumation of the HP-LT complex, however, was accommodated both by vertical extrusion and crustal extension. Late Cenozoic extensional faulting was contemporaneous with S-ward sweeping arc magmatism and affected by little to no kinematic changes. As both the AC and B&R experienced contractional deformation during K-Cz subduction and J-K shortening, respectively, it is critical to differentiate between contractional and extensional structures and fabrics. The lack of temporal constraints hampers the reconstructions of pre-extensional structural anatomies and extensional strain magnitudes or even the attribution of structures to specific geodynamic settings. Novel methodologies in

  17. Spectroscopic studies of humic acids from subsurface sediment samples collected across the Aegean Sea

    Directory of Open Access Journals (Sweden)

    F. SAKELLARIADOU

    2006-12-01

    Full Text Available Natural humic acids are biogenic, structurally complex and heterogeneous, refractory, acidic, yellow-to black-coloured organic polyelectrolytes of relatively high molecular weight. They occur in all soils, sediments, fresh waters, and seawaters. Humic acids represent the largest portion of nonliving soil organic matter. In the present paper, humic substances were isolated from marine subsurface sediment samples collected across the Aegean sea (in Greece and especially from a marine area extending northwards of the Samothraki plateau towards the north-eastern part of the island of Crete. In a following step, humic preparations were studied using infrared and fluorescence spectroscopy (emission, excitation and synchronous-scan excitation spectra were obtained. The infrared spectra suggested functional chemical groups such as as OH-, C-H aliphatic, C=C, C=O/COO-, salts of carboxylic acids, and also, in some cases, silicate anions or C-O from alcohols, esters and ethers. Fluorescence emission, excitation and synchronous scan excitation provided some valuable information concerning a probable origin (marine and/or terrestrial for the isolated humics.

  18. An analytical study of prehistoric lead and silver objects from the Aegean

    International Nuclear Information System (INIS)

    Pernicka, E.; Wagner, G.A.; Assimenos, K.; Doumas, C.; Begemann, F.; Todt, W.

    1983-01-01

    In the course of an archaeometallurgical study on the metal sources of archaic silver coinage it was discovered that lead-silver mines on the Cycladic island of Siphnos, which were known to Herodotus (III, 57) and exploited in archaic times, were already worked in the Early Bronze Age (EBA). In addition, new excavations in Thorikos have shown that the well-known lead-silver deposit of Laurion on Attika was also exploited as early as the EBA. In order to assess the role which these two mining districts and other possible ore sources played in the Bronze Age for the supply of lead and silver, we analyzed prehistoric lead and silver objects from the Aegean region. The methods employed were the same as have been used to characterize the ore deposits. In addition we wanted to study to what extent cupellation was practised in these early periods. Bulk composition and trace element concentrations were determined by instrumental and radiochemical neutron activation and atomic absorption spectrometry. Isotope abundance analyses were performed on a VARIAN MAT 261 mass spectrometer. Experimental details are given. Results are presented and discussed. (U.K.)

  19. Long-Term Marine Traffic Monitoring for Environmental Safety in the Aegean Sea

    Science.gov (United States)

    Giannakopoulos, T.; Gyftakis, S.; Charou, E.; Perantonis, S.; Nivolianitou, Z.; Koromila, I.; Makrygiorgos, A.

    2015-04-01

    The Aegean Sea is characterized by an extremely high marine safety risk, mainly due to the significant increase of the traffic of tankers from and to the Black Sea that pass through narrow straits formed by the 1600 Greek islands. Reducing the risk of a ship accident is therefore vital to all socio-economic and environmental sectors. This paper presents an online long-term marine traffic monitoring work-flow that focuses on extracting aggregated vessel risks using spatiotemporal analysis of multilayer information: vessel trajectories, vessel data, meteorological data, bathymetric / hydrographic data as well as information regarding environmentally important areas (e.g. protected high-risk areas, etc.). A web interface that enables user-friendly spatiotemporal queries is implemented at the frontend, while a series of data mining functionalities extracts aggregated statistics regarding: (a) marine risks and accident probabilities for particular areas (b) trajectories clustering information (c) general marine statistics (cargo types, etc.) and (d) correlation between spatial environmental importance and marine traffic risk. Towards this end, a set of data clustering and probabilistic graphical modelling techniques has been adopted.

  20. Coastal habitat mapping in the Aegean Sea using high resolution orthophoto maps

    Science.gov (United States)

    Topouzelis, Konstantinos; Papakonstantinou, Apostolos; Doukari, Michaela; Stamatis, Panagiotis; Makri, Despina; Katsanevakis, Stelios

    2017-09-01

    The significance of coastal habitat mapping lies in the need to prevent from anthropogenic interventions and other factors. Until 2015, Landsat-8 (30m) imagery were used as medium spatial resolution satellite imagery. So far, Sentinel-2 satellite imagery is very useful for more detailed regional scale mapping. However, the use of high resolution orthophoto maps, which are determined from UAV data, is expected to improve the mapping accuracy. This is due to small spatial resolution of the orthophoto maps (30 cm). This paper outlines the integration of UAS for data acquisition and Structure from Motion (SfM) pipeline for the visualization of selected coastal areas in the Aegean Sea. Additionally, the produced orthophoto maps analyzed through an object-based image analysis (OBIA) and nearest-neighbor classification for mapping the coastal habitats. Classification classes included the main general habitat types, i.e. seagrass, soft bottom, and hard bottom The developed methodology applied at the Koumbara beach (Ios Island - Greece). Results showed that UAS's data revealed the sub-bottom complexity in large shallow areas since they provide such information in the spatial resolution that permits the mapping of seagrass meadows with extreme detail. The produced habitat vectors are ideal as reference data for studies with satellite data of lower spatial resolution.

  1. 210Po activity concentrations in mussels at Aegean Turkish Coast

    International Nuclear Information System (INIS)

    Sekkin, F.; Tanbay, A.; Vener, V.

    2000-01-01

    In Turkey mussels (Mytilus galloprovincialis) are consumed in relatively large quantities. Therefore, analyses of mussel samples from different sampling sites in Aegean Sea were performed in order to evaluate the ingestion of 210 Po and 210 Pb by the Turkey population. Polonium analyses were performed with a complete dissolution of the sample in mineral acids. Polonium isotopes were plated onto a copper discs in 0.5 M HCl solution in the presence of ascorbic acid using a technique modified from Flynn (1968). The alpha activity measurements of polonium isotopes plated on copper discs were performed with ZnS(Ag) detector. The highest concentrations was found in Karaburun mussels as 254 Bq.kg -1 and the lowest one was at Inciralti as 18 Bq.kg -1 . Based on these 210 Po activity concentrations, annual dose equivalent rates delivered to biological tissues in mussels would vary widely, from 136 to 10 mSv.y -1 . It is concluded that in mussels living in the Aegean Sea a wide range of internal radiation dose exists and it is essentially sustained by 210 Po food-chain transfer. (author)

  2. Hydrology and circulation in the North Aegean (eastern Mediterranean throughout 1997 and 1998

    Directory of Open Access Journals (Sweden)

    V. ZERVAKIS

    2002-06-01

    Full Text Available The combination of two research projects offered us the opportunity to perform a comprehensive study of the seasonal evolution of the hydrological structure and the circulation of the North Aegean Sea, at the northern extremes of the eastern Mediterranean. The combination of brackish water inflow from the Dardanelles and the sea-bottom relief dictate the significant differences between the North and South Aegean water columns. The relatively warm and highly saline South Aegean waters enter the North Aegean through the dominant cyclonic circulation of the basin. In the North Aegean, three layers of distinct water masses of very different properties are observed: The 20-50 m thick surface layer is occupied mainly by Black Sea Water, modified on its way through the Bosphorus, the Sea of Marmara and the Dardanelles. Below the surface layer there is warm and highly saline water originating in the South Aegean and the Levantine, extending down to 350-400 m depth. Below this layer, the deeper-than-400 m basins of the North Aegean contain locally formed, very dense water with different θ /S characteristics at each subbasin. The circulation is characterised by a series of permanent, semi-permanent and transient mesoscale features, overlaid on the general slow cyclonic circulation of the Aegean. The mesoscale activity, while not necessarily important in enhancing isopycnal mixing in the region, in combination with the very high stratification of the upper layers, however, increases the residence time of the water of the upper layers in the general area of the North Aegean. As a result, water having out-flowed from the Black Sea in the winter, forms a separate distinct layer in the region in spring (lying between “younger” BSW and the Levantine origin water, and is still traceable in the water column in late summer.

  3. 1881 and 1949 earthquakes at the Chios-Cesme Strait (Aegean Sea and their relation to tsunamis

    Directory of Open Access Journals (Sweden)

    Y. Altinok

    2005-01-01

    Full Text Available The most earthquake-prone areas in the eastern central Aegean Sea are the Izmir Bay, the Karaburun peninsula and the island of Chios. The level of seismic activity and tsunami potential are influenced by the presence of normal faults around the region. There have been about 20 moderate-size earthquakes from 496 BC to 1949 AD. Among these earthquakes, the ones on the dates 20 March 1389, 13 November 1856, 19/22 January 1866, 3 April 1881 and 23 July 1949 produced tsunamis. The Chios-Cesme earthquake (1881, Mw 6.5 took place in the South of the Cesme strait while the Chios-Karaburun earthquake (1949, Mw 6.7 occurred in the North. The tsunamis caused by the earthquakes affected the coasts of Chios Island and Cesme. These waves are thought to be associated with the earthquakes and co-seismic underwater failures possibly occurred along the coasts of the Chios Island and Karaburun Peninsula or on the complex subaqueous morphology between these lands. Some sea waves or oscillations observed following the aftershocks are believed to be related to other natural phenomena; e.g. the seiches occurred mainly in open-narrow bays as triggered by the earthquakes.

  4. An Alternative Georoute: Approaching the Geological Heritage of the SE Part of Milos Island, Greece, via Hiking, Kayaking and Snorkeling

    Science.gov (United States)

    Mavrogonatos, Constantinos; Galanopoulos, Evangelos; Anastasatou, Marianthi; Chadjimpaloglou, Petros; Xydous, Stamatios

    2015-04-01

    Milos Island is located at the southwest edge of the Cyclades island complex, in the central part of the Aegean archipelago. It is part of the modern South Aegean Volcanic Arc (SAVA), which belongs to the Hellenic subduction zone. This on-going process has resulted in the coexistence of complex geological formations and geodynamic phenomena with sceneries of incomparable natural beauty, in many areas along the arc. Among them, Milos Island is widely known to be a place of astonishing geological and natural wealth, combined with a cultural heritage that dates back to the 8th millennium BC. As geotourism has been rapidly evolving worldwide over the last years, Milos Island was among the first places in Greece that developed a network of geotrails and featured many sites of special interest in terms of geology, volcanology and geoarchaeology. This study proposes an original georoute through land and sea, which aims t? emerge both overland and underwater areas of special interest. It is a novel way to approach the geological and cultural wealth of Milos and focuses on the Aghia Kiriaki area, at the South part of the island. This alternative georoute includes hiking, kayaking and snorkeling, and anyone who follows it, can be guided to a significant number of important geological, volcanic, morphological and geoarcheological sites, in a relatively narrow area, combining athletic activities as well. The proposed georoute has a total length of 3,2 km and an estimated time of completion of about 4 hours. It starts from Aghia Kiriaki area, where visitors can see remnants of one of the island's collapsed calderic domes in a panoramic view towards the East. In the same site, volcanic emanations create impressive scenery, which introduces the participants to aspects of the island's geologic and volcanic history. After about 800 meters of hiking, throughout an area that is dominated by products of phreatic eruptions, Aghia Kiriaki beach is the next stop. Impressive findings of

  5. Investigating the March 28th 1875 and the September 20th 1920 earthquakes/tsunamis of the Southern Vanuatu arc, offshore Loyalty Islands, New Caledonia

    Science.gov (United States)

    Ioualalen, Mansour; Pelletier, Bernard; Solis Gordillo, Gabriela

    2017-07-01

    New Caledonia's Loyalty Islands are located in the southwest region of the Pacific ocean in the highly seismogenic southern Vanuatu subduction zone and therefore may be subject to devastating local tsunamis. Over the past 150 years, two large tsunamis were triggered by major earthquakes on March 28th 1875 and September 20th 1920. In this study, we use historical observations of these tsunamis (mostly in the form of testimonials), earthquake scenarios, and tsunami modeling to derive the magnitudes of these earthquakes, as well as tsunami runup and inundation maps. Assuming that these earthquakes were located on the interplate megathrust zone, the 1875 earthquake's magnitude was Mw8.1-8.2 and the 1920 event's magnitude was Mw7.5-7.8. The tsunami damage inflicted on the Lifou and Maré islands was approximately proportional to these magnitudes, with Maré being less impacted due to favorable wave directivity. Damage at Ouvéa island may have varied irregularly with the magnitude due to the effects of resonance. This study demonstrates that the quantitative characteristics of historical tsunamigenic earthquakes may be derived from qualitative estimates of tsunami runup.

  6. Greece, Milos Island Geothermal Project

    International Nuclear Information System (INIS)

    Delliou, E.E.

    1990-01-01

    On Milos island (Aegean Sea) a high enthalpy, water dominated geothermal field of high salinity exists. At 1985, a 2MW geothermoelectric pilot plant was installed on the island. This plant has been provided by Mitsubishi Heavy Industries of Japan under a contract with Public Power Corporation of Greece. Due to high salinity of the geothermal fluid, unforeseen problems (scaling mainly) arisen in both steam and brine cycles. As a consequence, the operation (trial mainly) of the power plant have been interrupted several times for long periods, in order to identify the arisen, each time, problems and find the most appropriate technical solution. The above fact, as well as, some unfortunate coincidences described in this paper, led Milos people to react against geothermal development in their island. The sequence of the events, technical and non-technical, their approach and the relevant conclusions are reported in this presentation

  7. Distribution of organotin compounds in the bivalves of the Aegean Sea, Greece

    NARCIS (Netherlands)

    Chandrinou, S.; Pappas, K.; Nikolaou, A.; Stasinakis, A.S.; Wegener, J.W.M.; Alexandropoulos, Th.; Thomaidis, N.S.

    2007-01-01

    Five bivalve species - Mytilus galloprovinciallis (Mediterranean mussels), Venus gallina (stripped venus), Modiola barbatus L. (bearded horse mussels), Pecten jacobeus (scallops) and Callista chione (hard clams) - were collected from seven areas in Aegean Sea, Greece, between August 2001 and January

  8. Application of multivariate techniques to analytical data on Aegean ceramics

    International Nuclear Information System (INIS)

    Bieber, A.M.; Brooks, D.W.; Harbottle, G.; Sayre, E.V.

    1976-01-01

    The general problems of data collection and handling for multivariate elemental analyses of ancient pottery are considered including such specific questions as the level of analytical precision required, the number and type of elements to be determined and the need for comprehensive multivariate statistical analysis of the collected data in contrast to element by element statistical analysis. The multivariate statistical procedures of clustering in a multidimensional space and determination of the numerical probabilities of specimens belonging to a group through calculation of the Mahalanobis distances for these specimens in multicomponent space are described together with supporting univariate statistical procedures used at Brookhaven. The application of these techniques to the data on Late Bronze Age Aegean pottery (largely previously analysed at Oxford and Brookhaven with some new specimens considered) have resulted in meaningful subdivisions of previously established groups. (author)

  9. Early farmers from across Europe directly descended from Neolithic Aegeans

    Science.gov (United States)

    Hofmanová, Zuzana; Kreutzer, Susanne; Hellenthal, Garrett; Sell, Christian; Diekmann, Yoan; Díez-del-Molino, David; van Dorp, Lucy; López, Saioa; Kousathanas, Athanasios; Link, Vivian; Kirsanow, Karola; Cassidy, Lara M.; Martiniano, Rui; Strobel, Melanie; Scheu, Amelie; Kotsakis, Kostas; Halstead, Paul; Triantaphyllou, Sevi; Kyparissi-Apostolika, Nina; Ziota, Christina; Adaktylou, Fotini; Gopalan, Shyamalika; Bobo, Dean M.; Winkelbach, Laura; Blöcher, Jens; Unterländer, Martina; Leuenberger, Christoph; Çilingiroğlu, Çiler; Horejs, Barbara; Gerritsen, Fokke; Shennan, Stephen J.; Bradley, Daniel G.; Currat, Mathias; Veeramah, Krishna R.; Thomas, Mark G.; Papageorgopoulou, Christina; Burger, Joachim

    2016-01-01

    Farming and sedentism first appeared in southwestern Asia during the early Holocene and later spread to neighboring regions, including Europe, along multiple dispersal routes. Conspicuous uncertainties remain about the relative roles of migration, cultural diffusion, and admixture with local foragers in the early Neolithization of Europe. Here we present paleogenomic data for five Neolithic individuals from northern Greece and northwestern Turkey spanning the time and region of the earliest spread of farming into Europe. We use a novel approach to recalibrate raw reads and call genotypes from ancient DNA and observe striking genetic similarity both among Aegean early farmers and with those from across Europe. Our study demonstrates a direct genetic link between Mediterranean and Central European early farmers and those of Greece and Anatolia, extending the European Neolithic migratory chain all the way back to southwestern Asia. PMID:27274049

  10. TSUNAMI HAZARD ASSESSMENT IN THE NORTHERN AEGEAN SEA

    Directory of Open Access Journals (Sweden)

    Barbara Theilen-Willige

    2008-01-01

    Full Text Available Emergency planning for the assessment of tsunami hazard inundation and of secondary effects of erosion and landslides, requires mapping that can help identify coastal areas that are potentially vulnerable. The present study reviews tsunami susceptibility mapping for coastal areas of Turkey and Greece in the Aegean Sea. Potential tsunami vulnerable locations were identified from LANDSAT ETM imageries, Shuttle Radar Topography Mission (SRTM, 2000 data and QuickBird imageries and from a GIS integrated spatial database. LANDSAT ETM and Digital Elevation Model (DEM data derived by the SRTM-Mission were investigated to help detect traces of past flooding events. LANDSAT ETM imageries, merged with digitally processed and enhanced SRTM data, clearly indicate the areas that may be prone to flooding if catastrophic tsunami events or storm surges occur.

  11. Exergy analysis for a proposed binary geothermal power plant in Nisyros Island, Greece

    DEFF Research Database (Denmark)

    Koroneos, Christopher; Polyzakis, A.; Xydis, George

    2017-01-01

    and a measure of the quality of the different forms of energy in relation to given environmental conditions. In this paper, data from an experimental geothermal drill in the Greek Island of Nisyros, located in the south of the Aegean Sea, have been used in order to estimate the maximum available work...... resulted supporting technical feasibility of the proposed geothermal plant....

  12. A new species of Centaurea (Asteraceae) from the island of Samothraki (NE Greece)

    DEFF Research Database (Denmark)

    Strid, Arne; Tan, Kit

    2009-01-01

    Centaurea samothracica (subgen. Acrolophus) is described and illustrated. It is known from a single locality on (subgen. ) is described and illustrated. It is known from a single locality on the North Aegean island of Samothraki, and appears most closely related to C. chalcidicaea from Mt Athos....

  13. Discordant Early Miocene palaeomagnetic directions at the vicinity of the North Aegean Trough: tectonic or palaeofield feature?

    Science.gov (United States)

    Kontopoulou, D.; Valet, J. P.; Zananiri, I.; Voidomatis, P.

    2017-12-01

    The North Aegean Trough (N.A.T) is a major tectonic feature of North Aegean Sea. This is a large NE-SW transcurrent lineament that is interpreted as the continuation of the North Anatolian Fault, with a prominent dextral strike-slip motion. IAn intense igneous activity has developed along the N.A.T to its north through the presence of abundant plutonism and volcanism from Early Oligocene to Pliocene. A considerable amount of palaeomagnetic data display a systematic pattern of clockwise rotations with angles varying between 20°-40° since the Early Oligocene. In order to document the impact of the N.A.T to regional rotations, early Miocene lava flows have been extensively sampled in the islands of Samothrace and Lemnos located to the north and south of N.A.T, respectively. Two sets of directions have been defined from the palaeomagnetic studies. The first one corresponds to the expected North-East declinations with positive inclinations or to reversed South-West declinations with negative inclinations that were previously interpreted as a dextral rotations of this area. The second set, exhibits discordant and apparently erratic directions despite quite acceptable demagnetization behaviour and magnetic characteristics. In order to constrain further these directions we performed new samplings. The new measurements which include Thellier absolute palaeointensity experiments reveal that the intermediate directions are associated with low field values for Samothrace with a transitional field recorded between 21 and 17 Ma. The presence of single magnetization component and the variability of the lavas do not favor the possibility of self-reversal mechanisms. The consistency of the directions within each flow but also between lava flows of comparable ages in the two islands and the presence of normal and reverse polarities point to records of transitional directions. In both islands, the intermediate virtual geomagnetic poles exhibit a preference for equatorial latitudes

  14. Origin of depleted basalts during subduction initiation and early development of the Izu-Bonin-Mariana island arc: Evidence from IODP expedition 351 site U1438, Amami-Sankaku basin

    Science.gov (United States)

    Hickey-Vargas, R.; Yogodzinski, G. M.; Ishizuka, O.; McCarthy, A.; Bizimis, M.; Kusano, Y.; Savov, I. P.; Arculus, R.

    2018-05-01

    The Izu-Bonin-Mariana (IBM) island arc formed following initiation of subduction of the Pacific plate beneath the Philippine Sea plate at about 52 Ma. Site U1438 of IODP Expedition 351 was drilled to sample the oceanic basement on which the IBM arc was constructed, to better understand magmatism prior to and during the subduction initiation event. Site U1438 igneous basement Unit 1 (150 m) was drilled beneath 1460 m of primarily volcaniclastic sediments and sedimentary rock. Basement basalts are microcrystalline to fine-grained flows and form several distinct subunits (1a-1f), all relatively mafic (MgO = 6.5-13.8%; Mg# = 52-83), with Cr = 71-506 ppm and Ni = 62-342 ppm. All subunits are depleted in non-fluid mobile incompatible trace elements. Ratios such as Sm/Nd (0.35-0.44), Lu/Hf (0.19-0.37), and Zr/Nb (55-106) reach the highest values found in MORB, while La/Yb (0.31-0.92), La/Sm (0.43-0.91) and Nb/La (0.39-0.59) reach the lowest values. Abundances of fluid-mobile incompatible elements, K, Rb, Cs and U, vary with rock physical properties, indicating control by post-eruptive seawater alteration, but lowest abundances are typical of fresh, highly depleted MORBs. Mantle sources for the different subunits define a trend of progressive incompatible element depletion. Inferred pressures of magma segregation are 0.6-2.1 GPa with temperatures of 1280-1470 °C. New 40Ar/39Ar dates for Site U1438 basalts averaging 48.7 Ma (Ishizuka et al., 2018) are younger that the inferred age of IBM subduction initiation based on the oldest ages (52 Ma) of IBM forearc basalts (FAB) from the eastern margin of the Philippine Sea plate. FAB are hypothesized to be the first magma type erupted as the Pacific plate subsided, followed by boninites, and ultimately typical arc magmas over a period of about 10 Ma. Site U1438 basalts and IBM FABs are similar, but Site U1438 basalts have lower V contents, higher Ti/V and little geochemical evidence for involvement of slab-derived fluids. We

  15. Bermuda 3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  16. Bermuda 1 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  17. Tamarix minoa (Tamaricaceae), a new species from the island of Crete (Greece) based on morphological and plastid molecular sequence data

    Science.gov (United States)

    Tamarix minoa is described from material collected on the S Aegean island of Crete (Kriti), Greece. A morphological comparison with the species considered to be closest, T. africana and T. hampeana, is provided. An original illustration showing the main morphological characters of the new species is...

  18. Arc saw development report

    International Nuclear Information System (INIS)

    Deichelbohrer, P.R.; Beitel, G.A.

    1981-01-01

    The arc saw is one of the key components of the Contaminated Equipment Volume Reduction (CEVR) Program. This report describes the progress of the arc saw from its inception to its current developmental status. History of the arc saw and early contributors are discussed. Particular features of the arc saw and their advantages for CEVR are detailed. Development of the arc saw including theory of operation, pertinent experimental results, plans for the large arc saw and advanced control systems are covered. Associated topics such as potential applications for the arc saw and other arc saw installations in the world is also touched upon

  19. Islands in the Midst of the World

    Science.gov (United States)

    2002-01-01

    The Greek islands of the Aegean Sea, scattered across 800 kilometers from north to south and between Greece and western Turkey, are uniquely situated at the intersection of Europe, Asia and Africa. This image from the Multi-angle Imaging SpectroRadiometer includes many of the islands of the East Aegean, Sporades, Cyclades, Dodecanese and Crete, as well as part of mainland Turkey. Many sites important to ancient and modern history can be found here. The largest modern city in the Aegean coast is Izmir, situated about one quarter of the image length from the top, southeast of the large three-pronged island of Lesvos. Izmir can be located as a bright coastal area near the greenish waters of the Izmir Bay, about one quarter of the image length from the top, southeast of Lesvos. The coastal areas around this cosmopolitan Turkish city were a center of Ionian culture from the 11th century BC, and at the top of the image (north of Lesvos), once stood the ancient city of Troy.The image was acquired before the onset of the winter rains, on September 30, 2001, but dense vegetation is never very abundant in the arid Mediterranean climate. The sharpness and clarity of the view also indicate dry, clear air. Some vegetative changes can be detected between the western or southern islands such as Crete (the large island along the bottom of the image) and those closer to the Turkish coast which appear comparatively green. Volcanic activities are evident by the form of the islands of Santorini. This small group of islands shaped like a broken ring are situated to the right and below image center. Santorini's Thera volcano erupted around 1640 BC, and the rim of the caldera collapsed, forming the shape of the islands as they exist today.The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and views almost the entire globe every 9 days. This natural-color image was acquired by MISR's nadir (vertical-viewing) camera, and is a portion of the

  20. On the tectonic processes along the Hellenic Arc

    Directory of Open Access Journals (Sweden)

    A. G. GALANOPOULOS

    1974-06-01

    Full Text Available On the grounds of existing geophysical data one might be allowed lo conclude t h a t the origin of t h e stress field in the Ionian center (Ceplialonia-Zante-Patras at t h e northwestern margin of the Aegean microplate is r a t h e r shallow and in the southeastern center (Dodecanese-Crete is surely under the crust. In the area occupied by the second center of higher earthquake activity t h e relief of the Moho-discontinuity is shallower and smoother in comparison to t h a t derived from g r a v i t y and seismic d a t a for t he area of t h e northwestern center. Another difference derived from the fault-plane solutions is t h a t the Ionian center is seated in a region of horizontal pressure; the second center in the southeastern Aegean Sea belongs to a region of paramount horizontal tension. In the western side of the Hellenic arc the high sediment supply rate, combined with a thickening of the E a r t h ' s crust along the Ionian zone, is interpreted as evidence t h a t accretion has occurred there until recently or may still be occurring locally; plate consumption, if any, is rather low. The existence, 011 t h e other hand, of two very deep subparallel trenches with little fill southeast of Crete (Pliny trench, Strabo trench, combined with a very high subcrustal activity in the southeastern margin of t h e Aegean Bubplate, suggest that the subduction rate at the northern boundary of the African plate must be relatively high; 110 p l a t e accretion is expected to occur there.

  1. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

    Directory of Open Access Journals (Sweden)

    Z. KOKKINI

    2014-12-01

    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  2. Investigating plant–pollinator relationships in the Aegean: the approaches of the project POL-AEGIS (The pollinators of the Aegean archipelago: diversity and threats)

    OpenAIRE

    Petanidou, Theodora; Ståhls, Gunilla; Vujić, Ante; Olesen, Jens M.; Rojo Velasco, Santos; Thrasyvoulou, Andreas; Sgardelis, Stefanos; Kallimanis, Athanasios S.; Kokkini, Stella; Tscheulin, Thomas

    2013-01-01

    Worldwide, there is a well-documented crisis for bees and other pollinators which represent a fundamental biotic capital for wild life conservation, ecosystem function, and crop production. Among all pollinators of the world, bees (Hymenoptera: Apoidea) constitute the major group in species number and importance, followed by hover flies (Diptera: Syrphidae). The Aegean constitutes one of the world’s hotspots for wild bee and other pollinator diversity including flies (mainly hover flies and b...

  3. The new Hamburg Ocean Bottom Tiltmeter: A First Deployment at Columbo Seamount (Aegean Sea, Greece)

    Science.gov (United States)

    Hensch, M.; Hort, M.; Dahm, T.; Winter, S.; Klawonn, M.

    2009-04-01

    Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17" glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt >5°. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 and March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short-period deformations associated with local earthquakes and also observe long-period deformation processes

  4. Os and S isotope studies of ultramafic rocks in the Duke Island Complex, Alaska: variable degrees of crustal contamination of magmas in an arc setting and implications for Ni-Cu-PGE sulfide mineralization

    Science.gov (United States)

    Stifter, Eric C.; Ripley, Edward M.; Li, Chusi

    2016-10-01

    The Duke Island Complex is one of the several "Ural-Alaskan" intrusions of Cretaceous age that occur along the coast of SE Alaska. Significant quantities of magmatic Ni-Cu-PGE sulfide mineralization are locally found in the complex, primarily within olivine clinopyroxenites. Sulfide mineralization is Ni-poor, consistent with petrologic evidence which indicates that sulfide saturation was reached after extensive olivine crystallization. Olivine clinopyroxenites were intruded by magmas that produced sulfide-poor, adcumulate dunites. As part of a study to investigate the potential for Ni-rich sulfide mineralization in association with the dunites, a Re-Os and S isotope study of the dunites, as well as sulfide mineralization in the olivine clinopyroxenites, was initiated. Importantly, recent drilling in the complex identified the presence of sulfidic and carbonaceous country rocks that may have been involved in the contamination of magmas and generation of sulfide mineralization. γOs (110 Ma) values of two sulfidic country rocks are 1022 and 2011. δ34S values of the country rocks range from -2.6 to -16.1 ‰. 187Os/188Os ratios of sulfide minerals in the mineralization hosted by olivine clinopyroxenites are variable and high, with γOs (110 Ma) values between 151 and 2059. Extensive interaction with Re-rich sedimentary country rocks is indicated. In contrast, γOs (110 Ma) values of the dunites are significantly lower, ranging between 2 and 16. 187Os/188Os ratios increase with decreasing Os concentration. This inverse relation is similar to that shown by ultramafic rocks from several arc settings, as well as altered abyssal dunites and peridotites. The relation may be indicative of magma derivation from a sub-arc mantle that had experienced metasomatism via slab-derived fluids. Alternatively, the relation may be indicative of minor contamination of magma by crustal rocks with low Os concentrations but high 187Os/188Os ratios. A third alternative is that the low Os

  5. Coccolithophore assemblage response to Black Sea Water inflow into the North Aegean Sea (NE Mediterranean)

    Science.gov (United States)

    Karatsolis, B.-Th.; Triantaphyllou, M. V.; Dimiza, M. D.; Malinverno, E.; Lagaria, A.; Mara, P.; Archontikis, O.; Psarra, S.

    2017-10-01

    This study aims to presents the species composition of living coccolithophore communities in the NE Aegean Sea, investigating their spatial and temporal variations along a north-south transect in the area receiving the inflowing surface Black Sea Water (BSW) over the deeper Levantine Water (LW) layer. Coccolithophores in the area were relatively diverse and a total of 95 species over 3 sampling periods studied were recognized using Scanning Electron Microscope (SEM) techniques. R-mode hierarchical cluster analysis distinguished two coccolithophore Groups (I, IIa, IIb, IIc) with different ecological preferences. Emiliania huxleyi was the most abundant species of Group I, whereas Syracosphaera spp., Rhabdosphaera spp. and holococcolithophores were prevailing in the highly diversified Group II assemblages. Biometric analysis conducted on E. huxleyi coccoliths from Aegean water column and Black Sea sediment trap samples, indicated that during autumn, NE Aegean specimens in samples under BSW influence were featured by unimodal distribution concerning the coccolith relative tube width, with values similar to those provided by the Black Sea specimens. In early spring, coccoliths in the stations with increased BSW influx displayed a bimodal pattern of relative tube width with smaller values found mostly in the surface layers, while the distribution became again unimodal and dominated by larger values within the deeper LW layers. In the summer period, the typical LW holococcolithophore species (Group II) presented low cell numbers in the surface layer (huxleyi was almost absent in the NE Aegean during the summer sampling period.

  6. The ‘Mycenaeans’ in the south-eastern Aegean revisited

    NARCIS (Netherlands)

    Eerbeek, J.

    2014-01-01

    The main subject of this dissertation is the Mycenaean archaeological evidence from the south-eastern Aegean. The term "Mycenaean" is typically used to refer to the dominant archaeological culture of the central and southern Greek mainland during the Late Bronze Age, which is dated between about

  7. Surveillance at sea : The transactional politics of border control in the Aegean

    NARCIS (Netherlands)

    Dijstelbloem, H.; van Reekum, R.; Schinkel, W.

    2017-01-01

    The relationship between vision and action is a key element of both practices and conceptualizations of border surveillance in Europe. This article engages with what we call the ‘operative vision’ of surveillance at sea, specifically as performed by the border control apparatus in the Aegean. We

  8. THE IMPACT OF ORGANIZATIONAL STRUCTURE ON GLASS CEILING: AEGEAN REGION AGENCIES IN TURKEY

    OpenAIRE

    İNEL, Merve; GARAYEV, Vener; BAKAY, Aziz

    2014-01-01

    This study examined the relationship between organizationalstructure (mechanistic/organic) and glass ceiling, the concept known asnegative discrimination against women in workplace. The data collected fromrandomly selected 81 organizations in Aegean Region of Turkey was analyzedthrough hierarchical stepwise multiple regression. The results of the finalregression model suggest that glass ceiling is not dependent on organizationalstructure, while the control variable gender has a negative relat...

  9. ESA ResGrow: Trial cases for SAR lifting. Aegean Sea

    DEFF Research Database (Denmark)

    Badger, Merete; Hasager, Charlotte Bay; Hahmann, Andrea N.

    This report presents results related to lifting of wind maps retrieved from satellite Synthetic Aperture Radar (SAR) over the Aegean Sea. For this case study DTU Wind Energy collaborates with the Hellenic Wind Energy Association. Preliminary results have been presented to HWEA and their feedback...

  10. Assessing enigmatic boulder deposits in NE Aegean Sea: importance of historical sources as tool to support hydrodynamic equations

    Directory of Open Access Journals (Sweden)

    M. Vacchi

    2012-04-01

    Full Text Available Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea. Methods to infer the origin of boulder deposits (tsunami vs. storm wave are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 Ms Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events.

  11. O-pi e-de-i: on round building as an archetypical form of sacred space in the Aegean

    Directory of Open Access Journals (Sweden)

    Evyenia Yiannouli

    2011-12-01

    Full Text Available The archaeological record supports the general proposition that the simplest form of architecture, the round building type, variously persisted throughout the Aegean prehistory. This paper makes a case for the identification of round building as a distinct genre of sacred space in the Aegean Bronze Age, Mycenaean Crete in particular, combining evidence from architecture, iconography and the scripts. Certain archetypical features are thus delineated. It is argued that the historical understanding of the emerging LBA state requires a study of the architecture prior to the 2nd millennium BC as much as other relevant evidence issuing from the latest Aegean strata.

  12. Microbial activities at the benthic boundary layer in the Aegean Sea

    Science.gov (United States)

    Bianchi, A.; Tholosan, O.; Garcin, J.; Polychronaki, T.; Tselepides, A.; Buscail, R.; Duineveld, G.

    2003-05-01

    During the Aegean Sea component of the EU MTP-MATER project, benthic samples were acquired along a depth gradient from two continental margins in the Aegean Sea. Sampling was undertaken during spring and summer 1997 and the microbial metabolic activities measured (Vmax for aminopeptidase activity, 14C-glutamate respiration and assimilation) displayed seasonal variability even in deep-sea conditions. The metabolic rates encountered in the North Aegean (average depth 566±234 m), were approximately five-fold higher than in the deeper (1336±140 m) Southern part of the Aegean. The aminopeptidase rates, however, were the exception with higher values recorded in the more oligotrophic sediments of the Southern stations (1383±152 vs. 766±297 nmol MCA cm-2 h-1). A discrepancy in bacterial metabolism also appeared in the near bottom waters. In the Southern stations, 80% of the glutamate uptake was used for energy yielding processes and only 20% devoted to biomass production, while in the North Aegean, most of the used glutamate was incorporated into bacterial cells. During the early burial stages, bacterial mineralization rates estimated from 14C-glutamate respiration decreased drastically compared to the rates of biopolymer hydrolysis estimated by aminopeptidase assays. Thus, at the 2-cm depth layer, these rates were only 32 and up to 77% of the corresponding average values, respectively, in the superficial layer. Such a discrepancy between the evolution of these two metabolic activities is possibly due to the rapid removal of readily utilizable monomers in the surface deposits. The correlation between bacterial respiration and total organic carbon, or total organic nitrogen, is higher in the surficial sediment (0-2 and 2-4 cm) than in the underlying layer. Conversely, it is only at 4-cm depth layer that the hydrolysis rates appear correlated with organic carbon and nitrogen concentrations. This pattern confirms the drastic degradation of organic matter during the early

  13. Accurate relocation of seismicity along the North Aegean Trough and its relation to active tectonics

    Science.gov (United States)

    Konstantinou, K. I.

    2017-10-01

    The tectonics of northern Aegean are affected by the westward push of Anatolia and the gravitational spreading of the Aegean lithosphere that promote transtensional deformation in the area. This regime is also responsible for the creation of a series of pull-apart basins, collectively known as the North Aegean Trough. This work accurately relocates a total of 2300 earthquakes that were recorded along the North Aegean Trough during 2011-2016 by stations of the Hellenic Unified Seismic Network (HUSN) and strong-motion sensors. Absolute locations for these events were obtained using a nonlinear probabilistic algorithm and utilizing a minimum 1D velocity model with station corrections. The hypocentral depth distribution of these events shows a peak at 8 km diminishing gradually down to 20 km. A systematic overestimation of hypocentral depths is observed in the routine locations provided by the National Observatory of Athens where the majority of events appear to be deeper than 15 km. In order to obtain more accurate relative locations these events were relocated using the double-difference method. A total of 1693 events were finally relocated with horizontal and vertical uncertainties that do not exceed 0.11 km and 0.22 km respectively. Well-defined clusters of seismicity can be observed along the Saros and Sporades basins as well as the Kassandra and Sithonia peninsulas. These clusters either occur along the well-known NE-SW strike-slip faults bounding the basins, or along normal faults whose strike is perpendicular to the regional minimum stress axis. Locking depth along the North Aegean Trough is found to be remarkably stable between 13 and 17 km. This is likely a consequence of simultaneous reduction along the SW direction of heat flow (from 89 to 51 mW/m2) and strain rate (from 600 to 50 nstrain/yr) whose opposite effects are canceled out, precluding any sharp changes in locking depth.

  14. A 35 year high-resolution wave atlas for nearshore energy production and economics at the Aegean Sea

    OpenAIRE

    Lavidas, George; Venugopal, Vengatesan

    2017-01-01

    The study enhances the coastal resource knowledge and discusses opportunities for wave energy in theAegean Sea. A fine-resolution numerical wave model is utilised to provide results for the Greek coastalregions. The model ran for 35 years (1980e2014) estimating wave characteristics, and quantifying thewave energy potential in coastal areas. The results deliver the energy potential, variability, and sitecharacterisation for the Aegean Sea.The dataset is coupled with wave energy converters powe...

  15. Crustal growth of the Izu-Ogasawara arc estimated from structural characteristics of Oligocene arc

    Science.gov (United States)

    Takahashi, N.; Yamashita, M.; Kodaira, S.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.

    2011-12-01

    Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out seismic surveys using a multichannel reflection system and ocean bottom seismographs, and we have clarified crustal structures of whole Izu-Ogasawara (Bonin)-Marina (IBM) arc since 2002. These refection images and velocity structures suggest that the crustal evolution in the intra-oceanic island arc accompanies with much interaction of materials between crust and mantle. Slow mantle velocity identified beneath the thick arc crusts suggests that dense crustal materials transformed into the mantle. On the other hand, high velocity lower crust can be seen around the bottom of the crust beneath the rifted region, and it suggests that underplating of mafic materials occurs there. Average crustal production rate of the entire arc is larger than expected one and approximately 200 km3/km/Ma. The production rate of basaltic magmas corresponds to that of oceanic ridge. Repeated crustal differentiation is indispensable to produce much light materials like continental materials, however, the real process cannot still be resolved yet. We, therefore, submitted drilling proposals to obtain in-situ middle crust with P-wave velocity of 6 km/s. In the growth history of the IBM arc, it is known by many papers that boninitic volcanisms preceded current bimodal volcanisms based on basaltic magmas. The current volcanisms accompanied with basaltic magmas have been occurred since Oligocene age, however, the tectonic differences to develop crustal architecture between Oligocene and present are not understood yet. We obtained new refraction/reflection data along an arc strike of N-S in fore-arc region. Then, we estimate crustal structure with severe change of the crustal thickness from refraction data, which are similar to that along the volcanic front. Interval for location of the thick arc crust along N-S is very similar to that along the volcanic front. The refection image indicates that the basement of the fore-arc

  16. Gridded multibeam bathymetry of Rota Island, Commonwealth of the Northern Mariana Islands (CNMI)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry shelf, bank and slope environments of Rota Island, CNMI. Bottom coverage was achieved in depths between 0 and -1905 meters. The netCDF and Arc...

  17. Discrepancies in 14C dating as illustrated from the Egyptian new and middle kingdoms and from the Aegean bronze age and neolithic

    International Nuclear Information System (INIS)

    Hood, S.

    1978-01-01

    14 C dates available for the Middle and New Kingdoms in Egypt and for the Bronze Age and Neolithic in the Aegean are examined. The possibility is explored that calibrated dates vary from tree-ring dates by different margins in Egypt and the Aegean during the second millenium B.C. Apparent inconsistencies between 14 C dates from different Neolithic sites in the Aegean area are also noted. (author)

  18. The advance of Kos Plateau Tuff ignimbrite into the marine realm of the Kalymnos Basin, SE Aegean Sea.

    Science.gov (United States)

    Markakis, Emmanouil; Anastasakis, George

    2013-04-01

    The 161 ka Kos Plateau Tuff (KPT) eruption is considered to be the largest explosive Quaternary event in the eastern Mediterranean. It produced pumice rafts followed by "non-welded ignimbrites" that are up to 30m thick, especially widespread on Kos island and covering an area of > 80 Km2 that includes mainly islands and present marine regions. Pyroclastic flows travelled from the proposed vent, that lies between and around Yali and Nisyros islands, across present land and sea, the total volume of the tuff has been estimated as at least 100km3. KPT products principally consist of rhyolitic ash and pumice. Post 2010 Athens University oceanographic missions have mapped the seafloor around the volcanic islands of the SE Aegean Sea. Here we present new data on seafloor morphology and Upper Quaternary seafloor stratigraphy of the Kalymnos basin that extends over an area over 70km2 and map the advance and deposition of the KPT that was previously unknown in this region. The Kalymnos basin is roughly triangular in shape and essentially consists of two sedimentation depocenters: a) a roughly elliptical 400 m deep northern segment that is developed sub-parallel to Kalymnos Island and its W-SW shelf; b) a rather physiographically complex western sector developed NE of Astipalea island and reaching depths of over 620m. High resolution sparker profiles from the west Kos-Kalymnos shelf reveal an outstanding seismic stratigraphy of stacked and prograded coastal clinoform packets capped by erosional transgressive surfaces that record Quaternary eustatic lowstands deposits of sea level with clinoforms developing during forced regression and the erosional surfaces during transgression. We show that a massive gravity flow deposit is intercalated with the shelf sediments. Above it low sea level MIS 6 and 2 sedimentary sequences are fully developed and below stage 8-10 sediments are erratically preserved over stages 12 and 16 sediments. This gravity flow deposit swept across the shelf

  19. Heat Islands

    Science.gov (United States)

    EPA's Heat Island Effect Site provides information on heat islands, their impacts, mitigation strategies, related research, a directory of heat island reduction initiatives in U.S. communities, and EPA's Heat Island Reduction Program.

  20. Island biogeography

    DEFF Research Database (Denmark)

    Whittaker, Robert James; Fernández-Palacios, José María; Matthews, Thomas J.

    2017-01-01

    Islands provide classic model biological systems. We review how growing appreciation of geoenvironmental dynamics of marine islands has led to advances in island biogeographic theory accommodating both evolutionary and ecological phenomena. Recognition of distinct island geodynamics permits gener...

  1. Description of dogs naturally infected with Hepatozoon canis in the Aegean region of Turkey

    OpenAIRE

    PAŞA, Serdar; KIRAL, Funda; KARAGENÇ, Tülin; ATASOY, Abidin; SEYREK, Kamil

    2009-01-01

    Clinical and laboratory findings recorded in 10 dogs naturally infected with Hepatozoon canis in the Aegean region of Turkey were reported. The diagnosis was made by finding H. canis gamonts within leucocytes in Giemsa-stained blood smears. H. canis parasitaemia level was calculated manually by counting 500 neutrophils in blood smears. Parasitaemia varied from 1% to 23% of the circulating neutrophils. Anorexia, fever, depression, weight loss, and lymphadenopathy are the main clinical signs in...

  2. Symbols, spaces and materiality: a transmission-based approach to Aegean Bronze Age ritual.

    OpenAIRE

    Briault, C.

    2005-01-01

    This thesis explores the transmission of ritual practices in the second millennium BC Aegean. In contrast to previous approaches, which often overlook gaps in the diachronic record, emphasising continuity in cult practice over very long timescales, it is argued here that through charting the spatial and temporal distributions of three broad material types (cult symbols, spaces and objects), it is possible to document the spread of cult practice over time and space, and, crucially, to monitor ...

  3. Critically endangered fish species of Turkish Seas (Mediterranean and Aegean): Longfin gurnard, Chelidonichthys obscurus (Walbaum, 1792)

    OpenAIRE

    Cemal Turan; Deniz Ergüden; Mevlüt Gürlek

    2016-01-01

    Longfin gurnard Chelidonichthys obscurus (Walbaum, 1792) is reported several times from various researchers in the checklist of Turkish marine fishes. However, last three decades, the species is not occurred in the distributional range, comprising the northeastern Mediterranean Sea and Aegean Sea coast of Turkey. It is possibly critically endangered or absent in the Turkish Seas. Moreover, there has no any biological study been carried out on C. obscurus in Turkey. C. obscurus is considered t...

  4. Site index models for calabrian pine (Pinus brutia Ten. in Thasos Island, Greece

    Directory of Open Access Journals (Sweden)

    Kyriaki Kitikidou

    2011-01-01

    Full Text Available A site index model for Calabrian pine (Pinus brutia Ten. in Thasos island (North Aegean sea, Greece is presented. The model was fitted and validated from 150 stem analyses, obtained from 75 fixed-area plots from five experimental sites. Four height growth equations of difference form were tested and the BAILEY and CLUTTER (1974 function was considered appropriate due to its good performance with both fitting and validation data. The results show errors lower than 5% and little bias.

  5. SITE INDEX MODELS FOR CALABRIAN PINE (PinusbrutiaTen. IN THASOS ISLAND, GREECE

    Directory of Open Access Journals (Sweden)

    Kyriaki Kitikidou

    2011-03-01

    Full Text Available A site index model for Calabrian pine (Pinusbrutia Ten. in Thasos island (North Aegean sea, Greece is presented. The model was fitted and validated from 150 stem analyses, obtained from 75 fixed-area plots from five experimental sites. Four height growth equations of difference form were tested and the Bailey and Clutter (1974 function was considered appropriate due to its good performance with both fitting and validation data. The results show errors lower than 5% and little bias.

  6. Large-scale bioprospecting of cyanobacteria, micro- and macroalgae from the Aegean Sea.

    Science.gov (United States)

    Montalvão, Sofia; Demirel, Zeliha; Devi, Prabha; Lombardi, Valter; Hongisto, Vesa; Perälä, Merja; Hattara, Johannes; Imamoglu, Esra; Tilvi, Supriya Shet; Turan, Gamze; Dalay, Meltem Conk; Tammela, Päivi

    2016-05-25

    Marine organisms constitute approximately one-half of the total global biodiversity, being rich reservoirs of structurally diverse biofunctional components. The potential of cyanobacteria, micro- and macroalgae as sources of antimicrobial, antitumoral, anti-inflammatory, and anticoagulant compounds has been reported extensively. Nonetheless, biological activities of marine fauna and flora of the Aegean Sea have remained poorly studied when in comparison to other areas of the Mediterranean Sea. In this study, we screened the antimicrobial, antifouling, anti-inflammatory and anticancer potential of in total 98 specimens collected from the Aegean Sea. Ethanol extract of diatom Amphora cf capitellata showed the most promising antimicrobial results against Candida albicans while the extract of diatom Nitzschia communis showed effective results against Gram-positive bacterium, S. aureus. Extracts from the red alga Laurencia papillosa and from three Cystoseira species exhibited selective antiproliferative activity against cancer cell lines and an extract from the brown alga Dilophus fasciola showed the highest anti-inflammatory activity as measured in primary microglial and astrocyte cell cultures as well as by the reduction of proinflammatory cytokines. In summary, our study demonstrates that the Aegean Sea is a rich source of species that possess interesting potential for developing industrial applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Babylonian confusion of gudgeons in the west Aegean drainages inferred by the mitochondrial DNA analyses

    Directory of Open Access Journals (Sweden)

    Radek Sanda

    2015-11-01

    We have analysed control region (mitochondrial non coding DNA of gudgeon populations from all larger river drainages from the west Aegean region (Pinios to Marica basins. Included were also several populations from surrounding areas of the Danube River drainage and from the Black Sea rivers. The results are not at all congruent with the proposed taxonomy. MtDNA haplotypes of Romonagobio banarescui were found not only in the Vardar, but also in the lower Aliakmon River. Haplotypes of Romanogibo elimeus were found in the Pinios, upper Aliakmon and Loudias rivers. Situation of genus Gobio is completely confusing; there is no geographic structure in the distribution of haplotypes. Many different haplogroups are shared in some basins, especially in the drainages of the Struma, Mesta and Marica rivers. This indicates complicated evolutionary history of gudgeons in the region, probably having several historical refugia, and with multiple recent contacts of lineages. Our data indicate a contact between the Danubian, Black Sea and Aegean rivers. The taxonomic status of most of the populations of Gobio from the west Aegean area remains unclear.

  8. HOBIT-The new Hamburg Ocean Bottom Tiltmeter: A First Deployment at Columbo Seamount, Aegean Sea

    Science.gov (United States)

    Hort, M.; Hensch, M.; Winter, S.; Dahm, T.

    2007-12-01

    volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis σ1 of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a leak in the power supply leading to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. Following some regional earthquakes occurring during a seismic swarm we find a small, but permanent deformation associated with the earthquakes. Later during the deployment we also observe slow deformation processes occurring over a period of days. The implications of these findings as well as the general operational principle of these instruments will be discussed in detail in the presentation.

  9. Backarc extension, detachments and granitoids in the Aegean, their relations to slab tear and asthenospheric flow

    Science.gov (United States)

    Jolivet, Laurent; Menant, Armel; Rabillard, Aurélien; Arbaret, Laurent; Augier, Romain; Gumiaux, Charles

    2013-04-01

    The Cycladic granitoids (Ikaria, Mykonos, Naxos, Kos, Lavrion, Serifos, Tinos) intruded the Aegean crust during a rather short period (17-10 Ma) compared to the much longer Oligo-Miocene crustal thinning phase (35 Ma to the Present). Their geochemical characteristics show that their sources have changed through time and space, with a progressive decreasing component of continental crust contamination with time and from east to west. They all interacted with large-scale detachments, namely the North Cycladic Detachment System (NCDS) in the north and the West Cycladic Detachment System (WCDS) in the south. In Mykonos, Naxos, Serifos and Ikaria the plutons are also associated with a high-temperature metamorphic dome of Miocene age. Their intrusion period roughly covers the same time window as the fast clockwise rotation of the western Aegean evidenced by paleomagnetic measurements and they are contemporaneous with a surge of alkaline volcanism in the eastern Aegean that can be related to a slab tear imaged below western Anatolia. The continental crust component in the Middle Miocene Cycladic plutons is not found in the early Miocene plutons of the northern Aegean, like in Kavala and Vrondou. They thus probably record a quite sudden thermal event in the Cyclades that led to the partial melting of the extending deep crust. We propose a model involving slab tear starting at ~17 Ma, fast retreat of the slab west of the tear and southwestward influx of hot asthenospheric material below the Aegean crust, leading to melting of the lower crust. Partial melting of the whole lower crust above the hot asthenospheric flow could explain the flat Moho observed below the Cyclades. The close proximity of plutons with the detachments suggests that their ascent toward the upper crust is favoured by the extreme extension at work there. The first granitoids in the region of the tear (Ikaria) are the richest in crustal component and this component decreases while the crust thins more and

  10. Monitoring ARC services with GangliARC

    International Nuclear Information System (INIS)

    Cameron, D; Karpenko, D

    2012-01-01

    Monitoring of Grid services is essential to provide a smooth experience for users and provide fast and easy to understand diagnostics for administrators running the services. GangliARC makes use of the widely-used Ganglia monitoring tool to present web-based graphical metrics of the ARC computing element. These include statistics of running and finished jobs, data transfer metrics, as well as showing the availability of the computing element and hardware information such as free disk space left in the ARC cache. Ganglia presents metrics as graphs of the value of the metric over time and shows an easily-digestable summary of how the system is performing, and enables quick and easy diagnosis of common problems. This paper describes how GangliARC works and shows numerous examples of how the generated data can quickly be used by an administrator to investigate problems. It also presents possibilities of combining GangliARC with other commonly-used monitoring tools such as Nagios to easily integrate ARC monitoring into the regular monitoring infrastructure of any site or computing centre.

  11. Back-arc with frontal-arc component origin of Triassic Karmutsen basalt, British Columbia, Canada

    Science.gov (United States)

    Barker, F.; Sutherland, Brown A.; Budahn, J.R.; Plafker, G.

    1989-01-01

    The largely basaltic, ???4.5-6.2-km-thick, Middle to Upper Triassic Karmutsen Formation is a prominent part of the Wrangellian sequence. Twelve analyses of major and minor elements of representative samples of pillowed and massive basalt flows and sills from Queen Charlotte and Vancouver Islands are ferrotholeiites that show a range of 10.2-3.8% MgO (as normalized, H2O- and CO2-free) and related increases in TiO2 (1.0-2.5%), Zr (43-147 ppm) and Nb (5-16 ppm). Other elemental abundances are not related simply to MgO: distinct groupings are evident in Al2O3, Na2O and Cr, but considerable scatter is present in FeO* (FeO + 0.9Fe2O3) and CaO. Some of the variation is attributed to alteration during low-rank metamorphism or by seawater - including variation of Ba, Rb, Sr and Cu, but high-field-strength elements (Sc, Ti, Y, Zr and Nb) as well as Cr, Ni, Cu and rare-earth elements (REE's) were relatively immobile. REE's show chondrite-normalized patterns ranging from light-REE depleted to moderately light-REE enriched. On eleven discriminant plots these analyses fall largely into or across fields of within-plate basalt (WIP), normal or enriched mid-ocean-ridge tholeiite (MORB) and island-arc tholeiite (IAT). Karmutsen basalts are chemically identical to the stratigraphically equivalent Nikolai Greenstone of southern Alaska and Yukon Territory. These data and the fact that the Karmutsen rests on Sicker Group island-arc rocks of Paleozoic age suggest to us that: 1. (1) the basal arc, after minor carbonate-shale deposition, underwent near-axial back-arc rifting (as, e.g., the Mariana arc rifted at different times); 2. (2) the Karmutsen basalts were erupted along this rift or basin as "arc-rift" tholeiitite; and 3. (3) after subsequent deposition of carbonates and other rocks, and Jurassic magmatism, a large fragment of this basalt-sediment-covered island arc was accreted to North America as Wrangellia. The major- and minor-elemental abundances of Karmutsen basalt is modeled

  12. Electric arc hydrogen heaters

    International Nuclear Information System (INIS)

    Zasypin, I.M.

    2000-01-01

    The experimental data on the electric arc burning in hydrogen are presented. Empirical and semiempirical dependences for calculating the arc characteristics are derived. An engineering method of calculating plasma torches for hydrogen heating is proposed. A model of interaction of a hydrogen arc with a gas flow is outlined. The characteristics of plasma torches for heating hydrogen and hydrogen-bearing gases are described. (author)

  13. Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

    Science.gov (United States)

    Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

    2018-04-01

    Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

  14. Circulation and hydrological characteristics of the North Aegean Sea: a contribution from real-time buoy measurements

    Directory of Open Access Journals (Sweden)

    K. NITTIS

    2002-06-01

    Full Text Available In the framework of the POSEIDON Project, a network of open sea oceanographic buoys equipped with meteorological and oceanographic sensors has been operational in the Aegean Sea since 1998. The analysis of upper-ocean physical data (currents at 3m, temperature and salinity at 3-40m depths collected during the last 2 years from the stations of the North Aegean basin indicates a strong temporal variability of flow field and hydrological characteristics in both synoptic and seasonal time scales. The northern part of the basin is mainly influenced by the Black Sea Water outflow and the mesoscale variability of the corresponding thermohaline fronts, while the southern stations are influenced by the general circulation of the Aegean Sea with strong modulations caused by the seasonally varying atmospheric forcing.

  15. Continental Extensional Tectonics in the Basins and Ranges and Aegean Regions: A Review

    Science.gov (United States)

    Cemen, I.

    2017-12-01

    The Basins and Ranges of North America and the Aegean Region of Eastern Europe and Asia Minor have been long considered as the two best developed examples of continental extension. The two regions contain well-developed normal faults which were considered almost vertical in the 1950s and 1960s. By the mid 1980s, however, overwhelming field evidence emerged to conclude that the dip angle normal faults in the two regions may range from almost vertical to almost horizontal. This led to the discovery that high-grade metamorphic rocks could be brought to surface by the exhumation of mid-crustal rocks along major low-angle normal faults (detachment faults) which were previously either mapped as thrust faults or unconformity. Within the last three decades, our understanding of continental extensional tectonics in the Basins and Ranges and the Aegean Region have improved substantially based on fieldwork, geochemical analysis, analog and computer modeling, detailed radiometric age determinations and thermokinematic modelling. It is now widely accepted that a) Basin and Range extension is controlled by the movement along the San Andreas fault zone as the North American plate moved southeastward with respect to the northwestward movement of the Pacific plate; b) Aegean extension is controlled by subduction roll-back associated with the Hellenic subduction zone; and c) the two regions contain best examples of detachment faulting, extensional folding, and extensional basins. However, there are still many important questions of continental extensional tectonics in the two regions that remain poorly understood. These include determining a) precise amount and percentage of cumulative extension; b) role of strike-slip faulting in the extensional processes; c) exhumation history along detachment surfaces using multimethod geochronology; d) geometry and nature of extensional features in the middle and lower crust; e) the nature of upper mantle and asthenospheric flow; f) evolutions

  16. PREFACE: Donald D Harrington Symposium on the Geology of the Aegean

    Science.gov (United States)

    Catlos, Elizabeth J.

    2008-03-01

    This volume of the IOP Conference Series: Earth and Environmental Sciences presents a selection of papers given at the Donald D Harrington Symposium on the Geology of the Aegean held on the campus of the University of Texas at Austin on April 28-30, 2008. Donald D Harrington was born in Illinois in 1899 and moved westward after serving in the Army Air Corps during World War I. Mr Harrington took a position as a landman with Marlin Oil Company in Oklahoma. When the Texas Panhandle oil boom hit in 1926, he moved to Amarillo, Texas, where he met Sybil Buckingham—the granddaughter of one of Amarillo's founding families. They married in 1935 and went on to build one of the most successful independent oil and gas operations in Texas history. The couple created the Don and Sybil Harrington Foundation in 1951 to support worthy causes such as museums, medical research, education, and the arts. At the Harrington Symposium on the Geology of the Aegean, researchers presented papers organized under five general themes: (1) the geology of Aegean in general (2) the geologic history of specific domains within the Aegean (Cyclades, Menderes, Kazdag, Rhodope, Crete, southern Balkans, etc) (3) the dynamic tectonic processes that occur within the Aegean (4) its geo-archeological history, natural history and hazards and (5) comparisons of the Aegean to regions elsewhere (e.g., Basin and Ranges; Asian extensional terranes). The Aegean is a locus of dynamic research in a variety of fields, and the symposium provided an opportunity for geologists from a range of disciplines to interact and share new results and information about their research in the area. At the opening reception in the Harry S Ransom Center, Dr Clark Burchfiel (Massachusetts Institute of Technology, USA) provided a keynote address on the outstanding geologic problems of the Aegean region. His paper in this volume outlines a framework for future studies. We also call attention to a paper in this volume by Dr Y

  17. The Aegean crises’ effects on social behaviour. Stereotyping the alterity: the case of the Greek printed media (1974-1996)

    OpenAIRE

    Oana Camelia Stroescu

    2011-01-01

    The paper revisits the main characteristics of the Greek-Turkish relations, taking as its point of departure the Greek-Turkish dispute over the Aegean continental shelf (1974-1996), as in that period, a list of mutual grievances on issues of high politics still remained intact. The article examines how the main Greek Dailies: Kathimerini, Eleftheros Typos, Ta Nea, Makedonia and Rizospastis covered Aegean crises of 1976, 1987 and 1996. An effort is made to analyze the position of the above-men...

  18. U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Virgin Islands DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the Virgin...

  19. Magnetic anomalies over the Andaman Islands and their geological ...

    Indian Academy of Sciences (India)

    plate boundary zone (e.g., Gahalaut et al. 2008; ... Himalayan arc/collision system in the north and the Indonesian arc system .... prominent linear ridges, (b) geological map of the Andaman Islands (after Pal et al. 2003a) ... ophiolite rocks occur in N–S to NE–SW trending bodies. ... described above gave rise to three areas of.

  20. Energy balance and cost analysis for raisin production in Aegean Region in Turkey

    Directory of Open Access Journals (Sweden)

    Uysal Hülya

    2016-01-01

    Full Text Available The aim of this study is to determine energy consumption of input and output used in raisin production and making a cost analysis in Aegean Region. Energy output-input analysis is generally done to determine the scope of environment and energy efficiency of agricultural production. In this study the cost of raisin production was calculated by Manisa Viticulture Research Institute's records in 2015. Costs of inputs and prices of raisin were obtained from various sources such as Turkish Statistical Institute, Aegean Exporters' Association and Turkish Ministry of Food, Agriculture and Livestock. The total energy input necessity for raisin production was 39,066.91 MJ/ha. The research results indicated that the total energy input used for raisin was mainly dependent on non-renewable energy forms (%97. The high ratio of non-renewable energy in the total used energy inputs causes negative effects on the sustainability in agricultural production. Among input energy sources, diesel oil, chemical fertilizers and electricity contained highest energy shares with 34.30%, 26.96%, and 22.50% respectively. The energy ratio and energy productivity were found to be 6.04 and 0.51 kg/MJ. Gross production value and total variable costs for raisin were $ 8,600 and $ 4,528.25, respectively. As a result of cost analysis, gross margin was calculated as $ 4,071.75.

  1. Preceramic, Aceramic or Early Ceramic? The radiocarbon dated beginning of the Neolithic in the Aegean

    Directory of Open Access Journals (Sweden)

    Agathe Reingruber

    2015-12-01

    Full Text Available The Pre-Pottery-Neolithic refers to a period in the Eastern Mediterranean when ceramic containers were not yet in use (although small objects made of clay were already being created. This concept, which reflects a specific and quite unique stage in the development of human history, was introduced to Aegean prehistory under the term of Preceramic during the 1950’s (e.g., in Argissa Magoula and Sesklo. Shortly thereafter, a different term, the Aceramic, was applied in the Aegean (e.g., in Knossos for levels devoid of pottery, although ceramic products were supposedly used in the wider region. In some cases, the thin levels interpreted as Preceramic or as Aceramic contained sherds that were regarded as being intrusive from above (e.g., Argissa-Magoula, Franchthi Cave. The new sequences of radiocarbon dates allow a more precise description of this early period and thereby contribute, not least, also to the clarification of terminological issues.

  2. Geochemical characteristics of late Quaternary sediments from the southern Aegean Sea (Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    A. SIOULAS

    2000-12-01

    Full Text Available Ten cores from the southern Aegean Sea have been logged for their lithological composition and seventy-three sub-samples were analysed for the determination of major and trace elements concentrations. Four lithological units were identified, namely, mud, volcanic, turbidite and sapropel. On the basis of the “Z-2” Minoan ash layer radiocarbon age sedimentation rates for the southern Aegean Sea were estimated at 3.26 to 4.15 cm kyr -1. Simple correlation analysis revealed three groups of elements associated with: (1 biogenic carbonates; (2 terrigenous alumino-silicates and (3 sapropelic layers. R-mode factor analysis applied on the carbonate-free corrected data-set defined four significant factors: (1 the “detrital alumino-silicate factor” represented by Si, Al, Na, K, Rb, Zr, Pb and inversely related to Ca, Mg, and Sr; (2 a “hydrothermal factor” loaded with Cr, Ni, Co, Cu, Fe; (3 the “volcanic ash factor” with high loadings for Ti, Al, Fe, Na and (4 a “sapropel factor” represented by Ba, Mo, and Zn. High factor scores for the “hydrothermal factor” were observed in sediment samples proximal to Nisyros Isl., suggesting a potential hydrothermal influence. Red-brown oxides and crusts dredged from this area support further this possibility. The use of factor analysis enabled for a better understanding of the chemical elements associations that remained obscured by correlation analysis.

  3. Tokamak ARC damage

    International Nuclear Information System (INIS)

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage

  4. Tokamak ARC damage

    Energy Technology Data Exchange (ETDEWEB)

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage.

  5. Metal halide arc discharge lamp having short arc length

    Science.gov (United States)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  6. The new Hamburg Ocean-Bottom-Tiltmeter (OBT): A first deployment at Columbo Seamount (Aegean Sea, Greece)

    Science.gov (United States)

    Huebscher, C.; Hensch, M.; Hort, M.; Dahm, T.; Klawonn, M.; Winter, S.

    2008-12-01

    Assessing the state of volcanic activity of seamounts is quite more complicated than for onshore volcanoes, due to the difficulty of deploying instruments. At land, various techniques are applied (seismic networks, deformation studies, gas measurements etc.). At sea, mainly seismological observations are used. However, especially onshore deformation studies using INSAR have proven to be valuable in determining recharge of magmatic systems. We therefore developed a free fall, self leveling Ocean Bottom Tiltmeter (OBT) to observe deformation on the seafloor, using a two component high resolution tilt sensor with a resolution of about 1nrad (0.15μ°) and a maximum signal of about 0.045rad (0.5°). It is mounted inside a 17~inch glass sphere on a levelling stage, which relevels the instrument between ± 5° down to an accuracy of 0.006°. During the measurement this leveling stage is standing on the bottom of the glass sphere. For releveling, the instrument is pulled up by thin nylon strings and then locked to a gimbal system in order to compensate for tilt. This releveling procedure is done once every 48 hours. Data is recorded on an 18bit data logger at 50Hz sampling rate. Additionally to tilt and seismic signals (using a hydrophone), temperature, absolute pressure to measure uplift or subsidence, and orientation (electronic compass) are monitored. 4 OBT systems were deployed between June 2006 - March 2007 at Columbo seamount, a submarine volcano north-east of Santorini island, Aegean Sea, Greece, on a 3 km long profile perpendicular to the first principal stress axis σ_1 of the regional stressfield. Three of the instruments operated the whole time, one shut down due to a short circuit. First data processing indicates that small regional earthquakes as well as major tectonic earthquakes are properly recorded by the system. We find small, but permanent short- period deformations associated with local earthquakes and also observe long-period deformation processes

  7. Canary Islands

    Science.gov (United States)

    1992-01-01

    This easterly looking view shows the seven major volcanic islands of the Canary Island chain (28.0N, 16.5W) and offers a unique view of the islands that have become a frequent vacation spot for Europeans. The northwest coastline of Africa, (Morocco and Western Sahara), is visible in the background. Frequently, these islands create an impact on local weather (cloud formations) and ocean currents (island wakes) as seen in this photo.

  8. Temporal and spatial variability of nutrients and oxygen in the North Aegean Sea during the last thirty years

    Directory of Open Access Journals (Sweden)

    Ε. SOUVERMEZOGLOU

    2014-12-01

    Full Text Available Inorganic nutrient and dissolved oxygen data collected in the North Aegean Sea during 1986 - 2008 were analyzed in order to evaluate the role of the inflowing Black Sea originated surface water (BSW in the nutrient regime of the area.  In periods of high buoyancy inflow from Dardanelles strait, a reduction of inorganic nutrients in the surface layer is observed along the north-west route of the BSW; in parallel, the underlying layer of Levantine intermediate water revealed an increase of inorganic nutrients, receiving the degradation material from the surface layer. The above spatial patterns suggest a contribution of the BSW to the observed enhanced production of the North Aegean Sea. Anomalously low buoyancy inflow of BSW combined with severe winter meteorological conditions promote deep water formation events. The physical and chemical characteristics of the deep waters found in the different basins of the North Aegean Sea in 1997 (following the deep water formation in winters of 1992-1993 differed from those observed after the formation in winter 1987. These differences were probably related to the drastic changes occurred in the deep waters of the Eastern Mediterranean in the early 1990, by the Eastern Mediterranean Transient. Considering that deep water formation processes provide occasionally inorganic nutrients to the euphotic layer, it seems that BSW through its uninterrupted supply of small quantities of nutrients should play an additional role in the production in the North Aegean Sea.

  9. Neolithisation of the Aegean and Southeast Europe during the 6600–6000 calBC period of Rapid Climate Change

    Directory of Open Access Journals (Sweden)

    Bernhard Weninger

    2014-12-01

    Full Text Available In extension of the recently established ‘Rapid Climate Change (RCC Neolithisation Model’ (Clare 2013, in the present paper we demonstrate the existence of a remarkable coincidence between the exact (decadel-scale entry and departure dates of the Neolithic into/from the Aegean (~6600/6050 calBC with begin/end of RCC-conditions.

  10. Vacuum arc anode phenomena

    International Nuclear Information System (INIS)

    Miller, H.C.

    1976-01-01

    A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

  11. Filtered cathodic arc source

    International Nuclear Information System (INIS)

    Falabella, S.; Sanders, D.M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge is described. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45 degree to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles. 3 figures

  12. Seismic velocity variation along the Izu-Bonin arc estaimated from traveltime tomography using OBS data

    Science.gov (United States)

    Obana, K.; Tamura, Y.; Takahashi, T.; Kodaira, S.

    2014-12-01

    The Izu-Bonin (Ogasawara) arc is an intra-oceanic island arc along the convergent plate boundary between the subducting Pacific and overriding Philippine Sea plates. Recent active seismic studies in the Izu-Bonin arc reveal significant along-arc variations in crustal structure [Kodaira et al., 2007]. The thickness of the arc crust shows a remarkable change between thicker Izu (~30 km) and thinner Bonin (~10 km) arcs. In addition to this, several geological and geophysical contrasts, such as seafloor topography and chemical composition of volcanic rocks, between Izu and Bonin arc have been reported [e.g., Yuasa 1992]. We have conducted earthquake observations using ocean bottom seismographs (OBSs) to reveal seismic velocity structure of the crust and mantle wedge in the Izu-Bonin arc and to investigate origin of the along-arc structure variations. We deployed 40 short-period OBSs in Izu and Bonin area in 2006 and 2009, respectively. The OBS data were processed with seismic data recorded at routine seismic stations on Hachijo-jima, Aoga-shima, and Chichi-jima operated by National Research Institute for Earth Science and Disaster Prevention (NIED). More than 5000 earthquakes were observed during about three-months observation period in each experiment. We conducted three-dimensional seismic tomography using manually picked P- and S-wave arrival time data. The obtained image shows a different seismic velocity structures in the mantle beneath the volcanic front between Izu and Bonin arcs. Low P-wave velocity anomalies in the mantle beneath the volcanic front in the Izu arc are limited at depths deeper than those in the Bonin arc. On the other hand, P-wave velocity in the low velocity anomalies beneath volcanic front in the Bonin arc is slower than that in the Izu arc. These large-scale along-arc structure variations in the mantle could relate to the geological and geophysical contrasts between Izu and Bonin arcs.

  13. Single-Arc IMRT?

    International Nuclear Information System (INIS)

    Bortfeld, Thomas; Webb, Steve

    2009-01-01

    The idea of delivering intensity-modulated radiation therapy (IMRT) with a multileaf collimator in a continuous dynamic mode during a single rotation of the gantry has recently gained momentum both in research and industry. In this note we investigate the potential of this Single-Arc IMRT technique at a conceptual level. We consider the original theoretical example case from Brahme et al that got the field of IMRT started. Using analytical methods, we derive deliverable intensity 'landscapes' for Single-Arc as well as standard IMRT and Tomotherapy. We find that Tomotherapy provides the greatest flexibility in shaping intensity landscapes and that it allows one to deliver IMRT in a way that comes close to the ideal case in the transverse plane. Single-Arc and standard IMRT make compromises in different areas. Only in relatively simple cases that do not require substantial intensity modulation will Single-Arc be dosimetrically comparable to Tomotherapy. Compared with standard IMRT, Single-Arc could be dosimetrically superior in certain cases if one is willing to accept the spreading of low dose values over large volumes of normal tissue. In terms of treatment planning, Single-Arc poses a more challenging optimization problem than Tomotherapy or standard IMRT. We conclude that Single-Arc holds potential as an efficient IMRT technique especially for relatively simple cases. In very complex cases, Single-Arc may unduly compromise the quality of the dose distribution, if one tries to keep the treatment time below 2 min or so. As with all IMRT techniques, it is important to explore the tradeoff between plan quality and the efficiency of its delivery carefully for each individual case. (note)

  14. Assembling Ecological Pieces to Reconstruct the Conservation Puzzle of the Aegean Sea

    Directory of Open Access Journals (Sweden)

    Maria Sini

    2017-11-01

    Full Text Available The effective conservation of marine biodiversity through an integrated ecosystem-based management approach requires a sound knowledge of the spatial distribution of habitats and species. Although costly in terms of time and resources, acquiring such information is essential for the development of rigorous management plans and the meaningful prioritization of conservation actions. Located in the northeastern part of the Mediterranean, the Aegean Sea represents a stronghold for marine biodiversity. However, conservation efforts are hampered by the apparent lack of spatial information regarding marine habitats and species. This work is the first to address this knowledge gap by assembling, updating, and mapping information on the distribution of key ecological components. A range of data sources and methodological approaches was utilized to compile and complement the available data on 68 ecological features of conservation interest (58 animal species, six habitat categories, and four other vulnerable ecological features. A standardized data evaluation procedure was applied, based on five semi-quantitative data quality indicators in the form of a pedigree matrix. This approach assessed the sufficiency of the datasets and allowed the identification of the main sources of uncertainty, highlighting aspects that require further investigation. The overall dataset was found to be sufficient in terms of reliability and spatiotemporal relevance. However, it lacked in completeness, showing that there are still large areas of the Aegean that remain understudied, while further research is needed to elucidate the distribution patterns and conservation status of several ecological features; especially the less charismatic ones and those found in waters deeper than 40 m. Moreover, existing conservation measures appear to be inadequate to safeguard biodiversity. Only 2.3% of the study area corresponds to designated areas for conservation, while 41 of the

  15. Monitoring the Sumatra volcanic arc with InSAR

    Science.gov (United States)

    Chaussard, E.; Hong, S.; Amelung, F.

    2009-12-01

    The Sumatra volcanic arc is the result of the subduction of the Indo-Australian plate under the Sunda plate. The arc consists of 35 known volcanic centers, subaerials on the west coast of the Sumatra and Andaman Islands and submarines between these islands. Six active centers are known in the Sumatra volcanic arc. Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Here we present a satellite-based Interferometric synthetic aperture radar (InSAR) survey of the Sumatra volcanic arc using ALOS data. Spanning the years 2007 to beginning of 2009, our survey reveals the background level of activity of the 35 volcanoes. We processed data from 40 tracks (24 in descending orbit and 16 in ascending orbit) to cover the whole Sumatra arc. In the first results five of these six known active centers show no sign of activity: Dempo, Kaba, Marapi, Talang and Peuet. The remaining active volcano, Mount Kerinci, has an ambiguous signal. We used pair-wise logic and InSAR time series of the available ALOS data to determine if the observed InSAR signal is caused by ground deformation or by atmospheric delays.

  16. 3D instantaneous dynamics modeling of present-day Aegean subduction

    Science.gov (United States)

    Glerum, Anne; Spakman, Wim; van Hinsbergen, Douwe; Pranger, Casper

    2017-04-01

    To study the sensitivity of surface observables to subduction and mantle flow, i.e. the coupling of crustal tectonics and the underlying mantle dynamics, we have developed 3D numerical models of the instantaneous crust-mantle dynamics of the eastern Mediterranean. These models comprise both a realistic crust-lithosphere system and the underlying mantle. The focus for this presentation lies on the regional crustal flow response to the present-day Aegean subduction system. Our curved model domain measures 40°x40°x2900km with the Aegean subduction system taken as the geographic center. Model set-ups are based on geological and geophysical data of the eastern Mediterranean. We first create a 3D synthetic geometry of the crust-lithosphere system in a stand-alone program, including the present-day configuration of the plates in the region and crust and lithosphere thickness variations abstracted from Moho and LAB maps (Faccenna et al., 2014, Carafa et al., 2015). In addition we construct the geometry of the Aegean slab from a seismic tomography model (UU-P07; Amaru, 2007) and earthquake hypocenters (NCEDC, 2014). Geometries are then imported into the finite element code ASPECT (Kronbichler et al., 2012) using specially designed plugins. The mantle initial temperature conditions can include deviations from an adiabatic profile obtained from conversion of the UU-P07 seismic velocity anomalies to temperature anomalies using a depth-dependent scaling (Karato, 2008). We model compressible mantle flow for which material properties are obtained from thermodynamics P-T lookup-tables (Perple_X, Connolly, 2009) in combination with nonlinear viscoplastic rheology laws. Sublithospheric flow through the lateral model boundaries is left free via open boundary conditions (Chertova et al., 2012), while plate motion is prescribed at the model sides in terms of relative as well as absolute plate motion velocities (e.g. Doubrovine et al., 2012). So far, we used a free-slip surface, but

  17. Research on a dispersing solution for burnt crude oils: Aegean Sea oil spill

    International Nuclear Information System (INIS)

    Bergueiro, J.R.; Morales, N.; Dominguez, F.

    1993-01-01

    The oil tanker Aegean Sea spilled oil when it grounded during severe storm conditions near La Coruna, Spain. Much of the oil burned after an explosion was caused by the hull breaking apart. Oil which contaminated several beaches was affected by both combustion and weathering. Experiments were conducted on oil sampled from the beaches to investigate dispersion of the oil using Beep Enersperse 1990 at different shaking speeds. Biodegradation experiments were also conducted in the presence of Beep Enersperse 1990 but with seawater absent. Although emulsification of the burnt and weathered oil was very difficult, good dispersion and biodegradation were obtained. After 42 d in a stirred reactor, biodegradation of the oil reached at least 80%. 3 refs., 3 figs., 4 tabs

  18. Source Finding in the Era of the SKA (Precursors): Aegean 2.0

    Science.gov (United States)

    Hancock, Paul J.; Trott, Cathryn M.; Hurley-Walker, Natasha

    2018-03-01

    In the era of the SKA precursors, telescopes are producing deeper, larger images of the sky on increasingly small time-scales. The greater size and volume of images place an increased demand on the software that we use to create catalogues, and so our source finding algorithms need to evolve accordingly. In this paper, we discuss some of the logistical and technical challenges that result from the increased size and volume of images that are to be analysed, and demonstrate how the Aegean source finding package has evolved to address these challenges. In particular, we address the issues of source finding on spatially correlated data, and on images in which the background, noise, and point spread function vary across the sky. We also introduce the concept of forced or prioritised fitting.

  19. The Aegean in the Early 7th Millennium BC: Maritime Networks and Colonization.

    Science.gov (United States)

    Horejs, B; Milić, B; Ostmann, F; Thanheiser, U; Weninger, B; Galik, A

    The process of Near Eastern neolithization and its westward expansion from the core zone in the Levant and upper Mesopotamia has been broadly discussed in recent decades, and many models have been developed to describe the spread of early farming in terms of its timing, structure, geography and sociocultural impact. Until now, based on recent intensive investigations in northwestern and western Anatolia, the discussion has mainly centred on the importance of Anatolian inland routes for the westward spread of neolithization. This contribution focuses on the potential impact of east Mediterranean and Aegean maritime networks on the spread of the Neolithic lifestyle to the western edge of the Anatolian subcontinent in the earliest phases of sedentism. Employing the longue durée model and the concept of 'social memory', we will discuss the arrival of new groups via established maritime routes. The existence of maritime networks prior to the spread of farming is already indicated by the high mobility of Epipalaeolithic/Mesolithic groups exploring the Aegean and east Mediterranean seas, and reaching, for example, the Cyclades and Cyprus. Successful navigation by these early mobile groups across the open sea is attested by the distribution of Melian obsidian. The potential existence of an additional Pre-Pottery Neolithic (PPN) obsidian network that operated between Cappadocia/Cilicia and Cyprus further hints at the importance of maritime coastal trade. Since both the coastal and the high seas networks were apparently already well established in this early period, we may further assume appropriate knowledge of geographic routes, navigational technology and other aspects of successful seafaring. This Mesolithic/PPN maritime know-how package appears to have been used by later groups, in the early 7th millennium calBC, exploring the centre of the Anatolian Aegean coast, and in time establishing some of the first permanent settlements in that region. In the present paper, we

  20. Heavy metal contamination in the muscle of Aegean chub (Squalius fellowesii) and potential risk assessment.

    Science.gov (United States)

    Şaşi, Hüseyin; Yozukmaz, Aykut; Yabanli, Murat

    2018-03-01

    Especially after the industrial revolution, the amount of contaminants released in aquatic ecosystems has considerably increased. For this reason, the necessity to carry on research on the existence of contaminants, specifically heavy metals, has emerged. In this study, heavy metal concentrations in muscle tissues of Aegean chub, which was an endemic species of south western part of Turkey, gathered from Tersakan River were examined. Heavy metal concentrations of the samples were analyzed with ICP-MS. Estimated daily intakes (EDI), target hazard quotient (THQ), and carcinogenic risk (CR) of elements were calculated. The heavy metals detected in muscle tissues were Zn > Cu > Cr > Mn > Pb > Cd, consecutively. According to the results of the applied health risk assessment (EDI, THQ and CR) for heavy metal exposure from fish consumption in children and adults, it was determined that there was no any significant threat to human health.

  1. Consolidating NASA's Arc Jets

    Science.gov (United States)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  2. ALICE-ARC integration

    International Nuclear Information System (INIS)

    Anderlik, C; Gregersen, A R; Kleist, J; Peters, A; Saiz, P

    2008-01-01

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a module implementing the functionalities necessary to achieve AliEn job submission and management to ARC enabled sites

  3. Earthquakes Versus Surface Deformation: Qualitative and Quantitative Relationships From The Aegean

    Science.gov (United States)

    Pavlides, S.; Caputo, R.

    Historical seismicity of the Aegean Region has been revised in order to associate major earthquakes to specific seismogenic structures. Only earthquakes associated to normal faulting have been considered. All available historical and seismotectonic data relative to co-seismic surface faulting have been collected in order to evaluate the surface rup- ture length (SRL) and the maximum displacement (MD). In order to perform Seismic Hazard analyses, empirical relationships between these parameters and the magnitude have been inferred and the best fitting regression functions have been calculated. Both co-seismic fault rupture lengths and maximum displacements show a logarithmic re- lationships, but our data from the Aegean Region have systematically lower values than the same parameters world-wide though they are similar to those of the East- ern Mediterranean-Middle East region. The upper envelopes of our diagrams (SRL vs Mw and MD vs Mw) have been also estimated and discussed, because they give useful information of the wort-case scenarios; these curces will be also discussed. Further- more, geological and morphological criteria have been used to recognise the tectonic structures along which historical earthquakes occurred in order to define the geolog- ical fault length (GFL). Accordingly, the SRL/GFL ratio seems to have a bimodal distribution with a major peak about 0.8-1.0, indicating that several earthquakes break through almost the entire geological fault length, and a second peak around 0.5, re- lated to the possible segmentation of these major neotectonic faults. In contrast, no relationships can be depicted between the SRL/GFL ratio and the magnitude of the corresponding events.

  4. Impacts of continental arcs on global carbon cycling and climate

    Science.gov (United States)

    Lee, C. T.; Jiang, H.; Carter, L.; Dasgupta, R.; Cao, W.; Lackey, J. S.; Lenardic, A.; Barnes, J.; McKenzie, R.

    2017-12-01

    On myr timescales, climatic variability is tied to variations in atmospheric CO2, which in turn is driven by geologic sources of CO2 and modulated by the efficiency of chemical weathering and carbonate precipitation (sinks). Long-term variability in CO2 has largely been attributed to changes in mid-ocean ridge inputs or the efficiency of global weathering. For example, the Cretaceous greenhouse is thought to be related to enhanced oceanic crust production, while the late Cenozoic icehouse is attributed to enhanced chemical weathering associated with the Himalayan orogeny. Here, we show that continental arcs may play a more important role in controlling climate, both in terms of sources and sinks. Continental arcs differ from island arcs and mid-ocean ridges in that the continental plate through which arc magmas pass may contain large amounts of sedimentary carbonate, accumulated over the history of the continent. Interaction of arc magmas with crustal carbonates via assimilation, reaction or heating can significantly add to the mantle-sourced CO2 flux. Detrital zircons and global mapping of basement rocks shows that the length of continental arcs in the Cretaceous was more than twice that in the mid-Cenozoic; maps also show many of these arcs intersected crustal carbonates. The increased length of continental arc magmatism coincided with increased oceanic spreading rates, placing convergent margins into compression, which favors continental arcs. Around 50 Ma, however, nearly all the continental arcs in Eurasia and North America terminated as India collided with Eurasia and the western Pacific rolled back, initiating the Marianas-Tonga-Kermadec intra-oceanic subduction complex and possibly leading to a decrease in global CO2 production. Meanwhile, extinct continental arcs continued to erode, resulting in regionally enhanced chemical weathering unsupported by magmatic fluxes of CO2. Continental arcs, during their magmatic lifetimes, are thus a source of CO2, driving

  5. Vacuum Arc Ion Sources

    CERN Document Server

    Brown, I.

    2013-12-16

    The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

  6. Arc Heated Scramjet Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Arc Heated Scramjet Test Facility is an arc heated facility which simulates the true enthalpy of flight over the Mach number range of about 4.7 to 8 for free-jet...

  7. Generation of Silicic Melts in the Early Izu-Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea

    Science.gov (United States)

    Barth, A. P.; Tani, K.; Meffre, S.; Wooden, J. L.; Coble, M. A.; Arculus, R. J.; Ishizuka, O.; Shukle, J. T.

    2017-10-01

    A 1.2 km thick Paleogene volcaniclastic section at International Ocean Discovery Program Site 351-U1438 preserves the deep-marine, proximal record of Izu-Bonin oceanic arc initiation, and volcano evolution along the Kyushu-Palau Ridge (KPR). Pb/U ages and trace element compositions of zircons recovered from volcaniclastic sandstones preserve a remarkable temporal record of juvenile island arc evolution. Pb/U ages ranging from 43 to 27 Ma are compatible with provenance in one or more active arc edifices of the northern KPR. The abundances of selected trace elements with high concentrations provide insight into the genesis of U1438 detrital zircon host melts, and represent useful indicators of both short and long-term variations in melt compositions in arc settings. The Site U1438 zircons span the compositional range between zircons from mid-ocean ridge gabbros and zircons from relatively enriched continental arcs, as predicted for melts in a primitive oceanic arc setting derived from a highly depleted mantle source. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic melts that evolved toward more Th and U-rich compositions with time. Th, U, and light rare earth element enrichments beginning about 35 Ma are consistent with detrital zircons recording development of regional arc asymmetry and selective trace element-enriched rear arc silicic melts as the juvenile Izu-Bonin arc evolved.

  8. Electric contact arcing

    International Nuclear Information System (INIS)

    Cuthrell, R.E.

    1976-01-01

    Electrical contacts must function properly in many types of components used in nuclear weapon systems. Design, application, and testing of these components require detailed knowledge of chemical and physical phenomena associated with stockpile storage, stockpile testing, and operation. In the past, investigation of these phenomena has led to significant discoveries on the effects of surface contaminants, friction and wear, and the mechanics of closure on contact performance. A recent investigation of contact arcing phenomena which revealed that, preceding contact closure, arcs may occur at voltages lower than had been previously known is described. This discovery is important, since arcing may damage contacts, and repetitive testing of contacts performed as part of a quality assurance program might produce cumulative damage that would yield misleading life-test data and could prevent proper operation of the contacts at some time in the future. This damage can be avoided by determining the conditions under which arcing occurs, and ensuring that these conditions are avoided in contact testing

  9. Thermal Arc Spray Overview

    Science.gov (United States)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  10. Circular arc structures

    KAUST Repository

    Bo, Pengbo; Pottmann, Helmut; Kilian, Martin; Wang, Wen Ping; Wallner, Johannes

    2011-01-01

    and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where

  11. ALICE-ARC integration

    DEFF Research Database (Denmark)

    Anderlik, Csaba; Gregersen, Anders Rhod; Kleist, Josva

    2008-01-01

    Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The interoperation has two aspects, one is the data...

  12. Thermal Arc Spray Overview

    International Nuclear Information System (INIS)

    Malek, Muhamad Hafiz Abd; Saad, Nor Hayati; Abas, Sunhaji Kiyai; Shah, Noriyati Mohd

    2013-01-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  13. THE ARC TRAIL

    African Journals Online (AJOL)

    INTRODUCTION. The project, carried out by the 1985 Conservation. Team at Durban Girls1 High School, consisted of three main aims- Awareness, Recreation and conservation, which were incorporated into the naming of the ARC trail. The trail is situated in suburban Durban where it was felt that it was important to ...

  14. ARC Software and Models

    Science.gov (United States)

    Archives RESEARCH ▼ Research Areas Ongoing Projects Completed Projects SOFTWARE CONTACT ▼ Primary Contacts Researchers External Link MLibrary Deep Blue Software Archive Most research conducted at the ARC produce software code and methodologies that are transferred to TARDEC and industry partners. These

  15. ALICE: ARC integration

    CERN Document Server

    Anderlik, C; Kleist, J; Peters, A; Saiz, P

    2008-01-01

    AliEn or Alice Environment is the Grid middleware developed and used within the ALICE collaboration for storing and processing data in a distributed manner. ARC (Advanced Resource Connector) is the Grid middleware deployed across the Nordic countries and gluing together the resources within the Nordic Data Grid Facility (NDGF). In this paper we will present our approach to integrate AliEn and ARC, in the sense that ALICE data management and job processing can be carried out on the NDGF infrastructure, using the client tools available in AliEn. The inter-operation has two aspects, one is the data management part and the second the job management aspect. The first aspect was solved by using dCache across NDGF to handle data. Therefore, we will concentrate on the second part. Solving it, was somewhat cumbersome, mainly due to the different computing models employed by AliEn and ARC. AliEN uses an Agent based pull model while ARC handles jobs through the more 'traditional' push model. The solution comes as a modu...

  16. Cost-benefit analysis of remote hybrid wind-diesel power stations: Case study Aegean Sea islands

    International Nuclear Information System (INIS)

    Kaldellis, J.K.; Kavadias, K.A.

    2007-01-01

    More than one third of world population has no direct access to interconnected electrical networks. Hence, the electrification solution usually considered is based on expensive, though often unreliable, stand-alone systems, mainly small diesel-electric generators. Hybrid wind-diesel power systems are among the most interesting and environmental friendly technological alternatives for the electrification of remote consumers, presenting also increased reliability. More precisely, a hybrid wind-diesel installation, based on an appropriate combination of a small diesel-electric generator and a micro-wind converter, offsets the significant capital cost of the wind turbine and the high operational cost of the diesel-electric generator. In this context, the present study concentrates on a detailed energy production cost analysis in order to estimate the optimum configuration of a wind-diesel-battery stand-alone system used to guarantee the energy autonomy of a typical remote consumer. Accordingly, the influence of the governing parameters-such as wind potential, capital cost, oil price, battery price and first installation cost-on the corresponding electricity production cost is investigated using the developed model. Taking into account the results obtained, hybrid wind-diesel systems may be the most cost-effective electrification solution for numerous isolated consumers located in suitable (average wind speed higher than 6.0 m/s) wind potential regions

  17. Assessment of the sardine (Sardina pilchardus Walbaum, 1792 fishery in the eastern Mediterranean basin (North Aegean Sea

    Directory of Open Access Journals (Sweden)

    K. ANTONAKAKIS

    2011-06-01

    Full Text Available The aim of this study was to describe the biometric characteristics of the European sardine (Sardina pilchardus catches and assess the current status of sardine stock in North Aegean Sea based on population characteristics and abundance trends. The stock was dominated by age groups 1 and 2, not exceeding age group 4. The sardine stock in this area was assessed through an Integrated Catch-at-Age model which implements a separable Virtual Population Analysis on catch at age data with weighted tuning indices. Sardine landings data derived from the commercial purse seine fishery over the period 2000-2008 were combined with the age structure of the stock as resulted from fisheries independent acoustic surveys. Sensitivity analysis of the impact of natural mortality values on stock assessment results was applied. Additionally forecast of the sardine population parameters and catches under different exploitation scenarios was implemented in a medium term basis. Results indicated that the North Aegean Sea sardine stock is considered fully exploited with the fishery operating close but over the empirical exploitation level for sustainability. Finally, the status of the sardine stock in N. Aegean Sea is discussed in relation to the sardine stocks from the western and the central Mediterranean basin.

  18. Evidence of extensional and strike-slip deformation in the offshore Gökova-Kos area affected by the July 2017 Mw6.6 Bodrum-Kos earthquake, eastern Aegean Sea

    Science.gov (United States)

    Ocakoğlu, Neslihan; Nomikou, Paraskevi; İşcan, Yeliz; Loreto, Maria Filomena; Lampridou, Danai

    2018-01-01

    The interpretation of new multichannel seismic profiles and previously published high-resolution swath and seismic reflection data from the Gökova Gulf and southeast of Kos Island in the eastern Aegean Sea revealed new morphotectonic features related to the July 20, 2017 Mw6.6 Bodrum-Kos earthquake offshore between Kos Island and the Bodrum Peninsula. The seafloor morphology in the northern part of the gulf is characterized by south-dipping E-W-oriented listric normal faults. These faults bend to a ENE-WSW direction towards Kos Island, and then extend parallel to the southern coastline. A left-lateral SW-NE strike-slip fault zone is mapped with segments crossing the Gökova Gulf from its northern part to south of Kos Island. This fault zone intersects and displaces the deep basins in the gulf. The basins are thus interpreted as the youngest deformed features in the study area. The strike-slip faults also produce E-W-oriented ridges between the basin segments, and the ridge-related vertical faults are interpreted as reverse faults. This offshore study reveals that the normal and strike-slip faults are well correlated with the focal mechanism solutions of the recent earthquake and general seismicity of the Gökova Gulf. Although the complex morphotectonic features could suggest that the area is under a transtensional regime, kinematic elements normally associated with a transtensional system are missing. At present, the Gökova Gulf is experiencing strike-slip motion with dominant extensional deformation, rather than transtensional deformation.

  19. Evidence of extensional and strike-slip deformation in the offshore Gökova-Kos area affected by the July 2017 Mw6.6 Bodrum-Kos earthquake, eastern Aegean Sea

    Science.gov (United States)

    Ocakoğlu, Neslihan; Nomikou, Paraskevi; İşcan, Yeliz; Loreto, Maria Filomena; Lampridou, Danai

    2018-06-01

    The interpretation of new multichannel seismic profiles and previously published high-resolution swath and seismic reflection data from the Gökova Gulf and southeast of Kos Island in the eastern Aegean Sea revealed new morphotectonic features related to the July 20, 2017 Mw6.6 Bodrum-Kos earthquake offshore between Kos Island and the Bodrum Peninsula. The seafloor morphology in the northern part of the gulf is characterized by south-dipping E-W-oriented listric normal faults. These faults bend to a ENE-WSW direction towards Kos Island, and then extend parallel to the southern coastline. A left-lateral SW-NE strike-slip fault zone is mapped with segments crossing the Gökova Gulf from its northern part to south of Kos Island. This fault zone intersects and displaces the deep basins in the gulf. The basins are thus interpreted as the youngest deformed features in the study area. The strike-slip faults also produce E-W-oriented ridges between the basin segments, and the ridge-related vertical faults are interpreted as reverse faults. This offshore study reveals that the normal and strike-slip faults are well correlated with the focal mechanism solutions of the recent earthquake and general seismicity of the Gökova Gulf. Although the complex morphotectonic features could suggest that the area is under a transtensional regime, kinematic elements normally associated with a transtensional system are missing. At present, the Gökova Gulf is experiencing strike-slip motion with dominant extensional deformation, rather than transtensional deformation.

  20. Accessibility of islands: towards a new geography based on transportation modes and choices

    Directory of Open Access Journals (Sweden)

    Sofia Karampela

    2014-11-01

    Full Text Available Accessibility is a multifaceted concept that expresses the case of access between two points in space. For islands, accessibility is a key quality, since isolation and small size considered as inherent characteristics of “islandness”. In this paper, we discuss differences between geographical distance and accessibility potential in the Greek Aegean, combining different transportation modal choice (ferries and airplanes with the use of an accessibility index that incorporates modes and frequency of connection and data of actual usage. The findings indicate that geographical distance is not determining accessibility and new geographies emerge based more on the availability of transport modal choices.

  1. Investigation of Turbulence Parametrization Schemes with Reference to the Atmospheric Boundary Layer Over the Aegean Sea During Etesian Winds

    Science.gov (United States)

    Dandou, A.; Tombrou, M.; Kalogiros, J.; Bossioli, E.; Biskos, G.; Mihalopoulos, N.; Coe, H.

    2017-08-01

    The spatial structure of the marine atmospheric boundary layer (MABL) over the Aegean Sea is investigated using the Weather Research and Forecasting (WRF) mesoscale model. Two `first-order' non-local and five `1.5-order' local planetary boundary-layer (PBL) parametrization schemes are used. The predictions from the WRF model are evaluated against airborne observations obtained by the UK Facility for Airborne Atmospheric Measurements BAe-14 research aircraft during the Aegean-GAME field campaign. Statistical analysis shows good agreement between measurements and simulations especially at low altitude. Despite the differences between the predicted and measured wind speeds, they reach an agreement index of 0.76. The simulated wind-speed fields close to the surface differ substantially among the schemes (maximum values range from 13 to 18 m s^{-1} at 150-m height), but the differences become marginal at higher levels. In contrast, all schemes show similar spatial variation patterns in potential temperature fields. A warmer (1-2 K) and drier (2-3 g kg^{-1}) layer than is observed, is predicted by almost all schemes under stable conditions (eastern Aegean Sea), whereas a cooler (up to 2 K) and moister (1-2 g kg^{-1}) layer is simulated under near-neutral to nearly unstable conditions (western Aegean Sea). Almost all schemes reproduce the vertical structure of the PBL and the shallow MABL (up to 300 m) well, including the low-level jet in the eastern Aegean Sea, with non-local schemes being closer to observations. The simulated PBL depths diverge (up to 500 m) due to the different criteria applied by the schemes for their calculation. Under stable conditions, the observed MABL depth corresponds to the height above the sea surface where the simulated eddy viscosity reaches a minimum; under neutral to slightly unstable conditions this is close to the top of the simulated entrainment layer. The observed sensible heat fluxes vary from -40 to 25 W m^{-2}, while the simulated

  2. Contrasting sedimentary processes along a convergent margin: the Lesser Antilles arc system

    Science.gov (United States)

    Picard, Michel; Schneider, Jean-Luc; Boudon, Georges

    2006-12-01

    Sedimentation processes occurring in an active convergent setting are well illustrated in the Lesser Antilles island arc. The margin is related to westward subduction of the North and/or the South America plates beneath the Caribbean plate. From east to west, the arc can be subdivided into several tectono-sedimentary depositional domains: the accretionary prism, the fore-arc basin, the arc platform and inter-arc basin, and the Grenada back-arc basin. The Grenada back-arc basin, the fore-arc basin (Tobago Trough) and the accretionary prism on the east side of the volcanic arc constitute traps for particles derived from the arc platform and the South American continent. The arc is volcanically active, and provides large volumes of volcaniclastic sediments which accumulate mainly in the Grenada basin by volcaniclastic gravity flows (volcanic debris avalanches, debris flows, turbiditic flows) and minor amounts by fallout. By contrast, the eastern side of the margin is fed by ash fallout and minor volcaniclastic turbidites. In this area, the dominant component of the sediments is pelagic in origin, or derived from South America (siliciclastic turbidites). Insular shelves are the locations of carbonate sedimentation, such as large platforms which develop in the Limestone Caribbees in the northern part of the margin. Reworking of carbonate material by turbidity currents also delivers lesser amounts to eastern basins of the margin. This contrasting sedimentation on both sides of the arc platform along the margin is controlled by several interacting factors including basin morphology, volcanic productivity, wind and deep-sea current patterns, and sea-level changes. Basin morphology appears to be the most dominant factor. The western slopes of the arc platform are steeper than the eastern ones, thus favouring gravity flow processes.

  3. Underwater plasma arc cutting

    International Nuclear Information System (INIS)

    Leautier, R.; Pilot, G.

    1991-01-01

    This report describes the work done to develop underwater plasma arc cutting techniques, to characterise aerosols from cutting operations on radioactive and non-radioactive work-pieces, and to develop suitable ventilation and filtration techniques. The work has been carried out in the framework of a contract between CEA-CEN Cadarache and the Commission of European Communities. Furthermore, this work has been carried out in close cooperation with CEA-CEN Saclay mainly for secondary emissions and radioactive analysis. The contract started in May 1986 and was completed in December 1988 by a supplementary agreement. This report has been compiled from several progress reports submitted during the work period, contains the main findings of the work and encloses the results of comparative tests on plasma arc cutting

  4. Arc cathode spots

    International Nuclear Information System (INIS)

    Schrade, H.O.

    1989-01-01

    Arc spots are usually highly unstable and jump statistically over the cathode surface. In a magnetic field parallel to the surface, preferably they move in the retrograde direction; i.e., opposite to the Lorentzian rule. If the field is inclined with respect to the surface, the spots drift away at a certain angle with respect to the proper retrograde direction (Robson drift motion). These well-known phenomena are explained by one stability theory

  5. 5 m Gridded multibeam bathymetry of Rota Island, Commonwealth of the Northern Mariana Islands (CNMI)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Rota Island, CNMI. Bottom coverage was achieved in depths between 0 and -1905 meters; this 5-m grid has data only to -400 m. The netCDF and Arc ASCII grids include...

  6. Aperture modulated arc therapy

    International Nuclear Information System (INIS)

    Crooks, S M; Wu, Xiaodong; Takita, C; Watzich, M; Xing Lei

    2003-01-01

    We show that it is possible to translate an intensity modulated radiation therapy (IMRT) treatment plan and deliver it as a single arc. This technique is referred to in this paper as aperture modulation arc therapy (AMAT). During this arc, the MLC leaves do not conform to the projection of the target PTV and the machine output of the accelerator has a constant value. Dose was calculated using the CORVUS 4.0 IMRT system, which uses a pencil beam dose algorithm, and treatments were delivered using a Varian 2100C/D Clinac. Results are presented for a head and neck and a prostate case, showing the equivalence of the IMRT and the translated AMAT delivery. For a prostate AMAT delivery, coronal plane film dose for the IMRT and AMAT deliveries agreed within 7.19 ± 6.62%. For a meningioma the coronal plane dose distributions were similar to a value of 4.6 ± 6.62%. Dose to the isocentre was measured as being within 2% of the planned value in both cases

  7. Circular arc structures

    KAUST Repository

    Bo, Pengbo

    2011-07-01

    The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.

  8. Marshall Islands

    OpenAIRE

    World Bank

    2015-01-01

    This note aims to build understanding of the existing disaster risk financing and insurance (DRFI) tools in use in The Marshall Islands and to identify gaps where potential engagement could further develop financial resilience. The likelihood that a hazardous event will have a significant impact on the Marshall Islands has risen with the increasing levels of population and assets in the urban ...

  9. Anciet marble quarries in Lesvos island Greece

    Science.gov (United States)

    Mataragkas, M.; Mataragkas, D.

    2009-04-01

    ANCIENT MARBLE QUARRIES IN LESBOS ISLAND, GREECE Varti- Matarangas M.1 & Matarangas D. 1 Institute of Geological and Mining Exploration (IGME), Olympic Village, Entrance C, ACHARNAE 13677, GREECE myrsini@igme.gr , myrsini@otenet.g r A B S T R A C T Ten ancient marble quarries of Lesbos Island, most of them previously unknown, have been studied, in the frame of the research study on the ancient marble quarries in the Aegean Sea. In the present paper the geological, petrological and morphological features of the aforementioned quarries are examined. Concerning the six ancient quarries located in the areas of Tarti, Agia Paraskevi (Tsaf), Mageiras, Loutra, Latomi (Plomari) and Thermi, the authochthonous neopaleozoic unit constitutes their geological formation, while their hosting lithological formations are the included crystalline limestone lens like beds. In two ancient quarries in the areas Moria and Alyfanta, the geological formation is the authochthonous upper Triassic series and the hosting lithological formation the upper Triassic carbonate sequence, while in the areas of Akrasi-Abeliko and Karyni, the geological formation is the thrust Triassic unit and the lithological hosting formations are the included strongly deformed or not crystalline limestone lenticular beds. Furthermore, the petrographic features were also determined permitting the identification of the building stones that have been used.

  10. Sponge divers of the Aegean and medical consequences of risky compressed-air dive profiles.

    Science.gov (United States)

    Toklu, Akin Savas; Cimsit, Maide

    2009-04-01

    Historically, Turkey once had a substantial number of professional sponge divers, a population known for a relatively high incidence of diving-related conditions such as decompression sickness (DCS) and dysbaric osteonecrosis (DON). Sponge diving ended in the mid-1980s when nearly all of the sponges in the Aegean and Mediterranean Seas contracted a bacterial disease and the occupation became unprofitable. We reviewed the records of Turkish sponge divers for information on their level of knowledge, diving equipment, dive profiles, and occupational health problems. Information was collected by: 1) interviewing former sponge divers near Bodrum, where most of them had settled; 2) reviewing the relevant literature; and 3) examining the medical records of sponge divers who underwent recompression treatment. These divers used three types of surface-supplied equipment, including hard helmets, Fernez apparatus, and hookahs; the latter were preferred because they allowed divers the greatest freedom of movement while harvesting sponges underwater. These divers used profiles that we now know involved a high risk for DCS and DON. We were able to access the records of 58 divers who had received recompression treatment. All of the cases involved severe DCS and delays from dive to recompression that averaged 72 h. Complete resolution of symptoms occurred in only 11 cases (19%). Thus, we were able to document the several factors that contributed to the risks in this occupational group, including unsafe dive profiles, resistance to seeking treatment, long delays before recompression, and the fact that recompression treatment used air rather than oxygen.

  11. Viability and Management Targets of Mediterranean Demersal Fisheries: The Case of the Aegean Sea.

    Directory of Open Access Journals (Sweden)

    George Tserpes

    Full Text Available Management of the Mediterranean demersal stocks has proven challenging mainly due to the multi-species character of the fisheries. In the present work, we focus on the multi-species demersal fisheries of the Aegean Sea (eastern Mediterranean aiming to study the effects of different management measures on the main commercial stocks, as well as to explore the economic viability of the fisheries depending upon these resources, by means of simulated projections. Utilizing the limited available data, our results demonstrated that, under the current exploitation pattern, the economic viability of the fleets is threatened, particularly if fuel prices increase. Additionally, the biological targets set for the most exploited species, such as hake, will not be met under the current management regime. The projections also showed that the only management scenario under which both resource sustainability and economic viability of the fisheries are ensured is the decrease of fleet capacity in terms of vessel numbers. In this case, however, measures to support the fisheries-dependent communities need to be implemented to prevent the collapse of local economies due to employment decrease. Scenarios assuming selectivity improvements would be also beneficial for the stocks but they showed low economic performance and their application would threaten the viability of the fleets, particularly that of the trawlers.

  12. Biosynthetic potential of actinomycetes in brown forest soil on the eastern coast of the aegean sea

    Science.gov (United States)

    Shirokikh, I. G.; Shirokikh, A. A.

    2017-11-01

    The taxonomic and functional structures of the actinomycetal complex in the litter and upper horizon of the brown forest soil was studied in a Pinus brutia var. pendulifolia forest on the eastern coast of the Aegean Sea. The complex of actinomycetes included representatives of the Streptomyces and Micromonospora genera and oligosporus forms. Streptomycetes predominated (73.8%) in the soil, and micromonospores (66.7%) were dominants in the litter. Thirty isolates of ten Streptomyces species from five series and three sections prevailed. In the upper soil horizon, species of the Helvolo-Flavus Helvolus section predominated (48%); the S. felleus species occurred most frequently. Among the isolated cultures, the S. globisporus and S. sindenensis species capable to produce antitumor antibiotics were found. The testing of the antimicrobial activity of the natural isolates showed that five strains inhibit the growth of pathogenic Fusarium sp., Alternaria sp., Acremonium sp., and Bipolaris sorokiniana fungi. When testing the effect of streptomycetes on the production of cellulases, a high-efficient strain belonging to the S. noboritoensis species was revealed. All the streptomycetes isolated from the brown forest soil produced auxins at the rate of 7.8 to 19.7 μg of indole acetic acid/mL of the liquid medium in the presence of 200 mg/L of tryptophan. Twelve isolates of streptomycetes were transferred to the collection of biotechnologically promising cultures for studying their properties.

  13. Eltrombopag for the Treatment of Immune Thrombocytopenia: The Aegean Region of Turkey Experience

    Directory of Open Access Journals (Sweden)

    Füsun Özdemirkıran

    2015-12-01

    Full Text Available INTRODUCTION: OBJECTIVE: Immune thrombocytopenia (ITP is an immune mediated disease characterized by transient or persistent decrease of the platelet count to less than 100 × 109/l. Although it is included in a benign disease group, bleeding complications may be mortal. With a better understanding of the pathophysiology of the disease, thrombopoietin receptor agonists which came into use in recent years, seem to be an effective option in the treatment of resistant patients. METHODS: In this study, retrospective data of 40 patients who were treated with Eltrombopag due to the diagnosis of refractory ITP in the Aegean region were examined and evaluated. RESULTS: In the study total rate of response was 87%, and in the cases with response the median period that number of platelets reached over 50. × 109/l was determined as 19.5 (5-60 days. DISCUSSION AND CONCLUSION: CONCLUSION: In one patient venous sinus thrombosis was observed and showed no other additional risk factor due to/ related to thrombosis. The other patient with complete response and irregular follow-up for 12 months was lost due to sudden death as the result of propable acute myocardial infarction.

  14. Lithospheric Contributions to Arc Magmatism: Isotope Variations Along Strike in Volcanoes of Honshu, Japan

    Science.gov (United States)

    Kersting; Arculus; Gust

    1996-06-07

    Major chemical exchange between the crust and mantle occurs in subduction zone environments, profoundly affecting the chemical evolution of Earth. The relative contributions of the subducting slab, mantle wedge, and arc lithosphere to the generation of island arc magmas, and ultimately new continental crust, are controversial. Isotopic data for lavas from a transect of volcanoes in a single arc segment of northern Honshu, Japan, have distinct variations coincident with changes in crustal lithology. These data imply that the relatively thin crustal lithosphere is an active geochemical filter for all traversing magmas and is responsible for significant modification of primary mantle melts.

  15. Rhode Island, Connecticut, New York, and New Jersey ESI: FISHL (Fish Lines)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for anadromous fish species in coastal Rhode Island, Connecticut, New York, and New Jersey. Vector arcs in...

  16. St. Croix, U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1/3 arc-second St. Croix, U.S. Virgin Islands Coastal Digital Elevation Model will be used to support NOAA's tsunami forecast system and for tsunami inundation...

  17. Hybrid laser-arc welding

    DEFF Research Database (Denmark)

    Hybrid laser-arc welding (HLAW) is a combination of laser welding with arc welding that overcomes many of the shortfalls of both processes. This important book gives a comprehensive account of hybrid laser-arc welding technology and applications. The first part of the book reviews...... the characteristics of the process, including the properties of joints produced by hybrid laser-arc welding and ways of assessing weld quality. Part II discusses applications of the process to such metals as magnesium alloys, aluminium and steel as well as the use of hybrid laser-arc welding in such sectors as ship...... building and the automotive industry. With its distinguished editor and international team of contributors, Hybrid laser-arc welding, will be a valuable source of reference for all those using this important welding technology. Professor Flemming Ove Olsen works in the Department of Manufacturing...

  18. Gravity and magnetic anomalies of the Cyprus arc and tectonic implications

    Science.gov (United States)

    Ergün, M.; Okay, S.; Sari, C.; Oral, E. Z.

    2003-04-01

    In present day, eastern Mediterranean is controlled by the collision of the African and Eurasian plates and displacements of Arabian, Anatolian and Aegean micro-plates. The boundary between African and Eurasian plates is delineated by the Hellenic arc and Pliny-Strabo trench in the west and the Cyprus arc and a diffuse fault system of the Eastern Anatolian Fault zone in the east. The available gravity and magnetic data from the easternmost Mediterranean allow to subdivide this basin into three provinces: the northeastern Mediterranean north of the Cyprus Arc; the Levant Basin south of the Cyprus Arc and east of the line that roughly continues the Suez rift trend toward the Gulf of Antalya, between Cyprus and Anaximander Mountains; and the Mediterranean Ridge, Herodotus Basin west of this line. High anomalies observed in Cyprus and the sea region at the south is prominent in the gravity data. The Bouguer gravity anomaly reaches its maximum values over Cyprus, where it is most probably caused by high dense Troodos ophiolites. The uplifted oceanic crust causes high Bouguer anomaly also seen in the vicinity of Eratosthenes Seamount. Another result obtained from gravity data is that the crust under Herodotos and Rhodes basins is somehow oceanic and Anaximander, Eratosthenes and Cyprus are continental fragments. There are no linear magnetic anomalies in the Mediterranean. But there are magnetic anomalies over the Eratosthenes seamount and as well as from Cyprus to the Antalya basin due to the ophiolitic bodies. In Cyprus, the last compressional deformations were defined near the Miocene/Pliocene boundary. The extensional deformation associated with the Antalya basin appears to be separated by a zone of the Florence rise and Anaximander Mountains affected by differential tectonic movements. Eratosthenes Seamount is a positive crustal feature in the process of collision with Cyprus along an active margin; there is clearly a potential tectonic relationship to the onland

  19. Correlation methods in cutting arcs

    Energy Technology Data Exchange (ETDEWEB)

    Prevosto, L; Kelly, H, E-mail: prevosto@waycom.com.ar [Grupo de Descargas Electricas, Departamento Ing. Electromecanica, Universidad Tecnologica Nacional, Regional Venado Tuerto, Laprida 651, Venado Tuerto (2600), Santa Fe (Argentina)

    2011-05-01

    The present work applies similarity theory to the plasma emanating from transferred arc, gas-vortex stabilized plasma cutting torches, to analyze the existing correlation between the arc temperature and the physical parameters of such torches. It has been found that the enthalpy number significantly influence the temperature of the electric arc. The obtained correlation shows an average deviation of 3% from the temperature data points. Such correlation can be used, for instance, to predict changes in the peak value of the arc temperature at the nozzle exit of a geometrically similar cutting torch due to changes in its operation parameters.

  20. Correlation methods in cutting arcs

    International Nuclear Information System (INIS)

    Prevosto, L; Kelly, H

    2011-01-01

    The present work applies similarity theory to the plasma emanating from transferred arc, gas-vortex stabilized plasma cutting torches, to analyze the existing correlation between the arc temperature and the physical parameters of such torches. It has been found that the enthalpy number significantly influence the temperature of the electric arc. The obtained correlation shows an average deviation of 3% from the temperature data points. Such correlation can be used, for instance, to predict changes in the peak value of the arc temperature at the nozzle exit of a geometrically similar cutting torch due to changes in its operation parameters.

  1. Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

    Science.gov (United States)

    Ruch, J.; Vezzoli, L.; De Rosa, R.; Di Lorenzo, R.; Acocella, V.

    2016-02-01

    The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

  2. Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

    KAUST Repository

    Ruch, Joel

    2016-01-23

    The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic and structural field data along the strike-slip Central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion; consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activity steadily migrated eastward and currently focus on a 10 km long x 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter-term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the Central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

  3. Gas tungsten arc welder

    International Nuclear Information System (INIS)

    Christiansen, D.W.; Brown, W.F.

    1984-01-01

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable grinder, co-axial with the electrode, is provided in the enclosure for refurbishing the used electrode between welds. The specification also discloses means for loading of the cladding with fuel pellets and for placement of reflectors, gas capsules and end caps. Gravity feed conveyor and inerting means are also described. (author)

  4. The Coupling of Back-arc Extension, Extrusion and Subduction Dynamics in the Eastern Mediterranean

    Science.gov (United States)

    Capitanio, Fabio A.

    2017-04-01

    Extension in the Aegean Sea and lateral Anatolian extrusion are contrasting and seemingly unrelated examples of continental tectonics In the Eastern Mediterranean. It is acknowledged that these must reconcile with the dynamics of Tethys closure and following continental collision along the convergent margin, however the underlying mechanisms have been difficult to pinpoint, thus far. Three-dimensional numerical modelling of the dynamics of subduction and coupling with the mantle and upper plates allows probing the evolution of similar areas, supporting inferences on the ultimate causes for the continental tectonics. I will present models that reproduce the force balance of subducting slabs' buoyancy, mantle flow and upper plate interiors, and emphasise the role of perturbations in the force balance that may have followed slab breakoff, collision and trench land-locking reconstructed during the oceanic closure in the Eastern Mediterranean. These perturbations lead to a range of different margin motions and strain regimes in the upper plate, from rollback and back-arc spreading, to indentation and extrusion along the collisional margin. Different spatial and temporal fingerprints are illustrated for these processes, and while the trench rollback and back-arc spreading are rather stable features, extrusion is transient. When these regimes overlap, rapid and complex rearrangements of the tectonics in the upper plate are the result. The remarkable similarity between the models' and the Eastern Mediterranean tectonic regimes and geophysical observable allows proposing viable driving mechanisms and support inferences on the Miocene-to-Pliocene evolution of this puzzling area.

  5. Electric arc welding gun

    Science.gov (United States)

    Luttrell, Edward; Turner, Paul W.

    1978-01-01

    This invention relates to improved apparatus for arc welding an interior joint formed by intersecting tubular members. As an example, the invention is well suited for applications where many similar small-diameter vertical lines are to be welded to a long horizontal header. The improved apparatus includes an arc welding gun having a specially designed welding head which is not only very compact but also produces welds that are essentially free from rolled-over solidified metal. The welding head consists of the upper end of the barrel and a reversely extending electrode holder, or tip, which defines an acute angle with the barrel. As used in the above-mentioned example, the gun is positioned to extend upwardly through the vertical member and the joint to be welded, with its welding head disposed within the horizontal header. Depending on the design of the welding head, the barrel then is either rotated or revolved about the axis of the vertical member to cause the electrode to track the joint.

  6. Radioactivity and metal concentrations in marine sediments associated with mining activities in Ierissos Gulf, North Aegean Sea, Greece.

    Science.gov (United States)

    Pappa, F K; Tsabaris, C; Ioannidou, A; Patiris, D L; Kaberi, H; Pashalidis, I; Eleftheriou, G; Androulakaki, E G; Vlastou, R

    2016-10-01

    Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of (226)Ra, (235)U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Traditionally used wild edible greens in the Aegean Region of Turkey

    Directory of Open Access Journals (Sweden)

    Yunus Dogan

    2012-12-01

    Full Text Available Turkey has the largest coastal area in the Mediterranean, possesses an extraordinarily rich flora, and a great traditional knowledge. This diversity of plants naturally affects the traditional use of plants and is reflected in the rich Turkish cuisine. Consequently, the Mediterranean Diet (whose typical components are wild greens constitutes one of the important elements of Turkish cuisine. For this reason, the aim of this study was to determine the consumption of wild edible green plants for the Aegean Region of Turkey and to establish the similarities to or differences from consumption in other regions and other cuisine in the Mediterranean Basin. This study compiles and evaluates the ethnobotanical data currently available. There were 111 taxa that were identified as wild edible greens in the study area belonging to 26 different families. Asteraceae (21 taxa were the most commonly consumed as food. It was followed by Boraginaceae with 19 taxa, Apiaceae with 15 taxa and Lamiaceae with 7 taxa, respectively. Rumex and Erodium were the most represented genera with 4 species. Tamus communis and Asparagus acutifolius, Mediterranean elements and distributed in all of the Mediterranean Basin, are among the most widely consumed wild plants in the area. Wild edible plants are consumed in a variety of ways. The most common type of consumption (79 taxa was in salads. The fact that the majority of the plants used in the area are consumed in salads shows the close relationship between the local diet and the concept of the Mediterranean Diet. As a result, very promisingly, there is a renewed or increasing interest in consuming wild food plants as part of this diet.

  8. Tearing, segmentation, and backstepping of subduction in the Aegean: New insights from seismicity

    Science.gov (United States)

    Bocchini, G. M.; Brüstle, A.; Becker, D.; Meier, T.; van Keken, P. E.; Ruscic, M.; Papadopoulos, G. A.; Rische, M.; Friederich, W.

    2018-06-01

    This study revisits subduction processes at the Hellenic Subduction Zone (HSZ) including tearing, segmentation, and backstepping, by refining the geometry of the Nubian slab down to 150-180 km depth using well-located hypocentres from global and local seismicity catalogues. At the western termination of the HSZ, the Kefalonia Transform Fault marks the transition between oceanic and continental lithosphere subducting to the south and to the north of it, respectively. A discontinuity is suggested to exist between the two slabs at shallow depths. The Kefalonia Transform Fault is interpreted as an active Subduction-Transform-Edge-Propagator-fault formed as consequence of faster trench retreat induced by the subduction of oceanic lithosphere to the south of it. A model reconstructing the evolution of the subduction system in the area of Peloponnese since 34 Ma, involving the backstepping of the subduction to the back-side of Adria, provides seismological evidence that supports the single-slab model for the HSZ and suggests the correlation between the downdip limit of the seismicity to the amount of subducted oceanic lithosphere. In the area of Rhodes, earthquake hypocentres indicate the presence of a NW dipping subducting slab that rules out the presence of a NE-SW striking Subduction-Transform-Edge-Propagator-fault in the Pliny-Strabo trenches region. Earthquake hypocentres also allow refining the slab tear beneath southwestern Anatolia down to 150-180 km depth. Furthermore, the distribution of microseismicity shows a first-order slab segmentation in the region between Crete and Karpathos, with a less steep and laterally wider slab segment to the west and a steeper and narrower slab segment to the east. Thermal models indicate the presence of a colder slab beneath the southeastern Aegean that leads to deepening of the intermediate-depth seismicity. Slab segmentation affects the upper plate deformation that is stronger above the eastern slab segment and the seismicity

  9. South Aegean volcanic glass. Separation and analysis by INAA and EPMA

    International Nuclear Information System (INIS)

    Saminger, S.; Peltz, C.; Bichler, M.

    2000-01-01

    Pumice from the major volcanic sources (Milos, Nisyros, Yali, Kos and Santorini) in the South Aegean region was investigated to reveal the differences between the composition of the bulk material, which contains a certain percentage of crystallites, and the pure glass phase, which is the main constituent. The knowledge of these differences is important for the identification of vitric tephra layers found in the Eastern Mediterranean region in archaeological context, in deep sea drilling cores and lake sediments. Eruption products, deposited at some distance, show not only a decrease in their grain size, but also have usually lost their crystalline fraction due to gravity separation and consist only of glass shards. Major element distributions in such layers and in pumiceous glass are not sufficient for a reliable identification of the volcanic source, as several eruptions are known to have produced chemically very similar tephra layers in this region. Trace element data, especially of the rather immobile rare earth elements (REEs), can provide greater information on tephra originating from different volcanic eruptions. Therefore, a technique has been developed to separate the glass phase from different primary pumices to reveal differences in their trace element distributions. The concentrations of the major constituents, in particular Al, Ca, Fe, Mg, Mn, Na, Si, and Ti were determined by electron probe microanalysis (EPMA), those of Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Th, Ti, U, V, Yb and Zr by instrumental neutron activation analysis. Subtle differences between the compositions of the glass phase and the bulk material are explained by differentiation during partial crystallization. Their applicability to the classification of tephra layers is demonstrated. (author)

  10. The Aegean Sea incident: A quantitative evaluation of the fate of the oil

    International Nuclear Information System (INIS)

    Bergueiro Lopez, J.R.; Morales Correas, N.; Dominguez Laseca, F.

    1993-01-01

    In December 1992, the tanker Aegean Sea was shipwrecked at the entrance to a harbor in northwest Spain. The accident was partly due to bad weather conditions and possibly also to the poor condition of the ship, which subsequently broke in two and caught fire. The tanker was carrying 79,000 tons of low-viscosity light oil, of which 40-60% burned. The oil slick coming from the wrecked ship spread westward and northward into nearby bays, impacting 100-200 km of coast with varying degrees of severity. Strong winds and stormy sea conditions at the time of the incident favored evaporation and natural dispersion of much of the spilled oil. Spill response and countermeasures included restriction of fishing zones, manual and mechanical cleaning of beaches and nearby rocks, use of pumps and skimmers to recover oil from water and shore, and stirring oil-penetrated sand to ca 50 cm depth to facilitate oxygenation and ensure degradation of oil traces. About 6,000 m 3 of emulsified oil were collected from the water and another 1,000 m 3 from the shore; 5,000-6,000 tons of unspilled oil was recovered from the tanker. A simulation model estimated that if no burning had occurred, 2/3 of the oil would have dispersed in the sea or evaporated into the air in ca 3 d. Ecological impacts on plankton, benthos, and pelagic and bird communities appears to have been minor or at least relatively localized. Long-term ecological impacts are being studied. However, zones of fish/shellfish breeding were affected, with short-term damages estimated at over $45 million. 9 refs., 5 figs., 1 tab

  11. Arc-weld pool interactions

    International Nuclear Information System (INIS)

    Glickstein, S.S.

    1978-08-01

    The mechanisms involved in arc-weld pool interactions are extremely complex and no complete theory is presently available to describe much of the phenomena observed during welding. For the past several years, experimental and analytical studies have been undertaken at the Bettis Atomic Power Laboratory to increase basic understanding of the gas tungsten arc welding process. These studies have included experimental spectral analysis of the arc in order to determine arc temperature and analytical modeling of the arc and weld puddle. The investigations have been directed toward determining the cause and effects of variations in the energy distribution incident upon the weldment. In addition, the effect of weld puddle distortion on weld penetration was investigated, and experimental and analytical studies of weld process variables have been undertaken to determine the effects of the variables upon weld penetration and configuration. A review of the results and analysis of these studies are presented

  12. Episodic nature of continental arc activity since 750 Ma: A global compilation

    Science.gov (United States)

    Cao, Wenrong; Lee, Cin-Ty A.; Lackey, Jade Star

    2017-03-01

    Continental arcs have been recently hypothesized to outflux large amounts of CO2 compared to island arcs so that global flare-ups in continental arc magmatism might drive long-term greenhouse events. Quantitative testing of this hypothesis, however, has been limited by the lack of detailed studies on the spatial distribution of continental arcs through time. Here, we compile a worldwide database of geological maps and associated literature to delineate the surface exposure of granitoid plutons, allowing reconstruction of how the surface area addition rate of granitoids and the length of continental arcs have varied since 750 Ma. These results were integrated into an ArcGIS framework and plate reconstruction models. We find that the spatial extent of continental arcs is episodic with time and broadly matches the detrital zircon age record. Most vigorous arc magmatism occurred during the 670-480 Ma and the 250-50 Ma when major greenhouse events are recognized. Low continental arc activity characterized most of the Cryogenian, middle-late Paleozoic, and Cenozoic when climate was cold. Our results indicate that plate tectonics is not steady, with fluctuations in the nature of subduction zones possibly related in time to the assembly and dispersal of continents. Our results corroborate the hypothesis that variations in continental arc activity may play a first order role in driving long-term climate change. The dataset presented here provides a quantitative basis for upscaling continental arc processes to explore their effects on mountain building, climate, and crustal growth on a global scale.

  13. Geological constraints on continental arc activity since 720 Ma: implications for the link between long-term climate variability and episodicity of continental arcs

    Science.gov (United States)

    Cao, W.; Lee, C. T.

    2016-12-01

    Continental arc volcanoes have been suggested to release more CO2 than island arc volcanoes due to decarbonation of wallrock carbonates in the continental upper plate through which the magmas traverse (Lee et al., 2013). Continental arcs may thus play an important role in long-term climate. To test this hypothesis, we compiled geological maps to reconstruct the surface distribution of granitoid plutons and the lengths of ancient continental arcs. These results were then compiled into a GIS framework and incorporated into GPlates plate reconstructions. Our results show an episodic nature of global continental arc activity since 720 Ma. The lengths of continental arcs were at minimums during most of the Cryogenian ( 720-670 Ma), the middle Paleozoic ( 460-300 Ma) and the Cenozoic ( 50-0 Ma). Arc lengths were highest during the Ediacaran ( 640-570 Ma), the early Paleozoic ( 550-430 Ma) and the entire Mesozoic with peaks in the Early Triassic ( 250-240 Ma), Late Jurassic-Early Cretaceous ( 160-130 Ma), and Late Cretaceous ( 90-65 Ma). The extensive continental arcs in the Ediacaran and early Paleozoic reflect the Pan-African events and circum-Gondwana subduction during the assembly of the Gondwana supercontinent. The Early Triassic peak is coincident with the final closure of the paleo-Asian oceans and the onset of circum-Pacific subduction associated with the assembly of the Pangea supercontinent. The Jurassic-Cretaceous peaks reflect the extensive continental arcs established in the western Pacific, North and South American Cordillera, coincident with the initial dispersal of the Pangea. Continental arcs are favored during the final assembly and the early-stage dispersal of a supercontinent. Our compilation shows a temporal match between continental arc activity and long-term climate at least since 720 Ma. For example, continental arc activity was reduced during the Cryogenian icehouse event, and enhanced during the Early Paleozoic and Jurassic-Cretaceous greenhouse

  14. Arc fault detection system

    Science.gov (United States)

    Jha, K.N.

    1999-05-18

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard. 1 fig.

  15. Arc fault detection system

    Science.gov (United States)

    Jha, Kamal N.

    1999-01-01

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.

  16. The ARCS radial collimator

    International Nuclear Information System (INIS)

    Stone, M.B.; Abernathy, D.L.; Niedziela, J.L.; Overbay, M.A.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. The collimator is composed of collimating blades (or septa). The septa are 12 micron thick Kapton foils coated on each side with 39 microns of enriched boron carbide ( 10 B 4 C with 10 B > 96%) in an ultra-high vacuum compatible binder. The collimator blades represent an additional 22 m 2 of surface area. In the article we present collimator's design and performance and methodologies for its effective use

  17. Geophysical imaging of buried volcanic structures within a continental back-arc basin

    DEFF Research Database (Denmark)

    Stratford, Wanda Rose; Stern, T.A.

    2008-01-01

    Hidden beneath the ~2 km thick low-velocity volcaniclastics on the western margin of the Central Volcanic Region, North Island, New Zealand, are two structures that represent the early history of volcanic activity in a continental back-arc. These ~20×20 km structures, at Tokoroa and Mangakino, fo...

  18. Easter Island, Chile Digital Elevation Model 3 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Plasma's sweeping arc

    International Nuclear Information System (INIS)

    Pichon, Max

    2010-01-01

    Full text: It is purely elemental, returning materials to their basic atoms through extreme heat and then recondensing them in useful ways. Plasma arc gasification is the latest advanced waste treatment (AWT)concept to hit our shores, courtesy of Zenergy Australia. According to its fans, plasma technology can eliminate all domestic waste to landfill and turn it into beneficial by-products. Japan has toyed with it for a decade, but the idea is now creating a bit of buzz, in the US in particular. Consultancy URS last year undertook a review of 16 advanced technologies for the City of Los Angeles and determined plasma arc gasification was one of the most promising. The Waste Management Association of Australia (VVMAA), however, is cautious - too many AWT projects here have failed to live up to their promises. Plasma arc gasification works on the same principle as a welding machine. An inert gas is passed through an electrical arc between two electrodes and becomes ionised (called plasma), reaching temperatures as high as 13,900°C. It is then injected into the plasma converter holding the waste. Zenergy is working with US technology company Plasma Waste Recycling (PWR), which says it can convert 80 per cent of waste to syngas, a mixture of carbon monoxide and hydrogen that can be used to generate renewable electricity. The inorganic compounds in the waste come out as a solid, either molten metal to be cast as scrap steel or a slag that can be used as a building material aggregate or spun into mineral wool. “The plasma arc process is the next generation for AWT plants as there is no incineration involved, no fly ash, no bottom ash and nothing left to landfill,” said Zenergy Australia's Paul Prasad. He estimates a plant could convert up to 175,000 tonnes of household waste a year into energy or reusable by-products. Technically, it also gets around Australia's fears over incineration, though whether that is really the case in practice remains to be seen. Prasad says

  20. Arc Interference Behavior during Twin Wire Gas Metal Arc Welding Process

    Directory of Open Access Journals (Sweden)

    Dingjian Ye

    2013-01-01

    Full Text Available In order to study arc interference behavior during twin wire gas metal arc welding process, the synchronous acquisition system has been established to acquire instantaneous information of arc profile including dynamic arc length variation as well as relative voltage and current signals. The results show that after trailing arc (T-arc is added to the middle arc (M-arc in a stable welding process, the current of M arc remains unchanged while the agitation increases; the voltage of M arc has an obvious increase; the shape of M arc changes, with increasing width, length, and area; the transfer frequency of M arc droplet increases and the droplet itself becomes smaller. The wire extension length of twin arc turns out to be shorter than that of single arc welding.

  1. A parasitological, molecular and serological survey of Hepatozoon canis infection in dogs around the Aegean coast of Turkey.

    Science.gov (United States)

    Karagenc, Tulin Ilhan; Pasa, Serdar; Kirli, Gulcan; Hosgor, Murat; Bilgic, Huseyin Bilgin; Ozon, Yavuz Hakan; Atasoy, Abidin; Eren, Hasan

    2006-01-30

    Canine hepatozoonosis is caused by the tick-borne protozoon Hepatozoon spp. The prevalence of the infection in the Aegean coast of Turkey was investigated by examination of blood smear parasitology and polymerase chain reaction (PCR) using blood samples from 349 dogs collected from Central Aydin, Kusadasi, Selcuk, Central Manisa, Bodrum and Marmaris within the Aegean coast of Turkey. The indirect fluorescent antibody test (IFAT) for the detection of Hepatozoon canis antibodies was also used to detect the exposure rate to H. canis. PCR amplifying a 666bp fragment of 18S rRNA gene of Hepatozoon spp. was used in the epidemiological survey. The prevalence of Hepatozoon spp. infection was 10.6% by blood smear parasitology and 25.8% by PCR. IFAT revealed that 36.8% of serum samples were positive for antibodies reactive with Hepatozoon spp. The PCR products of 18S rRNA gene of Hepatozoon spp. isolated from six infected dogs, one isolate originating from each of the six different locations, were sequenced. The results of sequence analysis indicate that they are closely related to Indian and Japanese isolates of H. canis. This is the first epidemiological study on the prevalence of H. canis infection in the dog, in Turkey.

  2. Recovery of the commercial sponges in the central and southeastern Aegean Sea (NE Mediterranean after an outbreak of sponge disease

    Directory of Open Access Journals (Sweden)

    J. CASTRITSI-CATHARIOS

    2011-01-01

    Full Text Available The distribution and biometry of commercial sponges (Porifera in coastal areas of the central and southeastern Aegean Sea was investigated to estimate the recovery progress of the populations eight years after the first appearance of sponge disease. Signs of the disease were detected only in 1.6% of the harvested sponges. Multivariate analysis on the percentage abundance of sponges showed two distinct groups among the sixteen fishing grounds studied: the eight deep (50-110 m and the eight shallow ones (<40 m. The group from the deep depths consisted of Spongia officinalis adriatica, S. agaricina and S. zimocca. The infralittoral zone was characterized by the presence of Hippospongia communis, S. officinalis adriatica and S. officinalis mollissima. These bath sponges showed an enhanced abundance in the eastern Cretan Sea (S. Aegean Sea. In addition, their dimensions, particularly height, increased with increasing depth. It is indicated that the hydrographic conditions prevailing in the eastern Cretan Sea affected the repopulating processes of sponge banks. In each species, the biometric characteristics of the experimental specimens were similar to those of the sponges found in the market and harvested at respective depths prior to the appearance of sponge disease.

  3. Modelling the water mass circulation in the Aegean Sea. Part I: wind stresses, thermal and haline fluxes

    Directory of Open Access Journals (Sweden)

    I. A. Valioulis

    1994-07-01

    Full Text Available The aim of this work is to develop a computer model capable of simulating the water mass circulation in the Aegean Sea. There is historical, phenomenological and recent experimental evidence of important hydrographical features whose causes have been variably identified as the highly complex bathymetry, the extreme seasonal variations in temperature, the considerable fresh water fluxes, and the large gradients in salinity or temperature across neighbouring water masses (Black Sea and Eastern Mediterranean. In the approach taken here, physical processes are introduced into the model one by one. This method reveals the parameters responsible for permanent and seasonal features of the Aegean Sea circulation. In the first part of the work reported herein, wind-induced circulation appears to be seasonally invariant. This yearly pattern is overcome by the inclusion of baroclinicity in the model in the form of surface thermohaline fluxes. The model shows an intricate pattern of sub-basin gyres and locally strong currents, permanent or seasonal, in accord with the experimental evidence.

  4. Modelling the water mass circulation in the Aegean Sea. Part I: wind stresses, thermal and haline fluxes

    Directory of Open Access Journals (Sweden)

    I. A. Valioulis

    Full Text Available The aim of this work is to develop a computer model capable of simulating the water mass circulation in the Aegean Sea. There is historical, phenomenological and recent experimental evidence of important hydrographical features whose causes have been variably identified as the highly complex bathymetry, the extreme seasonal variations in temperature, the considerable fresh water fluxes, and the large gradients in salinity or temperature across neighbouring water masses (Black Sea and Eastern Mediterranean. In the approach taken here, physical processes are introduced into the model one by one. This method reveals the parameters responsible for permanent and seasonal features of the Aegean Sea circulation. In the first part of the work reported herein, wind-induced circulation appears to be seasonally invariant. This yearly pattern is overcome by the inclusion of baroclinicity in the model in the form of surface thermohaline fluxes. The model shows an intricate pattern of sub-basin gyres and locally strong currents, permanent or seasonal, in accord with the experimental evidence.

  5. Physical and chemical consequences of crustal melting in fossil mature intra-oceanic arcs

    Science.gov (United States)

    Berger, J.; Burg, J.-P.

    2012-04-01

    Seismic velocity models of active intra-oceanic arcs show roots with densities and P-wave velocities intermediate to classical lower oceanic crust (density; ~3.0, Vp: ~7.0 km/s) and uppermost harzburgitic mantle (density: 3.2-3.3, Vp: 7.9-8.0 km/s). Most studies on active and fossil exhumed island arcs interpret the petrological nature of this root as ultramafic cumulates crystallized from primitive melts and/or as pyroxenites formed via basalt-peridotite reactions. Igneous cumulates and pyroxenites have densities close to or above that of uppermost mantle rocks; they can consequently undergo gravity-driven delamination, a process thought to drive the bulk composition of the arc toward an andesitic, continental crust-like composition. Dehydration and melting reactions are reported from exposed arc roots (Jijal complex in Kohistan; Amalaoulaou arc in Mali; Fiordland arc in New-Zealand). Intense influx of mantle-derived basaltic magmas at high pressure in a thickening island arc can enable lower crustal rocks to locally cross the dehydration-melting solidus of hydrous subalkaline basalts. Thermodynamic modeling using Perple_X, geochemical analysis and compilation of experimental and field data have been combined to constrain processes, conditions and consequences of intra-arc melting. The position of the solidus in a P-T grid is strongly dependent of the bulk water content: at 1 GPa, it is as low as 750 °C for water saturated hornblende-gabbros (>1 wt% H2O) and 830°C for gabbros with 0.1 wt% H2O. Incipient melting (F conditions to trigger gravity-driven delamination of the root and could lead to introduction of fertile arc garnet pyroxenites within the upper mantle. However, in Kohistan and at Amalaoulaou, the dense garnet-clinopyroxene residues are dispersed in the arc roots; they are intermingled with hornblendite and pyroxenite bodies. The small density contrast between garnet granulites and the harzburgitic mantle, and the low volumes of garnet

  6. Additional Records of Two Rare Crabs, Ilia nucleus (Linnaeus, 1758 and Ethusa mascarone (Herbst, 1785 from Izmir Bay, Aegean Sea, Turkey

    Directory of Open Access Journals (Sweden)

    Okan AKYOL

    2016-11-01

    Full Text Available One specimen of Ilia nucleus and one specimen of Ethusa mascarone were collected from Urla coasts, Izmir Bay, Aegean Sea. Up to now, both rare species are being reported for the three and four times from Izmir Bay, respectively.

  7. Class renormalization: islands around islands

    International Nuclear Information System (INIS)

    Meiss, J.D.

    1986-01-01

    An orbit of 'class' is one that rotates about a periodic orbit of one lower class with definite frequency. This contrasts to the 'level' of a periodic orbit which is the number of elements in its continued fraction expansion. Level renormalization is conventionally used to study the structure of quasi-periodic orbits. The scaling structure of periodic orbits encircling other periodic orbits in area preserving maps is discussed here. Fixed points corresponding to the accumulation of p/q bifurcations are found and scaling exponents determined. Fixed points for q > 2 correspond to self-similar islands around islands. Frequencies of the island boundary circles at the fixed points are obtained. Importance of this scaling for the motion of particles in stochastic regions is emphasized. (author)

  8. Assessment of ENSEMBLES regional climate models for the representation of monthly wind characteristics in the Aegean Sea (Greece): Mean and extremes analysis

    Science.gov (United States)

    Anagnostopoulou, Christina; Tolika, Konstantia; Tegoulias, Ioannis; Velikou, Kondylia; Vagenas, Christos

    2013-04-01

    The main scope of the present study is the assessment of the ability of three of the most updated regional climate models, developed under the frame of the European research project ENSEMBLES (http://www.ensembles-eu.org/), to simulate the wind characteristics in the Aegean Sea in Greece. The examined models are KNMI-RACMO2, MPI-MREMO, and ICTP - RegCM3. They all have the same spatial resolution (25x25km) and for their future projections they are using the A1B SRES emission scenarios. Their simulated wind data (speed and direction) were compared with observational data from several stations over the domain of study for a time period of 25 years, from 1980 to 2004 on a monthly basis. The primer data were available every three or six hours from which we computed the mean daily wind speed and the prevailing daily wind direction. It should be mentioned, that the comparison was made for the grid point that was the closest to each station over land. Moreover, the extreme speed values were also calculated both for the observational and the simulated data, in order to assess the ability of the models in capturing the most intense wind conditions. The first results of the study showed that the prevailing winds during the winter and spring months have a north - northeastern or a south - south western direction in most parts of the Aegean sea. The models under examination seem to capture quite satisfactorily this pattern as well as the general characteristics of the winds in this area. During summer, winds in the Aegean Sea have mainly north direction and the models have quite good agreement both in simulating this direction and the wind speed. Concerning the extreme wind speed (percentiles) it was found that for the stations in the northern Aegean all the models overestimate the extreme wind indices. For the eastern parts of the Aegean the KNMI and the MPI model underestimate the extreme wind speeds while on the other hand the ICTP model overestimates them. Finally for the

  9. On arc efficiency in gas tungsten arc welding

    Directory of Open Access Journals (Sweden)

    Nils Stenbacka

    2013-12-01

    Full Text Available The aim of this study was to review the literature on published arc efficiency values for GTAW and, if possible, propose a narrower band. Articles between the years 1955 - 2011 have been found. Published arc efficiency values for GTAW DCEN show to lie on a wide range, between 0.36 to 0.90. Only a few studies covered DCEP - direct current electrode positive and AC current. Specific information about the reproducibility in calorimetric studies as well as in modeling and simulation studies (considering that both random and systematic errors are small was scarce. An estimate of the average arc efficiency value for GTAW DCEN indicates that it should be about 0.77. It indicates anyway that the GTAW process with DCEN is an efficient welding method. The arc efficiency is reduced when the arc length is increased. On the other hand, there are conflicting results in the literature as to the influence of arc current and travel speed.

  10. Microhabitat choice in island lizards enhances camouflage against avian predators.

    Science.gov (United States)

    Marshall, Kate L A; Philpot, Kate E; Stevens, Martin

    2016-01-25

    Camouflage can often be enhanced by genetic adaptation to different local environments. However, it is less clear how individual behaviour improves camouflage effectiveness. We investigated whether individual Aegean wall lizards (Podarcis erhardii) inhabiting different islands rest on backgrounds that improve camouflage against avian predators. In free-ranging lizards, we found that dorsal regions were better matched against chosen backgrounds than against other backgrounds on the same island. This suggests that P. erhardii make background choices that heighten individual-specific concealment. In achromatic camouflage, this effect was more evident in females and was less distinct in an island population with lower predation risk. This suggests that behavioural enhancement of camouflage may be more important in females than in sexually competing males and related to predation risk. However, in an arena experiment, lizards did not choose the background that improved camouflage, most likely due to the artificial conditions. Overall, our results provide evidence that behavioural preferences for substrates can enhance individual camouflage of lizards in natural microhabitats, and that such adaptations may be sexually dimorphic and dependent on local environments. This research emphasizes the importance of considering links between ecology, behaviour, and appearance in studies of intraspecific colour variation and local adaptation.

  11. Progressive enrichment of arc magmas caused by the subduction of seamounts under Nishinoshima volcano, Izu-Bonin Arc, Japan

    Science.gov (United States)

    Sano, Takashi; Shirao, Motomaro; Tani, Kenichiro; Tsutsumi, Yukiyasu; Kiyokawa, Shoichi; Fujii, Toshitsugu

    2016-06-01

    The chemical composition of intraplate seamounts is distinct from normal seafloor material, meaning that the subduction of seamounts at a convergent margin can cause a change in the chemistry of the mantle wedge and associated arc magmas. Nishinoshima, a volcanic island in the Izu-Bonin Arc of Japan, has been erupting continuously over the past 2 years, providing an ideal opportunity to examine the effect of seamount subduction on the chemistry of arc magmas. Our research is based on the whole-rock geochemistry and the chemistry of minerals within lavas and air-fall scoria from Nishinoshima that were erupted before 1702, in 1973-1974, and in 2014. The mineral phases within the analyzed samples crystallized under hydrous conditions (H2O = 3-4 wt.%) at temperatures of 970 °C-990 °C in a shallow (3-6 km depth) magma chamber. Trace element data indicate that the recently erupted Nishinoshima volcanics are much less depleted in the high field strength elements (Nb, Ta, Zr, Hf) than other volcanics within the Izu-Bonin Arc. In addition, the level of enrichment in the Nishinoshima magmas has increased in recent years, probably due to the addition of material from HIMU-enriched (i.e., high Nb/Zr and Ta/Hf) seamounts on the Pacific Plate, which is being subducted westwards beneath the Philippine Sea Plate. This suggests that the chemistry of scoria from Nishinoshima volcano records the progressive addition of components derived from subducted seamounts.

  12. LA-ICP-MS Pb-U Dating of Young Zircons from the Kos-Nisyros Volcanic Centre, SE Aegean Arc (Greece)

    Science.gov (United States)

    Guillong, M.; Von Quadt, A.; Peytcheva, I.; Bachmann, O.

    2014-12-01

    Zircon Pb-U dating has become a key technique for answering many important questions in geosciences. This paper describes a new LA-ICP-MS approach. We show, using previously dated samples of a large quaternary rhyolitic eruption in the Kos-Nisyros volcanic centre (the 161 ka Kos Plateau Tuff), that the precision of our LA-ICP-MS method is as good as via SHRIMP, while ID-TIMS measurements confirm the accuracy. Gradational age distribution over >140 ka of the Kos zircons and the near-absence of inherited cores indicate near-continuous crystallisation in a growing magma reservoir with little input from wall rocks. Previously undated silicic eruptions from Nisyros volcano (Lower Pumice, Nikia Flow, Upper Pumice), which are stratigraphically constrained to have happened after the Kos Plateau Tuff, are dated to be younger than respectively 124 ± 35 ka, 111 ± 42 ka and 70 ± 24 ka. Samples younger than 1 Ma were corrected for initial thorium disequilibrium using a new formula that also accounts for disequilibrium in 230Th decay. Guillong, M. et al., 2014, JAAS, 29, p. 963-967; doi: 10.1039/c4ja00009a.

  13. Electric arc radius and characteristics

    International Nuclear Information System (INIS)

    Fang, T.M.

    1980-01-01

    The heat transfer equation of an arc discharge has been solved. The arc is assumed to be a cylinder with negligible axial variation and the dominant heat transfer process is conduction radially inside the column and radiation/convection at the outside edge. The symmetric consideration allows a simple one-dimensional formulation. By taking into account proper variation of the electrical conductivity as function of temperature, the heat balance equation has been solved analytically. The radius of the arc and its current-field characteristics have also been obtained. The conventional results that E approx. I 0 5385 and R approx. I 0 7693 with E being the applied field, I the current, and R the radius of the cylindrical arc, have been proved to be simply limiting cases of our more general characteristics. The results can be applied quite widely including, among others, the neutral beam injection project in nuclear fusion and MHD energy conversion

  14. PC-based arc ignition and arc length control system for gas tungsten arc welding

    International Nuclear Information System (INIS)

    Liu, Y.; Cook, G.E.; Barnett, R.J.; Springfield, J.F.

    1992-01-01

    In this paper, a PC-based digital control system for gas tungsten arc welding (GTAW) is presented. This system controls the arc ignition process, the arc length, and the process of welding termination. A DT2818 made by Data Translation is used for interface and A/D and D/A conversions. The digital I/O ports of the DT2818 are used for control of wirefeed, shield gas, cooling water, welding power supply, etc. The DT2818 is housed in a PC. The welding signals and status are displayed on the screen for in-process monitoring. A user can control the welding process by the keyboard

  15. Energy Transition Initiative: Island Energy Snapshot - St. Lucia (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2015-02-01

    This profile provides a snapshot of the electricity generation or reduction technologies, including solar hot water heating, available to Saint Lucia, one of six Caribbean countries that make up the Windward Islands - the southern arc of the Lesser Antilles chain - at the eastern end of the Caribbean Sea. Heating and transportation fuels are not addressed.

  16. Arc modeling for welding analysis

    International Nuclear Information System (INIS)

    Glickstein, S.S.

    1978-04-01

    A one-dimensional model of the welding arc that considers heat generation by the Joule effect and heat losses by radiation and conduction has been used to study the effects of various gases and gas mixtures currently employed for welding applications. Minor additions of low ionization potential impurities to these gases are shown to significantly perturb the electrical properties of the parent gas causing gross changes in the radial temperature distribution of the arc discharge. Such changes are reflected in the current density distribution and ultimately in the input energy distribution to the weldment. The result is observed as a variation in weld penetration. Recently published experiments and analyses of welding arcs are also evaluated and shown to contain erroneous data and results. Contrary to previous beliefs, the inclusion of a radiation loss term in the basic energy balance equation is important and cannot be considered as negligible in an argon arc at temperatures as low as 10,000 0 K. The one-dimensional analysis of the welding arc as well as the evaluation of these earlier published reports helps to explain the effects of various gases used for welding, improves our understanding of the physics of the welding arc, and provides a stepping stone for a more elaborate model which can be applied to help optimize welding parameters

  17. The 2014 Mw6.9 Gokceada and 2017 Mw6.3 Lesvos Earthquakes in the Northern Aegean Sea: The Transition from Right-Lateral Strike-Slip Faulting on the North Anatolian Fault to Extension in the Central Aegean

    Science.gov (United States)

    Cetin, S.; Konca, A. O.; Dogan, U.; Floyd, M.; Karabulut, H.; Ergintav, S.; Ganas, A.; Paradisis, D.; King, R. W.; Reilinger, R. E.

    2017-12-01

    The 2014 Mw6.9 Gokceada (strike-slip) and 2017 Mw6.3 Lesvos (normal) earthquakes represent two of the set of faults that accommodate the transition from right-lateral strike-slip faulting on the North Anatolian Fault (NAF) to normal faulting along the Gulf of Corinth. The Gokceada earthquake was a purely strike-slip event on the western extension of the NAF where it enters the northern Aegean Sea. The Lesvos earthquake, located roughly 200 km south of Gokceada, occurred on a WNW-ESE-striking normal fault. Both earthquakes respond to the same regional stress field, as indicated by their sub-parallel seismic tension axis and far-field coseismic GPS displacements. Interpretation of GPS-derived velocities, active faults, crustal seismicity, and earthquake focal mechanisms in the northern Aegean indicates that this pattern of complementary faulting, involving WNW-ESE-striking normal faults (e.g. Lesvos earthquake) and SW-NE-striking strike-slip faults (e.g. Gokceada earthquake), persists across the full extent of the northern Aegean Sea. The combination of these two "families" of faults, combined with some systems of conjugate left-lateral strike-slip faults, complement one another and culminate in the purely extensional rift structures that form the large Gulfs of Evvia and Corinth. In addition to being consistent with seismic and geodetic observations, these fault geometries explain the increasing velocity of the southern Aegean and Peloponnese regions towards the Hellenic subduction zone. Alignment of geodetic extension and seismic tension axes with motion of the southern Aegean towards the Hellenic subduction zone suggests a direct association of Aegean extension with subduction, possibly by trench retreat, as has been suggested by prior investigators.

  18. Radiation dose assessment for /sup 137/Cs from fish in the Aegean Sea before and after the Chernobyl accident

    Energy Technology Data Exchange (ETDEWEB)

    Danali-Cotsaki, S; Liritzis, Y

    1988-02-15

    The effective doses in fish from the Aegean Sea were calculated for the nuclide /sup 137/Cs covering the period 1975-1982. The effective dose varies between 3x10/sup -5/ and 10x10/sup -5/ mSv y/sup -1/ for adults and 14x10/sup -5/ to 56x10/sup -5/ y/sup -1/ for children, while the cumulative effective dose for the period 1975-1982 equals to 40.86x10/sup -5/ and 229.57x10/sup -5/ for adults and children of 10 y old, resp. When compared to doses derived from the Chernobyl accident (May 1986) it was found that the additional dose incurred by Greek individuals in May 1986 was approximately equal to the cumulative dose of 8 y contribution period (1975-1982) for adults and to a year's contribution for children of 10 y old. (author) 9 refs.; 3 figs.

  19. Radiation dose assessment for 137Cs from fish in the Aegean Sea before and after the Chernobyl accident

    International Nuclear Information System (INIS)

    Danali-Cotsaki, S.; Liritzis, Y.

    1988-01-01

    The effective doses in fish from the Aegean Sea were calculated for the nuclide 137 Cs covering the period 1975-1982. The effective dose varies between 3x10 -5 and 10x10 -5 mSv y -1 for adults and 14x10 -5 to 56x10 -5 y -1 for children, while the cumulative effective dose for the period 1975-1982 equals to 40.86x10 -5 and 229.57x10 -5 for adults and children of 10 y old, resp. When compared to doses derived from the Chernobyl accident (May 1986) it was found that the additional dose incurred by Greek individuals in May 1986 was approximately equal to the cumulative dose of 8 y contribution period (1975-1982) for adults and to a year's contribution for children of 10 y old. (author) 9 refs.; 3 figs

  20. Observations on a population of the sea anemone Anemonia viridis (Forskal, 1775) in the North Aegean Sea

    Energy Technology Data Exchange (ETDEWEB)

    Chariton Chintiroglou, C. [Thessaloniki, Aristotle Univ. (Greece). Dept. of Zoology

    1996-12-31

    The present paper is concerned with the structural aspects of Anemonia viridis populations found in the North Aegean Sea. It was found that mean wet weight and density of anemone populations increases with depth and distance from shore. Differences in the structure of the Anemonia viridis populations were attributed both to the specific hydrodynamic characteristics of the biotopes and to a number biotic interactions. From our results and t previous investigations the adoption of three different lifestyles by the anemones was assumed.: (1) a colonial form, with population densities around 650 individuals per m{sup 2}, found in substrates exposed to increased hydrodynamism; (2) a colonial form, with lower densities (90 indiv. per m{sup 2}), found in less exposed sites; (3) finally, large individuals in deeper waters chose a solitary lifestyle, as mechanical stresses were much lower.

  1. Concentration factors of radionuclides and trace metals in Mytilus galloprovincialis in an estuarine ecosystem - North Aegean Sea - Greece

    International Nuclear Information System (INIS)

    Florou, H.; Catsiki, A.B.; Papaefthymiou, H.; Chaloulou, Ch.

    2004-01-01

    Mussels are worldwide recognized as pollution bio-indicator organisms (Mussel watch program of CIESM) because they accumulate pollutants in their tissues at elevated levels in terms of biological availability in the marine environment. In the present study, the levels of 137 Cs, Cr, Cu, Mn and Zn were measured in Mytilus galloprovincialis caught from Thermaikos gulf in North Aegean Sea Greece. The samples were collected seasonally from two aqua-cultures during the period 2000 2003. Measured and published concentrations of the above elements in seawater were used for the evaluation of concentration factors by applying a linear and a non-linear regression analysis. The variation in between the two stations and the seasonal evolution of bioaccumulation of the examined elements was also investigated. Some data on the concentrations of the measured elements in sediments from the area considered were evaluated as for determining the pollution conditions of the organism habitat. (author)

  2. Radioactivity and metal concentrations in marine sediments associated with mining activities in Ierissos Gulf, North Aegean Sea, Greece

    International Nuclear Information System (INIS)

    Pappa, F.K.; Tsabaris, C.; Ioannidou, A.; Patiris, D.L.; Kaberi, H.; Pashalidis, I.; Eleftheriou, G.; Androulakaki, E.G.; Vlastou, R.

    2016-01-01

    Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of "2"2"6Ra, "2"3"5U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk. - Highlights: • Baseline information of radionuclides in a coastal area near a mining site. • Trace metals measurements in marine sediment. • Dose rates assessment for marine biota using ERICA Assessment Tool.

  3. U-series isotopes in arc magma

    Energy Technology Data Exchange (ETDEWEB)

    Hawkesworth, C.; Turner, S.; McDermott, F.; Peate, D.; Van Calsteren, P.

    1997-12-31

    Thorium is not readily mobilized in the fluid component along destructive plate margins. Uranium is mobilized, and the resultant fractionation in U/Th can be used to estimate the rates of transfer slab derived components through the mantle wedge. The variations in Th/Yb, and by implication in the fractionation-corrected Th abundances of arc magmas largely depend on the contributions from subducted sediments. It is inferred that the distinctive high Th/Ta ratios of subduction related magmas primarily reflect the Th/Ta ratios of the subducted sediments, and that such high Th/Ta ratios are generated by processes other than those associated with recent subduction-related magmatism. Uranium and thorium isotopes have also been used to evaluate magma residence times within the crust. Thus, separated minerals and groundmass from six rocks erupted in the last 4,000 years from Soufriere on St. Vincent in the Lesser Antilles, scatter about a 50,000 year errorchron on the U-Th equiline diagram (Heath et al., 1977). Models are currently being developed to investigate how such apparent ages may relate to calculated replenishment times in steady state systems. Bulk continental crust has a lower U/Th ratio (0.25) than at least some estimates for the bulk Earth (0.26) and the depleted upper mantle (0.39). However, the island arc rocks with low U/Th ratios appear to have inherited those from subducted sediments, and arc rocks with a low sediment contribution have significantly higher U/Th. Consequently, the U/Th ratios of new crustal material generated along destructive plate margins are significantly higher than those of bulk continental crust. The low average U/Th of bulk crust may be primarily due to different crust generation processes in the Archaean, when U would be less mobile because conditions were less oxidising, and when residual garnet may have had more of a role in crust generation processes. Extended abstract. 4 figs., 23 refs.

  4. Investigating potential seismic hazard in the Gulf of Gökova (South Eastern Aegean Sea) deduced from recent shallow earthquake activity

    Science.gov (United States)

    Rontogianni, S.; Konstantinou, K. I.; Evangelidis, C.; Melis, N. S.

    2011-12-01

    The Gulf of Gökova is located in the southeast Aegean along the coast of the southwest Anatolia. It is surrounded by the Bodrum Peninsula to the north, Datça Peninsula to the south and the island of Kos to the west. The Gulf is under a N-S regional extensional tectonic regime related to the westerly escape of the Anatolian plate, as a result of the collision of the Arab-African and Eurasian plates. Multi-channel seismic reflection studies that took place in the area revealed a E-W trending buried listric normal fault to the south of the Gulf, the Datça Fault, the associated antithetic faults in the north of the Gulf and a younger NE active fault, named Gökova Tranfer Fault (GTF), in the central part of the Gulf. According to these studies, the activity of the Datça Fault has been decelerated, possibly since Pleistocene, while the continuing extension has been taken up by the faults in the northeast margin of the Gulf. For our analysis we selected all the shallow earthquake activity that took place in the Gulf, within the time window from 2002 to 2011 as provided by the two seismological centers NOA-IG (HL) and KOERI-NEMC (KO). We used data from 15 three component seismic stations surrounding the Gulf. This seismic activity is observed within three periods: (a) November 2002 - May 2003, (b) May 2004 - end of 2007 and (c) December 2008 - May 2011. The strongest events recorded took place in January 2005 and May 2011, with local magnitudes ML 5.1 and 4.9 respectively. After a thorough quality control, a dataset of 192 seismic events was selected, with criteria that at least 4P and 3S phases were available. Manually picked arrival times for these selected events were inverted in order to obtain a 1D velocity model with station corrections. Probabilistic nonlinear earthquake locations were calculated using this newly derived velocity model. The earthquake locations showed that the seismic activity extends from the island of Kos to the center of the Gulf, mainly

  5. Control of paleoshorelines by trench forebulge uplift, Loyalty Islands

    Science.gov (United States)

    Dickinson, William R.

    2013-07-01

    Unlike most tropical Pacific islands, which lie along island arcs or hotspot chains, the Loyalty Islands between New Caledonia and Vanuatu owe their existence and morphology to the uplift of pre-existing atolls on the flexural forebulge of the New Hebrides Trench. The configuration and topography of each island is a function of distance from the crest of the uplifted forebulge. Both Maré and Lifou are fully emergent paleoatolls upon which ancient barrier reefs form highstanding annular ridges that enclose interior plateaus representing paleolagoon floors, whereas the partially emergent Ouvea paleoatoll rim flanks a drowned remnant lagoon. Emergent paleoshoreline features exposed by island uplift include paleoreef flats constructed as ancient fringing reefs built to past low tide levels and emergent tidal notches incised at past high tide levels. Present paleoshoreline elevations record uplift rates of the islands since last-interglacial and mid-Holocene highstands in global and regional sea levels, respectively, and paleoreef stratigraphy reflects net Quaternary island emergence. The empirical uplift rates vary in harmony with theoretical uplift rates inferred from the different positions of the islands in transit across the trench forebulge at the trench subduction rate. The Loyalty Islands provide a case study of island environments controlled primarily by neotectonics.

  6. Clinical Characteristics of the Premature Ejaculation Sufferers in Aegean Region of the Turkey: A Multicentre, Observational Study

    Directory of Open Access Journals (Sweden)

    Ahmet Cihan

    2014-11-01

    Full Text Available Demonstration of the intra-vaginal ejaculation latency time (IELT distribution in male subjects and its clinical expressions among couples in the Aegean region of the Turkey. Materials and Methods Subjects were recruited to the study from six different urologic centers in the Aegean region. During the enrollment period subjects were recruited in to two group according to presence of premature ejaculation (PE. PE diagnosis was made according to DSM-4 definition. Subjects and their partners were evaluated with patient reported outcome measures (PRO related to the ejaculation-based questionnaire (Premature ejaculation patient profile questionnaire -PEPQ. Stopwatch measurements were also asked from each couple to record intravaginal ejaculation latency time (IELT. Couples who completed two clinical visits with 4 wk interval were recruited to the data analysis. Results Among 141 eligible subjects, mean age was 36.5±9.7 years and mean partner age was 32.9±9.8 years. Following the initial evaluation 80 subjects recruited to group 1(PE and 41 subjects recruited to the group 2 (non-PE. Geometric mean IELT of the subjects was significantly differed between PE and non- PE group (64.7±66.8 vs. 521.5±414.7 seconds, p<0.001. All of the PEPQ domain scores were also differed between groups. Subjects in the PE group gave poor ratings than non-PE subjects. Partner responses were similar pattern. Correlation analyses of the PEPQ scores demonstrated significant positive correlations between “perceived control over ejaculation” and “satisfaction with sexual intercourse” domains of the PEPQ and with IELT. Conclusion Geographic distribution of IELT and its impacts among couples by the several subjective aspects of PRO measures should be assessed during PE investigation

  7. Assessment of offshore wind power potential in the Aegean and Ionian Seas based on high-resolution hindcast model results

    Directory of Open Access Journals (Sweden)

    Takvor Soukissian

    2017-03-01

    Full Text Available In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against buoy measurements, offshore wind speed and wind direction at 10 m above sea level are statistically analyzed on the annual and seasonal time scale. The spatial distribution of the mean wind speed and wind direction are provided in the appropriate time scales, along with the mean annual and the inter-annual variability; these statistical quantities are useful in the offshore wind energy sector as regards the preliminary identification of favorable sites for exploitation of offshore wind energy. Moreover, the offshore wind power potential and its variability are also estimated at 80 m height above sea level. The obtained results reveal that there are specific areas in the central and the eastern Aegean Sea that combine intense annual winds with low variability; the annual offshore wind power potential in these areas reach values close to 900 W/m2, suggesting that a detailed assessment of offshore wind energy would be worth noticing and could lead in attractive investments. Furthermore, as a rough estimate of the availability factor, the equiprobable contours of the event [4 m/s ≤ wind speed ≤ 25 m/s] are also estimated and presented. The selected lower and upper bounds of wind speed correspond to typical cut-in and cut-out wind speed thresholds, respectively, for commercial offshore wind turbines. Finally, for seven offshore wind farms that are at the concept/planning phase the main wind climate and wind power density characteristics are also provided.

  8. Diet composition of the round sardinella Sardinella aurita Valenciennes, 1847 (Osteichthyes: Clupeidae in the Turkish Aegean Sea

    Directory of Open Access Journals (Sweden)

    Bahar Bayhan

    2015-12-01

    Full Text Available Sardinella aurita, a round sardinella from Clupeidae family, is a pelagic fish found in tropical and temperate seas, just like other members of its family. The species has a wide distribution and its contribution to Mediterranean and international fisheries production potential is high. In Turkey, this species has a wide distribution in the Mediterranean Sea and the Aegean Sea, on the other hand, it is rarely seen in the Black Sea and Marmara Sea. Apart from its economic contribution to the world fisheries industry, the species has an important role in the food chain in regions it is found as it takes part in diet composition of its predators such as greater amberjack, and common dolphinfish. Nowadays, trophic levels are used in order to develop ecosystem based fisheries management strategies. For this purpose, diet composition of the round sardinella was investigated. Samples were obtained from commercial fishermen, who generally use purse seine and gill nets in Izmir Bay concerned during October 2010 - September 2011. A total of 434 S. aurita were collected all year round, with total lengths ranging 12.1 to 27.1 cm. Fish were dissected immediately after capture, stomachs removed and stored in formalin (10% until the contents were analysed. Stomach contents examined using a SZX7 Olympus stereo microscope. Prey items were identified to the lowest possible taxon. Forty eight species were identified, belonging to six major groups: Polychaeta, Crustacea, Mollusca, Chaetognatha, Tunicate and Teleostei. Finally crustaceans were the most important food item in terms of index of relative importance. At least 31 copepod species were identified, where Calanoida, Oithona nana, Oncaea media and Oithona plumifera appeared all year round with %IRI ≥ 10. With this study, the feeding regime of round sardinella, was identified in detail for the Aegean Sea of Turkey for the first time.

  9. Physically based arc-circuit interaction

    International Nuclear Information System (INIS)

    Zhong-Lie, L.

    1984-01-01

    An integral arc model is extended to study the interaction of the gas blast arc with the test circuit in this paper. The deformation in the waveshapes of arc current and voltage around the current zero has been formulated to first approximation by using a simple model of arc voltage based on the arc core energy conservation. By supplementing with the time scale for the radiation, the time rates of arc processes were amended. Both the contributions of various arc processes and the influence of circuit parameters to the arc-circuit interaction have been estimated by this theory. Analysis generated a new method of calculating test circuit parameters which improves the accurate simulation of arc-circuit interaction. The new method agrees with the published experimental results

  10. The crustal thickness and lithospheric structure of active and inactive volcanic arc terrains in Fiji and Tonga

    Science.gov (United States)

    Chen, J.; Wiens, D.; Wei, S. S.; Zha, Y.; Julià, J.; Cai, C.; Chen, Y. J.

    2015-12-01

    In order to investigate the crustal thickness and lithospheric structure beneath active and inactive volcanic arcs in Fiji and Tonga, we analyzed receiver functions from teleseismic P waves as well as Rayleigh waves from teleseismic earthquakes and ambient noise. The data were recorded by stations from three previous temporary seismic arrays deployed on the islands during 1993-1995, 2001-2002, and 2009-2010. Receiver functions were calculated with an iterative deconvolution in the time domain. We used an H-k stacking method to get preliminary Moho depth estimates under the island arcs, after assuming constant seismic average crustal P velocity. We also determined the shear wave velocity structure beneath each station from a 1-D combined inversion of receiver functions and Rayleigh wave phase velocity dispersion curves from ambient noise cross correlation at 8s - 20s and teleseismic surface waves at 20s-90s. The joint inversion models reveal that the Moho beneath the main islands of the Fiji plateau is 26-31 km deep, whereas the crust under the outer islands - including the Lau Ridge - is generally thinner, with Moho depths of 21-23.5 km. The thinnest crust (16 km) is found beneath Moala Island located between the Fiji Platform and the Lau Ridge. Crustal thickness beneath several Tonga islands is about 18-20 km. A relatively high velocity lithosphere (Vs of 4.4 - 4.5 km/s) extends to only about 60 km depth beneath the outer Fiji Islands and Lau Ridge, but to depths of 90 km underneath the main islands of the Fiji Plateau. The much thicker crust and lithosphere of the Fiji plateau relative to the Lau Ridge and Tonga Arc reflects its much longer geological history of arc crust building, going back to the early Miocene.

  11. The Origin of Tholeiitic and Calc-Alkaline Trends in Arc Magmas

    Science.gov (United States)

    Luffi, P. I.; Lee, C.

    2012-12-01

    It has long been recognized that tholeiitic (TH, high-Fe/Mg) and calc-alkaline (CA, low-Fe/Mg) magmatic series define the two most important igneous differentiation trends shaping Earth's crust. While oceanic crust formation at mid-ocean ridges is typically confined to a TH trend, arc magmatism at convergent margins, considered to significantly contribute to continent formation, generates both TH and CA trends. Thus, the origin of these trends - a key issue to understanding how continental crust forms - is matter of ongoing debate. Prevalent factors thought to contribute to the TH-CA duality are: 1) redox conditions (oxygen fugacity, fO2) and H2O contents in magmas, which control the onset and abundance of high-Fe/Mg oxide mineral fractionation; 2) crystallization depths that regulate the fractionating solid assemblage and thereby the solid/liquid Kd(Fe-Mg). Relying on an extensive geochemical dataset of modern arc volcanics and thermodynamic phase equilibria modeling, here we examine the validity and relative importance of these factors in arc petrogenesis. First, to discriminate igneous rocks more efficiently, we formulate an improved CA/TH index solely based on FeO-MgO systematics. We then confirm on a quantitative basis that, on regional scales, arcs formed on thick crust tend to be more calk-alkaline than those emplaced on thinner crust are, and show that the effect of fO2 on the CA/TH index in arc magmas is more significant than that of H2O. Importantly, we demonstrate that CA trends typical for continental arcs only form when crystal fractionation is accompanied by the assimilation of oxidized crustal components; in the absence of buffering oxidized assimilants fractionating magmas follow a TH trend more common in island arcs, irrespective of their H2O content and initial fO2 level. We find that high-pressure fractionation of amphibole and garnet in arc magmas occurs too late to have a significant influence on the CA/TH index; in addition, garnet-melt and

  12. Arcing phenomena in fusion devices workshop

    International Nuclear Information System (INIS)

    Clausing, R.E.

    1979-01-01

    The workshop on arcing phenomena in fusion devices was organized (1) to review the pesent status of our understanding of arcing as it relates to confinement devices, (2) to determine what informaion is needed to suppress arcing and (3) to define both laboratory and in-situ experiments which can ultimately lead to reduction of impurities in the plasma caused by arcing. The workshop was attended by experts in the area of vacuum arc electrode phenomena and ion source technology, materials scientists, and both theoreticians and experimentalists engaged in assessing the importance of unipolar arcing in today's tokamaks. Abstracts for papers presented at the workshop are included

  13. Equilibrium motion of quict auroral arcs

    International Nuclear Information System (INIS)

    Lyatskij, V.B.; Leont'ev, S.V.

    1981-01-01

    Ionospheric plasma convection across auroral arc is investigated. It is shown that the existence of plasma area of increased concentration adjoining arc results not only from the arc but also is a factor supporting its existence. Under stable conditions the arc and plasma zone connected to it will move at a velocity different from a velocity of plasma convection. Arc velocity will be higher or lower as compared with convection velocity depending on arc orientation relative to an external electric field. At that the plasma zone is located either in front of or behind aurora polaris [ru

  14. Principles of arc flash protection

    Energy Technology Data Exchange (ETDEWEB)

    Hirschmann, R. B.

    2003-04-01

    Recent developments in NFPA 70E, the electrical safety standards in the United States and Canada, designed to provide for a safe industrial work environment, are discussed. The emphasis in this instance is on arc explosions. Development of an arc flash protective program is discussed under various major components of an electrical safety program. These are: appropriate qualifications and training for workers, safe work practices, appropriate hazard assessment practices for any task exceeding 50V where there is the potential of an arc flash accident, flash protection equipment commensurate with the hazard associated with the task to be performed, layering in protective clothing over all body surfaces, and strict adherence to rules regarding use of safety garments and equipment.

  15. Magnetically enhanced vacuum arc thruster

    International Nuclear Information System (INIS)

    Keidar, Michael; Schein, Jochen; Wilson, Kristi; Gerhan, Andrew; Au, Michael; Tang, Benjamin; Idzkowski, Luke; Krishnan, Mahadevan; Beilis, Isak I

    2005-01-01

    A hydrodynamic model of the vacuum arc thruster and its plume is described. Primarily an effect of the magnetic field on the plume expansion and plasma generation is considered. Two particular examples are investigated, namely the magnetically enhanced co-axial vacuum arc thruster (MVAT) and the vacuum arc thruster with ring electrodes (RVAT). It is found that the magnetic field significantly decreases the plasma plume radial expansion under typical conditions. Predicted plasma density profiles in the plume of the MVAT are compared with experimental profiles, and generally a good agreement is found. In the case of the RVAT the influence of the magnetic field leads to plasma jet deceleration, which explains the non-monotonic dependence of the ion current density, on an axial magnetic field observed experimentally

  16. Magnetically enhanced vacuum arc thruster

    Energy Technology Data Exchange (ETDEWEB)

    Keidar, Michael [University of Michigan, Ann Arbor 48109 MI (United States); Schein, Jochen [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Wilson, Kristi [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Gerhan, Andrew [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Au, Michael [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Tang, Benjamin [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Idzkowski, Luke [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Krishnan, Mahadevan [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Beilis, Isak I [Tel Aviv University, Tel Aviv (Israel)

    2005-11-01

    A hydrodynamic model of the vacuum arc thruster and its plume is described. Primarily an effect of the magnetic field on the plume expansion and plasma generation is considered. Two particular examples are investigated, namely the magnetically enhanced co-axial vacuum arc thruster (MVAT) and the vacuum arc thruster with ring electrodes (RVAT). It is found that the magnetic field significantly decreases the plasma plume radial expansion under typical conditions. Predicted plasma density profiles in the plume of the MVAT are compared with experimental profiles, and generally a good agreement is found. In the case of the RVAT the influence of the magnetic field leads to plasma jet deceleration, which explains the non-monotonic dependence of the ion current density, on an axial magnetic field observed experimentally.

  17. Unzipping of the volcano arc, Japan

    Science.gov (United States)

    Stern, R.J.; Smoot, N.C.; Rubin, M.

    1984-01-01

    A working hypothesis for the recent evolution of the southern Volcano Arc, Japan, is presented which calls upon a northward-progressing sundering of the arc in response to a northward-propagating back-arc basin extensional regime. This model appears to explain several localized and recent changes in the tectonic and magrnatic evolution of the Volcano Arc. Most important among these changes is the unusual composition of Iwo Jima volcanic rocks. This contrasts with normal arc tholeiites typical of the rest of the Izu-Volcano-Mariana and other primitive arcs in having alkaline tendencies, high concentrations of light REE and other incompatible elements, and relatively high silica contents. In spite of such fractionated characteristics, these lavas appear to be very early manifestations of a new volcanic and tectonic cycle in the southern Volcano Arc. These alkaline characteristics and indications of strong regional uplift are consistent with the recent development of an early stage of inter-arc basin rifting in the southern Volcano Arc. New bathymetric data are presented in support of this model which indicate: 1. (1) structural elements of the Mariana Trough extend north to the southern Volcano Arc. 2. (2) both the Mariana Trough and frontal arc shoal rapidly northwards as the Volcano Arc is approached. 3. (3) rugged bathymetry associated with the rifted Mariana Trough is replaced just south of Iwo Jima by the development of a huge dome (50-75 km diameter) centered around Iwo Jima. Such uplifted domes are the immediate precursors of rifts in other environments, and it appears that a similar situation may now exist in the southern Volcano Arc. The present distribution of unrifted Volcano Arc to the north and rifted Mariana Arc to the south is interpreted not as a stable tectonic configuration but as representing a tectonic "snapshot" of an arc in the process of being rifted to form a back-arc basin. ?? 1984.

  18. Along Arc Structural Variation in the Izu-Bonin Arc and its Implications for Crustal Evolution Processes

    Science.gov (United States)

    Kodaira, S.; Sato, T.; Takahashi, N.; Ito, A.; Kaneda, Y.

    2005-12-01

    A continental-type middle crust having Vp = 6.1 - 6.3 km/s has been imaged at several oceanic island arcs (e.g. northern Izu, Mariana, Tonga, Kyushu-Palau ridge) since Suyehiro et al. (1996) has found a felsic middle crust in the northern Izu arc. A high velocity lower crust (Vp > 7.3 km/s) underlying the felsic middle crust has been also underlined as a characteristic structure in the northern Izu arc. A bulk composition of the crust in the Izu arc may indicate more mafic than that of a typical continental crust due to a large volume of the high velocity lower crust. Since a crust becomes more mature toward the north along the Izu-Bonin arc, investigating structural variation along the volcanic front has been believed to provide a fundamental knowledge for a crustal evolution process. In 2004 and 2005, Japan Agency for Marine-Earth Science and Technology has conducted two along arc wide-angle seismic surveys from the Sagami-bay to the Kita-Iwo jima, a total profile length of about 1000 km. Although data from the Bonin-part of the profile which were acquired this year has not been processed yet, a result from the Izu-part, from the Sagami-bay to Tori shima, shows significant structural variations along the volcanic front. The crustal thickness are varied with a wavelength of several tens of km, i.e., thickened up to 25-30 km around the volcanoes (the Miyake jama, Hachijo jima, Aoga sima, Sumisu jima), while thinned down to 20 km between them. The fine seismic velocity image obtained by refraction tomography as well as a wide-angle reflection migration shows that the variation of the crustal block having 6.0 - 6.7 km/s, which is a typical continental crustal velocity, is mainly responsible for the observed variation of the crustal thickness. The thickness of the high velocity lower crust is not significantly varied along the arc. Therefore, an average crustal seismic velocity (varied 6.6 to 7.0 km/s) represents a higher velocity that that of a typical continental

  19. Water contents of clinopyroxenes from sub-arc mantle peridotites

    Science.gov (United States)

    Turner, Michael; Turner, Simon; Blatter, Dawnika; Maury, Rene; Perfit, Michael; Yogodzinski, Gene

    2017-01-01

    One poorly constrained reservoir of the Earth's water budget is that of clinopyroxene in metasomatised, mantle peridotites. This study presents reconnaissance Sensitive High-Resolution, Ion Microprobe–Stable Isotope (SHRIMP–SI) determinations of the H2O contents of (dominantly) clinopyroxenes in rare mantle xenoliths from four different subduction zones, i.e. Mexico, Kamchatka, Philippines, and New Britain (Tabar-Feni island chain) as well as one intra-plate setting (western Victoria). All of the sub-arc xenoliths have been metasomatised and carry strong arc trace element signatures. Average measured H2O contents of the pyroxenes range from 70 ppm to 510 ppm whereas calculated bulk H2O contents range from 88 ppm to 3 737 ppm if the variable presence of amphibole is taken into account. In contrast, the intra-plate, continental mantle xenolith from western Victoria has higher water contents (3 447 ppm) but was metasomatised by alkali and/or carbonatitic melts and does not carry a subduction-related signature. Material similar to the sub-arc peridotites can either be accreted to the base of the lithosphere or potentially be transported by convection deeper into the mantle where it will lose water due to amphibole breakdown.

  20. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-01-01

    the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how

  1. Comparative distribution of the fan mussel Atrina fragilis (Bivalvia, Pinnidae in protected and trawled areas of the north Aegean Sea (Thermaikos Gulf

    Directory of Open Access Journals (Sweden)

    K. FRYGANIOTIS

    2013-02-01

    Full Text Available The distribution of the fan mussel Atrina fragilis was studied at two contrasting areas of the north Aegean Sea (Thermaikos Gulf: one routinely trawled and one closed to trawlers for over 25 years. Significant differences were detected between the two areas with decreased values in density and size of A. fragilis individuals at the trawled area. As habitat differences, i.e. sediment composition and bathymetry, had non-significant effect, extensive trawling activities probably explain the observed results.

  2. Focal mechanisms in the southern Aegean from temporary seismic networks – implications for the regional stress field and ongoing deformation processes

    OpenAIRE

    Friederich, W.; Brüstle, A.; Küperkoch, L.; Meier, T.; Lamara, S.; Working Group, Egelados

    2014-01-01

    The lateral variation of the stress field in the southern Aegean plate and the subducting Hellenic slab is determined from recordings of seismicity obtained with the CYCNET and EGELADOS networks in the years from 2002 to 2007. First motions from 7000 well-located microearthquakes were analysed to produce 540 well-constrained focal mechanisms. They were complemented by another 140 derived by waveform matching of records from larger events. Most of these earth...

  3. Workshop on Compound Semiconductor Devices and Integrated Circuits held in Europe (24th) on May 29 - Jun 2, 2000 in Aegean Sea, Greece

    Science.gov (United States)

    2000-06-02

    XI WOCSDICE 2000 Aegean Sea. Greece May 29 - June 02. 2000 Prof. Elias Muiioz Universita Politecnica de Madrid ETSI Telecomunicacion , IEL...Beaumont", and P. Gibart" ’lEL, ETSl Telecomunicacion , Univ. Politecnica de Madrid, Ciudad Universitaria, 28040-Madrid, Spain 2CNRS-CRHEA, Pare Sophia...Gibart2 ’IEL, ETS1 Telecomunicacion , Univ. Politecnica de Madrid, Ciudad Universitaria, 28040-Madrid, Spain 2CNRS-CRHEA, Pare Sophia Antipolis

  4. Tenarife Island, Canary Island Archipelago, Atlantic Ocean

    Science.gov (United States)

    1991-01-01

    Tenarife Island is one of the most volcanically active of the Canary Island archipelago, Atlantic Ocean, just off the NW coast of Africa, (28.5N, 16.5W). The old central caldera, nearly filled in by successive volcanic activity culminating in two stratocones. From those two peaks, a line of smaller cinder cones extend to the point of the island. Extensive gullies dissect the west side of the island and some forests still remain on the east side.

  5. A rotating arc plasma invertor

    International Nuclear Information System (INIS)

    Reusch, M.F.; Jayaram, K.

    1987-02-01

    A device is described for the inversion of direct current to alternating current. The main feature is the use of a rotating plasma arc in crossed electric and magnetic fields as a switch. This device may provide an economic alternative to other inversion methods in some circumstances

  6. Study of gliding arc discharge plasma

    International Nuclear Information System (INIS)

    Yang Chi; Lin Lie; Wu Bin

    2006-01-01

    The electric parameters change during discharge is studied and the relationship between non-equilibrium degree and parameters is discussed for gliding arc discharges. Using two-channel model, the rules of arc moving due to effect of the airflow is simulated. The numerical simulation results can help analyzing the generation mechanism of gliding arc non-equilibrium plasma. (authors)

  7. Rapid arc - clinical rationale and results

    International Nuclear Information System (INIS)

    Cozzi, Lucca

    2008-01-01

    The presentation will focus on the background of Intensity modulation volumetric arc therapy Rapid Arc from Varian Medical Systems aiming to highlight the technical and clinical rational also from an historical perspective to the founding pillars of fast delivery with a minimum number of arcs and a minimum number of monitor units

  8. STRUVE arc and EUPOS® stations

    Science.gov (United States)

    Lasmane, Ieva; Kaminskis, Janis; Balodis, Janis; Haritonova, Diana

    2013-04-01

    The Struve Geodetic Arc was developed in Years 1816 to 1855, 200 years ago. Historic information on the points of the Struve Geodetic Arc are included in the UNESCO World Heritage list in 2005. Nevertheless, the sites of many points are still not identified nor included in the data bases nowadays. Originally STRUVE arc consisted of 258 main triangles with 265 triangulation points. Currently 34 of the original station points are identified and included in the in the UNESCO World Heritage list. identified original measurement points of the Meridian Arc are located in Sweden (7 points), Norway (15), Finland (83), Russia (1), Estonia (22), Latvia (16), Lithuania (18), Belorussia (28), Ukraine (59) and Moldova (27). In Year 2002 was initiated another large coverage project - European Position Determination System "EUPOS®". Currently there are about 400 continuously operating GNSS (Global Navigation Satellite Systems) stations covering EU countries Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Hungary, Bulgaria, Romania and East European countries Ukraine and Moldavia. EUPOS® network is a ground based GNSS augmentation system widely used for geodesy, land surveying, geophysics and navigation. It gives the opportunity for fast and accurate position determination never available before. It is an honorable task to use the EUPOS® system for research of the Struve triangulation former sites. Projects with Struve arc can popularize geodesy, geo-information and its meaning in nowadays GIS and GNSS systems. Struve Arc and its points is unique cooperation cross-border object which deserve special attention because of their natural beauty and historical value for mankind. GNSS in geodesy discovers a powerful tool for the verification and validation of the height values of geodetic leveling benchmarks established historically almost 200 years ago. The differential GNSS and RTK methods appear very useful to identify vertical displacement of landscape by means of

  9. Influence of arc current and pressure on non-chemical equilibrium air arc behavior

    Science.gov (United States)

    Yi, WU; Yufei, CUI; Jiawei, DUAN; Hao, SUN; Chunlin, WANG; Chunping, NIU

    2018-01-01

    The influence of arc current and pressure on the non-chemical equilibrium (non-CE) air arc behavior of a nozzle structure was investigated based on the self-consistent non-chemical equilibrium model. The arc behavior during both the arc burning and arc decay phases were discussed at different currents and different pressures. We also devised the concept of a non-equilibrium parameter for a better understanding of non-CE effects. During the arc burning phase, the increasing current leads to a decrease of the non-equilibrium parameter of the particles in the arc core, while the increasing pressure leads to an increase of the non-equilibrium parameter of the particles in the arc core. During the arc decay phase, the non-CE effect will decrease by increasing the arc burning current and the nozzle pressure. Three factors together—convection, diffusion and chemical reactions—influence non-CE behavior.

  10. Crustal evolution derived from the Izu-Bonin-Mariana arc velocity images

    Science.gov (United States)

    Takahashi, N.; Kodaira, S.; Tatsumi, Y.; Miura, S.; Sato, T.; Yamashita, M.; No, T.; Takahashi, T.; Noguchi, N.; Takizawa, K.; Kaiho, Y.; Kaneda, Y.

    2010-12-01

    The Izu-Bonin-Mariana arc is known as one of typical oceanic island arcs, which has developed by subduction between oceanic crusts producing continental materials. Japan Agency for Marine-Earth Science and Technology has carried out seismic surveys using a multi-channel reflection survey system (MCS) and ocean bottom seismographs (OBSs) in the Izu-Bonin-Mariana (IBM) arc since 2002, and reported these crustal images. As the results, we identified the structural characteristics of whole Izu-Bonin-Mariana arc. Rough structural characteristics are, 1) middle crust with Vp of 6 km/s, 2) upper part of the lower crust with Vp of 6.5-6.8 km/s, 3) lower part of the lower crust with Vp of 6.8-7.5 km/s, and 4) lower mantle velocity beneath the arc crusts. In addition, structural variation along the volcanic front, for example, thickness variation of andesitic layers was imaged and the distributions is consistent with those of rhyolite volcanoes, that is, it suggested that the cause the structural variation is various degree of crustal growth (Kodaira et al., 2007). Moreover, crustal thinning with high velocity lower crust across arc was also imaged, and it is interpreted that such crust has been influenced backarc opening (Takahashi et al., 2009). According to Tatsumi et al. (2008), andesitic middle crust is produced by differentiation of basaltic lower crust and a part of the restites are transformed to the upper mantle. This means that region showing much crustal differentiation has large volume of transformation of dense crustal materials to the mantle. We calculated volume profiles of the lower crust along all seismic lines based on the petrologic model, and compared them with observed real volumes obtained by seismic images. If the real volume of the lower crust is large, it means that the underplating of dense materials to the crustal bottom is dominant rather than transformation of dense materials to the upper mantle. According to obtained profiles to judge if the

  11. Particular ceramic forms in the central Balkan and northern shores of the Aegean sea in the late bronze age

    Directory of Open Access Journals (Sweden)

    Bulatović Aleksandar

    2011-01-01

    Full Text Available This paper deals with the appearance and development of particular ceramic forms that were prevalent on the wider territory from the lower Danube to the northern shores of the Aegean sea during the middle and Late Bronze Age. These forms relate to globular beakers, pear shaped vessels with everted rims with arch shaped handles, cups with handles with plastic applications on their upper surface, etc. Particular attention is devoted to the phenomenon of globular beakers of the LBA in the valleys of Varder, Mesta and Struma rivers. All information collected primarily through analysis of stylistic-typological characteristics of ceramics of the middle and Late Bronze Age - that took into account ritual burials, layout of settlements, trade routes and climactic conditions during that period - points to population movements from the north to the south already by the LBA, i.e. in 15th century BC. These movements contributed to the creation of particular cultural groups in the LBA in the central Balkans, such as the Brnjica cultural group. However, these movements cannot be clearly linked to the so-called Aegean Migration, and for this reason their character and chronology are subject to debate. Ultimately it can be concluded that beakers of the Zimnicea -Cherkovna-Plovdiv type appeared in the late Bronze Age in the Vlasine depression and the Danube valley through the evolution of beaker forms of cultural groups of earlier periods. Almost contemporaneously, during LBA, a variant of this ceramic form, richly ornamented (mostly with spirals and similar in manner to the cultural group Dubovac-Žuto Brdo-Grla Mare- Krna, appeared in the LBA culture in northern Greece. Clearly this stylistic mannerism, with spirals as characteristic elements, spread relatively quickly through successive migrations in the period of 15th-14th century BC, toward the south of the Balkan Peninsula, thus covering the wider territory from the southern tip of the Carpathian mountains

  12. Foraminifera eco-biostratigraphy of the southern Evoikos outer shelf, central Aegean Sea, during MIS 5 to present

    Science.gov (United States)

    Drinia, Hara; Antonarakou, Assimina; Tsourou, Theodora; Kontakiotis, George; Psychogiou, Maria; Anastasakis, George

    2016-09-01

    The South Evoikos Basin is a marginal basin in the Aegean Sea which receives little terrigenous supply and its sedimentation is dominated by hemipelagic processes. Late Quaternary benthic and planktonic foraminifera from core PAG-155 are investigated in order to understand their response to the glacial-interglacial cycles in this region. The quantitative analysis of planktonic foraminifera, coupled with accelerator mass spectrometry (14C-AMS) radiocarbon date measurements, provide an integrated chrono-stratigraphic time framework over the last 90 ka (time interval between late Marine Isotopic Stages 5 and 1; MIS5-MIS1). The temporary appearance and disappearance as well as several abundance peaks in the quantitative distribution of selected climate-sensitive planktonic species allowed the identification of several eco-bioevents, useful to accurately mark the boundaries of the eco-biozones widely recognized in the Mediterranean records and used for large-scale correlations. The established bio-ecozonation scheme allows a detailed palaecological reconstruction for the late Pleistocene archive in the central Aegean, and furthermore provides a notable contribution for palaeoclimatic studies, facilitating intercorrelations between various oceanographic basins. The quantitative analyses of benthic foraminifera identify four distinct assemblages, namely Biofacies: Elphidium spp., Haynesina spp. Biofacies, characterized by neritic species, dominated during the transition from MIS 5 to MIS 4; Cassidulina laevigata/carinata Biofacies dominated till 42 ka (transgressive trend from MIS 4 to MIS 3); Bulimina gibba Biofacies dominated from 42 ka to 9.5 ka (extensive regression MIS 3,2 through lowstand and early transgression; beginning of MIS 1); Bulimina marginata, Uvigerina spp. Biofacies dominated from 9.5 ka to the present (late transgression through early highstand; MIS 1)., This study showed that the South Evoikos Basin which is characterized by its critical depths and

  13. Microstructural Study on Oxygen Permeated Arc Beads

    Directory of Open Access Journals (Sweden)

    Kuan-Heng Liu

    2015-01-01

    Full Text Available We simulated short circuit of loaded copper wire at ambient atmosphere and successfully identified various phases of the arc bead. A cuprous oxide flake was formed on the surface of the arc bead in the rapid solidification process, and there were two microstructural constituents, namely, Cu-κ eutectic structure and solutal dendrites. Due to the arc bead formed at atmosphere during the local equilibrium solidification process, the phase of arc bead has segregated to the cuprous oxide flake, Cu-κ eutectic, and Cu phase solutal dendrites, which are the fingerprints of the arc bead permeated by oxygen.

  14. Transformation of juvenile Izu-Bonin-Mariana oceanic arc into mature continental crust: An example from the Neogene Izu collision zone granitoid plutons, Central Japan

    Science.gov (United States)

    Saito, Satoshi; Tani, Kenichiro

    2017-04-01

    Granitic rocks (sensulato) are major constituents of upper continental crust. Recent reviews reveal that the average composition of Phanerozoic upper continental crust is granodioritic. Although oceanic arcs are regarded as a site producing continental crust material in an oceanic setting, intermediate to felsic igneous rocks occurring in modern oceanic arcs are dominantly tonalitic to trondhjemitic in composition and have lower incompatible element contents than the average upper continental crust. Therefore, juvenile oceanic arcs require additional processes in order to get transformed into mature continental crust enriched in incompatible elements. Neogene granitoid plutons are widely exposed in the Izu Collision Zone in central Japan, where the northern end of the Izu-Bonin-Mariana (IBM) arc (juvenile oceanic arc) has been colliding with the Honshu arc (mature island arc) since Middle Miocene. The plutons in this area are composed of various types of granitoids ranging from tonalite to trondhjemite, granodiorite, monzogranite and granite. Three main granitoid plutons are distributed in this area: Tanzawa plutonic complex, Kofu granitic complex, and Kaikomagatake granitoid pluton. Tanzawa plutonic complex is dominantly composed of tonalite and trondhjemite and characterized by low concentration of incompatible elements and shows geochemical similarity with modern juvenile oceanic arcs. In contrast, Kofu granitic complex and Kaikomagatake granitoid pluton consists mainly of granodiorite, monzogranite and granite and their incompatible element abundances are comparable to the average upper continental crust. Previous petrogenetic studies on these plutons suggested that (1) the Tanzawa plutonic complex formed by lower crustal anatexis of juvenile basaltic rocks occurring in the IBM arc, (2) the Kofu granitic complex formed by anatexis of 'hybrid lower crust' comprising of both basaltic rocks of the IBM arc and metasedimentary rocks of the Honshu arc, and (3) the

  15. Intraspecific Colour Variation among Lizards in Distinct Island Environments Enhances Local Camouflage

    Science.gov (United States)

    Marshall, Kate L. A.; Philpot, Kate E.; Damas-Moreira, Isabel; Stevens, Martin

    2015-01-01

    Within-species colour variation is widespread among animals. Understanding how this arises can elucidate evolutionary mechanisms, such as those underlying reproductive isolation and speciation. Here, we investigated whether five island populations of Aegean wall lizards (Podarcis erhardii) have more effective camouflage against their own (local) island substrates than against other (non-local) island substrates to avian predators, and whether this was linked to island differences in substrate appearance. We also investigated whether degree of local substrate matching varied among island populations and between sexes. In most populations, both sexes were better matched against local backgrounds than against non-local backgrounds, particularly in terms of luminance (perceived lightness), which usually occurred when local and non-local backgrounds were different in appearance. This was found even between island populations that historically had a land connection and in populations that have been isolated relatively recently, suggesting that isolation in these distinct island environments has been sufficient to cause enhanced local background matching, sometimes on a rapid evolutionary time-scale. However, heightened local matching was poorer in populations inhabiting more variable and unstable environments with a prolonged history of volcanic activity. Overall, these results show that lizard coloration is tuned to provide camouflage in local environments, either due to genetic adaptation or changes during development. Yet, the occurrence and extent of selection for local matching may depend on specific conditions associated with local ecology and biogeographic history. These results emphasize how anti-predator adaptations to different environments can drive divergence within a species, which may contribute to reproductive isolation among populations and lead to ecological speciation. PMID:26372454

  16. Intraspecific Colour Variation among Lizards in Distinct Island Environments Enhances Local Camouflage.

    Directory of Open Access Journals (Sweden)

    Kate L A Marshall

    Full Text Available Within-species colour variation is widespread among animals. Understanding how this arises can elucidate evolutionary mechanisms, such as those underlying reproductive isolation and speciation. Here, we investigated whether five island populations of Aegean wall lizards (Podarcis erhardii have more effective camouflage against their own (local island substrates than against other (non-local island substrates to avian predators, and whether this was linked to island differences in substrate appearance. We also investigated whether degree of local substrate matching varied among island populations and between sexes. In most populations, both sexes were better matched against local backgrounds than against non-local backgrounds, particularly in terms of luminance (perceived lightness, which usually occurred when local and non-local backgrounds were different in appearance. This was found even between island populations that historically had a land connection and in populations that have been isolated relatively recently, suggesting that isolation in these distinct island environments has been sufficient to cause enhanced local background matching, sometimes on a rapid evolutionary time-scale. However, heightened local matching was poorer in populations inhabiting more variable and unstable environments with a prolonged history of volcanic activity. Overall, these results show that lizard coloration is tuned to provide camouflage in local environments, either due to genetic adaptation or changes during development. Yet, the occurrence and extent of selection for local matching may depend on specific conditions associated with local ecology and biogeographic history. These results emphasize how anti-predator adaptations to different environments can drive divergence within a species, which may contribute to reproductive isolation among populations and lead to ecological speciation.

  17. Intraspecific Colour Variation among Lizards in Distinct Island Environments Enhances Local Camouflage.

    Science.gov (United States)

    Marshall, Kate L A; Philpot, Kate E; Damas-Moreira, Isabel; Stevens, Martin

    2015-01-01

    Within-species colour variation is widespread among animals. Understanding how this arises can elucidate evolutionary mechanisms, such as those underlying reproductive isolation and speciation. Here, we investigated whether five island populations of Aegean wall lizards (Podarcis erhardii) have more effective camouflage against their own (local) island substrates than against other (non-local) island substrates to avian predators, and whether this was linked to island differences in substrate appearance. We also investigated whether degree of local substrate matching varied among island populations and between sexes. In most populations, both sexes were better matched against local backgrounds than against non-local backgrounds, particularly in terms of luminance (perceived lightness), which usually occurred when local and non-local backgrounds were different in appearance. This was found even between island populations that historically had a land connection and in populations that have been isolated relatively recently, suggesting that isolation in these distinct island environments has been sufficient to cause enhanced local background matching, sometimes on a rapid evolutionary time-scale. However, heightened local matching was poorer in populations inhabiting more variable and unstable environments with a prolonged history of volcanic activity. Overall, these results show that lizard coloration is tuned to provide camouflage in local environments, either due to genetic adaptation or changes during development. Yet, the occurrence and extent of selection for local matching may depend on specific conditions associated with local ecology and biogeographic history. These results emphasize how anti-predator adaptations to different environments can drive divergence within a species, which may contribute to reproductive isolation among populations and lead to ecological speciation.

  18. ATLAS DDM integration in ARC

    DEFF Research Database (Denmark)

    Behrmann, Gerd; Cameron, David; Ellert, Mattias

    2008-01-01

    The Nordic Data Grid Facility (NDGF) consists of Grid resources running ARC middleware in Denmark, Finland, Norway and Sweden. These resources serve many virtual organisations and contribute a large fraction of total worldwide resources for the ATLAS experiment, whose data is distributed and mana......The Nordic Data Grid Facility (NDGF) consists of Grid resources running ARC middleware in Denmark, Finland, Norway and Sweden. These resources serve many virtual organisations and contribute a large fraction of total worldwide resources for the ATLAS experiment, whose data is distributed...... and managed by the DQ2 software. Managing ATLAS data within NDGF and between NDGF and other Grids used by ATLAS (the Enabling Grids for E-sciencE Grid and the Open Science Grid) presents a unique challenge for several reasons. Firstly, the entry point for data, the Tier 1 centre, is physically distributed...

  19. Delimitation of the warm and cold period of the year based on the variation of the Aegean sea surface temperature

    Directory of Open Access Journals (Sweden)

    A. MAVRAKIS

    2004-06-01

    Full Text Available Knowledge of the warm and cold season onset is important for the living conditions and the occupational activities of the inhabitants of a given area, and especially for agriculture and tourism. This paper presents a way to estimate the onset/end of the cold and warm period of the year, based on the sinusoidal annual variation of the Sea Surface Temperature. The method was applied on data from 8 stations of the Hellenic Navy Hydrographic Service, covering the period from 1965-1995. The results showed that the warm period starts sometime between April 28th and May 21st while it ends between October 27th and November 19th in accordance with the findings of other studies. Characteristic of the nature of the parameter used is the very low variance per station – 15 days at maximum. The average date of warm period onset is statistically the same for the largest part of the Aegean, with only one differentiation, that between Kavala and the southern stations ( Thira and Heraklion.

  20. The 2014, MW6.9 North Aegean earthquake: seismic and geodetic evidence for coseismic slip on persistent asperities

    Science.gov (United States)

    Konca, Ali Ozgun; Cetin, Seda; Karabulut, Hayrullah; Reilinger, Robert; Dogan, Ugur; Ergintav, Semih; Cakir, Ziyadin; Tari, Ergin

    2018-05-01

    We report that asperities with the highest coseismic slip in the 2014 MW6.9 North Aegean earthquake persisted through the interseismic, coseismic and immediate post-seismic periods. We use GPS and seismic data to obtain the source model of the 2014 earthquake, which is located on the western extension of the North Anatolian Fault (NAF). The earthquake ruptured a bilateral, 90 km strike-slip fault with three slip patches: one asperity located west of the hypocentre and two to the east with a rupture duration of 40 s. Relocated pre-earthquake seismicity and aftershocks show that zones with significant coseismic slip were relatively quiet during both the 7 yr of interseismic and the 3-month aftershock periods, while the surrounding regions generated significant seismicity during both the interseismic and post-seismic periods. We interpret the unusually long fault length and source duration, and distribution of pre- and post-main-shock seismicity as evidence for a rupture of asperities that persisted through strain accumulation and coseismic strain release in a partially coupled fault zone. We further suggest that the association of seismicity with fault creep may characterize the adjacent Izmit, Marmara Sea and Saros segments of the NAF. Similar behaviour has been reported for sections of the San Andreas Fault, and some large subduction zones, suggesting that the association of seismicity with creeping fault segments and rapid relocking of asperities may characterize many large earthquake faults.

  1. Phytoplankton variability and community structure in relation to hydrographic features in the NE Aegean frontal area (NE Mediterranean Sea)

    Science.gov (United States)

    Lagaria, A.; Mandalakis, M.; Mara, P.; Frangoulis, C.; Karatsolis, B.-Th.; Pitta, P.; Triantaphyllou, M.; Tsiola, A.; Psarra, S.

    2017-10-01

    The structure of phytoplankton community in the salinity-stratified Northeastern Aegean frontal area adjacent to the Dardanelles Straits was investigated on a seasonal basis (autumn, spring and summer) and in relation to circulating water masses: the modified Black Sea Water (BSW) and the Levantine Water (LW). By employing High Performance Liquid Chromatography (HPLC) for the analysis of phytoplankton pigments in conjunction with conventional cell counting methodologies (i.e. inverted light microscopy, flow cytometry) and primary production measurements, a comprehensive qualitative and quantitative characterization of phytoplankton community composition and its activity was conducted. Chlorophyll-a normalized production and estimated growth rates presented the highest values within the 'fresh' BSW mass during summer, though generally growth rates were low (production. Large cell organisms, and in particular diatoms, were closely associated with the surface BSW masses outflowing from the Straits. Our results showed that all phytoplankton size components were significant over time and space suggesting a rather multivorous food web functioning of the system.

  2. Distribution pattern and genetic structure of Aedes zammitii (Diptera: Culicidae) along the Mediterranean and Aegean coasts of Turkey.

    Science.gov (United States)

    Yavasoglu, Sare Ilknur; Simsek, Fatih Mehmet; Ulger, Celal

    2016-06-01

    The Mariae species complex, consisting of Aedes mariae, Aedes phoeniciae, and Aedes zammitii, has a limited distribution worldwide. All three species are found in rocky habitats on the coastal areas of Mediterranean countries. Aedes phoeniciae and Ae. zammitii are two members of the Mariae complex that exist in Turkey. The aim of this study was to determine the distribution pattern and genetic structure of Ae. zammitii along the Mediterranean and Aegean regions. For this purpose, larval and adult samples of Ae. zammitii were collected from 19 different rocky habitats along the coastal regions of Antalya, Muğla, Aydın, İzmir, Balıkesir, and Çanakkale provinces. DNA isolation was performed primarily from collected samples, and mitochondrial NADH dehydrogenase 4 (ND4) gene was amplified by polymerase chain reaction. Based on ND4 sequence analyses, 21 haplotypes were detected along the distribution range of the species. Analyses of molecular variance (AMOVA) and spatial analyses of molecular variance (SAMOVA) indicated six groups, and most of the variation was among groups, demonstrating the population structuring at group level. Isolation by distance analyses (IBD) showed a correlation between geographic and genetic distances. © 2016 The Society for Vector Ecology.

  3. Potential risk assessment of metals in edible fish species for human consumption from the Eastern Aegean Sea.

    Science.gov (United States)

    Pazi, Idil; Gonul, L Tolga; Kucuksezgin, Filiz; Avaz, Gulsen; Tolun, Leyla; Unluoglu, Aydın; Karaaslan, Yakup; Gucver, S Mine; Koc Orhon, Aybala; Siltu, Esra; Olmez, Gulnur

    2017-07-15

    The levels of Hg, Cd, Pb, Cr, Cu and Zn were measured in the tissues of four edible fish species namely: Diplodus annularis, Pagellus erythrinus, Merluccius merluccius and Mullus barbatus, collected from the Turkish Coast of the Aegean Sea. Except for D. annularis, the levels of Cd and Pb in all fish tissues sampled in Aliaga Bay in 2009 were above the tolerable limits according to the Food and Agriculture Organization of the United Nations (FAO). Hg in P. erythrinus and M. barbatus were higher than the maximum permitted limits (FAO), while D. annularis and M. merluccius were lower than the limit for biota in the district of Aliaga. Although the Target Hazard Quotient (THQ) values for Cd, Pb, Cu, Cr, Zn in all fish samples were lower than 1.0, the THQ for Hg levels were higher than 1.0 for most of the samples. According to the THQ values, M. merluccius may be consumed in moderation from Aliaga Bay, while the consumption of M. barbatus and P. erythrinus collected from Aliaga Bay are potentially hazardous to human health due to the Hg concentrations. Fish collected from Izmir Bay can be consumed safely. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Erosion properties of unipolar arcs

    International Nuclear Information System (INIS)

    Chekalin, Eh.K.

    1982-01-01

    Processes modelling the formation of unipolar arcs on the elements of the first wall in limiters of the vacuum chamber and on active elements of tokamak divertor, are experimentally investigated. Erosion, processes that take place at two types of non-stationary cathode spots are considered. Experimental data prove the possibility of reducing erosion intensity by coating the surface of electrodes by oxide films, reduction of the temperature of electrode and discharge current

  5. Crustal evolution of Eocene paleo arc around Ogasawara region obtained by seismic reflection survey

    Science.gov (United States)

    Yamashita, M.; Takahashi, N.; Kodaira, S.; Miura, S.; Ishizuka, O.; Tatsumi, Y.

    2011-12-01

    The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. The existence of two paleo arc which consists of Oligocene and Eocene paleo age is known in IBM forearc region by geological and geophysical studies. The Ogasawara ridge is also known to locate the initial structure of arc evolution from geologic sampling of research submersible. In this region, IODP drilling site: IBM-2 is proposed in order to understand the temporal and spatial change in arc crust composition from 50 to 40Ma magmatism. Site IBM-2 consists of two offset drilling holes (BON-1, BON-2). BON-1 designed to first encounter forearc basalt and will reach the sheeted dykes. BON-2 will start in boninites and finish in fore arc basalts. The purpose of these drilling is sampling the full volcanic stratigraphy from gabbro to boninite. There is no seismic data around BON-1 and BON-2, therefore it is need to conduct the multi-channel seismic reflection survey. Japan Agency for Marine-Earth Science and Technology carried out multi-channel seismic reflection survey and wide-angle reflection survey using 7,800 cu.in. air gun, 5 km streamer with 444 ch hydrophones and 40 OBSs in March 2011. We obtained two seismic reflection profiles of lines KT06 and KT07 along the paleo arc around Ogasawara ridge. Line KT06 located the north side of Ogasawara ridge. Line KT07 located the trench side of Ogasawara ridge. Lines KT06 is also deployed the OBSs every 5 km interval. Thin sediments are covered with basement in both survey lines. There are some sediment filled in depression topography. The low-frequency reflection from the top of subducting Pacific plate is recognized in line KT06. The continuity of this reflection is not clear due to the complicated bathymetry. The displacement of basement in northern side of Ogasawara ridge is identified along the lineament of bathymetry in Line 06. This structure is

  6. Transition of magma genesis estimated by change of chemical composition of Izu-bonin arc volcanism associated with spreading of Shikoku Basin

    Science.gov (United States)

    Haraguchi, S.; Ishii, T.

    2006-12-01

    Arc volcanism in the Izu-Ogasawara arc is separated into first and latter term at the separate of Shikoku Basin. Middle to late Eocene early arc volcanism formed a vast terrane of boninites and island arc tholeiites that is unlike active arc systems. A following modern-style arc volcanism was active during the Oligocene, along which intense tholeiitic and calc-alkaline volcanism continued until 29Ma, before spreading of the back- arc basin. The recent arc volcanism in the Izu-Ogasawara arc have started in the middle Miocene, and it is assumed that arc volcanism were decline during spreading of back-arc basin. In the northern Kyushu-Palau Ridge, submarine bottom materials were dredged during the KT95-9 and KT97-8 cruise by the R/V Tansei-maru, Ocean Research Institute, university of Tokyo, and basaltic to andesitic volcanic rocks were recovered during both cruise except for Komahashi-Daini Seamount where recovered acidic plutonic rocks. Komahashi-Daini Seamount tonalite show 37.5Ma of K-Ar dating, and this age indicates early stage of normal arc volcanism. These volcanic rocks are mainly cpx basalt to andesite. Two pyroxene basalt and andesite are only found from Miyazaki Seamount, northern end of the Kyushu-Palau Ridge. Volcanic rocks show different characteristics from first term volcanism in the Izu-Ogasawara forearc rise and recent arc volcanism. The most characteristic is high content of incompatible elements, that is, these volcanics show two to three times content of incompatible elements to Komahashi-Daini Seamount tonalite and former normal arc volcanism in the Izu outer arc (ODP Leg126), and higher content than recent Izu arc volcanism. This characteristic is similar to some volcanics at the ODP Leg59 Site448 in the central Kyushu- Palau Ridge. Site448 volcanic rocks show 32-33Ma of Ar-Ar ages, which considered beginning of activity of Parece Vela Basin. It is considered that the dredged volcanic rocks are uppermost part of volcanism before spreading of

  7. Oxidation State of Iron in the Izu-Bonin Arc Initial Magma and Its Influence Factors

    Science.gov (United States)

    Li, H.; Arculus, R. J.; Brandl, P. A.; Hamada, M.; Savov, I. P.; Zhu, S.; Hickey-Vargas, R.; Tepley, F. J., III; Meffre, S.; Yogodzinski, G. M.; McCarthy, A.; Barth, A. P.; Kanayama, K.; Kusano, Y.; Sun, W.

    2014-12-01

    The redox state of mantle-derived magmas is a controversial issue, especially whether island arc basalts are more oxidized than those from mid-ocean ridges. Usually, arc magmas have higher Fe3+/Fe2+ and calculated oxygen fugacity (fO2) than mid-ocean ridge basalts (MORB). It is the high fO2 of arc magma that apparently delays onset of sulfide fractionation and sequestration of precious/base metals thereby facilitating the formation of many giant gold-copper deposits typically associated with subduction zones. But due to a paucity of Fe3+/Fe2+ data for primary mantle-derived arc magmas, the cause for high fO2 of these magma types is still controversial; causes may include inter alia subduction-released oxidized material addition to the mantle wedge source of arc magma, partial melting of subducted slab, and redox changes occurring during ascent of the magma. Fortunately, IODP expedition 351 drilling at IODP Site U1438 in the Amami-Sankaku Basin of the northwestern Philipine Sea, adjacent to the proto-Izu-Bonin Arc at the Kyushu-Palau Ridge (KPR), recovered not only volcaniclastics derived from the inception of Izu-Bonin Mariana (IBM) arc in the Eocene, but also similar materials for the Arc's subsequent evolution through to the Late Oligocene and abandonment of the KPR as a remnant arc. Samples of the pre-Arc oceanic crustal basement were also recovered enabling us to determine the fO2of the mantle preceding arc inception. As the oxidation state of iron in basaltic glass directly relates to the fO2 , the Fe3+/∑Fe ratio [Fe3+/(Fe3++ Fe2+)] of basaltic glass are quantified by synchrotron-facilitated micro X-ray Absorption Near Edge Structure (XANES) spectroscopy to reflect its fO2. Fe K-edge µ-XANES spectra were recorded in fluorescence mode at Beamline 15U1, Shanghai Synchrotron Radiation Facility (SSRF). Synthetic silicate glass with known Fe3+/∑Fe ratio was used in data handling. The experimental results as well as preliminary data from IODP Expedition 351

  8. Effect of arc behaviour on the temperature fluctuation of carbon electrode in DC arc discharge

    International Nuclear Information System (INIS)

    Liang, F; Tanaka, M; Choi, S; Watanabe, T

    2014-01-01

    Diffuse and multiple arc-anode attachment modes were observed in a DC arc discharge with a carbon electrode. During the arc discharge, the surface temperature of the electrode was successfully measured by two-colour pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature fluctuation of electrode surface was investigated. The diffuse arc-anode attachment mode leads to relatively large temperature fluctuation on anode surface due to the rotation of the arc spot. In the case of diffuse mode, the purity of synthesized multi-wall carbon nanotube was deteriorated with temperature fluctuation

  9. Bifurcation theory of ac electric arcing

    International Nuclear Information System (INIS)

    Christen, Thomas; Peinke, Emanuel

    2012-01-01

    The performance of alternating current (ac) electric arcing devices is related to arc extinction or its re-ignition at zero crossings of the current (so-called ‘current zero’, CZ). Theoretical investigations thus usually focus on the transient behaviour of arcs near CZ, e.g. by solving the modelling differential equations in the vicinity of CZ. This paper proposes as an alternative approach to investigate global mathematical properties of the underlying periodically driven dynamic system describing the electric circuit containing the arcing device. For instance, the uniqueness of the trivial solution associated with the insulating state indicates the extinction of any arc. The existence of non-trivial attractors (typically a time-periodic state) points to a re-ignition of certain arcs. The performance regions of arcing devices, such as circuit breakers and arc torches, can thus be identified with the regions of absence and existence, respectively, of non-trivial attractors. Most important for applications, the boundary of a performance region in the model parameter space is then associated with the bifurcation of the non-trivial attractors. The concept is illustrated for simple black-box arc models, such as the Mayr and the Cassie model, by calculating for various cases the performance boundaries associated with the bifurcation of ac arcs. (paper)

  10. Physical characteristics of welding arc ignition process

    Science.gov (United States)

    Shi, Linan; Song, Yonglun; Xiao, Tianjiao; Ran, Guowei

    2012-07-01

    The existing research of welding arc mainly focuses on the stable combustion state and the research on the mechanism of welding arc ignition process is quite lack. The tungsten inert gas(TIG) touch arc ignition process is observed via a high speed camera and the high time resolution spectral diagnosis system. The changing phenomenon of main ionized element provided the electrons in the arc ignition is found. The metallic element is the main contributor to provide the electrons at the beginning of the discharging, and then the excitated shielding gas element replaces the function of the metallic element. The electron density during the period of the arc ignition is calculated by the Stark-broadened lines of Hα. Through the discussion with the repeatability in relaxation phenomenon, the statistical regularity in the arc ignition process is analyzed. The similar rules as above are observed through the comparison with the laser-assisted arc ignition experiments and the metal inert gas(MIG) arc ignition experiments. This research is helpful to further understanding on the generation mechanism of welding arc ignition and also has a certain academic and practical significance on enriching the welding physical theoretical foundation and improving the precise monitoring on automatic arc welding process.

  11. Arc Shape Characteristics with Ultra-High-Frequency Pulsed Arc Welding

    Directory of Open Access Journals (Sweden)

    Mingxuan Yang

    2017-01-01

    Full Text Available Arc plasma possesses a constriction phenomenon with a pulsed current. The constriction is created by the Lorentz force, the radial electromagnetic force during arc welding, which determines the energy distribution of the arc plasma. Welding experiments were carried out with ultra-high-frequency pulsed arc welding (UHFP-AW. Ultra-high-speed camera observations were produced for arc surveillance. Hue-saturation-intensity (HSI image analysis was used to distinguish the regions of the arc plasma that represented the heat energy distribution. The measurement of arc regions indicated that, with an ultra-high-frequency pulsed arc, the constriction was not only within the decreased arc geometry, but also within the constricted arc core region. This can be checked by the ratio of the core region to the total area. The arc core region expanded significantly at 40 kHz at 60 A. A current level of 80 A caused a decrease in the total region of the arc. Meanwhile, the ratio of the core region to the total increased. It can be concluded that arc constriction depends on the increased area of the core region with the pulsed current (>20 kHz.

  12. Auroral arc classification scheme based on the observed arc-associated electric field pattern

    International Nuclear Information System (INIS)

    Marklund, G.

    1983-06-01

    Radar and rocket electric field observations of auroral arcs have earlier been used to identify essentially four different arc types, namely anticorrelation and correlation arcs (with, respectively, decreased and increased arc-assocaited field) and asymmetric and reversal arcs. In this paper rocket double probe and supplementary observations from the literature, obtained under various geophysical conditions, are used to organize the different arc types on a physical rather than morphological basis. This classification is based on the relative influence on the arc electric field pattern from the two current continuity mechanisms, polarisation electric fields and Birkeland currents. In this context the tangential electric field plays an essential role and it is thus important that it can be obtained with both high accuracy and resolution. In situ observations by sounding rockets are shown to be better suited for this specific task than monostatic radar observations. Depending on the dominating mechanism, estimated quantitatively for a number of arc-crossings, the different arc types have been grouped into the following main categories: Polarisation arcs, Birkeland current arcs and combination arcs. Finally the high altitude potential distributions corresponding to some of the different arc types are presented. (author)

  13. Clustering of arc volcanoes caused by temperature perturbations in the back-arc mantle.

    Science.gov (United States)

    Lee, Changyeol; Wada, Ikuko

    2017-06-29

    Clustering of arc volcanoes in subduction zones indicates along-arc variation in the physical condition of the underlying mantle where majority of arc magmas are generated. The sub-arc mantle is brought in from the back-arc largely by slab-driven mantle wedge flow. Dynamic processes in the back-arc, such as small-scale mantle convection, are likely to cause lateral variations in the back-arc mantle temperature. Here we use a simple three-dimensional numerical model to quantify the effects of back-arc temperature perturbations on the mantle wedge flow pattern and sub-arc mantle temperature. Our model calculations show that relatively small temperature perturbations in the back-arc result in vigorous inflow of hotter mantle and subdued inflow of colder mantle beneath the arc due to the temperature dependence of the mantle viscosity. This causes a three-dimensional mantle flow pattern that amplifies the along-arc variations in the sub-arc mantle temperature, providing a simple mechanism for volcano clustering.

  14. Researching Pacific island livelihoods:

    DEFF Research Database (Denmark)

    Egelund Christensen, Andreas; Mertz, Ole

    2010-01-01

    on contemporary theories of nissology and conceptual analytical frameworks for island research. Through a review of selected case-study-based island literature on changing livelihoods coming out of the South Pacific, we wish to illustrate and discuss advantages of finding common grounds for small island studies....... The focus is on two dimensions of island livelihood, migration and natural resource management, both of which are significant contributors in making island livelihoods and shaping Pacific seascapes. We argue that there is still a substantial lack of studies targeting small island dynamics that are empirical...

  15. Prototype arc saw design and cutting trials

    International Nuclear Information System (INIS)

    Allison, G.S.

    1980-09-01

    A program was initiated to develop the arc saw as a tool capable of removing the end fittings from spent nuclear fuel bundles. A special arc saw for this purpose was designed, installed at the Pacific Northwest Laboratory and satisfactorily operated to remove end fittings from simulated, nonradioactive fuel bundles. The design of the arc saw included consideration of the cutting environment, power supply size, control equipment, and work piece size. Several simulated fuel bundles were cut to demonstrate that the arc saw met design specifications. Although the arc saw development program was curtailed before significant performance data could be collected, tests indicate that the arc saw is a good means of cropping spent fuel bundles and is well suited to remote operation and maintenance

  16. Hurricane impact and recovery shoreline change analysis of the Chandeleur Islands, Louisiana, USA: 1855 to 2005

    Science.gov (United States)

    Fearnley, Sarah M.; Miner, Michael; Brock, John C.

    2011-01-01

    Results from historical (1855-2005) shoreline change analysis of the Chandeleur Islands, Louisiana, demonstrate that tropical cyclone frequency dominates the long-term evolution of this barrier-island arc. The detailed results of this study were published in December 2009 as part of a special issue of Geo-Marine Letters that documents early results from the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazard Susceptibility Project.

  17. Paleomagnetic Constraints on the Tectonic History of the Mesozoic Ophiolite and Arc Terranes of Western Mexico

    Science.gov (United States)

    Boschman, L.; Van Hinsbergen, D. J. J.; Langereis, C. G.; Molina-Garza, R. S.; Kimbrough, D. L.

    2017-12-01

    The North American Cordillera has been shaped by a long history of accretion of arcs and other buoyant crustal fragments to the western margin of the North American Plate since the Early Mesozoic. Accretion of these terranes resulted from a complex tectonic history interpreted to include episodes of both intra-oceanic subduction within the Panthalassa/Pacific Ocean, as well as continental margin subduction along the western margin of North America. Western Mexico, at the southern end of the Cordillera, contains a Late Cretaceous-present day long-lived continental margin arc, as well as Mesozoic arc and SSZ ophiolite assemblages of which the origin is under debate. Interpretations of the origin of these subduction-related rock assemblages vary from far-travelled exotic intra-oceanic island arc character to autochthonous or parautochthonous extended continental margin origin. We present new paleomagnetic data from four localities: (1) the Norian SSZ Vizcaíno peninsula Ophiolite; (2) its Lower Jurassic sedimentary cover; and (3) Barremian and (4) Aptian sediments derived from the Guerrero arc. The data show that the Mexican ophiolite and arc terranes have a paleolatitudinal plate motion history that is equal to that of the North American continent. This suggests that these rock assemblages were part of the overriding plate and were perhaps only separated from the North American continent by temporal fore- or back-arc spreading. These spreading phases resulted in the temporal existence of tectonic plates between the North American and Farallon Plates, and upon closure of the basins, in the growth of the North American continent without addition of any far-travelled exotic terranes.

  18. The contribution of the young Cretaceous Caribbean Oceanic Plateau to the genesis of late Cretaceous arc magmatism in the Cordillera Occidental of Ecuador

    Science.gov (United States)

    Allibon, J.; Monjoie, P.; Lapierre, H.; Jaillard, E.; Bussy, F.; Bosch, D.; Senebier, F.

    2008-12-01

    The eastern part of the Cordillera Occidental of Ecuador comprises thick buoyant oceanic plateaus associated with island-arc tholeiites and subduction-related calc-alkaline series, accreted to the Ecuadorian Continental Margin from Late Cretaceous to Eocene times. One of these plateau sequences, the Guaranda Oceanic Plateau is considered as remnant of the Caribbean-Colombian Oceanic Province (CCOP) accreted to the Ecuadorian Margin in the Maastrichtien. Samples studied in this paper were taken from four cross-sections through two arc-sequences in the northern part of the Cordillera Occidental of Ecuador, dated as (Río Cala) or ascribed to (Macuchi) the Late Cretaceous and one arc-like sequence in the Chogòn-Colonche Cordillera (Las Orquídeas). These three island-arcs can clearly be identified and rest conformably on the CCOP. In all four localities, basalts with abundant large clinopyroxene phenocrysts can be found, mimicking a picritic or ankaramitic facies. This mineralogical particularity, although not uncommon in island arc lavas, hints at a contribution of the CCOP in the genesis of these island arc rocks. The complete petrological and geochemical study of these rocks reveals that some have a primitive island-arc nature (MgO values range from 6 to 11 wt.%). Studied samples display marked Nb, Ta and Ti negative anomalies relative to the adjacent elements in the spidergrams characteristic of subduction-related magmatism. These rocks are LREE-enriched and their clinopyroxenes show a tholeiitic affinity (FeO T-TiO 2 enrichment and CaO depletion from core to rim within a single crystal). The four sampled cross-sections through the island-arc sequences display homogeneous initial Nd, and Pb isotope ratios that suggest a unique mantellic source for these rocks resulting from the mixing of three components: an East-Pacific MORB end-member, an enriched pelagic sediment component, and a HIMU component carried by the CCOP. Indeed, the ankaramite and Mg

  19. On the formation of auroral arcs

    International Nuclear Information System (INIS)

    Stasiewicz, K.

    1984-04-01

    A new mechanism for auroral arc formation is presented. The characteristic linear shape of auroral arcs is determined by magnetically connected plasma clouds in the distant equatorial magnetosphere. These clouds originate as high speed plasma beams in the magnetotail and in the solar wind. It is found that the free energy for driving an auroral arc is provided by the difference of pressure between the cloud and the ambient plasma. (author)

  20. Programming ArcGIS with Python cookbook

    CERN Document Server

    Pimpler, Eric

    2015-01-01

    Programming ArcGIS with Python Cookbook, Second Edition, is written for GIS professionals who wish to revolutionize their ArcGIS workflow with Python. Whether you are new to ArcGIS or a seasoned professional, you almost certainly spend time each day performing various geoprocessing tasks. This book will teach you how to use the Python programming language to automate these geoprocessing tasks and make you a more efficient and effective GIS professional.

  1. Arc saw and its application to decommissioning

    International Nuclear Information System (INIS)

    Deichelbohrer, P.R.

    1982-01-01

    The arc saw is a toothless, circular saw that cuts by arc erosion. A model was built to study the arc saw's usefulness in cutting up radioactively contaminated metal scrap. It was chosen because it cuts with very little contact to the work piece and because cutting is not affected by material hardness. After installation of several improvements it was found it could cut almost any combination of metals and that clamping or fixturing requirements were minimum. Cutting proceeds rapidly and efficiently

  2. Nomenclature of SLC Arc beamline components

    International Nuclear Information System (INIS)

    Silva, J.; Weng, W.T.

    1986-01-01

    This note defines I and C formal names for beamline components in the Arc as specified in the TRANSPORT decks ARCN FINAL and ARCS FINAL of June 5, 1985. The formal name consists of three fields: the primary name, the zone and the unit number. The general principles and guidelines are explained in Reference 1. The rationale and the final resolutions of the naming conventions for the Arc are explained

  3. Diffuse and spot mode of cathode arc attachments in an atmospheric magnetically rotating argon arc

    International Nuclear Information System (INIS)

    Chen, Tang; Wang, Cheng; Liao, Meng-Ran; Xia, Wei-Dong

    2016-01-01

    A model including the cathode, near-cathode region, and arc column was constructed. Specifically, a thermal perturbation layer at the arc fringe was calculated in order to couple sheath/presheath modelling with typical arc column modelling. Comparative investigation of two modes of attachment of a dc (100, 150, 200 A) atmospheric-pressure arc in argon to a thermionic cathode made of pure tungsten was conducted. Computational data revealed that there exists two modes of arc discharge: the spot mode, which has an obvious cathode surface temperature peak in the arc attachment centre; and the diffuse mode, which has a flat cathode surface temperature distribution and a larger arc attachment area. The modelling results of the arc attachment agree with previous experimental observations for the diffuse mode. A further 3D simulation is obviously needed to investigate the non-axisymmetrical features, especially for the spot mode. (paper)

  4. Automatic Control Of Length Of Welding Arc

    Science.gov (United States)

    Iceland, William F.

    1991-01-01

    Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

  5. Investigations Of A Pulsed Cathodic Vacuum Arc

    Science.gov (United States)

    Oates, T. W. H.; Pigott, J.; Denniss, P.; Mckenzie, D. R.; Bilek, M. M. M.

    2003-06-01

    Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed.

  6. The Abundance of Large Arcs From CLASH

    Science.gov (United States)

    Xu, Bingxiao; Postman, Marc; Meneghetti, Massimo; Coe, Dan A.; Clash Team

    2015-01-01

    We have developed an automated arc-finding algorithm to perform a rigorous comparison of the observed and simulated abundance of large lensed background galaxies (a.k.a arcs). We use images from the CLASH program to derive our observed arc abundance. Simulated CLASH images are created by performing ray tracing through mock clusters generated by the N-body simulation calibrated tool -- MOKA, and N-body/hydrodynamic simulations -- MUSIC, over the same mass and redshift range as the CLASH X-ray selected sample. We derive a lensing efficiency of 15 ± 3 arcs per cluster for the X-ray selected CLASH sample and 4 ± 2 arcs per cluster for the simulated sample. The marginally significant difference (3.0 σ) between the results for the observations and the simulations can be explained by the systematically smaller area with magnification larger than 3 (by a factor of ˜4) in both MOKA and MUSIC mass models relative to those derived from the CLASH data. Accounting for this difference brings the observed and simulated arc statistics into full agreement. We find that the source redshift distribution does not have big impact on the arc abundance but the arc abundance is very sensitive to the concentration of the dark matter halos. Our results suggest that the solution to the "arc statistics problem" lies primarily in matching the cluster dark matter distribution.

  7. Teaching with ArcGIS Pro

    OpenAIRE

    Theller, Larry

    2016-01-01

    For Fall semester 2016 the ABE department moved the course ASM 540 Basic GIS from ArcGIS Desktop 10.2 to ArcGIS Pro 1.3. This software from ESRI has a completely new look and feel, (ribbon-based rather than cascading menus) and is a true 64 bit application, capable of multi-threading, and built on Python 3. After ArcGIS Desktop 10.5 is released, desktop ends and the future release will be ArcGIS Pro; so it makes sense to switch sooner rather than later. This talk will discuss some issues and...

  8. Investigations Of A Pulsed Cathodic Vacuum Arc

    International Nuclear Information System (INIS)

    Oates, T.W.H.; Pigott, J.; Denniss, P.; Mckenzie, D.R.; Bilek, M.M.M.

    2003-01-01

    Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed

  9. The dual-electrode DC arc furnace-modelling brush arc conditions

    OpenAIRE

    Reynolds, Q.G.

    2012-01-01

    The dual-electrode DC arc furnace, an alternative design using an anode and cathode electrode instead of a hearth anode, was studied at small scale using computational modelling methods. Particular attention was paid to the effect of two key design variables, the arc length and the electrode separation, on the furnace behaviour. It was found that reducing the arc length to brush arc conditions was a valid means of overcoming several of the limitations of the dual-electrode design, namely high...

  10. U-Pb zircon geochronology of the Paleogene - Neogene volcanism in the NW Anatolia: Its implications for the Late Mesozoic-Cenozoic geodynamic evolution of the Aegean

    Science.gov (United States)

    Ersoy, E. Yalçın; Akal, Cüneyt; Genç, Ş. Can; Candan, Osman; Palmer, Martin R.; Prelević, Dejan; Uysal, İbrahim; Mertz-Kraus, Regina

    2017-10-01

    The northern Aegean region was shaped by subduction, obduction, collision, and post-collisional extension processes. Two areas in this region, the Rhodope-Thrace-Biga Peninsula to the west and Armutlu-Almacık-Nallıhan (the Central Sakarya) to the east, are characterized by extensive Eocene to Miocene post-collisional magmatic associations. We suggest that comparison of the Cenozoic magmatic events of these two regions may provide insights into the Late Mesozoic to Cenozoic tectonic evolution of the Aegean. With this aim, we present an improved Cenozoic stratigraphy of the Biga Peninsula derived from a new comprehensive set of U-Pb zircon age data obtained from the Eocene to Miocene volcanic units in the region. The compiled radiometric age data show that calc-alkaline volcanic activity occurred at 43-15 Ma in the Biga Peninsula, 43-17 Ma in the Rhodope and Thrace regions, and 53-38 Ma in the Armutlu-Almacık-Nallıhan region, which are slightly overlapping. We discuss the possible cause for the distinct Cenozoic geodynamic evolution of the eastern and western parts of the region, and propose that the Rhodope, Thrace and Biga regions in the north Aegean share the same Late Mesozoic to Cenozoic geodynamic evolution, which is consistent with continuous subduction, crustal accretion, southwestward trench migration and accompanying extension; all preceded by the Late Cretaceous - Paleocene collision along the Vardar suture zone. In contrast, the Armutlu-Almacık-Nallıhan region was shaped by slab break-off and related processes following the Late Cretaceous - Paleocene collision along the İzmir-Ankara suture zone. The eastern and western parts of the region are presently separated by a northeast-southwest trending transfer zone that was likely originally present as a transform fault in the subducted Tethys oceanic crust, and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the

  11. A Joint Evaluation of the Wind and Wave Energy Resources Close to the Greek Islands

    Directory of Open Access Journals (Sweden)

    Daniel Ganea

    2017-06-01

    Full Text Available The objective of this work is to analyze the wind and wave energy potential in the proximity of the Greek islands. Thus, by evaluating the synergy between wind and waves, a more comprehensive picture of the renewable energy resources in the target area is provided. In this study, two different data sources are considered. The first data set is provided by the European Centre for Medium-Range Weather Forecasts (ECMWF through the ERA-Interim project and covers an 11-year period, while the second data set is Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO and covers six years of information. Using these data, parameters such as wind speed, significant wave height (SWH and mean wave period (MWP are analyzed. The following marine areas are targeted: Ionian Sea, Aegean Sea, Sea of Crete, Libyan Sea and Levantine Sea, near the coastal environment of the Greek islands. Initially, 26 reference points were considered. For a more detailed analysis, the number of reference points was narrowed down to 10 that were considered more relevant. Since in the island environments the resources are in general rather limited, the proposed work provides some outcomes concerning the wind and wave energy potential and the synergy between these two natural resources in the vicinity of the Greek islands. From the analysis performed, it can be noticed that the most energetic wind conditions are encountered west of Cios Island, followed by the regions east of Tinos and northeast of Crete. In these locations, the annual average values of the wind power density (Pwind are in the range of 286–298.6 W/m2. Regarding the wave power density (Pwave, the most energetic locations can be found in the vicinity of Crete, north, south and southeast of the island. There, the wave energy potential is in the range of 2.88–2.99 kW/m.

  12. Transient crustal movement in the northern Izu-Bonin arc starting in 2004: A large slow slip event or a slow back-arc rifting event?

    Science.gov (United States)

    Arisa, Deasy; Heki, Kosuke

    2016-07-01

    The Izu-Bonin arc lies along the convergent boundary where the Pacific Plate subducts beneath the Philippine Sea Plate. Horizontal velocities of continuous Global Navigation Satellite System stations on the Izu Islands move eastward by up to 1 cm/year relative to the stable part of the Philippine Sea Plate suggesting active back-arc rifting behind the northern part of the arc. Here, we report that such eastward movements transiently accelerated in the middle of 2004 resulting in 3 cm extra movements in 3 years. We compare three different mechanisms possibly responsible for this transient movement, i.e. (1) postseismic movement of the 2004 September earthquake sequence off the Kii Peninsula far to the west, (2) a temporary activation of the back-arc rifting to the west dynamically triggered by seismic waves from a nearby earthquake, and (3) a large slow slip event in the Izu-Bonin Trench to the east. By comparing crustal movements in different regions, the first possibility can be shown unlikely. It is difficult to rule out the second possibility, but current evidence support the third possibility, i.e. a large slow slip event with moment magnitude of 7.5 may have occurred there.

  13. Plasma arc melting of zirconium

    International Nuclear Information System (INIS)

    Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

    1997-01-01

    Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming

  14. Amphibious Magnetotelluric Investigation of the Aleutian Arc: Mantle Melt Generation and Migration beneath Okmok Caldera

    Science.gov (United States)

    Zelenak, G.; Key, K.; Bennington, N. L.; Bedrosian, P.

    2015-12-01

    Understanding the factors controlling the release of volatiles from the downgoing slab, the subsequent generation of melt in the overlying mantle wedge, the migration of melt to the crust, and its evolution and emplacement within the crust are important for advancing our understanding of arc magmatism and crustal genesis. Because melt and aqueous fluids are a few orders of magnitude more electrically conductive than unmelted peridotite, the conductivity-mapping magnetotelluric (MT) method is well-suited to imaging fluids and melt beneath arc volcanoes. Here we present conductivity results from an amphibious MT profile crossing Okmok volcano in the central Aleutian arc. The Aleutian arc is one of the most volcanically active regions in North America, making it an ideal location for studying arc magnetism. Okmok volcano, located on the northeastern portion of Umnak Island, is among the most active volcanoes in the Aleutian chain. In addition to two caldera-forming events in the Holocene, numerous eruptions in the past century indicate a robust magmatic supply. Previous coarse resolution seismic studies have inferred a crustal magma reservoir. In order to investigate the role fluids play in melting the mantle wedge, how melts ascend through the corner flow regime of the mantle wedge, how melt migrates and is stored within the upper mantle and crust, and how this impacts explosive caldera forming eruptions, we carried out an amphibious geophysical survey across the arc in June-July 2015. Twenty-nine onshore MT stations and 10 offshore stations were collected in a 3D array covering Okmok, and 43 additional offshore MT stations completed a 300 km amphibious profile starting at the trench, crossing the forearc, arc and backarc. Thirteen onshore passive seismic stations were also installed and will remain in place for one year to supplement the twelve permanent stations on the island. Data collected by this project will be used to map seismic velocity and electrical

  15. Analogue modeling of arc and backarc deformation in the New Hebrides arc and North Fiji Basin

    NARCIS (Netherlands)

    Schellart, W. P.; Lister, G. S.; Jessell, M. W.

    In most backarc basins, extension is perpendicular to the arc. Thus individual spreading ridges extend approximately parallel to the arc. In the North Fiji Basin, however, several ancient and active spreading ridges strike 70°-90° to the New Hebrides arc. These high-angle spreading ridges relocated

  16. Insights into the benthic communities response to the inflow of Black Sea mesotrophic waters in the North Aegean Sea

    Science.gov (United States)

    Lampadariou, Nikolaos; Sevastou, Katerina; Podaras, Dimitrios; Tselepides, Anastasios

    2017-10-01

    The effects of the Dardanelles inflow of buoyant, modified Black Sea waters (BSW) of low salinity and temperature, on the meio- and macrobenthic communities of the north Aegean ecosystem was investigated during two cruises in October 2013 and March 2014. Sediment samples were collected from two stations subjected to the BSW effect, one shallow and one deep north of the Dardanelles Straits, and from two stations of similar bathymetry, which were considered to be outside the influence of BSW and were located to the south of the Dardanelles Straits. Results suggest that there is an effect of the BSW on benthos, as both meiofaunal and macrofaunal standing stocks were lower at the most distant, and therefore least affected from the inflow, station, and higher at the station of similar bathymetry which was affected the most by the BSW inflow. Univariate and multivariate non-parametric analyses (nMDS, PERMANOVA) provided further support, indicating differences between the two areas (North vs. South) in the case of the deep stations, while differences between depth categories were evident in the area outside the BSW influence zone. Distance-based linear modeling (DISTLM) indicated that meiofauna correlated with proxies of food availability and sediment characteristics. Macrofauna, on the other hand, showed a rather high significant correlation with depth only. Nematode species composition was statistically significant different between depth categories only, yet the nMDS ordination clearly separated the deep southern station from the rest, with non-selective deposit feeders dominating the stations under the influence of the BSW, and epistratum feeders being important at the stations outside the influence of the BSW. It is concluded that both the meiofaunal and macrofaunal communities at the northern stations benefit from a constant input of high amounts of organic matter to the seafloor, while those at the southern area may be occasionally affected by the thermohaline BSW

  17. An ecological risk investigation of marine sediment from the northern Mediterranean coasts (Aegean Sea) using multiple methods of pollution determination.

    Science.gov (United States)

    Tunca, Evren; Aydın, Mehmet; Şahin, Ülkü Alver

    2018-03-01

    The aim of this study is an assessment of metal pollution levels in Aegean Sea sediment. Sediment samples collected from 7 different locations (Yeniköy, Edremit, Ayvalık, Dikili, Aliağa, Hekimadası, and Ildır) along the northern Mediterranean region of Turkey were investigated for 11 elements (Cu, Fe, Zn, V, Cd, Ni, As, Pb, Mn, Co, and Cr). Graphite furnace atomic absorption spectrophotometry (GFAAS) and flame atomic absorption spectrophotometry (FAAS) were used for elemental analysis. The findings were evaluated with sediment assessment methods by taking two different values as a reference and then investigating the adverse biological effects of elemental profiles on living organisms. Pb, Mn, As, Cd, and Cr concentrations were within a moderate to significant range in terms of contamination factor [Formula: see text]), albeit varying according to reference and location. The most problematic region and elements regarding the enrichment factor (EF) was Ayvalık and As, Ni, Cu, Pb, Co, and Cd. However, according to the EF, the anthropogenic effect was not at an alarming level. This was further supported by the results of the geoaccumulation index (Igeo). The findings of the modified degree of contamination (mC d ) and the pollution load index (PLI) suggested that the accumulation was greatest in Ayvalık, and the least in Hekimadası and Ildır. The location with the highest elemental total toxic unit (ΣTU) was Edremit. The effect of the existing element profile on organisms was 21% in this location when the mean effect range-median quotient (m-ERM-q) was considered. As and Ni concentrations in all stations were found to be higher than threshold effect level (TEL) and Effect Range Low (ERL). Ni levels in Edremit exceeded the probable effect level (PEL) and Effect Range Median (ERM). Toxic unit (TU) values of these two elements in all stations ranged from 59.30 to 80.43%.

  18. Spatial distribution of helium isotopes in volcanic gases and thermal waters along the Vanuatu (New Hebrides) volcanic arc

    Science.gov (United States)

    Jean-Baptiste, P.; Allard, P.; Fourré, E.; Bani, P.; Calabrese, S.; Aiuppa, A.; Gauthier, P. J.; Parello, F.; Pelletier, B.; Garaebiti, E.

    2016-08-01

    We report the first helium isotope survey of volcanic gases, hot springs and some olivine phenocrysts along the Vanuatu island arc, from Tanna in the south to Vanua Lava in the north. Low CO2 content and low 3He/4He ratios in thermal fluids of Epi (4.0 ± 0.1 Ra), Efate (4.5 ± 0.1 Ra) and Pentecost (5.3 ± 0.5 Ra) islands coherently indicate reduced mantle gas leakage and crustal contamination by radiogenic helium on these extinct volcanic systems of the former (Pliocene) arc. Instead, presently active Vanuatu volcanoes display 3He/4He and C/3He ratios typical of subduction-related volcanic arcs: 3He/4He ratios range from 6.4 ± 0.5 Ra in southernmost Tanna and 7.23 ± 0.09 Ra in northernmost Vanua Lava to typical MORB values in the central islands of Gaua (7.68 ± 0.06 Ra), Ambrym (7.6 ± 0.8 Ra) and Ambae (7 ± 2 Ra in groundwaters, 7.9 ± 1.4 Ra in olivine phenocrysts, and 8.0 ± 0.1 Ra in summit fumaroles of Aoba volcano). On Ambrym, however, we discover that hydrothermal manifestations separated by only 10-15 km on both sides of a major E-W transverse fault zone crossing the island are fed by two distinct helium sources, with different 3He/4He signatures: while fluids in southwest Ambrym (Baiap and Sesivi areas) have typical arc ratios (7.6 ± 0.8 Ra), fluids on the northwest coast (Buama Bay area) display both higher 3He/4He ratios (9.8 ± 0.2 Ra in waters to 10.21 ± 0.08 Ra in bubbling gases) and lower C/3He ratios that evidence a hotspot influence. We thus infer that the influx of Indian MORB mantle beneath the central Vanuatu arc, from which Ambrym magmas originate, also involves a 3He-rich hotspot component, possibly linked to a westward influx of Samoan hotspot material or another yet unknown local source. This duality in magmatic He source at Ambrym fits with the bimodal composition and geochemistry of the erupted basalts, implying two distinct magma sources and feeding systems. More broadly, the wide He isotopic variations detected along the Vanuatu

  19. Diomede Islands, Bering Straight

    Science.gov (United States)

    2008-01-01

    The Diomede Islands consisting of the western island Big Diomede (also known as Imaqliq, Nunarbuk or Ratmanov Island), and the eastern island Little Diomede (also known as Krusenstern Island or Inaliq), are two rocky islands located in the middle of the Bering Strait between Russia and Alaska. The islands are separated by an international border and the International Date Line which is approximately 1.5 km from each island; you can look from Alaska into tomorrow in Russia. At the closest land approach between the United States, which controls Little Diomede, and Russia, which controls Big Diomede, they are 3 km apart. Little Diomede Island constitutes the Alaskan City of Diomede, while Big Diomede Island is Russia's easternmost point. The first European to reach the islands was the Russian explorer Semyon Dezhnev in 1648. The text of the 1867 treaty finalizing the sale of Alaska uses the islands to designate the border between the two nations. The image was acquired July 8, 2000, covers an area of 13.5 x 10.8 km, and is located at 65.8 degrees north latitude, 169 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.

  20. Tales of island tails

    NARCIS (Netherlands)

    Groot, de Alma V.; Oost, Albert P.; Veeneklaas, Roos M.; Lammerts, Evert Jan; Duin, van Willem E.; Wesenbeeck, van Bregje K.

    2016-01-01

    The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift side of an island consisting of salt marshes, dunes, beaches and beach plains, and green beaches. Currently, large parts of these tails are ageing and losing dynamics, partly due to human influence.

  1. Rhode Island unemployment

    OpenAIRE

    Leonard Lardaro

    2010-01-01

    How can a state like Rhode Island have such a high unemployment rate? This question has been asked often over the past year, especially since at one point, Rhode Island found itself with the dubious distinction of having the highest unemployment rate in the United States. Following that extreme, Rhode Island seemed to settle into a niche where its rank was third nationally.

  2. Evaluating optical hazards from plasma arc cutting.

    Science.gov (United States)

    Glassford, Eric; Burr, Gregory

    2018-01-01

    The Health Hazard Evaluation Program of the National Institute for Occupational Safety and Health evaluated a steel building materials manufacturer. The employer requested the evaluation because of concerns about optical radiation hazards from a plasma arc cutting system and the need to clarify eye protection requirements for plasma operators, other employees, and visitors. The strength of the ultraviolet radiation, visible radiation (light), and infrared radiation generated by the plasma arc cutter was measured at various distances from the source and at different operating amperages. Investigators also observed employees performing the plasma arc cutting. Optical radiation above safe levels for the unprotected eyes in the ultraviolet-C, ultraviolet-B, and visible light ranges were found during plasma arc cutting. In contrast, infrared and ultraviolet-A radiation levels during plasma arc cutting were similar to background levels. The highest non-ionizing radiation exposures occurred when no welding curtains were used. A plasma arc welding curtain in place did not eliminate optical radiation hazards to the plasma arc operator or to nearby employees. In most instances, the measured intensities for visible light, UV-C, and UV-B resulted in welding shade lens numbers that were lower than those stipulated in the OSHA Filter Lenses for Protection Against Radiant Energy table in 29 CFR 1910.133(a)(5). [1] Investigators recommended using a welding curtain that enclosed the plasma arc, posting optical radiation warning signs in the plasma arc cutter area, installing audible or visual warning cues when the plasma arc cutter was operating, and using welding shades that covered the plasma arc cutter operator's face to protect skin from ultraviolet radiation hazards.

  3. Volumetric modulated arc therapy: IMRT in a single gantry arc

    International Nuclear Information System (INIS)

    Otto, Karl

    2008-01-01

    In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg. of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship

  4. production of manual arc welding electrodes with local raw materials

    African Journals Online (AJOL)

    CHUKSSUCCESS 4 LOVE

    Manual arc welding using flux coated electrodes is carried out by producing an electric arc between ... major objectives: to form fusible slags, to stabilize the arc and to produce an inert gas shielding ... Current fusion welding techniques rely.

  5. Magnesium Isotopes as a Tracer of Crustal Materials in Volcanic Arc Magmas in the Northern Cascade Arc

    Directory of Open Access Journals (Sweden)

    Aaron W. Brewer

    2018-03-01

    Full Text Available Fifteen North Cascade Arc basalts and andesites were analyzed for Mg isotopes to investigate the extent and manner of crustal contributions to this magmatic system. The δ26Mg of these samples vary from within the range of ocean island basalts (the lightest being −0.33 ± 0.07‰ to heavier compositions (as heavy as −0.15 ± 0.06‰. The observed range in chemical and isotopic composition is similar to that of other volcanic arcs that have been assessed to date in the circum-pacific subduction zones and in the Caribbean. The heavy Mg isotope compositions are best explained by assimilation and fractional crystallization within the deep continental crust with a possible minor contribution from the addition of subducting slab-derived fluids to the primitive magma. The bulk mixing of sediment into the primitive magma or mantle source and the partial melting of garnet-rich peridotite are unlikely to have produced the observed range of Mg isotope compositions. The results show that Mg isotopes may be a useful tracer of crustal input into a magma, supplementing traditional methods such as radiogenic isotopic and trace element data, particularly in cases in which a high fraction of crustal material has been added.

  6. Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy

    Science.gov (United States)

    Liu, Liming; Chen, Minghua

    2011-09-01

    This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.

  7. Arcing and surface damage in DITE

    International Nuclear Information System (INIS)

    Goodall, D.H.J.; McCracken, G.M.

    1977-11-01

    An investigation into the arcing damage on surfaces exposed to plasmas in the DITE tokamak is described. It has been found that arcing occurs on the fixed limiters, on probes inserted into the plasma and on parts of the torus structure. For surfaces parallel to the toroidal field most of the arcs run across the surface orthogonal to the field direction. Observations in the scanning electron microscope show that the arc tracks are formed by a series of melted craters characteristic of cathode arc spots. The amount of metal removed from the surface is consistent with the concentration of metal observed in the plasma. In plasmas with hydrogen gas puffing during the discharge or with injection of low Z impurities, the arc tracks are observed to be much shallower than in normal low density discharges. Several types of surface damage other than arc tracks have also been observed on probes. These phenomena occur less frequently than arcing and appear to be associated with abnormal discharge conditions. (author)

  8. The next-generation ARC middleware

    DEFF Research Database (Denmark)

    Appleton, O.; Cameron, D.; Cernak, J.

    2010-01-01

    The Advanced Resource Connector (ARC) is a light-weight, non-intrusive, simple yet powerful Grid middleware capable of connecting highly heterogeneous computing and storage resources. ARC aims at providing general purpose, flexible, collaborative computing environments suitable for a range of use...

  9. The structure and singularities of arc complexes

    DEFF Research Database (Denmark)

    Penner, Robert

    A classical combinatorial fact is that the simplicial complex consisting of disjointly embedded chords in a convex planar polygon is a sphere. For any surface F with non-empty boundary, there is an analogous complex Arc(F) consisting of suitable equivalence classes of arcs in F connecting its bou...

  10. Verification of Timed-Arc Petri Nets

    DEFF Research Database (Denmark)

    Jacobsen, Lasse; Jacobsen, Morten; Møller, Mikael Harkjær

    2011-01-01

    of interesting theoretical properties distinguishing them from other time extensions of Petri nets. We shall give an overview of the recent theory developed in the verification of TAPN extended with features like read/transport arcs, timed inhibitor arcs and age invariants. We will examine in detail...

  11. Modeling and Simulation of Low Voltage Arcs

    NARCIS (Netherlands)

    Ghezzi, L.; Balestrero, A.

    2010-01-01

    Modeling and Simulation of Low Voltage Arcs is an attempt to improve the physical understanding, mathematical modeling and numerical simulation of the electric arcs that are found during current interruptions in low voltage circuit breakers. An empirical description is gained by refined electrical

  12. Risk assessment of metal vapor arcing

    Science.gov (United States)

    Hill, Monika C. (Inventor); Leidecker, Henning W. (Inventor)

    2009-01-01

    A method for assessing metal vapor arcing risk for a component is provided. The method comprises acquiring a current variable value associated with an operation of the component; comparing the current variable value with a threshold value for the variable; evaluating compared variable data to determine the metal vapor arcing risk in the component; and generating a risk assessment status for the component.

  13. Implementing RapidArc into clinical routine

    DEFF Research Database (Denmark)

    Van Esch, Ann; Huyskens, Dominique P; Behrens, Claus F

    2011-01-01

    With the increased commercial availability of intensity modulated arc therapy (IMAT) comes the need for comprehensive QA programs, covering the different aspects of this newly available technology. This manuscript proposes such a program for the RapidArc (RA) (Varian Medical Systems, Palo Alto...

  14. Arc generators of low-temperature plasma

    International Nuclear Information System (INIS)

    Krolikowski, Cz.; Niewiedzial, R.; Siwiec, J.

    1979-01-01

    This paper is a review of works concerning investigation and use of low-temperature plasma in arc plasma generators made in Electric Power Institute of PP. There are discussed: analytical approach to a problem of volt-current and operational characteristics of DC arc plasma generators, determination of limits of their stable work and possibilities of their use to technological aims. (author)

  15. St. Thomas and St. John, U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1/3 arc-second St. Thomas and St. John, U.S. Virgin Islands Coastal Digital Elevation Model will be used to support NOAA's tsunami forecast system and for...

  16. Diet, life-style and cardiovascular morbidity in the rural, free living population of Elafonisos island

    Directory of Open Access Journals (Sweden)

    Chris J. Kapelios

    2017-02-01

    Full Text Available Abstract Background There are about 70 small islands in the Aegean and Ionian Sea, of less than 300 Km2 and 5000 inhabitants each, comprising a total population of more than 75,000 individuals with geographical and socioeconomic characteristics of special interest. The objective of the present study was to assess lifestyle characteristics and the state of cardiovascular risk of the population of a small Eastern Mediterranean island, Elafonisos. Methods PERSEAS (Prospective Evaluation of cardiovascular Risk Surrogates in Elafonisos Area Study is an ongoing, population-based, longitudinal survey of cardiovascular risk factors, life-style characteristics and related morbidity/mortality performed in a small and relatively isolated island of the Aegean Sea, named Elafonisos. Validated, closed-ended questionnaires for demographic, socio-economic, clinical and lifestyle characteristics were distributed and analyzed. The MedDietScore, a validated Mediterranean diet score was also calculated. In addition, all participants underwent measurement of anthropometric parameters, blood pressure and a full blood panel for glucose and lipids. Results The analysis included 596 individuals who represented 74.5% of the target population. The mean age of the population was 49.5 ± 19.6 years and 48.2% were males. Fifty participants (8.4% had a history of cardiovascular disease (CVD. The rates of reported diabetes, hypertension, and hypercholesterolemia were 7.7%, 30.9% and 30.9% respectively, with screen-detection of each condition accounting for an additional 4.0%, 12.9%, and 23.3% of cases, respectively. Four hundred and seven individuals (68.3% were overweight or obese, 25% reported being physically inactive and 36.6% were active smokers. The median MedDietScore was 25 [interquartile range: 6, range 12–47] with higher values significantly associated with older age, better education, increased physical activity, absence of history of diabetes and known

  17. Electric arc behaviour in dynamic magnetic fields

    International Nuclear Information System (INIS)

    Put'ko, V.F.

    2000-01-01

    The behaviour of an electric arc in different time-dependent (dynamic) magnetic fields was investigated. New possibilities were found for spatial and energy stabilisation of a discharge, for intensifying heat exchange, extending the electric arc and distributed control of electric arc plasma. Rotating, alternating and travelling magnetic fields were studied. It was found that under the effect of a relatively low frequency of variations of dynamic magnetic fields (f 1000 Hz) the arc stabilised at the axis of the discharge chamber, the pulsation level decreased and discharge stability increased. The borders between these two arc existence modes were formed by a certain critical field variation frequency the period of which was determined by the heat relaxation time of the discharge. (author)

  18. Low voltage arc formation in railguns

    Science.gov (United States)

    Hawke, R.S.

    1985-08-05

    A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

  19. Metal transfer during vacuum consumable arc remelting

    International Nuclear Information System (INIS)

    Zanner, F.J.

    1977-11-01

    A description of the vacuum consumable arc remelt process as related to solidification and a review of vacuum arc literature is presented. Metal transfer at arc lengths less than or equal to 3 cm was found to occur when liquid metal spikes hanging from the cathode form a low resistance bridge (drop short) by touching the anode and subsequently rupturing. During the bridge lifetime (0.0003 to 0.020 s) the arc is extinguished and all of the electrical power is directed through the molten bridge. The formation and rupture of these molten metal bridges are confirmed with electrical resistance measurements. At long arc lengths (greater than 10 cm) the spikes separate before touching the anode

  20. Stability of alternating current gliding arcs

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Salewski, Mirko; Leipold, Frank

    2014-01-01

    on Ohm’s law indicates that the critical length of alternating current (AC) gliding arc discharge columns can be larger than that of a corresponding direct current (DC) gliding arc. This finding is supported by previously published images of AC and DC gliding arcs. Furthermore, the analysis shows......A gliding arc is a quenched plasma that can be operated as a non-thermal plasma at atmospheric pressure and that is thus suitable for large-scale plasma surface treatment. For its practical industrial use the discharge should be extended stably in ambient air. A simple analytical calculation based...... that the critical length can be increased by increasing the AC frequency, decreasing the serial resistance and lowering the gas flow rate. The predicted dependence of gas flow rate on the arc length is experimentally demonstrated. The gap width is varied to study an optimal electrode design, since the extended non...

  1. Neotectonics of central Japan and Izu-Bonin arc. Chuo Nippon no neotectonics to Izu Ogasawara ko

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, A. (Toyama Univ., Toyama (Japan). College of Liberal Arts)

    1991-08-25

    Central Japan is the boundary region among the Northeast Japan arc (NEJ), which was parted from the Honshu arc accompanying the basin in the Japan sea area and the bending of Japan Islands, the Southwest Japan arc (SWJ) and the end of the Izu-Bonin arc (IOA), and involves the specific volcanic activity. In this report, the geohistory of the Late Cainozoic era in the central Japan was re-arranged and the neotectonics of the central Japan was tried to reorganize. Especially from a viewpoint that the central Japan is a juncture between the north end of the volcanic arc IOA (Fuji, Norikura and Hakusan volcanic belts) and the southwest end of the volcanic arc NEJ (Nasu and Chokai volcanic belts), the relation between the volcanic activity and tectonics from the Pliocene to Pleistocene has been mainly handled in the Hida region east of the Hakusan and in the northern Fossa Magna region. In addition to it, the tectonics was pointed out to be an indication of mechanical jointing state with IOA. Then the results of IOA drilling according to ODP, Leg 129 were referred as well, in order to compare with the transition of more typical volcanic activity in IOA. 61 refs., 4 figs.

  2. Multivariate statistical tools for the radiometric features of volcanic islands

    International Nuclear Information System (INIS)

    Basile, S.; Brai, M.; Marrale, M.; Micciche, S.; Lanzo, G.; Rizzo, S.

    2009-01-01

    The Aeolian Islands represents a Quaternary volcanic arc related to the subduction of the Ionian plate beneath the Calabrian Arc. The geochemical variability of the islands has led to a broad spectrum of magma rocks. Volcanic products from calc-alkaline (CA) to calc-alkaline high in potassium (HKCA) are present throughout the Archipelago, but products belonging to shoshonitic (SHO) and potassium (KS) series characterize the southern portion of Lipari, Vulcano and Stromboli. Tectonics also plays an important role in the process of the islands differentiation. In this work, we want to review and cross-analyze the data on Lipari, Stromboli and Vulcano, collected in measurement and sampling campaigns over the last years. Chemical data were obtained by X-ray fluorescence. High resolution gamma-ray spectrometry with germanium detectors was used to measure primordial radionuclide activities. The activity of primordial radionuclides in the volcanic products of these three islands is strongly dependent on their chemism. The highest contents are found in more differentiated products (rhyolites). The CA products have lower concentrations, while the HKCA and Shoshonitic product concentrations are in between. Calculated dose rates have been correlated with the petrochemical features in order to gain further insight in evolution and differentiation of volcanic products. Ratio matching technique and multivariate statistical analyses, such as Principal Component Analysis and Minimum Spanning Tree, have been applied as an additional tool helpful to better describe the lithological affinities of the samples. (Author)

  3. Sedimentary architecture of a Plio-Pleistocene proto-back-arc basin: Wanganui Basin, New Zealand

    Science.gov (United States)

    Proust, Jean-Noël; Lamarche, Geoffroy; Nodder, Scott; Kamp, Peter J. J.

    2005-11-01

    The sedimentary architecture of active margin basins, including back-arc basins, is known only from a few end-members that barely illustrate the natural diversity of such basins. Documenting more of these basins types is the key to refining our understanding of the tectonic evolution of continental margins. This paper documents the sedimentary architecture of an incipient back-arc basin 200 km behind the active Hikurangi subduction margin, North Island, New Zealand. The Wanganui Basin (WB) is a rapidly subsiding, Plio-Pleistocene sedimentary basin located at the southern termination of the extensional back-arc basin of the active Central Volcanic Region (TVZ). The WB is asymmetric with a steep, thrust-faulted, outer (arc-ward) margin and a gentle inner (craton-ward) margin. It contains a 4-km-thick succession of Plio-Pleistocene sediments, mostly lying offshore, composed of shelf platform sediments. It lacks the late molasse-like deposits derived from erosion of a subaerial volcanic arc and basement observed in classical back-arc basins. Detailed seismic stratigraphic interpretations from an extensive offshore seismic reflection data grid show that the sediment fill comprises two basin-scale mega-sequences: (1) a Pliocene (3.8 to 1.35 Ma), sub-parallel, regressive "pre-growth" sequence that overtops the uplifted craton-ward margin above the reverse Taranaki Fault, and (2) a Pleistocene (1.35 Ma to present), divergent, transgressive, "syn-growth" sequence that onlaps: (i) the craton-ward high to the west, and (ii) uplifted basement blocks associated with the high-angle reverse faults of the arc-ward margin to the east. Along strike, the sediments offlap first progressively southward (mega-sequence 1) and then southeastward (mega-sequence 2), with sediment transport funnelled between the craton- and arc-ward highs, towards the Hikurangi Trough through the Cook Strait. The change in offlap direction corresponds to the onset of arc-ward thrust faulting and the rise of

  4. The characteristic of twin-electrode TIG coupling arc pressure

    International Nuclear Information System (INIS)

    Leng Xuesong; Zhang Guangjun; Wu Lin

    2006-01-01

    The coupling arc of twin-electrode TIG (T-TIG) is a particular kind of arc, which is achieved through the coupling of two arcs generated from two insulated electrodes in the same welding torch. It is therefore different from the single arc of conventional TIG in its physical characteristics. This paper studies the distribution of T-TIG coupling arc pressure, and analyses the influences of welding current, arc length, the distance between electrode tips and electrode shape upon arc pressure on the basis of experiment. It is expected that the T-TIG welding method can be applied in high efficiency welding according to its low arc pressure

  5. Chromosome mutagenesis in populations of aquatic biota in the Black Sea, Aegean Sea and Danube and Dnieper rivers, 1986-1989

    International Nuclear Information System (INIS)

    Tsytsugina, V.G.

    1991-01-01

    We studied the level of structural mutagenesis in the reproductive and somatic cells of aquatic biota of various taxa from natural populations of neustic and benthic communities in the Black and Aegean Seas and the Dnieper and Danube rivers between 1986 and 1989. The cytogenetic research covered embryos, larvae and adult worms of Nereidae, Naididae, Tubificidae and Turbellaria, adult Sagitta setosa, young Bivalvia molluscs, embryos of Mysidacea, and growing roe of Engraulis encrasicholus, Sprattus sprattus, Diplodus annularis, Mullus barbatus, Trachurus trachurus, Scophthalmus maeoticus, Abramis brama, Blicca bjoerkna, Rutilus rutilus and Stizostedion lucioperca. It was established that aquatic biota in the open waters of the Black and Aegean Seas had a lower level of chromosome mutagenesis than representatives of the fluvial communities. The intensity of mutagenesis was compared with the data published in the literature on radioactive contamination/chemical pollution of the aqueous medium in these areas. The paper sets out statistical regularities in chromosome mutagenesis (inter-individual variability in the chromosome aberration rate and distribution of chromosome damage in cells), noting different patterns of chromosome aberration distribution among cells. On the basis of a large quantity on our own data from field and experimental cytogenetic studies involving aquatic biota, the paper considers the possibility of using - for the purposes of radiochemical-ecological monitoring - chromosome damage distribution in cells as an indicator of whether mutagens are radiation-related or not. (author)

  6. 210Po and 210Pb variations in fish species from the Aegean Sea and the contribution of 210Po to the radiation dose

    International Nuclear Information System (INIS)

    Mat Çatal, Ebru; Uğur, Aysun; Özden, Banu; Filizok, Işık

    2012-01-01

    In recent years, there has been increasing interest in the significance of natural radionuclides, particularly 210 Po, in the marine environment. 210 Po, a naturally occurring alpha emitter, accumulates in marine organisms and reflects differences in their diets. In the literature, there is no data for 210 Po and 210 Pb activity concentrations for fish species on the Turkish coast of Aegean Sea. Therefore, in this study, multiple fish species were collected from six stations seasonally on the Turkish coast of Aegean Sea and were analyzed for their 210 Po and 210 Pb content. The 210 Po and 210 Pb concentrations in the fish samples were found to vary from undetectable levels to 499 ± 44 Bq kg −1 dry weight (dw) and from 1.0 ± 0.3 Bq kg −1 to 35 ± 4.0 Bq kg −1 (dw), respectively. There were no significant differences in the activity concentrations of 210 Po and 210 Pb in fish samples between seasons (ANOVA, P > 0.05). The highest dose contribution of 210 Po to humans was calculated to be 10,530 μSv year −1 .

  7. Impact of the Aegean Sea oil spill on the subtidal fine sand macrobenthic community of the Ares-Betanzos Ria (Northwest Spain)

    International Nuclear Information System (INIS)

    Gomez Gesteira, J.L.; Dauvin, J.C.

    2005-01-01

    Two sites located in the sublittoral fine-sand macrobenthic community of the Ares-Betanzos Ria were sampled over four years (December 1992-November 1996) in the wake of the Aegean Sea oil spill. This sampling revealed that the petroleum had affected the structure and abundance of this community, as well as the number of taxa present. In this context, the results of the biotic index and the biotic coefficient were insufficient; however, study of the synthetic parameters, particularly through multivariate analysis, showed that the community went through three successive and distinct phases over time. A short period of high mortality in some species, especially amphipods, was followed by a period of low abundance that lasted until the spring of 1995. A period of recovery began in the second half of 1995 and continued through to the end of 1996, when the survey ended. The community showed a gradual evolution back towards the conditions observed immediately after the spill, when abundance of the more resistant species was still high. Despite this similarity, the last period exhibits a new structure, clearly separate from the two previous periods. This study provides information about the short-term effects of the Aegean Sea oil spill on the fine sand bottoms of the sites surveyed in the Ares-Betanzos Ria. This information could also serve as a baseline for identifying the effects of a more recent accident, the Prestige oil spill, in which similar communities in other Galician rias were polluted in 2002-2003. (author)

  8. Paradise Islands? Island States and Environmental Performance

    Directory of Open Access Journals (Sweden)

    Sverker C. Jagers

    2016-03-01

    Full Text Available Island states have been shown to outperform continental states on a number of large-scale coordination-related outcomes, such as levels of democracy and institutional quality. The argument developed and tested in this article contends that the same kind of logic may apply to islands’ environmental performance, too. However, the empirical analysis shows mixed results. Among the 105 environmental outcomes that we analyzed, being an island only has a positive impact on 20 of them. For example, island states tend to outcompete continental states with respect to several indicators related to water quality but not in aspects related to biodiversity, protected areas, or environmental regulations. In addition, the causal factors previously suggested to make islands outperform continental states in terms of coordination have weak explanatory power in predicting islands’ environmental performance. We conclude the paper by discussing how these interesting findings can be further explored.

  9. Seismotectonics of the central segment of the Indonesian Arc

    Science.gov (United States)

    Eva, C.; Cattaneo, M.; Merlanti, F.

    1988-01-01

    In this paper, a revision of seismicity affecting the central segment of the Indonesian island arc ranging between 110° and 126° E is presented. Using the areal and in-depth distribution of seismic activity, strain release maps and focal mechanisms, lateral changes in the Wadati-Benioff zone have been analyzed to determine possible boundaries between portions of lithosphere with different subduction geometries. The seismicity pattern indicates that the Sumbawa-Flores-Wetar sector shows different forms of behaviour with respect to the adjacent sectors. These include driving mechanism, inclination and continuity of the subducting slab and subduction features. This area therefore seems to be isolated from the Sunda and Banda arcs by two principal boundaries, these having a nearly N-S trend in the Bali region and with a nearly E-W trend in the region ranging between Wetar-Northern Timor and Tanibar. The first boundary, characterized by an absolute minimum of seismic activity at all ranges of depth, has been interpreted in terms of subduction of the Roo Rise aseismic bathymetric ridge. For the second boundary, dividing a northwardly steeply-dipping slab from an E-W subducting slab dipping with an angle of 30 ° -40 °, a tear in the upper part (depth less than 300 km) and a hinge fault system in the deepest part of the lithosphere, have been proposed. From the analysis of focal mechanisms of shallow earthquakes, it was inferred that the central part of the Indonesian Arc is subject to a vortex-shaped stress field centred on the Savu Basin. In this model, the compressive axes appear to rotate counterclockwise (from SW to NNE) in the Sumba-Sumbawa-Western Flores region and clockwise (from W to NNW) in the Timor-Eastern Flores zone. To interpret these features, on the basis of seismological evidence, a lateral discontinuity in the arc-trench system close to Sumba, a collision between Sumba and Sumbawa and a rotation towards the north-northeast of Sumba have been

  10. Quaternary volcanism in Deception Island (Antarctica): South Shetland Trench subduction-related signature in the Bransfield Basin back arc domain; Vulcanismo cuaternario de la Isla Decepcion (Antartida): una signatura relacionada con la subduccion de la Fosa de las Shetland del Sur en el dominio de tras-arco de la Cuenca de Bransfield

    Energy Technology Data Exchange (ETDEWEB)

    Gale, C.; Ubide, T.; Lago, M.; Gil-Imaz, A.; Gil-Pena, I.; Galindo-Zaldivar, J.; Rey, J.; Maestro, A.; Lopez-Martinez, J.

    2014-06-01

    Deception Island shows a volcanism related to the Phoenix Plate subduction and roll-back under South Shetland Block in the present times. The development of the island is related to the evolution and collapse of a volcanic caldera, and this study is focused on the petrology, mineralogy and geochemistry of the post-caldera rocks. We have made a study of the lava flows, dikes and the youngest historic eruption in 1970. These rocks range from dacite to rhyolite and have a microporphyritic texture with olivine and minor clinopyroxene. A pre-caldera basaltic andesite has also been studied. It has a microporphyritic texture with clinopyroxene. The intermediate and acid compositions alternating in the volcanostratigraphic sequence suggest either mafic recharge events or melt extraction from different levels in the deep magmatic system. All the studied compositions share a subduction-related signature similar to other magmatics from the Bransfield Basin. However, compositional differences between pre-caldera and post-caldera rocks indicate a different magma source and depth of crystallisation. According to the geothermobarometric calculations the pre-caldera magmas started to crystallise at deeper levels (13.5-15 km) than the post-caldera magmas (6.2-7.8 km). Specifically, the postcaldera magmas indicate a smaller influence of the subducting slab in the southwestern part of the Bransfield Basin in respect to the available data from other sectors as well as the involvement of crustal contamination in the genesis of the magmas. (Author)

  11. The East Aegean Sea strong earthquake sequence of October–November 2005: lessons learned for earthquake prediction from foreshocks

    Directory of Open Access Journals (Sweden)

    G. A. Papadopoulos

    2006-01-01

    Full Text Available The seismic sequence of October–November 2005 in the Samos area, East Aegean Sea, was studied with the aim to show how it is possible to establish criteria for (a the rapid recognition of both the ongoing foreshock activity and the mainshock, and (b the rapid discrimination between the foreshock and aftershock phases of activity. It has been shown that before the mainshock of 20 October 2005, foreshock activity is not recognizable in the standard earthquake catalogue. However, a detailed examination of the records in the SMG station, which is the closest to the activated area, revealed that hundreds of small shocks not listed in the standard catalogue were recorded in the time interval from 12 October 2005 up to 21 November 2005. The production of reliable relations between seismic signal duration and duration magnitude for earthquakes included in the standard catalogue, made it possible to use signal durations in SMG records and to determine duration magnitudes for 2054 small shocks not included in the standard catalogue. In this way a new catalogue with magnitude determination for 3027 events was obtained while the standard catalogue contains 1025 events. At least 55 of them occurred from 12 October 2005 up to the occurrence of the two strong foreshocks of 17 October 2005. This implies that foreshock activity developed a few days before the strong shocks of 17 October 2005 but it escaped recognition by the routine procedure of seismic analysis. The onset of the foreshock phase of activity is recognizable by the significant increase of the mean seismicity rate which increased exponentially with time. According to the least-squares approach the b-value of the magnitude-frequency relation dropped significantly during the foreshock activity with respect to the b-value prevailing in the declustered background seismicity. However, the maximum likelihood approach does not indicate such a drop of b. The b-value found for the aftershocks that

  12. Grain size distribution, clay mineralogy and chemistry of bottom sediments from the outer Thermaikos Gulf, Aegean Sea, Greece

    Directory of Open Access Journals (Sweden)

    K.G. PEHLIVANOGLOU

    2004-06-01

    Full Text Available The Thermaikos Gulf constitutes the NW part of the North Aegean Sea and is limited eastward from the Chalkidiki Peninsula and westward from the Pieria Prefecture. Its plateau covers an area of 3,500 km2. The mechanisms responsible for the grain size distribution into the Gulf, the clay mineralogy and the chemistry of some bottom sediments from the outer Thermaikos Gulf, are examined. Source mixing during transportation, flocculation, differential settling processes and organic matter appear to be the main mechanisms for the distribution of clay minerals in shallow waters. All grain size fractions studied present a wide range of values confirming the extreme variations of the discharged load and the variability in marine processes. Plagioclases predominate over K-feldspars, while quartz is the most abundant mineral present. In addition, micas, chlorites, amphiboles and pyroxenes exist as primary and/or accessory minerals in all samples. Among clay minerals, illite predominates over smectite and smectite over chlorite (+ kaolinite. The ordered interstratified phase of I/S, with 30-35% S layers, is present in the 2-0.25µm fraction. The randomly interstratified phase of I/S, with 50% S layers, is present in the <0.25& micro; m fraction. On average the clay mineral content of the studied samples is: 48% I, 23% S, 17% Ch (+K and 12% others for the 2-0.25µm fraction and 50% I, 30% S and 20% Ch (+K for the <0.25 µm fraction. All these minerals are the weathering products of the rocks from the drainage basins of the rivers flowing into the Gulf, as well as of the Neogene and Quaternary unconsolidated sediments of the surrounding coasts. The terrigenous input, the water mass circulation and, to a lesser extent, the quality of the discharged material and the differential settling of grains, control the grain size distribution within the outer Thermaikos Gulf. The chemical composition of the analysed samples is generally in agreement with their mineral

  13. Electric Arc Furnace Modeling with Artificial Neural Networks and Arc Length with Variable Voltage Gradient

    Directory of Open Access Journals (Sweden)

    Raul Garcia-Segura

    2017-09-01

    Full Text Available Electric arc furnaces (EAFs contribute to almost one third of the global steel production. Arc furnaces use a large amount of electrical energy to process scrap or reduced iron and are relevant to study because small improvements in their efficiency account for significant energy savings. Optimal controllers need to be designed and proposed to enhance both process performance and energy consumption. Due to the random and chaotic nature of the electric arcs, neural networks and other soft computing techniques have been used for modeling EAFs. This study proposes a methodology for modeling EAFs that considers the time varying arc length as a relevant input parameter to the arc furnace model. Based on actual voltages and current measurements taken from an arc furnace, it was possible to estimate an arc length suitable for modeling the arc furnace using neural networks. The obtained results show that the model reproduces not only the stable arc conditions but also the unstable arc conditions, which are difficult to identify in a real heat process. The presented model can be applied for the development and testing of control systems to improve furnace energy efficiency and productivity.

  14. Intensity-modulated arc therapy simplified

    International Nuclear Information System (INIS)

    Wong, Eugene; Chen, Jeff Z.; Greenland, Jonathan

    2002-01-01

    Purpose: We present a treatment planning strategy for intensity-modulated radiation therapy using gantry arcs with dynamic multileaf collimator, previously termed intensity-modulated arc therapy (IMAT). Methods and Materials: The planning strategy is an extension of the photon bar arc and asymmetric arc techniques and is classified into three levels of complexity, with increasing number of gantry arcs. This principle allows us to generalize the analysis of the number of arcs required for intensity modulation for a given treatment site. Using a phantom, we illustrate how the current technique is more flexible than the photon bar arc technique. We then compare plans from our strategy with conventional three-dimensional conformal treatment plans for three sites: prostate (prostate plus seminal vesicles), posterior pharyngeal wall, and chest wall. Results: Our strategy generates superior IMAT treatment plans compared to conventional three-dimensional conformal plans. The IMAT plans spare critical organs well, and the trade-off for simplicity is that the dose uniformity in the target volume may not rival that of true inverse treatment plans. Conclusions: The analyses presented in this paper give a better understanding of IMAT plans. Our strategy is easier to understand and more efficient in generating plans than inverse planning systems; our plans are also simpler to modify, and quality assurance is more intuitive

  15. Depleted arc volcanism in the Alboran Sea and shoshonitic volcanism in Morocco: geochemical and isotopic constraints on Neogene tectonic processes

    Science.gov (United States)

    Gill, R. C. O.; Aparicio, A.; El Azzouzi, M.; Hernandez, J.; Thirlwall, M. F.; Bourgois, J.; Marriner, G. F.

    2004-12-01

    Samples of volcanic rocks from Alborán Island, the Alboran Sea floor and from the Gourougou volcanic centre in northern Morocco have been analyzed for major and trace elements and Sr-Nd isotopes to test current theories on the tectonic geodynamic evolution of the Alboran Sea. The Alborán Island samples are low-K tholeiitic basaltic andesites whose depleted contents of HFS elements (˜0.5×N-MORB), especially Nb (˜0.2×N-MORB), show marked geochemical parallels with volcanics from immature intra-oceanic arcs and back-arc basins. Several of the submarine samples have similar compositions, one showing low-Ca boninite affinity. 143Nd/ 144Nd ratios fall in the same range as many island-arc and back-arc basin samples, whereas 87Sr/ 86Sr ratios (on leached samples) are somewhat more radiogenic. Our data point to active subduction taking place beneath the Alboran region in Miocene times, and imply the presence of an associated back-arc spreading centre. Our sea floor suite includes a few more evolved dacite and rhyolite samples with ( 87Sr/ 86Sr) 0 up to 0.717 that probably represent varying degrees of crustal melting. The shoshonite and high-K basaltic andesite lavas from Gourougou have comparable normalized incompatible-element enrichment diagrams and Ce/Y ratios to shoshonitic volcanics from oceanic island arcs, though they have less pronounced Nb deficits. They are much less LIL- and LREE-enriched than continental arc analogues and post-collisional shoshonites from Tibet. The magmas probably originated by melting in subcontinental lithospheric mantle that had experienced negligible subduction input. Sr-Nd isotope compositions point to significant crustal contamination which appears to account for the small Nb anomalies. The unmistakable supra-subduction zone (SSZ) signature shown by our Alboran basalts and basaltic andesite samples refutes geodynamic models that attribute all Neogene volcanism in the Alboran domain to decompression melting of upwelling asthenosphere

  16. METHOD OF CONJUGATED CIRCULAR ARCS TRACING

    Directory of Open Access Journals (Sweden)

    N. Ageyev Vladimir

    2017-01-01

    Full Text Available The geometric properties of conjugated circular arcs connecting two points on the plane with set directions of tan- gent vectors are studied in the work. It is shown that pairs of conjugated circular arcs with the same conditions in frontier points create one-parameter set of smooth curves tightly filling all the plane. One of the basic properties of this set is the fact that all coupling points of circular arcs are on the circular curve going through the initially given points. The circle radius depends on the direction of tangent vectors. Any point of the circle curve, named auxiliary in this work, determines a pair of conjugated arcs with given boundary conditions. One more condition of the auxiliary circle curve is that it divides the plane into two parts. The arcs going from the initial point are out of the circle limited by this circle curve and the arcs coming to the final point are inside it. These properties are the basis for the method of conjugated circular arcs tracing pro- posed in this article. The algorithm is rather simple and allows to fulfill all the needed plottings using only the divider and ruler. Two concrete examples are considered. The first one is related to the problem of tracing of a pair of conjugated arcs with the minimal curve jump when going through the coupling point. The second one demonstrates the possibility of trac- ing of the smooth curve going through any three points on the plane under condition that in the initial and final points the directions of tangent vectors are given. The proposed methods of conjugated circular arcs tracing can be applied in solving of a wide variety of problems connected with the tracing of cam contours, for example pattern curves in textile industry or in computer-aided-design systems when programming of looms with numeric control.

  17. Plasma instability of a vacuum arc centrifuge

    International Nuclear Information System (INIS)

    Hole, M.J.; Dallaqua, R.S.; Simpson, S.W.; Del Bosco, E.

    2002-01-01

    Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a 'universal' instability, driven by the density gradient, in a plasma with finite conductivity

  18. Arc pressure control in GTA welding

    International Nuclear Information System (INIS)

    Cook, G.E.; Wells, F.M.; Levick, P.C.

    1986-01-01

    Relationships are established between the peak current of a pulsed, rectangular current waveform and the pulse current duty cycle under conditions of constant arc power. By appropriate choice of these interrelated parameters, it is shown that the arc pressure may be varied over a wide range even though the arc power is held constant. The methodology is suggested as a means of countering the effect of gravity in 5-G welding, while maintaining constant heat input to the weld. Combined with appropriate penetration sensors, the methodology is additionally suggested as a means of controlling penetration

  19. Arc saw and its application to decommissioning

    International Nuclear Information System (INIS)

    Deichelbohrer, P.R.

    1982-01-01

    The arc saw is a toothless, circular saw that cuts by arc erosion. A model was built to study the arc saw's usefulness in cutting up radioactively contaminated metal scrap. It was chosen because it cuts with very little contact to the work piece and because cutting is not affected by material hardness. After installation of several improvements it was found it could cut almost any combination of metals and that clamping or fixturing requirements were minimum. Cutting proceeds rapidly and efficiently. 10 figures

  20. Implementation av spridningsmodell i ArcGIS

    OpenAIRE

    Jou, Javid

    2012-01-01

    The project involves implementing a finished dispersion model into ArcGIS. The goal of the tool is to show how dangerous and toxic substances will travel in the ground after long periods. The goal of the project is to understand GIS in general, what it is used for and gain an insight into how developing tools for ArcGIS is, what challenges might exists. Understanding the type of data that can be stored and accessed in ArcGIS a long with the tools and functionality offered by the system when u...

  1. Across-arc versus along-arc Sr-Nd-Pb isotope variations in the Ecuadorian volcanic arc

    Science.gov (United States)

    Ancellin, Marie-Anne; Samaniego, Pablo; Vlastélic, Ivan; Nauret, François; Gannoun, Adbelmouhcine; Hidalgo, Silvana

    2017-03-01

    Previous studies of the Ecuadorian arc (1°N-2°S) have revealed across-arc geochemical trends that are consistent with a decrease in mantle melting and slab dehydration away from the trench. The aim of this work is to evaluate how these processes vary along the arc in response to small-scale changes in the age of the subducted plate, subduction angle, and continental crustal basement. We use an extensive database of 1437 samples containing 71 new analyses, of major and trace elements as well as Sr-Nd-Pb isotopes from Ecuadorian and South Colombian volcanic centers. Large geochemical variations are found to occur along the Ecuadorian arc, in particular along the front arc, which encompasses 99% and 71% of the total variations in 206Pb/204Pb and 87Sr/86Sr ratios of Quaternary Ecuadorian volcanics, respectively. The front arc volcanoes also show two major latitudinal trends: (1) the southward increase of 207Pb/204Pb and decrease of 143Nd/144Nd reflect more extensive crustal contamination of magma in the southern part (up to 14%); and (2) the increase of 206Pb/204Pb and decrease of Ba/Th away from ˜0.5°S result from the changing nature of metasomatism in the subarc mantle wedge with the aqueous fluid/siliceous slab melt ratio decreasing away from 0.5°S. Subduction of a younger and warmer oceanic crust in the Northern part of the arc might promote slab melting. Conversely, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc.

  2. Hydrothermal manganese oxide deposits from the Izu-Ogasawara (Bonin)-Mariana Arc and adjacent areas

    Energy Technology Data Exchange (ETDEWEB)

    Usui, A.; Nishimura, A. (Geological Survey of Japan, Tsukuba (Japan))

    1992-04-27

    Modern and fossil hydrothermal manganese oxide deposits were discovered from a number of locations in the Izu-Ogasawara(Bonin)-Mariana Arc and adjacent areas during the Hakurei-Maru cruises from 1984 to 1989. This paper describes the occurrence and characteristics of these manganese deposits and their geological significance. It was found that the mineralogical and chemical composition and microstructure of the deposits are typically different from manganese nodules and crusts of hydrogenetic or diagenetic origin. Hardpans, veinlets, sheets, and irregular mass of the hydrothermal manganese deposits often cover a large area of sea bed, which suggests possible high-temperature hydrothermal sulfide deposits in their vicinity. On the other hand, the manganese minerals sometimes occur as substrate of younger hydrogenetic crusts and as nucleus of hydrogenetic nodules, which can provide a geological history of low-temperature hydrothermal activity on the past island arcs. 45 refs., 19 figs., 3 tabs.

  3. Tanzania - Mafia Island Airport

    Data.gov (United States)

    Millennium Challenge Corporation — The evaluation design and subsequent data gathering activities will address the following key research questions: a) Has the Mafia Island Airport Upgrade Project...

  4. 49 CFR 195.226 - Welding: Arc burns.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn may...

  5. Sitka, Alaska 9 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Sitka, Alaska Elevation Grid provides bathymetric data in ASCII raster format of 9 arc-second resolution in geographic coordinates. This grid is strictly for...

  6. Retinal injury from a welding arc

    International Nuclear Information System (INIS)

    Naidoff, M.A.; Sliney, D.H.

    1974-01-01

    An 18-year-old man stared at a welding arc for approximately ten minutes, sustaining moderate facial erythema, keratoconjunctivitis, marked visual loss, a pupillary abnormality, and a retinal injury accompanied by a dense central scotoma and peripheral field constriction. A residual, partially pigmented foveal lesion remained after 16 months, with normal visual acuity. Since the degree of keratoconjunctivitis and facial erythema was known, we substantiated the duration of exposure to the arc by weighting the known action spectrum of moderate ultraviolet erythema with the ultraviolet spectral irradiance measurements of the arc. From the radiometric measurements of the visible brightness and visible and near infrared spectrum of the arc and from knowledge of pupil size, we calculated the retinal exposure dose rate, which was less than normally considered necessary to produce a chorioretinal burn. This case may provide a clinical example of photic maculopathy recently reported in experimental investigations

  7. Sitka, Alaska 1 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Sitka, Alaska Elevation Grid provides bathymetric data in ASCII raster format of 1 arc-second resolution in geographic coordinates. This grid is strictly for...

  8. Arc tracks on nanostructured surfaces after microbreakdowns

    International Nuclear Information System (INIS)

    Sinelnikov, D; Bulgadaryan, D; Kolodko, D; Kurnaev, V; Hwangbo, D; Ohno, N; Kajita, S

    2016-01-01

    Studying of initial steps of unipolar arc ignition process is important for reduction of probability of arcing between the plasma and the wall in thermonuclear devices. Tungsten nano-fuzz surface formed by helium plasma irradiation at high fluences and temperatures is a perfect material for arc ignition. Snowflake-like craters were detected on the fuzzy surfaces after short micro-breakdowns. Such sort of craters have not been observed before on any other metallic surfaces. These specific traces are formed due to unique properties of the fuzz structure. The nano-fuzz could be easily melted and vaporized by micro-breakdown current, due to its porosity and bad thermal conductivity, and formation of low conducting metallic vapour under the cathode spot causes discharge movement to the nearest place. Thus, even low current arc can easily move and leave traces, which could be easily observed by a secondary electron microscope. (paper)

  9. Sitka, Alaska 3 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Sitka, Alaska Elevation Grid provides bathymetric data in ASCII raster format of 3 arc-second resolution in geographic coordinates. This grid is strictly for...

  10. Seward, Alaska 3 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second Seward Alaska Elevation Grid provides bathymetric data in ASCII raster format of 2.67-second resolution in geographic coordinates. This grid is...

  11. Seldovia, Alaska 1 arc-second DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Seldovia, Alaska Elevation Grid provides bathymetric data in ASCII raster format of 1 arc-second resolution in geographic coordinates. This grid is strictly for...

  12. Basins in ARC-continental collisions

    Science.gov (United States)

    Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

    2012-01-01

    Arc-continent collisions occur commonly in the plate-tectonic cycle and result in rapidly formed and rapidly collapsing orogens, often spanning just 5-15 My. Growth of continental masses through arc-continent collision is widely thought to be a major process governing the structural and geochemical evolution of the continental crust over geologic time. Collisions of intra-oceanic arcs with passive continental margins (a situation in which the arc, on the upper plate, faces the continent) involve a substantially different geometry than collisions of intra-oceanic arcs with active continental margins (a situation requiring more than one convergence zone and in which the arc, on the lower plate, backs into the continent), with variable preservation potential for basins in each case. Substantial differences also occur between trench and forearc evolution in tectonically erosive versus tectonically accreting margins, both before and after collision. We examine the evolution of trenches, trench-slope basins, forearc basins, intra-arc basins, and backarc basins during arc-continent collision. The preservation potential of trench-slope basins is low; in collision they are rapidly uplifted and eroded, and at erosive margins they are progressively destroyed by subduction erosion. Post-collisional preservation of trench sediment and trench-slope basins is biased toward margins that were tectonically accreting for a substantial length of time before collision. Forearc basins in erosive margins are usually floored by strong lithosphere and may survive collision with a passive margin, sometimes continuing sedimentation throughout collision and orogeny. The low flexural rigidity of intra-arc basins makes them deep and, if preserved, potentially long records of arc and collisional tectonism. Backarc basins, in contrast, are typically subducted and their sediment either lost or preserved only as fragments in melange sequences. A substantial proportion of the sediment derived from

  13. Metal Vapor Arcing Risk Assessment Tool

    Science.gov (United States)

    Hill, Monika C.; Leidecker, Henning W.

    2010-01-01

    The Tin Whisker Metal Vapor Arcing Risk Assessment Tool has been designed to evaluate the risk of metal vapor arcing and to help facilitate a decision toward a researched risk disposition. Users can evaluate a system without having to open up the hardware. This process allows for investigating components at risk rather than spending time and money analyzing every component. The tool points to a risk level and provides direction for appropriate action and documentation.

  14. Managing Data and ArcGIS

    OpenAIRE

    Farr, Lucy

    2011-01-01

    Glenn Jobson (CRASSH) produced and edited this video in collaboration with the Incremental project. ESRI's ArcGIS data, and other vector data system, are highly vulnerable to partial or complete data loss over time because as the company makes frequent software updates, and the data themselves have so many moving parts. In this presentation, Lucy Farr (McDonald Institute for Archaeological Research) describes her experiences using ArcGIS, lessons learnt, and recommendations for best practi...

  15. ATLAS DDM integration in ARC

    International Nuclear Information System (INIS)

    Behrmann, G; Cameron, D; Ellert, M; Kleist, J; Taga, A

    2008-01-01

    The Nordic Data Grid Facility (NDGF) consists of Grid resources running ARC middleware in Denmark, Finland, Norway and Sweden. These resources serve many virtual organisations and contribute a large fraction of total worldwide resources for the ATLAS experiment, whose data is distributed and managed by the DQ2 software. Managing ATLAS data within NDGF and between NDGF and other Grids used by ATLAS (the Enabling Grids for E-sciencE Grid and the Open Science Grid) presents a unique challenge for several reasons. Firstly, the entry point for data, the Tier 1 centre, is physically distributed among heterogeneous resources in several countries and yet must present a single access point for all data stored within the centre. The middleware framework used in NDGF differs significantly from other Grids, specifically in the way that all data movement and registration is performed by services outside the worker node environment. Also, the service used for cataloging the location of data files is different from other Grids but must still be useable by DQ2 and ATLAS users to locate data within NDGF. This paper presents in detail how we solve these issues to allow seamless access worldwide to data within NDGF

  16. Klystron Gun Arcing and Modulator Protection

    International Nuclear Information System (INIS)

    Gold, S

    2004-01-01

    The demand for 500 kV and 265 amperes peak to power an X-Band klystron brings up protection issues for klystron faults and the energy dumped into the arc from the modulator. This situation is made worse when more than one klystron will be driven from a single modulator, such as the existing schemes for running two and eight klystrons. High power pulsed klystrons have traditionally be powered by line type modulators which match the driving impedance with the load impedance and therefore current limit at twice the operating current. Multiple klystrons have the added problems of a lower modulator source impedance and added stray capacitance, which converts into appreciable energy at high voltages like 500kV. SLAC has measured the energy dumped into klystron arcs in a single and dual klystron configuration at the 400 to 450 kV level and found interesting characteristics in the arc formation. The author will present measured data from klystron arcs powered from line-type modulators in several configurations. The questions arise as to how the newly designed solid-state modulators, running multiple tubes, will react to a klystron arc and how much energy will be dumped into the arc

  17. Recent ARC developments: Through modularity to interoperability

    International Nuclear Information System (INIS)

    Smirnova, O; Cameron, D; Ellert, M; Groenager, M; Johansson, D; Kleist, J; Dobe, P; Joenemo, J; Konya, B; Fraagaat, T; Konstantinov, A; Nilsen, J K; Saada, F Ould; Qiang, W; Read, A; Kocan, M; Marton, I; Nagy, Zs; Moeller, S; Mohn, B

    2010-01-01

    The Advanced Resource Connector (ARC) middleware introduced by NorduGrid is one of the basic Grid solutions used by scientists worldwide. While being well-proven in daily use by a wide variety of scientific applications at large-scale infrastructures like the Nordic DataGrid Facility (NDGF) and smaller scale projects, production ARC of today is still largely based on conventional Grid technologies and custom interfaces introduced a decade ago. In order to guarantee sustainability, true cross-system portability and standards-compliance based interoperability, the ARC community undertakes a massive effort of implementing modular Web Service (WS) approach into the middleware. With support from the EU KnowARC project, new components were introduced and the existing key ARC services got extended with WS technology based standard-compliant interfaces following a service-oriented architecture. Such components include the hosting environment framework, the resource-coupled execution service, the re-engineered client library, the self-healing storage solution and the peer-to-peer information system, to name a few. Gradual introduction of these new services and client tools into the production middleware releases is carried out together with NDGF and thus ensures a smooth transition to the next generation Grid middleware. Standard interfaces and modularity of the new component design are essential for ARC contributions to the planned Universal Middleware Distribution of the European Grid Initiative.

  18. Recent ARC developments: Through modularity to interoperability

    Energy Technology Data Exchange (ETDEWEB)

    Smirnova, O; Cameron, D; Ellert, M; Groenager, M; Johansson, D; Kleist, J [NDGF, Kastruplundsgade 22, DK-2770 Kastrup (Denmark); Dobe, P; Joenemo, J; Konya, B [Lund University, Experimental High Energy Physics, Institute of Physics, Box 118, SE-22100 Lund (Sweden); Fraagaat, T; Konstantinov, A; Nilsen, J K; Saada, F Ould; Qiang, W; Read, A [University of Oslo, Department of Physics, P. O. Box 1048, Blindern, N-0316 Oslo (Norway); Kocan, M [Pavol Jozef Safarik University, Faculty of Science, Jesenna 5, SK-04000 Kosice (Slovakia); Marton, I; Nagy, Zs [NIIF/HUNGARNET, Victor Hugo 18-22, H-1132 Budapest (Hungary); Moeller, S [University of Luebeck, Inst. Of Neuro- and Bioinformatics, Ratzeburger Allee 160, D-23538 Luebeck (Germany); Mohn, B, E-mail: oxana.smirnova@hep.lu.s [Uppsala University, Department of Physics and Astronomy, Div. of Nuclear and Particle Physics, Box 535, SE-75121 Uppsala (Sweden)

    2010-04-01

    The Advanced Resource Connector (ARC) middleware introduced by NorduGrid is one of the basic Grid solutions used by scientists worldwide. While being well-proven in daily use by a wide variety of scientific applications at large-scale infrastructures like the Nordic DataGrid Facility (NDGF) and smaller scale projects, production ARC of today is still largely based on conventional Grid technologies and custom interfaces introduced a decade ago. In order to guarantee sustainability, true cross-system portability and standards-compliance based interoperability, the ARC community undertakes a massive effort of implementing modular Web Service (WS) approach into the middleware. With support from the EU KnowARC project, new components were introduced and the existing key ARC services got extended with WS technology based standard-compliant interfaces following a service-oriented architecture. Such components include the hosting environment framework, the resource-coupled execution service, the re-engineered client library, the self-healing storage solution and the peer-to-peer information system, to name a few. Gradual introduction of these new services and client tools into the production middleware releases is carried out together with NDGF and thus ensures a smooth transition to the next generation Grid middleware. Standard interfaces and modularity of the new component design are essential for ARC contributions to the planned Universal Middleware Distribution of the European Grid Initiative.

  19. THE REDSHIFT DISTRIBUTION OF GIANT ARCS IN THE SLOAN GIANT ARCS SURVEY

    International Nuclear Information System (INIS)

    Bayliss, Matthew B.; Gladders, Michael D.; Koester, Benjamin P.; Oguri, Masamune; Hennawi, Joseph F.; Sharon, Keren; Dahle, Haakon

    2011-01-01

    We measure the redshift distribution of a sample of 28 giant arcs discovered as a part of the Sloan Giant Arcs Survey. Gemini/GMOS-North spectroscopy provides precise redshifts for 24 arcs, and 'redshift desert' constrains for the remaining 4 arcs. This is a direct measurement of the redshift distribution of a uniformly selected sample of bright giant arcs, which is an observable that can be used to inform efforts to predict giant arc statistics. Our primary giant arc sample has a median redshift z = 1.821 and nearly two-thirds of the arcs, 64%, are sources at z ∼> 1.4, indicating that the population of background sources that are strongly lensed into bright giant arcs resides primarily at high redshift. We also analyze the distribution of redshifts for 19 secondary strongly lensed background sources that are not visually apparent in Sloan Digital Sky Survey imaging, but were identified in deeper follow-up imaging of the lensing cluster fields. Our redshift sample for the secondary sources is not spectroscopically complete, but combining it with our primary giant arc sample suggests that a large fraction of all background galaxies that are strongly lensed by foreground clusters reside at z ∼> 1.4. Kolmogorov-Smirnov tests indicate that our well-selected, spectroscopically complete primary giant arc redshift sample can be reproduced with a model distribution that is constructed from a combination of results from studies of strong-lensing clusters in numerical simulations and observational constraints on the galaxy luminosity function.

  20. Partial pressure (or fugacity) of carbon dioxide, temperature, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer and other instruments from unknown platforms in the Adriatic Sea, Aegean Sea and others from 2012-01-01 to 2012-12-31 (NODC Accession 0059946)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0059946 includes Surface underway, chemical, meteorological and physical data collected from unknown platforms in the Adriatic Sea, Aegean Sea,...

  1. Partial pressure (or fugacity) of carbon dioxide, temperature, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from AEGAEO in the Aegean Sea and Mediterranean Sea from 2006-02-08 to 2006-02-13 (NODC Accession 0084543)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0084543 includes Surface underway, chemical, meteorological and physical data collected from AEGAEO in the Aegean Sea and Mediterranean Sea from...

  2. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from METEOR in the Aegean Sea, Mediterranean Sea and others from 2001-10-18 to 2001-11-11 (NODC Accession 0084620)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0084620 includes discrete sample and profile data collected from METEOR in the Aegean Sea, Mediterranean Sea, Mediterranean Sea - Eastern Basin,...

  3. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from METEOR in the Adriatic Sea, Aegean Sea and others from 2011-04-05 to 2011-04-28 (NODC Accession 0108079)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108079 includes discrete sample and profile data collected from METEOR in the Adriatic Sea, Aegean Sea, Alboran Sea, Ionian Sea, Mediterranean Sea,...

  4. Partial pressure (or fugacity) of carbon dioxide and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer and other instruments from POLARSTERN in the Adriatic Sea, Aegean Sea and others from 2014-03-09 to 2015-01-31 (NCEI Accession 0160489)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0160489 includes Surface underway, chemical and meteorological data collected from POLARSTERN in the Adriatic Sea, Aegean Sea, Alboran Sea, Arabian...

  5. PH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from PROFESSOR SIEDLECKI in the Adriatic Sea, Aegean Sea and others from 1988-11-17 to 1988-11-26 (NCEI Accession 0144306)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144306 includes discrete sample and profile data collected from PROFESSOR SIEDLECKI in the Adriatic Sea, Aegean Sea, Mediterranean Sea, Mediterranean...

  6. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer, Shower head chamber equilibrator for autonomous carbon dioxide (CO2) measurement and other instruments from Marcus G. Langseth in the Aegean Sea, Alboran Sea and others from 2015-04-13 to 2015-11-12 (NCEI Accession 0144534)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0144534 includes Surface underway data collected from Marcus G. Langseth in the Aegean Sea, Alboran Sea, Mediterranean Sea, Mediterranean Sea -...

  7. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from Surface underway observations using Carbon dioxide (CO2) gas analyzer and other instruments from Celebrity Equinox in the Adriatic Sea, Aegean Sea and others from 2016-01-02 to 2017-01-02 (NCEI Accession 0157264)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157264 includes Surface underway, chemical, meteorological and physical data collected from Celebrity Equinox in the Adriatic Sea, Aegean Sea,...

  8. Dissolved inorganic carbon, alkalinity, temperature, salinity and OXYGEN - APPARENT UTILIZATION (AOU) collected from discrete sample and profile observations using CTD, bottle and other instruments from UNKNOWN PLATFORMS in the Adriatic Sea, Aegean Sea and others from 1874-10-11 to 2000-04-26 (NODC Accession 0117350)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0117350 includes chemical, discrete sample, physical and profile data collected from UNKNOWN PLATFORMS in the Adriatic Sea, Aegean Sea, Alboran Sea,...

  9. The presence of the Indo-Pacific symbiont-bearing foraminifer Amphistegina lobifera in Greek coastal ecosystems (Aegean Sea, Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    M.V. TRIANTAPHYLLOU

    2009-12-01

    Full Text Available During the last decades, hundreds of species of Indo-Pacific origin from the Red Sea have traversed the Suez Canal and settled in the Eastern Mediterranean. Nowadays, Amphistegina lobifera Larsen, is known to be a successful immigrant that is widely distributed in the coastal ecosystems of the Eastern Mediterranean Sea. Amphistegina is the most common epiphytic, symbiont- bearing large foraminifer. In this study we provide additional data on the presence of this species in the coastal ecosystems of Aegean Sea, Greece. The high relative abundance of A. lobifera is the result of very successful adaptation of this species to local conditions and suggests that it has become a significant part of the epiphytic foraminiferal fauna.

  10. VoiLA: A multidisciplinary study of Volatile recycling in the Lesser Antilles Arc

    Science.gov (United States)

    Collier, J.; Blundy, J. D.; Goes, S. D. B.; Henstock, T.; Harmon, N.; Kendall, J. M.; Macpherson, C.; Rietbrock, A.; Rychert, C.; Van Hunen, J.; Wilkinson, J.; Wilson, M.

    2017-12-01

    Project VoiLA will address the role of volatiles in controlling geological processes at subduction zones. The study area was chosen as it subducts oceanic lithosphere formed at the slow-spreading Mid Atlantic Ridge. This should result in a different level and pattern of hydration to compare with subduction zones in the Pacific which consume oceanic lithosphere generated at faster spreading rates. In five project components, we will test (1) where volatiles are held within the incoming plate; (2) where they are transported and released below the arc; (3) how the volatile distribution and pathways relate to the construction of the arc; and (4) their relationship to seismic and volcanic hazards and the fractionation of economic metals. Finally, (5) the behaviour of the Lesser Antilles arc will be compared with that of other well-studied systems to improve our wider understanding of the role of water in subduction processes. To address these questions the project will combine seismology; petrology and numerical modelling of wedge dynamics and its consequences on dehydration and melting. So-far island-based fieldwork has included mantle xenolith collection and installation of a temporary seismometer network. In 2016 and 2017 we conducted cruises onboard the RRS James Cook that collected a network of passive-recording and active-recording ocean-bottom seismometer data within the back-arc, fore-arc and incoming plate region. A total of 175 deployments and recoveries were made with the loss of only 6 stations. The presentation will present preliminary results from the project.

  11. arcControlTower: the System for Atlas Production and Analysis on ARC

    International Nuclear Information System (INIS)

    Filipcic, Andrej

    2011-01-01

    PanDA, the Atlas management and distribution system for production and analysis jobs on EGEE and OSG clusters, is based on pilot jobs to increase the throughput and stability of the job execution on grid. The ARC middleware uses a specific approach which tightly connects the job requirements with cluster capabilities like resource usage, software availability and caching of input files. The pilot concept renders the ARC features useless. The arcControlTower is the job submission system which merges the pilot benefits and ARC advantages. It takes the pilot payload from the panda server and submits the jobs to the Nordugrid ARC clusters as regular jobs, with all the job resources known in advance. All the pilot communication with the PanDA server is done by the arcControlTower, so it plays the role of a pilot factory and the pilot itself. There are several advantages to this approach: no grid middleware is needed on the worker nodes, the fair-share between the production and user jobs is tuned with the arcControlTower load parameters, the jobs can be controlled by ARC client tools. The system could be extended to other submission systems using central distribution.

  12. Arc dynamics of a pulsed DC nitrogen rotating gliding arc discharge

    Science.gov (United States)

    Zhu, Fengsen; Zhang, Hao; Li, Xiaodong; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Tu, Xin

    2018-03-01

    In this study, a novel pulsed direct current (DC) rotating gliding arc (RGA) plasma reactor co-driven by an external magnetic field and a tangential gas flow has been developed. The dynamic characteristics of the rotating gliding arc have been investigated by means of numerical simulation and experiment. The simulation results show that a highly turbulent vortex flow can be generated at the bottom of the RGA reactor to accelerate the arc rotation after arc ignition, whereas the magnitude of gas velocity declined significantly along the axial direction of the RGA reactor. The calculated arc rotation frequency (14.4 Hz) is reasonably close to the experimental result (18.5 Hz) at a gas flow rate of 10 l min-1. In the presence of an external magnet, the arc rotation frequency is around five times higher than that of the RGA reactor without using a magnet, which suggests that the external magnetic field plays a dominant role in the maintenance of the arc rotation in the upper zone of the RGA reactor. In addition, when the magnet is placed outside the reactor reversely to form a reverse external magnetic field, the arc can be stabilized at a fixed position in the inner wall of the outer electrode at a critical gas flow rate of 16 l min-1.

  13. Amphibole Fractional Crystallization and Delamination in Arc Roots: Implications for the `Missing' Nb Reservoir in the Earth

    Science.gov (United States)

    Galster, F.; Chatterjee, R. N.; Stockli, D. F.

    2017-12-01

    Most geologic processes should not fractionate Nb from Ta but Earth's major silicate reservoirs have subchondritic Nb/Ta values. Nb/Ta of >10000 basalts and basaltic andesites from different tectonic settings (GEOROC) cluster around 16, indistinguishable from upper mantle values. In contrast, Nb/Ta in more evolved arc volcanics have progressively lower values, reaching continental crust estimates, and correlate negatively with SiO2 (see figure) and positively with TiO2 and MgO. This global trend suggests that differentiation processes in magmatic arcs could explain bulk crustal Nb/Ta estimates. Understanding processes that govern fractionation of Nb from Ta in arcs can provide key insights on continental crust formation and help identify Earth's `missing' Nb reservoir. Ti-rich phases (rutile, titanite and ilmenite) have DNb/DTa values in the evolved liquid. Lack of correlation between Nb/Ta and K2O in global volcanic rocks implies that biotite plays a minor role in fractionating Nb from Ta during differentiation. Experimental petrology and evidence from exposed arc sections indicate that amphibole fractionation and delamination of island arc roots can explain the andesitic composition of bulk continental crust. Experimental studies have shown that amphibole Mg# correlate with DNb/DTa and amphibole could effectively fractionate Nb from Ta. Preliminary data from lower to middle crustal amphiboles from preserved arcs show sub- to super-chondritic Nb/Ta up to >60. This suggests that delamination of amphibole-rich cumulates can be a viable mechanism for the preferential removal of Nb from the continental crust. Future examination of Nb/Ta ratios in lower crustal amphiboles from various preserved arcs will provide improved constraints on the Nb-Ta paradox of the silicate Earth.

  14. Operator Bias in the Estimation of Arc Efficiency in Gas Tungsten Arc Welding

    Directory of Open Access Journals (Sweden)

    Fredrik Sikström

    2015-03-01

    Full Text Available In this paper the operator bias in the measurement process of arc efficiency in stationary direct current electrode negative gas tungsten arc welding is discussed. An experimental study involving 15 operators (enough to reach statistical significance has been carried out with the purpose to estimate the arc efficiency from a specific procedure for calorimetric experiments. The measurement procedure consists of three manual operations which introduces operator bias in the measurement process. An additional relevant experiment highlights the consequences of estimating the arc voltage by measuring the potential between the terminals of the welding power source instead of measuring the potential between the electrode contact tube and the workpiece. The result of the study is a statistical evaluation of the operator bias influence on the estimate, showing that operator bias is negligible in the estimate considered here. On the contrary the consequences of neglecting welding leads voltage drop results in a significant under estimation of the arc efficiency.

  15. Method to reduce arc blow during DC arc welding of pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J. H.; Rueda-Morales, G.L.; Caleyo, F.; Hallen, J. M. [Instituto Politecnico Nacional, Mexico, (Mexico); Lopez-Montenegro, A.; Perz-Baruch, E. [Pemex Exploracion y Produccion, Tabasco, (Mexico)

    2010-07-01

    Steel pipelines are huge ferromagnetic structures and can be easily subjected to arc blow during the DC arc welding process. The development of methods to avoid arc blow during pipeline DC arc welding is a major objective in the pipeline industry. This study developed a simple procedure to compensate the residual magnetic field in the groove during DC arc welding. A Gaussmeter was used to perform magnetic flux density measurements in pipelines in southern Mexico. These data were used to perform magnetic finite element simulations using FEMM. Different variables were studied such as the residual magnetic field in the groove or the position of the coil with respect to the groove. An empirical predictive equation was developed from these trials to compensate for the residual magnetic field. A new method of compensating for the residual magnetic field in the groove by selecting the number of coil turns and the position of the coil with respect to the groove was established.

  16. Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

    International Nuclear Information System (INIS)

    Cong Haoxi; Li Qingmin; Xing Jinyuan; Li Jinsong; Chen Qiang

    2015-01-01

    The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low-voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines. (paper)

  17. Magnetic Method to Characterize the Current Densities in Breaker Arc

    International Nuclear Information System (INIS)

    Machkour, Nadia

    2005-01-01

    The purpose of this research was to use magnetic induction measurements from a low voltage breaker arc, to reconstruct the arc's current density. The measurements were made using Hall effect sensors, which were placed close to, but outside the breaking device. The arc was modelled as a rectangular current sheet, composed of a mix of threadlike current segments and with a current density varying across the propagation direction. We found the magnetic induction of the arc is a convolution product of the current density, and a function depending on the breaker geometry and arc model. Using deconvolution methods, the current density in the electric arc was determined.The method is used to study the arc behavior into the breaker device. Notably, position, arc size, and electric conductivity could all be determined, and then used to characterize the arc mode, diffuse or concentrated, and study the condition of its mode changing

  18. Emissions of chromium (VI) from arc welding.

    Science.gov (United States)

    Heung, William; Yun, Myoung-Jin; Chang, Daniel P Y; Green, Peter G; Halm, Chris

    2007-02-01

    The presence of Cr in the +6 oxidation state (Cr[VI]) is still observed in ambient air samples in California despite steps taken to reduce emissions from plating operations. One known source of emission of Cr(VI) is welding, especially with high Cr-content materials, such as stainless steels. An experimental effort was undertaken to expand and update Cr(VI) emission factors by conducting tests on four types of arc-welding operations: gas-metal arc welding (GMAW), shielded metal arc welding (SMAW), fluxcore arc welding, and pulsed GMAW. Standard American Welding Society hood results were compared with a total enclosure method that permitted isokinetic sampling for particle size-cut measurement, as well as total collection of the aerosol. The fraction of Cr(VI) emitted per unit mass of Cr electrode consumed was determined. Consistent with AP-42 data, initial results indicate that a significant fraction of the total Cr in the aerosol is in the +6 oxidation state. The fraction of Cr(VI) and total aerosol mass produced by the different arc welding methods varies with the type of welding process used. Self-shielded electrodes that do not use a shield gas, for example, SMAW, produce greater amounts of Cr(VI) per unit mass of electrode consumed. The formation of Cr(VI) from standard electrode wires used for welding mild steel was below the method detection limit after eliminating an artifact in the analytical method used.

  19. 'LTE-diffusion approximation' for arc calculations

    International Nuclear Information System (INIS)

    Lowke, J J; Tanaka, M

    2006-01-01

    This paper proposes the use of the 'LTE-diffusion approximation' for predicting the properties of electric arcs. Under this approximation, local thermodynamic equilibrium (LTE) is assumed, with a particular mesh size near the electrodes chosen to be equal to the 'diffusion length', based on D e /W, where D e is the electron diffusion coefficient and W is the electron drift velocity. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Use of the LTE-diffusion approximation for a 200 A arc with a thermionic cathode gives predictions of total arc voltage, electrode temperatures, arc temperatures and radial profiles of heat flux density and current density at the anode that are in approximate agreement with more accurate calculations which include an account of the diffusion of electric charges to the electrodes, and also with experimental results. Calculations, which include diffusion of charges, agree with experimental results of current and heat flux density as a function of radius if the Milne boundary condition is used at the anode surface rather than imposing zero charge density at the anode

  20. Vacuum arc ion charge state distributions

    International Nuclear Information System (INIS)

    Brown, I.G.; Godechot, X.

    1990-06-01

    We have measured vacuum arc ion charge state spectra for a wide range of metallic cathode materials. The charge state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. We have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th and U. The arc was operated in a pulsed mode with pulse length 0.25 msec; arc current was 100 A throughout. This array of elements extends and completes previous work by us. In this paper the measured distributions are cataloged and compared with our earlier results and with those of other workers. We also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

  1. Vacuum arc ion charge-state distributions

    International Nuclear Information System (INIS)

    Brown, I.G.; Godechot, X.

    1991-01-01

    The authors have measured vacuum arc ion charge-state spectra for a wide range of metallic cathode materials. The charge-state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. They have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th, and U. The arc was operated in a pulsed mode with pulse length 0.25 ms; arc current was 100 A throughout. This array of elements extends and completes previous work by the authors. In this paper the measured distributions are cataloged and compared with their earlier results and those of other workers. They also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

  2. Sweden: Autonomous Reactivity Control (ARC) Systems

    International Nuclear Information System (INIS)

    Qvist, Staffan A.

    2015-01-01

    The next generation of nuclear energy systems must be licensed, constructed, and operated in a manner that will provide a competitively priced supply of energy, keeping in consideration an optimum use of natural resources, while addressing nuclear safety, waste, and proliferation resistance, and the public perception concerns of the countries in which those systems are deployed. These issues are tightly interconnected, and the implementation of passive and inherent safety features is a high priority in all modern reactor designs since it helps to tackle many of the issues at once. To this end, the Autonomous Reactivity Control (ARC) system was developed to ensure excellent inherent safety performance of Generation-IV reactors while having a minimal impact on core performance and economic viability. This paper covers the principles for ARC system design and analysis, the problem of ensuring ARC system response stability and gives examples of the impact of installing ARC systems in well-known fast reactor core systems. It is shown that even with a relatively modest ARC installation, having a near-negligible impact on core performance during standard operation, cores such as the European Sodium Fast Reactor (ESFR) can be made to survive any postulated unprotected transient without coolant boiling or fuel melting

  3. Vancouver Island gas supply

    International Nuclear Information System (INIS)

    Des Brisay, C.

    2005-01-01

    Terasen Gas is pursuing alternatives for the supply of additional natural gas capacity to Vancouver Island. Its subsidiary, Terasen Gas (Vancouver Island) Inc. (TGVI), is responding to the need for delivery of increased gas supply and, is supporting plans for new gas-fired power generation on Vancouver Island. TGVI's proposal for new natural gas capacity involves a combination of compression and pipeline loops as well as the addition of a storage facility for liquefied natural gas (LNG) at Mt. Hayes to help manage price volatility. This presentation outlined the objectives and components of the resource planning process, including demand forecast scenarios and the preferred infrastructure options. tabs., figs

  4. Evaluation of volumetric modulated arc therapy for cranial radiosurgery using multiple noncoplanar arcs

    International Nuclear Information System (INIS)

    Audet, Chantal; Poffenbarger, Brett A.; Chang, Pauling; Jackson, Paul S.; Lundahl, Robert E.; Ryu, Stephen I.; Ray, Gordon R.

    2011-01-01

    Purpose: To evaluate a commercial volumetric modulated arc therapy (VMAT), using multiple noncoplanar arcs, for linac-based cranial radiosurgery, as well as evaluate the combined accuracy of the VMAT dose calculations and delivery. Methods: Twelve patients with cranial lesions of variable size (0.1-29 cc) and two multiple metastases patients were planned (Eclipse RapidArc AAA algorithm, v8.6.15) using VMAT (1-6 noncoplanar arcs), dynamic conformal arc (DCA, ∼4 arcs), and IMRT (nine static fields). All plans were evaluated according to a conformity index (CI), healthy brain tissue doses and volumes, and the dose to organs at risk. A 2D dose distribution was measured (Varian Novalis Tx, HD120 MLC, 1000 MU/min, 6 MV beam) for the ∼4 arc VMAT treatment plans using calibrated film dosimetry. Results: The CI (0-1 best) average for all plans was best for ∼4 noncoplanar arc VMAT at 0.86 compared with ∼0.78 for IMRT and a single arc VMAT and 0.68 for DCA. The volumes of healthy brain receiving 50% of the prescribed target coverage dose or more (V 50% ) were lowest for the four arc VMAT [RA(4)] and DCA plans. The average ratio of the V 50% for the other plans to the RA(4) V 50% were 1.9 for a single noncoplanar arc VMAT [RA(1nc)], 1.4 for single full coplanar arc VMAT [RA(1f)] and 1.3 for IMRT. The V 50% improved significantly for single isocenter multiple metastases plan when two noncoplanar VMAT arcs were added to a full single coplanar one. The maximum dose to 5 cc of the outer 1 cm rim of healthy brain which one may want to keep below nonconsequential doses of 300-400 cGy, was 2-3 times greater for IMRT, RA(1nc) and RA(1f) plans compared with the multiple noncoplanar arc DCA and RA(4) techniques. Organs at risk near (0-4 mm) to targets were best spared by (i) single noncoplanar arcs when the targets are lateral to the organ at risk and (ii) by skewed nonvertical planes of IMRT fields when the targets are not lateral to the organ at risk. The highest dose gradient

  5. Island formation without attractive interaction

    NARCIS (Netherlands)

    Jansen, A.P.J.

    2008-01-01

    We show that adsorbates on surfaces can form islands even if there are no attractive interactions. Instead, strong repulsion between adsorbates at short distances can lead to islands, because such islands increase the entropy of the adsorbates that are not part of the islands. We suggest that this

  6. Large-scale slope failure and active erosion occurring in the southwest Ryukyu fore-arc area

    Directory of Open Access Journals (Sweden)

    T. Matsumoto

    2001-01-01

    Full Text Available The southwestern Ryukyu area east of Taiwan Island is an arcuate boundary between Philippine Sea Plate and Eurasian Plate. The topographic features in the area are characterised by (1 a large-scale amphitheatre off Ishigaki Island, just on the estimated epicentre of the tsunamigenic earthquake in 1771, (2 lots of deep sea canyons located north of the amphitheatre, (3 15–20 km wide fore-arc basin, (4 15–20 km wide flat plane in the axial area of the trench, (5 E-W trending half grabens located on the fore-arc area, etc., which were revealed by several recent topographic survey expeditions. The diving survey by SHINKAI6500 in the fore-arc area on a spur located 120 km south of Ishigaki Island was carried out in 1992. The site is characterised dominantly by rough topography consisting of a series of steep slopes and escarpments. A part of the surface is eroded due to the weight of the sediment itself and consequently the basement layer is exposed. The site was covered with suspended particles during the diving, due to the present surface sliding and erosion. The same site was resurveyed in 1997 by ROV KAIKO, which confirmed the continuous slope failure taking place in the site. Another example that was observed by KAIKO expedition in 1997 is a largescale mud block on the southward dipping slope 80 km south of Ishigaki Island. This is apparently derived from the shallower part of the steep slope on the southern edge of the fan deposit south of Ishigaki Island. The topographic features suggest N-S or NE-SW tensional stress over the whole study area. In this sense, the relative motion between the two plates in this area is oblique to the plate boundary. So, the seaward migration of the plate boundary may occur due to the gravitational instability at the boundary of the two different lithospheric structures. This is evidenced by a lack of accretionary sediment on the fore-arc and the mechanism of a recent earthquake which occurred on 3 May 1998 in

  7. Electric arc, water jet cutting of metals

    International Nuclear Information System (INIS)

    Bruening, D.

    1991-01-01

    For thermal dismantling and cutting of metallic components, as electric arc, water jet cutting method was developed that can be used for underwater cutting work up to a depth of 20 m. Short-circuiting of a continuously fed electrode wire in contact with the metal generates an electric arc which induces partial melting of the metal, and the water jet surrounding the wire rinses away the molten material, thus making a continuous kerf in the material. The method was also tested and modified to allow larger area, surface cutting and removal of metallic surface coatings. This is achieved by melting parts of the surface with the electric arc and subsequent rinsing by the water jet. The cutting and melting depth for surface removal can be accurately controlled by the operating parameters chosen. (orig./DG) [de

  8. Theoretical model of polar cap auroral arcs

    International Nuclear Information System (INIS)

    Kan, J.R.; Burke, W.J.; USAF, Bedford, MA)

    1985-01-01

    A theory of the polar cap auroral arcs is proposed under the assumption that the magnetic field reconnection occurs in the cusp region on tail field lines during northward interplanetary magnetic field (IMF) conditions. Requirements of a convection model during northward IMF are enumerated based on observations and fundamental theoretical considerations. The theta aurora can be expected to occur on the closed field lines convecting sunward in the central polar cap, while the less intense regular polar cap arcs can occur either on closed or open field lines. The dynamo region for the polar cap arcs is required to be on closed field lines convecting tailward in the plasma sheet which is magnetically connected to the sunward convection in the central polar cap. 43 references

  9. Cathodic Vacuum Arc Plasma of Thallium

    International Nuclear Information System (INIS)

    Yushkov, Georgy Yu.; Anders, Andre

    2006-01-01

    Thallium arc plasma was investigated in a vacuum arc ion source. As expected from previous consideration of cathode materials in the Periodic Table of the Elements, thallium plasma shows lead-like behavior. Its mean ion charge state exceeds 2.0 immediately after arc triggering, reaches the predicted 1.60 and 1.45 after about 100 microsec and 150 microsec, respectively. The most likely ion velocity is initially8000 m/s and decays to 6500 m/s and 6200 m/s after 100 microsec and 150microsec, respectively. Both ion charge states and ion velocities decay further towards steady state values, which are not reached within the 300microsec pulses used here. It is argued that the exceptionally high vapor pressure and charge exchange reactions are associated with the establishment of steady state ion values

  10. Circular arc snakes and kinematic surface generation

    KAUST Repository

    Barton, Michael

    2013-05-01

    We discuss the theory, discretization, and numerics of curves which are evolving such that part of their shape, or at least their curvature as a function of arc length, remains unchanged. The discretization of a curve as a smooth sequence of circular arcs is well suited for such purposes, and allows us to reduce evolution of curves to the evolution of a control point collection in a certain finite-dimensional shape space. We approach this evolution by a 2-step process: linearized evolution via optimized velocity fields, followed by optimization in order to exactly fulfill all geometric side conditions. We give applications to freeform architecture, including "rationalization" of a surface by congruent arcs, form finding and, most interestingly, non-static architecture. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

  11. Optical diagnostics of a gliding arc

    DEFF Research Database (Denmark)

    Sun, Z.W.; Zhu, J.J.; Li, Z.S.

    2013-01-01

    Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera...... triggered by Townsend breakdown between the two legs of the gliding arc. The emission from the plasma column is shown to pulsate at a frequency of 62.5 kHz, i.e., twice the frequency of the AC power supply. Optical emission spectra of the plasma radiation show the presence of excited N2, NO and OH radicals...... suggesting that ground-state OH is not formed in the plasma column but in its vicinity. ©2013 Optical Society of America...

  12. Crustal rifting and magmatic underplating in the Izu-Ogasawara (Bonin) intra-oceanic arc detected by active source seismic studies

    Science.gov (United States)

    Takahashi, N.; Kodaira, S.; Yamashita, M.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.; Kaneda, Y.

    2009-12-01

    Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic experiments using a multichannel reflection system and ocean bottom seismographs (OBSs) in the Izu-Ogasawara (Bonin)-Mariana (IBM) arc region since 2002 to understand growth process of continental crust. The source was an airgun array with a total capacity of 12,000 cubic inches and the OBSs as the receiver were deployed with an interval of 5 km for all seismic refraction experiments. As the results, we obtained crustal structures across the whole IBM arc with an interval of 50 km and detected the structural characteristics showing the crustal growth process. The IBM arc is one of typical oceanic island arc, which crustal growth started from subduction of an oceanic crust beneath the other oceanic crust. The arc crust has developed through repeatedly magmatic accretion from subduction slab and backarc opening. The volcanism has activated in Eocene, Oligocene, Miocene and Quaternary (e.g., Taylor, 1992), however, these detailed locations of past volcanic arc has been remained as one of unknown issues. In addition, a role of crustal rifting for the crustal growth has also been still unknown issue yet. Our seismic structures show three rows of past volcanic arc crusts except current arc. A rear arc and a forearc side have one and two, respectively. The first one, which was already reported by Kodaira et al. (2008), distributes in northern side from 27 N of the rear arc region. The second one, which develops in the forearc region next to the recent volcanic front, distributes in whole of the Izu-Ogasawara arc having crustal variation along arc direction. Ones of them sometimes have thicker crust than that beneath current volcanic front and no clear topographic high. Last one in the forearc connects to the Ogasawara Ridge. However, thickest crust is not always located beneath these volcanic arcs. The initial rifting region like the northern end of the Mariana Trough and the Sumisu

  13. Coalescence of magnetic islands

    International Nuclear Information System (INIS)

    Pellat, R.

    1982-01-01

    The paper gives the analytical theory of the coalescence instability and of a new, one island, instability. These instabilities are expected to be relevant for the disruptions observed in Tokamak experiments and astrophysical plasmas

  14. Heat Island Compendium

    Science.gov (United States)

    Heat islands can be mitigated through measures like planting trees and vegetation, installing green roofs and cool roofs, and using cool pavements. The compendium describes all of these strategies and shows how communities around the country are being used

  15. On the Trail of Joan of Arc

    Directory of Open Access Journals (Sweden)

    Linda Joyce Forristal

    2013-12-01

    Full Text Available The year 2012 marked the 600th anniversary of the birthday of Joan of Arc (Fr., Jeanne d’Arc (1412–1431. Tributes to this national heroine can be found all over France. There are literally countless statues, streets and restaurants named after her and many sites dedicated to her life. However, despite widespread social and mechanical reproduction and cultural naming in relation to the Maid of Orléans, there is no official network or integrated signage in France to promote cultural heritage tourism to the numerous Joan of Arc sites and festivals, even though her life and death, by any measure, were seminal events in the country’s history. Unfortunately, the pilgrim who wants to follow or intersect with Joan of Arc’s trail through France, for cultural, historical or religious reasons, must do so without much help. Using Actor Network Theory and Site Sacralization Theory as framing devices, this paper explores human actors and tangible and intangible non-human factors that may have contributed to the lack of a unified tourism product despite the existence of an adequate Joan of Arc tourismscape. Insights gleaned from this research include Joan’s conflicted status as both/either saint and/or patriot, the existence of no cooperation or linkage between Joan of Arc sites, and cautious French tourism development policies. Several possible scenarios are suggested as suitable means to help implement or foster the creation of an on-the-ground or virtual Joan of Arc trail or tour.

  16. Sheath and arc-column voltages in high-pressure arc discharges

    International Nuclear Information System (INIS)

    Benilov, M S; Benilova, L G; Li Heping; Wu Guiqing

    2012-01-01

    Electrical characteristics of a 1 cm-long free-burning atmospheric-pressure argon arc are calculated by means of a model taking into account the existence of a near-cathode space-charge sheath and the discrepancy between the electron and heavy-particle temperatures in the arc column. The computed arc voltage exhibits a variation with the arc current I similar to the one revealed by the experiment and exceeds experimental values by no more than approximately 2 V in the current range 20-175 A. The sheath contributes about two-thirds or more of the arc voltage. The LTE model predicts a different variation of the arc voltage with I and underestimates the experimental values appreciably for low currents but by no more than approximately 2 V for I ≳ 120 A. However, the latter can hardly be considered as a proof of unimportance of the space-charge sheath at high currents: the LTE model overestimates both the resistance of the bulk of the arc column and the resistance of the part of the column that is adjacent to the cathode, and this overestimation to a certain extent compensates for the neglect of the voltage drop in the sheath. Furthermore, if the latter resistance were evaluated in the framework of the LTE model in an accurate way, then the overestimation would be still much stronger and the obtained voltage would significantly exceed those observed in the experiment.

  17. Arc-to-arc mini-sling 1999: a critical analysis of concept and technology

    Directory of Open Access Journals (Sweden)

    Paulo Palma

    2011-04-01

    Full Text Available PURPOSE: The aim of this study was to critically review the Arc-to-Arc mini-sling (Palma's technique a less invasive mid-urethral sling using bovine pericardium as the sling material. MATERIALS AND METHODS: The Arc-to-Arc mini-sling, using bovine pericardium, was the first published report of a mini-sling, in 1999. The technique was identical to the "tension-free tape" operation, midline incision and dissection of the urethra. The ATFP (white line was identified by blunt dissection, and the mini-sling was sutured to the tendinous arc on both sides with 2 polypropylene 00 sutures. RESULTS: The initial results were encouraging, with 9/10 patients cured at the 6 weeks post-operative visit. However, infection and extrusion of the mini-sling resulted in sling extrusion and removal, with 5 patients remaining cured at 12 months. CONCLUSION: The Arc-to-Arc mini-sling was a good concept, but failed because of the poor technology available at that time. Further research using new materials and better technology has led to new and safer alternatives for the management of stress urinary incontinence.

  18. Three Mile Island revisited

    International Nuclear Information System (INIS)

    MacLeod, G.K.

    1986-01-01

    The accident at Three Mile Island proved that the Pennsylvania Department of Health lacked the tools to deal with the serious health consequences that occurred during and after this emergency. Despite the relative safety of nuclear power generation, we must be better prepared for the health and medical consequences of serous radiation emergencies. The author reviews the Three Mile Island accident through the eyes of newspaper reporters

  19. Influence of a transverse magnetic field on arc root movements in a dc plasma torch: Diamagnetic effect of arc column

    International Nuclear Information System (INIS)

    Kim, Keun Su

    2009-01-01

    The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field

  20. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-12-01

    In recent decades, the popularity of freeform shapes in contemporary architecture poses new challenges to digital design. One of them is the process of rationalization, i.e. to make freeform skins or structures affordable to manufacture, which draws the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how to employ them nicely and repetitively in architectural design, in order to decrease the cost in manufacturing. Firstly, we study Darboux cyclides, which are algebraic surfaces of order ≤ 4. We provide a computational tool to identify all families of circles on a given cyclide based on the spherical model of M ̈obius geometry. Practical ways to design cyclide patches that pass through certain inputs are presented. In particular, certain triples of circle families on Darboux cyclides may be suitably arranged as 3-webs. We provide a complete classification of all possible 3-webs of circles on Darboux cyclides. We then investigate the circular arc snakes, which are smooth sequences of circu- lar arcs. We evolve the snakes such that their curvature, as a function of arc length, remains unchanged. The evolution of snakes is utilized to approximate given surfaces by circular arcs or to generated freeform shapes, and it is realized by a 2-step pro- cess. More interestingly, certain 6-arc snake with boundary constraints can produce a smooth self motion, which can be employed to build flexible structures. Another challenging topic is approximating smooth freeform skins with simple panels. We contribute to this problem area by approximating a negatively-curved 5 surface with a smooth union of rational bilinear patches. We provide a proof for vertex consistency of hyperbolic nets using the CAGD approach of the rational B ́ezier form. Moreover, we use Darboux transformations for the