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Sample records for aegean sea scattered

  1. Analytical chemistry in the Aegean Sea region: current status.

    PubMed

    Samanidou, Victoria F

    2012-12-01

    The Eighth Aegean Analytical Chemistry Days Conference took place in Urla, İzmir, Turkey, from 16-20 September 2012. This conference is held every 2 years, organized alternately by analytical chemistry departments of Turkish and Greek universities, so that analytical chemists from the region around the Aegean Sea can exchange experience and knowledge based on their research in a large number of fields. This report summarizes the most interesting presentations and posters pertaining to bioanalytical work.

  2. Assimilating Ferry Box data into the Aegean Sea model

    NASA Astrophysics Data System (ADS)

    Korres, G.; Ntoumas, M.; Potiris, M.; Petihakis, G.

    2014-12-01

    Operational monitoring and forecasting of marine environmental conditions is a necessary tool for the effective management and protection of the marine ecosystem. It requires the use of multi-variable real-time measurements combined with advanced physical and ecological numerical models. Towards this, a FerryBox system was originally installed and operated in the route Piraeus-Heraklion in 2003 for one year. Early 2012 the system was upgraded and moved to a new high-speed ferry traveling daily in the same route as before. This route is by large traversing the Cretan Sea being the largest and deepest basin (2500 m) in the south Aegean Sea. The HCMR Ferry Box is today the only one in the Mediterranean and thus it can be considered as a pilot case. The analysis of FerryBox SST and SSS in situ data revealed the presence of important regional and sub-basin scale physical phenomena, such as wind-driven coastal upwelling and the presence of a mesoscale cyclone to the north of Crete. In order to assess the impact of the FerryBox SST data in constraining the Aegean Sea hydrodynamic model which is part of the POSEIDON forecasting system, the in situ data were assimilated using an advanced multivariate assimilation scheme based on the Singular Evolutive Extended Kalman (SEEK) filter, a simplified square-root extended Kalman filter that operates with low-rank error covariance matrices as a way to reduce the computational burden. Thus during the period mid-August 2012-mid January 2013 in addition to the standard assimilating parameters, daily SST data along the ferryboat route from Piraeus to Heraklion were assimilated into the model. Inter-comparisons between the control run of the system (model run that uses only the standard data set of observations) and the experiment where the observational data set is augmented with the FerryBox SST data produce interesting results. Apart from the improvement of the SST error, the additional assimilation of daily of FerryBox SST

  3. Source mechanism of the 2014 Aegean Sea earthquake

    NASA Astrophysics Data System (ADS)

    Nakano, Masaru

    2016-04-01

    Rapid determination of centroid moment tensor (CMT) of earthquakes, namely the source centroid location, focal mechanism, and magnitude is important for early disaster responses and issuing Tsunami warnings. In order to evaluate capability of Turkey seismic network for rapid determinations of CMT, I investigate the source mechanism of the 2014 Aegean Sea earthquake (Mw 6.9). Although this event occur out of Turkey seismic network, I obtained stable CMT solution. The CMT solution of this earthquake represents a strike-slip fault, consistent with the geometry of the North Anatolian Fault (NAF), and the source-time function indicates that this event comprised several distinct subevents. Each subevent is considered to have ruptured a different fault segment. This observation indicates the existence of a mechanical barrier, namely a NAF segment boundary, at the hypocenter. I also determined CMT solutions of background seismicity. CMT solutions of background seismicity beneath the Aegean Sea represent strike-slip or normal faulting along the NAF or its branch faults. The tensional axes of these events are oriented northeast-southwest, indicating a transtensional tectonic regime. Beneath the Sea of Marmara, the CMT solutions represent mostly strike-slip faulting, consistent with the motion of the NAF, but we identified a normal fault event with a tensional axis parallel to the strike of the NAF. This mechanism indicates that a pull-apart basin, marking a segment boundary of the NAF, is developing there. Because ruptures of a fault system and large earthquake magnitudes are strongly controlled by the fault system geometry and fault length, mapping fault segments along NAF can help to improve the accuracy of scenarios developed for future disastrous earthquakes in the Marmara region.

  4. Mixed Layer Depth in the Aegean, Marmara, Black and Azov Seas: Part II: Relation to the Sonic Layer Depth

    DTIC Science & Technology

    2009-03-03

    r.com/ locate / jmarsysMixed layer depth in the Aegean, Marmara, Black and Azov Seas : Part II: Relation to the sonic layer depth Robert W. Helber a...index terms: The Aegean Sea The Black Sea The Azov Sea Keywords: Sound transmission Mixed layer depth Climatologyt analysis of the seasonal evolution of...the sonic layer depth (SLD) relative to the mixed layer depth (MLD) for the Aegean, Marmara, Black, and Azov Seas . SLD identifies the acoustic ducting

  5. Tsunami Propagation Database for the Mediterranean and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Kanoglu, U.; Hoto, O.; Kalligeris, N.; Flouri, E.; Aydin, B.; Moore, C. W.; Synolakis, C. E.

    2012-12-01

    Pre-computed tsunami scenario databases are common tools to develop long- or short-term forecasting methodologies and hazard assessment approaches for tsunami-prone regions worldwide. The benefits of such databases include the possibility of probabilistic studies (Gonzalez et al., 2009, J. Geophys. Res. 114, Article Number: C11023), inundation mapping (Barberopoulou et al., 2011, Pure Appl. Geophys. 168(11), 2133-2146), or real-time forecasting (Wei et al., 2008, Geophys. Res. Lett. 35(4), Article Number: L04609). As a result, several tsunami propagation databases have been developed including one by NOAA's Pacific Marine Environmental Laboratory (PMEL), and another by the Australian Bureau of Meteorology (BOM). Pre-computed tsunami scenario databases utilize different approaches. PMEL's tsunami propagation database is based on the concept of a pre-computed tsunami scenarios consisting of propagation results from 100km x 50km fault planes with a slip value of 1m referred to as tsunami source functions. PMEL's source functions are placed along the subduction zones in several rows, covering known faults throughout the major ocean basins. Linearity of the tsunami propagation in the open ocean allows scaling and/or combination of the pre-computed tsunami source functions to generate a desired scenario. The BOM database considers five earthquakes with magnitudes changing from 7.0 to 9.0 at each location with 100km intervals along the subduction zone. However, to date, no similar approach has been computed along the subduction zones in the Aegean and Mediterranean Seas, even though, historically, there have been a considerable number of tsunami events which caused damage in the region (Ambraseys and Synolakis, 2010, J. Earthquake Eng. 14 (3), 309-330, Article Number: PII 919600673). A new project was initiated between Greece and Turkey supported by General Secretariat for Research & Technology, The Ministry for Development (GSRT) of Greece and The Scientific and

  6. Mixed Layer Depth in the Aegean, Marmara, Black and Azov Seas: Part I: General Features

    DTIC Science & Technology

    2009-02-28

    r.com/ locate / jmarsysMixed layer depth in the Aegean, Marmara, Black and Azov Seas : Part I: General features A. Birol Kara a,⁎, Robert W. Helber a...suffer from lack of input T and S profiles in the Marmara and Azov Seas , thus they may not be representative.MonthlyMLDfields presented in this paper are...Boyer), .V.there has been no study which describes seasonal characteristics of MLD in the Aegean, Marmara, Black and Azov Seas , whose bottom

  7. Upper Cenozoic organic-rich sequences (offshore and onshore the south Aegean sea)

    SciTech Connect

    Anastasakis, G.

    1988-08-01

    The upper Cenozoic sedimentary column of the south Aegean Sea is composed mostly of marine sediments which have been deposited after the Seravallian breakup of the south Aegean landmass. Extensive submarine coring has revealed the frequent occurrence of Quaternary dark, organic-rich layers in the cores retrieved from water depths greater than 180 m. Moreover, deep-sea drilling (DSDP leg 42A) in the south Aegean basin recovered organic-rich layers as old as late Miocene. Onshore the south Aegean Sea islands, organic-rich sediments are found at the north and south territories of the region, on Milos and Crete islands. Especially on the island of Crete and south of it, on the smaller islands of Gavdos and Koufonisi, these organic-rich sediments represent a considerable portion of the widespread upper Cenozoic sediments. Stratigraphically they cover the interval between upper Seravallian and lower Pleistocene. The organic carbon content of all these mostly calcareous lithofacies, the so-called sapropels, ranges mostly between 0.5 and 6.5%. The most reliably chronostratigraphically correlated upper Pleistocene sapropels display similar compositional characteristics across the entire basin. Certain Pleistocene and older organic-rich layers contain increased proportions of siliceous tests. However the entire range of sapropels in the region (except those within the Messinian evaporites) can be described adequately by the same lithofacies association. To demonstrate this the authors compare the lower Tortonian Faneromeni Formation on Crete with the upper Quaternary sediments from the south Aegean Sea.

  8. Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

    NASA Technical Reports Server (NTRS)

    Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George

    2013-01-01

    We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.

  9. Shallow structure and recent evolution of the Aegean Sea deduced from the seismic reflection analysis

    SciTech Connect

    Laure, M.; Mascle, J.

    1988-08-01

    Together with the Tyrrhenian Sea, the Aegean Sea represents one of two marine basins still developing as a consequence of the subduction of the African lithosphere beneath Europe. Despite many geophysical similarities with the Tyrrhenian Sea, the Aegean displays a specific structural segmentation characterized by two distinct domains separated by the central Aegean. To the north of the basin, the so-called North Aegean trough likely represents the western marine extension of the transtensive Anatolian transform fault zone. The northern margin of this area contains a series of disconnected, often thickly sedimented small basins that probably initiated during the late Miocene as a consequence of a dominantly north-south extension; typical uppermost Miocene (Messinian) formations can be observed on seismic grounds. To the south, the Cretan Sea shows clear evidence of important distensive events occurring during two main episodes and following two main trends; a dominantly north-south-directed extension is responsibile for most of the structural features detected along both the Cretan and southern Cyclades margins.

  10. Phytoplankton size-based dynamics in the Aegean Sea (Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Ignatiades, L.; Psarra, S.; Zervakis, V.; Pagou, K.; Souvermezoglou, E.; Assimakopoulou, G.; Gotsis-Skretas, O.

    2002-07-01

    This study represents one component of the large MTP-II-MATER (MAST-III) multidisiplinary project in the Mediterranean supported by EU. Data were collected during three cruises performed in Spring and Autumn 1997 and Spring 1998 from six stations of the North and five stations of the South Aegean Sea. The work assessed the spatial, vertical and temporal variations of size fractionated chlorophyll α, primary production (in situ), photosynthetic parameters (in situ) and the taxonomic composition of phytoplankton. The population structure and dynamics were greatly influenced by the different hydrographic conditions prevailing in the Northern and Southern Aegean Sea due to the influence of Black Sea and Levantine Sea waters, respectively. The picoplankton fraction (0.2-1.2 μm) predominated and accounted for the 56% to 49% of total chl α and the 51% to 41% of total primary production in the N. and S. Aegean Sea, respectively. Throughout the sampling area, the levels of nano+microplankton (>3.0 μm) were next in abundance proportions of total chl α (21-31%) and primary production (20-33%) and the levels of the ultraplankton (1.2-3.0 μm) were the lowest, contributing the 18-22% of total chl α and the 20-23% of total primary production. There was a highly significant ( P≤0.005-0.01) spatial, vertical and temporal influence on the biomass and productivity of all size classes in the N. Aegean and of most of them in S. Aegean. Light utilization efficiency ( ɛ%) and quantum yield ( ϕmax) exhibited a temporal trend having higher values in Spring than in Autumn as well as a trend affected by cell size, being higher for picoplankton in relation to ultraplankton and nano+microplankton. Assimilation ratios ( PB) increased with cell size. Daily primary production in the N. Aegean (81.36 mg C m -2 day -1) was higher than that in the S. Aegean (38.88 mg C m -2 day -1) but both are characterized as the most oligotrophic areas of the eastern Mediterranean.

  11. Analysis and Modeling Using Multi-Year Satellite Observations in the Aegean and Eastern Mediterranean Seas

    DTIC Science & Technology

    2006-12-01

    a network of buoys in in the Mediterranean Sea, as observed by the TOPEX/Posei R9 Aegean Sea, maintained by the Hellenic Centre for radar altimeter...Ocean Associates, 2004], including an imaging found in the circulation of the Western Mediterranean radar on the Space Shuttle. Two sources of data...numerical simu- high-resolution visible images and synthetic aperture lation of circulation by Pinardi et al. [1997] showed radar (SAR) images. that

  12. Structure of flows in the Northern Aegean Sea from a pilot drifter array

    NASA Astrophysics Data System (ADS)

    Kourafalou, V.; Olson, D.; Johns, W.; Kontoyiannis, H.; Zervakis, V.

    2003-04-01

    An array of thirty drifters deployed in the northern Aegean are used to consider the circulation in a complex archipelago of islands. The circulation of the Aegean is largely influenced by a combination of buoyancy from freshwaters introduced from the Black Sea via the Dardenelles Straits and from coastal rivers and by wind forcing. The latter is highly structured as the winds along the axis of the Aegean Sea are channeled between the orography of the Greek peninsula and islands. The above mechanisms are revealed in the drifter tracts. Preferred pathways that mark transport and exchange between the northern and southern parts of the basin are also evident. The drifters equipped with hourly GPS location and holly sock drogues provide information of time and space scales that have not been routinely sampled before. After a brief review of the overall circulation outlined by the array, the statistics of the turbulent field and its variation for the various subbasins are described. Of special interest are coastal plumes, motions induced as fluid passes between sub-basins, and the nature of cyclonic flows trapped within deep topographic pockets through the Aegean. An initial comparison of eddy statistics in relationship to wind events is also reported.

  13. Diagnostics of Cyclogenesis Over the Aegean Sea Using Potential Vorticity Inversion

    NASA Astrophysics Data System (ADS)

    Flocas, H. A.

    In this study an attempt is made to investigate comprehensively the dynamics of a case of cyclogenesis over the Aegean Sea within the context of the potential vorticity. At early stages the cyclogenesis is manifested by a large scale development at the upper levels over Adriatic Sea and Yugoslavia associated with an upper tropospheric potential vorticity anomaly. At later stages a smaller scale development was generated over Aegean Sea associated with a low-level potential vorticity anomaly and a surface warm anomaly. By means of a two-dimensional potential vorticity inversion it is demonstrated that the scale, the position and the strength of the involved anomalies contribute to the surface development, however, the low-level potential vorticity anomaly seems to constitute the most significant feature, more likely to be associated with condensation.

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

    PubMed

    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.

  15. Peracarida populations of hard substrate assemblages in ports of the NW Aegean Sea (eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Chintiroglou, C.-C.; Antoniadou, C.; Baxevanis, A.; Damianidis, P.; Karalis, P.; Vafidis, D.

    2004-02-01

    This study deals with the structure of Peracarida populations in four ports in the NW Aegean Sea, Greece, and with the degree this structure is influenced by the particular biotic and abiotic conditions that prevail in the ports. Quantitative samples were taken during summer and winter in two successive years from artificial hard substrates and were analysed using common biocoenotic methods. The examination of approximately 81,250 specimens revealed the presence of 24 Peracarida species, the most dominant of which were Corophium acutum, Leptochelia savignyi and Elasmopus rapax. All species are very common and have been reported from many sites and assemblages in the N Aegean Sea. The ratios of certain Peracarida genera are discussed as possible indicators of environmental health that may be used in long-term biomonitoring programmes on the impact of pollution in harbours.

  16. Internal wave measurements on the Cycladic Plateau of the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Alford, Matthew H.; Gregg, Michael C.; Zervakis, Vassilis; Kontoyiannis, Harialos

    2012-01-01

    The internal wave climate in the southern Aegean Sea is examined with an array of two bottom-mounted acoustic Doppler current profilers and three profiling moorings deployed on the northern continental slope of the Cretan Sea for 3 months. Frequency spectra indicate an extremely weak internal wave continuum, about 4-10 times weaker than the Garrett-Munk and Levine reference levels. Spectra are instead dominated by semidiurnal internal tides and near-inertial waves, which are examined in detail by bandpass filtering. In the semidiurnal band, a barotropic tidal flow of ≈2 cm s-1 is observed, with a pronounced spring/neap modulation in phase with the lunar fortnightly cycle. One to two days following several of these spring tide periods, a distinct internal tide featuring 10-20 m vertical displacements and 15-20 cm s-1baroclinic velocities is detectable propagating upward and to the southeast. Time-mean energy increases a factor of 2-5 within about 100 m from the bottom, implying generation and/or scattering from the bottom, whose slope is nearly critical to semidiurnal internal waves over much of the array. Several strong, downward propagating near-inertial events are also seen, each of which occurs following a period of work done by the wind on the mixed layer as estimated from a nearby surface mooring. The high-frequency internal wave continuum is more temporally constant but increases substantially toward the end of the deployment. Significant but unexplained differences in kinetic energy occur between successive spring tide periods in the case of the internal tides and between successive wind events in the case of the near-inertial signals. Substantial variability is observed in the low-frequency flows, which likely contributes to the time variability of the internal wave signals.

  17. Static Stress Changes Inverted from Microseismicity in Eastern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Leptokaropoulos, Konstantinos; Papadimitriou, Eleftheria; Orlecka-Sikora, Beata; Karakostas, Vassilios

    2014-05-01

    In this study we attempted to derive static stress field variations from the changes of earthquake production rates in Kusadasi bay and Samos island (eastern Aegean), by applying the Dieterich et al. (2000) Rate/State formulation. The calculation of stress changes from earthquake occurrence rates fluctuations should be obtained from catalogues which achieve adequate spatial and temporal resolution and well determined hypocenter coordinates. For this reason we took advantage of the data from a regional network operating since July of 2007, providing continuous monitoring of microseismicity, along with data available from seismological stations of the permanent Hellenic Unified Seismological Network (HUSN). The high accuracy and large sized regional catalogue is utilized for inverting seismicity rate changes into stress variation through a Rate/State dependent friction model. After explicitly determining the physical parameters incorporating in the modeling (reference seismicity rates, characteristic relaxation time, constitutive properties of fault zones) we investigated stress changes in both space and time regime and their possible connection with earthquake clustering and fault interactions. The main interest is focused on the June 2009 Samos Mw=5.1 event, which was followed by an intense seismic activity for several days. We attempt to reproduce and interpret stress changes both before and after the initiation of this seismic burst. The differences between the earthquake occurrence rates before and after the main shock are used as input data in a stress inversion algorithm based upon the Rate/State dependent friction concept in order to provide an estimation of stress changes. Diverse assumptions and combinations of the parameters values are tested for the model performance and sensitivity to be evaluated. The approach followed here could provide evidence of the robustness of the seismicity rate changes usage as a stress meter for both positive and negative

  18. Assessment of organotin (butyltin species) contamination in marine biota from the Eastern Aegean Sea, Turkey.

    PubMed

    Kucuksezgin, F; Aydin-Onen, S; Gonul, L T; Pazi, I; Kocak, F

    2011-09-01

    The marine environment continues to be adversely affected by tributyltin (TBT) release from maritime traffic. Therefore the concentrations of TBT, dibutyltin (DBT) and monobutyltin (MBT) were measured in barnacles, mussels and fish along the Eastern Aegean coastline. The average concentrations of TBT ng Sn g⁻¹ were found to be 235 in fish, 116 in mussels and 635 in barnacles. The highest concentrations of TBT, DBT and MBT were observed in the barnacles which had been sampled in marinas and harbors. All mussels sampled showed values of TBT+DBT, which were below the "tolerable average residue level (TARL)" as currently accepted. This indicates a lack of risk to the consumer. However, 7 out of the 15 fish sampled displayed TBT+DBT levels above the TARL, which indicates that a fish consumer group may be at risk. Barnacles have high potential as biomonitors for the presence of organotin in the Aegean Sea.

  19. A new contribution to the Late Quaternary tephrostratigraphy of the Mediterranean: Aegean Sea core LC21

    NASA Astrophysics Data System (ADS)

    Satow, C.; Tomlinson, E. L.; Grant, K. M.; Albert, P. G.; Smith, V. C.; Manning, C. J.; Ottolini, L.; Wulf, S.; Rohling, E. J.; Lowe, J. J.; Blockley, S. P. E.; Menzies, M. A.

    2015-06-01

    Tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records. Recent developments in the detection of volcanic ash (tephra) at levels where none is macroscopically visible (so-called 'crypto-tephra') have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found. In this paper, crypto-tephra extraction techniques allow the recovery of 8 non-visible tephra layers to add to the 9 visible layers in a marine sediment core (LC21) from the SE Aegean Sea to form the longest, single core record of volcanic activity in the Aegean Sea. Using a novel, shard-specific methodology, sources of the tephra shards are identified on the basis of their major and trace element single-shard geochemistry, by comparison with geochemical data from proximal Mediterranean volcanic stratigraphies. The results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka BP: 9 from Santorini; 2 or 3 from Kos, Yali, or Nisyros; 2 from the Campanian province; and one from Pantelleria. The attributions of these tephra layers indicate that 1) inter-Plinian eruptions from Santorini may have produced regionally significant tephra deposits, 2) marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes, and 3) tephra from both Pantelleria and Campania may be used to correlate marine records from the Aegean Sea to those from the Tyrrhenian, Adriatic and Ionian Seas.

  20. Reconstructing Holocene sea surface salinity changes in the Northern Aegean Sea: evidence from morphological variations of Emiliania huxleyi-coccoliths

    NASA Astrophysics Data System (ADS)

    Herrle, Jens O.; Gebühr, Christina; Bollmann, Jörg; Giesenberg, Annika; Kranzdorf, Philip

    2013-04-01

    The Aegean Sea is a key area for our understanding of the impact of changes in the hydrological cycle on ocean circulation in the Mediterranean Sea. The Aegean Sea appears to be very sensitive to climate changes in Europe because of its small volume and the position between high- and low-latitude climate regimes. Therefore, it is assumed to record environmental change, especially changes in sea surface water salinity (SSS) without a significant time lag with respect to the forcing process (Rohling et al., 2002). However, up to date, SSS cannot be easily reconstructed from geological archives because several assumptions need to be made that lead to a significant error of the salinity estimates (e.g. Rohling, 2000). Here, we present the first high resolution SSS reconstruction from a Holocene sediment core based on a recently developed transfer function using the morphological variation of Emiliania huxleyi coccoliths (Bollmann & Herrle 2007, Bollmann et al., 2009). The core is located in the northern Aegean Sea (eastern Mediterranean Basin) and covers the time period 3 -11ka ago. Sea surface water salinity in the Aegean Sea has varied in concert with temperature oscillations as recorded in Greenland ice cores (iGISP2 ice core δ18O record) with a periodicity of about 900 years (Schulz & Paull, 2002). Four major SSS events can be identified at about 3.9, 4.7, 6.4, 7.4, and 8.2 ka in the northern Aegean Sea that correlate with increases in GISP2 δ18O (Schulz & Paull, 2002) as well as decreasing percentages of tree pollen studied at the same core expect for 3.9 ka (Kotthoff et al., 2008). The most prominent salinity increase occurred during the short-lived 8.2 kyr cold event (e.g., Rohling & Pälike, 2005), which was most likely triggered by a melt-water related perturbation of the Atlantic Meridional Overturning and associated decrease of ocean heat transport to the North Atlantic. We suggest that the salinity fluctuations in the northern Aegean Sea are related to

  1. Trichoptera biodiversity of the Aegean and Adriatic sea basins in the republic of Kosovo.

    PubMed

    Ibrahimi, Halil; Kučinić, Mladen; Gashi, Agim; Grapci-Kotori, Linda

    2014-01-01

    We present the first preliminary inventory of Trichoptera taxa in the Aegean and Adriatic Sea basins in Kosovo that have previously received poor and fragmentary attention. Adult caddisflies were collected using ultraviolet (UV) light traps in 13 stations in areas of the Aegean Sea and Adriatic Sea drainage basins in Kosovo. Nineteen species out of 82, reported in this article, are first records for the Kosovo caddisfly fauna. Five genera are recorded for the first time in Kosovo: Brachycentrus, Ecclisopteryx, Psilopteryx, Thremma, and Oecetis. During this investigation, we found several Southeastern European endemic and rare species whose previous known distribution was limited to particular areas of this region, as well as other species whose distribution is considerably enlarged by this investigation: Polycentropus ierapetra, Polycentropus irroratus, Chaetopteryx stankovici, Drusus schmidi, Drusus tenellus, Potamophylax goulandriourum, Oecetis notata, and Notidobia melanoptera. Even though this article is a result of a limited sampling effort, it increases the number of Trichoptera taxa recorded for the Republic of Kosovo to 131.

  2. Exploration of the Black, Aegean, and Mediterranean Seas Aboard E/V Nautilus

    NASA Astrophysics Data System (ADS)

    Bell, K. L.; Ballard, R. D.; Brennan, M. L.; Raineault, N. A.; Shank, T. M.; Mayer, L. A.; Roman, C.; Mitchell, G. A.; Coleman, D. F.

    2012-12-01

    In the summer of 2012, the Exploration Vessel (E/V) Nautilus undertook a two-month expedition to the Black, Aegean, and Mediterranean Seas. The primary goal of the Nautilus is to create a focus of international leadership for the development and integration of leading-edge technologies, educational programs, field operations, and public outreach programs for ocean exploration, in partnership with the NOAA Office of Ocean Exploration, National Geographic Society, Office of Naval Research, and corporate partners. To do so, the program uses a complement of deep submergence vehicle systems and telepresence technologies to engage scientists, educators and the public, both at sea and ashore, allowing them to become integral members of the on-board exploration team. When discoveries are made, experts ashore are notified and brought aboard virtually within a short period of time to help guide shipboard response before the ship moves on. The 2012 expedition is comprised of four areas of interest. Extensive sidescan mapping took place off the Turkish coasts of the southern Black Sea and eastern Aegean Sea, and was followed by remotely operated vehicle (ROV) dives on targets of archaeological, geological, and biological interest. In the Black Sea, additional work was done on the porewater chemistry of the sediments in the oxic, suboxic, and anoxic zones. Nautilus returned to the Anaximander Seamounts, including Kazan, Amserdam, Thessaloniki, and Athina, to further explore active and formerly active seep sites located in 2010. Finally, based on biological and geological discoveries made on Eratosthenes Seamount in the eastern Mediterranean Sea, we returned to further study chemosynthetic vent communities and tectonic processes.;

  3. Particulate and dissolved primary production along a pronounced hydrographic and trophic gradient (Turkish Straits System-NE Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Lagaria, A.; Psarra, S.; Gogou, A.; Tuğrul, S.; Christaki, U.

    2013-06-01

    The rates of particulate (PPp) and dissolved primary production (PPd) were estimated along a trajectory of variable environmental regimes formed in a narrow shelf area, following the course of Black Sea water masses (BSW) passing through the Turkish Straits System (TSS) into the NE Aegean Sea (BS-AS outflow). Seven stations in total were sampled, covering a transect from the eastern edge of the Marmara Sea basin to the NE Aegean Sea, during two consecutive cruises performed in October 2008 within the framework of the EU SESAME project. Along the BS-AS outflow, depth-integrated over the surface BSW layer PPp decreased considerably from 91 to < 16 mg C m- 2 h- 1 whereas PPd increased from 3 to 10 mg C m- 2 h- 1. As a consequence, the relative importance of PPd over total production (percentage extracellular release, PER) increased from 6% (± 3% sd) in the Marmara Sea to 37% (± 4% sd) in the NE Aegean Sea. Total chlorophyll a concentration gradually decreased and phytoplankton community size-structure was modified, with pico-phytoplankton, that originally represented 35% (± 9% sd) in the Marmara Sea, gradually becoming dominant in the NE Aegean (77% ± 2% sd), substituting large nano- and micro-phytoplankton cells (> 5 μm). This study showed that PER increased along a gradient from mesotrophy to oligotrophy, probably due to nutrient deficiency constraining phytoplankton growth and was closely related to phytoplankton size-structure. In the oligotrophic NE Aegean Sea, phytoplankton exudation was a significant source of dissolved organic carbon for heterotrophic prokaryotes.

  4. Observed TEC Anomalies by GNSS Sites Preceding the Aegean Sea Earthquake of 2014

    NASA Astrophysics Data System (ADS)

    Ulukavak, Mustafa; Yal&ccedul; ınkaya, Mualla

    2016-11-01

    In recent years, Total Electron Content (TEC) data, obtained from Global Navigation Satellites Systems (GNSS) receivers, has been widely used to detect seismo-ionospheric anomalies. In this study, Global Positioning System - Total Electron Content (GPS-TEC) data were used to investigate ionospheric abnormal behaviors prior to the 2014 Aegean Sea earthquake (40.305°N 25.453°E, 24 May 2014, 09:25:03 UT, Mw:6.9). The data obtained from three Continuously Operating Reference Stations in Turkey (CORS-TR) and two International GNSS Service (IGS) sites near the epicenter of the earthquake is used to detect ionospheric anomalies before the earthquake. Solar activity index (F10.7) and geomagnetic activity index (Dst), which are both related to space weather conditions, were used to analyze these pre-earthquake ionospheric anomalies. An examination of these indices indicated high solar activity between May 8 and 15, 2014. The first significant increase (positive anomalies) in Vertical Total Electron Content (VTEC) was detected on May 14, 2014 or 10 days before the earthquake. This positive anomaly can be attributed to the high solar activity. The indices do not imply high solar or geomagnetic activity after May 15, 2014. Abnormal ionospheric TEC changes (negative anomaly) were observed at all stations one day before the earthquake. These changes were lower than the lower bound by approximately 10-20 TEC unit (TECU), and may be considered as the ionospheric precursor of the 2014 Aegean Sea earthquake

  5. Operational monitoring and forecasting in the Aegean Sea: system limitations and forecasting skill evaluation.

    PubMed

    Nittis, K; Zervakis, V; Perivoliotis, L; Papadopoulos, A; Chronis, G

    2001-01-01

    The POSEIDON system, based on a network of 11 oceanographic buoys and a system of atmospheric/oceanic models, provides real-time observations and forecasts of the marine environmental conditions in the Aegean Sea. The buoy network collects meteorological, sea state and upper-ocean physical and biochemical data. The efficiency and functionality of the various system components are being evaluated during the present pre-operational phase and discussed in this paper. The problem of bio-fouling on optical and chemical sensors is found to be a main limitation factor on the quality of data. Possible solutions to this problem as well as quality control methods that are being developed are also described. Finally, an evaluation of the numerical models is presented through the estimation of their forecasting skill for selected periods.

  6. The Etesian wind system and wind energy potential over the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Dafka, Stella; Xoplaki, Elena; Garcia-Bustamante, Elena; Toreti, Andrea; Zanis, Prodromos; Luterbacher, Juerg

    2013-04-01

    The Mediterranean region lies in an area of great climatic interest since it is influenced by some of the most relevant mechanisms of the global climate system. In the frame of the three Europe 2020 priorities for a smart, sustainable and inclusive economy delivering high levels of employment, productivity and social cohesion, the Mediterranean energy plan is of paramount importance at the European level, being an area with a significant potential for renewable energy from natural sources that could play an important role in responding to climate change effects over the region. We present preliminary results on a study of the Etesian winds in the past, present and future time. We investigate the variability and predictability of the wind field over the Aegean. Statistical downscaling based on several methodologies will be applied (e.g. canonical correlation analysis and multiple linear regression). Instrumental time series, Era-Interim and the 20CR reanalyses will be used. Large-scale climate drivers as well as the influence of local/regional factors and their interaction with the Etesian wind field will be addressed. Finally, the Etesian wind resources on the present and future climate will be assessed in order to identify the potential areas suitable for the establishment of wind farms and the production of wind power in the Aegean Sea.

  7. Progress of KOERI Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Ozer Sozdinler, Ceren; Yilmazer, Mehmet; Cokacar, Tulay; Comoglu, Mustafa; Pinar, Ali; Kekovali, Kivanc

    2016-04-01

    This presentation provides a progress report on the activities of the Bogazici University / Kandilli Observatory and Earthquake Research Institute - Regional Earthquake and Tsunami Monitoring Center (KOERI-RETMC) which provides services as a Candidate Tsunami Service Provider (CTSP) of ICG/NEAMTWS in the Eastern Mediterranean, Aegean and Black Seas since 1 July 2012. KOERI continues to operate 178 BB and 97 strong motion and 6 short period sensors and the regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. One radar-type tide-gauge has been installed in Fethiye within the framework of "Inexpensive Device for Sea-Level Measurement" (IDSL) initiative offered as donation by the EC/JRC and planning is in progress for the possible installation of three more IDSLs in selected locations in the Aegean Sea coast of Turkey. The capabilities and the limitations of HF Radar technology for the purpose of tsunami detection in the Eastern Mediterranean has been identified and the maturity and the applicability of these systems for the possible use under the Tsunami Warning System has been determined. The development of the TsuComp as a user-friendly interface to be used in the assessment of tsunamigenic potential and as a single-point entry for message dissemination has been finalized. The work towards the creation of Tsunami Inundation Maps at the Tsunami Forecast Points in Turkey is near finalization. This work is partially funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839. The authors would like to thank EC/JRC and Mr. Alessandro Annunziato for their continuous support in the operational activities of RETMC and IDSL initiative.

  8. 8 January 2013 Mw=5.7 North Aegean Sea Earthquake Sequence

    NASA Astrophysics Data System (ADS)

    Kürçer, Akın; Yalçın, Hilal; Gülen, Levent; Kalafat, Doǧan

    2014-05-01

    The deformation of the North Aegean Sea is mainly controlled by the westernmost segments of North Anatolian Fault Zone (NAFZ). On January 8, 2013, a moderate earthquake (Mw= 5.7) occurred in the North Aegean Sea, which may be considered to be a part of westernmost splay of the NAFZ. A series of aftershocks were occurred within four months following the mainschock, which have magnitudes varying from 1.9 to 5.0. In this study, a total of 23 earthquake moment tensor solutions that belong to the 2013 earthquake sequence have been obtained by using KOERI and AFAD seismic data. The most widely used Gephart & Forsyth (1984) and Michael (1987) methods have been used to carry out stress tensor inversions. Based on the earthquake moment tensor solutions, distribution of epicenters and seismotectonic setting, the source of this earthquake sequence is a N75°E trending pure dextral strike-slip fault. The temporal and spatial distribution of earthquakes indicate that the rupture unilaterally propagated from SW to NE. The length of the fault has been calculated as approximately 12 km. using the afterschock distribution and empirical equations, suggested by Wells and Coppersmith (1994). The stress tensor analysis indicate that the dominant faulting type in the region is strike-slip and the direction of the regional compressive stress is WNW-ESE. The 1968 Aghios earthquake (Ms=7.3; Ambraseys and Jackson, 1998) and 2013 North Aegean Sea earthquake sequences clearly show that the regional stress has been transferred from SW to NE in this region. The last historical earthquake, the Bozcaada earthquake (M=7.05) had been occurred in the northeast of the 2013 earthquake sequence in 1672. The elapsed time (342 year) and regional stress transfer point out that the 1672 earthquake segment is probably a seismic gap. According to the empirical equations, the surface rupture length of the 1672 Earthquake segment was about 47 km, with a maximum displacement of 170 cm and average displacement

  9. Biodiversity of zoobenthic hard-substrate sublittoral communities in the Eastern Mediterranean (North Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Antoniadou, Chryssanthi; Chintiroglou, Chariton

    2005-03-01

    The spatial dispersion of zoobenthos from sublittoral hard substrate communities in the northern part of the Aegean Sea has been studied during summer 1997 and 1998. Material was collected by SCUBA diving, by totally scraping off five replicate quadrates (400 cm 2 each) at three depth levels (15, 30, 40 m) from six sites located in Chalkidiki peninsula, plus one in Kavala Gulf. The examination of the 19,343 living specimens collected revealed the presence of 314 species. Though the multivariate analyses showed high similarity between stations, the structure of this sciaphilic algal community seems to have an increased spatial heterogeneity. Four distinct facies were recorded in accordance with the occurrence of different algal forms, the degree of hard substrate inclination and the water clarity. A short review on the biodiversity of sublittoral communities in the Mediterranean revealed the affinity between the western and the eastern basin and also among the photophilic and the sciaphilic algal communities.

  10. Concentration of heavy metals in seawater and sediments from the northern Aegean Sea, Greece

    SciTech Connect

    Fytianos, K; Vasilikiotis, G.S.

    1983-01-01

    The aim of the study presented was to investigate the distribution of heavy metals in seawater and sediments in areas, which face increasing marine pollution problems, due to the industrialization and especially in the closed gulfs of Thermaikos and Kavala in north Aegean sea. The city of Thessaloniki with more than 1,200,000 inhabitants and the surrounding industrial area use Thermaikos Gulf as the final receiver for their liquid wastes. The Gulf of Thermaikos receives domestic, agricultural, industrial and natural runoff from a heavily populated and fairly industrialized area. The heavy metal contamination is mainly affected by industrial wastes from oil refinery, steel industry, a fertilizer plant and some other industries located in the industrial area, west of the city.

  11. Metal levels in sediments and transplanted mussels in Pagassitikos Gulf (Aegean Sea, Eastern Mediterranean).

    PubMed

    Tsangaris, Catherine; Kaberi, Helen; Catsiki, Vassiliki-Angelique

    2013-07-01

    Metal concentrations were determined in surface sediments and transplanted mussels in a shallow semi-enclosed bay, Pagassitikos Gulf, Aegean Sea. Cu, Zn, Pb, Hg, and As levels in sediments were enriched close to point sources of pollution, i.e., Volos Port and cement plant. Fe, Mn, Cr, and Ni spatial distributions in sediments were rather uniform with increasing concentrations towards deeper sites, suggesting natural enrichment, whereas levels found in the port, although elevated, were not the highest in the study area. Spatial variations in concentrations of most metals in mussels transplanted nearshore were generally in accordance to those in sediments, with the highest Fe, Mn, Cr, Ni, and Cu levels in the port and the highest Hg levels close to the cement plant. Concentrations of metals in sediments and transplanted mussels were comparable to those reported in Mediterranean areas. Results indicate that pollution point sources contribute to anthropogenic metal enrichment in the study area.

  12. Macrofauna biodiversity of mussel bed assemblages in Thermaikos Gulf (northern Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Chintiroglou, Chariton-Charles; Damianidis, Panagiotis; Antoniadou, Chryssanthi; Lantzouni, Marina; Vafidis, Dimitris

    2004-02-01

    Biomonitoring of mussel bed assemblages can provide valuable information about the impact of pollution on hard substrate assemblages. This study of Mytilus galloprovincialis mussel beds in Thermaikos Gulf (northern Aegean Sea) deals with the spatial and temporal structure of the associated fauna. Samples were collected and abiotic factors were measured in two successive years. Common biocoenotic methods were employed to analyze the data. The samples could be separated into three groups, with summer and winter samples being clearly different. A total of 100 species were found: polychaetes and crustaceans were the most dominant taxa. The assemblage shows high diversity with respect to species abundance. Biotic interactions within the assemblage appear to influence its composition, although the total evenness remains unaffected in space and time. The M. galloprovincialis assemblages can be found in clean as well as in polluted waters and, therefore, are of great interest in biomonitoring studies.

  13. Styela plicata: a new promising bioindicator of heavy metal pollution for eastern Aegean Sea coastal waters.

    PubMed

    Aydın-Önen, S

    2016-11-01

    As part of a research project, the concentrations of Cd, Cu, Pb, V, and Zn in the tissues of Styela plicata were investigated for the first time to determine if S. plicata is a suitable biological indicator for biomonitoring of heavy metals in eastern Aegean Sea coastal waters. To examine the relationships, heavy metal levels in suspended particulate matters (SPMs) and sediments were also determined. According to the results, the mean metal levels in SPM, sediments, and S. plicata samples could be arranged in the following order of abundance: Zn > Cu > Pb > V > Cd. As for heavy metal levels, significant positive correlations were noted between Cd-Pb, Cd-V, Cd-Zn, Cu-V, and Pb-V in SPM; Cd-Zn, Cu-Zn, Pb-Cd, Pb-Cu, and Pb-Zn in sediment; and Cu-Pb, Cu-Zn, and Pb-Zn in S. plicata samples. Positive relationships between these metals showed that they were originated from same sources and that they were associated with each other. Based on the findings, Zn, Cu, and Pb concentrations in suspended particulate matters, sediments, and S. plicata samples were generally represented with higher levels at stations that were used for boating, shipping, and related activities. As S. plicata is a strongest accumulator of V, the relatively low V levels observed in this study may indicate the lack of anthropogenic sources of this metal in the sampling stations. In conclusion, suspended particulate matter and sediment can be useful tool to detect the pollution status of the marine environment. Furthermore, the findings of this study highlighted that S. plicata is a promising alternative for the monitoring of heavy metal pollution for eastern Aegean Sea coasts.

  14. Centennial-scale paleoceanography during sapropel S1 deposition in the NE Aegean (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Triantaphyllou, Maria; Gogou, Alexandra; Dimiza, Margarita; Kostopoulou, Sofia; Parinos, Constantine; Roussakis, Grigoris; Geraga, Maria; Skampa, Elisavet; Bouloubassi, Ioanna; Fleitmann, Dominik; Zervakis, Vassilis; Velaoras, Dimitris; Diamantopoulou, Antonia; Sampatakaki, Angeliki; Lykousis, Vassilis

    2016-04-01

    Combined micropaleontological and geochemical analyses in the high-sedimentation gravity core M-4G, provided new centennial scale paleoceanographic data for the sapropel S1 deposition in the NE Aegean Sea. Sapropel layer S1a (10.2-8.0 ka) is deposited in dysoxic to oxic bottom waters; sediments are characterized by the high abundance of benthic foraminifers Chilostomella mediterranensis and Globobulimina affinis that are able to tolerate surface sediment and/or pore water oxygen depletion and the presence of the oxic mesotrophic-eutrophic U. mediterranea. Adequate preservation of organic matter is proven by the high organic carbon and loliolide and isololiolide contents, whereas the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. Both alkenone-based SSTs and δO18 G. bulloides records indicate coolings at 8.2 ka (S1a) and at ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7-6.4 ka) is characterized by rather oxic conditions marked by the prominent increase of U. mediterranea. The highly fluctuating SSTs demonstrate repeated coolings and associated dense water formation; major event at 7.4 ka, followed by cold spells at 7.0, 6.8, 6.5 ka. Besides, the increase of algal biomarkers, labile organic matter-feeding foraminifera and eutrophic planktonic species pinpoints rise in in situ marine productivity, which is enhanced by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine organic matter (OM) along with fresher terrestrial OM inputs after ~7.7 ka BP imply alternative/ additional than the north Aegean riverine borderland sources for the influx of organic matter at the south Limnos Basin, also related to the inflow of highly productive Marmara/Black Sea waters

  15. Performance of Statistical Temporal Downscaling Techniques of Wind Speed Data Over Aegean Sea

    NASA Astrophysics Data System (ADS)

    Gokhan Guler, Hasan; Baykal, Cuneyt; Ozyurt, Gulizar; Kisacik, Dogan

    2016-04-01

    Wind speed data is a key input for many meteorological and engineering applications. Many institutions provide wind speed data with temporal resolutions ranging from one hour to twenty four hours. Higher temporal resolution is generally required for some applications such as reliable wave hindcasting studies. One solution to generate wind data at high sampling frequencies is to use statistical downscaling techniques to interpolate values of the finer sampling intervals from the available data. In this study, the major aim is to assess temporal downscaling performance of nine statistical interpolation techniques by quantifying the inherent uncertainty due to selection of different techniques. For this purpose, hourly 10-m wind speed data taken from 227 data points over Aegean Sea between 1979 and 2010 having a spatial resolution of approximately 0.3 degrees are analyzed from the National Centers for Environmental Prediction (NCEP) The Climate Forecast System Reanalysis database. Additionally, hourly 10-m wind speed data of two in-situ measurement stations between June, 2014 and June, 2015 are considered to understand effect of dataset properties on the uncertainty generated by interpolation technique. In this study, nine statistical interpolation techniques are selected as w0 (left constant) interpolation, w6 (right constant) interpolation, averaging step function interpolation, linear interpolation, 1D Fast Fourier Transform interpolation, 2nd and 3rd degree Lagrange polynomial interpolation, cubic spline interpolation, piecewise cubic Hermite interpolating polynomials. Original data is down sampled to 6 hours (i.e. wind speeds at 0th, 6th, 12th and 18th hours of each day are selected), then 6 hourly data is temporally downscaled to hourly data (i.e. the wind speeds at each hour between the intervals are computed) using nine interpolation technique, and finally original data is compared with the temporally downscaled data. A penalty point system based on

  16. The Sponge Community of a Subtidal Area with Hydrothermal Vents: Milos Island, Aegean Sea

    NASA Astrophysics Data System (ADS)

    Pansini, M.; Morri, C.; Bianchi, C. N.

    2000-11-01

    Sponges were sampled by SCUBA diving at six subtidal rocky sites, three of which were close to hydrothermal vents, a common feature on the sea-floor off the south-east coast of Milos. Twenty-five species (2 Calcarea and 23 Demospongiae) were found, few compared with the 589 recorded for the Mediterranean, but an important addition to the scant information on the sponge fauna of the Aegean Sea. The number of species found at vent sites was consistently higher than that found at non-vent sites, but no vent-obligate species could be identified. However, Geodia cydonium and three species of Cliona ( C. copiosa, C. nigricans and C. rhodensis) showed a tendency to colonize vent areas. The former might take advantage of increased silica availability, the latter of the enhanced deposition of carbonates near vents. Substratum cover by sponges (estimated from wire-framed photographs of 0·7 m 2), varied greatly both among and within sites, mostly according to slope. Most sponge species preferred vertical to overhanging, shaded substrata. Proximity to vents seemed to have little or no influence on sponge cover, notwithstanding a primary effect on species diversity.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Sea cliff erosion in the eastern part of the North Aegean coastline, Northern Greece.

    PubMed

    Xeidakis, George S; Delimani, P K; Skias, S G

    2006-01-01

    The coastal zone is an area where many human activities are taking place. Erosion of the coast obstructs, in various ways, these activities creating occasionally serious socioeconomic and environmental problems. In this paper the coastal erosion problems encountered in the eastern Greek part of the North Aegean Sea Coast, a stretch of about 51 km long adjacent to the city of Alexandroupolis, are discussed. Given the observed type and location of erosion and other sea-action phenomena, the coast under study is divided in two parts/stretches. The western stretch, where the city of Alexandroupolis is presently extending, presents, mainly, cliff erosion problems and retreat of the coastline, very serious in some sections; whereas, the eastern stretch (to the east of the city) exhibits deposition and progression seawards due to the abundance of sediments supplied by Evros river delta. A classification of the coastline according to its relief, geologic material, erosion characteristics and rate, slope failure phenomena as well as the wave energy potential, is presented together with suggestions for case-appropriate mitigation and protection measures regarding the coastal erosion problems. The paper is focusing on the cliff erosion phenomena, since varying in height coastal cliffs made of soft rocks, cover the major part of the investigated coastline (western stretch).

  19. Climate change effects on the marine characteristics of the Aegean and Ionian Seas

    NASA Astrophysics Data System (ADS)

    Makris, Christos; Galiatsatou, Panagiota; Tolika, Konstantia; Anagnostopoulou, Christina; Kombiadou, Katerina; Prinos, Panayotis; Velikou, Kondylia; Kapelonis, Zacharias; Tragou, Elina; Androulidakis, Yannis; Athanassoulis, Gerasimos; Vagenas, Christos; Tegoulias, Ioannis; Baltikas, Vassilis; Krestenitis, Yannis; Gerostathis, Theodoros; Belibassakis, Kostantinos; Rusu, Eugen

    2016-12-01

    This paper addresses the effects of estimated climate change on the sea-surface dynamics of the Aegean and Ionian Seas (AIS). The main aim is the identification of climate change impacts on the severity and frequency of extreme storm surges and waves in areas of the AIS prone to flooding. An attempt is made to define design levels for future research on coastal protection in Greece. Extreme value analysis is implemented through a nonstationary generalized extreme value distribution function, incorporating time harmonics in its parameters, by means of statistically defined criteria. A 50-year time span analysis is adopted and changes of means and extremes are determined. A Regional Climate Model (RegCM3) is implemented with dynamical downscaling, forced by ECHAM5 fields under 20C3M historical data for the twentieth century and the SRES-A1B scenario for the twenty-first century. Storm surge and wave models (GreCSSM and SWAN, respectively) are used for marine climate simulations. Comparisons of model results with reanalysis and field data of atmospheric and hydrodynamic characteristics, respectively, are in good agreement. Our findings indicate that the dynamically downscaled RegCM3 simulation adequately reproduces the present general circulation patterns over the Mediterranean and Greece. Future changes in sea level pressure and mean wind fields are estimated to be small, yet significant for marine extremes. In general, we estimate a projected intensification of severe wave and storm surge events during the first half of the twenty-first century and a subsequent storminess attenuation leading to the resettlement of milder extreme marine events with increased prediction uncertainty in the second half of the twenty-first century.

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

    PubMed Central

    Tserpes, George; Maravelias, Christos; Carvalho, Natacha; Merino, Gorka

    2016-01-01

    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. PMID:28033348

  1. Polychaetes associated with the sciaphilic alga community in the northern Aegean Sea: spatial and temporal variability

    NASA Astrophysics Data System (ADS)

    Antoniadou, C.; Nicolaidou, A.; Chintiroglou, C.

    2004-10-01

    Polychaete biodiversity has received little attention despite its importance in biomonitoring. This study describes polychaete diversity, and its spatial and temporal variability in infralittoral, hard substrate assemblages. Seven stations were chosen in the central area of the northern Aegean Sea. At each station, one to three depth levels were set (15, 30 and 40 m). Five replicates were collected by scuba diving with a quadrat sampler (400 cm2) from each station and depth level during summer for the spatial analysis, and seasonally for the study of temporal changes. Common biocoenotic methods were employed (estimation of numerical abundance, mean dominance, frequency, Margalef's richness, Shannon-Weaver index and Pielou's evenness). A total of 5,494 individuals, belonging to 79 species, were counted and classified. Diversity indices were always high. Clustering and multidimensional scaling techniques indicated a high heterogeneity of the stations, although these were all characterized by the sciaphilic alga community. A clear seasonal pattern was not detectable. Summer and autumn samples discriminate, while winter and spring form an even group. The abundance/biomass comparison indicated a dominance of k-strategy patterns, characteristic of stable communities.

  2. Mesozooplankton stable isotope composition in Cyprus coastal waters and comparison with the Aegean Sea (eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Hannides, Cecelia C. S.; Zervoudaki, Soultana; Frangoulis, Constantin; Lange, Manfred A.

    2015-03-01

    Here we use bulk and amino acid-specific stable nitrogen (N) isotope analysis (AA-CSIA) to evaluate seasonal and regional change in mesozooplankton dynamics for the first time in coastal waters of the eastern Mediterranean. Cyprus mesozooplankton δ15N values were significantly higher in late winter (2.3‰) than in summer (1.2‰), and in all cases were less than the δ15N values of mesozooplankton in the northeast Aegean Sea (NEA; 3.4‰). AA-CSIA indicates that these differences can primarily be attributed to seasonal and regional change in mesozooplankton community trophic structure, with overall trophic position increasing by 0.2-0.3 in winter as compared to summer around Cyprus, and trophic position higher in the NEA than in Cyprus by 0.3-0.6. Such differences are most likely related to the larger contribution of carnivorous mesozooplankton observed in winter around Cyprus and in the NEA. Overall, our findings indicate change in bulk mesozooplankton δ15N value in the eastern Mediterranean is primarily driven by change in community trophic position, rather than variability in δ15N value at the base of the food web.

  3. Offshore wind speed and wind power characteristics for ten locations in Aegean and Ionian Seas

    NASA Astrophysics Data System (ADS)

    Bagiorgas, Haralambos S.; Mihalakakou, Giouli; Rehman, Shafiqur; Al-Hadhrami, Luai M.

    2012-08-01

    This paper utilizes wind speed data measured at 3 and 10 m above water surface level using buoys at 10 stations in Ionian and Aegean Seas to understand the behaviour of wind and thereafter energy yield at these stations using 5 MW rated power offshore wind turbine. With wind power densities of 971 and 693 W/m2 at 50 m above water surface level, Mykonos and Lesvos were found to be superb and outstanding windy sites with wind class of 7 and 6, respectively. Other locations like Athos, Santorini and Skyros with wind power density of more than 530 W/m2 and wind class of 5 were found to be the excellent sites. Around 15-16% higher winds were observed at 10 m compared to that at 3 m. Lower values of wind speed were found during summer months and higher during winter time in most of the cases reported in the present work. Slightly decreasing (~2% per year) linear trends were observed in annual mean wind speed at Lesvos and Santorini. These trends need to be verified with more data from buoys or from nearby onshore meteorological stations. At Athos and Mykonos, increasing linear trends were estimated. At all the stations the chosen wind turbine could produce energy for more than 70% of the time. The wind speed distribution was found to be well represented by Weibull parameters obtained using Maximum likelihood method compared to WAsP and Method of Moments.

  4. Bacterial pollution, activity and heterotrophic diversity of the northern part of the Aegean Sea, Turkey.

    PubMed

    Çiftçi Türetken, Pelin S; Altuğ, Gülşen

    2016-02-01

    Isolation and characterization studies of marine heterotrophic bacteria are important to describe and understand eco-metobolism of the marine environments. In this study, diversity and community structures of the culturable heterotrophic bacteria, metabollicaly active bacteria and bacterial pollution in the coastal and offshore areas of Gökçeada Island, in the Northern Aegean Sea, Turkey were investigated from March 2012 to November 2013. The primary hydrographic parameters were recorded in situ. The frequency of the metabolically active bacteria was determined by using a modified staining technique. The indicator bacteria were determined by using membrane filtration technique; 126 bacteria isolates, 24 of them first records for this region, were identified using an automated micro-identification system, VITEK2 Compact30. The results showed that detected bacterial community profiles were significantly different when compared with previous studies conducted in polluted marine areas of Turkey. High frequency of faecal bacteria detected at station 2 indicated that increasing human activities and terrestrial pollution sources are shaping factors for possible risks, regarding recreational uses of this region, in the summer seasons.

  5. Macrobenthic community structure over the continental margin of Crete (South Aegean Sea, NE Mediterranean)

    NASA Astrophysics Data System (ADS)

    Tselepides, Anastasios; Papadopoulou, Konstantia-N.; Podaras, Dimitris; Plaiti, Wanda; Koutsoubas, Drosos

    2000-08-01

    Macrobenthic faunal composition, abundance, biomass and diversity together with a suite of sedimentary environmental parameters were investigated on a seasonal basis in order to determine factors regulating faunal distribution over the oligotrophic continental margin of the island of Crete (South Aegean Sea, North Eastern Mediterranean). Macrofaunal species composition was similar to that of the western Mediterranean and the neighboring Atlantic having several common dominant species. Mean benthic biomass, abundance and diversity decreased with depth, with a major transition zone occurring at 540 m, beyond which values declined sharply. At comparable depths biomass and abundance values were considerably lower to those found in the Atlantic, high-lighting the extreme oligotrophy of the area. The continental margin of Crete was characterised by a high diversity upper continental shelf environment (dominated by surface deposit feeding polychaetes) and a very low diversity slope and deep-basin environment (dominated by carnivorous and filter feeding polychaetes). Classification and ordination analyses revealed the existence of four principle clusters divided by a faunal boundary between 200 and 540 m, as well as beyond 940 m depth. Significant correlations between macrofauna and sediment parameters led to the conclusion that besides depth, food availability (as manifested by the concentration of chloroplastic pigments) is the principle regulating factor in the system. Such being the case, the prevailing hydrographic features that structure the pelagic food web and are directly responsible for the propagation of organic matter to the benthos also affect its community structure.

  6. Evolution and fluxes of 137Cs in the Black Sea/Turkish Straits System/North Aegean Sea

    NASA Astrophysics Data System (ADS)

    Delfanti, R.; Özsoy, E.; Kaberi, H.; Schirone, A.; Salvi, S.; Conte, F.; Tsabaris, C.; Papucci, C.

    2014-07-01

    The vertical profiles of 137Cs were determined in the North Aegean, Marmara and Black Seas, to assess inventories and fluxes of the radionuclide in these basins. The inventory of 137Cs in the Western Black Sea integrated from the surface down to 400 m water depth is 3.4 ± 0.1 kBq m- 2, which is surprisingly close to the amount determined in 1988, decay corrected to 2007 (2.9 ± 0.1 kBq m- 2). On the other hand, based on the comparison of profiles roughly 20 years apart, it is estimated that about 1 kBq m- 2 has been transferred from above the halocline to depths below the halocline, emphasizing the effective redistribution of tracers within the same period. We estimate that about 12 TBq y- 1 of 137Cs presently leaves the Black Sea with the upper layer flow through the Bosphorus and only 2 TBq y- 1 is returned with the lower layer inflow of Mediterranean water from the Marmara Sea. Accounting for river fluxes, estimated on the order of 2 TBq y- 1 few years after the Chernobyl accident, and possibly decreased by now, we can thus estimate a net rate of loss of about 8-10 TBq y- 1. Investigating the effective redistribution in the upper water column, the supply by the inflowing Mediterranean water alone does not explain the increase of 137Cs concentration and inventory at intermediate depths in the Western Black Sea. The most important mechanism transferring 137Cs and dissolved contaminants from the surface water to the sub-pycnocline layer appears to be the turbulent entrainment of a larger quantity of Black Sea water into the inflowing plume of Mediterranean water through mixing processes on the southwestern shelf and continental slope following its exit from the Bosphorus. This process produces an extra export of some10 TBq y- 1 of 137Cs from the surface to the sub-pycnocline depths of the Black Sea, a quantity comparable in magnitude to the total export out from the basin. It is the entrainment flux resulting from the mixing, and the further advection and

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

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter

    2015-03-01

    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 continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  8. Particulate organic carbon export fluxes and size-fractionated POC/ 234Th ratios in the Ligurian, Tyrrhenian and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Speicher, E. A.; Moran, S. B.; Burd, A. B.; Delfanti, R.; Kaberi, H.; Kelly, R. P.; Papucci, C.; Smith, J. N.; Stavrakakis, S.; Torricelli, L.; Zervakis, V.

    2006-11-01

    Measurements of 234Th/ 238U disequilibria and particle size-fractionated (1, 10, 20, 53, 70, 100 μm) organic C and 234Th were made to constrain estimates of the export flux of particulate organic C (POC) from the surface waters of the Ligurian, Tyrrhenian and Aegean Seas in March-June 2004. POC exported from the surface waters (75-100 m depth) averaged 9.2 mmol m -2 d -1 in the Ligurian and Tyrrhenian Seas (2.3±0.5-14.9±3.0 mmol m -2 d -1) and 0.9 mmol m -2 d -1 in the Aegean Sea. These results are comparable to previous measurements of 234Th-derived and sediment-trap POC fluxes from the upper 200 m in the Mediterranean Sea. Depth variations in the POC/ 234Th ratio suggest two possible controls. First, decreasing POC/ 234Th ratios with depth were attributed to preferential remineralization of organic C. Second, the occurrence of maxima or minima in the POC/ 234Th ratio near the DCM suggests influence by phytoplankton dynamics. To assess the accuracy of these data, the empirical 234Th-method was evaluated by quantifying the extent to which the 234Th-based estimate of POC flux, PPOC, deviates from the true flux, FPOC, defined as the p-ratio ( p-ratio= PPOC/FPOC= STh/SPOC, where S=particle sinking rate). Estimates of the p-ratio made using Stokes' Law and the particle size distributions of organic C and 234Th yield values ranging from 0.93-1.45. The proximity of the p-ratio to unity implies that differences in the sinking rates of POC- and 234Th-carrying particles did not bias 234Th-normalized POC fluxes by more than a factor of two.

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

    NASA Astrophysics Data System (ADS)

    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 < 20 m), (ii) their limited terrestrial sediment supply, (iii) the substantial coastal development and (iv) the limited existing coastal protection. Modeling results indeed project severe impacts under mean and episodic SLRs, which by 2100 could be devastating. For example, under MSLR of 0.5 m - representative concentration pathway (RCP) 4.5 of the Fifth Assessment 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

  10. Geochemistry of natural and anthropogenic metals in the coastal sediments of the island of Lesvos, Aegean Sea.

    PubMed

    Aloupi, M; Angelidis, M O

    2001-01-01

    The geochemistry of metals in the harbor and coastal zone of the town of Mytilene (island of Lesvos, Aegean Sea, Greece) was studied after normalization of the metal data to a conservative element. In the study area, Li was proven to be better suited than Al for such normalization and it was able to describe successfully the natural metal variability of the coastal sediments. Metal contamination (Cd, Cu, Pb, Zn) was recorded in the harbor sediments, while no pollution signs were detected in the wider coastal zone or the sediments of the ancient harbor, at the northern part of the town. The geochemical normalization of metal data to Li is a method that can detect the degree of metal contamination taking into consideration the natural metal variability in the sediments of a study area.

  11. Potential Health Hazard Assessment in Terms of Some Heavy Metals Determined in Demersal Fishes Caught in Eastern Aegean Sea.

    PubMed

    Yabanli, Murat; Alparslan, Yunus

    2015-10-01

    A heavy metal risk assessment based on estimated daily intake (EDI) and target hazard quotient was made for children and adults. Five fish species captured from the eastern Aegean Sea were analyzed for Cr, Cu, Cd, Hg and Pb by inductively coupled plasma spectroscopy in muscle tissue of red mullet (Mullus barbatus), surmullet (Mullus surmuletus), sand steenbras (Lithognathus mormyrus), common two-banded seabream (Diplodus vulgaris) and common pandora (Pagellus erythinus). The ranges for mean metal concentration (mg/kg wet wt) in the five species were 0.27-0.39 Cr, 0.12-0.22 Cu, 0.09-0.10 Hg and 0.10-0.12 Pb. All means were identical for Cd at 0.03 mg/kg wet wt. The EDI values for each metal were ascertained not to exceed the tolerable daily intake amount. Fish did not contain sufficiently high levels of these metals to pose a carcinogenic risk.

  12. Air and seawater pollution and air-sea gas exchange of persistent toxic substances in the Aegean Sea: spatial trends of PAHs, PCBs, OCPs and PBDEs.

    PubMed

    Lammel, Gerhard; Audy, Ondřej; Besis, Athanasios; Efstathiou, Christos; Eleftheriadis, Kostas; Kohoutek, Jiři; Kukučka, Petr; Mulder, Marie D; Přibylová, Petra; Prokeš, Roman; Rusina, Tatsiana P; Samara, Constantini; Sofuoglu, Aysun; Sofuoglu, Sait C; Taşdemir, Yücel; Vassilatou, Vassiliki; Voutsa, Dimitra; Vrana, Branislav

    2015-08-01

    Near-ground air (26 substances) and surface seawater (55 substances) concentrations of persistent toxic substances (PTS) were determined in July 2012 in a coordinated and coherent way around the Aegean Sea based on passive air (10 sites in 5 areas) and water (4 sites in 2 areas) sampling. The direction of air-sea exchange was determined for 18 PTS. Identical samplers were deployed at all sites and were analysed at one laboratory. hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs) as well as dichlorodiphenyltrichloroethane (DDT) and its degradation products are evenly distributed in the air of the whole region. Air concentrations of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and o,p'-DDT and seawater concentrations of p,p'-DDE and p,p'-DDD were elevated in Thermaikos Gulf, northwestern Aegean Sea. The polychlorinated biphenyl (PCB) congener pattern in air is identical throughout the region, while polybrominated diphenylether (PBDE)patterns are obviously dissimilar between Greece and Turkey. Various pollutants, polycyclic aromatic hydrocarbons (PAHs), PCBs, DDE, and penta- and hexachlorobenzene are found close to phase equilibrium or net-volatilisational (upward flux), similarly at a remote site (on Crete) and in the more polluted Thermaikos Gulf. The results suggest that effective passive air sampling volumes may not be representative across sites when PAHs significantly partitioning to the particulate phase are included.

  13. Recurrent intrusions of transitional waters of Eastern Mediterranean origin in the Cretan Sea as a tracer of Aegean Sea dense water formation events

    NASA Astrophysics Data System (ADS)

    Velaoras, Dimitris; Krokos, George; Theocharis, Alexander

    2015-06-01

    Available temperature and salinity data in the Cretan Sea from 1955 up to 2014 as well as literature sources were revisited in order to trace the appearance of low salinity, temperature, oxygen and nutrient-rich waters inside the basin at depths below the intermediate layer. First appearing as far back as 1961 in literature, these waters were found originating in the layers that separate intermediate and deep waters of the Eastern Mediterranean Sea (EMed) and were named Transitional Mediterranean Water (TMW) in the 1990s. Data analysis showed that the appearance of TMW in the Cretan Sea is a recurrent phenomenon connected to water mass exchanges between the Aegean Sea and the EMed. In particular, the inflow of TMW in the Cretan basin acts as compensation for the outflow of equally dense or denser masses from the Aegean. This export is a result of dense water formation (DWF) events taking place inside the Aegean Sea triggering TMW compensatory inflow into the Cretan Sea through the Cretan Straits. In this context, TMW intrusions in the Cretan basin can be used as a tracer of DWF in the Aegean Sea while the depth of the intrusion can provide valuable information about the intensity of the DWF event. The importance of TMW intrusions is not solely restricted to the tracing and evaluation of DWF events but could additionally expand to the impact on local ecological processes as TMW is a nutrient carrier for the oligotrophic Cretan Sea. It is obvious that this low salinity, temperature and oxygen layer is what was later named TMW. The core temperature, salinity and oxygen values reported by Miller (1974) fall within the range of values observed during the PELAGOS project in 1994, as noted in Section 'Presence of low salinity water masses below the intermediate layer in the Cretan Sea during the EMT event'. Using the same dataset provided by MEDATLAS 2002 database, a salinity transect along the Cretan Sea is reconstructed in Fig. 5. The bottle data originate from the

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

    NASA Astrophysics Data System (ADS)

    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

  15. Chemical properties and fluorescence of DOM in relation to biodegradation in the interconnected Marmara-North Aegean Seas during August 2008

    NASA Astrophysics Data System (ADS)

    Zeri, C.; Beşiktepe, Ş.; Giannakourou, A.; Krasakopoulou, E.; Tzortziou, M.; Tsoliakos, D.; Pavlidou, A.; Mousdis, G.; Pitta, E.; Scoullos, M.; Papathanassiou, E.

    2014-07-01

    The dynamics of dissolved organic matter (DOM) in the Marmara Sea-Dardanelles Straits-North Aegean Sea were investigated using measurements of dissolved organic carbon and nitrogen (DOC, DON), PARAFAC modeling of 3-D excitation-emission fluorescence spectra and bacterial production (BP) and respiration (BR) rates. In the surface brackish waters, chemical parameters showed an increase from the Aegean to the Marmara (DOC: 65-217 μmol L- 1; DON: 3.08-9.34 μmol L- 1; Dissolved Inorganic Nitrogen (DIN): 0.044-1.38), followed by an increase in BP rates (7.2-195 nmol L- 1 d- 1). In the subsurface waters, DIN also showed an increase in the Marmara basin (0.085-9.79 μmol L- 1) followed by an increase in BP rates (3.3-17.4 nmol L- 1 d- 1). PARAFAC modeling revealed three fluorescent components: λex/λem: < 260(330)/464 nm, humic-like; λex/λem: <(260) 285/364 nm, quinone-like; λex/λem: 270/308 nm, tyrosine-like. DOC:DON ratios were found similar for the Marmara (21 ± 3) and the N. Aegean Sea (19 ± 2). The slopes ΔDOC:ΔDON suggested that in the Marmara Sea mineralization processes require more carbon relative to nitrogen (22.3), whereas in the N. Aegean there is preferential removal of nitrogen over carbon (5.66). The lack of significant correlation between DOC and AOU (apparent oxygen utilization) in the deep Marmara waters indicates that particulate organic matter is important in deep mineralization processes.

  16. Review of variations in Mw < 7 earthquake motions on position and TEC (Mw = 6.5 Aegean Sea earthquake sample)

    NASA Astrophysics Data System (ADS)

    Yildirim, Omer; Inyurt, Samed; Mekik, Cetin

    2016-02-01

    Turkey is a country located in the middle latitude zone, where tectonic activity is intensive. Recently, an earthquake of magnitude 6.5 Mw occurred offshore in the Aegean Sea on 24 May 2014 at 09:25 UTC, which lasted about 40 s. The earthquake was also felt in Greece, Romania, and Bulgaria in addition to Turkey. In recent years, ionospheric anomaly detection studies have been carried out because of seismicity with total electron content (TEC) computed from the global navigation satellite system's (GNSS) signal delays and several interesting findings have been published. In this study, both TEC and positional variations have been examined separately following a moderate size earthquake in the Aegean Sea. The correlation of the aforementioned ionospheric variation with the positional variation has also been investigated. For this purpose, a total of 15 stations was used, including four continuously operating reference stations in Turkey (CORS-TR) and stations in the seismic zone (AYVL, CANA, IPSA, and YENC), as well as international GNSS service (IGS) and European reference frame permanent network (EPN) stations. The ionospheric and positional variations of the AYVL, CANA, IPSA, and YENC stations were examined using Bernese v5.0 software. When the precise point positioning TEC (PPP-TEC) values were examined, it was observed that the TEC values were approximately 4 TECU (total electron content unit) above the upper-limit TEC value at four stations located in Turkey, 3 days before the earthquake at 08:00 and 10:00 UTC. At the same stations, on the day before the earthquake at 06:00, 08:00, and 10:00 UTC, the TEC values were approximately 5 TECU below the lower-limit TEC value. The global ionosphere model TEC (GIM-TEC) values published by the Centre for Orbit Determination in Europe (CODE) were also examined. Three days before the earthquake, at all stations, it was observed that the TEC values in the time period between 08:00 and 10:00 UTC were approximately 2 TECU

  17. Review of variations in Mw < 7 earthquake motions on position and tec (Mw = 6.5 aegean sea earthquake sample)

    NASA Astrophysics Data System (ADS)

    Yildirim, O.; Inyurt, S.; Mekik, C.

    2015-10-01

    Turkey is a country located in Middle Latitude zone and in which tectonic activity is intensive. Lastly, an earthquake of magnitude 6.5Mw occurred at Aegean Sea offshore on date 24 May 2014 at 12:25 UTC and it lasted approximately 40 s. The said earthquake was felt also in Greece, Romania and Bulgaria in addition to Turkey. In recent years seismic origin ionospheric anomaly detection studies have been done with TEC (Total Electron Contents) generated from GNSS (Global Navigation Satellite System) signals and the findings obtained have been revealed. In this study, TEC and positional variations have been examined seperately regarding the earthquake which occurred in the Aegean Sea. Then The correlation of the said ionospheric variation with the positional variation has been investigated. For this purpose, total fifteen stations have been used among which the data of four numbers of CORS-TR stations in the seismic zone (AYVL, CANA, IPSA, YENC) and IGS and EUREF stations are used. The ionospheric and positional variations of AYVL, CANA, IPSA and YENC stations have been examined by Bernese 5.0v software. When the (PPP-TEC) values produced as result of the analysis are examined, it has been understood that in the four stations located in Turkey, three days before the earthquake at 08:00 and 10:00 UTC, the TEC values were approximately 4 TECU above the upper limit TEC value. Still in the same stations, one day before the earthquake at 06:00, 08:00 and 10:00 UTC, it is being shown that the TEC values were approximately 5 TECU below the lower limit TEC value. On the other hand, the GIM-TEC values published by the CODE center have been examined. Still in all stations, it has been observed that three days before the earthquake the TEC values in the time portions of 08:00 and 10:00 UTC were approximately 2 TECU above, one day before the earthquake at 06:00, 08:00 and 10:00 UTC, the TEC values were approximately 4 TECU below the lower limit TEC value. Again, by using the same

  18. Variations in fault-slip data and cooling history reveal corridor of heterogeneous backarc extension in the eastern Aegean Sea region

    NASA Astrophysics Data System (ADS)

    Ring, Uwe; Gessner, Klaus; Thomson, Stuart

    2017-03-01

    We report fault-slip data across the boundary between the highly extended and largely submerged crust underlying the Aegean Sea from Samos in the north to eastern Crete in the south, and the much less extended and emergent crust of western Anatolia. We identify three brittle deformation increments, a late Miocene (mainly Pliocene) to Recent crustal stretching increment, an intermittent early to late Miocene shortening increment concurrent with extension and magmatism, and a Miocene extensional event. The youngest increment documents late Miocene to Recent NNE extension over large areas, but can locally also be oriented SE (Amorgos and Astipalea Islands), and ESE (eastern Crete) suggesting overall oblate strain geometry. The intermittent Miocene ( 24-5 Ma) fault-slip records suggest overall prolate strain geometry, where NNE stretching is accompanied by E-W shortening. The older extension event is mainly NNE directed but on Samos Island extension is E-W, probably reflecting local extension in a sinistral wrench corridor in the early/mid Miocene. Overall it seems that since the early Miocene NNE-trending extension is the dominant regime in the eastern Aegean with an intermittent component of short-lived E-W shortening. The existence of a corridor of heterogeneous crustal deformation - which is spatially associated with uncharacteristically old fission track ages - and the apparent change in strain geometry in time challenge concepts that propose that the eastern Aegean Sea and western Anatolia have been deformed as a continuous tectonic domain since the Miocene. We propose that the regional variation in extensional strain geometry resulted from a sinistral wrench component that was superimposed on the regional 'background' NNE extension by translation across a diffuse plate boundary. We conclude that the eastern shoreline of the Aegean Sea is controlled by a Miocene to Recent sinistral wrench corridor that accommodated movement between different lithospheric domains.

  19. Temporal trends of some trace metals in Lithophaga lithophaga (L., 1758) from Izmir Bay (Eastern Aegean Sea).

    PubMed

    Ozsuer, Meral; Sunlu, Ugur

    2013-10-01

    This study compared the levels of the trace metals zinc (Zn), cadmium (Cd), lead (Pb) and copper (Cu) in the bivalve Lithophaga lithophaga from Izmir Bay (Aegean Sea) between 2001 and 2011. Comparisons were made on the basis of season, as well as year. All values were measured by voltammetry. Median values of trace metals for all seasons in 2011 were 244.67 μg Zn g(-1), 1.09 μg Cd g(-1), 7.64 μg Pb g(-1) and 56.03 μg Cu g(-1) as dry weight. The results showed a general trend of decreasing Zn, Pb and Cu concentrations over time, but an increasing trend for Cd. Mean trace metal concentrations in individuals of L. lithophaga in 2011 exceeded the permissible limit published in the Turkish Food Codex for Pb, and closely approached the limit for Zn. The mean Cd concentration was within the permissible limit of the Turkish Food Codex, but exceeded the limit of the World Health Organization. Levels of Cu were within permissible limits of published regulations.

  20. Hydrodynamic features of the South Aegean Sea as derived from Argo T/ S and dissolved oxygen profiles in the area

    NASA Astrophysics Data System (ADS)

    Kassis, Dimitris; Krasakopoulou, Evangelia; Korres, Gerasimos; Petihakis, George; Triantafyllou, George S.

    2016-11-01

    In this work, the hydrodynamic picture of the South Aegean Sea is examined through an analysis of recent measurements in its sub-basins, the Myrtoan and Cretan Sea. Both sub-basins play an important role in the water circulation, exchange, and formation processes that affect the dynamics of the whole Eastern Mediterranean. For the first time, Bio-Argo floats were deployed in the area under the Greek Argo Research Infrastructure coordination. The acquired profiles cover an almost 2-year period (November 2013-July 2015) and are compared with previous Argo profiles and the re-processed time-series data recorded from the E1-M3A POSEIDON observatory operating in the area since 2007. The spatio-temporal distribution of the physical and chemical properties in each sub-basin is examined. Dense water formation events are revealed in the northern part (Myrtoan), while the wider area can be characterized as pre-conditioned. In the Cretan basin, a strong inter-annual variability of the salinity field at intermediate and deep layers is observed that is associated with water exchange from its open boundaries. Furthermore, comparison of the dissolved oxygen (DO) distribution with physical water properties within both the mixed layer, and at greater depths, indicated that relatively high but still under-saturated DO values are more likely to be associated with convection events. Finally, an updated picture of the physical properties and the DO distribution is presented based on the last 5 years of measurements and the recent introduction of Bio-Argo floats with DO sensors in the area.

  1. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Paris, R.; Nomikou, P.; Kelfoun, K.; Leibrandt, S.; Tappin, D. R.; McCoy, F. W.

    2016-07-01

    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidence of the 1650 AD tsunami was found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits consist of an irregular 5 to 30 cm thick layer of dark grey sand that overlies pumiceous deposits erupted during the Minoan eruption and are found at depths of 30-50 cm below the surface. Composition of the tsunami sand is similar to the composition of the present-day beach sand but differs from the pumiceous gravelly deposits on which it rests. The spatial distribution of the tsunami deposits was compared to available historical records and to the results of numerical simulations of tsunami inundation. Different source mechanisms were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of 2 × 1016 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases of the eruption. Caldera subsidence is not an efficient tsunami source mechanism as short (and probably unrealistic) collapse durations (< 5 min) are needed. Pyroclastic flows cannot be discarded, but the required flux (106 to 107 m3 · s- 1) is exceptionally high compared to the magnitude of the eruption.

  2. Source of the tsunami generated by the 1650 AD eruption of Kolumbo submarine volcano (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Paris, Raphael; Nomikou, Paraskevi; Tappin, Dave

    2016-04-01

    The 1650 AD explosive eruption of Kolumbo submarine volcano (Aegean Sea, Greece) generated a destructive tsunami. In this paper we propose a source mechanism of this poorly documented tsunami using both geological investigations and numerical simulations. Sedimentary evidences of the 1650 AD tsunami were found along the coast of Santorini Island at maximum altitudes ranging between 3.5 m a.s.l. (Perissa, southern coast) and 20 m a.s.l. (Monolithos, eastern coast), corresponding to a minimum inundation of 360 and 630 m respectively. Tsunami deposits correspond to an irregular 5 to 30 cm thick layer of dark grey sand intercalated in soil at depths between 30 and 50 cm. Composition of the tsunami sand is similar to the composition of the present-day beach and clearly differs from the pumiceous gravelly soil. Spatial distribution of the tsunami deposits was confronted to available historical records and to the results of numerical simulations of tsunami inundation. Different scenarios of source mechanism were tested: earthquakes, underwater explosions, caldera collapse, and pyroclastic flows. The most probable source of the 1650 AD Kolumbo tsunami is a 250 m high water surface displacement generated by underwater explosion with an energy of ~2 E15 J at water depths between 20 and 150 m. The tsunamigenic explosion(s) occurred on September 29, 1650 during the transition between submarine and subaerial phases. Caldera subsidence is not an efficient source of tsunami, as short (and probably unrealistic) collapse durations (< 5 minutes) are needed. Pyroclastic flows cannot be discarded, but the required flux (E6 to E7 m³.s-1) is exceptionally high compared to the magnitude of the eruption.

  3. Radiometric dating of sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea.

    PubMed

    Ugur, Aysun; Miquel, Juan-Carlos; Fowler, Scott W; Appleby, Peter

    2003-05-20

    Sediment cores from a hydrothermal vent zone off Milos Island in the Aegean Sea were dated using the 210Pb method. The average unsupported 210Pb inventory in the cores was calculated to be 3256 Bq m(-2). The corresponding mean annual 210Pb flux of 105 Bq m(-2) year(-1) is comparable to estimates of the atmospheric flux given in the literature. 210Pb fluxes calculated from the unsupported 210Pb inventories in cores are also comparable with the 210Pb vertical fluxes determined from settling particles off the coast of Milos Island. The highest unsupported 210Pb concentrations (89 Bq kg(-1)) were measured in the sediments nearest to the hydrothermal vent area suggesting that the sedimentation rate is lowest at this site. Direct gamma measurements of 210Pb were used to date three sediment cores that are located at different distances from the vent zone: one is in the immediate vicinity of the vent; and others are outside the zone. Sedimentation rates for these cores, calculated using the CRS and CIC models, ranged from 0.088+/-0.008 cm year(-1) to 0.14+/-0.01 cm year(-1). Where both models were applicable, the results given by the two methods were in good agreement. 137Cs concentrations in all three cores generally declined with depth but showed no clear signal of either the period of maximum fallout from weapons testing or the Chernobyl accident. 210Po activities were also measured and the maximum 210Po concentration was in the sediment surface layer (166 Bq kg(-1)).

  4. New particle formation in the southern Aegean Sea during the Etesians: importance for CCN production and cloud droplet number

    NASA Astrophysics Data System (ADS)

    Kalkavouras, Panayiotis; Bossioli, Elissavet; Bezantakos, Spiros; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Kouvarakis, Giorgos; Protonotariou, Anna P.; Dandou, Aggeliki; Biskos, George; Mihalopoulos, Nikolaos; Nenes, Athanasios; Tombrou, Maria

    2017-01-01

    This study examines how new particle formation (NPF) in the eastern Mediterranean in summer affects CCN (cloud condensation nuclei) concentrations and cloud droplet formation. For this, the concentration and size distribution of submicron aerosol particles, along with the concentration of trace gases and meteorological variables, were studied over the central (Santorini) and southern Aegean Sea (Finokalia, Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern surface winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5 × 104 particles cm-3; the fraction of nucleation-mode particles over Crete was relatively diminished, but a higher number of Aitken-mode particles were observed as a result of aging. Aerosol and photochemical pollutants covaried throughout the measurement period; lower concentrations were observed during the period of Etesian flow (e.g., 43-70 ppbv for ozone and 1.5-5.7 µg m-3 for sulfate) but were substantially enhanced during the period of moderate surface winds (i.e., increase of up to 32 for ozone and 140 % for sulfate). We find that NPF can double CCN number (at 0.1 % supersaturation), but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number only by 12 %. Therefore, although NPF events may strongly elevate CCN numbers, the relative impacts on cloud droplet number (compared to pre-event levels) is eventually limited by water vapor availability and depends on the prevailing cloud formation dynamics and the aerosol levels associated with the background of the region.

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

    NASA Astrophysics Data System (ADS)

    Aravadinou, Eirini; Xypolias, Paraskevas; Chatzaras, Vasileios; Iliopoulos, Ioannis; Gerogiannis, Nikolaos

    2016-10-01

    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 well-preserved eclogites and blueschists. Our data show that the early, main phase (D2) of ductile deformation in the CBU occurred synchronous with the transition from prograde to close-to-peak retrograde conditions. This deformation phase took place at middle Eocene and is related to ESE-directed thrusting that emplaced the metavolcano-sedimentary subunit over the Marble subunit. The subsequent exhumation-related (D3) deformation is characterized by gently NE-plunging folds and NE-directed contractional shear zones that formed parallel to the axial planes of folds. NE-directed shearing occurred under blueschist and transitional blueschist-/greenschist-facies conditions during late Eocene-Oligocene and caused the restacking of the early nappe pile. We suggest that a mechanism of ductile extrusion of the CBU in a tectonic setting of net compression could explain better the recorded exhumation-related deformation than a mechanism of syn- and post-orogenic extension. Our new kinematic results in combination with previous works in the Cyclades area reveal a regional scale change in tectonic transport direction from (W)NW-(E)SE at Late Cretaceous-middle Eocene to (E)NE-(W)SW at late Eocene-Oligocene times. The observed change in transport direction may be governed by the relative motion of Africa with respect to Europe during Alpine orogeny.

  6. Assessment of SMOS Salinity and SST in the Aegean Sea (Greece) and correlations with MODIS SST measurements. Exploring the SSS and SST correlation to 137Cs inventory

    NASA Astrophysics Data System (ADS)

    Sykioti, Olga; Florou, Heleni

    2014-05-01

    A program concept has been developed to utilize sea surface salinity (SSS) and sea surface temperature (SST) information for the inventory of artificial radionuclides, which are conservative and part of the sea salinity. As a pilot study, activity concentrations of 137Cs in the Aegean Sea (Greece) are combined to SMOS and other satellite data so as to develop an innovative tool for the remote radioactivity detection either for routine observations and emergency recordings. The presented first results are a part of an effort to attempt for the integration in space and time of field measurements to the respective satellite observations of salinity variations by model simulations, which might be also applicable for the prediction of the radiological impact of potential accidental events. The presented results involve the first assessment of SMOS SSS and SST measurements over the Aegean Sea. SMOS measurements are averaged over a surface of 40x40 sq km at an average distance of 100 km from the coastline. For this reason, totally thirty nine pixels from SMOS Level 2 data cover part of the Aegean Sea. Two time series are created that include all available measurements spanning December 2011 to current date, from descending and ascending passes, each one representing an acquisition frequency of about three days. The average SSS values in the Aegean Sea are 37-38psu following no distinct seasonal pattern. A general trend of increasing values is observed from north to south. Noise and uncertainty in the measurements are most probably due to land and RFI contamination. High island density is combined with radiofrequency interferences generated by illegal man-made emissions. The latter is a detected common issue in specific areas worldwide, such as the Mediterranean Sea. On the other hand, SST follows a clear typical seasonal variation pattern with maximum values observed in August and minimum ones around March and a general trend of increasing values from north to south

  7. Depositional environment, foraminifer content and ESR ages of Quaternary Gediz Delta Sediments (Eastern Aegean Sea, İzmir-Western Turkey)

    NASA Astrophysics Data System (ADS)

    Gökçe Benli, Ekin; Aydın, Hülya; İşintek, İsmail; Engin, Birol; Şengöçmen, Berna

    2016-04-01

    Sediments and fossil content of Gediz Delta (Eastern Aegean Sea - İzmir) were examined based on the drilling core samples of the YSK-C and SK-246 drilling. W-SW part of the Delta is represented by continental delta sediments up to 6 meters and shallow marine detritic sediments up to 35 meters in the YSK-C drilling. Continental part consists of an soiled, graveled, muddy and sandy sediment in terms of rich organic substance. As for marine part, it consists of bioclast, muddy, fine graveled sand and by repetition of pebble, sand and bioclast bearing mud layers. Bioclasts comprise of bivalvia, echinoid, ostracod, gastropod, foramifer and bryozoa fragments. Benthic foraminiferal fauna determinated in the marine levels are represented by 55 bethic, 2 planktonic species. These foraminifers and bioclasts reflect that the W-SW part of the delta, has been occured in marine conditions between 8-31m deep. E-NE part of the delta is generally represented by continental sediments up to 43.5m in SK-246 drilling. In addition, it includes marine levels in 18-19 m, 23-24 m and 36-37,5 m intervals. Continental sediments of E-NE part is generally represented by calcareous and sandy mud rocks which mostly includes ash, tuff, and pebble derived from Neogene volcanic rocks. As for marine levels, it is composed of calcareous mud stones and calcareous clay stones including very thin gastropod, bivalvia and ostracod in 18- 19 and 36-37.5 meters whereas it is represented by sandy mud stones including a great deal of bentic foraminifer, bivalvia, bryozoa, echinoid, gastropod in 23-24 metres. Thus show that E-NE part of the delta is usually in continental condition but it is occasionally covered by sea. In aging studies of YSK-C core done by ESR method, age of 8-9 m interval is determined to be 11. 376 ± 0,067 Ka; however ages of 10-11m and 24-25 m intervals are revealed to be 16.466 ± 0,016 Ka and 15.344 ± 0,021 Ka respectively; finally age of 25-26 m interval is found to be 19.995 ± 0

  8. Levels of (210)Po in some commercial fish species consumed in the Aegean Sea coast of Turkey and the related dose assessment to the coastal population.

    PubMed

    Aközcan, S

    2013-04-01

    Concentrations of (210)Po were determined in the edible muscle tissue of five species of marine fish: Sardine (Sardine plichardus) and Anchovy (Engraulis encrasicolus), Red mullet (Mullus barbatus), Horse mackerel (Trachurus trachurus) and Gilt-head sea bream (Sparus aurata) collected from five stations in the Aegean Sea Region of Turkey during the fishery season 2010. The (210)Po concentrations in the fish samples were found to vary from not detected levels to 389 ± 45 Bq kg(-1) dry wt. These variations in (210)Po content in different species are probably due to differences in metabolism and feeding patterns. The highest levels for (210)Po were observed in Anchovy (E. encrasicolus) species.

  9. Measurement of light scattering in deep sea

    NASA Astrophysics Data System (ADS)

    Maragos, N.; Balasi, K.; Domvoglou, T.; Kiskiras, I.; Lenis, D.; Maniatis, M.; Stavropoulos, G.

    2016-04-01

    The deep-sea neutrino telescope in the Mediterranean Sea, being prepared by the KM3NET collaboration, will contain thousands of optical sensors to readout. The accurate knowledge of the optical properties of deep-sea water is of great importance for the neutrino event reconstruction process. In this study we describe our progress in designing an experimental setup and studying a method to measure the parameters describing the absorption and scattering characteristics of deep-sea water. Three PMTs will be used to measure in situ the scattered light emitted from six laser diodes in three different wavelengths covering the Cherenkov radiation spectrum. The technique for the evaluation of the parameters is based on Monte Carlo simulations and our results show that we are able to determine these parameters with satisfying precision.

  10. Electromagnetic Scattering from a Ship at Sea

    DTIC Science & Technology

    1978-09-01

    each sub-area is represented by a polarization transforming reflec- tion coefficient derived from the bistatic radar cross-section of the patch. The...from the sea and a ship with conical hull. Hollow cone antenna pattern is used. SAH=00 , ATA=609, polarization is horizontal ...................... .. 2...I ix1 60 Total scattered signature from the sea and a ship with conical hull. Hollow c8ne antenna pattern is used. SAH=450, ATA=60 polarization is

  11. April 16, 2015 Crete Island Earthquake (Mw=5.9) Series and its Seismotectonic Significance, Southern Aegean Sea

    NASA Astrophysics Data System (ADS)

    Yalçın, Hilal; Kürçer, Akın; Gülen, Levent

    2016-04-01

    The active deformation of the southern Aegean Sea is a result of the northward motion of the African and Arabian Plates with respect to the Eurasian Plate in the Eastern Mediterranean Region. The Hellenic subduction zone plays a key role in the active tectonics of the region. On 16 April, 2015, a moderate earthquake occurred on the eastern part of Hellenic arc (south of Crete island), with a moment magnitude of Mw=5.9. A series of aftershocks were occurred within four months following the mainshock, which have magnitudes varying from Mw = 3.4 to 5.4. Source parameters of the 16 April 2015 earthquake have been modeled in order to reveal the regional stress tensor and the tectonic style of the region. In this study, the source parameters of the main shock and 36 aftershocks that have magnitudes M≥3.4 have been determined and modeled by seismic moment tensor waveform inversion method developed by Sokos and Zahradnik (2006) algorithm using the near-field and regional waveforms. The depth of earthquakes are varied from 2 to 61 km. Stress tensor can describe reliably principle stress axes (σ1, σ2, σ3), their relative size and stress field variations. Stress tensor inversions have been carried out using the Micheal method (1984, 1987). In this study, 16 April 2015 Crete Earthquake mainshock (Mw=5.9), a total of 36 earthquake moment tensor solutions that belong to the Crete earthquake sequence and 24 earthquake moment tensor solutions of previous main shocks in the region have been compiled and used in the stress inversion calculation. Orientations of σ1, σ2 and σ3 were computed and the principal directions are projected onto a lower hemisphere Wulff net. The best fit was attained for Phi = 0.38+/-0.13609 and indicated that the stress regime revealed strike-slip faulting with reverse component and for the azimuth and plunge pair of (-161.6°, 21.7°) for σ1, (-11.1°, 65.4°) for σ2 and (103.8°, 10.9°) for σ3. At the final step of the study, Gutenberg and

  12. Seismicity and active tectonics at Coloumbo Reef (Aegean Sea, Greece): Monitoring an active volcano at Santorini Volcanic Center using a temporary seismic network

    NASA Astrophysics Data System (ADS)

    Dimitriadis, I.; Karagianni, E.; Panagiotopoulos, D.; Papazachos, C.; Hatzidimitriou, P.; Bohnhoff, M.; Rische, M.; Meier, T.

    2009-02-01

    The volcanic center of Santorini Island is the most active volcano of the southern Aegean volcanic arc. Α dense seismic array consisting of fourteen portable broadband seismological stations has been deployed in order to monitor and study the seismo-volcanic activity at the broader area of the Santorini volcanic center between March 2003 and September 2003. Additional recordings from a neighbouring larger scale temporary network (CYCNET) were also used for the relocation of more than 240 earthquakes recorded by both arrays. A double-difference relocation technique was used, in order to obtain optimal focal parameters for the best-constrained earthquakes. The results indicate that the seismic activity of the Santorini volcanic center is strongly associated with the tectonic regime of the broader Southern Aegean Sea area as well as with the volcanic processes. The main cluster of the epicenters is located at the Coloumbo Reef, a submarine volcano of the volcanic system of Santorini Islands. A smaller cluster of events is located near the Anydros Islet, aligned in a NE-SW direction, running almost along the main tectonic feature of the area under study, the Santorini-Amorgos Fault Zone. In contrast, the main Santorini Island caldera is characterized by the almost complete absence of seismicity. This contrast is in very good agreement with recent volcanological and marine studies, with the Coloumbo volcanic center showing an intense high-temperature hydrothermal activity, in comparison to the corresponding low-level activity of the Santorini caldera. The high-resolution hypocentral relocations present a clear view of the volcanic submarine structure at the Coloumbo Reef, showing that the main seismic activity is located within a very narrow vertical column, mainly at depths between 6 and 9 km. The focal mechanisms of the best-located events show that the cluster at the Coloumbo Reef is associated with the "Kameni-Coloumbo Fracture Zone", which corresponds to the

  13. Suspended particulate matter estimates using optical and acoustic sensors: application in Nestos River plume (Thracian Sea, North Aegean Sea).

    PubMed

    Anastasiou, Sotiria; Sylaios, Georgios K; Tsihrintzis, Vassilios A

    2015-06-01

    The present study investigates the use of combined methods of optical and acoustic sensors, in collaboration with direct in situ measurements, for the calibration and validation of a model transforming acoustic backscatter intensity series into suspended particulate matter (SPM) concentration datasets. The model follows previously elaborated techniques, placing particular attention to the parameterization of the acoustic absorption index as a function of water physical properties. Results were obtained from the annual deployment (during 2007-2008) of an upward-facing acoustic Doppler current profiler (ADCP) (307 kHz), equipped with a Wave Array, and an optical backscatter sensor (OBS), at the bottom of Thassos Passage near Nestos River plume (Thracian Sea, Northern Greece). The OBS was calibrated through linear regression, using 2007 and 2012 field sampling data, exhibiting an error of 13-14 % due to chlorophyll presence. The ADCP signal was calibrated through simultaneous measurements of backscatter intensity and turbidity profiles. Harmonic analysis on the model-produced SPM concentrations explained the tidal influence on their variability, especially during the summer. Empirical orthogonal functions analysis revealed the impact of waves and wave-induced currents on SPM variability. Finally, Nestos River sediment load was found uncorrelated to the SPM change in Thassos Passage, due to the dispersal and sediment deposition near the river mouth.

  14. Investigation of heavy metal pollution in eastern Aegean Sea coastal waters by using Cystoseira barbata, Patella caerulea, and Liza aurata as biological indicators.

    PubMed

    Aydın-Önen, S; Öztürk, M

    2017-01-19

    In order to have an extensive contamination profile of heavy metal levels (Cd, Cu, Fe, Mn, Ni, Pb, and Zn), seawater, sediment, Patella caerulea, Cystoseira barbata, and Liza aurata were investigated by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Samples were collected from five coastal stations along the eastern Aegean Sea coast (Turkey) on a monthly basis from July 2002 through May 2003. According to the results of this study, heavy metal levels were arranged in the following sequence: Fe > Pb > Zn > Mn > Ni > Cu > Cd for water, Fe > Cu > Mn > Ni > Zn > Pb > Cd for sediment, Fe > Zn > Mn > Pb > Ni > Cd > Cu for C. barbata, Fe > Zn > Mn > Ni > Pb > Cu > Cd for P. caerulea, and Fe > Zn > Mn > Cu > Ni > Pb > Cd for L. aurata. Moreover, positive relationships between Fe in water and Mn in water, Fe in sediment and Mn in sediment, Fe in C. barbata and Mn in C. barbata, Fe in P. caerulea and Mn in P. caerulea, and Fe in L. aurata and Mn in L. aurata may suggest that these metals could be originated from the same anthropogenic source. C. barbata represented with higher bioconcentration factor (BCF) values, especially for Fe, Mn, and Zn values. This observation may support that C. barbata can be used as an indicator species for the determinations of Fe, Mn, and Zn levels. Regarding Turkish Food Codex Regulation's residue limits, metal values in L. aurata were found to be lower than the maximum permissible levels issued by Turkish legislation and also the recommended limits set by FAO/WHO guidelines. The results of the investigation indicated that P. caerulea, L. aurata, and especially C. barbata are quantitative water-quality bioindicators and biomonitoring subjects for biologically available metal accumulation for Aegean Sea coastal waters.

  15. Eastern-Mediterranean ventilation variability during sapropel S1 formation, evaluated at two sites influenced by deep-water formation from Adriatic and Aegean Seas

    NASA Astrophysics Data System (ADS)

    Filippidi, A.; Triantaphyllou, M. V.; De Lange, G. J.

    2016-07-01

    Present-day bottom-water ventilation in the Eastern Mediterranean basin occurs through deep-water convection originating from the two marginal basins, i.e. Adriatic and Aegean Seas. In the paleo record, long periods of enhanced deep-water formation have been alternating with shorter periods of reduced deep-water formation. The latter is related mainly to low-latitude humid climate conditions and the enhanced deposition and preservation of organic-rich sediment units (sapropels). This study focuses on sedimentary archives of the most-recent sapropel S1, retrieved from two sites under the direct influence of the two deep-water formation areas. Restricted oxygen conditions have developed rapidly at the beginning of S1 deposition in the Adriatic site, but bottom-water conditions have not persistently remained anoxic during the full interval of sapropel deposition. In fact, the variability in intensity and persistence of sedimentary redox conditions at the two deep-water formation sites is shown to be related to brief episodes of climate cooling. In the Adriatic site, sapropel deposition appears to have been interrupted twice. The 8.2 ka event, only recovered at the Adria site, is characterized by gradually increasing suboxic to possibly intermittently oxic conditions and decreasing Corg fluxes, followed by an abrupt re-establishment of anoxic conditions. Another important event that disrupted sapropel S1 formation, has taken place at ca. 7.4 cal ka BP. The latter event has been recovered at both sites. In the Adriatic site it is followed by a period of sedimentary conditions that gradually change from suboxic to more permanently oxic, as deduced from the Mn/Al pattern. Using the same proxy for suboxic/oxic sedimentary redox conditions, we observe that conditions in the Aegean Sea site shift to more permanently oxic from the 7.4 ka event onwards. However, at both sites the accumulation and preservation of enhanced amounts of organic matter have continued under these

  16. Implementation of a reduced order Kalman filter to assimilate ocean color data into a coupled physical-biochemical model of the North Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Kalaroni, Sofia; Tsiaras, Kostas; Economou-Amilli, Athena; Petihakis, George; Politikos, Dimitrios; Triantafyllou, George

    2013-04-01

    Within the framework of the European project OPEC (Operational Ecology), a data assimilation system was implemented to describe chlorophyll-a concentrations of the North Aegean, as well the impact on the European anchovy (Engraulis encrasicolus) biomass distribution provided by a bioenergetics model, related to the density of three low trophic level functional groups of zooplankton (heterotrophic flagellates, microzooplankton and mesozooplankton). The three-dimensional hydrodynamic-biogeochemical model comprises two on-line coupled sub-models: the Princeton Ocean Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). The assimilation scheme is based on the Singular Evolutive Extended Kalman (SEEK) filter and its variant that uses a fixed correction base (SFEK). For the initialization, SEEK filter uses a reduced order error covariance matrix provided by the dominant Empirical Orthogonal Functions (EOF) of model. The assimilation experiments were performed for year 2003 using SeaWiFS chlorophyll-a data during which the physical model uses the atmospheric forcing obtained from the regional climate model HIRHAM5. The assimilation system is validated by assessing the relevance of the system in fitting the data, the impact of the assimilation on non-observed biochemical parameters and the overall quality of the forecasts.

  17. Old stories and lost pieces of the Eastern Mediterranean puzzle: a new approach to the tectonic evolution of the Western Anatolia and the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Yaltırak, Cenk; Engin Aksu, Ali; Hall, Jeremy; Elitez, İrem

    2015-04-01

    During the last 20 or so years, the tectonic evolution of Aegean Sea and Western Anatolia has been dominantly explained by back-arc extension and escape tectonics along the North Anatolian Fault. Various datasets have been considered in the construction of general tectonic models, including the geometry of fault patterns, paleomagnetic data, extensional directions of the core complexes, characteristic changes in magmatism and volcanism, the different sense of Miocene rotation between the opposite sides of the Aegean Sea, and the stratigraphy and position of the Miocene and Pliocene-Quaternary basins. In these models, the roles of the Burdur-Fethiye Shear Zone, the Trakya-Eskişehir Fault Zone, the Anaximander Mountains and Isparta Angle have almost never been taken into consideration. The holistic evaluation of numerous land and marine researches in the Aegean Sea and western Anatolia suggest the following evolutionary stages: 1. during the early Miocene, Greece and western Anatolia were deformed under the NE-SW extensional tectonics associated with the back-arc extension, when core complexes and supra-detachment basins developed, 2. following the collision of the Anaximander Mountains and western Anatolia in early Miocene , the Isparta Angle locked this side of the western arc by generating a triangle-shaped compressional structure, 3. while the Isparta Angle penetrated into the Anatolia, the NE-striking Burdur-Fethiye Shear Zone in the west and NW-striking Trakya-Eskişehir Fault Zone in the north developed along the paleo-tectonic zones , 4. the formation of these two tectonic structures allowed the counterclockwise rotation of the western Anatolia in the middle Miocene and this rotation removed the effect of the back-arc extension on the western Anatolian Block, 5. the counterclockwise rotation developed with the early westward escape of the Western Anatolian reached up to 35-40o and Trakya-Eskişehir Fault Zone created a total dextral displacement of about 200

  18. Marine pollution risk in a coastal city: use of an eco-genotoxic tool as a stress indicator in mussels from the Eastern Aegean Sea.

    PubMed

    Kacar, Asli; Pazi, Idil; Gonul, Tolga; Kucuksezgin, Filiz

    2016-08-01

    Coastal areas, such as bays, estuaries, and harbors, are heavily polluted since these areas are the settlements to which toxic chemicals from industrial and domestic wastes are discharged. The genetic damage was evaluated using bioindicator mussel Mytilus galloprovincialis caused by toxic chemicals (metals and polycyclic aromatic hydrocarbons) in İzmir and Çandarlı Bays (the Eastern Aegean Sea) through comet assay. Three sampling sites from the two bays were selected and the study was conducted during the spring and autumn periods. The highest levels of DNA damage expressed as %Tail-DNA were observed in İzmir Bay (34.60 % Tail-DNA) in the spring. Analysis of the correlation between PAHs and metals in mussels and %T-DNA in the hemolymph and gill cells showed a statistically significant positive correlation between %T-DNA and ∑PAH, chromium (p < 0.05). This study determined the pollution level of the İzmir and Çandarlı Bays by using the DNA damage to the mussel, which can identify the effects of environmental pollutants at the cellular levels. These results confirm that comet assay can be used to determine the temporal and spatial differences of DNA damage, and as a suitable tool for the measurement of genotoxicity in regions with low pollutant concentrations.

  19. Long-term monitoring of the impact of a capture-based bluefin tuna aquaculture on water column nutrient levels in the Eastern Aegean Sea, Turkey.

    PubMed

    Aksu, Mehmet; Kaymakçi-Başaran, Asli; Egemen, Ozdemir

    2010-12-01

    Capture-based aquaculture of Atlantic bluefin tuna in the Mediterranean has been expanding rapidly but little is known about its environmental impact. In order to understand the consequences of this new sector, long-term monitoring is needed. For this purpose, we investigated the impact of a capture-based tuna farm located in the Gerence Bay (Aegean Sea) on the water column on a seasonal basis from 2005 to 2008, where in the water column, temperature, salinity, pH, dissolved oxygen, nutrients (nitrite, nitrate, ammonium, and phosphate), and chlorophyll a, in the sediment organic carbon variables were measured. Although highest nutrient concentrations were observed at the cage station as compared to the two controls in the production period, differences were not statistically significant between stations. Monitoring of physico-chemical parameters, nutrients, and chlorophyll a in water column together with organic carbon in sediment did not show detectable impact of fattening of Atlantic bluefin tuna. This was probably caused by strong currents present in the area, location of the cages away from the coast, hence high water depth, controlled feeding, and periodic presence of tuna farming activity in the study area.

  20. [Multiple scattering of visible and infrared light by sea fog over wind driving rough sea surface].

    PubMed

    Sun, Xian-Ming; Wang, Hai-Hua; Lei, Cheng-Xin; Shen, Jin

    2013-08-01

    The present paper is concerned with computing the multiple scattering characteristics of a sea fog-sea surface couple system within this context. The single scattering characteristics of sea fog were studied by Mie theory, and the multiple scattering of sunlight by single sea fog layer was studied by radiative transfer theory. The reflection function of a statistically rough ocean surface was obtained using the standard Kirchhoff formulation, with shadowing effects taken into account. The reflection properties of the combined sea fog and ocean surface were obtained employing the adding method, and the results indicated that the reflected light intensity of sea fog increased with the sea background.

  1. A new metamorphic map of Syros Island (Aegean Sea, Greece): implications for strain localization from prograde to retrograde path

    NASA Astrophysics Data System (ADS)

    Laurent, Valentin; Jolivet, Laurent; Roche, Vincent; Augier, Romain; Scaillet, Stéphane; Cardello, Luca

    2015-04-01

    The Aegean domain is located in the eastern part of the Mediterranean and has undergone a complex Alpine history that can be summarized in two successive episodes: (1) The formation of the Hellenides-Taurides belt due to the convergence between Eurasia and Africa; during this episode, a series of oceanic and continental nappes entered the subduction zone and were thrust on top of each other in a HP-LT metamorphic context. (2) From 35-30 Ma, an acceleration of slab retreat led to the collapse of the belt and the formation of large detachments. The island of Syros (Cycladic Blueschists belt) is worldwide known for the excellent preservation of HP-LT tectonic and metamorphic features associated with these processes, possibly providing one of the best places to study the deformation and metamorphic evolution of the subduction interface. Syros has recorded a complex deformation history during both the prograde and retrograde phase that resulted in the juxtaposition of two main units: (1) the Cycladic Blueschists Unit (CBU), and (2) the Vari unit cropping out in the SE of the island. Conflicting tectonic interpretations have been proposed to explain the evolution of the island, in part reflecting the lack of consensus about the detailed tectonic structure of the CBU. A new geological and metamorphic map of Syros is proposed to better characterize the different structures related to prograde and/or retrograde deformation stages. High-resolution field-mapping, combined with detailed structural-petrological observations, allows us to subdivide the CBU into three sub-units separated by major ductile shear zones. From top to bottom, these are: 1) the Kampos, 2) the Chroussa, and 3) the Posidonia units. Each of these units experienced similar peak eclogite-facies conditions (ca. 20 kbar - 550 °C), variably overprinted under blueschist- and greenschist-facies conditions across the nappe pile. New ductile structures have been discovered. Among those, a new large-scale top

  2. Tectono-stratigraphic evolution through successive extensional events of the Anydros Basin, hosting Kolumbo volcanic field at the Aegean Sea, Greece

    NASA Astrophysics Data System (ADS)

    Nomikou, P.; Hübscher, C.; Ruhnau, M.; Bejelou, K.

    2016-03-01

    The structural evolution of the South Aegean Sea is little explored due to the lack of marine seismic data. Our present day understanding is mainly based on some island outcrops and GPS measurements. In this study we discuss the rather incremental opening of the Anydros Basin in the Pliocene during six major tectonic pulses and the subsequent basin fill processes by interpreting seismic data and derived time isochore maps. Between the active pulses basin floor tilting persisted on a much lower rate. Seismic data illustrate the depositional processes in the emerging Anydros Basin. The observation of onlap fill strata, divergent reflection pattern, moat channels and contourite drifts imply that deposition was controlled by turbidity and contour currents as well as the tilting basin floor. The metamorphic Attico-Cycladic basement shows a rise that aligns along an NW-SE directed axis crossing Anydros island. This axis marks a structural change of the Santorini-Amorgos Ridge and thus represents a major structural boundary. Dip angles of NE-SW trending major faults, like the Santorini-Amorgos Fault, indicate normal faulting to be the superior mechanism forming the present horst and graben environment. Hence, the area is likely to be in a state of NW-SE directed extensional stresses forming the asymmetric graben structure of Anydros. Secondary fault clusters strike the same direction but show much steeper dip angles, possibly indicating strike-slip movement or resulting from deformational stresses along the hinge zones of the normal faults. The majority of the faults we discovered are located in the area of earthquake clusters, which is another indication of recent faulting. Ring faults around Kolumbo submarine volcano, result from caldera collapse and mark the diameter of the magma chamber approximately to 20 km.

  3. Distribution and diversity of sulfur-oxidizing Thiomicrospira spp. at a shallow-water hydrothermal vent in the Aegean Sea (Milos, Greece).

    PubMed

    Brinkhoff, T; Sievert, S M; Kuever, J; Muyzer, G

    1999-09-01

    A shallow-water hydrothermal vent system in the Aegean Sea close to the island of Milos (Greece) was chosen to study the diversity and distribution of the chemolithoautotrophic sulfur-oxidizing bacterium Thiomicrospira. Cell numbers in samples from different regions around a solitary vent decreased toward the center of the vent (horizontal distribution), as well as with depth (vertical distribution), corresponding to an increase in temperature (from ca. 25 to 60 degrees C) and a decrease in pH (from ca. pH 7 to 5). Thiomicrospira was one of the most abundant culturable sulfur oxidizers and was even dominant in one region. Phylogenetic analysis of Thiomicrospira spp. present in the highest most-probable-number (MPN) dilutions revealed that most of the obtained sequences grouped in two new closely related clusters within the Thiomicrospira branch. Two different new isolates, i.e., Milos-T1 and Milos-T2, were obtained from high-dilution (10(-5)) enrichments. Phylogenetic analysis indicated that isolate Milos-T1 is related to the recently described Thiomicrospira kuenenii and Hydrogenovibrio marinus, whereas isolate Milos-T2 grouped with the MPN sequences of cluster 2. The predominance of strain Milos-T2 was indicated by its identification in several environmental samples by hybridization analysis of denaturing gradient gel electrophoresis (DGGE) patterns and by sequencing of one of the corresponding bands, i.e., ML-1, from the DGGE gel. The results shown in this paper support earlier indications that Thiomicrospira species are important members of hydrothermal vent communities.

  4. Geomorphological characteristics of the onshore/offshore volcanic edifices with respect to their evolutionary stage in the South Aegean Sea, Greece.

    NASA Astrophysics Data System (ADS)

    Carey, S.; Nomikou, P.; Papanikolaou, D.; Alexandri, M.

    2014-12-01

    Volcanism in the South Aegean Sea first occurred about 3-4 million years ago, along four different volcanic island groups, including both onshore and recently discovered offshore volcanoes: 1) Starting from the west, the Methana group consists of the Methana stratovolcano, composed exclusively of volcaniclastics and lavas, creating cones and domes onland and the Paphsanias submarine cone in the Epidavros tectonic graben, bordered by E-W normal faults. It has a 2 km basal diameter at 400 m depth and its top rises to 150 m. 2) The Milos-Antimilos group consists of volcanic domes and calderas onland and three submarine domes to the east of Antimilos. A hydrothermal vent field is limited in the SE coastal zone of Milos, 3) The Santorini group consists of: (i) the older volcanic cones of Christianna islets and three submarine domes east of them, (ii) Santorini volcano which during the last 500 ka experienced repeated caldera collapses following Plinian eruptions and edifice rebuilding, represented by the growth of the Kamenes islands after the last catastrophic Late Bronze age eruption. (iii) a chain of about twenty submarine volcanic domes and craters in the Kolumbo zone northeast of Santorini. Kolumbo volcano is a 3 km diameter cone with a 1500 m wide crater, a crater rim as shallow as 18 m depth and a flat crater floor at 505 m depth containing an active hydrothermal vent field degassing 99% of CO2. 4) The Kos-Nisyros group at the eastern edge of the Hellenic Volcanic arc, comprises several domes and craters offshore and Nisyros volcano consists exclusively of alternating lava and pyroclastic deposits following several phases of reconstruction and caldera collapse. The rhyodacitic domes of Profitis Ilias are the latest evolutionary stage of Nisyros volcano which disrupted a pre-existed caldera and may be regarded as an earlier reconstruction phase similar to the Kameni islands at Santorini. The volcanic relief reaches 1100-1200 m in most cases. This is produced from

  5. Normalization to lithium for the assessment of metal contamination in coastal sediment cores from the Aegean Sea, Greece.

    PubMed

    Aloupi, M; Angelidis, M O

    2001-07-01

    Sediment cores from the harbour and the coastal zone of Mytilene, island of Lesvos, Greece, were used to study the metal contamination caused by the discharge of untreated urban effluents into the sea. In the harbour. the upper layers were highly enriched in Cd, Cu, Pb and Zn, while no metal enrichment was recorded in the cores from the wider coastal zone. The metal data were normalized to Li (conservative element) to compensate for the natural textural and mineralogical variability. It was found that only the upper 18 cm of the core collected from the harbour of Mytilene could be reported as metal contaminated. Also, through the normalization procedure, it was found that the surface layers of coastal sediments assumed 'clean' were enriched in Pb, probably as a result of atmospheric transportation of the metal from the nearby town.

  6. Evaluation of sediment contamination by monoaromatic hydrocarbons in the coastal lagoons of Gulf of Saros, NE Aegean Sea.

    PubMed

    Ünlü, Selma; Alpar, Bedri

    2017-03-19

    The concentrations and distribution of monoaromatic hydrocarbons (benzene, toluene, ethyl benzene and the sum of m-, p- and o-, xylenes) were determined in the sediments of coastal lagoons of the Gulf of Saros, using a static headspace GC-MS. The total concentrations of BTEX compounds ranged from 368.5 to below detection limit 0.6μgkg(-1) dw, with a mean value of 61.5μgkg(-1) dw. The light aromatic fraction of m-, p-xylene was the most abundant compound (57.1% in average), and followed by toluene (38.1%)>ethylbenzene (4.1%)>o-xylene (2.5%)>benzene (1.1%). The factor analysis indicated that the levels and distribution of BTEX compounds depend on the type of contaminant source (mobile/point), absorbance of compounds in sediment, and mobility of benzene compound and degradation processes. Point sources are mainly related to agricultural facilities and port activities while the dispersion of compounds are related with their solubility, volatility and effect of sea/saline waters on lagoons.

  7. New boron isotopic evidence for sedimentary and magmatic fluid influence in the shallow hydrothermal vent system of Milos Island (Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Wu, Shein-Fu; You, Chen-Feng; Lin, Yen-Po; Valsami-Jones, Eugenia; Baltatzis, Emmanuel

    2016-01-01

    Magmatic sources may contribute a significant amount of volatiles in geothermal springs; however, their role is poorly understood in submarine hydrothermal systems worldwide. In this study, new results of B and δ11B in 41 hydrothermal vent waters collected from the shallow hydrothermal system of Milos island in the Aegean Sea were combined with previously published data from other tectonic settings and laboratory experiments to quantify the effects of phase separation, fluid/sediment interaction and magmatic contribution. Two Cl-extreme solutions were identified, high-Cl waters (Cl as high as 2000 mM) and low-Cl waters (Cl < 80 mM). Both sets of waters were characterized by high B/Cl (~ 1.2-5.3 × 10- 3 mol/mol) and extremely low δ11B (1.4-6.3‰), except for the waters with Mg content of near the seawater value and δ11B = 10.3-17.4‰. These high-Cl waters with high B/Cl and low δ11B plot close to the vent waters in sediment-hosted hydrothermal system (i.e., Okinawa Trough) or fumarole condensates from on-land volcanoes, implying B addition from sediment or magmatic fluids plays an important role. This is in agreement with fluid/sediment interactions resulting in the observed B and δ11B, as well as previously reported Br/I/Cl ratios, supporting a scenario of slab-derived fluid addition with elevated B, 11B-rich, and low Br/Cl and I/Cl, which is derived from the dehydration of subducted-sediments. The slab fluid becomes subsequently mixed with the parent magma of Milos. The deep brine reservoir is partially affected by injections of magmatic fluid/gases during degassing. The results presented here are crucial for deciphering the evolution of the brine reservoirs involved in phase separation, fluid/sediment interaction and magmatic contribution in the deep reaction zone of the Milos hydrothermal system; they also have implications in the understanding of the formation of metallic vein mineralization.

  8. Aquatic animal resources in Prehistoric Aegean, Greece.

    PubMed

    Mylona, Dimitra

    2014-12-01

    This paper explores the early stages in the history of fishing in the Aegean Sea in Greece, and highlights its formative phases and its specific characteristics in different points in time. This is testified by various physical remains, such as fish bones, fishing tools, and representations in art, which are gathered in the course of archaeological research. The aquatic resources in the Aegean Sea have been exploited and managed for millennia by communities that lived near the water and often made a living from it. The earliest evidence for a systematic, intensive exploitation of marine resources in the Aegean Sea dates to the Mesolithic, eleven millennia ago. In the Neolithic period, the adoption of a sedentary, agro-pastoral way of life led to a reduction in the intensity of fishing and shellfish gathering. Its importance as an economic resource remained high only in certain regions of rich, eutrophic waters. In the Bronze Age, an era of social complexity and centralized economy, the exploitation of aquatic, mostly marine, resources became a complex, multi-faceted activity which involved subsistence, industry and ideology. The range of preferred fish and invertebrate species, the fishing technology, and the processing of fish and shellfish in order to produce elaborate foods or prestige items are all traceable aspects of the complex relationship between humans and the aquatic resources throughout the prehistory of fishing and shellfish gathering in the Aegean area. The broadening of collaboration between archaeology and physical sciences offers new means to explore these issues in a more thorough and nuanced manner.

  9. Two component mie scattering models of sargasso sea particles.

    PubMed

    Brown, O B; Gordon, H R

    1973-10-01

    The volume scattering function is calculated for particle suspensions consisting of two components systematically distributed in a manner consistent with Coulter Counter observations in the Sargasso Sea. The components are assigned refractive indices 1.01-0.01i and 1.15 to represent organic and inorganic particles, respectively. The only models found that reproduce observed scattering functions require a considerable fraction of the suspended particle volume to be organic in nature. This fraction, however, contributes less than 10% to the total scattering function. The model finally chosen indicates that the inorganic particles smaller than 2.5 micro do not occur in large enough concentrations to have a significant effect on the volume scattering function.

  10. Geochemistry of mylonitic gneisses from the Cycladic Basement Unit (Paros and Serifos, Aegean Sea): implications for protoliths of the high-grade gneisses

    NASA Astrophysics Data System (ADS)

    McGrath, Annette; Stouraiti, Christina; Windley, Brian

    2016-10-01

    The nature of the protolith(s) of high-grade gneisses from the Aegean Cycladic Basement Unit of the islands of Paros and Serifos is investigated using whole-rock geochemistry and Sr-Nd-O isotopes, in order to better understand their origin and to compare with possible equivalents from the southern Aegean region. On Paros, the basement unit consists of heterogeneous, mylonitized upper amphibolite-grade paragneisses and associated migmatitic rocks, whereas on Serifos, it consists of a mylonitized felsic gneiss, intercalated with layers and lenses of S-type leucogranites and minor mafic metavolcanics. New Nd, Sr and O isotope data suggest a predominantly crustal-derived source in the gneiss protolith from both islands: high initial 87Sr/86Sr ratios (≥7052 to 0.711, calculated at 300 Ma), negative initial ɛNd (-2.8 to -7.7) values for bulk-rock gneiss samples, and high δ18O values of quartz separates (+10 to +12.7 ‰). Major and trace-element variations corroborate that chemical differentiation within the NW Paros gneiss subunit results from progressive migmatitization. Peraluminous gneisses from eastern Paros share clear similarities with metapelitic gneisses from the Naxos gneiss dome, in terms of their trace-element patterns, ɛNd (300) and O isotope characteristics. The mineral assemblage, the fine grain size (due to intense mylonitization), and the metaluminous affinity of the South Serifos grey quartzofeldpathic gneiss do not allow for an unambiguous interpretation for these undated rocks; however, a combination of geochemical parameters and tectonic discrimination diagrams indicates an immature siliciclastic (greywacke) protolith from a continental island arc setting. Sr-Nd isotopic systematics indicates an increasing lower crustal component in gneisses from NW Paros, which is closer to the migmatitic core of the Paros dome. The overall isotopic trend of the gneissic Cycladic Basement Unit on Paros is spatially correlated with that of the Naxos gneiss dome.

  11. Wild fire effects on floristic diversity in three thermo-Mediterranean vegetation types in a small islet of eastern Aegean sea

    NASA Astrophysics Data System (ADS)

    Abraham, Eleni; Kyriazopoulos, Apostolos; Korakis, George; Parissi, Zoi; Chouvardas, Dimitrios

    2014-05-01

    Sclerophyllus scrub formations, the main vegetation type in many islands of the Aegean area, are characterized by their high biodiversity. Dominant shrub species of sclerophyllus formations are well adapted to dry season conditions by various anatomical and physiological mechanisms. As a result, their biomass acts as very flammable fine fuel, and consequently wild fires are very common in these ecosystems. Wildfire effects on vegetation and biodiversity in the Mediterranean basin have been studied and the results are diverse depending mainly on vegetation type and frequency of fire. The aim of this study was to evaluate the effects of wildfire on floristic diversity and species composition in three thermo-Mediterranean vegetation types 1) Sacropoterium spinosum phrygana, 2) low formations of Cistus creticus and 3) low formations of Cistus creticus in abandoned terraces. The research was conducted in Enoussa islet, which is located northeastern of Chios Island, in May 2013 (one year after the fire). Vegetation sampling was performed along five transects placed in recently burned and in adjacent unburned sites of each vegetation type. The plant cover and the floristic composition were measured, while diversity, evenness and dominance indices were determined for the vegetation data. Vegetation cover and the floristic diversity were significant lower and higher respectively in burned areas in comparison to the unburned. The woody species followed by the annual grasses and the annual forbs dominated in both burned and unburned areas. However, the woody species were significantly decreased in the burned areas in all vegetation types, while the annual grasses only in the burned areas of Sacropoterium spinosum phrygana and Cistus creticus in abandoned terraces. Inversely, the annual forbs significantly increased in the burned sites of Cistus creticus formations. The highest value of Morisita-Horn Index of similarity between burned and unburned sites (beta diversity) was

  12. Accuracy of Sea Surface Topography with GPS Scattered Signals

    NASA Astrophysics Data System (ADS)

    Zuffada, C.; Zavorotny, V. U.; Lowe, S.

    2001-12-01

    The concept of using GPS reflected signals for ocean and land remote sensing is based on the use of one airborne (or space-based) GPS receiver working simultaneously with a constellation of several signal-transmitting GPS satellites. This would offer an advantage in terms of spatial coverage compared to a conventional monostatic radar system and possibly allow new scientific applications to be pursued. However, the limited power of GPS transmitters and a relatively low surface cross section would require either large receiving antennas or longer integration times to optimize the signal-to-noise ratio. Analogously to the case of a conventional radar altimeter, the reflected GPS signal acquired by the receiver is the average power versus time (a range measurement) and generally represents the contributions from surfaces which scatter incoherently. This waveform is derived as a function of viewing geometry, system parameters, surface roughness and dielectric properties of underlying covers. This work investigates the spatial-temporal coherence properties and statistics of the measured reflected GPS signal that describes variability from one sample to another. This information is needed to choose an optimal strategy for a successful signal processing. We examine the above-mentioned properties of the modeled received power as a function of surface state and scattering geometry. Its impact on the accuracy of sea surface topography, both from airborne and orbital platforms is addressed. A characterization of error and expected spatial resolution in relation to existing instruments is discussed. Furthermore, in examining the coherence time, we analyze the spectral behavior of the reflected signal versus sea state parameters, such as wind vector. In addition, we compare the predictions with data available from recent airplane measurements taken in the Pacific Ocean off the coast of Southern California obtaining preliminary validations of our models.

  13. An autonomous underwater telescope for measuring the scattering of light in the deep sea

    NASA Astrophysics Data System (ADS)

    Balasi, K. G.; Domvoglou, T.; Kiskiras, I.; Lenis, D.; Maniatis, M.; Maragos, N.; Stavropoulos, G.

    2016-05-01

    The KM3NeT research infrastructure will be a deep sea multidisciplinary observatory in the Mediterranean Sea housing a neutrino telescope. Accurate knowledge of the optical properties of the sea water is important for the performance evaluation of the telescope. In this work we describe the deployment of the equipment that we had previously examined by Monte Carlo (MC) simulationsl, in the context of the scattering experiment in order to evaluate the parameters describing the scattering characteristics of the sea water. Four photomultipliers (PMTs) were used to measure in situ the scattered light emitted by six laser diodes in three different wavelengths covering the Cherenkov radiation spectrum.

  14. An integrated multi-parameter monitoring approach for the quantification and mitigation of the climate change impact on the coasts of Eastern Crete, S. Aegean Sea (Project AKTAIA)

    NASA Astrophysics Data System (ADS)

    Ghionis, George; Alexandrakis, George; Karditsa, Aikaterini; Sifnioti, Dafni; Vousdoukas, Michalis; Andreadis, Olympos; Petrakis, Stelios; Poulos, Serafim; Velegrakis, Adonis; Kampanis, Nikolaos; Lipakis, Michalis

    2014-05-01

    The AKTAIA project aims at the production of new knowledge regarding the forms of manifestation of the climate change and its influence on the stability and evolution of the coastal landforms along the shoreline of eastern Crete (approximate length: 757 km), taking into account the various aspects of human intervention. Aerial photographs, satellite images and orthophotomaps have been used to produce a detailed coastline map and to study the morphological characteristics of the coastal zone of Eastern Crete. More than 100 beach zones have been visited during three field campaigns, which included geomorphological and human intervention mapping, topographic, meteorological and oceanographic measurements and sedimentological sampling and observations. In addition, two pilot sites (one in the north and one in the south part of Crete) are being monitored, via the installation of coastal video monitoring systems, shore-based meteorological stations and wave-tide recorders installed in the nearshore zone. Detailed seafloor mapping with the use of side scan sonar and scuba diving and bathymetric surveys were conducted in the two pilot sites. Meteorological and oceanographic data from all existing land-based meteorological stations, oceanographic buoys and the ERA-interim dataset are used to determine the wind and wave climate of each beach. The collected climatic, sedimentological and coastal environmental data are being integrated in a GIS database that will be used to forecast the climatic trends in the area of Crete for the next decades and to model the impact of the climatic change on the future evolution of the coastal zone. New methodologies for the continuous monitoring of land-sea interaction and for the quantification of the loss of sensitive coastal zones due to sea-level rise and a modified Coastal Vulnerability Index for a comparative evaluation of the vulnerability of the coasts are being developed. Numerical modelling of the nearshore hydrodynamics and the

  15. New constraints on the active tectonic deformation of the Aegean

    USGS Publications Warehouse

    Nyst, M.; Thatcher, W.

    2004-01-01

    Site velocities from six separate Global Positioning System (GPS) networks comprising 374 stations have been referred to a single common Eurasia-fixed reference frame to map the velocity distribution over the entire Aegean. We use the GPS velocity field to identify deforming regions, rigid elements, and potential microplate boundaries, and build upon previous work by others to initially specify rigid elements in central Greece, the South Aegean, Anatolia, and the Sea of Marmara. We apply an iterative approach, tentatively defining microplate boundaries, determining best fit rigid rotations, examining misfit patterns, and revising the boundaries to achieve a better match between model and data. Short-term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long-term kinematics. We find that present day Aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them. The RMS misfit of model to data is about 2-sigma, very good when compared to the typical match between coseismic fault models and GPS data. The simplicity of the microplate description of the deformation and its good fit to the GPS data are surprising and were not anticipated by previous work, which had suggested either many rigid elements or broad deforming zones that comprise much of the Aegean region. The isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions. Strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain/year (nstrain/year, 10-9/year), 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries. Lower strain rates may exist elsewhere withi the microplates but are only resolved in Anatolia, where extension of 13 ?? 4 nstrain/ year is required by the data. Our results suggest that despite the detailed complexity of active continental deformation

  16. Investigation on the GPS single scattering from a 2-D largescale sea surface

    NASA Astrophysics Data System (ADS)

    Wei, Yiwen; Guo, Lixin

    2014-05-01

    Global positioning system (GPS) signals reflected from the ocean surface can be used for various remote sensing purposes. In this paper, we develop a facet model to simulate the received GPS single from a 2-D largescale sea surface. In this model, the sea surface is envisaged as a two-scale profile on which the long waves are locally approximated by planar facets. The microscopic profile within a facet is assumed to be represented by a set of sinusoidal ripple patches. The complex reflective function of each modified facet is evaluated by a modified formula of the original Bass and Fuks' two-scale model, in which the phase factor of each facet is with the capillary wave modification. The scattering field and the bistatic scattering coefficient of facet model is derived in detail. With received GPS single, we give a detail analysis of the polarization property, the scattering property of GPS scattering signal over the sea surface.

  17. Report on Scattering Physics of Multistatic Radar Sea Clutter

    DTIC Science & Technology

    2014-05-30

    clutter & targets, and assessing detection schemes using the observations and the results of data analysis. The panel recognises the potential value ...similar (as they should be, since they are based on some of the same data), whilst the GIT model has much smaller values of reflectivity at low sea...When the power is summed over range, averaged over many surface realisations and recalculated at various grazing angles and rms sea surface wave

  18. The recovery of microwave scattering parameters from scatterometric measurements with special application to the sea

    NASA Technical Reports Server (NTRS)

    Claassen, J. P.; Fung, A. K.

    1975-01-01

    As part of an effort to demonstrate the value of the microwave scatterometer as a remote sea wind sensor, the interaction between an arbitrarily polarized scatterometer antenna and a noncoherent distributive target was derived and applied to develop a measuring technique to recover all the scattering parameters. The results are helpful for specifying antenna polarization properties for accurate retrieval of the parameters not only for the sea but also for other distributive scenes.

  19. Low-Frequency Scattering from Heterogeneous Sea Beds

    DTIC Science & Technology

    2012-09-30

    4th Internat. Conf. Underwater Acoustic Measurements: Technology and Results (UAM2011), J.S. Papadakis and L. Bjorno (Eds), pp. 1615-1622. 14. A.N...Measurements: Technology and Results (UAM2011), J.S. Papadakis and L. Bjorno (Eds), pp. 1615-1622. A. N. Ivakin (2011), “Sound scattering from the ocean

  20. Observation of pressure ridges in SAR images of sea ice: Scattering theory and comparison with observations

    NASA Technical Reports Server (NTRS)

    Vesecky, J. F.; Daida, J. M.; Shuchman, R. A.; Onstott, R. H.; Camiso, J. C.

    1993-01-01

    Ridges and keels (hummocks and bummocks) in sea ice flows are important in sea ice research for both scientific and practical reasons. Sea ice movement and deformation is driven by internal and external stresses on the ice. Ridges and keels play important roles in both cases because they determine the external wind and current stresses via drag coefficients. For example, the drag coefficient over sea ice can vary by a factor of several depending on the fluid mechanical roughness length of the surface. This roughness length is thought to be strongly dependent on the ridge structures present. Thus, variations in ridge and keel structure can cause gradients in external stresses which must be balanced by internal stresses and possibly fracture of the ice. Ridging in sea ice is also a sign of fracture. In a practical sense, large ridges form the biggest impediment to surface travel over the ice or penetration through sea ice by ice-strengthened ships. Ridges also play an important role in the damage caused by sea ice to off-shore structures. Hence, observation and measurement of sea ice ridges is an important component of sea ice remote sensing. The research reported here builds on previous work, estimating the characteristics of ridges and leads in sea ice from SAR images. Our objective is to develop methods for quantitative measurement of sea ice ridges from SAR images. To make further progress, in particular, to estimate ridge height, a scattering model for ridges is needed. Our research approach for a ridge scattering model begins with a survey of the geometrical properties of ridges and a comparison with the characteristics of the surrounding ice. For this purpose we have used airborne optical laser (AOL) data collected during the 1987 Greenland Sea Experiment. These data were used to generate a spatial wavenumber spectrum for height variance for a typical ridge - the typical ridge is the average over 10 large ridges. Our first-order model radar scattering includes

  1. Measurement and Interpretation of North Atlantic Ocean Marine Radar Sea Scatter

    DTIC Science & Technology

    1988-05-31

    direction. The radar sea echo maximizes symmetrically about the wind direction, and this echo max - imum was used to select the region of scatter to be...Technology Society, Washington, D.C., 1984 pp. 134-137. 7. D.C. Scheler , "Radar Detection .. i Weibull Clutter," IEEE Trans., AES-12, 736-743 (1976). 8. J

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

    PubMed

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

    2008-09-27

    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 <5.2 Ma). These ecologically fairly homogenous islands thus provide a suitable biogeographic context for assessing the relative influences of past range fragmentation, colonization, gene flow and drift on taxon diversification. Indeed, recent molecular biogeographic studies on the Aegean Nigella arvensis complex, combining phylogenetic, phylogeographic and population level approaches, exemplify the importance of allopatry and genetic drift coupled with restricted gene flow in driving plant speciation in this continental archipelago at different temporal and spatial scales. While the recent (Late Pleistocene) radiation of Aegean Nigella, as well as possible instances of incipient speciation (in the Cyclades), is shown to be strongly conditioned by (palaeo)geographic factors (including changes in sea level), shifts in breeding system (selfing) and associated isolating mechanisms have also contributed to this radiation. By contrast, founder event speciation has probably played only a minor role, perhaps reflecting a migratory situation typical for continental archipelagos characterized by niche pre-emption because of a long established resident flora. Overall, surveys of neutral molecular markers in Aegean Nigella have so far revealed population genetic processes that conform remarkably well to predictions raised by genetic drift theory. The challenge is now to gain more direct insights into the relative importance of the role of genetic drift, as opposed to natural selection, in the phenotypic and reproductive divergence among these Aegean plant

  3. Estimates of oceanic surface wind speed and direction using orthogonal beam scatterometer measurements and comparison of recent sea scattering theories

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Fung, A. K.; Dome, G. J.; Birrer, I. J.

    1978-01-01

    The wind direction properties of radar backscatter from the sea were empirically modelled using a cosine Fourier series through the 4th harmonic in wind direction (referenced to upwind). A comparison with 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data, at incidence angles of 40 and 65, indicates that effects to third and fourth harmonics are negligible. Another important result is that the Fourier coefficients through the second harmonic are related to wind speed by a power law expression. A technique is also proposed to estimate the wind speed and direction over the ocean from two orthogonal scattering measurements. A comparison between two different types of sea scatter theories, one type presented by the work of Wright and the other by that of Chan and Fung, was made with recent scatterometer measurements. It demonstrates that a complete scattering model must include some provisions for the anisotropic characteristics of the sea scatter, and use a sea spectrum which depends upon wind speed.

  4. The spreading of the Chernobyl signature from the North Aegean waters to the Eastern Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Papucci, C.; Delfanti, R.; Lorenzelli, R.; Zervakis, V.; Georgopoulos, D.

    2003-04-01

    The Chernobyl accident (26 April 1986) produced a patchy deposition of radionuclides over the Eastern and Northern basins of the Mediterranean Sea, that was superimposed over the previous fallout from atmospheric nuclear weapon tests. The deposition of Chernobyl-derived 137Cs was particularly heavy onto the Black Sea (3000 TBq) and the Aegean -- Ionian Seas along the Greek coasts (800 TBq). Moreover, as the Black Sea still receives a delayed input of Chernobyl 137Cs from the rivers Danube and Dniepr, the output of surface water through the Dardanelles Straits constitutes a "permanent" point source of this conservative radionuclide into the North Aegean Sea. The water exiting the Dardanelles undergoes mixing with North Aegean surface water. Due to its low salinity this water acts as an insulation layer and, consequently, deep-water formation is rather infrequent in the North Aegean, taking place only at periods of reduced Black Sea outflow and/or exceptionally cold and dry winters. In the last 20 years there have been two major deep-water formation events in the North Aegean: in winter 1987 (just after the Chernobyl accident), and in winter 1993. Actually, these two episodes have deeply modified the vertical profiles of 137Cs with respect to 1984, before the Chernobyl accident. In 1999--2001, in the (isolated from advection) Lemnos and N-Skyros Basins, the 137Cs concentration increased from the surface to the bottom; in the deep waters it was about 5 Bq m-3, five times higher than in 1984. These deep waters formed in 1993, are characterised by high salinity and density and their major contributor was water of Levantine/Cretan origin. The Chernobyl input also caused a considerable increase in 137Cs concentrations in the Cretan Deep Waters flowing through the Antikythera Strait: the typical concentration in this water mass was, in 1999, 2.5 -- 2.8 Bq m-3, almost three times higher than that in the deep Cretan basin in 1984. This strong signal is spreading in the

  5. Nonlinear scattering of acoustic waves by natural and artificially generated subsurface bubble layers in sea.

    PubMed

    Ostrovsky, Lev A; Sutin, Alexander M; Soustova, Irina A; Matveyev, Alexander L; Potapov, Andrey I; Kluzek, Zigmund

    2003-02-01

    The paper describes nonlinear effects due to a biharmonic acoustic signal scattering from air bubbles in the sea. The results of field experiments in a shallow sea are presented. Two waves radiated at frequencies 30 and 31-37 kHz generated backscattered signals at sum and difference frequencies in a bubble layer. A motorboat propeller was used to generate bubbles with different concentrations at different times, up to the return to the natural subsurface layer. Theoretical consideration is given for these effects. The experimental data are in a reasonably good agreement with theoretical predictions.

  6. Characteristics of 13.9 GHz radar scattering from oil films on the sea surface

    NASA Technical Reports Server (NTRS)

    Johnson, J. W.; Croswell, W. F.

    1982-01-01

    Aircraft microwave scatterometer measurements are presented, which were made in 1979 as part of a project to study the response of a number of active and passive microwave and optical remote sensors to an oil-covered sea surface conducted by NASA Langley Research Center. A 13.9-GHz Doppler scatterometer with a fan beam antenna and coherent detection was used to measure radar backscatter as a function of incidence angle. The radar scattering signature of the clear surface and signatures of the surface covered with various crude oil films are compared. Reductions in Ku band microwave backscatter up to 14 dB are observed for both treated and untreated LaRosa and Murban crude oil films deposited on the sea surface. Maximum Ku band sensitivity to the effects of the oil in terms of differential scatter is observed in the 25-35 deg incidence angle region.

  7. Evolution of freshwater crab diversity in the Aegean region (Crustacea: Brachyura: Potamidae).

    PubMed

    Jesse, Ruth; Grudinski, Melanie; Klaus, Sebastian; Streit, Bruno; Pfenninger, Markus

    2011-04-01

    The aim of this study was to estimate the influence of the palaeogeographic and climatic history of the Aegean region on the diversity of freshwater crabs of the genus Potamon and to test whether this area served as source or reservoir in species diversity. Necessary species delimitation was accomplished by phylogenetic analyses of the mitochondrial markers COX1 and ND1, partial 16S rRNA gene and the tRNALeu gene. We found 14 genetic lineages of which nine could be assigned to previously recognised species. Temporal estimates of the splitting pattern in the phylogeny of Potamon indicated that a combination of geological and climatic events influenced their diversification. Within Potamon, the lineages separated into a western group and an eastern group. This first split in the genus occurred approximately 8.3-5.5 Mya, thus possibly correlated with the Messinian salinity crisis. A likelihood approach to geographic range evolution suggested for most species, occurring in the Aegean area, an origin in the Middle East. Moreover, there were no insular endemics in the central Aegean archipelago, therefore low sea-levels during the Pleistocene glacial periods possibly enabled dispersal to these islands, but subsequent rise in sea-level did not cause speciation. Nevertheless, the diversification of most lineages occurred during the Pleistocene epoch thus coinciding with Quaternary fluctuations of the climate.

  8. High-Resolution Radar Scattering Characteristics of a Disturbed Sea Surface and Floating Debris

    DTIC Science & Technology

    1977-07-29

    theoretically and experimentally. Oil drums, logs, and aluminum-covered plastic gallon milk bottles were considered and measured. A comparison of the echoing...covered plastic bottle ,38 N R tEPO R1 8 131 0 DBSM L LJ v ’ da) B 6 GH1 0 DSM -- DBSM ib) 9.2 GHz Ils Fig. 29 - Vertically polarized return from wave...j2 ’ NRL Report 8131 (~High-Resolution Radar Scattering Characteristics of a Disturbed Sea Surface and Floating Debris B. L. LEWIS. J. P. HANSEN. 1

  9. Measurements and modeling of the volume scattering function in the coastal northern Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Berthon, Jean-François; Shybanov, Eugeny; Lee, Michael E.-G.; Zibordi, Giuseppe

    2007-08-01

    We performed measurements of the volume scattering function (VSF) between 0.5° and 179° with an angular resolution of 0.3° in the northern Adriatic Sea onboard an oceanographic platform during three different seasons, using the multispectral volume scattering meter (MVSM) instrument. We observed important differences with respect to Petzold's commonly used functions, whereas the Fournier-Forand's analytical formulation provided a rather good description of the measured VSF. The comparison of the derived scattering, bp(λ) and backscattering, bbp(λ) coefficients for particles with the measurements performed with the classical AC-9 and Hydroscat-6 showed agreement to within 20%. The use of an empirical relationship for the derivation of bb(λ) from β(ψ,λ) at ψ=140° was validated for this coastal site although ψ=118° was confirmed to be the most appropriate angle. The low value of the factor used to convert β(ψ,λ) into bb(λ) within the Hydroscat-6 processing partially contributed to the underestimation of bb(λ) with respect to the MVSM. Finally, use of the Kopelevich model together with a measurement of bp(λ) at λ=555 nm allowed us to reconstruct the VSF with average rms percent differences between 8 and 15%.

  10. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios

    2016-04-01

    We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 2 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ~2°C at 1832 ± 15 yr AD could be related to the 1809 ΑD 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The palaeoclimatic evidence derived from M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death likely

  11. Climate variability and socio-environmental changes in the northern Aegean (NE Mediterranean) during the last 1500 years

    NASA Astrophysics Data System (ADS)

    Gogou, Alexandra; Triantaphyllou, Maria; Xoplaki, Elena; Izdebski, Adam; Parinos, Constantine; Dimiza, Margarita; Bouloubassi, Ioanna; Luterbacher, Juerg; Kouli, Katerina; Martrat, Belen; Toreti, Andrea; Fleitmann, Dominik; Rousakis, Gregory; Kaberi, Helen; Athanasiou, Maria; Lykousis, Vasilios

    2016-03-01

    We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 1 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ∼2 °C at 1832 ± 15 yr AD could be related to the 1809 ΑD 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The paleoclimatic evidence derived from the M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death

  12. Raman scattering and fluorescence spectra of water from the sea surface microlayer

    NASA Astrophysics Data System (ADS)

    Fadeev, V. V.; Burikov, S. A.; Volkov, P. A.; Lapshin, V. B.; Syroeshkin, A. V.

    2009-04-01

    The Raman scattering and fluorescence spectra were first obtained for the water of sea surface microlayers (SML) of 1 and 0.2 mm thickness (sampled with a Garrett net and a Lapshin capillary sampler, respectively). For reference, samples of water below the SML (from the layer of 0.5 m) were also taken. Substantial differences were found for the values of the normalized intensity of the fluorescence (the number of photons from the volume unit in response to a unit of excitation) between the aqueous humic substances and, presumably, oil hydrocarbons and proteins. Some slight but analyzable differences in the shapes and location of spectral bands were also found. These latter allow one to determine the content of salts and the characteristics of complicated organic compounds in the SML and to compare them to those within the water volume.

  13. Aegean tectonics, a record of slab-overriding plate interactions (Invited)

    NASA Astrophysics Data System (ADS)

    Jolivet, L.; Faccenna, C.; Huet, B.; Lecomte, E.; Labrousse, L.; Denèle, Y.; Le Pourhiet, L.; Lacombe, O.; Burov, E. B.; Meyer, B.; Suc, J.; Popescu, S.; Monié, P.; Philippon, M.; Gueydan, F.; Brun, J.; Paul, A.; Salaün, G.; Armijo, R.

    2010-12-01

    Two opposing visions of the Aegean backarc tectonics implicitly contain contrasting images of the rheological behaviour of the lihosphere, supported by different sets of observations. The propagation of the NAF and extension in the Corinth Rift suggest a strongly localising rheology whereas the formation of MCC in the Cyclades and the Rhodope suggests instead a more viscous behaviour. This paradox was the seminal question addressed by the ANR-EGEO programme (2007-2010) that leads to the following conclusions: (1) The exhumation of the Cycladic MCC’s is accommodated by the N-dipping North Cycladic Detachment System (NCDS) that partly reworks the Vardar suture and at the base by a series of thrusts, including the basal contact of the Cycladic Blueschists (CBS) over the Cycladic Basement (CB). The activity of LANF is due to the reactivation of pre-existing discontinuities such as thrusts or earlier detachments and much less to the interaction with granitic plutons. (2) Exhumation in the Cyclades has proceeded in two stages: (a) Eocene syn-orogenic exhumation within the subduction lower/upperplate interface while the post-orogenic Rhodope MCC formed further north, (b) Oligo-Miocene post-orogenic extension in an MCC mode coeval with syn-orogenic exhumation in Crete and the Peloponnese. (3) Both stages were associated with slab retreat, as early as the Eocene with an acceleration at 30-35 Ma. (4) The localisation of the presently active steeply-dipping normal faults on the southern margin of the Corinth Rift may have been preceded by a partial reworking of thrusts and syn-orogenic detachments by shallow-dipping decollements. (5) The localisation of the NAF in the Marmara Sea region and the Northern Aegean Sea is now accurately dated between 5.3 and 5 Ma Ma using the erosion and deposition surfaces that mark the Messinian salinity Crisis and nannofossils ages. (6) The formation of MCCs in the Cyclades resulted in the draining of the low viscosity lower crust from the

  14. Evolutionary processes in a continental island system: molecular phylogeography of the Aegean Nigella arvensis alliance (Ranunculaceae) inferred from chloroplast DNA.

    PubMed

    Bittkau, C; Comes, H P

    2005-11-01

    Continental shelf island systems, created by rising sea levels, provide a premier setting for studying the effects of past fragmentation, dispersal, and genetic drift on taxon diversification. We used phylogeographical (nested clade) and population genetic analyses to elucidate the relative roles of these processes in the evolutionary history of the Aegean Nigella arvensis alliance (= 'coenospecies'). We surveyed chloroplast DNA (cpDNA) variation in 455 individuals from 47 populations (nine taxa) of the alliance throughout its core range in the Aegean Archipelago and surrounding mainland areas of Greece and Turkey. The study revealed the presence of three major lineages, with largely nonoverlapping distributions in the Western, Central, and Eastern Aegean. There is evidence supporting the idea that these major lineages evolved in situ from a widespread (pan-Aegean) ancestral stock as a result of multiple fragmentation events, possibly due to the influence of post-Messinian sea flooding, Pleistocene eustatic changes and corresponding climate fluctuations. Over-sea dispersal and founder events appear to have played a rather insignificant role in the group's history. Rather, all analytical approaches identified the alliance as an organism group with poor seed dispersal capabilities and a susceptibility to genetic drift. In particular, we inferred that the observed level of cpDNA differentiation between Kikladian island populations of Nigella degenii largely reflects population history, (viz. Holocene island fragmentation) and genetic drift in the near absence of seed flow since their time of common ancestry. Overall, our cpDNA data for the N. arvensis alliance in general, and N. degenii in particular, indicate that historical events were important in determining the phylogeographical patterns seen, and that genetic drift has historically been relatively more influential on population structure than has cytoplasmic gene flow.

  15. box modeling of the eastern mediterranean sea

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Y.; Stone, P. H.

    2003-04-01

    Recently (~1990) a new source of deep water formation in the Eastern Mediterranean was found in the southern part of the Aegean sea. Till then, the only source of deep water formation in the Eastern Mediterranean was in the Adriatic sea; the rate of the deep water formation of the new Aegean source is 1Sv=10^6m^3/s, three times larger then the Adriatic source. We develop a simple 3 box-model to study the stability of the thermohaline circulation of the Eastern Mediterranean sea. The 3 boxes represent the Adriatic sea, Aegean sea, and the Ionian sea. The boxes exchange heat and salinity and may be described by a set of nonlinear differential equations. We analytically analyze these equations and find that the system may have one, two, or four stable flux states. We consider two cases for which the temperatures of the boxes are (i) fixed or (ii) variable. After setting the parameters to correspond to the Eastern Mediterranean we find that the system has two stable states, one with (i) two thermally dominant sources of deep water formation in the Adriatic and Aegean and the other with (ii) a salinity dominant source of deep water formation in the Adriatic and a thermally dominant source in the Aegean. While the Adriatic thermally dominant source is comparable to the observed flux of 0.3Sv the Aegean source has much smaller flux than the observed value. This situation is analogous to the state of the thermohaline circulation pre 1990 where the only source of deep water formation was in the Adriatic. If we decrease the atmospheric temperature of the Aegean box by 2C in accordance with recent observations, we find that the deep water formation of the Aegean increases significantly to a value comparable to the recently observed flux.

  16. Assessment of impact of geochemical and environmental properties on the meiofauna (benthic foraminifer, ostracod, mollusc) assemblages: A case study in The Late Quaternary Sediments In The Gulf Of Izmir (Eastern Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Yümün, Zeki Ü.

    2016-04-01

    The drilling samples collected from varying depths at 1.00-13.00 m at four different localities of Karsiyaka, Bayrakli, Inciralti and Urla (Çesmealti) in the Gulf of Izmir were studied for their geochemical, sedimantological and micropaleontological properties. The purpose of this study is to describe the meiofauna of the sediments, to determine the pollution history of the gulf and to show the effect of the pollution on the foraminifera and ostracoda. Examination of the loose sediments reveals that the gulf has been affected by the sea for a long time, and it had a rich microfaunal assemblages. Both foraminiferal tests and ostracod carapaces have coloring, and morphological abnormalities have been determined in foraminiferal tests. Peneroplis pertusus (Forskal) and P. planatus (Fichtel and Moll) have blue and black colored tests, while morphological abnormalities were observed on the tests of Ammonia compacta Hofker, Elphidium complanatum (d'Orbigny), E. crispum (Linné), E. macellum (Fichtel and Moll). The ostracod carapaces are generally gray-black colored. Heavy metal (Cr, Mn, Zn, Co, Ni, Cu) analyses have been carried out on the sediments of the Gulf of Izmir. Heavy metal concentrations are high in Bayrakli, and low in Urla (Çesmealti). Cr, Mn and Zn values are the highest in Bayrakli, whereas Co, Ni and Cu values are the highest in Inciralti. Scanning Electron Microscope (SEM) analyses were performed and no heavy metal was detected on the white and colored ostracod carapaces. When the white and colored ostracod carapaces are compared, the coloured ostracode carapace has higher Mg content, and also includes Fe, Al, N, Cl and K. Based on the results obtained, it is observed that the Bayrakli region have been more affected by the pollution than Urla (Çesmealti).

  17. First Cassini Radio Science Bistatic Scattering Observation of Titan's Northern Seas

    NASA Astrophysics Data System (ADS)

    Marouf, E. A.; Kliore, A. J.; Rappaport, N. J.; French, R. G.; Schinder, P. J.; Anabtawi, A.; Wong, K. K.; Armstrong, J. W.; Asmar, S. W.; Flasar, F. M.; Iess, L.; McGhee-French, C.; Nagy, A. F.; Tortora, P.; Barbinis, E.; Buccino, D.; Kahan, D. S.

    2014-12-01

    On May 17, 2014, the Cassini spacecraft completed its 101 flyby of Saturn's satellite Titan. Mirror-like (quasi-specular) reflections of radio signals transmitted by Cassini were observed on the Earth (bistatic scattering geometry). Three right circularly polarized (RCP) sinusoidal signals were transmitted (wavelength = 0.94, 3.6, and 13 cm). Both the RCP and LCP surface reflections were observed at the Canberra, Australia, complex of the NASA Deep Space Network. The signals probed the region extending from about (lat, long) = (79°N, 315°W) to about (74°N, 232°W). For the first time, two major Titan northern seas, the Ligeia Mare and the Kraken Mare, were probed. Clearly detectable RCP and LCP echo components were observed over both seas at all 3 wavelengths. The echoes were intermittent over the region in between the two seas. The echoes from the seas have narrowband spectra well modeled as pure sinusoids, suggesting very smooth surfaces over > ~1 cm scales. Over shorelines and river like channels the measured spectra reveal a second distinct broadband component, likely reflection from a rough bottom solid interface. Modeling the narrowband echo components as sinusoids, we estimate the RCP and LCP echo power profiles over the observation period. High resolution power profiles (several seconds time average; 0.2 to 2 km along the ground track) reveal remarkable structural detail. The statistical measurement uncertainty improves significantly when the resolution is degraded to about 1 m time average (3 to 30 km). Comparison of the 1 m power profiles with theoretical predictions computed assuming absent surface waves (negligible roughness) reveals excellent agreement with reflections from liquid hydrocarbons. The small statistical uncertainty promises to strongly constrain the liquid composition (ethane vs methane dominance). In principle, the measured RCP/LCP power ratio removes dependence on roughness and enables determination of the dielectric constant

  18. On the geodynamics of the Aegean rift

    NASA Astrophysics Data System (ADS)

    Agostini, Samuele; Doglioni, Carlo; Innocenti, Fabrizio; Manetti, Piero; Tonarini, Sonia

    2010-06-01

    The Aegean rift is considered to be either a classic backarc basin, or the result of the westward escape of Anatolia, or the effect of a gravitational collapse of an over-thickened lithosphere. Here these models are questioned. We alternatively present a number of geodynamic and magmatic constraints suggesting a simple model for the genesis of the extension as being related to the differential advancement of the upper lithosphere over a heterogeneous lower African plate. The Greek microplate overrides the Ionian oceanic segment of the African plate faster than the Anatolian microplate over the thicker Levantine more continental segment. This setting is evidenced by GPS-velocity gradient in the hangingwall of the Hellenic-Cyprus subduction system and requires a zone of rifting splitting the hangingwall into two microplates. This mechanism is unrelated to the replacement of retreated slab by the asthenosphere as typically occurs in the backarc of west-directed subduction zones. The supposed greater dehydration of the Ionian segment of the slab is providing a larger amount of fluids into the low velocity channel at the top of the asthenosphere, allowing a faster decoupling between the Greek microplate and the underlying mantle with respect to the Anatolian microplate. Slab ruptures associated with the differential retreat controlled by the inherited lithospheric heterogeneities in the lower plate and the proposed upwelling of the mantle suggested by global circulation models would explain the occurrence and coexistence of slab-related and slab-unrelated magmatism.

  19. Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles' radii

    NASA Astrophysics Data System (ADS)

    Bolghasi, Alireza; Ghadimi, Parviz; Chekab, Mohammad A. Feizi

    2016-09-01

    The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator (SSAS) developed based on optimization of the Helmholtz-Kirchhoff-Fresnel (HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS (MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall-Novarini model and optimized HKF method. The extended Hall-Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests (CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

  20. Seismic scattering and velocity structure near the Earth's core-mantle boundary beneath the South China Sea and north Indonesia

    NASA Astrophysics Data System (ADS)

    Yao, J.; Wen, L.

    2013-12-01

    We constrain seismic scatterers near the Earth's core-mantle boundary beneath the South China Sea and north Indonesia using the observed PKP precursory energy and velocity structure in the region using the travel time of the core-reflected phases. The PKP precursor data are collected from the seismic data recorded in the USArray and the core-reflected seismic data include ScS and ScP phases recorded in the China National Digital Seismographic Network, the F-net in Japan, the Global Seismographic Network and several regional arrays. Migration of PKP precursory energy reveals crescent-shaped scatterers distributed from the middle of the South China Sea to the north of Sulawesi Island. ScSH-SH differential-travel-times suggest a complex shear-velocity structure near the core-mantle boundary, changing from a low-velocity patch to a high shear-velocity patch and to another low shear-velocity patch from east to west beneath the middle of the South China Sea. ScP-P differential travel-time residuals reveal a low-velocity patch in northeast of Sulawesi Sea, a high-velocity patch in north of Sulawesi Sea, another low-velocity patch in the middle of Sulawesi Sea and another high-velocity patch in north of the Kalimantan Island. Overall, the seismic structure in the region can be characterized by alternative presence of high- and low-velocity patches near the core-mantle boundary, with the abrupt shear-wave velocity changes between the patches being the source of seismic scattering in the region.

  1. Theory and Numerical Modeling of Low-Frequency Acoustic Scattering from Bubble Plumes Near the Sea Surface

    DTIC Science & Technology

    1992-12-18

    of very general shape. They allow the surface to have creases and corners, but restrict their attention to uniform homogeneous interiors. We, however...from an infinite homogeneous exterior that will be needed for scattering from a near-surface plume - namely, the presence of the air/sea boundary. 2.3...density 1.8 gm/cc critical angle 59.0 deg Fig. 17 - Eigenray multipaths and simulation parameters the eigenrays that undergo total reflection at the

  2. Nestedness in centipede (Chilopoda) assemblages on continental islands (Aegean, Greece)

    NASA Astrophysics Data System (ADS)

    Simaiakis, Stylianos Michail; Martínez-Morales, Miguel Angel

    2010-05-01

    In natural ecosystems, species assemblages among isolated ecological communities such as continental islands often show a nested pattern in which biotas of sites with low species richness are non-random subsets of biotas of richer sites. The distribution of centipede (Chilopoda) species in the central and south Aegean archipelago was tested for nestedness. To achieve this aim we used distribution data for 53 species collected on 24 continental Aegean islands (Kyklades and Dodekanisa). Based on the first-order jackknife estimator, most of islands were comprehensively surveyed. In order to quantify nestedness, we used the nestedness temperature calculator (NTC) as well as the nestedness metric based on overlap and decreasing Fill (NODF). NTC indicated that data exhibited a high degree of nestedness in the central and south Aegean island complexes. As far as the Kyklades and Dodekanisa are concerned, NTC showed less nested centipede structures than the 24 islands. Likewise, NODF revealed a significant degree of nestedness in central and south Aegean islands. It also showed that biotas matrices without singletons were more nested than the complete ones (Aegean, Kyklades and Dodekanisa). The two commonest centipede taxa (lithobiomorphs and geophilomorphs) contributed differently to centipede assemblages. In the Kyklades and Dodekanisa, geophilomorphs did not show a reliable nested arrangement unlike lithobiomorphs. In relation to the entire data set, nestedness was positively associated with the degree of isolation. In the Kyklades altitudinal range best explained nestedness patterns, while in Dodekanisa habitat heterogeneity proved to be more important for the centipede communities. Island area does not seem to be a significant explanatory variable. Some of our results from the Kyklades were critically compared with those for terrestrial isopod and land snail nested assemblages from the same geographical area. The complex geological and palaeogeographical history of

  3. Vertical diffusion and oxygen consumption during stagnation periods in the deep North Aegean

    NASA Astrophysics Data System (ADS)

    Zervakis, Vassilis; Krasakopoulou, Evangelia; Georgopoulos, Dimitris; Souvermezoglou, Ekaterini

    2003-01-01

    Ventilation of the deep basins of the North Aegean Sea takes place during relatively scarce events of massive dense water formation in that region. In the time intervals between such events, the bottom waters of each sub-basin are excluded from interaction with other water masses through advection or isopycnal mixing and the only process that changes their properties is diapycnal mixing with overlying waters. In this work we utilize a simple one-dimensional model in order to estimate the vertical eddy diffusion coefficient Kρ based on the observed rate of change of density and stratification. Vertical diffusivity is estimated for each of three sub-basins of the North Aegean, one of convex shape of the seabed and the other two of concave topography. It is noteworthy that the convex sub-basin exhibited much higher vertical diffusivity than the two concave sub-basins, a fact consistent with theoretical predictions that internal-wave-induced mixing is higher over the former shape of seabed. Furthermore, the estimates of Kρ are exploited in computing the vertical transport of dissolved oxygen through diffusion and the rate of oxygen consumption by decaying organic matter. The different levels of the estimated diffusion and oxygen consumption rates testify to the dynamical and biogeochemical characteristics of each basin.

  4. Magnetotellurics and Transient Electromagnetics to Investigate the Geoelectric Structure of Southern Aegean, Greece

    NASA Astrophysics Data System (ADS)

    Makris, J. P.; Kalisperi, D.; Smirnov, M.; Rigakis, H.; Romano, G.; Kokologiannakis, A.; Pentes, G.; Pentaris, F.; Skoulakis, A.; Perrone, A.; Kouli, M.; Vallianatos, F.

    2014-12-01

    Since 2012 a great number of onshore magnetotelluric (MT) and Transient Electromagnetic (TEM) measurements have been conducted in Southern Aegean, Greece. The survey included Crete, almost all the islands of Dodecanese and Southern Cyclades, Southern Peloponnese, and the islands Kithira, Antikithira and Gavdos. Southern Aegean Sea, featuring the Southern Hellenic Arc (HA) of the Hellenic Subduction Zone (HSZ) and the Hellenic Volcanic Arc (HVA), depicts complex geotectonics and the most intense seismicity and geodynamics of Western Eurasia. In this work we summarize the most important results of the MT and TEM combined analysis and modelling. Furthermore, two permanent telemetric MT stations were installed and operated in Western Crete and Rhodes, respectively, to be used as remote reference and to investigate possible transient seismoelectromagnetic signals. The case of the October 12, 2013 strong earthquake (Mb6.4) is discussed. The research was conducted in the framework of the project entitled "MagnetoTellurics in studying Geodynamics of the hEllenic Arc (MT-GEAR)", co-funded by the European Social Fund (ESF) and National Resources within the context of the Action "Supporting Postdoctoral Researchers" of the Operational Programme 'Education and Lifelong Learning'.

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

    PubMed

    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

  6. Study of the blue-green laser scattering from the rough sea surface with foams by the improved two-scale method

    NASA Astrophysics Data System (ADS)

    Li, Xiangzhen; Qi, Xiao; Han, Xiang'e.

    2015-10-01

    The characteristics of laser scattering from sea surface have a great influence on application performance, from submarine communication, laser detection to laser diffusion communication. Foams will appear when the wind speed exceeds a certain value, so the foam can be seen everywhere in the upper layer of the ocean. Aiming at the volume-surface composite model of rough sea surface with foam layer driven by wind, and the similarities and differences of scattering characteristics between blue-green laser and microwave, an improved two-scale method for blue-green laser to calculate the scattering coefficient is presented in this paper. Based on the improved two-scale rough surface scattering theory, MIE theory and VRT( vector radiative transfer ) theory, the relations between the foam coverage of the sea surface and wind speed and air-sea temperature difference are analyzed. Aiming at the Gauss sea surface in blue-green laser, the dependence of back- and bistatie-scattering coefficient on the incident and azimuth angle, the coverage of foams, as well as the wind speed are discussed in detail. The results of numerical simulations are compared and analyzed in this paper. It can be concluded that the foam layer has a considerable effect on the laser scattering with the increase of wind speed, especially for a large incident angle. Theoretical analysis and numerical simulations show that the improved two-scale method is reasonable and efficient.

  7. Propagation and Directional Scattering of Ocean Waves in the Marginal Ice Zone and Neighboring Seas

    DTIC Science & Technology

    2015-09-30

    This project is designed to better understand the sea state and boundary layer physics of the emerging Arctic Ocean, by addressing aspects of the...first three points in the ONR DRI on Sea State Boundary Layer Physics of the Emerging Arctic, i.e. 1. Identify and parameterize factors affecting...the Marginal Ice Zone and Neighboring Seas William Perrie Bedford Institute of Oceanography 1 Challenger Dr. Dartmouth, Nova Scotia B2Y 4A2

  8. Application of a Three-Component Scattering Model for Snow-covered First-Year Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Hossain, M.; Yackel, J. J.

    2011-12-01

    In this study, we examine the utility of a three-component scattering model to quantify the sensitivity of radar incidence angle to snow thickness over landfast first-year sea ice (FYI) during the early spring melt transition. This model utilizes the Freeman-Durden decomposition technique to segregate total power (SPAN) of each pixel into three simple scattering mechanisms (Surface, Volume and Double-Bounce) which is well adopted for naturally occurring terrain (Freeman and Durden, 1992; 1998) using airborne Polarimetric synthetic aperture radar (AIRSAR) data. Our model is based on (i) surface scattering from top of the snow-covered FYI (Smooth, Rough and Deformed); (ii) volume scattering contributed from snow-ice and ice-water interface layers which consists of grain size, brine volume, wetness and orientation of snow grain to radar; (iii) double-bounce scattering contributed from ice ridges. This study used C-band fully Polarimetric synthetic aperture radar (POLSAR) data acquired on May 15 and 18, 2009 at Hudson Bay, Churchill during cold (≤ -8°C) surface air temperature at two specific incidence angles (28.9° & 39°). The model is used to discriminate snow-covered FYI types namely smooth ice (SI), rough ice (RI) and deformed ice (DI). This model is then used to quantify various snow-thicknesses on FYI. We observed that surface scattering (Ps) contributed the dominant scattering mechanism (Ps: SI-76.85% at 28.9° and 69.48% at 39°; RI-65.97% at 28.9° and 57.13% at 39°; and DI- 60.3% at 28.9° and 46.31% at 39°) which decreases with increasing incidence angle and surface roughness; volume scattering (Pv) contributed as a second dominant scattering mechanism (Pv: SI-20.01% at 28.9° and 28.29% at 39°; RI-32.18% at 28.9° and 40.68% at 39°; and DI-38.42% at 28.9° and 52.03% at 39°) which increases with surface roughness and incidence angle; and double-bounce scattering(Pd) contributed very negligible amount to the total scattering (Pd: SI-3.14% at 28.9

  9. Water column sound scattering and hydrography around the Pribilof Islands, Bering Sea

    NASA Astrophysics Data System (ADS)

    Coyle, Kenneth O.; Cooney, R. T.

    1993-07-01

    Water column structure around the Pribilof Islands is a complex mixture of salinity and temperature fronts. Elevated fluorescence and sound-scattering patterns were often observed in the upper 30 m around frontal regions during both 1987 and 1988. Salinity fronts with associated elevated sound scattering were particularly intense near the surface during 1987. During both years sound scattering was most intense over the shelf, decreased over the slope and was lowest over the deep basin. An epibenthic sound-scattering layer was often present but its distribution did not appear to be related to water column structure. Water column scattering patterns in 38- and 200-kHz data were similar, but epibenthic scattering peaks present in the 200-kHz data were absent from the 38-kHz data. Net samples indicate that a portion of the water column scattering was probably caused by large gelatinous zooplankton, while a portion of the 200-kHz peaks in the epibenthic layers probably resulted from sound reflected by euphausiid swarms.

  10. A Semiempirical Model for Doppler Spectral Features of Microwave Radar Sea Scatter.

    DTIC Science & Technology

    1985-10-16

    small to moderate wave heights, a point on the sea surface moves in a circular orbit as a large wave passes by. Under these conditions, the linear...Interactions on the Second-order Doppler Spectrum of Sea Echo," JGR 79, 5031-5037 (1974). 4. B.L. Hicks, N. Knable, J.J. Kovaly, G.S. Newell, J.P. Ruina , and

  11. Vertical coherence and forward scattering from the sea surface and the relation to the directional wave spectrum.

    PubMed

    Dahl, Peter H; Plant, William J; Dall'Osto, David R

    2013-09-01

    Results of an experiment to measure vertical spatial coherence from acoustic paths interacting once with the sea surface but at perpendicular azimuth angles are presented. The measurements were part of the Shallow Water 2006 program that took place off the coast of New Jersey in August 2006. An acoustic source, frequency range 6-20 kHz, was deployed at depth 40 m, and signals were recorded on a 1.4 m long vertical line array centered at depth 25 m and positioned at range 200 m. The vertical array consisted of four omni-directional hydrophones and vertical coherences were computed between pairs of these hydrophones. Measurements were made over four source-receiver bearing angles separated by 90°, during which sea surface conditions remained stable and characterized by a root-mean-square wave height of 0.17 m and a mixture of swell and wind waves. Vertical coherences show a statistically significant difference depending on source-receiver bearing when the acoustic frequency is less than about 12 kHz, with results tending to fade at higher frequencies. This paper presents field observations and comparisons of these observations with two modeling approaches, one based on bistatic forward scattering and the other on a rough surface parabolic wave equation utilizing synthetic sea surfaces.

  12. Contemporary kinematics of the southern Aegean and the Mediterranean Ridge

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Chamot-Rooke, Nicolas

    2004-06-01

    This study focuses on the kinematics of the southern Aegean and the Mediterranean Ridge (MR). A quantification of the deformation of the MR is essential for both evaluating physical models of accretionary wedges in general and for obtaining a self-consistent model of the surface deformation over the entire Nubia-Eurasia (NU-EU) plate boundary zone in the eastern Mediterranean. Previous kinematic studies have not properly considered the deformation field south of the Hellenic arc. Although this study focuses on the deformation field of the MR, we also discuss the kinematics of the southern Aegean, because the geometry and movement of the Hellenic arc determine to a large extent the kinematic boundary conditions for kinematic studies of the MR. We calculate a continuous velocity and strain rate field by interpolating model velocities that are fitted in a least-squares sense to published Global Positioning System (GPS) velocities. In the interpolation, we use information from a detailed data set of onshore and offshore active faulting to place constraints on the expected style and direction of the model strain rate field. In addition, we use the orientations of tracks left by seamounts travelling into the wedge to further constrain the offshore deformation pattern. Our model results highlight the presence of active shear partitioning within the Mediterranean ridge. High compressional strain rates between the ridge crest and the deformation front accommodate approximately 60-70 per cent of the total motion over the wedge, and the outward growth rate of the frontal thrust is ~ 4 mm yr-1. Strain partitioning within the wedge leads to 19-23 mm yr-1 of dextral motion at the wedge-backstop contact of the western MR, whereas the Pliny and Strabo trenches in the eastern MR accommodate 21-23 mm yr-1 of sinistral motion. The backstop of the western MR is kinematically part of the southern Aegean, which moves as a single block [the Aegean block (AE)] at 33-34 mm yr-1 in the

  13. Message-passing-interface-based parallel FDTD investigation on the EM scattering from a 1-D rough sea surface using uniaxial perfectly matched layer absorbing boundary.

    PubMed

    Li, J; Guo, L-X; Zeng, H; Han, X-B

    2009-06-01

    A message-passing-interface (MPI)-based parallel finite-difference time-domain (FDTD) algorithm for the electromagnetic scattering from a 1-D randomly rough sea surface is presented. The uniaxial perfectly matched layer (UPML) medium is adopted for truncation of FDTD lattices, in which the finite-difference equations can be used for the total computation domain by properly choosing the uniaxial parameters. This makes the parallel FDTD algorithm easier to implement. The parallel performance with different processors is illustrated for one sea surface realization, and the computation time of the parallel FDTD algorithm is dramatically reduced compared to a single-process implementation. Finally, some numerical results are shown, including the backscattering characteristics of sea surface for different polarization and the bistatic scattering from a sea surface with large incident angle and large wind speed.

  14. Separation of Coherent and Incoherent Scattering Components from Delay/Doppler Altimeter Waveforms over Sea-Ice

    NASA Astrophysics Data System (ADS)

    Egido, A.; Smith, W. H. F.

    2015-12-01

    One of the main benefits of the delay-Doppler altimeter (DDA) is the improved resolution of the system along the satellite track. By means of an unfocussed Synthetic Aperture Radar (SAR) processing technique, the altimeter footprint along the flight direction can be reduced by an order of magnitude with respect to conventional altimeters. However, with the delay-Doppler processing the resolution improvement occurs only on the along-track direction, while the across-track direction remains pulse-limited. The result is an elongated footprint perpendicular to the satellite flight path. The combination of the effects of several scatterers within the footprint can lead to random variations of the DDA waveforms, preventing conventional retracking techniques from retrieving geophysical parameters from altimeter data. This is particularly significant in the case of sea ice, where the coherent response from leads can completely exceed the response from the actual ice surface. We have developed a processing technique that allows the separation of the coherent and incoherent scattering components from SAR altimetry waveforms. The technique is similar to the one used in imaging SAR systems, and is based in the exploitation of the phase history of coherent targets during their illumination period with the antenna beam. For the development of the technique we have used the CryoSat-2 SAR Mode data. The starting point of our processing is the full bit rate (FBR) I/Q complex echo samples. By accounting for the phase evolution of the static targets in the scene, it is possible to correct the phase of the FBR complex echoes along the aperture, which allows to perform an inter-burst coherent averaging, potentially, as long as the target illumination time. This reduces the incoherent components of the radar signal, which results in a radar waveform that contains only the coherent scattering component. The coherent component can later be removed from the original delay-Doppler waveform

  15. Thermoelectricity Generation and Electron-Magnon Scattering in a Natural Chalcopyrite Mineral from a Deep-Sea Hydrothermal Vent.

    PubMed

    Ang, Ran; Khan, Atta Ullah; Tsujii, Naohito; Takai, Ken; Nakamura, Ryuhei; Mori, Takao

    2015-10-26

    Current high-performance thermoelectric materials require elaborate doping and synthesis procedures, particularly in regard to the artificial structure, and the underlying thermoelectric mechanisms are still poorly understood. Here, we report that a natural chalcopyrite mineral, Cu1+x Fe1-x S2 , obtained from a deep-sea hydrothermal vent can directly generate thermoelectricity. The resistivity displayed an excellent semiconducting character, and a large thermoelectric power and high power factor were found in the low x region. Notably, electron-magnon scattering and a large effective mass was detected in this region, thus suggesting that the strong coupling of doped carriers and antiferromagnetic spins resulted in the natural enhancement of thermoelectric properties during mineralization reactions. The present findings demonstrate the feasibility of thermoelectric energy generation and electron/hole carrier modulation with natural materials that are abundant in the Earth's crust.

  16. The application of laser-Raman light scattering to the determination of sulfate in sea and estuarine waters

    NASA Technical Reports Server (NTRS)

    Bandy, A. R.

    1973-01-01

    Laser-Raman light scattering is a technique for determining sulfate concentrations in sea and estuarine waters with apparently none of the interferences inherent in the gravimetric and titrametric methods. The Raman measurement involved the ratioing of the peak heights of an unknown sulfate concentration and a nitrate internal standard. This ratio was used to calculate the unknown sulfate concentration from a standard curve. The standard curve was derived from the Raman data on prepared nitrate-sulfate solutions. At the 99.7% confidence level, the accuracy of the Raman technique was 7 to 8.6 percent over the concentration range of the standard curve. The sulfate analyses of water samples collected at the mouth of the James River, Hampton, Virginia, demonstrated that in most cases sulfate had a constant concentration relative to salinity in this area.

  17. Pelagic-benthic coupling and diagenesis of nucleic acids in a deep-sea continental margin and an open-slope system of the Eastern Mediterranean.

    PubMed

    Dell'anno, Antonio; Corinaldesi, Cinzia; Stavrakakis, Spyros; Lykousis, Vasilis; Danovaro, Roberto

    2005-10-01

    Downward fluxes of nucleic acids adsorbed onto settling particles play a key role in the supply of organic phosphorus and genetic material to the ocean interior. However, information on pelagic-benthic coupling, diagenesis, and processes controlling nucleic acid preservation in deep-sea sediments is practically nonexistent. In this study, we compared nucleic acid fluxes, sedimentary DNA and RNA concentrations, and the enzymatically hydrolyzable fraction of DNA in a bathyal continental margin (North Aegean Sea) and an open-sea system (South Aegean Sea) of the Eastern Mediterranean. The two systems displayed contrasting patterns of nucleic acid fluxes, which increased significantly with depth in the North Aegean Sea and decreased with depth in the South Aegean Sea. These results suggest that in continental margin and open-ocean systems different processes control the nucleic acid supply to the sea floor. Differences in nucleic acid fluxes were reflected by nucleic acid concentrations in the sediments, which reached extremely high values in the North Aegean Sea. In this system, a large fraction of DNA may be buried, as suggested by the large fraction of DNA resistant to nuclease degradation and by estimates of burial efficiency (ca. eight times higher in the North than in the South Aegean Sea). Overall, the results reported here suggest that the preservation of DNA in deeper sediment layers may be favored in benthic systems characterized by high sedimentation rates.

  18. Scattering properties of a stratified air/snow/sea ice medium. Small slope approximation

    NASA Astrophysics Data System (ADS)

    Dusséaux, Richard; Afifi, Saddek; Dechambre, Monique

    2016-11-01

    The sea-ice thickness, a key parameter in Arctic studies, is derived from radar altimeter height measurements of the freeboard, taking into account not only snow load, but also the penetration depth of the electromagnetic waves inside the snow-this is the not generally the case. Within the framework of the small slope approximation method, we study in Ku-band (f = 13 GHz, λ = 2.31 cm in the air) the electromagnetic signature of an air/snow/sea ice rough layered medium. The snow is inhomogeneous and is represented as a stack of several layers with different relative permittivities. We show that the electromagnetic response is very sensitive to the isotropy factor of the air/snow interface and to the cross-correlation parameters of interfaces. xml:lang="fr"

  19. Detection of polycyclic aromatic hydrocarbon (PAH) compounds in artificial sea-water using surface-enhanced Raman scattering (SERS).

    PubMed

    Péron, Olivier; Rinnert, Emmanuel; Lehaitre, Michel; Crassous, Philippe; Compère, Chantal

    2009-07-15

    This paper reports an accurate synthesis of surface-enhanced Raman scattering (SERS) active substrates, based on gold colloidal monolayer, suitable for in situ environmental analysis. Quartz substrates were functionalized by silanization with (3-mercaptopropyl)trimethoxysilane (MPMS) or (3-aminopropyl)trimethoxysilane (APTMS) and they subsequently reacted with colloidal suspension of gold metal nanoparticles: respectively, the functional groups SH and NH(2) bound gold nanoparticles. Gold nanoparticles were prepared by the chemical reduction of HAuCl(4) using sodium tricitrate and immobilized onto silanized quartz substrates. Active substrate surface morphology was characterized with scanning electron microscopy (SEM) measurements and gold nanoparticles presented a diameter in the range 40-100 nm. Colloidal hydrophobic films, allowing nonpolar molecule pre-concentration, were obtained. The surfaces exhibit strong enhancement of Raman scattering from molecules adsorbed on the films. Spectra were recorded for two PAHs, naphthalene and pyrene, in artificial sea-water (ASW) with limits of detection (LODs) of 10 ppb for both on MPMS silanized substrates.

  20. A theory of wave scatter from an inhomogeneous medium with a slightly rough boundary and its application to sea ice

    NASA Technical Reports Server (NTRS)

    Parashar, S. K.; Fung, A. K.; Moore, R. K.

    1974-01-01

    An analytical theory of electromagnetic wave scattering from an inhomogeneous medium with a slightly rough boundary surface is formulated. The inhomogeneity in the medium is assumed to vary continuously in the vertical direction and to have a small random variation in the horizontal direction. The medium is assumed to consist of two layers. Maxwell's equations are solved by using the small perturbation method together with Fourier transform technique. The resulting differential equations are solved by using WKB and variation of parameter methods. Field amplitudes in each medium are determined by taking boundary conditions into account. The expressions for first order polarized radar backscatter cross-section are obtained. An attempt is made to apply the developed theory to compute sea ice scatter. Numerical calculations are performed for polarized radar backscatter cross-section at two frequencies, 13.3 GHz and 400 MHz. It is shown that WKB method is applicable at both of these frequencies. Theoretical results are compared with the experimental results obtained from NASA Earth Resources Program mission 126. Theoretical results and experimental results are in good agreement.

  1. Quantification of low elevation relief vertical movements from global sea level curves and scattered marine deposits (Armorican Massif, France)

    NASA Astrophysics Data System (ADS)

    Bessin, Paul; Guillocheau, François; Robin, Cécile; Bauer, Hugues; Schroëtter, Jean-Michel

    2016-04-01

    Amplitudes of vertical movements, amount of burial or of denudation are often too low or too old to be quantified from thermochronological or cosmogenic isotopes methods. This is the case for the vertical movements experienced by European Variscan basements of low relief during Cenozoic times. Some of these basements bear scattered thin Cenozoic marine sediments. Thus, we proposed to quantify Cenozoic vertical movements from i) current elevation of well dated marine sediments scattered on these basements, corrected from their bathymetry of deposition provided by their sedimentary facies and ii) elevation of global sea level at time of sediment deposition from a new compilation of available curves. This compilation highlights that i) curve which takes into account ocean basin volume change are consistent for the ca. 100 to 40 Ma "greenhouse" period whereas ii) curves based on coreholes backstripping methods better reflect global sea level changes since ca. 40 Ma. For their respective time intervals, both are in accordance with curves which together take into account ocean water volume and ocean basin volume changes. We quantify Cenozoic vertical movements of the Armorican Massif showcase. This massif is French Variscan basement of low relief (elevation < 420 m), two times buried then exhumed during Jurassic to Paleocene times, which bears numerous Cenozoic remnants of marine sediments of four periods: Bartonian, Rupelian, Langhian-Serravalian and Piacezian-Gelasian. We evidence a tree-step history of Cenozoic vertical movements and deformation: i) 38-34 Ma: a phase of near stability of the massif related to no to low deformation period for the Western Europe; ii) 30-16 Ma: a phase of low subsidence which coeval to a long wavelength subsidence of Western Europe which is proposed to be mantle-driven (dynamic topography); iii) 3.5-0 Ma: an overall bulging phase of the massif related to Apulia-Eurasia convergences due to Africa-Apulia and Iberia plates convergence which

  2. Forecasting skill assessment of an oil spill simulation system in the NE Aegean and atmospheric forcing perturbation experiments

    NASA Astrophysics Data System (ADS)

    Kailas, Marios; Chrysagi, Eyrydice; Sofianos, Sarantis

    2016-04-01

    In the present study, the predictive skill of an oil spill simulation system implemented in the Northern Aegean Sea was evaluated using field observations from surface drifters, provided in the framework of the TOSCA project. The system produces satisfactory results as in most cases the forecasting error is quite small, allowing the operational use of the forecast. In order to examine the sensitivity of the forecast to atmospheric forcing, additional simulations with perturbed atmospheric conditions were performed, using a time-shifting technique. In most experiments the differences between the simulations are relatively small, most likely due to slow oceanic response to variations in the wind fields. From the individual simulations an ensemble forecast was created, the results of which were also compared with the observations. The results suggest that by applying this method a safer forecast can be provided, especially regarding cases for which the wind-driven circulation is predominant. However, in cases where the circulation is characterized by intense velocity gradients (in the NE Aegean this is associated with the thermohaline front created by the Black Sea Water inflow), larger differences are present. They are related to imprecise representation of the location of the front. In these cases, the ensemble method produced no significant improvement since the relatively small differences between the trajectories of the ensemble members indicate that the position of the front in not significantly affected by the wind perturbations, based on the spatio-temporal scales examined. It is concluded that in regions with large spatio-temporal variability, an ensemble forecast produced by simulations generated from perturbed initial conditions could possibly lead to more robust results.

  3. An integrated approach to teaching Aegean archaeology and archaeological science

    NASA Astrophysics Data System (ADS)

    Pitcairn, Erica Glenn

    Outlined here is a course that would serve as an introduction to archaeological science, specifically within the context of Aegean Prehistory. The main objective of this course is to expose students early in their archaeological careers to a variety of methods and questions, and to depart from the culture-historical perspective that typifies introductory survey courses. The class structure is equal parts lecture and discussion, moving between learning how the methods work and evaluating case studies. All graded assignments build on one another, guiding the students through designing their own research project. The ultimate goals of the assignments are to build key writing and professional skills, develop a basic understanding of research design, and to instill confidence that the student can contribute to the production of knowledge, whatever field he or she decides to pursue.

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

    PubMed

    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; Urem-Kotsou, Dushka; 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; Wegmann, Daniel; Thomas, Mark G; Papageorgopoulou, Christina; Burger, Joachim

    2016-06-21

    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.

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

    PubMed Central

    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

  6. The North Cycladic Detachment System and associated mineralization, Mykonos, Greece: Insights on the evolution of the Aegean domain

    NASA Astrophysics Data System (ADS)

    Menant, Armel; Jolivet, Laurent; Augier, Romain; Skarpelis, Nikolaos

    2013-06-01

    the Aegean back-arc domain, some 30-35 Ma ago, an increase of the rate of slab retreat led to the initiation of post-orogenic extension, largely accommodated by large-scale structures such as the North Cycladic Detachment System (NCDS). Although this extension is still active nowadays, an E-W compressional regime developed in the Late Miocene with the propagation of the North Anatolian Fault. On Mykonos island (Cyclades), the NE-SW back-arc extension is particularly well expressed with the Livada and Mykonos detachments that belong to the NCDS and that are associated with NW-SE barite veins emplaced during the synkinematic cooling of the Mykonos intrusion. This study shows that the formation of the mineralization occurred when the pluton crossed the ductile-to-brittle transition during its exhumation below the NCDS at ~11-10 Ma. In addition, the kinematics of mineralized structures evolved with time: (1) most of the displacement was accommodated by the top-to-the-NE Livada and Mykonos detachments accompanied by the formation of mineralized normal faults that were (2) reworked in a strike-slip regime with an E-W direction of shortening and a persistent NE-SW stretching and (3) a late post-mineralization E-W compressional stage with a minor reworking of shallow-dipping faults (locally including the detachments themselves). We interpret this increase of the E-W shortening component recorded during the mineral deposition as a consequence of the initiation of the westward motion of Anatolia from 10 Ma, thus 4 Ma before the propagation of the North Anatolian Fault in the Dardanelles Strait and the localization of the strain on the Aegean Sea margins.

  7. The Middle Pleistocene archaeological record of Greece and the role of the Aegean in hominin dispersals: new data and interpretations

    NASA Astrophysics Data System (ADS)

    Tourloukis, Vangelis; Karkanas, Panagiotis

    2012-06-01

    In the debate about hominin dispersals, Greece is expected to have been among the core areas for the peopling of Eurasia, serving as a 'refugium' and source region for (re)colonizations. Yet, its early Pleistocene record is still scarce, forming a conspicuous 'gap' in the early human geography of the Mediterranean. Here we investigate this gap and provide for the first time a synthesis of the Lower Palaeolithic record of Greece. Our study adopts a geoarchaeological approach to explain the current status of the record and argues that the 'absence of evidence' should be understood as the result of the biasing effects of erosional geomorphic processes and not as an indication of a former absence of hominins. In this line, the potential for archaeological preservation and recovery is assessed as a function of landscape dynamics. Climatic seasonality, tectonic activity, high relief and marine inundations have altogether contributed to significant reworking and/or total loss of archaeological sites: in spatial terms, only about 2-5% of the Lower Palaeolithic record of Greece may have survived up to the present. On the other hand, we interpret recent geological data, which show that half of the Aegean Sea would have been subaerially exposed for most of the early Pleistocene. Our results emphasize the potentially central role of the Aegean region in hominin dispersals, both as a biogeographical landbridge and as a highly productive landscape for occupation. This conclusion opens up new prospects for future fieldwork in an area that was hitherto essentially neglected. Finally, in showing how geomorphic processes bias site distribution patterns, the results and methodological perspective developed here can be seen as having implications that are wider than the geographical limits of the Greek Peninsula: they are pertinent to the investigation and interpretation of the early Pleistocene archaeological records in the highly dynamic landscapes of southern Europe - if not in

  8. Development of ramp-flat structures during Aegean extension

    NASA Astrophysics Data System (ADS)

    Brun, Jean-Pierre; Sokoutis, Dimitrios

    2014-05-01

    Low-angle extensional shear is frequently observed in the Aegean metamorphic rocks. This deformation is commonly interpreted as being related to detachment at crustal scale, yet it often corresponds to ramp-flat extensional systems that, at many places, control the deposition of Neogene sedimentary basins. From a mechanical point of view, the development of a ramp-flat structure requires the presence of weak layers that can be activated as décollement between stronger rocks units. In the Aegean, the décollement generally develops within the upper brittle crust (i.e. with temperatures lower than about 400°C) that consists in recently exhumed metamorphic rocks. The process by which, these layers become weak enough to form efficient décollements in extension is somewhat intriguing and not well understood. In this contribution we examine the particular case of ramp-flat structures of the Southern Rhodope Core Complex that controlled the deposition of late Miocene to Pleistocene sediments in continental and marine basins. Field evidence is used to argue that the décollement corresponds to marble layers that separate orthogneisses at 2-3 km depth within an upper brittle crust whose thickness is around 5 km. Field observation and stable isotope measurements suggest that the ramp-flat structure observed on the island of Thassos occurred in a marble unit rich in fluids at a temperature of around 200°C. Using laboratory experiments, we explore the geometry of extensional structures (fault systems, rollovers, piggy-back basins…) that can develop at crustal-scale as a function of: i) décollement depth and dip, ii) number of décollements, and iii) strength contrast, between the décollement and overlying strong units. The results are compared with the situation observed in the Southern Rhodope Core Complex. We are convinced that the principles of ramp-flat extension discussed here have a strong potential of application in many other orogenic domains affected by large

  9. Chronology for the Aegean Late Bronze Age 1700-1400 B.C.

    PubMed

    Manning, Sturt W; Ramsey, Christopher Bronk; Kutschera, Walter; Higham, Thomas; Kromer, Bernd; Steier, Peter; Wild, Eva M

    2006-04-28

    Radiocarbon (carbon-14) data from the Aegean Bronze Age 1700-1400 B.C. show that the Santorini (Thera) eruption must have occurred in the late 17th century B.C. By using carbon-14 dates from the surrounding region, cultural phases, and Bayesian statistical analysis, we established a chronology for the initial Aegean Late Bronze Age cultural phases (Late Minoan IA, IB, and II). This chronology contrasts with conventional archaeological dates and cultural synthesis: stretching out the Late Minoan IA, IB, and II phases by approximately 100 years and requiring reassessment of standard interpretations of associations between the Egyptian and Near Eastern historical dates and phases and those in the Aegean and Cyprus in the mid-second millennium B.C.

  10. Elastic-Anelastic properties beneath the Aegean inferred from long period Rayleigh Waves

    NASA Astrophysics Data System (ADS)

    Kassaras, I.; Louis, F.; Makropoulos, K.; Kaviris, G.

    2007-12-01

    This work is towards contributing to the better knowledge of the deep structure of the Aegean by introducing experimental elastic and anelastic parameters via the study of long period Rayleigh waves. For this scope path- average phase velocities and attenuation coefficients of fundamental Rayleigh waves crossing the Aegean were extracted over the period range 10-100 s. It is mean worth that it is the first time that anelastic parameters of the long period wavefield are determined for the region. The wavetrains were recorded at the broadband stations installed some years ago in the Aegean region for the SEISFAULTGREECE project. The stochastic inversion algorithm has been used to derive 36 path-average models of shear velocity and 19 path-average models of inverse shear Q down to 200 km. Average over the study region shear Q values at depths from 0 to 200 km range between 29±13. The observed low shear Q likely indicate that fluids reside in lower crustal, as well as upper mantle depths. Furthermore, the elastic and anelastic 1-D path-average models were combined in a continuous regionalization tomographic scheme to obtain a 3-D model of shear velocity variation down to 200 km and a 3-D model of inverse shear Q variation down to 120 km. The most prominent features in the tomograms are: a) A low shear velocity zone in the back-arc region, especially in the central and north Aegean. This region is located south of the North Aegean Trough (the western edge of the North Anatolian Fault) and correlates well with the derived anelastic tomograms which present high attenuation in this area. b) A high velocity/low attenuation zone in South Aegean indicating the subducted African lithosphere beneath the Aegean. The zone in central and north Aegean characterized by low velocities/high attenuation is compatible with a region of high extensional strain rates, recent volcanism and high heat flow. These observations suggest a hot or perhaps partially molten upper mantle and

  11. Cluster analysis of indermediate deep events in the southeastern Aegean

    NASA Astrophysics Data System (ADS)

    Ruscic, Marija; Becker, Dirk; Brüstle, Andrea; Meier, Thomas

    2015-04-01

    The Hellenic subduction zone (HSZ) is the seismically most active region in Europe where the oceanic African litosphere is subducting beneath the continental Aegean plate. Although there are numerous studies of seismicity in the HSZ, very few focus on the eastern HSZ and the Wadati-Benioff-Zone of the subducting slab in that part of the HSZ. In order to gain a better understanding of the geodynamic processes in the region a dense local seismic network is required. From September 2005 to March 2007, the temporary seismic network EGELADOS has been deployed covering the entire HSZ. It consisted of 56 onshore and 23 offshore broadband stations with addition of 19 stations from GEOFON, NOA and MedNet to complete the network. Here, we focus on a cluster of intermediate deep seismicity recorded by the EGELADOS network within the subducting African slab in the region of the Nysiros volcano. The cluster consists of 159 events at 80 to 190 km depth with magnitudes between 0.2 and 4.1 that were located using nonlinear location tool NonLinLoc. A double-difference earthquake relocation using the HypoDD software is performed with both manual readings of onset times and differential traveltimes obtained by separate cross correlation of P- and S-waveforms. Single event locations are compared to relative relocations. The event hypocenters fall into a thin zone close to the top of the slab defining its geometry with an accuracy of a few kilometers. At intermediate depth the slab is dipping towards the NW at an angle of about 30°. That means it is dipping steeper than in the western part of the HSZ. The edge of the slab is clearly defined by an abrupt disappearance of intermediate depths seismicity towards the NE. It is found approximately beneath the Turkish coastline. Furthermore, results of a cluster analysis based on the cross correlation of three-component waveforms are shown as a function of frequency and the spatio-temporal migration of the seismic activity is analysed.

  12. Psychiatric Morbidity and Social Capital in Rural Communities of the Greek North Aegean Islands

    ERIC Educational Resources Information Center

    Tseloni, Andromachi; Zissi, Anastasia; Skapinakis, Petros

    2010-01-01

    Which facets of social capital affect mental health in rural settings? This study explores the association between different aspects of social capital and psychiatric morbidity in rural communities of the Greek North Aegean islands. A large number of individual and community characteristics that may influence psychiatric morbidity are concurrently…

  13. Carbonate assimilation during magma evolution at Nisyros (Greece), South Aegean Arc: Evidence from clinopyroxenite xenoliths

    NASA Astrophysics Data System (ADS)

    Spandler, Carl; Martin, Lukas H. J.; Pettke, Thomas

    2012-08-01

    To contribute to the understanding of magma evolution in arc settings we investigate the oldest volcanic unit (Kanafià Synthem) of Nisyros volcano, located in the eastern Aegean Sea (Greece). The unit consists of porphyritic pillow lavas of basaltic andesite composition with trace element signatures that are characteristic of island-arc magmas. Two lava types are distinguished on the basis of geochemistry and the presence or absence of xenoliths, with the xenolith-bearing lavas having distinctly elevated Sr, MREE/HREE and MgO/Fe2O3 compared to the xenolith-free lavas. Xenoliths include relatively rare quartzo-feldspathic fragments that represent continental-type material, and coarse clinopyroxenite xenoliths that consist largely of aluminous and calcic clinopyroxene, and accessory aluminous spinel. Anorthite-diopside reaction selvages preserved around the clinopyroxenite xenoliths demonstrate disequilibrium between the xenoliths and the host magma. The xenolith clinopyroxene is distinctly enriched in most lithophile trace elements compared to clinopyroxene phenocrysts in the host magmas. A notable exception is the Sr concentration, which is similar in both clinopyroxene types. The high Al and low Na contents of the clinopyroxenites preclude a cumulate, deep metamorphic, or mantle origin for these xenoliths. Instead, their composition and mineralogy are diagnostic of skarn rocks formed by magma-carbonate interaction in the mid/upper crust. The Kanafià lavas are interpreted to have undergone crystal fractionation, magma mixing/mingling and crustal assimilation while resident in the upper crust. We show that magma-carbonate reaction and associated skarn formation does not necessarily result in easily recognised modification of the melt composition, with the exception of increasing Sr contents. Carbonate assimilation also releases significant CO2, which will likely form a free vapour phase due to the low CO2 solubility of arc magmas. In the broader context, we stress

  14. On the Impacts of Different Surface Forcing Regimes for Deep Water Formation in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Josey, S.; Tsimplis, M.; Gomis, D.; Ruiz, S.; Marcos, M.; Somot, S.

    2009-04-01

    Deep water formation is known to occur at 3 major sites (the Gulf of Lions, Adriatic and Aegean Seas) in the Mediterranean basin. However, the role played by air-sea interaction in setting the frequency and strength of formation events (including major transient episodes such as that experienced in the Aegean sea in the early 1990s) is not well understood. We will explore this relationship using air-sea heat, freshwater and density flux fields, including output from downscaled versions (HIPOCAS and ARPERA) of the NCEP/NCAR and ECMWF reanalyses. The downscaled fields reveal small scale forcing features (including jet-like structures over the dense water formation sites) that are not present in the coarser resolution reanalysis datasets. They also show greater variability in the forcing of the Aegean and the Gulf of Lions than the Adriatic Sea. The differences between the forcing distributions of the Aegean and Adriatic will be discussed in detail and will be advanced as a potential cause for variations in frequency of dense water formation in these two regions.

  15. Anelastic attenuation structure of the southern Aegean subduction area

    NASA Astrophysics Data System (ADS)

    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

  16. Comparison of hyperspectral measurements of the attenuation and scattering coefficients spectra with modeling results in the north-eastern Baltic Sea

    NASA Astrophysics Data System (ADS)

    Sipelgas, Liis; Raudsepp, Urmas

    2015-11-01

    The spectral variations in the attenuation and scattering coefficients measured with a hyperspectral ac-spectra (Wetlabs) instrument were analyzed from a dataset collected in the vicinity of commercial harbors on the Estonian coast of the Gulf of Finland, Baltic Sea. In total, the measured TSM concentration varied from 0.4 to 30 mg L-1 and the concentration of Chl a varied from values below the detection limit (0.05) to 23 mg m-3. The reliability of the power law describing the particle attenuation cp (λ) and scattering bp(λ) coefficients was evaluated by means of a determination coefficient (R2). The power law described the particle attenuation spectra with high accuracy (R2 > 0.67), giving the dataset an average cp (λ) slope of 1.3. In the case of particle scattering coefficients, the power law did not represent the whole dataset. Depending on a particular spectrum, the R2 varied from 0 to 1.0 and the slope varied from 1.15 to -0.56. Decomposition of bp(λ) into dominant modes using principal component analyses resulted in the first principal mode accounting for the power law dependence of bp(λ), i.e. the "mineral-type" spectrum, and the second and third mode representing the characteristic bp(λ) of dominant algal particles, i.e. the "algae-type" spectrum. From our dataset we estimated that if Chl a concentration is above 10 mg m-3 or below 5 mg m-3 then most likely the "algae-type" or the "mineral-type" spectrum is dominant, respectively. There was strong linear relationship (R2 > 0.92) between TSM concentration and cp(555) and bp(555),irrespective of the dominant shape of the particle scattering spectra. The estimated TSM-specific attenuation and scattering coefficients at 555 nm were 0.8 m2 g-1 and 0.68 m2 g-1, respectively. Corresponding values for water samples with a dominant "mineral-type" spectrum were 0.85 m2 g-1 and 0.73 m2 g-1, respectively and for water samples with a dominant "algae-type" spectrum were 0.64 m2 g-1 and 0.52 m2 g-1, respectively.

  17. A Survey of Scattering, Attenuation, and Size Spectra Studies of Bubble Layers and Plumes Beneath the Air-Sea Interface.

    DTIC Science & Technology

    1991-08-30

    density. Raytraces were done from the layer source to the hydrophone at 267-m bottom depth and, finding refraction negligible out to 6-km radius, a... Radar ," in Wave Dynamics and Radio Probing of the Ocean Surface, Plenum, New York (1986). 56 [83] L. Kinsler and A. Frey, Fundamentals of Acoustics...Breaking in the Presence of Wind Drift and Swell," J. Fluid Mech. 66, 625-640 (1974). [1451 O.M. Phillips, " Radar Returns from the Sea Surface - Bragg

  18. The North Cycladic Detachment System and associated mineralization, Mykonos, Greece: insights on the evolution of stress regime in the Aegean domain

    NASA Astrophysics Data System (ADS)

    Menant, A.; Jolivet, L.; Augier, R.; Skarpelis, N.

    2012-04-01

    In the Aegean back-arc domain, some 30-35 Ma ago, the increasing rate of slab retreat led to the initiation of post-orogenic extension, largely accommodated by several large-scale structures such as the North Cycladic Detachment System (NCDS). Although the Aegean N-S extension is still active nowadays, particularly with the Evia and Corinth rifts, an E-W compressional regime developed 5-6 Ma ago with the propagation of the North Anatolian Fault and its extension within the Central Hellenic Shear Zone. On Mykonos island (Cyclades), the NE-SW back-arc extension is well expressed, particularly with two main shallow-dipping shear zones belonging to the NCDS: the Livada and Mykonos detachments associated with NW-SE banded barite and Fe-hydroxide vertical veins emplaced from 10-11 Ma. A structural study of detachments, veins and faults show an evolution of the kinematics of these tectonic structures. We show that (1) most of the displacement was first accommodated by the shallow-dipping Livada and Mykonos detachments with a N30°E direction of extension. Minor steep and shallow-dipping normal faults formed during this episode above and below the detachment and some of them were mineralized. (2) The normal faults and the veins were later reworked in a strike-slip regime with an E-W direction of compression and a persistent N-S to NE-SW extension. Alternating periods of extension with the same direction of the least principal stress are recorded during this stage. (3) The last stage is compressional with a minor reworking of shallow-dipping faults (locally including the detachment itself) with an E-W compression. We interpret this increase of the E-W compressional component during the activity of the detachments and the emplacement of ore deposits as a consequence of the initiation of the westward motion of Anatolia that we date at ~10 Ma, some 5 Ma before the propagation of the North Anatolian Fault and the localization of the strain on the margins of the Aegean Sea.

  19. Revisiting the insect mitochondrial molecular clock: the mid-Aegean trench calibration.

    PubMed

    Papadopoulou, Anna; Anastasiou, Ioannis; Vogler, Alfried P

    2010-07-01

    Phylogenetic trees in insects are frequently dated by applying a "standard" mitochondrial DNA (mtDNA) clock estimated at 2.3% My(-1), but despite its wide use reliable calibration points have been lacking. Here, we used a well-established biogeographic barrier, the mid-Aegean trench separating the western and eastern Aegean archipelago, to estimate substitution rates in tenebrionid beetles. Cytochrome oxidase I (cox1) for six codistributed genera across 28 islands (444 individuals) on both sides of the mid-Aegean trench revealed 60 independently coalescing entities delimited with a mixed Yule-coalescent model. One representative per entity was used for phylogenetic analysis of mitochondrial (cox1, 16S rRNA) and nuclear (Mp20, 28S rRNA) genes. Six nodes marked geographically congruent east-west splits whose separation was largely contemporaneous and likely to reflect the formation of the mid-Aegean trench at 9-12 Mya. Based on these "known" dates, a divergence rate of 3.54% My(-1) for the cox1 gene (2.69% when combined with the 16S rRNA gene) was obtained under the preferred partitioning scheme and substitution model selected using Bayes factors. An extensive survey suggests that discrepancies in mtDNA substitution rates in the entomological literature can be attributed to the use of different substitution models, the use of different mitochondrial gene regions, mixing of intraspecific with interspecific data, and not accounting for variance in coalescent times or postseparation gene flow. Different treatments of these factors in the literature confound estimates of mtDNA substitution rates in opposing directions and obscure lineage-specific differences in rates when comparing data from various sources.

  20. Reproductive biology of the prawn Melicertus kerathurus (Decapoda: Penaeidae) in Thermaikos Gulf (N. Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Kevrekidis, Kosmas; Thessalou-Legaki, Maria

    2013-03-01

    The reproductive biology including insemination frequency, ovarian maturation, gonadosomatic index (GSI), size at first maturity, and fecundity of Melicertus kerathurus were investigated using monthly samples from Thermaikos Gulf. Insemination was recorded by the presence of a spermatophore in the thelycum, and ovarian development was based on macroscopic ovarian staging (ST1-ST5). Inseminated females were found throughout the year with high percentages recorded from April to July. Although all ovarian stages were represented in mated females, insemination increased with size and ovarian maturation. High percentages of vitellogenic or mature ovarian stages were observed from May to July, while immature and developing ovaries were predominant mainly in winter. Spawned ovaries occurred from May to October. Carapace length at first maturity based on the presence of a spermatophore (CL50sp) was estimated at 39.20 mm, while that based on the presence of vitellogenic and mature ovaries (CL50ov) at 40.70 mm. The seasonal peak in the proportion of mature females (ST4) varied with size. Inseminated females at ST4 and GSI peaked in June-July. GSI varied in relation to insemination status and ovarian stage. In large females (>50 mm CL), the decline in mature ovaries and GSI increment with size indicates a relative reduction in the reproductive output. The number of oocytes ranged from 62,742 to 602,947 (mean ± SD: 268,000 ± 113,000). As the prawns are targeted during the spawning season, mainly by the artisanal fishery, and female size at first maturity is selected by artisanal net size, managerial measures toward artisanal fishery should be implemented.

  1. Benthic microbial abundance and activities in an intensively trawled ecosystem (Thermaikos Gulf, Aegean Sea)

    NASA Astrophysics Data System (ADS)

    Polymenakou, Paraskevi N.; Pusceddu, Antonio; Tselepides, Anastasios; Polychronaki, Thalia; Giannakourou, Antonia; Fiordelmondo, Carla; Hatziyanni, Eleni; Danovaro, Roberto

    2005-12-01

    Abundance of benthic bacteria, heterotrophic nanoflagellates and ciliates, extracellular enzymatic activities, bacterial C production, C mineralisation and sediment community oxygen consumption rates were measured in the Thermaikos Gulf (Northeastern Mediterranean), before (September 2001), and during intense trawling activities (October 2001 and February 2002). The biochemical composition of sedimentary organic matter has revealed that bottom trawling had an effect on the trophic state of Thermaikos Gulf. Changes on the benthic microbial food web were also recorded, during the three sampling seasons. Even though trawling-induced sediment resuspension did not alter significantly the abundance of the microbial components, with the exception of the most impacted station, it determined changes regarding their relative importance. Thus, the ratios of bacterium to nanoflagellates and ciliate to nanoflagellates abundance increased in the trawled stations, causing a sudden increase in bacterial C production, in comparison to the non-trawled station. Four months later, the effects of trawling on the microbial food web were less evident, masked possibly by the drastic decrease in the water temperature. The results of the present work suggest that bottom trawling induces alteration of the sedimentological variables and can be considered as a factor affecting the function of the microbial food web in marine coastal ecosystems. These alterations cause faster mobilisation of organic C buried in the sediment and increase nutrient concentrations and availability in the system, thus inducing an effect that could lead to coastal eutrophication.

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

    DTIC Science & Technology

    2012-03-01

    19  x Figure 11.  The Azores or Bermuda High and southwest and south-central Asia thermal low tend to produce a...of Frequency (green lines with triangle markers), moisture mixing ratio at the surface level (blue lines with rhombus markers) and moisture mixing...of Frequency (green lines with triangle markers), moisture mixing ratio at the surface level (blue lines with rhombus markers) and moisture mixing

  3. Network-Based Mitigation of Illegal Immigration in Aegean Sea (Greece)

    DTIC Science & Technology

    2010-09-01

    Network Mbps – Megabits per second MS – Microsoft NATO – North Atlantic Treaty Organization NLOS – Non Line of Site NOC – Network Operations Center... Mbps ) in the 2.4 gigahertz (GHz) bands but, in general, provides moderate throughput at moderate ranges. (802.11, n.d.) 6. Basic IEEE 802.16...police investigation. Solution: A broadband wireless CCTV network infrastructure was recommended with connection speeds up to 108 Mbps using

  4. Sediment geochemistry and mineralogy in Milos bay, SW Kyklades, Aegean Sea, Greece

    NASA Astrophysics Data System (ADS)

    Karageorgis, A.; Anagnostou, Ch.; Sioulas, A.; Chronis, G.; Papathanassiou, E.

    1998-10-01

    This work aims at studying the geochemistry and mineralogy of Milos bay surface sediments. The bay forms an enclosed marine area, supplied totally by volcanic formations. Totally 16 samples were subjected to sedimentological (grain size), mineralogical (microscope examination and X-ray diffraction of the bulk sample and the pelitic fraction), and geochemical analyses (X-ray fluorescence in the pelitic fraction). Also the carbonate content was determined. Sediments were sandy with a high carbonate content (14-58%). The dominant minerals recognized in the pelitic fraction were smectite, kaolinite and illite, followed by chlorite, quartz, calcite, Mg-calcite and feldspars. In general, element concentrations appeared to be within the normal range, except Pb and Zn, which exhibited relatively high values. The Index of Geoaccumulation Igeo was computed, in order to investigate a possible enrichment of the surface sediments in metals. The analysis revealed again high values of Igeo class for both Pb and Zn. A careful study of the area, in relation to the quality of the catchment basins petrology, lead to a non-anthropogenic origin of these high concentrations. The enrichment of the surface sediments in Pb and Zn is attributed to the weathering of several mineral deposits, pyroclastic rocks and lavas, covering almost all Milos vicinity. A study of the geochemical data correlation coefficient matrix revealed three major groups of elements: (i) the elements of detrital origin represented by Si, Al, K and a part of the metals; (ii) the carbonates group; and (iii) a Fe-Mn oxyhydroxides-oxides group, which attracts a part of Pb, Cr and Ni.

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

    NASA Astrophysics Data System (ADS)

    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

  6. Highly sensitive surface-enhanced Raman scattering detection of hexavalent chromium based on hollow sea urchin-like TiO2@Ag nanoparticle substrate.

    PubMed

    Zhou, Wen; Yin, Bin-Cheng; Ye, Bang-Ce

    2017-01-15

    As one of the most toxic heavy metals, hexavalent chromium (Cr(VI)) has long been a concern due to its threats to human health and the environment. In this work, we develop a sensitive surface-enhanced Raman scattering (SERS) sensor for highly specific detection of Cr(VI) using hollow sea urchin-like TiO2@Ag nanoparticles (NPs). The TiO2@Ag NPs are functionalized with glutathione (GSH) and used as substrates with 2-mercaptopyridine (2-MPy) as a Raman reporter for a recyclable SERS-active sensor, enabling ultrasensitive detection of Cr(VI). Excellent SERS signals of 2-MPy reporters are detected when GSH complexation with Cr(VI) causes aggregation of the TiO2@Ag NPs. The developed sensor exhibits good linearity in the range from 10nM to 2μM for Cr(VI) with a detection limit of ca. 1.45nM. It features excellent selectivity to Cr(VI) over other interfering metal ions, and good application for quantitative analysis of Cr(VI) in water samples. Moreover, the proposed SERS sensor can be fully regenerated when exposed to UV light as a result of the self-cleaning ability of the substrates. In contrast to the traditional SERS detection, the present work shed new light on the design and synthesis of hierarchically self-assembled 3D substrate for SERS, catalysis and biosensor development.

  7. A three-step model to assess shoreline and offshore susceptibility to oil spills: the South Aegean (Crete) as an analogue for confined marine basins.

    PubMed

    Alves, Tiago M; Kokinou, Eleni; Zodiatis, George

    2014-09-15

    This study combines bathymetric, geomorphological, geological data and oil spill predictions to model the impact of oil spills in two accident scenarios from offshore Crete, Eastern Mediterranean. The aim is to present a new three-step method of use by emergency teams and local authorities in the assessment of shoreline and offshore susceptibility to oil spills. The three-step method comprises: (1) real-time analyses of bathymetric, geomorphological, geological and oceanographic data; (2) oil dispersion simulations under known wind and sea current conditions; and (3) the compilation of final hazard maps based on information from (1) and (2) and on shoreline susceptibility data. The results in this paper show that zones of high to very-high susceptibility around the island of Crete are related to: (a) offshore bathymetric features, including the presence of offshore scarps and seamounts; (b) shoreline geology, and (c) the presence near the shore of sedimentary basins filled with unconsolidated deposits of high permeability. Oil spills, under particular weather and oceanographic conditions, may quickly spread and reach the shoreline 5-96 h after the initial accident. As a corollary of this work, we present the South Aegean region around Crete as a valid case-study for confined marine basins, narrow seaways, or interior seas around island groups.

  8. A detailed seismic zonation model for shallow earthquakes in the broader Aegean area

    NASA Astrophysics Data System (ADS)

    Vamvakaris, D. A.; Papazachos, C. B.; Papaioannou, Ch. A.; Scordilis, E. M.; Karakaisis, G. F.

    2016-01-01

    In the present work we propose a new seismic zonation model of area type sources for the broader Aegean area, which can be readily used for seismic hazard assessment. The definition of this model is based not only on seismicity information but incorporates all available seismotectonic and neotectonic information for the study area, in an attempt to define zones which show not only a rather homogeneous seismicity release but also exhibit similar active faulting characteristics. For this reason, all available seismological information such as fault plane solutions and the corresponding kinematic axes have been incorporated in the analysis, as well as information about active tectonics, such as seismic and active faults. Moreover, various morphotectonic features (e.g. relief, coastline) were also considered. Finally, a revised seismic catalogue is employed and earthquake epicentres since historical times (550 BC-2008) are employed, in order to define areas of common seismotectonic characteristics, that could constitute a discrete seismic zone. A new revised model of 113 earthquake seismic zones of shallow earthquakes for the broader Aegean area is finally proposed. Using the proposed zonation model, a detailed study is performed for the catalogue completeness for the recent instrumental period.Using the defined completeness information, seismicity parameters (such as G-R values) for the 113 new seismic zones have been calculated, and their spatial distribution was also examined. The spatial variation of the obtained b values shows an excellent correlation with the geotectonic setting in the area, in good agreement with previous studies. Moreover, a quantitative estimation of seismicity is performed in terms of the mean return period, Tm, of large (M ≥ 6.0) earthquakes, as well as the most frequent maximum magnitude, Mt, for a typical time period (T = 50 yr), revealing significant spatial variations of seismicity levels within the study area. The new proposed

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

    USGS Publications Warehouse

    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.

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

    USGS Publications Warehouse

    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).

  11. Sea-urchin-like Au nanocluster with surface-enhanced raman scattering in detecting epidermal growth factor receptor (EGFR) mutation status of malignant pleural effusion.

    PubMed

    Wang, Lei; Guo, Ting; Lu, Qiang; Yan, Xiaolong; Zhong, Daixing; Zhang, Zhipei; Ni, Yunfeng; Han, Yong; Cui, Daxiang; Li, Xiaofei; Huang, Lijun

    2015-01-14

    Somatic mutations in the epidermal growth factor receptor (EGFR) gene are common in patients with lung adenocarcinomas and are associated with sensitivity to the small-molecule tyrosine kinase inhibitors (TKIs). For 10%-50% of the patients who experienced malignant pleural effusion (MPE), pathological diagnosis might rely exclusively on finding lung cancer cells in the MPE. Current methods based on polymerase chain reaction were utilized to test EGFR mutation status of MPE samples, but the accuracy of the test data was very low, resulting in many patients losing the chance of TKIs treatment. Herein, we synthesized the sea-urchin-like Au nanocluster (AuNC) with an average diameter of 92.4 nm, composed of 15-nm nanopricks. By introducing abundant sharp nanopricks, the enhancement factor of AuNC reached at 1.97 × 10(7). After capped with crystal violet (CV), polyethylene glycol, and EGFR mutation specific antibody, the AuNC-EGFR had excellent surface-enhanced Raman scattering (SERS) activity and EGFR mutation targeted recognition capability in lung cancer cells. Characteristic SERS signal at 1617 cm(-1) of CV was linear correlation with the number of H1650 cells, demonstrating the minimum detection limit as 25 cells in a 1-mL suspension. The gold mass in single H1650 cells exposed to AuNC-E746_750 for 2 h ranged from 208.6 pg to 231.4 pg, which approximately corresponded to 56-62 AuNCs per cell. Furthermore, SERS was preclinically utilized to test EGFR mutation status in MPE samples from 35 patients with lung adenocarcinoma. Principal component analysis (PCA) and the support vector machine (SVM) algorithm were constructed for EGFR mutation diagnostic analysis, yielding an overall accuracy of 90.7%. SERS measurement based on sea-urchin-like AuNC was an efficient method for EGFR mutation detection in MPE, and it might show great potential in applications such as predicting gene typing of clinical lung cancer in the near future.

  12. Three-dimensional instantaneous dynamics modeling of present-day Aegean subduction

    NASA Astrophysics Data System (ADS)

    Glerum, Anne; Thieulot, Cedric; Pranger, Casper; van Hinsbergen, Douwe; Fraters, Menno; Spakman, Wim

    2015-04-01

    The Aegean region (Eastern Mediterranean) is exemplary of the interaction between crustal tectonics, plate motion, subduction and mantle flow: African subduction underneath the region has been continuous for at least the last 100 My, leading to about 2100-2500 km of subducted lithosphere residing in the mantle (van Hinsbergen et al., 2005). During this subduction, decoupled upper continental and oceanic crust accreted into a wedge of stacked nappes. In turn, these nappes have been significantly extended, predominantly during the last 25 My, due to the retreat of the African slab relative to Eurasia (van Hinsbergen and Schmid, 2012). As a first step to better understanding the coupling of the tectonic evolution of the crust and the underlying mantle dynamics, we are developing 3-D numerical models of the instantaneous dynamics of the present-day Aegean subduction system using the finite element code ASPECT (Kronbichler et al., 2012). The instantaneous models are set up with initial slab geometries derived from tomography and realistic plate boundary configurations and incorporate the major crustal weak zones of the overriding plate. Our modeling results in predictions of flow fields and stress, strain rate and rotation rate fields for the present-day tectonic setting of the Aegean region. By comparing our various model predictions to the widely available observations, such as focal mechanisms, GPS velocities and seismic anisotropy, we aim at an improved understanding of how mantle flow, subduction morphology and possibly slab segmentation, as well as the rheological behavior of the overriding plate, control present-day tectonic deformation. We expect to show preliminary results of this comparison. Kronbichler, M., Heister, T. and Bangerth, W. (2012), High Accuracy Mantle Convection Simulation through Modern Numerical Methods, Geophysical Journal International, 191, 12-29. Van Hinsbergen, D. J. J., Hafkenscheid, E., Spakman, W., Meulenkamp, J. E. and Wortel, R. (2005

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

    NASA Astrophysics Data System (ADS)

    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

  14. Carbon fluxes from hydrothermal vents off Milos, Aegean Volcanic Arc, and the influence of venting on the surrounding ecosystem.

    NASA Astrophysics Data System (ADS)

    Dando, Paul; Aliani, Stefano; Bianchi, Nike; Kennedy, Hilary; Linke, Peter; Morri, Carla

    2014-05-01

    The island of Milos, in the Aegean Sea, has extensive hydrothermal fields to the east and southeast of the island with additional venting areas near the entrance to and within the central caldera. A calculation of the total area of the vent fields, based on ship and aerial surveys, suggested that the hydrothermal fields occupy 70 km2, twice the area previously estimated. The vents ranged in water depth from the intertidal to 300 m. As a result of the low depths there was abundant free gas release: in places water boiled on the seabed. The stream of gas bubbles rising through the sandy seabed drove a shallow re-circulation of bottom seawater. The majority of the water released with the gas, with a mean pH of 5.5, was re-circulated bottom water that had become acidified in contact with CO2 gas and was often diluted by admixture with the vapour phase from the deeper fluids. The major component of the free gas, 80%, was CO2, with an estimated total flux of 1.5-7.5 x 1012 g a-1. The methane flux, by comparison, was of the order of 1010 g a.-1 Using methane as a tracer it was shown that the major gas export from the vents was below the thermocline towards the southwest, in agreement with the prevailing currents. Areas of hydrothermal brine seepage occurred between the gas vents and occasional brine pools were observed in seabed depressions. Under relatively calm conditions, many of the brine seeps were covered by thick minero-bacterial mats consisting of silica and sulphur and surrounded by mats of diatoms and cyanobacteria. The minerals were not deposited in the absence of bacteria. Storms disrupted the mats, leading to an export of material to the surrounding area. Stable isotope data from sediments and sediment trap material suggested that exported POM was processed by zooplankton. The combined effects of the geothermal heating of the seabed, the large gas flux, variation in the venting and the effect of the brine seeps had a dramatic effect on the surrounding

  15. Exocytosis of sea urchin egg cortical vesicles in vitro is retarded by hyperosmotic sucrose: kinetics of fusion monitored by quantitative light-scattering microscopy

    PubMed Central

    1985-01-01

    We have used the isolated planar cortex of sea urchin eggs to examine the role of osmotic forces in exocytosis by morphological and physiological methods. Electron micrographs of rotary-shadowed replicas show an en face view of exocytosis and demonstrate fusion of cortical vesicles to the underlying oolemma upon addition of calcium. Freeze- fracture replicas of rapidly frozen cortices reveal specialized attachment sites between cortical vesicles and the oolemma, and between the cortical vesicles themselves. We describe a novel light scattering assay for the kinetics of fusion which allows rapid changes of solutions and monitors exocytosis in real time. The rate and extent of fusion are found to be calcium dependent. The removal of calcium halts exocytosis. The validation of exocytosis in this system and development of tools for kinetic analysis allowed us to test predictions of the osmotic hypothesis of exocytosis: hyperosmotic media should inhibit exocytosis; calcium should cause vesicular swelling. Cortical vesicles were found to be permeant to sucrose, glucose, and urea. In media made hyperosmotic with 1.7 M sucrose, cortical vesicles were seen to shrink. Addition of calcium in hyperosmotic media led to a 10-fold decrease in the rate of exocytosis compared with the isotonic rate. The rate, while triggered by calcium, was no longer calcium-dependent. This slowing of exocytosis allowed us to photograph the swelling of cortical vesicles caused by calcium. Removal of calcium had no effect on subsequent exocytosis. Return of cortices to isotonic medium without calcium led to immediate exocytosis. These results are consistent with the idea that swelling of cortical vesicles is required for fusion of biological membranes. PMID:4066763

  16. A continuum model of continental deformation above subduction zones - Application to the Andes and the Aegean

    NASA Technical Reports Server (NTRS)

    Wdowinski, Shimon; O'Connell, Richard J.; England, Philip

    1989-01-01

    A continuum model of continental deformation above subduction zones was developed that combines the viscous sheet and the corner flow models; the continental lithosphere is described by a two-dimensional sheet model that considers basal drag resulting from the viscous asthenosphere flow underneath, and a corner flow model with a deforming overlying plate and a rigid subducting plate is used to calculate the shear traction that acts on the base of the lithosphere above a subduction zone. The continuum model is applied to the Andes and the Aegean deformations, which represent, respectively, compressional and extensional tectonic environments above subduction zones. The models predict that, in a compressional environment, a broad region of uplifted topography will tend to develop above a more steeply dippping slab, rather than above a shallower slab, in agreement with observations in the various segments of the central Andes. For an extensional environment, the model predicts that a zone of compression can develop near the trench, and that extensional strain rate can increase with distance from the trench, as is observed in the Aegean.

  17. Fault slip source models for the 2014 Mw 6.9 Samothraki-Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations

    NASA Astrophysics Data System (ADS)

    Saltogianni, Vasso; Gianniou, Michail; Taymaz, Tuncay; Yolsal-ćevikbilen, Seda; Stiros, Stathis

    2015-12-01

    The 24 May 2014, Mw 6.9, Samothraki-Gökçeada shallow (depth: 11 km) earthquake along the North Aegean Trough (NAT), at the westward extension of the North Anatolian Fault Zone (NAFZ), is investigated using constraints from seismological and geodetic data. A point source solution based on teleseismic long-period P and SH waveforms suggests an essentially strike-slip faulting mechanism consisting of two subevents, while from a finite fault inversion of broadband data the rupture area and slip history were estimated. Analysis of data from 11 permanent GPS stations indicated significant coseismic horizontal displacement but no significant vertical or postseismic slip. Okada-type inversion of horizontal slip vectors, using the new TOPological INVersion algorithm, allowed precise modeling of the fault rupture both as single and preferably as double strike-slip faulting reaching the surface. Variable slip models were also computed. The independent seismological and geodetic fault rupture models are broadly consistent with each other and with structural and seismological data and indicate reactivation of two adjacent fault segments separated by a bend of the NAT. The 2014 earthquake was associated with remote clusters of low-magnitude aftershocks, produced low accelerations, and filled a gap in seismicity along the NAT in the last 50 years; faulting in the NAT seems not directly related to the sequence of recent faulting farther east, along the NAFZ and the seismic gap in the Marmara Sea near Istanbul.

  18. Temporal patterns of detachment faulting along Cycladic extensional metamorphic domes, Aegean region

    NASA Astrophysics Data System (ADS)

    Schneider, D. A.; Grasemann, B.; Heizler, M.; Vogel, H.; Iglseder, C.

    2007-12-01

    The Aegean region together with the surrounding mainland areas are known for Miocene to Recent active, notably extensional tectonics that are the result of the retreating Hellenic slab, gravitational collapse of the region and, since the Late Miocene to Early Pliocene, the westward escape of Anatolia relative to Eurasia. Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) has collected an extensive modern structural dataset for the islands of Kea, Kithnos, and Serifos of the western Cyclades. On all three islands, crustal-scale, low-angle frictional-viscous shear zones have been identified and record strikingly consistent SSW-directed extensional kinematics together with a WNE-ESE shortening component. The geology of Kea is dominated by highly-strained, greenschist-facies schists, calc-silicates and marbles; a major, 100's m thick ultramylonite zone defines this northern island as a structural dome. White mica Ar-Ar thermochronometry performed on variably deformed units from different structural levels yield consistent Early Miocene (15-19 Ma) cooling ages across the entire island. Other pervasively deformed shallow crustal regions of the Cyclades (Tinos and Andros; b-type domes of Jolivet et al. 2004) also record similar Early Miocene cooling. Comparable geology and structure is exposed on Serifos although locally deformed under amphibolite-facies conditions and intruded in the south by a Late Miocene granodiorite. A major high strain zone that is present on the island is localized along an earlier (Late Eocene) granitic pluton. White micas from mylonites and gneisses along this shear zone and from rocks in the southern portion of the island yield Late Miocene (8-9 Ma) cooling ages, whereas greenschist-facies units in northern Serifos that are dominated by a different structural record of several phases of folding yield Oligocene (30-34 Ma) mica Ar-Ar cooling ages. Oligocene ages are similarly reported from Evvia and Sifnos, which are noted for

  19. Holocene seasonal sea-surface temperature variations in the southern Adriatic Sea inferred from a multiproxy approach

    NASA Astrophysics Data System (ADS)

    Sangiorgi, Francesca; Capotondi, Lucilla; Combourieu Nebout, Nathalie; Vigliotti, Luigi; Brinkhuis, Henk; Giunta, Simona; Lotter, Andrè F.; Morigi, Caterina; Negri, Alessandra; Reichart, Gert-Jan

    2003-12-01

    Holocene cooling events have been reconstructed for the southern Adriatic Sea (central Mediterranean) by means of analyses of organic walled dinoflagellate cysts, planktonic foraminifera, oxygen isotopes, calcareous nanoplankton, alkenones and pollen from a sediment core. Two cooling events have been detected, during which sea-surface temperatures (SSTs) were ca. 2°C lower. Unravelling the SST signal into dominant seasonal components suggests maximum winter cooling of 2°C at around 6.0 ka, whereas the cooling at ca. 3.0 ka might be the result of a spring temperature cooling of 2-3°C. The events, lasting several hundred years, are apparently synchronous with those in the Aegean Sea, where they have been related to known cooling events from the Greenland ice-core record. A distinct interruption in Adriatic Sea sapropel S1 is not clearly accompanied by a local drop in winter temperatures, but seems to be forced by ventilation, which probably occurred earlier in the Aegean Sea and was subsequently transmitted to the Adriatic Sea. Copyright

  20. Estimation of relative humidity based on artificial neural network approach in the Aegean Region of Turkey

    NASA Astrophysics Data System (ADS)

    Yasar, Abdulkadir; Simsek, Erdoğan; Bilgili, Mehmet; Yucel, Ahmet; Ilhan, Ilhami

    2012-01-01

    The aim of this study is to estimate the monthly mean relative humidity (MRH) values in the Aegean Region of Turkey with the help of the topographical and meteorological parameters based on artificial neural network (ANN) approach. The monthly MRH values were calculated from the measurement in the meteorological observing stations established in Izmir, Mugla, Aydin, Denizli, Usak, Manisa, Kutahya and Afyonkarahisar provinces between 2000 and 2006. Latitude, longitude, altitude, precipitation and months of the year were used in the input layer of the ANN network, while the MRH was used in output layer of the network. The ANN model was developed using MATLAB software, and then actual values were compared with those obtained by ANN and multi-linear regression methods. It seemed that the obtained values were in the acceptable error limits. It is concluded that the determination of relative humidity values is possible at any target point of the region where the measurement cannot be performed.

  1. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  2. Earthquake Scenario-Based Tsunami Wave Heights in the Eastern Mediterranean and Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Özel, Nurcan Meral

    2015-12-01

    We identified a set of tsunami scenario input parameters in a 0.5° × 0.5° uniformly gridded area in the Eastern Mediterranean, Aegean (both for shallow- and intermediate-depth earthquakes) and Black Seas (only shallow earthquakes) and calculated tsunami scenarios using the SWAN-Joint Research Centre (SWAN-JRC) code ( Mader 2004; Annunziato 2007) with 2-arcmin resolution bathymetry data for the range of 6.5—Mwmax with an Mw increment of 0.1 at each grid in order to realize a comprehensive analysis of tsunami wave heights from earthquakes originating in the region. We defined characteristic earthquake source parameters from a compiled set of sources such as existing moment tensor catalogues and various reference studies, together with the Mwmax assigned in the literature, where possible. Results from 2,415 scenarios show that in the Eastern Mediterranean and its connected seas (Aegean and Black Sea), shallow earthquakes with Mw ≥ 6.5 may result in coastal wave heights of 0.5 m, whereas the same wave height would be expected only from intermediate-depth earthquakes with Mw ≥ 7.0 . The distribution of maximum wave heights calculated indicate that tsunami wave heights up to 1 m could be expected in the northern Aegean, whereas in the Black Sea, Cyprus, Levantine coasts, northern Libya, eastern Sicily, southern Italy, and western Greece, up to 3-m wave height could be possible. Crete, the southern Aegean, and the area between northeast Libya and Alexandria (Egypt) is prone to maximum tsunami wave heights of >3 m. Considering that calculations are performed at a minimum bathymetry depth of 20 m, these wave heights may, according to Green's Law, be amplified by a factor of 2 at the coastline. The study can provide a basis for detailed tsunami hazard studies in the region.

  3. Impact of Diurnal Warming on Assimilation of Satellite Observations of Sea Surface Temperature

    DTIC Science & Technology

    2014-09-09

    insolation in the southeast, and conditions can be significantly cooler to the north in the Aegean Sea, a region exposed to cold continental wind...independent SST observations from drifting buoys. While all in situ surface-only observations are withheld from the assimilative model forecasts and...Other, similarly withheld surface in-situ observations such as those from fixed buoy locations or shipboard observations might be used, but the drifting

  4. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE.

  5. Towards an Absolute Chronology for the Aegean Iron Age: New Radiocarbon Dates from Lefkandi, Kalapodi and Corinth

    PubMed Central

    Toffolo, Michael B.; Fantalkin, Alexander; Lemos, Irene S.; Felsch, Rainer C. S.; Niemeier, Wolf-Dietrich; Sanders, Guy D. R.; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8th century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11th century BCE according to the Conventional Aegean Chronology and in the late 12th century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11th century BCE. PMID:24386150

  6. Some New Lidar Equations for Laser Pulses Scattered Back from Optically Thick Media Such as Clouds, Dense Aerosol Plumes, Sea Ice, Snow, and Turbid Coastal Waters

    NASA Technical Reports Server (NTRS)

    Davis, Anthony B.

    2013-01-01

    I survey the theoretical foundations of the slowly-but-surely emerging field of multiple scattering lidar, which has already found applications in atmospheric and cryospheric optics that I also discuss. In multiple scattering lidar, returned pulses are stretched far beyond recognition, and there is no longer a one-to-one connection between range and return-trip timing. Moreover, one can exploit the radial profile of the diffuse radiance field excited by the laser source that, by its very nature, is highly concentrated in space and collimated in direction. One needs, however, a new class of lidar equations to explore this new phenomenology. A very useful set is derived from radiative diffusion theory, which is found at the opposite asymptotic limit of radiative transfer theory than the conventional (single-scattering) limit used to derive the standard lidar equation. In particular, one can use it to show that, even if the simple time-of-flight-to-range connection is irretrievably lost, multiply-scattered lidar light can be used to restore a unique profiling capability with coarser resolution but much deeper penetration into a wide variety of optical thick media in nature. Several new applications are proposed, including a laser bathymetry technique that should work for highly turbid coastal waters.

  7. Temporal and spatial biomonitoring of heavy metals in eastern Aegean coastal waters using Amphibalanus amphitrite.

    PubMed

    Onen, S Aydin; Kucuksezgin, F; Kocak, F

    2011-11-01

    This biomonitoring study presents the spatial and temporal distributions of heavy metals in the soft tissues of a major fouling species Amphibalanus amphitrite living on hard substrate at different sites along the eastern Aegean coast. A. amphitrite has been chosen as a strong candidate for monitoring heavy metals. Sediment and seawater samples were also collected to detect their metal contents in order to gain more information on the environmental conditions and possible bioaccumulation patterns. The physico-chemical characteristics of sampling stations have been measured in order to characterize the sampling area. The order of metal concentrations in barnacles, sediment and seawater decreased in the following order Cu>Fe>Zn>Mn>Cd>Cr>Pb>Hg, Fe>Mn>Zn>Cu>Pb>Cr>Hg>Cd and Fe>Zn>Mn>Cu>Pb>Cr>Cd>Hg, respectively. These results showed that barnacles accumulate Cu in a higher degree than both sediment and seawater. Moreover, metal concentrations in barnacle have the potential for use in any future regulatory framework monitoring and eventually controlling ambient metal pollution levels.

  8. How far the postorogenic extensional tectonics in the Aegean domain is symmetric?

    NASA Astrophysics Data System (ADS)

    Augier, Romain; Jolivet, Laurent; Gadenne, Leslie; Driussi, Olivier

    2013-04-01

    Current models to explain the finite geometry of the Aegean domain and the exhumation of the eclogite-bearing HP rocks in the Aegean domain rely on the recognition of a synorogenic exhumation regime followed by a postorogenic back-arc extension. A first generation of low-angle normal faults (LANF) developed during the subduction and the formation of the Hellenic Eocene orogenic wedge contemporaneously with the overthrusting of the Cycladic Blueschists over basement units. Other LANF were formed subsequently and accompanied the development of Metamorphic Core Complexes (MCC) during the collapse of the internal zones in the back-arc domain. Most of the stretching during postorogenic extension was accommodated by N-dipping LANF with N- to NE-sense of shear pertaining to the North Cycladic Detachment System (NCDS). More recently, the description of the top-to-the-south West Cycladic Detachment System (WCDS) resulted in a more symmetrical character of the postorogenic extension. However, the transition in time and space between these major structures, particularly the NCDS and the WCDS, which is a key question to understand the dynamics of the back-arc extension, remains widely unclear. The Folegandros-Sikinos area, whose tectonometamorphic evolution appears poorly constrained, is however quite exemplary of this discussion. Located to the south of the Cycladic Archipelago, at short distance from the WCDS last outcrop in Serifos Island, this area offers the opportunity to study both the synorogenic deformation preserved at the vicinity of the Cycladic basement and the structural transition between areas characterised by top-to-the-North and top-to-the-South kinematics during the postorogenic history. Based on an extensive field survey making the link between kinematics of the noncoaxial deformation and changing metamorphic conditions, we show that (1) a E-W syn-blueschists facies deformation is preserved within the HP lenses; (2) a penetrative, post-blueschists facies

  9. Modelling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities

    NASA Astrophysics Data System (ADS)

    Karakostas, Vassilis; Papadimitriou, Eleftheria; Gospodinov, Dragomir

    2014-04-01

    The 2013 January 8 Mw 5.8 North Aegean earthquake sequence took place on one of the ENE-WSW trending parallel dextral strike slip fault branches in this area, in the continuation of 1968 large (M = 7.5) rupture. The source mechanism of the main event indicates predominantly strike slip faulting in agreement with what is expected from regional seismotectonics. It was the largest event to have occurred in the area since the establishment of the Hellenic Unified Seismological Network (HUSN), with an adequate number of stations in close distances and full azimuthal coverage, thus providing the chance of an exhaustive analysis of its aftershock sequence. The main shock was followed by a handful of aftershocks with M ≥ 4.0 and tens with M ≥ 3.0. Relocation was performed by using the recordings from HUSN and a proper crustal model for the area, along with time corrections in each station relative to the model used. Investigation of the spatial and temporal behaviour of seismicity revealed possible triggering of adjacent fault segments. Theoretical static stress changes from the main shock give a preliminary explanation for the aftershock distribution aside from the main rupture. The off-fault seismicity is perfectly explained if μ > 0.5 and B = 0.0, evidencing high fault friction. In an attempt to forecast occurrence probabilities of the strong events (Mw ≥ 5.0), estimations were performed following the Restricted Epidemic Type Aftershock Sequence (RETAS) model. The identified best-fitting MOF model was used to execute 1-d forecasts for such aftershocks and follow the probability evolution in time during the sequence. Forecasting was also implemented on the base of a temporal model of aftershock occurrence, different from the modified Omori formula (the ETAS model), which resulted in probability gain (though small) in strong aftershock forecasting for the beginning of the sequence.

  10. A distinct source and differentiation history for Kolumbo submarine volcano, Santorini volcanic field, Aegean arc.

    PubMed

    Klaver, Martijn; Carey, Steven; Nomikou, Paraskevi; Smet, Ingrid; Godelitsas, Athanasios; Vroon, Pieter

    2016-08-01

    This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely-operated vehicle that were analyzed for major element, trace element and Sr-Nd-Hf-Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave-bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52-60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low (206)Pb/(204)Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field.

  11. A distinct source and differentiation history for Kolumbo submarine volcano, Santorini volcanic field, Aegean arc

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Carey, Steven; Nomikou, Paraskevi; Smet, Ingrid; Godelitsas, Athanasios; Vroon, Pieter

    2016-08-01

    This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely-operated vehicle that were analyzed for major element, trace element and Sr-Nd-Hf-Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave-bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52-60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low 206Pb/204Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field.

  12. A distinct source and differentiation history for Kolumbo submarine volcano, Santorini volcanic field, Aegean arc

    PubMed Central

    Carey, Steven; Nomikou, Paraskevi; Smet, Ingrid; Godelitsas, Athanasios; Vroon, Pieter

    2016-01-01

    Abstract This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely‐operated vehicle that were analyzed for major element, trace element and Sr‐Nd‐Hf‐Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave‐bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52–60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low 206Pb/204Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field. PMID:27917071

  13. Geometry, thermal structure and kinematics of the metamorphic dome of Ikaria (eastern Cyclades, Greece): implication for Aegean tectonics

    NASA Astrophysics Data System (ADS)

    Beaudoin, Alexandre; Laurent, Valentin; Augier, Romain; Jolivet, Laurent; Lahfid, Abdeltif; Arbaret, Laurent; Rabillard, Aurélien

    2014-05-01

    The Aegean domain has been characterized since the Oligocene by extensional tectonics caused by the southward retreat of the African slab subducting beneath Eurasia. Structures and associated kinematics relative to this extensional tectonics are well constrained in the western Cyclades and the Menderes massif of western Turkey. Major extensional detachments such as the North Cycladic Detachment System (NCDS) or the Simav Detachment have accommodated the exhumation of a series of metamorphic core complexes (MCC) from Andros-Tinos-Mykonos in the west to the northern Menderes massif in the east. However, the transition between the NCDS and the Simav Detachment is currently not understood. This transition is located above a large-scale tear in the Aegean slab and its effects on the kinematics of deformation and P-T-t evolution of the overlying thinned crust are not known. The geology of Ikaria Island, located in this region, remains poorly known and the few existing studies are strikingly conflicting. This work attempts to clarify the geology of Ikaria by a new geological mapping and structural field study coupled with a thermometric study by Raman spectrometry of carbonaceous material (RSCM). Foliation over the whole island defines a structural dome, lately intruded by intrusive granitic bodies. Lineation shows a ca. N-S ductile stretching associated with an overall top-to-the-North sense of shear. Final exhumation of the dome was thus completed by a system of two top-to-the-North detachments, operating in the ductile and then the brittle fields. The proposed tectono-metamorphic evolution of the dome is consistent with the evolution of the northern Aegean area, suggesting that Ikaria belongs to the Aegean MCC and that the NCDS continues eastward. Besides, the distribution of RSCM temperatures within the dome and the presence of migmatites in the western part of the island comply with the description of migmatite-cored MCC such as Naxos or Mykonos. A better

  14. Light scattering by marine heterotrophic bacteria

    NASA Technical Reports Server (NTRS)

    Ulloa, Osvaldo; Sathyendranath, Shubha; Platt, Trevor; Quinones, Renato A.

    1992-01-01

    Mie theory is applied to estimate scattering by polydispersions of marine heterotrophic bacteria, and a simple expression is derived for the bacterial scattering coefficient. The error incurred in deriving bacterial optical properties by use of the van de Hulst approximations is computed. The scattering properties of natural bacterial assemblages in three marine environments, Georges Bank, Northeast Channel, and Sargasso Sea, are assessed by applying Mie theory to field data on bacterial size and abundance. Results are used to examine the potential contribution of bacteria to the scattering properties of seawater. The utility of using pigment data to predict the magnitude of scattering by bacteria is discussed.

  15. Mitochondrial DNA reveals genetic structuring of Pinna nobilis across the Mediterranean Sea.

    PubMed

    Sanna, Daria; Cossu, Piero; Dedola, Gian Luca; Scarpa, Fabio; Maltagliati, Ferruccio; Castelli, Alberto; Franzoi, Piero; Lai, Tiziana; Cristo, Benedetto; Curini-Galletti, Marco; Francalacci, Paolo; Casu, Marco

    2013-01-01

    Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima's and Fu's neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units.

  16. Mitochondrial DNA Reveals Genetic Structuring of Pinna nobilis across the Mediterranean Sea

    PubMed Central

    Sanna, Daria; Cossu, Piero; Dedola, Gian Luca; Scarpa, Fabio; Maltagliati, Ferruccio; Castelli, Alberto; Franzoi, Piero; Lai, Tiziana; Cristo, Benedetto; Curini-Galletti, Marco; Francalacci, Paolo; Casu, Marco

    2013-01-01

    Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima’s and Fu’s neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units. PMID:23840684

  17. Changing Arctic: A Strategic Analysis of United States Arctic Policy and the United Nations Convention on the Law of the Sea

    DTIC Science & Technology

    2013-05-01

    accomplished Canadian academic said: “What the Aegean Sea was to antiquity, what the Mediterranean was to the Roman world, what the Atlantic Ocean was to...Linda Jakobson and Stockholm International Peace Research Institute., "China Prepares for an Ice-Free Arctic," Stockholm International Peace Research...Quarterly (Jul 1, 2012): 45. Jakobson , Linda and Stockholm International Peace Research Institute. "China Prepares for an Ice-Free Arctic." Stockholm

  18. The seasonal cycles of stratification and circulation in the Thermaikos Gulf Region Of Freshwater Influence (ROFI), north-west Aegean

    NASA Astrophysics Data System (ADS)

    Hyder, P.; Simpson, J. H.; Christopoulos, S.; Krestenitis, Y.

    2002-11-01

    The Thermaikos Gulf is a shallow basin in the north-west Aegean. Communication with the open Aegean is restricted by the long (170 km), narrow (˜50 km) nature of the Gulf and the weak tidal flows. In consequence, the northern section of the Gulf experiences severe water quality problems arising from the untreated sewage from the city of Thessaloniki (population 1.1 million), pollutant discharges from industry around the Gulf, and nutrient input from three rivers, which flow in near the head of the Gulf. New observations over a 16-month period during 1994-95 indicate distinct winter and summer circulation regimes. In winter (December-April), strong freshwater input (˜350 m 3/s) generates a thin (5 m), low salinity, surface layer which flows southward over much of the Gulf, above relatively homogeneous high-salinity waters that flow to the north. In the low-salinity layer, close to the river deltas, short pulses of extremely low-salinity water occur daily, principally as the result of releases from the Aliakmon hydro-electric power dam. Between October and February, a cold, dense water mass is observed in the deeper water of the eastern Gulf, which appears to originate in the shallow waters of central Saloniki Bay as the result of cooling during northerly gales. During winter it appears that buoyancy forcing from high run-off, in combination with persistent southward wind stress results in wind-enhanced estuarine exchange. In summer (July-September), the surface low-salinity layer is not well defined and is confined to the western Gulf in the vicinity of the river sources. Throughout the Gulf, a thicker (10-20 m) mixed layer with low salinity, warm waters overlies a strong pycnocline. A weak barotropic gyre is observed in the Gulf at this time. Monthly estimates of the total freshwater content of the northern Gulf indicate that this layer results in an accumulation of freshwater in the Gulf over the summer, when the local river input is at a minimum. It appears

  19. Evaluations of heavy metal pollution in sediment and Mullus barbatus from the Izmir Bay (Eastern Aegean) during 1997-2009.

    PubMed

    Kucuksezgin, Filiz; Kontas, Aynur; Uluturhan, Esin

    2011-07-01

    Izmir Bay is one of the great natural bays of the Mediterranean. The surface sediment and fish samples were collected during 1997-2009. The sediment concentrations of inner bay showed significant enrichments during sampling periods. Outer and middle bays exhibited low levels of metal enrichments except the estuary of Gediz River. The concentrations were generally higher than the background levels from the Mediterranean and Aegean except Cd and Pb levels gradually decreased. Metal EF is used as an index to evaluate anthropogenic influences of metals in sediments. Maximum metal enrichment was found for Hg in the outer bay, while Pb indicated maximum enrichment in the middle-inner bays. Metal levels were evaluated in sediments in accordance with the numerical SQG of the USEPA. The levels of fish tissues were lower than the results reported from polluted areas of the Mediterranean. The highest BAFs were detected for Hg and Cd in fish.

  20. Geographic patterns of elemental deposition in the Aegean region of Turkey indicated by the lichen, Xanthoria parietina (L.) Th. Fr.

    PubMed

    Yenisoy-Karakaş, S; Tuncel, S G

    2004-08-15

    Lichen samples from different parts of the world have been known to accumulate elements to a greater degree than higher plants, if they are exposed to these elements from the atmosphere or from water and sediments. It has been hypothesized that lichens can be used to monitor air pollution around point and area emission sources. Local variation (variation in substrate, age and morphology of lichen samples) of element concentrations would not be large enough to affect the concentration patterns in large areas. We tested this hypothesis in the Aegean region of Turkey, which is very urbanized and industrialized. No such study has been conducted before in this part of the country. A total of 234 samples of the lichen Xanthoria parietina were collected from a 51,800-km2 area. Samples were washed and analyzed by INAA and ICP-AES for 35 elements. The range of the concentrations for most of the elements on a local scale was an order of magnitude lower than for the element concentrations on a regional scale. The mean local coefficient of variance (CV) was found to be 15, providing that the local variation did not affect the concentration of elements in the sampling region. According to cluster analysis, 8 (As, Hg, Pb, Sb, Fe, Mn, Na and K) elements are indicative of important local pollution locations and their zone of impact in the region. By mapping the concentrations of eight indicative elements in lichen Xanthoria parietina of the Aegean region, it was possible to relate deposition to the existence of known sources of pollution in certain areas. Location of pollution sources such as iron-steel plants, and coal burning in the cities, industrial activity and two important coal-fired power plants generally corresponded with locations of highest element accumulations in the lichens.

  1. Inferences on the Mesozoic evolution of the North Aegean from the isotopic record of the Chalkidiki block

    NASA Astrophysics Data System (ADS)

    Kydonakis, Konstantinos; Brun, Jean-Pierre; Poujol, Marc; Monié, Patrick; Chatzitheodoridis, Elias

    2016-07-01

    The Chalkidiki block is a major domain in the North Aegean that, contrary to other domains in the region, largely escaped thermal perturbations during Tertiary extension. As a result, the Chalkidiki block is an ideal candidate to glean information related to the timing of Mesozoic thermal events using appropriate geochronological techniques. We have undertaken a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study (U-Th-Pb on monazites and U-Pb on zircons) coupled with 40Ar/39Ar dating on nine samples from various structural levels within the thrust system of the Chalkidiki block. The eastern, and structurally lower part of the system revealed a complete isotopic reset of Carboniferous - Early Triassic monazites coeval with partial monazite destruction, REE-mobilisation and formation of apatite-allanite-epidote coronas at ~ 132 Ma, a reaction that is commonly observed in amphibolite-facies rocks. These coronas formed after crystallisation of garnet (i.e., at T > 580 °C) and, in all probability, either close to the peak-temperature conditions (~ 620 °C) on a prograde path or during retrogression between the peak-temperature and the low-temperature boundary of the amphibolite facies. Cooling of these rocks and arrival at mid-crustal levels occurred at 95-100 Ma. By contrast, the western, and structurally uppermost part of the system went through the same event by 120-125 Ma. Further structural considerations with respect to medium-temperature geochronology data imply that syn-metamorphic thrusting must have ceased by early Late Cretaceous. We emphasize that, with the sole exception of the Chalkidiki block, no pre-45 Ma medium-temperature geochronology data are preserved in other North Aegean domains, a feature that is clearly related to the extension-induced thermal perturbation of the region during the Tertiary.

  2. Response of the Mediterranean Sea thermohaline circulation to observed changes in the winter wind stress field in the period 1980-1993

    NASA Astrophysics Data System (ADS)

    Samuel, Sarah; Haines, Keith; Josey, Simon; Myers, Paul G.

    1999-04-01

    This paper seeks to model changes in deep water production in the eastern Mediterranean induced by changes in winter wind stress. An analysis of individual monthly wind stress fields over the Mediterranean for 1980-1993 from the SOC flux data set shows that an intensification of the winter mean (mainly January) wind stress over the Aegean Sea and Levantine basin occurred in the latter half of this period. A weakening of the Mistral occurred at the same time. Two monthly wind stress climatologies were created using the 1980-1987 and 1988-1993 periods, and these were used to force an ocean general circulation model of the Mediterranean, with climatological surface T, S relaxation. The Levantine intermediate water (LIW) dispersal path in the Ionian is altered in the 1988-1993 experiment with no pathway to the Adriatic and, consequently, greatly reduced exchange at Otranto and a collapse in Adriatic deep water formation. In contrast, there is an increased exchange of LIW at the Cretan arc straits and enhanced Aegean deep water production in the 1988-1993 experiment. Much more Aegean water exits into the Levantine and Ionian basins as is shown by an east-west cross section south of Crete, along a similar path to the Meteor cruise in 1995. Changes in air-sea fluxes are diagnosed from the model showing a small increase in wintertime cooling over the Aegean and reduced cooling over the Adriatic after 1987. While the changes in air-sea fluxes are probably underrepresented by this simulation, the large changes induced by the wind forcing suggest this could be a mechanism in the altered thermohaline state of the eastern Mediterranean since 1987.

  3. Peeking through the trapdoor: Historical biogeography of the Aegean endemic spider Cyrtocarenum Ausserer, 1871 with an estimation of mtDNA substitution rates for Mygalomorphae.

    PubMed

    Kornilios, P; Thanou, E; Kapli, P; Parmakelis, A; Chatzaki, M

    2016-05-01

    The Aegean region, located in the Eastern Mediterranean, is an area of rich biodiversity and endemism. Its position, geographical configuration and complex geological history have shaped the diversification history of many animal taxa. Mygalomorph spiders have drawn the attention of researchers, as excellent model systems for phylogeographical investigations. However, phylogeographic studies of spiders in the Aegean region are scarce. In this study, we focused on the phylogeography of the endemic ctenizid trap-door spider Cyrtocarenum Ausserer, 1871. The genus includes two morphologically described species: C. grajum (C.L. Koch, 1836) and C. cunicularium (Olivier, 1811). We sampled 60 specimens from the distributions of both species and analyzed four mitochondrial and two nuclear markers. Cyrtocarenum served as an example to demonstrate the importance of natural history traits in the inference of phylogeographic scenarios. The mtDNA substitution rates inferred for the genus are profoundly higher compared to araneomorph spiders and other arthropods, which seems tightly associated with their biology. We evaluate published mtDNA substitution rates followed in the literature for mygalomorph spiders and discuss potential pitfalls. Following gene tree (maximum likelihood, Bayesian inference) and species tree approaches ((*)BEAST), we reconstructed a time-calibrated phylogeny of the genus. These results, combined with a biogeographical ancestral-area analysis, helped build a biogeographic scenario that describes how the major palaeogeographic and palaeoclimatic events of the Aegean may have affected the distribution of Cyrtocarenum lineages. The diversification of the genus seems to have begun in the Middle Miocene in the present west Aegean area, while major phylogenetic events occurred at the Miocene-Pliocene boundary for C. cunicularium, probably related to the Messinian Salinity Crisis. Our results also demonstrate the clear molecular distinction of the two

  4. Variation of the Earth tide-seismicity compliance parameter the last 50 years for the west site of the Aegean Volcanic Arc, Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arabelos, D. N.; Vergos, G.; Spatalas, S.

    2015-07-01

    Based on the results of our studies for the tidal triggering effect on the seismicity of the Hellenic area, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality for earthquake occurrence and we check if the recent increase in the seismic activity at the west site of the Aegean Volcanic Arc indicate faulting maturity for a stronger earthquake. In this paper we present the results of this test which are positive.

  5. Acoustic Scattering Kernels from Arctic Sea Ice.

    DTIC Science & Technology

    1986-10-01

    84-C-0180 S. PErfORMING ORGANIZATION NAME AND AOMRSSS 10. PROGRAM ELEMENT. PROJECT . TASK Science Applications International Corp. AREA & WORK UNIT...al. (1986) described an implementation of SISM/ICE for the ASTRAL and PE models. The concepts are also relevant to other models, including FACT, FFP...Even if the ice field contains keels of only a single size, the projected keel width intercepted by any particular track will take on a range of

  6. The Strategic Value of Aegean Islands and Today’s NATO Policy

    DTIC Science & Technology

    1988-04-01

    Soviet Navy In the ,ear, add "irwrtant ccm- p i ex itie The Psycological ir1pact of the geographical ccnfigllratlmr, uponi N/vTtrQ States ii ttic- area...political threat in the Mediterranean and an increasing politico -naval challenge to the American Sixth Fleet in the inlcnc sea. (4:LI) Of capital importance...time even approaching the outskirts of the Ottoarn capital . During the Balkan War of 1912-13, Forces reached the outer defense girdle of Constantinople

  7. Late Miocene cooling and extension identified on Serifos, western Cyclades: Development of an Aegean metamorphic core complex

    NASA Astrophysics Data System (ADS)

    Vogel, H.; Schneider, D. A.; Heizler, M.; Grasemann, B.; Iglseder, C.; ACCEL Team

    2007-12-01

    The island of Serifos is located in the Western Cyclades archipelago, a region noted for Miocene extension, where slab roll-back of the African-Arabian plate and gravitational collapse of a thickened crust has resulted in north-south to northeast-southwest directed extension. Bedrock lithologies on the island are composed of calc- silicates, schists, gneisses, and marbles metamorphosed to greenschist- to lower amphibolite-facies conditions. Project ACCEL (Aegean Core Complexes along an Extended Lithosphere) has recently documented a major low-angle shear zone consisting of (ultra)mylonitic marbles and orthogneisses with stretching lineations and kinematic indicators that record consistent SSW-directed extensional shear. The orthogneisses found within this shear zone are thought to be a syn-kinematic granite that yield preliminary U-Pb zircon rim ages of c. 37 Ma, suggesting a Late Eocene magmatic and deformation event. The southern part of the island is dominated by a largely undeformed, I-type granodiorite pluton of Late Miocene age. Serifos contains all the hallmarks of a classic Aegean metamorphic core complex, and a thermochronology campaign is underway to elucidate the timing of extension and unroofing. Analysis of fourteen mica separates using Ar-Ar thermochronmetry reveals two distinct cooling age populations, separated by a steep age gradient that is coincident with the well-defined shear zone in the northern region of the island. Samples taken from the southern units of the island, within the shear zone, and adjacent to the granodiorite pluton, give cooling ages of 8-9 Ma, illustrating bedrock cooling and exhumation coeval with intrusion of the granodiorite. Lower grade lithologies from the northern portion of the island yield mica cooling ages of 32-35 Ma. Eocene cooling ages present on Serifos are identical to deformation ages reported from the Cycladic Blueschist unit (CBU), present on nearby islands in the Cyclades and Evvia. The cooling and

  8. Global sea level rise

    SciTech Connect

    Douglas, B.C. )

    1991-04-15

    Published values for the long-term, global mean sea level rise determined from tide gauge records exhibit considerable scatter, from about 1 mm to 3 mm/yr. This disparity is not attributable to instrument error; long-term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year. Instead, the differing estimates of global sea level rise appear to be in large part due to authors' using data from gauges located at convergent tectonic plate boundaries, where changes of land elevation give fictitious sea level trends. In addition, virtually all gauges undergo subsidence or uplift due to postglacial rebound (PGR) from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling PGR by the ICE-3G model of Tushingham and Peltier (1991) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. The value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 is 1.8 mm/yr {plus minus} 0.1. This result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality.

  9. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system.

    PubMed

    Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai

    2016-06-17

    Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report (3)He/(4)He measurements in CO2-dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a (3)He/(4)He signature of at least 7.0 Ra (being Ra the (3)He/(4)He ratio of atmospheric He equal to 1.39×10(-6)), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like (3)He/(4)He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano.

  10. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system

    PubMed Central

    Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N.; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai

    2016-01-01

    Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report 3He/4He measurements in CO2–dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a 3He/4He signature of at least 7.0 Ra (being Ra the 3He/4He ratio of atmospheric He equal to 1.39×10−6), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like 3He/4He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano. PMID:27311383

  11. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system

    NASA Astrophysics Data System (ADS)

    Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N.; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai

    2016-06-01

    Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report 3He/4He measurements in CO2–dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a 3He/4He signature of at least 7.0 Ra (being Ra the 3He/4He ratio of atmospheric He equal to 1.39×10‑6), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like 3He/4He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano.

  12. Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea.

    PubMed

    Kousteni, V; Kasapidis, P; Kotoulas, G; Megalofonou, P

    2015-03-01

    Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed.

  13. Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

    PubMed Central

    Kousteni, V; Kasapidis, P; Kotoulas, G; Megalofonou, P

    2015-01-01

    Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed. PMID:25469687

  14. Radio emission of sea surface at centimeter wavelengths and is fluctuations

    NASA Technical Reports Server (NTRS)

    Tseytlin, N. M.; Shutko, A. M.; Zhislin, G. M.

    1981-01-01

    The eigen thermal radio emission of the sea was examined as well as the agitated surface of the sea when the reflection (scattering) is similar in nature to diffused scattering. The contribution of this emission to the total emission of the sea is practically constant in time, and the time fluctuations of the radio emissions of the sea are basically determined only by a change in the eigen emission of the sea, connected with the agitation.

  15. Scattering models in the microwave regime

    NASA Technical Reports Server (NTRS)

    Fung, A. K.

    1984-01-01

    Results of first and second year research efforts are summarized in a series of complete articles and abstracts. The goal of the first year efforts was to calculate scattering from an inhomogeneous layer with irregular boundaries to model natural terrains. The model was applied to interpret measurements from vegetation, snow, and sea ice. The goal of the second year was to extend the scattering model to handle disc shaped scatterers which are comparable to incident wavelength and to use the model to investigate the relative merits between active versus passive sensing of soil moisture over vegetated terrain.

  16. Sea level variation

    NASA Technical Reports Server (NTRS)

    Douglas, Bruce C.

    1992-01-01

    Published values for the long-term, global mean sea level rise determined from tide gauge records range from about one to three mm per year. The scatter of the estimates appears to arise largely from the use of data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends, and the effects of large interdecadal and longer sea level variations on short (less than 50+ years) or sappy records. In addition, virtually all gauges undergo subsidence or uplift due to isostatic rebound from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling rebound by the ICE-3G model of Tushingham and Peltier (1990) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. A global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 yields the global sea level rise value 1.8 mm/year +/- 0.1. Greenhouse warming scenarios commonly forecast an additional acceleration of global sea level in the next 5 or 6+ decades in the range 0.1-0.2 mm/yr2. Because of the large power at low frequencies in the sea level spectrum, very long tide gauge records (75 years minimum) have been examined for past apparent sea level acceleration. For the 80-year period 1905-1985, 23 essentially complete tide gauge records in 10 geographic groups are available for analysis. These yielded the apparent global acceleration -0.011 (+/- 0.012) mm/yr2. A larger, less uniform set of 37 records in the same 10 groups with 92 years average length covering the 141 years from 1850-1991 gave 0.001 (+/- 0.008) mm/yr2. Thus there is no evidence for an apparent acceleration in the past 100+ years that is significant either statistically, or in comparison to values associated with global warming. Unfortunately, the large interdecadal fluctuations of sea level severely affect

  17. Comparative phylogeography of tenebrionid beetles in the Aegean archipelago: the effect of dispersal ability and habitat preference.

    PubMed

    Papadopoulou, Anna; Anastasiou, Ioannis; Keskin, Bekir; Vogler, Alfried P

    2009-06-01

    Comparative phylogeographical studies in island archipelagos can reveal lineage-specific differential responses to the geological and climatic history. We analysed patterns of genetic diversity in six codistributed lineages of darkling beetles (Tenebrionidae) in the central Aegean archipelago which differ in wing development and habitat preferences. A total of 600 specimens from 30 islands and eight adjacent mainland regions were sequenced for mitochondrial cytochrome oxidase I and nuclear Muscular protein 20. Individual gene genealogies were assessed for the presence of groups that obey an independent coalescent process using a mixed Yule coalescent model. The six focal taxa differed greatly in the number of coalescent groups and depth of lineage subdivision, which was closely mirrored by the degree of geographical structuring. The most severe subdivision at both mitochondrial DNA and nuclear DNA level was found in flightless lineages associated with presumed stable compact-soil habitats (phrygana, maquis), in contrast to sand-obligate lineages inhabiting ephemeral coastal areas that displayed greater homogeneity across the archipelago. A winged lineage, although associated with stable habitats, showed no significant phylogenetic or geographical structuring. Patterns of nucleotide diversity and local genetic differentiation, as measured using PhiST and hierarchical AMOVA, were consistent with high levels of ongoing gene flow in the winged taxon; frequent local extinction and island recolonisation for flightless sand-obligate taxa; and very low gene flow and geographical structure largely defined by the palaeogeographical history of the region in flightless compact-soil taxa. These results show that differences in dispersal rate, mediated by habitat persistence, greatly influence the levels of phylogeographical subdivision in lineages that are otherwise subjected to the same geological events and palaeoclimatic changes.

  18. Tracing metal pollution sources of plants and soils in Güzelhisar Basin of Aegean Region, Turkey

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Görsch, Carolin; Colak Esetlili, Bihter; Esetlili, Tolga; Tepecik, Mahmut; Kurucu, Yusuf; Anac, Dilek; Düring, Rolf-Alexander

    2016-04-01

    The study area Güzelhisar Basin is 6 km far from the city Aliaga, Aegean Region in the west part of Turkey which represents a rather industrialized area having five large iron and steel mills, but also areas of agriculture. A grid system of 2.5 km to the east and 2.5 km to the west of the Güzelhisar Stream was studied. The area was grouped into three main areas as West, Middle, and East region. Every 500 meters soil samples were taken after the rainfall (April-May) in 2014 from the GPS determined points at 0-30 and 30-60 cm depth. Soil reaction of the study area was determined within the range from 5.87 to 6.61. Even though, the West and the Middle regions had weak carbonate concentrations, the East region was poor in carbonates and relatively high electrical conductivity was measured. Topsoil contamination was examined by all investigated elements with the exception of Cd. An increase in pseudo total metal contents of Cr, Cu, Mn, Ni, and Zn was observed with the increasing distance from the coast with a simultaneous decrease in pH. Moreover, high plant metal concentrations [mg kg-¹, ± sd] were detected for B [20.7 ± 23.9], Cu [7.99 ± 5.17], Mn (79.3 ± 89.2), Ni (3.50 ± 3.48), and Zn (25.5 ± 20.1). Transfer of the elements from soil to plants increased in the following order: Co < As < Cr < Pb < Mn < Ni < Cu < Zn < Cd << B.

  19. Relative sea-level change in the central Cyclades (Greece) since the Early Bronze Age

    NASA Astrophysics Data System (ADS)

    Draganits, E.

    2012-04-01

    The Aegean is a focus of important cultural achievements in Europe since the Neolithic period. The resulting abundance of archaeological remains, many of them below sea-level represent an advantageous area for the study of local relative sea-level change. We have carried out detailed mapping of Despotiko Island (SW of Antiparos) and its surrounding. Despotiko is situated almost exactly in the center of the Cyclades (as defined nowadays), more so than Delos, and therefore is very well suited for sea-level studies of the Cyclades. This beneficial location, combined with a spacious and protected bay, additionally may explain its former importance as stepping-stone in the Aegean Sea. The island is uninhabited at present, but Early Bronze Age settlement sites and graveyards as well as a large Archaic sanctuary proof its former importance. The sanctuary is situated on a gently northeast dipping slope in the northeast part of Despotiko, in range of sight of the Órmos Despotiko. Since 1997 large parts of this important sanctuary have been excavated during several excavation campaigns. Tectonically, Despotiko, Antiparos and Paros, belong to the Attic-Cycladic Crystalline of the Central Hellenides, a stack of metamorphic tectonic nappes, mainly comprising variable types of gneiss, schist, marble and amphibolite, and tectonic slices of unmetamorphosed sediments on top, separated by low-angle normal faults from the metamorphic units below. Submerged archaeological structures at the sea bottom of the Órmos Despotiko, a Classical marble inscription from the sanctuary and partly submerged agriculture trenches at the east coast Despotiko, indicate that the relative sea-level in this area was some 3 m lower during the Early Bronze Age and still more than 1 m lower during Classical time. These values of relative sea-level rise indicate a subsidence component additional to the global sea-level rise in the investigated time period. Neglecting possible vertical tectonic movements and

  20. Comparison of two different sea-salt aerosol schemes as implemented in air quality models applied to the Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Jimenez-Guerrero, P.; Jorba, O.; Pay, M. T.; Montavez, J. P.; Jerez, S.; Gomez-Navarro, J. J.; Baldasano, J. M.

    2010-12-01

    A number of attempts have been made to incorporate sea-salt aerosols (SSA) source functions in chemistry transport models with varying results according to the complexity of the scheme considered. This contribution compares the inclusion of two different SSA algorithms in two chemistry transport models: CMAQ and CHIMERE. The main goal is to examine the differences in average SSA mass and composition and to study the seasonality of the prediction of SSA when applied to the Mediterranean area with high resolution in a reference year. Dry and wet deposition schemes are also analyzed to better understand the differences observed between both models in the target area. The applied emission algorithm in CHIMERE uses a semi-empirical formulation which obtains the surface emission rate of SSA as a function of the surface wind speed cubed and particle size. The emission parameterization included within CMAQ is somehow more sophisticated, since fluxes of SSA are corrected with relative humidity. In order to evaluate their strengths and weaknesses, the participating algorithms as implemented in the chemistry transport models were evaluated against AOD measurements from Aeronet and available surface measurements in Southern Europe and the Mediterranean area, showing biases around -0.003 and -1.2 μg m-3, respectively. The results indicate that both models represent accurately the patterns and dynamics of SSA and its non-uniform behavior in the Mediterranean basin, showing a strong seasonality. The levels of SSA vary strongly across the Western and the Eastern Mediterranean, reproducing CHIMERE higher annual levels in the Aegean Sea (12 μg m-3) and CMAQ in the Gulf of Lion (9 μg m-3). The large difference found for the ratio PM2.5/total SSA in CMAQ and CHIMERE is also investigated. The dry and wet removal rates are very similar for both models despite the different schemes implemented. Dry deposition essentially follows the surface drag stress patterns, meanwhile wet

  1. Comparison of two different sea-salt aerosol schemes as implemented in air quality models applied to the Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Jiménez-Guerrero, P.; Jorba, O.; Pay, M. T.; Montávez, J. P.; Jerez, S.; Gómez-Navarro, J. J.; Baldasano, J. M.

    2011-05-01

    A number of attempts have been made to incorporate sea-salt aerosol (SSA) source functions in chemistry transport models with varying results according to the complexity of the scheme considered. This contribution compares the inclusion of two different SSA algorithms in two chemistry transport models: CMAQ and CHIMERE. The main goal is to examine the differences in average SSA mass and composition and to study the seasonality of the prediction of SSA when applied to the Mediterranean area with high resolution for a reference year. Dry and wet deposition schemes are also analyzed to better understand the differences observed between both models in the target area. The applied emission algorithm in CHIMERE uses a semi-empirical formulation which obtains the surface emission rate of SSA as a function of the particle size and the surface wind speed raised to the power 3.41. The emission parameterization included within CMAQ is somehow more sophisticated, since fluxes of SSA are corrected with relative humidity. In order to evaluate their strengths and weaknesses, the participating algorithms as implemented in the chemistry transport models were evaluated against AOD measurements from Aeronet and available surface measurements in Southern Europe and the Mediterranean area, showing biases around -0.002 and -1.2 μg m-3, respectively. The results indicate that both models represent accurately the patterns and dynamics of SSA and its non-uniform behavior in the Mediterranean basin, showing a strong seasonality. The levels of SSA strongly vary across the Western and the Eastern Mediterranean, reproducing CHIMERE higher annual levels in the Aegean Sea (12 μg m-3) and CMAQ in the Gulf of Lion (9 μg m-3). The large difference found for the ratio PM2.5/total SSA in CMAQ and CHIMERE is also investigated. The dry and wet removal rates are very similar for both models despite the different schemes implemented. Dry deposition essentially follows the surface drag stress patterns

  2. Phylogeography of the Atlanto-Mediterranean sea cucumber Holothuria (Holothuria) mammata: the combined effects of historical processes and current oceanographical pattern.

    PubMed

    Borrero-Pérez, G H; González-Wangüemert, M; Marcos, C; Pérez-Ruzafa, A

    2011-05-01

    We assessed the genetic structure of populations of the widely distributed sea cucumber Holothuria (Holothuria) mammata Grube, 1840, and investigated the effects of marine barriers to gene flow and historical processes. Several potential genetic breaks were considered, which would separate the Atlantic and Mediterranean basins, the isolated Macaronesian Islands from the other locations analysed, and the Western Mediterranean and Aegean Sea (Eastern Mediterranean). We analysed mitochondrial 16S and COI gene sequences from 177 individuals from four Atlantic locations and four Mediterranean locations. Haplotype diversity was high (H=0.9307 for 16S and 0.9203 for COI), and the haplotypes were closely related (π=0.0058 for 16S and 0.0071 for COI). The lowest genetic diversities were found in the Aegean Sea population. Our results showed that the COI gene was more variable and more useful for the detection of population structure than the 16S gene. The distribution of mtDNA haplotypes, the pairwise F(ST) values and the results of exact tests and amova revealed: (i) a significant genetic break between the population in the Aegean Sea and those in the other locations, as supported by both mitochondrial genes, and (ii) weak differentiation of the Canary and Azores Islands from the other populations; however, the populations from the Macaronesian Islands, Algarve and West Mediterranean could be considered to be a panmictic metapopulation. Isolation by distance was not identified in H. (H.) mammata. Historical events behind the observed findings, together with the current oceanographic patterns, were proposed and discussed as the main factors that determine the population structure and genetic signature of H. (H.) mammata.

  3. Source Strength and Scattering Properties of Organic Marine Aerosols

    DTIC Science & Technology

    1999-09-20

    aerosol LONG-TERM GOAL My long term goal is to quantify the role played by sea salt in radiative scattering in the marine environment. This project studies...the number of aerosol particles produced from sea salt under different marine conditions. Studying the chemical composition of those particles...provides important information about their behavior in the atmosphere. OBJECTIVES I would like to see whether the number of sea salt particles observed in

  4. Rayleigh scattering. [molecular scattering terminology redefined

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1981-01-01

    The physical phenomena of molecular scattering are examined with the objective of redefining the confusing terminology currently used. The following definitions are proposed: molecular scattering consists of Rayleigh and vibrational Raman scattering; the Rayleigh scattering consists of rotational Raman lines and the central Cabannes line; the Cabannes line is composed of the Brillouin doublet and the central Gross or Landau-Placzek line. The term 'Rayleigh line' should never be used.

  5. Salish Sea

    EPA Pesticide Factsheets

    The Health of the Salish Sea Report is a collaboration between EPA and Environment Canada to examine the health of the Salish Sea ecosystem in Washington and British Columbia, encompassing the Puget Sound and Georgia Basin.

  6. Red Sea

    Atmospheric Science Data Center

    2013-04-16

    article title:  The Red Sea     View Larger Image ... 2000. Located between the East African coast and the Saudi Arabian peninsula, the Red Sea got its name because the blooms of a type of ... 2000 - The Red Sea between the East Africa coast and Saudi Arabian peninsula. project:  MISR category:  ...

  7. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The skies of the Bering Sea were relatively clear again in this SeaWiFS image showing a band of aquamarine colored water. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  8. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Much of the Bering Sea is clear in this SeaWiFS image. The large expanse of bright aquamarine water is clearly visible. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  9. Ecosystem Structure Changes in the Turkish Seas as a Response to Overfishing

    NASA Astrophysics Data System (ADS)

    Gazihan Akoglu, Ayse; Salihoglu, Baris; Akoglu, Ekin; Kideys, Ahmet E.

    2013-04-01

    Human population in Turkey has grown more than five-fold since its establishment in 1923 and more than 73 million people are currently living in the country. Turkey is surrounded by partially connected seas (the Black Sea, the Sea of Marmara, the Aegean Sea and the Mediterranean Sea) each of which has significantly different productivity levels and ecosystem characteristics. Increasing human population with its growing socio-economic needs has generated an intensive fishing pressure on the fish stocks in its exclusive economic zone. Fishing grounds in the surrounding seas were exploited with different fishing intensities depending upon their productivity level and catch rates. Hence, the responses of these different ecosystems to overfishing have been realized differently. In this study, changes of the ecosystem structures in the Turkish Seas were comparatively investigated by ecosystem indices such as Marine Trophic Index (MTI), Fishing in Balance (FiB) and Primary Production Required (PPR) to assess the degree of sustainability of the fish stocks for future generations.

  10. Using existing data and focused surveys to highlight Cuvier's beaked whales favourable areas: a case study in the central Tyrrhenian Sea.

    PubMed

    Gannier, Alexandre

    2011-01-01

    This study focuses on the necessary elements to implement strategic mitigation in order to avoid Cuvier's beaked whale (CBW) strandings linked to intense sound sources, such as military active sonars, in the Mediterranean Sea. A careful review of stranding data and the analysis of existing survey results are required to highlight the main characters of the species regional distribution. Focused and repeated surveys are needed to confirm that possible favourable areas, such as the Balearic, Tyrrhenian or Aegean Seas, are really favourable CBW habitats. These surveys should be carried out with sea states 0 to 1 in order to minimize the risk of false absence data. Among the regions of interest, the central Tyrrhenian Sea was surveyed with a 12 m sailboat in 2007 and 2008. With 907 km of effective effort, a mean sighting rate of 1.9 CBW school/100 km was obtained, which is amongst the highest densities recorded in the Mediterranean.

  11. Deserts on the sea floor: Edward Forbes and his azoic hypothesis for a lifeless deep ocean.

    PubMed

    Anderson, Thomas R; Rice, Tony

    2006-12-01

    While dredging in the Aegean Sea during the mid-19th century, Manxman Edward Forbes noticed that plants and animals became progressively more impoverished the greater the depth they were from the surface of the water. By extrapolation Forbes proposed his now infamous azoic hypothesis, namely that life would be extinguished altogether in the murky depths of the deep ocean. The whole idea seemed so entirely logical given the enormous pressure, cold and eternal darkness of this apparently uninhabitable environment. Yet we now know that the sea floor is teeming with life. Curiously, it took 25 years for the azoic hypothesis to fall from grace. This was despite the presence of ample contrary evidence, including starfishes, worms and other organisms that seemingly originated from the deep seabed. This is a tale of scientists ignoring observations that ran counter to their deep-seated, yet entirely erroneous, beliefs.

  12. Late Holocene sea level changes along the coast of Southwestern Turkey

    NASA Astrophysics Data System (ADS)

    Kızıldaǧ, Nilhan; Özdaş, Harun; Özel, Erdeniz

    2014-05-01

    A multi-disciplinary survey has been performed along the coast of southwestern Turkey in order to determine relative sea level changes during the Late Holocene. Especially, the submergence of harbour structures of the ancient coastal settlements provides noticeable evidence for eustatic sea level rise and/or tectonic subsidence. In addition, the traces of bioerosion produced by some organisms along the limestone coasts formed at mean sea level position represent a remarkable data of paleoshorelines. These traces can be found below the current sea level nowadays due to relative sea level rise. Both archaeological and biological data provide an important source on the amount and period of relative sea level rise along the coasts of southwestern Turkey-southeastern Aegean Sea. This region is under the influence of active tectonism as a result of the collision of the Arab-African and Eurasian plates. Thus, a large number of earthquakes have occurred in this zone which must have been an impact on submergence of ancient harbour structures and geomorphological formations. This area is located very important zone in terms of being tectonically active, having a large number of ancient coastal settlements, and consisting of limestone lithology. A number of submerged archaeological structures and bioerosion formations have been investigated by measuring the depths of remains with respect to the present sea level. By comparing the eustatic sea level change, current elevations and construction time of archaeological remains, which dated taking into account construction techniques and ceramic findings, we determine the amount of relative sea level change. In addition, numerous active faults have been detected by performing seismic survey. The results indicate that the vertical tectonic movement has much more effect on submergence of archaeological and geomorphological features than eustatic sea level rise. Uncovering the role of the tectonic movement and sea level changes on the

  13. Doppler characteristics of sea clutter.

    SciTech Connect

    Raynal, Ann Marie; Doerry, Armin Walter

    2010-06-01

    Doppler radars can distinguish targets from clutter if the target's velocity along the radar line of sight is beyond that of the clutter. Some targets of interest may have a Doppler shift similar to that of clutter. The nature of sea clutter is different in the clutter and exo-clutter regions. This behavior requires special consideration regarding where a radar can expect to find sea-clutter returns in Doppler space and what detection algorithms are most appropriate to help mitigate false alarms and increase probability of detection of a target. This paper studies the existing state-of-the-art in the understanding of Doppler characteristics of sea clutter and scattering from the ocean to better understand the design and performance choices of a radar in differentiating targets from clutter under prevailing sea conditions.

  14. The Sea Peoples, from Cuneiform Tablets to Carbon Dating

    PubMed Central

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13th century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192–1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

  15. The Sea Peoples, from cuneiform tablets to carbon dating.

    PubMed

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13(th) century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192-1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations.

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

    NASA Astrophysics Data System (ADS)

    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

  17. Modelling tsunamis in the Eastern Mediterranean Sea. Application to the Minoan Santorini tsunami sequence as a potential scenario for the biblical Exodus

    NASA Astrophysics Data System (ADS)

    Periáñez, R.; Abril, J. M.

    2014-11-01

    A numerical model which simulates the propagation of tsunamis in the Eastern Mediterranean has been developed. Several tsunami sources have been considered: earthquakes associated to geological faults, submarine landslides, entry of pyroclastic flows into the sea and the collapse of a volcano caldera. The model has been applied to different past events for which historic data or previous simulations exist, to test its performance. Then it has been applied to simulate tsunamis triggered by the explosion of Santorini volcano (17th century BC) in the Aegean Sea. While the model accounts for run-ups in the Aegean coasts, it fails to explain the isochronous tsunamigenic deposits reported in eastern Sicily and the levantine coasts. A scenario of a sequence of intense tectonics strain release triggering a series of tsunamis could better fit the whole dataset. Thus, a submarine landslide at the Gulf of Sirte may explain the Augias megaturbidite and the sedimentary deposits reported in Augusta Bay (Sicily). Similarly, a sequential tsunami in the eastern Nile Delta may explain the tsunamigenic deposits found in Israel and Gaza. Considering the former coastline at 3500 years BP, it could also provide a plausible scenario for the biblical sea crossing related in the Exodus.

  18. Parity Violation in Electron Scattering

    SciTech Connect

    Beise, Elizabeth

    2007-10-26

    About thirty years ago, electron scattering from nucleons was used [1] to identify, and then measure, the properties of the weak interaction, the only force of nature known to violate the symmetry parity. The basic technique has not fundamentally changed, which is to look for a small asymmetry in count rate from scattering a polarized electron beam from an unpolarized target. Since then, parity-violating (PV) electron scattering has developed substantially, a result of significant improvements in polarized electron beams, accelerator advancements, and developments in cryogenic targets that make it possible to carry out experiments with much higher statistical precision. In the last decade PV experiments have focused on using the complementary electron-quark flavor coupling of the weak interaction to identify and place limits on contributions of strange quark-antiquark pairs to the charge and magnetism of the proton. This observable provides a unique window into the structure of the proton since strange quark contributions can arise only from the sea of quarks and gluons that are responsible for the vast majority of the nucleon's mass. This paper will report on recent results aimed at this goal, along with a brief overview of future directions.

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

    DTIC Science & Technology

    2000-06-02

    Orlando, USA 3.00pm III.3 ŗD. Ultra Thin Chip Stacking: Methods and Results" J.P. BAILBE, S.Pinel, J.Tasselli, and A.Marty Laboratoire d’Analyse et...degreased in acetone and methanol, with the SiC additionally cleaned by the RCA method . All substrates were then subjected to an 1100°C anneal for 10... capacitance -voltage (C-V) measurements of two different AlGaN/GaN/AlGaN/sapphire transistor structures. The profile depicted by the solid line is of a

  20. Meiofauna, microflora and geochemical properties of the late quaternary (Holocene) core sediments in the Gulf of Izmir (Eastern Aegean Sea, Turkey)

    NASA Astrophysics Data System (ADS)

    Yümün, Zeki Ü.; Meriç, Engin; Avşar, Niyazi; Nazik, Atike; Barut, İpek F.; Yokeş, Baki; Sagular, Enis K.; Yildiz, Ayşegül; Eryilmaz, Mustafa; Kam, Erol; Başsari, Asiye; Sonuvar, Bora; Dinçer, Feyza; Baykal, Kubilay; Kaya, Seyhan

    2016-12-01

    The Gulf of Izmir has seen the construction of marinas at four locations; Karşıyaka, Bayraklı, İnciraltı and Urla (Çeşmealtı). Six drilling holes have been structured for each location. Morphological abnormities observed in foraminifer tests, obtained from these core drillings, and coloring encountered in both foraminifer tests and ostracod carapeces, provide evidence of natural and unnatural environmental pollution. The objectives of this study are to identify micro and macro fauna, foraminifers in particular, contained within sediments in the above-mentioned locations; to investigate the background of pollution in the Gulf Region; and to determine pollution's impact upon benthic foraminifer and ostracods. Çeşmealtı foraminifera tests did not lead to color and morphological changes. But foraminifera tests samples collected from Karşıyaka, Bayraklı and İnciraltı led them to turn black (Plate 4-6). However, concentrations of heavy metals (Ni, Cr and Mn) obtained from the sediments of Karşıyaka, Bayraklı and İnciraltı locations are higher than those obtained from the Çeşmealtı samples and high concentrations of these elements may be the cause of the color change in the samples during the foraminifera tests. In Karşıyaka and Bayraklı ostracod samples, Bosquetina carinella, Pterygocythereis jonesi, Semicytherura species; in the Çeşmealtı/Urla zone, Cyprideis torosa; in İnciraltı, Pseudopsammocythere reniformis; and in four zones, Loxoconcha and Xestoleberis species were observed in the range of relative frequency. The same analyses were done on nannoplankton but they did not lead to color and morphological changes.

  1. Shallow seismic study of the geothermal areas in the Gülbahçe Bay and İzmir Gulf (Aegean Sea, Western Turkey)

    NASA Astrophysics Data System (ADS)

    Altan, Zehra; Ocakoğlu, Neslihan

    2016-12-01

    The two seismic units, i.e., the basement and the basin sediments are interpreted as Miocene and Plio-Quaternary deposits, respectively. The basin sediments of approximately 255 m thickness are risen and compressed through the active strike-slip faults, GF1-GF3 extending in N-S direction towards the outer Gülbahçe Bay. These compressed sediments are interpreted as upwelling zones with weak reflection character and internal frequency attenuation. The most significant one is marked as a possible mud diaper zone with a 320 m width and the approximately 500 m. A synthetic model of the field data gathered from the diaper indicates that the top of the diapir is characterised by a strong positive reflection character while the internal diaper is represented by polarity reversals and weak reflections due to a velocity decrease with depth. Moreover, phase changes are observed at the border of the diapiric structure. A relatively thicker basin sediment unit of approximately 700 m was observed on the pro-delta sediments of the Gediz River and the sediments below in the İzmir Gulf. The active strike-slip faults, İF1-İF5 deform the basement and basin deposits. Moreover, two active normal faults, İF6 and İF7 are marked from inner to outer part of the gulf. The seismic attribute sections indicate weak reflection zones and frequency attenuation particularly both inside the pro-delta sediments and the sediments below. Observations suggest to us the existence of possible fluid and/or gas discharges and saturations in the Gülbahçe Bay and İzmir Gulf.

  2. Multi-Biomarker Responses After Exposure to Pollution in the Mediterranean Mussels (Mytilus galloprovincialis L.) in the Aegean Coast of Turkey.

    PubMed

    Ozkan, Dilara; Dagdeviren, Melih; Katalay, Selma; Guner, Adem; Yavaşoğlu, N Ülkü Karabay

    2017-01-01

    In this study, sublethal effects on the Mediterranean mussels (Mytilus galloprovincialis L.) collected from the Aegean coast of Turkey were determined. Enzymes such as glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and acetylcholinesterase (AChE), metallothionein (MT) mRNA expressions, thiobarbituric acid reactive substances (TBARS) contents, determination of 14 heavy metals and micronucleus frequency were selected as multibiomarkers. Results show that heavy metals and an increase in the level of MT gene expression have been determined in tissues of mussels collected from all stations. The GST, SOD and CAT enzymes were increased in mussels of Aliaga and Old Foca, compared to the mussels of Urla, while it was showed inhibition at AChE levels. Extensive LP is determined on mussels of Aliaga. It was determined that mussels in Aliaga region have exposed more oxidative stress than Old Foca and Urla. These biomarkers were carried out for the first time in these stations to assess environmental quality.

  3. 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

    USGS Publications Warehouse

    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.

  4. Molecular Basis of β-Thalassemia in the Population of the Aegean Region of Turkey: Identification of A Novel Deletion Mutation.

    PubMed

    Ozkinay, Ferda; Onay, Huseyin; Karaca, Emin; Arslan, Esra; Erturk, Biray; Ece Solmaz, Asli; Tekin, Ismihan Merve; Cogulu, Ozgur; Aydinok, Yeşim; Vergin, Canan

    2015-01-01

    β-Thalassemia (β-thal) is the most common monogenic disorder in Turkey. The aim of this study was to investigate the spectrum of β-thal mutations in the Aegean region of Turkey. The data was derived from 1171 unrelated β-thal subjects, detected in a regional reference hospital between November 2004 and December 2013. Screening for the 22 common mutations was performed using the polymerase chain reaction (PCR)-reverse dot-blot method, and direct automated DNA sequencing for the unknown samples. Thirty-one different β-thal alleles were identified. Seven mutations, namely IVS-I-110 (G > A) (41.7%), IVS-I-1 (G > A) (8.9%), IVS-II-745 (C > G) (8.6%), codon 8 (-AA) (7.7%), IVS-II-1 (G > A) (7.2%), IVS-I-6 (T > C) (6.6%), codon 39 (C > T) (4.6%) accounted for 85.3% of the mutated alleles. Frequencies of the remaining 24 β-thal mutations were less than 2.2%; these included one novel mutation [HBB: c.206_212del (p.Leu69Profs*19)], and four others [-56 (G > C), codon 16 (-C), IVS-I (-3) (C > T) (codon 29), codon 76 (-C)] found in Turkey for the first time. The results will help to prevent severe β-thal through genetic counseling and prenatal diagnosis (PND) in the Aegean region of Turkey.

  5. Abyssal and deep circulation in the Eastern Mediterranean Sea (Ionian Sea)

    NASA Astrophysics Data System (ADS)

    Artale, Vincenzo; Bensi, Manuel; Falcini, Federico; Marullo, Salvatore; Rubino, Angelo

    2016-04-01

    In the mid-1990s, experimental evidences on the Eastern Mediterranean Transient (EMT) were presented and it was shown that the Mediterranean abyssal circulation is not in a steady state but can be subjected to episodic sudden changes (Roether et al., 1996). In the last 10 years the Ionian Sea, the central and deepest part of the Mediterranean Sea, was subjected to relevant scientific interests from a theoretical and experimental point of view. Among these, there is the discovery of the BiOS (Bimodal Oscillating System), one new mechanism that drives a periodic (almost decadal) redistribution of surface and subsurface waters in the Eastern Mediterranean, with considerable feedbacks in the variability of the deep-water formation both in the southern Adriatic and in the Levantine and Aegean sub-basins (Gačić et al., 2010). In the Ionian Sea, numerous recent observational campaigns have been conducted to investigate the behaviour of deep and abyssal waters, at depths between 2000-4000m that are comparable to the mean global ocean depth (Rubino and Hainbucher, 2007; Bensi et al., 2013). There, advection, diffusion and vertical stability of the water masses can assume an important role on the internal quasi-periodical variability, creating the preconditions for catastrophic events such as the EMT or reversals of the Ionian circulation (Pisacane et al., 2006). Since there are no significant deep heat sources in the world ocean, waters that fill the deep ocean can only return to the sea surface as a result of downward mixing of heat from the sea surface to the bottom and vice versa and this occurs through eddy diffusion. Along our presentation, mainly through the analysis of the deepest CTD casts taken from 2009 to 2011 in the eastern basins and in particular in the Ionian Sea, we will show a significant change in the deep thermohaline structure (including its biogeochemical and hydrological characteristics), giving an indication on the time scale of the renewal of deep

  6. Optics as Scattering

    ERIC Educational Resources Information Center

    di Francia, Giuliano Toraldo

    1973-01-01

    The art of deriving information about an object from the radiation it scatters was once limited to visible light. Now due to new techniques, much of the modern physical science research utilizes radiation scattering. (DF)

  7. Polarimetric signatures of sea ice. 1: Theoretical model

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

    1995-01-01

    Physical, structral, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarmetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies to interpretation of sea ice polarimetric signatures.

  8. Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

    1995-01-01

    Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

  9. Caspian Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this Moderate-resolution Imaging Spectroradiometer (MODIS) image from December 3, 2001, winter sea ice can be seen forming in the shallow waters of the northern Caspian (left) and Aral (upper right) Seas. Despite the inflow of the Volga River (upper left), the northern portion of the Caspian Sea averages only 17 feet in depth, and responds to the region's continental climate, which is cold in winter and hot and dry in the summer. The southern part of the Sea is deeper and remains ice-free throughout the winter. The dirty appearance of the ice may be due to sediment in the water, but may also be due to wind-driven dust. The wind in the region can blow at hurricane-force strength and can cause the ice to pile up in hummocks that are anchored to the sea bottom. The eastern portion of the Aral Sea is also beginning to freeze. At least two characteristics of the Aral Sea 'compete' in determining whether its waters will freeze. The Sea is shallow, which increases the likelihood of freezing, but it is also very salty, which means that lower temperatures are required to freeze it than would be required for fresh water. With average December temperatures of 18oF, it's clearly cold enough to allow ice to form. As the waters that feed the Aral Sea continue to be diverted for agriculture, the Sea becomes shallower and the regional climate becomes even more continental. This is because large bodies of water absorb and retain heat, moderating seasonal changes in temperature. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  10. Scattering from binary optics

    NASA Technical Reports Server (NTRS)

    Ricks, Douglas W.

    1993-01-01

    There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

  11. Offshore Seismic Observation in the Western Marmara Sea, Turkey

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Takahashi, N.; Citak, S.; Kalafat, D.; Pinar, A.; Gurbuz, C.; Kaneda, Y.

    2014-12-01

    The North Anatolian Fault (NAF) extends 1600 km westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea, accommodating about 25 mm/yr of right-lateral motion between Anatolia and the Eurasian plate. Since 1939, devastating earthquakes with magnitude greater than seven ruptured NAF westward, starting from 1939 Erzincan at the eastern Turkey and including the latest 1999 Izmit-Golcuk and the Duzce earthquakes in the Marmara region. Considering the fault segments ruptured by the May 24th, 2014 Northern Aegean earthquake, the only un-ruptured segments left behind NAF locate beneath the Marmara Sea and those segments keep their mystery due to their underwater location. To clarify the detailed fault geometry beneath the western Marmara Sea, we started to operate a series of ocean bottom seismographic (OBS) observations. As a first step, we deployed 3 pop-up type OBSs on 20th of March 2014 as a trial observation, and recovered them on 18thof June 2014. Although one of the OBSs worked only 6 days from the start of the observation, other two OBSs functioned properly during the whole 3-month observation period. Only 8 earthquakes were reported near the OBS network in 3 months periods according to the Kandilli Observatory and Earthquake Research Institute catalogue. Thus, we first searched for the microearthquakes missing by the land seismic network and estimated their precious location by using the initial 6 days data. We could identify about 50 earthquakes with more than 5 picking data of P and S first arrivals, and half of them located near the NAF. We also tested the hypocenter relocation by combining the land and OBS seismic data for the 8 earthquakes, and found that these earthquakes are located in between 12-24 km depths. Next, we are planning to deploy 10 OBSs from September 2014 to June 2015 as a second step for our observation. At the AGU fall meeting, we will be able to

  12. Multiple scattering technique lidar

    NASA Technical Reports Server (NTRS)

    Bissonnette, Luc R.

    1992-01-01

    The Bernouilli-Ricatti equation is based on the single scattering description of the lidar backscatter return. In practice, especially in low visibility conditions, the effects of multiple scattering can be significant. Instead of considering these multiple scattering effects as a nuisance, we propose here to use them to help resolve the problems of having to assume a backscatter-to-extinction relation and specifying a boundary value for a position far remote from the lidar station. To this end, we have built a four-field-of-view lidar receiver to measure the multiple scattering contributions. The system has been described in a number of publications that also discuss preliminary results illustrating the multiple scattering effects for various environmental conditions. Reported here are recent advances made in the development of a method of inverting the multiple scattering data for the determination of the aerosol scattering coefficient.

  13. SAR image simulation from composite sea-ship scene based on a weighted multipath model

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Zhao, Ye; Nie, Ding

    2016-10-01

    A weighted multi-path model for the composite electromagnetic (EM) scattering and SAR image application of sea surface with a ship target is presented according to the distribution characteristics of specular reflection facets on a deterministic rough sea surface. This model reasonably includes the influence of non-negligible roughness of sea surface in the coupling scattering calculation, which could avoid the error caused by planar approximation in the traditional four-path model. Numerical simulation results show that the entire simulator could provide a preliminary prediction on the radar cross sections (RCS) for the composite scene with electrically large size. In addition, the total scattering contribution contains both the amplitude and phase information of the scattering facets on the composite ship-sea surface, which can be effectively applied in the scattering characteristics identification of ship target on the sea surface and SAR image simulation.

  14. Arabian Sea

    Atmospheric Science Data Center

    2013-04-16

    ... sometimes results in copious phytoplankton production and oxygen depletion of the subsurface waters. Although red phytoplankton fluorescences have been associated with the low oxygen concentrations in the intermediate and deep waters of the Arabian Sea, ...

  15. Sea Legs

    NASA Astrophysics Data System (ADS)

    Macdonald, Kenneth C.

    Forty-foot, storm-swept seas, Spitzbergen polar bears roaming vast expanses of Arctic ice, furtive exchanges of forbidden manuscripts in Cold War Moscow, the New York city fashion scene, diving in mini-subs to the sea floor hot srings, life with the astronauts, romance and heartbreak, and invading the last bastions of male exclusivity: all are present in this fast-moving, non-fiction account of one woman' fascinating adventures in the world of marine geology and oceanography.

  16. Hyperspectral imaging simulation of object under sea-sky background

    NASA Astrophysics Data System (ADS)

    Wang, Biao; Lin, Jia-xuan; Gao, Wei; Yue, Hui

    2016-10-01

    Remote sensing image simulation plays an important role in spaceborne/airborne load demonstration and algorithm development. Hyperspectral imaging is valuable in marine monitoring, search and rescue. On the demand of spectral imaging of objects under the complex sea scene, physics based simulation method of spectral image of object under sea scene is proposed. On the development of an imaging simulation model considering object, background, atmosphere conditions, sensor, it is able to examine the influence of wind speed, atmosphere conditions and other environment factors change on spectral image quality under complex sea scene. Firstly, the sea scattering model is established based on the Philips sea spectral model, the rough surface scattering theory and the water volume scattering characteristics. The measured bi directional reflectance distribution function (BRDF) data of objects is fit to the statistical model. MODTRAN software is used to obtain solar illumination on the sea, sky brightness, the atmosphere transmittance from sea to sensor and atmosphere backscattered radiance, and Monte Carlo ray tracing method is used to calculate the sea surface object composite scattering and spectral image. Finally, the object spectrum is acquired by the space transformation, radiation degradation and adding the noise. The model connects the spectrum image with the environmental parameters, the object parameters, and the sensor parameters, which provide a tool for the load demonstration and algorithm development.

  17. Diet and trophic ecology of the lanternfish Electrona risso (Cocco 1829) in the Strait of Messina (central Mediterranean Sea) and potential resource utilization from the Deep Scattering Layer (DSL)

    NASA Astrophysics Data System (ADS)

    Battaglia, Pietro; Andaloro, Franco; Esposito, Valentina; Granata, Antonia; Guglielmo, Letterio; Guglielmo, Rosanna; Musolino, Simona; Romeo, Teresa; Zagami, Giacomo

    2016-07-01

    The feeding habits of the mesopelagic lanternfish Electrona risso from the Strait of Messina (central Mediterranean Sea) were analyzed for the first time. A total of 326 individuals were collected stranded along the Sicilian coast of the Strait of Messina from October 2012 to May 2013. Specimens ranged from 12.0 to 53.8 mm LS (mean LS = 38.6 ± 8.4 mm). Their stomach content was examined and prey composition and feeding strategy were investigated. The results indicate that E. risso is a specialist predator, which feeds mainly on the small mesopelagic fish Cyclothone braueri (%IRI = 74.06) and in minor proportion on zooplankton, with a prevalence of copepods. The specialized feeding strategy of E. risso is confirmed by the low value of Levins standardized index (Bj = 0.141), which indicated a restricted niche breadth. The value of the index of trophic level (TROPH) for E. risso resulted 4.20. The prey composition suggests that E. risso can be considered a weakly vertical migrating species, that feeds on the DSL crustacean and fish communities below 300 m of depth.

  18. Biochemical biomarker responses to pollution in selected sentinel organisms across the Eastern Mediterranean and the Black Sea.

    PubMed

    Catherine, Tsangaris; Vanessa, Moschino; Evangelia, Strogyloudi; Valentina, Coatu; Andreja, Ramšak; Rana, Abu Alhaija; Susana, Carvalho; Serena, Felline; Alisa, Kosyan; Yiota, Lazarou; Ioannis, Hatzianestis; Andra, Oros; Daniela, Tiganus

    2016-01-01

    Pollution effects were assessed by means of biochemical biomarkers (catalase, glutathione S-transferase and acetylcholinesterase activities, and metallothioneins content) in five species at selected coastal sites across the Eastern Mediterranean and the Black Sea. The mussel Mytilus galloprovincialis, a well-established sentinel species, was investigated in the Adriatic Sea, Aegean Sea, and Black Sea. The mussel Brachidontes pharaonis and the striped red mullet Mullus surmuletus were used in the Levantine Sea where M. galloprovincialis is not present. The white seabream Diplodus sargus sargus and the gastropod Rapana venosa were additionally sampled in the Adriatic and the Black Sea, respectively. Mussels showed catalase, glutathione S-transferase, and acetylcholinesterase responses to pollution in most geographical areas while the response of metallothioneins was restricted to a few sites. R. venosa showed marked responses of catalase and metallothioneins whereas both fish species did not generally exhibit variations in biomarker values among sites. The approach based on the reference deviation concept using the "Integrated Biological Responses version 2" index was useful for the interpretation of overall biomarker responses.

  19. Newly Formed Sea Ice in Arctic Leads Monitored by C- and L-Band SAR

    NASA Astrophysics Data System (ADS)

    Johansson, A. Malin; Brekke, Camilla; Spreen, Gunnar; King, Jennifer A.; Gerland, Sebastian

    2016-08-01

    We investigate the scattering entropy and co-polarization ratio for Arctic lead ice using C- and L-band synthetic aperture radar (SAR) satellite scenes. During the Norwegian Young sea ICE (N-ICE2015) cruise campaign overlapping SAR scenes, helicopter borne sea ice thickness measurements and photographs were collected. We can therefore relate the SAR signal to sea ice thickness measurements as well as photographs taken of the sea ice. We show that a combination of scattering and co-polarization ratio values can be used to distinguish young ice from open water and surrounding sea ice.

  20. Modeling of Wind Direction Signals in Polarimetric Sea Surface Brightness Temperatures

    NASA Technical Reports Server (NTRS)

    Yueh, S. H.

    1995-01-01

    Sea surface brightness temperatures are the radiometric power measure of blackbody radiation from sea water. This radiation is the electromagnetic waves excited by the random thermal motion of charged particles in the sea water. The energy transmitted through the air- water interface produces a scattering of electromagnetic waves into the atmosphere. Polarimetric microwave emissions are investigated.

  1. High resolution neodymium characterization along the Mediterranean Sea margins: implications for ɛNd modeling.

    NASA Astrophysics Data System (ADS)

    Ayache, Mohamed; Dutay, Jean-claude; Arsouze, Thomas; Jeandel, Catherine; Revillon, Sidonie

    2016-04-01

    An extensive compilation of published neodymium (Nd) concentrations and isotopic compositions (ɛNd) was realized in order to establish a new database and a map (using a high resolution geological map of the area) of the distribution of these parameters for all the Mediterranean margins. Data were extracted from different kinds of samples: river solid discharge deposited on the shelf, sedimentary material collected on the margin or geological material outcropping above or close to a margin. Additional analyses of surface sediments were done, in order to improve this dataset in key areas (e.g Sicilian strait). The Mediterranean margin Nd isotopic signatures vary from non-radiogenic values around the Gulf of Lions, (ɛNd values -11) to radiogenic values around the Aegean and the Levantine sub-basins up to +6. Using a high resolution regional oceanic model (1/12° of horizontal resolution), ɛNd distribution was simulated for the first time in the Mediterranean Sea. The high resolution of the model provides the opportunity to study in more details the processes governing the Nd isotope distribution in the marine environment. This work highlights that a significant interannual variability of ɛNd distribution in seawater could occur. In particular, important hydrological events such as the Eastern Mediterranean Transient (EMT), associated with deep water formed in the Aegean sub-basin, could induce a shift in Nd IC at intermediate depths that could be noticeable in the Western part of the basin. This highlights that the temporal and geographical variations of ɛNd could represent an interesting insight of Nd as a quasi-conservative tracer of water masses in the Mediterranean Sea, in particular in the context of paleo-oceanographic applications, i.e. to explore if EMT-type signatures occurred in the past (Roether et al., 2014, Gacic et al., 2011).

  2. Partially strong WW scattering

    SciTech Connect

    Cheung Kingman; Chiang Chengwei; Yuan Tzuchiang

    2008-09-01

    What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the WW scattering. After partial unitarization by the light Higgs boson, the WW scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong WW scattering.

  3. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Maung, Khin Maung; Wilson, John W.; Buck, Warren W.

    1989-01-01

    The derivations of the Lippmann-Schwinger equation and Watson multiple scattering are given. A simple optical potential is found to be the first term of that series. The number density distribution models of the nucleus, harmonic well, and Woods-Saxon are used without t-matrix taken from the scattering experiments. The parameterized two-body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to the imaginary part of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen as our solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  4. Changes in ventilation of the Mediterranean Sea during the past 25 year

    NASA Astrophysics Data System (ADS)

    Schneider, A.; Tanhua, T.; Roether, W.; Steinfeldt, R.

    2014-01-01

    Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

  5. Optical scatter: an overview

    NASA Astrophysics Data System (ADS)

    Stover, John C.

    1991-12-01

    Optical scatter is a bothersome source of optical noise, limits resolution and reduces system throughput. However, it is also an extremely sensitive metrology tool. It is employed in a wide variety of applications in the optics industry (where direct scatter measurement is of concern) and is becoming a popular indirect measurement in other industries where its measurement in some form is an indicator of another component property - like roughness, contamination or position. This paper presents a brief review of the current state of this technology as it emerges from university and government laboratories into more general industry use. The bidirectional scatter distribution function (or BSDF) has become the common format for expressing scatter data and is now used almost universally. Measurements made at dozens of laboratories around the country cover the spectrum from the uv to the mid- IR. Data analysis of optical component scatter has progressed to the point where a variety of analysis tools are becoming available for discriminating between the various sources of scatter. Work has progressed on the analysis of rough surface scatter and the application of these techniques to some challenging problems outside the optical industry. Scatter metrology is acquiring standards and formal test procedures. The available scatter data base is rapidly expanding as the number and sophistication of measurement facilities increases. Scatter from contaminants is continuing to be a major area of work as scatterometers appear in vacuum chambers at various laboratories across the country. Another area of research driven by space applications is understanding the non-topographic sources of mid-IR scatter that are associated with Beryllium and other materials. The current flurry of work in this growing area of metrology can be expected to continue for several more years and to further expand to applications in other industries.

  6. Sea Ice

    NASA Technical Reports Server (NTRS)

    Perovich, D.; Gerland, S.; Hendricks, S.; Meier, Walter N.; Nicolaus, M.; Richter-Menge, J.; Tschudi, M.

    2013-01-01

    During 2013, Arctic sea ice extent remained well below normal, but the September 2013 minimum extent was substantially higher than the record-breaking minimum in 2012. Nonetheless, the minimum was still much lower than normal and the long-term trend Arctic September extent is -13.7 per decade relative to the 1981-2010 average. The less extreme conditions this year compared to 2012 were due to cooler temperatures and wind patterns that favored retention of ice through the summer. Sea ice thickness and volume remained near record-low levels, though indications are of slightly thicker ice compared to the record low of 2012.

  7. Aral Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This series of MODIS images shows the dwindling Aral Sea. Once one of the world's largest freshwater lakes, the Aral Sea has decreased by as much as 60% over the past few decades due to diversion of the water to grow cotton and rice. These diversion have dropped the lake levels, increased salinity, and nearly decimated the fishing industry. The previous extent of the lake is clearly visible as a whitish perimeter in these image from April 16, May 18, and June 3, 2002. s. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  8. Black Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Black Sea in eastern Russia is experiencing an ongoing phytoplankton bloom. This image, the most recent in a series that began in early may, shows the waters to be even more colorful than before. part of the increased brightness may be due to the presence of sun glint , especially in the center of the sea. However, more organisms appear to be present as well, their photosynthetic pigments reflecting different wavelengths of light.This Moderate Resolution Imaging Spectroradiometer (MODIS) image was captured on June 15, 2002.

  9. 3-D Acoustic Scattering from 2-D Rough Surfaces Using A Parabolic Equation Model

    DTIC Science & Technology

    2013-12-01

    acoustic propagation signals, especially at mid- frequencies and higher (e.g., acoustic communications systems). For many years, the effects of rough...of the effect of surface scattering on 3-D propagation , which is critical in evaluating the variability in underwater acoustic propagation . Results...14. SUBJECT TERMS Acoustic Propagation , Acoustic Scattering, Sea Surface Perturbations, Split- Step Fourier Algorithm, Finite Difference Algorithm

  10. Purely bianisotropic scatterers

    NASA Astrophysics Data System (ADS)

    Albooyeh, M.; Asadchy, V. S.; Alaee, R.; Hashemi, S. M.; Yazdi, M.; Mirmoosa, M. S.; Rockstuhl, C.; Simovski, C. R.; Tretyakov, S. A.

    2016-12-01

    The polarization response of molecules or meta-atoms to external electric and magnetic fields, which defines the electromagnetic properties of materials, can either be direct (electric field induces electric moment and magnetic field induces magnetic moment) or indirect (magnetoelectric coupling in bianisotropic scatterers). Earlier studies suggest that there is a fundamental bound on the indirect response of all passive scatterers: It is believed to be always weaker than the direct one. In this paper, we prove that there exist scatterers which overcome this bound substantially. Moreover, we show that the amplitudes of electric and magnetic polarizabilities can be negligibly small as compared to the magnetoelectric coupling coefficients. However, we prove that if at least one of the direct-excitation coefficients vanishes, magnetoelectric coupling effects in passive scatterers cannot exist. Our findings open a way to a new class of electromagnetic scatterers and composite materials.

  11. Inelastic Light Scattering Processes

    NASA Technical Reports Server (NTRS)

    Fouche, Daniel G.; Chang, Richard K.

    1973-01-01

    Five different inelastic light scattering processes will be denoted by, ordinary Raman scattering (ORS), resonance Raman scattering (RRS), off-resonance fluorescence (ORF), resonance fluorescence (RF), and broad fluorescence (BF). A distinction between fluorescence (including ORF and RF) and Raman scattering (including ORS and RRS) will be made in terms of the number of intermediate molecular states which contribute significantly to the scattered amplitude, and not in terms of excited state lifetimes or virtual versus real processes. The theory of these processes will be reviewed, including the effects of pressure, laser wavelength, and laser spectral distribution on the scattered intensity. The application of these processes to the remote sensing of atmospheric pollutants will be discussed briefly. It will be pointed out that the poor sensitivity of the ORS technique cannot be increased by going toward resonance without also compromising the advantages it has over the RF technique. Experimental results on inelastic light scattering from I(sub 2) vapor will be presented. As a single longitudinal mode 5145 A argon-ion laser line was tuned away from an I(sub 2) absorption line, the scattering was observed to change from RF to ORF. The basis, of the distinction is the different pressure dependence of the scattered intensity. Nearly three orders of magnitude enhancement of the scattered intensity was measured in going from ORF to RF. Forty-seven overtones were observed and their relative intensities measured. The ORF cross section of I(sub 2) compared to the ORS cross section of N2 was found to be 3 x 10(exp 6), with I(sub 2) at its room temperature vapor pressure.

  12. Automatic identification of fault surfaces through Object Based Image Analysis of a Digital Elevation Model in the submarine area of the North Aegean Basin

    NASA Astrophysics Data System (ADS)

    Argyropoulou, Evangelia

    2015-04-01

    The current study was focused on the seafloor morphology of the North Aegean Basin in Greece, through Object Based Image Analysis (OBIA) using a Digital Elevation Model. The goal was the automatic extraction of morphologic and morphotectonic features, resulting into fault surface extraction. An Object Based Image Analysis approach was developed based on the bathymetric data and the extracted features, based on morphological criteria, were compared with the corresponding landforms derived through tectonic analysis. A digital elevation model of 150 meters spatial resolution was used. At first, slope, profile curvature, and percentile were extracted from this bathymetry grid. The OBIA approach was developed within the eCognition environment. Four segmentation levels were created having as a target "level 4". At level 4, the final classes of geomorphological features were classified: discontinuities, fault-like features and fault surfaces. On previous levels, additional landforms were also classified, such as continental platform and continental slope. The results of the developed approach were evaluated by two methods. At first, classification stability measures were computed within eCognition. Then, qualitative and quantitative comparison of the results took place with a reference tectonic map which has been created manually based on the analysis of seismic profiles. The results of this comparison were satisfactory, a fact which determines the correctness of the developed OBIA approach.

  13. Sea Clutter

    DTIC Science & Technology

    1990-09-28

    OE-10, 47i- 476, (1985). 15. S. Tang and 0. H. Shemdin , "Measurement of High-frequency Waves using a Wave Fol- lower," J. Geophys. Res. 88. 9832...DESCRIPTION OF THE SEA SURFACE ................................................................... 2 The Wave Spectrum...Very Low Grazing Angles ......................................................................... 16 At HF and mm- Wave Frequencies

  14. Acoustic studies of zooplankton in the Sea of Japan and Eastern Arctic

    NASA Astrophysics Data System (ADS)

    Akulichev, V. A.; Bulanov, V. A.; Storozhenko, A. V.

    2016-09-01

    We present the results of sound scattering studies to estimate the distribution and dynamics of zooplankton in the upper sea layer under various conditions. The measurements of the sound scattering coefficients were carried out over different pathways during the ship motion and at individual stations at frequencies of 100-250 kHz. The studies were carried out in 2004-2014 in the Sea of Japan and in 2013 in the Eastern Arctic seas. The studies of sound scattering were performed simultaneously with net catches of plankton in situ. These data allowed us to study the details of correlation between the sound scattering coefficient and zooplankton concentration. The studies revealed significantly stronger sound scattering in the Eastern Arctic, which is related to the greater concentration of zooplankton, the migration of which differs strongly from the migration of plankton in the warm seas.

  15. Storm surges in the Mediterranean Sea: Variability and trends under future climatic conditions

    NASA Astrophysics Data System (ADS)

    Androulidakis, Yannis S.; Kombiadou, Katerina D.; Makris, Christos V.; Baltikas, Vassilis N.; Krestenitis, Yannis N.

    2015-09-01

    The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1951-2100) are explored, using a high-resolution storm surge model. Numerical simulations are forced by the output of regional climate simulations with RegCM3, which uses IPCC's historical data on greenhouse gasses emissions for the (past) period 1951-2000, and IPCC's A1B climate scenario for the (future) period 2001-2100. Comparisons between observations and modeling results show good agreement and confirm the ability of our model to estimate the response of the sea surface to future climatic conditions. We investigate the future trends, the variability and frequency of local extremes and the main forcing mechanisms that can induce strong surges in the Mediterranean region. Our results support that there is a general decreasing trend in storminess under the considered climate scenario, mostly related to the frequency of local peaks and the duration and spatial coverage of the storm surges. The northward shift in the location of storm tracks is a possible reason for this storminess attenuation, especially over areas where the main driving factor of extreme events is the inverted barometer effect. However, the magnitudes of sea surface elevation extremes may increase in several Mediterranean sub-regions, i.e., Southern Adriatic, Balearic and Tyrrhenian Seas, during the 21st century. There are clear distinctions in the contributions of winds and pressure fields to the sea level height for various regions of the Mediterranean Sea, as well as on the seasonal variability of extreme values; the Aegean and Adriatic Seas are characteristic examples, where high surges are predicted to be mainly induced by low pressure systems and favorable winds, respectively.

  16. From Sea to Shining Sea

    ERIC Educational Resources Information Center

    Scott, Beverly

    2005-01-01

    Deep down in the depths of the sea, beautiful fish, mysterious ocean life, and unusual plants glimmer and glow in the eerie atmosphere of an ever-changing ocean. This article describes how, with this vision and a purpose in mind, three teachers pulled open classroom walls and joined forces so their second graders could create a mammoth 30 x 75"…

  17. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Buck, Warren W.; Maung, Khin M.

    1989-01-01

    Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  18. Nuclear PDFs from neutrino deep inelastic scattering

    SciTech Connect

    I. Schienbein; J. Y. Yu; C. Keppel; J. G. Morfin; F. Olness; J.F. Owens

    2007-11-13

    We study nuclear effects in charged current deep inelastic neutrino--iron scattering in the framework of a chi^2-analysis of parton distribution functions. We extract a set of iron PDFs and show that under reasonable assumptions it is possible to constrain the valence, light sea and strange quark distributions. We compare our results with nuclear parton distribution functions from the literature and find good agreement. Our iron PDFs are used to compute nuclear correction factors which are required in global analyses of free nucleon PDFs.

  19. Global Model for Sound Absorption in Sea Water

    DTIC Science & Technology

    1987-05-14

    scattering. -31 - A -(dBirm) Tasnen Sea pH7.9 4’C .01 .001 , // l A2 A .01 F1 . :’ Frequency (kHz) Figure 30: Tasman Sea data and mudel. In the deep... Tasman Sea by Bannister et. a1. 1241 in Figure 30 are typical. In both experiments shown, measurements were made In the deep channel and the maximum...in the South Tasman Sea ", J. Acoust. Soc. Am. 62 647-859 (1977) 25. A. C. Kibblewhite, N. R. Bedford and S. K. Mitchell, "Regional dependence of low

  20. Environment scattering in GADRAS.

    SciTech Connect

    Thoreson, Gregory G.; Mitchell, Dean J; Theisen, Lisa Anne; Harding, Lee T.

    2013-09-01

    Radiation transport calculations were performed to compute the angular tallies for scattered gamma-rays as a function of distance, height, and environment. Greens Functions were then used to encapsulate the results a reusable transformation function. The calculations represent the transport of photons throughout scattering surfaces that surround sources and detectors, such as the ground and walls. Utilization of these calculations in GADRAS (Gamma Detector Response and Analysis Software) enables accurate computation of environmental scattering for a variety of environments and source configurations. This capability, which agrees well with numerous experimental benchmark measurements, is now deployed with GADRAS Version 18.2 as the basis for the computation of scattered radiation.

  1. Rayleigh Scattering Diagnostics Workshop

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard (Compiler)

    1996-01-01

    The Rayleigh Scattering Diagnostics Workshop was held July 25-26, 1995 at the NASA Lewis Research Center in Cleveland, Ohio. The purpose of the workshop was to foster timely exchange of information and expertise acquired by researchers and users of laser based Rayleigh scattering diagnostics for aerospace flow facilities and other applications. This Conference Publication includes the 12 technical presentations and transcriptions of the two panel discussions. The first panel was made up of 'users' of optical diagnostics, mainly in aerospace test facilities, and its purpose was to assess areas of potential applications of Rayleigh scattering diagnostics. The second panel was made up of active researchers in Rayleigh scattering diagnostics, and its purpose was to discuss the direction of future work.

  2. Positron-rubidium scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.

    1990-01-01

    A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements.

  3. CONTINUOUS ROTATION SCATTERING CHAMBER

    DOEpatents

    Verba, J.W.; Hawrylak, R.A.

    1963-08-01

    An evacuated scattering chamber for use in observing nuclear reaction products produced therein over a wide range of scattering angles from an incoming horizontal beam that bombards a target in the chamber is described. A helically moving member that couples the chamber to a detector permits a rapid and broad change of observation angles without breaching the vacuum in the chamber. Also, small inlet and outlet openings are provided whose size remains substantially constant. (auth)

  4. Microcavity Enhanced Raman Scattering

    NASA Astrophysics Data System (ADS)

    Petrak, Benjamin J.

    Raman scattering can accurately identify molecules by their intrinsic vibrational frequencies, but its notoriously weak scattering efficiency for gases presents a major obstacle to its practical application in gas sensing and analysis. This work explores the use of high finesse (≈50 000) Fabry-Perot microcavities as a means to enhance Raman scattering from gases. A recently demonstrated laser ablation method, which carves out a micromirror template on fused silica--either on a fiber tip or bulk substrates-- was implemented, characterized, and optimized to fabricate concave micromirror templates ˜10 mum diameter and radius of curvature. The fabricated templates were coated with a high-reflectivity dielectric coating by ion-beam sputtering and were assembled into microcavities ˜10 mum long and with a mode volume ˜100 mum 3. A novel gas sensing technique that we refer to as Purcell enhanced Raman scattering (PERS) was demonstrated using the assembled microcavities. PERS works by enhancing the pump laser's intensity through resonant recirculation at one longitudinal mode, while simultaneously, at a second mode at the Stokes frequency, the Purcell effect increases the rate of spontaneous Raman scattering by a change to the intra-cavity photon density of states. PERS was shown to enhance the rate of spontaneous Raman scattering by a factor of 107 compared to the same volume of sample gas in free space scattered into the same solid angle subtended by the cavity. PERS was also shown capable of resolving several Raman bands from different isotopes of CO2 gas for application to isotopic analysis. Finally, the use of the microcavity to enhance coherent anti-Stokes Raman scattering (CARS) from CO2 gas was demonstrated.

  5. Tracing organic and inorganic pollution sources of agricultural crops and water resources in Güzelhisar Basin of the Aegean Region - Turkey

    NASA Astrophysics Data System (ADS)

    Czarnecki, Sezin; Colak Esetlili, Bihter; Esetlili, Tolga; Tepecik, Mahmut; Anac, Dilek; Düring, Rolf-Alexander

    2014-05-01

    The study area Güzelhisar Basin is 6 km far from the city Aliaga, Aegean Region in Turkey which represents a rather industrialized area having five large iron and steel factories, but also areas of agriculture. Steel industry in Aliaga is causing metal pollution. Around Güzelhisar Basin and nearby, the dominant crop fields are cotton, maize, vegetables, olive trees and vineyards. Güzelhisar stream and dam water is used for irrigation of the agricultural land. Due to contamination from metal industry in Aliaga, organic farming is not allowed in this region. Industrial activities in the region present a threat on sustainable agriculture. The region is a multi-impacted area in terms of several pollutant sources affecting soil and water quality. The overall objective of the project is to trace back plant nutrients (N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, and B), hazardous substances (i. e. persistent organic pollutants), radionuclides (40K, 232Th, 226Ra/238U), and metal contents (As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, and Zn) by examining the soils, agricultural crops and natural plants from Güzelhisar Basin and water and sediments from Güzelhisar stream and dam. Spatial distribution of pollution will be evaluated by regionalization methods. For this, an advanced analytical methodology will be applied which provides an understanding of sources and occurrence of the respective substances of concern. An innovative multi-tracer approach comprising organic and inorganic marker substances, will identify and quantitatively assess sources and their impact on water pollution and the pollutant pathways in this agricultural crop production system.

  6. Horizontal distributions of biogenic and lithogenic elements of suspended particulate matter in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Price, N. B.; Brand, T.; Pates, J. M.; Mowbray, S.; Theocharis, A.; Civitarese, G.; Miserocchi, S.; Heussner, S.; Lindsay, F.

    1999-08-01

    A study has been made of the distribution of terrigenous (Al and Mn ex, Fe ex) and biogenic (POC, PN tot, P org, Si bio, Ba ex) elements of suspended particulate matter (SPM) on a series of transects in three marginal areas of the Mediterranean Sea; the NW Mediterranean, the western Adriatic to the Strait of Otranto and the southern (Cretan) and northern Aegean Sea, with the intention of assessing the influence that river discharges have on their concentrations. In the Adriatic, high Al concentrations (60-200 μgl -1) occur as a consequence of direct discharge from the River Po but importantly from sediment resuspension the amount of which, under steady state conditions, is also related to riverine discharge. In the Otranto Strait high Al concentrations overlie its western shelf and slope. On the NW Mediterranean only waters influenced by the River Rhone, as off Banyuls-sur-mer, show high Al. Particulate Mn is mostly river derived, but principally exists in marginal areas from redox cycling in surficial sediments, a consequence of high biological production induced by nutrient discharges from rivers. High particulate Mn ex concentrations were measured in the northern Adriatic, off Banyuls-sur-mer and the northern Aegean, where there are strong river influences. In contrast, the more oligotrophic seawaters off Marseilles, the Balearics and the Cretan Sea show lower concentrations of Mn ex, and depth profiles of Mn ex especially in the latter area are similar to those found in ocean waters. Of the biogenic elements studied, the assumed presence of terrigenous organic carbon, especially on the Adriatic shelf, largely precludes POC concentrations from being an indicator of marine production. A better guide to productivity induced by river nutrient discharges is seen in the distribution of P org and Si bio concentrations, which show a gradual southward reduction along the Adriatic shelf and higher concentrations off Banyuls-sur-mer than on other transects in the NW

  7. SCRIT electron scattering facility

    NASA Astrophysics Data System (ADS)

    Tsukada, Kyo

    2014-09-01

    Electron scattering is the most powerful and reliable tool to investigate the nuclear structure because this reaction has the great advantage that the electron is structureless particle and its interaction is well described by the quantum electrodynamics. As is well known, the charge density distributions of many stable nuclei were determined by elastic electron scattering. Recently, many efforts for studies of unstable nuclei have been made, and the precise information of the structure of unstabe nuclei have been strongly desired. However, due to the difficulty of preparing a short-lived unstable nuclear target, there is no electron scattering on unstable nuclei with a few important exceptions, such as on 3H, 14C and so on. Under these circumstances, we have established a completely new target-forming technique, namely SCRIT (Self-Confining Radioactive isotope Ion Target) which makes electron scattering on unstable nuclei possible. A Dedicated electron scattering facility at RIKEN consists of an electron accelerator with the SCRIT system, an ERIS (Electron-beam-driven RI separator for SCRIT), and a WiSES (Window-frame Spectrometer for Electron Scattering). Feasibility test of the SCRIT and ERIS system have been successfully carried out using the stable nuclei, and more than 1026 [cm-2s-1] luminosity was already achieved. Furthermore, 132Sn, which is one of the important target at the beginning of this project, was also successfully separated in the ERIS. The WiSES with momentum resolution of Δp/p ~ 10-3 consisting of the wide acceptance dipole magnet, two set of drift chambers together with trigger scintillation hodoscope is under construction. Electron scattering on unstable nuclei will start within a year. In this talk, the introduction of our project and the progress of the preparation status will be presented.

  8. The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

    PubMed Central

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S.; Gasol, Josep M.; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M.; Lotze, Heike K.; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Saša; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-01-01

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1). PMID:20689844

  9. The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

    PubMed

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S; Gasol, Josep M; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M; Lotze, Heike K; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Sasa; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-08-02

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1).

  10. Scattering of electromagnetic waves from a half-space of randomly distributed discrete scatterers and polarized backscattering ratio law

    NASA Technical Reports Server (NTRS)

    Zhu, P. Y.

    1991-01-01

    The effective-medium approximation is applied to investigate scattering from a half-space of randomly and densely distributed discrete scatterers. Starting from vector wave equations, an approximation, called effective-medium Born approximation, a particular way, treating Green's functions, and special coordinates, of which the origin is set at the field point, are used to calculate the bistatic- and back-scatterings. An analytic solution of backscattering with closed form is obtained and it shows a depolarization effect. The theoretical results are in good agreement with the experimental measurements in the cases of snow, multi- and first-year sea-ice. The root product ratio of polarization to depolarization in backscattering is equal to 8; this result constitutes a law about polarized scattering phenomena in the nature.

  11. Testing hypotheses of population structuring in the Northeast Atlantic Ocean and Mediterranean Sea using the common cuttlefish Sepia officinalis.

    PubMed

    Pérez-Losada, Marcos; Nolte, Mark J; Crandall, Keith A; Shaw, Paul W

    2007-07-01

    Population structuring in species inhabiting marine environments such as the Northeast Atlantic Ocean (NEA) and Mediterranean Sea (MS) has usually been explained based on past and present physical barriers to gene flow and isolation by distance (IBD). Here, we examined the relative importance of these factors on population structuring of the common cuttlefish Sepia officinalis by using methods of phylogenetic inference and hypothesis testing coupled with coalescent and classical population genetic parameter estimation. Individuals from 10 Atlantic and 15 Mediterranean sites were sequenced for 659 bp of the mitochondrial COI gene (259 sequences). IBD seems to be the main factor driving present and past genetic structuring of Sepia populations across the NEA-MS, both at large and small geographical scales. Such an evolutionary process agrees well with some of the biological features characterizing this cuttlefish species (short migrations, nektobenthic habit, benthic eggs hatching directly to benthic juveniles). Despite the many barriers to migration/gene flow suggested in the NEA-MS region, genetic population fragmentation due to past isolation of water masses (Pleistocene; 0.56 million years ago) and/or present-day oceanographic currents was only detected between the Aegean-Ionian and western Mediterranean Seas. Restricted gene flow associated with the Almería-Oran hydrographic front was also suggested between southern and eastern Spanish populations. Distinct population boundaries could not be clearly determined, except for the Aegean-Ionian stock. Two Atlantic and five Mediterranean samples showed evidence of current decline in genetic diversity, which may indicate over-exploitation of Sepia in both marine regions.

  12. Stable carbon isotope gradients in benthic foraminifera as proxy for organic carbon fluxes in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Theodor, Marc; Schmiedl, Gerhard; Jorissen, Frans; Mackensen, Andreas

    2016-11-01

    We have determined stable carbon isotope ratios of epifaunal and shallow infaunal benthic foraminifera in the Mediterranean Sea to relate the inferred gradient of pore water δ13CDIC to varying trophic conditions. This is a prerequisite for developing this difference into a potential transfer function for organic matter flux rates. The data set is based on samples retrieved from a well-defined bathymetric range (400-1500 m water depth) of sub-basins in the western, central, and eastern Mediterranean Sea. Regional contrasts in organic matter fluxes and associated δ13CDIC of pore water are recorded by the δ13C difference (Δδ13CUmed-Epi) between the shallow infaunal Uvigerina mediterranea and epifaunal species (Planulina ariminensis, Cibicidoides pachydermus, Cibicides lobatulus). Within epifaunal taxa, the highest δ13C values are recorded for P. ariminensis, providing the best indicator for bottom water δ13CDIC. In contrast, C. pachydermus reveals minor pore water effects at the more eutrophic sites. Because of ontogenetic trends in the δ13C signal of U. mediterranea of up to 1.04 ‰, only tests larger than 600 µm were used for the development of the transfer function. The recorded differences in the δ13C values of U. mediterranea and epifaunal taxa (Δδ13CUmed-Epi) range from -0.46 to -2.13 ‰, with generally higher offsets at more eutrophic sites. The measured δ13C differences are related to site-specific differences in microhabitat, depth of the principal sedimentary redox boundary, and TOC content of the ambient sediment. The Δδ13CUmed-Epi values reveal a consistent relation to Corg fluxes estimated from satellite-derived surface water primary production in open-marine settings of the Alboran Sea, Mallorca Channel, Strait of Sicily, and southern Aegean Sea. In contrast, Δδ13CUmed-Epi values in areas affected by intense resuspension and riverine organic matter sources of the northern to central Aegean Sea and the canyon systems of the Gulf of Lion

  13. Monte Carlo eikonal scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Dedonder, J. P.

    2012-08-01

    Background: The eikonal approximation is commonly used to calculate heavy-ion elastic scattering. However, the full evaluation has only been done (without the use of Monte Carlo techniques or additional approximations) for α-α scattering.Purpose: Develop, improve, and test the Monte Carlo eikonal method for elastic scattering over a wide range of nuclei, energies, and angles.Method: Monte Carlo evaluation is used to calculate heavy-ion elastic scattering for heavy nuclei including the center-of-mass correction introduced in this paper and the Coulomb interaction in terms of a partial-wave expansion. A technique for the efficient expansion of the Glauber amplitude in partial waves is developed.Results: Angular distributions are presented for a number of nuclear pairs over a wide energy range using nucleon-nucleon scattering parameters taken from phase-shift analyses and densities from independent sources. We present the first calculations of the Glauber amplitude, without further approximation, and with realistic densities for nuclei heavier than helium. These densities respect the center-of-mass constraints. The Coulomb interaction is included in these calculations.Conclusion: The center-of-mass and Coulomb corrections are essential. Angular distributions can be predicted only up to certain critical angles which vary with the nuclear pairs and the energy, but we point out that all critical angles correspond to a momentum transfer near 1 fm-1.

  14. Laser light scattering review

    NASA Technical Reports Server (NTRS)

    Schaetzel, Klaus

    1989-01-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  15. Melting Ice, Rising Seas

    NASA Video Gallery

    Sea level rise is an indicator that our planet is warming. Much of the world's population lives on or near the coast, and rising seas are something worth watching. Sea level can rise for two reason...

  16. Mammals of the Sea.

    ERIC Educational Resources Information Center

    Naturescope, 1986

    1986-01-01

    Presents information on sea mammals, including definitions and characteristics of cetaceans, pinnipeds, and sirenians. Contains descriptions of the teaching activities "Whale Music,""Draw A Whale to Scale,""Adopt a Sea Mammal," and "Sea Mammal Sleuths." (TW)

  17. Non-line-of-sight active imaging of scattered photons

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Velten, Andreas

    2013-10-01

    Laser Gated Viewing is a prominent sensing technology for optical imaging in harsh environments and can be applied to the vision through fog, smoke and other degraded environmental conditions as well as to the vision through sea water in submarine operation. A direct imaging of non-scattered photons (or ballistic photons) is limited in range and performance by the free optical path length i.e. the length in which a photon can propagate without interaction with scattering particles or object surfaces. The imaging and analysis of scattered photons can overcome these classical limitations and it is possible to realize a non-line-of-sight imaging. The spatial and temporal distribution of scattered photons can be analyzed by means of computational optics and their information of the scenario can be restored. In the case of Lambertian scattering sources the scattered photons carry information of the complete environment. Especial the information outside the line of sight or outside the visibility range is of high interest. Here, we discuss approaches for non line of sight active imaging with different indirect and direct illumination concepts (point, surface and volume scattering sources).

  18. Sound scattering in shallow water in presence of internal solitons

    NASA Astrophysics Data System (ADS)

    Katsnelson, Boris G.; Pereselkov, Serguey A.; Petnikov, Valery G.

    2002-05-01

    Sound scattering by localized inhomogeneity (object) in a shallow-water waveguide is studied. Influence of internal solitons (IS) traveling in the sea, on the scattered field is considered. The problem is analyzed within the framework of theory of the sound scattering in the waveguide developed by the authors, where the scattering matrix is expressed through modal decomposition including the scattering amplitude of the object in free space. The peculiarity of the given work is the taking into account of additional modes conversion due to IS. The waveguide and IS are modeled on the basis of experimental data (sound-speed profile, bottom relief, IS parameters, etc.) collected in the Japan Sea. The inhomogeneity is selected in the form of soft spheroids with dimensions characteristic of gray whales (eschrichtius). Calculations of amplitude fluctuations of the low-frequency sound field at the receiving point are carried out for moving spheroid and different orientations of acoustic track with respect to direction of propagation of IS. It is shown that sound fluctuations have essentially different characteristics for longitudinal and transversal propagation of IS. [Work supported by RFBR, Grant No. 00-05-64752.

  19. Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Cavalieri, Donald J.

    2005-01-01

    Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

  20. Electromagnetic scattering theory

    NASA Technical Reports Server (NTRS)

    Bird, J. F.; Farrell, R. A.

    1986-01-01

    Electromagnetic scattering theory is discussed with emphasis on the general stochastic variational principle (SVP) and its applications. The stochastic version of the Schwinger-type variational principle is presented, and explicit expressions for its integrals are considered. Results are summarized for scalar wave scattering from a classic rough-surface model and for vector wave scattering from a random dielectric-body model. Also considered are the selection of trial functions and the variational improvement of the Kirchhoff short-wave approximation appropriate to large size-parameters. Other applications of vector field theory discussed include a general vision theory and the analysis of hydromagnetism induced by ocean motion across the geomagnetic field. Levitational force-torque in the magnetic suspension of the disturbance compensation system (DISCOS), now deployed in NOVA satellites, is also analyzed using the developed theory.

  1. Λ scattering equations

    NASA Astrophysics Data System (ADS)

    Gomez, Humberto

    2016-06-01

    The CHY representation of scattering amplitudes is based on integrals over the moduli space of a punctured sphere. We replace the punctured sphere by a double-cover version. The resulting scattering equations depend on a parameter Λ controlling the opening of a branch cut. The new representation of scattering amplitudes possesses an enhanced redundancy which can be used to fix, modulo branches, the location of four punctures while promoting Λ to a variable. Via residue theorems we show how CHY formulas break up into sums of products of smaller (off-shell) ones times a propagator. This leads to a powerful way of evaluating CHY integrals of generic rational functions, which we call the Λ algorithm.

  2. Dynamic Scattering Mode LCDs

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

  3. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

    ZALIZNYAK,I.A.; LEE,S.H.

    2004-07-30

    Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science

  4. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  5. The Harp probe - An in situ Bragg scattering sensor

    NASA Technical Reports Server (NTRS)

    Mollo-Christensen, E.; Huang, N. E.; Long, S. R.; Bliven, L. F.

    1984-01-01

    A wave sensor, consisting of parallel, evenly spaced capacitance wires, whose output is the sum of the water surface deflections at the wires, has been built and tested in a wave tank. The probe output simulates Bragg scattering of electromagnetic waves from a water surface with waves; it can be used to simulate electromagnetic probing of the sea surface by radar. The study establishes that the wave probe, called the 'Harp' for short, will simulate Bragg scattering and that it can also be used to study nonlinear wave processes.

  6. Low-Frequency Scattering from Heterogeneous Elastic Sea Beds

    DTIC Science & Technology

    2011-09-01

    in, Proc. 4th Internat. Conf. Underwater Acoustic Measurements: Technology and Results (UAM2011), J.S. Papadakis and L. Bjorno (Eds), pp. 1615-1622...Measurements: Technology and Results (UAM2011), J.S. Papadakis and L. Bjorno (Eds), pp. 1615-1622. 14. A.N. Ivakin (2011), “Geoacoustic modeling based on

  7. The Growth, Structure, and Properties of Sea Ice,

    DTIC Science & Technology

    1982-11-01

    111 94. Simulated returned power/incident power vs depth 112 95. Scattering albedo vs scatterer size to wavelength ratio for ice overlying...fresh water ----------------------- 116 96. Changes in brightness temperature plotted against scat- tering albedo with the layer thickness to... Antarctica ; and finally Zotikov et al. (1980) obtained a0 values of 5 mm from sea ice formed on the base of the 416-m-thick Ross Ice Shelf. Figure 40 shows a

  8. Small Angle Neutron Scattering

    SciTech Connect

    Urban, Volker S

    2012-01-01

    Small Angle Neutron Scattering (SANS) probes structural details at the nanometer scale in a non-destructive way. This article gives an introduction to scientists who have no prior small-angle scattering knowledge, but who seek a technique that allows elucidating structural information in challenging situations that thwart approaches by other methods. SANS is applicable to a wide variety of materials including metals and alloys, ceramics, concrete, glasses, polymers, composites and biological materials. Isotope and magnetic interactions provide unique methods for labeling and contrast variation to highlight specific structural features of interest. In situ studies of a material s responses to temperature, pressure, shear, magnetic and electric fields, etc., are feasible as a result of the high penetrating power of neutrons. SANS provides statistical information on significant structural features averaged over the probed sample volume, and one can use SANS to quantify with high precision the structural details that are observed, for example, in electron microscopy. Neutron scattering is non-destructive; there is no need to cut specimens into thin sections, and neutrons penetrate deeply, providing information on the bulk material, free from surface effects. The basic principles of a SANS experiment are fairly simple, but the measurement, analysis and interpretation of small angle scattering data involves theoretical concepts that are unique to the technique and that are not widely known. This article includes a concise description of the basics, as well as practical know-how that is essential for a successful SANS experiment.

  9. Nanowire electron scattering spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D. (Inventor); Bronikowski, Michael (Inventor); Wong, Eric W. (Inventor); von Allmen, Paul (Inventor); Oyafuso, Fabiano A. (Inventor)

    2009-01-01

    Methods and devices for spectroscopic identification of molecules using nanoscale wires are disclosed. According to one of the methods, nanoscale wires are provided, electrons are injected into the nanoscale wire; and inelastic electron scattering is measured via excitation of low-lying vibrational energy levels of molecules bound to the nanoscale wire.

  10. Fluorescence and Light Scattering

    ERIC Educational Resources Information Center

    Clarke, Ronald J.; Oprysa, Anna

    2004-01-01

    The aim of the mentioned experiment is to aid students in developing tactics for distinguishing between signals originating from fluorescence and light scattering. Also, the experiment provides students with a deeper understanding of the physicochemical bases of each phenomenon and shows that the techniques are actually related.

  11. Ice Types in the Beaufort Sea, Alaska

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Determining the amount and type of sea ice in the polar oceans is crucial to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite remote sensing instruments; the synthetic aperture radar (SAR) on board the RADARSAT satellite and the Multi-angle Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea off the north coast of Alaska was classified and mapped in these concurrent images acquired March 19, 2001 and mapped to the same geographic area.

    To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center constructs ice charts using several data sources including RADARSAT SAR images such as the one shown at left. SAR classifies sea ice types primarily by how the surface and subsurface roughness influence radar backscatter. In the SAR image, white lines delineate different sea ice zones as identified by the National Ice Center. Regions of mostly multi-year ice (A) are separated from regions with large amounts of first year and younger ice (B-D), and the dashed white line at bottom marks the coastline. In general, sea ice types that exhibit increased radar backscatter appear bright in SAR and are identified as rougher, older ice types. Younger, smoother ice types appear dark to SAR. Near the top of the SAR image, however, red arrows point to bright areas in which large, crystalline 'frost flowers' have formed on young, thin ice, causing this young ice type to exhibit an increased radar backscatter. Frost flowers are strongly backscattering at radar wavelengths (cm) due to both surface roughness and the high salinity of frost flowers, which causes them to be highly reflective to radar energy.

    Surface roughness is also registered by MISR, although the roughness observed is at a different spatial scale. Older, rougher ice areas are predominantly backward scattering to

  12. The sedimentary records of Holocene environmental changes from the Central High of the Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Filikci, Betul; Çağatay, Namık; Kadir Eriş, Kürşad; Akyol, Mustafa; Yalamaz, Burak; Uçarkuş, Gülsen; Henry, Pierre

    2015-04-01

    The Sea of Marmara (SoM) is located between the Aegean Sea and the Black Sea, to which it is connected via the Istanbul (Bosphorus) and Canakkale (Dardanelles) straits having sill depths of 65 and 35 m, respectively. It has a two-way water mass exchange with a permanent pycnocline located at 20-25 m water depth. With the objective of determining Holocene paleoenvironmental changes, we studied a 8.36 m-long piston core recovered from the Central High of the SoM at a water depth of 835 m, using multiproxy analyses such as total organic and inorganic carbon, high resolution µ-XRF core scanner analysis, grain size, magnetic susceptibility and density. A 2 cm-thick tephra layer with high K and Zr and relatively low magnetic susceptibility occurs at 2.1 meter below sea floor (mbsf), which is correlated with the Avellino (Somma-Vesuvius, Italy) eruption dated at 3.9 ka BP, according to the previous studies. Using this age and assuming a uniform sedimentation rate, the base of the core dates back to ca 8 ka BP. The core includes organic-rich (sapropelic) sediments with 1.5 % to 2.2%) in its top 3.5 m and bottom 1 m. Sapropelic layers are olive green and in part laminated, and contain occasional reddish brown spots and laminae formed by oxidation of iron monosulphides. The core also contains some few mm- to cm-thick sandy-silty mass-flow units below 2.4 mbsf, some of which could have been triggered by the earthquake activity on the Central High segment of the North Anatolian Fault, just a few km away from the core location. Variations in Ca-Ti ratio suggest millennial-scale climatic changes during the Holocene. Keywords: Sea of Marmara, Holocene paleoenvironmental records, tephra, turbidites, TOC analysis, XRF analysis, physical properties.

  13. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  14. 137Caesium distribution in the eastern Mediterranean Sea: recent changes and future trends.

    PubMed

    Papucci, C; Delfanti, R

    1999-09-30

    A series of sampling campaigns were carried out in the eastern Mediterranean in the period 1995-1997, to examine the relationship between the distribution of 137Cs in the water column and water mass circulation. 137Cs concentration in the surface water ranges between 3.3 and 4.0 mBq/l all over the area, indicating that the input due to the Chernobyl accident has been transferred to deep water layers by convection processes. In fact, in the vertical profiles, relative maxima are observed in the intermediate (4 mBq/l) and deep waters (approximately 2.5 mBq/l) formed after the Chernobyl accident. A clear Chernobyl signal also traces the new deep waters formed in the Aegean Sea that, exiting from the Cretan Arc Straits, since 1991 are spreading in the bottom layer of the eastern Mediterranean. The changes in 137Cs vertical profiles related to the new thermohaline circulation of the intermediate and deep waters of the eastern Mediterranean are being monitored at a deep station in the western Ionian Sea. The 1997 profile shows a decrease in 137Cs concentration both in the Levantine intermediate water and in the eastern Mediterranean deep water with respect to 1996. The decrease in Levantine intermediate water is likely due to seasonal/interannual variability, while the changes in the deep layer are related to the spreading westward into the Ionian of the new Aegean dense water. Along the path towards the western Mediterranean, 137Cs content in the Levantine intermediate water decreases from approximately 4 mBq/l in the W-Ionian Sea to approximately 2 mBq/l at the western sill of the Sicily Straits, due to mixing with underlying water, with lower caesium content, near the Malta Sill. Time-series measurements at the western sill of the Sicily Straits show that, while 137Cs concentration in the surface water entering the eastern Mediterranean remained constant (approximately 3.5 mBq/l) in the period 1993-1997, its level in the Levantine intermediate water leaving the basin

  15. A Discrete Scatterer Technique for Evaluating Electromagnetic Scattering from Trees

    DTIC Science & Technology

    2016-09-01

    ARL-TR-7799 ● SEP 2016 US Army Research Laboratory A Discrete Scatterer Technique for Evaluating Electromagnetic Scattering from...longer needed. Do not return it to the originator. ARL-TR-7799 ● SEP 2016 US Army Research Laboratory A Discrete Scatterer Technique ... Technique for Evaluating Electromagnetic Scattering from Trees 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  16. The Classical Scattering of Waves: Some Analogies with Quantum Scattering

    DTIC Science & Technology

    1992-01-01

    Code . Approved for public release; distribution is unlimited. 13. Abstract (Maximum 200 words). The scattering of waves in classical physics and quantum...both areas. 92-235222’ 14. Subject Terms. IS. Number of Page. Acoustic scattering , shallow water, waveguide propagation . 27 16. Price Code . 17. Security...Numbers. The Classical Scattering of Waves: Some Analogies with Quantum Scattering Contract ,~~ ~ -V ,~Pom Element NO- 0601153N 6. Author(s). t

  17. Radar Remote Sensing of Ice and Sea State and Air-Sea Interaction in the Marginal Ice Zone

    DTIC Science & Technology

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Radar Remote Sensing of Ice and Sea State and Air-Sea...Interaction in the Marginal Ice Zone Hans C. Graber RSMAS – Department of Ocean Sciences Center for Southeastern Tropical Advanced Remote Sensing...scattering and attenuation process of ocean waves interacting with ice . A nautical X-band radar on a vessel dedicated to science would be used to follow the

  18. FDTD scattered field formulation for scatterers in stratified dispersive media.

    PubMed

    Olkkonen, Juuso

    2010-03-01

    We introduce a simple scattered field (SF) technique that enables finite difference time domain (FDTD) modeling of light scattering from dispersive objects residing in stratified dispersive media. The introduced SF technique is verified against the total field scattered field (TFSF) technique. As an application example, we study surface plasmon polariton enhanced light transmission through a 100 nm wide slit in a silver film.

  19. Angle resolved scatter measurement of bulk scattering in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Sharma, Saurabh; Miller, J. Keith; Shori, Ramesh K.; Goorsky, Mark S.

    2015-02-01

    Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. Angle Resolved Scatter (ARS) measurement allows for the spatial mapping of scattered light at all possible angles about a sample, mapping the intensity for both forward scatter and back-scatter regions. The cumulative scattered light intensity, in the forward scatter direction, away from the specular beam is used for the comparison of bulk scattering between samples. This technique employ the detection of scattered light at all angles away from the specular beam directions and represented as a 2-D polar map. The high sensitivity of the ARS technique allows us to compare bulk scattering in different PLM samples which otherwise had similar transmitted beam wavefront distortions.

  20. An ocean scatter propagation model for aeronautical satellite communication applications

    NASA Technical Reports Server (NTRS)

    Moreland, K. W.

    1990-01-01

    In this paper an ocean scattering propagation model, developed for aircraft-to-satellite (aeronautical) applications, is described. The purpose of the propagation model is to characterize the behavior of sea reflected multipath as a function of physical propagation path parameters. An accurate validation against the theoretical far field solution for a perfectly conducting sinusoidal surface is provided. Simulation results for typical L band aeronautical applications with low complexity antennas are presented.

  1. Colorful Underwater Sea Creatures

    ERIC Educational Resources Information Center

    McCutcheon, Heather

    2011-01-01

    In this article, the author describes a project wherein students created colorful underwater sea creatures. This project began with a discussion about underwater sea creatures and how they live. The first step was making the multi-colored tissue paper that would become sea creatures and seaweed. Once students had the shapes of their sea creatures…

  2. A technique for measuring the sea water optical parameters with a dedicated laser beam and a multi-PMT optical module

    SciTech Connect

    Papaikonomou, A. Leisos, A. Tsirigotis, A.; Tzamarias, S.; Manthos, I.; Collaboration: KM3NeT Collaboration

    2014-11-18

    The KM3NeT research infrastructure will be a deep sea multidisciplinary observatory in the Mediterranean Sea housing a neutrino telescope. Accurate knowledge of the optical properties of the sea water is important for the performance evaluation of the telescope. In this work we describe a technique for the evaluation of the parameters describing the scattering characteristics of the sea water using one multi-PMT optical module that detects scattered optical photons which are emitted from a laser. Our results show that we are able to determine these parameters with satisfying precision and are able to resolve the scattering length values with less than half a meter accuracy.

  3. Scattering of fermions by gravitons

    NASA Astrophysics Data System (ADS)

    Ulhoa, S. C.; Santos, A. F.; Khanna, Faqir C.

    2017-04-01

    The interaction between gravitons and fermions is investigated in the teleparallel gravity. The scattering of fermions and gravitons in the weak field approximation is analyzed. The transition amplitudes of M\\varnothing ller, Compton and new gravitational scattering are calculated.

  4. Interface scattering in polycrystalline thermoelectrics

    SciTech Connect

    Popescu, Adrian; Haney, Paul M.

    2014-03-28

    We study the effect of electron and phonon interface scattering on the thermoelectric properties of disordered, polycrystalline materials (with grain sizes larger than electron and phonons' mean free path). Interface scattering of electrons is treated with a Landauer approach, while that of phonons is treated with the diffuse mismatch model. The interface scattering is embedded within a diffusive model of bulk transport, and we show that, for randomly arranged interfaces, the overall system is well described by effective medium theory. Using bulk parameters similar to those of PbTe and a square barrier potential for the interface electron scattering, we identify the interface scattering parameters for which the figure of merit ZT is increased. We find the electronic scattering is generally detrimental due to a reduction in electrical conductivity; however, for sufficiently weak electronic interface scattering, ZT is enhanced due to phonon interface scattering.

  5. Beaufort Sea: information update

    SciTech Connect

    Becker, P.R.

    1988-04-01

    The report is based on a multi-disciplinary meeting held March 6-7, 1985, as part of preparations for the Beaufort Sea Sale 97. The chapters are based on presentations given: The causeway effect: Modification of nearshore thermal regime resulting from causeways; Summertime sea ice intrusions in the Chukchi Sea; The deepwater limit of ice gouging on the Beaufort Sea shelf; Distribution, abundance, migration, harvest, and stock identity of Belukha Whales in the Beaufort Sea; Ringed seals in the Beaufort Sea; Beaufort Sea socioeconomics; The Baffin Island Oil Spill, (BIOS) Project.

  6. Changes in sea urchins and kelp following a reduction in sea otter density as a result of the Exxon Valdez oil spill

    USGS Publications Warehouse

    Dean, T.A.; Bodkin, J.L.; Jewett, S.C.; Monson, D.H.; Jung, D.

    2000-01-01

    Interactions between sea otters Enhydra lutris, sea urchins Strongylocentrotus droebachiensis, and kelp were investigated following the reduction in sea otter density in Prince William Sound, Alaska, after the Exxon Valdez oil spill in 1989. At northern Knight Island, a heavily oiled portion of the sound, sea otter abundance was reduced by a minimum of 50% by the oil spill, and from 1995 through 1998 remained at an estimated 66% lower than in 1973. Where sea otter densities were reduced, there were proportionally more large sea urchins. However, except in some widely scattered aggregations, both density and biomass of sea urchins were similar in an area of reduced sea otter density compared with an area where sea otters remained about 10 times more abundant. Furthermore, there was no change in kelp abundance in the area of reduced sea otter density. This is in contrast to greatly increased biomass of sea urchins and greatly reduced kelp density observed following an approximate 90% decline in sea otter abundance in the western Aleutian Islands. The variation in community response to a reduction in sea otters may be related to the magnitude of the reduction and the non-linear response by sea urchins to changes in predator abundance. The number of surviving sea otters may have been high enough to suppress sea urchin populations in Prince William Sound, but not in the Aleutians. Alternatively, differences in response may have been due to differences in the frequency or magnitude of sea urchin recruitment. Densities of small sea urchins were much higher in the Aleutian system even prior to the reduction in sea otters, suggesting a higher rate of recruitment.

  7. Coherent Scatter Imaging Measurements

    NASA Astrophysics Data System (ADS)

    Ur Rehman, Mahboob

    In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.

  8. Syzygies probing scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao

    2016-09-01

    We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.

  9. Magnetic diffuse scattering

    SciTech Connect

    Cable, J.W.

    1987-01-01

    The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recent neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs.

  10. Molecular-beam scattering

    SciTech Connect

    Vernon, M.F.

    1983-07-01

    The molecular-beam technique has been used in three different experimental arrangements to study a wide range of inter-atomic and molecular forces. Chapter 1 reports results of a low-energy (0.2 kcal/mole) elastic-scattering study of the He-Ar pair potential. The purpose of the study was to accurately characterize the shape of the potential in the well region, by scattering slow He atoms produced by expanding a mixture of He in N/sub 2/ from a cooled nozzle. Chapter 2 contains measurements of the vibrational predissociation spectra and product translational energy for clusters of water, benzene, and ammonia. The experiments show that most of the product energy remains in the internal molecular motions. Chapter 3 presents measurements of the reaction Na + HCl ..-->.. NaCl + H at collision energies of 5.38 and 19.4 kcal/mole. This is the first study to resolve both scattering angle and velocity for the reaction of a short lived (16 nsec) electronic excited state. Descriptions are given of computer programs written to analyze molecular-beam expansions to extract information characterizing their velocity distributions, and to calculate accurate laboratory elastic-scattering differential cross sections accounting for the finite apparatus resolution. Experimental results which attempted to determine the efficiency of optically pumping the Li(2/sup 2/P/sub 3/2/) and Na(3/sup 2/P/sub 3/2/) excited states are given. A simple three-level model for predicting the steady-state fraction of atoms in the excited state is included.

  11. Polarization in Scattering

    DTIC Science & Technology

    2010-09-01

    we refer to the linear polarization as parallel if the polarization vector is in the scattering plane or perpendicular if the polarization vector is...obvious that the different polarization states can all be represented as linear combinations of any of the independent pairs of polarization states...J.C. (1976) “Improvement of underwater visibility by reduction of backscatter with a circular polarization technique, Applied Optics, 6, 321-330

  12. Instantons and scattering

    NASA Astrophysics Data System (ADS)

    Bonelli, G.; Bonora, L.; Nesti, F.; Tomasiello, A.; Terna, S.

    This is a review of some recent developments in the study of classical solutions of Yang-Mills theories in various dimensions and their significance in the path integral of the corresponding theories. These particular solutions are called instantons because of their kinship with ordinary instantons. Just as ordinary instantons interpolate between different vacua, the new instantons interpolate between different asymptotic states. Therefore they represent scattering phenomena. Here we review the two dimensional and four dimensional Yang-Mills case.

  13. Inverse Scattering and Tomography

    DTIC Science & Technology

    1989-11-27

    404. [3] J. Duchon, Interpolation des Fonctions de Deux Variables Suivant le Principe de la Flexion des Plaques Minces, RAIRO Analyse Numerique, 10...d’Interpolation des Fonctions de Pusleurs Variables par les D M-splines, RAIRO Analyse Numerigue 12 (1978), 325 - 334. [6] R. Franke, Scattered data...splines, RAIRO Analyse Numerigue 12 (1978), 325-334. [7] I. M. Gelfand and N. Ya. Vilenkin, Generalized Functions, Vol. 4, Academic Press, New York

  14. Optics of the Sea (Interface and In-water Transmission and Imaging)

    DTIC Science & Technology

    biologiques affectant la propagation de la lumiere dans les eaux de mer, Refractive index fluctuations in sea water, Variation of optical sea parameters...with depth, Diffusion de la lumiere par les eaux de mer. resultats experimentaux et approche theorique, Theory of small angle scattering

  15. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  16. Light Scattering by Spheroids

    NASA Astrophysics Data System (ADS)

    Xie, Ya-Ming; Ji, Xia

    Nowadays, with the development of technology, particles with size at nanoscale have been synthesized in experiments. It is noticed that anisotropy is an unavoidable problem in the production of nanospheres. Besides, nonspherical nanoparticles have also been extensively used in experiments. Comparing with spherical model, spheroidal model can give a better description for the characteristics of nonspherical particles. Thus the study of analytical solution for light scattering by spheroidal particles has practical implications. By expanding incident, scattered, and transmitted electromagnetic fields in terms of appropriate vector spheroidal wave functions, an analytic solution is obtained to the problem of light scattering by spheroids. Unknown field expansion coefficients can be determined with the combination of boundary conditions and rotational-translational addition theorems for vector spheroidal wave functions. Based on the theoretical derivation, a Fortran code has been developed to calculate the extinction cross section and field distribution, whose results agree well with those obtain by FDTD simulation. This research is supported by the National Natural Science Foundation of China No. 91230203.

  17. Nanowire Electron Scattering Spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano

    2009-01-01

    Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

  18. Book review: Nonlinear ocean waves and the inverse scattering transform

    USGS Publications Warehouse

    Geist, Eric L.

    2011-01-01

    Nonlinear Ocean Waves and the Inverse Scattering Transform is a comprehensive examination of ocean waves built upon the theory of nonlinear Fourier analysis. The renowned author, Alfred R. Osborne, is perhaps best known for the discovery of internal solitons in the Andaman Sea during the 1970s. In this book, he provides an extensive treatment of nonlinear water waves based on a nonlinear spectral theory known as the inverse scattering transform. The writing is exceptional throughout the book, which is particularly useful in explaining some of the more difficult mathematical concepts.  Review info: Nonlinear Ocean Waves and the Inverse Scattering Transform. By Alfred R. Osborne, 2010. ISBN: 978-125286299, 917 pp.

  19. Rutherford scattering of electron vortices

    NASA Astrophysics Data System (ADS)

    Van Boxem, Ruben; Partoens, Bart; Verbeeck, Johan

    2014-03-01

    By considering a cylindrically symmetric generalization of a plane wave, the first-order Born approximation of screened Coulomb scattering unfolds two new dimensions in the scattering problem: transverse momentum and orbital angular momentum of the incoming beam. In this paper, the elastic Coulomb scattering amplitude is calculated analytically for incoming Bessel beams. This reveals novel features occurring for wide-angle scattering and quantitative insights for small-angle vortex scattering. The result successfully generalizes the well-known Rutherford formula, incorporating transverse and orbital angular momentum into the formalism.

  20. Bidirectional air-sea exchange and accumulation of POPs (PAHs, PCBs, OCPs and PBDEs) in the nocturnal marine boundary layer

    NASA Astrophysics Data System (ADS)

    Lammel, Gerhard; Meixner, Franz X.; Vrana, Branislav; Efstathiou, Christos I.; Kohoutek, Jiři; Kukučka, Petr; Mulder, Marie D.; Přibylová, Petra; Prokeš, Roman; Rusina, Tatsiana P.; Song, Guo-Zheng; Tsapakis, Manolis

    2016-05-01

    As a consequence of long-range transported pollution, air-sea exchange can become a major source of persistent organic pollutants in remote marine environments. The vertical gradients in the air were quantified for 14 species, i.e. four parent polycyclic aromatic hydrocarbons (PAHs), three polychlorinated biphenyls (PCBs), three organochlorine pesticides (OCPs) and two polybrominated diphenylethers (PBDEs) in the gas-phase at a remote coastal site in the southern Aegean Sea in summer. Most vertical gradients were positive (Δc/Δz > 0), indicating downward (net depositional) flux. Significant upward (net volatilisational) fluxes were found for three PAHs, mostly during daytime, and for two OCPs, mostly during night-time, as well as for one PCB and one PBDE during part of the measurements. While phenanthrene was deposited, fluoranthene (FLT) and pyrene (PYR) seem to undergo flux oscillation, hereby not following a day-night cycle. Box modelling confirms that volatilisation from the sea surface has significantly contributed to the night-time maxima of OCPs. Fluxes were quantified based on eddy covariance. Deposition fluxes ranged from -28.5 to +1.8 µg m-2 day-1 for PAHs and -3.4 to +0.9 µg m-2 day-1 for halogenated compounds. Dry particle deposition of FLT and PYR did not contribute significantly to the vertical flux.

  1. Microwave remote sensing of snow-covered sea ice

    NASA Technical Reports Server (NTRS)

    Borgeaud, M.; Kong, J. A.; Lin, F. C.

    1986-01-01

    Snow and ice are modeled as random media characterized by different dielectric constants and correlation functions. In order to model the brine inclusions of sea ice, the random medium is assumed to be anisotropic. A three-layer model is used to simulate a snow-covered ice field with the top layer being snow, the middle layer being ice, and the bottom layer being sea water. The theoretical results are illustrated for thick first-year sea ice covered by dry snow, and for artificial, thin first-year sea ice covered by wet snow as measured in controlled model tank experiments. The radar backscattering cross sections are seen to increase with snow cover for snow-covered sea ice owing to large volume scattering effects of snow.

  2. The Mediterranean Sea as you have never seen it : results from systematic swath mapping during the last decade.

    NASA Astrophysics Data System (ADS)

    Mascle, J. R.; Loubrieu, B.

    2005-12-01

    Since about 10 years systematic swath mapping of the Mediterranean sea has been undertaken by several european oceanographic Institutions, particularly from France, Italy, Spain, Greece and the Netherlands. Under the sponsorship of CIESM, IFREMER and Geosciences-Azur (CNRS) the bathymetric data have been compiled at a 500 meter grid to construct two maps of the Western and Eastern Mediteranean basin at a 1/ 2000 000 scale. - Most of the northern western Mediterranean, including the Rhone margin and its deep terrigenous cone, and the tectonically active and magmatic Thyrrenian sea, are now well documented; the seismically active steep northern African margin is currently under investigation. - In Eastern Mediterranean, 80 per cent of the deep (below 800 meters) domain, including the Ionian and Levantine basins and the prominent Mediterranean ridge and Nile margin/deep sea fan, are now well imaged by swath bathymetric data. These precise morphologic data enligth the complex interplays between tectonic (including salt tectonic) sedimentary and fluid/mud expulsion mechanisms. They have also been the basis to organize several deep in situ studies, particularly of the numerous fluid releases whic characterize most of the areas. Parts of the shallower extensionnal, back arc type, Aegean, sea have also been surveyed, while the Calabrian Ridge, an accretionnary wedge similar to the Mediterranean ridge, which lies south-east of the Italian peninsula, has just been mapped by OGS-Trieste (summer 2005). The complex Mediterranean sea is probably one of the best surveyed oceanic spaces using swath mapping tools whose results are particularly significant to better image and understand the different processes which concurr to shape the sea floor of this progressively closing oceanic space.

  3. Gravitational scattering of electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Brooker, J. T.; Janis, A. I.

    1980-01-01

    The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.

  4. Application of physical optics to ocean surface radar scattering with CUDA

    NASA Astrophysics Data System (ADS)

    Ling-Hu, Long-xiang; Wu, Zhen-sen; Guo, Xing

    2013-09-01

    The problem of electromagnetic waves scattering at rough boundaries is of practical interest and has been addressed many times in different papers. Theories for investigation of rough surface scattering primarily two kinds of methods: numerical method and approximate method. As the classic analytical methods cannot calculate the electromagnetic scattering characteristics at Low Grazing Angle (LGA) accurately, in this paper, a novel method is presented by utilizing the Radar Cross Section (RCS) of the low grazing two-dimensional sea surface based on the triangles-based Physical Optics (PO) method. Firstly, the Monte Carlo method is applied to simulate the two-dimension rough sea surface in different wind speeds based on the PM sea spectrum. Then, the sea surface is generally meshed by 1/8~1/10 length of the incident wave. Secondly, the complex permittivity of the sea surface is calculated by two-Debye method and compared with the experiment. The physical optical is used to calculate the backscattering coefficient of the random rough sea surface. Considering the problem of low grazing, it is especially sampled more densely between the scattering angles 70°~90°. Then the self-shadow and inter-shadow of the sea surface at low grazing angle is taken into account, the Z-BUFFER method is used to judgment of the shadow effect. The numerical result is compared with the FEKO and good agreement is obtained. As the frequency increasing, the sea surface will have more triangles to be calculated, it will take more time. Finally, we propose a novel graphic processing unit (GPU)-accelerated decoding system. The result is 68.96 faster than its CPU counterpart.

  5. Improved scatter correction using adaptive scatter kernel superposition

    NASA Astrophysics Data System (ADS)

    Sun, M.; Star-Lack, J. M.

    2010-11-01

    Accurate scatter correction is required to produce high-quality reconstructions of x-ray cone-beam computed tomography (CBCT) scans. This paper describes new scatter kernel superposition (SKS) algorithms for deconvolving scatter from projection data. The algorithms are designed to improve upon the conventional approach whose accuracy is limited by the use of symmetric kernels that characterize the scatter properties of uniform slabs. To model scatter transport in more realistic objects, nonstationary kernels, whose shapes adapt to local thickness variations in the projection data, are proposed. Two methods are introduced: (1) adaptive scatter kernel superposition (ASKS) requiring spatial domain convolutions and (2) fast adaptive scatter kernel superposition (fASKS) where, through a linearity approximation, convolution is efficiently performed in Fourier space. The conventional SKS algorithm, ASKS, and fASKS, were tested with Monte Carlo simulations and with phantom data acquired on a table-top CBCT system matching the Varian On-Board Imager (OBI). All three models accounted for scatter point-spread broadening due to object thickening, object edge effects, detector scatter properties and an anti-scatter grid. Hounsfield unit (HU) errors in reconstructions of a large pelvis phantom with a measured maximum scatter-to-primary ratio over 200% were reduced from -90 ± 58 HU (mean ± standard deviation) with no scatter correction to 53 ± 82 HU with SKS, to 19 ± 25 HU with fASKS and to 13 ± 21 HU with ASKS. HU accuracies and measured contrast were similarly improved in reconstructions of a body-sized elliptical Catphan phantom. The results show that the adaptive SKS methods offer significant advantages over the conventional scatter deconvolution technique.

  6. Climatological variations of total alkalinity and total dissolved inorganic carbon in the Mediterranean Sea surface waters

    NASA Astrophysics Data System (ADS)

    Gemayel, E.; Hassoun, A. E. R.; Benallal, M. A.; Goyet, C.; Rivaro, P.; Abboud-Abi Saab, M.; Krasakopoulou, E.; Touratier, F.; Ziveri, P.

    2015-12-01

    A compilation of data from several cruises between 1998 and 2013 was used to derive polynomial fits that estimate total alkalinity (AT) and total dissolved inorganic carbon (CT) from measurements of salinity and temperature in the Mediterranean Sea surface waters. The optimal equations were chosen based on the 10-fold cross-validation results and revealed that second- and third-order polynomials fit the AT and CT data respectively. The AT surface fit yielded a root mean square error (RMSE) of ± 10.6 μmol kg-1, and salinity and temperature contribute to 96 % of the variability. Furthermore, we present the first annual mean CT parameterization for the Mediterranean Sea surface waters with a RMSE of ± 14.3 μmol kg-1. Excluding the marginal seas of the Adriatic and the Aegean, these equations can be used to estimate AT and CT in case of the lack of measurements. The identified empirical equations were applied on the 0.25° climatologies of temperature and salinity, available from the World Ocean Atlas 2013. The 7-year averages (2005-2012) showed that AT and CT have similar patterns with an increasing eastward gradient. The variability is influenced by the inflow of cold Atlantic waters through the Strait of Gibraltar and by the oligotrophic and thermohaline gradient that characterize the Mediterranean Sea. The summer-winter seasonality was also mapped and showed different patterns for AT and CT. During the winter, the AT and CT concentrations were higher in the western than in the eastern basin. The opposite was observed in the summer where the eastern basin was marked by higher AT and CT concentrations than in winter. The strong evaporation that takes place in this season along with the ultra-oligotrophy of the eastern basin determines the increase of both AT and CT concentrations.

  7. Long term seismic observation using ocean bottom seismographs in Marmara Sea, Turkey

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Pinar, A.; Kalafat, D.; Yamamoto, Y.; Citak, S.; Comoglu, M.; Çok, Ö.; Ogutcu, Z.; Suvarikli, M.; Tunc, S.; Gurbuz, C.; Ozel, N.; Kaneda, Y.

    2015-12-01

    The North Anatolian Fault crosses the Marmara Sea with a direction of E-W. There are many large earthquakes repeatedly along the fault with a linkage each other. Due to recent large eastern Aegean earthquake with M6, the Marmara Sea is the "blank zone". Japan and Turkey have a SATREPS collaborative study to clarify the structural characters, construct fault models, simulate the strong motion and tsunami, evaluate these risks with hazard maps and educate disaster prevention for local governments and residents. Our activity is one of the most basic studies, and the objectives are to clarify hypocenter locations, monitor the move, and construct fault models referring seismic/magnetotelluric structures, geodetic nature and trenching works. The target area is from western Marmara Sea to the off Istanbul area along the north Anatolian Fault. We deployed ten Ocean Bottom Seismographs (OBSs) between the Tekirdag Basin and the Central Basin in September, 2014. Then, we added five Japanese OBSs and deployed them at the western end of the Marmara Sea and the eastern Central Basin to extend observed area in March, 2015. The OBS has a three-component velocity sensor with a natural frequency of 4.5 Hz and a hydrophone. Japanese team have clarified seismicity around Japan using the OBS. The magnitude of the detected events is 1.0-1.5. We retrieved all 15 OBSs in July, 2015 and deployed them again on the same locations after data copy and battery maintenance. We started OBS data analysis combined with land stations data. Now we detect events automatically using these data and succeeded detection of over one thousand around the north Anatolian Fault. The tentative results show heterogeneous seismicity. The western and central basins have relative high seismicity and the seismogenic zone becomes thicker rather than previous estimation. Then we will evaluate hypocenter locations with high resolution and discuss the shape of faults in each segment and their linkage.

  8. The timing of the Black Sea flood event: Insights from modeling of glacial isostatic adjustment

    NASA Astrophysics Data System (ADS)

    Goldberg, Samuel L.; Lau, Harriet C. P.; Mitrovica, Jerry X.; Latychev, Konstantin

    2016-10-01

    We present a suite of gravitationally self-consistent predictions of sea-level change since Last Glacial Maximum (LGM) in the vicinity of the Bosphorus and Dardanelles straits that combine signals associated with glacial isostatic adjustment (GIA) and the flooding of the Black Sea. Our predictions are tuned to fit a relative sea level (RSL) record at the island of Samothrace in the north Aegean Sea and they include realistic 3-D variations in viscoelastic structure, including lateral variations in mantle viscosity and the elastic thickness of the lithosphere, as well as weak plate boundary zones. We demonstrate that 3-D Earth structure and the magnitude of the flood event (which depends on the pre-flood level of the lake) both have significant impact on the predicted RSL change at the location of the Bosphorus sill, and therefore on the inferred timing of the marine incursion. We summarize our results in a plot showing the predicted RSL change at the Bosphorus sill as a function of the timing of the flood event for different flood magnitudes up to 100 m. These results suggest, for example, that a flood event at 9 ka implies that the elevation of the sill was lowered through erosion by ∼14-21 m during, and after, the flood. In contrast, a flood event at 7 ka suggests erosion of ∼24-31 m at the sill since the flood. More generally, our results will be useful for future research aimed at constraining the details of this controversial, and widely debated geological event.

  9. Moho depth and crustal thinning in the Marmara Sea region from gravity data inversion

    NASA Astrophysics Data System (ADS)

    Kende, Julia; Henry, Pierre; Bayrakci, Gaye; Özeren, Sinan; Grall, Céline

    2016-04-01

    With a width comparable to the brittle crust thickness, the Sea of Marmara strike-slip basin appears as an intermediate case between two much studied end-member cases of basin-width-to-brittle-crust-thickness ratio: the Dead Sea and the Death Valley. But geophysical studies have shown evidences of at least 5 km of mantle uplift under the Marmara Sea, much larger than in the two other cases. We compiled data from reflection, refraction and tomography seismic studies to correct satellite and survey vessel gravity data (acquired during MARSITE cruise of Ifremer R/V Pourquoi Pas ?) from the effect of topography and sedimentary basins. Assuming that no other crustal mass heterogeneity affects the gravity measurement, we inverted the residual, with constraints from seismic studies, to calculate the topography of the Moho. The 3D model obtained shows a mantle uplift broadly correlated with the Marmara deep basins, but the crustal thinning spreads southward further than the basin limits, This is explained by ductile flow in the lower crust between a northern zone where the thinning is closely related to the Marmara Fault strike-slip basins and a southern zone where extension appears associated with older crustal detachment systems. Finally, we estimated the extension budget in the area during the Marmara Sea formation by comparing our 3D crust volume with an initial crust of constant thickness. The increase in surface area, 2100±300 km2, is compatible with present day GPS velocity field measurement assuming steady state and an initiation of extension in the area about 5 Myr ago. We conclude that although the zone went through tectonic reorganizations during the Pliocene as the North Anatolian Fault system propagated westward, the overall extension rate in the area could have been stable, or decreasing with time, and thus should be understood in a broader geodynamic framework comprising the Aegean subduction.

  10. Neodymium isotopes in the Mediterranean Sea: comparison between seawater and sediment signals

    NASA Astrophysics Data System (ADS)

    Tachikawa, K.; Roy-Barman, M.; Michard, A.; Thouron, D.; Yeghicheyan, D.; Jeandel, C.

    2004-07-01

    Nine depth-profiles of dissolved Nd concentrations and isotopic ratios (ɛ Nd) were obtained in the Levantine Basin, the Ionian, the Aegean, the Alboran Seas and the Strait of Gibraltar. Thirteen core-top sediments and Nile River particle samples were also analyzed (leached with 1 N HCl, acetic acid or hydroxylamine hydrochloride). The seawater ɛ Nd values become more radiogenic during the eastward circulation in the Mediterranean Sea. The relationship between salinity and the seawater ɛ Nd shows that the Nd isotopic signature is more conservative than salinity in the Mediterranean Sea. The water mass with the highest ɛ Nd (-4.8) is found at about 200 m in the easternmost Levantine basin. The average ɛ Nd value for deep waters is -7.0 in the eastern basin, 2.5 ɛ-units higher than in the western basin. By examining the sensitivity of seawater ɛ Nd to Nd inputs from the Nile, we conclude that the most significant radiogenic Nd source is partially dissolved Nile River particles. The Nd flux from the Nile River water has a minor influence on the Mediterranean seawater ɛ Nd. Except for the easternmost Levantine Basin, the leachate ɛ Nd values are consistent with the seawater values. In the easternmost Levantine Basin, the leachate ɛ Nd values obtained with HCl leaching are systematically higher than the seawater values. The relationship between leachate and residual ɛ Nd values indicates that the HCl leaching partially dissolves lithogenic Nd, so the dissolution of Nile River particles is the cause of the observed shift. Some ɛ Nd values obtained with hydroxylamine hydrochloride leaching are higher than those obtained with HCl leaching. Although the reason for this shift is not clear, 87Sr/ 86Sr successfully detects the presence of a nonmarine component in the leachate. Our results suggest that leaching performance may vary with the mineralogy of marine sediments, at least in the case of the Mediterranean Sea.

  11. Polarization-Based Radar Detection in Sea Clutter

    DTIC Science & Technology

    2015-02-27

    information. 15. SUBJECT TERMS polarization mode dispersion; radar; sea surface; electromagnetic modeling; target identification; target detection 16...Stationarity and Ergodicity 34 5. Example Statistics 35 E. Concluding remarks 37 IV. ELECTROMAGNETIC SURFACE SCATTERING MODEL 38 A. Reflection from a...Dielectric Boundary at Oblique Incidence 38 1. Complex Dielectric Permittivity 38 2. Reflection and Refraction of Electromagnetic Waves 39 3

  12. Laser measure of sea salinity, temperature and turbidity in depth

    NASA Technical Reports Server (NTRS)

    Hirschberg, J. G.; Wouters, A. W.; Byrne, J. D.

    1974-01-01

    A method is described in which a pulsed laser is used to probe the sea. Backscattered light is analyzed in time, intensity and wavelength. Tyndall, Raman and Brillouin scattering are used to obtain the backscatter turbidity, sound velocity, salinity, and the temperature as a function of depth.

  13. Theoretical models for microwave remote sensing of snow-covered sea ice

    NASA Technical Reports Server (NTRS)

    Lin, F. C.; Kong, J. A.; Shin, R. T.

    1987-01-01

    The volume scattering effects of snow-covered sea ice are studied with a three-layer random medium model for microwave remote sensing. Theoretical results are illustrated by matching experimental data for dry snow-covered thick first-year sea ice at Point Barrow. The radar backscattering cross sections are seen to increase with snow cover for snow-covered sea ice, due to the increased scattering effects in the snow layer. The results derived can also be applied to passive remote sensing.

  14. Scattering Solar Thermal Concentrators

    SciTech Connect

    Giebink, Noel C.

    2015-01-31

    This program set out to explore a scattering-based approach to concentrate sunlight with the aim of improving collector field reliability and of eliminating wind loading and gross mechanical movement through the use of a stationary collection optic. The approach is based on scattering sunlight from the focal point of a fixed collection optic into the confined modes of a sliding planar waveguide, where it is transported to stationary tubular heat transfer elements located at the edges. Optical design for the first stage of solar concentration, which entails focusing sunlight within a plane over a wide range of incidence angles (>120 degree full field of view) at fixed tilt, led to the development of a new, folded-path collection optic that dramatically out-performs the current state-of-the-art in scattering concentration. Rigorous optical simulation and experimental testing of this collection optic have validated its performance. In the course of this work, we also identified an opportunity for concentrating photovoltaics involving the use of high efficiency microcells made in collaboration with partners at the University of Illinois. This opportunity exploited the same collection optic design as used for the scattering solar thermal concentrator and was therefore pursued in parallel. This system was experimentally demonstrated to achieve >200x optical concentration with >70% optical efficiency over a full day by tracking with <1 cm of lateral movement at fixed latitude tilt. The entire scattering concentrator waveguide optical system has been simulated, tested, and assembled at small scale to verify ray tracing models. These models were subsequently used to predict the full system optical performance at larger, deployment scale ranging up to >1 meter aperture width. Simulations at an aperture widths less than approximately 0.5 m with geometric gains ~100x predict an overall optical efficiency in the range 60-70% for angles up to 50 degrees from normal. However, the

  15. Sound extinction by fish schools: forward scattering theory and data analysis.

    PubMed

    Raveau, M; Feuillade, C

    2015-02-01

    A model used previously to study collective back scattering from fish schools [Feuillade et al., J. Acoust. Soc. Am. 99(1), 196-208 (1996)], is used to analyze the forward scattering properties of these objects. There is an essential physical difference between back and forward scattering from fish schools. Strong frequency dependent interference effects, which affect the back scattered field amplitude, are absent in the forward scattering case. This is critically important for data analysis. There is interest in using back scattering and transmission data from fish schools to study their size, the species and abundance of fish, and fish behavior. Transmission data can be processed to determine the extinction of the field by a school. The extinction of sound depends on the forward scattering characteristics of the school, and data inversion to provide information about the fish should be based upon a forward scattering paradigm. Results are presented of an analysis of transmission data obtained in September 1995 during an experiment performed in the Gulf of Lion in the Mediterranean Sea [Diachok, J. Acoust. Soc. Am. 105(4), 2107-2128 (1999)]. The analysis shows that using forward scattering leads to significantly larger estimates of fish abundance than previous analysis based upon back scattering approaches.

  16. Scattering from Superquadric Surfaces

    DTIC Science & Technology

    1988-06-01

    for any purpose other than in connection with a definitely related Government procurement operation, the United States Government thereby incurs no...Clomparative C’PU times in VPU (VAX 780 Processing Units ) 44 3 I I I I I I I I I I * Chapter 1 | INTRODUCTION I The electromagnetic scattering from a...in the Shadow region (2.4) where ft is the unit normal to the surface. Physical Optics is useful because the form of the assumed currents is 3 simple

  17. Inferences of Integrated Lithospheric Strength from Plate-Scale Analyses of Deformation Observed in the Aegean-Anatolian Region and the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Houseman, Gregory

    2016-04-01

    In the context of a comprehensive review of the rheology and strength of the lithosphere (Marine and Petroleum Geology, 2011, doi:10.1016/j.marpetgeo.2011.05.008), Evgene Burov described the difficulty of extrapolating rock deformation laws derived from laboratory experiments to the time and length scales that apply when the Earth's lithosphere is deformed. Not only does the extrapolation introduce a large uncertainty, but even the relative importance of different possible mechanisms of deformation may be uncertain. Even though lithospheric deformation has a strong conceptual and theoretical basis, it is therefore essential, as Burov argued, that deformation laws for the lithosphere must be calibrated by using observations of deformation that occurs on a lithospheric length scale and at geological strain rates. The influence of regionally varying factors like crustal thickness, geothermal gradient and tectonic environment may induce large variations in how rapidly the lithosphere may deform in response to an applied load, not least in the contrast from continent to ocean. Plates may be deformed by different loading mechanisms but, when deformation is distributed over a broad region, the strain-rate field may be approximately constant with depth and we may integrate the in-plane stress components across the thickness of the lithosphere to derive a depth-averaged constitutive law for the deformation. This approximation is the basis for the thin viscous sheet formulation of lithospheric deformation and, in combination with appropriate observations, it allows us to calibrate the integrated resistance to processes like regional extension or convergence. In this talk I will summarise what we learn about effective lithospheric rheology from two recent studies of the distribution and rates of diffuse deformation of the lithosphere in, firstly the Anatolian-Aegean region, and secondly the Central Indian Ocean. In the first case the distribution of deformation is consistent

  18. Temporal Variability of Zooplankton (2000-2013) in the Levantine Sea: Significant Changes Associated to the 2005-2010 EMT-like Event?

    PubMed

    Ouba, Anthony; Abboud-Abi Saab, Marie; Stemmann, Lars

    2016-01-01

    In this study, we investigated, for the first time, the potential impact of environmental changes on zooplankton abundance over a fourteen year period (2000-2013) at an offshore station in the Eastern Mediterranean Sea (the Levantine basin, offshore Lebanon). Samples were collected monthly and analyzed using the semi-automated system ZooScan. Salinity, temperature and phytoplankton abundance (nano and microphytoplankton) were also measured. Results show no significant temporal trend in sea surface temperature over the years. Between 2005-2010, salinity in the upper layer (0-80 m) of the Levantine basin increased (~0.3°C). During this 5 year period, total zooplankton abundance significantly increased. These modifications were concomitant to the activation of Aegean Sea as a source of dense water formation as part of the "Eastern Mediterranean Transient-like" event. The results of the present study suggested that zooplankton benefited from enhanced phytoplankton production during the mixing years of the event. Changes in the phenology of some taxa were observed accordingly with a predominantly advanced peak of zooplankton abundance. In conclusion, long-term changes in zooplankton abundance were related to the Levantine thermohaline circulation rather than sea surface warming. Sampling must be maintained to assess the impact of long-term climate change on zooplankton communities.

  19. Temporal Variability of Zooplankton (2000-2013) in the Levantine Sea: Significant Changes Associated to the 2005-2010 EMT-like Event?

    PubMed Central

    Ouba, Anthony; Abboud-Abi Saab, Marie; Stemmann, Lars

    2016-01-01

    In this study, we investigated, for the first time, the potential impact of environmental changes on zooplankton abundance over a fourteen year period (2000–2013) at an offshore station in the Eastern Mediterranean Sea (the Levantine basin, offshore Lebanon). Samples were collected monthly and analyzed using the semi-automated system ZooScan. Salinity, temperature and phytoplankton abundance (nano and microphytoplankton) were also measured. Results show no significant temporal trend in sea surface temperature over the years. Between 2005–2010, salinity in the upper layer (0–80 m) of the Levantine basin increased (~0.3°C). During this 5 year period, total zooplankton abundance significantly increased. These modifications were concomitant to the activation of Aegean Sea as a source of dense water formation as part of the “Eastern Mediterranean Transient-like” event. The results of the present study suggested that zooplankton benefited from enhanced phytoplankton production during the mixing years of the event. Changes in the phenology of some taxa were observed accordingly with a predominantly advanced peak of zooplankton abundance. In conclusion, long-term changes in zooplankton abundance were related to the Levantine thermohaline circulation rather than sea surface warming. Sampling must be maintained to assess the impact of long-term climate change on zooplankton communities. PMID:27459093

  20. Radioactivity concentrations in mussel (Mytilus galloprovincialis) of Turkish Sea coast and contribution of ²¹⁰Po to the radiation dose.

    PubMed

    Kılıç, Önder; Belivermiş, Murat; Cotuk, Yavuz; Topçuoğlu, Sayhan

    2014-03-15

    Radionuclides levels were determined in indigenous and transplanted mussels (Mytilus galloprovincialis) collected from Turkish marine environment. Radioactivity concentrations of ¹³⁷Cs, ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ²¹⁰Po and ²¹⁰Pb were determined in the soft tissues of the mussel samples collected in Bosphorus Strait, Coasts of Black Sea, Marmara Sea and Aegean Sea. Mussel transplantation was carried out by using mussel cages in Levantine Sea coast since M. galloprovincialis did not naturally adapt along the coast. The average activity concentrations of ¹³⁷Cs, ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ²¹⁰Po and ²¹⁰Pb in the coastline of Turkey were found to be 0.7±0.1, 469±24, 0.9±0.1, 1.0±0.1, 122±4 and 10.9±0.9 Bq kg⁻¹ in dry weight (dw), respectively. The average of ²¹⁰Po/²¹⁰Pb ratio was found to be ∼14. Total annual effective ²¹⁰Po dose was calculated to be in the range of 0.25-3.30 μSv due to mussel consumption. Radioactivity and dose levels were compared with those of similar studies carried out in Mediterranean countries.

  1. Apparent optical density of the scattering medium: influence of scattering

    NASA Astrophysics Data System (ADS)

    Kiseleva, Irina A.; Sinichkin, Yurii P.

    2002-07-01

    Comparative analysis of manifestation of finite absorption in scattering media is carried out for different detection geometries. Reflectance spectra were studied for phantom scattering media containing blood and melanin as absorbers. Apparent optical density spectra of phantom media are compared with similar spectra of water solutions of the blood and melanin for same concentrations of absorbers. The influence of scattering properties on optical density spectra is discussed with use of the model of diffuse light propagation in semi-infinite media.

  2. Aral Sea basin: a sea dies, a sea also rises.

    PubMed

    Glantz, Michael H

    2007-06-01

    The thesis of this article is quite different from many other theses of papers, books, and articles on the Aral Sea. It is meant to purposely highlight the reality of the situation in Central Asia: the Aral Sea that was once a thriving body of water is no more. That sea is dead. What does exist in its place are the Aral seas: there are in essence three bodies of water, one of which is being purposefully restored and its level is rising (the Little Aral), and two others which are still marginally connected, although they continue to decline in level (the Big Aral West and the Big Aral East). In 1960 the level of the sea was about 53 m above sea level. By 2006 the level had dropped by 23 m to 30 m above sea level. This was not a scenario generated by a computer model. It was a process of environmental degradation played out in real life in a matter of a few decades, primarily as a result of human activities. Despite wishes and words to the contrary, it will take a heroic global effort to save what remains of the Big Aral. It would also take a significant degree of sacrifice by people and governments in the region to restore the Big Aral to an acceptable level, given that the annual rate of flow reaching the Amudarya River delta is less than a 10th of what it was several decades ago. Conferring World Heritage status to the Aral Sea(s) could spark restoration efforts for the Big Aral.

  3. The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes

    NASA Astrophysics Data System (ADS)

    Grant, K. M.; Grimm, R.; Mikolajewicz, U.; Marino, G.; Ziegler, M.; Rohling, E. J.

    2016-05-01

    The Mediterranean basin is sensitive to global sea-level changes and African monsoon variability on orbital timescales. Both of these processes are thought to be important to the deposition of organic-rich sediment layers or 'sapropels' throughout the eastern Mediterranean, yet their relative influences remain ambiguous. A related issue is that an assumed 3-kyr lag between boreal insolation maxima and sapropel mid-points remains to be tested. Here we present new geochemical and ice-volume-corrected planktonic foraminiferal stable isotope records for sapropels S1 (Holocene), S3, S4, and S5 (Marine Isotope Stage 5) in core LC21 from the southern Aegean Sea. The records have a radiometrically constrained chronology that has already been synchronised with the Red Sea relative sea-level record, and this allows detailed examination of the timing of sapropel deposition relative to insolation, sea-level, and African monsoon changes. We find that sapropel onset was near-synchronous with monsoon run-off into the eastern Mediterranean, but that insolation-sapropel/monsoon phasings were not systematic through the last glacial cycle. These latter phasings instead appear to relate to sea-level changes. We propose that persistent meltwater discharges into the North Atlantic (e.g., at glacial terminations) modified the timing of sapropel deposition by delaying the timing of peak African monsoon run-off. These observations may reconcile apparent model-data offsets with respect to the orbital pacing of the African monsoon. Our observations also imply that the previous assumption of a systematic 3-kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation-sapropel phasings. Finally, we surmise that both sea-level rise and monsoon run-off contributed to surface-water buoyancy changes at times of sapropel deposition, and their relative influences differed per sapropel case, depending on their magnitudes. Sea-level rise was clearly important for

  4. A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

    SciTech Connect

    Lavelle, Christopher M; Liu, C; Stone, Matthew B

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  5. Protostring scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  6. 7 CFR 1437.310 - Sea grass and sea oats.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss... boundaries; and (3) Be managed and maintained using acceptable growing practices for the geographical...

  7. 7 CFR 1437.310 - Sea grass and sea oats.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss... boundaries; and (3) Be managed and maintained using acceptable growing practices for the geographical...

  8. 7 CFR 1437.310 - Sea grass and sea oats.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss... boundaries; and (3) Be managed and maintained using acceptable growing practices for the geographical...

  9. 7 CFR 1437.310 - Sea grass and sea oats.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss..., as determined by CCC. (e) The land, waterbed, or facility in which the eligible commodity was...

  10. 7 CFR 1437.310 - Sea grass and sea oats.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Sea grass and sea oats. 1437.310 Section 1437.310... Determining Coverage Using Value § 1437.310 Sea grass and sea oats. (a) Sea grass and sea oats are value loss..., as determined by CCC. (e) The land, waterbed, or facility in which the eligible commodity was...

  11. Rayleigh, Raman and particulate scattering

    NASA Technical Reports Server (NTRS)

    Cochran, W. D.

    1982-01-01

    Analysis of the visible and near infrared spectra of planetary atmospheres and the multiple scattering of photons within the atmosphere are discussed. Photons detected within the spectral region are solar photons which were scattered by the gas and particles in the planetary atmosphere. An example is given for the incident and emitted fluxes for a hypothetical planet with an effective temperature of 100 K. The absorption spectrum of the planetary atmosphere is discussed in terms of the various scattering processes photons undergo within the atmosphere. Three different physical processes are considered. Rayleigh scattering and Raman scattering by the gas molecules, and scattering by any cloud or dust aerosol particles in the atmosphere. The physics of each of these processes is examined.

  12. Weak Deeply Virtual Compton Scattering

    SciTech Connect

    Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin

    2007-03-01

    We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.

  13. Deep sea waste disposal

    SciTech Connect

    Kester, D.R.; Burt, W.V.; Capuzzo, J.M.; Park, P.K.; Ketchum, B.W.; Duedall, I.W.

    1985-01-01

    The book presents papers on the marine disposal of wastes. Topics considered include incineration at sea, the modelling and biological effects of industrial wastes, microbial studies of ocean dumping, deep-sea mining wastes, the chemical analysis of ferromanganese nodules, and economic aspects of deep-sea disposal.

  14. All That Unplowed Sea

    ERIC Educational Resources Information Center

    MOSAIC, 1975

    1975-01-01

    Hunting and gathering at sea may fast be approaching their productive limits. Aquaculture - farming at sea - linked to conservation represents the sea's promise. If the system works, it might prove to be the key to supplying large amounts of food and fresh water at no cost in nonrenewable energy resources. (BT)

  15. Optical characteristics of regolith from the Sea of Fertility, Sea of Tranquillity, and Ocean of Storms

    NASA Technical Reports Server (NTRS)

    Antipova-Karatayeva, I. I.; Stakheyev, Y. I.; Florenskiy, K. P.

    1974-01-01

    A diffuse reflection spectra analysis is reported for regolith returned by the Luna 16 automatic station and by the Apollo 11 and Apollo 12 expeditions. The spectra of the specular reflection of Sea of Fertility regolith, as well as the spectra of diffuse reflection from polished sections of lunar rocks from the Sea of Tranquillity and the Ocean of Storms have no well-defined structures and are close to each other. The lowest reflectivity is exhibited by the Sea of Tranquillity regolith, and the highest -- by the Ocean of Storms regolith. A weak absorption band with a maximum near 1 nm is noted in the spectra, corresponding to the Fe-2(+) ion in the octahedral position in the lattice of regolith mineral constituents. When the indicatrix of scattering of the regolith was recorded, a specular component was detected.

  16. Advances in total scattering analysis

    SciTech Connect

    Proffen, Thomas E; Kim, Hyunjeong

    2008-01-01

    In recent years the analysis of the total scattering pattern has become an invaluable tool to study disordered crystalline and nanocrystalline materials. Traditional crystallographic structure determination is based on Bragg intensities and yields the long range average atomic structure. By including diffuse scattering into the analysis, the local and medium range atomic structure can be unravelled. Here we give an overview of recent experimental advances, using X-rays as well as neutron scattering as well as current trends in modelling of total scattering data.

  17. Electromagnetic scattering from turbulent plasmas

    SciTech Connect

    Resendes, D.G. Instituto Superior Tecnico, Rua Rovisco Pais, Lisboa )

    1992-11-15

    A self-consistent multiple-scattering theory of vector electromagnetic waves scattered from a turbulent plasma is presented. This approach provides a general and systematic treatment to all orders in turbulence of the scattering of electromagnetic waves in terms of the properties of the turbulent structure of the scattering system and is applicable in the full regime from underdense to overdense plasmas. To illustrate the theory, a plasma consisting of a finite number density of discrete scatterers with a simple geometry and statistical properties is chosen. In this approach the exact solution for a single scatterer is obtained first. From it the configuration-dependent solution for {ital N} scatterers is constructed. Rather than solving explicitly for this solution and then averaging, the averaging operation will be taken first in order to find an approximate equation obeyed by the mean or coherent field. The coherent and incoherent scattering are then determined in terms of the coherent field and the backscatter is evaluated. The coherent and incoherent scattering, our principal results, are expressed in a plane-wave basis in a form suitable for numerical computation. A number of interesting phenomena which may readily be incorporated into the theory are indicated.

  18. Polarization imaging through scattering media

    NASA Astrophysics Data System (ADS)

    Morgan, Stephen P.; Khong, Manping; Somekh, Michael G.

    1995-12-01

    The imaging resolution in turbid media is severely degraded by light scattering. Resolution can be improved by extracting the unscattered or weakly scattered light. In this paper the state of polarization of the emerging light is used to discriminate photon pathlength, the more weakly scattered photons maintaining their original polarization state. It is experimentally demonstrated that over a wide range of scatterer concentrations, different particle sizes possess different characteristics. Three distinct regimes are described in detail along with the techniques to improve resolution within these regimes.

  19. Review of light scattering literature

    NASA Astrophysics Data System (ADS)

    Potts, Marie K.

    1994-06-01

    This report reviews the recent literature of static and dynamic light scattering of dilute and semidilute polymer solutions and gels, as obtained from the Chemical Abstracts Macromolecular Sections, and an electronic literature search. In general, this review has been confined to the interests of the Polymer Research Branch, specifically experimental light scattering studies of synthetic polymers in solution. In order to further limit the size of this review, light scattering for phase separation studies or particle size analysis have been excluded, as well as light scattering used strictly for size exclusion chromatography detection.

  20. Neutron Scattering Stiudies

    SciTech Connect

    Kegel, Gunter H.R.; Egan, James J

    2007-04-18

    This project covers four principal areas of research: Elastic and inelastic neutron scattering studies in odd-A terbium, thulium and other highly deformed nuclei near A=160 with special regard to interband transitions and to the investigation of the direct-interaction versus the compound-nucleus excitation process in these nuclei. Examination of new, fast photomultiplier tubes suitable for use in a miniaturized neutron-time-of-flight spectrometer. Measurement of certain inelastic cross sections of 238U. Determination of the multiplicity of prompt fission gamma rays in even-A fissile actinides. Energies and mean lives of fission isomers produced by fast fission of even-Z, even-A actinides. Study of the mean life of 7Be in different host matrices and its possible astro-physical significance.

  1. Climate Impacts on Sea Turtle Breeding Phenology in Greece and Associated Foraging Habitats in the Wider Mediterranean Region.

    PubMed

    Patel, Samir H; Morreale, Stephen J; Saba, Vincent S; Panagopoulou, Aliki; Margaritoulis, Dimitris; Spotila, James R

    2016-01-01

    Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7°N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3°N) and Rethymno, Crete (latitude: 35.4°N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabès and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0°-45.8°N) for loggerhead turtles nesting in Greece will rise by 3-5°C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50-74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population.

  2. Climate Impacts on Sea Turtle Breeding Phenology in Greece and Associated Foraging Habitats in the Wider Mediterranean Region

    PubMed Central

    Morreale, Stephen J.; Saba, Vincent S.; Panagopoulou, Aliki; Margaritoulis, Dimitris; Spotila, James R.

    2016-01-01

    Sea turtles are vulnerable to climate change impacts in both their terrestrial (nesting beach) and oceanic habitats. From 1982 to 2012, air and sea surface temperatures at major high use foraging and nesting regions (n = 5) of loggerhead turtles (Caretta caretta) nesting in Greece have steadily increased. Here, we update the established relationships between sea surface temperature and nesting data from Zakynthos (latitude: 37.7°N), a major nesting beach, while also expanding these analyses to include precipitation and air temperature and additional nesting data from two other key beaches in Greece: Kyparissia Bay (latitude: 37.3°N) and Rethymno, Crete (latitude: 35.4°N). We confirmed that nesting phenology at Zakynthos has continued to be impacted by breeding season temperature; however, temperature has no consistent relationship with nest numbers, which are declining on Zakynthos and Crete but increasing at Kyparissia. Then using statistically downscaled outputs of 14 climate models assessed by the Intergovernmental Panel on Climate Change (IPCC), we projected future shifts in nesting for these populations. Based on the climate models, we projected that temperature at the key foraging and breeding sites (Adriatic Sea, Aegean Sea, Crete, Gulf of Gabès and Zakynthos/Kyparissia Bay; overall latitudinal range: 33.0°—45.8°N) for loggerhead turtles nesting in Greece will rise by 3–5°C by 2100. Our calculations indicate that the projected rise in air and ocean temperature at Zakynthos could cause the nesting season in this major rookery to shift to an earlier date by as much as 50–74 days by 2100. Although an earlier onset of the nesting season may provide minor relief for nest success as temperatures rise, the overall climatic changes to the various important habitats will most likely have an overall negative impact on this population. PMID:27332550

  3. The Caspian Sea Environment

    NASA Astrophysics Data System (ADS)

    Kostianoy, Andrey; Kosarev, A.

    The systematic description of the knowledge accumulated on the physical oceanography, marine chemistry and pollution, and marine biology of the Caspian Sea forms the basis of this book. It presents the principal characteristic features of the environmental conditions of the sea and their changes in the second half of the 20th century. At present, the principal problems of the Caspian Sea are related to the interannual sea level changes and their forecast and to the estimation of the intensity of the chemical pollution of the sea and its impact upon the biota.

  4. The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes

    NASA Astrophysics Data System (ADS)

    Grant, Katharine; Grimm, Rosina; Mikolajewicz, Uwe; Marino, Gianluca; Rohling, Eelco

    2016-04-01

    The periodic deposition of organic rich layers or 'sapropels' in eastern Mediterranean sediments can be linked to orbital-driven changes in the strength and location of (east) African monsoon precipitation. Sapropels are therefore an extremely useful tool for establishing orbital chronologies, and for providing insights about African monsoon variability on long timescales. However, the link between sapropel formation, insolation variations, and African monsoon 'maxima' is not straightforward because other processes (notably, sea-level rise) may have contributed to their deposition, and because there are uncertainties about monsoon-sapropel phase relationships. For example, different phasings are observed between Holocene and early Pleistocene sapropels, and between proxy records and model simulations. To address these issues, we have established geochemical and ice-volume-corrected planktonic foraminiferal stable isotope records for sapropels S1, S3, S4, and S5 in core LC21 from the southern Aegean Sea. The records have a radiometrically constrained chronology that has already been synchronised with the Red Sea relative sea-level record, and this allows us to examine in detail the timing of sapropel deposition relative to insolation, sea-level, and African monsoon changes. Our records suggest that the onset of sapropel deposition and monsoon run-off was near synchronous, yet insolation-sapropel/monsoon phasings varied, whereby monsoon/sapropel onset was relatively delayed (with respect to insolation maxima) after glacial terminations. We suggest that large meltwater discharges into the North Atlantic modified the timing of sapropel deposition by delaying the timing of peak African monsoon run-off. Hence, the previous assumption of a systematic 3-kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation-sapropel phasings. We also surmise that both monsoon run-off and sea-level rise were important buoyancy-forcing mechanisms for

  5. Dust Storm, Aral Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Aral Sea has shrunk to less than half its size since 1985. The Aral Sea receives little water (sometimes no water) from the two major rivers that empty into it-the Syr Darya and Amu Darya. Instead, the river water is diverted to support irrigation for the region's extensive cotton fields. Recently, water scarcity has increased due to a prolonged drought in Central Asia. As the Aral Sea recedes, its former sea bed is exposed. The Aral's sea bed is composed of fine sediments-including fertilizers and other agricultural chemicals-that are easily picked up by the region's strong winds, creating thick dust storms. The International Space Station crew observed and recorded a large dust storm blowing eastward from the Aral Sea in late June 2001. This image illustrates the strong coupling between human activities (water diversions and irrigation), and rapidly changing land, sea and atmospheric processes-the winds blow across the

  6. Some Broadband Calculated RF Scatter from the Trihedral Corner Reflector

    NASA Astrophysics Data System (ADS)

    Mokole, E. L.; Gold, B. T.; Taylor, D. J.; Sarkar, T. K.; Hansen, J. P.

    To understand the target-like artifacts in radar returns called sea spikes 1 that are induced by ocean scatter,2 the WIPL-D3 and WIPL-DP4 electromagnetics codes are used to calculate monostatic and bistatic radar cross sections (RCSs) of a trihedral comer reflector at 1.5, 3.8, and 7 GHz for vertically and horizontally polarized fields. These computations are part of a larger effort to provide theoretical comparisons for recent scatter data from a 1-m trihedral reflector that was collected over 1.9 to 11.5 GHz in the open ocean with a short-pulse ultrawideband (UWB) system. Over the last eight years, this UWB experimental radar, called the microwave microscope (MWM), has been used in a series of measurements at the Atlantic Underwater Test and Experiment Center (AUTEC) in the Bahamas to investigate the low-elevation (grazing angles less than 4°)scatter of RF signals from the open ocean in an attempt to understand and mitigate the sea-spike phenomenon.

  7. Impact of Viral Infection on Absorption and Scattering Properties of Marine Bacteria and Phytoplankton

    DTIC Science & Technology

    2001-09-30

    The long-range goal of our research is to document the role of viruses in light scattering in the sea. The current DEPSCoR project is a joint venture between the University of New England and its affiliate, Bigelow Laboratory for Ocean Sciences.

  8. Fractal radar scattering from soil.

    PubMed

    Oleschko, Klaudia; Korvin, Gabor; Figueroa, Benjamin; Vuelvas, Marco Antonio; Balankin, Alexander S; Flores, Lourdes; Carreón, Dora

    2003-04-01

    A general technique is developed to retrieve the fractal dimension of self-similar soils through microwave (radar) scattering. The technique is based on a mathematical model relating the fractal dimensions of the georadargram to that of the scattering structure. Clear and different fractal signatures have been observed over four geosystems (soils and sediments) compared in this work.

  9. Residue-based scattering factors.

    PubMed

    Xu, Hongliang

    2016-11-01

    A glob is defined as a group of atoms in the crystal which can be chosen in various ways. Globs themselves can be used as scattering elements in the theory of structure determination, just as atoms are used at present. In this paper, amino-acid residues are chosen to form globs and empirical formulas for residue-based scattering factors have been developed.

  10. Scattering matrix theory for stochastic scalar fields.

    PubMed

    Korotkova, Olga; Wolf, Emil

    2007-05-01

    We consider scattering of stochastic scalar fields on deterministic as well as on random media, occupying a finite domain. The scattering is characterized by a generalized scattering matrix which transforms the angular correlation function of the incident field into the angular correlation function of the scattered field. Within the accuracy of the first Born approximation this matrix can be expressed in a simple manner in terms of the scattering potential of the scatterer. Apart from determining the angular distribution of the spectral intensity of the scattered field, the scattering matrix makes it possible also to determine the changes in the state of coherence of the field produced on scattering.

  11. Resonance enhanced dynamic light scattering.

    PubMed

    Plum, Markus A; Menges, Bernhard; Fytas, George; Butt, Hans-Jürgen; Steffen, Werner

    2011-01-01

    We present a novel light scattering setup that enables probing of dynamics near solid surfaces. An evanescent wave generated by a surface plasmon resonance in a metal layer is the incident light field in the dynamic light scattering experiment. The combination of surface plasmon resonance spectroscopy and dynamic light scattering leads to a spatiotemporal resolution extending a few hundred nanometers from the surface and from microseconds to seconds. The comparison with evanescent wave dynamic light scattering identifies the advantages of the presented technique, e.g., surface monitoring, use of metal surfaces, and biorelevant systems. For both evanescent wave geometries, we define the scattering wave vector necessary for the analysis of the experimental relaxation functions.

  12. Potential Elevation Biases for Laser Altimeters from Subsurface Scattered Photons: Laboratory and Model Exploration of Green Light Scattering in Snow

    NASA Astrophysics Data System (ADS)

    Greeley, A.; Neumann, T.; Markus, T.; Kurtz, N. T.; Cook, W. B.

    2015-12-01

    Existing visible light laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographic Laser Altimeter System) on NASA's upcoming ICESat-2 mission - and ATM (Airborne Topographic Mapper) on NASA's Operation IceBridge mission provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters like sea ice freeboard and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons travelling into snow, ice, or water before scattering back to the altimeter receiving system (subsurface photons) travel farther and longer than photons scattering off the surface only, causing a bias in the measured elevation. We seek to identify subsurface photons in a laboratory setting using a flight-tested laser altimeter (MABEL) and to quantify their effect on surface elevation estimates for laser altimeter systems. We also compare these estimates with previous laboratory measurements of green laser light transmission through snow, as well as Monte Carlo simulations of backscattered photons from snow.

  13. Remote sensing of the sea surface by millimeterwave SAR

    NASA Astrophysics Data System (ADS)

    Essen, H.; Fuchs, H.-H.; Pagels, A.

    2006-09-01

    On several occasions the sea surface has been measured with the mmW radar MEMPHIS in SAR geometry. This research was mainly aimed to investigate the ability of SAR for imaging of disturbances of the water surface at mm-wave radar bands and to gather data on the statistical properties of sea clutter. It can be suspected, that the probability density functions for the reflectivity of sea clutter is as well dependent on the radar wavelength as on resolution, as different scattering processes may significantly contribute. While most of the available millimeterwave data have been collected with a resolution of 75 cm, improvements of the MEMPHIS radar now allow a resolution of about 20 cm. The paper describes the measurement set-up, the evaluation methods and discusses the influence of resolution and radar frequency on sea clutter characteristics as found during the experiments.

  14. Pathological effects of cyanobacteria on sea fans in southeast Florida.

    PubMed

    Kiryu, Y; Landsberg, J H; Peters, E C; Tichenor, E; Burleson, C; Perry, N

    2015-07-01

    In early August 2008, observations by divers indicated that sea fans, particularly Gorgonia ventalina, Gorgonia flabellum, and Iciligorgia schrammi, were being covered by benthic filamentous cyanobacteria. From August 2008 through January 2009 and again in April 2009, tissue samples from a targeted G. ventalina colony affected by cyanobacteria and from a nearby, apparently healthy (without cyanobacteria) control colony, were collected monthly for histopathological examination. The primary cellular response of the sea fan to overgrowth by cyanobacteria was an increase in the number of acidophilic amoebocytes (with their granular contents dispersed) that were scattered throughout the coenenchyme tissue. Necrosis of scleroblasts and zooxanthellae and infiltration of degranulated amoebocytes were observed in the sea fan surface tissues at sites overgrown with cyanobacteria. Fungal hyphae in the axial skeleton were qualitatively more prominent in cyanobacteria-affected sea fans than in controls.

  15. Toward RADSCAT measurements over the sea and their interpretation

    NASA Technical Reports Server (NTRS)

    Claassen, J. P.; Fung, A. K.; Wu, S. T.; Chan, H. L.

    1973-01-01

    Investigations into several areas which are essential to the execution and interpretation of suborbital observations by composite radiometer - scatterometer sensor (RADSCAT) are reported. Experiments and theory were developed to demonstrate the remote anemometric capability of the sensor over the sea through various weather conditions. It is shown that weather situations found in extra tropical cyclones are useful for demonstrating the all weather capability of the composite sensor. The large scale fluctuations of the wind over the sea dictate the observational coverage required to correlate measurements with the mean surface wind speed. Various theoretical investigations were performed to establish a premise for the joint interpretation of the experiment data. The effects of clouds and rains on downward radiometric observations over the sea were computed. A method of predicting atmospheric attenuation from joint observations is developed. In other theoretical efforts, the emission and scattering characteristics of the sea were derived. Composite surface theories with coherent and noncoherent assumptions were employed.

  16. Sea Quark Contribution to the Nucleon Spin

    NASA Astrophysics Data System (ADS)

    Benmokhtar, Fatiha

    2015-10-01

    The widespread belief is that proton and neutron, commonly known as nucleons, are each composed of three elementary particles called quarks. But in the last two decades experiments showed that the mass, momentum, spin and electromagnetic properties of the three quarks do not add up to the known proprieties of the nucleon. Theory predicts that a ``sea'' of virtual pairs of quarks and anti-quarks, along with the strong force carrier particles called gluons, should account for the difference. I will present ongoing work on the preparation of an experiment to isolate the contributions of the sea to the nucleon spin using semi-inclusive deep inelastic scattering technique at the Thomas Jefferson National Accelerator Facility.

  17. Potential for airborne offbeam lidar measurements of snow and sea ice thickness

    NASA Astrophysics Data System (ADS)

    VáRnai, TamáS.; Cahalan, Robert F.

    2007-12-01

    This article discusses the capabilities and limitations of a new approach to airborne measurements of snow and sea ice thickness. Such measurements can help better understand snow and sea ice processes and can also contribute to the validation of satellite measurements. The approach discussed here determines physical snow and sea ice thickness by observing the horizontal spread of lidar pulses: The bright halo observed around an illuminated spot extends farther out in thicker layers because photons can travel longer without escaping through the bottom. Since earlier studies suggested the possibility of such sea ice retrievals, this article presents a theoretical analysis of additional uncertainties that arise in airborne observations of snow and sea ice. Snow and sea ice retrievals pose somewhat different challenges because while sea ice is usually much thicker, snow contains a much higher concentration of scatterers. As a result, sea ice halos are larger, but snow halos are brighter. The results indicate that airborne sea ice retrievals are possible at night and that snow retrievals are possible during both night and day. For snow thicknesses less than about 50 cm, observational issues, such as calibration uncertainty, can cause retrieval uncertainties on the order of 10% in 1-km-resolution retrievals. For moderate snow and sea ice thicknesses (<30 cm and 3 m, respectively), these issues cause similar (˜10%) uncertainties in sea ice thickness retrievals as well. These results indicate that offbeam lidars have the potential to become an important component of future snow and sea ice observing systems.

  18. Quantum theory of Thomson scattering

    NASA Astrophysics Data System (ADS)

    Crowley, B. J. B.; Gregori, G.

    2014-12-01

    The general theory of the scattering of electromagnetic radiation in atomic plasmas and metals, in the non-relativistic regime, in which account is taken of the Kramers-Heisenberg polarization terms in the Hamiltonian, is described from a quantum mechanical viewpoint. As well as deriving the general formula for the double differential Thomson scattering cross section in an isotropic finite temperature multi-component system, this work also considers closely related phenomena such as absorption, refraction, Raman scattering, resonant (Rayleigh) scattering and Bragg scattering, and derives many essential relationships between these quantities. In particular, the work introduces the concept of scattering strength and the strength-density field which replaces the normal particle density field in the standard treatment of scattering by a collection of similar particles and it is the decomposition of the strength-density correlation function into more familiar-looking components that leads to the final result. Comparisons are made with previous work, in particular that of Chihara [1].

  19. Mitochondrial control region variability in Mytilus galloprovincialis populations from the central-Eastern Mediterranean Sea.

    PubMed

    Giantsis, Ioannis A; Abatzopoulos, Theodore J; Angelidis, Panagiotis; Apostolidis, Apostolos P

    2014-06-30

    The variable domain 1 (VD1) domain of the control region and a small segment of the rrnaL gene of the F mtDNA type were sequenced and analyzed in 174 specimens of Mytilus galloprovincialis. Samples were collected from eight locations in four Central-Eastern (CE) Mediterranean countries (Italy, Croatia, Greece and Turkey). A new primer, specific for the F mtDNA type, was designed for the sequencing procedure. In total 40 different haplotypes were recorded, 24 of which were unique. Aside from the two populations situated in Thermaikos gulf (Northern Aegean, Greece), relatively high levels of haplotype and nucleotide diversity were estimated for both Central and Eastern Mediterranean populations. Eight out of the 40 haplotypes were shared by at least three populations while two of them were found in all populations. ΦST and cluster analysis revealed lack of structuring among CE Mediterranean populations with the exception of those located at the Sea of Marmara and Croatian coast which were highly differentiated. Apart from the species' inherit dispersal ability, anthropogenic activities, such as the repeated translocations of mussel spat, seem to have played an important role in shaping the current genetic population structure of CE M. galloprovincialis mussels.

  20. Decadal variability of the Turner Angle in the Mediterranean Sea and its implications for double diffusion

    NASA Astrophysics Data System (ADS)

    Meccia, Virna L.; Simoncelli, Simona; Sparnocchia, Stefania

    2016-08-01

    The physical reanalysis component of the Mediterranean Forecasting System is used to construct a high-resolution three-dimensional atlas of the Turner Angle. An assessment of the model quality shows a maximum degree of agreement with observations in the water column between 150 and 1000 m depth. The mean state of the favourable conditions for double diffusion processes is evaluated and the recent decadal variability is studied in terms of changes in the water mass properties. The results show that approximately 50% of the Mediterranean Sea is favourable to double diffusion processes, from which around 47% is associated with salt fingering. The Tyrrhenian, Ionian and southwestern Mediterranean are the most vulnerable basins to salt fingering, and the strongest processes can occur in the Tyrrhenian deep waters. Diffusive convection is most likely to occur in the Ionian, Aegean and eastern Mediterranean at vertical levels deeper than 1000 m. The observed gradual warming and salinification of the Mediterranean after 1997 decreased and increased the possibilities of the occurrence of salt fingers and double diffusive convections, respectively. The climatological atlas that is presented in this paper provides a three-dimensional picture of the regions that are either doubly stable or favourable to double diffusion instability and allows for the characterization of the diffusive properties of the water masses.

  1. Mitochondrial Control Region Variability in Mytilus galloprovincialis Populations from the Central-Eastern Mediterranean Sea

    PubMed Central

    Giantsis, Ioannis A.; Abatzopoulos, Theodore J.; Angelidis, Panagiotis; Apostolidis, Apostolos P.

    2014-01-01

    The variable domain 1 (VD1) domain of the control region and a small segment of the rrnaL gene of the F mtDNA type were sequenced and analyzed in 174 specimens of Mytilus galloprovincialis. Samples were collected from eight locations in four Central-Eastern (CE) Mediterranean countries (Italy, Croatia, Greece and Turkey). A new primer, specific for the F mtDNA type, was designed for the sequencing procedure. In total 40 different haplotypes were recorded, 24 of which were unique. Aside from the two populations situated in Thermaikos gulf (Northern Aegean, Greece), relatively high levels of haplotype and nucleotide diversity were estimated for both Central and Eastern Mediterranean populations. Eight out of the 40 haplotypes were shared by at least three populations while two of them were found in all populations. ΦST and cluster analysis revealed lack of structuring among CE Mediterranean populations with the exception of those located at the Sea of Marmara and Croatian coast which were highly differentiated. Apart from the species’ inherit dispersal ability, anthropogenic activities, such as the repeated translocations of mussel spat, seem to have played an important role in shaping the current genetic population structure of CE M. galloprovincialis mussels. PMID:24983478

  2. A Model with Ellipsoidal Scatterers for Polarimetric Remote Sensing of Anisotropic Layered Media

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Kong, J. A.; Shin, R. T.

    1993-01-01

    This paper presents a model with ellipsoidal scatterers for applications to polarimetric remote sensing of anisotropic layered media at microwave frequencies. The physical configuration includes an isotropic layer covering an anisotropic layer above a homogeneous half space. The isotropic layer consists of randomly oriented spheroids. The anisotropic layer contains ellipsoidal scatterers with a preferential vertical alignment and random azimuthal orientations. Effective permittivities of the scattering media are calculated with the strong fluctuation theory extended to account for the nonspherical shapes and the scatterer orientation distributions. On the basis of the analytic wave theory, dyadic Green's functions for layered media are used to derive polarimetric backscattering coefficients under the distorted Born approximation. The ellipsoidal shape of the scatterers gives rise to nonzero cross-polarized returns from the untilted anisotropic medium in the first-order approximation. Effects of rough interfaces are estimated by an incoherent addition method. Theoretical results and experimental data are matched at 9 GHz for thick first-year sea ice with a bare surface and with a snow cover at Point Barrow, Alaska. The model is then used to study the sensitivity of polarimetric backscattering coefficients with respect to correlation lengths representing the geometry of brine inclusions. Polarimetric signatures of bare and snow-covered sea ice are also simulated based on the model to investigate effects of different scattering mechanisms.

  3. Quantitative Scattering of Melanin Solutions

    NASA Astrophysics Data System (ADS)

    Riesz, J.; Gilmore, J.; Meredith, P.

    2006-06-01

    The optical scattering coefficient of a dilute, well solubilised eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute less than 6% of the total optical attenuation between 210 and 325nm. At longer wavelengths (325nm to 800nm) the scattering was less than the minimum sensitivity of our instrument. This indicates that UV and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient vs wavelength was found to be consistent with Rayleigh Theory for a particle radius of 38+-1nm.

  4. Interstellar scattering and resolution limitations

    NASA Astrophysics Data System (ADS)

    Dennison, Brian

    Density irregularities in both the interplanetary medium and the ionized component of the interstellar medium scatter radio waves, resulting in limitations on the achievable resolution. Interplanetary scattering (IPS) is weak for most observational situations, and in principle the resulting phase corruption can be corrected for when observing with sufficiently many array elements. Interstellar scattering (ISS), on the other hand, is usually strong at frequencies below about 8 GHz, in which case intrinsic structure information over a range of angular scales is irretrievably lost. With the earth-space baselines now planned, it will be possible to search directly for interstellar refraction, which is suspected of modulating the fluxes of background sources.

  5. Synthetic Fourier transform light scattering.

    PubMed

    Lee, Kyeoreh; Kim, Hyeon-Don; Kim, Kyoohyun; Kim, Youngchan; Hillman, Timothy R; Min, Bumki; Park, Yongkeun

    2013-09-23

    We present synthetic Fourier transform light scattering, a method for measuring extended angle-resolved light scattering (ARLS) from individual microscopic samples. By measuring the light fields scattered from the sample plane and numerically synthesizing them in Fourier space, the angle range of the ARLS patterns is extended up to twice the numerical aperture of the imaging system with unprecedented sensitivity and precision. Extended ARLS patterns of individual microscopic polystyrene beads, healthy human red blood cells (RBCs), and Plasmodium falciparum-parasitized RBCs are presented.

  6. Timelike Compton Scattering at Jlab

    SciTech Connect

    Paremuzyan, Rafayel G.

    2014-01-01

    It is demonstrated, that with exclusive final state, data from electron scattering experiments that are recorded with loose trigger requirements can be used to analyze photoproduction reactions. A preliminary results on Timelike Compton Scattering using the electroproduction data from the CLAS detector at Jefferson Lab are presented. In particular, using final state (pe{sup -}e{sup +}) photoproduction of vector mesons and timelike photon is studied. Angular asymmetries in Timelike Compton Scattering region is compared with model predictions in the framework of Generalized Parton Distribution.

  7. Superconductivity, antiferromagnetism, and neutron scattering

    NASA Astrophysics Data System (ADS)

    Tranquada, John M.; Xu, Guangyong; Zaliznyak, Igor A.

    2014-01-01

    High-temperature superconductivity in both the copper-oxide and the iron-pnictide/chalcogenide systems occurs in close proximity to antiferromagnetically ordered states. Neutron scattering has been an essential technique for characterizing the spin correlations in the antiferromagnetic phases and for demonstrating how the spin fluctuations persist in the superconductors. While the nature of the spin correlations in the superconductors remains controversial, the neutron scattering measurements of magnetic excitations over broad ranges of energy and momentum transfers provide important constraints on the theoretical options. We present an overview of the neutron scattering work on high-temperature superconductors and discuss some of the outstanding issues.

  8. Driving trajectories in chaotic scattering.

    PubMed

    Macau, Elbert E N; Caldas, Iberê L

    2002-02-01

    In this work we introduce a general approach for targeting in chaotic scattering that can be used to find a transfer trajectory between any two points located inside the scattering region. We show that this method can be used in association with a control of chaos strategy to drive around and keep a particle inside the scattering region. As an illustration of how powerful this approach is, we use it in a case of practical interest in celestial mechanics in which it is desired to control the evolution of two satellites that evolve around a large central body.

  9. East Siberian Sea, Russia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The winter sea ice in the east Siberian Sea is looking a bit like a cracked windshield in these true-color Moderate Resolution Imaging Spectroradiometer (MODIS) images from June 16 and 23, 2002. North of the thawing tundra, the sea ice takes on its cracked, bright blue appearance as it thins, which allows the reflection of the water to show through. Numerous still-frozen lakes dot the tundra. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  10. Wave propagation, scattering and emission in complex media

    NASA Astrophysics Data System (ADS)

    Jin, Ya-Qiu

    I. Polarimetric scattering and SAR imagery. EM wave propagation and scattering in polarimetric SAR interferometry / S. R. Cloude. Terrain topographic inversion from single-pass polarimetric SAR image data by using polarimetric stokes parameters and morphological algorithm / Y. Q. Jin, L. Luo. Road detection in forested area using polarimetric SAR / G. W. Dong ... [et al.]. Research on some problems about SAR radiometric resolution / G. Dong ... [et al.]. A fast image matching algorithm for remote sensing applications / Z. Q. Hou ... [et al.]. A new algorithm of noised remote sensing image fusion based on steerable filters / X. Kang ... [et al.]. Adaptive noise reduction of InSAR data based on anisotropic diffusion models and their applications to phase unwrapping / C. Wang, X. Gao, H. Zhang -- II. Scattering from randomly rough surfaces. Modeling tools for backscattering from rough surfaces / A. K. Fung, K. S. Chen. Pseudo-nondiffracting beams from rough surface scattering / E. R. Méndez, T. A. Leskova, A. A. Maradudin. Surface roughness clutter effects in GPR modeling and detection / C. Rappaport. Scattering from rough surfaces with small slopes / M. Saillard, G. Soriano. Polarization and spectral characteristics of radar signals reflected by sea-surface / V. A. Butko, V. A. Khlusov, L. I. Sharygina. Simulation of microwave scattering from wind-driven ocean surfaces / M. Y. Xia ... [et al.]. HF surface wave radar tests at the Eastern China Sea / X. B. Wu ... [et al.] -- III. Electromagnetics of complex materials. Wave propagation in plane-parallel metamaterial and constitutive relations / A. Ishimaru ... [et al.]. Two dimensional periodic approach for the study of left-handed metamaterials / T. M. Grzegorczyk ... [et al.]. Numerical analysis of the effective constitutive parameters of a random medium containing small chiral spheres / Y. Nanbu, T. Matsuoka, M. Tateiba. Wave propagation in inhomogeneous media: from the Helmholtz to the Ginzburg -Landau equation / M

  11. Nonline-of-sight laser gated viewing of scattered photons

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Velten, Andreas

    2014-02-01

    Laser gated viewing is a prominent sensing technology for optical imaging in harsh environments and can be applied for vision through fog, smoke, and other degraded environmental conditions as well as for the vision through sea water in submarine operation. A direct imaging of nonscattered photons (or ballistic photons) is limited in range and performance by the free optical path length, i.e., the length in which a photon can propagate without interaction with scattering particles or object surfaces. The imaging and analysis of scattered photons can overcome these classical limitations and it is possible to realize a nonline-of-sight imaging. The spatial and temporal distributions of scattered photons can be analyzed by means of computational optics and their information of the scenario can be restored. In particular, the information outside the line of sight or outside the visibility range is of high interest. We demonstrate nonline-of-sight imaging with a laser gated viewing system and different illumination concepts (point and surface scattering sources).

  12. The K+ K+ scattering length from Lattice QCD

    SciTech Connect

    Silas Beane; Thomas Luu; Konstantinos Orginos; Assumpta Parreno; Martin Savage; Aaron Torok; Andre Walker-Loud

    2007-09-11

    The K+K+ scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the MILC asqtad-improved gauge configurations with fourth-rooted staggered sea quarks. Three-flavor mixed-action chiral perturbation theory at next-to-leading order, which includes the leading effects of the finite lattice spacing, is used to extrapolate the results of the lattice calculation to the physical value of mK + /fK + . We find mK^+ aK^+ K^+ = â~0.352 ± 0.016, where the statistical and systematic errors have been combined in quadrature.

  13. Microwave scattering from laser spark in air

    SciTech Connect

    Sawyer, Jordan; Zhang Zhili; Shneider, Mikhail N.

    2012-09-15

    In this paper, microwave Mie scattering from a laser-induced plasma in atmospheric air is computed. It shows that the scattered microwave transitions from coherent Rayleigh scattering to Mie scattering based on the relative transparency of the laser-induced plasma at the microwave frequency. The microwave penetration in the plasma alters from total transparency to partial shielding due to the sharp increase of the electron number density within the avalanche ionization phase. The transition from Rayleigh scattering to Mie scattering is verified by both the temporal evolution of the scattered microwave and the homogeneity of polar scattering plots.

  14. Airborne sound propagation over sea during offshore wind farm piling.

    PubMed

    Van Renterghem, T; Botteldooren, D; Dekoninck, L

    2014-02-01

    Offshore piling for wind farm construction has attracted a lot of attention in recent years due to the extremely high noise emission levels associated with such operations. While underwater noise levels were shown to be harmful for the marine biology, the propagation of airborne piling noise over sea has not been studied in detail before. In this study, detailed numerical calculations have been performed with the Green's Function Parabolic Equation (GFPE) method to estimate noise levels up to a distance of 10 km. Measured noise emission levels during piling of pinpiles for a jacket-foundation wind turbine were assessed and used together with combinations of the sea surface state and idealized vertical sound speed profiles (downwind sound propagation). Effective impedances were found and used to represent non-flat sea surfaces at low-wind sea states 2, 3, and 4. Calculations show that scattering by a rough sea surface, which decreases sound pressure levels, exceeds refractive effects, which increase sound pressure levels under downwind conditions. This suggests that the presence of wind, even when blowing downwind to potential receivers, is beneficial to increase the attenuation of piling sound over the sea. A fully flat sea surface therefore represents a worst-case scenario.

  15. Pelagic sea snakes dehydrate at sea

    PubMed Central

    Lillywhite, Harvey B.; Sheehy, Coleman M.; Brischoux, François; Grech, Alana

    2014-01-01

    Secondarily marine vertebrates are thought to live independently of fresh water. Here, we demonstrate a paradigm shift for the widely distributed pelagic sea snake, Hydrophis (Pelamis) platurus, which dehydrates at sea and spends a significant part of its life in a dehydrated state corresponding to seasonal drought. Snakes that are captured following prolonged periods without rainfall have lower body water content, lower body condition and increased tendencies to drink fresh water than do snakes that are captured following seasonal periods of high rainfall. These animals do not drink seawater and must rehydrate by drinking from a freshwater lens that forms on the ocean surface during heavy precipitation. The new data based on field studies indicate unequivocally that this marine vertebrate dehydrates at sea where individuals may live in a dehydrated state for possibly six to seven months at a time. This information provides new insights for understanding water requirements of sea snakes, reasons for recent declines and extinctions of sea snakes and more accurate prediction for how changing patterns of precipitation might affect these and other secondarily marine vertebrates living in tropical oceans. PMID:24648228

  16. Pelagic sea snakes dehydrate at sea.

    PubMed

    Lillywhite, Harvey B; Sheehy, Coleman M; Brischoux, François; Grech, Alana

    2014-05-07

    Secondarily marine vertebrates are thought to live independently of fresh water. Here, we demonstrate a paradigm shift for the widely distributed pelagic sea snake, Hydrophis (Pelamis) platurus, which dehydrates at sea and spends a significant part of its life in a dehydrated state corresponding to seasonal drought. Snakes that are captured following prolonged periods without rainfall have lower body water content, lower body condition and increased tendencies to drink fresh water than do snakes that are captured following seasonal periods of high rainfall. These animals do not drink seawater and must rehydrate by drinking from a freshwater lens that forms on the ocean surface during heavy precipitation. The new data based on field studies indicate unequivocally that this marine vertebrate dehydrates at sea where individuals may live in a dehydrated state for possibly six to seven months at a time. This information provides new insights for understanding water requirements of sea snakes, reasons for recent declines and extinctions of sea snakes and more accurate prediction for how changing patterns of precipitation might affect these and other secondarily marine vertebrates living in tropical oceans.

  17. Integration rules for scattering equations

    NASA Astrophysics Data System (ADS)

    Baadsgaard, Christian; Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.

    2015-09-01

    As described by Cachazo, He and Yuan, scattering amplitudes in many quantum field theories can be represented as integrals that are fully localized on solutions to the so-called scattering equations. Because the number of solutions to the scattering equations grows quite rapidly, the contour of integration involves contributions from many isolated components. In this paper, we provide a simple, combinatorial rule that immediately provides the result of integration against the scattering equation constraints fo any Möbius-invariant integrand involving only simple poles. These rules have a simple diagrammatic interpretation that makes the evaluation of any such integrand immediate. Finally, we explain how these rules are related to the computation of amplitudes in the field theory limit of string theory.

  18. NEW APPROACHES: Deep inelastic scattering

    NASA Astrophysics Data System (ADS)

    Allday, J.

    1998-01-01

    Feynman diagrams can be used to explain deep inelastic scattering, but it must be remembered that the emission and absorption of a photon are not independent events - the underlying field is important.

  19. Scattering theory with path integrals

    SciTech Connect

    Rosenfelder, R.

    2014-03-15

    Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

  20. Double Compton scatter telescope calibration

    NASA Technical Reports Server (NTRS)

    Dayton, B.; Simone, J.; Green, M.; Long, J.; Zanrosso, E.; Zych, A. D.; White, R. S.

    1981-01-01

    Calibration techniques for a medium energy gamma ray telescope are described. Gain calibration using Compton edge spectra involves comparisons of pulse height spectra with spectra simulated by a Monte Carlo computer code which includes Compton scattering and pair production, plural scattering and variable energy resolution, and cell size. The telescope considered comprises 56 cells of liquid scintillator in four size groups, with a total liquid volume of 325 l; each cell has its own photomultiplier tube. Energy and angular resolutions and the PMT gain calibration procedure are verified with double scatter data for monoenergetic gamma rays at a known location. Detection probabilities for any cell combination in the two telescope arrays are calculated per steradian as a function of the scattering for a number of different energies with a Van de Graaff accelerator.

  1. Structured light, transmission, and scattering

    NASA Astrophysics Data System (ADS)

    Andrews, David L.

    2011-03-01

    Numerous theoretical and experimental studies have established the principle that beams conveying orbital angular momentum offer a rich scope for information transfer. However, it is not clear how far it is practicable to operate such a concept at the single-photon level - especially when such a beam propagates through a system in which scattering can occur. In cases where scattering leads to photon deflection, it produces losses; however in terms of the retention of information content, there should be more concern over forward scattering. Based on a quantum electrodynamical formulation of theory, this paper aims to frame and resolve the key issues. A quantum amplitude is constructed for the representation of single and multiple scattering events in the propagation an individual photon, from a suitably structured beam. The analysis identifies potential limitations of principle, undermining complete fidelity of quantum information transmission.

  2. Combined effect of vacuum-packaging and oregano essential oil on the shelf-life of Mediterranean octopus (Octopus vulgaris) from the Aegean Sea stored at 4 degrees C.

    PubMed

    Atrea, I; Papavergou, A; Amvrosiadis, I; Savvaidis, I N

    2009-04-01

    The present study evaluated the use of vacuum packaging (alone) or with addition of oregano essential oil (EO), as an antimicrobial treatment for shelf-life extension of fresh Mediterranean octopus stored under refrigeration for a period of 23 days. Four different treatments were tested: A, control sample; under aerobic storage in the absence of oregano essential oil; VP, under vacuum packaging in the absence of oregano essential oil; and VO1, VO2, treated samples with oregano essential oil 0.2 and 0.4% (v/w), respectively, under VP. Of all the microorganisms enumerated, Pseudomonas spp., H2S-producing bacteria and lactic acid bacteria (LAB) were the groups that prevailed in octopus samples, irrespective of antimicrobial treatment. With regard to the chemical freshness indices determined, thiobarbituric acid (TBA) values were low in all octopus samples, as could have been expected from the low fat content of the product. Both trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values of oregano treated under VP octopus samples were significantly lower compared to control samples during the entire refrigerated storage period. Based primarily on sensory evaluation (odor), the use of VP, VO1 and VO2 extended the shelf-life of fresh Mediterranean octopus by ca. 3, 11 and 20 days, respectively.

  3. SeaQuaKE: Sea-optimized Quantum Key Exchange

    DTIC Science & Technology

    2014-11-01

    SeaQuaKE: Sea-optimized Quantum Key Exchange Technical Progress Report No. 3 Prepared for: Office...From - To) September 2014  November 2014 4. TITLE AND SUBTITLE SeaQuaKE: Sea-optimized Quantum Key Exchange Technical Progress Report No. 1...ONRBAA13-001 14. ABSTRACT This is the 3rd quarterly Technical Progress Report summarizing progress on the Sea-optimized Quantum Key Exchange (SeaQuaKE

  4. Bay of Bengal Surface and Thermocline and the Arabian Sea

    DTIC Science & Technology

    2014-09-30

    to the atmosphere. How low the SSS gets in the Bay of Bengal or how high in the Arabian Sea, depends on the oceanic exchanges between them via a...potential impact on the SST. 3 Figure 1a: Sea surface temperature (SST) and salinity ( SSS ) relationship during ASIRI 2013 cruises. The left panel...shows the hull ADCP vector, color-coded for SSS . The SST/ SSS scatter falls along a line from the warm/salty southern regions to the cool/fresher

  5. Optical Waveguide Scattering Reduction. II.

    DTIC Science & Technology

    1980-12-01

    FAD-AOAR 815 BATTELLEWCOLUMBUS LABS ON F/S 20/6 OPTICAL WAVEGUIDE SCATTER ING REDUC TION. II.(U) 7 DEC 80 0 W VAHEY, N F HARTMAN, R C SHERMAN F3361... OPTICAL WAVEGUIDE SCATTERING REDUCTION II M BATTELLE COLUMBUS LABORATORIES 505 KING AVENUE COLUMBUS, OHIO 43201 DTIC ELECTEf MAY 12 198111 December...reviewed and is approved for publication. DOUGLAS AWIWILLE, Project Engineer KENNETH R. HUTCHINSON, Chief Electro- Optics Techniques and Electro- Optics

  6. C-Band Backscatter Measurements of Winter Sea-Ice in the Weddell Sea, Antarctica

    NASA Technical Reports Server (NTRS)

    Drinkwater, M. R.; Hosseinmostafa, R.; Gogineni, P.

    1995-01-01

    During the 1992 Winter Weddell Gyre Study, a C-band scatterometer was used from the German ice-breaker R/V Polarstern to obtain detailed shipborne measurement scans of Antarctic sea-ice. The frequency-modulated continuous-wave (FM-CW) radar operated at 4-3 GHz and acquired like- (VV) and cross polarization (HV) data at a variety of incidence angles (10-75 deg). Calibrated backscatter data were recorded for several ice types as the icebreaker crossed the Weddell Sea and detailed measurements were made of corresponding snow and sea-ice characteristics at each measurement site, together with meteorological information, radiation budget and oceanographic data. The primary scattering contributions under cold winter conditions arise from the air/snow and snow/ice interfaces. Observations indicate so e similarities with Arctic sea-ice scattering signatures, although the main difference is generally lower mean backscattering coefficients in the Weddell Sea. This is due to the younger mean ice age and thickness, and correspondingly higher mean salinities. In particular, smooth white ice found in 1992 in divergent areas within the Weddell Gyre ice pack was generally extremely smooth and undeformed. Comparisons of field scatterometer data with calibrated 20-26 deg incidence ERS-1 radar image data show close correspondence, and indicate that rough Antarctic first-year and older second-year ice forms do not produce as distinctively different scattering signatures as observed in the Arctic. Thick deformed first-year and second-year ice on the other hand are clearly discriminated from younger undeformed ice. thereby allowing successful separation of thick and thin ice. Time-series data also indicate that C-band is sensitive to changes in snow and ice conditions resulting from atmospheric and oceanographic forcing and the local heat flux environment. Variations of several dB in 45 deg incidence backscatter occur in response to a combination of thermally-regulated parameters

  7. Analytical optical scattering in clouds

    NASA Technical Reports Server (NTRS)

    Phanord, Dieudonne D.

    1989-01-01

    An analytical optical model for scattering of light due to lightning by clouds of different geometry is being developed. The self-consistent approach and the equivalent medium concept of Twersky was used to treat the case corresponding to outside illumination. Thus, the resulting multiple scattering problem is transformed with the knowledge of the bulk parameters, into scattering by a single obstacle in isolation. Based on the size parameter of a typical water droplet as compared to the incident wave length, the problem for the single scatterer equivalent to the distribution of cloud particles can be solved either by Mie or Rayleigh scattering theory. The super computing code of Wiscombe can be used immediately to produce results that can be compared to the Monte Carlo computer simulation for outside incidence. A fairly reasonable inverse approach using the solution of the outside illumination case was proposed to model analytically the situation for point sources located inside the thick optical cloud. Its mathematical details are still being investigated. When finished, it will provide scientists an enhanced capability to study more realistic clouds. For testing purposes, the direct approach to the inside illumination of clouds by lightning is under consideration. Presently, an analytical solution for the cubic cloud will soon be obtained. For cylindrical or spherical clouds, preliminary results are needed for scattering by bounded obstacles above or below a penetrable surface interface.

  8. An analysis of scatter decomposition

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Saltz, Joel H.

    1990-01-01

    A formal analysis of a powerful mapping technique known as scatter decomposition is presented. Scatter decomposition divides an irregular computational domain into a large number of equal sized pieces, and distributes them modularly among processors. A probabilistic model of workload in one dimension is used to formally explain why, and when scatter decomposition works. The first result is that if correlation in workload is a convex function of distance, then scattering a more finely decomposed domain yields a lower average processor workload variance. The second result shows that if the workload process is stationary Gaussian and the correlation function decreases linearly in distance until becoming zero and then remains zero, scattering a more finely decomposed domain yields a lower expected maximum processor workload. Finally it is shown that if the correlation function decreases linearly across the entire domain, then among all mappings that assign an equal number of domain pieces to each processor, scatter decomposition minimizes the average processor workload variance. The dependence of these results on the assumption of decreasing correlation is illustrated with situations where a coarser granularity actually achieves better load balance.

  9. The 2015, Mw 6.5, Leucas (Ionian Sea, Greece) earthquake: Seismological and Geodetic Modelling

    NASA Astrophysics Data System (ADS)

    Saltogianni, Vasso; Taymaz, Tuncay; Yolsal-Çevikbilen, Seda; Eken, Tuna; Moschas, Fanis; Stiros, Stathis

    2016-04-01

    A cluster of earthquakes (6Aegean Arc in the Ionian Sea, the most seismically active region in Greece, in the last 30 years. The most recent earthquake was the 2015 (Mw 6.5) Leucas (Lefkada) earthquake. The modelling of these earthquakes, some of which are double events (2003 Leucas; 2014 Cephalonia) is a challenge for two main reasons. First, the geography of the area limits the distribution of the available seismological and GNSS stations and the correlations of INSAR data. Second, the structural pattern of the area indicates distributed thrusting but recent earthquakes are confined to the west margin of the Aegean Arc, usually assigned to the Cephalonia Transform Fault (CTF), and are dominated by strike slip faulting. In order to contribute to the understanding active tectonics along this critical region, our study was based on the independent analysis of the seismological and geodetic signature of the 2015 earthquake and the on the joint evaluation of the inferred models on the basis of the fault pattern of the area and of previous earthquakes. First, based on teleseismic long-period P- and SH- and broad-band P-waveforms a point-source solution at the SW part of Leucas yielded dominantly right-lateral strike-slip faulting mechanisms (strike: 23o, dip: 68o, rake: -170o) with a shallow focal depth (h: 9 km) and with seismic moment of Mo: 10.4x1018 Nm. Furthermore, the rupture history of the earthquake was obtained by applying a new back-projection method that uses teleseismic P-waveforms to integrate the direct P-phase with reflected phases from structural discontinuities near the source. In the slip inversion the faulting occurs on a single fault plane (strike and dip are obtained from the best fitting point-source solution) and slip (rake) angle varied during the whole rupture process. Second, co-seismic displacements were derived from eight permanent and one campaign GPS

  10. Surviving the Messinian Salinity Crisis? Divergence patterns in the genus Dendropoma (Gastropoda: Vermetidae) in the Mediterranean Sea.

    PubMed

    Calvo, Marta; Alda, Fernando; Oliverio, Marco; Templado, José; Machordom, Annie

    2015-10-01

    Four genetically distinct clades were recently described under the name Dendropoma petraeum, a Mediterranean endemic vermetid gastropod. The aim of this work is to date the processes that drove to the diversification within this taxon and to relate them to the corresponding historical events occurred in the Mediterranean Sea. Sequences from mitochondrial and nuclear markers were obtained from specimens collected in 29 localities spanning over 4000km across the entire distribution range of D. petraeum species complex. The phylogenetic and coalescent-based analyses confirmed the four well-supported and largely differentiated lineages of D. petraeum, clearly delimited geographically along a west-east axis within the Mediterranean Sea: Western, Tyrrhenian-Sicilian, Ionian-Aegean and Levantine lineages. Divergence time estimates, obtained using a range of known substitution rates for other marine gastropods, indicated two main stages of diversification. In the first period (between 9.5 and 4.5mya), the ancestral D. petraeum diverged into the current four lineages. The most recent period occurred between 3.72 and 0.66mya in the late Pliocene-early Pleistocene, and included the main within-lineage diversification events. Therefore, if the divergence time between the major lineages of Dendropoma in the Mediterranean actually predated or coincided with the Messinian Salinity Crisis, then they should have survived to this dramatic period within the Mediterranean, as supported by Bayes Factors model comparison. Conversely, if the divergence started after the crisis, congruent with the idea that no true marine organism survived the Messinian Salinity Crisis, then our results indicate substitution rates of Dendropoma much higher than usual (5.16% per million years for COI, 3.04% for 16S). More recent climate changes seem to have conditioned the demographic history of each lineage differently. While Western and Tyrrhenian-Sicilian lineages both underwent an increase in their

  11. White Sea - Russia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    At bottom center of this true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from April 13, 2001, the White Sea in western Russia is becoming free of ice in its southern extent. Meanwhile, the blue-green waters along the coast of the peninsula jutting out into the Barents Sea to the northeast could be due to a phytoplankton bloom.

  12. Sea Anemone: Investigations.

    ERIC Educational Resources Information Center

    Hunt, John D.

    1982-01-01

    Several investigations can be undertaken with live sea anemones. A sea anemone's feeding response, fighting power, color, and symbiotic relationships to other invertebrates (such as a marine hermit crab) can be investigated in the high school classroom. Background information and laboratory procedures are provided. (Author/JN)

  13. Red sea drillings.

    PubMed

    Ross, D A; Whitmarsh, R B; Ali, S A; Boudreaux, J E; Coleman, R; Fleisher, R L; Girdler, R; Manheim, F; Matter, A; Nigrini, C; Stoffers, P; Supko, P R

    1973-01-26

    Recent drilling in the Red Sea has shown that much of the basin is underlain by evaporites of a similar age to that of evaporites found in the Mediterranean Sea. These evaporites and their structural positions indicate that other brine areas are present-and, indeed, several others have been discovered.

  14. Getting Your Sea Legs

    PubMed Central

    Stoffregen, Thomas A.; Chen, Fu-Chen; Varlet, Manuel; Alcantara, Cristina; Bardy, Benoît G.

    2013-01-01

    Sea travel mandates changes in the control of the body. The process by which we adapt bodily control to life at sea is known as getting one's sea legs. We conducted the first experimental study of bodily control as maritime novices adapted to motion of a ship at sea. We evaluated postural activity (stance width, stance angle, and the kinematics of body sway) before and during a sea voyage. In addition, we evaluated the role of the visible horizon in the control of body sway. Finally, we related data on postural activity to two subjective experiences that are associated with sea travel; seasickness, and mal de debarquement. Our results revealed rapid changes in postural activity among novices at sea. Before the beginning of the voyage, the temporal dynamics of body sway differed among participants as a function of their (subsequent) severity of seasickness. Body sway measured at sea differed among participants as a function of their (subsequent) experience of mal de debarquement. We discuss implications of these results for general theories of the perception and control of bodily orientation, for the etiology of motion sickness, and for general phenomena of perceptual-motor adaptation and learning. PMID:23840560

  15. Small-slope scattering from rough elastic ocean floors: general theory and computational algorithm.

    PubMed

    Gragg, R F; Wurmser, D; Gauss, R C

    2001-12-01

    In this article acoustic scattering by a random rough interface that separates a fluid incident medium from an underlying uniform scattering medium, either fluid or elastic solid, in cases for which the Bragg scale lies within the power-law tail of the roughness spectrum is dealt with. The physical foundation is an inherently reciprocity-preserving, local small-slope theory. A fully bistatic formulation is developed for the scattering strength, together with a robust numerical implementation that allows a wide range of spectral exponent values. The practical result for ocean acoustics is a significantly improved description of the interface component of sea floor scattering. Calculations are presented to demonstrate the advantage of this approach over perturbation theory, and to illustrate its dependence on frequency and environmental parameters as well as its operation in bistatic geometries.

  16. Black Sea in Bloom

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image shows bright, turquoise-colored swirls across the surface of the Black Sea, signifying the presence of a large phytoplankton bloom. Scientists have observed similar blooms recurring annually, roughly this same time of year. The Sea of Azov, which is the smaller body of water located just north of the Black Sea in this image, also shows a high level of biological activity currently ongoing. The brownish pixels in the Azov are probably sediments carried in from high waters upstream. This scene was acquired by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, on May 4, 2002. According to the Black Sea Environment Programme's Marine Hydrophysical Institute, the Black Sea is 'one of the marine areas of the world most damaged by human activities.' The coastal zone around these Eastern European inland water bodies is densely populated-supporting a permanent population of roughly 16 million people and another 4 million tourists each year. Six countries border with the Black Sea, including Ukraine to the north, Russia and Georgia to the east, Turkey to the south, and Bulgaria and Romania to the west. Because it is isolated from the world's oceans, and because there is an extensive drainage network of rivers that empty into it, the Black Sea has a unique and delicate water balance which is very important for supporting its marine ecosystem. Of particular concern to scientists is the salinity, water level, and nutrient levels of the Black Sea's waters, all of which are, unfortunately, being impacted by human activities. Within the last three decades the combination of increased nutrient loads from human sources together with pollution and over-harvesting of fisheries has resulted in a sharp decline in water quality. Scientists from each of the Black Sea's bordering nations are currently working together to study the issues and formulate a joint, international strategy for saving this unique marine ecosystem

  17. Sea Otter Enhydra lutris

    USGS Publications Warehouse

    Bodkin, James L.; Ballachey, Brenda E.

    1997-01-01

    The sea otter, Enhydra lutris, is the largest member of the Mustelidae family and is the only one which lives entirely in marine waters. Sea otters are unique among marine mammals because, unlike whales, dolphins and seals, they do not have a layer of fat or blubber to keep them warm in the cool oceans of the North Pacific. Instead, sea otters depend on dense fur that traps tiny air bubbles to insulate them from the cold water. To stay warm, they also must maintain a very high metabolic rate, requiring the sea otter to eat about 25% of its body weight per day. Sea otters eat mostly invertebrates - clams, crabs, urchins, and mussels - found in shallow coastal waters.

  18. Presenting the Rain-Sea Interaction Facility

    NASA Technical Reports Server (NTRS)

    Bliven, Larry F.; Elfouhaily, Tonas M.

    1993-01-01

    The new Rain-Sea Interaction Facility (RSIF) was established at GSFC/WFF and the first finds are presented. The unique feature of this laboratory is the ability to systematically study microwave scattering from a water surface roughened by artificial rain, for which the droplets are at terminal velocity. The fundamental instruments and systems (e.g., the rain simulator, scatterometers, and surface elevation probes) were installed and evaluated during these first experiments - so the majority of the data were obtained with the rain simulator at 1 m above the water tank. From these initial experiments, three new models were proposed: the square-root function for NCS vs. R, the log Gaussian model for ring-wave elevation frequency spectrum, and the Erland probability density distribution for back scattered power. Rain rate is the main input for these models, although the coefficients may be dependent upon other factors (drop-size distribution, fall velocity, radar configuration, etc.). The facility is functional and we foresee collaborative studies with investigators who are engaged in measuring and modeling rain-sea interaction processes.

  19. Investigation of electromagnetic backscattering from nearshore sea surfaces modulated by shoaling effect

    NASA Astrophysics Data System (ADS)

    Nie, D.; Zhang, M.; Li, J.

    2016-10-01

    The electromagnetic (EM) scattering features of radar scattered echoes from nearshore sea surfaces are investigated using the second-order small-slope approximation (SSA-II). The joint influences of wind fetch and water depth on the normalized radar cross section (NRCS) of and Doppler spectra for echoes from nearshore sea surfaces are mainly studied. The numerical results show that with a further increasing fetch, the excess of NRCS for small depth sea over that for deeper sea increases, and Doppler spectral features are also intensely influenced by nonlinear interactions between waves in the large wind fetch and small water depth marine environment. These both indicate that the effects of the finite depth are more prominent with increasing wind fetch, especially for HH polarization.

  20. Offshore seismicity in the western Marmara Sea, Turkey, revealed by ocean bottom observation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yojiro; Takahashi, Narumi; Citak, Seckin; Kalafat, Doǧan; Pinar, Ali; Gürbüz, Cemil; Kaneda, Yoshiyuki

    2015-04-01

    The North Anatolian Fault (NAF) extends 1600 km westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea, accommodating about 25 mm/yr of right-lateral motion between Anatolia and the Eurasian plate. Since 1939, devastating earthquakes with magnitude greater than seven ruptured NAF westward, starting from 1939 Erzincan (Ms=7.9) at the eastern Turkey and including the latest 1999 Izmit-Golcuk (Ms=7.7) and the Duzce (Ms=7.4) earthquakes in the Marmara region. Considering the fault segments ruptured by the May 24th, 2014 Northern Aegean earthquake (Mw=6.9), the only un-ruptured segments left behind the 1600 km long NAF locate beneath the Marmara Sea and those segments keep their mystery due to their underwater location. To consider the earthquake hazard and disaster mitigation, the detailed information about fault geometry and its stick-slip behavior beneath the western Marmara Sea is very important. Thus, we started to operate a series of ocean bottom seismographic (OBS) observations to estimate the fault geometry from microearthquake distribution. As a first step, we deployed 3 pop-up type OBSs on 20th of March 2014 as a trial observation, and recovered them on 18th of June 2014. Although one of the OBSs worked only 6 days from the start of the observation, other two OBSs functioned properly during the whole 3-month observation period. We first searched for the microearthquakes missing by the land seismic network and estimated their precious location by using the initial 6 days data, i.e., using all the temporary OBS stations. Although there are only 3 earthquakes listed on the Kandilli Observatory and Earthquake Research Institute (KOERI) catalogue, we could identify 41 earthquakes with more than 5 picking data of P and S first arrivals, and two-third of them located within the OBS network. We found the earthquake cluster along the main NAF and whose depth interval is 12

  1. Development of a cost-effective method for nitrate and nitrite determination in leafy plants and nitrate and nitrite contents of some green leafy vegetables grown in the Aegean region of Turkey.

    PubMed

    Ozdestan, Ozgül; Uren, Ali

    2010-05-12

    An accurate, fast, easily applicable, and cost-effective method for the determination of nitrate and nitrite was developed. This method was much more reliable than the cadmium column reduction method, which is a tedious and time-consuming procedure and not easily applicable. The principle of the method was reduction of nitrate to nitrite with cadmium acetate solution and zinc powder and then treatment with Griess reagent. Recovery of the method changed from 92.9 to 102.8%, and detection limit was found as 31.4 mg/kg. Coefficient of variation was 3.16% for intraday precision. Nitrate and nitrite contents of 10 types of leafy vegetables native to the Aegean region of Turkey were determined. Wild radish, chicory, fennel, blessed thistle, blue mallow, and chard were analyzed for the first time. Nitrate contents were found between 354.8 mg/kg for iceberg lettuce and 4653 mg/kg for wild radish. Tested vegetables contained <26.33 mg/kg nitrite.

  2. A Simple Model for Inelastic Scattering.

    ERIC Educational Resources Information Center

    Loeser, J. G.; And Others

    1981-01-01

    Describes a model for inelastic scattering obtained by suitably generalizing scattering from a square well. The generalization introduces matrices into the quantum-mechanical scattering equations, which may be solved exactly to give an explicit expression for the scattering matrix. Discusses the results it predicts for a simple example. (Author/SK)

  3. Equilibrium Tail Distribution Due to Touschek Scattering

    SciTech Connect

    Nash,B.; Krinsky, S.

    2009-05-04

    Single large angle Coulomb scattering is referred to as Touschek scattering. In addition to causing particle loss when the scattered particles are outside the momentum aperture, the process also results in a non-Gaussian tail, which is an equilibrium between the Touschek scattering and radiation damping. Here we present an analytical calculation for this equilibrium distribution.

  4. Deterministic Tectonic Origin Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, O.; Meral Ozel, N.

    2014-12-01

    Accurate earthquake source parameters are essential for any tsunami hazard assessment and mitigation, including early warning systems. Complex tectonic setting makes the a priori accurate assumptions of earthquake source parameters difficult and characterization of the faulting type is a challenge. Information on tsunamigenic sources is of crucial importance in the Eastern Mediterranean and its Connected Seas, especially considering the short arrival times and lack of offshore sea-level measurements. In addition, the scientific community have had to abandon the paradigm of a ''maximum earthquake'' predictable from simple tectonic parameters (Ruff and Kanamori, 1980) in the wake of the 2004 Sumatra event (Okal, 2010) and one of the lessons learnt from the 2011 Tohoku event was that tsunami hazard maps may need to be prepared for infrequent gigantic earthquakes as well as more frequent smaller-sized earthquakes (Satake, 2011). We have initiated an extensive modeling study to perform a deterministic Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas. Characteristic earthquake source parameters (strike, dip, rake, depth, Mwmax) at each 0.5° x 0.5° size bin for 0-40 km depth (total of 310 bins) and for 40-100 km depth (total of 92 bins) in the Eastern Mediterranean, Aegean and Black Sea region (30°N-48°N and 22°E-44°E) have been assigned from the harmonization of the available databases and previous studies. These parameters have been used as input parameters for the deterministic tsunami hazard modeling. Nested Tsunami simulations of 6h duration with a coarse (2 arc-min) and medium (1 arc-min) grid resolution have been simulated at EC-JRC premises for Black Sea and Eastern and Central Mediterranean (30°N-41.5°N and 8°E-37°E) for each source defined using shallow water finite-difference SWAN code (Mader, 2004) for the magnitude range of 6.5 - Mwmax defined for that bin with a Mw increment of 0.1. Results show that not only the

  5. Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas

    NASA Astrophysics Data System (ADS)

    Necmioglu, Ocal; Meral Ozel, Nurcan

    2015-04-01

    Accurate earthquake source parameters are essential for any tsunami hazard assessment and mitigation, including early warning systems. Complex tectonic setting makes the a priori accurate assumptions of earthquake source parameters difficult and characterization of the faulting type is a challenge. Information on tsunamigenic sources is of crucial importance in the Eastern Mediterranean and its Connected Seas, especially considering the short arrival times and lack of offshore sea-level measurements. In addition, the scientific community have had to abandon the paradigm of a ''maximum earthquake'' predictable from simple tectonic parameters (Ruff and Kanamori, 1980) in the wake of the 2004 Sumatra event (Okal, 2010) and one of the lessons learnt from the 2011 Tohoku event was that tsunami hazard maps may need to be prepared for infrequent gigantic earthquakes as well as more frequent smaller-sized earthquakes (Satake, 2011). We have initiated an extensive modeling study to perform a deterministic Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas. Characteristic earthquake source parameters (strike, dip, rake, depth, Mwmax) at each 0.5° x 0.5° size bin for 0-40 km depth (total of 310 bins) and for 40-100 km depth (total of 92 bins) in the Eastern Mediterranean, Aegean and Black Sea region (30°N-48°N and 22°E-44°E) have been assigned from the harmonization of the available databases and previous studies. These parameters have been used as input parameters for the deterministic tsunami hazard modeling. Nested Tsunami simulations of 6h duration with a coarse (2 arc-min) grid resolution have been simulated at EC-JRC premises for Black Sea and Eastern and Central Mediterranean (30°N-41.5°N and 8°E-37°E) for each source defined using shallow water finite-difference SWAN code (Mader, 2004) for the magnitude range of 6.5 - Mwmax defined for that bin with a Mw increment of 0.1. Results show that not only the earthquakes resembling the

  6. A Computer Model for Bistatic Sea Surface Microwave Reflectivity

    DTIC Science & Technology

    2014-08-14

    surface for transmit and receive grazing angles less than 10 degrees and any relative geometry through 360 degrees. In the forward scatter region...microwave reflectivity of the sea surface. This report will only address low grazing angles, as encountered with shipboard radar systems, but include...both in-plane and out-of-plane geometries. Higher grazing angles as well as airborne or space- based radars will need additional models. In the

  7. Multiple Scattering Theory of XAFS

    NASA Astrophysics Data System (ADS)

    Zabinsky, Steven Ira

    A multiple scattering theory of XAFS for arbitrary materials with convergence to full multiple scattering calculations and to experiment is presented. It is shown that the multiple scattering expansion converges with a small number of paths. The theory is embodied in an efficient automated computer code that provides accurate theoretical multiple scattering standards for use in experimental analysis. The basis of this work is a new path enumeration and filtering algorithm. Paths are constructed for an arbitrary cluster in order of increasing path length. Filters based on the relative importance of the paths in the plane wave approximation and on the random phase approximation limit the number of paths so that all important paths with effective path length up to the mean free path length (between 10 and 20 A) can be considered. Quantitative expressions for path proliferation and relative path importance are presented. The calculations are compared with full multiple scattering calculations for Cu and Al. In the case of fcc Cu, the path filters reduce the number of paths from 60 billion to only 56 paths in a cluster of radius 12.5 A. These 56 paths are sufficient to converge the calculation to within the uncertainty inherent in the band structure calculation. Based on an analysis of these paths, a new hypothesis is presented for consideration: Single scattering, double scattering, and all orders of scattering that involve only forward or back scattering are sufficient to describe XAFS. Comparison with experiment in Cu, Pt and Ti demonstrate the accuracy of the calculation through the fourth shell. The correlated Debye model is used to determine Debye-Waller factors--the strengths and weaknesses of this approach are discussed. Preliminary results for calculations of the x -ray absorption near edge structure (XANES) have been done. The calculations compare well with Cu, Pt and Ti experiments. The white line in the Pt absorption edge is calculated correctly. There are

  8. Marine caves of the Mediterranean Sea: a sponge biodiversity reservoir within a biodiversity hotspot.

    PubMed

    Gerovasileiou, Vasilis; Voultsiadou, Eleni

    2012-01-01

    Marine caves are widely acknowledged for their unique biodiversity and constitute a typical feature of the Mediterranean coastline. Herein an attempt was made to evaluate the ecological significance of this particular ecosystem in the Mediterranean Sea, which is considered a biodiversity hotspot. This was accomplished by using Porifera, which dominate the rocky sublittoral substrata, as a reference group in a meta-analytical approach, combining primary research data from the Aegean Sea (eastern Mediterranean) with data derived from the literature. In total 311 species from all poriferan classes were recorded, representing 45.7% of the Mediterranean Porifera. Demospongiae and Homoscleromorpha are highly represented in marine caves at the family (88%), generic (70%), and species level (47.5%), the latter being the most favored group along with Dictyoceratida and Lithistida. Several rare and cave-exclusive species were reported from only one or few caves, indicating the fragmentation and peculiarity of this unique ecosystem. Species richness and phylogenetic diversity varied among Mediterranean areas; the former was positively correlated with research effort, being higher in the northern Mediterranean, while the latter was generally higher in caves than in the overall sponge assemblages of each area. Resemblance analysis among areas revealed that cavernicolous sponge assemblages followed a pattern quite similar to that of the overall Mediterranean assemblages. The same pattern was exhibited by the zoogeographic affinities of cave sponges: species with Atlanto-Mediterranean distribution and Mediterranean endemics prevailed (more than 40% each), 70% of them having warm-water affinities, since most caves were studied in shallow waters. According to our findings, Mediterranean marine caves appear to be important sponge biodiversity reservoirs of high representativeness and great scientific interest, deserving further detailed study and protection.

  9. A numerical study of the interannual variability of the Adriatic Sea (2000-2002).

    PubMed

    Oddo, Paolo; Pinardi, Nadia; Zavatarelli, Marco

    2005-12-15

    A free-surface, three-dimensional finite-difference numerical model based on the Princeton Ocean Model (POM) has been implemented in order to simulate the interannual variability of the Adriatic Sea circulation. The implementation makes use of an interactive surface momentum and heat flux computation that utilizes the European Centre for Medium-Range Weather Forecasts (ECMWF) 6-h analyses and the model predicted sea surface temperatures. The model is also nested at its open boundary with a coarse-resolution Mediterranean general circulation model, utilizing the same surface forcing functions. The simulation and analysis period spans 3 years (1 Jan 2000 to 31 Dec 2002) coinciding with the "Mucilage in the Adriatic and the Tyrrhenian" (MAT) Project monitoring activities. Model results for the simulated years show a strong interannual variability of the basin averaged proprieties and circulation patterns, linked to the atmospheric forcing variability and the Po river runoff. In particular, the years 2000 and 2002 are characterized by a weak surface cooling (with respect to the climatological value) and well-marked spring and autumn river runoff maxima. Conversely, 2001 is characterized by stronger wind and heat (autumn cooling) forcings but no river runoff autumn peak, even though the total amount of water inflow during winter and spring is sustained. The circulation is characterized by similar patterns in 2000 and 2002 but very different structures in 2001. During the latter, deep water is not formed in the northern Adriatic. A comparison with the observed data shows that the major model deficiencies are connected to the low salinity of the waters, probably connected to the missed inflow of salty Ionian waters of Aegean origin and to the numerical overestimation of the vertical mixing processes.

  10. Marine Caves of the Mediterranean Sea: A Sponge Biodiversity Reservoir within a Biodiversity Hotspot

    PubMed Central

    Gerovasileiou, Vasilis; Voultsiadou, Eleni

    2012-01-01

    Marine caves are widely acknowledged for their unique biodiversity and constitute a typical feature of the Mediterranean coastline. Herein an attempt was made to evaluate the ecological significance of this particular ecosystem in the Mediterranean Sea, which is considered a biodiversity hotspot. This was accomplished by using Porifera, which dominate the rocky sublittoral substrata, as a reference group in a meta-analytical approach, combining primary research data from the Aegean Sea (eastern Mediterranean) with data derived from the literature. In total 311 species from all poriferan classes were recorded, representing 45.7% of the Mediterranean Porifera. Demospongiae and Homoscleromorpha are highly represented in marine caves at the family (88%), generic (70%), and species level (47.5%), the latter being the most favored group along with Dictyoceratida and Lithistida. Several rare and cave-exclusive species were reported from only one or few caves, indicating the fragmentation and peculiarity of this unique ecosystem. Species richness and phylogenetic diversity varied among Mediterranean areas; the former was positively correlated with research effort, being higher in the northern Mediterranean, while the latter was generally higher in caves than in the overall sponge assemblages of each area. Resemblance analysis among areas revealed that cavernicolous sponge assemblages followed a pattern quite similar to that of the overall Mediterranean assemblages. The same pattern was exhibited by the zoogeographic affinities of cave sponges: species with Atlanto-Mediterranean distribution and Mediterranean endemics prevailed (more than 40% each), 70% of them having warm-water affinities, since most caves were studied in shallow waters. According to our findings, Mediterranean marine caves appear to be important sponge biodiversity reservoirs of high representativeness and great scientific interest, deserving further detailed study and protection. PMID:22808070

  11. Time Dependent Nuclear Scattering Calculations

    NASA Astrophysics Data System (ADS)

    Weeks, David

    2005-04-01

    A new time dependent method for calculating scattering matrix elements of two and three body nuclear collisions below 50 Mev is being developed. The procedure closely follows the channel packet method (CPM) used to compute scattering matrix elements for non-adiabatic molecular reactions.ootnotetextT.A.Niday and D.E.Weeks, Chem. Phys. Letters 308 (1999) 106 Currently, one degree of freedom calculations using a simple square well have been completed and a two body scattering calculation using the Yukawa potential is anticipated. To perform nuclear scattering calculations with the CPM that will incorporate the nucleon-nucleon tensor force, we plan to position initial reactant and product channel packets in the asymptotic limit on single coupled potential energy surfaces labeled by the spin, isospin, and total angular momentum of the reactant nucleons. The wave packets will propagated numerically using the split operator method augmented by a coordinate dependant unitary transformation used to diagonalize the potential. Scattering matrix elements will be determined by the Fourier transform of the correlation function between the evolving reactant and product wave packets. A brief outline of the Argonne v18 nucleon-nucleon potentialootnotetextR.B.Wiringa, V.G.J.Stoks, and R.Schiavilla, Physical Review C 51(1995) 38 and the proposed wave packet calculations will be presented.

  12. Scattering apodizer for laser beams

    DOEpatents

    Summers, M.A.; Hagen, W.F.; Boyd, R.D.

    1984-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  13. Scattering apodizer for laser beams

    DOEpatents

    Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.

    1985-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  14. Thomson scattering from laser plasmas

    SciTech Connect

    Moody, J D; Alley, W E; De Groot, J S; Estabrook, K G; Glenzer, S H; Hammer, J H; Jadaud, J P; MacGowan, B J; Rozmus, W; Suter, L J; Williams, E A

    1999-01-12

    Thomson scattering has recently been introduced as a fundamental diagnostic of plasma conditions and basic physical processes in dense, inertial confinement fusion plasmas. Experiments at the Nova laser facility [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)] have demonstrated accurate temporally and spatially resolved characterization of densities, electron temperatures, and average ionization levels by simultaneously observing Thomson scattered light from ion acoustic and electron plasma (Langmuir) fluctuations. In addition, observations of fast and slow ion acous- tic waves in two-ion species plasmas have also allowed an independent measurement of the ion temperature. These results have motivated the application of Thomson scattering in closed-geometry inertial confinement fusion hohlraums to benchmark integrated radiation-hydrodynamic modeling of fusion plasmas. For this purpose a high energy 4{omega} probe laser was implemented recently allowing ultraviolet Thomson scattering at various locations in high-density gas-filled hohlraum plasmas. In partic- ular, the observation of steep electron temperature gradients indicates that electron thermal transport is inhibited in these gas-filled hohlraums. Hydrodynamic calcula- tions which include an exact treatment of large-scale magnetic fields are in agreement with these findings. Moreover, the Thomson scattering data clearly indicate axial stagnation in these hohlraums by showing a fast rise of the ion temperature. Its timing is in good agreement with calculations indicating that the stagnating plasma will not deteriorate the implosion of the fusion capsules in ignition experiments.

  15. Nonlinear scattering in plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Chu, Shi-Wei

    2016-09-01

    Nonlinear phenomena provide novel light manipulation capabilities and innovative applications. Recently, we discovered nonlinear saturation on single-particle scattering of gold nanospheres by continuous-wave laser excitation and innovatively applied to improve microscopic resolution down to λ/8. However, the nonlinearity was limited to the green-orange plasmonic band of gold nanosphere, and the underlying mechanism has not yet been fully understood. In this work, we demonstrated that nonlinear scattering exists for various material/geometry combinations, thus expanding the applicable wavelength range. For near-infrared, gold nanorod is used, while for blue-violet, silver nanospheres are adopted. In terms of mechanism, the nonlinearity may originate from interband/intraband absorption, hot electron, or hot lattice, which are spectrally mixed in the case of gold nanosphere. For gold nanorod and silver nanosphere, nonlinear scattering occurs at plasmonic resonances, which are spectrally far from interband/intraband absorptions, so they are excluded. We found that the nonlinear index is much larger than possible contributions from hot electrons in literature. Therefore, we conclude that hot lattice is the major mechanism. In addition, we propose that similar to z-scan, which is the standard method to characterize nonlinearity of a thin sample, laser scanning microscopy should be adopted as the standard method to characterize nonlinearity from a nanostructure. Our work not only provides the physical mechanism of the nonlinear scattering, but also paves the way toward multi-color superresolution imaging based on non-bleaching plasmonic scattering.

  16. Oceanographic influences on Deep Scattering Layers across the North Atlantic

    NASA Astrophysics Data System (ADS)

    Fennell, Sheena; Rose, George

    2015-11-01

    The distribution and density of Deep Scattering Layers (DSLs) were quantified along North Atlantic transits from Ireland to the Grand Banks of Newfoundland in the springs of 2012, 2013 and 2014 employing a calibrated Simrad EK60 echo sounder at 38 kHz. Concurrently, Sippican T5 XBTs (eXpendable Bathy Thermographs) were used to profile temperatures to 1800 m. In each year the scattering layers spanned the deep basin at depths ranging from near surface to approximately 900 m, but annual mean densities differed significantly. Higher DSL densities were recorded during years that exhibited higher sea temperatures at the depths of major DSL concentration (400-600 m), higher sea level anomalies and stronger eastward geostrophic currents. The highest concentration of the DSLs in each year was found in the area east of the Grand Banks that corresponded with areas of anticyclonic eddies. In this region DSL densities in 2014 were among the highest recorded worldwide (>7000 m2 nautical mile-2). Midwater fishing indicated DSLs were dominated by Myctophids and Sternoptychids. Anticyclonic eddy formation is discussed as a possible means of transport and aggregation of the DSLs in that region, where oceanographic influences may play a dominant role in the distribution and density of the DSLs and upper trophic level fishes.

  17. EMODNet Hydrography - Seabed Mapping - Developing a higher resolution digital bathymetry for the European seas

    NASA Astrophysics Data System (ADS)

    Schaap, Dick M. A.; Moussat, Eric

    2013-04-01

    In December 2007 the European Parliament and Council adopted the Marine Strategy Framework Directive (MSFD) which aims to achieve environmentally healthy marine waters by 2020. This Directive includes an initiative for an overarching European Marine Observation and Data Network (EMODNet). The EMODNet Hydrography - Seabed Mapping projects made good progress in developing the EMODNet Hydrography portal to provide overview and access to available bathymetric survey datasets and to generate an harmonised digital bathymetry for Europe's sea basins. Up till end 2012 more than 8400 bathymetric survey datasets, managed by 14 data centres from 9 countries and originated from 118 institutes, have been gathered and populated in the EMODNet Hydrography Data Discovery and Access service, adopting SeaDataNet standards. These datasets have been used as input for analysing and generating the EMODNet digital terrain model (DTM), so far for the following sea basins: • the Greater North Sea, including the Kattegat • the English Channel and Celtic Seas • Western and Central Mediterranean Sea and Ionian Sea • Bay of Biscay, Iberian coast and North-East Atlantic • Adriatic SeaAegean - Levantine Sea (Eastern Mediterranean). • Azores - Madeira EEZ The Hydrography Viewing service gives users wide functionality for viewing and downloading the EMODNet digital bathymetry: • water depth in gridded form on a DTM grid of a quarter a minute of longitude and latitude • option to view QC parameters of individual DTM cells and references to source data • option to download DTM tiles in different formats: ESRI ASCII, XYZ, CSV, NetCDF (CF), GeoTiff and SD for Fledermaus 3 D viewer software • option for users to create their Personal Layer and to upload multibeam survey ASCII datasets for automatic processing into personal DTMs following the EMODNet standards The NetCDF (CF) DTM files are fit for use in a special 3D Viewer software package which is based on the existing open

  18. Estimating aerosol light-scattering enhancement from dry aerosol optical properties at different sites

    NASA Astrophysics Data System (ADS)

    Titos, Gloria; Jefferson, Anne; Sheridan, Patrick; Andrews, Elisabeth; Lyamani, Hassan; Ogren, John; Alados-Arboledas, Lucas

    2014-05-01

    Microphysical and optical properties of aerosol particles are strongly dependent on the relative humidity (RH). Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in-situ measurements with satellite and remote sensing retrievals. The scattering enhancement factor, f(RH), is defined as the ratio of the scattering coefficient at a high and reference RH. Predictive capability of f(RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we explore the relationship between aerosol light-scattering enhancement and dry aerosol optical properties such as the single scattering albedo (SSA) and the scattering Ångström exponent (SAE) at multiple sites around the world. The measurements used in this study were conducted by the US Department of Energy at sites where different aerosol types predominate (pristine marine, polluted marine, dust dominated, agricultural and forest environments, among others). In all cases, the scattering enhancement decreases as the SSA decreases, that is, as the contribution of absorbing particles increases. On the other hand, for marine influenced environments the scattering enhancement clearly increases as the contribution of coarse particles increases (SAE decreases), evidence of the influence of hygroscopic coarse sea salt particles. For other aerosol types the relationship between f(RH) and SAE is not so straightforward. Combining all datasets, f(RH) was found to exponentially increase with SSA with a high correlation coefficient.

  19. Nuclear Scattering from Transition Metals

    NASA Astrophysics Data System (ADS)

    Hira, Ajit; McKeough, James; Valerio, Mario; Cathey, Tommy

    2016-03-01

    In view of the continued interest in the scattering of light projectiles by metallic nuclei, we present a computational study of the interactions between different nuclear species of atoms such as H through F (Z <= 9) and the nuclei of Silver, Palladium and other metals. Recent work has shown that neutron scattering can be used to record holographic images of materials. We have developed a FORTRAN computer program to compute stopping cross sections and scattering angles in Ag and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 50 to 210 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies also have potential applications in nuclear physics and in nuclear medicine. Funding from National Science Foundation.

  20. Scattering Polarization in the Chromosphere

    NASA Technical Reports Server (NTRS)

    Keller, C. U.; Sheeley, N. R., Jr.

    1999-01-01

    Scattering polarization from the photosphere observed close to the solar limb has recently become of interest to study turbulent magnetic fields, abundances, and radiative transfer effects. We extend these studies by measuring the scattering polarization off the limb, i.e. in the chromosphere. However, instrumental effects are much more pronounced and more complicated than those affecting on-disk measurements. In particular, scattered light from the telescope mirrors leads to a new type of instrumental polarization that we describe in detail. The differences between the linearly polarized spectra on the disk and off the limb are often very substantial. Here we show the profiles of HeI D(sub 3), the OI triplet at 777 nm, and the Nal D lines. The change in the latter is in reasonable agreement with the recent modeling efforts of atomic polarization in the lower level by Landi Degl'Innocenti (1998).

  1. Scattering calculations and confining interactions

    NASA Technical Reports Server (NTRS)

    Buck, Warren W.; Maung, Khin M.

    1993-01-01

    Most of the research work performed under this grant were concerned with strong interaction processes ranging from kaon-nucleon interaction to proton-nucleus scattering calculations. Research performed under this grant can be categorized into three groups: (1) parametrization of fundamental interactions, (2) development of formal theory, and (3) calculations based upon the first two. Parametrizations of certain fundamental interactions, such as kaon-nucleon interaction, for example, were necessary because kaon-nucleon scattering amplitude was needed to perform kaon-nucleus scattering calculations. It was possible to calculate kaon-nucleon amplitudes from the first principle, but it was unnecessary for the purpose of the project. Similar work was also done for example for anti-protons and anti-nuclei. Formal developments to some extent were also pursued so that consistent calculations can be done.

  2. Theory of waves incoherently scattered

    NASA Technical Reports Server (NTRS)

    Bauer, P.

    1974-01-01

    Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

  3. Scattering functions of Platonic solids

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Li, Xin; Liu, Emily; Pynn, Roger; Shew, Chwen-Yang; Smith, Gregory Scott; Myles, Dean A A; He, Lilin; Meilleur, Flora

    2011-01-01

    In this report the single-particle scattering properties of five Platonic solids, including tetrahedron, hexahedron, octahedron, dodecahedron and icosahedron, are investigated in a systematic manner. For each given geometry, the Debye spatial autocorrelation function (r), pair distance distribution function (PDDF) p (r) and intraparticle structure factor (form factor) P (Q) are respectively calculated and compared to the corresponding scattering function of the spherical referential system. Based on our theoretical models, the empirical relationship between the dodecahedral and icosahedral structural characteristics and those of the equivalent spheres is found. Moreover, the single-particle scattering properties of the icosahedral and the spherical shells with the same volume are further investigated and the prospect of using different data analysis approaches to explore their structural difference is also presented and discussed.

  4. Scattering functions of Platonic solids

    SciTech Connect

    Li, Xin; Shew, Chwen-Yang; He, Lilin; Meilleur, Flora; Myles, Dean A A; Liu, Emily; Zhang, Yang; Smith, Greg; Herwig, Kenneth W; Pynn, Roger; Chen, Wei-Ren

    2011-01-01

    The single-particle small-angle scattering properties of five Platonic solids, including the tetrahedron, hexahedron, octahedron, dodecahedron and icosahedron, are systematically investigated. For each given geometry, the Debye spatial autocorrelation function, pair distance distribution function and intraparticle structure factor (form factor) are calculated and compared with the corresponding scattering function of a spherical reference system. From the theoretical models, the empirical relationship between the dodecahedral and icosahedral structural characteristics and those of the equivalent spheres is found. Moreover, the single-particle scattering properties of icosahedral and spherical shells with identical volume are investigated, and the prospect of using different data analysis approaches to explore their structural differences is presented and discussed.

  5. Positron-alkali atom scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.; Ward, S. J.

    1990-01-01

    Positron-alkali atom scattering was recently investigated both theoretically and experimentally in the energy range from a few eV up to 100 eV. On the theoretical side calculations of the integrated elastic and excitation cross sections as well as total cross sections for Li, Na and K were based upon either the close-coupling method or the modified Glauber approximation. These theoretical results are in good agreement with experimental measurements of the total cross section for both Na and K. Resonance structures were also found in the L = 0, 1 and 2 partial waves for positron scattering from the alkalis. The structure of these resonances appears to be quite complex and, as expected, they occur in conjunction with the atomic excitation thresholds. Currently both theoretical and experimental work is in progress on positron-Rb scattering in the same energy range.

  6. Dead sea water intoxication.

    PubMed

    Levy-Khademi, Floris; Brooks, Rebecca; Maayan, Channa; Tenenbaum, Ariel; Wexler, Isaiah D

    2012-08-01

    Near drowning in the Dead Sea is associated with both respiratory manifestations and severe electrolyte abnormalities. It is often difficult to distinguish between the contributions of sea water aspiration or ingestion to clinical manifestations. We present a unique case of accidental ingestion of a large amount of Dead Sea water through a gastrostomy tube in which a patient with familial dysautonomia presented with severe electrolyte disturbances. Forced diuresis with large amounts of intravenous fluids resulted in clinical and biochemical improvement. Full recovery was achieved after 2 days of treatment.

  7. Light Scattering in Exoplanet Transits

    NASA Astrophysics Data System (ADS)

    Robinson, Tyler D.; Fortney, Jonathan J.

    2016-10-01

    Transit spectroscopy is currently the leading technique for studying exoplanet atmospheric composition, and has led to the detection of molecular species, clouds, and/or hazes for numerous worlds outside the Solar System. The field of exoplanet transit spectroscopy will be revolutionized with the anticipated launch of NASA's James Webb Space Telescope (JWST) in 2018. Over the course of the design five year mission for JWST, the observatory is expected to provide in-depth observations of many tens of transiting exoplanets, including some worlds in the poorly understood 2-4 Earth-mass regime. As the quality of transit spectrum observations continues to improve, so should models of exoplanet transits. Thus, certain processes initially thought to be of second-order importance should be revisited and possibly added to modeling tools. For example, atmospheric refraction, which was commonly omitted from early transit spectrum models, has recently been shown to be of critical importance in some terrestrial exoplanet transits. Beyond refraction, another process that has seen little study with regards to exoplanet transits is light multiple scattering. In most cases, scattering opacity in exoplanet transits has been treated as equivalent to absorption opacity. However, this equivalence cannot always hold, such as in the case of a strongly forward scattering, weakly absorbing aerosol. In this presentation, we outline a theory of exoplanet transit spectroscopy that spans the geometric limit (used in most modern models) to a fully multiple scattering approach. We discuss a new technique for improving model efficiency that effectively separates photon paths, which tend to vary slowly in wavelength, from photon absorption, which can vary rapidly in wavelength. Using this newly developed approach, we explore situations where cloud or haze scattering may be important to JWST observations of gas giants, and comment on the conditions necessary for scattering to become a major

  8. Teaching of the subject "density difference caused by salinity", one of the reasons that plays role in the occurrence of currents in straits, seas and oceans by the use of a teaching material

    NASA Astrophysics Data System (ADS)

    Gumussoy, Verim

    2015-04-01

    Large masses of moving water in seas and oceans are called currents. Root causes of currents are steady winds that occur due to the global atmospheric system and the density differences caused by different heat and salinity levels of water masses. Different feeding and evaporation characteristics of seas and oceans result in salinity and density levels. As a result, subsurface currents occur in straits where seas with different salinity and density levels meet and in the nearby seas. The Bosporus in Istanbul where I live and the school I am working at is has these subsurface currents. In the Black Sea where the rivers the Danube, Dnieper, Don, Yesilirmak, Kizilirmak and Sakarya flow into and the evaporation level is less due to the latitude effect, salinity level is less compared to Marmara and Aegean Seas. As Marmara Sea has higher salt amount than Black Sea, there is a great density difference between these two seas. Marmara Sea has a higher concentration of salt and therefore a higher density than Black Sea. And this leads to occurrence of subsurface currents in the Bosporus. I get my students to carry out a small demonstration to help them understand the occurrence of ocean currents and currents in the seas and the Bosporus by the use of a material. We need very simple materials to carry out this demonstration. These are an aquarium, a bowl, water, salt, dye and a mixer. The demonstration is carried out as follows: we put water, salt and dye in the bowl and mix it well. The salt will increase the density of the water and the dye will help distinguish the salty water. Then we put tap water half way to the aquarium and pour the mixture in the bowl to the aquarium slowly. As a result, the colored salty water sinks down due to its higher density, setting an example of a subsurface current. Natural events occur in very long periods by great dynamic systems, making understanding of them difficult. It is important to use different kinds of materials that address to

  9. The north Sulu Sea productivity

    NASA Astrophysics Data System (ADS)

    Xiao, Z.

    2009-12-01

    The Sulu Sea is a part of the western North Pacific. It is a closed sea for its deep water and a semi-closed sea for its upper layer. The Sulu Sea exchanges mainly surface waters with the South China Sea and the Celebes Sea. The Sulu Sea is more productive than the adjacent South China Sea (Jones, 2002). On the basis of MERIS satellite observations from 2002 to 2008, we focus on the high-chlorophyll area as an indicator of the abundance of primary productivity in the Sulu Sea. Strong chlorophyll concentration in the north Sulu Sea close to the Mindoro Strait mainly occurs from December to March and low chlorophyll concentration happens in April to November. The adjacent South China Sea on the other side of Mindoro Strait has shown persistent signs of low chlorophyll concentration. Based on 1/8° Global Navy Coastal Ocean Model, the intrusion of the South China Sea waters through the Mindoro Strait to the Sulu Sea from April to November is the main reason for the low chlorophyll concentration observed in the north Sulu Sea. During April to November, the South China Sea waters flow through the Mindoro Strait and stay on the surface of the north Sulu Sea because of their low density. The north Sulu Sea waters mix with fresher waters coming from the South China Sea without new nutrients supply. When the inflow from South China Sea to Sulu Sea ceases in December to March, the upwelling due to the summer monsoon wind becomes an important mechanism supplying deep nutrients to the surface water which lead to high chlorophyll concentration. Jones, I.S.F., 2002. Primary production in the Sulu Sea. Proceedings of the Indian Academy of Sciences-Earth and Planetary Sciences 111, 209-213.

  10. Stimulated Brillouin Scattering Microscopic Imaging

    PubMed Central

    Ballmann, Charles W.; Thompson, Jonathan V.; Traverso, Andrew J.; Meng, Zhaokai; Scully, Marlan O.; Yakovlev, Vladislav V.

    2015-01-01

    Two-dimensional stimulated Brillouin scattering microscopy is demonstrated for the first time using low power continuous-wave lasers tunable around 780 nm. Spontaneous Brillouin spectroscopy has much potential for probing viscoelastic properties remotely and non-invasively on a microscopic scale. Nonlinear Brillouin scattering spectroscopy and microscopy may provide a way to tremendously accelerate the data aquisition and improve spatial resolution. This general imaging setup can be easily adapted for specific applications in biology and material science. The low power and optical wavelengths in the water transparency window used in this setup provide a powerful bioimaging technique for probing the mechanical properties of hard and soft tissue. PMID:26691398

  11. Electron Scattering from Silicon 30.

    DTIC Science & Technology

    1983-01-01

    COMPLETING FORM I. REPORT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER AFIT/CI/NR 83-3 T___ __ _ . 4. TITLE (and Subtitle) S . TYPE OF...REPORT & PERIOD COVERED ElectrogScattering from Silicon 30 THESIS/P AA~7Aj1AN 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(q) S . CONTRACT OR GRANT NUMBER( s ...spectrometers. The machines used in the 1950’ s allowed electron scattering with a resolution of 4p/p f5xlO- and with currents of a few tenths of a micro

  12. Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments

    NASA Astrophysics Data System (ADS)

    Røstad, Anders; Kaartvedt, Stein; Aksnes, Dag L.

    2016-07-01

    We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than 10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics.

  13. Using near infrared light for deep sea mining observation systems

    NASA Astrophysics Data System (ADS)

    Lu, Huimin; Li, Yujie; Li, Xin; Yang, Jianmin; Serikawa, Seiichi

    2015-10-01

    In this paper, we design a novel deep-sea near infrared light based imaging equipment for deep-sea mining observation systems. The spectral sensitivity peaks are in the red region of the invisible spectrum, ranging from 750nm to 900nm. In addition, we propose a novel underwater imaging model that compensates for the attenuation discrepancy along the propagation path. The proposed model fully considered the effects of absorption, scattering and refraction. We also develop a locally adaptive Laplacian filtering for enhancing underwater transmission map after underwater dark channel prior estimation. Furthermore, we propose a spectral characteristic-based color correction algorithm to recover the distorted color. In water tank experiments, we made a linear scale of eight turbidity steps ranging from clean to heavily scattered by adding deep sea soil to the seawater (from 500 to 2000 mg/L). We compared the results of different turbidity underwater scene, illuminated alternately with near infrared light vs. white light. Experiments demonstrate that the enhanced NIR images have a reasonable noise level after the illumination compensation in the dark regions and demonstrates an improved global contrast by which the finest details and edges are significantly enhanced. We also demonstrate that the effective distance of the designed imaging system is about 1.5 meters, which can meet the requirement of micro-terrain observation around the deep-sea mining systems. Remotely Operated Underwater Vehicle (ROV)-based experiments also certified the effectiveness of the proposed method.

  14. Habitat Selection Response of Small Pelagic Fish in Different Environments. Two Examples from the Oligotrophic Mediterranean Sea

    PubMed Central

    Bonanno, Angelo; Giannoulaki, Marianna; Barra, Marco; Basilone, Gualtiero; Machias, Athanassios; Genovese, Simona; Goncharov, Sergey; Popov, Sergey; Rumolo, Paola; Di Bitetto, Massimiliano; Aronica, Salvatore; Patti, Bernardo; Fontana, Ignazio; Giacalone, Giovanni; Ferreri, Rosalia; Buscaino, Giuseppa; Somarakis, Stylianos; Pyrounaki, Maria-Myrto; Tsoukali, Stavroula; Mazzola, Salvatore

    2014-01-01

    A number of scientific papers in the last few years singled out the influence of environmental conditions on the spatial distribution of fish species, highlighting the need for the fisheries scientific community to investigate, besides biomass estimates, also the habitat selection of commercially important fish species. The Mediterranean Sea, although generally oligotrophic, is characterized by high habitat variability and represents an ideal study area to investigate the adaptive behavior of small pelagics under different environmental conditions. In this study the habitat selection of European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus is analyzed in two areas of the Mediterranean Sea that largely differentiate in terms of environmental regimes: the Strait of Sicily and the North Aegean Sea. A number of environmental parameters were used to investigate factors influencing anchovy and sardine habitat selection. Acoustic surveys data, collected during the summer period 2002–2010, were used for this purpose. The quotient analysis was used to identify the association between high density values and environmental variables; it was applied to the entire dataset in each area in order to identify similarities or differences in the “mean” spatial behavioral pattern for each species. Principal component analysis was applied to selected environmental variables in order to identify those environmental regimes which drive each of the two ecosystems. The analysis revealed the effect of food availability along with bottom depth selection on the spatial distribution of both species. Furthermore PCA results highlighted that observed selectivity for shallower waters is mainly associated to specific environmental processes that locally increase productivity. The common trends in habitat selection of the two species, as observed in the two regions although they present marked differences in hydrodynamics, seem to be driven by the oligotrophic

  15. 2011 Sea Ice Minimum

    NASA Video Gallery

    This video shows Arctic sea ice from March 7, 2011, to Sept. 9, 2011, ending with a comparison of the 30-year average minimum extent, shown in yellow, and the Northwest Passage, in red. (no audio) ...

  16. Sea ice ecosystems.

    PubMed

    Arrigo, Kevin R

    2014-01-01

    Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

  17. Record Sea Ice Minimum

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

  18. Sea level change

    SciTech Connect

    Meier, M.F.

    1996-12-31

    The IPCC (Intergovernmental Panel on Climate Change) 1995 Scientific Assessment, Chapter 7. Sea Level Change, presents a modest revision of the similar chapter in the 1990 Assessment. Principal conclusions on observed sea-level change and the principal terms in the sea-level equation (ocean thermal expansion, glaciers, ice sheets, and land hydrology), including our knowledge of the present-day (defined as the 20th Century) components of sea-level rise, and projections of these for the future, are presented here. Some of the interesting glaciological problems which are involved in these studies are discussed in more detail. The emphasis here is on trends over decades to a century, not on shorter variations nor on those of the geologic past. Unfortunately, some of the IPCC projections had not been agreed at the time of writing of this paper, and these projections will not be given here. 15 refs., 2 figs.

  19. Dead Sea Scrolls

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A consortium of researchers from Jet Propulsion Laboratory and three other organizations used charged coupled devices (CCDs) and other imaging enhancement technology to decipher previously unreadable portions of the Dead Sea Scrolls. The technique has potentially important implications for archeology.

  20. Alaska: Beaufort Sea

    Atmospheric Science Data Center

    2014-05-15

    ... to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite ... the same geographic area. To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center ...

  1. Sea Ice Minimum 2016

    NASA Video Gallery

    This animation shows the evolution of the Arctic sea ice cover from its wintertime maximum extent, which was reached on Mar. 24, 2016, and was the lowest on record for the second year in a row, to ...

  2. A Sea Experience.

    ERIC Educational Resources Information Center

    Glickstein, Neil

    1989-01-01

    Described is a teacher education program organized by the Sea Education Association in Woods Hole (Massachusetts). The experience, including activities and examples of studies conducted, is discussed. Contact information for future cruises is included. (CW)

  3. Sea Ice Ecosystems

    NASA Astrophysics Data System (ADS)

    Arrigo, Kevin R.

    2014-01-01

    Polar sea ice is one of the largest ecosystems on Earth. The liquid brine fraction of the ice matrix is home to a diverse array of organisms, ranging from tiny archaea to larger fish and invertebrates. These organisms can tolerate high brine salinity and low temperature but do best when conditions are milder. Thriving ice algal communities, generally dominated by diatoms, live at the ice/water interface and in recently flooded surface and interior layers, especially during spring, when temperatures begin to rise. Although protists dominate the sea ice biomass, heterotrophic bacteria are also abundant. The sea ice ecosystem provides food for a host of animals, with crustaceans being the most conspicuous. Uneaten organic matter from the ice sinks through the water column and feeds benthic ecosystems. As sea ice extent declines, ice algae likely contribute a shrinking fraction of the total amount of organic matter produced in polar waters.

  4. Sensing the sea bed

    NASA Astrophysics Data System (ADS)

    2009-07-01

    William Wilcock and a team of scientists and engineers drilled holes in the sea floor, and inadvertently provided a breeding ground for octopuses, in their attempt to understand deep-ocean hydrothermal venting.

  5. Sea Raiders of Acadia

    ERIC Educational Resources Information Center

    Dickason, Olive Patricia

    1976-01-01

    One of the French allies, the Micmac, waged much of the war against the English on the sea. This article discusses the determined stand by the Micmac seamen of the eastern coasts for their lands and way of life. (NQ)

  6. A Sea Floor Penetrometer.

    DTIC Science & Technology

    processed through an analog-to-digital (A/D) converter, and stored in the memory of a mini-computer. Computer algorithms are applied to the deceleration data to provide real-time sea floor classification.

  7. Teacher at Sea.

    ERIC Educational Resources Information Center

    Beighley, Karl

    1998-01-01

    Outlines the experiences of a teacher in the National Oceanic and Atmospheric Administration's (NOAA) Teacher At Sea Program in which teachers are placed on NOAA vessels to work with professional scientists doing critical, real world research. (DDR)

  8. South China Sea

    USGS Publications Warehouse

    Morton, Brian; Blackmore, Graham

    2001-01-01

    The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scientific community. The South China Sea has an area of some 3.3 million km2 and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely confined within the Tropic of Cancer and, therefore, experiences a monsoonal climate being influenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major influence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Pacific biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of the three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflicts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the South

  9. South China Sea.

    PubMed

    Morton, B; Blackmore, G

    2001-12-01

    The South China Sea is poorly understood in terms of its marine biota, ecology and the human impacts upon it. What is known is most often contained in reports and workshop and conference documents that are not available to the wider scientific community. The South China Sea has an area of some 3.3 million km2 and depths range from the shallowest coastal fringe to 5377 m in the Manila Trench. It is also studded with numerous islets, atolls and reefs many of which are just awash at low tide. It is largely confined within the Tropic of Cancer and, therefore, experiences a monsoonal climate being influenced by the Southwest Monsoon in summer and the Northeast Monsoon in winter. The South China Sea is a marginal sea and, therefore, largely surrounded by land. Countries that have a major influence on and claims to the sea include China, Malaysia, the Philippines and Vietnam, although Thailand, Indonesia and Taiwan have some too. The coastal fringes of the South China Sea are home to about 270 million people that have had some of the fastest developing and most vibrant economies on the globe. Consequently, anthropogenic impacts, such as over-exploitation of resources and pollution, are anticipated to be huge although, in reality, relatively little is known about them. The Indo-West Pacific biogeographic province, at the centre of which the South China Sea lies, is probably the world's most diverse shallow-water marine area. Of three major nearshore habitat types, i.e., coral reefs, mangroves and seagrasses, 45 mangrove species out of a global total of 51, most of the currently recognised 70 coral genera and 20 of 50 known seagrass species have been recorded from the South China Sea. The island groups of the South China Sea are all disputed and sovereignty is claimed over them by a number of countries. Conflicts have in recent decades arisen over them because of perceived national rights. It is perhaps because of this that so little research has been undertaken on the

  10. Black Sea Becomes Turquoise

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image shows bright, turquoise-colored swirls across the surface of the Black Sea, signifying the presence of a large phytoplankton bloom. Scientists have observed similar blooms recurring annually, roughly this same time of year. The Sea of Azov, which is the smaller body of water located just north of the Black Sea in this image, also shows a high level of color variance. The brownish pixels in the Azov are probably due to sediments carried in from high waters and snowmelt from upstream. This scene was acquired by the Moderate Resolution Imaging Spectroradiometer, flying aboard NASA's Terra satellite, on May 14, 2002. According to the Black Sea Environment Programme's Marine Hydrophysical Institute, the Black Sea is ?one of the marine areas of the world most damaged by human activities.? The coastal zone around these Eastern European inland water bodies is densely populated'supporting a permanent population of roughly 16 million people and another 4 million tourists each year. Six countries border with the Black Sea, including Ukraine to the north, Russia and Georgia to the east, Turkey to the south, and Bulgaria and Romania to the west. Because it is isolated from the world's oceans, and because there is an extensive drainage network of rivers that empty into it, the Black Sea has a unique and delicate water balance which is very important for supporting its marine ecosystem. Of particular concern to scientists is the salinity, water level, and nutrient levels of the Black Sea's waters, all of which are, unfortunately, being impacted by human activities. Within the last three decades the combination of increased nutrient loads from human sources together with pollution and over-harvesting of fisheries has resulted in a sharp decline in water quality. Scientists from each of the Black Sea's bordering nations are currently working together to study the issues and formulate a joint, international strategy for saving this unique marine ecosystem

  11. Low frequency seabed scattering at low grazing angles.

    PubMed

    Zhou, Ji-Xun; Zhang, Xue-Zhen

    2012-04-01

    Low-frequency (LF) seabed scattering at low grazing angles (LGA) is almost impossible to directly measure in shallow water (SW), except through inversion from reverberation. The energy flux method for SW reverberation is briefly introduced in this paper. The closed-form expressions of reverberation in an isovelocity waveguide, derived from this method, indicate that in the three-halves law range interval multimode/ray sea bottom scattering with different incident and scattering angles in forming the reverberation may equivalently be represented by the bottom backscattering at a single range-dependent angle. This equivalent relationship is used to derive the bottom backscattering strength (BBS) as a function of angle and frequency. The LF&LGA BBS is derived in a frequency band of 200-2500 Hz and in a grazing angle range of 1.1°-14.0° from reverberation measurements at three sites with sandy bottoms. This is based on three previous works: (1) The closed-form expressions of SW reverberation [Zhou, (Chinese) Acta Acustica 5, 86-99 (1980)]; (2) the effective geo-acoustic model of sandy bottoms that follows the Biot model [Zhou et al., J. Acoust. Soc. Am. 125, 2847-2866 (2009)] and (3) A quality database of wideband reverberation level normalized to source level [Zhou and Zhang, IEEE J. Oceanic Eng. 30, 832-842 (2005)].

  12. Egypt and Red Sea

    NASA Technical Reports Server (NTRS)

    1982-01-01

    A panaramic view of eastern Egypt, The Red Sea and Saudi Arabia beyond (24.0N, 33.0E). In this desert country, where water is life, the high Aswan Dam and the impounded waters of the Nile River in the foreground assure water availability into the next century. The Red Sea beyond, part of the Suez Canal seaway, serves as a commercial link to the world and separates Egypt from Saudi Arabia.

  13. Analysis of sea level and sea surface temperature changes in the Black Sea

    NASA Astrophysics Data System (ADS)

    Betul Avsar, Nevin; Jin, Shuanggen; Kutoglu, Hakan; Erol, Bihter

    2016-07-01

    The Black Sea is a nearly closed sea with limited interaction with the Mediterranean Sea through the Turkish Straits. Measurement of sea level change will provide constraints on the water mass balance and thermal expansion of seawaters in response to climate change. In this paper, sea level changes in the Black Sea are investigated between January 1993 and December 2014 using multi-mission satellite altimetry data and sea surface temperature (SST) data. Here, the daily Maps of Sea Level Anomaly (MSLA) gridded with a 1/8°x1/8° spatial resolution from AVISO and the NOAA 1/4° daily Optimum Interpolation Sea Surface Temperature (OISST) Anomaly data set are used. The annual cycles of sea level and sea surface temperature changes reach the maximum values in November and January, respectively. The trend is 3.16±0.77 mm/yr for sea level change and -0.06±0.01°C/yr for sea surface temperature during the same 22-year period. The observed sea level rise is highly correlated with sea surface warming for the same time periods. In addition, the geographical distribution of the rates of the Black Sea level and SST changes between January 1993 and December 2014 are further analyzed, showing a good agreement in the eastern Black Sea. The rates of sea level rise and sea surface warming are larger in the eastern part than in the western part except in the northwestern Black Sea. Finally, the temporal correlation between sea level and SST time series are presented based on the Empirical Orthogonal Function (EOF) analysis.

  14. Contemporary sea level rise.

    PubMed

    Cazenave, Anny; Llovel, William

    2010-01-01

    Measuring sea level change and understanding its causes has considerably improved in the recent years, essentially because new in situ and remote sensing observations have become available. Here we report on most recent results on contemporary sea level rise. We first present sea level observations from tide gauges over the twentieth century and from satellite altimetry since the early 1990s. We next discuss the most recent progress made in quantifying the processes causing sea level change on timescales ranging from years to decades, i.e., thermal expansion of the oceans, land ice mass loss, and land water-storage change. We show that for the 1993-2007 time span, the sum of climate-related contributions (2.85 +/- 0.35 mm year(-1)) is only slightly less than altimetry-based sea level rise (3.3 +/- 0.4 mm year(-1)): approximately 30% of the observed rate of rise is due to ocean thermal expansion and approximately 55% results from land ice melt. Recent acceleration in glacier melting and ice mass loss from the ice sheets increases the latter contribution up to 80% for the past five years. We also review the main causes of regional variability in sea level trends: The dominant contribution results from nonuniform changes in ocean thermal expansion.

  15. Interferometric Rayleigh Scattering Measurement System

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel (Inventor); Danehy, Paul M. (Inventor); Lee, Joseph W. (Inventor)

    2008-01-01

    A method and apparatus for performing simultaneous multi-point measurements of multiple velocity components in a gas flow is described. Pulses of laser light are directed to a measurement region of unseeded gas to produce Rayleigh or Mie scattered light in a plurality of directions. The Rayleigh or Mie scattered light is collected from multiple directions and combined in a single collimated light beam. The Rayleigh or Mie scattered light is then mixed together with a reference laser light before it is passed through a single planar Fabry-Perot interferometer for spectral analysis. At the output of the interferometer, a high-sensitivity CCD camera images the interference fringe pattern. This pattern contains the spectral and spatial information from both the Rayleigh scattered light and the reference laser light. Interferogram processing software extracts and analyzes spectral profiles to determine the velocity components of the gas flow at multiple points in the measurement region. The Rayleigh light rejected by the interferometer is recirculated to increase the accuracy and the applicability of the method for measurements at high temperatures without requiring an increase in the laser energy.

  16. Neutrino Scattering from 12C

    NASA Astrophysics Data System (ADS)

    Hayes, Anna

    2017-01-01

    Neutrino scattering cross-sections from 12C, which have been measure for pion decay-at-rest and pion decay-in-flight neutrino energies, are difficult to reproduce theoretically. In this talk I discuss the physics issues involved and show the importance of a proper treatment of the conservation of the vector current.

  17. Electron Scattering and Nuclear Structure

    ERIC Educational Resources Information Center

    Trower, W. P.; Ficenec, J. R.

    1971-01-01

    Presents information about the nucleus gained by studies of electron scattering. Discusses what can be implied about the shape of the charge distribution, the nucleus positions, the vibrational modes of the nucleus, the momentum of the nucleus, and the granularity and core structures of the nucleus. (DS)

  18. Pauli Principle and Pion Scattering

    DOE R&D Accomplishments Database

    Bethe, H. A.

    1972-10-01

    It is pointed out that if the Pauli principle is taken into account in the discussion of pion scattering by complex nuclei (as it ought, of course, to be) some rather implausible consequences of some earlier treatments of this problem can be avoided. (auth)

  19. Measurement of backscattering from sea with an airborne radar at L band

    NASA Astrophysics Data System (ADS)

    Luo, Xianyun; Zhang, Zhongzhi; Yin, Zhiying; Sun, Fang; Kang, Shifeng; Wang, Laibu; Yu, Yunchao; Wen, Fangru

    1998-08-01

    Measurements of electromagnetic backscattering from sea surface at L band have been done with airborne side-looking radar system. Several flights are made for various sea states. Coherent radar data ta HH polarization and some truth data such as wave height, wind velocity and direction, temperature of sea water are recorded. Corner reflectors and active backscattering coefficient can be derived from the radar data and the cinematic data. The result presented in this paper include scattering coefficient and statistical analysis of radar echo with typical probability distribution functions such as Rayleigh, Weibull, Log-normal and K distribution.

  20. Alpha particle collective Thomson scattering in TFTR

    SciTech Connect

    Machuzak, J.S.; Woskov, P.P.; Rhee, D.Y.; Gilmore, J.; Bretz, N.L.; Park, H.K.; Aamodt, R.E.; Cheung, P.Y.; Russell, D.A.; Bindslev, H.

    1993-11-01

    A collective Thomson scattering diagnostic is being implemented on TFTR to measure alpha particle, energetic and thermal ion densities and velocity distributions. A 60 GHz, 0.1-1 kW gyrotron will be used as the transmitter source, and the scattering geometry will be perpendicular to the magnetic field in the extraordin