1,721,078 research outputs found
Biomarker indices and concentrations and biomarker-based temperature estimates from Iberian Margin cores MD99-2331, MD95-2040 and MD95-2042
No full textBiomarker metadata and data for cores MD99-2331, MD95-2040, and MD95-2042: depth, age, summed OH-GDGT, iGDGT, and di-unsaturated and tri-unsaturated C37 alkenone concentrations, OH-GDGT-based, iGDGT-based, and alkenone-based paleothermometric indices, GDGT-2/GDGT-3 ratio, and biomarker-based sea surface temperature (SST) and 0‐ to 200‐m sea temperature (subT; gamma function probability distribution for target temperatures with a = 4.5 and b = 15) estimates. The 1σ analytical uncertainties are 0.008 (0.5 °C) for RI-OH, 0.007 (0.2 °C) for RI-OH′, 0.003 (0.1 °C) for TEX86, 0.263 for GDGT-2/GDGT-3, and 0.010 (0.26 °C) for UK′37. RI-OH′-SST estimates are from the following global calibration: SST = (RI-OH′ + 0.029)/0.0422 (Fietz et al., 2020). RI-OH-SST estimates are from the following global calibration: SST = (RI-OH − 1.11)/0.018 (Lü et al., 2015). TEX86H-SST estimates are from the following regional paleocalibration: SST = 68.4 × TEX86H + 33.0 (Darfeuil et al., 2016). UK′37-SST estimates are from the following global calibration: SST = 29.876 × UK′37 − 1.334 (Conte et al., 2006). Bayesian calibrations were also used for TEX86-SST and TEX86-subT estimates (BAYSPAR; Tierney & Tingley, 2014, 2015) and for UK′37-SST estimates (BAYSPLINE; Tierney & Tingley, 2018). Core MD95-2040 UK′37 and summed di-unsaturated and tri-unsaturated C37 alkenone concentration data are from Pailler and Bard (2002). Core MD95-2042 UK′37 and summed di-unsaturated and tri-unsaturated C37 alkenone concentration data covering the 70–45 ka BP period are from Darfeuil et al. (2016). GDGT data for core MD95-2042 samples with TEX86 values below 0.4 are deemed anomalous and are thus excluded from any description and analysis. MIS, Marine Isotope Stage; DO, Dansgaard–Oeschger event; GS, Greenland stadial; H, Heinrich event; GDGT, glycerol dialkyl glycerol tetraether; and N/A, not available
Susceptibility measured on 13 sediment cores from METEOR cruise M12/1
No full textWährend der Meteor-Fahrt M12/1 wurden am gesamten gewonnenen Kernmaterial - Schwerelotkerne und Großkastengreifer - folgende sedimentphysikalischen Arbeiten durchgeführt: - Messung der Kompressionswellengeschwindigkeiten - Messung der magnetischen Suszeptibilität - Beprobungen für paläo- und gesteinsmagnetische Analysen
Messung der magnetischen Suszeptibilität
Wie in den vergangeneu Jahren wurden bereits an Bord die magnetischen Suszeptibilitäten der ganzen Kerne bestimmt. Es wurden sämtliche Schwerelotkerne sowie alle Stechrohre der Großkastengreifer mit einer Bartington Suszeptibilitätsmeßbrücke, Typ MS2.C, in Abständen von einem Zentimeter vermessen. Da nach den Erfahrungen früherer Fahrten im Arbeitsgebiet im allgemeinen sehr niedrige Meßwerte (0 bis 30*10-6 SI-Einheiten) zu erwarten waren, wurde dieses Jahr von Beginn an mit einer höheren Empfindlichkeit von 0,1*10-6 SI-Einheiten gemessen (früher 1,0*10-6 SI-Einheiten). Bei dieser Genauigkeit steigt allerdings die Meßzeit um einen Faktor 10 und der zeitliche Gerätegang ist nicht mehr zu vernachlässigen. Aus diesem Grunde wurde generell nach jeweils 10 Meßwerten eine Messung mit leerer Sonde durchgeführt und der dabei ermittelte Gang linear interpoliert zur Recluktion der Kernmeßpunkte verwendet
Physikalische Strukturen von Tiefseesedimenten des Südatlantiks und ihre Erfassung in Echolotregistrierungen.
No full textIn this thesis geophysical data from two RV METEOR cruises M 6-6 (1988) and M 9-4 (1989) in the Equatorial South Atlantic was used to investigate the genesis of reflections in analogue and digital echosounder records. Analogue black-white paper records of the PARASOUND echosounder system (Krupp Atlas Elektronik) enable a qualitative description of sedimentation- and erosion processes. Three profiles from the Western African continental rise show a decreasing sharpness of the reflection pattern with increasing biogenie productivity and sedimentation rate. Echosounder records from pelagic regions like Walfish Ridge, Angola and Guinea Basin, Mid-Atlantic Ridge and Brasil Basin show clearly stratified reflection patterns, interrupted by topographie highs.Measurements of sediment physical properties on gravity cores allow to calculate synthetic seismogramms and to compare them with analogue PARASOUND echograms and digital PARASOUND seismograms. Detailled core descriptions enable to evaluate the influence of lithologie variations on the reflection patterns in the echosounder records. Acoustic properties like acoustic impedance and reflectivity are mainly controlled by P-wave velocity and wet bulk density. Therefore the dependance of these two parameters on porosity, carbonate and sand content was investigated. Physical properties allow to distinguish between five types of sediment from different depositional environments (continental rise, oceanic highs, deep-sea basins).Terrigeneous turbidite layers produce strong reflection horizons in synthetic seismograms. Smaller variations of the acoustic impedance are caused by carbonate, silt or sand content. Since the carbonate content is linked to glacial/interglacial cycles, acoustic impedance and reflection patterns can contain paleoclimatic signals.Generally there is a good correlation between the synthetic seismograms and analogue and digital PARASOUND records. Additionally, synthetic seismograms and digital echosounder signals provide some semi-quantitative information relating to the amplitudes of reflections, whereas the PARASOUND paper records alone merely shows the energy distribution with depth above a certain threshold level.1
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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