46 resultados para Analytical geometry
Resumo:
Die erneute moorkundlich-pollenanalytische Bearbeitung Nordfrieslands galt u.a. der Klärung folgender Fragen: 1. Sind die in größerer Entfernung von der Küste gewonnenen Erfahrungen über den Verlauf der Waldgeschichte der Nacheiszeit ohne weiteres auf die Marschen zu Übertragen? 2. Welche Einflüsse der Meeresüberflutungen auf die Entwicklung der Moore und ihrer Vegetation lassen sich feststellen ? 3. Wie ist der zeitliche Ablauf der postglazialen Meeresspiegelschwankungen in Nordfriesland, und ist es möglich, Fehldatierungen auszuschließen, welche durch Abtragung, Umlagerung oder Durchmischung der in das Marschprofil eingeschlossenen pollenführenden Moorschichten bedingt sind?
Resumo:
It is well established that orbital scale sea-level changes generated larger transport of sediments into the deep-sea during the last glacial maximum than the Holocene. However, the response of sedimentary processes to abrupt millennial-scale climate variability is rather unknown. Frequency of distal turbidites and amounts of advected detrital carbonate are estimated off the Lisbon-Setúbal canyons, within a chronostratigraphy based on radiometric ages, oxygen isotopes and paleomagnetic key global anomalies. We found that: 1) Higher frequency of turbidites concurred with Northern Hemisphere coldest temperatures (Greenland Stadials [GS], including Heinrich [H] events). But more than that, an escalating frequency of turbidites starts with the onset of global sea-level rising (and warming in Antarctica) and culminates during H events, at the time when rising is still in its early-mid stage, and the Atlantic Meridional Overturning Circulation (AMOC) is re-starting. This short time span coincides with maximum gradients of ocean surface and bottom temperatures between GS and Antarctic warmings (Antarctic Isotope Maximum; AIM 17, 14, 12, 8, 4, 2) and rapid sea-level rises. 2) Trigger of turbidity currents is not the only sedimentary process responding to millennial variability; land-detrital carbonate (with a very negative bulk d18O signature) enters the deep-sea by density-driven slope lateral advection, accordingly during GS. 3) Possible mechanisms to create slope instability on the Portuguese continental margin are sea-level variations as small as 20 m, and slope friction by rapid deep and intermediate re-accommodation of water masses circulation. 4) Common forcing mechanisms appear to drive slope instability at both millennial and orbital scales.
(Table 1) Sample information and analytical data for bulk material with standard deviation (1 Sigma)
Resumo:
CHIM method involves extracting metal ions of electromobile forms in either anodes or cathodes, facilitated by a man-made electric field. This paper presents two newly developed CHIM alternatives that are electrified by a low voltage dipole. The firstly improved technique enables cationic ions to be extracted in a single cathode, whereas the secondly improved technique allows both anionic and cationic species to be extracted simultaneously in an anode and in a cathode. Compared with the traditional CHIM methods, the innovative techniques developed in this paper are characterized by simple instrumentation, low cost and easy operation in field, and in particular enables simultaneous extraction of anionic and cationic species of elements, from which more information can be derived with higher extraction efficiency. Field tests at several well-known mine areas in China confirm the effectiveness and efficiency of the new techniques in exploring for deeply buried ore bodies.