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Petrology, rock magnetism and stratigraphy of late quaternary Ice-rafted detritus at the southeast Grand Banks slope of Newfoundland, Atlantic Canada
No full textThe Quaternary sediments of the Atlantic Canada margin usually contain numerous evidences of paleoclimate oscillations. The short-lived, abrupt and episodic surges of sediment-laden armadas of icebergs calved from Laurentide Ice Sheet (LIS) into the North Atlantic Ocean via ice stream conduits has deposited ice-rafted detritus (IRD) all across the northern North Atlantic oceanic basin. Such events have had considerable impact on ocean water circulation system (i.e. Atlantic meridional overturning circulation – AMOC) and deep water formation owing to the huge influx of meltwater delivered by subglacial discharge and iceberg melting.
This catastrophic instability of the LIS has resulted in a stratigraphic sequence of detrital-rich Heinrich Layers (HL) during the cold phases of the Late Quaternary period. As IRD fragments are the direct evidence of the interplay between ice sheets and the North Atlantic Ocean, we still lack understanding of their hidden information on ice sheet dynamics, location of ice margins, the provenance and spatial dispersion of distinct terrigenous materials and the petromagnetic properties and contributions of different IRD species to magnetic HL records.
In this PhD thesis, I investigated a sediment core (GeoB 18530-1) acquired at the foot of
Southeast Grand Banks Slope of Newfoundland, that represents a continuous Late Pleistocene stratigraphic sequence of Heinrich Event layers 1 - 6 (H1 – H6). Discrete sample sets were taken at a very high resolution of 2 cm for various analyses including digital light microscopy, thin section petrography, X-ray fluorescence, rock magnetics, and grain-size sieving. In a first step of the thesis project, a total of 8243 coarse-grained (>1 mm) IRD particles were petrologically identified and their lithologies petrographically classified into 22 microscopically distinguishable categories. The abundances of these IRD lithologies were determined by counting individual particles at a high resolution of 2 cm steps throughout the continuous stratigraphic sequence of HLs (H1 – H6). This revealed the temporal and spatial change in the deposition of each IRD lithology. It was found that dolomitic IRD predominates the mid-part of all HLs whilst muscovite-biotite granite was found in greater abundance at the top and bottom of the HLs. Additionally, the statistical investigation of the count records of the 22 IRD lithologies manifested three well-defined groups based on whether their deposition is higher within HLs or interlayers or similar in both. Compositionally, it was found that H1, H2, H4, and H5 are kindred to each other while H3 and H6 are individually distinct. The second step of the thesis was an advancement of the finding from the initial part where the petrological information that was gleaned is used for magnetic analysis of particularly HLs and individual IRD lithologies. The pronounced magnetic susceptibility signal of HLs is usually intriguing compared to the interlayer units thus, it is momentous to discern the IRD lithology that influences the signal. Though, the >1 mm IRD underrepresents the total amount of IRD where finer grains are much more abundant, a lithology-specific identification can only be conducted using the coarser IRD fractions. From the magnetic properties of the coarse IRD it was found that out of the 22 different lithologies, as many as 16 possess a relatively lower
magnetic susceptibility than the background sediment. Only 6 IRD lithologies are typified by a higher susceptibility among which the muscovite-biotite granite is four-fold higher magnetic than the background. With the complementary XRF data is was revealed clearly that the viii susceptibility enhancement by the (K/Fe denoted) granite is partly compensated by the (Ca/Sr represented) dolomitic IRD. Therefore, with the muscovite-biotite granite being second in abundance to dolomitic IRD, it mainly controls the pronounced magnetic susceptibility signals of HLs. In modeling magnetic susceptibility based on coarse-grained IRD count data a misfit of the model was observed proposing that IRD sedimentation does not only occur through detritus rain-out from icebergs but rather through other transport processes like advection or gravitational flow, at least for the terminal part of the sediment’s trajectory.
Lastly, traditional magnetic susceptibility measurements are obtained in ways, where the
inhomogeneity of sediment records is mostly played down. This is because the sensor coils of whole-core magnetic susceptometers average signals over a large volume, thereby integrating the microscale susceptibility distribution over a considerable volume. Split-core susceptibility logs produced with a spot sensor at high resolution average the magnetic signal over a much smaller volume of a material. Using a novel protocol, this spot sensor technique provides the freedom to scan across an entire split core. By logging multiple parallel tracts at a high resolution of 1 cm along and between each tract, the derived contour plot reveals coarse IRD distribution, where the color spectrum denotes lateral variability in magnetic susceptibility
IPP-Info Ausgabe 21 "Innovative Lehre in Public Health und Pflegewissenschaft"
No full textIm Fokus unseres jährlich erscheinenden IPP-Info steht jeweils ein aktuelles Thema aus den Bereichen Public Health und Pflegeforschung. Daneben finden Sie in jeder Ausgabe Informationen zu den aktuellen Aktivitäten unserer Mitglieder in Forschung, Lehre und Transfer sowie Veranstaltungs- und Publikationshinweise. Herausgebende des IPP-Info sind die Mitglieder des Direktoriums des IPP, die Redaktion wird jeweils von einer/m Hochschullehrer:in bzw. vom Team einer Abteilung oder Arbeitsgruppe des IPP übernommen.18Ausgabe 21. Winter 202
How temperature shapes marine protist communities – Mechanistic assessment across seasonal and spatial scales
No full textGemeinschaften von Protisten spielen eine entscheidende Rolle in marinen Ökosystemen, da sie die Grundlage des marinen Nahrungsnetzes bilden, wesentlich zum Sauerstoffgehalt der Atmosphäre beitragen und einen wichtigen Teil biogeochemischer Kreisläufe darsellen. Anthropogene Einflüsse, einschließlich der globalen Erwärmung, können die Meeresumwelt erheblich beeinflussen und dadurch zu Veränderungen in der Zusammensetzung dieser Gemeinschaften führen. Angesichts der großen funktionellen Vielfalt innerhalb der Gruppe der Protisten kann dies erhebliche Auswirkungen auf das Ökosystem haben. Für die Vorhersage künftiger Ökosystemdynamiken ist es daher wichtig, zu identifizieren nach welchen Prinzipien sich diese Gemeinschaften verändern und reorganisieren. Obwohl sich Ökolog*innen seit einiger Zeit auf die Erwärmung der Ozeane konzentrieren, fehlt eine mechanistische Analyse der temperaturbedingten Veränderungen von Protistengemeinschaften in verschiedenen Systemen. Um diese Lücke zu schließen, untersucht die vorliegende Doktorarbeit die Reaktionen mariner Protistengemeinschaften auf Temperaturveränderungen und die damit verbundenen Ökosystemfunktionen systematisch, indem übergreifende Muster und systemspezifische Merkmale über verschiedene saisonale und räumliche Skalen hinweg ermittelt werden. Die Studie konzentriert sich auf zwei Regionen, die ozeanographisch miteinander verbunden und von der globalen Erwärmung besonders betroffen sind: den arktischen Ozean und die Nordsee.
Aufgrund der 'arktischen Verstärkung' erwärmt sich der arktische Ozean fast viermal so schnell wie der globale Durchschnitt. Darüber hinaus sehen sich die arktischen Protistengemeinschaften einer verstärkten Konkurrenz durch Organismen aus gemäßigten Breiten ausgesetzt, die mit den salzigeren und wärmeren Strömungen zunehmend aus niedrigeren Breiten in die Arktis eindringen – die sogenannte 'Atlantifizierung'. Nach einer übergreifenden Einleitung befasst sich Kapitel 2 daher mit den Auswirkungen der Erwärmung auf das Invasionspotenzial gemäßigter Arten. Dafür wurde eine Gemeinschaft aus einer Mischzone von atlantischem und arktischem Wasser bei unterschiedlichen Temperaturen inkubiert. Die Ergebnisse zeigen eine drastische Zunahme temperater Arten erst bei einer Erwärmung von 9 °C. Darüber hinaus zeigte sich für viele arktische Arten eine thermische Grenze zwischen 6 °C und 9 °C, was die Bedeutung der thermischen Historie für die Umstrukturierung von Gemeinschaften bei Erwärmung unterstreicht.
Die thermische Vergangenheit der Arten wurde auch als Hauptfaktor für die Umstrukturierung der Protistengemeinschaft in einer Frühlingsinkubation in der Nordsee identifiziert, sowohl für phototrophe (Kapitel 3.1) als auch für heterotrophe Organismen (Kapitel 3.3). Es zeigt sich, dass die Arten der gemäßigten Breiten deutlich höhere Temperaturen tolerieren, als ihre arktischen Artgenossen und ihre Diversität sogar bei Temperaturen von + 12 °C stabil halten. Obwohl die Shannon-Diversität der phototrophen Protisten durch Erwärmung insgesamt nicht beeinflusst wurde, veränderte sich ihre Zusammensetzung und die daraus resultierenden Ökosystemfunktionen. Erwärmung schwächte auch die trophische Kopplung (Kapitel 3.3) und erhöhte die Variabilität zwischen den Replikaten. Darüber hinaus führte die gleichzeitige Veränderung des N:P-Verhältnisses und der Erwärmungsrate zu teilweise umgekehrten Reaktionen hinsichtlich der Wachstumsrate der Gemeinschaft (Kapitel 3.2). Dies identifiziert Nährstoffe als potenzielle Modulatoren von Temperaturreaktionen und unterstreicht die Bedeutung eines geeigneten experimentellen Designs.
Um zu untersuchen, ob die identifizierten Mechanismen saisonal spezifisch sind oder ob die gleichen Muster im Sommer gelten und um die Auswirkungen kurzfristiger Schwankungen zusätzlich zur mittleren Erwärmung zu bewerten, wurde eine Sommergemeinschaft in der Nordsee einer marinen Hitzewelle ausgesetzt, sowohl unter Umgebungsbedingungen als auch unter einem potentiellen Zukunftsszenario (+ 3 °C, N:P-Verhältnis von 25, pCO2 von 1000 ppm). In der Sommergemeinschaft wurde die Anfälligkeit gegenüber abiotischen Veränderungen durch den trophischen Modus bestimmt (Kapitel 4.1). Die Studie ergab, dass die Vielfalt der heterotrophen Protisten gegenüber Hitzewellen resistent und gegenüber globalen Veränderungen weitgehend resilient war. Die phototrophe Vielfalt wurde jedoch von beiden Szenarien beeinflusst, was sich auf das gesamte planktonische Nahrungsnetz auswirkte (Kapitel 4.2). Insbesondere der Temperaturabfall am Ende der Hitzewelle übte einen starken Selektionsdruck auf die phototrophen Protisten aus, übereinstimmend mit den Reaktionen der Gemeinschaft auf die niedrigsten Temperaturen in den anderen Inkubationen (Kapitel 2 und 3). Trotz der unterschiedlichen Auswirkungen der Temperatur auf die heterotrophe und phototrophe Diversität änderte sich ihr relatives Verhältnis in allen drei Experimenten nicht, was den Vorhersagen der metabolischen Theorie der Ökologie widerspricht.
Zusammenfassend lässt sich sagen, dass diese Arbeit systematische Einblicke in die Temperaturreaktionen von marinen Protistengemeinschaften aus verschiedenen Lebensräumen bietet. Anhand der Ergebnisse von drei verschiedenen Experimenten konnte ich zeigen, wie wichtig die thermische Vergangenheit der Arten für die Umstrukturierung von Gemeinschaften ist. Die weltweit verbreitete Gattung Phaeocystis profitiert hauptsächlich bei mittlerer Erwärmung, während Kieselalgen diverse thermische Nischen besetzen, aber weniger konkurrenzfähig sind, wenn die Nährstoffe knapp werden. Der relative Beitrag dieser beiden Gruppen bestimmt die funktionelle Leistung in allen Experimenten, so dass der Grad der Erwärmung ein entscheidender Faktor für künftige Ökosysteme ist. Die Erwärmung des Ozeans wird sich wahrscheinlich besonders negativ auf die arktischen Frühlings- und gemäßigten Sommergemeinschaften auswirken, was an der Nähe dieser Lebensräume zur oberen thermischen Grenze der Arten liegt. Insgesamt unterstreicht diese Arbeit, wie wichtig es ist, Ergebnisse aus verschiedenen räumlichen und saisonalen Maßstäben zu integrieren, und verdeutlicht damit die Vorteile, die sich aus der Durchführung von gemeinschaftsweiten Studien ergeben könnten
Holocene and modern reef island dynamics in a monsoon-dominated setting: Carbonate sediments from the Spermonde Archipelago, Indonesia
No full textThis cumulative dissertation starts with a brief introduction to carbonate sedimentology, the current state of research in the field of reef islands and a presentation of the study area, before moving on to the three main chapters. Two of these main chapters contain studies on Holocene and modern island dynamics in the Spermonde Archipelago in the context of sea level fluctuations, changes in the monsoon system and ecological shifts in the sediment-producing biota. The third study highlights the influence of the monsoon on the facies distribution in seafloor sediments throughout the study area. The extended discussion summarizes the results from the two reef island studies, places their hypotheses in a broader context and establishes a connection to the implications from the seafloor sediment study. Finally, possible future research questions arising from the presented work are outlined
Groundwater pollution: occurrence, sources, behavior, transport and fate of mercury, benzene and nitrate in soil–groundwater systems in the Eastern Niger Delta, Nigeria
No full textThe Benin Formation aquifer in the eastern Niger Delta of Nigeria faces many threats from anthropogenic activities. These activities include indiscriminate sewage disposal, the usage of pit latrines, and several impacts of oil and gas activities capable of releasing various pollutants into the environment. The Benin Formation aquifer is the primary source of drinking water for most of the region. Hence, the release of pollutants into the aquifer may cause adverse health effects on the population. Despite the area's high level of anthropogenic activities, the sources and processes affecting various groundwater pollutants remain understudied. This study investigated, for the first time, the occurrence, sources, transport and fate of mercury, benzene and nitrate in the groundwater of the eastern Niger Delta, Nigeria. The investigation was conducted across five communities (i.e., Alesa, Ogale, Ebubu, Alode and Okochiri). Results may be transferable to other locations with similar incidences.
At a site impacted by crude oil refining in Okochiri, hydrocarbon contamination in the ground and drinking water was already known. However, the concentration, source, speciation and mobility of mercury (Hg), an oil refining byproduct, was unknown. To address this, groundwater at the impacted site was investigated. Hg levels in groundwater along the wastewater discharge outlet (WDO) of the refinery ranged from 0.2 and 6 µg/L. 63 % of the Hg occurred as Hg bound to particles larger than 0.45 µm (Hgpart). Operationally-defined Hg speciation shows that 33 % occurred as inorganic, reactive Hg2+, and 4 % as dissolved organic matter-bound Hg2+ despite the high DOC (up to 47 mg/L) and BTEX (up to 2,888 µg/L) levels, indicating that the DOC, which is mainly hydrocarbon, does not bind Hg. Overall, Hg levels in groundwater were elevated where oil and gas production wastewater was introduced into the aquifer.
The Hg concentration in sediments collected at the wastewater discharge point (WDP) was up to 529 µg/kg, and the carbon (C) content reached 40 %. The batch leaching experiments showed that up to 23.5 % of THg in the quartz-dominant sediment could be mobilized into groundwater under oxic conditions. In general, Hg retention in the sediment is controlled by the sediment’s natural organic matter (NOM).
The ground and drinking water in Alode, Ogale, and Okochiri, where several oil and gas production facilities are present, showed elevated BTEX levels, of up to 3,904 µg/L, 1,573 µg/L and 2,888 µg/L, respectively. Similarly, benzene levels were up to 3,500 µg/L, 1,300 µg/L and 2,700 µg/L in Alode, Ogale and Okochiri, respectively. Here, benzene was the dominant BTEX compound. DOC, which reflects the total hydrocarbon load in the groundwater, was up to 47 mg/L in Alode, 49 mg/L in Ogale and 33 mg/L in Okochiri. Benzene was detected in private supply wells (PSW) close to an underground petroleum pipeline passing through the three communities. Its concentration decreased with increasing distance from the pipeline, indicating probable leakage of petroleum from the pipeline into the aquifer.
The aquifer’s dissolved oxygen level (up to 7.5 (95 %) mg/L) and BTEX biodegradation capacity (up to 2.11 mg/L for DO) appear sufficient to support the BTEX degradation. However, the degradation may be weakened by the high groundwater temperature (32.5 °C). As a result, based on the calculated benzene (0.128 to 0.693) and BTEX (0.086 to 0.556) daily attenuation rates for this study, up to 66.5 years and 85 years would be required to attenuate benzene and BTEX. Thus, active remedial measures are required to reduce the time required for complete benzene attenuation in the affected groundwater.
Given the extensive animal husbandry, pit latrine usage, and indiscriminate municipal and domestic waste disposal practices, the groundwater and municipal sewage were investigated for nitrate (NO3−) in Alesa, Ogale, Ebubu, Alode and Okochiri. NO3− levels in the groundwater were highly variable: up to 142 mg/L in Alesa, 211 mg/L in Ogale, 120 mg/L in Ebubu, 55 mg/L in Alode and 10 mg/L in Okochiri. The major ion comparison showed that 71 %, 90 %, 87 %, and 92 % of the groundwater samples exceeded the reference site concentrations for Ca2+, Na+, K+, and Cl−, respectively, suggesting anthropogenic (sewage) influence. Similarly, the NO3−/Cl− ratio showed that 100 % (Alesa), 77 % (Ogale), and 84 % (Ebubu) of NO3− in the groundwater is derived from the ongoing anthropogenic activities (sewage). Furthermore, the isotopic evidence (15N-NO3− and 18O-NO3−) confirmed that the NO3− originates from sewage-derived NH4+ nitrification. Despite the high dissolved oxygen (DO) level, up to 8.9 mg/L, our results have shown evidence of denitrification in the area. This suggests that both biogeochemical processes occur simultaneously in the groundwater. However, the high DO and NO3− levels do not support a complete NO3− attenuation in the affected communities, hence the need for safe domestic and municipal sewage management practices. Consequently, there is a risk of NO3− export from shallow aquifers into the nearby surface waters in Okochiri and into the coastal ocean.
It can be concluded that the ongoing anthropogenic activities in the eastern Niger Delta have contributed a substantial amount of pollutants (i.e., mercury, benzene and nitrate) to the ground and drinking water at levels above the WHO guideline values. The (1) high concentration of the pollutants, (2) their continuous release into the aquifer, and (3) the impact of the high groundwater temperature on the prevailing redox conditions in the aquifer appear to weaken the natural attenuation of these pollutants from the aquifer. To protect the health of the growing population in the affected areas, measures to encourage immediate discontinuous use of the contaminated wells and alternative safe water sources (e.g., bottled, sachet, or a centralized water supply system) should be explored. Also, the local authorities need to implement measures to ensure a decline in the concentration of the investigated pollutants, including the remediation of the contaminated sediments and groundwater
Innovative Weiterbildung: Didaktisches-Design des SMALO Lern-Ökosystems
No full textEin vielfach beklagtes Problem ist die Intransparenz der Weiterbildungslandschaft und der marktförmig organisierte „Weiterbildungsdschungel“. Das Matching zwischen Weiterbildungsinteressierten und Weiterbildungsangeboten wird als problematisch wahrgenommen. Diese Problematik greift das Projekt SMALO auf und zielt auf die Entwicklung einer KI-basierten Weiterbildungsplattform im Sinne eines digitalen Lern-Ökosystems. Anspruch eines solchen virtuellen Lern- raums ist es, die differenten Einbettungs- und Handlungslogiken wie z. B. individuelle Motivation, betrieblicher Weiterbildungsbedarf, institutionelle Umsetzungsmöglichkeiten miteinander zu ver- knüpfen. Anspruch des SMALO-Lern-Ökosystems ist die Verbesserung der Transparenz innerhalb der Weiterbildungslandschaft in der Logistikbranche. Das Ziel ist es, am Beispiel der Logistikbranche, Adressat*innen und Akteur*innen in der beruflichen Weiterbildung stärker zu vernetzen und mittels einer KI-basierten Anwendung das Lernen zu personalisieren, individualisieren und zu flexibilisieren. Das vorliegende didaktische Design liefert durch die Zusammenführung der Ansätze von Arnold et al. (2019), Seufert (2018) und Reinmann (2015) die Rahmenbedingungen zur Gestaltung eines digitalen Lern-Ökosystems für die berufliche Weiterbildung am Beispiel der Logistikbranche.Bundesministerium für Bildung und Forschung (BMBF
Ranging with ultra-reliable and low latency mm-wave communication
No full textIn the face of growing demand, the way rail infrastructure is used must change. Although it is obvious that the infrastructure is underutilized, conventional safety systems and the lack of direct communication between trains are the main reasons for the limited use of railroad tracks. One of the applications that has the potential to enable a significantly more efficient use of railroad infrastructure is Automatic Train Coupling (ATC). ATC is a method for automatically coupling and decoupling train wagons. This can be done while one wagon is standing still or while both wagons are in motion. ATC has the potential to increase track utilization for passenger and cargo trains by allowing easy physical coupling of wagons when they occupy the same track block and decoupling when they otherwise do not.
The aim of this work is to address the theoretical and practical aspects of the realization of ATC. A wireless Train-to-Train (T2T) communication system capable of accurate ranging is required for the realization of ATC. To this end, standardized and non-standardized communication systems are analyzed and a communication system is recommended on the basis of the investigations. To evaluate the communication and ranging performance of the proposed communication system in realistic railroad environments, a measurement campaign was conducted with two train wagons. The measurement data was used to derive a channel model and thereby evaluate the performance of the communication system. Results from modelling ATC systems and their interactions show that using the proposed mm-Wave communication system and the proposed ranging estimation method allow a guaranteed safety integrity level SIL-4 throughout the ATC maneuver
Image Schemas, Cognitive Metaphor, and Film: Bridging Discourses
No full textThere has been active exploration of the role of cognitive metaphor theory and image schemas in the audiovisual analysis of film for a considerable time. Starting from primarily literary concerns, however, many of these remain interpretative in orientation. This means that likely metaphors, blends, and image schemas are proposed for pieces of film and adopted as scaffolds for largely discursive analysis. In the meantime, there has been considerable progress in refining the notion of image schemas and suggestions have been made both for logical formalisations of image schemes and for explicit connections to computational work and reasoning. Until now, these two areas of research involving image schemas have had little contact. In this position paper, I offer a brief review of the current state of the art in discussing film in terms of image schemas and metaphor and consider methods by which this could be brought together more closely with formal and computational accounts with benefits for both sides. As potential lines of development for the future, it is suggested that: (a) filmic representations may offer a highly appropriate method for depicting image schemas, and (b) we still need to consider formalisations of image schemas that directly engage with issues of first-person embodiment and simulation
Elucidating carbon flow in settling aggregates
No full textThe ocean inherits a major role in atmospheric CO2 drawdown. A key driver in carbon sequestration the biological carbon pump, where primary producers photosynthetically fix CO2 in surface waters, convert it into particulate organic forms and transport it into the ocean interior. The main fraction of the particulate organic carbon occurs in forms of sinking phyto- and zooplankton, detritus, zooplankton fecal pellets and microbes. When these marine particles coagulate, they form macroscopic aggregates. The formation of aggregates and the resulting specific sinking velocity are considered as key factors determining the efficiency of carbon export, whereby the sinking velocity defines the time an aggregate is exposed to mineralization and consumption processes, conducted by microbes and zooplankton. Within this thesis I investigated the process of aggregate formation influenced by nutrient availability, possible causes of episodic flux events and the overall carbon and nitrogen flow in the biological carbon pump
Large-scale multiple testing under arbitrary covariance dependency and topological data analysis for mass spectrometry imaging applications
No full textThis work addresses two highly relevant biomedical questions in the context of Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) data analysis. The first one involves discovering molecular masses that are highly associated with the outcome variable, describing cancer types or subtypes. The second task considered is tumor classification.
The thesis commences with Chapter 1, entitled Synopsis, which provides readers with motivation, presents an overview of the research methods employed, and outlines the remaining content of the thesis. The following two chapters deal with discovering the most associative explanatory variables by means of large-scale multiple testing under arbitrary covariance dependency among test statistics. In a nutshell, these frameworks approximate the false discovery proportion of a thresholding procedure for the marginal p-values. The false discovery proportion represents the proportion of false discoveries among all rejections.
Following this, Chapter 4 addresses the task of tumor classification. Briefly, it introduces a new approach to exploiting peak-related information in the context of MALDI data by employing reduced persistence transformation.
Chapter 5 serves as the concluding discussion of the thesis, drawing conclusions for each of the proposed frameworks, addressing computational challenges in the context of MALDI, outlining contributions, and suggesting future research directions