Entwicklung einer Bouillon-Mikrodilutionsmethode für die Biozid-Empfindlichkeitsprüfung von Bakterien:
Biozide sind für die Kontrolle bakterieller Krankheitserreger in vielen Bereichen wichtig. Es gibt zahlreiche Berichte über biozidresistente Bakterien und zudem können Biozide auch zur Entwicklung und Verbreitung von bakteriellen Krankheitserregern beitragen, die gleichzeitig gegen Biozide und antimikrobielle Wirkstoffe kreuzresistent sind. Es besteht daher die dringende Notwendigkeit, die Entstehung und das Ausmaß von Biozidresistenzen zu überwachen. Dafür sind standardisierte Methoden erforderlich, die reproduzierbare und vergleichbare Informationen liefern. Eine dazu geeignete Methode muss ein Hochdurchsatz-Screening ermöglichen, einfach anzuwenden sein und gleichzeitig sehr präzise Ergebnisse liefern. Hierbei ist nicht nur die Testmethode selbst zu berücksichtigen, sondern auch ein Verfahren zur Überprüfung der korrekten Inokulumdichte, die einen wichtigen Testparameter darstellt. Das Ziel dieser Studie war es, eine Bouillon-Mikrodilutionsmethode für die Biozid-Empfindlichkeitsprüfung zu entwickeln und zu untersuchen, ob die Bestimmung der Inokulumdichte während der Biozid-Empfindlichkeitsprüfung vereinfacht werden kann, ohne die Qualität der Ergebnisse zu beeinträchtigen. Zur Entwicklung der Bouillon-Mikrodilutionsmethode wurden mehrere Parameter untersucht, um die minimalen Hemmkonzentrationen (MHKs) für Benzalkoniumchlorid, Chlorhexidin, Glutardialdehyd (2-fache Verdünnungsreihe) und Isopropanol (2 %-Schritte) mittels Bouillon-Mikrodilution in sieben unabhängigen Tests zu bestimmen. Die Referenzstämme Staphylococcus aureus ATCC® 6538, Enterococcus hirae ATCC® 10541, Escherichia coli ATCC® 10536 und Pseudomonas aeruginosa ATCC® 15442 wurden mit Trypton-Soja-Bouillon als Testmedium untersucht. Die Mikrotiterplatten enthielten ein Endvolumen von 200 µL/Vertiefung. Es wurden vergleichende Studien durchgeführt, da bestehende Methoden für Biozid-Wirksamkeitstests und antimikrobielle Empfindlichkeitsprüfungen unterschiedliche Parameter verwenden. Um eine geeignete Bouillon-Mikrodilutionsmethode für die Biozid-Empfindlichkeitsprüfung zu entwickeln, wurde der Einfluss dieser verschiedenen Parameter eingehend untersucht. Die vergleichenden Untersuchungen umfassten die folgenden Parameter: (i) die Verwendung unterschiedlicher Subkulturen (1. oder 2. Subkultur, SK), (ii) unterschiedliche Arten der Inokulumsuspension (direkte Kolonie-Suspensionsmethode mit oder ohne Verwendung von Glasperlen), (iii) unterschiedliche Inokulumdichten, entweder gemäß DVG (Deutsche Veterinärmedizinische Gesellschaft e.V.) oder gemäß CLSI (Clinical and Laboratory Standards Institute) und (iv) Ablesen der Ergebnisse nach aerober Bebrütung bei 37 °C und drei verschiedenen Inkubationszeiten (24 h, 48 h und 72 h). Für jede Stamm-Biozid-Kombination wurden 168 MHK-Werte bestimmt. Insgesamt lagen die meisten Ergebnisse innerhalb ± einer Verdünnungsstufe vom am häufigsten gemessenen Wert, was als akzeptabler Bereich definiert wurde. Die Ergebnisse der vergleichenden Untersuchungen wurden auf ihre Stabilität hin bewertet, indem die Abweichungen vom akzeptablen Bereich berechnet wurden. Basierend auf den Ergebnissen wird folgendes Protokoll vorgeschlagen: Verwendung einer frischen Übernacht-Kultur (1. oder 2. SK), Herstellung der Inokulumsuspension über die direkte Kolonie-Suspensionsmethode mit oder ohne Glasperlen, Inokulumdichte gemäß DVG oder CLSI und Inkubation bei 37 °C für 24 h. Methoden zur Bestimmung der Inokulumdichte beziehen sich üblicherweise auf Zellzahlen und wurden für die Biozid-Wirksamkeitsprüfung durch die DVG und für die antimikrobielle Empfindlichkeitsprüfung durch das CLSI beschrieben. Um die beiden Methoden zur Zellzahlbestimmung vergleichend zu untersuchen, wurde jeder der vier Referenzstämme 28-mal mit der Inokulumpräparation nach DVG und CLSI vergleichend getestet. Die Ergebnisse wurden mit Hilfe von Bland-Altman-Plots und 95 %-Übereinstimmungsgrenzen statistisch ausgewertet und die Zellzahlen mit der optischen Dichte der verwendeten Bakteriensuspensionen korreliert. Die beobachteten Abweichungen zwischen den beiden Methoden lagen innerhalb eines log10-Schrittes und die gemessene Anzahl der koloniebildenden Einheiten unterschied sich nicht systematisch. Daher erwiesen sich beide Methoden als geeignet für die Zellzahlbestimmung. Die CLSI-Methode ist zu empfehlen, da sie weniger Verdünnungsschritte erfordert. Die vorgeschlagene Bouillon-Mikrodilutionsmethode für die Biozid-Empfindlichkeitsprüfung und die vorgeschlagene Methode für die Bestimmung der Zellzahl sind einfach durchzuführen und liefern stabile Ergebnisse, was die Biozid-Empfindlichkeitsprüfung von Bakterienisolaten erleichtern kann und somit einen Schritt in Richtung Harmonisierung darstellt.View less
Abdominelle Aortenaneurysmen (AAA) sind eine krankhafte Aufweitung der Aorta, die einen potentiell letalen Verlauf haben und im Falle einer Ruptur mit einer Letalität von über 70 % einhergehen. Obwohl bekannt ist, dass inflammatorische Prozesse eine zentrale Rolle bei der Entstehung und Progression von Aortenaneurysmen einzunehmen scheinen, ist die genaue Pathophysiologie weiterhin unbekannt. Ziel dieses Projektes war es, im Tiermodell den Effekt des anti-oxidativen therapeutischen Wirkstoffes Baicalein auf das AAA und die Inflammation zu untersuchen sowie den Einfluss einzelner inflammatorischer Signalwege bei der Entstehung des AAAs besser zu verstehen. Als Modell diente das etablierte AAA-Mausmodell, bei dem ApoE-/--Mäusen durch eine subkutan implantierte osmotische Pumpe (ALZET Modell 2004) über 4 Wochen Angiotensin II (1500 ng/kg/min) appliziert wird. Von den vier verwendeten Tiergruppen erhielten die Gruppen NaCl BAI- und NaCl BAI+ (n=10) physiologische Kochsalzlösung während die Tiergruppen Ang II BAI- und Ang II BAI+ (n= 30) Angiotensin II appliziert bekamen. Die Gruppen NaCl BAI+ und Ang II BAI+ bekamen zusätzlich täglich Baicalein (i.p. 1,5 mg/kg/Tag). Der Aorten-Diameter, die mittlere Fließgeschwindigkeit und der durchschnittliche systolische Spitzenfluss wurden wöchentlich duplexsonographisch gemessen. Nach dem Ende der Experimente wurde die Aorta entnommen, um anhand histologischer Färbungen die Mediadegeneration zu quantifizieren (Grad 0-III). Mittels histologischer und immunhistochemischer Färbungen erfolgte der Nachweis von Immunzellen sowie der Präsenz weiterer inflammatorischer Proteine in der Aortenwand. Zusätzlich wurde der Nachweis von apoptotischen Zellen im Aneurysma der Versuchstiere erbracht. Die Baicalein-Therapie hatte keinen signifikanten Einfluss auf die Gesamtmortalität, die Aneurysma-spezifische Mortalität, die Diameterentwicklung und die bei 30 Prozent liegende Inzidenz von Aneurysmen in der Verumgruppe. Die vorliegende Arbeit zeigte, dass bei einer Dosis von 1,5 mg/kg/Tag Baicalein keine signifikanten Effekte auf die Präsenz von inflammatorischen Proteinen im Aneurysma erkennbar sind. Trotzdem ist eine tendenzielle Abnahme bei der Inzidenz und der Aneurysma-spezifischen Mortalität ersichtlich. Zusätzlich deutet sich eine Wirkung von BAI auf die Degeneration der Media an. In Verbindung mit der Abnahme der AAA-Inzidenz und der Verringerung des AAA-Diameters in anderen Arbeiten weisen die Ergebnisse dieser Arbeit auf die Wirkung von Baicalein auf die AAA-Entwicklung hin.View less
River incision into bedrock is an important process in the context of landscape evolution. Climate can affect the river incision process in several ways. Firstly, precipitation is the main source of river discharge that is required to initiate the motion of river sediment and expose the riverbed to erosion. However, the relationship between river incision and river discharge is often non-linear, in that river discharge has to exceed a certain erosional threshold to mobilize bedload sediment and expose the riverbed to erosion. Whether this erosion threshold plays a significant role, or not, depends on the flux and grain size distribution of river sediment. Besides its effect on discharge, the climate’s influence on bedrock weathering also affects river incision, by changing bedrock erodibility as well as the grain size distribution of river sediment. Finally, climate sets discharge variability, which determines how often and by how much river discharge exceeds the erosion threshold. Discharge variability is typically high in arid regions, whereas river discharge is less variable in humid regions. Although it is evident that climate has an effect on river incision, studies that have investigated the effect of climate on 10Be-derived erosion rates – which in a steady state landscape equal river incision rates – have often found ambiguous relationships. This is most likely because other non-climatic factors (e.g., tectonic uplift rates, lithology, biota) interplay to obscure potential climatic trends.
In this PhD thesis, I investigate the role of climate on various aspects of the river incision process in the Coastal Cordillera of central Chile. I focus on regions that are underlain by similar granodioritic lithology, but are exposed to contrasting climate regimes (arid, semi-arid, mediterranean, and humid-temperate). Using this approach, I aimed to reduce the variations in non-climatic factors that may obscure the climatic effect on erosion and river incision processes. I used in situ cosmogenic-10Be in river sediment to quantify erosion and river incision rates. In situ cosmogenic 10Be is produced in quartz grains in the upper few meters of the earth’s surface by high energy cosmic rays. The 10Be concentration reflects the time that grains are exposed to cosmic rays, which is proportional to the residence time of grains in the surface layer (i.e., inversely to the erosion rate). As a result of this, cosmogenic-10Be is frequently measured in river sediment to constrain catchment average erosion rates, which in steady state landscapes should equal river incision rates.
In the first study (Chapter 3), I investigate grain size-dependent 10Be concentrations in river sediment. In most studies, the sand fraction of river sediment is used to measure 10Be-derived erosion rates, however, in catchments where 10Be concentrations vary between different grain size classes, this may result in biased erosion rate estimates. I investigate the controls of precipitation, hillslope angle, lithology and abrasion on grain size-dependent 10Be concentrations in Chile and in other landscapes around the world. I sampled 7 different grain size classes in 4 catchments located in the above-described climate regions in the Chilean Coastal Cordillera. The results reveal that regional precipitation regime affects grain size-dependent 10Be concentrations through its effect on 1) the depth of erosion processes, and 2) the depth of biotic soil mixing, which produces a constant 10Be concentration over depth. To put this in a broader perspective, I compiled 10Be concentrations across different grain sizes sampled at the same sample location for 73 catchments around the world. Based on this global compilation, I conclude that grain size-dependent changes in 10Be concentrations have a high likelihood of occurring in catchments with thin soil layers, where deep-seated erosion processes (e.g., landslides) excavate coarse grains from greater depth, where 10Be concentrations are lower. Typically, such catchment characteristics are found in landscapes that feature steep topography (>25°) and high mean annual precipitation rates (>2000 mm yr-1). I additionally find that the modification of the grain size distribution by fluvial abrasion can result in grain size-dependent 10Be concentrations. This mainly occurs in catchments with easily erodible lithologies and long sediment travel distances (>2300–7000 m, depending on lithology). I conclude that roughly 50% of the previously published 10Be-derived catchment average erosion rates potentially contain a grain size bias, because the catchments feature one or more of the catchment characteristics that can lead to grain size-dependent 10Be concentrations.
In the second study (Chapter 4), I investigated how climatic forcing can affect discharge variability, by studying El Niño Southern Oscillation (ENSO)-induced hydrological extremes along a climate gradient in central Chile (~28-42°S). This study focusses on discharge time series of 183 river catchments, that are located in the high elevation Andes and the low elevation coastal region, and feature different hydrological regimes: snowmelt-dominated (nival) versus rainfall-dominated (pluvial). The river discharge data shows that the hydrological response to ENSO differs strongly along the climate gradient and shows clear contrasts between basins with the nival and pluvial discharge regimes. The semi-arid region experiences the strongest river discharge anomalies during both El Niño (increasing discharge) and La Niña events (decreasing discharge), whereas the hydrological anomalies are the smallest in the humid-temperate region. Furthermore, the magnitude and frequency of extreme discharge events increases in the semi-arid and mediterranean regions during the warm and wet El Niño phase, whereas discharges in the humid-temperate region are most sensitive to rainfall deficits during La Niña events revealed by a higher frequency of low flow conditions. Snow dynamics introduce large contrasts in the hydrological response between basins with the nival and pluvial discharge regimes. First of all, snowmelt dynamics induce a delayed discharge peak. Snowmelt-dominated basins, experience the largest El Niño-induced discharge peak during the snowmelt season in summer, whereas the ENSO-induced climatic anomalies are most extreme during winter and autumn. Moreover, the discharge variability is lower for snowmelt-dominated basins because snowmelt produces non-flashy river discharge over a longer hydrological response time. Finally, basins with the nival-type of discharge regime are not as strongly affected by droughts than pluvial type of basins during La Niña, because snowmelt-generated runoff provides a minimum river discharge level. The results of this study reveal that ENSO-induced climatic and hydrological anomalies contribute strongly to the high discharge variability that has been observed in the semi-arid region. Which implies that ENSO has an important effect on river incision processes in the semi-arid region. Finally, I discuss the implications of the results of this study for water resource management in Chile.
In the next study (Chapter 5), I investigated long-term catchment average erosion rates in catchments along a climate gradient in Chile. I sampled ~10 catchments in three of the four climate regions (semi-arid, mediterranean, and humid-temperate). I specifically selected catchments that feature differences in normalized channel steepness (ksn) between the catchments, which is a topographic metric that reflects tectonic uplift rates in a steady state landscape. The 10Be-derived catchment average erosion rates revealed an increasing trend with ksn. Besides this, however, a secondary influence of climate was evident: the slope of ksn-erosion rate relationships was markedly steeper for the humid-temperate region compared to the semi-arid region. In other words, for a given normalized channel steepness index, the highest erosion rates were observed for the humid-temperate region and the lowest for the semi-arid region. I compiled and recalculated previously published 10Be-derived erosion rates of ~150 catchments in Chile to compare my results to the large-scale erosional dynamics in Chile. While my new results agreed well with published erosion rates from other catchments in the Coastal Cordillera, erosion rates in the Andes are higher, which I posit is due to higher precipitation rates and steeper topography. Where previous studies had difficulties with depicting a consistent climatic signal along the latitudinal gradient, new data analysis suggests, that the erosion rates in Chile reflect a combined tectonic and climatic signal, which agrees with my own data from the Coastal Cordillera. The large degree of scatter in the compiled dataset is likely induced by non-climatic factors (e.g., lithology or biota). I conclude that, in Chile, the erosional efficiency increases with increasing precipitation, which provides empirical evidence for the understanding that arid landscapes have to become steeper than humid landscapes to reach erosion rates that equal tectonic uplift rates in a steady state landscape.
In the final study (Chapter 6), I tested whether erosion thresholds, which are set by the amount and grain size of river sediment, play a significant role in the river incision processes in catchments in the Chilean Coastal Cordillera. I applied the stochastic-threshold stream power model, calibrated with field data, and compared the best fit model results to the 10Be-derived erosion rates and median grain sizes that I measured for each river catchment. The results reveal that erosion thresholds do play a role in the relatively gently sloping catchments of the Chilean Coastal Cordillera. A sensitivity test revealed that the modelled erosion rates of the semi-arid region rapidly decrease under erosion thresholds that are set by a grain size of > 1 cm. River incision still seems to occur in the humid-temperate region for erosion thresholds that are set by considerable grain sizes, but rapidly decrease for grain sizes of >10 cm. I conclude that in gently sloping basins the sensitivity of river incision rates to erosion thresholds strongly depends on river discharge, because the channel steepness is too low to facilitate the mobilization of river sediment. The results suggest that river incision occurs rather infrequently in the semi-arid region, whereas it occurs more continuously in the humid-temperate region. I have planned to further test the sensitivity of the model to input parameters and investigate the magnitude and reoccurrence time of river incision processes in the different climate regions of the Chilean Coastal Cordillera to validate these findings, and to better understand river incision processes in gently sloping landscapes. This is the first study that tests the threshold-behaviour of the process of river incision in gently sloping basins in regions that are exposed to different climates.
To conclude, in this PhD thesis I investigated the effect of climate on several aspects that are relevant in the process of river incision. This study contributes to the general understanding of the effect of climate on landscape evolution in gently sloping mountain ranges that cover roughly ~15% of the Earth's surface.View less
The international goods trade and passenger transport has caused a progressively severe problem with exotic mosquitoes reaching Europe and becoming invasive in many areas. These exotic mosquitoes may have the ability to transmit pathogens for a number of diseases affecting humans and other mammals, for which efficient vectors do not yet exist in the invaded area. Moreover, they can introduce the pathogens and trigger epidemics and epizootics that way. Climate change contributes to the fact that species adapted to tropical, subtropical and Mediterranean climates can increasingly establish themselves in Central Europe, while also dramatically increasing the risk of arbovirus-related disease outbreaks. The increased risk of infection is related in part to the virus incubation period, which is exponentially negatively correlated with the ambient temperature.
Due to the increased threat posed by the exotic mosquitoes, it is of utmost importance to map their expansion and to investigate their habitat preferences, dispersal behavior, population trends and vector potential. For this purpose, the monitoring project “CuliMo” and the research project “CuliFo” were founded, involving researchers from several scientific institutions in Germany. As a result of monitoring work and the citizen-based science project “Mückenatlas”, a large amount of mosquito species data are now available in a database. My goal was to develop modelling methods that make optimal use of the species occurrence data from this joint project database, as well as biological and ecological knowledge about the invasive species, in order to predict their current and future potential distribution in Germany.
The models were set up for the Asian bush mosquito (Aedes japonicus japonicus), a species that was first detected in Germany in 2008, and has since spread rapidly in many parts of the country from the multiple locations where it was introduced. Aedes j. japonicus is a potential vector species for a wide range of pathogens harmful to humans and animals. Some laboratory experiments have demonstrated high transmission efficiency for West Nile virus (WNV), which has been detected in mosquito populations in Germany since 2018, and has resulted in incidences of disease in birds, horses and humans. This dissertation describes a stepwise process of modelling the current and future ecological niche of the Asian bush mosquito in Germany as well as the generation of a flight model based on the created detailed habitat map, which is coupled to a WNV transmission model.View less
Campylobacter concisus impaired colonic epithelial sodium channel (ENaC) function with the transcriptional downregulation of regulatory ENaC subunits (-β and -γ). The activation of intracellular mitogen-activated protein kinase (MAPK) enzyme extracellular signal-regulated kinase (ERK) by C. concisus is ascertained as an intracellular cell signaling pathway in inducing ENaC dysfunction. The transcriptional upregulation of interleukin (IL)-32 plays a pivotal role in C. concisus-induced ENaC dysfunction as the bioinformatics prediction from ingenuity pathway analysis (IPA) identified IL-32 as a potential activator of the ERK signaling pathway. The increase in expression of tight junction (TJ) protein claudin-8 following steroid stimulation prevents paracellular back-leakage of sodium (Na+) ions absorbed by ENaC in colonic epithelium. Claudin-8 protein expression was decreased along with the subcellular redistribution off the tight junction (TJ) domain by C. concisus infection in the colonic epithelial cells stimulated by steroids. Therefore, claudin-8 disruption in the colonic epithelium is another cellular pathomechanism of C. concisus in the context of Na+-malabsorptive diarrhea.
The epithelial barrier dysfunction induced by C. concisus was more pronounced under the influence of immune response in the co-culture model of colonic epithelial cells and macrophages. The macrophage activation by C. concisus in the co-culture setup was accompanied by an increase in the release of proinflammatory cytokines, tumor necrosis factor (TNF)-α, IL-1β and IL-6. Concomitantly, the expression of TJ proteins occludin and tricellulin was decreased along with the subcellular redistribution of these proteins from the TJ domains. Moreover, C. concisus infection increased the flux of fluorescein (332 Da) in the monoculture and co-culture cell monolayers. In contrast, the flux of the macromolecule fluorescein isothiocyanate (FITC)-dextran (4 kDa) was increased only in the co-culture monolayers after infection. Furthermore, C. concisus induced epithelial apoptosis in the co-culture monolayers. However, the quantification data implied no significant difference in the apoptotic cell numbers between the infected monolayers in monoculture and co-culture conditions. Therefore, the epithelial apoptotic leaks and the functional loss of occludin by C. concisus infection contribute to the increase in the flux of small molecules as fluorescein (332 Da). However, under the regulatory influence of macrophage immune response, C. concisus additionally enhances the flux of macromolecules as dextran 4 kDa by the opening of the leak pathway through tricellulin disruption in the tTJ.View less
Die Hypocalcämie ist immer noch mit einem hohen Risikopotential für die Kühe nach der Kalbung und mit hohen Kosten durch die Behandlung und den Folgekosten verbunden. Trotz intensiver Forschungsarbeit sind immer noch nicht alle Zusammenhänge über die Entstehung von Hypocalcämien bei Milchkühen geklärt. Als eine der häufigsten Produktionskrankheiten ist es wichtig, Ansatzpunkte zu erforschen, die eine Möglichkeit bieten, der Hypocalcämie vorzubeugen. Dazu werden im Rahmen dieser Arbeit 109 pluripare Kühe der Rasse Holstein-Friesian im peripartalen Zeitraum betrachtet. Vor der Kalbung erfolgen die Untersuchungen ab 3 Wochen vor dem errechneten Kalbedatum montags und donnerstags um 6 Uhr im wöchentlichen Abstand. Direkt nach der Kalbung (Tag 0) findet eine Untersuchung statt und dann an den folgenden 3 Tagen täglich eine Untersuchung um 9 Uhr. Die Untersuchungen erfassen dabei den allgemeinen Gesundheitsstatus mittels einer Allgemeinuntersuchung und den Body Condition Score. Entsprechend dem Probenplan werden Blut- und Harnuntersuchungen sowie Rückenfettdickemessungen und Wägungen durchgeführt. Zusätzlich werden die Fütterungs-, Milchleistungs- und Krankheitsdaten erhoben. Die erfassten Daten werden unter Anwendung der Regressionsanalyse und dem Varianzmodell mit den Calciumkonzentrationen in Beziehung gesetzt. Die Calciumkonzentration im Serum nach der Kalbung wird von vielen verschiedenen Faktoren signifikant beeinflusst. Vor der Kalbung hat vor allem die Laktationszahl und die Futteraufnahme am Tag 1 a.p. eine Beziehung zu der Serumcalciumkonzentration nach der Kalbung. Mit zunehmender Laktationszahl steigt das Risiko nach der Kalbung eine Hypocalcämie zu steigen. Die Futteraufnahme um die Kalbung hat einen starken Einfluss auf die Calciumkonzentration. Je höher die Futteraufnahme in diesem Zeitraum ist, desto höher ist die Calciumkonzentration im Serum nach der Kalbung. Nach der Kalbung zeigen die Ohrtemperatur, die Pansenfüllung, die Futteraufnahme, die Calciumkonzentration, die Phosphorkonzentration und die Magnesiumkonzentration im Serum eine signifikante Korrelation mit der Calciumkonzentration im Serum p.p. Vereinzelt treten noch Zusammenhänge mit anderen Laborwerten auf. Diese sind aber nicht sehr signifikant. Wärmere Ohren und eine stärkere Pansenfüllung haben einen positiven Effekt auf eine höhere Calciumkonzentration p.p. Eine Beeinflussung durch Medikamente ist nur begrenzt möglich. Ein Zusammenhang mit der Witterung konnte nicht hergestellt werden. Durch die geringe Variabilität der DCAB konnte in dieser Arbeit kein Zusammenhang mit der Calciumkonzentration hergestellt werden, des Weiteren wird der Einfluss durch die Fütterungselemente durch die Futteraufnahme überlagert. Die Futteraufnahme zeigt ab Tag 1 a.p. einen Zusammenhang mit den Calciumkonzentrationen im Serum. Die Messwerte von Calcium, Phosphor und Magnesium im Serum beeinflussen die Calciumkonzentration im Serum p.p. entweder nur am selben Tag oder maximal ein Tag im Vorhinein. Dabei sind die Calciumkonzentrationen untereinander sowie mit den Phosphorkonzentrationen positiv miteinander korreliert. Im Gegensatz dazu zeigt sich zwischen den Magnesiumkonzentrationen mit den Calciumkonzentrationen eine negative Korrelation. Mittels der Parameter des roten Blutbildes a.p. und der Harnuntersuchung wird die Calciumkonzentration im Serum p.p. nicht stark beeinflusst.View less
The Economy for the Common Good (ECG) is a social movement that claims that all economic activity should serve the common good. The common good balance sheet (CGB) developed by the movement is a corporate social responsibility (CSR) management tool that tracks the socio-ecological commitment of a company in a comparable way. Addressing the lack of research on the common good approach in entrepreneurial practice and its potential impacts on macro and micro levels, I surveyed 332 employees from companies that joined the ECG and conducted eleven interviews with ECG company representatives. Our results show that in their management practices, the companies are guided by values such as transparency, democracy, diversity, independence, cooperation, fairness, and ecological sustainability. This is exemplified by a high degree of corporate transparency, democratic ownership and decision-making structures, cooperative trade relations, the redistribution of surpluses and a preference for local and socio-ecological suppliers. The common good orientation is intrinsically motivated and part of the core business. In single owner companies it is anchored in a top-down direction via a delegation system, while it is implemented bottom-up in a company’s self-conception as a socio-ecological collective. The companies studied are willing to accept profit setbacks in order to implement their socio-ecological principles. Among the companies, I identified examples of sufficiency-oriented practices.Some companies in my sample do not aim to grow, while others consider further company growth to be necessary. Due to the interaction of their re-evaluation in values, reconceptualisation, restructuration and relocalisation of corporate structures and business practices, redistribution of power and reduction of their environmental impact they bear the potential to contribute to a societal transition towards degrowth. The more common good oriented a company acts, the more CSR is perceived by employees, and the more satisfied employees declare themselves with their jobs. With increasing fair distribution of work and higher workplace quality, employees experience fewer job demands. Furthermore, workplace quality positively influencees the perceived support from the company. While the fair and transparent distribution of income has a correlation on pay level satisfaction, I could not prove an effect between the public welfare-oriented investment of profits on pay level satisfaction. The value and social impact of products and services is related to the perceived meaningfulness of work, but has no influence on the extent to which employees identify with their companies. However, employees in companies with high transparency and co-determination identify better with their companies. I also found that employees are more willing to take on tasks that are not part of their official job description but serve the company if the company is cooperative with other companies. However, the outward cooperative behaviour of the company has no influence on whether employees behave cooperatively with each other. The scoring of the CGB so far includes only few aspects that explain differences in job satisfaction between the companies; a circumstance that should be remedied in the further development of the CGB. Overall, I conclude from my study that the ECG has the potential to promote the sustainability transformation of the economy, as it connects, strengthens and makes visible pioneers of socio-ecological change.View less
While technological improvements enable the production of a myriad of new products, assuring consumer safety has become an essential preoccupation for authorities. Indeed, consumers are potentially exposed to chemical risks with health consequences upon product usage. Polymer-based products have proliferated around the globe in the last decades and are appreciated for their cheap and flexible usage. However, they also often release hazardous substances that may be ingested, dermally absorbed or inhaled. This thesis focuses on the emissions of volatile organic compounds (VOCs) from plastic-based and wooden consumer products such as toys. Exposure data to apprehend the risks arising from such articles are scarce although the affected consumer group of children represent a vulnerable population. This data gap on exposure assessment is largely due to a lack of adequate analytical methods. Strategies existing for emission measurements from construction products are unsuitable for consumer products: Large emission test chambers (50 L to 20 m3) are not adapted to consumer product size. Alternative and more economical methods such as dynamic headspace (DHS, 20 mL or 1 L), microchambers (44 or 114 mL), glass chambers (24 L) and the flask method were investigated in this thesis. DHS sampling allowed semi-quantitative emission results and was further used for sample pre-selection. Both microchambers and 24 L glass chambers provided results that correlate with bigger emission test chambers: These devices would be suitable for market surveillance. The standardized flask method for formaldehyde emissions from wooden toys was not appropriate for exposure assessment. Furthermore, an assessment of the potential exposures from polymer-based consumer products was carried out. First, the samples were selected via DHS sampling and the constituting polymers were characterized. Then, the high-emitting samples were studied in conventional emission test chambers, 24 L glass chambers or microchambers. An exposure assessment was performed considering indoor air scenarios for short-term (a few hours) to long-term (28 days) exposure. Results were compared to existing toxicologically based guideline values. Emitted concentrations from single products do not typically exceed thresholds. However, scenarios with numerous products or smaller breathing zones are more concerning. Indeed, the cyclohexanone guideline value was exceeded during the study of the exposure from costume masks investigated with a doll’s head setup. This work is the first to systematically examine strategies for inhalation exposure assessment in official control laboratories. The exposure assessment data generated in the frame of this thesis give insights in the possible health risks associated with the use of polymer-based consumer products.View less
In the liver, as an important metabolic organ, a large number of complex signaling pathways occur, often simultaneously. Not only hepatocytes are involved in these signaling pathways, also Kupffer cells, the largest population of liver macrophages, are part of these pathways. In this work, structure-dependent molecular cell responses were established based on the adverse effects of bisphenol A and its derivatives in the hepatocyte-like cell line HepG2 indirectly co-cultured with the differentiated macrophage-like cell line THP-1 cells. The causal relationship between the effects of two additional methyl groups in bisphenol A and the depolarisation of the mitochondrial membrane, along with subsequently induced intrinsic apoptosis, has been shown. This adverse effect of the additional methyl groups could be detected through the increased secretion of the prognostic factor TNF α in the cell culture system. So, there is evidence that increases in TNF-α secretion mirrors a potentially increased chemical sensitivity in the indirect co-culture of the cells investigated. Based on the data of this work, this increased sensitivity is correlated with the increased expression and activity of metabolizing enzymes (e.g., cytochrome P450-dependent monooxygenase 1A1) and the accelerated β-oxidation of intracellular fatty acids, which results in the reduction of intracellular lipid droplets. All of these changes are due to the pro-inflammatory influence of the differentiated THP-1 cell line. Its secretion of soluble factors (e.g., cytokines) initiates certain signaling pathways. By looking into the correlation networks of these cytokines, an additive effect of the two cell lines used in this co-culture becomes obvious. However, when this indirect co-culture is replaced by using more primary cells, such as primary human immortalized hepatocytes (Fa2N-4) and primary human monocyte derived macrophages (MDM), cytokine-dependent cell-cell communication can be observed in the correlation network as well. The “inflammatory status” of the system can be influenced by the ratio of MDM to Fa2N-4 cells. For instance, an increase in the MDM cell number is associated with altered gene expression (based on transcriptome data of Fa2N-4 cells) related to an acute phase reaction. The cell system established in this work responds to the treatment with pharmaceuticals such as diclofenac and adalimumab, and to lipopolysaccharides, in terms of altered cytokine secretion. Parallels to the in vivo situation can be seen here. In conclusion, the present work provides evidence for an increased chemical sensitivity of HepG2 cells when growing in an indirect co-culture system along with THP-1 cells. Furthermore, it could be shown that indirect co-cultivation of Fa2N-4 cells and MDM would be advantageous in the detection of chemical-induced adversity in liver cells.View less
Die empirisch-quantitative Arbeit befasst sich explorativ mit der Umweltberichterstattung der Medien und ihren Mustern der Nachrichtenauswahl und -verarbeitung. Dabei spielt die geringere Medienwirksamkeit seit Wandel der Problemstruktur eine wichtige Rolle (fort von eher sichtbaren Problemen bzw. unmittelbaren Gefahren, hin zu schleichenden, langfristigen Problemen). Mittels Inhaltsanalyse von Qualitätszeitungen wurden die Muster der Umweltberichterstattung ermittelt (Frankfurter Rundschau, Süddeutsche Zeitung, Frankfurter Allgemeine Zeitung und Die Welt in einer für 2005 repräsentativen Zufallsstichprobe; 583 Artikel). In einem weiteren Schwerpunkt wurden mittels Medienresonanzanalyse (I-O-Analyse) Restriktionen und Erfolgsbedingungen medialer Umweltkommunikation ermittelt. Dabei wurde die Nachrichtenauswahl v.a. mittels Nachrichtenwerttheorie (Nachrichtenfaktoren) und der Umwelt-PR von Bundesumweltministerium und Umweltwissenschaft als Medieninput analysiert. 60 Pressemitteilungen riefen in einer Stichprobe div. Medienarten 60 Medienbeiträge hervor (2007/8). Die Inhaltsanalyse zeigte (auf Basis der normativen Heranziehung der umweltpolitologischen Literatur) beträchtliche Defizite der Umweltberichterstattung. Auch die Gesamtrelevanz der Nachrichtenwerttheorie beim Themengebiet Umwelt/Nachhaltigkeit fiel eher mäßig, wenngleich offenkundig aus (Gültigkeit der Nachrichtenwerttheorie abhängig von der Thematik). Die herausgearbeiteten Restriktionen medialer Umweltkommunikation erwiesen sich als relativ stark; Erfolgsbedingungen betrafen nachhaltigkeitsrelevante Themen eher am Rand. Speziell Wissenschaft, zunehmend wichtig etwa als nachhaltigkeits-/klimabezogene Wissensgrundlage, fand sehr begrenzt systematische Medienaufmerksamkeit (Medienresonanz). Auch Umweltthemen wachsender Bedeutung (schleichende Belastungen, Erneuerbare Energien, „Industrieller Stoffwechsel“) in Pressemitteilungen wurden meist nicht in Artikeln verarbeitet. Die PR zu Nachhaltigkeitsstrategien, der Begriff selbst und div. SD-Konzepte wurde ebenfalls selten zu Medienthemen; u.a. die Popularisierung von Nachhaltigkeitspolitik stark erschwerend. Ein massives (PR-)Angebot umweltbezogener Lösungen seitens der Umweltakteure stieß auf konträre mediale Selektionsmuster („Only bad news are good news“), so dass offenbar beträchtliche Inkompatibilität besteht. Gemäß ihrer Blattrichtung wiesen die Qualitätszeitungen zudem News Bias auf: FR, SZ und FAZ (grob dem politischen Spektrum von links nach rechts entprechend) berichteten in deutlich abnehmender Häufigkeit über Umwelt. Zudem stellten FR und SZ Branchen häufiger als Verursacher von Umweltbelastung dar als die konservative FAZ / Welt. Ergänzend wurden praxisbezogene Verbesserungen medialer Umweltkommunikation untersucht. Dabei ging es um Umwelt-Selbstverpflichtungen in der Medienbranche und um den gezielten und kreativen Einsatz von Nachrichtenfaktoren in der Umwelt-PR.View less
Mediterranean-type ecosystems (MTEs) are among the global biodiversity hotspots most vulnerable to multiple factors of global change, such as climate warming and elevated atmospheric CO2. Global change is likely to exacerbate current ecosystem degradation in MTEs, with severe consequences for the long-term provision of multiple ecosystem services on which people depend, such as carbon sequestration, water and nutrient supply. Ecological restoration is increasingly aimed at counteracting the decline and improving the long-term provision of multiple ecosystem services. For successful restoration, however, ecologists require a fundamental understanding of the link between vegetation composition, related functions and services, and influencing environmental factors. Measurable traits of plant species such as specific leaf area have been recognized as a quantifiable link between vegetation composition and ecosystem functions underlying ecosystem services. Given this link, restoration can select plant species based on their traits in order to improve desired ecosystem functions. In this thesis, I aimed at assessing the linkage between plant traits and the provision of multiple ecosystem functions, as well as trade-offs among these functions under the influence of multiple changing environmental factors, to support the restoration of degraded MTEs towards multifunctionality world-wide. Through a literature review, I found that current trait-based research lacks a complete understanding of the combined effects of multiple environmental factors on the long-term provision of multiple ecosystem functions and a quantification of the trade-offs and synergies among these factors. To address this gap, I proposed a theoretical framework that complements trait-based empirical research with process-based simulation modelling. Based on this framework, I successfully developed the individual- and trait-based simulation model ModEST (Modelling Ecosystem Services and Functions based on Traits) that calculates the coupled dynamics of soil water, soil nutrients, and individual woody plants characterized by traits. ModEST allows quantification of ecosystem functions for a given planted trait composition over time under varying environmental conditions. As a first step, I supplemented a large-scale restoration project in Western Australia (called the Ridgefield Experiment) by evaluating all possible combinations of plant species locally available for restoration under both current and future climatic conditions using ModEST. The simulation results revealed that multifunctionality was increased by higher levels of planted species richness under current, but not under future climatic conditions. In general, multifunctionality could not be fully achieved because of trade-offs among functions that were attributable to sets of traits that affected the functions differently. Trade-offs and synergies among functions shifted with climate change as a result of differential direct and indirect impacts of environmental factors on functions. To understand how the link between plant traits and functions found in Ridgefield, as well as trade-offs and synergies among functions, can be applied to other Mediterranean-type ecosystems, I applied ModEST to several abiotic and biotic conditions found in Mediterranean-type ecosystems across the globe. Specifically, I simulated a full-factorial design of all possible combinations of six plant functional types, constructed from trait values of woody Mediterranean plant species, and various abiotic settings (i.e. mean annual precipitation, mean annual temperature, solar radiation, and soil texture) characteristic of the Mediterranean biome. I found that the maximization of multiple functions achieved by particular plant trait compositions as well as trade-offs among the maximized functions were dependent on the abiotic context. I could show that plant traits alone affected by the environment were not fully responsible for the differences in the functioning but that additionally abiotic conditions in interaction directly shaped ecosystem functioning. With this work, I have shown that there is a clear linkage between multiple environmental factors that directly and indirectly, via changes in plant traits, affect multiple ecosystem functions in MTEs, as well as trade-offs and synergies among them. My findings imply that restoration ecologists face a significant challenge in achieving their long-term multifunctionality goals in degraded MTEs across the world. I demonstrated that an integrated trait-based empirical and simulation modelling approach can unravel the complex multi-layered relationship of multiple plants traits on ecosystem functioning affected by the abiotic environment to support restoration towards multifunctionality in MTEs if not globally.View less
Since the beginning of the 21st century, a renaissance of photochemistry has led to the development of new synthetic methods that use light as a sustainable reagent to achieve organic transformations. In particular, photocatalysis allows to harvest visible light and activate reagents and intermediates by means of catalytic amounts of a suitable chromophore. Due to the presence of heteroatoms in multiple natural products and active pharmaceutical ingredients, methodologies for the formation and cleavage of carbon-heteroatom bonds are highly valuable in synthetic organic chemistry. Cross-couplings are among the most powerful tools available to the synthetic organic chemist, enabling strategic bond constructions. Previously dominated by transition metal catalysis, crosscoupling reactions were revolutionized by photochemical approaches (Chapter 2). Photocatalysis allows to initiate radical couplings by selective reduction or oxidation of the coupling partners under mild reaction conditions. Alternatively, a photocatalyst (PC) can be used to regulate the reactivity of a transition metal catalyst. Photochemical strategies that do not require a PC rely on photoactive starting materials or formation of electron donor-acceptor complexes or catalytic intermediates that can be activated with light. Nickel is an appealing, sustainable alternative to palladium in transition metal-catalyzed crosscouplings, but the reaction of aryl halides and nucleophiles is hampered by the stability of nickel(II) intermediates. Visible light irradiation and a photocatalyst can enable nickel-catalyzed cross-coulings. While most dual nickel/photocatalytic methods rely on homogeneous iridium or ruthenium-polypyridyl complexes as photocatalysts, semiconductor materials emerged as sustainable, inexpensive alternatives. Carbon nitrides are a class of metal-free semiconductors that can be prepared from inexpensive, abundant commodity chemicals and absorb visible light. The carbon nitride CN-OA-m was combined with nickel catalysts to promote carbon–heteroatom cross-couplings. Aryl iodides and carboxylic acids are coupled using a combination of a nickel(II) salt, a bipyridyl ligand, CNOA-m and visible light irradiation (Chapter 3). The same approach was later extended to the coupling of aryl bromides with alcohols and aryl iodides with thiols (Chapter 4). The heterogeneous CN-OA-m is straightforward to separate from the reaction mixture and was reused several times without loss in reactivity. The ligand 5,5’-dicarbazolyl-2,2’-bipyridyl (czbpy) forms nickel complexes that absorb visible light up to 450 nm. A complex prepared in situ from NiCl2·glyme and czbpy can promote the coupling of aryl iodides with sodium sulfinates, carboxylic acids and sulfonamides under blue light irradiation, without an additional photocatalyst (Chapter 5). Polymerization of czbpy resulted in a polymeric ligand network that enables immobilization of nickel. The heterogeneous material catalyzes carbon–heteroatom cross-coupling under visible-light irradiation and was recycled multiple times. Benzyl ethers are convenient protective groups in carbohydrate chemistry due to their high stability. Harsh reaction conditions required for their cleavage by catalytic hydrogenation, Birch reduction or ozonolysis have poor functional-group compatibility and limit their use. Visible-light photocatalysis using iridium-polypyridyl complexes or organic dyes as PC are suitable for the cleavage of electron-rich para-methoxy benzyl ethers but do not affect benzylic ones. Upon visible light irradiation, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) forms a highly oxidizing triplet state that can cleave benzyl ethers. Combinations of DDQ and tert-butyl nitrite in presence of air catalyze the selective, oxidative cleavage of benzyl ethers in carbohydrate structures in presence of many other common functional groups (Chapter 6).View less
This research presents a multi-scalar work on the effects of human disturbance on high Andean forests in Colombia. It focuses on the analysis of vegetation composition and structure and on the dynamics of forest cover change and connectivity through time in selected localities around Bogotá. Additionally, a distribution model exercise is carried out to further the understanding of the environmental constraints driving the present distribution of a distinctive Andean treeline species and to examine its response to climate change in the future. High Andean forests are a unique and highly biodiverse ecosystem, located at high elevations in one of the world’s biodiversity hotspots, the Tropical Andes. Unfortunately, these forests are extremely fragmented and particularly vulnerable to climate change. Despite the fact that they provide essential ecosystem services to neighboring high Andean cities, such as the capital of Colombia, Bogotá, overall, high Andean forests have been poorly studied. Their fragility and their great value in terms of environmental services, together with their outstanding diversity, make them ecosystems with high priority for conservation. Nevertheless, especially around Bogotá, the vegetation studies carried out often have been rather circumscribed, rarely incorporating more complex parameters such as landscape fragmentation and anthropic disturbance metrics nor assessing functional and phylogenetic diversity attributes and ecosystem services. Also, there is a lack of studies that consider multiple vegetation strata at once and that address long-term changes in the extent and structure of high Andean forests, pairing plot-based work with forest cover change analysis. Lastly, few efforts have been made so far to model the response to climate change of high Andean forests and their species. Investigating these aspects could provide meaningful insights into species’ responses to anthropic influences and community assembly mechanisms, broadening our understanding of high Andean forests and strengthening strategies to conserve them. The aim of the present study is to explore the relationship between human disturbance and the condition of high Andean forest in the surroundings of Bogotá, the growing capital city of Colombia. Therefore, three parallel approaches were developed and implemented. On one hand, permanent plots establishment and plot-based fieldwork was carried out in several localities in the surroundings of Bogotá. Here, tree viii layer and understory vegetation were assessed and analyzed in terms of their taxonomic, functional and phylogenetic diversity, but also as to their structure and above-ground biomass production. A broad array of environmental factors and anthropic disturbance-related indicators was compiled and subsequently used to characterize the tree layer and understory plant communities using a cluster analysis in combination with ordination techniques (Non-metric Multidimensional Scaling and partial Redundancy Analysis). Finally, environmental and disturbance predictors were related to tree and understory diversity metrics and above-ground biomass by means of Generalized Linear Models (GLMs). As a result, a noticeable effect of anthropic related predictors on both tree and understory layer community composition and also a direct negative effect on tree layer diversity and above-ground biomass production have been documented. On the other hand, a thorough analysis of aerial pictures from the studied localities of the first study has been conducted, covering the period between the 1940s to early 2000s, in order to deepen the understanding of the history of forest fragmentation in the area. The images were classified into three land cover classes (Forest, Grasslands and Bare ground), utilizing texture analysis and object-based image segmentation. Then, the extent of forested areas was assessed through time. Additionally, forest connectivity metrics were calculated by performing a Morphological Spatial Pattern Analysis (MSPA) and correlated with the forest cover dynamics over the same period. For the period 1940-2000, in all except one of the studied localities a general restoration of forest cover and connectivity was determined. The highlighted forest cover and connectivity trends were related to the individual history of each locality in terms of population displacement and urban expansion. Lastly, to further expand the geographical and temporal coverage of this study, species distribution models were performed for Weinmannia fagaroides (Cunoniaceae), a tree species that was found to be distinctive of the higher elevation forest fragments that were studied in this project. This species is found throughout the Central and Northern Andes, and is a typical component of high elevation treelines, ecotonal zones that are believed to be highly vulnerable to climate change impacts. The main aim was to understand which are the focal drivers of the current distribution of W. fagaroides, and to hypothesize its response to climate change in the future. At the same time, a comparison of the efficacy of environmental predictors pertaining to three different climate datasets (Chelsa 1.2, Worldclim 1.4 and Worldclim 2) and of ix three different modelling algorithms (GLMs, Random Forests - RF, MaxEnt) was carried out for predicting the current distribution of W. fagaroides. The current species distribution was found to be driven mostly by one temperature, one precipitation and one soil-related variables. In regards to the performance of the three different climate datasets no significant difference was found, although Chelsa 1.2 retrieved slightly higher model evaluation scores. As to the algorithms, RF and MaxEnt retrieved the highest model evaluation scores. Moreover, the modeled distribution of W. fagaroides was predicted to decrease by 38% and to shift towards higher elevations in the period 2060-2080 for a high CO2 emission scenario. Considering that at present only around 22% of the modeled species distribution is situated in protected areas, an adaptation of currently implemented conservation efforts is strongly recommended to protect this and other fragile high Andean treeline species. Overall, this study contributes to the characterization of forest fragments in the vicinity of Bogotá and is an important addition for a better understanding of the effects of anthropic disturbances on high Andean forests and their species. Also, several methodological approaches are provided that may serve as a basis to better understand the situation of other species and ecosystems in similar regions.View less
Superconductivity and magnetism are two phenomena which seem to be incompatible on macropscopic view. Microscopically, this can be traced back to the different spin-orders of both phases: Spin-singlet Cooper pairs versus ferromagnetic spin order. In this thesis we investigate magnetic Fe atoms on the quasi-2D superconductor 2H-NbSe2 by means of combined scanning tunneling microscopy and spectroscopy. The magnetic moment of the Fe atoms locally interacts with the Cooper pair condensate and gives rise to in-gap quasiparticle states - the so-called Yu-Shiba-Rusinov (YSR) states. The peculiar properties of NbSe2 manifest in versatile features of the YSR states which we explore in detail. Capable of atomic manipulation we assemble customized structures - atomic dimers and extended chains - and investigate the hybridization within these structures.
We start by characterizing the pure substrate which exhibits an incommensurate charge-density wave (CDW) that coexists with superconductivity at low temperatures. Both correlated phases are driven by electron-phonon coupling yielding a highly anisotropic superconducting order parameter which appears as a peculiar quasiparticle peak distribution in differential conductance spectra around the superconducting gap.
Fe atoms adsorbed on the surface exhibit multiple YSR resonances with extended wave functions due to the quasi-2D nature of the substrate. The CDW wave induces local variations of the density of states which affect the energy and symmetry of the YSR states. Hence, apart from the two different crystalline hollow sites, the incommensurate CDW creates a multitude of inequivalent sites for Fe atoms. The influence of the CDW on the YSR states was systematically investigated and could be qualitatively modeled in collaboration with theorists.
We study the influence of the CDW on the hybridization between the long-ranged YSR states within the versatile energetic landscape arising from the incommensurate CDW. We assemble various dimers and show that equal positions relative to the CDW are a prerequisite for substantial hybridization. Further, we detect signatures of the quantum spin nature in the coupling of atomic dimers.
We go beyond dimers and stepwise assemble a dilute chain where the coupling between adjacent atoms is entirely mediated via the substrate. We track the formation of YSR bands which are identified by tunneling into their van Hove singularities. In longer chains, the incommensurate CDW induces band bending of the YSR bands. As a last step we investigate chains consisting of densely packed Fe atoms in which direct exchange between d orbitals drives the formation of Fe2 molecules on the surface.View less
Posttraumatic stress disorder (PTSD) and borderline personality disorder (BPD) are highly comorbid. Patients with both disorders report the highest likelihood of lifetime suicide attempts and the lowest mental health related quality of life. Given the high likelihood of comorbid PTSD and BPD and the great burden on those affected, mutual biological and behavioural characteristics of both disorders and their causes seem worthwhile investigating. The current dissertation project aims at further describing overlapping and distinct alterations in stress-regulating systems, stress-relevant brain regions and their interplay in patients with PTSD and BPD, to better explain the evolvement of clinical symptoms, such as affect dysregulation and dissociation that characterize both disorders. As a secondary aim, the current project focusses on the role of childhood trauma (CT), as a mutual environmental factor and possible cause of overlapping symptoms and characteristics in PTSD and BPD. Both disorders are associated with exposure to traumatic events. Traumatic events, such as physical and sexual childhood abuse, in the early phase of development especially increase the risk of developing a psychiatric disorder, among them PTSD and BPD. The organism is especially sensitive to environmental influences in the early period of ontogeny, and changes of stress-regulating systems and stress-relevant brain regions occur in response to stressful environments. Therefore, research has focused on stress-regulating systems and stress-relevant brain regions in both disorders. Especially, the hypothalamic-pituitary-adrenal (HPA) axis, the sympathetic nervous system (SNS), fronto-limbic networks and the influences of glucocorticoids on memory retrieval and its neural activity have been investigated. Results suggest that some common features in patients with PTSD and BPD may be related to CT, in addition to distinct features that are related to e.g. genetics or single-event trauma. However, there has been little systematic investigation of distinct and overlapping features in PTSD and BPD, or of how CT is related to features that are present in both patient groups. To further characterize distinct and overlapping features in PTSD and BPD, and the role of CT, the following research questions are examined: 1. How do female patients with PTSD differ in their physiological and subjectively perceived stress response to an acute psychosocial stressor, compared with healthy women, and how do these differences relate to CT? 2. How does amygdala and hippocampus resting state functional connectivity (RSFC) differ between female patients with PTSD and BPD and healthy women, in a placebo condition and after hydrocortisone administration, and how does amygdala or hippocampus RSFC in the placebo or hydrocortisone condition relate to CT? 3. How do female patients with PTSD and BPD differ from healthy women in their neural activity during autobiographical memory (AM) retrieval after hydrocortisone administration compared with a placebo condition, and how do these differences relate to CT? To investigate the psychosocial stress response, we used the Trier Social Stress Test, a well-established psychosocial stressor. To examine the effect of hydrocortisone on RSFC and on neural activity during AM retrieval, we used a standardized resting state scan and an autobiographical memory task adapted for functional magnet resonance imaging. The main results of this dissertation are as follows. First, female patients with PTSD are characterized by a blunted cortisol response to a psychosocial stressor compared with healthy women. Measure of cortisol changes over time in response to a psychosocial stressor correlated negatively with severity of CT. We found no evidence for increased SNS reactivity in female patients with PTSD. Secondly, hippocampus dorsomedial prefrontal cortex (dmPFC) RSFC is reduced in female patients with PTSD and BPD. Hippocampus dmPFC RSFC correlated negatively with severity of CT and clinical symptoms. There were no differences between female patients and healthy women in amygdala RSFC. In addition, there was no influence of hydrocortisone on either amygdala or hippocampus RSFC, nor an interaction of hydrocortisone with group. Thirdly, female PTSD and BPD patients and healthy women did not differ in their neural activity during AM retrieval, neither in the placebo condition nor after hydrocortisone administration. Severity of CT correlated with a hydrocortisone induced pattern of neural activity. To conclude, the conducted studies extend findings on the physiological stress response and fronto-limbic network functioning and on the influence of glucocorticoids on memory retrieval and neural activity in patients with PTSD and BPD. Particularly, the revealed association of CT with a blunted cortisol stress response, decreased hippocampus dmPFC RSFC and a hydrocortisone induced neural activity pattern during AM retrieval, suggest an influence of CT on overlapping features in PTSD and BPD. This dissertation project condenses the current findings into a model that describes how CT might induce changes that partially account for overlapping features in PTSD and BPD. The model focusses on glucocorticoid receptor (GR) functioning and its consequences on HPA axis, SNS and fronto-limbic network functioning, and on the influence of glucocorticoids on memory retrieval and its associated neural activity. The current dissertation project yields important new insights into how CT as a common environmental factor in both disorders results in changes in stress-regulating systems and stress-relevant brain regions, and how these explain overlapping symptoms in both disorders.View less
It has long been known that the injection of fluids into the earth’s subsurface can cause seismic activity. Usually, magnitudes of this anthropogenic seismicity are too small to be felt at the surface, but several cases of large-magnitude earthquakes related to fluid operations are known. A deeper understanding of the physical mechanisms and controlling parameters of this anthropogenic seismicity is therefore of interest for science as well as for society.
This thesis aims to improve the characterization of source mechanisms of fracturing-induced seismicity. For this, I develop a framework that takes the effect of seismic anisotropy on the source process into account. Microseismic events induced by hydraulic fracturing are typically located in shales, that can exhibit high degrees of anisotropy. This can affect the radiation pattern of events and thus can lead to a misinterpretation of source deformation if not accounted for correctly. In this thesis, I describe a methodology that considers adequately the anisotropy both in the source region and along the propagation path. I examine the influence of various anisotropy parameters on different seismic sources and propose a visualization that directly represents the strain caused by a microseismic source.
The source process of most earthquakes can be approximated by double-couple faulting, that is the rupture occurs as shear on a fault plane and does not contain opening or closing components. For such sources, I propose a decomposition that can be used to analyze different source orientations. Additionally, I suggest a new visualization tool to evaluate the diversity of many mechanisms at the same time. This could be applied to potentially distinguish between natural and induced seismicity. The new decomposition and the source type plot are particularly beneficial for the analysis of fracturing-induced seismicity as it explicitly incorporates the half-moon faulting type, which is typical in this environment.
Subsequently, I use these two theoretical tools to invert and analyze source mechanisms of hydraulic fracturing-induced seismicity. I show that anisotropy has a notable effect on the determined mechanisms and that accounting for this effect correctly, creates a more coherent distribution of mechanisms. The decomposition shows two main types of faulting, (1) strike-slip faulting and (2) dip-slip faulting on nearly vertical fault planes. Strike-slip faulting is characteristic for the tectonic seismicity of the region, the second mechanism type, frequently called half-moon faulting, is a typical source mechanism for hydraulic fracturing.
Half-moon events are observed hardly anywhere in natural seismicity but are typically observed during hydraulic fracturing stimulations. Therefore, this event type seems to be directly related to the fracturing process. I provide an explanation for the occurrence of these events, by using geomechanical modeling. This involves the quantification of fracturing-induced changes of the local stress field which triggers these earthquakes. I elaborate that half-moon events require special stress conditions in the subsurface, for instance, local rotations of the principal stresses. 2D geomechanical modeling shows that these conditions are created in the vicinity of the tips of hydraulic fractures and at layer boundaries that are crossed by the fracture. This model can be used to study hydraulic fracturing under normal-faulting conditions. I complement the modeling with a 3D model that is also capable of modeling hydraulic fracturing under general strike-slip conditions. I compare this model to the studied dataset and show that several field characteristics can be reproduced and explained. The study demonstrates the importance of the integration of data analysis and numerical modeling to accurately capture the physical processes in the source.
Altogether, this thesis provides two new theoretical tools that can be applied to any microseismic dataset in order to achieve more accurate and more consistent results. It further provides new insights into the long-standing discussion on the physical conditions responsible for the occurrence of half-moon events. Consequently, this thesis yields an important contribution to the general physical understanding of fluid-induced seismicity.View less
Carbohydrates are the most abundant biomolecules on earth and play pivotal roles in biological events. These carbohydrates exist as polymers, and as glycoconjugates, are connected to proteins, peptides, and lipids. Consequently, tremendous efforts to understand functions of carbohydrates have been made. Automated solid-phase oligosaccharide synthesis showed possibilities to make synthetic routes straightforward and streamlined for even non- specialists as a general and robust instrument like DNA and peptide synthesizer. Tremendous efforts were made over the past decades to advance automated systems and to produce various structures of oligosaccharides. In the extension of these investigations, the ultimate goal of this thesis is to show the possibility to establish the logic of automated glycan assembly (AGA) by developing new methods for automated glycan assembly to prepare different classes of glycans. Therefore, various oligosaccharides using generalized protocols have been procured and conjugation-ready carbohydrates serve as molecular tools. After a comprehensive introduction into automated oligosaccharide synthesis in Chapter 1, Chapter 2 describes the automated glycan assembly of oligo-N-acetyllactosamine (oligo-LacNAc) and keratin sulfates using building blocks bearing three temporary protecting groups. Following purification protocols using HPLC allowed for access to a small library of linear and branched LacNAc structures including sulfated KSs. Additionally, glycan microarray screening performed using seven LacNAc structures and fluorescence-labeled recombinant AAV particles revealed that one specific virus, AAV 10 identified disulfated tetrasaccharide LacNAc as a relevant epitope. Automated synthesis of oligosaccharides containing challenging 1,2-cis-glycosidic linkages or disarmed building blocks is demonstrated in Chapter 3. Assembly of Lc4 and nLc4 core structures containing only 1,2-trans-glycosidic linkages was executed with building blocks employing a participating group at C2. The stereoselective installation of α-(12)- fucosidic linkage was achieved with the corresponding fucose building blocks depending on the sequence of the core structure, Lc4 or nLc4 in order to synthesize H-type I and II. For the synthesis of three α-Gal epitopes, the last glycosylation reaction formed α-(13)-galactosidic linkage. The stereoselectivity was found to be affected by the sequence of the acceptor bound to the solid support. Identification of the most reactive glucuronic acid building block bearing Lev protecting group on 3-O allowed for the synthesis of HNK-1 epitope pentasaccharide in strictly linear approach. From this investigation it was concluded that identification of approved building blocks was key to accomplish the assembly of synthetically challenging oligosaccharides by using AGA. Chapter 4 of this dissertation presents the automated synthesis of oligosaccharides containing challenging 1,2-cis glycosidic linkages, one of the most challenging carbohydrates to date. In contrast to previous result, leaving groups affected the automated installation of α- galactosidic or β-mannosidic linkages. Remote participation effects by acetyl group(s) at C3 and C4/C6 was in depth studied to identify a set of building blocks introducing 1,2-cis glycosidic linkages with good to excellent stereoselectivity. Taking advantage of “approved” building blocks enabled the synthesis of Globo-H and α-glucans containing multiple 1,2-cis glycosidic linkages. As a result of researches performed in previous Chapters 2 to 4, Chapter 5 describes the reliable and rapid assembly of oligosaccharides using the commercially available automated glycan synthesizer, Glyconeer 2.1, monosaccharide building blocks, and a linker- functionalized polystyrene solid support. Protocols for purification using HPLC and quality- control using IM-MS for the oligosaccharide products have been standardized. Synthetic glycans prepared in this way are useful reagents as the basis for glycan arrays, diagnostics, and carbohydrate based vaccines.View less
Pluripotent stem cells (PSCs) have the ability to undergo indefinite self-renewal while giving rise to the three germ layers. This remarkable capacity has turned PSCs to be a fundamental cell source for regenerative medicine research and applications. The derivation of induced pluripotent stem cells (iPSCs) over a decade ago has sparked a widespread enthusiasm and opportunity for personalized autologous cell-based therapies in a wide array of diseases. However, the development of optimized disease models and iPSC-derived products heavily relies on the generation of homogenous culture systems for the cell type of interest, which currently presents one of the major hindrances towards the use of PSC derivatives in therapeutic applications. The cerebral cortex is an excellent example of a tissue with enormous heterogeneity that introduces immense challenges for in vitro disease models and therapeutic applications. Our lab mainly focuses on studying the development of the cerebral cortex, particularly investigating the development of cortical neural stem cells (NSCs). Our goal is to devise approaches for the differentiation of PSCs into founder NSC building blocks. We put particular emphasis on achieving high purity that will enable studying authentic cell fate decisions that are associated with regional patterning, self-renewal and differentiation processes that shape the cortex. A homogeneous early cortical population will also enable extracting a more reliable molecular identity of those cells, which can then be used for meaningful disease modeling and for devising sophisticated approaches to induce or maintain self-renewal of such populations in vitro. However, recent research from our lab has shown that current methods to derive early cortical progenitors from PSCs are highly diverse and yield heterogeneous populations containing both cortical and non-cortical cell types. This results in heterogeneous founder NSC populations, limiting their use as a universal pure NSC source. To overcome this hurdle, our lab established a streamlined method known as Triple-i paradigm to derive homogenous starting cortical progenitors both in neural rosettes (2D) and in organoids (3D) platforms. The main objectives of this thesis are to identify early signals that modulate temporal and regional fates within developing founder cortical NSC populations, focusing on small non-coding RNA (miRNAs), which are known to be key regulators of many developmental processes including stem cell proliferation and lineage specifications. These miRNAs guide the early development in a spatiotemporal manner by regulating the expression of multiple gene networks at the post-transcriptional level. They are abundantly expressed in the developing neural tube that eventually gives rise to different regions of central nervous system, including the cerebral cortex. However, it is unknown whether they have the capacity to specify a particular brain region in the cortex such as archicortex that consists of cortical hem, hippocampus and choroid plexus. In this study, we have identified a miRNA important for the specification of archicortex and interrogated its role in cell fate specification using a battery of molecular and cellular studies. First, we employed in vitro human embryonic stem cell-based models (2D monolayer and 3D cerebral organoid) for the derivation of founder neural stem cell and their progression. We then identified a list of miRNAs that are specifically expressed in this early neural stem cell stage, among which we found hsa-miR-20b-5p to be one of the highly expressed microRNAs in early NSCs derived under both monolayer culture and cerebral organoids. Second, by overexpressing hsa-miR-20b-5p in cerebral organoids, we provided evidence that this miRNA is involved in the stepwise specification of choroid plexus of archicortex, by caudalizing the early cortical NSC, due to modulation of WNT and BMP signalling components. In addition, cellular immunostainings displayed a characteristic presence of giant but thin single- layer vesicles positive for choroid plexus markers in miR-20b overexpressing organoids, as opposed to pseudostratified cortical neural rosettes in wildtype organoids. Furthermore, we showed that co-overexpression of miR-20b with of its main target CCND1, lead to the generation of cortical hem/hippocampus organoids. Altogether, through an extensive miRNA-sequencing, single cell RNA-sequencing and cellular immunofluorescence studies, we revealed the expression of hsa-miR-20b-5p in early neural stem cells, its role in the specification of the archicortex lineages and its part as a cell fate modulator for converting cortical organoids towards choroid plexus structures.View less
Different physical cues are known to affect mesenchymal stem cell (MSC) behavior, indicating a complex relationship between the cell and its microenvironment. Mechanical strain and temperature changes are examples of cues that are relevant in vitro and in vivo. However, the combined effects of multiple physical cues on MSCs remained unclear. Traditional mechanical devices used in cell research have limitations on the integration of various factors and high-throughput applications. The requirement of new biomaterials to integrate the multiple external stimuli was arising to figure out the complex cellular mechanisms. The thermoresponsive mechanical strain was investigated to achieve the aim of using active biomaterials to study the combined effects on human MSCs. Poly (ℇ-caprolactone)-butyl acrylate (PCL-BA) copolymer sheet actuators were programmed so that the reversible shape change could be controlled by temperature changes between 37 °C and 10 °C. A thermochamber was used to culture the human adipose-derived stem cells (ADSCs) on the shape-memory polymer sheet actuators. 50 × 50 µm grids were created on the underside of the actuator sheets to observe the shape change of polymer and cells. Cell morphology, orientation, and migration were observed and recorded using time-lapse microscopy. The dual stimuli of temperature change and mechanical strain were translated into intracellular signals, such as calcium oscillation and nuclei translocation of the mechanical sensors, which were characterized using chemical reagents and immunostaining. Further, epigenetic histone modification of hADSCs was analyzed using chromatin immunoprecipitation quantitative real-time PCR (ChIP-qPCR). Finally, adipogenesis and osteogenesis of the hADSCs were studied to evaluate MSC differentiation capacity with the combined physical cues. The effect of temperature changes on adipocyte dedifferentiation was demonstrated by quantifying lipid accumulation in mature adipocytes. The expression of lipid accumulation-related genes and cell proliferation capacity were analyzed to investigate the dedifferentiation properties. In this work, the PCL-BA shape-memory polymer actuator elongated more than 10% at 10 °C, and contracted when returned to 37 °C. The mechanical strain was generated with the polymer actuator's elongation, which modified the cell morphology and increased cell migration. The periodic temperature change and mechanical strain induced calcium influx into cells; meanwhile, the mechanical strain promoted nuclei translocation of the YAP and RUNX2. The dual stimuli further increased the epigenetic acetylation of histone H3 lysine 9 (H3K9ac) and enhanced the expression level of osteogenesis-related genes and proteins. In addition, the dual stimuli of temperature change and mechanical strain induced the focal adhesion activation by regulation of integrin and myosin light chain (MLC) phosphorylation. As a result, cytoskeleton organization and focal adhesion activation were reduced by pretreatment of the MSCs with temperature changes but enhanced with mechanical strain changes. Temperature change alone decreased the cell migration velocity on SMPA substrate, while temperature change and mechanical strain combined increased cell migration velocity. Further, the cyclic temperature change (10 - 37 °C) decreased intracellular lipid of mature adipocytes and increased free fatty acids (FFA) outside. Simultaneously, mature adipocyte marker FABP4 was significantly down-regulated, while the brown adipocyte-related genes UCP1, PGC-1α, and PRDM16 were up-regulated. Ki67 represents the proliferation marker that was increased after the treatment of temperature change. The transformation of mature adipocytes and increasing proliferation capacity indicates the promotion of adipocyte dedifferentiation. The shape-memory polymer actuator sheet is an active biomaterial that can generate mechanical strain with simple temperature control. This artificial muscle allows the combined influence of multiple physical cues on stem cells to be studied. We found the combinative effects of the interplay of mechanical and temperature stimuli on MSC behavior and lineage commitment change, instead of the typical single effect on MSCs. We also established the adipocyte dedifferentiation with periodic temperature changes, which might be used to generate alternative stem cell sources and improve the MSC-based cell therapy in regenerative medicine.View less
Over the last few years, data has often been described as the oil of the 21st century, e.g., by Bhageshpur (2019). Just as access to oil dominated power and development in the last century, this claim implies that personal data is not only assumed to be similarly valuable, but also equally as influential in politics and society as oil once was. However, oil sources mainly diverge in their accessibility, quality, quantity, and cost of exploitation but, once extracted and refined theses sources may lead to roughly similar products. Data also differs in these four categories but, additionally, data sources typically lead to very specific insights. One single data source is often neither sufficient to answer important and complex scientific (or economic) questions nor to make any predictions with fine granularity and high precision. In such cases, combining data from different sources that provide additional aspects to the problem at hand is one promising approach to achieve these aims.
In this dissertation, combining data sources is conducted for two purposes. Part I of this work focuses on combining data to achieve additional understanding. In the paper presented in Part I, the authors analyze reasons why students drop out of undergraduate courses in economics and business administration. From a university perspective, administrative data is readily available, e.g., which modules are completed in which semester, how many educational credit points are achieved by each student in each semester. Socioeconomic data at individual level, however, is usually unavailable to university administrations. In order to overcome this hurdle, the authors proposed and executed a novel prospective study design. A survey was conducted on students starting the second semester and the data was combined with administrative longitudinal data. Hence, the authors were able to analyze individual studying behavior conditioned on a large pool of socio-demographic variables. Among other results, the authors were able to show that college admission grades have a negligibly small impact on the achievements made on Bachelor degree courses. This finding stands in strong contrast to college admission policies in Germany that strongly focus on high-school grades for college admission.
The second purpose of data-combination, as discussed in this work, is the combination of data-sources to improve the precision of predictions. Part II consists of three papers from the field of small area estimation (SAE). In SAE problems, there is some survey data typically available that contains the (VOI). However, an indicator of interest needs to be estimated on some subgroup level by a function of the VOI. Such levels usually consist of a geographic region but are not limited to this. In the context of SAE, these subgroups are called areas. With an increasing number of areas, the quantity of observations available per area decreases, often leading to areas with very few or even without any observations (out-of-sample areas). In such situations, a prediction with reasonable reliability becomes impossible when only relying on the available survey data. One possibility to overcome this burden is to couple the survey data with additional data, such as administrative or census data. Frequently, these data sources do not contain the VOI, thus rendering a direct estimation of the indicator impossible. However, if similar covariates are available in the survey and census, a feasible approach is to assume a model for the VOI that holds, both in the survey and census, to estimate the model on the survey data and then to combine the model estimates with the more numerous census data that enables prediction. This general method is often referred to as “borrowing strength.” Such model-based approaches are roughly divided into two classes, depending on the data availability and resulting requirements on the models. First, if the data is available for each individual of interest, e.g., a citizen or household, unit-levels are used. For area-level models, on the other hand, data is only available in aggregated form at area level.
Many common methods in SAE assume normally distributed residuals, not only for the model estimation, but more crucially when using the census data for prediction and the estimation of precision. Therefore, deviations from normality have severe consequences and lead to less precise point estimates and misleading shrunk error estimates. The paper presented in Chapter 2 proposes the use of data-driven transformations, resulting in smaller deviations from normality and thus improved point and precision estimates. Chapter 3 presents the R-package emdi that implements not only the latter methodology, but also allows for the usage of various area-level Fay-Herriot models. emdi focuses on user-friendliness and provides many useful functionalities to support the user through every step, from model estimation through the analysis of model assumptions to visualize the results end enable their exportation. However, when deviations from normality are too severe, different model types are more suitable. Chapter 4 presents the R-package ammlogit, which allows the user to work with a multinomial VOI. The corresponding paper introduces a new methodology for prediction and a revised bootstrap mean squared error estimation. Like emdi, ammlogit is designed to be user-friendly and narrow the gap between research and practitioners. Still, the method used in ammlogit also uses distributional assumptions, as the counts are assumed to be conditionally multinomially distributed and the area-level error terms are assumed to be identically normally distributed.
A model class without distributional assumptions are quantile-type regression models. M-Quantile models have been used in SAE since Chambers and Tzavidis (2006). However, the related mixed quantile regression models have not yet been consequently applied to small area problems, even though they are a naturally robust alternative to the widely used linear mixed regression models that dominate research and application. In parts, this may be due to remaining uncertainties about their symptotic properties. Therefore, in the paper presented in Part III, the asymptotic normality of the corresponding maximum likelihood estimates is proven and a plugin-variance estimator is derived.View less