Untersuchungen zur genetischen Differenzierung von Vitis Genotypen und Unterlagsrebsorten sowie deren Klone mit Hilfe der RAPD-, AFLP- und SAMPL-Analyse

Im Rahmen dieser Arbeit wurde eine Routinemethode zur Differenzierung und Identifizierung von Unterlagssorten in jedem Verarbeitungsstadium, wie Holz, Pfropfrebe, bereits im Weinberg gepflanzte Rebe, entwickelt. Hierfür wurde eine Methode erarbeitet, die es ermöglicht, DNA aus Blättern, Holz und Wurzeln gleichermaßen zu extrahieren. Vermischungen von Unterlagssorten in einem Unterlagenholzbündel konnten bis zu 10% Fremd-Unterlagenholz durch eine RAPD-PCR nachgewiesen werden. Mit den 12mer Primer #722b und #722c wurden sortenspezifische Banden für die Unterlagssorten Börner, 8B, 3309C und 5BB festgestellt. Der Primers # 751 war in der Lage von 151 Unterlagssorten und Wildarten 144 Genotypen zu unterschieden. Mit Hilfe der Optimierung von RAMP-Zeiten konnten die Bandenmuster der sieben in Deutschland am häufigsten verwendeten Unterlagssorten auf zwei unterschiedlichen Thermocyclern reproduziert werden. Aufgrund der Optimierung der RAPD-PCR war es möglich, die zur Unterscheidung notwendigen Banden durch eine lineare Transformation anhand einer ermittelten Referenzbande mathematisch und graphisch darzustellen. Klone der Unterlagssorten SO4, 125AA und 5C, sowie die Unterlagssorte Binova, wurden auf die Unterscheidungsmöglichkeit hin mit RAPD, AFLP und SAMPL untersucht. Innerhalb der AFLP-/SAMPL-Methode bildeten die zu einer Sorte gehörenden Unterlagenklone ein Cluster, wobei Binova innerhalb der SO4 Klone zu finden war. Es wurden ‚unterlagssortenspezifische Banden’, ‚wiederholende Banden’ und ‚Einzelbanden’ gefunden.

Sedimentology and tectonic history of late Archaean sedimentary successions in Zimbabwe

ZusammenfassungSpätarchaische Sedimentgesteine (ca. 2,65 Milliarden Jahre alt) wurden in Grünsteingürteln des Simbabwe Kratons untersucht. In dem Belingwe Grünsteingürtel ist granitoides Grundgebirge von einer allochthonen Einheit aus vulkanischen Gesteinen und Vorlandbeckensedimenten überlagert. Die sedimentäre Abfolge besteht aus Flachwasserkalken und Turbiditen. Unterschiedliche Faziestypen der Kalksteine sind in sedimentäre Verflachungszyklen angeordnet. Eustatische Meeresspiegelschwankungen werden als Ursache der zyklischen Sedimentation angenommen. Sedimentologische, geochemische und strukturelle Analysen zeigen die Bedeutung horizontal-tektonischer Prozesse für die Entstehung dieses Grünsteingürtels an.Sedimentgesteine des Midlands Grünsteingürtels lagern zwischen ozeanischen, mafischen Vulkaniten und kontinentalen, granitoiden Gneisen. Die Art der Abfolge sedimentärer Fazies, beginnend mit Turbiditen und überlagert von flachmarinen Schelfsedimenten und alluvialen Ablagerungen, sowie geologische und geochemische Hinweise aus den benachbarten Gesteinsserien lassen auf Ablagerung während der Kollision zwischen einem ozeanischen Plateau/Inselbogen und einem kontinentalen Krustenfragmentes schließen.In dem Bindura-Shamva Grünsteingürtel können zwei Sedimentgesteinseinheiten unterschieden werden, eine alluvial—flachmarine Abfolge und eine tiefmarin—fluviatile Abfolge. Extensionstektonik verursachte wahrscheinlich die Bildung des Sedimentbeckens. Die spätere Phase der Beckenbildung war jedoch ähnlich jener in modernen Vorlandbecken.Schichtparallele Eisensteinhorizonte sind häufig entlang von Sediment-Vulkanit-Kontakten zu finden. Diese Gesteine werden als silifizierte und von Sulfiden imprägnierte Scherzonen interpretiert. Syntektonische hydrothermale Alteration von Gesteinen entlang der Störungszonen führte zur Bildung dieser 'tektonischen Eisensteine'.

Decay of imprinted surface waves in polymers

CONCLUSIONS The focus of this work was the investigation ofanomalies in Tg and dynamics at polymer surfaces. Thethermally induced decay of hot-embossed polymer gratings isstudied using laser-diffraction and atomic force microscopy(AFM). Monodisperse PMMA and PS are selected in the Mwranges of 4.2 to 65.0 kg/mol and 3.47 to 65.0 kg/mol,respectively. Two different modes of measurement were used:the one mode uses temperature ramps to obtain an estimate ofthe near-surface glass temperature, Tdec,0; the other modeinvestigates the dynamics at a constant temperature aboveTg. The temperature-ramp experiments reveal Tdec,0 valuesvery close to the Tg,bulk values, as determined bydifferential scanning calorimetry (DSC). The PMMA of65.0 kg/mol shows a decreased value of Tg, while the PS samples of 3.47 and 10.3 kg/mol (Mwramp and DSC measurements, but confirm thecourse of the values with increasing Mw. The comparison of the fragilities (temperaturedependence of the polymer properties at Tg) near the surfaceand in the bulk shows a higher fragility for PS near thesurface, a lower one for PMMA with molecular weights of 4.2and 65.0 kg/mol. The different surface behavior of PS istraced back to a lower degree of cooperation and a largerfree volume fraction.

Mutually catalytic branching at infinite rate

The purpose of this doctoral thesis is to prove existence for a mutually catalytic random walk with infinite branching rate on countably many sites. The process is defined as a weak limit of an approximating family of processes. An approximating process is constructed by adding jumps to a deterministic migration on an equidistant time grid. As law of jumps we need to choose the invariant probability measure of the mutually catalytic random walk with a finite branching rate in the recurrent regime. This model was introduced by Dawson and Perkins (1998) and this thesis relies heavily on their work. Due to the properties of this invariant distribution, which is in fact the exit distribution of planar Brownian motion from the first quadrant, it is possible to establish a martingale problem for the weak limit of any convergent sequence of approximating processes. We can prove a duality relation for the solution to the mentioned martingale problem, which goes back to Mytnik (1996) in the case of finite rate branching, and this duality gives rise to weak uniqueness for the solution to the martingale problem. Using standard arguments we can show that this solution is in fact a Feller process and it has the strong Markov property. For the case of only one site we prove that the model we have constructed is the limit of finite rate mutually catalytic branching processes as the branching rate approaches infinity. Therefore, it seems naturalto refer to the above model as an infinite rate branching process. However, a result for convergence on infinitely many sites remains open.

Charakterisierung zellulärer Interaktionspartner des großen Hüllproteins des Hepatitis-B-Virus

Im Mittelpunkt dieser Arbeit stand das große L-Hüllprotein (L) des Hepatitis B - Virus. L bildet eine ungewöhnliche duale Topologie in der ER-Membran aus, welche auch im reifen Viruspartikel erhalten bleibt. In einem partiellen, posttranslationalen Reifungsprozess wird die sogenannte PräS-Region von der zytosolischen Seite der Membran aus in das ER-Lumen transloziert. Aufgrund seiner dualen Topologie und der damit verbundenen Multifunktionalität übernimmt L eine Schlüsselfunktion im viralen Lebenszyklus. Ein Schwerpunkt dieser Arbeit lag deshalb darin, neue zelluläre Interaktionspartner des L-Hüllproteins zu identifizieren. Ihre Analyse sollte helfen, das Zusammenspiel des Virus mit der Wirtszelle besser zu verstehen. Hierfür wurde das Split - Ubiquitin Hefe - Zwei - Hybrid System eingesetzt, das die Interaktionsanalyse von Membranproteinen und Membran-assoziierten Proteinen ermöglicht. Zwei der neu identifizierten Interaktionspartner, der v-SNARE Bet1 und Sec24A, die Cargo-bindende Untereinheit des CoPII-vermittelten vesikulären Transports, wurden weitergehend im humanen Zellkultursystem untersucht. Sowohl für Bet1 als auch für Sec24A konnte die Interaktion mit dem L-Hüllprotein bestätigt und der Bindungsbereich eingegrenzt werden. Die Depletion des endogenen Bet1 reduzierte die Freisetzung L-haltiger, nicht aber S-haltiger subviraler Partikel (SVP) deutlich. Im Gegensatz zu Bet1 interagierte Sec24A auch mit dem mittleren M- und kleinen S-Hüllprotein von HBV. Die Inhibition des CoPII-vermittelten vesikulären Transportweges durch kombinierte Depletion der vier Sec24 Isoformen blockierte die Freisetzung sowohl L- als auch S-haltiger SVP. Dies bedeutet, dass die HBV - Hüllproteine das ER CoPII-vermittelt verlassen, wobei sie aktiv Kontakt zur Cargo-bindenden Untereinheit Sec24A aufnehmen. Der effiziente Export der Hüllproteine aus dem ER ist für die Virusmorphogenese und somit für den HBV - Lebenszyklus essentiell. rnEin weiterer Schwerpunkt dieser Arbeit basierte auf der Interaktion des L-Hüllproteins mit dem ER-luminalen Chaperon BiP. In der vorliegenden Arbeit wurde überprüft, ob BiP, ähnlich wie das zytosolische Chaperon Hsc70, an der Ausbildung der dualen Topologie des L-Hüllproteins beteiligt ist. Hierfür wurde BiP durch die ektopische Expression seiner Ko-Chaperone BAP und ERdj4 in seiner Substrat-bindenen Kapazität manipuliert. ERdj4, ein Mitglied der Hsp40 - Proteinfamilie, stimuliert die ATPase-Aktivität von BiP, was die Substratbindung stabilisiert. Der Nukleotid - Austauschfaktor BAP hingegen vermittelt die Auflösung des BiP - Substrat - Komplexes. Die Auswirkung der veränderten in vivo-Aktivität von BiP auf die posttranslationale PräS-Translokation wurde mit Proteaseschutz - Versuchen untersucht. Die ektopische Expression des positiven als auch des negativen Regulators von BiP resultierte in einer drastischen Reduktion der posttranslationalen PräS-Translokation. Ein vergleichbarer Effekt wurde nach Manipulation des BiP ATPase - Zyklus durch Depletion der zellulären ATP - Konzentration beobachtet. Dies spricht dafür, dass das ER-luminale Chaperon BiP, zusammen mit Hsc70, eine zentrale Rolle in der Ausbildung der dualen Topologie des L-Hüllproteins spielt. rnZwei weitere Proteine, Sec62 und Sec63, die sich für die posttranslationale Translokation in der Hefe als essentiell erwiesen haben, wurden in die Analyse der dualen Topologie des L-Hüllproteins einbezogen. Interessanterweise konnte eine rein luminale Ausrichtung der PräS-Region nach kombinierter Depletion des endogenen Sec62 und Sec63 beobachtet werden. Dies deutet an, dass sowohl Sec62 als auch Sec63 an der Ausbildung der dualen Topologie des L-Hüllproteins beteiligt sind. In Analogie zur Posttranslokation der Hefe könnte Sec62 als Translokon-assoziierter Rezeptor für Substrate der Posttranslokation, und damit der PräS-Region, dienen. Sec63 könnte mit seiner J-Domäne BiP zum Translokon rekrutieren und daraufhin dessen Substrat-bindende Aktivität stimulieren. BiP würde dann, einer molekularen Ratsche gleich, die PräS-Region durch wiederholtes Binden und Freisetzen aktiv in das ER-Lumen hereinziehen, bis eine stabile duale Topologie des L-Hüllproteins ausgebildet ist. Die Bedeutung von Sec62 und Sec63 für den HBV - Lebenszyklus wird dadurch untermauert, dass sowohl die ektopische Expression als auch die Depletion des endogenen Sec63 die Freisetzung L-haltiger SVP deutlich reduziert. rn

Patterns in and kinetics of phase separation in binary mixtures

This work focused mainly on two aspects of kinetics of phase separation in binary mixtures. In the first part, we studied the interplay of hydrodynamics and the phase separation of binary mixtures. A considerably flat container (a laterally extended geometry), at an aspect ratio of 14:1 (diameter: height) was chosen, so that any hydrodynamic instabilities, if they arise, could be tracked. Two binary mixtures were studied. One was a mixture of methanol and hexane, doped with 5% ethanol, which phase separated under cooling. The second was a mixture of butoxyethanol and water, doped with 2% decane, which phase separated under heating. The dopants were added to bring down the phase transition temperature around room temperature.rnrnAlthough much work has been done already on classical hydrodynamic instabilities, not much has been done in the understanding of the coupling between phase separation and hydrodynamic instabilities. This work aimed at understanding the influence of phase separation in initiating any hydrodynamic instability, and also vice versa. Another aim was to understand the influence of the applied temperature protocol on the emergence of patterns characteristic to hydrodynamic instabilities. rnrnOn slowly cooling the system continuously, at specific cooling rates, patterns were observed in the first mixture, at the start of phase separation. They resembled the patterns observed in classical Rayleigh-Bénard instability, which arises when a liquid continuously is heated from below. To suppress this classical convection, the cooling setup was tuned such that the lower side of the sample always remained cooler by a few millikelvins, relative to the top. We found that the nature of patterns changed with different cooling rates, with stable patterns appearing for a specific cooling rate (1K/h). On the basis of the cooling protocol, we estimated a modified Rayleigh number for our system. We found that the estimated modified Rayleigh number is near the critical value for instability, for cooling rates between 0.5K/h and 1K/h. This is consistent with our experimental findings. rnrnThe origin of the patterns, in spite of the lower side being relatively colder with respect to the top, points to two possible reasons. 1) During phase separation droplets of either phases are formed, which releases a latent heat. Our microcalorimetry measurements show that the rise in temperature during the first phase separation is in the order of 10-20millikelvins, which in some cases is enough to reverse the applied temperature bias. Thus phase separation in itself initiates a hydrodynamic instability. 2) The second reason comes from the cooling protocol itself. The sample was cooled from above and below. At sufficiently high cooling rates, there are situations where the interior of the sample is relatively hotter than both top and bottom of the sample. This is sufficient to create an instability within the cell. Our experiments at higher cooling rates (5K/h and above) show complex patterns, which hints that there is enough convection even before phase separation occurs. Infact, theoretical work done by Dr.Hayase show that patterns could arise in a system without latent heat, with symmetrical cooling from top and bottom. The simulations also show that the patterns do not span the entire height of the sample cell. This is again consistent with the cell sizes measured in our experiment.rnrnThe second mixture also showed patterns at specific heating rates, when it was continuously heated inducing phase separation. In this case though, the sample was turbid for a long time until patterns appeared. A meniscus was most probably formed before the patterns emerged. We attribute the reason of patterns in this case to Marangoni convection, which is present in systems with an interface, where local differences in surface tension give rise to an instability. Our estimates for the Rayleigh number also show a significantly lower number than that's required for RB-type instability.rnrnIn the first part of the work, therefore, we identify two different kinds of hydrodynamic instabilities in two different mixtures. Both are observed during, or after the first phase separation. Our patterns compare with the classical convection patterns, but here the origins are from phase separation and the cooling protocol.rnrnIn the second part of the work, we focused on the kinetics of phase separation in a polymer solution (polystyrene and methylcyclohexane), which is cooled continuously far down into the two phase region. Oscillations in turbidity, denoting material exchange between the phases are seen. Three processes contribute to the phase separation: Nucleation of droplets, their growth and coalescence, and their subsequent sedimentation. Experiments in low molecular binary mixtures had led to models of oscillation [43] which considered sedimentation time scales much faster than the time scales of nucleation and growth. The size and shape of the sample therefore did not matter in such situations. The oscillations in turbidity were volume-dominated. The present work aimed at understanding the influence of sedimentation time scales for polymer mixtures. Three heights of the sample with same composition were studied side by side. We found that periods increased with the sample height, thus showing that sedimentation time determines the period of oscillations in the polymer solutions. We experimented with different cooling rates and different compositions of the mixture, and we found that periods are still determined by the sample height, and therefore by sedimentation time. rnrnWe also see that turbidity emerges in two ways; either from the interface, or throughout the sample. We suggest that oscillations starting from the interface are due to satellite droplets that are formed on droplet coalescence at the interface. These satellite droplets are then advected to the top of the sample, and they grow, coalesce and sediment. This type of an oscillation wouldn't require the system to pass the energy barrier required for homogenous nucleation throughout the sample. This mechanism would work best in sample where the droplets could be effectively advected throughout the sample. In our experiments, we see more interface dominated oscillations in the smaller cells and lower cooling rates, where droplet advection is favourable. In larger samples and higher cooling rates, we mostly see that the whole sample becomes turbid homogenously, which requires the system to pass the energy barrier for homogenous nucleation.rnrnOscillations, in principle, occur since the system needs to pass an energy barrier for nucleation. The height of the barrier decreases with increasing supersaturation, which in turn is from the temperature ramp applied. This gives rise to a period where the system is clear, in between the turbid periods. At certain specific cooling rates, the system can follow a path such that the start of a turbid period coincides with the vanishing of the last turbid period, thus eliminating the clear periods. This means suppressions of oscillations altogether. In fact we experimentally present a case where, at a certain cooling rate, oscillations indeed vanish. rnrnThus we find through this work that the kinetics of phase separation in polymer solution is different from that of a low molecular system; sedimentation time scales become relevant, and therefore so does the shape and size of the sample. The role of interface in initiating turbid periods also become much more prominent in this system compared to that in low molecular mixtures.rnrnIn summary, some fundamental properties in the kinetics of phase separation in binary mixtures were studied. While the first part of the work described the close interplay of the first phase separation with hydrodynamic instabilities, the second part investigated the nature and determining factors of oscillations, when the system was cooled deep into the two phase region. Both cases show how the geometry of the cell can affect the kinetics of phase separation. This study leads to further fundamental understandings of the factors contributing to the kinetics of phase separation, and to the understandings of what can be controlled and tuned in practical cases. rn

Cellular localization and mechanism of amyloid precursor protein (APP) homodimer formation in an oxidizing environment

The amyloid precursor protein (APP) is a type I transmembrane glycoprotein, which resembles a cell surface receptor, comprising a large ectodomain, a single spanning transmembrane part and a short C-terminal, cytoplasmic domain. It belongs to a conserved gene family, with over 17 members, including also the two mammalian APP homologues proteins APLP1 and APLP2 („amyloid precursor like proteins“). APP is encoded by 19 exons, of which exons 7, 8, and 15 can be alternatively spliced to produce three major protein isoforms APP770, APP751 and APP695, reflecting the number of amino acids. The neuronal APP695 is the only isoform that lacks a Kunitz Protease Inhibitor (KPI) domain in its extracellular portion whereas the two larger, peripheral APP isoforms, contain the 57-amino-acid KPI insert. rnRecently, research effort has suggested that APP metabolism and function is thought to be influenced by homodimerization and that the oligomerization state of APP could also play a role in the pathology of Alzheimer's disease (AD), by regulating its processing and amyloid beta production. Several independent studies have shown that APP can form homodimers within the cell, driven by motifs present in the extracellular domain, as well as in the juxtamembrane (JM) and transmembrane (TM) regions of the molecule, whereby the exact molecular mechanism and the origin of dimer formation remains elusive. Therefore, we focused in our study on the actual subcellular origin of APP homodimerization within the cell, an underlying mechanism, and a possible impact on dimerization properties of its homologue APLP1. Furthermore, we analyzed homodimerization of various APP isoforms, in particular APP695, APP751 and APP770, which differ in the presence of a Kunitz-type protease inhibitor domain (KPI) in the extracellular region. In order to assess the cellular origin of dimerization under different cellular conditions, we established a mammalian cell culture model-system in CHO-K1 (chinese hamster ovary) cells, stably overexpressing human APP, harboring dilysine based organelle sorting motifs at the very C-terminus [KKAA-Endoplasmic Reticulum (ER); KKFF-Golgi]. In this study we show that APP exists as disulfide-bound, SDS-stable dimers, when it was retained in the ER, unlike when it progressed further to the cis-Golgi, due to the KKFF ER exit determinant. These stable APP complexes were isolated from cells, and analyzed by SDS–polyacrylamide gel electrophoresis under non-reducing conditions, whereas strong denaturing and reducing conditions completely converted those dimers to monomers. Our findings suggested that APP homodimer formation starts early in the secretory pathway and that the unique oxidizing environment of the ER likely promotes intermolecular disulfide bond formation between APP molecules. We particularly visualized APP dimerization employing a variety of biochemical experiments and investigated the origin of its generation by using a Bimolecular Fluorescence Complementation (BiFC) approach with split GFP-APP chimeras. Moreover, using N-terminal deletion constructs, we demonstrate that intermolecular disulfide linkage between cysteine residues, exclusively located in the extracellular E1 domain, represents another mechanism of how an APP sub-fraction can dimerize within the cell. Additionally, mutational studies revealed that cysteines at positions 98 and 105, embedded in the conserved loop region within the E1 domain, are critical for interchain disulfide bond formation. Using a pharmacological treatment approach, we show that once generated in the oxidative environment of the ER, APP dimers remain stably associated during transport, reaching the plasma membrane. In addition, we demonstrate that APP isoforms, encompassing the KPI domain, exhibit a strongly reduced ability to form cis-directed dimers in the ER, whereas trans-directed cell aggregation of Drosophila Schneider (S2)-cells was isoform independent, mediating cell-cell contacts. Thus, suggesting that steric properties of KPI-APP might be the cause for weaker cis-interaction in the ER, compared to APP695. Finally, we provide evidence that APP/APLP1 heterointeractions are likewise initiated in the ER, suggesting a similar mechanism for heterodimerization. Therefore, dynamic alterations of APP between monomeric, homodimeric, and possibly heterodimeric status could at least partially explain some of the variety in the physiological functions of APP.rn

Stable isotope composition of atmospheric carbon monoxide : a modelling study

Stable isotope composition of atmospheric carbon monoxide: A modelling study.rnrnThis study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ13C, δ18O and Δ17O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC−1 measurement platform.rnrnThe systematically underestimated 13CO/12CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in 13C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH4) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH4 to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in 13C, were found significant when explicitly simulated. The inaccurate surface emissions, likely underestimated over East Asia, are responsible for roughly half of the discrepancies between the simulated and observed 13CO in the northern hemisphere (NH), whereas the remote southern hemisphere (SH) compositions suggest an underestimated fractionation during the oxidation of CO by the hydroxyl radical (OH). A reanalysis of the kinetic isotope effect (KIE) in this reaction contrasts the conventional assumption of a mere pressure dependence, and instead suggests an additional temperature dependence of the 13C KIE, which is driven by changes in the partitioning of the reaction exit channels. This result is yet to be confirmed in the laboratory.rnrnApart from 13CO, for the first time the atmospheric distribution of the oxygen mass-independent fractionation (MIF) in CO, Δ17O, has been consistently simulated on the global scale with EMAC. The applicability of Δ17O(CO) observations to unravelling changes in the tropospheric CH4-CO-OH system has been scrutinised, as well as the implications of the ozone (O3) input to the CO isotope oxygen budget. The Δ17O(CO) is confirmed to be the principal signal for the CO photochemical age, thus providing a measure for the OH chiefly involved in the sink of CO. The highly mass-independently fractionated O3 oxygen is estimated to comprise around 2% of the overall tropospheric CO source, which has implications for the δ18O, but less likely for the Δ17O CO budgets. Finally, additional sensitivity simulations with EMAC corroborate the nearly equal net effects of the present-day CH4 and CO burdens in removing tropospheric OH, as well as the large turnover and stability of the abundance of the latter. The simulated CO isotopologues nonetheless hint at a likely insufficient OH regeneration in the NH high latitudes and the upper troposphere / lower stratosphere (UTLS).rn

Stochastic foundations of dynamic trade and labor market models

This dissertation consists of three self-contained papers that are related to two main topics. In particular, the first and third studies focus on labor market modeling, whereas the second essay presents a dynamic international trade setup.rnrnIn Chapter "Expenses on Labor Market Reforms during Transitional Dynamics", we investigate the arising costs of a potential labor market reform from a government point of view. To analyze various effects of unemployment benefits system changes, this chapter develops a dynamic model with heterogeneous employed and unemployed workers.rn rnIn Chapter "Endogenous Markup Distributions", we study how markup distributions adjust when a closed economy opens up. In order to perform this analysis, we first present a closed-economy general-equilibrium industry dynamics model, where firms enter and exit markets, and then extend our analysis to the open-economy case.rn rnIn Chapter "Unemployment in the OECD - Pure Chance or Institutions?", we examine effects of aggregate shocks on the distribution of the unemployment rates in OECD member countries.rn rnIn all three chapters we model systems that behave randomly and operate on stochastic processes. We therefore exploit stochastic calculus that establishes clear methodological links between the chapters.

Development, characterization, and application of flowing atmospheric-pressure afterglow ionization for mass spectrometric analysis of ambient organic aerosols

Addressing current limitations of state-of-the-art instrumentation in aerosol research, the aim of this work was to explore and assess the applicability of a novel soft ionization technique, namely flowing atmospheric-pressure afterglow (FAPA), for the mass spectrometric analysis of airborne particulate organic matter. Among other soft ionization methods, the FAPA ionization technique was developed in the last decade during the advent of ambient desorption/ionization mass spectrometry (ADI–MS). Based on a helium glow discharge plasma at atmospheric-pressure, excited helium species and primary reagent ions are generated which exit the discharge region through a capillary electrode, forming the so-called afterglow region where desorption and ionization of the analytes occurs. Commonly, fragmentation of the analytes during ionization is reported to occur only to a minimum extent, predominantly resulting in the formation of quasimolecular ions, i.e. [M+H]+ and [M–H]– in the positive and the negative ion mode, respectively. Thus, identification and detection of signals and their corresponding compounds is facilitated in the acquired mass spectra. The focus of the first part of this study lies on the application, characterization and assessment of FAPA–MS in the offline mode, i.e. desorption and ionization of the analytes from surfaces. Experiments in both positive and negative ion mode revealed ionization patterns for a variety of compound classes comprising alkanes, alcohols, aldehydes, ketones, carboxylic acids, organic peroxides, and alkaloids. Besides the always emphasized detection of quasimolecular ions, a broad range of signals for adducts and losses was found. Additionally, the capabilities and limitations of the technique were studied in three proof-of-principle applications. In general, the method showed to be best suited for polar analytes with high volatilities and low molecular weights, ideally containing nitrogen- and/or oxygen functionalities. However, for compounds with low vapor pressures, containing long carbon chains and/or high molecular weights, desorption and ionization is in direct competition with oxidation of the analytes, leading to the formation of adducts and oxidation products which impede a clear signal assignment in the acquired mass spectra. Nonetheless, FAPA–MS showed to be capable of detecting and identifying common limonene oxidation products in secondary OA (SOA) particles on a filter sample and, thus, is considered a suitable method for offline analysis of OA particles. In the second as well as the subsequent parts, FAPA–MS was applied online, i.e. for real time analysis of OA particles suspended in air. Therefore, the acronym AeroFAPA–MS (i.e. Aerosol FAPA–MS) was chosen to refer to this method. After optimization and characterization, the method was used to measure a range of model compounds and to evaluate typical ionization patterns in the positive and the negative ion mode. In addition, results from laboratory studies as well as from a field campaign in Central Europe (F–BEACh 2014) are presented and discussed. During the F–BEACh campaign AeroFAPA–MS was used in combination with complementary MS techniques, giving a comprehensive characterization of the sampled OA particles. For example, several common SOA marker compounds were identified in real time by MSn experiments, indicating that photochemically aged SOA particles were present during the campaign period. Moreover, AeroFAPA–MS was capable of detecting highly oxidized sulfur-containing compounds in the particle phase, presenting the first real-time measurements of this compound class. Further comparisons with data from other aerosol and gas-phase measurements suggest that both particulate sulfate as well as highly oxidized peroxyradicals in the gas phase might play a role during formation of these species. Besides applying AeroFAPA–MS for the analysis of aerosol particles, desorption processes of particles in the afterglow region were investigated in order to gain a more detailed understanding of the method. While during the previous measurements aerosol particles were pre-evaporated prior to AeroFAPA–MS analysis, in this part no external heat source was applied. Particle size distribution measurements before and after the AeroFAPA source revealed that only an interfacial layer of OA particles is desorbed and, thus, chemically characterized. For particles with initial diameters of 112 nm, desorption radii of 2.5–36.6 nm were found at discharge currents of 15–55 mA from these measurements. In addition, the method was applied for the analysis of laboratory-generated core-shell particles in a proof-of-principle study. As expected, predominantly compounds residing in the shell of the particles were desorbed and ionized with increasing probing depths, suggesting that AeroFAPA–MS might represent a promising technique for depth profiling of OA particles in future studies.