Universitätspublikationen
Refine
Year of publication
Document Type
- Article (13636)
- Part of Periodical (3484)
- Doctoral Thesis (3326)
- Contribution to a Periodical (2163)
- Book (2100)
- Working Paper (1888)
- Preprint (1687)
- Review (1063)
- Report (909)
- Conference Proceeding (699)
Language
- English (17340)
- German (13990)
- Portuguese (231)
- Spanish (123)
- Italian (66)
- French (64)
- Multiple languages (64)
- Turkish (12)
- Ukrainian (10)
- slo (7)
Keywords
- Deutschland (132)
- COVID-19 (98)
- inflammation (95)
- Financial Institutions (92)
- ECB (69)
- Capital Markets Union (67)
- SARS-CoV-2 (64)
- Financial Markets (61)
- Adorno (58)
- Banking Regulation (52)
Institute
- Medizin (6644)
- Präsidium (5125)
- Physik (3483)
- Wirtschaftswissenschaften (2296)
- Gesellschaftswissenschaften (2021)
- Biowissenschaften (1763)
- Frankfurt Institute for Advanced Studies (FIAS) (1669)
- Sustainable Architecture for Finance in Europe (SAFE) (1401)
- Biochemie und Chemie (1400)
- Informatik (1390)
A thylakoid membrane preparation isolated from the blue-green alga Anacystis nidulans was freed from carboxysomes, soluble enzymes and the pigment P750 by floating in a discontinuous sucrose density gradient. In a buffer containing sucrose and the zwitterionic detergent Miranol S2M-SF the thylakoids were loaded on a linear 10-18% sucrose density gradient which also contained Miranol. The sedimentation yielded three bands, the lower two of which were green and the upper one was orange. The light green band in the middle of the gradient was the only one to show any photosystem II activity. This was measured as light-induced electron transport from diphenylcarbazide (DPC) to dichlorophenol-indophenol (DCPIP). The activity was sensitive to dichlorophenyl-dimethylurea (DCMU).
The red absorption maximum of the particles in this middle band - henceforth called photosystem II particles - was found at 672 nm and the maximum of their low temperature fluorescence emission spectrum at 685 nm upon excitation with blue light. Cytochrome b559 was the only cytochrome found in these particles; it was present at an average ratio of one molecule cytochrome per 40 -50 molecules chlorophyll a. C550 photoreduction with accompanying photooxidation of cytochrome b559 was also observed in the photosystem II particles. Good photosystem II preparations did not contain any detectable amounts of P 700.
By means of sodium dodecylsulfate polyacrylamide gel electrophoresis the polypeptide composition of the photosystem II particles was studied. Dissolution of the chlorophyll protein complexes was done under strongly denaturing conditions; consequently, no green bands were observed on the gels. The polypeptide pattern of the photosystem II particles showed two strong predominant bands of protein components with apparent molecular weights (app. mol. wts.) of about 50 000 and 48 000. These two bands are unique for photosystem II. Two other weaker bands were also found characteristic for photosystem II, the band of a polypeptide with an app. mol. wt. of 38 000 and that of a polypeptide with an app. mol. wt. of 31 000. Sometimes in addition the weak band of a polypeptide with the app. mol. wt. 27 000 was observed on the gel. The polypeptide 38 000 aggregated upon boiling of the sample in the presence of the denaturing agents prior to the electrophoresis, yielding an aggregate with an app. mol. wt. of 50 000. Additional polypeptides which were often found in the photosystem II particle preparation could be identified as subunits of the coupling factor of photophosphorylation CF1. None of the polypeptides described as characteristic for photosystem II are due to proteolytic activity.
As the observed photosystem II activity was found to be DCMU-sensitive it appears that the DCMU-binding protein is among the here described photosystem II polypeptides. Moreover, the authors have reason to believe that one of the major protein components found characteristic for photosystem II is cytochrome b559.
We characterize optimal redistribution in a dynastic family model with human capital. We show how a government can improve the trade-off between equality and incentives by changing the amount of observable human capital. We provide an intuitive decomposition for the wedge between human-capital investment in the laissez faire and the social optimum. This wedge differs from the wedge for bequests because human capital carries risk: its returns depend on the non-diversi
able risk of children's ability. Thus, human capital investment is encouraged more than bequests in the social optimum if human capital is a bad hedge for consumption risk.
We present empirical evidence on the heterogeneity in monetary policy transmission across countries with different home ownership rates. We use household-level data together with shocks to the policy rate identified from high-frequency data. We find that housing tenure reacts more strongly to unexpected changes in the policy rate in Germany and Switzerland –the OECD countries with the lowest home ownership rates– compared with existing evidence for the U.S. An unexpected decrease in the policy rate by 25 basis points increases the home ownership rate by 0.8 percentage points in Germany and by 0.6 percentage points in Switzerland. The response of non-housing consumption in Switzerland is less heterogeneous across renters and mortgagors, and has a different pattern across age groups than in the U.S. We discuss economic explanations for these findings and implications for monetary policy.
In der vorliegenden Arbeit wurde erstmals die Interaktion von A. baumannii mit humanem Plasminogen untersucht. Mit dem Translations-Elongationsfaktor TufAb, dem äußeren Membranprotein OmpW sowie dem Lipoprotein p41 konnten insgesamt drei Plasminogen-bindende Proteine von A. baumannii identifiziert werden. Außerdem wurde ein grundlegender Beitrag zur funktionellen Charakterisierung von TufAb sowie p41 von A. baumannii erbracht.
Es konnte nachgewiesen werden, dass gereinigtes TufAb humanes Plasminogen bindet und diese Interaktion teilweise durch Lysin-Reste vermittelt und von der Ionenstärke beeinflusst ist. An TufAb-gebundenes Plasminogen war für den Plasminogen-Aktivator u-PA zugänglich und konnte zu Plasmin aktiviert werden, welches das chromogene Substrat S-2251, das physiologische Substrat Fibrinogen und die zentrale Komplementkomponente C3b proteolytisch spaltete. Schließlich konnte TufAb als „Moonlighting“-Protein auf der Zelloberfläche von A. baumannii identifiziert werden.
Für das Lipoprotein p41 konnte ebenfalls gezeigt werden, dass dieses an Plasminogen bindet. Die Bindung von Plasminogen an p41 erfolgte ebenfalls über Lysin-Reste, zeigte sich allerdings von der Ionenstärke unbeeinflusst. Im Fall von p41 konnte mit Hilfe von C-terminal verkürzten p41-Konstrukten gezeigt werden, dass C-terminale Lysin-Reste an der Bindung von Plasminogen beteiligt sind. Weitere Versuche mit p41-Proteinen, bei welchen vier C-terminale Lysin-Reste durch Alanin-Reste substituiert wurden, ergaben, dass die beiden Lysin-Reste K368 und K369 essentiell für die Bindung von Plasminogen an p41 sind. Zudem konnte gezeigt werden, dass sowohl Kringle-Domäne 1 als auch Kringle-Domäne 4 von Plasminogen bei der Interaktion mit p41 involviert sind. An p41 gebundenes Plasminogen ließ sich durch u-PA zu Plasmin aktivieren, welches Fibrinogen sowie die zentrale Komplementkomponente C3b degradierte. p41 ist außerdem in der Lage, die Komplementkomponenten C3, C3b und C5 zu binden und den alternativen Weg zu inhibieren. Zudem ergaben Untersuchungen im Rahmen dieser Arbeit erste Hinweise darauf, dass zumindest die Plasminogen-bindende Region auf der Zelloberfläche von A. baumannii lokalisiert ist.
Die Inaktivierung des p41-kodierenden Gens führte zu einer signifikanten Abnahme im Überleben von A. baumannii-Zellen in der Gegenwart von NHS. Zudem zeigte die Mutante Δp41 einen Defekt in der Plasmin-abhängigen Transmigration durch einen Endothelzell-Monolayer. Beide Versuche untermauern die physiologische Relevanz für die Interaktion von A. baumannii mit Plasminogen.
Translation elongation factor Tuf of Acinetobacter baumannii is a plasminogen-binding protein
(2015)
Acinetobacter baumannii is an important nosocomial pathogen, causing a variety of opportunistic infections of the skin, soft tissues and wounds, urinary tract infections, secondary meningitis, pneumonia and bacteremia. Over 63% of A. baumannii infections occurring in the United States are caused by multidrug resistant isolates, and pan-resistant isolates have begun to emerge that are resistant to all clinically relevant antibiotics. The complement system represents the first line of defense against invading pathogens. However, many A. baumannii isolates, especially those causing severe bacteremia are resistant to complement-mediated killing, though the underlying mechanisms remain poorly understood. Here we show for the first time that A. baumannii binds host-derived plasminogen and we identify the translation elongation factor Tuf as a moonlighting plasminogen-binding protein that is exposed on the outer surface of A. baumannii. Binding of plasminogen to Tuf is at least partly dependent on lysine residues and ionic interactions. Plasminogen, once bound to Tuf can be converted to active plasmin and proteolytically degrade fibrinogen as well as the key complement component C3b. Thus, Tuf acts as a multifunctional protein that may contribute to virulence of A. baumannii by aiding in dissemination and evasion of the complement system.
This thesis deals with several aspects of non-perturbative calculations in low-dimensional quantum field theories. It is split into two main parts:
The first part focuses on method development and testing. Using exactly integrable QFTs in zero spacetime dimensions as toy models, the need for non-perturbative methods in QFT is demonstrated. In particular, we focus on the functional renormalization group (FRG) as a non-perturbative exact method and present a novel fluid-dynamic reformulation of certain FRG flow equations. This framework and the application of numerical schemes from the field of computational fluid dynamics (CFD) to the FRG is tested and benchmarked against exact results for correlation functions. We also draw several conclusions for the qualitative understanding and interpretation of renormalization group (RG) flows from this fluid-dynamic reformulation and discuss the generalization of our findings to realistic higher-dimensional QFTs.
The topics discussed in the second part are also manifold. In general, the second part of this thesis deals with the Gross-Neveu (GN) model, which is a prototype of a relativistic QFT. Even though being a model in two spacetime dimensions, it shares many features of realistic models and theories for high-energy particle physics, but also emerges as a limiting case from systems in solid state physics. Especially, it is interesting to study the model at non-vanishing temperatures and densities, thus, its thermodynamic properties and phase structure.
First, we use this model to test and apply our findings of the first part of this thesis in a realistic environment. We analyze how the fluid-dynamic aspects of the FRG realize themselves in the RG flow of a full-fledged QFT and how we profit from this numeric framework in actual calculations. Thereby, however, we also aim at answering a long-standing question: Is there still symmetry breaking and condensation at non-zero temperatures in the GN model, if one relaxes the commonly used approximation of an infinite number of fermion species and works with a finite number of fermions? In short: Is matter (in the GN model) in a single spatial dimension at non-zero temperature always gas-like?
In general, we also use the GN model to learn about the correct description of QFTs at non-zero temperatures and densities. This is of utmost relevance for model calculations in low-energy quan- tum chromodynamics (QCD) or other QFTs in medium and we draw several conclusions for the requirements for stable calculations at non-zero chemical potential.
We continue previous investigations of the (inhomogeneous) phase structure of the Gross-Neveu model in a noninteger number of spatial dimensions (1≤d<3) in the limit of an infinite number of fermion species (N→∞) at (non)zero chemical potential μ. In this work, we extend the analysis from zero to nonzero temperature T.
The phase diagram of the Gross-Neveu model in 1≤d<3 spatial dimensions is well known under the assumption of spatially homogeneous condensation with both a symmetry broken and a symmetric phase present for all spatial dimensions. In d=1 one additionally finds an inhomogeneous phase, where the order parameter, the condensate, is varying in space. Similarly, phases of spatially varying condensates are also found in the Gross-Neveu model in d=2 and d=3, as long as the theory is not fully renormalized, i.e., in the presence of a regulator. For d=2, one observes that the inhomogeneous phase vanishes, when the regulator is properly removed (which is not possible for d=3 without introducing additional parameters).
In the present work, we use the stability analysis of the symmetric phase to study the presence (for 1≤d<2) and absence (for 2≤d<3) of these inhomogeneous phases and the related moat regimes in the fully renormalized Gross-Neveu model in the μ,T-plane. We also discuss the relation between "the number of spatial dimensions" and "studying the model with a finite regulator" as well as the possible consequences for the limit d→3.
The phase diagram of the (1+1)-dimensional Gross-Neveu model is reanalyzed for (non-)zero chemical potential and (non-)zero temperature within the mean-field approximation. By investigating the momentum dependence of the bosonic two-point function, the well-known second-order phase transition from the Z2 symmetric phase to the so-called inhomogeneous phase is detected. In the latter phase the chiral condensate is periodically varying in space and translational invariance is broken. This work is a proof of concept study that confirms that it is possible to correctly localize second-order phase transition lines between phases without condensation and phases of spatially inhomogeneous condensation via a stability analysis of the homogeneous phase. To complement other works relying on this technique, the stability analysis is explained in detail and its limitations and successes are discussed in context of the Gross-Neveu model. Additionally, we present explicit results for the bosonic wave-function renormalization in the mean-field approximation, which is extracted analytically from the bosonic two-point function. We find regions -- a so-called moat regime -- where the wave function renormalization is negative accompanying the inhomogeneous phase as expected.
The phase diagram of the (1+1)-dimensional Gross-Neveu model is reanalyzed for (non-)zero chemical potential and (non-)zero temperature within the mean-field approximation. By investigating the momentum dependence of the bosonic two-point function, the well-known second-order phase transition from the Z2 symmetric phase to the so-called inhomogeneous phase is detected. In the latter phase the chiral condensate is periodically varying in space and translational invariance is broken. This work is a proof of concept study that confirms that it is possible to correctly localize second-order phase transition lines between phases without condensation and phases of spatially inhomogeneous condensation via a stability analysis of the homogeneous phase. To complement other works relying on this technique, the stability analysis is explained in detail and its limitations and successes are discussed in context of the Gross-Neveu model. Additionally, we present explicit results for the bosonic wave-function renormalization in the mean-field approximation, which is extracted analytically from the bosonic two-point function. We find regions -- a so-called moat regime -- where the wave function renormalization is negative accompanying the inhomogeneous phase as expected.
The phase diagram of the (1+1)-dimensional Gross-Neveu model is reanalyzed for (non-)zero chemical potential and (non-)zero temperature within the mean-field approximation. By investigating the momentum dependence of the bosonic two-point function, the well-known second-order phase transition from the Z2 symmetric phase to the so-called inhomogeneous phase is detected. In the latter phase the chiral condensate is periodically varying in space and translational invariance is broken. This work is a proof of concept study that confirms that it is possible to correctly localize second-order phase transition lines between phases without condensation and phases of spatially inhomogeneous condensation via a stability analysis of the homogeneous phase. To complement other works relying on this technique, the stability analysis is explained in detail and its limitations and successes are discussed in context of the Gross-Neveu model. Additionally, we present explicit results for the bosonic wave-function renormalization in the mean-field approximation, which is extracted analytically from the bosonic two-point function. We find regions -- a so-called moat regime -- where the wave function renormalization is negative accompanying the inhomogeneous phase as expected.
Gene targeting in embryonic stem (ES) cells remains best practice for introducing complex mutations into the mouse germline. One aspect in this multistep process that has not been streamlined with regard to the logistics and ethics of mouse breeding is the efficiency of germline transmission: the transmission of the ES cell-derived genome through the germline of chimeras to their offspring. A method whereby male chimeras transmit exclusively the genome of the injected ES cells to their offspring has been developed. The new technology, referred to as goGermline, entails injecting ES cells into blastocysts produced by superovulated homozygous Tsc22d3 floxed females mated with homozygous ROSA26-Cre males. This cross produces males that are sterile due to a complete cell-autonomous defect in spermatogenesis. The resulting male chimeras can be sterile but when fertile, they transmit the ES cell-derived genome to 100% of their offspring. The method was validated extensively and in two laboratories for gene-targeted ES clones that were derived from the commonly used parental ES cell lines Bruce4, E14, and JM8A3. The complete elimination of the collateral birth of undesired, non-ES cell-derived offspring in goGermline technology fulfills the reduction imperative of the 3R principle of humane experimental technique with animals. genesis 54:326-333, 2016. © 2016 The Authors. Genesis Published by Wiley Periodicals, Inc.
The p53-family member p73 plays a role in various cellular signaling pathways during development and growth control and it can have tumor suppressor properties. Several isoforms of p73 exist with considerable differences in their function. Whereas the functions of the N-terminal isoforms (TA and delta Np73) and their opposing pro- and antiapoptotic roles have become evident, the functional differences of the distinct C-terminal splice forms of TAp73 have remained unclear. Here, we characterized the global genomic binding sites for TAp73alpha and TAp73beta by chromatin immunoprecipitation sequencing as well as the transcriptional responses by performing RNA sequencing. We identified a specific p73 consensus binding motif and found a strong enrichment of AP1 motifs in close proximity to binding sites for TAp73alpha. These AP1 motif-containing target genes are selectively upregulated by TAp73alpha, while their mRNA expression is repressed upon TAp73beta induction. We show that their expression is dependent on endogenous c-Jun and that recruitment of c-Jun to the respective AP1 sites was impaired upon TAp73beta expression, in part due to downregulation of c-Jun. Several of these AP1-site containing TAp73alpha-induced genes impinge on apoptosis induction, suggesting an underlying molecular mechanism for the observed functional differences between TAp73alpha and TAp73beta.
Im Rahmen dieser Beispielanalyse werden Aspekte und Phänomene der Textgrammatik (vgl. Rickheit & Schade 2002, Stede 2007) veranschaulicht. Am Beispiel einer privaten E-Mail wird gezeigt, wie ein satzgrenzenüberschreitender Zusammenhang und damit Textkohärenz hergestellt werden kann. Dabei werden vor allem die Besonderheiten eines konzeptionell mündlichen Textes (vgl. Schwitalla 2006) der neuen Medien in Bezug auf Kohärenzherstellung herausgearbeitet.
Die vorliegende Beispielerhebung erfasst und analysiert die Sprachbiographien von Freiburger Studierenden mit Migrationshintergrund. Sprachbiographien dienen der Darstellung eines Lebens bzw. einer Lebensspanne unter dem Gesichtspunkt der Sprachentwicklung mit dem Ziel der Rekonstruktion eines Gesamtbildes der sprachlichen Entwicklung einer Person in ihrem gesellschaftlichen Umfeld. Mithilfe der Sprachbiographien lassen sich Rückschlüsse auf die sprachliche und soziale Identität der Personen sowie auf den Zusammenhang zwischen der individuellen Sprachentwicklung und den für sie relevanten Lebensbedingungen ziehen. Besondere Bedeutung kommt hierbei der Rolle von (sprachlicher) Identität beim Integrationsprozess zu.
Behavior is characterized by sequences of goal oriented conducts, such as food uptake, socializing and resting. Classically, one would define for each task a corresponding satisfaction level, with the agent engaging, at a given time, in the activity having the lowest satisfaction level. Alternatively, one may consider that the agent follows the overarching objective to generate sequences of distinct activities. To achieve a balanced distribution of activities would then be the primary goal, and not to master a specific task. In this setting the agent would show two types of behaviors, task-oriented and task-searching phases, with the latter interseeding the former. We study the emergence of autonomous task switching for the case of a simulated robot arm. Grasping one of several moving objects corresponds in this setting to a specific activity. Overall, the arm should follow a given object temporarily and then move away, in order to search for a new target and reengage. We show that this behavior can be generated robustly when modeling the arm as an adaptive dynamical system. The dissipation function is in this approach time dependent. The arm is in a dissipative state when searching for a nearby object, dissipating energy on approach. Once close, the dissipation function starts to increase, with the eventual sign change implying that the arm will take up energy and wander off. The resulting explorative state ends when the dissipation function becomes again negative and the arm selects a new target. We believe that our approach may be generalized to generate self-organized sequences of activities in general.
The YaeJ protein is a codon-independent release factor with peptidyl-tRNA hydrolysis (PTH) activity, and functions as a stalled-ribosome rescue factor in Escherichia coli. To identify residues required for YaeJ function, we performed mutational analysis for in vitro PTH activity towards rescue of ribosomes stalled on a non-stop mRNA, and for ribosome-binding efficiency. We focused on residues conserved among bacterial YaeJ proteins. Additionally, we determined the solution structure of the GGQ domain of YaeJ from E. coli using nuclear magnetic resonance spectroscopy. YaeJ and a human homolog, ICT1, had similar levels of PTH activity, despite various differences in sequence and structure. While no YaeJ-specific residues important for PTH activity occur in the structured GGQ domain, Arg118, Leu119, Lys122, Lys129 and Arg132 in the following C-terminal extension were required for PTH activity. All of these residues are completely conserved among bacteria. The equivalent residues were also found in the C-terminal extension of ICT1, allowing an appropriate sequence alignment between YaeJ and ICT1 proteins from various species. Single amino acid substitutions for each of these residues significantly decreased ribosome-binding efficiency. These biochemical findings provide clues to understanding how YaeJ enters the A-site of stalled ribosomes.
A convex body is unconditional if it is symmetric with respect to reflections in all coordinate hyperplanes. We investigate unconditional lattice polytopes with respect to geometric, combinatorial, and algebraic properties. In particular, we characterize unconditional reflexive polytopes in terms of perfect graphs. As a prime example, we study the signed Birkhoff polytope. Moreover, we derive constructions for Gale-dual pairs of polytopes and we explicitly describe Gröbner bases for unconditional reflexive polytopes coming from partially ordered sets.
Eisbildende Prozesse sind für die Wolkenbildung von großer Bedeutung und haben erhebliche Auswirkungen auf das Wetter und Klima der Erde, indem sie den Strahlungsantrieb und die Niederschlagsbildung beeinflussen. In den mittleren Breiten entsteht der meiste Niederschlag in sogenannten Mischphasenwolken (MPC), welche sowohl aus unterkühlten Wolkentröpfchen als auch aus Eiskristallen bestehen. Bei Temperaturen zwischen 0°C und -38°C erfolgt die Bildung von Eiskristallen in MPC in Gegenwart von Aerosolpartikeln, die als sogenannte Eiskeime (INP) die Fähigkeit besitzen, auf ihrer Oberfläche Eis zu nukleieren. Trotz der großen wissenschaftlichen Fortschritte in den letzten Jahrzehnten, weist der heterogene Eisbildungsprozess, als einer der wichtigsten in der Atmosphäre auftretenden Aerosol-Wolken-Wechselwirkungsprozesse, immer noch große Unsicherheiten auf. Um zukünftige Klimavorhersagen und -projektionen in Modellen besser abbilden zu können, ist es somit notwendig den Wissensgrad der räumlichen und zeitlichen Heterogenität von INP in Bezug auf Herkunft, Anzahl und Zusammensetzung zu erhöhen. Im Zentrum dieser Arbeit steht der Eiskeimzähler FINCH (Fast Ice Nucleus Chamber), der für Labor- und Feldexperimente von der Johann Wolfgang Goethe-Universität in Frankfurt am Main entwickelt wurde. Durch das Mischen des Probenstroms mit einem warm-feuchten und einem kalten-trockenen Luftstrom wird eine Übersättigung in der in-situ Eiskammer erreicht, die benötigt wird, eisbildende Partikel zu aktivieren. Die aktivierten Partikel können beim Durchströmen der Kammer zu Wassertropfen oder Eiskristallen anwachsen. Am Ausgang der Kammer wird die Anzahl und Größe der Partikel durch die FINCH-Optik erfasst. Als grundlegender Schritt und aufbauend auf den Charakterisierungsmessungen von Frank (2017) wurden in der vorliegenden Arbeit die Leistung, die Zuverlässigkeit sowie die Reproduzierbarkeit von FINCH in Validierungsexperimenten im Labor überprüft. Im Zuge dessen wurden heterogene Gefrierexperimente mit definierten Referenzaerosolproben (bspw. K-Feldspat) bei wasserübersättigten Bedingungen und verschiedenen Gefriertemperaturen durchgeführt. Für den Großteil der erzielten Resultate konnte eine zufriedenstellende Übereinstimmung mit Literaturwerten von anderen INP-Messinstrumenten aus der ganzen Welt erzielt werden. Es zeigte sich, dass die Leistungsfähigkeit von FINCH messtechnische Limitationen für Messexperimente bei Temperaturen >-10°C und <-30°C aufweist, was eine Einschränkung des Messbereichs bedeutet. Hinsichtlich der Quantifizierung des Unsicherheitsbereiches des Messgerätes in Bezug auf Temperatur und relativer Feuchte bedarf es im Nachgang an dieser Arbeit weiterer Charakterisierungsmessungen. Im Rahmen der Ice Nuclei Research Unit (INUIT) Forschergruppe wurde FINCH mit einem gepumpten Gegenstrom-Impaktor PCVI und dem online Einzelpartikel-Massenspektrometer ALABAMA gekoppelt. Diese spezielle Messmethodik dient zur chemischen und mikrophysikalischen Charakterisierung der INP und der Eispartikelresiduen (IPR). Der Fokus lag zunächst darauf die Funktionalität des gekoppelten Messsystems im Labor zu überprüfen. Ausführliche Charakterisierungsmessungen zeigten unter eisübersättigten und unterkühlten Bedingungen, dass das Prinzip der Trennung der INP von nicht-aktivierten Aerosolen und unterkühlten Tropfen hinter FINCH durch den PCVI funktioniert. Ebenso konnten erste quantitative Aussagen zur chemischen Zusammensetzung der IPR getroffen werden. Es zeigte sich, dass bei den Aktivierungsexperimenten ein geringer Anteil an Partikeltypen metallischer Art von ALABAMA detektiert wurden, der nicht dem untersuchten Aerosoltyp zugeordnet werden konnte. Der Ursprung dieser Kontamination konnte im Rahmen dieser Arbeit nicht abschließend geklärt werden und bedarf weiterer Validierungsmessungen im Labor. Atmosphärische Eiskeimkonzentrationen wurden im Rahmen von Feldmesskampagnen an der Hochalpinen Forschungsstation Jungfraujoch (JFJ) in den Schweizer Alpen und am Campus Riedberg der Johann Wolfgang Goethe-Universität in Frankfurt am Main untersucht. Hier konnten erste Erfahrungen mit Außenluftmessungen bezüglich der Leistungsfähigkeit und der Nachweisgrenze (LOD) des Messgerätes gesammelt werden. Durch den Einfluss der freien Troposphäre am JFJ waren die Messungen hauptsächlich von aerosolpartikelarmer Luft mit einer geringen Anzahl von Eiskeimen geprägt, so dass sich die gemessenen INP-Konzentrationen oftmals unter die Nachweisgrenze von FINCH fielen. Unter Einsatz eines Aerosolkonzentrators konnte die Detektionseffizienz verbessert und das LOD herabgesetzt werden. Am JFJ wurden die INP im Mittel bei einer Temperatur von -23°C und einem Wassersättigungsverhältnis von 107% beprobt. Die mediane (mittlere) INP-Konzentration inklusive LOD lag bei 2,1 (3,3) sL-1 und oberhalb des LOD bei 3,1 (4,5) sL-1. Ein Vergleich mit den Messungen am Campus Riedberg unter annähernd gleichen Bedingungen resultiert in ähnlichen Konzentrationen.