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Habilitation
Algorithmic Methods for Mixed Recurrence Equations, Zeros of Classical Orthogonal Polynomials and Classical Orthogonal Polynomial Solutions of Three-Term Recurrence Equations
(2019-07)
Using an algorithmic approach, we derive classes of mixed recurrence equations satisfied by classical orthogonal polynomials. Starting from certain structure relations satisfied by classical orthogonal polynomials or their connection formulae, we show that our mixed recurrence equations are structurally valid. However, they couldn't be easily obtained with classical methods and for this reason, our algorithmic approach is important. The main algorithmic tool used here is an extended version of Zeilberger's ...
Aufsatz
Beating the limits with initial correlations
(2017-11-28)
Fast and reliable reset of a qubit is a key prerequisite for any quantum technology. For real world open quantum systems undergoing non-Markovian dynamics, reset implies not only purification, but in particular erasure of initial correlations between qubit and environment. Here, we derive optimal reset protocols using a combination of geometric and numerical control theory. For factorizing initial states, we find a lower limit for the entropy reduction of the qubit as well as a speed limit. The time-optimal solution ...
Aufsatz
Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron
(2017-07-07)
This study was motivated by our recent observation that the analytical reagent Nitron (2) is an “instant carbene”, whose reaction with coinage metal salts MX afforded complexes of its carbenic tautomer 1,4-diphenyl-3-phenylamino-1,2,4-triazol-5-ylidene (2′). Our aim was to establish an alkyl homologue of 2 in order to achieve a carbenic tautomer of higher donicity. For this purpose 1-tert-butyl-4-methyl-1,2,4-triazol-4-ium-3-tert-butylaminide (6) was synthesized. Its reactions with MX afforded complexes of the carbenic ...
Dissertation
Abhängigkeit des Exchange-Bias Feldes und des Koerzitivfeldes von der mittels Röntgendiffraktometrie gemessenen Kornvolumenverteilung des Antiferromagneten in Exchange-Bias Schichtsystemen
(2019-10-02)
Der Exchange-Bias Effekt wird in vielen technischen Anwendungen, wie z.B. in magnetischen Speichermedien oder in Magnetsensorköpfen zum Pinnen der Magnetisierungsrichtung der Referenzelektrode, eingesetzt. Dieser Effekt tritt ausschließlich in dünnen Schichtsystemen, in denen sich ein dünner Ferromagnet mit einem dünnen Antiferromagneten in Kontakt befindet, auf und bewirkt eine Verschiebung der Hysteresekurve entlang der Magnetfeldachse. Solche Exchange-Bias Schichtsysteme können mittels Ionenbeschuss, d.h., leichte ...
Dissertation
Synthese neuartiger konjugierter mesomerer Betaine und ihr Koordinationsverhalten
(2019-12)
Lange Zeit galten Carbene als transiente Spezies, deren Labilität bzw. hohe Reaktivität gegen eine Isolierbarkeit in Substanz sprach. Erst nach der richtungsweisenden Entdeckung durch ARDUENGO et al., die ein stabiles freies Carben kristallin erhalten konnten, wurden mehr und mehr stabile Carbene isoliert. Das ARDUENGO-Carben gehört zu der Klasse der N-heterocyclischen Carbene (NHCs). Die Stabilität solcher Carbene wird durch zwei Aminosubstituenten am CCarben-Atom und des Weiteren durch die Eingliederung dieses ...
Dissertation
BamB facilitates folding of outer membrane protein A (OmpA) via interactions of its β-propeller with the membrane surface and via a conformation change induced by phosphatidylglycerol
(2019-10-17)
A sufficient folding and insertion of OMPs into the OM of Gram-negative bacteria requires the conserved β-barrel assembly machinery (BAM) complex. The present thesis concerns the structural properties and folding behavior of the lipoprotein BamB and describes its relevance in the synchronized mechanism of membrane insertion and folding of the β-barrel protein OmpA. Furthermore, specific binding sites in BamB involved in the interaction to the lipid membrane or the periplasmic domain of BamA (PD-BamA) were identified ...
Aufsatz
The Diacylglycerol Analogs OAG and DOG Differentially Affect Primary Events of Pheromone Transduction in the Hawkmoth Manduca sexta in a Zeitgebertime-Dependent Manner Apparently Targeting TRP Channels
(2018-07-24)
For the hawkmoth Manduca sexta accumulating evidence suggests that pheromone transduction acts via a metabotropic signal transduction cascade, with G-protein-dependent phospholipase C (PLC) activations generating diacylglycerol (DAG) and inositol trisphosphate as the primary events in hawkmoth pheromone transduction. In contrast, ionotropic olfactory receptor (OR) coreceptor (Orco)-dependent mechanisms do not appear to be involved. In hawkmoths pheromones activated a specific sequence of PLC-dependent ion channels ...
Aufsatz
SSPIM: a beam shaping toolbox for structured selective plane illumination microscopy
(2018-07-03)
Selective plane illumination microscopy (SPIM) represents a preferred method in dynamic tissue imaging, because it combines high spatiotemporal resolution with low phototoxicity. The OpenSPIM system was developed to provide an accessible and flexible microscope set-up for non-specialist users. Here, we report Structured SPIM (SSPIM), which offers an open-source, user-friendly and compact toolbox for beam shaping to be applied within the OpenSPIM platform. SSPIM is able to generate digital patterns for a wide range ...
Aufsatz
Direct evidence for radiative charge transfer after inner-shell excitation and ionization of large clusters
(2018-01-16)
We directly observe radiative charge transfer (RCT) in Ne clusters by dispersed vacuum-ultraviolet photon detection. The doubly ionized Ne^2+ – Ne_n-1 initial states of RCT are populated after resonant 1s–3p photoexcitation or 1s photoionization of Ne_n clusters with {n} \approx 2800. These states relax further producing Ne^+ – Ne^+ – Ne_n-2 final states, and the RCT photon is emitted. Ab initio calculations assign the observed RCT signal to the Ne^2+(2p^-2 [^1D]) - Ne_n-1 initial state, while transitions from other ...
Aufsatz
Circular Dichroism in Fluorescence Emission Following the C 1s→π* Excitation and Resonant Auger Decay of Carbon Monoxide
(2018-06-26)
Dichroism in angle-resolved spectra of circularly polarized fluorescence from freely-rotating CO molecules was studied experimentally and theoretically. For this purpose, carbon monoxide in the gas phase was exposed to circularly polarized soft X-ray synchrotron radiation. The photon energy was tuned across the C 1s→π* resonant excitation, which decayed via the participator Auger transition into the CO+ A 2Π state. The dichroic parameter β1 of the subsequent CO+ (A 2Π → X 2Σ+) visible fluorescence was measured by ...