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Novel Pseudocyclopeptides Containing 1,4-Disubstituted 1,2,3-Triazole Subunits for Anion Recognition (2017)

Disha Mungalpara

Anion recognition is one of the most rapidly growing areas in the field of Supramolecular Chemistry due to the vital role of anions in the environment, in biology and in industry. The development of new anion binding motifs that can also be combined with known ones in a novel receptor is a timely topic. In this context, we have synthesized three cyclic pseudopeptides 16, 17 and 18, containing conventional H-bond donors (amide) in combination with, respectively, triazole C–H or triazole C–I functions. All three receptors were synthesized by using a combination of peptide and click chemistry. Structural studies show that all three pseudopeptides adopt conformations with the triazole C-H or C-I groups pointing into the cavity center to allow them to contribute to binding. Quantitative binding studies showed that the cyclic pseudohexapeptide 1 coordinates to oxoanions (sulfate, dihydrogenphosphate, and hydrogenpyrophosphate) with different binding strengths and complex stoichiometries in 2.5 vol% water/DMSO. Anion selectivity of 16 significantly changes when the cavity size of this pseudopeptide is increased to obtain the larger analog 17. This pseudooctapeptide forms well defined complexes with protonated phosphate anions. The complexation involves sandwiching of a cyclic tetramer of dihydrogenphosphate or a dimer of dihydrogenpyrophosphate anions by two pseudopeptide rings. Both complexes were characterized structurally in the solid state. They are stable in solution (2.5 vol% water/DMSO) as result of the interaction between hydrogen bond donors of 17 and the oxygen atoms of the anionic aggregates. The complexes can also be transferred to the gas phase without decomposition. Anion selectivity of 16 was further altered by introducing iodine atom in the C5 position of the 1,4-disubstituted 1,2,3-triazole units. The corresponding cyclic pseudohexapeptide 18 features a smaller cavity diameter than 17 as a result of the iodide atoms and was therefore found to only coordinate to smaller spherical anions such as chloride. It forms 1:1 complexes with chloride, bromide and iodide in 2.5 vol% water/DMSO. Among the halides, 18 has highest affinity for chloride followed by bromide and iodide. The same stability trend was also observed in the gas phase by ESI/MS. Concluding, I prepared three new macrocyclic pseudopeptides during my PhD and characterized their complexes with anions in terms of structure and affinity. All of these pseudopeptides were shown to interact with phosphate-derived anions, which renders them unique among the anion receptors developed in the Kubik group before.

Cryo Tagging Infrared Spectroscopy and Temperature Controlled Kinetic Studies in a Tandem Trap Mass Spectrometer (2017)

Jennifer Mohrbach

In the present work, the interaction of diatomic molecules with charged transition metal clusters and complexes was investigated. Temperature controlled isothermal kinetic studies served to elucidate the adsorption behavior of transition metal clusters. Infrared multiple photon dissociation (IR-MPD) experiments in conjunction with density functional theory (DFT) computations enabled the analysis of adsorbate induced changes on the structure and spin multiplicity of transition metal cores. A tandem cryo trap setup was used for the kinetic and spectroscopic investigations of the given compounds as isolated species in the gas phase. The presented investigations enabled insight into the metal-adsorbate bonding and provided cluster size and adsorbate coverage dependent information on cluster surface morphologies.

Prozesstechnologie für Cyclic Butylene Terephthalate im Faser-Kunststoff-Verbund (2010)

Markus Steeg

Textiles Formgebungsverhalten beim kontinuierlichen Preforming (2016)

Timo Grieser

Bei der Herstellung von Faser-Kunststoff-Verbunden durch Harzinjektionsverfahren wird ein textiler Vorformling, die Preform, mit einem Harzsystem imprägniert und anschließend ausgehärtet. Die Erzeugung der Preform, auch Preforming genannt, beinhaltet dabei eine Vielzahl an Arbeitsschritten, welche maßgeblich die Kosten des herzustellenden Bauteils bestimmen. Die Automatisierung des Preformings birgt daher ein enorm hohes Potential zur Kostenreduzierung. Im Rahmen dieser Arbeit wurde deshalb ein neues Preforming System entwickelt, welches die kontinuierliche Herstellung von Profil-Preforms aus textilen Halbzeugen ermöglicht. Erstmalig wurde dabei zur kontinuierlichen Fixierung die Nähtechnik verwendet, welche ein energieund zeiteffizientes Preforming zulässt. Allerdings hat sich bei der Herstellung von Profil-Preforms mit unterschiedlichen textilen Halbzeugen gezeigt, dass die maximal erreichbare Prozessgeschwindigkeit ohne relative Textilschädigung variiert. Ursache hierfür ist das Textilverhalten während der Formgebung. Durch die Wahl geeigneter Material- und Prozessparameter besteht allerdings ein hohes Potential, einen Preforming Prozess zu optimieren. Daher war es das Ziel dieser Arbeit, Richtlinien für Material- und Prozessparameter zu entwickeln, die sowohl eine robuste als auch effiziente Preformherstellung ermöglichen. Als kritische Textileigenschaften wurden das Kompaktierungs-, das Reibungs- und das Biegeverhalten identifiziert. Diese wurden in separaten Parameterstudien hinsichtlich der Auswirkungen von Materialparametern (z. B. Bindungsart) und Prozessparametern (z. B. Prozessgeschwindigkeit) untersucht. Die Ergebnisse konnten anschließend in Richtlinien zusammengefasst werden, welche für eine prozessorientierte Materialauswahl oder für Prozessmodifikationen beim Preforming genutzt werden können. Bei der Übertragung auf einen Preforming Prozess muss jedoch berücksichtigt werden, dass sich Effekte verursacht durch Kompaktierung, Reibung und Biegung in Abhängigkeit des Faservolumengehaltes der Preforms überlagern können. Daher wurden anhand einer weiteren Studie dominierende Textileigenschaften in Abhängigkeit des Ziel-FVG der Profil-Preforms beim entwickelten Preforming Prozess identifiziert. Abschließend wurden die entwickelten Richtlinien verifiziert, indem sowohl eine prozessorientierte Materialauswahl als auch prozessseitig eine Vorkompaktierungseinheit validiert wurden.

Nachhaltige katalytische Transformationen von Carbonsäuren (2017)

Dagmar Hackenberger

Im Rahmen dieser Arbeit wurden neue nachhaltige Methoden zur selektiven C−C Bindungsknüpfung ausgehend von Carbonsäuren entwickelt. Dabei wurden die Reaktionskonzepte der decarboxylierenden Biarylsynthese sowie der Carboxylat-dirigierten Arylierung verfolgt. Geleitet von eingehenden DFT-Studien wurde ein Katalysatorsystem entwickelt, mit dem die Reaktionstemperatur der Kupfer/Palladium-katalysierten decarboxylierenden Kreuzkupplung von ursprünglich über 150 °C auf 100−120 °C abgesenkt werden konnte. Dazu wurden bidentate P,N-Liganden eingesetzt, die die Katalysatormetalle verbrückend koordinieren können und so die geschwindigkeitsbestimmende Transmetallierung erleichtern. Daneben gelang es, ein bimetallisches Kupfer/Palladium Katalysatorsystem zu entwickeln, welches die Synthese 3-substituierter 2 (Hetero-)Arylpyridine bei nur 130 °C ermöglicht. Dies basierte auf der Entdeckung, dass ein Substituent ortho zur Carboxygruppe der Pyridin-2-carbonsäure ebenso wie im Fall von Benzoesäuren eine Decarboxylierung begünstigt. Neben den decarboxylierenden ipso-Arylierungen wurden auch neue Protokolle für Carboxylat-dirigierte ortho-Arylierungen von Benzoesäuren entwickelt. So wurde diese erstmals mit Aryldiazoniumsalzen als Kupplungspartner realisiert. Das neue Protokoll unter Verwendung eines Iridium-basierten Katalysatorsystems gewährleistet eine Reaktionsführung unter vergleichsweise milden Bedingungen. Zudem wird eine Orthogonalität zu Kupplungen mit Arylhalogeniden geschaffen. Daneben wurde ein Protokoll für die ortho-Arylierung von Benzoesäuren mit Arylhalogeniden entwickelt, welches erstmals auf kostengünstigen Ruthenium-Katalysatoren basiert. Die Überlegenheit der Carboxylatgruppe im Vergleich zu anderen dirigierenden Gruppen konnte demonstriert werden, indem sie im Anschluss an die jeweilige ortho-Arylierung entfernt sowie als Ankerpunkt in weiteren Funktionalisierungen genutzt wurde. Weiterhin gelang es, eine Kupfer/Palladium-katalysierte decarboxylierende Mizoroki-Heck-Reaktion von Zimtsäuren mit Arylhalogeniden zu entwickeln, welche selektiv 1,1 Diarylalkene zugänglich macht. Dabei agiert die Carboxylatgruppe als abfallende dirigierende Gruppe. Das synthetische Potential der neu entwickelten Methoden wurde jeweils anhand eines diversen Substratspektrums demonstriert. Darüber hinaus lieferten mechanistische Studien zu den Carboxylat-dirigierten Transformationen Einblicke zum Ablauf der Reaktionen.

Viscoelastic Modeling of Calving Processes at Antarctic Ice Shelves (2017)

Julia Christmann

In this thesis viscoelastic material models are established to investigate the nature of continuous calving processes at Antarctic ice shelves. Physics-based descriptions of calving require appropriate fracture criteria to separate icebergs from the remaining ice shelf. Hence, criteria of the stress, the strain, and the self-similarity criterion are considered within finite-element computations. Crucial parameters in the models to determine the position of calving are the accurate knowledge of the geometry, especially the freeboard height, while the material parameters mainly influence the time span between two successive calving events. The extension to nonlinear material models is necessary to properly analyze the internal forces also for large deformations that occur for longer times of the viscous ice flow.

Smartphonegestützte Analyse von siedlungsökologischen Risiko- und Potenzialflächen (2017)

Martin Fabisch

Im Rahmen dieser Dissertation wurde ein Verfahren entwickelt, dass es kleinen Gemeinden erlaubt, selbstständig die siedlungsökologische Situation innerhalb ihrer Siedlung zu analysieren. Das entwickelte Matrix-Verfahren beruht dabei nicht auf der Messung oder Simulation der Klimaparameter, sondern auf der Abschätzung der Eintrittswahrscheinlichkeit in Abhängigkeit von verschiede-nen siedlungsklimarelevanten Indikatoren. Dabei werden die Indikatoren nicht isoliert betrachtet, sondern paarweise in einer Matrix gegenübergestellt. An-hand der Ausprägungsintensität der Indikatoren kann aus dieser Matrix die Ein-trittswahrscheinlichkeit eines Stadtklimaphänomens abgeschätzt werden. Durch Anwendung des entwickelten Verfahrens können die für kleine Siedlun-gen relevanten Themenbereiche „urbane Überwärmung“, „urbane Frisch- und Kaltluftversorgung“ und „urbaner Wasserhaushalt“ untersucht werden. Eng mit der Entwicklung der Matrix-Methode verknüpft, wurde parallel ein Be-standsaufnahmeverfahren entwickelt, dass für die Erfassung der Indikatoren genutzt wird. Für die Bestandsaufnahme vor Ort wurde die Android-App „ÖkoHaSie“ entwickelt, die den Anwender Schritt-für-Schritt durch die Be-standsaufnahme leitet. Die Kombination aus den beiden entwickelten Komponenten „Matrix-Methode“ und „ÖkoHaSie“ ermöglicht es Gemeinden schnell und selbstständig siedlungsökologische Risiko- und Potenzialflächen zu identifizieren. Durch den im Vergleich zu anderen Siedlungsklimaanalysemethoden geringen Arbeits-aufwand und die deutlich günstigeren Anschaffungskosten von technischen Geräten und Softwarelizenzen kann die Matrix-Methode als einzige „low-cost“-Lösung angesehen werden, die es Gemeinden ermöglicht, selbstständig die siedlungsökologische Situation vor Ort zu analysieren.

An Intersection-Theoretic Approach to Correspondence Problems in Tropical Geometry (2016)

Andreas Gross

The main theme of this thesis is the interplay between algebraic and tropical intersection theory, especially in the context of enumerative geometry. We begin by exploiting well-known results about tropicalizations of subvarieties of algebraic tori to give a simple proof of Nishinou and Siebert’s correspondence theorem for rational curves through given points in toric varieties. Afterwards, we extend this correspondence by additionally allowing intersections with psi-classes. We do this by constructing a tropicalization map for cycle classes on toroidal embeddings. It maps algebraic cycle classes to elements of the Chow group of the cone complex of the toroidal embedding, that is to weighted polyhedral complexes, which are balanced with respect to an appropriate map to a vector space, modulo a naturally defined equivalence relation. We then show that tropicalization respects basic intersection-theoretic operations like intersections with boundary divisors and apply this to the appropriate moduli spaces to obtain our correspondence theorem. Trying to apply similar methods in higher genera inevitably confronts us with moduli spaces which are not toroidal. This motivates the last part of this thesis, where we construct tropicalizations of cycles on fine logarithmic schemes. The logarithmic point of view also motivates our interpretation of tropical intersection theory as the dualization of the intersection theory of Kato fans. This duality gives a new perspective on the tropicalization map; namely, as the dualization of a pull-back via the characteristic morphism of a logarithmic scheme.

Magnetic and Structural Characterization of Isolated Gaseous Ions by XMCD and IRMPD Spectroscopy (2017)

Joachim Hewer

This thesis comprises four independent research studies on the magnetic and structural characterization of isolated ions in the gas phase. The electrospray ionization (ESI) technique is used for the transfer of (multi-)metallic complexes and organic molecules from solution into the gas phase. The subsequent storage of molecular ions in ion traps allows for a variety of spectroscopic methods in order to investigate the intrinsic properties of the isolated species void of solvent, crystal lattice, bulk or supporting surface effects. The magnetic properties of metal complexes are elucidated by gas phase X-ray magnetic circular dichroism (XMCD) spectroscopy. The element selective technique in combination with sum rule analysis allows for a separate determination of spin and orbital magnetic moments at different metal centers. Structural investigations on isolated molecular ions in terms of coordination sphere, binding motifs and hydrogen bonds are conducted using infrared multiple photon dissociation (IRMPD) spectroscopy. A resonant two color IRMPD technique serves to increase fragmentation yields, overcome dissociation bottlenecks and reveal otherwise dark bands. Comparison of experimental IRMPD spectra with calculated harmonic absorption spectra by density functional theory (DFT) provides structural assignments for a profound understanding of intra- and intermolecular interactions.

Conception and First Implementation of Novel Sensory Signal Conditioning and Digital Conversion Electronics Based on Spiking Neuron Ensembles for Inherently Robust Processing in Aggressively Scaled Integration Technologies (2017)

Abhaya Chandra Kammara Subramanyam

”In contemporary electronics 80% of a chip may perform digital functions but the 20% of analog functions may take 80% of the development time.” [1]. Aggravating this, the demands on analog design is increasing with rapid technology scaling. Most designs have moved away from analog to digital domains, where possible, however, interacting with the environment will always require analog to digital data conversion. Adding to this problem, the number of sensors used in consumer and industry related products are rapidly increasing. Designers of ADCs are dealing with this problem in several ways, the most important is the migration towards digital designs and time domain techniques. Time to Digital Converters (TDC) are becoming increasingly popular for robust signal processing. Biological neurons make use of spikes, which carry spike timing information and will not be affected by the problems related to technology scaling. Neuromorphic ADCs still remain exotic with few implementations in sub-micron technologies Table 2.7. Even among these few designs, the strengths of biological neurons are rarely exploited. From a previous work [2], LUCOS, a high dynamic range image sensor, the efficiency of spike processing has been validated. The ideas from this work can be generalized to make a highly effective sensor signal conditioning system, which carries the promise to be robust to technology scaling. The goal of this work is to create a novel spiking neural ADC as a novel form of a Multi-Sensor Signal Conditioning and Conversion system, which • Will be able to interface with or be a part of a System on Chip with traditional analog or advanced digital components. • Will have a graceful degradation. • Will be robust to noise and jitter related problems. • Will be able to learn and adapt to static errors and dynamic errors. • Will be capable of self-repair, self-monitoring and self-calibration Sensory systems in humans and other animals analyze the environment using several techniques. These techniques have been evolved and perfected to help the animal sur- vive. Different animals specialize in different sense organs, however, the peripheral neural network architectures remain similar among various animal species with few ex- ceptions. While there are many biological sensing techniques present, most popularly used engineering techniques are based on intensity detection, frequency detection, and edge detection. These techniques are used with traditional analog processing (e.g., colorvi sensors using filters), and with biological techniques (e.g. LUCOS chip [2]). The local- ization capability of animals has never been fully utilized. One of the most important capabilities for animals, vertebrates or invertebrates, is the capability for localization. The object of localization can be predator, prey, sources of water, or food. Since these are basic necessities for survival, they evolve much faster due to the survival of the fittest. In fact, localization capabilities, even if the sensors are different, have convergently evolved to have same processing methods (coincidence detection) in their peripheral neurons (for e.g., forked tongue of a snake, antennae of a cockroach, acoustic localization in fishes and mammals). This convergent evolution increases the validity of the technique. In this work, localization concepts based on acoustic localization and tropotaxis are investigated and employed for creation of novel ADCs. Unlike intensity and frequency detection, which are not linear (for e.g. eyes saturate in bright light, loose color perception in low light), localization is inherently linear. This is mainly because the accurate localization of predator or prey can be the difference between life and death for an animal. Figure 1 visually explains the ADC concept proposed in this work. This has two parts. (1) Sensor to Spike(time) Conversion (SSC), (2) Spike(time) to Digital Conversion(SDC). Both of the structures have been designed with models of biological neurons. The combination of these two structures is called SSDC. To efficiently implement the proposed concept, a comparison of several biological neural models is made and two models are shortlisted. Various synapse structures are also studied. From this study, Leaky Integrate and Fire neuron (LIF) is chosen since it fulfills all the requirements of the proposed structure. The analog neuron and synapse designs from Indiveri et. al. [3], [4] were taken, and simulations were conducted using cadence and the behavioral equivalence with biological counterpart was checked. The LIF neuron had features, that were not required for the proposed approach. A simple LIF neuron stripped of these features and was designed to be as fast as allowed by the technology. The SDC was designed with the neural building blocks and the delays were designed using buffer chains. This SDC converts incoming Time Interval Code (TIC) to sparse place coding using coincidence detection. Coincidence detection is a property of spiking neurons, which is a time domain equivalent of a Gaussian Kernel. The SDC is designed to have an online reconfigurable Gaussian kernel width, weight, threshold, and refractory period. The advantage of sparse place codes, which contain rank order coding wasvii Figure 1: ADC as a localization problem (right), Jeffress model of sound localization visualized (left). The values t 1 and t 2 indicate the time taken from the source to s1 and s2 respectively. described in our work [5]. A time based winner take all circuit with memory was created based on a previous work [6] for reading out of sparse place codes asynchronously. The SSC was also initially designed with the same building blocks. Additionally, a differential synapse was designed for better SSC. The sensor element considered wasviii a Wheatstone full bridge AMR sensor AFF755 from Sensitec GmbH. A reconfigurable version of the synapse was also designed for a more generic sensor interface. The first prototype chip SSDCα was designed with 257 modules of coincidence detectors realizing the SDC and the SSC. Since the spike times are the most important information, the spikes can be treated as digital pulses. This provides the capability for digital communication between analog modules. This creates a lot of freedom for use of digital processing between the discussed analog modules. This advantage is fully exploited in the design of SSDCα. Three SSC modules are multiplexed to the SDC. These SSC modules also provide outputs from the chip simultaneously. A rising edge detecting fixed pulse width generation circuit is used to create pulses that are best suited for efficient performance of the SDC. The delay lines are made reconfigurable to increase robustness and modify the span of the SDC. The readout technique used in the first prototype is a relatively slow but safe shift register. It is used to analyze the characteristics of the core work. This will be replaced by faster alternatives discussed in the work. The area of the chip is 8.5 mm 2 . It has a sampling rate from DC to 150 kHz. It has a resolution from 8-bit to 13-bit. It has 28,200 transistors on the chip. It has been designed in 350 nm CMOS technology from ams. The chip has been manufactured and tested with a sampling rate of 10 kHz and a theoretical resolution of 8 bits. However, due to the limitations of our Time-Interval-Generator, we are able to confirm for only 4 bits of resolution. The key novel contributions of this work are • Neuromorphic implementation of AD conversion as a localization problem based on sound localization and tropotaxis concepts found in nature. • Coincidence detection with sparse place coding to enhance resolution. • Graceful degradation without redundant elements, inherent robustness to noise, which helps in scaling of technologies • Amenable to local adaptation and self-x features. Conceptual goals have all been fulfilled, with the exception of adaptation. The feasibility for local adaptation has been shown with promising results and further investigation is required for future work. This thesis work acts as a baseline, paving the way for R&D in a new direction. The chip design has used 350 nm ams hitkit as a vehicle to prove the functionality of the core concept. The concept can be easily ported to present aggressively-scaled-technologies and future technologies.

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