Structure and stimuli-responsiveness of all-DNA dendrimers: theory and experiment

We present a comprehensive theoretical and experimental study of the solution phase properties of DNA-based family of nanoparticles - dendrimer-like DNA molecules (DL-DNA). These charged DNA dendrimers are novel macromolecular aggregates, which hold high promise in targeted self-assembly of soft matter systems in the bulk and at interfaces. To describe the behavior of this family of dendrimers (with generations ranging from G1 to G7), we use a theoretical model in which base-pairs of a single DL-DNA molecule are modeled by charged monomers, whose interactions are chosen to mimic the equilibrium properties of DNA correctly. Experimental results on the sizes and conformations of DL-DNA are based on static and 1dynamic light scattering; at the same time, Molecular Dynamics simulations are employed to model the equilibrium properties of DL-DNA, which compare favorably with the findings from experiments while at the same time providing a host of additional information and insight into the molecular structure of the nanostructures. We also examine the salt-responsiveness of these macromolecules, finding that despite the strong screening of electrostatic interactions, brought about by the added salt, the macromolecules shrink only slightly, their size robustness stemming from the high bending rigidity of the DNA-segments. The study of these charged dendrimer systems is an important field of research in the area of soft matter due to their potential role for various interdisciplinary applications, ranging from molecular cages and carriers for drug delivery in a living organism to the development of dendrimer- and dendron-based ultra-thin films in the area of nanotechnology. These findings are essential to determine if DL-DNA is a viable candidate for the experimental realization of cluster crystals in the bulk, a novel form of solids with multiple site occupancy.Comment: 38 pages, 17 figure

Systems of Differential Algebraic Equations in Computational Electromagnetics

Starting from space-discretisation of Maxwell's equations, various classical formulations are proposed for the simulation of electromagnetic fields. They differ in the phenomena considered as well as in the variables chosen for discretisation. This contribution presents a literature survey of the most common approximations and formulations with a focus on their structural properties. The differential-algebraic character is discussed and quantified by the differential index concept

The Electron Capture in 163^{163} Ho Experiment - a Short Update

The definition of the absolute neutrino mass scale is one of the main goals of the Particle Physics today. The study of the end-point regions of the β- and electron capture (EC) spectrum offers a possibility to determine the effective electron (anti-)neutrino mass in a completely model independent way, as it only relies on the energy and momentum conservation. The ECHo (Electron Capture in 163Ho) experiment has been designed in the attempt to measure the effective mass of the electron neutrino by performing high statistics and high energy resolution measurements of the 163 Ho electron capture spectrum. To achieve this goal, large arrays of low temperature metallic magnetic calorimeters (MMCs) implanted with with 163Ho are used. Here we report on the structure and the status of the experiment

Selbstorganisation von DNA Dendrimeren im Bulk und an Zwischenflächen

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersDendrimere sind synthetische Makromoleküle, die durch ihre stark ver-zweigte und reguläre interne Struktur charakterisiert sind. Sogenannte“dendrimer-like DNA” (DL-DNA) Moleküle können mittels Selbst-Assemblierung von DNA-Strängen im Labor synthetisiert werden. Diese elektrisch geladenen Dendrimer sind neuartige makromolekulare Aggregate,die vielfältige Anwendungen für gezielte Selbst-Organisation im Bereich der Weichen Materie verheißen.Im Rahmen dieser Arbeit wird eine theoretische Untersuchung dieser neuartigen Makromoleküle präsentiert und mit experimentellen Ergebnissen ergänzt. Basierend auf einem “bead-spring” Modell für DL-DNAs, beidem die Basenpaare als Monomere modelliert werden, werden Simulationen dieser Teilchen durchgeführt um solche Systeme bei verschiedenen Dichten, sowie an Grenzflächen zu untersuchen. Anhand der Simulationsdaten werden strukturelle Größen, wie zum Beispiel die radiale Verteilungsfunktion und der Strukturfaktor, berechnet und mit den entsprechenden Ergebnissen von Lichtstreuexperimenten verglichen.Weiters werden effektive Potentiale dieser Moleküle mit einem Algorithmus, der auf der “Widom insertion” Methode basiert, berechnet. Mittels dieser effektiven Potentiale können größere Systeme über längere Zeiträume simuliert werden.Aufgrund der vielversprechenden Anwendungsmg̈lichkeiten in der Nanotechnologie, zum Beispiel ultra-dünne Filme und Molekülkäfige, können von Untersuchungen dieser elektrisch geladenen Dendrimere maßge- blichen Impulse in Bereichen der Nanotechnologie erwartet werden.Dendrimers are synthetic macromolecules, characterised by a highlybranched and regular internal architecture. Recently, dendrimer-like DNAs(DL-DNAs) were synthesised via enzymatic ligation of Y-shaped DNAbuilding blocks. These electrically charged dendrimers represent a novelmacro-molecular aggregate, which holds high promise in bringing abouttargeted self-assembly of soft-matter systems in the bulk and at interfaces.In this work, a joint simulational-experimental study of these novel macro-molecules is presented. Based on a bead-spring model for the DL-DNAs,simulations are performed in order to investigate dilute and bulk systemsas well as DL-DNAs at interfaces. The results of structural quantities,e.g., the radial distribution function (RDF), extracted from simulations arecompared to the corresponding experimental results obtained via light scat-tering experiments.Furthermore, we compute in the limit of vanishing density an effective,coarse-grained potential between DL-DNAs, based on Widoms particle-insertion method. With this potential at hand, investigations of large-scalesystems of DL-DNAs at high concentrations become feasible.The study of these electrically charged dendrimer systems represents arelevant field of research in the area of soft matter due to the potential roleof such particles for various interdisciplinary applications, ranging frommolecular cages for drug delivery to the development of dendrimer-basedultra-thin films in the area of nanotechnology.16

Dissipative Mehr-Teilchen-Quantensysteme

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersZusammenfassung in deutscher SpracheWithin the scope of this thesis, we show that a driven-dissipative system with few ultracold atoms can exhibit dissipatively bound states, even if the atom-atom interaction is purely repulsive. This bond arises due to the dipole-dipole interaction, which is restricted to one of the lower electronic energy states, resulting in the distance-dependent coherent population trapping. The quality of this already established method of dissipative binding is improved and the application is extended to higher dimensions and a larger number of atoms. Here, we simulate two- and three-atom systems using an adapted approach to the Monte Carlo wave-function method and analyse the results. Finally, we examine the possibility of finding a setting allowing trimer states but prohibiting dimer states. In the context of open quantum systems, such a three-body bound states corresponds to the driven-dissipative analogue of a Borromean state. These states can be detected in modern experiments with dipolar and Rydberg-dressed ultracold atomic gases.8

Building structure-oriented numerical factual databases: The Beilstein example

The generation of one of the world's largest organic chemical databases, the Beilstein Database, is described. This project started in October 1983 and will result in a first online version by late 1987. The contents of the database and its data structure are based on the Beilstein Handbook which so far has been published in over 300 volumes. The data structure consists of more than 400 numerical factual fields making the database numerically searchable. The database will not only contain the handbook data but also portions of the abstracts of the fifth supplementary series which will not be published in the handbook in the near future. The new Beilstein abstracting system for paperless, decentralized abstracting of factual numerical data from the primary literature on microcomputers is also discussed. The database will be accessible via major online hosts. Inhouse versions and selected portions on CD-ROMS are also planned.