Universiẗat Diss., 2007--Kassel.

Würzburg, Univ., Diss., 2008

Ulm, Univ., Diss., 2001.

München, Techn. University, Diss., 2007.

Merocyaninchromophore spielen eine herausragende Rolle bei der Entwicklung von photorefraktiven Materialien für Anwendungen in der Holographie. Der photorefraktive Effekt beruht auf einer Orientierung der dipolaren Merocyanine in einem elektrischen Feld. Diese können umso effektiver ausgerichtet werden, je größer ihr Dipolmoment ist. Folglich sollten Merocyanine mit sehr großen Dipolmomenten den gewünschten Effekt hervorbringen. Es hat sich jedoch gezeigt, dass solche Merocyanine Dimere mit antiparalleler zentrosymmetrischer Struktur bilden. In dieser Anordnung addieren sich die Dipolmomente destruktiv, so dass die dipolare Eigenschaft des Materials verloren geht. In dieser Arbeit ist es gelungen, Merocyanine über sechsfache Wasserstoffbrückenbindungen zu supramolekularen Strukturen mit großen resultierenden Dipolmomenten zu assoziieren. Diese Komplexe werden in schwach polaren Lösungsmitteln sogar bei sehr niedrigen Farbstoffkonzentrationen gebildet. / Merocyanine dyes play a major role in the development of photorefractive materials to be applied in holography. The photorefractive effect is based on the orientation of dipolar merocyanine dyes by an external electric field. Merocyanine dyes with very high dipole moments are supposed to be the most suitable for achieving an optimal effect because, with increasing dipole moment, a higher degree of orientation can be achieved are the more efective is the their orientation. However, strongly dipolar merocyanine dyes form antiparallel dimers with vanishing dipole moment due to their dipolar interaction. Thus, the dimers can not be oriented by an electric field. In this thesis, merocyanine dyes were successfully assembled through six-fold hydrogen-bonding into supramolecular structures with large resulting dipole moments. In less polar solvents, these complexes are formed even at very low dye concentration.

A realistic description of ionization in intense laser fields is implemented into the Non-Adiabatic Quantum Molecular Dynamics (NA-QMD) formalism. First, the error of a finite basis expansion is considered and a new measure is proposed for time-dependent calculations. This is used to investigate systematically the influence of the used basis set in calculations on the hydrogen atom in intense laser fields. Second, absorbing boundary conditions in basis expansion are introduced via an imaginary potential into the effective one-particle Hamiltonian. It is shown that the used form of the absorber potential is valid in many-electron time-dependent density functional theory calculations, i.e. that only ionized states are affected by the absorbing potential. The absorber is then tested on reference calculations that exist for H and aligned H+2 in intense laser fields. Excellent agreement is found. Additionally, an approximative treatment of the missing electron-nuclear correlations is proposed. It is found in calculations on H+2 that a qualitative improvement of the description of nuclear dynamics results. The extension of the NA-QMD formalism is then used to investigate the alignment behavior of diatomic molecules. Recent experiments on H+2 and H2 are reviewed and explained. It is found that dynamic alignment, i.e. the laser induced rotation of the molecule, plays a central role. The alignment behavior of H+2 and H2 and its intensity dependence is investigated after that. A drastic difference between H+2 and H2 is found in NA-QMD as well as model calculations. Then, the focus is on an astonishing new effect that has been found in N2 calculations. This effect which is called "rotational destabilization" is studied on the model system H+2. Yet, it might be observable only in heavy dimers and might have already been found in an experiment on I2.

A realistic description of ionization in intense laser fields is implemented into the Non-Adiabatic Quantum Molecular Dynamics (NA-QMD) formalism. First, the error of a finite basis expansion is considered and a new measure is proposed for time-dependent calculations. This is used to investigate systematically the influence of the used basis set in calculations on the hydrogen atom in intense laser fields. Second, absorbing boundary conditions in basis expansion are introduced via an imaginary potential into the effective one-particle Hamiltonian. It is shown that the used form of the absorber potential is valid in many-electron time-dependent density functional theory calculations, i.e. that only ionized states are affected by the absorbing potential. The absorber is then tested on reference calculations that exist for H and aligned H+2 in intense laser fields. Excellent agreement is found. Additionally, an approximative treatment of the missing electron-nuclear correlations is proposed. It is found in calculations on H+2 that a qualitative improvement of the description of nuclear dynamics results. The extension of the NA-QMD formalism is then used to investigate the alignment behavior of diatomic molecules. Recent experiments on H+2 and H2 are reviewed and explained. It is found that dynamic alignment, i.e. the laser induced rotation of the molecule, plays a central role. The alignment behavior of H+2 and H2 and its intensity dependence is investigated after that. A drastic difference between H+2 and H2 is found in NA-QMD as well as model calculations. Then, the focus is on an astonishing new effect that has been found in N2 calculations. This effect which is called "rotational destabilization" is studied on the model system H+2. Yet, it might be observable only in heavy dimers and might have already been found in an experiment on I2.

The desire for repair of tissue defects and injury is the major need prompting research into tissue engineering. Engineering of anisotropic tissues requires production of ordered substrates that orient cells preferentially and support cell viability and differentiation. Towards this goal, this thesis investigated methodologies to align extracellular matrix structures in vitro to guide stem/progenitor cell behaviour for tissue regeneration. Aligned collagen fibrils were deposited on planar substrates from collagen solutions streaming through a microfluidic channel system. Collagen solution concentration, degree of gelation, shear rate and pre-coating of the substrate were demonstrated to determine the orientation and density of the immobilized fibrils. The degree of collagen fibril orientation increased with increasing flow rates of the solution while the matrix density increased at higher collagen solution concentrations and on hydrophobic polymer pre-coatings. Additionally, the length of the immobilized collagen fibrils increased with increasing solution concentration and gelation time. Aligned collagen matrices were refined by incorporating the glycosaminoglycan heparin to study multiple extracellular matrix components in a single system. Multilineage (osteogenic/adipogenic/chondrogenic) differentiation of mesenchymal stem and progenitor cells was maintained by the aligned structures. Most noticeable was the observation that during osteogenesis, aligned collagen substrates choreographed ordered matrix mineralization. Likewise, myotube assembly of C2C12 cells was profoundly influenced by aligned topographic features resulting in enhanced myotube organization and length. Neurites from neural stem cells were highly oriented in the direction of the underlying fibrils. Neurite outgrowth was enhanced on aligned collagen compared to non-aligned collagen or poly-D-lysine substrates, while neural differentiation and cell survival were not influenced by the type of substrate. Using the new method to align collagen type I, the interior walls of cellulose hollow fiber membranes were coated with longitudinally aligned collagen fibrils to fabricate an advanced guidance conduit for nerve regeneration. First cell culture experiments showed that the tubes coated with aligned collagen supported viability and adherence of spinal cord-derived neurospheres. Together, these results demonstrate the feasibility of aligned collagen matrices as a versatile platform to control cell behaviour towards tissue regeneration. Ultimately, the new method to align collagen fibrils and to coat hollow membranes may become an integral component of tissue engineering, working synergistically with other emerging techniques to promote functional tissue replacements.

The desire for repair of tissue defects and injury is the major need prompting research into tissue engineering. Engineering of anisotropic tissues requires production of ordered substrates that orient cells preferentially and support cell viability and differentiation. Towards this goal, this thesis investigated methodologies to align extracellular matrix structures in vitro to guide stem/progenitor cell behaviour for tissue regeneration. Aligned collagen fibrils were deposited on planar substrates from collagen solutions streaming through a microfluidic channel system. Collagen solution concentration, degree of gelation, shear rate and pre-coating of the substrate were demonstrated to determine the orientation and density of the immobilized fibrils. The degree of collagen fibril orientation increased with increasing flow rates of the solution while the matrix density increased at higher collagen solution concentrations and on hydrophobic polymer pre-coatings. Additionally, the length of the immobilized collagen fibrils increased with increasing solution concentration and gelation time. Aligned collagen matrices were refined by incorporating the glycosaminoglycan heparin to study multiple extracellular matrix components in a single system. Multilineage (osteogenic/adipogenic/chondrogenic) differentiation of mesenchymal stem and progenitor cells was maintained by the aligned structures. Most noticeable was the observation that during osteogenesis, aligned collagen substrates choreographed ordered matrix mineralization. Likewise, myotube assembly of C2C12 cells was profoundly influenced by aligned topographic features resulting in enhanced myotube organization and length. Neurites from neural stem cells were highly oriented in the direction of the underlying fibrils. Neurite outgrowth was enhanced on aligned collagen compared to non-aligned collagen or poly-D-lysine substrates, while neural differentiation and cell survival were not influenced by the type of substrate. Using the new method to align collagen type I, the interior walls of cellulose hollow fiber membranes were coated with longitudinally aligned collagen fibrils to fabricate an advanced guidance conduit for nerve regeneration. First cell culture experiments showed that the tubes coated with aligned collagen supported viability and adherence of spinal cord-derived neurospheres. Together, these results demonstrate the feasibility of aligned collagen matrices as a versatile platform to control cell behaviour towards tissue regeneration. Ultimately, the new method to align collagen fibrils and to coat hollow membranes may become an integral component of tissue engineering, working synergistically with other emerging techniques to promote functional tissue replacements.

Berger, Natalia: The Jewish Museum. History and Memory, Identity and Art from Vienna to the Bezalel National Museum, Jerusalem [= Ben-Rafael, Eliezer/Gorny, Yosef/Liwerant, Judit Bokser (Hg.): Jewish Identities in a Changing World, Band 29], Leiden/Boston: Brill 2018, 584 S., ISBN: 978-90-04-35387-9, EUR 160,00. Besprochen von Dorothea Warneck.