- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 31 to 33 of 33 (0.076 seconds)| 31 |
Switching of surface composition and morphology of binary polymer brushes / Schalten der Oberflächenzusammensetzung und Morphologie binärer PolymerbürstenUsov, Denys 24 April 2004 (has links) (PDF)
Switching of surface composition and morphology of binary polymer brushes in response to changes in solvent selectivity, heating above glass transition temperatures, and contact with a rubbery stamp was studied. The binary brushes: polystyrene/poly(2-vinyl pyridine) (PS/P2VP), poly(styrene-co-2,3,4,5,6-pentafluorostyrene)/poly(methyl (meth)acrylate) (PSF/P(M)MA), and PS/PMMA were synthesized via two-step surface-initiated radical polymerization. Wetting experiments show that switching of brushes? surface composition upon exposure to solvents of various thermodynamic quality occurs faster than in 6 s. It takes longer time (5-10 min), if rate of solvent diffusion into the brush film is low. Discontinuous switching of surface composition of binary brushes is found upon exposure to binary solvents with gradually changed selectivity. X-ray Photoelectron Spectroscopy (XPS) shows quantitatively that the top brush layer (1) is dominated by respective favourite polymers after exposure to solvents of opposite selectivity and (2) comprises both brush constituents in almost symmetric ratio after exposure to non-selective solvents. Morphologies of binary brushes obtained after exposure to the solvents were studied with Atomic Force Microscopy (AFM). Local top layer composition was sensed with X-ray Photoemission Electron Microscopy (XPEEM). The morphologies are relevant to the particular solvents, reproducible, and independent on previous solvents. Phase segregation beneath the brush top layers was visualized with plasma etching. Qualitative agreement of the experimentally observed morphologies and predicted with self-consistent field theory is found. Enrichment of a binary brush top layer with the polymer providing lower surface energy takes place after annealing. Perpendicular segregation of binary brush constituents was sensed with XPEEM on perpendicular walls of imprinted elevations after wet microcontact printing.
|
| 32 |
Switching of surface composition and morphology of binary polymer brushesUsov, Denys 26 May 2004 (has links)
Switching of surface composition and morphology of binary polymer brushes in response to changes in solvent selectivity, heating above glass transition temperatures, and contact with a rubbery stamp was studied. The binary brushes: polystyrene/poly(2-vinyl pyridine) (PS/P2VP), poly(styrene-co-2,3,4,5,6-pentafluorostyrene)/poly(methyl (meth)acrylate) (PSF/P(M)MA), and PS/PMMA were synthesized via two-step surface-initiated radical polymerization. Wetting experiments show that switching of brushes? surface composition upon exposure to solvents of various thermodynamic quality occurs faster than in 6 s. It takes longer time (5-10 min), if rate of solvent diffusion into the brush film is low. Discontinuous switching of surface composition of binary brushes is found upon exposure to binary solvents with gradually changed selectivity. X-ray Photoelectron Spectroscopy (XPS) shows quantitatively that the top brush layer (1) is dominated by respective favourite polymers after exposure to solvents of opposite selectivity and (2) comprises both brush constituents in almost symmetric ratio after exposure to non-selective solvents. Morphologies of binary brushes obtained after exposure to the solvents were studied with Atomic Force Microscopy (AFM). Local top layer composition was sensed with X-ray Photoemission Electron Microscopy (XPEEM). The morphologies are relevant to the particular solvents, reproducible, and independent on previous solvents. Phase segregation beneath the brush top layers was visualized with plasma etching. Qualitative agreement of the experimentally observed morphologies and predicted with self-consistent field theory is found. Enrichment of a binary brush top layer with the polymer providing lower surface energy takes place after annealing. Perpendicular segregation of binary brush constituents was sensed with XPEEM on perpendicular walls of imprinted elevations after wet microcontact printing.
|
| 33 |
Oberflächenplasmonenresonanz-basierte DNA-Chips und Nucleobasen-SequenzentwurfKick, Alfred 27 September 2013 (has links)
Die vorliegende Dissertation beschreibt die Erarbeitung anwendbarer Methoden zum Aufbau Oberflächenplasmonenresonanz (SPR)-basierter DNA-Mikroarrays. Es werden die Beziehungen zwischen allen Teilschritten der Entwicklung eines DNA-Biosensors aufgezeigt. Die Sondendichte auf der Sensoroberfläche ist entscheidend für die Leistungsfähigkeit eines DNA-Chips. In dieser Arbeit werden thiolmodifizierte Sonden und solche mit Phosphorothioatgruppen verwendet und verglichen.
Der Aufbau selbstorganisierender Monoschichten, bestehend aus Mercaptoalkoholen und thiolmodifizierten DNA-Einzelsträngen, wird mittels Röntgenphotoelektronenspektroskopie untersucht. Es werden bis zu 180 Spots auf einem SPR-Chip aufgetragen. Eine weitere Erhöhung der Anzahl an Sondenorten pro Chip wird mit einer hydrophil/hydrophoben Strukturierung der Arrayoberfläche erreicht. Dies erfolgt durch das Mikrokontaktdrucken mit Alkanthiolen.
Die selektiven Hybridisierungen der Produkte der Polymerase-Kettenreaktion (PCR) werden bei SPR-Messungen auf DNA-Mikroarrays detektiert. Eine schnelle markierungsfreie Echtzeitanalyse wird bei Hybridisierungen im mikrofluidischen Kanal innerhalb weniger Minuten erzielt. Die Anwendbarkeit dieser Methoden wurde anhand der Mutationsanalyse der Fusionsgene AML1-ETO und CBFB-MYH11 bei der akuten myeloischen Leukämie bestätigt.
Die Hybridisierungseffizienz auf DNA-Mikroarrays hängt stark von der Sodensequenz ab. SPR-Experimente zeigen, dass die Ausbildung der Haarnadelstrukturen die Ursache dafür ist. Ein Computerprogramm (EGNAS) auf Grundlage eines neu entwickelten Nucleobasen-Sequenzentwurf-Algorithmus, ermöglicht die Generierung vollständiger Sequenzsätze. Die Intra- und Interstrangeigenschaften dieser Sequenzen können kontrolliert werden, um Haarnadelstrukturen und Kreuzhybridisierungen zu vermeiden. Dadurch können optimierte Sequenzen für Anwendungen auf DNA-Chips oder in der DNA-Nanobiotechnologie entworfen werden.
|
Page generated in 0.0798 seconds