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  • 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.
11

Nickelspeziesanalyse im Cytosol humaner intestinaler Gewebeproben mittels online-Kopplung von Kapillarelektrophorese und induktiv gekoppeltem Plasma-Massenspektrometer - Nickelspeziesanalysis in the cytosol of human intestinal tissue with online coupling of capillary-electrophoresis with inductively coupled plasma mass spectrometry

Bonsack, Sven 30 April 2003 (has links)
This thesis deals with the nickelspecies-analysis in cytosol of human intestinal tissue. The aim was, to find the differences in nickelspecies between the cytosol of malignant and normal tissue of the same patient with CE/ICP-MS resp. SEC/ICP-MS coupling. The result was, that the area ratio of two nickelspecies in the cytosol of malignant tissue are significant higher than in the cytosol of normal tissue. Maybe the two nickelspecies can be an oncogenproduct.
12

Nukleophile aromatische Substitution zur Synthese mehrzähniger Komplexliganden und Herstellung geordneter bimetallischer Nanopartikel

Muth, Oliver 13 May 2005 (has links)
Als Schlüsselreaktion zum Aufbau von para-chinoiden Triphenylenfarbstoffen mit komplexierungsfähigen Funktionalitäten für Metallionen sowie von Methylen- und Methin-verbrückten Oligopyridinen eignet sich hervorragend die nukleophile aromatische Substitution. Für die Synthese der funktionalisierten para-chinoiden pi-Systeme diente dabei ein Triarylmethylkation mit einem sterisch abgeschirmten zentralen Kohlenstoffatom und zweier peripherer Fluorsubstituenten an aromatischen Ringen, die bei der Umsetzung mit Nukleophilen als elektrophilen Bausteinen 2-Fluor- und 2,6-Difluorpyridin mit 2-Methyllithiumpyridin eröffnete den effizienten Zugang zur Familie der Methylen- und Methin-verbrückten mehrzähnigen Oligopyridin-Liganden in sehr guten Ausbeuten von meistens 90% und mehr. Die hieraus resultierenden Methylen-verbrückten Pyridin-Liganden konnten ihrerseits wieder als nukleophile Bausteine erfolgreich mit 2-Fluor- und 2,6-Difluorpyridin umgesetzt werden. Mit den hergestellten Pentakispyridinen wurden mehrere Kupfer(II)-Komplexe hergestellt. Der zweite Abschnitt der Arbeit befasst sich mit der Herstellung von geordneten FePt-Nanopartikeln. Dabei wurde eine literaturbekannte Herstellungsmethode ausgehend von Pt(acac)2, 1,2-Hexadecandiol...
13

Diffusionsmessungen an Polyethylenglykolen mittels PFG-NMR-Spektroskopie und dynamischer Lichtstreuung / Diffusion measurements of poly(etylene glycol) in solution by Pulsed Field Gradient NMR spectroscopy and Dynamic Light Scattering

Dunkhorst, Kirsten 06 May 2005 (has links)
The Pulsed Field Gradient (PFG) NMR spectroscopy was uesd to determine, via the diffusion coefficient, the molecular weights and the molecular weight distributions for sampels of poly(etylene glycol) (PEG) in D2O. Additional it was investigated, whether the components of mixtures of poly(ethylene glycol) with different molecular weights could be quantitatively determined by the differences in diffusion coefficient. The results of this study are compared with the result of the Dynamic Light Scattering (DLS) technique, the standard methode for the determination of molecular weights. The PFG NMR findings shows that the the molecular weights and the molecular weight distributions agreed well with values provided by the manufacturer. The mixtures could not be determined quantitativley, because of considerable overlaps in the molecular weight distributions. But it could be shown that the PFG NMR spectroscopy and the DLS technique complement one another.
14

UV/Vis and CD Spectral Studies of the Interaction between Pinacyanol Chloride and Alginates, g-Cyclodextrin, and Aerosol-OT

Al-Khouri, Sa'ib 07 May 2003 (has links)
A quantitative study of the aggregation behaviour of the cationic cyanine dye pinacyanol chloride in aqueous solution and in the presence of various organic matrices (anionic alginates, anionic Aerosol-OT and g-cyclodextrin) is presented based on UV/Visible absorption and Circular Dichroism (CD) spectroscopy. The spectral data have been analysed using derivative spectra and a program (PeakFit) to model the mixtures of different absorbing species with strongly overlapping absorption bands. The structures of the aggregates have been analysed and discussed in terms of qualitative (H- vs. J-type aggregation) and quantitative arguments based on a program (OSCI) for the calculation of oscillator and rotatory strengths assuming an exciton-like delocalisation of molecular excitations through the entire aggregate. Models for the various complexes of the dye in the presence of various organic matrices have been proposed
15

Synthese und Reaktivität von Pentafluorphenylfluoroboraten sowie von Kalium-1H,1H,2H,2H-Perfluoroctyltrifluoroborat - Synthesis and reactivity of pentafluorophenylfluoroborates and potassium-1H,1H,2H,2H-perfluorooctyltrifluoroborate

Fritzen, Petra 06 June 2003 (has links)
The potassium pentafluorophenylfluoroborates were prepared by hydroxy-fluoride-substitution of fluoroorganoalkoxyboranes and -borates with potassium bifluoride. Those intermediate boranes and borates were obtained by the reaction of fluoroorganomagnesium reagents and alkoxyboranes. The introduction of one or two pentafluorophenylgroups into various alkoxyboranes is investigated to optimize the yield of potassium pentafluorophenyltrifluoroborate and bis(pentafluorophenyl)difluoroborate. Reactions of pentafluorophenylfluoroborates with the Lewis acids borontrifluoride and tris(pentafluorophenyl)borane show the Lewis acidity of pentafluorophenyldifluoroborane compared with borontrifluoride and tris(pentafluorophenyl)borane. Pentalfuorophenylfluoroborate salts reacted with iodinepentafluoride by transfer of a pentafluorophenylgroup to iodinepentafluoride. To develop an alternative method to fluorooganofluoroborates systematic investigations on the reactivity of fluoroorganoboranes to fluorides were undertaken. Potassium-1H,1H,2H,2H-perfluorooctyltrifluoroborate is prepared by the reaction of an organogrignard reagent with chlorodimethoxyborane and hydrolysis and hydoxy-fluoride-substitution of the product. Treatment of the borate wit borontrifluoride provides the corresponding difluoroborane with ponytailgroup.
16

Darstellung und Charakterisierung von Kofaktoren des Elektronentransfers in artifizieller und nativer Proteinumgebung / Synthesis and characterization of electron tranfer cofactors in artificial and native protein environment

Breitenstein, Christoph 14 June 2006 (has links)
The protein Myoglobin was used as matix-molecule to produce monomeric porphyrins in solution. The protein complexes of differen zinc pheophorbides and zinc protoporphyrin have been studied by UV/Vis and NMR spectroscopy. The protein stability versus unfolding and NMR results Based on quantum mechanical calculations analysis of EPR- and ENDOR-spectra of the light excited triplet state yielded identification of α-protons and methyl β-protons have been identified for the first time. The data acquired agrees well with previously published data on native reaction centers. The terminal electron acceptors, [4Fe4S] centers FA and FB in Photosystem I (PSI), have been modelled by peptides with 16 amino acid length synthezied by SPPS Fmoc strategy. Both peptides incorporated a [4Fe4S] cluster in oxidation state 2 /1 as prooven by UV/Vis, EPR and Mössbauer spectroscopy. The redoxpotential for the one electron reduction was found to be -470 mV for both modell peptides.
17

Quellung von waessrigen Polyethylenoxid-Gelen unter besonderer Berücksichtigung des Phasenübergangs des Loesemittels - Swelling of aqueous polyethyleneoxide gels in consideration of the phase transition of the solvent

Kischel, Michael 13 June 2003 (has links)
Temperature dependent swelling of different polymer networks was performed in the liquid and gaseous solvent water. To determine the swelling ratio in the water vapour gravimetrically, depending on the change of temperature, a new measure device was developed. Object of this thesis was, to qualify the shape of the swelling curves in the region of the boiling point. Swelling curves were analysed with the results of the statistic theory of swelling additionally. Together with the results of measurements of the same polymer networks in crystalline water, a mathematical description of the swelling curves was performed in solid, liquid and gaseous phase for the first time.
18

Optische Beobachtung von oberflächengebundenen und frei beweglichen Nanopartikeln / Optical detection of free and adsorbed nanoparticles

Finder, Christiane 17 June 2005 (has links)
Two new optical analysis methods in the field of nanotechnology are introduced. Both methods are based on optical microscopy coupled with a digital image analysis system. The first method can be used as a low cost quality control process for nanoimprint lithography. Here, fluorescence microscopy is used in combination with a standard printable polymer labeled with a fluorescent dye. The optical detection allows for the observation of imprinted structures down to 100 nm of lateral size. The second method uses either dark field or fluorescence microscopy for analysis of the particle size distribution of dispersed nanoparticles with diameters between 100 and 1000 nm. Both methods are characterized by a high reliability and reproducibility as well as user-friendliness and quickness.
19

Darstellung und Charakterisierung atmosphaerenrelevanter Fluorverbindungen - Synthesis and Characterization of Fluorine Compounds of atmospheric Relevance

Ahsen, Stefan von 20 June 2003 (has links)
The present study is a contribution to the synthesis and extensive characterization of fundamental C, F, O containing compounds, which play an important role in the chemistry of the atmosphere due to their appearance in degradation processes of CFCs and their substitutes. The formation of the peroxy radicals CF3OO, FC(O)OO, CF3OC(O)OO, CF3C(O)OO, and CH3C(O)OO is achieved by low pressure thermolysis of suitable precursors, highly diluted in argon or neon and subsequent quenching of the reaction mixture as a matrix. In addition, the radicals CF3OCO, SF5, and CF3OOO are formed in matrix. All investigated radicals are characterized as matrix isolated species by IR- and UV-spectroscopy. The properties of the studied fluorocarbon peroxy radicals are comprehensively discussed. The first preparation of pure trifluoromethyl nitrate, CF3ONO2, is reported via different synthetic routes. The compound is completely characterized (IR, Raman, UV, NMR, melting and boiling point, vapour pressure, gas electron diffraction), a nd its chemistry is evaluated. It is demonstrated, that trifluoromethyl nitrate acts neither for CF3O radicals, nor for nitrogen dioxide as a reservoir species. With the synthesis of bistrifluoromethyl trioxydicarbonate, CF3OC(O)OO-OC(O)OCF3, a novel open-chain trioxide is obtained, which is thermally stable below -20°C. CF3OC(O)OOOC(O)OCF3 is characterized by IR, Raman, UV, NMR spectroscopy and is used in the generation of the previously unknown peroxy radical CF3OC(O)OO. For all investigated species quantum chemical calculations are performed. The consistent use of the density functional method B3LYP with the basis set 6-311G(d,p) allows a comprehensive theoretical study. In addition, band assignments of the spectra of the characterized compounds were supported by these calculations.
20

Oligosaccharide und ihre Wechselwirkung mit Calciumionen - Computerchemie von Biofilmkomponenten / Interaction between Oligsaccharides and Calcium Ions - Computational Chemistry of Biofilm Components

Richter, Nicole 12 July 2004 (has links)
This work at hand deals with two monosaccharides, beta-D-mannuronic acid (M) and alpha-L-guluronic acid (G), units of bacterial and algal alginates. Bacterial alginates are metabolic products of particular species of bacteria. They are thought to be the main structural components of biofilms, and play an important role in water technology. Water-soluble alginates chains build a 3-dimensional network with calcium ions. The goal of this work was to understand how the monomers of bacterial alginate interact with calcium ions to build this network. This was examined with theoretical models, i. e. forcefield calculations with molecular dynamics simulations

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