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Ein Ergebnis der interkulturellen Beziehungen in Südostasien sind die immer noch existierenden portugiesisch-basierten Kreolsprachen Papia Kristang und Macaísta, die zu Muttersprachen von Generationen von Menschen in Malakka und Macau geworden sind. Welche Faktoren bewirken den Sprachwandel dieser Idiome, und wie ist dieser erkennbar? Dieser Band beschäftigt sich nicht nur mit der Sprachdynamik der portugiesisch-basierten Kreolsprachen Südostasiens, sondern auch mit anderen wesentlichen Fragestellungen der Variationslinguistik. Als Basis dienen die Ergebnisse einer empirischen Datenerhebung, die insbesondere die Veränderungen im Sprachgebrauch dokumentieren. Darüber hinaus stellt der Autor neue Resultate hinsichtlich der Sprachidentifikationen vor, die nicht nur für die Kreolistik von Bedeutung sind, sondern auch fachübergreifend für das Interesse der allgemeinen Sprachwissenschaft.
Understanding the changes that follow UV-excitation in thionucleobases is of great importance for the study of light-induced DNA lesions and, in a broader context, for their applications in medicine and biochemistry. Their ultrafast photophysical reactions can alter the chemical structure of DNA - leading to damages to the genetic code - as proven by the increased skin cancer risk observed for patients treated with thiouracil for its immunosuppressant properties.
In this thesis, I present four research papers that result from an investigation of the ultrafast dynamics of 2-thiouracil by means of ultrafast x-ray probing combined with electron spectroscopy. A molecular jet in the gas phase is excited with a uv pulse and then ionized with x-ray radiation from a Free Electron Laser. The kinetic energy of the emitted electrons is measured in a magnetic bottle spectrometer. The spectra of the measured photo and Auger electrons are used to derive a picture of the changes in the geometrical and electronic configurations. The results allow us to look at the dynamical processes from a new perspective, thanks to the element- and site- sensitivity of x-rays. The custom-built URSA-PQ apparatus used in the experiment is described. It has been commissioned and used at the FL24 beamline of the FLASH2 FEL, showing an electron kinetic energy resolution of ∆E/E ~ 40 and a pump-probe timing resolution of 190 f s. X-ray only photoelectron and Auger spectra of 2-thiouracil are extracted from the data and used as reference. Photoelectrons following the formation a 2p core hole are identified, as well as resonant and non-resonant Auger electrons. At the L 1 edge, Coster-Kronig decay is observed from the 2s core hole.
The UV-induced changes in the 2p photoline allow the study the electronic-state dynamics. With the use of an Excited-State Chemical Shift (ESCS) model, we observe a ultrafast ground-state relaxation within 250 f s. Furthermore, an oscillation with a 250 f s period is observed in the 2p binding energy, showing a coherent population exchange between electronic states. Auger electrons from the 2p core hole are analyzed and used to deduce a ultrafast C −S bond expansion on a sub 100 f s scale. A simple Coulomb-model, coupled to quantum chemical calculations, can be used to infer the geometrical changes in the molecular structure.