Two-Photon Excited Fluorescence Depolarisation : Experimental and Theoretical Development

We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D2h, D2 and C2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid

Newtons kraftlagar – från ord till begrepp med interaktiva metoder

Elevers konceptuella förståelse för begrepp som kraft och rörelse studeras inom ramen för Fysik 1 vid en gymnasieskola . Ett diagnostiskt prov togs fram och genomfördes före och efter genomgången kurs. Under kursen betonades interaktiva moment och fyra stycken interaktiva workshops utvecklades där eleverna mötte koncepten i praktiken. Intervjuer och statistisk analys av resultaten på det diagnostiska provet före och efter kursen visar att eleverna tillägnat sig koncepten ovanligt väl under kursen.

The Boy Scouts Program and the construction of new citizenship in the Nanjing Decade (1928-1937)

Session 42: Man in the Making: Manhood and Its Transformation from Late Ming to Republican ChinaAAS-ICAS Joint Conference 2011 is a special joint meeting of the Association for Asian Studies and the International Convention of Asia Scholars in celebration of 70 years of Asian StudiesRobert Baden-Powell established the world's first Boy Scouts in Britain in 1907. With unexpected quickness, the first Chinese Boy Scouts was established by missionary schools in 1912. In 1928, the Nationalist Party (KMT) started to turn the Scouts into a tool to mould ideal future citizens of the country by indoctrinating the Scouts with the Three People's Principles and training them with practical living skills. In the 1930s, stimulated by the Japanese invasion and inspired by Fascist Italy and Nazi Germany’s extensive use of youth organizations to train highly militarized youth to serve the nation’s needs, Chiang Kai-shek entrusted the Blue Shirts, who were led by the graduates of the Whampoa Military Academy, to be responsible for the Scout affairs. They changed the focus of remodeling the Scouts from politicization to militarization. The KMT believed that the “reformed” Scouts program would produce a patriotic and disciplined youth who had the will and the ability to contribute to the nation. By analyzing Boy Scouts textbooks and monthlies published by the Commercial Press and the KMT respectively in the 1930s, this paper will first discuss how the KMT responded to the same dilemma faced by Baden-Powell in Britain in the 1910s: should the purpose of the Boy Scouts program be to train future citizens or future soldiers? Second, how the youth was transformed from childhood to adulthood in the KMT Boy Scouts program?link_to_OA_fulltex

The Radiocarbon Intracavity Optogalvanic Spectroscopy Setup at Uppsala

Accelerator mass spectrometry (AMS) is by far the predominant technology deployed for radiocarbon tracer studies. Applications are widespread from archaeology to biological, environmental, and pharmaceutical sciences. In spite of its excellent performance, AMS is expensive and complicated to operate. Consequently, alternative detection techniques for 14C are of great interest, with the vision of a compact, user-friendly, and inexpensive analytical method. Here, we report on the use of intracavity optogalvanic spectroscopy (ICOGS) for measurements of the 14C/12C ratio. This new detection technique was developed by Murnick et al. (2008). In the infrared (IR) region, CO2 molecules have strong absorption coefficients. The IR-absorption lines are narrow in line width and shifted for different carbon isotopes. These properties can potentially be exploited to detect 14CO2, 13CO2, or 12CO2 molecules unambiguously. In ICOGS, the sample is in the form of CO2 gas, eliminating the graphitization step that h is required in most AMS labs. The status of the ICOGS setup in Uppsala is presented. The system is operational but not yet fully developed. Data are presented for initial results that illustrate the dependence of the optogalvanic signal on various parameters, such as background and plasma-induced changes in the sample gas composition

One- and two-photon time-resolved fluorescence study of neurotransmitter amino acid-5,6-benzocoumarin conjugates

The time-resolved photophysical characterisation of a set of fluorescent conjugates of neurotransmitter amino acids (glutamic acid, tyrosine and beta-alanine) based on a methoxylated 5,6-benzocoumarin fluorophore was performed Both one- and two-photon excitation were employed to excite the fluorophore and the cross-section with wavelength for the two-photon process determined The photophysical characterisation was supported using a molecular modelling study, which helped elucidate the molecular transitions (by a ZINDO calculation) and differences in the electron density between the HOMO and LUMO in geometry (PM3) optimised structures The effect of prolonged irradiation of the conjugates was monitored via fluorimetry and differences in the kinetics of the process observed were found to depend on the amino acid employed. (C) 2010 Elsevier B.V. All rights reserved- The authors wish to thank the Fundacao para a Ciencia e Tecnologia (Portugal) for financial support through project PTDC/QUI/69607/2006 (FCOMP-01-0124-FEDER-007449) and a Ph.D. grant to M.J.G.F. (SFRH/BD/36695/2007)

Evaluation of Intracavity Optogalvanic Spectroscopy for Radiocarbon Measurements

Ever since the first publication of intracavity optogalvanic spectroscopy (ICOGS) in 2008, this novel technique for measuring the ¹⁴C/¹²C ratio in carbon dioxide has rendered considerable attention. As a result, there are currently at least five different research groups pursuing research on ICOGS. With a claimed limit of detection of 10^–15 (¹⁴C/¹²C), i.e., in the same order as accelerator mass spectroscopy, achieved with a relatively inexpensive and uncomplicated table-top system, ICOGS has major scientific and commercial implications. However, during the past 5 years, no research group has been able to reproduce these results or present additional proof for ICOGS’s capability of unambiguous ¹⁴C detection, including the authors of the original publication. Starting in 2010, our group has set up a state-of-the-art ICOGS laboratory and has investigated the basic methodology of ICOGS in general and tried to reproduce the reported experiments in particular. We have not been able to reproduce the reported results concerning the optogalvanic signals dependence on ¹⁴C concentration and wavelength and, ultimately, not seen any evidence of the capability of ICOGS to unambiguously detect ¹⁴C at all. Instead, we have found indications that the reported results can be products of measurement uncertainties and mistakes. Furthermore, our results strongly indicate that the reported limit of detection is likely to be overestimated by at least 2 orders of magnitude, based on the results presented in the original publication. Hence, we conclude that the original reports on ICOGS cannot be confirmed and therefore must be in error