Analysis of the acoustlc transients in the pulse response of the linear electro-optic effect

The pulse response of the linear electro-optic effect is investigated with high temporal and spatial resolution in KDP, KD*P, and biaxial LiCOOH · H2O. Experimental results, which are explained theoretically, show that the piezo-optic transients induced by the piezoelectric effect, are generated by stress release waves. Starting from the surfaces, these excite by reflection, diffraction, and superposition, due to the finite crystal dimensions, normal vibration modes too. It is shown that the direct electro-optic effect can be measured for all crystal classes at the beginning of the pulse response. The pulse method also yields static electro-optic, piezo-optic, and elastic constants. The values of r63, r63, p66 and c66 measured in KDP, agree well with those of other authors. Measurement of the direct electro-optic effect of LiCOOH · H2O in some directions yields values within 1 to 4 × 10-12 m/V

Polyvinyl butyral nanobeads: preparation, characterization, biocompatibility and cancer cell uptake

We describe the synthesis of spherical poly(vinyl butyral) (PVB) nanobeads by controlled pptn. via addn. of non-solvent. Effects of various reaction parameters on nanoparticle size were investigated by dynamic light scattering and electron microscopy. The ability to incorporate dopant mols. was studied using a fluorescent perylene deriv. as a model additive, and the dye-doped nanoparticles were investigated by confocal microscopy. In an optimized exptl. protocol, PVB nanoparticles were obtained that were efficiently taken up by human cancer cells devoid of coating. The novel nanospheres are economic, easy to prep. and capable of incorporating additives. Lacking cytotoxicity in vitro, PVB nanobeads are attractive with respect to various potential applications such as optical imaging and particle tracking, diagnostics, and drug delivery. [on SciFinder(R)

Functionalized derivatives of 1,4-dimethylnaphthalene as precursors for biomedical applications: synthesis, structures, spectroscopy and photochemical activation in the presence of dioxygen

Decomposition of endoperoxide containing molecules is an attractive approach for the delayed release of singlet oxygen under mild reaction conditions. Here we describe a new method for the adaptation of the corresponding decay times by controlling the supramolecular functional structure of the surrounding matrix in the immediate vicinity of embedded singlet oxygen precursors. Thus, a significant prolongation of the lifetime of the endoperoxide species is possible by raising the energy barrier of the thermal (1)O(2)-releasing step via a restriction of the free volume of the applied carrier material. Enabling such a prolonged decomposition period is crucial for potential biomedical applications of endoperoxide containing molecules, since sufficient time for appropriate cell uptake and transport to the desired target region must be available under physiological conditions before the tissue damaging-power of the reactive oxygen species formed is completely exhausted. Two novel polyaromatic systems for the intermediate storage and transport of endoperoxides and the controlled release of singlet oxygen in the context of anticancer and antibiotic activity have been prepared and characterized. These compounds are based on functionalized derivatives of the 1,4-dimethylnaphthalene family which are readily forming metastable endoperoxide species in the presence of dioxygen, a photosensitizer molecule such as methylene blue and visible light. In contrast to previously known systems of similar photoreactivity, the endoperoxide carrying molecules have been designed with optimized molecular properties in terms of potential chemotherapeutic applications. These include modifications of polarity to improve their incorporation into various biocompatible carrier materials, the introduction of hydrogen bonding motifs to additionally influence the endoperoxide decay kinetics, and the synthesis of bifunctional derivatives to enable synergistic effects of multiple singlet oxygen binding sites with an enhanced local concentration of reactive species. With these compounds, a promising degree of endoperoxide stability adjustment within the carrier matrix has been achieved (polymer films or nanoparticles), which now opens the stage for appropriate targeting of the corresponding pro-drugs into live cells. First results on cytocidal and cytostatic properties of these compounds embedded in ethylcellulose nanoparticles are presented. Furthermore, an efficient low-cost method for the photochemical production of reactive endoperoxides based on high-power 660 nm LED excitation at room temperature and ambient conditions in ethanol solution is reported

Kultivierte Haltungen von Lehrkräften zu Digitalen Medien?

Im Jahr 2013 nach dem Stellenwert der Medienbildung und dem Einsatz Digitaler Medien in der Schule zu fragen, scheint zunächst nicht auf der Höhe der Zeit zu sein. Längst sind Digitale Medien allerorten vorzufinden, eine Welt ohne Medien ist nicht mehr denkbar. Der Vermittlung von Medienkompetenz und Medienbildung sollte gerade in der Schule eine besondere Rolle zukommen, diese sollte in allen Fächern und Schulstufen präsent sein und zum Einsatz kommen. Durch den Pädagogen, die Pädagogin, die Lehrkräfte erhalten Medien im besten Fall einen (sinnvollen) handlungsleitenden Rahmen