In the frame of BMBF project "BioLiP", new physical treatment techniques aiming at medical treatment of the human skin have been developed. The acronym BioLiP stands for "Desinfektion, Entkeimung und biologische Stimulation der Haut durch gesundheitsfördernde Licht-und Plasmaquellen" (Disinfection, germ reduction and biological stimulation of the human skin by health promoting light and plasma sources). A source applying a low-temperature dielectric barrier discharge plasma (DBD) has been investigated on its effectiveness for skin disinfection and stimulation of biological material. Alternatively an atmospheric plasma source consisting of a microwave resonator combined with a solid state power oscillator has been examined. This concept which allows for a compact and efficient design avoiding external microwave power supply and matching units has been optimized with respect to nitrogen monoxide (NO) production in high yields. In both cases various application possibilities in the medical and biological domain are opened up. Light sources in the visible spectral range have been investigated with respect to the proliferation of human cell types. Intensive highly selective blue light sources based on LED technology can slow down proliferation rates without inducing toxic effects which offers new opportunities for treatments of so-called hyperproliferative skin conditions (e.g. with psoriasis or in wound healing) using UV-free light.
Large polycyclic aromatic hydrocarbons (PAHs) and fullerenes have been studied using nozzle/molecular beam sampling from flames and from a sublimator with subsequent resonance enhanced multi‐photon ionization (REMPI) mass spectrometry. The mass spectrometer was of the time‐of‐flight type with an ion reflector. The sublimator for large molecules generated a definite gas phase concentration of the respective PAHs or fullerene which was controlled by determining the mass loss of the substance in a stream of heated nitrogen. The purpose of these calibrations is the quantitative analysis of these large molecules when sampling fuel‐rich flames. Twenty‐three PAHs with masses up to 596 u (dicoronylene), some oxygen‐containing PAHs, C60, C70, and C84 were used. Sublimation energies of low‐volatility PAHs and of fullerenes were determined.
Multi‐photon ionization of PAHs and fullerenes was investigated as function of the effective laser power density in the ion source and the wavelength. Furthermore, ion fragmentation of large PAHs and fullerenes was studied for different power densities and wavelengths. For PAHs with up to about 20 C atoms a wavelength of 265 nm with laser power densities of 0.5 to 1 MW/cm2 are suitable. For larger PAHs, C60. and C70 a wavelength of 208 nm is more favorable. At the shorter wavelength PAHs have considerably higher ionization efficiencies and the fullerenes do not show delayed ionization and fragmentation. Quantitative relationships between the ion signal and the absolute number density for a large number of PAHs and fullerenes in the source were determined for standardized inflow and ionization conditions.
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