Experience in investigation of components of alkali-metal-vapor space power systems

Components of reactor-powered alkali metal-vapor turbogenerator space power syste

Cytochrome C oxidase Inhibition and Cold Plasma-derived Oxidants Synergize in Melanoma Cell Death Induction

Despite striking advances in the treatment of metastasized melanoma, the disease is often still fatal. Attention is therefore paid towards combinational regimens. Oxidants endogenously produced in mitochondria are currently targeted in pre-clinical and clinical studies. Cytotoxic synergism of mitochondrial cytochrome c oxidase (CcO) inhibition in conjunction with addition of exogenous oxidants in 2D and 3D melanoma cell culture models were examined. Murine (B16) and human SK-MEL-28 melanoma cells exposed to low-dose CcO inhibitors (potassium cyanide or sodium azide) or exogenous oxidants alone were non-toxic. However, we identified a potent cytotoxic synergism upon CcO inhibition and plasma-derived oxidants that led to rapid onset of caspase-independent melanoma cell death. This was mediated by mitochondrial dysfunction induced by superoxide elevation and ATP depletion. This observation was validated by siRNA-mediated knockdown of COX4I1 in SK-MEL-28 cells with cytotoxicity in the presence of exogenous oxidants. Similar effects were obtained with ADDA 5, a recently identified specific inhibitor of CcO activity showing low toxicity in vivo. Human keratinocytes were not affected by this combinational treatment, suggesting selective effects on melanoma cells. Hence, targeting mitochondrial CcO activity in conjunction with exogenous pro oxidant therapies may constitute a new and effective melanoma treatment modality

Treatment of Candida albicans biofilms with low-temperature plasma induced by dielectric barrier discharge and atmospheric pressure plasma jet

Because of some disadvantages of chemical disinfection in dental practice (especially denture cleaning), we investigated the effects of physical methods on Candida albicans biofilms. For this purpose, the antifungal efficacy of three different low-temperature plasma devices (an atmospheric pressure plasma jet and two different dielectric barrier discharges (DBDs)) on Candida albicans biofilms grown on titanium discs in vitro was investigated. As positive treatment controls, we used 0.1% Chlorhexidine digluconate (CHX) and 0.6% sodium hypochlorite (NaOCl). The corresponding gas streams without plasma ignition served as negative treatment controls. The efficacy of the plasma treatment was determined evaluating the number of colony-forming units (CFU) recovered from titanium discs. The plasma treatment reduced the CFU significantly compared to chemical disinfectants. While 10 min CHX or NaOCl exposure led to a CFU log 10 reduction factor of 1.5, the log10 reduction factor of DBD plasma was up to 5. In conclusion, the use of low-temperature plasma is a promising physical alternative to chemical antiseptics for dental practice. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas

Electron heating and ionization dynamics in capacitively coupled radio frequency (RF) atmospheric pressure microplasmas operated in helium are investigated by Particle in Cell simulations and semi-analytical modeling. A strong heating of electrons and ionization in the plasma bulk due to high bulk electric fields are observed at distinct times within the RF period. Based on the model the electric field is identified to be a drift field caused by a low electrical conductivity due to the high electron-neutral collision frequency at atmospheric pressure. Thus, the ionization is mainly caused by ohmic heating in this "Omega-mode". The phase of strongest bulk electric field and ionization is affected by the driving voltage amplitude. At high amplitudes, the plasma density is high, so that the sheath impedance is comparable to the bulk resistance. Thus, voltage and current are about 45{\deg} out of phase and maximum ionization is observed during sheath expansion with local maxima at the sheath edges. At low driving voltages, the plasma density is low and the discharge becomes more resistive resulting in a smaller phase shift of about 4{\deg}. Thus, maximum ionization occurs later within the RF period with a maximum in the discharge center. Significant analogies to electronegative low pressure macroscopic discharges operated in the Drift-Ambipolar mode are found, where similar mechanisms induced by a high electronegativity instead of a high collision frequency have been identified

Reproducibility of `COST Reference Microplasma Jets'

Atmospheric pressure plasmas have been ground-breaking for plasma science and technologies, due to their significant application potential in many fields, including medicinal, biological, and environmental applications. This is predominantly due to their efficient production and delivery of chemically reactive species under ambient conditions. One of the challenges in progressing the field is comparing plasma sources and results across the community and the literature. To address this a reference plasma source was established during the `Biomedical Applications of Atmospheric Pressure Plasmas' EU COST Action MP1101. It is crucial that reference sources are reproducible. Here, we present the reproducibility and variance across multiple sources through examining various characteristics, including: absolute atomic oxygen densities, absolute ozone densities, electrical characteristics, optical emission spectroscopy, temperature measurements, and bactericidal activity. The measurements demonstrate that the tested COST jets are mainly reproducible within the intrinsic uncertainty of each measurement technique

Antiseptic efficacy of selected agents and tissue tolerable plasma (TTP) on C. albicans biofilms - has the biofilm maturity influence on it?

Background: The formation of biofilms is crucial to the pathogenesis of many dental microbial infections. Oral candidosis are common and often found under removable partial dentures. Nonthermal atmospheric plasma (tissue tolerable plasma, TTP) was tested for its antimicrobial activity against different matured Candida albicans biofilms. Methods: We assessed the efficacy of selected agents (chlorhexidine, sodium hypochlorite, fluconazol) and TTP against in vitro biofilms of C. albicans grown 12 h (young), 24 h and 48 h (mature) in microtiter plates. Results: One minute TTP-treatment was shown to have significant effects on biofilm formation during the whole measurement period of young and mature biofilms. Only the effects of fluconazol and TTP could reduce formation of young biofilms for a longer period. Conclusions: The maturity level of biofilms influences the antiseptic efficacy of different agents. Young biofilms are very sensitive to antimicrobial effects, but they recover from it very fast. Mature biofilms show lower but long-term effects. Single plasma treatment for 1 min reduces the formation of young as well as mature biofilms. For the future physical treatment by TTP may get an alternative to chemical antisepsis.Hintergrund: Orale Candidosen, insbesondere unter Prothesen, sind weit verbreitet. Daher wurde die antimykotische Wirksamkeit eines kalten Atmosphärendruckplasmas (tissue tolerable plasma, TTP) gegen unterschiedlich reife Candida albicans -Biofilme untersucht. Methoden: Die Wirksamkeit ausgewählter Substanzen (Chlorhexidin, Natriumhypochlorit, Fluconazol) und von TTP gegen Biofilme, die 12 h (jung), 24 h und 48 h (reif) in Mikrotiterplatten wuchsen, wurde ermittelt. Ergebnisse: Einminütige TTP-Behandlung zeigte über den gesamten Messzeitraum eine signifikante Verminderung der Biofilmbildung bei jungen und reifen Biofilmen gegenüber der unbehandelten Kontrolle. Neben TTP konnte nur Fluconazol die Biofilmbildung des jungen Biofilms langfristig reduzieren. Schlussfolgerung: Der Reifegrad von Biofilmen hat einen Einfluss auf die antiseptische Wirksamkeit verschiedener Substanzen. Junge Biofilme sind sehr empfindlich, erholen sich allerdings sehr schnell. Reife Biofilme zeigen weniger ausgeprägte Effekte, die allerdings lang anhaltender sind. Die einminütige TTP-Anwendung reduziert die Biofilmbildung von jungen und reifen Biofilmen signifikant und könnte in Zukunft eine Alternative zur chemischen Antiseptik darstellen