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- ItemThe ECOMA 2007 campaign: Rocket observations and numerical modelling of aerosol particle charging and plasma depletion in a PMSE/NLC layer(München : European Geopyhsical Union, 2009) Brattli, A.; Lie-Svendsen, Ø.; Svenes, K.; Hoppe, U.-P.; Strelnikova, I.; Rapp, M.; Latteck, R.; Torkar, K.; Gumbel, J.; Megner, L.; Baumgarten, G.The ECOMA series of rocket payloads use a set of aerosol particle, plasma, and optical instruments to study the properties of aerosol particles and their interaction with the ambient plasma environment in the polar mesopause region. In August 2007 the ECOMA-3 payload was launched into a region with Polar Mesosphere Summer Echoes (PMSE) and noctilucent clouds (NLC). An electron depletion was detected in a broad region between 83 and 88 km, coincident with enhanced density of negatively charged aerosol particles. We also find evidence for positive ion depletion in the same region. Charge neutrality requires that a population of positively charged particles smaller than 2 nm and with a density of at least 2×108 m−3 must also have been present in the layer, undetected by the instruments. A numerical model for the charging of aerosol particles and their interaction with the ambient plasma is used to analyse the results, showing that high aerosol particle densities are required in order to explain the observed ion density depletion. The model also shows that a very high photoionisation rate is required for the particles smaller than 2 nm to become positively charged, indicating that these may have a lower work function than pure water ice.
- ItemModel simulations of chemical effects of sprites in relation with observed HO2 enhancements over sprite-producing thunderstorms(Katlenburg-Lindau : European Geosciences Union, 2021) Winkler, Holger; Yamada, Takayoshi; Kasai, Yasuko; Berger, Uwe; Notholt, JustusRecently, measurements by the Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) satellite instrument have been presented which indicate an increase in mesospheric HO2 above sprite-producing thunderstorms. The aim of this paper is to compare these observations to model simulations of chemical sprite effects. A plasma chemistry model in combination with a vertical transport module was used to simulate the impact of a streamer discharge in the altitude range 70–80 km, corresponding to one of the observed sprite events. Additionally, a horizontal transport and dispersion model was used to simulate advection and expansion of the sprite air masses. The model simulations predict a production of hydrogen radicals mainly due to reactions of proton hydrates formed after the electrical discharge. The net effect is a conversion of water molecules into H+OH. This leads to increasing HO2 concentrations a few hours after the electric breakdown. Due to the modelled long-lasting increase in HO2 after a sprite discharge, an accumulation of HO2 produced by several sprites appears possible. However, the number of sprites needed to explain the observed HO2 enhancements is unrealistically large. At least for the lower measurement tangent heights, the production mechanism of HO2 predicted by the model might contribute to the observed enhancements.
- ItemInvestigating the Mutagenicity of a Cold Argon-Plasma Jet in an HET-MN Model(San Francisco, California, US : PLOS, 2016) Kluge, Susanne; Bekeschus, Sander; Bender, Claudia; Benkhai, Hicham; Sckell, Axel; Below, Harald; Stope, Matthias B.; Kramer, Axel; Yousfi, MohammedObjective: So-called cold physical plasmas for biomedical applications generate reactive oxygen and nitrogen species and the latter can trigger DNA damage at high concentrations. Therefore, the mutagenic risks of a certified atmospheric pressure argon plasma jet (kINPen MED) and its predecessor model (kINPen 09) were assessed. Methods: Inner egg membranes of fertilized chicken eggs received a single treatment with either the kINPen 09 (1.5, 2.0, or 2.5 min) or the kINPen MED (3, 4, 5, or 10 min). After three days of incubation, blood smears (panoptic May-Grünwald-Giemsa stain) were performed, and 1000 erythrocytes per egg were evaluated for the presence of polychromatic and normochromic nuclear staining as well as nuclear aberrations and binucleated cells (hen’s egg test for micronuclei induction, HET-MN). At the same time, the embryo mortality was documented. For each experiment, positive controls (cyclophosphamide and methotrexate) and negative controls (NaCl-solution, argon gas) were included. Additionally, the antioxidant potential of the blood plasma was assessed by ascorbic acid oxidation assay after treatment. Results: For both plasma sources, there was no evidence of genotoxicity, although at the longest plasma exposure time of 10 min the mortality of the embryos exceeded 40%. The antioxidant potential in the egg’s blood plasma was not significantly reduced immediately (p = 0.32) or 1 h (p = 0.19) post exposure to cold plasma. Conclusion: The longest plasma treatment time with the kINPen MED was 5–10 fold above the recommended limit for treatment of chronic wounds in clinics. We did not find mutagenic effects for any plasma treatment time using the either kINPen 09 or kINPen MED. The data provided with the current study seem to confirm the lack of a genotoxic potential suggesting that a veterinary or clinical application of these argon plasma jets does not pose mutagenic risks.
- ItemEfficiency of plasma-processed air for biological decontamination of crop seeds on the premise of unimpaired seed germination(Hoboken, NJ : Wiley Interscience, 2021) Wannicke, Nicola; Wagner, Robert; Stachowiak, Joerg; Nishime, Thalita M.C.; Ehlbeck, Joerg; Weltmann, Klaus‐Dieter; Brust, HenrikeIn this study, the antimicrobial effect of plasma-processed air (PPA) generated by a microwave-induced nonthermal plasma was investigated for preharvest utilization using three crop species: Barley, rape, and lupine. Bacillus atrophaeus spores were chosen as a model, inoculated onto seeds, and subsequently treated with PPA at two different flow rates, different filling regimes, and gas exposure times. PPA treatment was efficient in reducing viable spores of B. atrophaeus, reaching sporicidal effects in all species at certain parameter combinations. Maximum germination of seeds was strongly reduced in barley and rape seeds at some parameter combination, whereas it had a modest effect on lupine seeds. Seed hydrophilicity was not altered. Overall, PPA investigated in this study proved suitable for preharvest applications.
- ItemVerified modeling of a low pressure hydrogen plasma generated by electron cyclotron resonance(Bristol : IOP Publ., 2022) Sigeneger, F.; Ellis, J.; Harhausen, J.; Lang, N.; van Helden, J.H.A self-consistent fluid model has been successfully developed and employed to model an electron cyclotron resonance driven hydrogen plasma at low pressure. This model has enabled key insights to be made on the mutual interaction of microwave propagation, power density, plasma generation, and species transport at conditions where the critical plasma density is exceeded. The model has been verified by two experimental methods. Good agreement with the ion current density and floating potential—as measured by a retarding energy field analyzer—and excellent agreement with the atomic hydrogen density—as measured by two-photon absorption laser induced fluorescence—enables a high level of confidence in the validity of the simulation.
- ItemRedox Stimulation of Human THP-1 Monocytes in Response to Cold Physical Plasma(Austin, Tex. : Landes Bioscience, 2015) Bekeschus, Sander; Schmidt, Anke; Bethge, Lydia; Masur, Kai; von Woedtke, Thomas; Hasse, Sybille; Wende, KristianIn plasma medicine, cold physical plasma delivers a delicate mixture of reactive components to cells and tissues. Recent studies suggested a beneficial role of cold plasma in wound healing. Yet, the biological processes related to the redox modulation via plasma are not fully understood. We here used the monocytic cell line THP-1 as a model to test their response to cold plasma in vitro. Intriguingly, short term plasma treatment stimulated cell growth. Longer exposure only modestly compromised cell viability but apparently supported the growth of cells that were enlarged in size and that showed enhanced metabolic activity. A significantly increased mitochondrial content in plasma treated cells supported this notion. On THP-1 cell proteome level, we identified an increase of protein translation with key regulatory proteins being involved in redox regulation (hypoxia inducible factor 2α), differentiation (retinoic acid signaling and interferon inducible factors), and cell growth (Yin Yang 1). Regulation of inflammation is a key element in many chronic diseases, and we found a significantly increased expression of the anti-inflammatory heme oxygenase 1 (HMOX1) and of the neutrophil attractant chemokine interleukin-8 (IL-8). Together, these results foster the view that cold physical plasma modulates the redox balance and inflammatory processes in wound related cells.
- ItemEnhancing surface production of negative ions using nitrogen doped diamond in a deuterium plasma(Bristol : IOP Publ., 2020) Smith, Gregory J.; Ellis, James; Moussaoui, Roba; Pardanaud, Cédric; Martin, Céline; Achard, Jocelyn; Issaoui, Riadh; Gans, Timo; Dedrick, James P.; Cartry, GillesThe production of negative ions is of significant interest for applications including mass spectrometry, particle acceleration, material surface processing, and neutral beam injection for magnetic confinement fusion. Methods to improve the efficiency of the surface production of negative ions, without the use of low work function metals, are of interest for mitigating the complex engineering challenges these materials introduce. In this study we investigate the production of negative ions by doping diamond with nitrogen. Negatively biased (-20 V or-130 V), nitrogen doped micro-crystalline diamond films are introduced to a low pressure deuterium plasma (helicon source operated in capacitive mode, 2 Pa, 26 W) and negative ion energy distribution functions are measured via mass spectrometry with respect to the surface temperature (30 °C to 750 °C) and dopant concentration. The results suggest that nitrogen doping has little influence on the yield when the sample is biased at-130 V, but when a relatively small bias voltage of-20 V is applied the yield is increased by a factor of 2 above that of un-doped diamond when its temperature reaches 550 °C. The doping of diamond with nitrogen is a new method for controlling the surface production of negative ions, which continues to be of significant interest for a wide variety of practical applications. © 2020 The Author(s). Published by IOP Publishing Ltd.
- ItemRecent advances in nano-photonic techniques for pharmaceutical drug monitoring with emphasis on Raman spectroscopy(Berlin : de Gruyter, 2019) Frosch, Timea; Knebl, Andreas; Frosch, TorstenInnovations in Raman spectroscopic techniques provide a potential solution to current problems in pharmaceutical drug monitoring. This review aims to summarize the recent advances in the field. The developments of novel plasmonic nanoparticles continuously push the limits of Raman spectroscopic detection. In surface-enhanced Raman spectroscopy (SERS), these particles are used for the strong local enhancement of Raman signals from pharmaceutical drugs. SERS is increasingly applied for forensic trace detection and for therapeutic drug monitoring. In combination with spatially offset Raman spectroscopy, further application fields could be addressed, e.g. in situ pharmaceutical quality testing through the packaging. Raman optical activity, which enables the thorough analysis of specific chiral properties of drugs, can also be combined with SERS for signal enhancement. Besides SERS, micro- and nano-structured optical hollow fibers enable a versatile approach for Raman signal enhancement of pharmaceuticals. Within the fiber, the volume of interaction between drug molecules and laser light is increased compared with conventional methods. Advances in fiber-enhanced Raman spectroscopy point at the high potential for continuous online drug monitoring in clinical therapeutic diagnosis. Furthermore, fiber-array based non-invasive Raman spectroscopic chemical imaging of tablets might find application in the detection of substandard and counterfeit drugs. The discussed techniques are promising and might soon find widespread application for the detection and monitoring of drugs in various fields.
- ItemSecondary charging effects due to icy dust particle impacts on rocket payloads(München : European Geopyhsical Union, 2012) Kassa, M.; Rapp, M.; Hartquist, T.W.; Havnes, O.We report measurements of dust currents obtained with a small probe and a larger probe during the flight of the ECOMA-4 rocket through the summer polar mesosphere. The payload included two small dust probes behind a larger dust probe located centrally at the front. For certain phases of the payload rotation, the current registered by one of the small dust probes was up to 2 times the current measured with the larger probe, even though the effective collection area of the larger probe was 4 times that of the small one. We analyze the phase dependence of the currents and their difference with a model based on the assumption that the small probe was hit by charged dust fragments produced in collisions of mesospheric dust with the payload body. Our results confirm earlier findings that secondary charge production in the collision of a noctilucent cloud/Polar Summer Mesospheric Echo (NLC/PMSE) dust particle with the payload body must be several orders of magnitude larger than might be expected from laboratory studies of collisions of pure ice particles with a variety of clean surfaces. An important consequence is that for some payload configurations, one should not assume that the current measured with a detector used to study mesospheric dust is simply proportional to the number density of ambient dust particles. The higher secondary charge production may be due to the NLC/PMSE particles containing multiple meteoric smoke particles.
- ItemA linear model for amplitude modulation of Langmuir waves in weak electron-beam plasma interaction(Göttingen : Copernicus, 2013) Baumgärtel, K.A simple linear approach to the phenomenon of amplitude modulation of Langmuir waves in weak beam plasma interaction is presented. During the short growth phase of the instability and within the longer period after saturation, the waves are described by their linear kinetic dispersion properties.The amplitude modulation appears as result of the beating of waves with different wavelengths and amplitudes that have grown from noise in the initial phase. The Langmuir wave fields are calculated via FFT (fast Fourier transform) technique. The resulting waveforms in temporal representation are quite similar to those observed by spacecraft.