A radio-frequency atmospheric pressure argon plasma jet is used for the inactivation of bacteria (Pseudomonas aeruginosa) in solutions. The source is characterized by measurements of power ...dissipation, gas temperature, absolute UV irradiance as well as mass spectrometry measurements of emitted ions. The plasma-induced liquid chemistry is studied by performing liquid ion chromatography and hydrogen peroxide concentration measurements on treated distilled water samples. Additionally, a quantitative estimation of an extensive liquid chemistry induced by the plasma is made by solution kinetics calculations. The role of the different active components of the plasma is evaluated based on either measurements, as mentioned above, or estimations based on published data of measurements of those components. For the experimental conditions being considered in this work, it is shown that the bactericidal effect can be solely ascribed to plasma-induced liquid chemistry, leading to the production of stable and transient chemical species. It is shown that HNO2, ONOO− and H2O2 are present in the liquid phase in similar quantities to concentrations which are reported in the literature to cause bacterial inactivation. The importance of plasma-induced chemistry at the gas-liquid interface is illustrated and discussed in detail.
The gas temperature in non-equilibrium plasmas is often obtained from the plasma-induced emission by measuring the rotational temperature of a diatomic molecule in its excited state. This is ...motivated by both tradition and the availability of low budget spectrometers. However, non-thermal plasmas do not automatically guarantee that the rotational distribution in the monitored vibrational level of the diatomic molecule is in equilibrium with the translational (gas) temperature. Often non-Boltzmann rotational molecular spectra are found in non-equilibrium plasmas. The deduction of a gas temperature from these non-thermal distributions must be done with care as clearly the equilibrium between translational and rotational degrees of freedom cannot be achieved. In this contribution different methods and approaches to determine the gas temperature are evaluated and discussed. A detailed analysis of the gas temperature determination from rotational spectra is performed. The physical and chemical background of non-equilibrium rotational population distributions in molecular spectra is discussed and a large range of conditions for which non-equilibrium occurs are identified. Fitting procedures which are used to fit (non-equilibrium) rotational distributions are analyzed in detail. Lastly, recommendations concerning the conditions for which the gas temperatures can be obtained from diatomic spectra are formulated.
The 2012 Plasma Roadmap Samukawa, Seiji; Hori, Masaru; Rauf, Shahid ...
Journal of physics. D, Applied physics,
06/2012, Letnik:
45, Številka:
25
Journal Article
Recenzirano
Odprti dostop
Low-temperature plasma physics and technology are diverse and interdisciplinary fields. The plasma parameters can span many orders of magnitude and applications are found in quite different areas of ...daily life and industrial production. As a consequence, the trends in research, science and technology are difficult to follow and it is not easy to identify the major challenges of the field and their many sub-fields. Even for experts the road to the future is sometimes lost in the mist. Journal of Physics D: Applied Physics is addressing this need for clarity and thus providing guidance to the field by this special Review article, The 2012 Plasma Roadmap. Although roadmaps are common in the microelectronic industry and other fields of research and development, constructing a roadmap for the field of low-temperature plasmas is perhaps a unique undertaking. Realizing the difficulty of this task for any individual, the plasma section of the Journal of Physics D Board decided to meet the challenge of developing a roadmap through an unusual and novel concept. The roadmap was divided into 16 formalized short subsections each addressing a particular key topic. For each topic a renowned expert in the sub-field was invited to express his/her individual visions on the status, current and future challenges, and to identify advances in science and technology required to meet these challenges. Together these contributions form a detailed snapshot of the current state of the art which clearly shows the lifelines of the field and the challenges ahead. Novel technologies, fresh ideas and concepts, and new applications discussed by our authors demonstrate that the road to the future is wide and far reaching. We hope that this special plasma science and technology roadmap will provide guidance for colleagues, funding agencies and government institutions. If successful in doing so, the roadmap will be periodically updated to continue to help in guiding the field.
Plasma-liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol ...science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas.
Laser scattering provides a very direct method for measuring the local densities and temperatures inside a plasma. We present new experimental results of laser scattering on an argon atmospheric ...pressure microwave plasma jet operating in an air environment. The plasma is very small so a high spatial resolution is required to study the effect of the penetration of air molecules into the plasma. The scattering signal has three overlapping contributions: Rayleigh scattering from heavy particles, Thomson scattering from free electrons and Raman scattering from molecules. The Rayleigh scattering signal is filtered out optically with a triple grating spectrometer. The disentanglement of the Thomson and Raman signals is done with a newly designed fitting method. With a single measurement we determine profiles of the electron temperature, electron density, gas temperature, partial air pressure and the N sub(2)/O sub(2) ratio, with a spatial resolution of 50 mu m, and including absolute calibration.
Cold atmospheric pressure plasma (CAP) oxidizes organic compounds in water through the generation of a variety of reactive species including O
3
and OH radicals. While the energy efficiency and rate ...of decomposition of the chemical compound in water is already extensively studied, only few studies focused on the reactive species responsible for the decomposition. We report on an investigation of the chemical reactive species involved in the decomposition of crystal violet (CV), a model organic compound, by an RF driven plasma jet in different gas mixtures. Different gas mixtures lead to different concentrations of reactive species responsible for the decolorization of CV. Moreover, the effect of transport limitations on the efficiency of the plasma treatment is reported. A study of positive control measurements, the effect of scavengers of relevant reactive species and particle imaging velocimetry reveal the dominant role of short-lived species at the plasma–liquid interface in which OH most likely plays an important role. Moreover, the decolorization rate is limited by transport of CV to the near boundary region. The results suggest that for the optimization of water treatment by the short-lived species generated by a plasma, an optimum transport of the to-be-treated compounds to the interface might be more critical than effective reactive species production in the plasma.
Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temperature plasma ...science and technology. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temperature plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temperature plasma field in the development of plasmas as an enabling technology for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technological challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.
A time modulated RF atmospheric pressure plasma jet, operated in ambient air with a flow of argon with a few per cent of air, N2 or O2, was characterized by measuring the gas temperature with ...Rayleigh scattering, the absolute NO density with laser-induced fluorescence, and the emission of NO A and N2 C with time resolved optical emission spectroscopy. The gas temperature, NO density and the emission measurements are carried out both time and spatially resolved. The atmospheric pressure plasma jet has the advantage that the plasma dissipated power can be measured, and it was found that the gas temperature depends on the power, rather than the gas mixture. The NO density increases with increasing plasma power, and was found to have a maximum around 1.5 × 1021 m−3 at an air admixture of 2%. The N2 C emission is modulated by the 13.9 MHz RF frequency, while the NO A emission front increases with much slower velocity during the 20 kHz duty cycle, which gives an insight into the excitation mechanisms in the plasma. Through the addition of either N2 or O2 to the plasma it was experimentally confirmed that the production of atomic N radicals are of key importance for the NO production in this atmospheric pressure plasma jet.
Megakaryoblastic leukemia 1 (MKL1) promotes the regulation of essential cell processes, including actin cytoskeletal dynamics, by coactivating serum response factor. Recently, the first human with ...MKL1 deficiency, leading to a novel primary immunodeficiency, was identified. We report a second family with 2 siblings with a homozygous frameshift mutation in MKL1. The index case died as an infant from progressive and severe pneumonia caused by Pseudomonas aeruginosa and poor wound healing. The younger sibling was preemptively transplanted shortly after birth. The immunodeficiency was marked by a pronounced actin polymerization defect and a strongly reduced motility and chemotactic response by MKL1-deficient neutrophils. In addition to the lack of MKL1, subsequent proteomic and transcriptomic analyses of patient neutrophils revealed actin and several actin-related proteins to be downregulated, confirming a role for MKL1 as a transcriptional coregulator. Degranulation was enhanced upon suboptimal neutrophil activation, whereas production of reactive oxygen species was normal. Neutrophil adhesion was intact but without proper spreading. The latter could explain the observed failure in firm adherence and transendothelial migration under flow conditions. No apparent defect in phagocytosis or bacterial killing was found. Also, monocyte-derived macrophages showed intact phagocytosis, and lymphocyte counts and proliferative capacity were normal. Nonhematopoietic primary fibroblasts demonstrated defective differentiation into myofibroblasts but normal migration and F-actin content, most likely as a result of compensatory mechanisms of MKL2, which is not expressed in neutrophils. Our findings extend current insight into the severe immune dysfunction in MKL1 deficiency, with cytoskeletal dysfunction and defective extravasation of neutrophils as the most prominent features.
•MKL1-deficient neutrophils show severe functional defects due to defective actin polymerization and downregulation of actin-related proteins.•MKL1 deficiency does not alter primary fibroblast morphology, F-actin content, or migratory behavior.
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