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- ItemReduce and refine: Plasma treated water vs conventional disinfectants for conveyor-belt cleaning in sustainable food-production lines(Melville, NY : American Inst. of Physics, 2021) Weihe, Thomas; Schnabel, Uta; Winter, Hauke; Möller, Timon; Stachowiak, Jörg; Neumann, Sabine; Schlüter, Oliver; Ehlbeck, JörgSustainable and microbiologically secure foodstuff production lines are of increasing scientific interest and are in the focus of recent research programs. Additionally, they are of great importance for the production industry due to the prevention of food-borne illnesses caused by pathogens such as Salmonella sp., Listeria monocytogenes, or Escherichia coli. These pathogens are responsible for production losses, loss of customer acceptance, and severe food-borne illnesses. A pathogenic threat is frequently combated with sanitizing steps of the production lines. For conveyor band cleaning, this study compares the cleaning abilities of nitric acid (HNO3) and plasma treated water (PTW), which have been sprayed via a commercially available nozzle on two different polymeric surfaces (polysiloxane and polyurethane). Additionally, the cleaning agents HNO3 and PTW have been characterized through their pH and their conductivity. These findings have been underpinned by experiments that focus on a possible influence of nozzle abrasion, such as brass and stainless-steel nanoparticles, on the antimicrobial potential of PTW and HNO3. Adversely acting effects like an enhanced abrasion of conveyer band materials due to PTW or HNO3 treatment have been checked by using light microscopic micrographs and topographic scans in high-resolution mode. Based on the presented results of the experiments, the suitability of an in-place sanitation step in foodstuff production lines has been demonstrated on a laboratory scale.
- ItemReactive species driven oxidative modifications of peptides—Tracing physical plasma liquid chemistry(Melville, NY : American Inst. of Physics, 2021) Wenske, Sebastian; Lackmann, Jan-Wilm; Busch, Larissa Milena; Bekeschus, Sander; von Woedtke, Thomas; Wende, KristianThe effluence of physical plasma consists of a significant share of reactive species, which may interact with biomolecules and yield chemical modifications comparable to those of physiological processes, e.g., post-translational protein modifications (oxPTMs). Consequentially, the aim of this work is to understand the role of physical plasma-derived reactive species in the introduction of oxPTM-like modifications in proteins. An artificial peptide library consisting of ten peptides was screened against the impact of two plasma sources, the argon-driven MHz-jet kINPen and the helium-driven RF-jet COST-Jet. Changes in the peptide molecular structure were analyzed by liquid chromatography–mass spectrometry. The amino acids cysteine, methionine, tyrosine, and tryptophan were identified as major targets. The introduction of one, two, or three oxygen atoms was the most common modification observed. Distinct modification patterns were observed for nitration (+N + 2O–H), which occurred in kINPen only (peroxynitrite), and chlorination (+Cl–H) that was exclusive for the COST-Jet in the presence of chloride ions (atomic oxygen/hypochlorite). Predominantly for the kINPen, singlet oxygen-related modifications, e.g., cleavage of tryptophan, were observed. Oxidation, carbonylation, and double oxidations were attributed to the impact of hydroxyl radicals and atomic oxygen. Leading to a significant change in the peptide side chain, most of these oxPTM-like modifications affect the secondary structure of amino acid chains, and amino acid polarity/functionality, ultimately modifying the performance and stability of cellular proteins.
- ItemInvestigation of the radially resolved oxygen dissociation degree and local mean electron energy in oxygen plasmas in contact with different surface materials(Melville, NY : American Inst. of Physics, 2017) Tsutsumi, T.; Greb, A.; Gibson, A. R.; Hori, M.; O'Connell, D.; Gans, T.Energy Resolved Actinometry is applied to simultaneously measure the radially resolved oxygen dissociation degree and local mean electron energy in a low-pressure capacitively coupled radio-frequency oxygen plasma with an argon tracer gas admixture. For this purpose, the excitation dynamics of three excited states, namely, Ar(2p1), O(3p3P), and O(3p5P), were determined from their optical emission at 750.46 nm, 777.4 nm, and 844.6 nm using Phase Resolved Optical Emission Spectroscopy (PROES). Both copper and silicon dioxide surfaces are studied with respect to their influence on the oxygen dissociation degree, local mean electron energy, and the radial distributions of both quantities and the variation of the two quantities with discharge pressure and driving voltage are detailed. The differences in the measured dissociation degree between different materials are related back to atomic oxygen surface recombination probabilities.
- ItemEffect of a high-voltage mesh electrode on the volume and surface characteristics of pulsed dielectric barrier discharges(Melville, NY : American Inst. of Physics, 2020) Kettlitz, M.; van Rooij, O.; Höft, H.; Brandenburg, R.; Sobota, A.Electrical breakdown in a pulsed asymmetric dielectric barrier discharge between a glass-covered mesh electrode and a grounded metal electrode in the air at atmospheric pressure is investigated. Volume discharge forms between the metal tip and the dielectric surface and spreads over the dielectric surface. Breakdown and discharge behaviors depend on the polarity of the charged electrode covered with glass compared to the metal rod electrode. In the case of the dielectric cathode (covered mesh), volume discharge features a stronger and longer-lasting emission. Volume discharge is weaker with outstretched surface discharge developing on the opposite glass electrode sustained by the embedded mesh when the metal rod functions as a cathode. The development and spatial distribution of the surface discharge depend on the relative polarity of the dielectrics caused by the charge deposition of the preceding discharge and is independent of the polarity of the applied high voltage. The discharge emission is brighter for the metal cathode and dielectric anode than for the metal anode, with a branching discharge developing and spreading in a star-like structure along the embedded grid, while a ring-like structure was observed for the metal anode and dielectric cathode. The duty cycle influences the discharge development and properties through the effects of the gas phase and surface pre-ionization.