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In dieser Arbeit wurde die Wirksamkeit der Antiseptika Chlorhexidindigluconat CHX 0,0001 % u. 0,00000625 %), Polihexamethylenbiguanid (PHMB 0,0001 % u. 0,000025 %) und Octenidinhydrochlorid (OCT 0,0002 % u. 0,00005 %) mit gewebekompatiblen Atmosphärendruckplasmen (TTP) mit dem Edelgas Argon als Trägergas mit und ohne Zumischung von 1% Sauerstoff, generiert mit dem kINPen09 und einer Hohlelektroden-Dielectric-Barrier Discharge Plasmaquelle (HDBD) sowie der alleinigen Gasbehandlung (Trägergas ohne Plasmagenerierung) in Bezug auf die Vermehrungshemmung bzw. Eradikation von C. albicans ATCC 10231, C. albicans SC 5314, P. aeruginosa ATCC 9027, P. aeruginosa SG 81, S. epidermidis ATCC 12228, S. epidermidis RP 62A, S. mutans DSM 20523 und S. sanguinis DSM 20068 untersucht. Die Antiseptika wirkten über den gesamten Untersuchungszeitraum von 32 h auf die Mikroorganismen ein, die TTP-Behandlungen nur 60 s. Die Vermehrung der Mikroorganismen wurde alle 30 min anhand der optischen Dichte der Testkulturen gemessen und die Fläche unter dem resultierenden Graphen (Area under the curve, AUC) charakterisiert. Bei C. albicans ATCC 10231 und SC 5314 wurde die Vermehrung vollständig von OCT 0,0002 % und der Plasmabehandlung mit HDBD mit Sauerstoffzuführung gehemmt. Die HDBD-und kINPen09- Behandlungen ohne Sauerstoffzufuhr waren beim ATCC-Stamm nur unwesentlich weniger effektiv. Die restlichen Antiseptika zeigten nur eine geringe Wirkung. Bei der Behandlung von P. aeruginosa SG 81 kam es weder durch die verwendeten Antiseptika noch durch das Plasma zu einer vollständigen Vermehrungshemmung. Insgesamt stellten sich hier die Plasmabehandlungen als deutlich effektiver heraus als die Behandlungen mit den Antiseptika. Auch bei P. aeruginosa ATCC 9027 zeigte die Behandlung mit den Antiseptika einen geringeren Effekt. Im Ganzen reagierten die gramnegativen P. aeruginosa in diesen Versuchen am wenigsten empfindlich auf die antiseptischen Behandlungen. Bei der Behandlung von S. epidermidis RP 62A bewirkten die Antiseptika PHMB 0,0001 % und OCT 0,0002 % eine vollständige Vermehrungshemmung. Die Argongaskontrolle und die Plasmabehandlung mit dem kINPen09 waren ebenso wie die Behandlung mit CHX 0,0001 % etwas weniger wirksam. Beim nicht biofilmbildenden ATCC 12228 Stamm von S. epidermidis, der nicht mit Plasma behandelt wurde, führte nur OCT 0,0002 % zu einer vollständigen Vermehrungshemmung. Bei S. mutans DSM 20523 konnte keine der untersuchten antiseptischen Behandlungen zu einer vollständigen Vermehrungshemmung führen. Am effektivsten stellten sich die Behandlungen mit OCT, PHMB und die Plasmaanwendung mit dem kINPen09 ohne und mit 1 % Sauerstoffbeimischung heraus. Die Behandlung von S. sanguinis DSM 20068 wurde ausschließlich mit Plasma bzw. deren Gaskontrollen durchgeführt. Hier waren die Plasmabehandlungen mit dem kINPen09 und deren Gaskontrollen den HDBD-Behandlungen überlegen. Von allen getesteten Antiseptika stellte sich Octenidin 0,0002 % als das am breitesten wirksame und effektivste Antiseptikum heraus. Bei der Behandlung der Candida- und S. epidermidis-Stämme führte dies zu einer vollständigen Hemmung der Proliferation bis zum Ende des Beobachtungszeitraums von 32 h. CHX 0,0001 % und PHMB 0,0001 % unterschieden sich bis auf die Behandlung von S. epidermidis RP 62A und S. mutans DSM 20523 mit der Überlegenheit für PHMB 0,0001 % nicht in ihrer Wirksamkeit. Die Plasmabehandlungen von 60 s waren mit Ausnahme von S. epidermidis den über den gesamten Untersuchungszeitraum einwirkenden Antiseptika ebenbürtig oder signifikant überlegen. Die Behandlung mit TTP könnte damit eine wirksame Alternative oder Ergänzung zu den herkömmlichen Antiseptika darstellen, um z.B. die Vermehrung von Mikroorganismen in einer infizierten Wunde zu hemmen und somit die Immunabwehr zu unterstützen und Entzündungen zu verzögern oder zu verhindern.
Gegenstand der hier vorgestellten Arbeit ist die Beschichtung von Wundauflagen mit Zinkoxid- und Silberhaltigen antibakteriellen Schichten. Die Aufbringung der Schichten erfolgt dabei auf den Wundauflagen mittels Atmosphärendruckplasma. Die Matrix der Schichten besteht aus Siliziumdioxid, in welcher die Wirkstoffe eingelagert sind. Auf diesem Weg hergestellten Wundauflagen wurden hinsichtlich ihrer antibakteriellen Wirkung und zytotoxischen Eigenschaften charakterisiert. Ziele waren ein minimaler Einsatz an Wirkstoffen und die Nutzung eines modernen Beschichtungsverfahrens. Der zytotoxische Einfluss der Wundauflagen wurde an 3D-Hautmodellen im Vergleich zu den am Markt befindlichen Produkten validiert.
Objectives:
This study investigates the effectiveness of the Cold AP on the alteration of the enamel surface
without using acid etchant by using Conventional photo-activated resin bond to bond the
orthodontic brackets.
Materials and Methods:
One hundred and twenty-five Enamel specimens are prepared from disinfected bovine
mandibular incisors are divided into five groups. Group I: brackets are attached on the enamel
surface with the standard adhesive technique (etch + primer +bond). Group II: the brackets are
attached with the Standard Orthodontic adhesive technique without etching. Group III: the
enamel surface is conditioned with pure Argon Cold atmospheric plasma before the application
of the primer without using an acid etchant. Group IV: the enamel surface is conditioned with
the admixture of Argon Cold atmospheric plasma with 0.5 % Oxygen before the application of
the primer without using acid etchant Group V: after the application of Argon Cold atmospheric
plasma with 0.5 % Oxygen the surface is rewetted by deionized water before the application
of the primer and adhesive. After that, the samples are exposed to thermal cycling. The shear
bond strength of the samples is tested by the universal testing machine which measured the
maximum force at which the brackets are deboned from the tooth surface at a speed of
1mm/minute is measured.
Results:
Significant intergroup differences were found. Group V showed the highest shear bond
strength followed by Group I, VI, III, II respectively. There isn’t a statistical difference in the
values of The Shear bond strength values between Group III and IV.
Conclusions:
this study implies that Cold Atmospheric Plasma is a safe method to change the chemical
surface characteristics of the enamel surface.in addition to the significant importance of plasma
treatment followed by water rewetting, which could enhance adhesion between the orthodontic
attachments and the enamel layer
The present experimental work investigates plasma turbulence in the edge region of magnetized high-temperature plasmas. A main topic is the turbulent dynamics parallel to the magnetic field, where hitherto only a small data basis existed, especially for very long scale lengths in the order of ten of meters. A second point of special interest is the coupling of the dynamics parallel and perpendicular to the magnetic field. This anisotropic turbulent dynamics is investigated by two different approaches. Firstly, spatially and temporally high-resolution measurements of fluctuating plasma parameters are investigated by means of two-point correlation analysis. Secondly, the propagation of signals externally imposed into the turbulent plasma background is studied. For both approaches, Langmuir probe arrays were utilized for diagnostic purposes. The main findings can be summarized as follows: Greatly elongated fluctuation structures exist in plasma edge turbulence. The structures are aligned along the confining magnetic field (k|| = 0). The correlation degree of fluctuations for a short connection length of 0.75m is greater than 80%. For much longer connection lengths of 23m and 66m, the correlation degree is reduced to approximately 40%. A conceptual interpretation of these observations is the coexistence of two different fluctuation components. One component has a correlation length parallel to the magnetic field below 20m and the other component a correlation length greater than 70m. Sine signals in the frequency range 1-100 kHz were injected into the turbulent plasma background. The propagation parallel and perpendicular to the magnetic field of the signals was studied. In poloidal direction, an asymmetry is observed, that can be explained by a copropagation of the signal with the background E × B-rotation of the plasma. The signal propagation parallel to the magnetic field shows no such asymmetry. As an advanced approach, spatio-temporal wave patters were injected into the edge plasma. The waves launched that way can be seen as test waves' in a turbulent background. The coupling strength of the imposed wave patterns to the background turbulence relies on the match of the imposed waves to the dynamics of turbulent structures. If the propagation direction of the imposed waves is parallel to the propagation direction of the background plasma, improved coupling is observed. This finding underlines the importance of the background plasma rotation for future attempts of controlling the plasma edge turbulence. Further optimization of frequency and wave vector of the imposed waves is probably a promising approach for achieving a significant and systematic influence of turbulence. Taking into account the present experimental state-of-the-art, for a deeper insight into the mechanism of the plasma edge turbulence of magnetized high-temperature plasmas a joint effort of numerical modeling and experimental results is a valuable approach. Such a cooperation should cover the explanation of the correlation observations as well as the experiments on signal injection into background turbulence. A quantitative comparison between the results presented in this work and a dedicated numerical drift wave simulation would be a significant step forward to a better understanding of plasma edge turbulence.
Manipulating and utilizing plasmas becomes a more and more important task in various research fields of physics and in industrial developments. Especially in nowadays spacerelevant applications there are different ideas to modify plasmas concerning particular tasks.
One major point of interest is the ability to influence plasmas using magnetic fields. To study the underlying physical effects that were achieved by these magnetic fields for both scenarios Particle-in-Cell simulations were done. Two examples are discussed in this thesis.
The first example originates from an experiment performed by the European Space Agency ESA in collaboration with the German Space Agency DLR. To verify the possibility of heat-flux reduction by magnetic fields onto the thermal protection system of a space vehicle a simplified experiment on earth was developed. Most of the heat that is created during re-entry comes from compression of the air ahead of the hypersonic vehicle, as a result of the basic thermodynamic relation between temperature and pressure. The shock front, which builds up in front of the vehicle deflects most of the heat and prohibits the surface of the space vehicle from direct contact with the maximum flux. State of the art spacecrafts use highly developed materials like ceramics to handle the enormous heat. An attractive approach to reduce costs is to use magnetic fields for heat-flux reduction. This would allow the use of cheaper materials and thus reduce costs for the whole space mission. A partially-ionized Argon beam was used to create a certain heat-flux onto a target. The main finding of the experimental campaign was a large mitigation of heat-flux by applying a dipole-like magnetic field. The Particle-in-Cell method was able to reproduce experimental observations like the heat-flux reduction. An additionally implemented optical diagnostics module allowed to confirm the results of the spectroscopy done during the experiment. The underlying effect that is responsible for the heat-flux reduction was identified as a coupling between the modified plasma and the dominating neutral flux component. The plasma, that is guided towards the target, act as a shield in front of the target surface for arriving neutrals. These neutrals are slowed down by charge-exchange collisions. Furthermore the magnetic field induces an increased turbulent transport that is also needed to reach a reduction in heat-ux. The turbulent transport was also obtained by three-dimensional Direct Simulation Monte Carlo simulations. Unfortunately, such source driven turbulence can not be expected in space, so that a heat flux reduction in real space applications is questionable. Nevertheless, other effects like the induced turbulence by the rotating vehicle can compensate the missing source driven effect.
The second scenario in which a magnetic field is used to modify the heat flux of a plasma is the operation of the pulsed cathodic arc thruster. The same Particle-in-Cell code was used to simulate a typical pulse of this newly developed thruster of Neumann Space Pty Ltd. The typical behavior of the thruster could be reproduced numerically. The thrust is mainly produced by fast electrons. These electrons are accelerated by electric fields as a result of a plasma-beam instability. This plasma-beam instability was verified by a phase space diagnostics for the electrons. To demonstrate the influence of the magnetic field a simulation of the cathodic arc thruster without magnetic field and one with magnetic field were compared. It was shown that the use of a magnetic field leads to a ten times larger thrust by directing the heat ux. The resulting narrow plume is an additional Advantage of the particle guiding magnetic field. This narrowness of the plume reduces the danger of interaction with other components of the space vehicle.
Both scenarios demonstrate the different capabilities for electromagnetic fields to manipulate plasmas and especially the corresponding heat-flux with respect to certain tasks. The possibilities range from reducing the heat-flux onto a target to maximizing the thrust by directing the heat-ux. This thesis demonstrates that simulations are a great tool to support experiments and to deliver an improved physics understanding. They help to identify the basic physics principles in the different systems, because they can deliver information not accessible to experiments.
In particular, a better understanding of the influence of electromagnetic fields on the heat-flux distribution in space-relevant applications was obtained. This can be the basis for further simulation-guided optimization, e.g. for the design of more effective cathodic arc thrusters. Here, the goal is to minimize costs for prototypes by replacing the hardware by virtual prototypes in the simulations. This allows to test basic design ideas in advance and get more highly-optimized designs at a fraction of time and costs.