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Can low-temperature plasma technology play a role in medicine? This is a question that many investigators today are trying hard to give a positive answer to. It did not quite start out this way. Almost two decades ago, few "curious" electrical engineers and physicists with the help of few "brave" biologists! microbiologists asked themselves more basic questions: What happens to biological cells if they were exposed to low-temperature plasma? Will they die? Will they survive? If they survive, will they come out the same or somehow "injured"? If injured, will they be able to repair the damage and recover? What kind of damage? Which plasma agent causes the damage? etc. As will be shown in this paper, some of these fundamental questions have been partially or fully answered, but until today, a complete picture has yet to emerge. This is good and not so good. It is good because if we already knew all the answers, we would not be looking forward to a more exciting research. It is not so good because after all these years, we are still quite a ways from an implementable medical application. In this review paper, the present state of knowledge regarding the effects of cold plasma on bacteria cells (prokaryotes) and on eukaryotic cells (such as mammalian cells) will be presented. As medical applications where low-temperature plasma is showing signs of success, blood coagulation and wound healing will be described. [ABSTRACT FROM AUTHOR]

The aim of this paper was to assess the effectiveness, safety, stability, and mechanism of tooth whitening using a direct current cold atmospheric pressure air plasma microjet (PMJ) with the assistance of whitening gels (blank or containing 3% H2O2). The results were compared with those obtained from teeth treated with blank gel only and with gel containing 35% H2O2 in a cold light bleaching system. Tooth whitening effectiveness right after various treatments as well as 18 months after treatment was evaluated via CIELAB colorimetry. Type K thermocouple, scanning electron microscope and energy dispersive spectroscopy were employed to study the temperature of pulp chamber, tooth surface morphology, and elemental composition of enamel surface, respectively. Teeth in the plasma groups were effectively whitened in 5 min, though no significant difference was observed between the two plasma groups. Pulp chamber temperature was shown to remain below 35 °C. Morphological and surface elemental analysis showed similar changes to tooth enamel in the plasma groups and in the cold light group. These observations suggested that PMJ with blank gel was more effective for tooth whitening with acceptable safety and good stability. Optical emission spectroscopy results revealed that reactive oxygen species, such as O, •OH, and NO, in plasma may play a dominant role in the process of plasma tooth whitening. [ABSTRACT FROM AUTHOR]

This paper is an essay narrating the recent history of the introduction of the biomedical applications of nonthermal plasmas to the plasma science research community. [ABSTRACT FROM AUTHOR]

Two dielectric barrier discharge (DBD) reactors, one small, the other about 40 times larger, associated equipment, and a dedicated MATLAB code have been used to carry out precise determinations of electrical energy, $E_{g}$ , dissipated per discharge cycle of the applied a.c. voltage, $V_{a}$. In the smaller reactor, this was done over the frequency range $5 \le f\le 50$ kHz and using twin pairs of several different insulating materials (2.54-cm-diameter disks) with relative permittivities between $2.1 \le \kappa _{\text {die}}^{\prime }\le 9.5$ as dielectric barriers in DBDs for four different gases: He, Ne, Ar, and N2. In the large reactor, $f$ was restricted to 20 kHz in Ar and He; this latter system primarily serves for plasma polymerization experiments in which organic “monomers” are admixed with the flow of Ar as carrier gas. We report the method for exactly evaluating $E_{g}$ , and then present and compare values measured under different conditions. To the extent possible, these are compared between the small and large reactors, and with results published in the literature. The reliability of the method is confirmed, for example, by reproducing published breakdown fields of the gases examined, and by several other original results. [ABSTRACT FROM AUTHOR]

Endoscopy is an important tool that can be used to identify and treat diseases and is essential to avoid cross infection when used on different people. Cold atmospheric-pressure plasmas (CAPs) offer the prospect of a future basic technology for decontaminating and sterilizing of endoscope. In this paper, we intend to design an endoscope sterilization device based on CAPs. The various lengths of gap between electrodes and electrodes themselves are considered, and the plasma distribution and its evolution are investigated. [ABSTRACT FROM PUBLISHER]

Plasma bullets have recently been used in novel applications in biology and medicine, which spurred interesting developments in the new interdisciplinary field of “Plasma Medicine.” In this paper, using high speed ICCD camera images we show that during their lifetime, plasma bullets undergo three distinctive phases: a launching phase during which the bullet velocity increases rapidly, a propagation phase during which the bullet velocity is temporarily maintained but later steadily decreases, and an ending phase during which the bullet collapses. [ABSTRACT FROM AUTHOR]

It is now well known that low-temperature plasmas can inactivate bacteria effectively. At low doses, these plasmas can also help in the proliferation of healthy fibroblasts and detach damaged cells without causing necrosis. The combination of these characteristics leads to the possibility of using plasmas in biomedical applications such as wound healing. Although only limited understanding is available as to the mechanisms whereby plasmas interact with cells (prokaryotic or eukaryotic), it is now well established that the effects of plasmas on biological cells depend on the cell type, the cell concentration, and the medium supporting them. In this paper, we present clear visual evidence of these dependencies in the case of bacteria. Through simple imaging, we show that the size and shape of the inactivation zone depend on the type of bacteria, their initial concentrations, and the medium supporting the cells. [ABSTRACT FROM AUTHOR]

This contribution presents the results of a study of the germination rate and growth parameters of wheat seeds after atmospheric pressure surface coplanar dielectric barrier discharge (DBD) plasma treatment. The germination rate and biometric parameters such as the root, shoot length, mass of the seedlings, and the $\alpha $ -amylase enzyme activity were studied at different plasma exposure time. The seed coat surface wettability and morphology were determined by apparent contact angle measurement and scanning electron microscope (SEM) analysis. Seed surface disinfection and the presence of filamentous fungi have also been investigated at different discharge parameters. It is shown that the optimal plasma treatment duration for increasing the growth parameters and enhancing the enzymatic activity is 5–15 s. It was found that the longer plasma exposure requires complete sterilization of the seed surface from pathogens, compared to the optimal treatment time for high germination. Based on the obtained results, the possible mechanisms of the positive effect of plasma treatment on the enhanced germination of wheat seeds are discussed. [ABSTRACT FROM AUTHOR]

We showed that nonthermal dielectric barrier discharge (DBD) plasma compromises the integrity of the cell membrane of Deinococcus radiodurans, an extremophile organism. In samples of D. radiodurans, which were dried in a laminar flow hood, we observe that DBD plasma exposure resulted in a six-log reduction in CFU (colony-forming unit) count after 30 mm of treatment. When the Deinococcus radiodurans cells were suspended in distilled water and treated, it took only 15s to achieve a four-log reduction of CFU count. [ABSTRACT FROM AUTHOR]

With an externally applied uniform magnetic field, a Kadomtsev-Petviashivili (KP) equation is derived to study the perpendicular nonlinear wave in a collisionless plasma consisting electrons, positrons, and ions for weak relativistic limit. The stationary solution was presented for the group velocity, amplitude, and width of the soliton. It is shown that both the externally imposed magnetic field and the ratio of the ion equilibrium density to the electron equilibrium density influence strongly the group velocity, amplitude, and width of the KP soliton. By using the figure analysis, we study the interaction law of the two parallel line-solitons. [ABSTRACT FROM AUTHOR]

The downstream uniformity of the atmospheric-pressure plasma jet array is a key technical problem in regards to large-scale applications. This paper presents a 2-D array device of five jets arranged in four different shapes designed from the perspective of symmetry. Various schemes were tested to determine the effects of jet arrangement on the downstream uniformity of the array: the completely symmetrical array X, the completely asymmetrical array J, and semi-symmetrical arrays T and U. The interactions in the arrays were observed via optical imaging as well as electrical and spectroscopic characterizations. The results show that the downstream plume pattern markedly changes with the jet arrangement. Peripheral plumes suppress the internal plumes to varying extent under different jet arrangements. The emission intensity of the helium line at 706.5 nm was taken as a criterion to find that downstream uniformity under the arrangements J, T, U, and X gradually decreases as the jet arrangement grows increasingly symmetrical. The electric field simulation shows that different jet arrangements cause various degrees of inhomogeneous electric field distributions, which in turn affect the charge transferred into each plasma jet and the distributions of active particles resulting in downstream uniformity variations. The results presented here may provide a theoretical foundation for improving the downstream uniformity of the plasma jet arrays and achieving large-scale plasma jet sources.

In this paper, we present a four-layer tunable wideband electromagnetic shield based on cold plasma. It consists of two dielectric matched layers, one backside housing dielectric layer and one vacuum chamber in between where cold plasma can be produced through a glow discharge. No plasma is produced within the vacuum chamber when low-power communication signal impinges on the shield and it can easily propagate through with very low return and absorption loss. When a high-power microwave pulse impinges on the shield, cold plasma can be timely produced within the chamber to reflect and absorb the high-intensity microwave energy. Input impedance, standing wave ratio, transmission and reflection coefficients and shielding effectiveness for proposed four-layer structure electromagnetic shield are deduced and formulated. Transparent mode of the electromagnetic shield for communication frequency at 3.5GHz is developed based on transmission line and plane wave theory. Simulation results show that the transmission coefficient is close to unity, and the reflection coefficient is near to zero. The half-power transmission bandwidth is 16% for proposed structure with central communication frequency of 3.5GHz. The impact of plasma frequency and plasma collision frequency on the absorption, reflection, shielding effectiveness for interference frequency between 0-6GHz are investigated. Simulation results show that higher the plasma frequency, better the shielding effectiveness is in the investigated frequency band when plasma collision frequency is fixed. It was also demonstrated that the shielding effectiveness of proposed structure can be tuned by changing plasma collision frequency.

The experimental results of dielectric barrier discharge (DBD) plasma treatment on barley (Hordeum Valgare L cv. Yusef) seed germination and seedling growth are analyzed and presented. The seeds were exposed to DBD plasma with 40-, 80-, and 120-W powers for 15 s. All treatments showed positive effects on seed germination, seedling growth, and vigor index. The scanning electron microscope (SEM) images and water imbibition evaluations of plasma-treated seeds revealed that the treatments improved water absorption in the seeds. Similar positive improvements were observed for the plasma-treated seeds in the seedling stage. The best germination characteristics were obtained in 80-W DBD plasma, which included an 18.28% increment in total germination percentage, and 13.35%, 66.83%, 38.55%, and 31.93% increment on the seed germination potential, vigor index, shoot height, and root length, respectively. Moreover, the seed germination of the plasma-treated barley was studied after 2, 7, 14, and 30 days of storage, which indicated the desirable effect of plasma over the storage time. It is concluded that the use of cold plasma can significantly improve the germination and seedling growth of barley seeds. [ABSTRACT FROM AUTHOR]

A large-scale atmospheric pressure plasma jet (APPJ) device with variable discharge cells is developed using a special designed electrode configuration, and a maximum of fifteen APPJ cells work simultaneously. The properties of APPJ arrays are investigated from plasma profile and statistical parameters. From one to fifteen cells, the peak value of discharge current rises gradually when increasing cell numbers. The APPJ images and current waveforms present good synchronism and repeatability of discharge, and the effective plasma area up to 20 cm \(^{\vphantom {\big (}2}\) is achieved. [ABSTRACT FROM PUBLISHER]

The pressure-driven charge transport processes in microdischarges with a nanoporous zeolite cathode (ZC) are examined according to enhanced effect of electric field. The distributed resistance of the ZC and the impact of the ionizing component of the plasma on the control of the stable operation of a gas discharge electronic device at atmospheric pressure (AP) are investigated for the first time. The contribution of charge carriers in conductivity varied in a wide pressure range up to AP air microplasmas in postbreakdown mode is discussed. The results show that the ionic transport predominated in low electric field while electronic transport predominated in the opposite conditions. Moreover, uniform gas discharge light emission inside the ZCs develops from the surface and can be generated in air up to AP. [ABSTRACT FROM PUBLISHER]

A large-area atmospheric pressure plasma with low temperature and high electron density was realized using mesh covered tube-plate electrodes at an RF power as low as 4 W. The gas temperature is less than 351 K, while the electron temperature is about 5000 K. The estimated electron density is on the order of 10^12\ \cm^-3. Electrical measurements indicate that the discharges are capacitive and operated in an abnormal glow discharge mode. In addition, a self-bias observed at the powered tube electrode increases with increasing power and is positive at high powers. [ABSTRACT FROM PUBLISHER]

The purpose of this study is to evaluate the changes in dental enamel (morphology, elemental composition, microhardness, and roughness) after applying hydrogen peroxide in conjunction with a nonthermal plasma to bleach the teeth. Extracted human teeth were randomly placed in six groups. Two control groups (one group with no bleaching agent and no plasma treatment of the teeth and another one with only hydrogen peroxide as the bleaching agent) and four plasma groups (receiving hydrogen peroxide of varying concentrations 6%, 15%, 25%, and 35%, in conjunction with a plasma treatment) were prepared. The surface morphology before and after treatment was assessed using a scanning electron microscope (SEM), and the change in the elemental composition was analyzed by an energy-dispersive X-ray spectroscopy system. A total of 36 extracted teeth were used to evaluate the change in enamel microhardness and surface roughness. The use of hydrogen peroxide as a bleaching agent, even in the absence of plasma exposure, causes various etching patterns that are attributable to demineralization during the treatment process. These patterns are more pronounced as the hydrogen peroxide concentration increases. The surface roughness tests confirmed the findings from the SEM analysis. We only found minor essentially insignificant changes in the elemental composition of the enamel and in the surface microhardness as a result of the treatment using hydrogen peroxide and a cold plasma. The use of a cold plasma in conjunction with hydrogen peroxide of varying concentrations in tooth bleaching causes minor changes in the tooth enamel changes that are comparable to those resulting from the standard treatment using 35 % hydrogen peroxide gel without a plasma. [ABSTRACT FROM PUBLISHER]

A syringe needle assembled with a glass tube has been used as a plasma jet device for biomedical applications. According to the various types of ground electrode installed at the glass tube, argon plasma from an atmospheric pressure discharge has been investigated with a dc–ac inverter of several tens of kilohertz. When the ground electrode is absent or floated, the length of the plasma jet is about 10 mm at an ignition voltage of about 3 kV, and it extends further to a few tens of millimeters as the voltage increases to 5 kV. If the ground electrode is inserted inside the end of the glass tube, all plasma current is sunk directly to the ground electrode so that the plasma plume cannot emit out of the glass tube. For the case of an external ground electrode which is similar to a dielectric barrier discharge, the ignition voltage is as low as 1 kV, and the plume length is easily adjustable to be 1–10 mm in the voltage range of 1–3 kV. [ABSTRACT FROM AUTHOR]