Applied Sciences

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15 pages, 993 KiB

Open AccessArticle

A Prospective, Randomised, Controlled, Split-Face Clinical Trial to Assess the Safety and the Efficacy of Cold Atmospheric Plasma in the Treatment of Acne Vulgaris

by Sigrid Karrer, Mark Berneburg, Florian Zeman, Michael Koller and Karolina Müller

Appl. Sci. 2021, 11(23), 11181; https://doi.org/10.3390/app112311181 - 25 Nov 2021

Cited by 3 | Viewed by 2971

Abstract

The increase in antibiotic resistance requires effective non-antibiotic therapies for acne. Cold atmospheric plasma (CAP) inactivates bacteria and improves wound healing, but its effect on acne has not been investigated. The objective of this controlled split-face study was to assess safety and efficacy [...] Read more.

The increase in antibiotic resistance requires effective non-antibiotic therapies for acne. Cold atmospheric plasma (CAP) inactivates bacteria and improves wound healing, but its effect on acne has not been investigated. The objective of this controlled split-face study was to assess safety and efficacy of CAP in moderate acne. One side of the face received 8–10 treatments with cold helium plasma within 4–6 weeks; follow-up was two and four weeks thereafter. Acne lesions were counted, followed by global acne severity ratings. Of the 34 patients included, 29 completed the study. No serious adverse events occurred. The two facial sides did not significantly differ in the number of inflammatory and non-inflammatory lesions. An interaction effect of number and type of treatment was found for inflammatory lesions. Lesion reduction after 10 treatments was significantly higher on the treated than on the untreated side. Percentage of patients reporting improved aesthetics was higher for the treated than for the untreated side after treatment completion (79% vs. 45%) and at the two- (72% vs. 45%) and four-week follow-up (79% vs. 52%). In conclusion, CAP was safe with excellent tolerability, showed moderate reduction in acne lesions and led to higher patient-based ratings of aesthetics than non-treatment. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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14 pages, 7176 KiB

Open AccessArticle

Characterization of an X-ray Source Generated by a Portable Low-Current X-Pinch

by Alexandros Skoulakis, Evaggelos Kaselouris, Antonis Kavroulakis, Christos Karvounis, Ioannis Fitilis, John Chatzakis, Vasilis Dimitriou, Nektarios A. Papadogiannis and Michael Tatarakis

Appl. Sci. 2021, 11(23), 11173; https://doi.org/10.3390/app112311173 - 25 Nov 2021

Cited by 2 | Viewed by 1745

Abstract

An X-pinch scheme of a low-current generator (45 kA, 50 ns rise time) is characterized as a potential efficient source of soft X-rays. The X-pinch target consists of wires of 5 μm in diameter—made from either tungsten (W) or gold (Au)-plated W—loaded at [...] Read more.

An X-pinch scheme of a low-current generator (45 kA, 50 ns rise time) is characterized as a potential efficient source of soft X-rays. The X-pinch target consists of wires of 5 μm in diameter—made from either tungsten (W) or gold (Au)-plated W—loaded at two angles of 55° and 98° between the crossed wires. Time-resolved soft X-ray emission measurements are performed to provide a secure correlation with the optical probing results. A reconstruction of the actual photodiode current profile procedure was adopted, capable of overcoming the limits of the slow rising and falling times due to the “slow” response of the diodes and the noise. The pure and Au-plated W deliver an average X-ray yield, which depends only on the angle of the crossed wires, and is measured to be ~50 mJ and ~70 mJ for the 98° and 55° crossed wire angles, respectively. An additional experimental setup was developed to characterize the X-pinch as a source of X-rays with energy higher than ~6 keV, via time-integrated measurements. The X-ray emission spectrum was found to have an upper limit at 13 keV for the Au-plated W configuration at 55°. The portable tabletop X-pinch proved to be ideal for use in X-ray radiography applications, such as the detection of interior defects in biological samples. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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11 pages, 3652 KiB

Open AccessArticle

Authentication and Testing of Banknotes Using Laser Multiphoton Electron Extraction Spectroscopy (MEES)

by Danny Fisher, Valery Bulatov and Israel Schechter

Appl. Sci. 2021, 11(21), 10465; https://doi.org/10.3390/app112110465 - 8 Nov 2021

Cited by 3 | Viewed by 2615

Abstract

In laser multiphoton electron extraction spectroscopy (MEES), the photo-charges extracted from a surface by a pulsed laser beam are recorded as a function of laser wavelength. We report the first application of this spectroscopy to banknotes. Various banknotes from different countries, authentic and [...] Read more.

In laser multiphoton electron extraction spectroscopy (MEES), the photo-charges extracted from a surface by a pulsed laser beam are recorded as a function of laser wavelength. We report the first application of this spectroscopy to banknotes. Various banknotes from different countries, authentic and counterfeit, have been tested. The results indicate that MEES spectra are both informative (many peaks) and reproducible. The spectra allow for clear distinction between authentic and counterfeit banknotes. Actually, MEES provides a unique fingerprint of the banknotes, so that distinction between various forgery methods (printer used) is also possible. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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14 pages, 3720 KiB

Open AccessArticle

Non-Thermal O₂ Plasma Efficacy on C. albicans and Its Effect on Denture Base Resin Color

by Christina Maillet, Serge Odof, Mikaël Meuret, Florian Le Bras, Frédéric Velard and Marie-Paule Gelle

Appl. Sci. 2021, 11(21), 10367; https://doi.org/10.3390/app112110367 - 4 Nov 2021

Cited by 1 | Viewed by 2078

Abstract

Denture stomatitis is a disease involving C. albicans, which can affect elderly and immuno-compromised people. To avoid any recurrence of this pathology, it is necessary to treat patients regularly and disinfect dentures. However, the denture cleansers’ efficacy is not optimal and often [...] Read more.

Denture stomatitis is a disease involving C. albicans, which can affect elderly and immuno-compromised people. To avoid any recurrence of this pathology, it is necessary to treat patients regularly and disinfect dentures. However, the denture cleansers’ efficacy is not optimal and often leads to adverse color effects on the denture base resins. The aim of this study was to investigate the efficacy of a low-pressure non-thermal O₂ plasma (NTP) treatment on C. albicans seeded on ProBase^®Hot resin (Ivoclar Vivadent). The viability reduction of C. albicans was assessed by colony forming units (CFU) analysis and by scanning electron microscopy (SEM). The effect of repeated treatments on the resin color was evaluated by spectrophotometry. The resin samples were placed in a sealed bag in which O₂ plasma was generated in low-pressure conditions. The results showed that a 120-min O₂ NTP treatment led to a 6-log reduction of C. albicans viability (p < 0.05) and to yeasts’ major alterations observed by SEM. Furthermore, significant slight color changes of the resin (∆E₀₀ = 1.33) were noted only after six plasma treatments (p < 0.05). However, the denture aesthetic was preserved, as the color changes were not perceptible and remained below the acceptability threshold (∆E₀₀ < 4). Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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13 pages, 4433 KiB

Open AccessFeature PaperArticle

Optical Diagnostics during Pulsed Laser Ablation in Liquid (PLAL) for the Production of Metallic Nanoparticles

by Marcella Dell’Aglio and Alessandro De Giacomo

Appl. Sci. 2021, 11(21), 10344; https://doi.org/10.3390/app112110344 - 3 Nov 2021

Cited by 4 | Viewed by 2513

Abstract

Pulsed laser ablation in liquid (PLAL) is gaining an important role as a methodology for producing nanostructures without the use of chemicals and stabilizers. Several nanomaterials have been produced and the engineering of PLAL is becoming an important task for the dissemination of [...] Read more.

Pulsed laser ablation in liquid (PLAL) is gaining an important role as a methodology for producing nanostructures without the use of chemicals and stabilizers. Several nanomaterials have been produced and the engineering of PLAL is becoming an important task for the dissemination of this approach for nanostructure production. Monitoring the processes involved in the PLAL during nanostructure production can be extremely useful for improving the experimental methods and for pushing PLAL to new material formation. In this paper, we discuss the use of optical techniques for investigating the specific stages involved in the production of nanomaterials with PLAL. In particular, the recent advancements of these optical techniques for each specific stage of the PLAL process will be discussed: optical emission spectroscopy and imaging for the investigation of the plasma phase, shadowgraph imaging for the investigation of the cavitation bubble dynamics and different scattering techniques for the visualization of the produced nanostructure. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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13 pages, 1431 KiB

Open AccessArticle

A Study of Current Controlled Discharge in a Nitrogen Filled Tube

by Michal Nevrkla, Jakub Hubner, Jiri Sisma, Pavel Vrba, Miroslava Vrbova, Nadezhda Bobrova, Pavel Sasorov and Alexandr Jancarek

Appl. Sci. 2021, 11(21), 10253; https://doi.org/10.3390/app112110253 - 1 Nov 2021

Viewed by 1445

Abstract

Time dependencies of the electrical resistance and electron density evolution in the discharge in a tube, with nitrogen at different pressures, with a diameter of

9.2 mm

and a length of

10 cm

were studied. A current pulse with an amplitude of [...] Read more.

Time dependencies of the electrical resistance and electron density evolution in the discharge in a tube, with nitrogen at different pressures, with a diameter of

9.2 mm

and a length of

10 cm

were studied. A current pulse with an amplitude of

500 A

and duration of

10 μ s

has created the discharge in the tube. Instantaneous electron densities are estimated from the interference pattern in Mach–Zehnder interferometer using femtosecond Ti: sapphire laser beam. Laboratory results are compared with results of computer modelling by MHD computer codes NPINCH and ZSTAR. Time development of the discharge resistance according to experiment is measured and evaluated. Minimum measurable value of the electron density in the experiment is determined as

2 \times 10^{15} {cm}^{- 3}

. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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21 pages, 791 KiB

Open AccessFeature PaperArticle

Laser–Accelerated Plasma–Propulsion System

by Daniele Palla and Gabriele Cristoforetti

Appl. Sci. 2021, 11(21), 10154; https://doi.org/10.3390/app112110154 - 29 Oct 2021

Cited by 1 | Viewed by 3094

Abstract

In this paper, the laser-accelerated plasma–propulsion system (LAPPS) for a spacecraft is revisited. Starting from the general properties of relativistic propellants, the relations between specific impulse, engine thrust and rocket dynamics have been obtained. The specific impulse is defined in terms of the [...] Read more.

In this paper, the laser-accelerated plasma–propulsion system (LAPPS) for a spacecraft is revisited. Starting from the general properties of relativistic propellants, the relations between specific impulse, engine thrust and rocket dynamics have been obtained. The specific impulse is defined in terms of the relativistic velocity of the propellant using the Walter’s parameterization, which is a suitable and general formalism for closed–cycle engines. Finally, the laser-driven acceleration of light ions via Target Normal Sheath Acceleration (TNSA) is discussed as a thruster. We find that LAPPS is capable of an impressive specific impulse

I_{s p}

in the

10^{5}

s range for a laser intensity

I_{0} ≃ 10^{21}

W / {cm}^{2}

. The limit of

I_{s p} ≲ 10^{4}

s, which characterizes most of the other plasma-based space electric propulsion systems, can be obtained with a relatively low laser intensity of

I_{0} ≳ 10^{19}

W / {cm}^{2}

. Finally, at fixed laser energy, the engine thrust can be larger by a factor

10^{2}

with respect to previous estimates, making the LAPPS potentially capable of thrust-power ratios in the N/MW range. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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12 pages, 3453 KiB

Open AccessArticle

Influence of Oxygen Admixture on Plasma Nitrocarburizing Process and Monitoring of an Active Screen Plasma Treatment

by Jan Böcker, Anke Dalke, Alexander Puth, Christian Schimpf, Jürgen Röpcke, Jean-Pierre H. van Helden and Horst Biermann

Appl. Sci. 2021, 11(21), 9918; https://doi.org/10.3390/app11219918 - 23 Oct 2021

Cited by 5 | Viewed by 1629

Abstract

The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the resulting [...] Read more.

The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the resulting process gas composition at different levels of oxygen admixture using O₂ and CO₂, respectively, as well as the long-term trends of the concentration of major reaction products over the duration of a material treatment of ARMCO^® iron. The short-term studies of the resulting process gas composition, as a function of oxygen addition to the process feed gases N₂ and H_2, showed that a stepwise increase in oxygen addition led to the formation of oxygen-containing species, such as CO, CO₂, and H₂O, and to a significant decrease in the concentrations of hydrocarbons and HCN. Despite increased oxygen concentration within the process gas, no oxygen enrichment was observed in the compound layer of ARMCO^® iron; however, the diffusion depth of nitrogen and carbon increased significantly. Increasing the local nitrogen concentration changed the stoichiometry of the ε-Fe₃(N,C)_1+x phase in the compound layer and opens up additional degrees of freedom for improved process control. Full article

(This article belongs to the Special Issue Recent Advances in Plasma Technology and Applications)

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