Browsing by Author "Cejas, Ezequiel"
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Item Ambient Species Density and Gas Temperature Radial Profiles Derived from a Schlieren Technique in a Low Frequency Non-thermal Oxygen Plasma Jet.(2017) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Kelly, Héctor; Mancinelli, Beatriz; Fischfeld, GerardoA quantitative interpretation of the schlieren technique applied to a non-thermal atmospheric-pressure oxygen plasma jet driven at low-frequency (50 Hz) is reported. The jet was operated in the turbulent regime with a hole-diameter based Reynolds number of 13,800. The technique coupled to a simplified kinetic model of the jet effluent region allowed deriving the temporally-averaged values of the gas temperature of the jet by processing the gray-level contrast values of digital schlieren images. The penetration of the ambient air into the jet due to turbulent diffusion was taken into account. The calibration of the optical system was obtained by fitting the sensitivity parameter so that the oxygen fraction at the nozzle exit was unity. The radial profiles of the contrast in the discharge off case were quite symmetric on the whole outflow, but with the discharge on, relatively strong departures from the symmetry were evident in the near field. The time-averaged gas temperature of the jet was relatively high, with a maximum departure of about 55 K from the room temperature; as can be expected owing to the operating molecular gas. The uncertainty in the temperature measurements was within 6 K, primarily derived from errors associated to the Abel inversion procedure. The results showed an increase in the gas temperature of about 8 K close to the nozzle exit; thus suggesting that some fast-gas heating (with a heating rate *0.3 K/ls) still occurs in the near field of the outflow.Item Cathode-sheath model for field emission sustained atmospheric pressure discharges(2021) Cejas, Ezequiel; Prevosto, Leandro; Minotti, Fernando; Ferreyra, Matías; Chamorro, Juan Camilo; Fina, BrendaThe cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1–102 A/cm2 , which spans from normal glow discharge, through abnormal glow discharge, up to the early stages of the arcing transition. It is shown that the glow-to-arc transition arises from a field-emission instability at the cathode when the cur rent density is larger than 10 A/cm2 , i.e., when the cathode field exceeds a critical value of about 45 V/lm for the conditions considered. It is also shown that the cathode temperature significantly influences the cathode-sheath region. The proposed model is validated by comparing the numerical results with available experimental data.Item Cathode-sheath model for field emission sustained atmospheric pressure discharges.(2021-03-16) Cejas, Ezequiel; Prevosto, Leandro; Minotti, Fernando Oscar; Ferreyra, Matías; Chamorro, Juan CamiloThe cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1–102 A/cm2 , which spans from normal glow discharge, through abnormal glow discharge, up to the early stages of the arcing transition. It is shown that the glow-to-arc transition arises from a field-emission instability at the cathode when the cur rent density is larger than 10 A/cm2 , i.e., when the cathode field exceeds a critical value of about 45 V/lm for the conditions considered. It is also shown that the cathode temperature significantly influences the cathode-sheath region. The proposed model is validated by comparing the numerical results with available experimental data.Item Desarrollo de una diagnóstica refractiva para el estudio de plasmas no-térmicos de alta presión.(UTN FRVT, 2017-03-09) Cejas, Ezequiel; Alí, Daniel; Ferreyra , DanielEste Proyecto Final consiste en la interpretación cuantitativa de la técnica Schlieren aplicada a un jet de plasma no térmico, cuasi-estacionario (50 Hz), y a presión atmosférica. El jet fue operado en régimen turbulento con un número de Reynolds (basado en el diámetro de la tobera) de 13800. Se utilizó oxígeno puro como gas de trabajo. El arreglo experimental usado consistió en un sistema óptico con espejos parabólicos de haz paralelo. La técnica permitió medir los promedios temporales de la temperatura del gas en el jet de plasma por medio del procesamiento de las imágenes digitales Schlieren. En la interpretación de resultados se consideró la penetración del aire ambiente en el jet de plasma debido a la difusión turbulenta. La calibración del sistema óptico se obtuvo ajustando el parámetro de sensibilidad de modo que la fracción de oxígeno en la salida de la tobera sea igual a la unidad. Los perfiles radiales del contraste con la descarga apagada resultaron ser bastante simétricos en todo el flujo de salida, pero con la descarga encendida se evidenciaron fuertes desviaciones de la simetría en el campo cercano. La temperatura respecto del gas en el jet de plasma resultó relativamente alta, con una elevación máxima de -55 K respecto de la temperatura ambiente; como puede esperarse debido a que el jet fue operado con un gas molecular. La incertidumbre en la medición de la temperatura resultó dentro de -6 K, principalmente asociada a errores en el procedimiento de inversión. Los resultados mostraron que entre 0 y 5 mm desde la salida de la tobera se produce un aumento en la temperatura del gas de - 8 K; sugiriendo que en el campo cercano existe todavía algún tipo de calentamiento rápido del gas (con una velocidad de - 0,3 K /us).Item Detección temprana de fractura de hueso escafoides en carpo.(UTN FRVT, 2023-09-11) Biana, María Julieta; Peperno Venessio, Soledad; Reniero, Betiana; Garma, Manuel; Cejas, EzequielSe reportan los métodos diagnósticos con mayor especificidad para el diagnóstico de una fractura de escafoides, los cuales permitan la evaluación de fracturas inadvertidas tales que puedan ocasionar futuras complicaciones. La recolección de muestras diagnosticas se realizó en los servicios médicos de Villa Cañas, Chañar Ladeado, Arias (Cba) y Venado Tuerto, de las cuales se extrajeron los casos clínicos con fractura de escafoides a ser estudiados en base a las diferentes evoluciones y tratamientos. La valoración funcional es esencial en el manejo de los problemas del miembro superior, tanto para la toma de decisiones diagnósticas y terapéuticas como para valorar la evolución y la efectividad de los tratamientos. El tratamiento para una fractura de escafoides es variado dependiendo del tipo de rotura, es importante tener en cuenta que el escafoides es un hueso con poca vascularización lo que determina el grado de consolidación de la misma. Todo esto es fundamental para determinar el grado de complicación ante una fractura de este hueso, teniendo en cuenta que la mano/muñeca puede sufrir lesiones como pérdida de fuerza, inestabilidad, hormigueo entre otras. Siendo esto motivo de rechazo frente a la incorporación de un trabajo o complicaciones en la vida cotidiana.Item Effect of in–package cold plasma treatments on the quality of minimally processed apples.(2023) Denoya, Gabriela Inés; Polenta, Gustavo Alberto; Apóstolo, Nancy Mariel; Cejas, Ezequiel; Fina, Brenda; Chamorro, Juan Camilo; Ferreyra, Matías; Prevosto, Leandro; Vaudagna, SergioCold plasma technology is being increasingly used for food preservation and, incipiently, for minimal processing of fruit. Therefore, the objective of this work was to study the effect of in-package cold plasma (generated in atmospheric–pressure air by a low–frequency -50 Hz- dielectric barrier discharge operated at 30 kV) on the quality of minimally processed apples during refrigerated storage. Apple slices were subjected to the different treatments following a completely randomized design with 3 x 3 factorial arrangement. The independent variables were the exposure time (0, 1, 3 min) and the storage times (1, 4, 7 days). Cold plasma treatments preserved the quality of the fruit, maintaining the tissue structure. Plasma treatment applied for 1 min rendered apple slices with the highest antioxidant content but only at day 1. Even though polyphenoloxidase activity was reduced by the treatment, it was not sufficient to stabilize the antioxidant content during storage.Item Effects of non-thermal plasma technology on Diaporthe longicolla cultures and mechanisms involved.(2021-01-05) Pérez Pizá, María Cecilia; Grijalba, Pablo Enrique; Cejas, Ezequiel; Chamorro, Juan Camilo; Ferreyra, Matías; Zilli, Carla; Vallecorsa, Pablo; Yannarelli, Gustavo; Prevosto, Leandro; Balestrasse, Karina; Santa Cruz, DiegoBACKGROUND: The Diaporthe/Phomopsis complex (D/P) is a group of soybean seed-borne fungi. The use of chemical fungicides, either for seed treatment or during the crop cycle, is the most adopted practice for treating fungal diseases caused by this complex. Worldwide, there is a search for alternative seed treatments that are less harmful to the environment than chemicals. Non-thermal plasma (NTP) is a novel seed treatment technology for pathogen removal. This research aimed to evaluate the effects of NTP on the in vitro performance of pure cultures of Diaporthe longicolla and elucidate the mechanisms underlying these effects. RESULTS: Active D. longicolla mycelium, growing in vitro, was exposed to different NTP treatments, employing a dielectric bar rier discharge arrangement with different carrier gases (N2 or O2). Fungal growth, fresh biomass and colony appearance were negatively affected by plasma treatments (TN3 and TO3). Lipid peroxidation and antioxidant activities were higher in plasma treated colonies comparison with non-exposed colonies (control). Fungal asexual spores (conidia) were also exposed to NTP, showing high susceptibility. CONCLUSION: Exposure of D. longicolla colonies to NTP severely compromised fungal biology. Ozone production during treat ment and lipid peroxidation of fungal cell membranes appeared to be involved in the observed effects. © 2020 Society of Chemical IndustryItem Effects of non–thermal plasmas on seed-borne Diaporthe/Phomopsis complex and germination parameters of soybean seeds.(2018) Pérez Pizá, María Cecilia; Prevosto, Leandro; Zilli, Carla; Cejas, Ezequiel; Kelly, Héctor; Balestrasse, KarinaDiaporthe/Phomopsis (D/P) is a complex of seed-borne fungi that severely affects soybean (Glycine max (L.) Merrill), one of the most important crops worldwide. Non-thermal plasma treatment is a fast, economic and ecological friendly technology that can destroy seed-borne fungi and improve seed quality. Soybean seeds were exposed for 1, 2 and 3 minutes to a quasi-stationary (50 Hz) dielectric barrier discharge plasma operating at atmospheric pressure air. Different carrying gases (O2 and N2) and barrier-insulating materials were used. In this work we focused on the ability of plasma to control D/P in soybean seeds and to enhance seed quality. To support these results, different antioxidant enzymes (catalase, superoxide dismutase and guaiacol peroxidase), lipid peroxidation and phytohormones (ABA and AIA) content in seeds were evaluated. The results demonstrated reductions of 29% in catalase activity and increments of 30% in glutathione content after plasma treatment, reversing the oxidative damage caused by D/P fungi. This eco-friendly technology improved soybean seed quality and, for the first time, its efficiency in controlling soybean seed-borne pathogen fungi that colonize the inside of seeds was demonstrated.Item Effects of the Plasma-Activated Water on the Quality and Preservation of Fresh-Cut Lettuce.(2023) Chamorro, Juan Camilo; Denoya, Gabriela Inés; Santamaría, Brenda; Fina, Brenda; Ferreyra, Matías; Cejas, Ezequiel; Rodriguez, Anabel; Vaudagna, Sergio; Prevosto, Leandro— The effect of the application of plasma-activated water (PAW) on the quality and preservation of fresh-cut lettuce is reported in this article. PAW was produced by using a liquid cathode air discharge. The average (bulk) water temperature was kept at ∼22 ◦ C during the activation procedure and stored at 4 ◦ C for up to five days. The pH value, electrical conductivity, and concentrations of H2O2 and NO− in liquid at day 1 were 2.81, 1492µS/cm, and 77.8 and 223.4 mg/L, respectively, with slight variations over the whole storage time. No measurable amounts of NO− 10 2 were found. Twenty pieces of lettuce leaves were washed for 1 and 5 min in 1 L of PAW and stored for one and five days. PAW treatments were compared to tap water treatments. The lettuce samples were stored at 4 ◦ C and analyzed on days 1, 3, and 7. The chromatic parameter results suggest that PAW treatments significantly reduce the degradation of lettuce chlorophyll from day 3 of refrigerated storage. The lettuce firmness was not significantly modified. The microbiological results of aerobic mesophilic, enterobacteriaceae, and psychrotrophs populations have shown that lettuce treated with PAW after three days of storage exhibited the strongest inactivation efficiency. Psychrotrophs counts were maintained for up to seven days. Similar inactivation efficiencies were found regardless of the PAW storage time. PAW treatments also favored both the antioxidant capacity FRAP, ABTS, and DPPH, and the total phenolic.Item Enhancement of soybean nodulation by seed treatment with non–thermal plasmas(2020-03-18) Pérez Pizá, María Cecilia; Cejas, Ezequiel; Zilli, Carla; Prevosto, Leandro; Mancinelli, Beatriz; Santa Cruz, Diego; Yannarelli, Gustavo; Balestrasse, KarinaSoybean (Glycine max (L.) Merrill) is one of the most important crops worldwide providing dietary protein and vegetable oil. Most of the nitrogen required by the crop is supplied through biological N2 fxation. Non-thermal plasma is a fast, economical, and environmental-friendly technology that can improve seed quality, plant growth, and crop yield. Soybean seeds were exposed to a dielectric barrier discharge plasma operating at atmospheric pressure air with superimposed fows of O2 or N2 as carrying gases. An arrangement of a thin phenolic sheet covered by polyester flms was employed as an insulating barrier. We focused on the ability of plasma to improve soybean nodulation and biological nitrogen fxation. The total number of nodules and their weight were signifcantly higher in plants grown from treated seeds than in control. Plasma treatments incremented 1.6 fold the nitrogenase activity in nodules, while leghaemoglobin content was increased two times, indicating that nodules were fxing nitrogen more actively than control. Accordingly, the nitrogen content in nodules and the aerial part of plants increased by 64% and 23%, respectively. Our results were supported by biometrical parameters. The results suggested that diferent mechanisms are involved in soybean nodulation improvement. Therefore, the root contents of isofavonoids, glutathione, auxin and cytokinin, and expansin (GmEXP1) gene expression were determined. We consider this emerging technology is a suitable pre-sowing seed treatment.Item Factores predisponentes relacionados con hábitos de vida en el diagnóstico de osteoporosis en mujeres adultas de la región de Arias (Cba).(UTN FRVT, 2022-12) Coello, Jésica Mariel; Stolle, Fátima; Cejas, Ezequiel; Lehmann, AnalíaLas fracturas osteoporóticas son un importante problema de salud mundial, convirtiéndose en una importante carga económica y social. Se determinó la densidad mineral ósea (DMO) a nivel de cadera y columna lumbar aplicando la técnica de absorciometría de rayos X de energía dual (DXA) en un estudio transversal en mujeres posmenopáusicas realizado en un centro de atención privada de Arias (Cba). Se correlacionó la DMO con distintos factores de riesgo y hábitos de vida por medio de un modelo de regresión lineal múltiple, y se analizó la probabilidad de fractura mayor y de cadera empleando el modelo FRAX® con y sin DMO. En ambos casos, se realizó una evaluación y análisis estadístico; y se estudió la comparación y concordancia entre los modelos FRAX®. Los resultados indicaron que el índice de masa corporal, la exposición solar, la duración del período no–fértil y el consumo de alcohol influyeron significativamente sobre los valores de DMO obtenidos. Por otro lado, la concordancia entre los modelos FRAX® en mujeres osteopénicas se encontraba influida por la existencia de errores sistemáticos. Como conclusión de este trabajo de Tesina, entendemos haber realizado una contribución dentro del área clínica, en particular en el entendimiento del impacto de hábitos de vida sobre la DMO.Item Glow Discharge in a High-Velocity Air Flow: The Role of the Associative Ionization Reactions Involving Excited Atoms.(2019) Cejas, Ezequiel; Mancinelli, Beatriz; Prevosto, LeandroA kinetic scheme for non-equilibrium regimes of atmospheric pressure air discharges is developed. A distinctive feature of this model is that it includes associative ionization with the participation of N(2D, 2P) atoms. The thermal dissociation of vibrationally excited nitrogen molecules and the electronic excitation from all the vibrational levels of the nitrogen molecules are also accounted for. The model is used to simulate the parameters of a glow discharge ignited in a fast longitudinal flow of preheated (T0 = 1800–2900 K) air. The results adequately describe the dependence of the electric field in the glow discharge on the initial gas temperature. For T0 = 1800 K, a substantial acceleration in the ionization kinetics of the discharge is found at current densities larger than 3 A/cm2 , mainly due to the N(2P) + O(3P) → NO+ + e process; being the N(2P) atoms produced via quenching of N2(A3P u +) molecules by N(4S) atoms. Correspondingly, the reduced electric field noticeably falls because the electron energy (6.2 eV) required for the excitation of the N2(A3P u +) state is considerably lower than the ionization energy (9.27 eV) of the NO molecules. For higher values of T0, the associative ionization N(2D) + O(3P) → NO+ + e process (with a low–activation barrier of 0.38 eV) becomes also important in the production of charged particles. The N(2D) atoms being mainly produced via quenching of N2(A3P u +) molecules by O(3P) atoms.Item Improvement of growth and yield of soybean plants through the application of non-thermal plasmas to seeds with different health status.(2019) Pérez Pizá, María; Prevosto, Leandro; Grijalba, Pablo; Zilli, Carla; Cejas, Ezequiel; Mancinelli, Beatriz; Balestrasse, KarinaSoybean (Glycine max (L.) Merrill) is a globally important crop, providing oil and protein. Diaporthe/Phomopsis complex includes seed-borne pathogens that affect this legume. Non-thermal plasma treatment is a fast, cost-effective and environmental-friendly technology. Soybean seeds were exposed to a quasi stationary (50 Hz) dielectric barrier discharge plasma operating at atmospheric pressure air. Different carrying gases (O2 and N2) and barrier insulating materials were used. This work was performed to test if the effects of non-thermal plasma treatment applied to healthy and infected seeds persist throughout the entire cycle of plants. To this aim, lipid peroxidation, activity of catalase, superoxide dismutase and guaiacol peroxidase, vegetative growth and agronomic traits were analysed. The results here reported showed that plants grown from infected seedsdid not trigger oxidative stress due to the reduction of pathogen incidence in seeds treated with cold plasma. Vegetative growth revealed a similar pattern for plants grown from treated seeds than that found for the healthy control. Infected control, by contrast, showed clear signs of damage. Moreover, plasma treatment itself increased plant growth, promoted a normal and healthy physiological performance and incremented the yield of plants. The implementation of this technology for seeds treatment before sowing could help reducing the use of agrochemicals during the crop cycle.Item Métodos complementarios para la detección precoz del cáncer de mama.(UTN FRVT, 2022-11-04) González, María Eugenia; Faraone Berlingeri, Amorina; Lehmann, Analía; Cejas, EzequielEl cáncer de mama es un problema de alta relevancia en la salud de las mujeres argentinas dado que representa la primera causa de muerte por tumores. El diagnóstico temprano de la patología empleando métodos complementarios (MC) a la mamografía, resulta de vital importancia y altamente benéfico para las pacientes. En base a esto, se abordó el estudio mamográfico como método estándar en el screening mamario. Para la identificación de los MC más usuales se realizaron entrevistas no–estructuras a profesionales del área de diagnóstico por imágenes; se analizaron distintos MC de diagnóstico y se estudiaron una serie de casos clínicos para evaluar los beneficios de la aplicación de MC. Se estableció que el principal motivo de consulta es la realización de controles, con un alto acatamiento en la ejecución de otros estudios; con una alta diversidad de MC, relacionándose directamente con el hallazgo detectado, y se determinó que, en su mayoría, es necesario incluir uno o más MC a los hallazgos detectados en la mamografía convencional. Como conclusión de este trabajo de Tesina, el empleo de MC disponibles en la actualidad y zona de influencia, permitieron la determinación del diagnóstico temprano del cáncer de mamaItem Modelling of an Atmospheric–Pressure Air Glow Discharge Operating in High–Gas Temperature Regimes: The Role of the Associative Ionization Reactions Involving Excited Atoms.(2020) Cejas, Ezequiel; Prevosto, Leandro; Mancinelli, BeatrizA model of a stationary glow-type discharge in atmospheric-pressure air operated in high-gas-temperature regimes (1000 K < Tg < 6000 K), with a focus on the role of associative ionization reactions involving N(2D,2P)-excited atoms, is developed. Thermal dissociation of vibrationally excited nitrogen molecules, as well as electronic excitation from all the vibrational levels of the nitrogen molecules, is also accounted for. The calculations show that the near-threshold associative ionization reaction, N(2D) + O(3P) → NO+ + e, is the major ionization mechanism in air at 2500 K < Tg < 4500 K while the ionization of NO molecules by electron impact is the dominant mechanism at lower gas temperatures and the high-threshold associative ionization reaction involving ground-state atoms dominates at higher temperatures. The exoergic associative ionization reaction, N(2P) + O(3P) → NO+ + e, also speeds up the ionization at the highest temperature values. The vibrational excitation of the gas significantly accelerates the production of N2(A3P u +) molecules, which in turn increases the densities of excited N(2D,2P) atoms. Because the electron energy required for the excitation of the N2(A3P u +) state from N2(X1P g +, v) molecules (e.g., 6.2 eV for v = 0) is considerably lower than the ionization energy (9.27 eV) of the NO molecules, the reduced electric field begins to noticeably fall at Tg > 2500 K. The calculated plasma parameters agree with the available experimental data.Item Non-thermal plasma application improves germination, establishment and productivity of Gatton panic grass (Megathyrsus maximus) without compromising forage quality.(2022) Pérez Pizá, María Cecilia; Clausen, Liliana; Cejas, Ezequiel; Ferreyra, Matías; Chamorro, Juan Camilo; Fina, Brenda; Zilli, Carla; Vallecorsa, Pablo; Prevosto, Leandro; Balestrasse, KarinaMegathyrsus maximus (Gatton panic) is a tropical grass highly valued both for its use as forage and for its biofuel potential. A major constraint in establishing pastures of this cultivar is the low viability and germination ofseeds and the poorinitialseedling establishment. We used non-thermal plasma (NTP, partially ionised gas) as a novel technology to treat seeds of this grass, aiming to improve their quality (i.e. germination traits). We also followed the performance of seedlings grown from NTP-treated seeds under field conditions by assessing seedling establishment, biomass production and forage quality during the first regrowth period, which is the critical period for pasture establishment. Two NTP treatments were performed through dielectric barrier discharges employing N2 as carrier gas. Non-treated seeds served as the control. Results showed that the viability of NTP treated seeds was, on average, 1.5-fold higher than the control, and that germination energy and germination percentage of treated seeds was superior to the control by 2.1-fold and 2.2-fold, respectively. A field experiment showed that seedling establishment parameters (dynamics of cumulative emergence, emergence coefficient, and weighted average emergence rate) and pasture early productivity (represented by shoot dry matter) were enhanced by NTP treatment (phenolic sheet–polyester film barrier and 3 min exposure), showing 1.4–2.6-fold higher values than the control, confirming the results of the laboratory assays. Although NTP markedly increased the shoot dry matter production of the pasture, which was related to higher tiller population density and greater tiller weight, it did not affect the forage quality of the plants grown in the field. We conclude that NTP technology is suitable to improve seed germination of Gatton panic, in turn leading to improvements in seedling establishment and biomass production under field conditions without compromising forage quality.Item Non-thermal plasma as emerging technology for Tribolium castaneum pest-management in stored grains and flours.(2022) Zilli, Carla; Pedrini, Nicolás; Prieto, Eduardo; Girotti, Juan Roberto; Vallecorsa, Pablo; Ferreyra, Matías; Chamorro, Juan Camilo; Cejas, Ezequiel; Fina, Brenda; Prevosto, Leandro; Balestrasse, KarinaThe red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is a major secondary pest on wheat stored in metal bins, silo-bags and is also frequently found in wheat products such as flour. Non-thermal plasmas (NTPs) are (quasi-neutral) partially ionized gases that may be produced by a variety of electrical dis charges. We propose the use of an atmospheric pressure dielectric barrier discharge (DBD) as an emerging technology in post-harvest integrated pest management. To this aim, a series of experiments were performed in order to test the lethality of such plasmas on three life stages of T. castaneum by measuring insect mortality and their impacts on physiological and biochemical parameters affecting insect fitness. The different NTP treatments were performed by increasing the time of exposure to either O2 or N2 used as carrier gases. After 24 hours, high levels of mortality (30–100%) were reached for each applied treatment, in both larval and adult populations. Mortality seems to be related to a significant water content loss and redox imbalance. Atomic force microscopy (AFM) scanning of the prothoracic surface showed that nitrogen causes more severe damage than oxygen. As a consequence of the cuticle damage, the quinone-containing secretions of the prothoracic and abdominal glands were affected. We also carried out experiments on egg-containing flours to test the ovicidal activity of NTP. The flours were evaluated at three and twelve weeks after treatments. A 3-min nitrogen treatment showed ovicidal properties, while the remaining NTPs partially killed the eggs and delayed the emergence of larvae and adults. In conclusion, we propose an inexpensive physical treatment, which controls the entire life cycle of a major grain pest, avoiding chemical residues.Item Non‑Thermal Plasmas Afect Plant Growth and DNA Methylation Patterns in Glycine max.(2021) Pérez Pizá, María Cecilia; Ibañez, Verónica; Varela, Anabella; Ferreyra, Matías; Chamorro, Juan Camilo; Zilli, Carla; Vallecorsa, Pablo; Fina, Brenda; Prevosto, Leandro; Marfil, Carlos; Cejas, Ezequiel; Balestrasse, KarinaNon-thermal plasmas (NTP) are partially ionized gases that represent a promising technology for seed treatment to enhance seed health while promoting germination and vigor in a fast, cost-efective, and eco-friendly way. The seed treatment with NTP generates phenotypic variations in plants that could be related to changes in DNA methylation. This work analyses the efects of two diferent NTP: nitrogen for 3 min (PMN3) and oxygen for 2 min (PMO2) applied to soybean (Glycine max) seeds. Growth parameters of plants grown from treated and untreated seeds were evaluated at two growth stages: 6 and 20 days after sowing (DAS). MSAP (Methylation Sensitive Amplifed Polymorphism) markers were assayed to evaluate epigenetic changes induced by NTP treatments. Plants obtained from PMN3 and PMO2-treated seeds were phenotypically similar to each other: exhibited a superior growth at both stages. At 6 DAS root and shoot length and fresh weight surpassed the Control, while at 20 DAS root length and fresh and dry weight were higher than Control. PMN3 and PMO2 induced DNA methylation changes with respect to the Control plants, with higher diferentiation at 20 DAS than at 6 DAS. The epigenetic variability and the phenotypic variability correlated only at 20 DAS (R2=0.5). The observed phenotypic diferences among Control and NTP-treated plants could not be explained by overall changes in the methylation levels, but both demethylation and methylation changes at specifc loci appear to be operating in response to NTP treatments.Item Numerical Simulation of the Voltage–Current Characteristic of an Atmospheric Pressure Discharge: The Glow‑to‑Arc Transition.(2024) Cejas, Ezequiel; Prevosto, Leandro; Minotti, FernandoThe glow-to-arc transition of a convection-stabilized atmospheric pressure air discharge is numerically investigated. Two separate models are considered: a one-dimensional axisym metric time-dependent fuid model of the positive column, describing the thermal-instabil ity, and a sheath model of a cold cathode describing the feld-emission instability, which must then be properly matched together. The fuid model considers the most important chemical reactions in air plasma, including thermal ionization in atomic collisions. The radial electric feld in the plasma is obtained from the Poisson equation. The voltage–cur rent characteristic of the discharge is simulated for a time-varying current up to 300 mA. It is found that at some critical value slightly above 200 mA, the contraction of the positive column arises from a vibrational–translational energy relaxation. The subsequent increases in the discharge current density in the positive column drive in turn a feld-emission insta bility in the cathode, which is accompanied by a large voltage drop. Simulation results are validated against available experimental data.Item On the dynamic behavior of the anode–arc–root at the nozzle surface in a non-transferred plasma torch(2012) Prevosto, Leandro; Risso, Marcelo Natalio; Infante, Damián Leandro; Cejas, Ezequiel; Kelly, Héctor; Mancinelli, BeatrizThe dynamic behavior of the anode–arc–root at the nozzle surface of a plasma torch was experimentally investigated in this work. A gas (N2) vortex–stabilized non–transferred arc torch with a thoriated tungsten rod (2wt %) cathode (3.2 mm diameter) and a coaxial anode (5 mm diameter, 30 mm length) was used in the experiment. By using a sweeping Langmuir probe in floating condition, the voltage of the plasma jet outside the nozzle was inferred. Arc voltage waveforms were also obtained. Data have been obtained for an arc current of 100 A and a gas flow rate of 30 Nl min-1. A typical sawtooth shape (i.e., restrike mode) (with a fluctuating level of º 25 %) and a dominant frequency of º 6.5 kHz was observed in the arc voltage waveforms, which is attributed to anode–arc–root movements along the anode surface followed by a restrike at a certain point close to the cathode. By performing a time correlation between the probe and arc voltage oscillograms together with simple estimations, the amplitude of the movement of the arc–root along the anode surface as well its velocity were inferred.