Facultad Regional Venado Tuerto
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Item Determinación de la resistencia al aplastamiento en madera Pino Elliotti.(UTN FRVT, 2021) Bianchi, Silvina; Martínez Merlo, HugoEl comportamiento estructural de maderas provenientes de especies cultivadas en bosques implantados en Argentina se rige según nuestro Reglamento CIRSOC 601. En el suplemento 4, destinado a uniones, contiene una tabla de valores de resistencia al aplastamiento basada en la existente de las NDS 2005 (National Design Specifications for Wood Construction), pero para verificar su aplicabilidad es necesario determinar este parámetro en maderas de uso corriente de nuestro país. El presente trabajo tiene como objetivo calcular la resistencia al aplastamiento y las deformaciones sobre los elementos de fijación tipo clavija realizadas con pernos rígidos, y luego comparar los resultados obtenidos con los valores dados por el CIRSOC 601. Para ello se realizaron los ensayos en dirección paralela a la fibra con un perno rígido de 7 mm de diámetro, de acuerdo a las prescripciones de la Norma UNE-EN 383:2007. Los valores de resistencia característica al aplastamiento obtenidos resultaron sensiblemente inferiores respecto a los propuestos en la tabla S.4.1.1-1 del suplemento 4 del Reglamento CIRSOC 601. Publicaciones anteriores, para otras especies cultivadas en la Argentina, presentan comportamientos similares, por lo que los valores con origen en las NDS 2005 deben ser utilizados con precaución.Item Efecto sobre la tensión de rotura en flexión de la altura de la sección en elementos estructurales de pino ponderosa.(UTN FRVT., 2023) Guillaumet, Alfredo; Manavella, Roberto; Filippetti, María Cecilia; Meyer, Lía Caren; Tosco, AndreaLa influencia de las dimensiones de la sección transversal en la resistencia a la flexión es un efecto contemplado en distintos reglamentos de estructuras de madera. En las normativas europeas y de Argentina la expresión de ajuste es común para todas las especies y procedencias, mientras que en la de Estados Unidos de Norteamérica y Chile se considera el grado estructural o la especie. Se han realizado numerosos estudios para verificar la precisión de las expresiones de ajuste para cada combinación de especie -procedencia. En este trabajo se analiza el efecto de la altura de la sección transversal, sobre la resistencia en flexión, en piezas de tamaño estructural de pino ponderosa cultivado en la región andino-patagónica norte de Argentina. Los ensayos de flexión se realizaron sobre 440 cuerpos de prueba de tamaño estructural según las normas argentinas. Los resultados indicaron una tendencia decreciente de la tensión de rotura en flexión con el aumento de la altura, el efecto de la altura resultó superior en la madera de inferior calidad. Los resultados obtenidos convalidan, para elementos estructurales de pino ponderosa, la aplicación del criterio de ajuste propuesto en la norma IRAM 9664 (2013) y el reglamento INTI-CIRSOC 601 (2016).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 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 Quantitative Schlieren Diagnostics Applied to a Millisecond Pulsed‑DC Hybrid Discharge in Atmospheric Pressure Air.(2022) Cejas, Ezequiel; Chamorro, Juan Camilo; Prevosto, LeandroThe gas temperature of a hybrid discharge in atmospheric pressure air is investigated by using quantitative schlieren imaging. The discharge is stabilized in a pin-to-plate electrode geometry and operated in a millisecond pulsed-DC regime with current amplitudes up to 75 mA and a duration of 10 ms, applied at a frequency of 100 Hz. An equilibrium com position model is considered to account for the production of N, O, and NO, which infu ence the Gladstone–Dale coefcient of air at high-gas temperatures. Also, a procedure is described which allows the determination of the errors introduced in the time-average gas refraction index due to gas temperature fuctuations. The results show that the axial values of the gas temperature profles span a large range from~1000 to 5000 K, nearly following the evolution of the discharge current. The temperature values found agree well with those reported in the literature for atmospheric pressure air plasmas, ranging from micro-glow to hybrid discharges.Item Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects.(2022) Ferreyra, Matías; Fina, Brenda; Milardovich, Natalio; Chamorro, Juan Camilo; Santamaría, Brenda; Balestrasse, Karina; Prevosto, LeandroIn recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO3 −), nitrite (NO2 −) and hydrogen peroxide (H2O2 ), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O3 ) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.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 Physicochemical Properties and Time Stability of Plasma Activated Water by a Liquid-Cathode Glow-Type Discharge in Air: The Effect of Air Confinement.(2023) Santamaría, Brenda; Ferreyra, Matías; Chamorro, Juan Camilo; Cejas, Ezequiel; Fina, Brenda; Prevosto, LeandroNonthermal discharges in atmospheric pressure air in contact with water produce large amounts of reactive species in the gas phase that can enter into the water by diffusion, thus inducing the formation of secondary reactive species in the liquid phase, including those long-lived species such as NO2 NO3, and H2O2. Depending on the controllable parameters of the discharge, the plasma activated water (PAW) may acquire differ 8 ent physicochemical properties, resulting in various applications. Physicochemical measurements of PAW obtained by means of a water-cathode glow-type discharge in atmospheric pressure air operating in open and closed reactor conditions are reported. The discharge was operated in a millisecond pulsed-dc regime at an rms current value of 100 mA and a power of 100 W. A large volume of 1 L of distilled water was treated for 30 min. In both cases, low pH values of ∼2.5 and very high levels of NO3(up to 250 mg/L) in PAW were obtained; however, in the closed system, no H2O2 was found and high concentrations of nitrite (120 mg/L) were measured, while in the open system, large levels of H2O2 were observed (45 mg/L) and no NO 2 was found. Likewise, the electrical conductivity value for the closed reactor (≈2000 µS/cm) was significantly higher than for the open reactor (≈1000 µS/cm). The reasons for these different behaviors in terms of PAW chemistry are discussed. Also, the time stability of PAW was measured.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.