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Zuniga G.E.,University of Santiago de Chile | Junqueira-Goncalves M.P.,University of Santiago de Chile | Pizarro M.,University of Santiago de Chile | Contreras R.,University of Santiago de Chile | And 2 more authors.
Radiation Physics and Chemistry | Year: 2012

Incorporating antimicrobial compounds into edible films or coatings provides a novel way to improve the safety and shelf life of ready-to-eat foods. Diverse studies with Quillaja saponaria Mol. (popularly named quillay) extracts have demonstrated their potential as antifungal agents against phytopathogenic fungi. Crosslinking induced by ionizing radiation is an effective method for the improvement of both barrier and mechanical properties of the edible films and coatings based on milk proteins. However there are few reports about the effects of γ-radiation on plant extracts. The aim of this work was to evaluate the effect of ionizing radiation (0, 5, 10, 15, 20, 25 and 35. kGy) on extracts prepared from in vitro plants of Q. saponaria to be used as antimicrobial agent in irradiated edible coating based on calcium caseinate and whey protein isolated, and also to establish the concentration of Q. saponaria extract to be added as an antifungal agent in the coating. Gamma irradiation since 15. kGy affects negatively the antimicrobial activity and metabolites composition of extract of Q. saponaria by reducing compounds of phenolic nature. Otherwise no effect on saponins profile was observed even at higher doses. It was possible to conclude that the antifungal activity of Q. saponaria extract is mainly related to phenolic compounds content. In addition, our work also shows that to obtain an efficient antifungal protection is necessary to add a minimum concentration of 6% of the extract after the coating irradiation. © 2011 Elsevier Ltd. Source

Cardenas M.,Comision Chilena de Energia Nuclear | Cardenas M.,Center for Research and Applications in Plasma Physics and Pulsed Power
Plasma Physics and Controlled Fusion | Year: 2010

We postulate that what determines neutron yield from discharges in a deuterium-filled plasma focus apparatus is the amount of energy passed from the capacitor bank to the individual deuterons participating in the pinch. We study plasma focus discharges within the framework of the snow plow model and write down an expression for the energy passed from the capacitor bank to the particles forming the pinch. Provided the shape of the plasma focus apparatus is fixed, this expression turns out to depend on only two dimensionless parameters comprising the electric and geometric features of the system altogether. We found that the energy per particle at pinching has a unique maximum value as a function of these dimensionless parameters, so that a criterion for optimizing plasma focus performance (i.e. neutron yield) results. We use the current formalism to evaluate the performance of a collection of practical plasma focus systems of various sizes and shapes. Finally, we indicate some modifications - obtained within the framework of the snow plow model - to be introduced in a number of practical systems under examination in order to improve their performance. © 2010 IOP Publishing Ltd. Source

Bora B.,Comision Chilena de Energia Nuclear | Bora B.,Center for Research and Applications in Plasma Physics and Pulsed Power
Plasma Sources Science and Technology | Year: 2015

In recent years, dual capacitively coupled radio frequency (CCRF) glow discharge plasma has been widely studied in the laboratory because of its simpler design and high efficiency for different material processing applications such as thin-film deposition, plasma etching, sputtering of insulating materials etc. The main objective of studies on dual frequency CCRF plasma has been the independent control of ion energy and ion flux using an electrical asymmetry effect (EAE). Most studies have been reported in electrode configurations that are either geometrically symmetric (both electrodes are equal) or completely asymmetric (one electrode is infinitely bigger than the other). However, it seems that most of the laboratory CCRF plasmas have finite electrode geometry. In addition, plasma series resonance (PSR) and electron bounce resonance (EBR) heating also come into play as a result of geometrical asymmetry as well as EAE. In this study, a dual frequency CCRF plasma has been studied in which the dual frequency CCRF has been coupled to the lumped circuit model of the plasma and the time-independent fluid model of the plasma sheath, in order to study the effect of finite geometrical asymmetry on the generation of dc-self bias and plasma heating. The dc self-bias is found to strongly depend on the ratio of the area between the electrodes. The dc self-bias is found to depend on the phase angle between the two applied voltage waveforms. The EAE and geometrical asymmetry are found to work differently in controlling the dc self-bias. It can be concluded that the phase angle between the two voltage waveforms in dual CCRF plasmas has an important role in determining the dc self-bias and may be used for controlling the plasma properties in the dual frequency CCRF plasma. © 2015 IOP Publishing Ltd. Source

Soto L.,Comision Chilena de Energia Nuclear | Soto L.,Center for Research and Applications in Plasma Physics and Pulsed Power
Journal of Physics: Conference Series | Year: 2016

The following ideas are widely accepted in Chile with respect to scientific activity: is carried out mainly in universities and science is considered a naturally university activity, that was developed in a period of more than 150 years by isolated individual efforts, c) it was transformed into an institutionalized activity at the universities after the university reform movement at the end of the 1960 decade, d) the activity is finally institutionalized in the country with the creation of the "Comisión Nacional de Investigatión Científica y Tecnológica, CONICYT (National Commission for Scientific and Technological Research) in 1967. This work presents preliminary findings showing that there are other institutional initiatives, different to the efforts from universities and directly dependent of the Chilean Government, in order to produce science and technology in Chile. This governmental initiatives start at the beginning of the Republic of Chile circa of 1810. © Published under licence by IOP Publishing Ltd. Source

Soto L.,Comision Chilena de Energia Nuclear | Soto L.,Center for Research and Applications in Plasma Physics and Pulsed Power | Soto L.,Andres Bello University | Pavez C.,Comision Chilena de Energia Nuclear | And 8 more authors.
Physics of Plasmas | Year: 2014

Recent observations of an azimuthally distributed array of sub-millimeter size sources of fusion protons and correlation between extreme ultraviolet (XUV) images of filaments with neutron yield in PF-1000 plasma focus have re-kindled interest in their significance. These filaments have been described variously in literature as current filaments and vortex filaments, with very little experimental evidence in support of either nomenclature. This paper provides, for the first time, experimental observations of filaments on a table-top plasma focus device using three techniques: framing photography of visible self-luminosity from the plasma, schlieren photography, and interferometry. Quantitative evaluation of density profile of filaments from interferometry reveals that their radius closely agrees with the collision-less ion skin depth. This is a signature of relaxed state of a Hall fluid, which has significant mass flow with equipartition between kinetic and magnetic energy, supporting the "vortex filament" description. This interpretation is consistent with empirical evidence of an efficient energy concentration mechanism inferred from nuclear reaction yields. © 2014 AIP Publishing LLC. Source

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