Utilização de radiação Ultravioleta (UV-C) como tecnologia alternativa aos sulfitos para a estabilização microbiológica de vinho tinto:resultados prévios

Neste trabalho avaliou -se o efeito da radiação UV -C sobre a estabilidade microbiológica do vinho tinto e, também, a sua influência sobre alguns parâmetros físico -químicos e sobre o perfil sensorial. Assim, o vinho sem sulfitos foi submetido a radiação UV -C com duas doses diferentes, 778 J.L-1 e 1415 J.L-1, e procedeu -se ainda à preparação de um controlo a que foi adicionado 40 mg.L-1 de dióxido de enxofre. Os vinhos (C, dose 1 e dose 2) foram analisados ao longo do tempo (0, 1, 2, 3, 6 e 9 meses). Os resultados obtidos demonstram que a tecnologia UV -C é eficaz no controlo microbiológico do vinho, não se diferenciando do tratamento tradicional para os parâmetros considerados. No que respeita às características físico -químicas, não se verificou diferenças entre os vários tratamentos para a maioria dos parâmetros analisados. Verifica -se que esta tecnologia tem um efeito muito positivo sobre a estabilidade da cor (intensidade e tonalidade) ao longo do tempo, comparativamente com o vinho com dióxido de enxofre. A análise sensorial revelou que os vinhos submetidos ao tratamento com radiação UV -C apresentaram uma melhor estabilização da cor, contudo verificou -se alguma depreciação no aroma e no sabor dos vinhos, que se atenuou ao longo do tempo.This work consisted in the evaluation of the effect of UV -C radiation on the microbiological stability of red wine as well as its and also its influence on some physical and chemical parameters and on the sensory profile. Thus, wine without sulfites was subjected to UV -C radiation in two different doses, 778 J.L-1 and 1415 J.L-1, and a control sample was also prepared to which 40 mg.L-1 of sulfur dioxide was added. The wines (C dose 1 and dose 2) were analyzed over time (0, 1, 2, 3, 6 and 9 months). The results show that UV -C technology is effective in the microbiological control of wine, without any differences to the standard method for the considered parameters. As for the physical -chemical characteristics, there were no differences between the various treatments for the majority of parameters which were analyzed. It has been verified that this technology has a very positive effect on the stability of the colour (intensity and hue) over time, compared with the wine with sulfur dioxide. The sensory analysis of the wines showed that the wine subjected to treatment with UV -C radiation had better stabilization of colour, but there was some depreciation in the aroma and flavour of the wine, which attenuated over time.info:eu-repo/semantics/publishedVersio

Ultrasonic evidence of an uncorrelated cluster formation temperature in manganites with first-order magnetic transition at T_C

Ultrasonic attenuation and phase velocity measurements have been carried out in the ferromagnetic perovskites La_{2/3}Ca_{1/3}MnO_3 and La_{2/3}Sr_{1/3}MnO_3. Data show that the transition at the Curie temperature, T_C, changes from first- to second-order as Sr replaces Ca in the perovskite. The compound with first-order transition shows also another transition at a temperature T* > T_C. We interpret the temperature window T_C < T < T* as a region of coexistence of a phase separated regime of metallic and insulating regions, in the line of recent theoretical proposals.Comment: 4 pages, 2 figure

Field-induced magnetic anisotropy in La0.7Sr0.3CoO3

Magnetic anisotropy has been measured for the ferromagnetic La0.7Sr0.3CoO3 perovskite from an analysis of the high-field part of the magnetization vs. field curves, i.e., the magnetic saturation regime. These measurements give a magnetic anistropy one order of magnitude higher than that of reference manganites. Surprisingly, the values of the magnetic anisotropy calculated in this way do not coincide with those estimated from measurements of coercive fields which are one order of magnitude smaller. It is proposed that the reason of this anomalous behaviour is a transition of the trivalent Co ions under the external magnetic field from a low-spin to an intermediate-spin state. Such a transition converts the Co3+ ions into Jahn-Teller ions having an only partially quenched orbital angular momentum, which enhances the intra-atomic spin-orbit coupling and magnetic anisotropy.Comment: Accepted of publication in Europhysics Letters, 11 pages, 5 figure

Bifurcation Phenomena in Two-Dimensional Piecewise Smooth Discontinuous Maps

In recent years the theory of border collision bifurcations has been developed for piecewise smooth maps that are continuous across the border, and has been successfully applied to explain nonsmooth bifurcation phenomena in physical systems. However, many switching dynamical systems have been found to yield two-dimensional piecewise smooth maps that are discontinuous across the border. The theory for understanding the bifurcation phenomena in such systems is not available yet. In this paper we present the first approach to the problem of analysing and classifying the bifurcation phenomena in two-dimensional discontinuous maps, based on a piecewise linear approximation in the neighborhood of the border. We explain the bifurcations occurring in the static VAR compensator used in electrical power systems, using the theory developed in this paper. This theory may be applied similarly to other systems that yield two-dimensional discontinuous maps

Multiferroic behavior in the new double-perovskite Lu2_2MnCoO6_6

We present a new member of the multiferroic oxides, Lu$_2$MnCoO$_6$, which we have investigated using X-ray diffraction, neutron diffraction, specific heat, magnetization, electric polarization, and dielectric constant measurements. This material possesses an electric polarization strongly coupled to a net magnetization below 35 K, despite the antiferromagnetic ordering of the $S = 3/2$ Mn$^{4+}$ and Co$^{2+}$ spins in an $\uparrow \uparrow \downarrow \downarrow$ configuration along the c-direction. We discuss the magnetic order in terms of a condensation of domain boundaries between $\uparrow \uparrow$ and $\downarrow \downarrow$ ferromagnetic domains, with each domain boundary producing a net electric polarization due to spatial inversion symmetry breaking. In an applied magnetic field the domain boundaries slide, controlling the size of the net magnetization, electric polarization, and magnetoelectric coupling

Confección de claves de identificación para los parques urbanos de Melilla. Un recurso didáctico

En el marco de un proyecto de innovación docente, desarrollado en la Facultad de Educación de Melilla, se están confeccionando materiales didácticos para el ciclo superior de Educación Primaria, entre ellos claves botánicas cientifico-didácticas para los parques de la ciudad de Melilla. En este trabajo se describe el proceso de diseño y elaboración, así como su implementación en varios colegios, tanto en salidas de campo como en la versión virtual, poniéndose de manifiesto el alto valor didáctico de estos documentos que favorecen el acercamiento del niño al trabajo del científico. La botánica, en este caso, se convierte en un recurso valioso para abordar objetivos y competencias preconizados en la legislación para diferentes áreas, especialmente Conocimiento del Medio y las instrumentales de Lengua y Matemáticas

No evidence of an 11.16 MeV 2+ state in 12C

An experiment using the 11B(3He,d)12C reaction was performed at iThemba LABS at an incident energy of 44 MeV and analyzed with a high energy-resolution magnetic spectrometer, to re-investigate states in 12C published in 1971. The original investigation reported the existence of an 11.16 MeV state in 12C that displays a 2+ nature. In the present experiment data were acquired at laboratory angles of 25-, 30- and 35- degrees, to be as close to the c.m. angles of the original measurements where the clearest signature of such a state was observed. These new low background measurements revealed no evidence of the previously reported state at 11.16 MeV in 12C