3,608 research outputs found
Predicción de la frescura del aceite de oliva virgen extra durante el almacenamiento mediante espectroscopÃa de fluorescencia
Virgin olive oil quality relates to flavor and unique health benefits. Some of these properties are
at the most desirable level when the oil is just extracted, since it is not a product that improves with age. On the
contrary, the concentrations of many compounds change during its shelf-life. These changes reveal the aging of
the oil but do not necessarily mean decay in sensory properties, so in some cases an aged oil from healthy olives
may be better qualified than a fresh one from olives affected by fermentation. The aim of this work is to analyze
different methodologies proposed for assessing the quality of virgin olive oil with implications in freshness and
aging of the oil, and to highlight the possibilities of rapid spectrofluorimetric techniques for assessing oil freshness by checking the evolution of pigments during storage. The observed change in the selected spectral features
and mathematical modelling over time was compared with the accepted model for predicting the amount of
pyropheophytin a, which is based on isokinetic studies. The best regression was obtained for 655 nm (adjustedR2
= 0.91) wavelength, which matches the distinctive band of pigments. The two mathematical models described
in this study highlight the usefulness of pigments in the prediction of the shelf-life of extra virgin olive oil.La calidad del aceite de oliva virgen está relacionada con su flavor y sus beneficios
únicos para la salud. Algunas de estas propiedades se encuentran en el nivel más deseable cuando el aceite está
recién extraÃdo, ya que no es un producto que mejore con el tiempo. Por el contrario, las concentraciones de
muchos compuestos cambian a lo largo de la vida útil. Estos cambios revelan el envejecimiento del aceite, pero
no implican necesariamente la alteración de las propiedades sensoriales, por lo que en algunos casos un aceite
envejecido procedente de aceitunas sanas puede presentar mejor calidad que uno fresco procedente de aceitunas
afectadas por procesos de fermentación. El objetivo de este trabajo es estudiar diferentes metodologÃas propuestas para evaluar la calidad del aceite de oliva virgen con implicaciones en la frescura y el envejecimiento del
aceite, destacando las posibilidades de las rápidas técnicas espectrofluorométricas para evaluar la frescura del
aceite verificando la evolución de los pigmentos durante el almacenamiento. El cambio observado en las caracterÃsticas espectrales seleccionadas y su modelado matemático a lo largo del tiempo se comparó con el modelo
aceptado para predecir la cantidad de pirofeofitina a, que se basa en estudios isocinéticos. Los dos modelos
matemáticos descritos en este estudio pusieron de manifiesto la utilidad de los pigmentos en la predicción de la
vida útil del aceite de oliva virgen extra. La mejor regresión se obtuvo para 655 nm (R2
-ajustado = 0,91), longitud de onda que coincide con la banda distintiva de pigmentos.SecretarÃa de Estado de Investigación, Desarrollo e Innovación de España-AGL2015-69320-
On the inconsistency of the Malmquist-Luenberger index
Apart from the well-known weaknesses of the standard Malmquist productivity index
related to infeasibility and not accounting for slacks, already addressed in the literature,
we identify a new and significant drawback of the Malmquist-Luenberger index
decomposition that questions its validity as an empirical tool for environmental
productivity measurement associated with the production of bad outputs. In particular,
we show that the usual interpretation of the technical change component in terms of
production frontier shifts can be inconsistent with its numerical value, thereby resulting
in an erroneous interpretation of this component that passes on to the index itself. We
illustrate this issue with a simple numerical example. Finally, we propose a solution for
this inconsistency issue based on incorporating a new postulate for the technology
related to the production of bad output
Predicción de la frescura del aceite de oliva virgen extra durante el almacenamiento mediante espectroscopÃa de fluorescencia
Virgin olive oil quality relates to flavor and unique health benefits. Some of these properties are
at the most desirable level when the oil is just extracted, since it is not a product that improves with age. On the
contrary, the concentrations of many compounds change during its shelf-life. These changes reveal the aging of
the oil but do not necessarily mean decay in sensory properties, so in some cases an aged oil from healthy olives
may be better qualified than a fresh one from olives affected by fermentation. The aim of this work is to analyze
different methodologies proposed for assessing the quality of virgin olive oil with implications in freshness and
aging of the oil, and to highlight the possibilities of rapid spectrofluorimetric techniques for assessing oil freshness by checking the evolution of pigments during storage. The observed change in the selected spectral features
and mathematical modelling over time was compared with the accepted model for predicting the amount of
pyropheophytin a, which is based on isokinetic studies. The best regression was obtained for 655 nm (adjustedR2
= 0.91) wavelength, which matches the distinctive band of pigments. The two mathematical models described
in this study highlight the usefulness of pigments in the prediction of the shelf-life of extra virgin olive oil.La calidad del aceite de oliva virgen está relacionada con su flavor y sus beneficios
únicos para la salud. Algunas de estas propiedades se encuentran en el nivel más deseable cuando el aceite está
recién extraÃdo, ya que no es un producto que mejore con el tiempo. Por el contrario, las concentraciones de
muchos compuestos cambian a lo largo de la vida útil. Estos cambios revelan el envejecimiento del aceite, pero
no implican necesariamente la alteración de las propiedades sensoriales, por lo que en algunos casos un aceite
envejecido procedente de aceitunas sanas puede presentar mejor calidad que uno fresco procedente de aceitunas
afectadas por procesos de fermentación. El objetivo de este trabajo es estudiar diferentes metodologÃas propuestas para evaluar la calidad del aceite de oliva virgen con implicaciones en la frescura y el envejecimiento del
aceite, destacando las posibilidades de las rápidas técnicas espectrofluorométricas para evaluar la frescura del
aceite verificando la evolución de los pigmentos durante el almacenamiento. El cambio observado en las caracterÃsticas espectrales seleccionadas y su modelado matemático a lo largo del tiempo se comparó con el modelo
aceptado para predecir la cantidad de pirofeofitina a, que se basa en estudios isocinéticos. Los dos modelos
matemáticos descritos en este estudio pusieron de manifiesto la utilidad de los pigmentos en la predicción de la
vida útil del aceite de oliva virgen extra. La mejor regresión se obtuvo para 655 nm (R2
-ajustado = 0,91), longitud de onda que coincide con la banda distintiva de pigmentos.SecretarÃa de Estado de Investigación, Desarrollo e Innovación de España-AGL2015-69320-
Thermal phase transitions for Dicke-type models in the ultra-strong coupling limit
We consider the Dicke model in the ultra-strong coupling limit to investigate
thermal phase transitions and their precursors at finite particle numbers
for bosonic and fermionic systems. We derive partition functions with
degeneracy factors that account for the number of configurations and derive
explicit expressions for the Landau free energy. This allows us to discuss the
difference between the original Dicke (fermionic) and the bosonic case. We find
a crossover between these two cases that shows up, e.g., in the specific heat.Comment: 4 pages Brief Report styl
A virtual robot solution to support programming
Computer programming is a valuable skill. But learning programming is sometimes difficult, time-consuming, even frustrating. In this context, there is a need for new approaches to help in the process of learning programming. Here it is presented a solution based on a virtual robot with progressive system and supported in a generic and portable language. Those features answer to some needs. First, the virtual robot allows for certain level tangibility to the results. Then, the implementation as a progressive system allows for the support of the learning process. Finally, the use of a generic and portable language allows for the installation of the system on many platforms.info:eu-repo/semantics/acceptedVersio
Interpretation of the evolution parameter of the Feynman parametrization of the Dirac equation
The Feynman parametrization of the Dirac equation is considered in order to
obtain an indefinite mass formulation of relativistic quantum mechanics. It is
shown that the parameter that labels the evolution is related to the proper
time. The Stueckelberg interpretation of antiparticles naturally arises from
the formalism.Comment: 6 pages, RevTex, no figures, submitted to Phys. Lett.
Cultural impacts on e-learning systems' success
E-learning systems are enablers in the learning process, strengthening their importance as part of the educational strategy. Understanding the determinants of e-learning success is crucial for defining instructional strategies. Several authors have studied e-learning implementation and adoption, and various studies have addressed e-learning success from different perspectives. However, none of these studies have verified whether students' cultural characteristics, such as individualism versus collectivism (individualism/collectivism), play a determinant role in the perceived e-learning success. This study provides a deeper understanding of the impact of students' cultural characteristics, for individualism/collectivism, on the perceived outcomes of e-learning systems use. This study proposes an e-learning systems success model that includes a cultural construct, individualism/collectivism. This paper reports an empirical study developed through an electronic survey distributed to higher education students belonging to various learning levels and from various universities. The study applies quantitative methods to obtain results. Our findings demonstrate that learners' perceived individual impact is positively influenced by their satisfaction and e-learning systems' use. Results demonstrate the determinant role of individualism/collectivism on individual and organizational impacts. Students influenced by collective culture perceive more individual and organizational impacts than individualistic culture students. Individualism/collectivism also moderates the users' perceived satisfaction on individual impact, and from individual impacts to organizational impacts. The result shows that for the students with a stronger individualistic culture, satisfaction plays a central role in the way they assess the individual impacts, and individual impacts on organizational impacts. This empirical research discusses the theoretical and practical implications.info:eu-repo/semantics/acceptedVersio
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