Reconstruction subgrid models for nonpremixed combustion

Large-eddy simulation of combustion problems involves highly nonlinear terms that, when filtered, result in a contribution from subgrid fluctuations of scalars, Z, to the dynamics of the filtered value. This subgrid contribution requires modeling. Reconstruction models try to recover as much information as possible from the resolved field Z, based on a deconvolution procedure to obtain an intermediate field ZM. The approximate reconstruction using moments (ARM) method combines approximate reconstruction, a purely mathematical procedure, with additional physics-based information required to match specific scalar moments, in the simplest case, the Reynolds-averaged value of the subgrid variance. Here, results from the analysis of the ARM model in the case of a spatially evolving turbulent plane jet are presented. A priori and a posteriori evaluations using data from direct numerical simulation are carried out. The nonlinearities considered are representative of reacting flows: power functions, the dependence of the density on the mixture fraction (relevant for conserved scalar approaches) and the Arrhenius nonlinearity (very localized in Z space). Comparisons are made against the more popular beta probability density function (PDF) approach in the a priori analysis, trying to define ranges of validity for each approach. The results show that the ARM model is able to capture the subgrid part of the variance accurately over a wide range of filter sizes and performs well for the different nonlinearities, giving uniformly better predictions than the beta PDF for the polynomial case. In the case of the density and Arrhenius nonlinearities, the relative performance of the ARM and traditional PDF approaches depends on the size of the subgrid variance with respect to a characteristic scale of each function. Furthermore, the sources of error associated with the ARM method are considered and analytical bounds on that error are obtained

Modeling Individual and Organizational Effects on Chilean Journalism: A Multilevel Analysis of Professional Role Conceptions

Using a representative survey of Chilean journalists (n= 570) and data collected from each news media organization (n= 114), this paper examines individual and organizational effects on professional role conceptions via hierarchical linear modeling. The findings demonstrate the existence of significant contextual effects on the importance that journalists give to their different functions in society, although not all professional roles are equally affected in form and magnitude by the news media context. This study shows that the journalism’s more political roles are modeled for an interrelation between individual and organizational factors, where journalists’ background and beliefs tend to be more predictive than news media characteristics. In turn, professional functions linked to the need of the public and to the commercialization of news, appeared to be more tied to the structural characteristics of the news organizations where the journalists belong. The results also reveal that individual and organizational political factors predict the majority of the professional roles, while ownership and media type do not have any direct influence on the journalists’ attitudes

Evaluation of open digital resources for digital and media competence from an educational-communicative perspective

La creación y uso de Recursos Educativos Digitales en Abierto emerge como uno de los elementos prioritarios de la Competencia Digital Docente en su vertiente digital y mediática, fundamental para la construcción y divulgación de conocimiento fiable frente a la expansión de las noticias falsas. Este trabajo propone y describe un proceso de evaluación educomunicativa de este tipo de recursos dirigidos a la formación de estudiantes y profesorado en Competencia Digital Docente en el ámbito de la educación superior. Para ello se ha elaborado un cuestionario propio de escala tipo Likert (CEREDA) que se ha mostrado fiable a la hora de evaluar recursos digitales. Los resultados informan de una validación del cuestionario y de los recursos evaluados, estableciendo asociaciones que indican las cualidades que debe reunir los recursos digitales para ser considerados como innovadores, además de hallar diferencias significativas entre profesorado y alumnado en las percepciones que manifiestan sobre el nivel de accesibilidad de los recursos creados y evaluados.The creation and use of Open Educational Digital Resources emerges as one of the priority elements of Digital Competence in Education in its digital and media aspect, fundamental for the construction and dissemination of reliable knowledge in the face of the spread of fake news. This paper proposes and describes a process of educommunicative evaluation of this type of resources aimed at training students and teachers in Digital Competence in Education in the field of higher education. For this purpose, a specific Likert-type scale questionnaire (CEREDA) has been developed, which has proved to be reliable when evaluating digital resources. The results report a validation of the questionnaire and the resources evaluated, establishing associations that indicate the qualities that digital resources must have in order to be considered innovative, as well as finding significant differences between teaching staff and students in the perceptions they express about the level of accessibility of the resources created and evaluated.El trabajo forma parte del proyecto Erasmus+ “EU-TeachPaaS” (2021-1-ES01-KA220-HED-000022911), financiado por la Comisión Europea

Transformación de arsénico por bacterias aisladas de sedimentos enriquecidos con el metaloide

Las bacterias presentes en ambientes contaminados con arsénico son capaces de resistir esta presión ambiental y adaptarse mediante mecanismos de resistencia, lo que involucra, entre otros, la oxidación y/o reducción del metaloide. El objetivo del presente trabajo fue investigar las propiedades redox en bacterias tolerantes a arsénico, aisladas de sedimentos naturales.  Los sedimentos se obtuvieron del río Camarones(I región, Chile). Las muestras se incubaron en medio mineral durante 7 días, a temperatura ambiente. Diluciones apropiadas fueron sembradas en agar R2A se incubaron a 25 ºC, hasta 7 días. Los niveles de tolerancia para cada metal se determinaron mediante dilución seriada en placa. La propiedad de oxidar o reducir arsénico se investigó mediante nitrato de plata. Los resultados muestran la presencia de bacterias resistentes a arsenito y arseniato, con niveles de tolerancia > 8mM. El 36,84% de las cepas aisladas de sedimentos ricos en arsénico presentaron actividades reductoras(>50%). En cambio, en bacterias aisladas de sedimentoscon bajas concentraciones del metaloide, la actividad reductora varió entre un 10% y 25%. Se puede concluir que la presencia de arsénico selecciona bacterias con la capacidad de tolerar concentraciones altas de arsénico a través de la transformación de As(V) en As(III)

The contextualization of the watchdog and civic journalistic roles: Reevaluating journalistic role performance in U.S. newspapers

This study examines the two dominant U.S. journalism models-the watchdog and civic-oriented professional performance-in the aftermath of the economic crises. The study, based on a content analysis of 1,421 news stories published by five national U.S. dailies, measures journalists' role conception through a content analysis of newspaper articles, examining the concept of journalistic role performance. The findings indicate different contextualizations of the two roles: The civic journalism performance was mostly found in stories dealing with issues such as human rights, demonstrations, and religion. The watchdog model was found in stories dealing with religion as well, but was found more frequently than the civic model in stories covering the government, police and crime. While the overall results indicate shifting roles of journalists toward a more civic approach, the traditional watchdog role remains important in covering politics. The roles journalists perform and their implications for U.S. news coverage are discussed

El fraseologismo "por momentos": principales valores semánticos y algunos apuntes diatópicos

En este trabajo se lleva a cabo un análisis inductivo del fraseologismo (FR) por momentos basado en corpus que tiene por objeto (1) estudiar los significados más frecuentes de por momentos en España en relación con los del área de mayor frecuencia de uso (zona rioplatense) y (2) describir los elementos contextuales y los colocados verbales de por momentos en los dos significados más frecuentes. El objetivo último de nuestra investigación es llamar la atención sobre la coexistencia de dos valores fundamentales del FR por momentos: uno temporal distributivo (‘algunas veces, durante/en breves espacios de tiempo’), característico del español rioplatense, y otro modal (‘cada vez más, visible y rápidamente’), dominante en el español peninsular. Con ambos valores se aprecia una clara tendencia al empleo del FR en contextos de intensificación; además, el segundo muestra una connotación evidencial que se ve reforzada por elementos contextuales.In this paper we make an inductive corpus-based analysis of the Spanish idiom por momentos. The aim of the analysis is (1) to study the most common meaning of por momentos in Spain and in Río de la Plata, and (2) to describe the contextual elements and the verbal collocates with the two most common meanings of the idiom. The ultimate aim of our study is to draw attention to the coexistence of two fundamental meanings of por momentos: one of them is a temporal and distributive meaning (‘sometimes, in short periods of time’) and the other is a modal meaning (‘more and more, visibly, quickly’). The former is characteristic of Spanish in Río de la Plata while the latter is the most frequent in Spain. With the two meanings there is a clear tendency to use the idiom in the context of intensifi cation; moreover, the second has evidential connotation. This connotation is emphasized by numerous contextual elements

Pre-ingestive selection capacity and endoscopic analysis in the sympatric bivalves Mulinia edulis and Mytilus chilensis exposed to diets containing toxic and non-toxic dinoflagellates

This study investigates the effects of toxic and non-toxic dinoflatellates on two sympatric bivalves, the clam Mulinia edulis and the mussel Mytilus chilensis. Groups of bivalves were fed one of three diets: (i) the toxic paralytic shellfish producing (PSP) Alexandrium catenella + Isochrysis galbana; (ii) the non-toxic Alexandrium affine + Isochrysis galbana and (iii) the control diet of Isochrysis galbana. Several physiological traits were measured, such as, clearance rate, pre-ingestive selection efficiency and particle transport velocity in the gill. The clearance rates of both M. chilensis and M. edulis showed a significant reduction when fed a mixed toxic diet of 50% Alexandrium catenella: 50% Isochrysis galbana. Similarly, when both species of bivalves were fed with the non-toxic diet (50% A. affine: 50% I. galbana), clearance rate was significantly lower compared with a diet of 100% I. galbana. Under all the experimental diets, M. chilensis showed higher clearance rate values, slightly more than double that of M. edulis. M. edulis and M. chilensis have the ability to select particles at the pre-ingestive level, thus eliminating a larger proportion of the toxic dinoflagellate A. catenella as well as the non-toxic A. affine in the form of pseudofaeces. Higher values of selection efficiency were registered in M. edulis than in M. chilensis when exposed to the toxic diet. Similar results were observed when these two species were exposed to the diet containing the non-toxic dinoflagellate, explained by the fact that the infaunal Mulinia edulis is adapted to dealing with larger particle sizes and higher particle densities (Navarro et al., 1993). The lower transport particle velocity observed in the present work for both species, is related to the reduced clearance rate, the higher particle concentration, and the presence of larger, toxic dinoflagellates. In addition, the species differ in their feeding responses to diets, with and without A. catenella or A. affine, largely reflecting their adaptations to different environmental conditions. The results suggest that the presence of a dinoflagellate bloom, whether toxic or non-toxic spp in Yaldad Bay, is likely to have a greater impact on the Mytilus chilensis than the infaunal Mulinia edulis, based on the combined effects on clearance rate, selection efficiency and particle transport velocity

Classical Topological Order in Kagome Ice

We examine the onset of classical topological order in a nearest-neighbor kagome ice model. Using Monte Carlo simulations, we characterize the topological sectors of the groundstate using a non-local cut measure which circumscribes the toroidal geometry of the simulation cell. We demonstrate that simulations which employ global loop updates that are allowed to wind around the periodic boundaries cause the topological sector to fluctuate, while restricted local loop updates freeze the simulation into one topological sector. The freezing into one topological sector can also be observed in the susceptibility of the real magnetic spin vectors projected onto the kagome plane. The ability of the susceptibility to distinguish between fluctuating and non-fluctuating topological sectors should motivate its use as a local probe of topological order in a variety of related model and experimental systems.Comment: 17 pages, 9 figure