Advanced Computational Fluid Dynamics Study of the Dissolved Oxygen Concentration within a Thin-Layer Cascade Reactor for Microalgae Cultivation

High concentration of dissolved oxygen within microalgae cultures reduces the performance of corresponding microalgae cultivation system (MCS). The main aim of this study is to provide a reliable computational fluid dynamics (CFD)-based methodology enabling to simulate two relevant phenomena governing the distribution of dissolved oxygen within MCS: (i) mass transfer through the liquid–air interface and (ii) oxygen evolution due to microalgae photosynthesis including the inhibition by the same dissolved oxygen. On an open thin-layer cascade (TLC) reactor, a benchmark numerical study to assess the oxygen distribution was conducted. While the mass transfer phenomenon is embedded within CFD code ANSYS Fluent, the oxygen evolution rate has to be implemented via user-defined function (UDF). To validate our methodology, experimental data for dissolved oxygen distribution within the 80 meter long open thin-layer cascade reactor are compared against numerical results. Moreover, the consistency of numerical results with theoretical expectations has been shown on the newly derived differential equation describing the balance of dissolved oxygen along the longitudinal direction of TLC. We argue that employing our methodology, the dissolved oxygen distribution within any MCS can be reliably determined in silico, and eventually optimized or/and controlled

La función discursiva y la distribución social de los marcadores "por ser" y "onda" en el corpus del PRESEEA de Santiago de Chile

Studies about “discourse markers” have coincided in stressing their importance to the production and comprehension of discourse, both oral and written, in different languages. Despite their importance, one of the less investigated dimensions in the Spanish language is the social and dialectal variation in the use of the aforementioned particles. Thus, the majority of the approaches to the discursive functions of the markers have a tendency to be based on peninsular Spanish and on reconstructed examples or on written language. In this study, the pragmatic functioning and sociolinguistic stratification of two markers used in the Spanish spoken in Santiago, Chile are analyzed: por ser and onda. The objectives of this article are to identify the functions said discourse markers fulfill and to correlate their use frequency with the sex, age, and level of education sociodemographic variables. For this purpose, the behavior of these particles in the interviews that make up the sociolinguistic corpus of the PRESEEA of Santiago will be analyzed.Los estudios sobre los denominados “marcadores del discurso” han coincidido en destacar su importancia para la producción y la comprensión del discurso, tanto oral como escrito, en diferentes lenguas. Pese a su importancia, una de las dimensiones menos indagadas en la lengua española es la variación social y dialectal del uso de las mencionadas partículas. De este modo, la mayor parte de las aproximaciones a las funciones discursivas de los marcadores ha tendido a basarse en muestras del español peninsular y en ejemplos reconstruidos o de la lengua escrita. En este estudio, se analiza el funcionamiento pragmático y la estratificación sociolingüística de dos marcadores empleados en el español hablado en Santiago de Chile: "por ser" y "onda". Los objetivos de este artículo son identificar las funciones que cumplen dichos marcadores del discurso y correlacionar sus frecuencias de empleo con las variables sociodemográficas sexo, edad y nivel de estudios de los informantes. Para tal propósito, se analizará el comportamiento de estas partículas en las entrevistas que conforman el corpus sociolingüístico del PRESEEA de Santiago

Análisis pragmático y sociolingüístico de los marcadores discursivos de reformulación en el habla de Santiago de Chile

The aim of this study is to analyze, from the pragmatic and sociolinguistic points of view, the markers of reformulation in a sample of spoken Chilean Spanish in Santiago, Chile. For this purpose, the particles that fulfill the above function were identified in a sample of 72 interviews of Chilean Spanish speakers in Santiago. We first analyze the behavior of such markers in the sample and then provide the sociolinguistic distribution of use of these markers in a socially stratified sample. For the study of these particles in the present study, we have applied the Martin Zorraquino & Portolés (1999) and Portolés (2001) concept and classification of discourse markers. We have also followed the suggestions by Cortes (1988) and Carbonero & Santana (2010) for the quantitative analysis of their social variation. Our analysis considers the reformulation function as a sociolinguistic variable with different values or variants (markers). Consequently, socio-demographic factors were correlated with subjects’ use of such markers. Thus, based on the functionalpragmatic commutability of the discourse markers identified, we proceeded to their quantitative analysis according to the following variables: age, sex-gender and socio-economic group of the interviewees.El objetivo de este estudio es analizar los marcadores de reformulación en una muestra del español hablado en Santiago de Chile, desde los puntos de vista pragmático y sociolingüístico. Para tal propósito, se identificaron las partículas que cumplían la mencionada función en una muestra de 72 entrevistas de hablantes santiaguinos. Por un lado, se analiza el comportamiento de este tipo de marcadores en la muestra antes indicada y, por otro, se establece la distribución sociolingüística de su empleo. Para el estudio de dichas partículas se aplicaron el concepto y la clasificación de los marcadores del discurso de Martín Zorraquino y Portolés (1999) y Portolés (2001), así como las sugerencias de Cortés (1998) y de Carbonero y Santana (2010) para el análisis cuantitativo de su variación social. En el análisis se consideró la función de reformulación como un caso de variable sociolingüística con diferentes valores o variantes (marcadores). Consecuentemente, se correlacionaron los factores sociodemográficos de los sujetos con el empleo de dichos marcadores. De este modo, basándonos en la conmutabilidad funcional –pragmática y discursiva– de los marcadores relevados se procedió a su análisis cuantitativo, según las variables: edad, sexo-género y grupo socioeconómico de los sujetos entrevistados

Improvement of real-scale raceway bioreactors for microalgae production using Computational Fluid Dynamics (CFD)

In this work, the design and hydrodynamic of a 500 m2 raceway bioreactor were optimized using Computational Fluid Dynamics (CFD). First, the influence of the bend type (traditional, isle partition and baffle partition) and the liquid velocity was studied, after that the dynamic behavior of the optimal configuration was analyzed. A monophasic analysis employing the Finite Element Method (FEM) with COMSOL Multiphysics™ allows to confirm that the utilization of deflectors in the baffle partition bend type provide the best performance in terms of fluid velocity, reduction of dead zones, shorter residence time and a suitable cell Reynolds number. A multiphasic analysis using the Finite Volume Method (FVM) with ANSYS Fluent was performed to complete the analysis, it considering the geometry and rotation speed of the paddlewheel. Different angular velocities from 14 to 20 rpm were studied. Results shows that at 18 rpm average liquid velocity of 0.38 m·s-1 were achieved and stabilized at 240 s, the pressure drop in the overall system stabilizes at 700 Pa at 330 s, power consumption in the rage of 30 W·m-3, a maximum turbulence intensity of 0.4 and vorticity greater than 9 s-1 in areas adjacent to the paddlewheel being determined. In addition, it was determined that more than 14% of the total volume is useful for mass transfer with the atmosphere as well as to water loss by evaporation. This study provides a robust start point for improving large-scale raceway reactors, a highly relevant issue because these are the most used reactors in large-scale microalgae production.This work was forms part of the SABANA Project of the European Unions' Horizon 2020 - Research and Innovation Framework Programme (Grant Agreement 727,874) and the AL4BIO Project, funded by the Spanish Ministry of Science, Innovation and Universities (RTI2018–099495-A-C22). Thanks to the personnel from IFAPA research centre in Almeria for their support during this research.Peer ReviewedPostprint (author's final draft

Antibiotic activity of Emerimicin IV isolated from <i>Emericellopsis minima</i> from Talcahuano Bay, Chile

<p>Due to the increasing emergence of resistance of bacterial pathogens to current antibiotics, we have examined the marine fungi present in sea sediments obtained 200 m offshore to discover new antibacterial compounds active against multidrug-resistant bacteria. One strain, identified as <i>Emericellopsis minima</i>, was isolated from sediments of Talcahuano Bay (Chile). From the liquid culture of <i>E. minima</i>, we isolated Emerimicin IV, a unique fungal peptaibol that exhibited antibacterial activity. The structure of this compound was assigned by interpretation of ¹H NMR and HR-LCMS data. Emerimicin IV showed bacteriostatic activity against clinical isolates of methicillin-resistant <i>Staphylococcus aureus</i> and vancomycin-resistant <i>Enterococcus faecalis</i> with MIC values ranging between 100 and 12.5 μg/mL.</p