On disturbances caused by pressure taps in highly elastic flows

The objective of this work is to characterise the onset of laterally asymmetric flow of viscoelastic solutions around a confined microfluidic cylinder, which was encountered in a recent study [Rodrigues et al., $\textit{J. Non-Newton. Fluid Mech.}$ $\textbf{289}$, 104406 (2020)]. To this end, two non-Newtonian fluids were employed in the same micro-geometry. Two microchannels were studied, both with a cylinder of diameter 75 $\mathrm{\mu}$m, aspect ratio (channel height over width) of 0.37 and blockage ratio (cylinder diameter over channel width) of 0.28, differing only on the width of the pressure taps, located 500 $\mathrm{\mu}$m up- and downstream from the respective cylinder face, on opposing walls. The working fluids consist of two poly(ethylene oxide) (PEO) solutions: a weakly shear-thinning elastic fluid and an elastic shear-thinning fluid. Micro-Particle Image Velocimetry ($\mathrm{\mu}$PIV) and streak imaging techniques were used to evaluate the flow over a Weissenberg number range: $100\leq Wi\leq500$, while maintaining a low Reynolds number, $Re<1$. The elastic shear-thinning solution showed laterally asymmetric flow past the cylinder with both pressure tap designs, while with the weakly shear-thinning solution asymmetric flow was only observed with the wider pressure tap intake. In both cases, the fluids preferentially chose the cylinder/wall gap opposing the upstream pressure tap, which was found to influence the flow greatly, seemingly associated with time-dependent flow and possibly the lateral flow asymmetry itself. This work brings to light the necessary compromise between optimal pressure tap design for quality pressure measurements and minimal flow interference, due to the increased susceptibility of elastic microfluidic flows to flow perturbations

Presentación del simposio

Admission to Higher Education (ES) presents students with different demands and opportunities, derived from their needs to meet educational goals, to regulate their learning, to manage study and leisure time, to participate on campus and in school. the classrooms and student representation, in a context of greater development and personal, social and emotional autonomy. Among the wide range of psychosocial and contextual variables that may be related to the experiences of this adaptation process, the academic expectations of the students in the first year of ES constitute the center of interest of this symposium. Just over half (57%) of full-time first-year students graduate in 4 years, sometimes being up to 6 years to get it. The percentage of students dropping out of school is mainly during the first year of study in the ES. Students who drop out without completing their studies are spending their time, money and Invested by the public sector in the educational process without, in the end, producing the desired benefits. That is why there is concern in recent years about the rates of academic graduation (Swail, 2004).La entrada en la Enseñanza Superior (ES) presenta a los estudiantes diversas exigencias y oportunidades, derivadas de sus necesidades de afrontamiento de metas educativas, de regulación de su aprendizaje, de gestión del tiempo de estudio y ocio, de participación en el campus y en las aulas y de representación estudiantil, en un contexto de mayor desarrollo y de autonomía tanto personal como social y emocional. De entre el amplio conjunto de variables psicosociales y contextuales que pueden estar relacionadas con las experiencias de este proceso de adaptación, las expectativas académicas de los estudiantes en el primer año de ES constituyen el centro de interés de este simposio. Poco más de la mitad (57 %) de los estudiantes de primer año a tiempo completo se gradúan en 4 años, siendo a veces necesarios hasta 6 años para conseguirlo. El porcentaje de abandono de los estudios se produce fundamentalmente durante el primer año de estudio en la ES. Los estudiantes que abandonan sin finalizar sus estudios suponen un gasto de su tiempo, de su dinero y delinvertido por el sector público en el proceso educativo sin que, a la postre, se produzcan los beneficios deseados. Es por eso que existe preocupación en los últimos años por las tasas de graduación académica (Swail, 2004)

Gender differences in first-year college students’ academic expectations

Based on a multidimensional definition of academic expectations (AEs), the authors examine students’ AE component scores across countries and genders. Two samples (343 Portuguese and 358 Spanish students) completed the Academic Perceptions Questionnaire (APQ) six months after enrolling in their universities. Factorial invariance was ensured across countries and genders, allowing us to study AEs using the APQ for both genders and in both countries. No significant differences in factor means were found between countries, indicating that AEs are not an obstacle to student mobility. Gender differences were found in some AE factor means, Training for employment, Personal and social development, Student mobility, Political engagement and citizenship, and Social pressure, with males exhibiting higher scores. Because these differences are not supported by most literature in this domain, further studies are needed to clarify the causes of women’s lower expectations and, therefore, risk of adaptation difficulties

Factorial equivalence of the Spanish and Portuguese versions of a questionnaire of academic expectations

Este estudio presenta los resultados de una investigación sobre expectativas académicas de estudiantes universitarios de primer año de Enseñanza Superior (ES) pertenecientes al norte de Portugal y noroeste de España. Su objetivo es replicar las propiedades psicométricas del instrumento utilizado obtenidas con una versión anterior del mismo. La muestra está integrada por 1.268 estudiantes de primer año de ES con edades comprendidas entre los 17 y 52 años (Mdn = 18, siendo de más de 23 años el 7.4%). Proceden de la región noroeste de España 413 estudiantes (Galicia, Universidad de Vigo) y 855 de la región norte de Portugal (Minho, Universidade do Minho). El 58.1% del total de la muestra son mujeres. Por ámbito de estudio, el 58.4% cursa titulaciones del ámbito científico-tecnológico y los demás del ámbito jurídico-social. Se aplicó el Cuestionario de Percepciones Académicas-Expectativas (CPA-E), estructurado en siete dimensiones: Formación para el empleo/carrera, Desarrollo personal y social, Movilidad estudiantil, Implicación político/ciudadana, Presión social, Calidad de formación e Interacción social. La invarianza del modelo factorial oblicuo del CPA-E fue testada con el LISREL 8.80 mediante el método bivariado latente normal y la estimación de máxima verosimilitud, con la corrección de Satorra y Bentler (1994). Todos los ítems representaron bien a sus respectivos factores y los factores mostraron una buena validez y fiabilidad para los países y el género. Se obtuvo, por tanto, invarianza factorial del modelo para los países y el género. Se asume una versión final del cuestionario común para España y Portugal, así como para mujeres y hombres.We present the results of a study conducted with first-year students from the Euro- region of Galicia-North Portugal, with the aim of replicating the psychometric properties of the instrument as obtained from a prior version. Participants included 1268 first-year students with ages ranging from 17 to 52 years (Mdn = 18; 7.4% with ages above 23 years). Four-hundred and thirteen students are from the North Spanish region (Galicia, University of Minho) and 855 are from the North Portuguese region (Minho, University of Minho), and 58.1% of the students are women. Students are enrolled in scientific-technological courses (58.4%) and juridical-social studies. We administered the Academic Perceptions Questionnaire- Expectations (APQ-E), which is structured in seven dimensions: Training for career development, Personal and social development, Student mobility, Political engagement and citizenship, Social pressure, Training quality, and Social interaction. The invariance of the factorial model of the APQ-E was tested with LISREL 8.80, based on a bivariate latent model and maximum likelihood estimation, with Satorra and Bentler correction (1994). All items contributed to the representation of the factors, and the factors showed good validity and reliability for country and gender. Therefore, we obtained factorial invariance of the measurement model for country and gender. We present the final version of the common questionnaire for Portugal and Spain, and for women and men

Microfluidic systems for the analysis of the viscoelastic fluid flow phenomena in porous media

In this study, two microfluidic devices are proposed as simplified 1-D microfluidic analogues of a porous medium. The objectives are twofold: firstly to assess the usefulness of the microchannels to mimic the porous medium in a controlled and simplified manner, and secondly to obtain a better insight about the flow characteristics of viscoelastic fluids flowing through a packed bed. For these purposes, flow visualizations and pressure drop measurements are conducted with Newtonian and viscoelastic fluids. The 1-D microfluidic analogues of porous medium consisted of microchannels with a sequence of contractions/ expansions disposed in symmetric and asymmetric arrangements. The real porous medium is in reality, a complex combination of the two arrangements of particles simulated with the microchannels, which can be considered as limiting ideal configurations. The results show that both configurations are able to mimic well the pressure drop variation with flow rate for Newtonian fluids. However, due to the intrinsic differences in the deformation rate profiles associated with each microgeometry, the symmetric configuration is more suitable for studying the flow of viscoelastic fluids at low De values, while the asymmetric configuration provides better results at high De values. In this way, both microgeometries seem to be complementary and could be interesting tools to obtain a better insight about the flow of viscoelastic fluids through a porous medium. Such model systems could be very interesting to use in polymer-flood processes for enhanced oil recovery, for instance, as a tool for selecting the most suitable viscoelastic fluid to be used in a specific formation. The selection of the fluid properties of a detergent for cleaning oil contaminated soil, sand, and in general, any porous material, is another possible application

Microdevices for extensional rheometry of low viscosity elastic liquids : a review

Extensional flows and the underlying stability/instability mechanisms are of extreme relevance to the efficient operation of inkjet printing, coating processes and drug delivery systems, as well as for the generation of micro droplets. The development of an extensional rheometer to characterize the extensional properties of low viscosity fluids has therefore stimulated great interest of researchers, particularly in the last decade. Microfluidics has proven to be an extraordinary working platform and different configurations of potential extensional microrheometers have been proposed. In this review, we present an overview of several successful designs, together with a critical assessment of their capabilities and limitations

Rationale and design of the CONFIRM2 (Quantitative COroNary CT Angiography Evaluation For Evaluation of Clinical Outcomes: An InteRnational, Multicenter Registry) study.

BACKGROUND In the last 15 years, large registries and several randomized clinical trials have demonstrated the diagnostic and prognostic value of coronary computed tomography angiography (CCTA). Advances in CT scanner technology and developments of analytic tools now enable accurate quantification of coronary artery disease (CAD), including total coronary plaque volume (TPV) and low attenuation plaque volume (LAP). The primary aim of CONFIRM2, (Quantitative COroNary CT Angiography Evaluation For Evaluation of Clinical Outcomes: An InteRnational, Multicenter Registry) is to perform comprehensive quantification of CCTA findings, including coronary, non-coronary cardiac, non-cardiac vascular, non-cardiac findings, and relate them to clinical variables and cardiovascular clinical outcomes. DESIGN CONFIRM2 is a multicenter, international observational cohort study designed to evaluate multidimensional associations between quantitative phenotype of cardiovascular disease and future adverse clinical outcomes in subjects undergoing clinically indicated CCTA. The targeted population is heterogenous and includes patients undergoing CCTA for atherosclerotic evaluation, valvular heart disease, congenital heart disease or pre-procedural evaluation. Automated software will be utilized for quantification of coronary plaque, stenosis, vascular morphology and cardiac structures for rapid and reproducible tissue characterization. Up to 30,000 patients will be included from up to 50 international multi-continental clinical CCTA sites and followed for 3-4 years. SUMMARY CONFIRM2 is one of the largest CCTA studies to establish the clinical value of a multiparametric approach to quantify the phenotype of cardiovascular disease by CCTA using automated imaging solutions

Numerical methods for the computation of the confluent and Gauss hypergeometric functions

The two most commonly used hypergeometric functions are the confluent hypergeometric function and the Gauss hypergeometric function. We review the available techniques for accurate, fast, and reliable computation of these two hypergeometric functions in different parameter and variable regimes. The methods that we investigate include Taylor and asymptotic series computations, Gauss-Jacobi quadrature, numerical solution of differential equations, recurrence relations, and others. We discuss the results of numerical experiments used to determine the best methods, in practice, for each parameter and variable regime considered. We provide 'roadmaps' with our recommendation for which methods should be used in each situation

Basic Methods for Computing Special Functions

This paper gives an overview of methods for the numerical evaluation of special functions, that is, the functions that arise in many problems from mathematical physics, engineering, probability theory, and other applied sciences. We consider in detail a selection of basic methods which are frequently used in the numerical evaluation of special functions: converging and asymptotic series, including Chebyshev expansions, linear recurrence relations, and numerical quadrature. Several other methods are available and some of these will be discussed in less detail. We give examples of recent software for special functions where these methods are used. We mention a list of new publications on computational aspects of special functions available on our website