Influence of wettability on liquid water transport in gas diffusion layer of proton exchange membrane fuel cells (PEMFC)

Water management is a key factor that limits PEFC's performance. We show how insights into this problem can be gained from pore-scale simulations of water invasion in a model fibrous medium. We explore the influence of contact angle on the water invasion pattern and water saturation at breakthrough and show that a dramatic change in the invasion pattern, from fractal to compact, occurs as the system changes from hydrophobic to hydrophilic. Then, we explore the case of a system of mixed wettability, i.e. containing both hydrophilic and hydrophobic pores. The saturation at breakthrough is studied as a function of the fraction of hydrophilic pores. The results are discussed in relation with the water management problem, the optimal design of a GDL and the fuel cell performance degradation mechanisms. We outline how the study could be extended to 3D systems, notably from binarised images of GDLs obtained by X ray microtomography

Vertical mixing and coherent anticyclones in the ocean: the role of stratification

The role played by wind-forced anticyclones in the vertical transport and mixing at the ocean mesoscale is investigated with a primitive-equation numerical model in an idealized configuration. The focus of this work is to determine how the stratification impacts such transport. <br><br> The flows, forced only at the surface by an idealized wind forcing, are predominantly horizontal and, on average, quasigeostrophic. Inside vortex cores and intense filaments, however, the dynamics is strongly ageostrophic. <br><br> Mesoscale anticyclones appear as "islands" of increased penetration of wind energy into the ocean interior and they represent the maxima of available potential energy. The amount of available potential energy is directly correlated with the degree of stratification. <br><br> The wind energy injected at the surface is transferred at depth through the generation and subsequent straining effect of Vortex Rossby Waves (VRWs), and through near-inertial internal oscillations trapped inside anticyclonic vortices. Both these mechanisms are affected by stratification. Stronger transfer but larger confinement close to the surface is found when the stratification is stronger. For weaker stratification, vertical mixing close to the surface is less intense but below about 150 m attains substantially higher values due to an increased contribution of both VRWs, whose time scale is on the order of few days, and of near-inertial motions, with a time scale of few hours

Effect of sodium hypochlorite on microleakage of composite restorations bonded with a polyalkenoic containing adhesive system

Abstract no. 905published_or_final_versio

Positive correlational shift between crevicular antimicrobial peptide LL-37, pain and periodontal status following non-surgical periodontal therapy. A pilot study

Background: Periodontitis has a high prevalence and uncertain recurrence. Unlike the pro-inflammatory cytokine profile, little is known about the anti-inflammatory cytokine and antimicrobial peptide overview following treatment. The present study aimed to evaluate if any of the antimicrobial peptide LL-37, interleukin (IL) 4, 10 and 6 together with the volume of gingival crevicular fluid (GCF) and total protein concentration in GCF could be used as correlative biomarkers for the severity in periodontitis as well as prognostic factors in the management of the disease. Methods: Forty-five participants were recruited and allocated to the healthy (15), Stage I-II (15) or Stage III-IV periodontitis (15) group. Along with periodontal examination, GCF samples were obtained at baseline and 4–6 weeks following scaling and root planing (SRP) for the periodontitis groups. GCF samples were analyzed by ELISA kits to quantify LL-37 and IL-4, -6 and − 10. One-way ANOVA followed by Dunnett’s test was used to determine differences among the three groups at baseline. Two-way ANOVA followed by Sidak’s post-hoc test was used to compare between pre- and post-SRP in the two periodontitis groups. Results: The amount of GCF volume was significantly correlated to the severity of periodontitis and decreased following SRP, particularly in the Stage III-IV group (p < 0.01). The levels of LL-37, IL-6, and pain and periodontal clinical parameters were significantly correlated to the severity of periodontitis. IL-4 and IL-10 in the periodontitis groups were significantly lower than the healthy group (p < 0.0001) and barely improved following SRP up to the level of the healthy group. Conclusions: With the limitations of this study, crevicular LL-37 may be a candidate for a biomarker of periodontitis and the associated pain upon probing. Trial registration: The study was registered in clinical trials.gov, with number NCT04404335, dated 27/05/2020

Antecedents and consequences of knowledge management performance: the role of IT infrastructure

Purpose: In this paper, we assess the role of knowledge management (KM) practices as a key antecedent of KM performance. Also, we examine how Information technology (IT) infrastructure is used as a driver of KM performance, organizational performance and innovation. In addition, the effects of IT infrastructure can be indirect. Specifically, we show that KM performance is a mediator between organizational performance and innovation. Design/methodology/approach: Applying a variance-based structural equation modelling (PLS), we have carried out a study among a sample of 82 Andalusian technology-intensive innovative companies. Findings: First, KM practices and IT infrastructure are significant antecedents of KM performance. Second, KM performance has a direct influence on business performance and innovation outcomes. Third, IT infrastructure does not have a direct influence on business performance and innovation outcomes, but does have a significant indirect effect on them via KM performance. Practical implications: This research provides insights for why some firms may not be realizing benefits from investing in IT infrastructure. KM performance is strongly needed for the successful implementation of IT infrastructure in the organizations. Originality/value: The findings are important for practitioners and researchers because this study makes a contribution to the literature in KM by supporting the perspective that the business and organizational performance are function of the KM performance, a complementary resource through the value of IT infrastructure is enhanced.Peer Reviewe

Effects of benzene and several pharmaceuticals on the growth and microcystin production in Microcystis ruginosa PCC 7806

Currently, the presence of several pharmaceuticals and other organic compounds called ‘emerging’ contaminants has increased in water bodies. These compounds do not need to persist in the environment to cause negative effects because they are continuously introduced. Hence, assessing the effects of these compounds on aquatic ecosystems is essential. Therefore, the aim of the present study was to analyse the effects of several emerging contaminants (ibuprofen, atenolol, diclofenac and paracetamol) and benzene on Microcystis aeruginosa PCC 7806 growth and toxicity. For this purpose, the growth and intracellular microcystin concentration in M. aeruginosa PCC 7806 were measured in presence of the four emerging contaminants and benzene. The growth rate was estimated by chlorophyll a concentration, and no relevant changes were found. Changes in the expression of the operon mcy were examined by semi-quantitative RT-PCR. Intracellular microcystin production was determined using a MicroCystest¿R kit, and no changes were observed compared to control cells. Thus, the tested concentrations of the contaminants analysed in this study do not have a significant effect on microcystin production in this strain under laboratory conditions

Shear bond strength of composite bonded to different treated dentin surfaces

Abstract no. 16published_or_final_versio

Bonding to Er-YAG laser-treated dentin

published_or_final_versio

Síndrome de Burnout en profesores de escuela y universidad: un análisis psicométrico y comparativo en la ciudad de Arequipa

In the present study, the manifestations of burnout syndrome in school and university professors living in the city of Arequipa were analyzed comparatively. A total of 413 intentionally selected professors were evaluated, and the Maslach Burnout Inventory was applied. It  yielded adequate levels of reliability for our sample and three factors obtained through confirmatory factorial analysis, confirming the theory of Maslach and Jackson (1981). It was found that there are significant differences in terms of sex, marital status and teaching level of teachers, resulting in higher levels of exhaustion for female teachers at school level and moderate levels of depersonalization for university teachers, in whom negative correlations were obtained regarding the number of children and the  burnout syndrome.En el presente estudio se analizaron comparativamente las manifestaciones del síndrome de burnout en profesores de escuela y de universidad, radicados en la ciudad de Arequipa. Se evaluó a un total de 413 profesores, que fueron seleccionados de manera intencional, y se les aplicó el Inventario de Burnout de Maslach, que arrojó adecuados niveles de confiabilidad para nuestra muestra y tres factores obtenidos mediante análisis factorial confirmatorio, que confirman la teoría de Maslach y Jackson (1981). Se encontró que existen diferencias significativas en función del sexo, el estado civil y el nivel de enseñanza de los profesores, resultando en mayores niveles de agotamiento para las profesoras de nivel escolar y niveles moderados de despersonalización para los profesores universitarios, en quienes se obtuvieron correlaciones negativas con el número de hijos y el síndrome de burnout