Zener fractional order determination and biomechanical blood flow characterization

El propósito principal de la presente publicación consiste en la determinación adecuada del orden fraccional en el modelo viscoelástico de Zener y el análisis de las implicaciones que se derivan de la precisión en la obtención del mismo. Esto se realiza empleando el método numérico de Levenberg-Marquardt a partir de valores reportados en la literatura. Los parámetros utilizados son obtenidos para un segmento de arteria empleando un experimento de relajación a los esfuerzos. Una vez determinado el orden fraccional se procede a determinar la solución del modelo empleando la función de dos parámetros de Mittag-Leffler y la operación de convolución, con la finalidad de comparar el comportamiento del modelo de orden fraccional con el de orden entero e identificar sus principales diferencias. Se obtienen además las deformaciones que experimenta la arteria bajo el estímulo de un pulso sanguíneo normal y otros disímiles, simulando el efecto provocado en el flujo sanguíneo por una arritmia y el ocasionado por el proceso de ventilación mecánica. Por último se analiza la respuesta dinámica del material bajo una serie de pulsos, utilizando la operación de convolución y el método numérico de Gauss-Kronrod, identificando la precisión en la reproducción de los mismos en el modelo de orden fraccional comparado con el de orden entero.The main purpose of this publication is the proper determination of the fractional order at the Zener viscoelastic models and the analysis of the implications derived from the accuracy in obtaining this. The procedure is performed using the numerical method of Levenberg-Marquardt from values reported in the literature. The parameters used are obtained from an artery segment using a stress relaxation test. After determining the fractional order is proceeded to find the model solution using, the function of Mittag-Leffler with two parameters and the convolution operation in order to compare the behavior of the fractional model vs the integer order and identify their key differences. The displacements present on the artery are obtained, under the stimulus of a normal blood pulse and two dissimilar, simulating the effect in blood flow caused by an arrhythmia and by mechanical ventilation process. Finally the dynamic response from the pulses is analyzed using the convolution operation and Gauss Kronrod numeric method, where the solutions accuracy obtained by the fractional model is observed, an compared with the integer order model.Peer Reviewe

Editorial: Coaches' role in youth sports performance: early specialization versus long-term development

Youth sports are planned sports programs for children and adolescents with designated coaches, organized practices, and scheduled competitions. Such programs can be organized and implemented at schools (by physical education teachers instead of coaches), as well as in other sports organizations (i.e., federations, associations, local clubs). Primary aim should be to focus on providing young athletes with fundamental motor skills in tandem to their maturation stage. Indeed, these programs are aimed at mass participation rather than on developing elite athletes. The participation in such programs during childhood and adolescence showed to have major benefits in children’s and adolescent’s physical, psychological, and social development. On the other hand, youth sports programs can also serve as a link to talent identification and development programs aiming to identify young athletes with potential for success in adult/elite sport. As they aremass orientated,many youth athletes can be observed which will increase the likelihood of talent identification. Afterwards, these athletes can be guided to high-performance programs aiming to achieve eventually an elite level.info:eu-repo/semantics/publishedVersio

Stability analysis and prediction of pacing in elite 1500 m freestyle male swimmers

This study aimed to analyse the stability of elite male long-distance swimmers (1500 m), and to identify the main predictors related to the pace. The performance of 16 elite male swimmers (22.59 ± 2.10 years-old) participating in the 1500 m event at the 2016 (London) and 2018 (Glasgow) LEN European Aquatic Championships were analysed. The lap performance, clean swim performance, turn performance, and a set of stroke mechanics variables were assessed. The lap performance presented a significant and moderate variation with all laps included (p < 0.001) and deleting the first and last lap (p = 0.002). Swimmers were significantly faster in the first half in comparison of the second. The total turn also presented a significant and moderate variation. The hierarchical linear modelling retained the time (estimate = 0.0019, p = 0.007), stroke frequency (estimate = -27.49, p < 0.001) and stroke length (estimate = -6.55, p < 0.001) as the main predictors of the clean swim performance. By contrast to the analysis based on the lap performance, clean swim performance presented a non-significant variation. Coaches should be aware that stroke length maintenance could negatively affect the clean swim performance, whereas a small increase of stroke frequency may present a meaningful enhancement of the total race time.This project was supported by the National Funds through FCT - Portuguese Foundation for Science and Technology [UIDB/DTP/04045/2020]info:eu-repo/semantics/publishedVersio

The contour method for residual stress determination applied to an AA6082-T6 friction stir butt weld

Residual stresses parallel to the welding direction on a cross-section of a 3 mm thick friction stir butt-welded aluminium alloy AA6082-T6 plate were determined using the contour method. This is a destructive relaxation based measurement technique capable of determining the full- eld residual stresses perpendicular to a plane of interest. A wire electro discharge machining cut was performed revealing the plane of interest. The residual stresses present before the straight cut lead to a deformed cutting plane. Then, a coordinate measuring machine was used to acquire the cutting plane shape of both plate halves after the cut. A data reduction scheme for noise and error elimination was used. The measured deformation was applied to a linear elastic nite elements model considering the real specimen geometry. A full contour map of longitudinal residual stresses on a weld cross section was determined in this way, revealing detailed information on the residual stress distribution in the inside of a friction stir weld, especially in the nugget zone. A typical M-shape, usually described for the residual stress distribution in friction stir welds, was found. The maximum residual stresses are below the yield strength of the material in the shoulder region and, outside of the welding region, low tensile and compressive residual stresses are responsible for the necessary stress equilibrium on the plane of interest. A comparison was made with the established incremental hole drilling technique on an equivalent plate for validation and good agreement of both techniques was obtained. The distribution, as well as the magnitude of the residual stresses measured by both techniques, is very similar, thus validating both the experimental and numerical procedures used for the contour method application, which is presented and discussed in the paper.The present work was partially funded by the project PTDC/EME-TME/66362/2006 and PhD scholarship SFRH / BD / 41061 / 2007 of the Portuguese Fundação para a Ciência e Tecnologia. Dr. P. Moreira acknowledges POPH - QREN-Tipologia 4.2 - Promotion of scientific employment funded by the ESF and MCTES. The help of José Fernando Rocha Almeida is also acknowledged

NOD2 Modulates Serotonin Transporter and Interacts with TLR2 and TLR4 in Intestinal Epithelial Cells

Background/Aims: Serotonin (5-HT) is a chief modulator of intestinal activity. The effects of 5-HT depend on its extracellular availability, which is mainly controlled by serotonin transporter (SERT), expressed in enterocytes. On the other hand, innate immunity, mediated by Toll-like receptors (TLRs) and nucleotide oligomerization domain (NOD)-like receptors (NLRs), is known to control intestinal microbiota and maintain intestinal homeostasis. The dysregulation of the intestinal serotonergic system and innate immunity has been observed in in ammatory bowel diseases (IBD), the incidence of which has severely increased all over the world. The aim of the present study, therefore, was to analyze the effect of NOD2 on intestinal SERT activity and expression, as well as to study the crosstalk of NOD2 with TLR2 and TLR4. Methods: Intestinal epithelial cell line Caco-2/TC7 was used to analyze SERT activity and SERT, NOD2, TLR2 and TLR4 molecular expression by real-time PCR and western blotting. Moreover, intestinal tract (ileum and colon) from mice de cient in TLR2, TLR4 or TLR2/4 receptors was used to test the interdependence of NOD2 with these TLR receptors. Results: NOD2 activation inhibits SERT activity in Caco-2/TC7 cells, mainly due to the decrement of SERT molecular expression, with RIP2/RICK being the intracellular pathway involved in this effect. This inhibitory effect on SERT would yield an increment of extracellular 5-HT availability. In this sense, 5-HT strongly inhibits NOD2 expression. In addition, NOD2 showed greater interdependence with TLR2 than with TLR4. Indeed, NOD2 expression signi cantly increased in both cells treated with TLR2 agonists and the intestinal tract of Tlr2-/- mice. Conclusions: It may be inferred from our data that NOD2 could play a role in intestinal pathophysiology not only through its inherent innate immune role but also due to its interaction with other receptors as TLR2 and the modulation of the intestinal serotonergic system decreasing SERT activity and expression

Top-down structures of mafic enclaves within the Valle Fértil magmatic complex (Early Ordovician, San Juan, Argentina)

Magmatic structures related to the mechanical interaction between mafic magmas and granitoids have been studied in the Valle Fértil calc-alkaline igneous complex, Argentina. Excepcional outcrops with vertical walls of more than 300 m high allow us the study of three-dimensional geometries of individual blobs of mafic magma as well as the geometry of pipe-like structures in which mafic microgranular enclaves are concentrated in more than 50 times the normal abundance in the granodiorite mass. The shape of enclaves and pipe-like structures are interpreted as the ressult of top-to-down intrusions of a mafic magma into a granodiorite-tonalite mass. These sinking structures are the result of a reverselly stratified magma chamber with gabbros and diorites at the top and granodiorite-tonalite at the bottom. They may account for most of the structures found in microgranular enclaves and magma mingling zones that characterize calc-alkaline batholiths. Synplutonic intrusions from the top is the only plausible mechanism to account for the observed structures. The model may be of general application to calc-alkaline batholiths characterized by the presence of mafic microgranular enclaves. An implication of these reverselly stratified magma chambers is the presence of a petrological inversion which may be the consequence of cold diapirs emplaced below the mantle wedge in a suprasubduction setting

Toll-like receptor 9 modifies intestinal serotonergic system.

Introduction: Toll-like receptor 9 (TLR9) is expressed in intestinal epithelial cells, which recognize microbiota developing different responses 1. Several studies have shown that TLR9 seems to be involved in Inflammatory Bowel Diseases (IBD) due to an inappropriate defensive response against microorganisms 2. Moreover, intestinal serotonergic system is also altered in IBD, where extracellular serotonin (5–HT) levels are increased 3. 5-HT bioavailability is mainly regulated by the serotonin transporter (SERT), expressed in enterocytes 4. Aims & Methods: The aim of the present study was to analyse whether TLR9 activation affects SERT expression and activity, and expression of other elements from the serotonergic system (TPH1, TPH2 and 5-HT receptors). Human enterocyte-like Caco-2 cells, and ileum and colon from TLR9-/- mice and Dextran Sulphate Sodium (DSS) mouse colitis model were used as experimental models. mRNA expression was determined by RT-qPCR, and protein expression by western blot..