Thermodynamics, transition dynamics, and texturing in polymer-dispersed liquid crystals with mesogens exhibiting a direct isotropic/smectic-A transition

Experimental and modeling/simulation studies of phase equilibrium and growth morphologies of novel polymer-dispersed liquid crystal (PDLC) mixtures of PS (polystyrene) and liquid crystals that exhibit a direct isotropic/smectic-A (lamellar) mesophase transition were performed for PS/10CB (decyl- cyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl). Partial phase diagrams were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) for different compositions of both materials, determining both phase separation (liquid/liquid demixing) and phase ordering (isotropic/smectic-A transition) temperatures. The Flory-Huggins theory of isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid crystalline ordering were used to computationally determine phase diagrams for both systems, showing good agreement with the experimental results. In addition to thermodynamic observations, growth morphology relations were found depending on phase transition sequence, quench rate, and material composition. Three stages of liquid crystal-rich domain growth morphology were observed: spherical macroscale domain growth ("stage I"), highly anisotropic domain growth ("stage II"), and sub-micron spheroid domain growth ("stage III"). Nano-scale structure of spheroidal and spherocylindrical morphologies were then determined via two-dimensional simulation of a high-order Landau-de Gennes model. Morphologies observed during stage II growth are typical of di- rect isotropic/smectic-A phase transitions, such as highly anisotropic "batonnets" and filaments. These morphologies, which are found to be persistent in direct isotropic/smectic-A PDLCs, could provide new functionality and applications for these functional materials.Comment: First Revision, 21 pages, 11 figures, submitted to Macromolecules as an article 17JUL200

Thermodynamic Modelling of Phase Equilibrium in Nanoparticles-Nematic Liquid Crystals Composites

In this work, a theoretical study of phase equilibrium in mixtures of a calamitic nematic liquid crystal and hard spherical nanoparticles is presented. A mean-field thermodynamic model is used, where the interactions are considered to be proportional to the number of contacts, which in turn are proportional to the areas and area fractions of each component. It is shown that, as the radius of the particle is increased, the effect of the particles on the isotropic-nematic transition is less pronounced, and that for large radius the miscibility increases as the particle radius increases.Comment: This is an Author's Accepted Manuscript of an article published in "Molecular Crystals and Liquid Crystals" (see reference), available online at: http://www.tandfonline.com/doi/abs/10.1080/15421406.2011.60944

Multiple interfaces in diffusional phase transitions in binary mesogen-non-mesogen mixtures undergoing metastable phase separations

Theory and simulations of simultaneous chemical demixing and phase ordering are performed for a mixed order parameter system with an isotropic-isotropic (I-I) phase separation that is metastable with respect to an isotropic-nematic (I-N) phase ordering transition. Under certain conditions, the disordered phase transforms into an ordered phase via the motion of a double front containing a metastable phase produced by I-I demixing, a thermodynamically driven mechanism not previously reported. Different kinetic regimes are found depending on the location of the initial conditions in the thermodynamic phase diagram and the ratio between diffusional and nematic phase ordering mobilities. For a diffusional process, depending if the temperature is above or below the critical co-dissolution point, an inflection point or a phase separation takes place in the depletion layer. This phase separation leads to the formation of a second interface where the separation of the two metastable isotropic phases grows monotonically with time. The observed deviations from the typical Fickian concentration profiles are associated with strong positive deviations of the mixture from ideality due to couplings between concentration and nematic ordering. Although systems of interest include liquid crystalline nanocomposites, this novel mechanism may apply to any mixture that can undergo an order-disorder transition and demix.Comment: 24 pages, 8 figures, final accepted authors version, published version in http://pre.aps.org/abstract/PRE/v86/i1/e01160

Effects of Copenhagen Adduction Exercise on the Architectural Characteristics of Adductors in U-17 Male Soccer Players : A Randomized Controlled Trial

[Abstract] Groin injuries are one of the most prevalent in male soccer players, especially due to the hip adductor muscles’ weakness which is considered as a risk factor in these injuries. The Copenhagen adduction (CA) exercise has been demonstrated to increase the strength of adductor muscles, but its effects on the architectural characteristics of adductor muscles have not been studied yet. This study aimed to analyze the effects of the CA exercise on the muscle thickness of the adductors. Twelve male U-17 soccer players were randomized into two groups: the control group with no intervention and the experimental group with an intervention based on an eight-week training with CA exercise. The muscle thickness of adductors was measured before and after the intervention using ultrasound imaging. A significant increase in muscle thickness was found in both control (p = 0.002) and experimental group (p < 0.001), but the experimental group did not show additional effects in comparison with the control group. In conclusion, an 8-week CA exercise intervention does not increase the muscle thickness of adductors in U-17 soccer players more than their regular training

Interrater Reliability of the Test of Gross Motor Development—Third Edition Following Raters’ Agreement on Measurement Criteria

We aimed to calculate interrater reliability of the Test of Gross Motor Development—Third Edition (TGMD-3) after raters reached a consensus regarding measurement criteria. Three raters measured the fundamental movement skills of 25 children on the TGMD-3 at two different times: (a) once when simply following the measurement criteria in the TGMD-3 manual and (b) after a 9-month washout period, following the raters’ consensus building for the measurement criteria for each skill. After calculating and comparing the interrater reliability of these three raters across these two rating times, we found improved interrater reliability after the raters’ consensus-building discussions on ratings of both locomotor skills (moderate-to-good reliability on two of six skills initially and at least moderate-to-excellent on four of six skills following criteria consensus building) and ball skills (moderate-to-good reliability on one of seven skills initially and at least moderate-to-excellent reliability on four of seven skills following criteria consensus building). For subtest scores and overall test scores, raters achieved at least moderate-to-good reliability on their second, postconsensus-building ratings. Based on this improved reliability following consensus building, we recommend that researchers include rater consensus building before assessing children’s fundamental movement skills or guiding curriculum interventions in physical education from TGMD-3 data.This work was supported by MCIN/AEI/10.13039/501100011033/ and European Regional Development Fund (ERDF), a way to make Europe, under grant PID2021-128640OB-I00. Carballo-Fazanes was supported by the Spanish Ministry of Science, Innovation and Universities under grant FPU19/02017. This study was approved by the Ethical Committee of the Faculty of Education and Sport Sciences of the University of Vigo, Spain.S

Evaluation of the protective capacity of the novel vaccine strain Delta-pgm in bovines

La brucelosis bovina es una zoonosis ampliamente distribuida en el mundo y que continúa produciendo importantes pérdidas económicas y problemas de salud en humanos. Si bien existen varias vacunas que inducen diversos grados de protección, cada una de ellas posee una o más desventajas, que van desde una baja capacidad para inducir un nivel adecuado de inmunidad hasta interferencias con los métodos de diagnóstico de rutina actualmente utilizados en la lucha contra la enfermedad. Por estos motivos sigue siendo importante el desarrollo de nuevas vacunas que posean ventajas con respecto a las que se encuentran disponibles en el mercado. En este trabajo se presentan los resultados de una prueba de potencia en bovinos en la que se compara la capacidad protectiva de la cepa Delta-pgm con la de la S-19, cepa empleada en la Argentina, en la actualidad. Se analizaron diversos parámetros de protección sobre 32 animales vacunados con las dos cepas sujetas a comparación o no vacunados: serología de los animales durante toda la experiencia, bacteremia por hemocultivo de las madres, tiempo de gestación, estado de los terneros al parto (vivos, muertos, prematuros) y excreción en leche. Los resultados mostraron que la cepa Delta-pgm aplicada en dos dosis (una antes de los 6 meses de edad y un refuerzo de adultos) no genera interferencia con los actuales métodos diagnósticos de la enfermedad e induce un grado de protección al menos equivalente al generado por la cepa S-19. Nuestros resultados indican que Delta-pgm podría ser una potencial nueva herramienta para la vacunación de animales adultos.Fil: Comerci, Diego José. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentina. Universidad Nacional de San Martín; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rey Serantes, Diego. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Carballo, Ezequiel. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Paramidani, Eduardo. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Bagnat, Eduardo. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Ugalde, Juan Esteban. Universidad Nacional de San Martín; Argentina. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentin

No sport for old players. A longitudinal study of aging effects on match performance in elite soccer

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGObjectives: This study aimed to examine the effects of age on match-related physical and technical–tactical performance in elite soccer players using a longitudinal design. Methods: Data were collected from 154 players who competed in the Spanish first division (LaLiga) between the 2012–13 and 2019–20 seasons. A total of 14,092 individual match observations were analyzed using a computerized tracking system (TRACAB, Chyronhego, New York, NY). The players were classified into five positional roles: central defenders (n = 37); external defenders (n = 44); central midfielders (n = 34); external midfielders (n = 22); and forwards (n=17). Results: The main results showed that (a) soccer players decreased by an average of 0.56% their total distance covered for each year that they got older. Similarly, the number of high-intensity efforts and distance covered at high-intensity running decreased by 1.80% and 1.42% per year, respectively; (b) players significantly increased their pass accuracy by an average of 0.25% each year that they got older; (c) the detrimental effect of age on total distance and high-intensity runningwas greater for external defenders, external midfielders, and forwards; and (d) the positive effect of age on pass accuracy was greater for central defenders and central midfielders. Conclusions: Elite soccer players with long-term careers were unable to maintain their match-related physical performance as they got older. However, players can annually improve their technical–tactical skills with increasing age as a possible compensation mechanism against physical performance declines related to aging

Reliability and usefulness of the 30-15 intermittent fitness test in male and female professional futsal players

The purpose of this study was to determine the reliability and usefulness of the 30-15 Intermittent Fitness Test (30-15IFT) in professional male and female futsal players. Thirteen male (24.4 ± 5.6 years; 174.5 ± 10.3 cm; 70.3 ± 9.9 kg) and fourteen female (23.3 ± 4.5 years; 165.8 ± 6.2 cm; 61.7 ± 5.5 kg) professional futsal players performed the 30-15IFT on two occasions, separated by 5 days. Maximal intermittent running velocity (VIFT) and heart rate at exhaustion (HRpeak) data were collected for both tests. Reliability was assessed by the intraclass correlation coefficient (ICC), typical error (TE) expressed as a coefficient of variation (CV), and smallest worthwhile change (SWC). VIFT demonstrated very good reliability between sessions, both for male (ICC = 0.92) and female (ICC = 0.96) players. As the TE for VIFT and HRpeak was similar to the calculated SWC for both male and female players, the usefulness of the test was rated as “medium”. A change in performance of at least 2 stages in male players, or a change of more than 1 stage in female players could be interpreted as a meaningful change in aerobic futsal fitness. The results of this study demonstrate that the 30-15IFT is both a reliable and useful test for male and female professional futsal players

Medición del aprendizaje organizacional en las grandes y medianas empresas de Sogamoso, Colombia

Artículo de investigaciónEl presente artículo expone los resultados de la investigación titulada “Estudio de aprendizaje organizacional en las medianas y grandes empresas de la ciudad de Sogamoso en Boyacá - Colombia”. Se referirá a las características de los procesos de gestión del Aprendizaje Organizacional (AO), los factores positivos y negativos del mismo y la identificación de las causas e impactos relevantes del Aprendizaje Organizacional en estas compañías. Con base en esto, presentará una breve propuesta de mejoramiento. En el estudio, llevado a cabo por el grupo de investigación Management de la Universidad Pedagógica y Tecnológica de Colombia, se encuestó 43 empresas objeto de estudio (25 medianas y 18 grandes empresas), dando cuenta de 1333 encuestas, distribuidas entre los 43 gerentes y 1290 empleados de las compañías (30 por cada entidad). En lo que tiene que ver con la parte metodológica, el tipo y método de estudio fue el descriptivo e inductivo; la técnica estadística utilizada fue el análisis descriptivo por medio de tablas de frecuenci