Fluid balance of elite Brazilian youth soccer players during consecutive days of training

In this study we investigated pre-training hydration status, fluid intake, and sweat loss in 20 elite male Brazilian adolescent soccer players (mean?±?s: age 17.2?±?0.5 years; height 1.76?±?0.05?m; body mass 69.9?±?6.0?kg) on three consecutive days of typical training during the qualifying phase of the national soccer league. Urine specific gravity (USG) and body mass changes were evaluated before and after training sessions to estimate hydration status. Players began the days of training mildly hypohydrated (USG?>?1.020) and fluid intake did not match fluid losses. It was warmer on Day 1 (33.1?±?2.4°C and43.4?±?3.2% relative humidity; P?相似文献   

Magnetophoretic manipulation in microsystem using carbonyl iron-polydimethylsiloxane microstructures

This paper reports the use of a recent composite material, noted hereafter i-PDMS, made of carbonyl iron microparticles mixed in a PolyDiMethylSiloxane (PDMS) matrix, for magnetophoretic functions such as capture and separation of magnetic species. We demonstrated that this composite which combine the advantages of both components, can locally generate high gradients of magnetic field when placed between two permanent magnets. After evaluating the magnetic susceptibility of the material as a function of the doping ratio, we investigated the molding resolution offered by i-PDMS to obtain microstructures of various sizes and shapes. Then, we implemented 500 μm i-PDMS microstructures in a microfluidic channel and studied the influence of flow rate on the deviation and trapping of superparamagnetic beads flowing at the neighborhood of the composite material. We characterized the attraction of the magnetic composite by measuring the distance from the i-PDMS microstructure, at which the beads are either deviated or captured. Finally, we demonstrated the interest of i-PDMS to perform magnetophoretic functions in microsystems for biological applications by performing capture of magnetically labeled cells.     

Reification and recognition in teenage years in the contemporary world: An interpretation based on a critical look at Axel Honneth's theses

Abstract

This article seeks to explore the theoretical contributions of Axel Honneth, particularly in his works, The Struggle for Recognition and Reification, aiming at diving deep into the debate on the contemporary ideological expressions and their incidence in the process of subjective constitution in teenage years. This particular interest springs from the need to interweave the concepts of reification, forgetfulness and recognition within a fruitful theoretical field in order to interpret a project work called Hip-Hop: cultures and identities, developed with teenagers in a public school in the city of São Paulo, Brazil. From our point of view, the concepts of reification and forgetfulness are fundamental to identify how the conservative ideological expressions are present in the imaginary of adolescents in the contemporary world. Although rereading the concepts of reification and forgetfulness, as proposed by the author, is regarded as essential for understanding the ideological expressions that are based on and guided by consumption. However, even though we acknowledge Honneth's efforts toward moving forward with the concept of reification, it is crucial to emphasize the mediation concept Lukács explored in his work, History and Class Consciousness, so as to elucidate how the forgetfulness of the primary recognition relations is processed.     

Validity of a device designed to measure braking power in bicycle disc brakes

Real-world cycling performance depends not only on exercise capacities, but also on efficiently traversing the bicycle through the terrain. The aim of this study was to determine if it was possible to quantify the braking done by a cyclist in the field. One cyclist performed 408 braking trials (348 on a flat road; 60 on a flat dirt path) over 5 days on a bicycle fitted with brake torque and angular velocity sensors to measure brake power. Based on Newtonian physics, the sum of brake work, aerodynamic drag and rolling resistance was compared with the change in kinetic energy in each braking event. Strong linear relationships between the total energy removed from the bicycle-rider system through braking and the change in kinetic energy were observed on the tar-sealed road (r² = 0.989; p < 0.0001) and the dirt path (r² = 0.952; p < 0.0001). T-tests revealed no difference between the total energy removed and the change in kinetic energy on the road (p = 0.715) or dirt (p = 0.128). This study highlights that brake torque and angular velocity sensors are valid for calculating brake power on the disc brakes of a bicycle in field conditions. Such a device may be useful for investigating cyclists’ ability to traverse through various terrains.     

Influences of population size and density on birthplace effects

Contextual influences on talent development (e.g., birthplace effects) have become a topic of interest for sport scientists. Birthplace effects occur when being born in a certain city size leads to participation or performance advantages, typically for those born in smaller or mid-sized cities. The purpose of this study was to investigate birthplace effects in Portuguese volleyball players by analysing city size, as well as population density – an important but infrequently used variable. Participants included 4062 volleyball players (M_age = 33), 53.2% of whom were men. Using Portuguese national census data from 1981, we compared participants (within each sex) across five population categories. In addition, we used ANOVAs to study expertise and population density. Results indicated that men and women athletes born in districts of 200,000–399,999 were 2.4 times more likely to attain elite volleyball status, while all other districts decreased the odds of expert development. For men, being born in high-density areas resulted in less chance of achieving expertise, whereas there were no differences for women. The results suggest that athletes’ infrastructure and social structure play an important role in talent development, and that these structures are influenced by total population and population density, respectively.     

Long- and Short-Term Portfolio Choices of Paintings

In their paper on price comovements of paintings, Ginsburgh and Jeanfils show that in three important markets (London, Paris and New York), prices of well-known and lesser known painters 'move together' (are cointegrated). They conclude that therefore, an investor may be indifferent between the two groups of painters. We show that this is not the case, since well-known painters are less risky, and that though returns may be comparable, the share of well-known painters in a portfolio of paintings might be as high as 90%. We also construct long-run and short-run portfolios and show that these may be very different. These short-term portfolios give interesting insights which help in characterizing each of the three markets.     

Early Nonparental Care and Social Behavior in Elementary School: Support for a Social Group Adaptation Hypothesis

This study examined the contribution of nonparental child‐care services received during the preschool years to the development of social behavior between kindergarten and the end of elementary school with a birth cohort from Québec, Canada (N = 1,544). Mothers reported on the use of child‐care services, while elementary school teachers rated children's shyness, social withdrawal, prosociality, opposition, and aggression. Children who received nonparental child‐care services were less shy, less socially withdrawn, more oppositional, and more aggressive at school entry (age 6 years). However, these differences disappeared during elementary school as children who received exclusive parental care caught up with those who received nonparental care services. This “catch‐up” effect from the perspective of children's adaptation to the social group is discussed.