Predição da potência aeróbia (VO 2máx) de crianças e adolescentes em teste incremental na esteira rolante

The maximal oxygen uptake (VO2max) is the maximal quantity of energy that can be produced by the aerobic metabolism in certain time unity. It can be determined direct or indirectly by predictive equations. The objective of this study was to make a specific predictive equation to determine the VO 2max from boys aged 10-16 years-old. Forty-two boys underwent a treadmill running ergospirometric test, with the initial velocity set at 9 km/h, until voluntary exhaustion. By the multiple linear regression was possible to develop the following equation for the indirect determination of the VO 2max: VO2max (ml/min) = -1574.06 + (141.38 x Vpeak) + (48.34 * Body mass), with standard error of estimate = 191.5 ml/min (4.10 ml/kg/min) and coefficient of determination = 0.934. We suggest that this formula is appropriate to predict VO2max for this population.

Variabilidade de parâmetros eletromiográficos e cinemáticos em diferentes condições de marcha em idosos

The main goal of this study was to investigate the influence of fear of fall and dual task on electromyographic and kinematic variability parameters on the gait of older females. Seventeen college students (21,47 ± 2,06 years old) and eighteen older female adults, both groups were physically fit and performed the gait test on three different conditions: walking at self-select speed, fear of fall and dual task. Electromyographic activity was measured on muscles of dominant leg and stride time was recorded. ANOVA two-way (p<0.05) was used. Electromyographic and kinematic gait variability were higher in older adult groups. However, for the comparison between gait conditions was only found significant difference for electromyographic variability. In line with this, the higher EMG and kinematic variability in older adults suggest that aging contributes for a higher motor challenge while walking, which may be predispose these individuals a higher risk of fall.

Colombia: capital público y productividad de la industria manufacturera

Incluye Bibliografía

A simple derivation of the Lindblad equation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desarrollo productivo en economías abiertas

Incluye Bibliografía

Productive development in open economies

Includes bibliography

Braneworlds scenarios in a gravity model with higher order spatial three-curvature terms

In this work we study a Hořava-like 5-dimensional model in the context of braneworld theory. The equations of motion of such model are obtained and, within the realm of warped geometry, we show that the model is consistent if and only if λ takes its relativistic value 1. Furthermore, we show that the elimination of problematic terms involving the warp factor second order derivatives are eliminated by imposing detailed balance condition in the bulk. Afterwards, Israel's junction conditions are computed, allowing the attainment of an effective Lagrangian in the visible brane. In particular, we show that the resultant effective Lagrangian in the brane corresponds to a (3 + 1)-dimensional Hořava-like model with an emergent positive cosmological constant but without detailed balance condition. Now, restoration of detailed balance condition, at this time imposed over the brane, plays an interesting role by fitting accordingly the sign of the arbitrary constant β, insuring a positive brane tension and a real energy for the graviton within its dispersion relation. Also, the brane consistency equations are obtained and, as a result, the model admits positive brane tensions in the compactification scheme if, and only if, β is negative and the detailed balance condition is imposed. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Quasi-homologous spherically symmetric branes and their symmetry breaking

We revisit the dynamical system-based approach of spherically symmetric vacuum braneworlds, pointing out and studying the existence of a transcritical bifurcation as the dark pressure parameter changes its sign, we analyze some consequences of not discard the brane cosmological constant. For instance, it is noteworthy that the existence of an isothermal state equation between the dark fluid parameters cannot be obtained via the requirement of a quasi-homologous symmetry of the vacuum. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Composição de cores através da calibração radiométrica e fotométrica de LEDs: Teoria e experimento

In the present work, the basic concepts of radiometric, photometric and colorimetric calibration are presented, which were applied to three light-emitting diodes (LEDs) used to compose the different color sensations that the human eye perceives in the visible region of the electromagnetic spectrum. In this sense, an experimental setup comprising a LED drive circuit and a home-made integrating sphere was assembled for the initial radiometric and photometric calibration as well as to obtain a set of intensity and spectral combinations associated to different colorimetric CIE (Commission Internationale de l'Eclairage) coordinates. The reader can, therefore, understand, in a simple manner, the process of color composition inside a color monitor or display picture element (pixel ). © Sociedade Brasileira de Física.

Modelo de Marcus, elementos de matriz de tunelamento, efeitos de solvente e controle nuclear em reações de transferência de elétrons

This paper aims to give an initial presentation to physics students of the area of electron transfer, addressing its major aspects. The subject is then presented in an introductory way, highlighting and discussing the key points. Primarily, the problem is approached in a simplified manner through a two-state system, and aspects of calculating the matrix-element are discussed. Then, the electron transfer problem, influenced by nuclear reaction coordinates, is addressed and treated by the Marcus theory. Time scales and the concepts of adiabatic and nonadiabatic phenomena are discussed in the context of electron transfer. The classical, semi-classical and quantum formalisms of for the nuclear reactions coordinates are presented, and aspects of solvents are also discussed. Finally, we conclude by examining some recent examples of problems discussed in the literature.

An experimental verification of newton's second law

We describe an experimental procedure to probe the validity of Newton's second law. The experimental arrangement allows us to accelerate a glider on an air track by means of forces that are both steady and known. We also show how to determine acceleration from average speeds calculated for successive time intervals of the motion measured by using several electronic counters connected to a single-crystal oscillator circuit. Within experimental errors, the experiments clearly show the proportionality between acceleration and force for a fixed mass and between acceleration and inverse of mass for a fixed force. © by the Sociedade Brasileira de Física.

Influência da aptidão aeróbia no running anaerobic sprint test (RAST)

The aim of this study was to investigate the possible influence of different levels of aerobic fitness (VO2MAX) on the parameters of the running anaerobic sprint test (RAST). Thirty-eight subjects (Age = 18.1 ± 2.5 years, Height = 173 ± 1 cm and Body mass = 65.1 ± 6.5 kg) were classified into two groups, low and high aerobic fitness (LAF: n = 22 and HAF: n = 16). The VO2MAX was determined by an incremental exercise performed until exhaustion. The RAST was composed of six maximal efforts of 35m separated by 10s passive recovery. The VO2MAX was significantly different between groups (LAF = 51.7 ± 1.9 mL.kg -1.min-1; HAF = 58.6 ± 3.1 mL.kg -1.min-1). The mean power (MP) was significantly higher in the LAF (552.7 ± 132.1 W) in relation to the HAF group (463.6 ± 132.8 W). The impulse (ImP) was significantly correlated with the VO 2MAX in HAF. It can be concluded that there is an indication that the aerobic metabolism exerts an influence on the completion of RAST.

Nível de atividade física, comorbidades e idade de pacientes hipertensos

Physical inactivity is associated with chronic diseases in older adults. There are different domains of physical activity, such as leisure and locomotion. This study investigate the associations between different domains of physical activity, comorbidities and aging in hypertensive adults. Participants included 192 hypertensive respondents classified in groups of active and insufficiently active for leisure-time, locomotion, occupation and total time. They were stratified in age groups. Waist circumference was measured and comorbidities were self-reported. The chi-square test analyzed these associations; a one-way ANOVA compared the age groups (significance at p <0.05). The mean total time and occupational physical activity were lower for groups ages over 60 and 70 years, respectively. Occupational activity was associated with age in the female group, and with cholesterol and diabetes in males, who also had physical activity of locomotion associated with waist circumference. Physical activity of hypertensive patients is associated with comorbidities in different age groups and sex.

Estabilidade locomotora durante a condução de um cão

The purpose of this study was to evaluate how walking a dog on a leash influenced haptic perception and stability during human locomotion. Fourteen adults, with and without sight restriction, walked on a narrow balance beam by themselves, or holding a leash attached to a dog that walked on a parallel narrow bench. The performance of participants who walked with the dog, but blindfolded, significantly (p < 0.05) improved as compared to the condition without the dog. Their locomotion performance was assessed via the duration of the total displacement on the balance beam, durations of the double support phase, swing phase, stepping cycle, stepping length, and linear velocity, as well as variability of the inter-limb relative phase. With vision, these parameters were not affected by the presence of the dog. We conclude that these adults were able to use the dog's leash to detect haptic properties in order to achieve postural control (e.g., stability in speed performance) while walking.

Experiência subjetiva de idosas durante exercício em ambiente virtual

This quali-quantitative study aimed to verify subjective exercise experiences of older women before and after exercise sessions in actual and virtual conditions, as well as, the preferred exercise condition. The sample was composed by 20 older women (71.1±6.5 years-old) who practiced dance sessions in actual and virtual conditions, and answered the Subjective Exercise Experiences Scale (SEES) before and after the activity. In virtual condition it was used the virtual game Just Dance I from the Nintendo Wii® console. In actual condition participants reproduced the same game movements, as demonstrated by the researcher. Wilcoxon and Mann-Whitney tests were used for data analyses (p<0.05). Significant decrease was observed in the psychological distress score of SEES after both conditions. Increase in positive well being score was found only in the virtual condition. Most of the older women chose the actual condition as the preferred.