Some applications of quasi-velocities in optimal control

In this paper we study optimal control problems for nonholonomic systems defined on Lie algebroids by using quasi-velocities. We consider both kinematic, i.e. systems whose cost functional depends only on position and velocities, and dynamic optimal control problems, i.e. systems whose cost functional depends also on accelerations. The formulation of the problem directly at the level of Lie algebroids turns out to be the correct framework to explain in detail similar results appeared recently (Maruskin and Bloch, 2007). We also provide several examples to illustrate our construction.Comment: Revtex 4.1, 20 pages. To appear in Int. J. Geom. Meth. Modern Physic

A sufficient condition for confinement in QCD

This letter is about confinement in QCD. At the moment we have pictures of confinement to complete our understanding of the physics of strongly interacting particles, interaction which asks for confinement.As it is said in [1] : " In principle it should be possible to derive the confinement hypothesis from the QCD Lagrangian. At this time, no rigorous derivation exists, so it is not absolutely clear that the confinement hypothesis is a bone fide prediction of QCD" . In this letter we show that a sufficient (of course not necessary) condition for confinement is that topological structure of vacuum in Nature does not correspond to the $\theta$-vacuum. Therefore, if different vacua with nontrivial winding number cannot be connected by tunneling, we obtain confinement as a consequence.Comment: 10 page

Effective nonlinear Ehrenfest hybrid quantum-classical dynamics

The definition of a consistent evolution equation for statistical hybrid quantum-classical systems is still an open problem. In this paper we analyze the case of Ehrenfest dynamics on systems defined by a probability density and identify the relations of the non-linearity of the dynamics with the obstructions to define a consistent dynamics for the first quantum moment of the distribution. This first quantum moment represents the physical states as a family of classically-parametrized density matrices $\hat \rho(\xi)$, for $\xi$ a classical point; and it is the most common representation of hybrid systems in the literature. Due to this obstruction, we consider higher order quantum moments, and argue that only a finite number of them are physically measurable. Because of this, we propose an effective solution for the hybrid dynamics problem based on approximating the distribution by those moments and representing the states by them.Comment: 21 pages. Minor correction in the list of affiliation

Hybrid Koopman C*-formalism and the hybrid quantum-classical master equation

Based on Koopman formalism for classical statistical mechanics, we propose a formalism to define hybrid quantum-classical dynamical systems by defining (outer) automorphisms of the C*-algebra of hybrid operators and realizing them as linear transformations on the space of hybrid states. These hybrid states are represented as density matrices on the Hilbert space obtained from the hybrid C*-algebra by the GNS theorem. We also classify all possible dynamical systems which are unitary and obtain the possible hybrid Hamiltonian operators.Comment: 20 page

Isokinetic leg strength and power in elite handball players

Isokinetic strength evaluation of the knee flexion and extension in concentric mode of contraction is an important part of the comprehensive evaluation of athletes. The aims of this study were to evaluate the isokinetic knee peak torque in both the extension and flexion movement in the dominant and non-dominant leg, and the relationship with jumping performance. Twelve elite male handball players from the top Spanish handball division voluntary participated in the study (age 27.68 ± 4.12 years; body mass 92.89 ± 12.34 kg; body height 1.90 ± 0.05 m). The knee extensor and flexor muscle peak torque of each leg were concentrically measured at 60º/s and 180º/s with an isokinetic dynamometer. The Squat Jump and Countermovement Jump were performed on a force platform to determine power and vertical jump height. Non-significant differences were observed between legs in the isokinetic knee extension (dominant= 2.91 ± 0.53 Nm/kg vs non-dominant = 2.70 ± 0.47 Nm/kg at 60º/s; dominant = 1.90 ± 0.31 Nm/kg vs non-dominant = 1.83 ± 0.29 Nm/kg at 180º/s) and flexion peak torques (dominant = 1.76 ± 0.29 Nm/kg vs non-dominant = 1.72 ± 0.39 Nm/kg at 60º/s; dominant = 1.30 ± 0.23 Nm/kg vs non-dominant = 1.27 ± 0.35 Nm/kg at 180º/s). Low and non-significant correlation coefficients were found between the isokinetic peak torques and vertical jumping performance (SJ = 31.21 ± 4.32 cm; CMJ = 35.89 ± 4.20 cm). Similar isokinetic strength was observed between the legs; therefore, no relationship was found between the isokinetic knee flexion and extension peak torques as well as vertical jumping performance in elite handball players.Actividad Física y Deport

Optimización energética de un sistema de climatización condensado con torre de refrigeración

El aumento del consumo energético en los últimos años ha propiciado la aparición de políticas de eficiencia energética en numerosos países, cuyo principal objetivo es la disminución de las emisiones de CO2. Este incremento se ha visto afectado por el creciente uso de sistemas de climatización debido a los nuevos estándares de confort. En este ámbito, la condensación evaporativa se presentan como una de las elecciones más eficientes para la disipación de calor ya que opera con bajas temperaturas de agua, y a iguales condiciones de funcionamiento, el consumo y los costes del equipo son menores respecto a otros sistemas como los de condensación por aire. A pesar de su buen comportamiento térmico, las torres de refrigeración han sido sustituidas por sistemas secos debido a sus problemas medioambientales. Si bien el estudio de las torres se ha fundamentado principalmente en el relleno, se han llevado a cabo diversos trabajos en los que se determina su característica térmica para diferentes sistemas de distribución y separadores de gotas, pero no se han encontrado estudios que traten la influencia de diferentes configuraciones en climatización. Este trabajo modeliza en TRNSYS una torre de refrigeración para dos sistemas de distribución de agua y seis separadores de gotas, validando cada combinación a través de datos experimentales térmicos y de consumo eléctrico. Posteriormente se define una enfriadora comercial agua-agua, evaluando el punto óptimo de funcionamiento torreenfriadora para unas condiciones ambientales. Finalmente se simula una instalación de climatización en diferentes ubicaciones geográficas, definiendo un edificio de referencia atendiendo a la normativa vigente y evaluando tanto el consumo energético como el gasto de agua. Los resultados muestran un consumo mínimo para una frecuencia de giro del ventilador de la distinta a la nominal, apreciándose la influencia de los separadores de gotas y los sistemas de distribución tanto en el consumo energético final como en el gasto de agua.Este trabajo se enmarca en el Plan Nacional “Estudio para la mejora de instalaciones de energía solar térmica y enfriamiento evaporativo en edificios y centrales termosolares” (ENE2013-48696-C2-1-R)

Endotoxin increase after fat overload is related to postprandial hypertriglyceridemia in morbidly obese patients.

The low-grade inflammation observed in obesity has been associated with a high-fat diet, though this relation is not fully understood. Bacterial endotoxin, produced by gut microbiota, may be the linking factor. However, this has not been confirmed in obese patients. To study the relationship between a high-fat diet and bacterial endotoxin, we analyzed postprandial endotoxemia in morbidly obese patients after a fat overload. The endotoxin levels were determined in serum and the chylomicron fraction at baseline and 3 h after a fat overload in 40 morbidly obese patients and their levels related with the degree of insulin resistance and postprandial hypertriglyceridemia. The morbidly obese patients with the highest postprandial hypertriglyceridemia showed a significant increase in lipopolysaccharide (LPS) levels in serum and the chylomicron fraction after the fat overload. Postprandial chylomicron LPS levels correlated positively with the difference between postprandial triglycerides and baseline triglycerides. There were no significant correlations between C-reactive protein (CRP) and LPS levels. The main variables contributing to serum LPS levels after fat overload were baseline and postprandial triglyceride levels but not glucose or insulin resistance. Additionally, superoxide dismutase activity decreased significantly after the fat overload. Postprandial LPS increase after a fat overload is related to postprandial hypertriglyceridemia but not to degree of insulin resistance in morbidly obese patients

Beyond the Glycaemic Control of Dapagliflozin: Impact on Arterial Stiffness and Macroangiopathy

Dapagliflozin is a selective sodium–glucose cotransporter 2 inhibitor (SGLT2i) indicated for the treatment of type 2 diabetes mellitus (T2DM), heart failure with reduced ejection fraction and chronic kidney disease. In all indications, treatment can be initiated in adults with estimated glomerular filtration rate of at least 25 mL/min/1.73 m2. As monotherapy or as an additive therapy, dapagliflozin has been shown to promote better glycaemic control, associated with a reduction in body weight and blood pressure in a wide range of patients. In addition, dapagliflozin has a positive impact on arterial stiffness, helps to control the lipid profile and contributes to a reduced risk of cardiovascular complications. This article reviews the current scientific evidence on the role of dapagliflozin in cardiovascular risk factors including arterial stiffness, cardiovascular disease and heart failure in patients with T2DM, with the aim of helping to translate this evidence into clinical practice. The underuse of SGLT2i in actual clinical practice is also discussed

Body composition features in different playing position of professional team indoor players

The aim of the present research was to analyze the body composition (BC) and the differences in BC among different playing position in professional basketball, handball and futsal players. BC was assessed in 70 professional indoor team sport players. Players were divided in 4 groups depending on the playing position: group 1, point guard, center/wings and defense; group 2, shooting guard/small forward, handed and midfielder; group 3, power forward/center, pivot and forward; and group 4 goalkeeper. Significant differences between playing positions in basketball in body mass (BM), height, proteins, minerals and arms, legs and trunk BM were found. In handball, significant differences between center/wings and pivot in BM and muscle mass, and between goalkeepers and handed in percentage of fat were measured. Significant differences were also found in BM of each playing position groups in the three sports and in arms and legs BM in groups 1 and 2, and trunk BM and height in group 2. Group 3 presented significant differences between futsal and basketball in skeletal muscle mass and trunk BM, and between basketball and handball in left leg BM and total BM. In group 4 significant differences in BM, height and trunk and leg BM between futsal and handball were found. BC in indoor team sports depend on the playing position and the sport discipline, the BC being result of the specific game actions of each playing position.Actividad Física y Deport