Entrenament d'un ciclista esprinter mitjançant la força explosiva: avaluació dels efectes d'un entrenament específic

La principal fita dels ciclistes ha estat sempre l’entrenament per millorar les seves condicions i prestacions fisiològiques. Al llarg dels anys, el ciclisme com pràcticament tot l’esport s’ha anat modernitzant, no només tecnològicament. Això ha provocat l’aparició d’especialistes, corredors destinats a destacar, només en unes determinades condicions, per sobre els demés. Una d’aquestes condicions més restringides son les arribades massives, terreny dels anomenats esprinters, els quals brillen per sobre els demés degut a la seva potència, velocitat punta i arrancada. L’entrenament d’aquesta tipologia d’especialitat ha deixat entreveure varies ambigüitats i algunes problemàtiques de fonament teòric. L’esprint en el ciclisme es dona després d’un gran desgast de les reserves energètiques i de fatiga muscular. Per tant, entrenar-lo amb blocs de velocitat no té lògica. Tampoc es una opció viable el recurs que molts equips utilitzen: agafar corredors joves de la pista, i que la seva genètica (fibres ràpides) i les seves característiques de pistard1 facin la resta, perquè al pas dels anys perden aquesta exclusivitat. Aquest estudi es proposa buscar una manera de treballar i potenciar l’esprint del ciclista a partir de la força explosiva, garantint preservar les condicions aeròbiques per tal de que no perjudiqui per altra banda la seva resistència. Per tal d’aconseguir-ho, s’efectuaran uns tests. Un focalitzat en mesurar les prestacions en un esprint dels subjectes. L’altra es basarà en avaluar la força explosiva d’aquets, a partir de salts verticals. Un cop obtinguts els resultats de la primera tanda, els subjectes seran sotmesos a un entrenament combinat de sobrecàrrega, per tal de observar, en la segona tanda, si els resultats son significatius. Com a conclusió, es podria destacar el fet de millora en la majoria d’aspectes en tots els tests per part de tots els subjectes, i que probablement, hi ha una correlació significativa entre la força explosiva i la capacitat per esprintar, tot i que s’haurien de corroborar els resultats amb una mostra més gran.

Test of the fluctuation theorem for stochastic entropy production in a nonequilibrium steady state

We derive a simple closed analytical expression for the total entropy production along a single stochastic trajectory of a Brownian particle diffusing on a periodic potential under an external constant force. By numerical simulations we compute the probability distribution functions of the entropy and satisfactorily test many of the predictions based on Seiferts integral fluctuation theorem. The results presented for this simple model clearly illustrate the practical features and implications derived from such a result of nonequilibrium statistical mechanics.

Parametric and semiparametric estimation of sample selection models: an empirical application to the female labour force in Portugal

This comment corrects the errors in the estimation process that appear in Martins (2001). The first error is in the parametric probit estimation, as the previously presented results do not maximize the log-likelihood function. In the global maximum more variables become significant. As for the semiparametric estimation method, the kernel function used in Martins (2001) can take on both positive and negative values, which implies that the participation probability estimates may be outside the interval [0,1]. We have solved the problem by applying local smoothing in the kernel estimation, as suggested by Klein and Spady (1993).

Collusion and fights in an experiment with price-setting firms and production in advance

We present results from 50-round market experiments in which firms decide repeatedly both on price and quantity of a completely perishable good. Each firm has capacity to serve the whole market. The stage game does not have an equilibrium in pure strategies. We run experiments for markets with two and three identical firms. Firms tend to cooperate to avoid fights, but when they fight bankruptcies are rather frequent. On average, pricing behavior is closer to that for pure quantity than for pure price competition and price and efficiency levels are higher for two than for three firms. Consumer surplus increases with the number of firms, but unsold production leads to higher efficiency losses with more firms. Over time prices tend to the highest possible one for markets both with two and three firms.

Social capital and government in the production of public goods

As a response to the rapidly growing empirical literature on social capital and the evidence of its correlation with government performance, we build a theoretical framework to study the interactions between social capital and government's action. This paper presents a model of homogeneous agents in an overlapping generations framework incorporating social capital as the values transmitted from parent to child. The government's role is to provide public goods. First, government expenditure is exogenously given. Then, it will be chosen at the preferred level of the representative agent. For both setups the equilibrium outcomes are characterized and the resulting dynamics studied. Briefly we include an analysis of the effect of productivity growth on the evolution of social capital. The results obtained caution caution against both the crowding out effect of the welfare state and the impact of sustained economic growth on social capital.

Increasing quasiconcave production and utility functions with diminishing returns to scale

In microeconomic analysis functions with diminishing returns to scale (DRS) have frequently been employed. Various properties of increasing quasiconcave aggregator functions with DRS are derived. Furthermore duality in the classical sense as well as of a new type is studied for such aggregator functions in production and consumer theory. In particular representation theorems for direct and indirect aggregator functions are obtained. These involve only small sets of generator functions. The study is carried out in the contemporary framework of abstract convexity and abstract concavity.

Rational sabotage in cooperative production

In this paper we consider a model of cooperative production in which rational agents have the possibility to engage in sabotage activities that decrease output. It is shown that sabotage depends on the interplay between the degree of congestion, the technology of sabotage, the number of agents the degree of meritocracy and the form of the sharing rule. In particular it is shown that, ceteries paribus, meritocratic systems give more incentives to sabotage than egalitarian systems. We address two questions: The degree of meritocracy that is compatible with absence of sabotage and the existence of a Nash equilibrium with and without sabotage.

An input-output analysis of the "key" sectors in CO2 emissions from a production perspective: an application to the spanish economy

Here we present an approach that allows the identification of the "key" productive sectors responsible for CO2 emission. For this purpose, we develop an input–output methodology from a supply perspective. We focus on the impact of an increase in the value-added of the different productive sectors on total CO2 emissions and we identify the productive sectors responsible for the increase in CO2 emissions when there is an increase in the income of the economy. The approach shows the contribution of the various sectors to CO2 emission from a production perspective and allows us to identify the sectors that deserve more consideration for mitigation policies. This analysis is complementary to the input–output analysis from a demand perspective. The methodology is applied to the Spanish economy.

Economic impacts of alternative water policy scenarios in the Spanish production system: an input-output analysis

The objective of this paper is to analyse the economic impacts of alternative water policies implemented in the Spanish production system. The methodology uses two versions of the input-output price model: a competitive formulation and a mark-up formulation. The input-output framework evaluates the impact of water policy measures on production prices, consumption prices, intermediate water demand and private welfare. Our results show that a tax on the water used by sectors considerably reduces the intermediate water demand, and increases the production and consumption prices. On the other hand, according to Jevons' paradox, an improvement in technical efficiency, which leads to a reduction in the water requirements of all sectors and an increase in water production, increases the amount of water consumed. The combination of a tax on water and improved technical efficiency takes the pressure off prices and significantly reduces intermediate water demand. JEL Classification: C67 ; D57 ; Q25. Keywords: Production prices; Consumption prices; Water uses; Water policy; Water taxation.

Cooperative production and efficiency

We characterize the sharing rule for which a contribution mechanism achieves efficiency in a cooperative production setting when agents are heterogeneous. The sharing rule bears no resemblance to those considered by the previous literature. We also show for a large class of sharing rules that if Nash equilibrium yields efficient allocations, the production function displays constant returns to scale, a case in which cooperation in production is useless.

Artificial diets for the production of natural enemies (predators and parasitoids) of greenhouse pest insects

The aim of this contract was to finalise in vitro rearing on artificial diets of entomophagous insects useful to control insect pests mainly in greenhouses through an analytical and rational approach. The work focuses on the development and optimisation of artificial diets for one coccinellid (Harmonia axyridis), two heteropteran predators (Orius laevigatus, Dicyphus tamaninii), and a braconid parasitoid of aphids (Aphidius ervi). The definition of the artificial diets was based on biochemical analyses of their natural food (aphids) or substitution food for the predators (Ephestia kuehniella eggs). Reliable quality control parameters of the entomophages produced were used in order to adjust dietary composition and formulation of the different diets tested.

Production and carcass quality of ten beef cattle breeds of the southwest of Europe

A sample of about 70 young bulls of each of ten beef cattle breeds reared in their typical production systems has been studied regarding growth and carcass quality traits. Breeds included were Asturiana de los Valles (AV), Asturiana de la Montaña (AM), Avileña-Negra Ibérica (A-NI), Bruna dels Pirineus (BP), Morucha (Mo), Pirenaica (Pi) and Retinta (Re) from Spain, and Aubrac (Au), Gasconne (Ga) and Salers (Sal) from France. There existed large differences between breeds and also within breeds. AV and Pi were the breeds with more muscle and less fat, whereas A-NI, Mo and Re were in the opposite side. BP and AM occupied an intermediate position. This allows to classify the Spanish breeds in three groups: AV and Pi would belong to the group of late maturity, A-NI, Mo and Re, would be early maturing breeds, whereas BP and AM, despite the small size of the last, will be of intermediate maturity. In the French populations, Au was the breed with the highest carcass weight and Ga exhibited the lowest. Sal occupied an intermediate position, showing the longer and thinner thigh. In a wide range of carcass weight, the general relationships among carcass traits have been confirmed. Animals with the better conformation were also the leaner and longer carcasses tended to be lowly associated with a poorer conformation and fatter carcasses. Bone content was clearly opposed to carcass conformation and muscle content and was associated with longer carcasses

Meat quality of ten cattle breeds of the Southwest of Europe

A sample of about 70 young bulls of each of ten beef cattle breeds reared in their typical production systems has been characterised with respect to meat quality traits. Breeds included were Asturiana de los Valles, Asturiana de la Montaña, Avileña-Negra Ibérica, Bruna dels Pirineus, Morucha, Pirenaica and Retinta from Spain, and Aubrac, Gasconne and Salers from France. As was previously showed regarding carcass traits, there exist large differences both between and within breed – systems. In general, rustic breeds tended to present darker and redder meats with higher haematin contents, whereas less precocious and more specialised breeds showed brighter meats with bigger water losses. Protein content was similar, whereas intramuscular fat presented the larger variations both between and within breeds. ICDH content was higher in the more rustic breeds, showing the predominantly oxidative character of their fibres. Texture measurements showed in general large within breed-system variations, the differences between breeds being less evident. Within breed-system, daily gain weight was positively associated with brighter and tender meats. In the range studied, increasing slaughter weight within breed did not have influence on meat quality. Conformation was related to lower water holding capacity and less dry matter and intramuscular fat, as well as to a lower haematin content giving brighter meats. The increase in fatness scores was related to an augment of toughness in meat specialised breeds, although in Avileña-Negra Ibérica breed fatness carcasses were related to more tender meats. Redness parameter a* was positively related to fatter animals and opposed to conformation, the opposite being true for the L* (lightness) parameter. There was a small trend of fatter carcasses to be related to oxidative fibres, whereas the muscular fibres of the more conformed carcasses were more glycolytic. Texture measurements maximum load, maximum stress and toughness were very closely related. Shear force was opposed to tenderness. Losses at cooking were opposed to juiciness, but only in the Spanish breeds. No consistent trends regarding relationships between carcass characteristics and tenderness could be observed. Overall acceptability was primarily related with tenderness and flavour, and later on juiciness.

Business Cycle Regimes in CEECs Production: A Threshold SURE Approach

We use a threshold seemingly unrelated regressions specification to assess whether the Central and East European countries (CEECs) are synchronized in their business cycles to the Euro-area. This specification is useful in two ways: First, it takes into account the common institutional factors and the similarities across CEECs in their process of economic transition. Second, it captures business cycle asymmetries by allowing for the presence of two distinct regimes for the CEECs. As the CEECs are strongly affected by the Euro-area these regimes may be associated with Euro-area expansions and contractions. We discuss representation, estimation by maximum likelihood and inference. The methodology is illustrated by using monthly industrial production in 8 CEECs. The results show that apart from Lithuania the rest of the CEECs experience “normal” growth when the Euro-area contracts and “high” growth when the Euro-area expands. Given that the CEECs are “catching up” with the Euro-area this result shows that most CEECs seem synchronized to the Euro-area cycle. Keywords: Threshold SURE; asymmetry; business cycles; CEECs. JEL classification: C33; C50; E32.