Variación de peso y aporte energético del pasto en vacas de cría en condiciones de montaña: efecto de la época de parto

Se analizaron las variaciones de peso durante la estación de pastoreo de vacas multíparas de raza Parda Alpina con partos en otoño (n = 152) o primavera (n = 123) durante el período 1989-1996. Los animales pasta- ron en áreas boscosas (900-1.500 m, 0,2 vacas/ha) y en pastos supraforestales (1.500-2.200 m, 1,2 vacas/ha). Las vacas con parto en otoño presentaron mayores recuperaciones de peso en pastoreo que las de primavera (0,661 vs 0,071 kg/día, P < 0,001), diferencia observada tanto en los pastos forestales como en los supraforestales. Las variaciones de peso en pastoreo se relacionaron negativamente con las observadas en estabulación (r = –0,20, P < 0,05) y también con el peso a la salida al pasto (r = –0,32, P < 0,05). La contribución energética del pasto a los aportes recibidos anualmente de la dieta fue similar en ambas parideras (43,6 p. 100 y 42,2 p. 100 en otoño y primavera, respectivamente, NS), aunque la pauta de reparto de la energía hacia las funciones fisiológicas en los distintos períodos de manejo fue diferente.

CM points and weight 3=2 modular forms

"Vegeu el resum a l'inici del document del fitxer adjunt."

Decentralization and the Gains from Monitoring

This paper analyzes the delegation of contracting capacity in a moral hazard environment with sequential production in a project which involves a principal and two agents. The agent in charge of the …nal production can obtain soft information about the other agent's effort choice by investing in monitoring. I investigate the circumstances under which it is optimal for the principal to use a centralized organization in which she designs the contracts with both agents or to use a decentralized organization in which she contracts only one agent, and delegates the power to contract the other agent. It is shown that in this setting a decentralized organization can be superior to a centralized organization. This is because the principal is better off under monitoring and the incentives for an agent to invest in monitoring can be higher in a decentralized organization. The circumstances under which this is true are related to the monitoring costs and the importance of each agent for production. The results explain the recent application of the design-build method in public procurement. Journal of Economic Literature Classi…cation Numbers: D23, D82, L14, L22. Keywords: Decentralization of Contracting, Monitoring, Moral Hazard.

A characterization of two weight norm inequalities for maximal singular integrals

"Vegeu el resum a l'inici del document del fitxer adjunt."

Two weight inequalities for discrete positive operators

"Vegeu el resum a l'inici del document del fitxer adjunt."

Two weight inequalities for maximal truncations of dyadic Calderón-Zygmund operators

"Vegeu el resum a l'inici del document del fitxer adjunt."

Simulating the Impact of Sectorial Productivity Gains on Two Regional Economies: Key Sectors from a Supply Side Perspective

In this paper we simulate and analyse the economic impact that sectorial productivity gains have on two regional Spanish economies (Catalonia and Extremadura). In particular we study the quantitative effect that each sector’s productivity gain has on household welfare (real disposable income and equivalent variation), on the consumption price indices and factor relative prices, on real production (GDP) and on the government’s net income (net taxation revenues of social transfers to households). The analytical approach consists of a computable general equilibrium model, in which we assume perfect competition and cleared markets, including factor markets. All the parameters and exogenous variables of the model are calibrated by means of two social accounting matrices, one for each region under study. The results allow us to identify those sectors with the greatest impact on consumer welfare as the key sectors in the regional economies. Keywords: Productivity gains, key sectors, computable general equilibrium

Chebyshev-type quadrature formulas for new weight classes

We give Chebyshev-type quadrature formulas for certain new weight classes. These formulas are of highest possible degree when the number of nodes is a power of 2. We also describe the nodes in a constructive way, which is important for applications. One of our motivations to consider these type of problems is the Faraday cage phenomenon for discrete charges as discussed by J. Korevaar and his colleagues.

Association between GIS-based exposure to urban air pollution during pregnancy and birth weight in the INMA Sabadell Cohort

Background: There is growing evidence that traffic-related air pollution reduces birth weight. Improving exposure assessment is a key issue to advance in this research area.Objective: We investigated the effect of prenatal exposure to traffic-related air pollution via geographic information system (GIS) models on birth weight in 570 newborns from the INMA (Environment and Childhood) Sabadell cohort.Methods: We estimated pregnancy and trimester-specific exposures to nitrogen dioxide and aromatic hydrocarbons [benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene (BTEX)] by using temporally adjusted land-use regression (LUR) models. We built models for NO2 and BTEX using four and three 1-week measurement campaigns, respectively, at 57 locations. We assessed the relationship between prenatal air pollution exposure and birth weight with linear regression models. We performed sensitivity analyses considering time spent at home and time spent in nonresidential outdoor environments during pregnancy.Results: In the overall cohort, neither NO2 nor BTEX exposure was significantly associated with birth weight in any of the exposure periods. When considering only women who spent < 2 hr/day in nonresidential outdoor environments, the estimated reductions in birth weight associated with an interquartile range increase in BTEX exposure levels were 77 g [95% confidence interval (CI), 7–146 g] and 102 g (95% CI, 28–176 g) for exposures during the whole pregnancy and the second trimester, respectively. The effects of NO2 exposure were less clear in this subset.Conclusions: The association of BTEX with reduced birth weight underscores the negative role of vehicle exhaust pollutants in reproductive health. Time–activity patterns during pregnancy complement GIS-based models in exposure assessment.

The capital gains from trade are not enough: Evidence from the environmental accounts of Venezuela and Mexico

In principle, a country can not endure negative genuine savings for longperiods of time without experiencing declining consumption. Nevertheless,theoreticians envisage two alternatives to explain how an exporter ofnon-renewable natural resources could experience permanent negativegenuine savings and still ensure sustainability. The first one allegesthat the capital gains arising from the expected improvement in theterms of trade would suffice to compensate for the negative savings ofthe resource exporter. The second alternative points at technologicalchange as a way to avoid economic collapse. This paper uses the dataof Venezuela and Mexico to empirically test the first of these twohypotheses. The results presented here prove that the terms oftrade do not suffice to compensate the depletion of oil reservesin these two open economies.

Spinning welfare: The gains from process innovation in cotton and car production

Economists and economic historians want to know how much better life is today than in the past.Fifty years ago economic historians found surprisingly small gains from 19th century US railroads,while more recently economists have found relatively large gains from electricity, computers and cellphones. In each case the implicit or explicit assumption is that researchers were measuring the valueof a new good to society. In this paper we use the same techniques to find the value to society ofmaking existing goods cheaper. Henry Ford did not invent the car, and the inventors of mechanisedcotton spinning in the industrial revolution invented no new product. But both made existing productsdramatically cheaper, bringing them into the reach of many more consumers. That in turn haspotentially large welfare effects. We find that the consumer surplus of Henry Ford s production linewas around 2% by 1923, 15 years after Ford began to implement the moving assembly line, while themechanisation of cotton spinning was worth around 6% by 1820, 34 years after its initial invention.Both are large: of the same order of magnitude as consumer expenditure on these items, and as largeor larger than the value of the internet to consumers. On the social savings measure traditionally usedby economic historians, these process innovations were worth 15% and 18% respectively, makingthem more important than railroads. Our results remind us that process innovations can be at least asimportant for welfare and productivity as the invention of new products.

Reflections on gains and losses: A 2x2x7 experiment

We test whether risk attitudes change when losses instead of gains areinvolved. The study of gain-loss asymmetries has been largely confinedto reflected choices, where all the money amounts of a positiveprospect are multiplied by minus one. We define the decomposition reflection = translation + probability switch, and experimentally findboth a translation effect (risk attraction becomes more frequent whengains are translated into losses) and a probability switch effect (riskattraction becomes more frequent when the probability of the best outcomedecreases). Surprisingly, the switch effect is somewhat stronger than thetranslation effect, negating a conventional reflection effect when onestarts with choices between gains with a low probability of the bestoutcome. We conclude by arguing that, while both the translation effectand the switch effect contradict the expected utility hypothesis, thetranslation effect implies a deeper violation of standard preference theory.

The elusive costs and the immaterial gains of fiscal contraints

We study whether and how fiscal restrictions alter the business cycle features macrovariables for a sample of 48 US states. We also examine the 'typical' transmission properties of fiscal disturbances and the implied fiscal rules of states with different fiscal restrictions. Fiscal constraints are characterized with a number of indicators. There are similarities in second moments of macrovariables and in the transmission properties of fiscal shocks across states with different fiscal constraints. The cyclical response of expenditure differs in size and sometimes in sign, but heterogeneity within groups makes point estimates statistically insignificant. Creative budget accounting isresponsible for the pattern. Implications for the design of fiscal rules and thereform of the Stability and Growth Pact are discussed.