On square permutations

Severini and Mansour introduced in [4]square polygons, as graphical representations of square permutations, that is, permutations such that all entries are records (left or right, minimum or maximum), and they obtained a nice formula for their number. In this paper we give a recursive construction for this class of permutations, that allows to simplify the derivation of their formula and to enumerate the subclass of square permutations with a simple record polygon. We also show that the generating function of these permutations with respect to the number of records of each type is algebraic, answering a question of Wilf in a particular case.

Formal deformations of Poisson structures in low dimensions

In this paper, we study formal deformations of Poisson structures, especially for three families of Poisson varieties in dimensions two and three. For these families of Poisson structures, using an explicit basis of the second Poisson cohomology space, we solve the deformation equations at each step and obtain a large family of formal deformations for each Poisson structure which we consider. With the help of an explicit formula, we show that this family contains, modulo equivalence, all possible formal eformations. We show moreover that, when the Poisson structure is generic, all members of the family are non-equivalent.

On Strategy-proofness and symmetric single-peakedness

We characterize the class of strategy-proof social choice functions on the domain of symmetric single-peaked preferences. This class is strictly larger than the set of generalized median voter schemes (the class of strategy-proof and tops-only social choice functions on the domain of single-peaked preferences characterized by Moulin (1980)) since, under the domain of symmetric single-peaked preferences, generalized median voter schemes can be disturbed by discontinuity points and remain strategy-proof on the smaller domain. Our result identifies the specific nature of these discontinuities which allow to design non-onto social choice functions to deal with feasibility constraints.

Rethinking economy-wide rebound measures: an unbiased proposal

In spite of having been first introduced in the last half of the ninetieth century, the debate about the possible rebound effects from energy efficiency improvements is still an open question in the economic literature. This paper contributes to the existing research on this issue proposing an unbiased measure for economy-wide rebound effects. The novelty of this economy-wide rebound measure stems from the fact that not only actual energy savings but also potential energy savings are quantified under general equilibrium conditions. Our findings indicate that the use of engineering savings instead of general equilibrium potential savings downward biases economy-wide rebound effects and upward-biases backfire effects. The discrepancies between the traditional indicator and our proposed measure are analysed in the context of the Spanish economy.

Anàlisi i disseny d'un magatzem de valoracions

El treball consisteix a analitzar i dissenyar una aplicació que ha de permetre emmagatzemar i gestionar les valoracions que es fan amb un valorador.

Gestió Acadèmica d'un centre de formació

Aquest treball s'ha desenvolupat sota la plataforma .NET 2.0 i consisteix en l'anàlisi, disseny i implementació d'una aplicació web per a gestionar el servei de gestió acadèmica d'un centre de formació o acadèmia.

Arnau de Montrodon y la catedral de San Carlomagno. Sobre la imagen y el culto al emperador carolingio en Gerona

In 1345, the unique worship of Saint Charlemagne was institutionalized in the cathedral of Gerona. The roots (and for many, the reasons) of this celebration are found in the existence of an old local legend, the well-known testimonies to which go back to the eleventh century. Nevertheless, a lengthy analysis of the facts that marked the life of the cathedral during the long permanence Amau de Montrodon had there—first in quality of canon (1297-1335) and later as bishop (1333-1348)- make it possible for us to verify that the promotion of the cult to San Charlemagne falls within a complex program of ideological and symbolic exaltation of the See of Girona that was designed by this notable and restlessly active ecclesiastic

Product market deregulation and the U.S. employment miracle

We consider the dynamic relationship between product market entry regulation and equilibrium unemployment. The main theoretical contribution is combining a job matchingmodel with monopolistic competition in the goods market and individual wage bargaining.Product market competition affects unemployment by two channels: the output expansion effect and a countervailing effect due to a hiring externality. Competition is then linked to barriers to entry. We calibrate the model to US data and perform a policy experiment to assess whether the decrease in trend unemployment during the 1980 s and 1990 s could be attributed to product market deregulation. Our quantitative analysis suggests that under individual bargaining, a decrease of less than two tenths of a percentage point of unemployment rates can be attributed to product market deregulation, a surprisingly small amount.

Immigration and the survival of the welfare state

This paper analyzes the political sustainability of the welfare state in a model where immigration policy is also endogenous. In the model, the skills of the native population are affected by immigration and skill accumulation. Moreover, immigrants affect future policies, once they gain the right to vote. The main finding is that the long-run survival of redistributive policies is linked to an immigration policy specifying both skill and quantity restrictions. In particular, in steady state the unskilled majority admits a limited inflow of unskilled immigrants in order to offset growth in the fraction of skilled voters and maintain a high degree of income redistribution.Interestingly, equilibrium immigration policy shifts from unrestricted skilled immigration,when the country is skill-scarce, to restricted unskilled immigration, as the fraction of native skilled workers increases. The analysis also suggests a new set of variables that may help explain international differences in immigration restrictions.

Creixement urbà i producció de l'espai a Lleida (1940-1980)

Aquest article té com a objecte establir la relació existent entre les formes materials que adopta el creixement urbi i les caracteristiques del mercat del sòl i del m rcat immobiliari. La proposició inicial de la qual es parteix és l'afirmació e la dependència de les primeres respecte al grau de desenvolupament del mercat; i això en dos aspectes: primer, en l'origen d'una determinada forma urbaba; segon, en la seva posterior evolució. El cas analitzat, el procés de creixement urbà de Lleida en uns anys de gran creixement econòmic -canvi agrícola basat en l'especialització fruitera i en la difusió de les granges d'estabulació ramadera- i demogràfic -41.464 habitants el 1940, 106.814 habitants el 1981- pretén servir per treure unes remarques qenerals, formulades en el present treball com a hipòtesis, que poden orientar aquelles recerques que busquen en les característiques d'una formació social la variable independent que ha de permetre la comprensió d'unes morfologies. El marc eneral de referència és la teoria sobre la "producció de l'espai", encara que matisada i acotada a aquells aspectes que poden ser més rellevants en la comprensió del sorgiment de les formes materials urbanes.

Interrogating eleven fast-evolving genes for signatures of recent positive selection in worldwide human populations

Different signatures of natural selection persist over varying time scales in our genome, revealing possible episodes of adaptative evolution during human history. Here, we identify genes showing signatures of ancestral positive selection in the human lineage and investigate whether some of those genes have been evolving adaptatively in extant human populations. Specifically, we compared more than 11,000 human genes with their orthologs inchimpanzee, mouse, rat and dog and applied a branch-site likelihood method to test for positive selection on the human lineage. Among the significant cases, a robust set of 11 genes were then further explored for signatures of recent positive selection using SNP data. We genotyped 223 SNPs in 39 worldwide populations from the HGDP Diversity panel and supplemented this information with available genotypes for up to 4,814 SNPs distributed along 2 Mb centered on each gene. After exploring the allele frequency spectrum, population differentiation and the maintainance of long unbroken haplotypes, we found signals of recent adaptative phenomena in only one of the 11 candidate gene regions. However, the signal ofrecent selection in this region may come from a different, neighbouring gene (CD5) ratherthan from the candidate gene itself (VPS37C). For this set of positively-selected genes in thehuman lineage, we find no indication that these genes maintained their rapid evolutionarypace among human populations. Based on these data, it therefore appears that adaptation forhuman-specific and for population-specific traits may have involved different genes.

L'aventura imaginària. Una visió antropològica de les activitats físiques d'aventura a la natura

Las actividades físicas de aventura en la naturaleza han tendido a analizarse hasta el momento desde la perspectiva de la praxis. Este artículo pone el énfasis en la perspectiva del discurso: se mantiene que la identidad diferenciada de los denominados deportes de aventura no proviene de sus aspectos prácticos o materiales, sino de su dimensión imaginaria o simbólica. La aventura aparece como una escenografía para la gestión controlada de las emociones, en que las acciones se subordinan a las percepciones y los riesgos reales a los peligros imaginarios. En este sentido, se analizan algunas imágenes persistentes en los medios de comunicación, se establecen asociaciones con fenómenos como las rutas del ocio de los jóvenes, se subrayan los aspectos rituales que encubren estas actividades y se acaba proponiendo un análisis de la aventura como hecho social total.

Use of nitrification inhibitor DMPP to improve nitrogen recovery in irrigated wheat on a calcareous soil

The 3,4-dimethyilpyirazole phosphate (DMPP), commercialized as Entec, is a nitrification inhibitor developed by BASF (Germany) that may help to minimize N losses and to obtain a higher profit from N fertilizers. A two-year field trial was established in 2001 in the Northeast of Spain to assess the effects of DMPP on N use efficiency (NUE) and to determine the economic returns. Seven treatments have been carried out comparing the effect of DMPP on pig slurry and on mineral fertilizers. The application of DMPP resulted in better efficiency indexes on mineral fertilizers. An apparent nitrogen recovery of 0.465 kg kg-1, on average, was obtained for the Entec treatment. A net benefit of € 809 ha-1, on average, was obtained for the Entec treatment compared with € 607 ha-1 for the control treatment. The results of this study suggest that the nitrification inhibitor could improve farmer profit in irrigated wheat on a calcareous soil.

La aventura imaginaria. Una visión antropológica de las actividades físicas de aventura en la naturaleza

Las actividades físicas de aventura en la naturaleza han tendido a analizarse hasta el momento desde la perspectiva de la praxis. Este artículo pone el énfasis en la perspectiva del discurso: se mantiene que la identidad diferenciada de los denominados deportes de aventura no proviene de sus aspectos prácticos o materiales, sino de su dimensión imaginaria o simbólica. La aventura aparece como una escenografía para la gestión controlada de las emociones, en que las acciones se subordinan a las percepciones y los riesgos reales a los peligros imaginarios. En este sentido, se analizan algunas imágenes persistentes en los medios de comunicación, se establecen asociaciones con fenómenos como las rutas del ocio de los jóvenes, se subrayan los aspectos rituales que encubren estas actividades y se acaba proponiendo un análisis de la aventura como hecho social total.

The Transatlantic Productivity Gap : Is R&D the Main Culprit?

The literature has pointed to different causes to explain the productivity gap between Europe and United States in the last decades. This paper tests the hypothesis that the lower European productivity performance in comparison with the US can be explained not only by a lower level of corporate R&D investment, but also by a lower capacity to translate R&D investment into productivity gains. The proposed microeconometric estimates are based on a unique longitudinal database covering the period 1990-2008 and comprising 1.809 US and European companies for a total of 16.079 observations. Consistent with previous literature, we find robust evidence of a significant impact of R&D on productivity, however – using different estimation techniques - the R&D coefficients for the US firms always turn out to be significantly higher. To see to what extent these transatlantic differences may be related to the different sectoral structures in the US and the EU, we differentiated the analysis by sectors. The result is that both in manufacturing, services and high-tech sectors US firms are more efficient in translating their R&D investments into productivity increases.