Price level convergence, purchasing power parity and multiple structural breaks: an application to US cities

This article provides a fresh methodological and empirical approach for assessing price level convergence and its relation to purchasing power parity (PPP) using annual price data for seventeen US cities. We suggest a new procedure that can handle a wide range of PPP concepts in the presence of multiple structural breaks using all possible pairs of real exchange rates. To deal with cross-sectional dependence, we use both cross-sectional demeaned data and a parametric bootstrap approach. In general, we find more evidence for stationarity when the parity restriction is not imposed, while imposing parity restriction provides leads toward the rejection of the panel stationar- ity. Our results can be embedded on the view of the Balassa-Samuelson approach, but where the slope of the time trend is allowed to change in the long-run. The median half-life point estimate are found to be lower than the consensus view regardless of the parity restriction.

Estudi d'eines CASE que suporten OCLper a la generació automàtica de codi Java

Es tracta d'una recerca d'eines CASEque actualment suporten OCL en la generació automàtica de codi Java per estudiar-les ianalitzar-les a través d'un model de proves consistent en un diagrama de classes del modelestàtic de l'UML i una mostra variada d'instruccions OCL, amb l'objectiu de detectar lesseves mancances, analitzant el codi obtingut i determinar si controla o no cada tipus derestricció, i si s'han implementat bé en el codi.

Bargaining failures and merger policy

In this paper we study the optimal ex-ante merger policy in a model where merger proposals are the result of strategic bargaining among alternative candidates. We allow for firm asymmetries and, in particular, we emphasize the fact that potential synergies generated by a merger may vary substantially depending on the identity of the participating firms. The model demonstrates that, under some circumstances, relatively inefficient mergers may take place. That is, a particular merger may materialize despite the existence of an alternative merger capable of generating higher social surplus and even higher profits. Such bargaining failures have important implications for the ex-ante optimal merger policy. We show that a more stringent policy than the ex-post optimal reduces the scope of these bargaining failures and raises expected social surplus. We use a bargaining model that is flexible, in the sense that its strategic structure does not place any exogenous restriction on the endogenous likelihood of feasible mergers.

Sistema d'avaluació de l'impacte organitzatiu i sobre les condicions de seguretat i salut en el treball per l'aplicació de la normativa REACH

L’aparició de la nova normativa sobre productes químics de l’Unió Europea,anomenada REACH ( Registration, Evaluation, Authorization and restriction ofChemicals) i recollida en el reglament (CE) nº1907/2006 del Parlament Europeu i delConsell de 18 de desembre de 2006, suposa un canvi en la forma d’actuació respectea la manipulació de productes químics per part de fabricants, d’importadors, dedistribuïdors i de consumidors finals.Aquesta nova normativa de caràcter europeu es caracteritza per la seva complexitat iper la seva incidència sobre diferents sectors socials, per això dintre de l’estudi s’handefinit els següents objectius:Un primer objectiu d’aquest estudi serà exposar la nova normativa d’abast europeusobre productes químics REACH (Registration, Evaluation, Authorization andrestriction of Chemicals), que ha entrat en vigor el juliol de 2007._ _Un segon objectiu consistirà en avaluar l’acció o impacte que podria causar laimplantació de la normativa sobre les indústries químiques i el seu entorn, tant a nivellde negoci, com a nivell personal.Finalment es definirà una petita empresa fabricant de productes químics a partir de laqual es veuran els impactes que causarà l’aplicació de la nova normativa REACH.Aquest estudi pretén ajudar a quantificar els possibles impactes que puguin sorgir apartir de l’entrada en vigor de la nova normativa sobre productes químics. Aquestsimpactes poden influir sobre la salut dels treballadors, sobre el medi ambient i tambésobre l’economia, tant a nivell local com a nivell internacional.Per poder aconseguir establir els impactes, serà necessari en primer lloc tenir un bonconeixement tant de les lleis químiques actuals, com de les que aniran sorgintsuccessivament, com la nova normativa REACH.D’altra banda, també serà necessari veure els possibles impactes que podrien afectara una petita empresa química, per poder, si és necessari, extrapolar els resultats per aempreses del mateix tipus influenciades també per la normativa REACH.Així doncs, aquest estudi servirà de guia d’iniciació per aquells empresaris i/opersones relacionades amb el món de la química a nivell industrial, que vulguincomençar a determinar el grau en que es veuran afectats per la nova normativa.L’impacte que causarà la nova normativa s’analitzarà a partir d’una empresa virtualdedicada a la fabricació d’adhesius situada a la provincia de Girona.Els impactes es centraran en dos productes, una cola produïda en grans quantitats,però sense gaires implicacions pel medi ambient ni per la seguretat de les persones, iuna altra que es produeix en quantitats més reduïdes però que inclou substànciesperilloses pel medi ambient i per les personesA partir de l’anàlisi dels diferents impactes (pel medi aquàtic, pel sòl, per l’atmosfera, iper la seguretat de les persones al lloc de treball), s’han realitzat unes matriusd’impacte que ajudaran a determinar l’impacte econòmic que causarà la normativasobre l’empresa en qüestió

Anharmonicity contributions to the vibrational second hyperpolarizability of conjugated oligomers

Restricted Hartree-Fock 6-31G calculations of electrical and mechanical anharmonicity contributions to the longitudinal vibrational second hyperpolarizability have been carried out for eight homologous series of conjugated oligomers - polyacetylene, polyyne, polydiacetylene, polybutatriene, polycumulene, polysilane, polymethineimine, and polypyrrole. To draw conclusions about the limiting infinite polymer behavior, chains containing up to 12 heavy atoms along the conjugated backbone were considered. In general, the vibrational hyperpolarizabilities are substantial in comparison with their static electronic counterparts for the dc-Kerr and degenerate four-wave mixing processes (as well as for static fields) but not for electric field-induced second harmonic generation or third harmonic generation. Anharmonicity terms due to nuclear relaxation are important for the dc-Kerr effect (and for the static hyperpolarizability) in the σ-conjugated polymer, polysilane, as well as the nonplanar π systems polymethineimine and polypyrrole. Restricting polypyrrole to be planar, as it is in the crystal phase, causes these anharmonic terms to become negligible. When the same restriction is applied to polymethineimine the effect is reduced but remains quantitatively significant due to the first-order contribution. We conclude that anharmonicity associated with nuclear relaxation can be ignored, for semiquantitative purposes, in planar π-conjugated polymers. The role of zero-point vibrational averaging remains to be evaluated

A fractionally integrated approach to monetary policy and inflation dynamics

This paper relaxes the standard I(0) and I(1) assumptions typically stated in the monetary VAR literature by considering a richer framework that encompasses the previous two processes as well as other fractionally integrated possibilities. First, a timevarying multivariate spectrum is estimated for post WWII US data. Then, a structural fractionally integrated VAR (VARFIMA) is fitted to each of the resulting time dependent spectra. In this way, both the coefficients of the VAR and the innovation variances are allowed to evolve freely. The model is employed to analyze inflation persistence and to evaluate the stance of US monetary policy. Our findings indicate a strong decline in the innovation variances during the great disinflation, consistent with the view that the good performance of the economy during the 80’s and 90’s is in part a tale of good luck. However, we also find evidence of a decline in inflation persistence together with a stronger monetary response to inflation during the same period. This last result suggests that the Fed may still play a role in accounting for the observed differences in the US inflation history. Finally, we conclude that previous evidence against drifting coefficients could be an artifact of parameter restriction towards the stationary region. Keywords: monetary policy, inflation persistence, fractional integration, timevarying coefficients, VARFIMA. JEL Classification: E52, C32

Transcription factor map alignment of promoter regions

We address the problem of comparing and characterizing the promoter regions of genes with similar expression patterns. This remains a challenging problem in sequence analysis, because often the promoter regions of co-expressed genes do not show discernible sequence conservation. In our approach, thus, we have not directly compared the nucleotide sequence of promoters. Instead, we have obtained predictions of transcription factor binding sites, annotated the predicted sites with the labels of the corresponding binding factors, and aligned the resulting sequences of labels—to which we refer here as transcription factor maps (TF-maps). To obtain the global pairwise alignment of two TF-maps, we have adapted an algorithm initially developed to align restriction enzyme maps. We have optimized the parameters of the algorithm in a small, but well-curated, collection of human–mouse orthologous gene pairs. Results in this dataset, as well as in an independent much larger dataset from the CISRED database, indicate that TF-map alignments are able to uncover conserved regulatory elements, which cannot be detected by the typical sequence alignments.