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.

Heterogeneity as a coordination device

A model of directed search with a finite number of buyers and sellers is considered, where sellers compete in direct mechanisms. Buyer heterogeneity and Nash equilibrium results in perfect sorting. The restriction to complementary inputs, that the match value function Q is supermodular, in addition coordinates the sellers strategies. In that case, equilibrium implements positive assortative matching, which is efficient and consistent with the stable (cooperative equilibrium) outcome. This provides a non-cooperative and decentralizedsolution for the Assignment Game. Conversely, if buyers are identical, no such coordination is possible, and there is a continuum of equilibria, one of which exhibits price posting, another yields competition in auctions.

Geometric and long run aspects of Granger causality

This paper extends multivariate Granger causality to take into account the subspacesalong which Granger causality occurs as well as long run Granger causality. The propertiesof these new notions of Granger causality, along with the requisite restrictions, are derivedand extensively studied for a wide variety of time series processes including linear invertibleprocess and VARMA. Using the proposed extensions, the paper demonstrates that: (i) meanreversion in L2 is an instance of long run Granger non-causality, (ii) cointegration is a specialcase of long run Granger non-causality along a subspace, (iii) controllability is a special caseof Granger causality, and finally (iv) linear rational expectations entail (possibly testable)Granger causality restriction along subspaces.

Stochastic uncoupled dynamics and Nash equilibrium

In this paper we consider dynamic processes, in repeated games, that are subject to the natural informational restriction of uncoupledness. We study the almost sure convergence to Nash equilibria, and present a number of possibility and impossibility results. Basically, we show that if in addition to random moves some recall is introduced, then successful search procedures that are uncoupled can be devised. In particular, to get almost sure convergence to pure Nash equilibria when these exist, it su±ces to recall the last two periods of play.

Valuation bubbles and sequential bubbles

Price bubbles in an Arrow-Debreu valuation equilibrium in infinite-timeeconomy are a manifestation of lack of countable additivity of valuationof assets. In contrast, known examples of price bubbles in sequentialequilibrium in infinite time cannot be attributed to the lack of countableadditivity of valuation. In this paper we develop a theory of valuation ofassets in sequential markets (with no uncertainty) and study the nature ofprice bubbles in light of this theory. We consider an operator, calledpayoff pricing functional, that maps a sequence of payoffs to the minimumcost of an asset holding strategy that generates it. We show that thepayoff pricing functional is linear and countably additive on the set ofpositive payoffs if and only if there is no Ponzi scheme, and providedthat there is no restriction on long positions in the assets. In the knownexamples of equilibrium price bubbles in sequential markets valuation islinear and countably additive. The presence of a price bubble indicatesthat the asset's dividends can be purchased in sequential markers at acost lower than the asset's price. We also present examples of equilibriumprice bubbles in which valuation is nonlinear but not countably additive.

On p-beauty contest integer games

In this paper we provide a full characterization of the pure-strategyNash Equilibria for the p-Beauty Contest Game when we restrict player schoices to integer numbers. Opposed to the case of real number choices,equilibrium uniqueness may be lost depending on the value of p and thenumber of players: in particular, as p approaches 1 any symmetric profileconstitutes a Nash Equilibrium. We also show that any experimental p-BeautyContest Game can be associated to a game with the integer restriction andthus multiplicity of equilibria becomes an issue. Finally, we show thatin these games the iterated deletion of weakly dominated strategies maynot lead to a single outcome while the iterated best-reply process alwaysdoes (though the outcome obtained depends on the initial conditions).

On the complexity of rationalizing behavior

We study the complexity of rationalizing choice behavior. We do so by analyzing two polar cases, and a number of intermediate ones. In our most structured case, that is where choice behavior is defined in universal choice domains and satisfies the "weak axiom of revealed preference," finding the complete preorder rationalizing choice behavior is a simple matter. In the polar case, where no restriction whatsoever is imposed, either on choice behavior or on choice domain, finding the complete preordersthat rationalize behavior turns out to be intractable. We show that the task of finding the rationalizing complete preorders is equivalent to a graph problem. This allows the search for existing algorithms in the graph theory literature, for the rationalization of choice.

Visualitzador de molècules d'ADN per laboratori virtual

RESUM Com a continuació del treball de final de carrera “Desenvolupament d’un laboratori virtual per a les pràctiques de Biologia Molecular” de Jordi Romero, s’ha realitzat una eina complementaria per a la visualització de molècules integrada en el propi laboratori virtual. Es tracta d’una eina per a la visualització gràfica de gens, ORF, marques i seqüències de restricció de molècules reals o fictícies. El fet de poder treballar amb molècules fictícies és la gran avantatge respecte a les solucions com GENBANK que només permet treballar amb molècules pròpies. Treballar amb molècules fictícies fa que sigui una solució ideal per a l’ensenyament, ja que dóna la possibilitat als professors de realitzar exercicis o demostracions amb molècules reals o dissenyades expressament per a l’exercici a demostrar. A més, permet mostrar de forma visual les diferents parts simultàniament o per separat, de manera que ofereix una primera aproximació interpretació dels resultats. Per altra banda, permet marcar gens, crear marques, localitzar seqüències de restricció i generar els ORF de la molècula que nosaltres creem o modificar una ja existent. Per l’implementació, s’ha continuat amb l’idea de separar la part de codi i la part de disseny en les aplicacions Flash. Per fer-ho, s’ha utilitzat la plataforma de codi lliure Ariware ARPv2.02 que proposa un marc de desenvolupament d’aplicacions Flash orientades a objectes amb el codi (classes ActionScript 2.0) separats del movieclip. Per al processament de dades s’ha fet servir Perl per ser altament utilitzat en Bioinformàtica i per velocitat de càlcul. Les dades generades es guarden en una Base de Dades en MYSQL (de lliure distribució), de la que s’extreuen les dades per generar fitxers XML, fent servir tant PHP com la plataforma AMFPHP com a enllaç entre Flash i la resta de parts.

SIMSAFADIM-CLASTIC: A new approach to mathematical 3D forward simulation modelling for terrigenous and carbonate marine sedimentation

Most sedimentary modelling programs developed in recent years focus on either terrigenous or carbonate marine sedimentation. Nevertheless, only a few programs have attempted to consider mixed terrigenous-carbonate sedimentation, and most of these are two-dimensional, which is a major restriction since geological processes take place in 3D. This paper presents the basic concepts of a new 3D mathematical forward simulation model for clastic sediments, which was developed from SIMSAFADIM, a previous 3D carbonate sedimentation model. The new extended model, SIMSAFADIM-CLASTIC, simulates processes of autochthonous marine carbonate production and accumulation, together with clastic transport and sedimentation in three dimensions of both carbonate and terrigenous sediments. Other models and modelling strategies may also provide realistic and efficient tools for prediction of stratigraphic architecture and facies distribution of sedimentary deposits. However, SIMSAFADIM-CLASTIC becomes an innovative model that attempts to simulate different sediment types using a process-based approach, therefore being a useful tool for 3D prediction of stratigraphic architecture and facies distribution in sedimentary basins. This model is applied to the neogene Vallès-Penedès half-graben (western Mediterranean, NE Spain) to show the capacity of the program when applied to a realistic geologic situation involving interactions between terrigenous clastics and carbonate sediments.