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.

Discrete devaluations and multiple equilibria in a first generation model of currency crises

The first generation models of currency crises have often been criticized because they predict that, in the absence of very large triggering shocks, currency attacks should be predictable and lead to small devaluations. This paper shows that these features of first generation models are not robust to the inclusion of private information. In particular, this paper analyzes a generalization of the Krugman-Flood-Garber (KFG) model, which relaxes the assumption that all consumers are perfectly informed about the level of fundamentals. In this environment, the KFG equilibrium of zero devaluation is only one of many possible equilibria. In all the other equilibria, the lack of perfect information delays the attack on the currency past the point at which the shadow exchange rate equals the peg, giving rise to unpredictable and discrete devaluations.

Contracting externalities and multiple equilibria in sectors: Theory and evidence

We consider an economy where the production technology has constantreturns to scale but where in the descentralized equilibrium thereare aggregate increasing returns to scale. The result follows froma positive contracting externality among firms. If a firms issurrounded by more firms, employees have more opportunitiesoutside their own firm. This improves employees' incentives toinvest in the presence of ex post renegotiation at the firm level,at not cost. Our leading result is that if a region is sparselypopulated or if the degree of development in the region is lowenough, there are multiple equilibria in the level of sectorialemployment. From the theoretical model we derive a non-linearfirst-order censored difference equation for sectoral employment.Our results are strongly consistent with the multiple equilibriahypothesis and the existence of a sectoral critical scale (belowwich the sector follows a delocation process). The scale of theregions' population and the degree of development reduce thecritical scale of the sector.

Raman scattering and photoluminescence analysis of silicon on insulator structures obtained by single and multiple oxygen implants

An analysis of silicon on insulator structures obtained by single and multiple implants by means of Raman scattering and photoluminescence spectroscopy is reported. The Raman spectra obtained with different excitation powers and wavelengths indicate the presence of a tensile strain in the top silicon layer of the structures. The comparison between the spectra measured in both kinds of samples points out the existence in the multiple implant material of a lower strain for a penetration depth about 300 nm and a higher strain for higher penetration depths. These results have been correlated with transmission electron microscopy observations, which have allowed to associate the higher strain to the presence of SiO2 precipitates in the top silicon layer, close to the buried oxide. The found lower strain is in agreement with the better quality expected for this material, which is corroborated by the photoluminescence data.

Cooperative Transmission and Radio Resources Management for Wireless Networks

Report for the scientific sojourn at the Multimedia Communications Laboratory, University of Texas at Dallas, USA, from September to December 2005. The cooperative transmission has been analyzed taking a broadcast relay channel which assumes a scenario with one source and multiple destinations. Moreover, in order to improve the performance in terms of mutual information, it has been considered that for each destination there is another nearby terminal (called relay) which will help to improve the performance of the destination. This scheme combines different types of channels considered in the information theory, such as the relay channel, broadcast channel and interference channel (if the relays transmit information intended only to its associated destination). In this work, the author has studied the optimal way to encode the signals for the different users, known as capacity region (i.e. related to radio resources management ), of the broadcast relay channel.

Deconstructing Shocks and Persistence in OECD Real Exchange Rates

This paper analyzes the persistence of shocks that affect the real exchange rates for a panel of seventeen OECD developed countries during the post-Bretton Woods era. The adoption of a panel data framework allows us to distinguish two different sources of shocks, i.e. the idiosyncratic and the common shocks, each of which may have di¤erent persistence patterns on the real exchange rates. We first investigate the stochastic properties of the panel data set using panel stationarity tests that simultaneously consider both the presence of cross-section dependence and multiple structural breaks that have not received much attention in previous persistence analyses. Empirical results indicate that real exchange rates are non-stationary when the analysis does not account for structural breaks, although this conclusion is reversed when they are modeled. Consequently, misspecification errors due to the non-consideration of structural breaks leads to upward biased shocks' persistence measures. The persistence measures for the idiosyncratic and common shocks have been estimated in this paper always turn out to be less than one year.

Teaching foreign languages through translation: considering multiple intelligences

Aquest treball de recerca tracta de la relació existent entre pedagogia, traducció, llengües estrangeres i intel•ligències múltiples. El debat sobre si la traducció és una eina útil a la classe de llengües estrangeres és un tema actual sobre el qual molts investigadors encara indaguen. Estudis recents, però, han demostrat que qualsevol tasca de traducció -en la qual s’hi poden incloure treballs amb les diferents habilitats- és profitosa si la considerem un mitjà, no una finalitat en ella mateixa. Evidentment, l’ús de la traducció dins l’aula és avantatjosa, però també hem de tenir presents certs desavantatges d’aquesta aplicació. Un possible desavantatge podria ser la creença que, al principi, molta gent té referent a l’equivalència, paraula per paraula, d’una llengua vers una altra. Però després de presentar vàries tasques de traducció als estudiants, aquests poden arribar a controlar, fins i tot, les traduccions inconscients i poden assolir un cert nivell de precisió i flexibilitat que val la pena mencionar. Però l’avantatge principal és que s’enfronten a una activitat molt estesa dins la societat actual que combina dues llengües, la llengua materna i la llengua objecte d’estudi, per exemple. De tot això en podem deduir que utilitzar la llengua materna a la classe no s’ha de considerar un crim, com fins ara, sinó una virtut, evidentment si és emprada correctament. En aquest treball de recerca s’hi pot trobar una síntesi tant de les principals teories d’adquisició i aprenentatge de llengües com de les teories de traducció. A la pregunta de si les teories, tant de traducció com de llengües estrangeres, s’haurien d’ensenyar implícita o explícitament, es pot inferir que segons el nivell d’estudis on estiguin els aprenents els convindrà aprendre les teories explícitament o les aprendran, de totes maneres, implícitament. Com que qualsevol grup d’estudiants és heterogeni -és a dir que cada individu té un ritme i un nivell d’aprenentatge concret i sobretot cadascú té diferents estils de percepció (visual, auditiu, gustatiu, olfactiu, de moviment) i per tant diferents intel•ligències-, els professors ho han de tenir en compte a l’hora de planificar qualsevol programa d’actuació vers els alumnes. Per tant, podem concloure que les tasques o projectes de traducció poden ajudar als alumnes a aprendre millor, més eficaçment i a aconseguir un aprenentatge més significatiu.

Law and the practise of principle in diverse societies

Projecte de recerca elaborat a partir d’una estada a la London School of Economics and Political Science, United Kingdom, entre 2007 i 2009. L’objecte principal del projecte ha estat analitzar les implicacions jurídico-polítiques i institucionals d’una teoria de la justícia i la igualtat liberals aplicada a societats multiculturals amb un marcat predomini de la diversitat cultural. L’anàlisi desenvolupa una línia d'investigació interdisciplinar - entre el dret i la teoria política - iniciada en una tesis doctoral sobre multiculturalisme i drets de les minories culturals (UPF, 2000) que va culminar en la publicació de Group Rights as Human Rights (Springer, 2006). La recerca adopta com a punt de partida les conclusions de l'esmentada obra, en especial, la rellevància del reconeixement de drets col•lectius; tanmateix, el tipus de qüestions plantejades, l’enfoc i la metodologia emprades són substancialment diferents. En concret, s'adrecen preguntes específiques sobre el model i aspiracions del constitucionalisme democràtic i el paper del dret en contextos multiculturals. També s’atorga un pes central a la dimensió institucional dels models de gestió de la diversitat que s’analitzen, prioritzant un enfocament comparatiu a partir de l’estudi de controvèrsies concretes. L’objectiu és superar algunes limitacions importants de la literatura actual, com ara la tendència a examinar en abstracte la compatibilitat de determinades demandes amb el constitucionalisme democràtic, sense abordar el funcionament d'estratègies de gestió de la diversitat cultural emprades en contextos concrets. Els treballs producte d'aquest projecte articulen les línies bàsiques d’un model pluralista, basat en principis més que en regles, que desafia els plantejaments dominants actualment. Aquest model es caracteritza pel compromís amb la legitimitat i igualtat comparatives, rebutjant el paternalisme i les visions liberals típiques sobre el paper de la regulació. La presumpció de l’“standing” moral dels grups identitaris és fonamental per tal de considerar-los interlocutors vàlids amb interessos genuïns. També s’argumenta que la integració social en contextos multiculturals no depèn tant de l’eliminació del conflicte sinó, sobre tot, d’una gestió eficient que eviti abusos de poder sistemàtics. El model defensa el rol del dret en la institucionalització del diàleg intercultural, però admet que el diàleg no necessàriament condueix a l’acord o a una estructura reguladora coherent i uniforme. Les aspiracions del ordre jurídic pluralista són més modestes: afavorir la negociació i resolució en cada conflicte, malgrat la persistència de la fragmentació i la provisionalitat dels acords. La manca d'un marc regulador comú esdevé una virtut en la mesura que permet la interacció de diferents subordres; una interacció governada per una multiplicitat de regles no necessàriament harmòniques. Els avantatges i problemes d’aquest model s'analitzen a partir de l'anàlisi de l’estructura fragmentària de l'ordre jurídic internacional i del règim Europeu de drets humans.

Gross Hemoglobinuria and Oliguria are Common Transient Complications of Sclerotherapy for Venous Malformations: Review of 475 Procedures.

Estudi retrospectiu per analitzar la incidència, factors de risc i tractament de la hemoglobinuria macroscòpica i oliguria després del tractament de malformacions venoses amb escleroteràpia. Un total de 475 procediments es van realitzar en 131 malalts usant etanol, sulfat tetradecil sòdic o ambdos. Hemoglobinuria temporal es va donar després del 34% de procediments i el 57% d’aquests es van asociar amb oliguria temporal. Aquest risc augmenta amb el increment de dosis. La resolució de la hemoglobinuria i oliguria va ser satisfactòria en tots els malalts. El risc d’hemoglobinuria augmenta a les malformacions que afecten les extremitats inferiors i a les de localitzacions mútiples.

Coherent forecasting of multiple-decrement life tables: a test using Japanese cause of death data

Planners in public and private institutions would like coherent forecasts of the components of age-specic mortality, such as causes of death. This has been di cult toachieve because the relative values of the forecast components often fail to behave ina way that is coherent with historical experience. In addition, when the group forecasts are combined the result is often incompatible with an all-groups forecast. It hasbeen shown that cause-specic mortality forecasts are pessimistic when compared withall-cause forecasts (Wilmoth, 1995). This paper abandons the conventional approachof using log mortality rates and forecasts the density of deaths in the life table. Sincethese values obey a unit sum constraint for both conventional single-decrement life tables (only one absorbing state) and multiple-decrement tables (more than one absorbingstate), they are intrinsically relative rather than absolute values across decrements aswell as ages. Using the methods of Compositional Data Analysis pioneered by Aitchison(1986), death densities are transformed into the real space so that the full range of multivariate statistics can be applied, then back-transformed to positive values so that theunit sum constraint is honoured. The structure of the best-known, single-decrementmortality-rate forecasting model, devised by Lee and Carter (1992), is expressed incompositional form and the results from the two models are compared. The compositional model is extended to a multiple-decrement form and used to forecast mortalityby cause of death for Japan

Surface registration from range image fusion

The registration of full 3-D models is an important task in computer vision. Range finders only reconstruct a partial view of the object. Many authors have proposed several techniques to register 3D surfaces from multiple views in which there are basically two aspects to consider. First, poor registration in which some sort of correspondences are established. Second, accurate registration in order to obtain a better solution. A survey of the most common techniques is presented and includes experimental results of some of them

The suitability of steam exploded vitis vinifera and alkaline lignin for the manufacture of fiberboard

The main objective of this study was to explore the suitability of Vitis vinifera as a raw material and alkaline lignin as a natural binder for fiberboard manufacturing. In the first step, Vitis vinifera was steam- exploded through a thermo-mechanical vapor process in a batch reactor, and the obtained pulp was dried, ground, and pressed to produce the boards. The effects of pretreatment factors and pressing conditions on the chemical composition of the fibers and the physico-mechanical properties of binderless fiberboards were evaluated, and the conditions that optimize these properties were found. A response surface method based on a central composite design and multiple-response optimization was used. The variables studied and their respective variation ranges were: pretreatment temperature (Tr: 190-210ºC), pretreatment time (tr: 5-10 min), pressing temperature (Tp: 190-210ºC), pressing pressure (Pp: 8-16MPa), and pressing time (tp: 3-7min). The results of the optimization step show that binderless fiberboards have good water resistance and weaker mechanical properties. In the second step, fiberboards based on alkaline lignin and Vitis vinifera pulp produced at the optimal conditions determined for binderless fiberboards were prepared and their physico-mechanical properties were tested. Our results show that the addition of about 15% alkaline lignin leads to the production of fiberboards that fully meet the requirements of the relevant standard specifications

A simple model of multiple equilibria based on risk

This paper shows how risk may aggravate fluctuations in economies with imperfect insurance and multiple assets. A two period job matching model is studied, in which risk averse agents act both as workers and as entrepreneurs. They choose between two types of investment: one type is riskless, while the other is a risky activity that creates jobs.Equilibrium is unique under full insurance. If investment is fully insured but unemployment risk is uninsured, then precautionary saving behavior dampens output fluctuations. However, if both investment and employment are uninsured, then an increase in unemployment gives agents an incentive to shift investment away from the risky asset, further increasing unemployment. This positive feedback may lead to multiple Pareto ranked equilibria. An overlapping generations version of the model may exhibit poverty traps or persistent multiplicity. Greater insurance is doubly beneficial in this context since it can both prevent multiplicity and promote risky investment.

The three horsemen of riches: Plague, war and urbanization in early modern Europe

How did Europe escape the "Iron Law of Wages?" We construct a simple Malthusian model withtwo sectors and multiple steady states, and use it to explain why European per capita incomes andurbanization rates increased during the period 1350-1700. Productivity growth can only explain a smallfraction of the rise in output per capita. Population dynamics changes of the birth and death schedules were far more important determinants of steady states. We show how a major shock to population cantrigger a transition to a new steady state with higher per-capita income. The Black Death was such ashock, raising wages substantially. Because of Engel's Law, demand for urban products increased, andurban centers grew in size. European cities were unhealthy, and rising urbanization pushed up aggregatedeath rates. This effect was reinforced by diseases spread through war, financed by higher tax revenues.In addition, rising trade also spread diseases. In this way higher wages themselves reduced populationpressure. We show in a calibration exercise that our model can account for the sustained rise in Europeanurbanization as well as permanently higher per capita incomes in 1700, without technological change.Wars contributed importantly to the "Rise of Europe", even if they had negative short-run effects. We thustrace Europe s precocious rise to economic riches to interactions of the plague shock with the belligerentpolitical environment and the nature of cities.

Identification of geometrically consistent interest points for 3D scene reconstruction

We propose an algorithm that extracts image features that are consistent with the 3D structure of the scene. The features can be robustly tracked over multiple views and serve as vertices of planar patches that suitably represent scene surfaces, while reducing the redundancy in the description of 3D shapes. In other words, the extracted features will off er good tracking properties while providing the basis for 3D reconstruction with minimum model complexity