Paper de les técniques d’imatge en la sel•leccio i seguiment dels pacients amb insuficiencia cardiaca candidats a terapia de reisincronització cardiaca

Estudi elaborat a partir d’una estada a la Leiden University Medical Center durant l’any 2007. La teràpia de resincronització cardíaca (TRC), mitjançant l'estimulació biventricular, millora el pronòstic dels pacients amb insuficiència cardíaca i asincronia ventricular. Tot i així, fins a una tercera part dels pacients que reben TRC no presenten cap milloria clínica ni en la funció cardíaca. L'absència d'asincronia ventricular és una de les raons que explicarien la falta de resposta. Les tècniques actuals d'ecocardiografia permeten caracteritzar la mecànica ventricular i definir l'asincronia ventricular acuradament. Mitjançant tècniques ecocardiogràfiques s’ha estudiat la mecànica i sincronia ventriculars dels pacients amb insuficiència cardíaca tractats amb TRC per obtenir predictors de resposta a aquesta teràpia per optimitzar la seva relació cost-eficàcia. En 161 pacients tractats amb TRC es varen realitzar ecocardiografies seriades (abans i després de la implantació del marcapàs biventricular, amb el dispossitiu activat i desactivat). Els volums i la fracció d'ejecció ventriculars esquerres varen ser quantificats. L'asincronia ventricular esquerra va ser estudiada amb imatge en 2D strain, calculant el retard d'activació entre diferents segments ventriculars en diferents direccions: longitudinal, circumferencial i radial. Tanmateix, els efectes de la TRC sobre el remodelat i la mecànica ventricular esquerra es varen avaluar amb tècniques de 2D strain, mesurant el pic sistòlic d'escurçament longitudinal (GLPSS). Una reducció d'un 15% o més del volum telesistòlic del ventricle esquerre al final del seguiment va ser considerat com a marcador de resposta favorable a la TRC. Els resultats han mostrat que les tècniques de 2D strain permeten estudiar àmpliament la sincronia i mecànica ventriculars esquerres per identificar pacients que potencialment responedors a la TRC.

Anàlisi i tècniques de processat del senyal per a la generació de mapes eòlics

L’emplaçament del projecte es situa a un parc eòlic marítim, on es vol observar el vent a través del radar VAD, Velocity Azimuth Display, per poder controlar la velocitat de rotació dels aerogeneradors, i poder substituir els actuals anemòmetres. No ens centrarem en el control d’aquest, sinó que l’objectiu principal d’aquest projecte és analitzar el funcionament i processat de dades del VAD. Es proposaran, simularan i estudiaran noves tècniques d’estimació espectral per obtenir una millora important amb les mesures de velocitat, direcció i divergència del vent, per tal de construir un radar més robust a pertorbacions. A més a més, també il·lustrarem mapes eòlics obtinguts a partir de tot el processat.

Textural classification of land cover using support vector machines: an empirical comparison with parametric, non parametric and hybrid classifiers in the Bolivian Amazon

Land cover classification is a key research field in remote sensing and land change science as thematic maps derived from remotely sensed data have become the basis for analyzing many socio-ecological issues. However, land cover classification remains a difficult task and it is especially challenging in heterogeneous tropical landscapes where nonetheless such maps are of great importance. The present study aims to establish an efficient classification approach to accurately map all broad land cover classes in a large, heterogeneous tropical area of Bolivia, as a basis for further studies (e.g., land cover-land use change). Specifically, we compare the performance of parametric (maximum likelihood), non-parametric (k-nearest neighbour and four different support vector machines - SVM), and hybrid classifiers, using both hard and soft (fuzzy) accuracy assessments. In addition, we test whether the inclusion of a textural index (homogeneity) in the classifications improves their performance. We classified Landsat imagery for two dates corresponding to dry and wet seasons and found that non-parametric, and particularly SVM classifiers, outperformed both parametric and hybrid classifiers. We also found that the use of the homogeneity index along with reflectance bands significantly increased the overall accuracy of all the classifications, but particularly of SVM algorithms. We observed that improvements in producer’s and user’s accuracies through the inclusion of the homogeneity index were different depending on land cover classes. Earlygrowth/degraded forests, pastures, grasslands and savanna were the classes most improved, especially with the SVM radial basis function and SVM sigmoid classifiers, though with both classifiers all land cover classes were mapped with producer’s and user’s accuracies of around 90%. Our approach seems very well suited to accurately map land cover in tropical regions, thus having the potential to contribute to conservation initiatives, climate change mitigation schemes such as REDD+, and rural development policies.

Detecció i localització d'impactes a estructures aeroespacials

Projecte de recerca elaborat a partir d’una estada a la Universidad Politécnica de Madrid, Espanya, entre setembre i o desembre del 2007. Actualment la indústria aeroespacial i aeronàutica té com prioritat millorar la fiabilitat de las seves estructures a través del desenvolupament de nous sistemes per a la monitorització i detecció d’impactes. Hi ha diverses tècniques potencialment útils, i la seva aplicabilitat en una situació particular depèn críticament de la mida del defecte que permet l’estructura. Qualsevol defecte canviarà la resposta vibratòria de l’element estructural, així com el transitori de l’ona que es propaga per l’estructura elàstica. Correlacionar aquests canvis, que poden ser detectats experimentalment amb l’ocurrència del defecte, la seva localització i quantificació, és un problema molt complex. Aquest treball explora l’ús de l'Anàlisis de Components Principals (Principal Component Analysis - PCA-) basat en la formulació dels estadístics T2 i Q per tal de detectar i distingir els defectes a l'estructura, tot correlacionant els seus canvis a la resposta vibratòria. L’estructura utilitzada per l’estudi és l’ala d’una turbina d’un avió comercial. Aquesta ala s’excita en un extrem utilitzant un vibrador, i a la qual s'han adherit set sensors PZT a la superfície. S'aplica un senyal conegut i s'analitzen les respostes. Es construeix un model PCA utilitzant dades de l’estructura sense defecte. Per tal de provar el model, s'adhereix un tros d’alumini en quatre posicions diferents. Les dades dels assajos de l'estructura amb defecte es projecten sobre el model. Les components principals i les distàncies de Q-residual i T2-Hotelling s'utilitzaran per a l'anàlisi de les incidències. Q-residual indica com de bé s'adiu cadascuna de les mostres al model PCA, ja que és una mesura de la diferència, o residu, entre la mostra i la seva projecció sobre les components principals retingudes en el model. La distància T2-Hotelling és una mesura de la variació de cada mostra dins del model PCA, o el que vindria a ser el mateix, la distància al centre del model PCA.

Perspectives of auto-correcting lens distortions in mosaic-based underwater navigation

When unmanned underwater vehicles (UUVs) perform missions near the ocean floor, optical sensors can be used to improve local navigation. Video mosaics allow to efficiently process the images acquired by the vehicle, and also to obtain position estimates. We discuss in this paper the role of lens distortions in this context, proving that degenerate mosaics have their origin not only in the selected motion model or in registration errors, but also in the cumulative effect of radial distortion residuals. Additionally, we present results on the accuracy of different feature-based approaches for self-correction of lens distortions that may guide the choice of appropriate techniques for correcting distortions

Stochastic optimal bid to electricity markets with environmental risk constraints

There are many factors that influence the day-ahead market bidding strategies of a generation company (GenCo) in the current energy market framework. Environmental policy issues have become more and more important for fossil-fuelled power plants and they have to be considered in their management, giving rise to emission limitations. This work allows to investigate the influence of both the allowances and emission reduction plan, and the incorporation of the derivatives medium-term commitments in the optimal generation bidding strategy to the day-ahead electricity market. Two different technologies have been considered: the coal thermal units, high-emission technology, and the combined cycle gas turbine units, low-emission technology. The Iberian Electricity Market and the Spanish National Emissions and Allocation Plans are the framework to deal with the environmental issues in the day-ahead market bidding strategies. To address emission limitations, some of the standard risk management methodologies developed for financial markets, such as Value-at-Risk (VaR) and Conditional Value-at-Risk (CVaR), have been extended. This study offers to electricity generation utilities a mathematical model to determinate the individual optimal generation bid to the wholesale electricity market, for each one of their generation units that maximizes the long-run profits of the utility abiding by the Iberian Electricity Market rules, the environmental restrictions set by the EU Emission Trading Scheme, as well as the restrictions set by the Spanish National Emissions Reduction Plan. The economic implications for a GenCo of including the environmental restrictions of these National Plans are analyzed and the most remarkable results will be presented.

Contextual effects on subjective national identity and nationalist vote in Catalonia

The important inflow of foreign population to western countries has boosted the study of acculturation processes among scholars in the last decades. By using the case of Catalonia, a receiver region of international and national migration since the fifties, this paper seeks to intersect a classic acculturation model and a newly reemerging literature in political science on contextual determinants on individual behavior. Does the context matters for understanding individual’s subjective national identity and, therefore, its voting behavior? Multilevel models show that environment matters. Percentage of Spain-born population in the town is statistically significant to account for variance in the subjective national identity and nationalist vote, even after controlling for age, sex, origin, language and left – right orientation and other contextual factors. This conclusion invites researchers not to underestimate the direct effect of the environment on individual outcomes such as feelings of belonging and vote orientation in contexts of rival identities.

Characterization of myocardial deformation in patients with different etiologies of left ventricular hypertrophy by using strain distribution from Magnetic Resonance Imaging

Introducción y objetivos. Se ha señalado que, en la miocardiopatía hipertrófica (MCH), la desorganización de las fibras regionales da lugar a segmentos en los que la deformación es nula o está gravemente reducida, y que estos segmentos tienen una distribución no uniforme en el ventrículo izquierdo (VI). Esto contrasta con lo observado en otros tipos de hipertrofia como en el corazón de atleta o la hipertrofia ventricular izquierda hipertensiva (HVI-HT), en los que puede haber una deformación cardiaca anormal, pero nunca tan reducida como para que se observe ausencia de deformación. Así pues, proponemos el empleo de la distribución de los valores de strain para estudiar la deformación en la MCH. Métodos. Con el empleo de resonancia magnética marcada (tagged), reconstruimos la deformación sistólica del VI de 12 sujetos de control, 10 atletas, 12 pacientes con MCH y 10 pacientes con HVI-HT. La deformación se cuantificó con un algoritmo de registro no rígido y determinando los valores de strain sistólico máximo radial y circunferencial en 16 segmentos del VI. Resultados. Los pacientes con MCH presentaron unos valores medios de strain significativamente inferiores a los de los demás grupos. Sin embargo, aunque la deformación observada en los individuos sanos y en los pacientes con HVI-HT se concentraba alrededor del valor medio, en la MCH coexistían segmentos con contracción normal y segmentos con una deformación nula o significativamente reducida, con lo que se producía una mayor heterogeneidad de los valores de strain. Se observaron también algunos segmentos sin deformación incluso en ausencia de fibrosis o hipertrofia. Conclusiones. La distribución de strain caracteriza los patrones específicos de deformación miocárdica en pacientes con diferentes etiologías de la HVI. Los pacientes con MCH presentaron un valor medio de strain significativamente inferior, así como una mayor heterogeneidad de strain (en comparación con los controles, los atletas y los pacientes con HVI-HT), y tenían regiones sin deformación.

Immigration and housing booms: Evidence from Spain

We estimate empirically the effect of immigration on house prices and residentialconstruction activity in Spain over the period 1998-2008. This decade is characterized by both aspectacular housing market boom and a stunning immigration wave. We exploit the variation inimmigration across Spanish provinces and construct an instrument based on the historicallocation patterns of immigrants by country of origin. The evidence points to a sizeable causaleffect of immigration on both prices and quantities in the housing market. Between 1998 and2008, the average Spanish province received an immigrant inflow equal to 17% of the initialworking-age population. We estimate that this inflow increased house prices by about 52% andis responsible for 37% of the total construction of new housing units during the period. Thesefigures imply that immigration can account for roughly one third of the housing boom, both interms of prices and new construction.

With a bang, not a whimper: Pricking Germany's "stock market bubble" in 1927 and the slide into depression

In May 1927, the German central bank intervenedindirectly to reduce lending to equity investors.The crash that followed ended the only stockmarket boom during Germany s relative stabilization 1924-28. This paper examines thefactors that lead to the intervention as well asits consequences. We argue that genuine concernabout the exuberant level of the stock market,in addition to worries about an inflow offoreign funds, tipped the scales in favour ofintervention. The evidence strongly suggeststhat the German central bank under HjalmarSchacht was wrong to be concerned aboutstockprices-there was no bubble. Also, theReichsbank was mistaken in its belief thata fall in the market would reduce theimportance of short-term foreign borrowing,and help to ease conditions in the money market.The misguided intervention had important realeffects. Investment suffered, helping to tipGermany into depression.

Crossing the Rio Grande: Migrations, business cycles and the welfare state

In this paper we study the macroeconomic effects of an inflow oflow-skilled workers into an economy where there is capital accumulation and two types of agents. We find that there are substantial dynamic effects following unexpected migrations with adjustments that resemble those triggered by a sudden disruption of the capital stock. We look at the interrelations between these dynamic effects and three different fiscal systems for the redistribution of income and find that these schemes can change the dynamics and lead to prolonged periods of adjustments. Theaggregate welfare implications are sensitive to the welfare system: while there are welfare gains without redistribution, these gains may be turned into costs when the state engages in redistribution.

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.