Markov chain montecarlo method applied to rounding zeros of compositional data: first approach

As stated in Aitchison (1986), a proper study of relative variation in a compositional data set should be based on logratios, and dealing with logratios excludes dealing with zeros. Nevertheless, it is clear that zero observations might be present in real data sets, either because the corresponding part is completelyabsent ���essential zeros��� or because it is below detection limit ���rounded zeros. Because the second kind of zeros is usually understood as ���a trace too small to measure���, it seems reasonable to replace them by a suitable small value, and this has been the traditional approach. As stated, e.g. by Tauber (1999) and byMart��n-Fern��ndez, Barcel��-Vidal, and Pawlowsky-Glahn (2000), the principal problem in compositional data analysis is related to rounded zeros. One should be careful to use a replacement strategy that does not seriously distort the general structure of the data. In particular, the covariance structure of the involvedparts ���and thus the metric properties��� should be preserved, as otherwise further analysis on subpopulations could be misleading. Following this point of view, a non-parametric imputation method isintroduced in Mart��n-Fern��ndez, Barcel��-Vidal, and Pawlowsky-Glahn (2000). This method is analyzed in depth by Mart��n-Fern��ndez, Barcel��-Vidal, and Pawlowsky-Glahn (2003) where it is shown that thetheoretical drawbacks of the additive zero replacement method proposed in Aitchison (1986) can be overcome using a new multiplicative approach on the non-zero parts of a composition. The new approachhas reasonable properties from a compositional point of view. In particular, it is ���natural��� in the sense thatit recovers the ���true��� composition if replacement values are identical to the missing values, and it is coherent with the basic operations on the simplex. This coherence implies that the covariance structure of subcompositions with no zeros is preserved. As a generalization of the multiplicative replacement, in thesame paper a substitution method for missing values on compositional data sets is introduced

A Formal Framework for Specifying, Reusing and Implementing Learning Processes. First level

This file contains the ontology of patterns of educational settings, as part of the formal framework for specifying, reusing and implementing educational settings. Furthermore, it includes the set of rules that extend the ontology of educational scenarios as well as a brief description of the level of patters of such ontological framework.

Behavioural Flexibility: evolutionary past and its role in a changing world

A trav��s de la historia de la vida, gran parte de los organismos han desarrollado estrategias para responder a un mundo en constante cambio. Hoy en d��a, las actividades humanas producen cambios ambientales a una velocidad sin precedentes, lo cual se traduce en grandes desaf��os para la persistencia de biodiversidad. Esta investigaci��n eval��a las respuesta de los animales a los cambios ambientales enfoc��ndose en la flexibilidad del comportamiento como estrategia adaptativa. En una primera aproximaci��n a una escala evolutiva, se otorgan evidencias del v��nculo hasta ahora tenue entre la cognici��n e historias de vida, entregando un claro apoyo a la relaci��n entre longevidad, vida reproductiva y el tama��o del cerebro en mam��feros. La longevidad es el centro de muchas hip��tesis respecto a las ventajas de desarrollar un cerebro grande, como por ejemplo en la hip��tesis del buffer cognitivo y las respuestas flexibles frente a nuevos ambientes. En un segundo nivel, se abordan factores extr��nsecos e intr��nsecos que podr��an explicar las diferencias individuales en innovaci��n, un componente clave en la flexibilidad del comportamiento. Por medio de una aproximaci��n experimental, se eval��an potenciales escenarios que podr��an conducir a consistentes diferencias individuales en uno de los principales factores subyacentes a la innovaci��n (i.e. la motivaci��n), y el potencial control endocrino sobre estos escenarios. Posteriormente, con el objetivo de evaluar la respuesta de los animales frente a los cambios ambientales actuales, se explora la respuesta de los animales frente a una de las actividades humanas mas disruptivas sobre los ecosistemas, la urbanizaci��n. Por medio de un analisis filogenetico comparativo a nivel global en aves se abordan los mecanismos implicados en la perdida de biodiversidad observada en ambientes urbanos. Los resultados entregan evidencias sobre la importancia de procesos de dispersi��n local junto con el papel clave de los rasgos de historia de vida, pero en un sentido diferente al clasicamente pensado. Finalmente por medio de una revisi��n bibliogr��fica se entregan evidencias te��ricas y emp��ricas que respaldan el rol clave de la flexibilidad del comportamiento en confrontar los desaf��os de una vida urbana. La integraci��n de estos resultados muestra c��mo el pasado evolutivo contribuye a hacer frente a los retos ambientales actuales, y pone de relieve posibles consecuencias ante un planeta m��s cambiante que nunca.

Cultural self-identification(s) and personal social networks among first and second-generation immigrants

L���estudi examina les relacions entre (1) les xarxes socials personals de la poblaci�� immigrant resident a Barcelona i (2) les seves identitats culturals m��ltiples. L���objectiu principal de l���estudi ��s entendre com el contingut i l���estructura de les relacions socials dels immigrants facilita o dificulta (1) tenir un sentiment de pertinen��a a les noves cultures d���acollida, la catalana i la espanyola, i (2) la integraci�� d���aquestes noves identitats socioculturals amb la seva identitat d���origen en una nova identitat bicultural cohesiva. El nostre plantejament inicial era que els immigrants amb xarxes socials m��s diverses des del punt de vista de la seva composici�� cultural tindrien m��s recursos socials i experi��ncies cognitives m��s diverses , factors que afavoreixen les identificacions m��ltiples i la participaci�� c��vica. Els resultats de l���estudi mostren que el grau d���identificaci�� dels participants amb la seva cultura ��tnica o d���origen ��s for��a alt i, en certa mesura, m��s alt en comparaci�� amb les cultures d���acollida ( catalana, c��vica i espanyola). Tanmateix, el vincle dels participants amb les cultures d���acollida (p. ex., la cultura catalana) ��s prou rellevant per a indicar una orientaci�� bicultural (catalana i ��tnica). Les an��lisis de correlacions revelen que sentir-se catal�� no impedeix sentir-se part de la comunitat etnocultural d���origen. A m��s, existeix una interrelaci�� entre l'orientaci�� cultural catalana i la identificaci�� amb les comunitats c��viques locals. De la mateixa manera, tenir compet��ncies en llengua catalana no va en detriment de les compet��ncies en llengua castellana. Les an��lisis tamb�� mostren que factors com l���orientaci�� cultural catalana, l�����s del catal�� i la identificaci�� amb la cultura catalana tenen una correlaci�� positiva amb el grau de chohesio de la indentitat bicultural, afavoreixen el benestar psicol��gic i disminueixen l���estr��s aculturatiu. L���an��lisi de les xarxes socials mostra que la identificaci�� amb la cultura catalana, l���orientaci�� cultural catalana i la integraci�� de la identitat s��n factors clau per tenir xarxes socials m��s diverses des del punt de vista ��tnic i ling����stic, amb menys membres del col���lectiu d���origen, i amb subgrups o ���cliques��� culturalment m��s heterogenis. La identificaci�� espanyola tamb�� prediu, en mesura m��s redu��da, la diversitat de les xarxes. Els nostres resultats contribueixen a la recerca actual i les teories sobre interculturalitat i identitat cultural.

Electronic and vibrational contributions to first hyperpolarizability of donor-acceptor-substituted azobenzene

In this study we report on the electronic and vibrational (hyper)polarizabilities of donor���acceptorsubstituted azobenzene. It is observed that both electronic and vibrational contributions to the electricdipole first hyperpolarizability of investigated photoactive molecule substantially depend on the conformation. The contributions to the nuclear relaxation first hyperpolarizability are found to be quite important in the case of two considered isomers (cis and trans). Although the double-harmonic term is found to be the largest in terms of magnitude, it is shown that the total value of the nuclear relaxation contribution to vibrational first hyperpolarizability is a result of subtle interplay of higher-order contributions. As a part of the study, we also assess the performance of long-range-corrected densityfunctional theory in determining vibrational contributions to electric dipole (hyper)polarizabilities. In most cases, the applied long-range-corrected exchange correlation potentials amend the drawbacks of their conventional counterparts

Sickness presenteeism in Spanish-born and immigrant workers in Spain

Background: Previous studies have shown that immigrant workers face relatively worse working and employment conditions, as well as lower rates of sickness absence than native-born workers. This study aims to assess rates of sickness presenteeism in a sample of Spanish-born and foreign-born workers according to different characteristics. Methods: A cross-sectional survey was conducted amongst a convenience sample of workers (Spanish-born and foreign-born), living in four Spanish cities: Barcelona, Huelva, Madrid and Valencia (2008-2009). Sickness presenteeism information was collected through two items in the questionnaire ("Have you had health problems in the last year?" and "Have you ever had to miss work for any health problem?") and was defined as worker who had a health problem (answered yes, first item) and had not missed work (answered no, second item). For the analysis, the sample of 2,059 workers (1,617 foreign-born) who answered yes to health problems was included. After descriptives, logistic regressions were used to establish the association between origin country and sickness presenteeism (adjusted odds ratios aOR; 95% confidence interval 95%CI). Analyses were stratified per time spent in Spain among foreign-born workers. Results: All of the results refer to the comparison between foreign-born and Spanish-born workers as a whole, and in some categories relating to personal and occupational conditions. Foreign-born workers were more likely to report sickness presenteeism compared with their Spanish-born counterparts, especially those living in Spain for under 2 years [Prevalence: 42% in Spanish-born and 56.3% in Foreign-born; aOR 1.77 95%CI 1.24-2.53]. In case of foreign-born workers (with time in Spain < 2 years), men [aOR 2.31 95%CI 1.40-3.80], those with university studies [aOR 3.01 95%CI 1.04-8.69], temporary contracts [aOR 2.26 95%CI 1.29-3.98] and salaries between 751-1,200��� per month [aOR 1.74 95% CI 1.04-2.92] were more likely to report sickness presenteeism. Also, recent immigrants with good self-perceived health and good mental health were more likely to report presenteeism than Spanish-born workers with the same good health indicators. Conclusions: Immigrant workers report more sickness presenteeism than their Spanish-born counterparts. These results could be related to precarious work and employment conditions of immigrants. Immigrant workers should benefit from the same standards of social security, and of health and safety in the workplace that are enjoyed by Spanish workers.

Supporting life-long competence development using the TENCompetence infrastructure: a first experiment

This paper describes an experiment to explore the effects of the TENCompetence infrastructure for supporting lifelong competence development which is now in development. This infrastructure provides structured, multi-leveled access to learning materials, based upon competences. People can follow their own learning path, supported by a listing of competences and their components, by competence development plans attached to competences and by the possibility to mark elements as complete. We expected the PCM to have an effect on (1) control of participants of their own learning, and (2) appreciation of their learning route, (3) of the learning resources, (4) of their competence development, and (5) of the possibilities of collaboration. In the experiment, 44 Bulgarian teachers followed a distance learning course on a specific teaching methodology for six weeks. Part of them used the TENCompetence infrastructure, part used an infrastructure which was similar, except for the characterizing elements mentioned above. The results showed that in the experimental condition, more people passed the final competence assess-ment, and people felt more in control of their own learning. No differences between the two groups were found on the amount and appreciation of collaboration and on further measures of competence development.

Joint determinants of education enrolment and first birth timing in France and West Germany

We examined the reciprocal influence between educational decisions and the timing of first births, using the Family and Fertility Surveys of France and West Germany. Since these two processes are potentially endogenous, we modelled them jointly, using event history models. We hypothesise that the reciprocal impact of educational and fertility careers, as well as the impact of the common determinants of both processes, are gender specific and context specific.The results show a significant endogeneity for women and men in both countries. This endogeneity is stronger for women than for men, while no substantial differences are found between the two countries. Removing this shared and unobserved heterogeneity, the results show a stronger reciprocal impact between the processes for women than for men. A similar impact of being enrolled in education on first birth in both countries is found, while the effect of the birth (and especially of the pregnancy) of the first child on terminating one���s education appeared to be more marked in West Gernany than in France.

Improving social measurements: the experience of the ESS first rounds in Spain

With the two aims of monitoring social change and improving social measurement, the European Social Survey is now closing its third round. This paper shows how the accumulated experience of the two first rounds has been used to validate the questionnaire, better adapt the sampling design to the country characteristics and efficiently commit fieldwork in Spain. For example, the dynamic character of the population nowadays makes necessary to estimated design effects at each round from the data of the previous round. The paper also demonstrates how, starting with a response rate of 52% at first round, a 66% response rate is achieved at the third round thanks to an extensive quality control conducted by the polling agency and the ESS national team and based on a detailed analysis of the non-response cases and the incidences reported by the interviewed in the contact form.

Body Size, Activity, Employment and Wages in Europe: A First Approach

In this article we present the first empirical analysis on the associations between body size, activity, employment and wages for several European countries. The main advantage of the present work with respect to the previous literature is offered by the comparability of the data and its large geographical coverage. According to our results, for Spanish women, being obese is associated with both a 9% lower wage and probability of being employed, while for Swedish and Danish, obesity is associated with a 12% lower probability of being employed, and a 10% lower wage respectively. In Belgium, obesity is associated with a 19% lower probability of being employed for men. These robust estimates are strongly informative and may be used as a simple statistical rule of thumb to decide the countries in which lab and field experiments should be run.

First impressions matter: Signalling as a source of policy dynamics

We first establish that policymakers on the Bank of England's Monetary PolicyCommittee choose lower interest rates with experience. We then reject increasingconfidence in private information or learning about the structure of the macroeconomy as explanations for this shift. Instead, a model in which voters signal theirhawkishness to observers better fits the data. The motivation for signalling is consistent with wanting to control inflation expectations, but not career concerns orpleasing colleagues. There is also no evidence of capture by industry. The papersuggests that policy-motivated reputation building may be important for explainingdynamics in experts' policy choices.

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.

Improving social measurements: The experience of the ESS first rounds in Spain

With the two aims of monitoring social change and improving social measurement, the European Social Survey is now closing its third round. This paper shows how the accumulated experience of the two first rounds has been used to validate the questionnaire, better adapt the sampling design to the country characteristics and efficiently commit fieldwork in Spain. For example, the dynamic character of the population nowadays makes necessary to estimated design effects at each round from the data of the previous round. The paper also demonstrates how, starting with a response rate of 52% at first round, a 66% response rate is achieved at the third round thanks to an extensive quality control conducted by the polling agency and the ESS national team and based on a detailed analysis of the non-response cases and the incidences reported by the interviewed in the contact form.

The Spanish motor industry in the first third of the 20th Century: A lost opportunity

The Spanish automobile industry had a late start. Although the country proved capable of short production runs of high-quality vehicles during the first third of the century it never managed to build up its own industry, unlike Great Britain, France, or Italy. What then, were the critical shortcomings that prevented the establishment of large Spanish motor manufacturers? Put another way, why did all of the companies set up during the first half-century fail to survive? This paper attempts to shed some light on these questions, employing a wide-ranging analysis of both internal and external factors affecting the industry. A feeble internal market, lack of resources and production factors are usually adduced as reasons, as are Spain's general economic backwardness and the role played by the public authorities. However, this paper mainly focuses on the internal factors concerning company strategy and organisation. A comparison with the Italian case helps put the traditional arguments in proper perspective and highlights those covering business strategies. Finally, we argue that a broad range of factors needs to be analysed to fully understand why Spain failed to establish a motor industry.

Body size, activity, employment and wages in Europe: A first approach

This paper examines the associations between obesity, employment status and wages for several European countries. Our results provide weak evidence that obese workers are more likely to be unemployed or tend to be more segregated in self-employment jobs than their non-obese counterparts. We also find difficult to detect statistically significant relationships between obesity and wages. As previously reported in the literature, the association between obesity, unemployment and wages seems to be different for men and women. Moreover, heterogeneity is also found across countries. Such heterogeneity can be somewhat explained by some labor market institutions, such as the collective bargaining coverage and the employer-provided health insurance.