Design and optimization of the graft pretension protocol for the reconstruction of the anterior cruciate ligament (ACL)

Anterior cruciate ligament (ACL) rupture is one of the mayor concerns of today’s professional high demand athletes due to its high probabilities of happening and slow recovery. In general, the grafts used in ACL reconstruction surgeries are tendons taken from the same patient in order to reduce the possibility of rejection. However, these soft tissue grafts share viscoelastic properties which produce an elongation of the graft after its implantation, which if too much can lead to an invalid surgery. Thus, in order to eliminate this undesired property, the tendon needs to be preconditioned after its removal from the patient and before the re-implantation. This procedure involves a graft board to be able to apply a specific load to the tendon, thus being able to elongate it before its final implantation in the affected person. However, this protocol has not been standardized to date, hence each surgeon proceeds in their own way. The main goal of this project is to design and optimize a graft pretension protocol for the reconstruction of the anterior cruciate ligament. Digital Extensor Bovine tendons were used in order to test the quality and efficiency of the proposed protocols. Using a hydraulic machine, an ACL reconstruction surgery was simulated. A successful surgical procedure is determined by the graft elongation after its implantation in the knee, which if elongated too much invalids the reconstruction, not being able to achieve the natural ACL functions. Thus, out of all the parameters obtained, the most important one and so, taken into account for the discussion, is the elongation of the graft in the rehabilitation process. Using this parameter, protocols can be compared. Two out of the three protocols proposed show to be statistical different from the control group. The third one produced a high elongation of the tendon grafts due to the small value load applied to them. As no significant difference was found between the two successful protocols, we can determine that the one implying less load would be the best one for its reproducibility in the operating room. In conclusion, a pretension protocol is beneficial to the grafts as it reduces post-surgery elongation and it has to consist of at least 89 N in order to be able to eliminate part of the graft’s intrinsic viscoelastic properties.Ingeniería Biomédica (Plan 2010

Identidad sin sujeto: Arendt y el mutuo reconocimiento

This article discusses whether, from Hannah Arendt’s point of view, the being-in-common of singularities can be conceived in terms of mutual recognition. Although it is shown that Arendt’s theory of action involves the idea that the identity of singularities is relational, it is also stressed that it is a fluid identity, thrown into contingency. Therefore, it is not a more solid self consciousness what individuals achieve when they open themselves to each other and when they recognize themselves in their difference. What they achieve is to be exposed to the fact of coexistence, to an experience of plurality in which others are more than just a mirror in which they recognize and affirm themselves

Estimating non-linear models with multiple fixed effects : a computational note

En este trabajo se estudia la estimación de modelos no lineales de datos de panel que incluyen efectos fijos múltiples. La estimación de estos modelos es complicada tanto por la dificultad de estimar especificaciones con miles de coeficientes, como por el problema de los parámetros incidentales, esto es, cuando la dimensión temporal del panel es corta la imprecisión en la estimación de los efectos individuales contamina la de los parámetros comunes debido a la no linealidad del modelo. En el artículo se propone una variación simple de los estimadores de verosimilitudes corregidas de sesgo, que permite explotar la aditividad de los efectos en la optimización numérica, evitando así el cálculo de los efectos estimados para valores dados de los parámetros comunes. Simulaciones muestran el rendimiento del estimador propuest

Modelling heterogeneity and dynamics in the volatility of individual wages

Incluye bibliografíaIn this paper I consider a model for the heterogeneity and dynamics of the conditional mean and the conditional variance of standarized individual wages. In particular, I propose a dynamic panel data model with individual effects both in the mean and in a conditional ARCH type variance function. I posit a distribution for earning shocks and I build a modified likelihood function for estimation and inference in a fixed-T context. Using a newly developed bias-corrected likelihood approach makes it possible to reduce the estimation bias to a term of order 1 over T squared. The small sample performance of bias corrected estimators is investigated in a Monte Carlo simulation study. The simulation results show that the bias of the maximum likelihood estimator is substantially corrected for designs that are broadly calibrated to the PSID. The empirical analysis is conducted on data drawn from the 1968-1993 PSID. I find that it is important to account for individual unobserved heterogeneity and dynamics in the variance, and that the latter is driven by job mobility. I also find that the model explains the non-normality observed in logwage dat

The cycle of earnings inequality : evidence from Spanish Social Security data

We use detailed information on labor earnings and employment from Social Security records to document earnings inequality in Spain from 1988 to 2010. Male earnings inequality was strongly countercyclical: it increased around the 1993 recession, showed a substantial decrease during the 1997-2007 expansion and then a sharp increase during the recent recession. These developments were partly driven by the cyclicality of employment and earnings in the lower-middle part of the distribution. We emphasize the importance of the housing boom and subsequent housing bust, and show that demand shocks in the construction sector signifi cantly impacted aggregate labor market outcomesEn este trabajo se utiliza información detallada de ingresos salariales y empleo procedente de registros de la Seguridad Social para documentar la evolución de la desigualdad salarial en España desde 1988 a 2010. La desigualdad salarial para los hombres ha sido fuertemente contracíclica: aumentó alrededor de la recesión de 1993, mostró un descenso sustancial en el período de expansión de 1997 a 2007 y evidenció un marcado incremento durante la crisis reciente. Esta evolución se ha debido, en parte, a la evolución cíclica del empleo y de los salarios en la parte baja-media de la distribución salarial. Enfatizamos la importancia del boom de la construcción y su posterior caída, y mostramos que los shocks de demanda en este sector han tenido efectos signifi cativos sobre variables agregadas del mercado laboral españo

Retirement patterns of couples in Europe

En este trabajo analizamos las pautas de jubilación de parejas en el contexto europeo utilizando datos de la Survey of Health, Aging and Retirement in Europe (SHARE). En concreto, evaluamos si las salidas del mercado de trabajo de las mujeres (hombres) están causadas por el hecho de que sus maridos (mujeres) dejen de trabajar, usando la variación institucional en las edades oficiales de jubilación (anticipada y normal) específicas de cada país como instrumento. Explotando las discontinuidades en los incentivos a la jubilación de cada país, encontramos que la jubilación de los maridos tiene un efecto significativo de entre 16 y 18 puntos porcentuales en la probabilidad de dejar de trabajar de sus mujeres. Para los hombres el efecto es similar en magnitud, pero no es estadísticamente significativo. Este efecto indirecto de la jubilación conjunta puede tener importantes consecuencias para la implementación de reformasIn this paper we study the retirement patterns of couples in a multi-country setting using data from the Survey of Health, Aging and Retirement in Europe. In particular, we test whether women’s (men’s) transitions out of the labor force are causally related to the actual realization of their husbands’ (wives’) transition, using the institutional variation in country-specific early and full statutory retirement ages to instrument the latter. Exploiting the discontinuities in retirement behavior across countries, we find a significant joint retirement effect, especially for women, of around 16 to 18 percentage points. For men, we find a similar but less precise effect. Our empirical strategy allows us to give a causal interpretation to the effect we estimate. In addition, this effect has important implications for policy analysi

Gender gaps in the evaluation of research: evidence from submissions to Economics Conferences

Este artículo estudia las diferencias de género en la evaluación de artículos enviados a conferencias de economía. Utilizando datos del Congreso Anual de la Asociación Europea de Economía (2015-2017), el Simposio Anual de la Asociación Española de Economía (2012-2017) y la Reunión Anual de la Asociación de Jóvenes Economistas (2017), encontramos que la probabilidad de que sean aceptados los artículos escritos exclusivamente por mujeres es 3,2 puntos porcentuales (6,8 %) menor que la de que sean aceptados los escritos únicamente por hombres. Esta brecha está presente después de controlar por: i) número de autores; ii) efectos fi jos de evaluador; iii) área de investigación; iv) número de citas del documento en el año de la solicitud; v) número de publicaciones previas de los autores, y vi) calidad de las afi liaciones de los autores. También encontramos que la brecha se debe en su totalidad a las evaluaciones realizadas por hombres: las evaluadoras mujeres dan una puntuación similar a los artículos escritos por hombres o por mujeres, pero los evaluadores hombres son más favorables a los artículos escritos por hombres.We study gender differences in the evaluation of submissions to economics conferences. Using data from the Annual Congress of the European Economic Association (2015-2017), the Annual Meeting of the Spanish Economic Association (2012-2017), and the Spring Meeting of Young Economists (2017), we find that all-female-authored papers are 3.2 p.p. (6.8%) less likely to be accepted than all-male-authored papers. This gap is present after controlling for (i) number of authors, (ii) referee fixed effects, (iii) fi eld, (iv) cites of the paper at submission year, (v) previous publication record of the authors, and (vi) the quality of the affiliations of the authors. We also find that the gap is entirely driven by male referees—female referees evaluate male and female-authored papers similarly, but male referees are more favorable towards papers written by men

The Spanish productivity puzzle in the Great Recession

Desde mediados de los años noventa hasta 2007, la economía española presentó tasas de crecimiento de la productividad inferiores a las de otros países de Europa, como Alemania, Francia o el Reino Unido. Esa tendencia, sin embargo, cambió con la llegada de la crisis. La evolución de la productividad agregada en España durante la Gran Recesión ha respondido en gran medida a las condiciones adversas del mercado de trabajo, pero no solo. Este trabajo utiliza una muestra longitudinal de empresas manufactureras y de servicios entre 1995 y 2012 y señala que el reciente aumento en la tasa de crecimiento de la productividad agregada española también responde a la evolución de la productividad total de los factores (PTF) y a efectos composición. Mediante la combinación de la información procedente de los balances contables, el tipo de convenio colectivo y las importacionesexportaciones, se documenta que el acceso a mercados externos y el hecho de disponer de un convenio colectivo a nivel de empresa están positivamente correlacionados con el nivel medio de la PTF de la empresa durante todo el período. Además, las estimaciones indican que la PTF presentó una correlación negativa con la proporción de trabajadores temporales durante el período de expansión —1995-2007—, mientras que el signo de esa correlación se invirtió entre 2008 y 2012. Por último, el cambio en el signo de la correlación parece estar relacionado con la diferente composición de los trabajadores temporales que continúan empleadosWhile Spain has traditionally underperformed its European peers in terms of labor productivity, the trend reverses after 2007. The evolution of aggregate productivity in Spain during the Great Recession is shaped largely, albeit not exclusively, by the adverse conditions in the labor market. Using a longitudinal sample of Spanish manufacturing and services companies between 1995 and 2012, we show that the recent increase in Spanish aggregate productivity is also responsive to the behavior of total factor productivity (TFP) and to composition effects. By combining the information at fi rm level on balance sheet items, collective agreements and imports-exports, we are able to establish that a collective agreement at the fi rm level and access to external markets are positively related to TFP performance during the whole period. In addition, our estimates indicate that fi rm TFP was negatively correlated to the proportion of temporary workers during the expansionary period, 1995-2007, whereas the sign of that correlation reversed during the crisis, 2008-2012. Finally, we relate this sign reversal to the changing composition of temporary workers in the labor marke

The challenge of measuring digital platform work

Artículo de revistaThe article presents an overview of digital platform work in Spain and analyses the challenge of quantifying this work in view of the lack of reliable and comprehensive data available. Digital platforms are technological infrastructures that act as intermediaries, facilitating interaction between two or more persons, for the provision of services through IT applications in exchange for payment. Although it is estimated that platform work accounts for less than 5% of the global workforce, this share is expected to increase. In 2018, according to the COLLEEM survey, platform work was the main job of 2.6% of the Spanish population over 16. Including occasional platform work, the figure rose to 18.5%, the highest percentage among the 16 European countries included in the survey. Nevertheless, in practice it is difficult to obtain precise figures, since to date official statistics are not designed to include the gig economy. The article compares the demographic characteristics of platform workers in Spain, according to the COLLEEM survey, and those of self-employed workers and employees according to two Spanish surveys of individuals and households, namely the 2018 Labour Force Survey (Encuesta de Población Activa) and the 2017 Survey of Household Finances (Encuesta Financiera de las Familias). The comparison shows that digital platform workers make up a specific group that is not directly comparable with either employees or the self-employed. To conclude, a number of ways to obtain a better measure of digital platform work are considered. One option would be to include direct questions on these work arrangements in employment survey questionnaires. Another would be to develop integrated datasets, combining the information from administrative records, which include digital platform activities, with surveys of the workers included in those records. In any event, in order for these administrative records and surveys to reflect platform work accurately, labour legislation needs to clearly define the relationship between those providing the services and the platforms