Brownian motion of multidimensional systems in nonpotential velocity-dependent fields of force

We study the Brownian motion in velocity-dependent fields of force. Our main result is a Smoluchowski equation valid for moderate to high damping constants. We derive that equation by perturbative solution of the Langevin equation and using functional derivative techniques.

Magnetic microstructures from magnetic force microscopy and Monte Carlo simulation in CoFe-Ag-Cu granular films

CoFe-Ag-Cu granular films, prepared by rf sputtering, displayed magnetic domain microstructures for ferromagnetic concentrations above about 32% at, and below the percolation threshold. All samples have a fcc structure with an (111) texture perpendicular to the film plane. Magnetic force microscopy (MFM) showed a variety of magnetic domain microstructures, extremely sensitive to the magnetic history of the sample, which arise from the balance of the ferromagnetic exchange, the dipolar interactions and perpendicular magnetocrystalline anisotropy, MFM images indicate that in virgin samples, magnetic bubble domains with an out-of-plane component of the magnetization are surrounded by a quasicontinuous background of opposite magnetization domains. The application of a magnetic field in different geometries drastically modifies the microstructure of the system in the remanent state: i) for an in-plane field, the MFM images show that most of the magnetic moments are aligned along the film plane, ii) for an out-of-plane field, the MFM signal increases about one order of magnitude, and out-of-plane striped domains with alternating up and down magnetization are stabilized. Numerical simulations show that a variety of metastable domain structures (similar to those observed experimentally) can be reached, depending on magnetic history, in systems with competing perpendicular anisotropy, exchange and dipolar interactions.

First-passage-time statistics for diffusion processes with an external random force

We present exact equations and expressions for the first-passage-time statistics of dynamical systems that are a combination of a diffusion process and a random external force modeled as dichotomous Markov noise. We prove that the mean first passage time for this system does not show any resonantlike behavior.

Agglomeration and labour productivity in Spanish industry: a long-term analysis

This paper analyzes the relationship between spatial density of economic activity and interregional differences in the productivity of industrial labour in Spain during the period 1860-1999. In the spirit of Ciccone and Hall (1996) and Ciccone (2002), we analyze the evolution of this relationship over the long term in Spain. Using data on the period 1860-1999 we show the existence of an agglomeration effect linking the density of economic activity with labour productivity in the industry. This effect was present since the beginning of the industrialization process in the middle of the 19th century but has been decreasing over time. The estimated elasticity of labour productivity with respect to employment density was close to 8% in the subperiod 1860-1900, reduces to a value of around 7% in the subperiod 1914-1930, to 4% in the subperiod 1965-1979 and becomes insignificant in the final subperiod 1985-1999. At the end of the period analyzed there is no evidence of the existence of net agglomeration effects in the industry. This result could be explained by an important increase in the congestion effects in large industrial metropolitan areas that would have compensated the centripetal or agglomeration forces at work. Furthermore, this result is also consistent with the evidence of a dispersion of industrial activity in Spain during the last decades.

Outcomes from studies of Antineutrophil Cytoplasm Antibody Associated Vasculitis: a systematic review by the European League Against Rheumatism systemic vasculitis task force.

Objectives: We undertook a systematic literature review as a background to the European League Against Rheumatism (EULAR) recommendations for conducting clinical trials in anti-neutrophil cytoplasm antibody associated vasculitis (AAV), and to assess the quality of evidence for outcome measures in AAV. Methods: Using a systematic Medline search, we categorised the identified studies according to diagnoses. Factors affecting remission, relapse, renal function and overall survival were identified. Results: A total of 44 papers were reviewed from 502 identified by our search criteria. There was considerable inconsistency in definitions of end points. Remission rates varied from 30% to 93% in Wegener granulomatosis (WG), 75% to 89% in microscopic polyangiitis (MPA) and 81% to 91% in Churg¿Strauss syndrome (CSS). The 5-year survival for WG, MPA and CSS was 74¿91%, 45¿76% and 60¿97%. Relapse (variably defined) was common in the first 2 years but the frequency varied: 18% to 60% in WG, 8% in MPA, and 35% in CSS. The rate of renal survival in WG varied from 23% at 15 months to 23% at 120 months. Methods used to assess morbidity varied between studies. Ignoring the variations in definitions of the stage of disease, factors influencing remission, relapse, renal and overall survival included immunosuppressive therapy used, type of organ involvement, presence of ANCA, older age and male ender. Conclusions: Factors influencing remission, relapse, renal and overall survival include the type of immunosuppressive therapy used, pattern of organ involvement, presence of ANCA, older age and male gender. Methodological variations between studies highlight the need for a consensus on terminology and definitions for future conduct of clinical studies in AAV.

Fine-Tuning Translation Kinetics Selection as the Driving Force of Codon Usage Bias in the Hepatitis A Virus Capsid

Hepatitis A virus (HAV), the prototype of genus Hepatovirus, has several unique biological characteristics that distinguish it from other members of the Picornaviridae family. Among these, the need for an intact eIF4G factor for the initiation of translation results in an inability to shut down host protein synthesis by a mechanism similar to that of other picornaviruses. Consequently, HAV must inefficiently compete for the cellular translational machinery and this may explain its poor growth in cell culture. In this context of virus/cell competition, HAV has strategically adopted a naturally highly deoptimized codon usage with respect to that of its cellular host. With the aim to optimize its codon usage the virus was adapted to propagate in cells with impaired protein synthesis, in order to make tRNA pools more available for the virus. A significant loss of fitness was the immediate response to the adaptation process that was, however, later on recovered and more associated to a re-deoptimization rather than to an optimization of the codon usage specifically in the capsid coding region. These results exclude translation selection and instead suggest fine-tuning translation kinetics selection as the underlying mechanism of the codon usage bias in this specific genome region. Additionally, the results provide clear evidence of the Red Queen dynamics of evolution since the virus has very much evolved to re-adapt its codon usage to the environmental cellular changing conditions in order to recover the original fitness.

Nanometer-scale oxidation of Si(100) surfaces by tapping mode atomic force microscopy

The nanometer¿scale oxidation of Si(100) surfaces in air is performed with an atomic force microscope working in tapping mode. Applying a positive voltage to the sample with respect to the tip, two kinds of modifications are induced on the sample: grown silicon oxide mounds less than 5 nm high and mounds higher than 10 nm (which are assumed to be gold depositions). The threshold voltage necessary to produce the modification is studied as a function of the average tip¿to¿sample distance.

Agglomeration and labour productivity in Spanish industry: a long-term analysis

This paper analyzes the relationship between spatial density of economic activity and interregional differences in the productivity of industrial labour in Spain during the period 1860-1999. In the spirit of Ciccone and Hall (1996) and Ciccone (2002), we analyze the evolution of this relationship over the long term in Spain. Using data on the period 1860-1999 we show the existence of an agglomeration effect linking the density of economic activity with labour productivity in the industry. This effect was present since the beginning of the industrialization process in the middle of the 19th century but has been decreasing over time. The estimated elasticity of labour productivity with respect to employment density was close to 8% in the subperiod 1860-1900, reduces to a value of around 7% in the subperiod 1914-1930, to 4% in the subperiod 1965-1979 and becomes insignificant in the final subperiod 1985-1999. At the end of the period analyzed there is no evidence of the existence of net agglomeration effects in the industry. This result could be explained by an important increase in the congestion effects in large industrial metropolitan areas that would have compensated the centripetal or agglomeration forces at work. Furthermore, this result is also consistent with the evidence of a dispersion of industrial activity in Spain during the last decades.

Estudio sobre los procesos de integración laboral de los inmigrantes. Study of immigrants' labour integration process

El presente trabajo pretende mostrar los resultados de un estudio cuya intención era identificar posibles variables que afectan a los procesos y estrategias de integración laboral de personas procedentes de otros países; las necesidades formativas en relación al colectivo de referencia y ampliar el conocimiento del fenómeno en aras de la intervención psicoeducativa y social. A partir de una metodología de investigación de orientación cualitativa se ha concluido que las diferencias en cuanto a las estrategias de integración y sus logros están más determinadas por los niveles de cualificación en el país de origen que por las propias diferencias culturales. The article shows the results of a study carried out by the authors to identify possible variables that affect the processes and strategies of occupational integration of people coming from other countries, to establish training needs in relation to the reference group and to extend the knowledge of the phenomenon for the sake of the educational and social intervention. Using a qualitative research methodology, it was concluded that the differences in integration strategies and their accomplishments are better explained by the levels of qualification attained in the country of origin than by cultural differences.

Estudio sobre los procesos de integración laboral de los inmigrantes. Study of immigrants' labour integration process

El presente trabajo pretende mostrar los resultados de un estudio cuya intención era identificar posibles variables que afectan a los procesos y estrategias de integración laboral de personas procedentes de otros países; las necesidades formativas en relación al colectivo de referencia y ampliar el conocimiento del fenómeno en aras de la intervención psicoeducativa y social. A partir de una metodología de investigación de orientación cualitativa se ha concluido que las diferencias en cuanto a las estrategias de integración y sus logros están más determinadas por los niveles de cualificación en el país de origen que por las propias diferencias culturales. The article shows the results of a study carried out by the authors to identify possible variables that affect the processes and strategies of occupational integration of people coming from other countries, to establish training needs in relation to the reference group and to extend the knowledge of the phenomenon for the sake of the educational and social intervention. Using a qualitative research methodology, it was concluded that the differences in integration strategies and their accomplishments are better explained by the levels of qualification attained in the country of origin than by cultural differences.

Atomic force microscopy: probing the nanoworld

Atomic Force Microscope and related techniques have played a key role in the development of the nanotechnology revolution that is taking place in science. This paper reviews the basic principles behind the technique and its different operation modes and applications, pointing out research worksperformed in the Nanometric Techniques Unit of the CCiTUB in order to exemplify the vast array of capabilities of these instruments.

¿Y después del trabajo, qué? Más allá de la integración laboral de las personas con discapacidad = What happens after work? Going further than labour integration for disabled people

La actividad profesional es fundamental en la vida de cualquier persona y en el caso de las que padecen una discapacidad tiene una gran importancia para contribuir a configurar su identidad adulta. En este sentido, la finalidad del artículo es valorar la importancia del trabajo en los procesos de participación social y de calidad de vida de las personas con discapacidad. Por ello, en el artículo se pone de manifiesto la relación que se establece entre la dimensión laboral y la integración social de los individuos con discapacidad mediante el análisis de investigaciones desarrolladas en nuestro contexto, entre las que figuran diversos estudios realizados por nuestro grupo de investigación durante los últimos años. Con la voluntad de conocer con más detalle esta cuestión, se presenta una investigación reciente realizada por nuestro equipo. En ella desarrollamos un estudio de casos centrado en personas con discapacidad psíquica que han participado en experiencias de integración laboral en el mercado ordinario, con el objetivo de obtener información sobre la incidencia de la inserción laboral en diferentes dimensiones de la vida de los trabajadores con discapacidad. Los resultados nos permiten valorar que la experiencia genera cambios positivos, sobre todo a nivel personal (expectativas personales, potenciación del proyecto de vida, mejora de competencias…). Sin embargo, a pesar de que se aprecian mejoras en la dimensión social, el estudio plantea la necesidad de emprender acciones alternativas para potenciar la participación comunitaria de las personas implicadas en la investigación. El artículo concluye con algunas propuestas orientadas a mejorar los procesos de inserción social del colectivo

Coworker networks in the labour market

This paper studies the role coworker-based networks play for individual labour marketoutcomes. I analyse how the provision of labour market relevant information by formercoworkers affects the employment probabilities and, if hired, the wages of male workerswho have previously become unemployed as the result of an establishment closure. Toidentify the causal effect of an individual worker's network on labour market outcomes, Iexploit exogenous variation in the strength of these networks that is due to the occurrenceof mass-layoffs in the establishments of former coworkers. The empirical analysis is basedon administrative data that comprise the universe of workers employed in Germany between1980 and 2001. The results suggest a strong positive effect of a higher employmentrate in a worker's network of former coworkers on his re-employment probability afterdisplacement: a 10 percentage point increase in the prevailing employment rate in thenetwork increases the re-employment probability by 7.5 percentage points. In contrast,there is no evidence of a statistically significant effect on wages.

Construcción de un índice de calidad ocupacional (ICO) para el análisis de la inserción profesional de los graduados universitarios = Building an employment quality index (EQI) to analyse graduates’ access to the labour market

En este trabajo se propone la construcción de un índice de calidad ocupacional (ICO) a partir de los datos de la Encuesta de Inserción Laboral de los Graduados de las Universidades Catalanas realizada por la Agencia para la Calidad del Sistema Universitario de Catalunya (AQU), que ha de permitir un mejor análisis de la información que proporciona la encuesta y facilitar su comparación con estudios similares. La encuesta se realiza tres años después de la graduación. En este artículo, se utiliza la segunda encuesta realizada el año 2005 entre 11.456 graduados (52,63%) de la promoción 2001 (AQU, 2005, Serra-Ramoneda, 2007). El índice se ha elaborado a partir de los indicadores objetivos ‘tipo y duración del contrato laboral’, ‘retribución económica’, ‘adecuación entre la formación universitaria y el empleo’ a los que se otorga una puntuación ponderada según las respuestas dadas por los graduados. La suma de las puntuaciones se matiza con un coeficiente derivado del indicador subjetivo ‘satisfacción con el trabajo en general’. A partir de la información proporcionada por el índice, se realiza un análisis comparativo del nivel de calidad ocupacional que han logrado los graduados de áreas de conocimiento, ámbitos de trabajo, ramas de actividad y ubicaciones territoriales del empleo diferentes. Los resultados obtenidos permiten observar que entre los graduados catalanes los siguientes hechos son buenos predictores de la calidad de la ocupación: haber estudiado una carrera que no sea de Humanidades, ser un hombre, haber desempeñado durante la carrera un trabajo relacionado con los estudios, estar ocupado en la construcción, en instituciones financieras o en servicios a empresas, haber tenido algún tipo de movilidad por motivos de trabajo, trabajar fuera de Cataluña y hacerlo en empresas grandes, especialmente con más de 500 trabajadores. Finalmente, se presentan algunas reflexiones y propuestas que pueden resultar de interés para la orientación de los estudiantes y la planificación universitaria