Liquid droplets on a free-standing glassy membrane: deformation through the glass transition

In this study, micro-droplets are placed on thin, glassy, free-standing films where the Laplace pressure of the droplet deforms the free-standing film, creating a bulge. The film's tension is modulated by changing temperature continuously from well below the glass transition into the melt state of the film. The contact angle of the liquid droplet with the planar film as well as the angle of the bulge with the film are measured and found to be consistent with the contact angles predicted by a force balance at the contact line.Comment: 6 pages, 5 figure

Liquid droplets act as "compass needles" for the stresses in a deformable membrane

We examine the shape of droplets atop deformable thin elastomeric films prepared with an anisotropic tension. As the droplets generate a deformation in the taut film through capillary forces, they assume a shape that is elongated along the high tension direction. By measuring the contact line profile, the tension in the membrane can be completely determined. Minimal theoretical arguments lead to predictions for the droplet shape and membrane deformation that are in excellent agreement with the data. On the whole, the results demonstrate that droplets can be used as probes to map out the stress field in a membrane

The Effect of Stellar Metallicity on the Sizes of Star Clusters

Observations indicate blue globular clusters have half-light radii systematically larger than those of red globular clusters. In this paper, we test whether the different metallicity-dependent stellar evolution timescales and mass-loss rates within the clusters can impact their early dynamical evolution. By means of N-body simulations including stellar evolution recipes we simulate the early evolution of small centrally concentrated clusters with and without primordial mass segregation. Our simulations include accurate metallicity-dependent mass loss from massive stars. We find blue clusters to be larger than red clusters regardless of whether the clusters have been primordially mass segregated. In addition, the size difference is found to be larger and consistent with observations for initial models with a low central concentration. These results indicate that the systematic size difference found between red and blue clusters can, at least in part, be attributed to the dynamical effects of differing stellar evolution histories, driven by metallicity.Comment: 8 pages, 5 figures, accepted by MNRA

Time asymmetries in quantum cosmology and the searching for boundary conditions to the Wheeler-DeWitt equation

The paper addresses the quantization of minisuperspace cosmological models by studying a possible solution to the problem of time and time asymmetries in quantum cosmology. Since General Relativity does not have a privileged time variable of the newtonian type, it is necessary, in order to have a dynamical evolution, to select a physical clock. This choice yields, in the proposed approach, to the breaking of the so called clock-reversal invariance of the theory which is clearly distinguished from the well known motion-reversal invariance of both classical and quantum mechanics. In the light of this new perspective, the problem of imposing proper boundary conditions on the space of solutions of the Wheeler-DeWitt equation is reformulated. The symmetry-breaking formalism of previous papers is analyzed and a clarification of it is proposed in order to satisfy the requirements of the new interpretation.Comment: 25 pages, 1 figur

Hilbert Spaces from Path Integrals

It is shown that a Hilbert space can be constructed for a quantum system starting from a framework in which histories are fundamental. The Decoherence Functional provides the inner product on this "History Hilbert space". It is also shown that the History Hilbert space is the standard Hilbert space in the case of non-relativistic quantum mechanics.Comment: 22 pages. Minor updates to match published versio

Scientific authorship in the areas of science and technology. International policies and editorial practices in Spanish scholarly journals

La autoría científica está ligada al crédito, al mérito científico y a la ética personal, existiendo evidencias sobre comportamientos inadecuados que plantean mejorar la regulación de las condiciones para otorgar la autoría de un trabajo científico. Esta regulación es competencia de las asociaciones de edición científica y de las propias revistas, por lo que el objetivo de este trabajo es analizar cuál es la situación de las políticas internacionales sobre autoría científica y de las prácticas editoriales de las revistas españolas en las áreas de ciencia y tecnología. Se realizo un análisis de contenido transversal de los manuales de edición científica y de una muestra de 37 revistas españolas de prestigio y se comprobaron los criterios sobre autoría, las responsabilidades derivadas, la función de los agradecimientos, el número de autores, orden de firma y la responsabilidad de correspondencia. Se observa como resultados centrales datos preocupantes: solo el 15% de los manuales aciertan a especificar de forma adecuada los criterios y entre las revistas solo el 8%. Se comparan los datos con estudios similares realizados en las áreas biomédicas. Se discute la incidencia de la no regulación en el comportamiento de los autores así como las implicaciones de la coautoría en los procesos de evaluación de la actividad científica.Scientific authorship is tied to scientific recognition, merit, and personal ethics. There is evidence of inappropriate behaviours associated with several factors that call for a better regulation of the conditions in which authorship of a scientific work is assigned. This regulation falls within the competences of the associations of scientific publishers and the journals themselves. The aim of this paper is to analyse the situation of international policies and editorial practices of Spanish journals in the areas of Science and Technology. A transversal content analysis of the manuals of good practices in academic publishing and a sample of 37 Spanish prestigious journals was carried out, with special attention paid to the criteria for authorship, derived liabilities, the role of acknowledgements, number of authors, author ordering, and responsibilities of the corresponding author. The results give cause for concern: only 15% of the manuals and 8% of the journals manage to declare these criteria properly. We compare these results with those of other areas, such as Biomedicine, where similar studies have been carried out, and we discuss the impact of non-regulation on authors’ behaviour and scientific ethics, as well as the implications of co-authorship in scholarly evaluation procedures