Segmental relaxation in semicrystalline polymers: a mean field model for the distribution of relaxation times in confined regimes

The effect of confinement in the segmental relaxation of polymers is considered. On the basis of a thermodynamic model we discuss the emerging relevance of the fast degrees of freedom in stimulating the much slower segmental relaxation, as an effect of the constraints at the walls of the amorphous regions. In the case that confinement is due to the presence of crystalline domains, a quasi-poissonian distribution of local constraining conditions is derived as a result of thermodynamic equilibrium. This implies that the average free energy barrier $\Delta F$ for conformational rearrangement is of the same order of the dispersion of the barrier heights, $\delta (\Delta F)$, around $\Delta F$. As an example, we apply the results to the analysis of the $\alpha$-relaxation as observed by dielectric broad band spectroscopy in semicrystalline poly(ethylene terephthalate) cold-crystallized from either an isotropic or an oriented glass. It is found that in the latter case the regions of cooperative rearrangement are significantly larger than in the former.Comment: 10 pages, 4 figures .ep

The effect of wage proposals on efficiency and income distribution

Pre-play non-binding communication in organizations is prevalent. We study the implications of pre-play wage proposals and information revelation in a labour relationship in a laboratory experiment. In the baseline, that depicts a typical labour market interaction, the employer makes a wage offer to the worker who may then accept or reject it. In a subsequent treatment, workers, moving first, make private, non-binding, wage proposals to the employer. Our findings suggest that wage proposals promote higher wages, efficiency, and income equality. We run an additional experiment as a robustness check where we make the wage proposals public. We find that most of the results hold. Similar wage proposals are observed in the Public and Private information treatments, while accepted wages in the public treatment are higher than the baseline and significantly lower than under private information. It seems that workers conform to the available information on the wage of their co-worker from the last period when proposals are public. Interestingly, while both benefit over the baseline, public information on wage proposals benefits firms more than workers. We also develop a theoretical model to rationalize our results. The experimental results provide broad support for our hypotheses

De la comunidad al comunismo (Nota sobre Kant y Marx)

El concepto de “comunidad” puede entenderse de dos maneras: como communio o como commercium. La Gemeinschaft kantiana (tercera categoría de la relación) tiene el sentido, como señala Kant, de commercium: acción recíproca entre lo que actúa y lo que padece (Wechselwirkung zwischen dem Handelnden und Leidenden). A mi juicio el comunismo del joven Marx (el de los Ökonomisch-philosophische Manuskripte aus dem ahre 1844) es deudor de tal concepto de comunidad. El comunismo, en efecto, pretende restituir una genuina ¿no alienada¿ relación comunitaria entre el hombre y la naturaleza. The concept of "community" can be understood in two ways: as communio or as commercium. The Kantian Gemeinschaft (third category of the relation) has the meaning, as Kant points out, of commercium: reciprocity between action and passion (Wechselwirkung zwischen dem Handelnden und Leidenden). In my opinion the communism of the young Marx (that of the Okonomisch-philosophische Manuskripte aus dem ahre 1844) is indebted to such a concept of community. Communism, in effect, aims to restore a genuine -not alienated- community relationship between man and nature

El Forn de raig

Recuperación y puesta en valor de un horno tradicional para producción de calPeer Reviewe

The potential of drones and sensors to enhance detection of archaeological cropmarks: a comparative study between multi-spectral and thermal imagery

Abstract This paper presents experimentation carried out at the Roman Republican city of La Caridad (Teruel, Spain), where different tools have been applied to obtain multispectral and thermal aerial images to enhance detection of archaeological cropmarks. Two different drone systems were used: a Mikrokopter designed by Tecnitop SA (Zaragoza, Spain) and an eBee produced by SenseFly Company (Cheseaux-sur-Lausanne, Switzerland). Thus, in this study, we have combined in-house manufacturing with commercial products. Six drone sensors were tested and compared in terms of their ability to identify buried remains in archaeological settlements by means of visual recognition. The sensors have different spectral ranges and spatial resolutions. This paper compares the images captured with different spectral range sensors to test the potential of this technology for archaeological benefits. The method used for the comparison of the tools has been based on direct visual inspection, as in traditional aerial archaeology. Through interpretation of the resulting data, our aim has been to determine which drones and sensors obtained the best results in the visualization of archaeological cropmarks. The experiment in La Caridad therefore demonstrates the benefit of using drones with different sensors to monitor archaeological cropmarks for a more cost-effective assessment, best spatial resolution and digital recording of buried archaeological remains