La persecución de un imposible: dictadura y aperturismo. El diario Ya durante el régimen de Franco

Ya se convirtió en un importante apoyo al régimen de Franco a partir de 1952. Pero antes debió soportar un director impuesto, quedando fuertemente controlado por el gobierno: su empresa editora resultaba sospechosa porque había aceptado la Segunda República (1931-1936). Entre 1953 y 1959 vivió una época de expansión y también de radicales divisiones internas, entre los partidarios del régimen de Franco y los contrarios a él. Ya siguió las orientaciones de Ángel Herrera Oria: la apertura hacia otras fuerzas (los “restos católicos” de la Institución Libre de Enseñanza) para ampliar la base del régimen de Franco y sostenerlo. Finalmente, los sectores que no apoyaban estos planes fueron expulsados de la empresa. A partir de 1966 hubo cierta libertad de prensa. El objetivo de Ya fue entonces la apertura política desde las instituciones franquistas. Demandó un aumento del pluralismo ideológico y de la representatividad de las instituciones. Las ideas de Ya resultaban contradictorias: era imposible crear un sistema político democrático sin herir de muerte a la dictadura. Tras la muerte de Franco la transición empleó elementos válidos que el sistema anterior ofrecía. Esto fue lo que propuso entre 1973 y 1975 el grupo Tácito, originado en la redacción de Ya

Phenomenology of the SU(3)_c X SU(3)_L X U(1)_X model with right-handed neutrinos

A phenomenological analysis of the three-family local gauge group $SU(3)_c\otimes SU(3)_L\otimes U(1)_X$ with right-handed neutrinos is carried out. Instead of using the minimal scalar sector able to break the symmetry in a proper way, we introduce an alternative set of four Higgs scalar triplets, which combined with an anomaly-free discrete symmetry, produces a quark mass spectrum without hierarchies in the Yukawa coupling contants. We also embed the structure into a simple gauge group and show some conditions to achieve a low energy gauge coupling unification, avoiding possible conflict with proton decay bounds. By using experimental results from the CERN-LEP, SLAC linear collider and atomic parity violation data, we update constraints on several parameters of the model.Comment: RevTeX, 10 pages, 4 figures. v2: 13 pages. Substantial changes. New section about RGE analysis. Experimental data updated. v3: Discussions about bounds from unitarity violation of the CKM matrix and from FCNC included. Accepted for publication in Eur. Phys. J.

Jamming during the discharge of grains from a silo described as a percolating transition

We have looked into an experiment that has been termed the ‘‘canonical example’’ of jamming: granular material, clogging the outlet of a container as it is discharged by gravity. We present quantitative data of such an experiment. The experimental control parameter is the ratio between the radius of the orifice and the radius of the beads. As this parameter is increased, the jamming probability decreases. However, in the range of parameters explored, no evidence of criticality—in the sense of a jamming probability that becomes infinitely small for a finite radius—has been found. We draw instead a comparison with a simple model that captures the main features of the phenomenon, namely, percolation in one dimension. The model gives indeed a phase transition, albeit a special one

Modified iterative versus Laplacian Landau gauge in compact U(1) theory

Compact U(1) theory in 4 dimensions is used to compare the modified iterative and the Laplacian fixing to lattice Landau gauge in a controlled setting, since in the Coulomb phase the lattice theory must reproduce the perturbative prediction. It turns out that on either side of the phase transition clear differences show up and in the Coulomb phase the ability to remove double Dirac sheets proves vital on a small lattice.Comment: 14 pages, 8 figures containing 23 graphs, v2: 2 figures removed, 2 references adde

Jamming and critical outlet size in the discharge of a two-dimensional silo

We present an experimental study of jamming in the discharge of grains through an opening in a two-dimensional silo. For a wide range of outlet sizes, we obtain the size distribution of avalanche defined as the number of grains that fall between two consecutive jams. From these distributions, we obtain the probability that the silo jams before N particles pass through the orifice. Then a simple model of arch formation is proposed that predicts the shape of the jamming probability function and reveals that it does not exist a critical size of the orifice above which there is not jamming

Jamming during the discharge of granular matter from a silo

In this work, we present an experimental study of the jamming that stops the free flow of grains from a silo discharging by gravity. When the outlet size is not much bigger than the beads, granular material jams the outlet of the container due to the formation of an arch. Statistical data from the number of grains fallen between consecutive jams are presented. The information that they provide can help one to understand the jamming phenomenon. As the ratio between the size of the orifice and the size of the beads is increased, the probability that an arch blocks the outlet decreases. We show here that there is a power-law divergence of the mean avalanche size for a finite critical radius. Beyond this critical radius, no jamming can occur and the flow is never stopped. The dependence of the arch formation on the shape and the material of the grains has been explored. It has been found that the material properties of the grains do not affect the arch formation probability. On the contrary, the shape of the grains deeply influences it. A simple model to interpret the results is also discussed

Slow relaxation dynamics of clogs in a vibrated granular silo

We experimentally explore the vibration-induced unclogging of arches halting the flow in a two-dimensional silo. The endurance of arches is determined by carrying out a survival analysis of their breaking times. By analyzing the dynamics of two morphological variables, we demonstrate that arches evolve toward less regular structures and it seems that there may exist a certain degree of irregularity that the arch reaches before collapsing. Moreover, we put forward that ¿ (the standard deviation of all angles between consecutive beads) describes faithfully the morphological evolution of the arch. Focusing on long-lasting arches, we study ¿ calculating its two-time autocorrelation function and its mean-squared displacement. In particular, the apparent logarithmic increase of the correlation and the decrease of the mean-squared displacement of ¿ when the waiting time is increased reveal a slowing down of the dynamics. This behavior is a clear hallmark of aging phenomena and confirms the lack of ergodicity in the unclogging dynamics. Our findings provide new insights on how an arch tends to destabilize and how the probability that it breaks with a long sustained vibration decreases with time

Neuroprotective properties of marrow-isolated adult multilineage-inducible cells in rat hippocampus following global cerebral ischemia are enhanced when complexed to biomimetic microcarriers

Cell-based therapies for global cerebral ischemia represent promising approaches for neuronal damage prevention and tissue repair promotion. We examined the potential of marrow-isolated adult multilineage-inducible (MIAMI) cells, a homogeneous subpopulation of immature human mesenchymal stromal cell, injected into the hippocampus to prevent neuronal damage induced by global ischemia using rat organotypic hippocampal slices exposed to oxygen-glucose deprivation and rats subjected to asphyxial cardiac arrest. We next examined the value of combining fibronectin-coated biomimetic microcarriers (FN-BMMs) with epidermal growth factor (EGF)/basic fibroblast growth factor (bFGF) pre-treated MIAMI compared to EGF/bFGF pre-treated MIAMI cells alone, for their in vitro and in vivo neuroprotective capacity. Naive and EGF/bFGF pre-treated MIAMI cells significantly protected the Cornu Ammonis layer 1 (CA1) against ischemic death in hippocampal slices and increased CA1 survival in rats. MIAMI cells therapeutic value was significantly increased when delivering the cells complexed with FN-BMMs, probably by increasing stem cell survival and paracrine secretion of pro-survival and/or anti-inflammatory molecules as concluded from survival, differentiation and gene expression analysis. Four days after oxygen and glucose deprivation and asphyxial cardiac arrest, few transplanted cells administered alone survived in the brain whereas stem cell survival improved when injected complexed with FN-BMMs. Interestingly, a large fraction of the transplanted cells administered alone or in complexes expressed betaIII-tubulin suggesting that partial neuronal transdifferentiation may be a contributing factor to the neuroprotective mechanism of MIAMI cells

Clogging transition of vibration-driven vehicles passing through constrictions

We report experimental results on the competitive passage of elongated self-propelled vehicles rushing through a constriction. For the chosen experimental conditions, we observe the emergence of intermittencies similar to those reported previously for active matter passing through narrow doors. Noteworthy, we find that, when the number of individuals crowding in front of the bottleneck increases, there is a transition from an unclogged to a clogged state characterized by a lack of convergence of the mean clog duration as the measuring time increases. It is demonstrated that this transition-which was reported previously only for externally vibrated systems such as colloids or granulars-appears also for self-propelled agents. This suggests that the transition should also occur for the flow through constrictions of living agents (e.g., humans and sheep), an issue that has been elusive so far in experiments due to safety risks