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Cognola G.,University of Trento | Elizalde E.,Facultat de Ciencies | Zerbini S.,University of Trento
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

By making use of the background field method, the one-loop quantization for Euclidean Einstein-Weyl quadratic gravity model on the de Sitter universe is investigated. Using generalized zeta function regularization, the on-shell and off-shell one-loop effective actions are explicitly obtained, and one-loop renormalizability, as well as the corresponding one-loop renormalization group equations, is discussed. The so-called critical gravity is also considered. © 2013 American Physical Society. Source

Lopez-Revelles A.J.,Facultat de Ciencies
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Two different realistic F(R) modified gravity models are considered in the framework of the Friedmann-Lemetre-Robertson-Walker universe. The parameters of these two models are adjusted to reach coherence with the most recent and accurate observations of the current Universe. A study of the growth of matter density perturbations is done, and several parametrizations of the growth index are developed for both models. The ansatz for the growth index given by γ=γ0+γ1z/(1+z) seems to be the best parametrization for the two models considered. Finally, the values obtained for γ0 and γ1 can be used in order to characterize these two models and to differentiate them from others such as the Hu-Sawicki model. © 2013 American Physical Society. Source

Ferraz M.A.M.M.,University Utrecht | Morato R.,Facultat de Ciencies | Yeste M.,Autonomous University of Barcelona | Arcarons N.,Autonomous University of Barcelona | And 5 more authors.
Theriogenology | Year: 2014

The present study examined the relationship between the relative amount of high motile sperm and sperm-oocyte interactions obtained from Holstein bull ejaculates. Post-thaw sperm motility was analyzed using a computer-assisted sperm analyzer system and evaluated to determine the sperm motility subpopulations. Adhesion and penetration of zona pellucida (ZP) and pronucleus formation using post-thawed samples (15 ejaculates form 5 different bulls) with different percentages of sperm in the subpopulation with the fastest and most progressive subpopulation (subpopulation 4 [SP4]) were analyzed. The correlation between the proportion of sperm in SP4 and the number of spermatozoa bound to the zona pellucida (ZBA), the penetration rate, and the rate of pronucleus formation were calculated. A significant (P < 0.05) and positive correlation was found between the number of spermatozoa bound to the zona pellucida, the penetration rate, and the rate of pronucleus formation with the proportion of sperm in SP4 (r = 0.79, r = 0.66, and r = 0.63, respectively). Our results suggest that this specific high motile and progressive subpopulation is positively and significantly correlated with the ability of a thawed bull semen sample to interact properly with the oocyte and its extracellular vestments. These findings emphasize the relevance of analyzing semen subpopulation composition to predict bull sperm fertilizing ability and to select Holstein bulls for breeding purposes. © 2014 Elsevier Inc. Source

Jang B.,ETH Zurich | Pellicer E.,Facultat de Ciencies | Guerrero M.,Facultat de Ciencies | Chen X.,ETH Zurich | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2014

Electrodeposition is a versatile method, which enables the fabrication of a variety of wire-like nanoarchitectures such as nanowires, nanorods, and nanotubes. By means of template-assisted electrodeposition, segmented Au/Co/Au nanowires are grown in anodic aluminum oxide templates from two different electrolytes. To tailor the properties of the cobalt segments, several electrochemical conditions are studied as a function of current density, pulse deposition, and pH. The morphology, crystal structure, and magnetic properties are accordingly investigated. Changes in the deposition conditions affect the cobalt electrocrystallization process directly. Cobalt tends to crystallize mainly in the hexagonal close-packed structure, which is the reason cobalt might not accommodate satisfactorily on the face-centered cubic Au surface or vice versa. We demonstrate that by modifying the electrolyte and the applied current densities, changes in the texture and the crystalline structure of cobalt lead to a good quality connection between dissimilar segments. In particular, lowering the bath pH, or using pulse plating at a high overpotential, produces polycrystalline fcc Co and thus well-connected Co/Au bimetallic junctions with smooth interface. These are crucial factors to be carefully considered taking into account that nanowires are potential building blocks in micro- and nanoelectromechanical systems. © 2014 American Chemical Society. Source

Fraga H.,Facultat de Ciencies | Ventura S.,Facultat de Ciencies | Ventura S.,Autonomous University of Barcelona
Current Protein and Peptide Science | Year: 2012

The process of oxidative folding in the intermembrane mitochondrial space (IMS) is an exciting field of research because folding is simultaneously coupled to protein translocation and functional regulation. Contrary to the endoplasmatic reticulum ER where several chaperones of the disulfide isomerase family exist, oxidative folding in the IMS is exclusively catalyzed by the oxoreductase Mia40 that recognizes a group of proteins with characteristic cysteine motifs organized in twin CX 3C, twin CX 9C or CX 2C motifs. In this review, we discuss the structural and biochemical studies leading to our current understanding of the Mia40 pathway as well as the open questions on the field. In fact, despite significant advances, several key points on the Mia40 pathway remain to clarify namely on the molecular mechanism trough which substrate oxidative folding is catalyzed. This issue is receiving increasing attention since failures in the import, sorting and folding of mitochondrial proteins is related to an increasing number of debilitating human disorders. © 2012 Bentham Science Publishers. Source

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