INJECTABLE HYBRID SYSTEM FOR STRONTIUM LOCAL DELIVERY TO PROMOTE BONE REGENERATION

In bone tissue regeneration strategies, injectable bone substitutes are very attractive since they can be applied with minimally invasive surgical procedures and can perfectly fill irregular defects created in cases of trauma, infection or tumor resection. These materials must combine adequate mechanical properties with the ability to induce new bone formation. Incorporating strontium (Sr) in bone substitute biomaterials may be a strategy to achieve high Sr concentrations, not in a systemic but in a local environment, taking advantage of the osteoanabolic and anti-osteoclastic activity of Sr, for the enhancement of new bone formation. In this context, the aim of the present work was to evaluate the response of a Sr-hybrid injectable system for bone regeneration, designed by our group, consisting of hydroxyapatite microspheres doped with Sr and an alginate vehicle crosslinked in situ with Sr, in an in vivo scenario. Two different animal models were used, rat (Wistar) and sheep (Merino Branco) critical sized bone defect. Non Sr-doped similar materials (Ca-hybrid) or empty defects were used as control. Sr-hybrid system led to an increased bone formation in both center and periphery of a rat critical sized defect compared to a non Sr–doped similar system, where new bone formation was restricted to the periphery. Moreover newly formed bone was identified as early as one week after its implantation in a sheep model. After eight weeks, the bone surrounded the microspheres, both in the periphery and in the center of the defect. Most importantly, the hybrid system provided a scaffold for cell migration and tissue ingrowth and offered structural support, as observed in both models. The effective improvement of local bone formation suggests that this might be a promising approach for bone regeneration, especially in osteoporotic conditions

A control on quantum fluctuations in 2+1 dimensions

A functional method is discussed, where the quantum fluctuations of a theory are controlled by a mass parameter and the evolution of the theory with this parameter is connected to its renormalization. It is found, in the framework of the gradient expansion, that the coupling constant of a N=1 Wess-Zumino theory in 2+1 dimensions does not get quantum corrections.Comment: Comments adde

Compact stars within an asy-soft quark-meson-coupling model

We investigate compact star properties within the quark meson coupling model (QMC) with a soft symmetry energy density dependence at large densities. In particular, the hyperon content and the mass/radius curves for the families of stars obtained within the model are discussed. The hyperon-meson couplings are chosen according to experimental values of the hyperon nuclear matter potentials, and possible uncertainties are considered. It is shown that a softer symmetry energy gives rise to stars with less hyperons, smaller radii and larger masses. Hyperon-meson couplings may also have a strong effect on the mass of the star.Comment: 7 pages, revtex, accepted in Phys. Rev.

Induced N=2 composite supersymmetry in 2+1 dimensions

Starting from N=1 scalar supermultiplets in 2+1 dimensions, we build explicitly the composite superpartners which define a N=2 superalgebra induced by the initial N=1 supersymmetry. The occurrence of this extension is linked to the topologically conserved current out of which the composite superpartners are constructed.Comment: 11 pages LATEX, no figure

Gravitational Self-Force Correction to the Binding Energy of Compact Binary Systems

Using the first law of binary black-hole mechanics, we compute the binding energy E and total angular momentum J of two non-spinning compact objects moving on circular orbits with frequency Omega, at leading order beyond the test-particle approximation. By minimizing E(Omega) we recover the exact frequency shift of the Schwarzschild innermost stable circular orbit induced by the conservative piece of the gravitational self-force. Comparing our results for the coordinate invariant relation E(J) to those recently obtained from numerical simulations of comparable-mass non-spinning black-hole binaries, we find a remarkably good agreement, even in the strong-field regime. Our findings confirm that the domain of validity of perturbative calculations may extend well beyond the extreme mass-ratio limit.Comment: 5 pages, 1 figure; matches the published versio

Electron Mass Operator in a Strong Magnetic Field and Dynamical Chiral Symmetry Breaking

The electron mass operator in a strong magnetic field is calculated. The contribution of higher Landau levels of virtual electrons, along with the ground Landau level, is shown to be essential in the leading log approximation. The effect of the electron dynamical mass generation by a magnetic field is investigated. In a model with N charged fermions, it is shown that some critical number N_{cr} exists for any value of the electromagnetic coupling constant alpha, such that the fermion dynamical mass is generated with a doublet splitting for N < N_{cr}, and the dynamical mass does not arise at all for N > N_{cr}, thus leaving the chiral symmetry unbroken.Comment: 4 pages, REVTEX4, 3 figure

Mercury-T: a new code to study tidally evolving multi-planet systems: applications to Kepler-62

A large proportion of observed planetary systems contain several planets in a compact orbital configuration, and often harbor at least one close-in object. These systems are then most likely tidally evolving. We investigate how the effects of planet-planet interactions influence the tidal evolution of planets. We introduce for that purpose a new open-source addition to the Mercury N-body code, Mercury-T, which takes into account tides, general relativity and the effect of rotation-induced flattening in order to simulate the dynamical and tidal evolution of multi-planet systems. It uses a standard equilibrium tidal model, the constant time lag model. Besides, the evolution of the radius of several host bodies has been implemented (brown dwarfs, M-dwarfs of mass 0.1 M-circle dot, Sun-like stars, Jupiter). We validate the new code by comparing its output for one-planet systems to the secular equations results. We find that this code does respect the conservation of total angular momentum. We applied this new tool to the planetary system Kepler-62. We find that tides influence the stability of the system in some cases. We also show that while the four inner planets of the systems are likely to have slow rotation rates and small obliquities, the fifth planet could have a fast rotation rate and a high obliquity. This means that the two habitable zone planets of this system, Kepler-62e ad f are likely to have very different climate features, and this of course would influence their potential at hosting surface liquid water

Anomalous magnetic moment in parity-conserving QED3

In this article we derive the anomalous magnetic moment of fermions in (2+1)-dimensional parity-conserving QED3, in the presence of an externally applied constant magnetic field. We use a spectral representation of the photon propagator to avoid infrared divergences. We also discuss the scaling with the magnetic field intensity in the case of strong external fields, where there is dynamical mass generation for fermions induced by the magnetic field itself (magnetic catalysis). The results of this paper may be of relevance to the physics of high-temperature superconductors.Comment: 27 pages LATEX, three eps figures incorporate

Biology of the iberian chub (Squalius carolitertii) in an atlantic-type stream (river Lima basin-north Portugal). A preliminary approach

The iberian chub (Squalius carolitertii) is an endemic species whose biology is yet largely unknown and which is catalogued as being endangered. Therefore more information about its biology is essential to develop appropriate management strategies. The Estorâos River population has been studied from December 1995 to March 2002 through regular electro-fishing surveys. Additionally, a fish trap installed in the river from November 2001 to July 2002 allowed for the collection of information on population movements and reproduction. The results revealed some fluctuations in the density estimates, though the Squalius carolitertii population in the Estorâos River is quite low. Six age classes (0+ to 5+) were identified. Iberian chub growth is isometric and can reach a final length of 33.5 cm. Sexual dimorphism is evident, with males maturing earlier and at smaller sizes. An increase of the Iberian chub movements was detected from middle April onwards. These movements were related to the beginning of the reproductive period and were mainly correlated with the rise of water temperature. Our results indicate that the population characteristics do not differ substantially from those of other endemic chub populations in the Iberic peninsula.El bordallo (Squalius carolitertii) es una especie cuya biología es en gran parte desconocida y que está catalogada en peligro de extinción. El estudio de su biología es importante para la gestión de sus poblaciones y de su hábitat. La población del río Estorâos (Cuenca del río Límia) ha sido estudiada de Diciembre de 1995 a Marzo de 2002 mediante muestreos con pesca eléctrica. Un sistema de redes utilizado de Noviembre de 2001 a Julio de 2002 permitió la obtención de información sobre los movimientos y parámetros reproductivos de la población. Los datos indican fluctuaciones de la densidad, a pesar de la población presentar valores muy bajos. Seis clases de edad (0+ a 5+) han sido identificadas. El crecimiento de Squalius carolitertii es isométrico y puede llegar a una talla final de 33,5 cm. El dimorfismo sexual es evidente y los machos maduran más temprano y con tallas inferiores a de las hembras. Un creciente de movimientos del bordallo ha sido encontrado a mediados del mes de Abril, lo que está de acuerdo con la fecha del período reproductivo y también con el incremento de la temperatura del agua. Nuestros datos indican que esta población no es muy distinta de otras poblaciones de bordallos endémicos de la península Ibérica