Phase diagram for a single flexible Stockmayer polymer at zero field

The equilibrium conformations of a flexible permanent magnetic chain that consists of a sequence of linked magnetic colloidal nanoparticles with short-ranged Lennard-Jones attractive interactions (Stockmayer polymer) are thoroughly analysed via Langevin dynamics simulations. A tentative phase diagram is presented for a chain of length $N=100$. The phase diagram exhibits several unusual conformational phases when compared with the non-magnetic chains. These phases are characterised by a large degree of conformational anisotropy, and consist of closed chains, helicoidal-like states, partially collapsed states, and very compact disordered states. The phase diagram contains several interesting features like the existence of at least two 'triple points'

Interpolation of families

We identify the intermédiate space of a complex interpolation family - in the sense of Coifman, Cwikel, Rochberg, Sagher and Weissof LP spaces with change of measure, for the complex interpolation method associated to an analytic functional

Sampling of real multivariate polynomials and pluripotential theory

We consider the problem of stable sampling of multivariate real polynomials of large degree in a general framework where the polynomials are defined on an affine real algebraic variety $M$, equipped with a weighted measure. In particular, this framework contains the well-known setting of trigonometric polynomials (when $M$ is a torus equipped with its invariant measure), where the limit of large degree corresponds to a high frequency limit, as well as the classical setting of one-variable orthogonal algebraic polynomials (when $M$ is the real line equipped with a suitable measure), where the sampling nodes can be seen as generalizations of the zeros of the corresponding orthogonal polynomials. It is shown that a necessary condition for sampling, in the general setting, is that the asymptotic density of the sampling points is greater than the density of the corresponding weighted equilibrium measure of $M$, as defined in pluripotential theory. This result thus generalizes the well-known Landau type results for sampling on the torus, where the corresponding critical density corresponds to the Nyqvist rate, as well as the classical result saying that the zeros of orthogonal polynomials become equidistributed with respect to the logarithmic equilibrium measure, as the degree tends to infinity

Physiological mechanisms during egg hydration in teleosts: Towards the development of new cryopreservation methods

The development of marine fish farming requires the availability of domesticated fish strains presenting optimum growth and reproduction levels. Moreover, breeding programs, need efficient cryopreservation methods for both gametes and embryos, making it possible to establish comprehensive genetic banks distributing selected individuals within the aquaculture industry. However, both controlled freezing and vitrification techniques have resulted in very low survival rates for fish embryos, mainly due to the embryo's low permeability to cryoprotectants and their remarkable water content (hydration). In this short review, we summarise current knowledge of the biological mechanisms leading to the hydration of fish eggs. Some of the recent findings in this field may be the starting point for biotechnological strategies directed towards the development of new cryopreservation methods for female gametes and embryos from aquacultural fish species.El futuro desarrollo del cultivo de peces marinos requiere la disponibilidad de líneas domesticadas con un óptimo crecimiento y eficiencia reproductora. No obstante, los programas de selección genética necesitan de eficaces métodos de criopreservación, tanto de gametos como de embriones, lo que permite el establecimiento de bancos genéticos completos y la correcta distribución de los individuos seleccionados dentro de la industria. Hasta la fecha, tanto los métodos de congelación controlada como de vitrificación de embriones de peces han dado como resultado tasas muy bajas de supervivencia, debido principalmente a su baja permeabilidad a las sustancias crioprotectoras y a su elevado contenido en agua (hidratación). En esta breve revisión se resumirá el conocimiento actual sobre los mecanismos biológicos implicados durante la hidratación de los huevos (y embriones) de peces, aspecto de enorme trascendencia para su crioconservación. Algunos de los recientes hallazgos en este campo pueden suponer el punto de partida para el desarrollo de nuevas estrategias biotecnológicas dirigidas a la criopreservación de gametos femeninos y embriones de peces de interés acuícola.Instituto Español de Oceanografí