Scalar Field Dark Matter mass model and evolution of rotation curves for Lsb galaxies

We study the evolution of gas rotation curves within the scalar field dark matter (SFDM) model. In this model the galactic haloes are astronomical Bose-Einstein Condensate drops of scalar field. These haloes are characterized by a constant-density core and are consistent with observed rotation curves of dark matter dominated galaxies, a missing feature in CDM haloes resulting from DM-only simulations. We add the baryonic component to the SFDM haloes and simulate the evolution of the dark matter tracer in a set of grid-based hydrodynamic simulations aimed to analyse the evolution of the rotation curves and the gas density distribution in the case of dark matter dominated galaxies. Previous works had found that when considering an exact analytic solution for a static SF configuration, the free parameters of the model allows for good fits to the rotation curves, we confirm that in our simulations but now taking into account the evolution of the baryonic component in a static dark matter and stellar disk potential. Including live gas is a step forward from the previous work using SFDM, as for example, the rotation velocity of the gas is not always exactly equal to the circular velocity of a test particle on a circular orbit. Contrasting with the data the cored mass model presented here is preferred instead of a cuspy one.Comment: 8 pages, 8 figures. Accepted for publication in MNRA

Neural Regulation of Sexual Solicitation in Female Syrian Hamsters: Role of Oxytocin

In most animal species, reproductive success depends critically on precopulatory or solicitational behaviors that occur prior to mating. The specific sensory systems and behavioral strategies employed in precopulatory behaviors vary across species; in all cases, however, animals must be able to identify potential mating partners and solicit sexual interest. Female Syrian hamsters (Mesocricetus auratus) engage in multiple forms of precopulatory behaviors that are preferentially expressed to males or their odors, including vaginal scent marking and sexual odor preference. Conspecific odors relevant for precopulatory behaviors are processed by a network of forebrain areas that includes the bed nucleus of the stria terminalis (BNST) and the medial preoptic area (MPOA). The precise functional and neurochemical mechanisms whereby these areas regulate the expression of precopulatory behaviors, however, are unknown. Therefore, the aim of this dissertation is to address the following research questions: (1) Is the neuropeptide oxytocin (OT), acting within BNST or MPOA, necessary for the normal expression of odor-­guided precopulatory behaviors? (2) Is BNST or (3) MPOA required for the preferential expression of vaginal marking or investigation towards male odors?, and (4) Does OT interact with social odor processing to regulate vaginal marking? We found that blockade of OT receptors (OTRs) in MPOA and BNST decreased vaginal marking to male odors. There was no effect of OTR blockade on sexual odor preference. Selective lesions of BNST also disrupted preferential vaginal marking responses to male odors, without affecting sexual odor preference. In contrast, lesions of MPOA disrupted odor preference without affecting vaginal marking responses. Finally, central blockade of OTRs eliminated the normal pattern of increased activation of neurons to male vs. female odors in BNST, but not MPOA. Considered together, these results suggest that OT normally acts within BNST to drive preferential vaginal marking responses to male odors via selective facilitation of neural responses to these odors, and further, that there are separate and distinct neural circuits that regulate different forms of odor-guided precopulatory behaviors in females

New insights in the origin and evolution of the old, metal-rich open cluster NGC 6791

NGC 6791 is one of the most studied open clusters, it is massive ($\sim5000\,M_{\odot}$), located at the solar circle, old ($~8\,$Gyr) and yet the most metal-rich cluster (${\rm [Fe/H]}\simeq0.4$) known in the Milky Way. By performing an orbital analysis within a Galactic model including spiral arms and a bar, we found that it is plausible that NGC 6791 formed in the inner thin disc or in the bulge, and later displaced by radial migration to its current orbit. We apply different tools to simulate NGC 6791, including direct $N$-body summation in time-varying potentials, to test its survivability when going through different Galactic environments. In order to survive the 8 Gyr journey moving on a migrating orbit, NGC 6791 must have been more massive, $M_0 \geq 5\times10^4 M_{\odot}$, when formed. We find independent confirmation of this initial mass in the stellar mass function, which is observed to be flat; this can only be explained if the average tidal field strength experienced by the cluster is stronger than what it is at its current orbit. Therefore, the birth place and journeys of NGC 6791 are imprinted in its chemical composition, in its mass loss, and in its flat stellar mass function, supporting its origin in the inner thin disc or in the bulge.Comment: 14 pages, 10 Figures, 3 Tables. Accepted for publication in MNRA

Temperature dependent charge transport mechanisms in carbon sphere/polymer composites

Carbon spheres (CS) with diameters in the range $2 - 10 \mu m$ were prepared via hydrolysis of a sucrose solution at $200^o C,$ and later annealed in $N_2$ at $800^o C.$ The spheres were highly conducting but difficult to process into thin films or pressed pellets. In our previous work, composite samples of CS and the insulating polymer polyethylene oxide (PEO) were prepared and their charge transport was analyzed in the temperature range $80 K < T < 300 K.$ Here, we analyze charge transport in CS coated with a thin polyaniline (PANi) film doped with hydrochloric acid (HCl), in the same temperature range. The goal is to study charge transport in the CS using a conducting polymer (PANi) as a binder and compare with that occurring at CS/PEO. A conductivity maxima was observed in the CS/PEO composite but was absent in CS/PANi. Our data analysis shows that variable range hopping of electrons between polymeric chains in PANi-filled gaps between CS takes on a predominant part in transport through CS/PANi composites, whereas in CS/PEO composites, electrons travel through gaps between CS solely by means of direct tunneling. This difference in transport mechanisms results in different temperature dependences of the conductivity.Comment: 7 pages, 6 figure

Evolutionary stability and resistance to cheating in an indirect reciprocity model based on reputation

Indirect reciprocity is one of the main mechanisms to explain the emergence and sustainment of altruism in societies. The standard approach to indirect reciprocity is reputation models. These are games in which players base their decisions on their opponent's reputation gained in past interactions with other players (moral assessment). The combination of actions and moral assessment leads to a large diversity of strategies; thus determining the stability of any of them against invasions by all the others is a difficult task. We use a variant of a previously introduced reputation-based model that let us systematically analyze all these invasions and determine which ones are successful. Accordingly, we are able to identify the third-order strategies (those which, apart from the action, judge considering both the reputation of the donor and that of the recipient) that are evolutionarily stable. Our results reveal that if a strategy resists the invasion of any other one sharing its same moral assessment, it can resist the invasion of any other strategy. However, if actions are not always witnessed, cheaters (i.e., individuals with a probability of defecting regardless of the opponent's reputation) have a chance to defeat the stable strategies for some choices of the probabilities of cheating and of being witnessed. Remarkably, by analyzing this issue with adaptive dynamics we find that whether an honest population resists the invasion of cheaters is determined by a Hamilton-like rule, with the probability that the cheat is discovered playing the role of the relatedness parameter.This work has been supported by the Ministerio de Ciencia e Innovación (Spain) through grants MOSAICO and PRODIEVO, by the European Research Area Complexity-Net through grant RESINEE, and by Comunidad de Madrid (Spain) through grant MODELICO-CM. L.A.M.-V. was supported by a postdoctoral fellowship from Alianza 4 Universidades