Magnetic field evolution and equilibrium configurations in neutron star cores: the effect of ambipolar diffusion

As another step towards understanding the long-term evolution of the magnetic field in neutron stars, we provide the first simulations of ambipolar diffusion in a spherical star. Restricting ourselves to axial symmetry, we consider a charged-particle fluid of protons and electrons carrying the magnetic flux through a motionless, uniform background of neutrons that exerts a collisional drag force on the former. We also ignore the possible impact of beta decays, proton superconductivity, and neutron superfluidity. All initial magnetic field configurations considered are found to evolve on the analytically expected time-scales towards "barotropic equilibria" satisfying the "Grad-Shafranov equation", in which the magnetic force is balanced by the degeneracy pressure gradient, so ambipolar diffusion is choked. These equilibria are so-called "twisted torus" configurations, which include poloidal and toroidal components, the latter restricted to the toroidal volumes in which the poloidal field lines close inside the star. In axial symmetry, they appear to be stable, although they are likely to undergo non-axially symmetric instabilities.Comment: MNRAS, accepte

Self-modulation of nonlinear Alfven waves in a strongly magnetized relativistic electron-positron plasma

We study the self-modulation of a circularly polarized Alfven wave in a strongly magnetized relativistic electron-positron plasma with finite temperature. This nonlinear wave corresponds to an exact solution of the equations, with a dispersion relation that has two branches. For a large magnetic field, the Alfven branch has two different zones, which we call the normal dispersion zone (where d omega/dk > 0) and the anomalous dispersion zone (where d omega/dk < 0). A nonlinear Schrodinger equation is derived in the normal dispersion zone of the Alfven wave, where the wave envelope can evolve as a periodic wave train or as a solitary wave, depending on the initial condition. The maximum growth rate of the modulational instability decreases as the temperature is increased. We also study the Alfven wave propagation in the anomalous dispersion zone, where a nonlinear wave equation is obtained. However, in this zone the wave envelope can evolve only as a periodic wave train.CONICyT 21100839 74110049FONDECyT 1110135 1110729 1080658 1121144CNPqEuropean Commission for a Marie Curie International Incoming FellowshipInstitute for Fusion Studie

VERBS OF SPEECH AND COGNITION: STRUCTURAL PATTERNS IN NEW MEXICAN SPANISH

From a usage-based approach, this dissertation explores the relationship between structural variability and discourse subjectivity in a series of interviews from the New Mexico and Southern Colorado Spanish Survey (Bills and Vigil 2008). Focusing on the use of cognitive and speech verbs, the analysis will demonstrate that a) structural patterns arising from said interaction form a continuum ranging from schematic to fixed constructions; b) the degree of morpho-syntactic variability of these constructions correlates to the speakers stance towards the information being communicated; and c) in actual interaction, speakers frequently introduce subjective nuances, even if the topic of the discourse may be associated with mere transmission of propositional information. To address the aforementioned goals, a set of features is proposed to determine whether frequent subject-tense combinations are becoming prefabs or formulaic expressions, or whether they are schematic constructions merely transmitting propositional information. Previous studies have explored structural patterns of subjectivity in conversation, either examining a wide range of verbal classes (Scheibman 2002) or focusing on specific verbs and their relation to other items in the semantic class (Tao 2001; Weber and Bentivoglio 1991), as well as the subjectification of specific verbs (Company Company 2006a; Company Company 2006b; Travis 2005; Travis 2006a; Travis 2006b). This study contributes to the understanding of emergent grammar, subjectivity, and subjectification across languages by addressing the patterning of frequently used semantic classes and verbs in a context of language and sociocultural contact. The study aims to contribute as well to the revalorization of New Mexican Spanish by demonstrating that structural patterns emerging from the discourse of its speakers are as systematic as those arising from the discourse of speakers of more prestigious dialects of the language

Examining the Relationship Between Adverse Childhood Experiences and COVID-19 Vaccine Status using 2022 BRFSS Data: A Cross-Sectional Study

Abstract: Objective.To determine the association between adverse childhood experiences (ACEs) scores with COVID-19 vaccination outcomes before and after adjusting for demographic variables. Methods. Data were from 2022 Behavioral Risk Factor Surveillance System (BRFSS) surveys regarding 13 categories of ACEs, COVID-19 vaccination, and demographic variables. Data was weight adjusted for survey respondent data. This complex design combined the core and optional modules. Participants who received at least one dose of the COVID-19 vaccine were categorized as vaccinated. The sample size is 12,514. Results. Participants who were female (OR=1.35, 95% CI: [1.19,1.52]), greater than or equal to 65 years old (OR=4.76, 95% CI: [3.82,5.93]), and graduated college (OR=4.18, 95% CI: [3.26,5.34]) had higher odds of receiving at least one dose of the COVID-19 vaccine. After adjustment, ACEs scores were found not to be significantly associated with COVID-19 vaccination status (AOR= 0.99, 95% CI: [0.86,1.13]). Conclusion. The association between COVID-19 vaccine uptake and ACEs scores may be accounted for by factors other than socioeconomic factors. Differences in COVID-19 vaccine uptake between females and males could be influenced by proactive lifestyle health behaviors

Marked mitigation of transplant vascular sclerosis in FasL(gld) (CD95L) mutant recipients. I. The role of alloantibodies in the development of chronic rejection

Background. In the acute rejection of allografts, the interaction between Fas (CD95) and its ligand (FasL; CD95L) has been shown to be involved in mediating apoptotic cell death. The role, however, of these molecules in the pathogenesis of transplant vascular sclerosis is as yet undetermined. The present study was therefore designed to address this issue. Material. C3H/HEJ FasL(gld) (FasL-; H2(k)) spontaneously mutant mice were used either as donors or recipients of aortic allografts; wild-type C57BI/6 (B6; H2b) were used as corresponding recipients or donors (n=6/group), respectively. Controls included aortas transplanted across appropriate allogeneic and syngeneic strain combinations. For histopathological evaluations, the grafts were harvested at day 40 after transplantation, at which time, splenocytes and sera were also obtained for mixed leukocyte reaction and complement- mediated microcytotoxicity assays, respectively. Results. Similar to aortas obtained from allogeneic controls, allografts harvested from FasL-→B6 recipients had morphological evidence of chronic rejection characterized by circumferential intimal thickening with partial disruption of the elastic membranes. Correspondingly, heightened antidonor cellular reactivity was also witnessed in these recipients. On the contrary, B6 allografts harvested from the majority of C3H→FasL- recipients exhibited marked preservation of aortic morphology. Although these recipients had diminished antidonor cellular proliferation, the titers of alloantibodies were markedly elevated. Conclusion. The presence of FasL-expressing functional cytotoxic T cells is required for the pathogenesis of transplant vascular sclerosis. The significant reduction and/or absence of chronic rejection with the concomitant retention of antidonor humoral response in C3H FasL- recipients of B6 aortas prompt us to suggest that perhaps posttransplantation vasculopathy is initiated by cell-mediated cytotoxicity with its perpetuation facilitated by alloantibodies

Multi-Fluid Simulation of the Magnetic Field Evolution in Neutron Stars

Using a numerical simulation, we study the effects of ambipolar diffusion and ohmic diffusion on the magnetic field evolution in the interior of an isolated neutron star. We are interested in the behavior of the magnetic field on a long time scale, over which all Alfven and sound waves have been damped. We model the stellar interior as an electrically neutral plasma composed of neutrons, protons and electrons, which can interact with each other through collisions and electromagnetic forces. Weak interactions convert neutrons and charged particles into each other, erasing chemical imbalances. As a first step, we assume that the magnetic field points in one fixed Cartesian direction but can vary along an orthogonal direction. We start with a uniform-density background threaded by a homogeneous magnetic field and study the evolution of a magnetic perturbation as well as the density fluctuations it induces in the particles. We show that the system evolves through different quasi-equilibrium states and estimate the characteristic time scales on which these quasi-equilibria occur.Comment: It will be published in AIP Proceedings of the Conference '40 Years of Pulsars: Milisecond Pulsars, Magnetars and More' held at University of McGill, Montreal, Canada, August 2007. Contributed Talk at Conference '40 Years of Pulsars: Milisecond Pulsars, Magnetars and More