92 research outputs found
Core-crust transition pressure for relativistic slowly rotating neutron stars
We study the influence of core-\textit{crust} transition pressure changes on
the general dynamical properties of neutron star configurations. First we study
the matching conditions in core-\textit{crust} transition pressure region,
where phase transitions in the equation of state causes energy density jumps.
Then using a surface \textit{crust} approximation, we can construct
configurations where the matter is described by the equation of state of the
core of the star and the core-\textit{crust} transition pressure. We will
consider neutron stars in the slow rotation limit, considering perturbation
theory up to second order in the angular velocity so that the deformation of
the star is also taken into account. The junction determines the parameters of
the star such as total mass, angular and quadrupolar momentum.Comment: 4 pages, 1 figur
Non-Abelian Chern-Simons-Higgs vortices with a quartic potential
We have constructed numerically non-Abelian vortices in an SU(2)
Chern-Simons-Higgs theory with a quartic Higgs potential. We have analyzed
these solutions in detail by means of improved numerical codes and found some
unexpected features we did not find when a sixth-order Higgs potential was
used. The generic non-Abelian solutions have been generated by using their
corresponding Abelian counterparts as initial guess. Typically, the energy of
the non-Abelian solutions is lower than that of the corresponding Abelian one
(except in certain regions of the parameter space). Regarding the angular
momentum, the Abelian solutions possess the maximal value, although there exist
non-Abelian solutions which reach that maximal value too. In order to classify
the solutions it is useful to consider the non-Abelian solutions with
asymptotically vanishing component of the gauge potential, which may be
labelled by an integer number . For vortex number and above, we have
found uniqueness violation: two different non-Abelian solutions with all the
global charges equal. Finally, we have investigated the limit of infinity Higgs
self-coupling parameter and found a piecewise Regge-like relation between the
energy and the angular momentum.Comment: 9 pages, 13 figure
New model of relativistic slowly rotating neutron stars with surface layer \textit{crust}: application to giant \textit{glitches} of Vela Pulsar
Introducing a surface layer of matter on the edge of a neutron star in slow
rigid rotation, we analyze, from an intrinsic point of view, the junction
conditions that must be satisfied between the interior and exterior solutions
of the Einstein equations. In our model the core-\textit{crust} transition
pressure arise as an essential parameter in the description of a configuration.
As an application of this formalism, we describe giant \textit{glitches} of the
Vela pulsar as a result of variations in the transition pressure, finding that
these small changes are compatible with the expected temperature variations of
the inner crust during \textit{glitch} time.Comment: 4 pages, 2 figures, to appear in Proceedings of Spanish Relativity
Meeting 2010 (ERE 2010) held in Granada, Spai
Universal relations for quasinormal modes of neutron stars in gravity
We construct quasinormal modes for neutron stars in gravity in the
Einstein frame, considering scalar masses in the sub-neV range. In particular,
we investigate the fundamental quadrupole fluid f-modes and the dipole fluid
F-modes. Employing six equations of state covering matter content with
nucleons, hyperons, and quarks, we then propose universal relations for the
quadrupole f-modes and dipole F-modes. The dipole F-modes are ultra-long lived
and, for the lower scalar masses, their frequencies are inversely proportional
to the corresponding Compton wavelength.Comment: 25 pages, 23 figures; Some figures update
General Relativity and Weyl Geometry
We show that the general theory of relativity can be formulated in the
language of Weyl geometry. We develop the concept of Weyl frames and point out
that the new mathematical formalism may lead to different pictures of the same
gravitational phenomena. We show that in an arbitrary Weyl frame general
relativity, which takes the form of a scalar-tensor gravitational theory, is
invariant with respect to Weyl tranformations. A kew point in the development
of the formalism is to build an action that is manifestly invariant with
respect to Weyl transformations. When this action is expressed in terms of
Riemannian geometry we find that the theory has some similarities with
Brans-Dicke gravitational theory. In this scenario, the gravitational field is
not described by the metric tensor only, but by a combination of both the
metric and a geometrical scalar field. We illustrate this point by, firstly,
discussing the Newtonian limit in an arbitrary frame, and, secondly, by
examining how distinct geometrical and physical pictures of the same phenomena
may arise in different frames. To give an example, we discuss the gravitational
spectral shift as viewed in a general Weyl frame. We further explore the
analogy of general relativity with scalar-tensor theories and show how a known
Brans-Dicke vacuum solution may appear as a solution of general relativity
theory when reinterpreted in a particular Weyl frame. Finally, we show that the
so-called WIST gravity theories are mathematically equivalent to Brans-Dicke
theory when viewed in a particular frame.Comment: LATEX, 22 page
Phenomenological Relations for Axial Quasi-normal Modes of Neutron Stars with Realistic Equations of State
Here we investigate the axial w quasi-normal modes of neutron stars for
several equations of state. In particular, we study the influence of the
presence of hyperons in the core of the neutron stars. We have obtained that
w-modes can be used to distinguish between neutron stars with hyperons and
without hyperons for compact enough stars. We present phenomenological
relations for the frequency and damping times with the compactness of the
neutron star for wI and wII modes showing the differences of the stars with
hyperons in the core. Also, we obtain a new phenomenological relation between
the real part and the imaginary part of the frequency of the w quasi-normal
modes, which can be used to estimate the central pressure of the neutron stars.
We are able to construct explicitly the low compactness limit configuration for
which the fundamental wII mode vanishes. Finally, we have studied the influence
of changes in the core-crust transition pressure obtaining that it is very
small. To obtain these results we have developed a new method based on the
Exterior Complex Scaling technique with variable angle, appropriate for the
treatment of the exterior part of the quasi-normal modes, which allow us to
impose constringent enough conditions to generate pure outgoing quasi-normal
modes. For the interior part we use a piece-wise polytrope approximation for
several equations of state. A complete study of the junction conditions have
been done.Comment: 17 pages, 16 figures, 3 table
Enhancing the immunogenicity of tumour lysate-loaded dendritic cell vaccines by conjugation to virus-like particles
BACKGROUND: Tumour cell lysates are an excellent source of many defined and undefined tumour antigens and have been used clinically in immunotherapeutic regimes but with limited success. METHODS: We conjugated Mel888 melanoma lysates to rabbit haemorrhagic disease virus virus-like particles (VLP), which can act as vehicles to deliver multiple tumour epitopes to dendritic cells (DC) to effectively activate antitumour responses. RESULTS: Virus-like particles did not stimulate the phenotypic maturation of DC although, the conjugation of lysates to VLP (VLP-lysate) did overcome lysate-induced suppression of DC activation. Lysate-conjugated VLP enhanced delivery of antigenic proteins to DC, while the co-delivery of VLP-lysates with OK432 resulted in cross-priming of naïve T cells, with expansion of a MART1(+) population of CD8(+) T cells and generation of a specific cytotoxic response against Mel888 tumour cell targets. The responses generated with VLP-lysate and OK432 were superior to those stimulated by unconjugated lysate with OK432. CONCLUSION: Collectively, these results show that the combination of VLP-lysate with OK432 delivered to DC overcomes the suppressive effects of lysates, and enables priming of naïve T cells with superior ability to specifically kill their target tumour cells
Everolimus plus minimized tacrolimus on kidney function in liver transplantation: REDUCE, a prospective, randomized controlled study
Background and aim: reduction in calcineurin inhibitor levels is considered crucial to decrease the incidence of kidney dysfunction in liver transplant (LT) recipients. The aim of this study was to evaluate the safety and impact of everolimus plus reduced tacrolimus (EVR + rTAC) vs. mycophenolate mofetil plus tacrolimus (MMF + TAC) on kidney function in LT recipients from Spain. Methods: the REDUCE study was a 52-week, multicenter, randomized, controlled, open-label, phase 3b study in de novo LT recipients. Eligible patients were randomized (1:1) 28 days post-transplantation to receive EVR + rTAC (TAC levels <_ 5 ng/mL) or to continue with MMF + TAC (TAC levels = 6-10 ng/mL). Mean estimated glomerular filtration rate (eGFR), clinical benefit in renal function, and safety were evaluated. Results: in the EVR + rTAC group (n = 105), eGFR increased from randomization to week 52 (82.2 [28.5] mL/min/1.73 m2 to 86.1 [27.9] mL/min/1.73 m2) whereas it decreased in the MMF + TAC (n = 106) group (88.4 [34.3] mL/min/1.73 m2 to 83.2 [25.2] mL/min/1.73 m2), with significant (p < 0.05) differences in eGFR throughout the study. However, both groups had a similar clinical benefit regarding renal function (improvement in 18.6 % vs. 19.1 %, and stabilization in 81.4 % vs. 80.9 % of patients in the EVR + rTAC vs. MMF + TAC groups, respectively). There were no significant differences in the incidence of acute rejection (5.7 % vs. 3.8 %), deaths (5.7 % vs. 2.8 %), and serious adverse events (51.9 % vs. 44.0 %) between the 2 groups. Conclusion: EVR + rTAC allows a safe reduction in tacrolimus exposure in de novo liver transplant recipients, with a significant improvement in eGFR but without significant differences in renal clinical benefit 1 year after liver transplantation
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