Schwarzschild-like black holes: Light-like trajectories and massless scalar absorption

Black holes are among the most intriguing objects in nature. They are believed to be fully described by General Relativity (GR), and the astrophysical black holes are expected to belong to the Kerr family, obeying the no-hair theorems. Alternative theories of gravity or parameterized deviations of GR allow black hole solutions, which have additional parameters other than mass and angular momentum. We analyze a Schwarzschild-like metric, proposed by Johannsen and Psaltis, characterized by its mass and a deformation parameter. We compute the absorption cross section of massless scalar waves for different values of this deformation parameter and compare it with the corresponding scalar absorption cross section of the Schwarzschild black hole. We also present analytical approximations for the absorption cross section in the high-frequency regime. We check the consistence of our results comparing the numerical and analytical approaches, finding excellent agreement.Comment: 8 pages, 14 figure

Asymmetric wormholes in Palatini f(R)f(\mathcal{R}) gravity: Energy conditions, absorption and quasibound states

We investigate the absorption properties of reflection-asymmetric wormholes constructed via the thin-shell formalism in Palatini $f({\cal R})$ gravity. Such wormholes come from the matching of two Reissner-Nordstr\"om spacetimes at a time-like hypersurface (shell), which, according to the junction conditions in Palatini $f({\cal R})$ gravity, can have positive or negative energy density. Using numerical methods we investigate several configurations that satisfy the junction conditions, and analyze how the parameters of the system affect the absorption spectra. We confirm that the absorption cross section of wormholes at low frequencies significantly departs from that of black holes, and observe that in configurations made out of two naked singularities, the absorption spectra exhibit new features due to the effective light ring associated to the wormhole throat. The possibility of observing the presence of resonances at high frequencies is also discussed.Comment: 18 pages, 13 figures, revtex4-2 styl

Singular space-times with bounded algebraic curvature scalars

We show that the absence of unbounded algebraic curvature invariants constructed from polynomials of the Riemann tensor cannot guarantee the absence of strong singularities. As a consequence, it is not sufficient to rely solely on the analysis of such scalars to assess the regularity of a given space-time. This conclusion follows from the analysis of incomplete geodesics within the internal region of asymmetric wormholes supported by scalar matter which arise in two distinct metric-affine gravity theories. These wormholes have bounded algebraic curvature scalars everywhere, which highlights that their finiteness does not prevent the emergence of pathologies (singularities) in the geodesic structure of space-time. By analyzing the tidal forces in the internal wormhole region, we find that the angular components are unbounded along incomplete radial time-like geodesics. The strength of the singularity is determined by the evolution of Jacobi fields along such geodesics, finding that it is of strong type, as volume elements are torn apart as the singularity is approached. Lastly, and for completeness, we consider the wormhole of the quadratic Palatini theory and present an analysis of the tidal forces in the entire space-time.Comment: 15 pages, 5 figure

Análogos de insulina no tratamento do diabetes gestacional

Pregnancy affects both maternal and fetal metabolism, and even in non-diabetic women, it exerts a diabetogenic effect. Among pregnant women, 2% to 14% develop gestational diabetes. Pregnancy can also occur in women with preexisting diabetes, which may predispose the fetus to many alterations in organogenesis, restrict growth, and the mother, to some diabetes-related complications, such as retinopathy and nephropathy, or to acceleration of the course of these complications, if they are already present. Women with gestational diabetes generally start their treatment with diet and lifestyle changes; when these changes are not enough for optimal glycemic control, insulin therapy must then be considered. Women with type 2 diabetes using oral hypoglycemic agents are advised to change to insulin therapy. Those with preexisting type 1 diabetes should start intensive glycemic control. As basal insulin analogues have frequently been used off-label in pregnant women, there is a need to evaluate their safety and efficacy. The aim of this review is to report the use of both short- and long-acting insulin analogues during pregnancy and to enable clinicians, obstetricians, and endocrinologists to choose the best insulin treatment for their patients

Protein methyltransferase 7 deficiency in Leishmania major increases neutrophil associated pathology in murine model

Leishmania major is the main causative agent of cutaneous leishmaniasis in the Old World. In Leishmania parasites, the lack of transcriptional control is mostly compensated by post-transcriptional mechanisms. Methylation of arginine is a conserved post-translational modification executed by Protein Arginine Methyltransferase (PRMTs). The genome from L. major encodes five PRMT homologs, including the cytosolic protein associated with several RNA-binding proteins, LmjPRMT7. It has been previously reported that LmjPRMT7 could impact parasite infectivity. In addition, a more recent work has clearly shown the importance of LmjPRMT7 in RNA-binding capacity and protein stability of methylation targets, demonstrating the role of this enzyme as an important epigenetic regulator of mRNA metabolism. In this study, we unveil the impact of PRMT7-mediated methylation on parasite development and virulence. Our data reveals that higher levels of LmjPRMT7 can impair parasite pathogenicity, and that deletion of this enzyme rescues the pathogenic phenotype of an attenuated strain of L. major. Interestingly, lesion formation caused by LmjPRMT7 knockout parasites is associated with an exacerbated inflammatory reaction in the tissue correlated with an excessive neutrophil recruitment. Moreover, the absence of LmjPRMT7 also impairs parasite development within the sand fly vector Phlebotomus duboscqi. Finally, a transcriptome analysis shed light onto possible genes affected by depletion of this enzyme. Taken together, this study highlights how post-transcriptional regulation can affect different aspects of the parasite biology

Erratum to: The study of cardiovascular risk in adolescents – ERICA: rationale, design and sample characteristics of a national survey examining cardiovascular risk factor profile in Brazilian adolescents

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