Quasinormal modes of black holes in f(T) gravity

We calculate the quasinormal modes (QNM) frequencies of a test massless scalar field and an electromagnetic field around static black holes in $f(T)$ gravity. Focusing on quadratic $f(T)$ modifications, which is a good approximation for every realistic $f(T)$ theory, we first extract the spherically symmetric solutions using the perturbative method, imposing two ans$\ddot{\text{a}}$tze for the metric functions, which suitably quantify the deviation from the Schwarzschild solution. Moreover, we extract the effective potential, and then calculate the QNM frequency of the obtained solutions. Firstly, we numerically solve the Schr$\ddot{\text{o}}$dinger-like equation using the discretization method, and we extract the frequency and the time evolution of the dominant mode applying the function fit method. Secondly, we perform a semi-analytical calculation by applying the WKB method with the Pade approximation. We show that the results for $f(T)$ gravity are different compared to General Relativity, and in particular we obtain a different slope and period of the field decay behavior for different model parameter values. Hence, under the light of gravitational-wave observations of increasing accuracy from binary systems, the whole analysis could be used as an additional tool to test General Relativity and examine whether torsional gravitational modifications are possible.Comment: 22 pages, 7 figure

The effective field theory approach to the strong coupling issue in f(T)f(T) gravity

We investigate the scalar perturbations and the possible strong coupling issues of $f(T)$ around a cosmological background, applying the effective field theory (EFT) approach. We revisit the generalized EFT framework of modified teleparallel gravity and apply it by considering both linear and second-order perturbations for $f(T)$ theory. No new scalar mode is present in linear and second-order perturbations in $f(T)$ gravity, which suggests a strong coupling problem. However, based on the ratio of cubic to quadratic Lagrangians, we provide a simple estimation of the strong coupling scale, a result which shows that the strong coupling problem can be avoided at least for some modes. In conclusion, perturbation behaviors that at first appear problematic may not inevitably lead to a strong coupling problem, as long as the relevant scale is comparable with the cutoff scale $M$ of the applicability of the theory.Comment: 18 page

Ncapg dynamically coordinates the myogenesis of fetal bovine tissue by adjusting chromatin accessibility

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. NCAPG is a subunit of condensin I that plays a crucial role in chromatin condensation during mitosis. NCAPG has been demonstrated to be associated with farm animal growth traits. However, its role in regulating myoblast differentiation is still unclear. We used myoblasts derived from fetal bovine tissue as an in vitro model and found that NCAPG was expressed during myogenic differentiation in the cytoplasm and nucleus. Silencing NCAPG prolonged the mitosis and impaired the differentiation due to increased myoblast apoptosis. After 1.5 days of differentiation, silencing NCAPG enhanced muscle-specific gene expression. An assay for transposase-accessible chromatinhigh throughput sequencing (ATAC-seq) revealed that silencing NCAPG altered chromatin accessibility to activating protein 1 (AP-1) and its subunits. Knocking down the expression of the AP-1 subunits fos-related antigen 2 (FOSL2) or junB proto-oncogene (JUNB) enhanced part of the muscle-specific gene expression. In conclusion, our data provide valuable evidence about NCAPG’s function in myogenesis, as well as its potential role in gene expression

Strange stars with different quark mass scalings

We investigate the stability of strange quark matter and the properties of the corresponding strange stars, within a wide range of quark mass scaling. The calculation shows that the resulting maximum mass always lies between 1.5 solor mass and 1.8 solor mass for all the scalings chosen here. Strange star sequences with a linear scaling would support less gravitational mass, and a change (increase or decrease) of the scaling around the linear scaling would lead to a larger maximum mass. Radii invariably decrease with the mass scaling. Then the larger the scaling, the faster the star might spin. In addition, the variation of the scaling would cause an order of magnitude change of the strong electric field on quark surface, which is essential to support possible crusts of strange stars against gravity and may then have some astrophysical implications.Comment: 5 pages, 6 figures, 1 table. accepted by M

hSef potentiates EGF-mediated MAPK signaling through affecting EGFR trafficking and degradation

Sef (similar expression to fgf genes) was identified as an effective antagonist of fibroblast growth factor (FGF) in vertebrates. Previous reports have demonstrated that Sef interacts with FGF receptors (FGFRs) and inhibits FGF signaling, however, its role in regulating epidermal growth factor receptor (EGFR) signaling remains unclear. In this report, we found that hSef localizes to the plasma membrane (PM) and is subjected to rapid internalization and well localizes in early/recycling endosomes while poorly in late endosomes/lysosomes. We observed that hSef interacts and functionally colocalizes with EGFR in early endosomes in response to EGF stimulation. Importantly, we demonstrated that overexpression of hSef attenuates EGFR degradation and potentiates EGF-mediated mitogen-activated protein kinase (MAPK) signaling by interfering EGFR trafficking. Finally, our data showed that, with overexpression of hSef, elevated levels of Erk phosphorylation and differentiation of rat pheochromocytoma (PC12) cells occur in response to EGF stimulation. Taken together, these data suggest that hSef plays a positive role in the EGFR-mediated MAPK signaling pathway. This report, for the first time, reveals opposite roles for Sef in EGF and FGF signalings

Does HF prefer to be attached to X or M of XHHM (X = F, Cl, Br; M = Li, Na, K) system? A B3LYP and MP2 theoretical investigation into cooperativity effect

The cooperativity effects are investigated in the possible linear dihydrogen-bonded ternary complexes, F–H∙∙∙X–H∙∙∙H–M and X–H∙∙∙H–M∙∙∙F–H, and non-dihydrogen-bonded quaternary systems, F–H∙∙∙X–∙∙∙H–H∙∙∙M+ and X–∙∙∙H–H∙∙∙M+∙∙∙F–H (X=F, Cl, Br; M=Li, Na, K) using the DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) methods. The result shows that for the dihydrogen-bonded complex, remarkable cooperativity effect is found and the cooperativity effect of the H∙∙∙H bond on the H∙∙∙X or M∙∙∙F interaction is more pronounced than that of the H∙∙∙X or M∙∙∙F contact on the H∙∙∙H interaction. The complexation energy and cooperativity effect in F–H∙∙∙X–H∙∙∙H–M are larger than those of the corresponding X–H∙∙∙H–M∙∙∙F–H system. Thus, the F–H∙∙∙X–H∙∙∙H–M complex is preferentially formed and F–H prefers to be attached to the X end. For the non-dihydrogen-bonded quaternary system, due to the stronger complexation energy and cooperativity effect of Cl–∙∙∙H–H∙∙∙Li+∙∙∙F–H or F–H∙∙∙Br–∙∙∙H–H∙∙∙K+ as compared to those of F–H∙∙∙Cl–∙∙∙H–H∙∙∙Li+ or Br–∙∙∙H–H∙∙∙K+∙∙∙F–H, F–H prefers to be attached to Li+ or Br–. Cooperativity effect is analyzed using the charges on hydrogen in the H∙∙∙H moiety, surface electrostatic potentials and atoms in molecules analysis.