1,354 research outputs found
Time-Dependent Scalar Fields in Modified Gravities in a Stationary Spacetime
Most no-hair theorems involve the assumption that the scalar field is
independent of time. Recently in [Phys. Rev. D90 (2014) 041501(R)] the
existence of time-dependent scalar hair outside a stationary black hole in
general relativity was ruled out. We generalize this work to modified gravities
and non-minimally coupled scalar field with an additional assumption that the
spacetime is axisymmetric. It is shown that in higher-order gravity such as
metric gravity the time-dependent scalar hair doesn't exist. While in
Palatini gravity and non-minimally coupled case the time-dependent
scalar hair may exist.Comment: 6 pages, no figure
Thrombectomy with and without computed tomography perfusion imaging for large-vessel occlusion stroke in the extended time window: a meta-analysis of randomized clinical trials
ObjectiveIn recent years, several studies have used computed tomography perfusion (CTP) to assess whether mechanical thrombectomy can be performed in patients with large-vessel occlusion (LVO) stroke in an extended time window. However, it has the disadvantage of being time-consuming and expensive. This study aimed to compare the impact of the CTP group with the non-CTP group [non-contrast CT (NCCT) ± CT angiography (CTA)] on the prognosis of this patient population.MethodsA search of PubMed, EMBASE, and the Cochrane Library databases was conducted to collect randomized controlled trials (RCTs) comparing the two strategies. Outcome indicators and factors influencing prognosis were summarized by standardized mean differences, ratios, and relative risks with 95% confidence intervals using a random-effects model.ResultsA total of two RCTs were included in the combined analysis. There were no significant differences in the main outcome indicators (modified Rankin Scale score at 90 days, successful postoperative reperfusion rate) or the incidence of adverse events (90-day mortality and symptomatic intracranial hemorrhage) between the NCCT ± CTA and CTP groups. The time from the last puncture appeared to be significantly shorter in the NCCT ± CTA group than in the CTP group (SMD: −0.14; 95% CI: −0.24, −0.04). Among them, age (OR: 0.96; 95% CI: 0.94, 0.98), ASPECTS (OR: 1.18; 95% CI: 1.12, 1.24), NIHSS score (OR: 0.90; 95% CI: 0.89, 0.91), and diabetes (OR: 0.69; 95% CI: 0.54, 0.88) were associated with a 90-day independent functional outcome.ConclusionThese findings suggest that the choice of NCCT ± CTA (without CTP) for the assessment of mechanical thrombectomy within 6–24 h after LVO in the anterior circulation is not significantly different from CTP; instead, the choice of NCCT ± CTA significantly reduces the time from onset to arterial puncture
Mirror QCD phase transition as the origin of the nanohertz Stochastic Gravitational-Wave Background detected by the Pulsar Timing Arrays
Recent independent announcements by several collaborations have shown strong
evidence of a Stochastic Gravitational-Wave Background (SGWB) detected through
Pulsar Timing Arrays (PTAs). In this study, we investigate the implications of
a first-order phase transition occurring within the early universe's dark
quantum chromodynamics (dQCD) epoch, specifically within the framework of the
mirror twin Higgs dark sector model. Our analysis indicates a distinguishable
SGWB signal originating from this phase transition, which can explain the
measurements obtained by PTAs. Remarkably, a significant portion of the
parameter space within the mirror twin Higgs model that accounts for the SGWB
signal also effectively resolves the existing tensions in both the and
measurements in Cosmology. This intriguing correlation suggests a
possible common origin for these three phenomena. Furthermore, the parameter
region, , where the mirror dark matter
component constitutes less than of the total dark matter abundance, can
accommodate all current cosmological observations and PTA measurements.Comment: 6 pages, 3 figure
Central gas entropy excess as a direct evidence for AGN feedback in galaxy groups and clusters
By analyzing Chandra X-ray data of a sample of 21 galaxy groups and 19 galaxy
clusters, we find that in 31 sample systems there exists a significant central
( kpc) gas entropy excess (), which
corresponds to keV per gas particle, beyond the power-law
model that best fits the radial entropy profile of outer regions. We also find
a distinct correlation between the central entropy excess and
-band luminosity of the central dominating galaxies (CDGs), which is
scaled as , where is tightly
associated with the mass of the supermassive black hole hosted in the CDG. In
fact, if an effective mass-to-energy conversion-efficiency of 0.02 is assumed
for the accretion process, the cumulative AGN feedback yields an extra heating of keV per particle, which is sufficient to explain the central entropy
excess. In most cases the AGN contribution can compensate the radiative loss of
the X-ray gas within the cooling radius ( keV per particle),
and apparently exceeds the energy required to deviate the scaling relations
from the self-similar predictions ( keV per particle). In
contrast to the AGN feedback, the extra heating provided by supernova
explosions accounts for keV per particle in groups and is
almost negligible in clusters. Therefore, the observed correlation between
and can be considered as a direct evidence for AGN
feedback in galaxy groups and clusters.Comment: 14 pages, 3 figures, accepted by RA
Estrogen receptor α (ERα) mediates 17β-estradiol (E2)-activated expression of HBO1
BACKGROUND: HBO1 (histone acetyltransferase binding to ORC1) is a histone acetyltransferase (HAT) which could exert oncogenic function in breast cancer. However, the biological role and underlying mechanism of HBO1 in breast cancer remains largely unknown. In the current study, we aimed to investigate the role of HBO1 in breast cancer and uncover the underlying molecular mechanism. METHODS: Immunohistochemistry was applied to detect HBO1 protein expression in breast cancer specimens (n = 112). The expression of protein level was scored by integral optical density (IOD) for further statistical analyses using SPSS. Real-time PCR was used to simultaneously measure mRNA levels of HBO1. The HBO1 protein expression in breast cancer cells was confirmed by western blot. RESULTS: HBO1 was highly expressed in breast cancer tissues and significantly correlated with estrogen receptor α (ERα) (p < 0.001) and progestational hormone (PR) (p = 0.002). HBO1 protein level also correlated positively with histology grade in ERα positive tumors (p = 0.016) rather than ERα negative tumors. 17β-estradiol (E2) could upregulate HBO1 gene expression which was significantly inhibited by ICI 182,780 or ERα RNAi. E2-increased HBO1 protein expression was significantly suppressed by treatment with inhibitor of MEK1/2 (U0126) in T47 D and MCF-7 cells. CONCLUSIONS: HBO1 was an important downstream molecule of ERα, and ERK1/2 signaling pathway may involved in the expression of HBO1 increased by E2
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