4,935 research outputs found
Cloud of strings in f(R) gravity
We derive the solution for a spherically symmetric string cloud configuration
in a d-dimensional spacetime in the framework of f(R) theories of gravity. We
also analyze some thermodynamic properties of the joint black hole - cloud of
strings solution. For its Hawking temperature, we found that the dependence of
the mass with the horizon is significantly different in both theories. For the
interaction of a black hole with thermal radiation, we found that the shapes of
the curves are similar, but shifted. Our analysis generalizes some known
results in the literature.Comment: Version accepted for CP
Long-Term Global and Focal Cerebral Atrophy in Perimesencephalic Subarachnoid Hemorrhage—a Case–Control Study
Purpose: Non-aneurysmal perimesencephalic subarachnoid hemorrhage (PmSAH) represents 6.8% of spontaneous subarachnoid hemorrhage, and usually has a benign clinical course. However, patients might have early cerebral ischemic lesions and long-term neurocognitive complaints. Cerebral atrophy has been described in patients after aneurysmal SAH, but not in PmSAH. We aimed to investigate if PmSAH associates with increased brain volume loss.
Methods: In this prospective study, we included consecutive patients with PmSAH that performed MR in the first 10 days after hemorrhage, and follow-up MR 6-7 years later. Automated volumetric measurements of intracranial, white matter, gray matter, whole brain, lateral ventricles, hippocampus, and amygdala volumes were performed. Volumes were compared to a normal population, matched for age.
Results: Eight patients with PmSAH were included, with a mean age of 51.5 (SE 3.6) at baseline. The control group included 22 patients with a mean age of 56.3 (SE 2.0). A relative reduction of all volumes was found in both groups; however, PmSAH patients had significant reductions in intracranial, white and gray matter, whole brain, and hippocampal volumes when compared to controls. These changes had a higher magnitude in whole brain volume, with a significant absolute decrease of 6.5% in PmSAH patients (versus 1.9% in controls), and a trend for an increase in lateral ventricle volume (absolute 21.3% increase, versus 3.9% in controls).
Conclusion: Our cohort of PmSAH patients showed significant long-term parenchymal atrophy, and higher global and focal parenchymal volume loss rates when compared to a non-SAH population.info:eu-repo/semantics/publishedVersio
Tsallis holographic dark energy in the Brans-Dicke cosmology
Using the Tsallis generalized entropy, holographic hypothesis and also
considering the Hubble horizon as the IR cutoff, we build a holographic model
for dark energy and study its cosmological consequences in the Brans-Dicke
framework. At first, we focus on a non-interacting universe, and thereinafter,
we study the results of considering a sign-changeable interaction between the
dark sectors of the cosmos. Our investigations show that, compared with the
flat case, the power and freedom of the model in describing the cosmic
evolution is significantly increased in the presence of the curvature. The
stability analysis also indicates that, independent of the universe curvature,
both the interacting and non-interacting cases are classically unstable. In
fact, both the classical stability criterion and an acceptable behavior for the
cosmos quantities, including the deceleration and density parameters as well as
the equation of state, are not simultaneously obtainable.Comment: Accepted version, Eur. Phys. J. C (2018
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