374 research outputs found
General solutions of Einstein's spherically symmetric gravitational equations with junction conditions
Einstein's spherically symmetric interior gravitational equations are
investigated. Following Synge's procedure, the most general solution of the
equations is furnished in case and are prescribed. The
existence of a total mass function, , is rigorously proved. Under
suitable restrictions on the total mass function, the Schwarzschild mass
, implicitly defines the boundary of the spherical body as .
Both Synge's junction conditions as well as the continuity of the second
fundamental form are examined and solved in a general manner. The weak energy
conditions for an \emph{arbitrary boost} are also considered. The most general
solution of the spherically symmetric anisotropic fluid model satisfying both
junction conditions is furnished. In the final section, various exotic
solutions are explored using the developed scheme including gravitational
instantons, interior -domains and -dimensional generalizations.Comment: 23 pages, 1 figure, uses AMS packages. Updated version has corrected
typos as well as added comments and extension regarding ISLD junction
conditions. Accepted for publication in Journal of Mathematical Physic
On 3D Reconstruction of Porous Media by Using Spatial Correlation Functions
The challenging process of 3D porous media reconstruction from a single 2D image is investigated in this paper. The
reconstruction of the 3D model is based on the statistical information derived from a 2D thin image of the material, by
applying a spatial correlation function. For the first time, this paper reviews the commonly used auto-correlation
functions for material characterization and discusses their properties making them useful for 3D porous media
reconstruction. A set of experiments is conducted in order to analyze the reconstruction capabilities of the studied
correlation functions, while some useful conclusions are drawn. Finally, by taking into account the reconstruction
performance of the existed correlation functions, some desirable properties that need to be satisfied by an ideal
correlation function towards the improvement of the reconstruction accuracy are determined
Giant birefringence in optical antenna arrays with widely tailorable optical anisotropy
The manipulation of light by conventional optical components such as a
lenses, prisms and wave plates involves engineering of the wavefront as it
propagates through an optically-thick medium. A new class of ultra-flat optical
components with high functionality can be designed by introducing abrupt phase
shifts into the optical path, utilizing the resonant response of arrays of
scatters with deeply-subwavelength thickness. As an application of this
concept, we report a theoretical and experimental study of birefringent arrays
of two-dimensional (V- and Y-shaped) optical antennas which support two
orthogonal charge-oscillation modes and serve as broadband, anisotropic optical
elements that can be used to locally tailor the amplitude, phase, and
polarization of light. The degree of optical anisotropy can be designed by
controlling the interference between the light scattered by the antenna modes;
in particular, we observe a striking effect in which the anisotropy disappears
as a result of destructive interference. These properties are captured by a
simple, physical model in which the antenna modes are treated as independent,
orthogonally-oriented harmonic oscillators
Bosentan treatment for Raynauds phenomenon and skin fibrosis in patients with Systemic Sclerosis and pulmonary arterial hypertension: an open-label, observational, retrospective study.
Raynaud's phenomenon (RP) and cutaneous fibrosis are the distinctive manifestations of scleroderma, in which Endothelin-1 plays a fundamental pathogenetic role. Bosentan, an Endothelin-1 receptor antagonist used for the treatment of pulmonary arterial hypertension, retards the beginning of new sclerodermic digital ulcers (DU). This open-label, observational, retrospective study verified the effect of Bosentan on RP and skin fibrosis in sclerodermic outpatients affected by pulmonary arterial hypertension without DU. Fourteen subjects (13 women, 1 man; mean age 60 ± 7.5 years; ten with limited and four with diffuse scleroderma) were observed at baseline (T0) and after four (T1), twelve (T2), twenty-four (T3) and forty-eight (T4) weeks during treatment with Bosentan. They were evaluated for daily quantity and duration of RP attacks and skin thickness (using modified Rodnan total skin score, MRSS). Videocapillaroscopic evaluation was performed at TO and T4. Bosentan decreased significantly the number and duration of RP attacks, beginning at T2 (p<0.05). Videocapillaroscopy showed significant improvement of microcirculatory patterns at T4 (p<0.05). MRSS decreased throughout the study, reaching the statistical significance at T3 and T4 (p<0.01) in the whole cohort. The present data suggest that Bosentan is effective in stabilmng the microcirculation involvement and in improving skin fibrosis irrespective of scleroderma patterns
The modulation of adult neuroplasticity is involved in the mood-improving actions of atypical antipsychotics in an animal model of depression
Depression is a prevalent psychiatric disorder with an increasing impact in global public health. However, a large proportion of patients treated with currently available antidepressant drugs fail to achieve remission. Recently, antipsychotic drugs have received approval for the treatment of antidepressant-resistant forms of major depression. The modulation of adult neuroplasticity, namely hippocampal neurogenesis and neuronal remodeling, has been considered to have a key role in the therapeutic effects of antidepressants. However, the impact of antipsychotic drugs on these neuroplastic mechanisms remains largely unexplored. In this study, an unpredictable chronic mild stress protocol was used to induce a depressive-like phenotype in rats. In the last 3 weeks of stress exposure, animals were treated with two different antipsychotics: haloperidol (a classical antipsychotic) and clozapine (an atypical antipsychotic). We demonstrated that clozapine improved both measures of depressive-like behavior (behavior despair and anhedonia), whereas haloperidol aggravated learned helplessness in the forced-swimming test and behavior flexibility in a cognitive task. Importantly, an upregulation of adult neurogenesis and neuronal survival was observed in animals treated with clozapine, whereas haloperidol promoted a downregulation of these processes. Furthermore, clozapine was able to re-establish the stress-induced impairments in neuronal structure and gene expression in the hippocampus and prefrontal cortex. These results demonstrate the modulation of adult neuroplasticity by antipsychotics in an animal model of depression, revealing that the atypical antipsychotic drug clozapine reverts the behavioral effects of chronic stress by improving adult neurogenesis, cell survival and neuronal reorganization.This work was co-funded by the Life and Health Sciences Research Institute (ICVS), and Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) (Projects NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000023). This work has been also funded by FEDER funds, through the Competitiveness Factors Operational Programme (COMPETE) and by National funds, through the FCT, under the scope of the project POCI-01-0145-FEDER-007038. We thank Luís Martins and Ana Lima for the technical assistanceinfo:eu-repo/semantics/publishedVersio
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