72 research outputs found
Charged gravastars admitting conformal motion
We propose a new model of a {\it gravastar} admitting conformal motion. While
retaining the framework of the Mazur-Mottola model, the gravastar is assumed to
be internally charged, with an exterior defined by a Reissner-Nordstr{\"o}m
rather than a Schwarzschild line element. The solutions obtained involve (i)
the interior region, (ii) the shell, and (iii) the exterior region of the
sphere. Of these three cases the first case is of primary interest since the
total gravitational mass vanishes for vanishing charge and turns the total
gravitational mass into an {\it electromagnetic mass} under certain conditions.
This suggests that the interior de Sitter vacuum of a charged gravastar is
essentially an electromagnetic mass model that must generate the gravitational
mass. We have also analyzed various other aspects such as the stress energy
tensor in the thin shell and the entropy of the system.Comment: Minor addition, Accepted in Phys. Lett.
An Innovative Platform Merging Elemental Analysis and Ftir Imaging for Breast Tissue Analysis
Histopathology and immunohistology remain the gold standard for breast cancer diagnostic. Yet, these approaches do not usually provide a sufficiently detailed characterization of the pathology. The purpose of this work is to demonstrate for the first time that elemental analysis and Fourier transform infrared spectroscopy microscopic examination of breast tissue sections can be merged into one dataset to provide a single set of markers based on both organic molecules and inorganic trace elements. For illustrating the method, 6 mammary tissue sections were used. Fourier transform infrared (FTIR) spectroscopy images reported a fingerprint of the organic molecules present in the tissue section and laser ablation elemental analysis (LA-ICP-MS) images brought inorganic element profiles. The 6 tissue sections provided 31 106 and 150,000 spectra for FTIR and LA-ICP-MS spectra respectively. The results bring the proof of concept that breast tissue can be analyzed simultaneously by FTIR spectroscopy and laser ablation elemental analysis (LA-ICP-MS) to provide in both case reasonably high resolution images. We show how to bring the images obtained by the two methods to a same spatial resolution and how to use image registration to analyze the data originating from both techniques as one block of data. We finally demonstrates the elemental analysis is orthogonal to all FTIR markers as no significant correlation is found between FTIR and LA-ICP-MS data. Combining FTIR and LA-ICP-MS imaging becomes possible, providing two orthogonal methods which can bring an unprecedented diversity of information on the tissue. This opens a new avenue of tissue section analyses providing unprecedented diagnostic potential. - 2019, The Author(s).This study was made possible by a NPRP Award [7–1267–3–328] from the Qatar National Research Fund (a member of The Qatar Foundation). E.G. is Research Director with the National Fund for Scientific Research (Belgium). The statements made herein are solely the responsibility of the authors.Scopu
SPECTRAL ANALYSIS OF THE COMPLEX HILL OPERATOR ON THE STAR GRAPH
[EN] The analysis of Hill operator is extended from the real line to a star graph. Generalizing the problem, a detailed analysis of the Hill operator on L2(G) is provided. An explicit description of the resolvent is given and the spectrum is described exactly, solved inverse problem.Research supported by the Erasmus Mundus project ELECTRA, 2014.Rakib F. Efendiev; GarcĂa-Raffi, LM. (2014). SPECTRAL ANALYSIS OF THE COMPLEX HILL OPERATOR ON THE STAR GRAPH. Proceedings of the Institute of Mathematics and Mechanics. 40(Special Issue 2014):124-132. http://hdl.handle.net/10251/66296S12413240Special Issue 201
Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity
This paper discusses a new type of thin-shell wormhole constructed by
applying the cut-and-paste technique to two copies of a charged black hole in
generalized dilaton-axion gravity, which was inspired by low-energy string
theory. After analyzing various aspects of this thin-shell wormhole, we discuss
its stability to linearized spherically symmetric perturbations.Comment: Minor changes, 6 pages, 4 figures. Accepted for publication in Gen.
Rel. Gra
Investigation of the effect of PD-L1 blockade on triple negative breast cancer cells using fourier transform infrared spectroscopy
Interactions between programmed death-1 (PD-1) with its ligand PD-L1 on tumor cells can antagonize T cell responses. Inhibiting these interactions using immune checkpoint inhibitors has shown promise in cancer immunotherapy. MDA-MB-231 is a triple negative breast cancer cell line that expresses PD-L1. In this study, we investigated the biochemical changes in MDA-MB-231 cells following treatment with atezolizumab, a specific PD-L1 blocker. Our readouts were Fourier Transform Infrared (FTIR) spectroscopy and flow cytometric analyses. Chemometrical analysis, such as principal component analysis (PCA), was applied to delineate the spectral differences. We were able to identify the chemical alterations in both protein and lipid structure of the treated cells. We found that there was a shift from random coil and ?-helical structure to ?-sheet conformation of PD-L1 on tumor cells due to atezolizumab treatment, which could hinder binding with its receptors on immune cells, ensuring sustained T cell activation for potent immune responses. This work provides novel information about the effects of atezolizumab at molecular and cellular levels. FTIR bio-spectroscopy, in combination with chemometric analyses, may expedite research and offer new approaches for cancer immunology. - 2019 by the authors. Licensee MDPI, Basel, Switzerland.Diabetes Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation (QF), P.O. Box 34110 Doha, Qatar Cancer Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation (QF), P.O. Box 34110 Doha, Qatar Department of Chemistry and Earth Sciences, Qatar University (QU), P.O. Box 2713 Doha, Qatar Qatar Computing Research Institute, Hamad Bin Khalifa University (HBKU), Qatar Foundation (QF), P.O. Box 34110 Doha, Qatar Qatar Environment & Energy Research Institute (QEERI), Hamad Bin Khalifa University (HBKU), Qatar Foundation (QF), P.O. Box 34110 Doha, Qatar Correspondence: [email protected] (M.H.M.A.); [email protected] (E.E.
Radial stability analysis of the continuous pressure gravastar
Radial stability of the continuous pressure gravastar is studied using the
conventional Chandrasekhar method. The equation of state for the static
gravastar solutions is derived and Einstein equations for small perturbations
around the equilibrium are solved as an eigenvalue problem for radial
pulsations. Within the model there exist a set of parameters leading to a
stable fundamental mode, thus proving radial stability of the continuous
pressure gravastar. It is also shown that the central energy density possesses
an extremum in rho_c(R) curve which represents a splitting point between stable
and unstable gravastar configurations. As such the rho_c(R) curve for the
gravastar mimics the famous M(R) curve for a polytrope. Together with the
former axial stability calculations this work completes the stability problem
of the continuous pressure gravastar.Comment: 17 pages, 5 figures, References corrected, minor changes wrt v1,
matches published versio
Thin-shell wormholes from regular charged black holes
We investigate a new thin-shell wormhole constructed by surgically grafting
two regular charged black holes arising from the action using nonlinear
electrodynamics coupled to general relativity. The stress-energy components
within the shell violate the null and weak energy conditions but obey the
strong energy condition. We study the stability in two ways: (i) taking a
specific equation of state at the throat and (ii) analyzing the stability to
linearized spherically symmetric perturbations about a static equilibrium
solution. Various other aspects of this thin-shell wormhole are also analyzed.Comment: 8 pages and 19 figure
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