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Constanta, Romania

Ovidius University of Constanta is a public higher education institution in Constanţa, founded in 1961 as a Pedagogical Institute and transformed into a comprehensive university in 1990. As the Charter of the university states, the Pedagogical Institute was founded by Order of the Ministry of Education no. 654 of 1961, comprising four faculties. By State Council Decree no. 209 of 1977 the institute was transformed in Higher Education Institute and reorganized. By Government Decision 209 of 1990 the institute was transformed in university and, a year later, by Order of the Ministry of Education and Science no. 4894 of 1991 the university was given the present name. Wikipedia.

Culetu H.,Ovidius University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Finite entropy and energy are obtained for the horizon of a Rindler observer on the grounds of the nonstatic character of the geometry beyond the horizon. Edery-Constantineau prescription is used to find the dynamical phase space of this particular spacetime. The number of microstates rooted from the ignorance of a Rindler observer of the parameter t from the nonstationary region are calculated. The entropy expression is also obtained from the electric field on the Rindler horizon generated in the comoving system of a uniformly accelerated charge.We suggest that the gravitational energy density constructed by means of the horizon energy and using the Holographic Principle is proportional to g2, similar with a result recently obtained by Padmanabhan. © 2011 Elsevier B.V. Source

Culetu H.,Ovidius University
International Journal of Theoretical Physics | Year: 2015

A modified version of the Reissner-Nordstrom metric is proposed on the grounds of the nonlinear electrodynamics model. The source of curvature is an anisotropic fluid with pr=−ρ which resembles the Maxwell stress tensor at r>>q2/2m, where q and m are the mass and charge of the particle, respectively. We found the black hole horizon entropy obeys the relation S=|W|/2T=AH/4, with W the Komar energy and AH the horizon area. The electric field around the source depends not only on its charge but also on its mass. The corresponding electrostatic potential Φ(r) is finite everywhere, vanishes at the origin and at r=q2/6m and is nonzero asymptotically, with Φ∞=3m/2q${\Phi }_{\infty } = 3m/2q$. © 2015, Springer Science+Business Media New York. Source

Bordei P.,Ovidius University
Journal of Bone and Joint Surgery - Series B | Year: 2011

Platelet-derived growth factor (PDGF) is known to stimulate osteoblast or osteoprogenitor cell activity. We investigated the effect of locally applied PDGF from poly-D,L-lactide (PDLLA)-coated implants on fracture healing in a rat model. A closed fracture of the right tibia of four-month-old Sprague-Dawley rats (n = 40) was stabilised with implants coated with a biodegradable PDLLA versus implants coated with PDLLA and PDGF. Radiographs were taken throughout the study, and a marker of DNA activity, bromodeoxyuridine (BrdU), was injected before the rats were killed at three, seven and ten days. The radiographs showed consolidation of the callus in the PDGF-treated group compared with the control group at all three time points. In the PDGF-treated group, immunohistochemical staining of BrdU showed that the distribution of proliferating cells in all cellular events was higher after ten days compared with that at three and seven days. These results indicate that local application of PDGF from biodegradable PDLLA-coated implants significantly accelerates fracture healing in experimental animals. Further development may help fracture healing in the clinical situation. ©2011 British Editorial Society of Bone and Joint Surgery. Source

Popa C.,Ovidius University
Inverse Problems | Year: 2010

The algebraic reconstruction of images in computerized tomography gives rise to large, sparse and ill-conditioned inverse problems, in which the 'effect' (measurement of the attenuation of x-ray intensities after penetration of the analyzed body) is used to compute the 'cause' (the values of the attenuation function inside the body, i.e. the image). Algebraic reconstruction techniques (ART), on both their successive or simultaneous formulation, have been developed since the early 1970s as efficient 'row action methods' for solving the image reconstruction problem in computerized tomography. In this respect, two important development directions were concerned with their extension to the inconsistent case of the reconstruction problem as well as with their combination with constraining strategies, imposed by the particularities of the reconstructed image. In our paper we analyze, from these two points of view, the diagonal weighting (DW) algorithm proposed by Y Censor, D Gordon and R Gordon in 2001 as an improvement of the classical Cimmino's reflection method. In the first part of the paper we introduce general extended and constraining procedures for ART, based on a minimal set of sufficient assumptions that ensure the convergence of the corresponding algorithms. Starting from this general context we then design an extended form of the DW algorithm together with a constraining procedure for which we prove convergence under appropriate assumptions. Numerical experiments are presented on two phantoms widely used in the literature. © 2010 IOP Publishing Ltd. Source

Popa C.,Ovidius University
Mathematics and Computers in Simulation | Year: 2010

The present paper is a theoretical contribution to the field of iterative methods for solving inconsistent linear least squares problems arising in image reconstruction from projections in computerized tomography. It consists on a hybrid algorithm which includes in each iteration a CG-like step for modifying the right-hand side and a Kaczmarz-like step for producing the approximate solution. We prove convergence of the hybrid algorithm for general inconsistent and rank-deficient least-squares problems. Although the new algorithm has potential for more applied experiments and comparisons, we restrict them in this paper to a regularized image reconstruction problem involving a 2D medical data set. © 2010 IMACS. Source

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