West University of Timioara

RO, Romania

West University of Timioara

RO, Romania
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Ambru V.E.,West University of Timioara | Winstanley E.,University of Sheffield
Classical and Quantum Gravity | Year: 2017

Making use of the symmetries of anti-de Sitter space-time, we derive an analytic expression for the bispinor of parallel transport, from which we construct in closed form the vacuum Feynman Green's function of the Dirac field on this background. Using the imaginary time anti-periodicity property of the thermal Feynman Green's function, we calculate the thermal expectation values of the fermion condensate and stress-energy tensor and highlight the effect of quantum corrections as compared to relativistic kinetic theory results. © 2017 IOP Publishing Ltd.

Iano R.,Polytechnic University of Mozambique | Lazu R.,Polytechnic University of Mozambique | Barvinschi P.,West University of Timioara
Advanced Powder Technology | Year: 2011

MgAl2O4 was successfully used as crystalline host network for the synthesis of cobalt-based blue ceramic pigments. Different compositions of Mg1-xCoxAl2O 4 (x = 0.1-0.3) powders have been prepared by the combustion reaction of corresponding metal nitrates with mixtures of urea and β-alanine. The resultant powders were characterized by means of XRD, TG-DTA, EDAX, SEM, BET surface area, diffuse reflectance spectrometry and CIELab color measurement. For x = 0.2, thermal analysis investigations evidenced that combustion reaction occurs at 276 °C. XRD analysis certified the formation of the designed solid solution, no additional thermal treatment being required. EDAX elemental analysis confirmed the purity of the as-prepared compound. The resulted powders had large surface areas, which varied from 8.7 to 62.6 m2/g. The crystallite size of Mg1-xCoxAl 2O4 powders was less than 15 nm. Experimental results evidenced that as the proportion of Co2+ increased, the crystallite size decreased and the specific surface area increased. The diffuse reflectance spectra of the Mg1-xCoxAl2O 4 pigments confirmed the presence of tetrahedrally coordinated Co2+. CIELab chromatic coordinates indicated that the bluest color was obtained for x = 0.2. © 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Tudoran R.M.,West University of Timioara | Grban A.,Polytechnic University of Mozambique
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper we will describe some relevant dynamical properties of the Rikitake dynamo system from the Poisson geometry point of view. © 2009 Elsevier Ltd. All rights reserved.

Nicoara S.,West University of Timioara
International Journal of Geometric Methods in Modern Physics | Year: 2011

In this paper we give a method to stabilize asymptotically the Lyapunov stable equilibrium states of a system describing the planar motions of an autonomous underwater vehicle. © 2011 World Scientific Publishing Company.

Ivan G.,West University of Timioara | Ivan M.,West University of Timioara
International Journal of Geometric Methods in Modern Physics | Year: 2011

The main purpose of this paper is to give the Lax representation of the general Euler top system. © 2011 World Scientific Publishing Company.

Putz M.V.,West University of Timioara | Lazea M.,West University of Timioara | Sandjo L.P.,West University of Timioara | Sandjo L.P.,University of Yaounde I
Molecules | Year: 2011

Combined experimental and quantitative structure inter-activity relationship (QSIAR) computation methods were advanced in order to establish the structural and mechanistic influences that steroids and triterpenes, either as newly synthesized or naturally isolated products, have on human HT1080 mammalian cancer cells. The main Hansch structural indicators such as hydrophobicity (LogP), polarizability (POL) and total energy (Etot) were considered and both the structure-projected as well as globally computed correlations were reported; while the inter-activity correlation of the global activity with those projected on structural information was revealed as equal to the direct structural-activity one for the trial sets of compounds, the prediction for the testing set of molecules reported even superior performances respecting those characteristic for the calibration set, validating therefore the present QSInAR models; accordingly, it follows that the LogP carries the most part of the cytotoxic signal, while POL has little influence on inhibiting tumor growth\-A complementary behavior with their earlier known influence on genotoxic carcinogenesis. Regarding the newly hemisynthetic compounds it was found that stigmasta-4,22-dien-3-one is not adapted for cell membrane diffusion; it is recommended that aminocinnamyl chlorohydrate be further modified in order to acquire better steric influence, while aminocinnamyl-2,3,4,6-O- tétraacétyl-a-D-glucopyranoside was identified as being inhibited in the tumor cell by other molecular mechanisms-here not revealed-although it has a moderate-high anti-cancer structurally predicted activity.

Birtea P.,West University of Timioara | Tudoran R.M.,West University of Timioara
International Journal of Geometric Methods in Modern Physics | Year: 2012

In this paper we will give a formula for computing conservation laws for a Hamiltonian system that admits non-Noether infinitesimal symmetry. The formula involves the differential operator associated with the dual Lefschetz operator corresponding to a symplectic form. © 2012 World Scientific Publishing Company.

Pascu G.,West University of Timioara
Modern Physics Letters A | Year: 2012

New spherical scalar modes on the expanding part of Sitter spacetime, eigenfunctions of a conserved Hamiltonian-like operator are found by solving the Klein-Gordon equation in the appropriate coordinate chart, with the help of a time evolution picture technique specially developed for spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) charts. Transition coefficients are computed between these modes and the rest of the scalar spherical and plane wave modes, either momentum or energy eigenfunctions on the spatially flat FLRW chart. © 2012 World Scientific Publishing Company.

Mihe D.,West University of Timioara
Fuzzy Sets and Systems | Year: 2010

A stability result for the additive Cauchy functional equation in non-Archimedean fuzzy normed spaces over a field with valuation is given by using the concept of countable extension of a t-norm. © 2010 Elsevier B.V. All rights reserved.

Nicolaevici N.,West University of Timioara
International Journal of Modern Physics A | Year: 2011

We comment on a previous calculation1 for the scattering amplitude for the Dirac field in an external Coulomb potential in the expanding de Sitter space. The result implies that for initial and final fermion states with identical momenta |pi|=|pf| the helicity of the particle is conserved. We make a classical analysis of the scattering problem in the small scattering angle approximation using the BargmannMichelTelegdi equation and show that helicity conservation also manifests in the classical case. We also show that in Minkowski space there is a complete agreement between the classical and quantum polarization angle of the scattered particle. © 2011 World Scientific Publishing Company.

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