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Rms-flux relation in the optical fast variability data of BL Lacertae object S5 0716+714
Gabriela-Raluca Mocanu,Bulcsu Sandor
Physics , 2012, DOI: 10.1007/s10509-012-1164-9
Abstract: The possibility that BL Lac S5 0716+714 exhibits a linear root mean square (rms)-flux relation in its IntraDay Variability (IDV) is analysed. The results may be used as an argument in the existing debate regarding the source of optical IDV in Active Galactic Nuclei. 63 time series in different optical bands were used. A linear rms-flux relation at a confidence level higher than 65% was recovered for less than 8% of the cases. We were able to check if the magnitude is log-normally distributed for eight timeseries and found, with a confidence > 95%, that this is not the case.
Self-organized criticality in boson clouds around black holes
Gabriela-Raluca Mocanu,Daniel Grumiller
Physics , 2012, DOI: 10.1103/PhysRevD.85.105022
Abstract: Boson clouds around black holes exhibit interesting physical phenomena through the Penrose process of superradiance, leading to black hole spin-down. Axionic clouds are of particular interest, since the axion Compton wavelength could be comparable to the Schwarzschild radius, leading to the formation of "gravitational atoms" with a black hole nucleus. These clouds collapse under certain conditions, leading to a "Bosenova". We model the dynamics of such unstable boson clouds by a simple cellular automaton and show that it exhibits self-organized criticality. Our results suggest that the evolution through the black hole Regge plane is due to self-organized criticality.
Power Spectral Distribution of the BL Lacertae Object S5 0716+714
Gabriela-Raluca Mocanu,Alexandru Marcu
Physics , 2011, DOI: 10.1002/asna.201111645
Abstract: Observational data in the BVRI bands of the variable BL Lacertae Object S5 0716+714 is discussed from the point of view of its Power Spectral Distribution (PSD). Analysis of the noise properties exhibited by the source. Assessment of the validity of a turbulent model. We fitted a model of the type $P(f) = \beta f^{-\alpha} + \gamma$ to the data for two null hypothesis and calculated the Bayesian p parameter for the fits. Different theoretical models are discussed and applied to these data and a special focus is placed on the MagnetoRotational Instability (MRI). The $P(f) = \beta f^{-\alpha}$ fit provides slopes with values ranging from 0.376 to 2.237, with medium values for each band of $\bar{\alpha}_B = 1.756$, $\bar{\alpha}_V = 1.704$, $\bar{\alpha}_R = 1.780$ and $\bar{\alpha}_I = 1.272$ respectively. An interval for the calculated effective $\alpha_{SS}$ parameter is obtained to be $[0.18,1.72]\cdot 10^{-2}$, corresponding to the order of magnitude previously inferred through both observational and numerical investigations. Structure function analysis, fractal dimension analysis and DFT analysis (all performed in other studies) plus our own analysis establish that the source is turbulent in a nontrivial way, i.e. there is "intrinsic" noise superimposed on the deterministic behavior of the source. We propose that embedding a weakly stochastic magnetic field component in the MRI (MagnetoRotational Instability) framework and taking into account stochastic reconnection of magnetic field lines might explain microvariability in AGN objects.
Self Organized Criticality in an one dimensional magnetized grid. Application to GRB X-ray afterglows
Tiberiu Harko,Gabriela Raluca Mocanu,Nicoleta Stroia
Physics , 2015, DOI: 10.1007/s10509-015-2228-4
Abstract: A simplified one dimensional grid is used to model the evolution of magnetized plasma flow. We implement diffusion laws similar to those so-far used to model magnetic reconnection with Cellular Automata. As a novelty, we also explicitly superimpose a background flow. The aim is to numerically investigate the possibility that Self-Organized Criticality appears in a one dimensional magnetized flow. The cellular automaton's cells store information about the parameter relevant to the evolution of the system being modelled. Under the assumption that this parameter stands for the magnetic field, the magnetic energy released by one volume during one individual relaxation event is also computed. Our results show that indeed in this system Self-Organized Criticality is established. The possible applications of this model to the study of the X-ray afterglows of GRBs is also briefly considered.
Gray Curvature Identities for Almost Contact Metric Manifolds
Raluca Mocanu,Marian Ioan Munteanu
Mathematics , 2007,
Abstract: The aim of this research is the study of Gray curvature identities, introduced by Alfred Gray in \cite{kn:Gra76} for the class of almost hermitian manifolds. As known till now, there is no equivalent for the class of almost contact manifolds. For this purpose we use the Boohby-Wang fibration and the warped manifolds construction in order to establish which identities could be satisfied by an almost contact manifold.
Cosmological evolution of finite temperature Bose-Einstein Condensate dark matter
Tiberiu Harko,Gabriela Mocanu
Physics , 2012, DOI: 10.1103/PhysRevD.85.084012
Abstract: Once the temperature of a bosonic gas is smaller than the critical, density dependent, transition temperature, a Bose - Einstein Condensation process can take place during the cosmological evolution of the Universe. Bose - Einstein Condensates are very strong candidates for dark matter, since they can solve some major issues in observational astrophysics, like, for example, the galactic core/cusp problem. The presence of the dark matter condensates also drastically affects the cosmic history of the Universe. In the present paper we analyze the effects of the finite dark matter temperature on the cosmological evolution of the Bose-Einstein Condensate dark matter systems. We formulate the basic equations describing the finite temperature condensate, representing a generalized Gross-Pitaevskii equation that takes into account the presence of the thermal cloud in thermodynamic equilibrium with the condensate. The temperature dependent equations of state of the thermal cloud and of the condensate are explicitly obtained in an analytical form. By assuming a flat Friedmann-Robertson-Walker (FRW) geometry, the cosmological evolution of the finite temperature dark matter filled Universe is considered in detail in the framework of a two interacting fluid dark matter model, describing the transition from the initial thermal cloud to the low temperature condensate state. The dynamics of the cosmological parameters during the finite temperature dominated phase of the dark matter evolution are investigated in detail, and it is shown that the presence of the thermal excitations leads to an overall increase in the expansion rate of the Universe.
Stochastic oscillations of general relativistic disks
Tiberiu Harko,Gabriela Mocanu
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.20530.x
Abstract: We analyze the general relativistic oscillations of thin accretion disks around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modeled via a friction force, and a random force, respectively. The general equations describing the stochastically perturbed disks are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force we show that the dynamics of the stochastically perturbed disks can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the disks in the Schwarzschild and Kerr geometries are considered in detail, and they are analyzed by numerically integrating the corresponding Langevin equations. The vertical displacements, velocities and luminosities of the stochastically perturbed disks are explicitly obtained for both the Schwarzschild and the Kerr cases.
VITAMIN E INVOLVEMENT IN OXIDATIVE STRESS ASSOCIATED WITH CARCINOGENESIS
Teodor Oboroceanu,Veronica Mocanu,Raluca Haliga,Veronica Luca
Analele ?tiin?ifice Ale Universit??ii Alexandru Ioan Cuza din Ia?i,Sectiunea II A : Genetica si Biologie Moleculara , 2008,
Abstract: Vitamin E is known as a substance with powerful antioxidant proprieties in vivo, along her vitaminic function, her intake reducing the oxidative stress produced by free radicals generators (ORS, etc): ionizing radiations, toxic compounds from air, water, food, etc. It’s well known her effect in numerous human affections, more or less; studies are done over the role & effects in other diseases: diabetes mellitus, cancer, etc. Aim: These researches are following to determine vitamin E effect in carcinogenesis associated OS and so with cancer, vitamin being used as food additive in diet for cancer patients (particularly head and neck cancers used in our study). Following OS reduction, obtaining so, an general status amelioration to subjects, associated with disease, in parallel with specific treatment recommended by medic (chemo- or radiotherapy). We supplementing with vitamin E the food, in calculated doses based on literature studies, with measurements of biochemical parameters in biological fluids from patients as integral blood, serum, plasma and urine – general: glucose, calcium, cholesterol, HDL-cholesterol, triglycerides, creatinine – OS specific: MDA, GSH, SOD, CAT, vitamin E, etc. We use an healthy subjects witness lot which receive an placebo and an witness lot with vitamin E, an subjects lot with cancer receiving an placebo and one with our vitamin E doses, biochemical analysis results up obtained being interpreted, resulting conclusions conducting us to the steps to follow, correlated with results. Expected effect is that one of carcinogenesis (cancer) associated OS reduction, with benefic effects on patient general status.
Riemannian submersions from almost contact metric manifolds
Stere Ianus,Adrian Mihai Ionescu,Raluca Mocanu,Gabriel Eduard Vilcu
Mathematics , 2011, DOI: 10.1007/s12188-011-0049-0
Abstract: In this paper we obtain the structure equation of a contact-complex Riemannian submersion and give some applications of this equation in the study of almost cosymplectic manifolds with Kaehler fibres.
Strategic Thinking in the EU – Aspiration or Reality?
Oana Mocanu,Mihai Sebe,Gabriela Andreica
Romanian Journal of European Affairs (RJEA) , 2011,
Abstract: The aim of this paper is to show the most important points of view presented by high officials and representatives of the academic milieu from European countries on the occasion of the EPIN conference regarding the strategic thinking in the EU, held in Bucharest on September 30th, 2011. There were proposed to the audience several topics related to macro-regional strategies such as: Danube Strategy and Baltic Sea Strategy, the Europe 2020 Strategy and some key points on strategic thinking in EU foreign policy. The conference consisted of three sessions in which speakers stressed out the main topics of the day. The first session outlined the main aspects regarding the Baltic Sea Strategy and the Danube Strategy. The Europe 2020 Strategy was the central point of the second session of the conference, and in the last session, the speakers highlighted some important aspects on the strategic thinking in EU Foreign Policy. The series of speeches was completed by a Conclusions session in which the most important results of the debate were brought to the attention. Also, it left open for further discussion the need for the strategic thinking of the EU to become a reality.
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