Volume 63, Number 910, 2018
Theoretical, Mathematical, and Computational Physics
The Founders of Modern Physics in Romania as Seen from the Archive of Revue Roumaine de Physique D. Mihalache, V. Baran, B. Constantinescu, O. Cozar, D. Dascalu, A.I. Nicolin, A. Sandulescu Romanian Journal of Physics 63,
113 (2018)
Motivated by a study of the archive of Revue Roumaine de Physique, published under this name in the period 19641992 and afterwards under the name Romanian Journal of Physics, we present here a series of short scientific portraits of the founders of Modern Physics in Romania: Eugen Bădărău (18871975), Horia Hulubei (18961972), Ion I. Agârbiceanu (19071971), Şerban ۟Ţiţeica (19081985), Radu Grigorovici (19112008), and Ioan Ursu (19282007). The aforementioned founders of Modern Physics in Romania were the heirs of the traditions in education and research from the historical provinces of Romania. These traditions rekindled after the Second World War and bloomed through the foundation and subsequent development of the M۟ăgurele Physics Campus, now a Historic Site of the European Physical Society. Studying the archive of Revue Roumaine de Physique, we have identified eleven Laureates of the Nobel Prize, either for Physics or for Chemistry, who were closely connected with the development of physics in Romania and published in Revue Roumaine de Physique: C.V. Raman (18881970), L. de Broglie (18921987), L. Pauling (19011994), N.F. Mott (19051996), I.M. Frank (19081990), G.T. Seaborg (19121999), A.M. Prokhorov (19162002), K. Siegbahn (19182007), N.G. Basov (19222001), A. Salam (19261996), and C. Rubbia. This article is intended as a personal contribution to the centennial celebrations that mark 100 years that have passed since 1918 when all Romanian historical provinces were united in a single nation state.
Integrable Discretisation of Coupled AblowitzLadik Equations with Branched Dispersion Corina N. Babalic Romanian Journal of Physics 63,
114 (2018)
We construct an integrable discretization of differentialdifference multicomponent AblowitzLadik system with branched dispersion relation, using the Hirota bilinear formalism. The multisoliton solutions are also discussed, first for the fully discrete version of AblowitzLadik equation, second for the coupled AblowitzLadik system with $2$ and $N$ equations.
Nuclear Physics
Half Lives and Q Values of Nuclei Appearing in the αDecay Chains of Recently Reported New Isotopes H. M. Devaraja, Y. K. Gambhir, A. Bhagwat, M. Gupta, S. Heinz, G. Münzenberg Romanian Journal of Physics 63,
304 (2018)
Microscopic investigations for the observed properties of the recently reported five unstable new isotopes are carried out. The ground state properties are calculated in the relativistic mean field (RMF) framework and the results reproduce the experiment well as expected. The $\alpha $  decay lifetimes are calculated in the double folding model using WKB approximation which requires the relevant $Q$ – values of $\alpha $  decay and the $\alpha $  daughter ($V_{\alpha D}$) potential. The latter is obtained by folding the effective M3Y nucleon – nucleon potential with the RMF nucleon density distributions for the daughter nucleus and that of the $\alpha $ particle which is assumed to be of Gaussian shape. The corresponding decay half  lives obtained by using available phenomenological expression are also presented, discussed and compared. It is observed that the use of accurate $Q$ – values (very close to the experimental values) is crucial for the reliable description of the experimental $\alpha $  decay halflives in the WKB framework.
Study of the Optical Band Gap Energy Associated to Optical Materials Exposed to Low Doses of GammaRays A. Celarel, C. Tuta, G.V. Ioan Romanian Journal of Physics 63,
305 (2018)
In this paper, the analysis of the absorption spectra and the experimentally determination of the forbidden band structure associated to a batch of optical materials with high potential to be used in ionizing radiation environments was studied. The present study was focused on the low absorbed gammaray doses region (<105 Gy) and the chosen optical materials were BK7 and ZF7 glasses. The variation of the optical band gap energy, for the direct and respectively indirect types of optical absorption, as a function of the absorbed dose value is presented. For the dense flint ZF7 type glass, a relative decrease of 2.7% of the optical band gap energy for the direct transition, respectively 2.9% for the one corresponding to the indirect transition were determined. In the case of borosilicate BK7 type glass, the relative decrease of the optical band gap energy was found to be 7.8% for the direct transition and 4.8% for the indirect one. These kinds of studies allow obtaining more complex information regarding the optical phenomena occurring at the propagation of the light through optical glass materials, phenomena that influence the optical parameters of the studied materials. The main goal of the present study was to investigate, in an more complex manner, the fundamental properties of the two chosen types of optical materials when interacting with ionizing radiation and, as a result, to characterize their radiation hardness and the possibility of being used in gammaray dosimetry.
Lasers, Plasmas, and Beam Physics
The Effect of Gas Admixture on the Low Pressure Arc Properties A.Kaminska Romanian Journal of Physics 63,
502 (2018)
The influence of Ar, N$_2$, CO$_2$ and H$_2$ injected into lowpressure plasma stream on the operating conditions of the plasmatron is studied. Experiments showed that this gas is drawn to the arc area due to arc spot movement, and cyclic arc shrinking and expanding as results of the power supply pulsation. It changes the arc dynamics, voltage fluctuations and anode voltage drop. Based on the analysis of arc resistance, voltage waveforms and optical emission spectroscopy it was proved that the gas introduced into the plasma stream remains in the cold boundary layer, and not mixing with the hot plasma core.
Effects of Magnetic Drifts on Ion 1 Transport in Turbulent Tokamak Plasmas A. Croitoru Romanian Journal of Physics 63,
503 (2018)
The stochastic advection of low energy deuterium ions is studied in a three dimensional realistic turbulence model in conditions relevant for current tokamak fusion experiments. The diffusion coefficients are calculated starting from the test particles trajectories in the framework of the semianalytical statistical model called the Decorrelation Trajectory Method. We show that trajectory trapping determined by the space correlation of the velocity field is the main cause for anomalous diffusion and we obtain the transport regimes corresponding to different values of the parameters of the turbulence model and a trapping condition in the limit of frozen turbulence. Depending on the value of the parameters of the model, the interaction between turbulence and magnetic drifts leads to both an increase (with transport in the poloidal direction increasing up to an order of magnitude) and a decrease of the particle transport.
The SchrödingerPoissonInduction System: Rotational Effects in the Fluid Turbulence of a 2D Quantum Plasma D.I. Palade, V. Baran Romanian Journal of Physics 63,
504 (2018)
The Quantum Hydrodynamic Model is used to describe the dynamics of a quantum plasma. In this framework we relax the standard assumption of irrotational velocity field by including a natural solenoidal component. Using a Madelung transformation, it is shown that the fluid equations can be embedded in a nonlinear Schrödinger equation in the presence of a selfconsistent electrostatic potential and a pseudomagnetic potential obeying an inductionlike equation. This novel system is used to investigate the quantum fluid turbulence of a twodimensional quantum plasma. While qualitative phenomena, like the dual cascade, are confirmed numerically, it is found that the inclusion of rotational effects changes significantly the evolution of the turbulence spectrum.
Condensed and Soft Matter Physics
Magnetocaloric Effect on Tb_{1x}Y_{x}Co_{2} Compounds A. Bezergheanu, G. Souca, S. Mican, R. Dudric, I.G. Deac, R.Tetean Romanian Journal of Physics 63,
612 (2018)
The structural, magnetic and magnetocaloric properties of several Tb_{1x}Y_{x}Co_{2} compounds were investigated. The investigated compounds are ferrimagnetically ordered. The decrease of the transition temperatures and cobalt moments, when increasing Y content, were attributed to diminution of the exchange interactions. A secondorder magnetic phase transition at T_{C} was evidenced. The magnetocaloric effect was also studied. The obtained maximum entropy change values were found to decrease from 5.3 J/kgK for x = 1 to 1.9 J/kgK for x = 6 for a magnetic field change from 0 to 4 T. It was found that RCP(ΔS)/ΔB values are quite independent of Y concentration.
General Green’s Functions Method for Thermoacoustic Generation in Anisotropic Organic Conductors Biljana Mitreska, Danica Krstovska Romanian Journal of Physics 63,
613 (2018)
The thermoacoustic generation in anisotropic layered organic conductors was considered using Green's functions method to solve the equation for temperature distribution and the acoustic wave equation. The proposed method was demonstrated by applying a heat current as a thermal source at the conductor's surface. The corresponding expressions for the temperature distribution and acoustic wave amplitude are obtained in the case of low temperature when the depth of thermal skin layer is substantially larger than the depth of electromagnetic skin layer. The thermoacoustic generation is studied in detail for the simplest dispersion relation for the quasitwo dimensional charge carriers which, in many cases, allows a correct understanding of the electron transport and dynamics in layered organic conductors. The diversity of the phenomenon studied through its angular and magnetic field dependence is reflected in a number of features which provide a rich material for studying the properties of charge carriers in low dimensional conducting systems under the influence of different thermal and mechanical conditions.
Biophysics and Medical Physics
Influence of Magnetic Field on the Electrical Properties of Membranes Based on Magnetorheological BioSuspensions I. Bica Romanian Journal of Physics 63,
704 (2018)
Selective release of bioactive components for various medical treatments can be achieved in magnetorheological suspensionsbased membranes by exploiting the magnetodielectric effects. Here, we manufacture a bioactive membrane consisting of honey, turmeric powder and carbonyl iron soaked into a microfiber textile. The membrane is used as a dielectric material for fabrication of a plane capacitor. In the presence of a static magnetic field superimposed on an alternating electric field of fixed frequency, we measure the electrical capacitance and resistance of the equivalent electrical circuits of the capacitor. From the measured data we extract information concerning the electrical conductivity, relative dielectric permittivity and the dielectric loss tangent of the obtained membrane. We show that for fixed values of magnetic flux densities, the release of turmeric powder and honey can be controlled, which is useful in fabrication of various medical devices.
Processing of Polyvinyl Chloride Surfaces with Atmospheric Pressure Dielectric Barrier Discharges for Urology Applications E.C. Stancu, M.D. Ionita, E.R. Ionita, M. Teodorescu, M.T. Radu, G. Dinescu Romanian Journal of Physics 63,
705 (2018)
Plates and films prepared from PVC material used in medical applications were exposed to a cold argon plasma jet generated by a dielectric barrier discharge at atmospheric pressure aiming to produce surface hydrophilization. Water contact angle decrease was significant for both sample types surface, with only small changes in surface roughness at low exposure times. Moreover, the modified films were less prone to hydrophobic recovery than plates. An innovative dielectric barrier discharge concept for in line processing the outer surface of objects with complex shape such as catheters is presented.
Applied and Interdisciplinary Physics
An Investigation into Scattering of Optical Radiation in Night Vision Applications C. Plesa, D. Oancea, C. Todirica Romanian Journal of Physics 63,
907 (2018)
This paper presents some aspects regarding the influence of aerosols on radiation propagation from visible and nearinfrared domain through atmosphere, using an algorithm for determination of scattering coefficients. Based on this calculation algorithm, the scattering coefficients were determined for several types of aerosols. The investigation shows how the intensity of the radiation from visible and near infrared domains is influenced by the dimension of the attenuating particles, the refractive index, the wavelength of the radiation, and also by the shape of the particles, in case of night vision applications.
Fresnel LensType Energy Concentrator for SpaceBased Solar Power Systems V. Sergentu, V. Ursaki, A.Ioisher, E. Adar Romanian Journal of Physics 63,
908 (2018)
In this paper a new concept of designing Fresnel lens concentrators on the basis of magnetic microwires with a complex spatial distribution of their density is proposed. The optical properties of microwires are analyzed in terms of their scattering indicatrix, and the design of the lens in the form of a sandwich consisting of two discs with concentric rings with current running inside and the microwires confined in between the discs is discussed. It is shown that such a design allows one to ensure the configuration of a complex spatial distribution of microwires and their effective control by changing the currents in the system. A comparative analysis is performed for microwires with diamagnetic, paramagnetic and ferromagnetic core.
