Volume 72, Number 3, 2020
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS
 
Dependence of universe deceleration parameter on cosmological constant: mechanism of vacuum pressure excitation by matter
D.YU. TSIPENYUK, W.B. BELAYEV
Rom. Rep. Phys. 72, 113 (2020)
Abstract. Based on Sakharov's idea of a 'metrical elasticity' of space, i.e., of the emergence of a generalized force, preventing distortion of space, we detect the pressure of the vacuum as per the geometry of the space around the local gravity system. The gravitational defect of mass is interpreted as the transfer of energy to the vacuum, which becomes apparent from its deformation. We determine the gravitational impact of matter on the vacuum and opposite in the sign pressure of it in case of weakly gravitating static centrally symmetric distribution of matter using appropriate solution of Einstein's equations. A possibility to extend the obtained results to arbitrary gravitational systems is evaluated. A non-conservation of energy in gravitational systems is interpreted by the Extended Space Model (ESM) as the rotation of the energy-momentum vector in 5-dimensional space. A proposed approach to determining pressure as a source of gravity leads to a revision of the dependence of the deceleration parameter of the Universe on the density parameters. Under this condition we examine the ratio between the density parameters of dark energy and cosmological constant depending on the deceleration parameter.
Article no. 113: PDF 
Simulations and analysis of the first black hole populations
R.A. BALASOV, L.I. CARAMETE
Rom. Rep. Phys. 72, 114 (2020)
Abstract. We simulate various black hole populations using the GIZMO code package for cosmological N-body/Smoothed-particle hydrodynamics (SPH) problems. The objective of this analysis is to use the results of the simulations in order to compare them with the present black hole mass distribution. In doing this, we can predict the initial population of black holes, the mass distribution and the black hole merger rate, which will be a direct contribution to the future gravitational waves observatories (such as the LISA Space Mission).
Article no. 114: PDF 
Determining the output port from the distance
IULIA GHIU
Rom. Rep. Phys. 72, 115 (2020)
Abstract. In this paper we discuss the following scenario. Suppose that two distant observers share an entangled state of two D-level systems. The two observers, Alice and Bob, have to send randomly their particles through a multi-input multi-output device. The task is to determine the nature of this device or black-box, such that Alice will be able to determine with certainty the output port of Bob's particle. We prove that this black-box is the multi-input-port quantum sorter. Further, we investigate if it is possible to determine the output port in the case when three observers are involved by analyzing the cases when the Greenberger-Horne-Zeilinger (GHZ) state and the W state are used.
Article no. 115: PDF 
Vortex solutions in atomic Bose-Einstein condensates via the Adomian decomposition method
TIBERIU HARKO, MAN KWONG MAK, CHUN SING LEUNG
Rom. Rep. Phys. 72, 116 (2020)
Abstract. We study the dynamics of vortices with arbitrary topological charges in weakly interacting Bose-Einstein condensates using the Adomian Decomposition Method to solve the nonlinear Gross-Pitaevskii equation in polar coordinates. The solutions of the vortex equation are expressed in the form of inginite power series. The power series representations are compared with the exact numerical solutions of the Gross-Pitaevskii equation for the uniform and the harmonic potential, respectively. We find that there is a good agreement between the analytical and the numerical results.
Article no. 116: PDF 
Chaotic and solitonic solutions for a new time-fractional two-mode Korteweg-de Vries equation
MARWAN ALQURAN, IMAD JARADAT, SHAHER MOMAN, DUMITRU BALEANU
Rom. Rep. Phys. 72, 117 (2020)
Abstract. The two-mode Korteweg-de Vries (TMKdV) equation is a nonlinear dispersive wave model that describes the motion of two different directional wave modes with the same dispersion relations but with various phase velocities, nonlinearity, and dispersion parameters. In this work, we study the dynamics of the model analytically in a time-fractional sense to ensure the stability of the extracted waves of the TMKdV equation. We use the fractional power series technique to conduct our analysis. We show that there is a homotopy mapping of the solution as the Caputo time-fractional derivative order varies over (0,1] and that both waves have the same physical shapes but with reflexive relation.
Article no. 117: PDF 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
Competition between 296Lv α decay and fission as function of the excitation energy
M. MIREA, A. SANDULESCU
Rom. Rep. Phys. 72, 202 (2020)
Abstract. The deformation energy for the 296Lv superheavy element is calculated in the framework of the macroscopic-microscopic model based on the the Woods-Saxon two-center shell model. The inertia is obtained within the cranking approach. The superasymmetric fission and the near symmetric fission of 296Lv nucleus are investigated. The fission paths are obtained by minimizing the action integral constrained by a final configuration pertaining to the fission or to the α-decay process. In both cases, the potential barrier exhibits a two-humped structure characterized by a deep second well. The ratio between α-decay and cold fission decay probabilities are reported for different excitation energies of the parent nucleus.
Article no. 202: PDF 
 
OPTICS AND PHOTONICS, PLASMAS, LASER AND BEAM PHYSICS
 
Mid-infrared nanophotonics for biochemical sensing: a review
O. TAKAYAMA
Rom. Rep. Phys. 72, 408 (2020)
Abstract. The mid-infrared (IR) wavelength region is widely utilized for absorption spectroscopy to detect molecules in gas, liquid, and solid phases by taking the advantage of characteristic infrared absorption peaks unique to molecular bonding. MidIR absorption spectroscopy offers a unique label-free detection method with a wide variety of applications from environmental monitoring to medical diagnosis. However, the challenge lies in the huge mismatch of molecular sizes, typically on the order of nanometer as opposed to microns of mid-IR wavelengths, making detection of low concentration of them extremely challenging. Various nanophotonic phenomena enable us to localize mid-IR light at nanoscale to enhance light absorption by molecules and thus sensitivity. We present an overview of nanophotonic phenomena, such as waveguide modes, both propagating and localized plasmon modes, together with micro- and nanostructured platforms that host these phenomena, including dielectric planar waveguides, photonic crystals, plasmonic, and phononic nanostructures.
Article no. 408: PDF 
Cleansing data from the high-power laser system in ELI-NP: a holistic system approach
G. KOLLIOPOULOS, G. PRODAN, B. BOISDEFFRE, I. DANCUS
Rom. Rep. Phys. 72, 409 (2020)
Abstract. A method aiming to reduce the amount of data that should be stored at the ELI-NP data center is presented here. Based on a holistic system approach ([1] L. Bertalanffy, General System Theory, George Braziller, Inc. 1968) on the High Power Laser System (HPLS), it consists of a binary classifier which marks the records either as 'useful' or 'useless'.
Article no. 409: PDF 
Ultrashort pulses in photonic crystals made of carbon nanotubes with nonlinear absorption
I.S. DVUZHILOV, Y.V. DVUZHILOVA, N.N. KONOBEEVA, M.B. BELONENKO
Rom. Rep. Phys. 72, 410 (2020)
Abstract. In this paper, we consider the problem of the propagation of three-dimensional ultrashort optical pulses in a photonic crystal made of zig-zag carbon nanotubes under the condition of nonlinear absorption and amplification. The nonlinear absorption is described phenomenologically using data from real experiments. The possibility of stable optical pulse propagation under the conditions of external pump and damping field is shown. We analyze the dependence of the pulse shape on various parameters of the medium, such as the period of carbon nanotubes inhomogeneity in a photonic crystal and the modulation depth of the refractive index.
Article no. 410: PDF 
Travelling-wave analysis of extended cavity diode lasers
V. TRONCIU, B. ARAR, H. WENZEL
Rom. Rep. Phys. 72, 411 (2020)
Abstract. We report results of numerical simulations of the dynamic properties of single-transverse mode diode lasers subject to an external optical feedback provided by a volume holographic Bragg grating. We use the traveling-wave model for the simulation and analysis of the nonlinear dynamics of the considered devices. We show that the numerical results obtained for a sample device are in a good agreement with the experiment. We investigate the influence of relevant device parameters, such as front and rear facet reflectivities and intra-cavity transmission losses on the laser behaviour.
Article no. 411: PDF 
Nonlinear waves in a crystal characterized by the jump switching between self-focusing and defocusing Kerr nonlinearities
S.E. SAVOTCHENKO
Rom. Rep. Phys. 72, 412 (2020)
Abstract. In this paper, we propose a new optical nonlinearity model describing a sharp change from a self-focusing Kerr-type nonlinearity to a defocusing one and vice versa, depending on the electric field amplitude. Three new types of transverse electric nonlinear surface waves can propagate along the interfaces between media characterized by nonlinearities of the proposed type. The light beam propagating along the interface significantly changes the optical properties of regions near that interface. The structure of nonlinear surface waves and peculiarities of the optical domain formation near the interface are described analytically.
Article no. 412: PDF 
 
CONDENSED AND SOFT MATTER PHYSICS
 
Influence of a transverse magnetic field and of hydrostatic pressure on the elasticity state of anisotropic magnetorheological elastomers
I. BICA, E. M. ANITAS, M. BUNOIU
Rom. Rep. Phys. 72, 505 (2020)
Abstract. We manufacture an anisotropic magnetorheological elastomer (aMRE) based on silicone rubber and carbonyl iron microparticles. A plane capacitor having aMRE as dielectric material is obtained by placing the aMRE between two electroconductive disks, followed by polymerization in a transverse magnetic field. The electrical capacitance of the capacitor in the magnetic field, and respectively under mechanical compression is measured by using a new experimental setup. It is shown that in a magnetic field, the capacitance depends sensibly on the direction of application of the magnetic field intensity. Under the action of mechanical compression, the capacitance is equivalent to the one measured when the transverse magnetic field is applied. The modification of the electric capacitance is the effect of magneto-striction of aMRE in the magnetic field. We describe the observed effects by using the dipolar approximation and linear elasticity theory for small deformations.
Article no. 505: PDF 
Microstructural and electrical transport properties of RBa2Cu3O7-γ (R=Y, Pr) based thin films and ramp-type Josephson junctions
V. LECA, N.D. SCARISOREANU, M. DINESCU
Rom. Rep. Phys. 72, 506 (2020)
Abstract. The results of a study on the fabrication and properties of RBa2Cu3O7-γ (R = Y, Pr) - based thin films and ramp-type Josephson junctions are presented. The films were grown on (001) SrTiO3 substrates by radio frequency plasma-assisted pulsed laser deposition (PLD) or by conventional PLD and their morphological, structural, and electrical properties were analyzed. The ramp morphology and the quality of the interfaces with the barrier and the top-electrode were found to be critical factors limiting the transport of charge carrier between the superconducting electrodes of the junctions.
Article no. 506: PDF 
Ferromagnetism of manganese-aluminium alloyed with 0-3% carbon from direct induction melting and subsequent annealing
T. CHAROENSUK, P. SAETANG, C. RUTTANAPUN, C. PHROMPET, S. PINITSOONTORN, C. SIRISATHITKUL
Rom. Rep. Phys. 72, 507 (2020)
Abstract.The transformation from ε to τ phase is investigated in manganesealuminium (Mn55Al45) alloyed by the induction melting. By annealing Mn55Al45 at 450–550 °C for 2 h, the ferromagnetic τ-MnAl is enhanced at the expense of ε phase. The largest coercivity of 1139 Oe and remanent magnetization of 3.71 emu/g are obtained after annealing at 550 °C. The additions of 1 and 2% carbon affect the phase and magnetic properties of Mn55Al45 but the 2 h annealing at 550 °C still leads to the largest coercivity. Interestingly, substantial coercivity and magnetizations are directly obtained in (Mn55Al45)98C2 and (Mn55Al45)97C3 by the induction melting without further heat treatments.
Article no. 507: PDF 
 
BIOPHYSICS AND MEDICAL PHYSICS
 
Biophysics of protein folding. A short review
CLAUDIA G. CHILOM, AUREL I. POPESCU
Rom. Rep. Phys. 72, 604 (2020)
Abstract. A cell expresses over 10,000 proteins for metabolism driving, cellular morphology maintaining, and signaling towards other cells. All these proteins are properly operating only if they possess a native 3D structure. Protein folding is the dynamical process by which a protein attains its unique functional native 3D conformation. Two factors mainly contribute to protein folding: the physical and chemical properties of its amino acids and the influence of the crowded cellular microenvironment of the nascent protein. Although the number of the intermediate states, starting from linear unfolded nascent chain to the native state, is huge, the folding is very rapid implying thus energetically favoured folding paths. Protein folding not only generates biologically active structures, but also protects the protein from degradation by proteases and reduces the probability of abnormal aggregation as in the case of some diseases (e.g., Alzheimer).
Article no. 604: PDF 
A nonlinear heuristic model for estimation of Covid-19 impact to world population
SERGEY V. ERSHKOV, VICTOR CHRISTIANTO, ALLA RACHINSKAYA, E. YU. PROSVIRYAKOV
Rom. Rep. Phys. 72, 605 (2020)
Abstract. In the current model of first approximation, we suggest a nonlinear heuristic approach by appropriate mathematical modelling, with the main aim estimate the part of humankind which will survive definitely (in optimistic scenario). As a historical example, let us recall the fate of Inca civilization as pessimistic scenario. It seems to be natural, by the existing traditions in theoretical biology, to use theory of recurrent sets (chains of recurrent sets) for describing how population evolves over time. Such an approach actually determines a non-linear dependence of self-similar rate of evolution process (or dynamics of infected population) in regard to the proper residual capacity of non-infected part of all the humankind to overcome the pandemic of K-virus (Covid-19). The last is assumed to be associated with 'potential of the niche for absorbing the infection', defining a catastrophic acceleration (or optimistic deceleration) for the dynamics of the infected part of population.
Article no. 605: PDF 
Bioactive phyto-nanosilver particles 'green' synthesized from Clary Sage, Burdock, Southernwood and Asparagus
M.E. BARBINTA-PATRASCU, N. BADEA, C. UNGUREANU, D. BESLIU, S. ANTOHE
Rom. Rep. Phys. 72, 606 (2020)
Abstract. This study reports the 'green' synthesis and biophysical characterization of silver nanoparticles (AgNPs) generated from natural extracts of Salvia sclarea (Clary sage), Arctium lappa (Burdock), Artemisia abrotanum (Southernwood) and Asparagus officinalis (Asparagus), for biomedical purposes. UV-Vis absorption spectroscopy revealed SPR bands for AgNPs, between 438 and 467 nm. DLS measurements showed the nano-dimensions of particles ranging from 51.05±0.99 to 123.6±2.05 nm. Zeta potential values of these biogenic AgNPs revealed their good physical stability. The developed AgNPs exhibited impressive antioxidant potential (evaluated by chemiluminescence and ABTS methods) and also antibacterial effect against Escherichia coli bacterium. These materials could be exploited in biomedical field to fight against bacteria and to combat oxidative stress by scavenging short-life & long-life free radicals.
Article no. 606: PDF 
Removal of repetitive magnetic interferences upon unshielded fetal magnetocardiograms
B. ARVINTI, A. ISAR, R. STOLZ, M. COSTACHE
Rom. Rep. Phys. 72, 607 (2020)
Abstract. Fetal magnetocardiograms are highly sensitive to interferences in unshielded environments, the measurements being realized indirectly. We aimed at removing repetitive deterministic interferences, applying the Wiener filter in the wavelet domain. An effective compression of data is performed using the Walsh-Hadamard Transform. Real fetal data has been analyzed, with promising results for the development of an automated diagnosis system.
Article no. 607: PDF 
 
ENVIRONMENTAL AND EARTH PHYSICS
 
Effects of polyethylene glycol and sodium chloride stress on water absorption of magneto-primed triticale seeds
J. ALVAREZ, E. MARTINEZ, V. CARBONELL, M. FLOREZ
Rom. Rep. Phys. 72, 708 (2020)
Abstract. The effect of drought and salt stress was studied by generating the same water potential (Ψ) with polyethylene glycol (PEG) and sodium chloride (NaCl). In addition, as the magneto-priming was demonstrated to be a non-invasive method to improve germination, the study was performed by comparing water absorption of magnetically treated and non-treated seeds of triticale (X Triticosecale Wittmack) under stress conditions. Seeds water uptake was inversely proportional to the PEG and NaCl concentration, although the absorption was greater for magnetically treated seeds in comparison to the untreated ones (increments up to 11%). Seeds magnetically treated absorbed more water under the influence of NaCl than PEG, especially with low Ψ levels. The adverse effect of salinity and drought on water absorption can be circumvented by exposing seeds to magnetic treatment with a stationary magnetic field induction of 3.71 mT (milliTeslas) during 10 h.
Article no. 708: PDF 
Experimental characterization of an in-situ spectrotracer used in geophysical explorations
I. RADULESCU, R. STOCHICI, M. R. CALIN, M. VISAN, C. DIACOPOLOS, G. GRIGORAS
Rom. Rep. Phys. 72, 709 (2020)
Abstract. The selection of an appropriate detector for field measurements, in case of natural radioactivity, is an important task taking into account constraints given by data reliability, time and cost effectiveness. This paper provides the necessary data when choosing a portable spectrometer Gamma Surveyor based on BGO crystal (6.3 in3). The proven efficiency of the crystal, the weaker energy resolution but still good comparable results with HPGe results, obtained for 238U, 232Th, 40K often makes it a good choice. Thus, in this paper some functional parameters, as energy calibration, energy resolution and background of the system are analyzed. In addition, field data, concentrations of radionuclides 238U, 232Th, 40K (ppm) in surface soil on the Bucharest area are compared with laboratory measurements using HPGe detector. The obtained data, for all three radionuclides, are well correlated.
Article no. 709: PDF 
 
APPLIED AND INTERDISCIPLINARY PHYSICS
 
A Monte Carlo study on the dose distribution in the volume of the glass samples used in dosimetry applications
M. ZADEHRAFI, C. OLARU, G. ORMENISAN, S. CIOBANU
Rom. Rep. Phys. 72, 804 (2020)
Abstract. In this paper, a Monte Carlo study on the dose distribution in the volume of the glass samples used in dosimetry applications was performed. Due to the fact that in glass-based dosimetry the calibration process plays a very important role, it must be carefully approached. In this mater, a study on the influence of the energy of the involved ionizing radiation as well as the position (rotational plan) of the glass samples to the resulting dose distribution was done. Three arbitrary photon energy values, namely 100 keV, 150 keV, and 200 keV, and two angular positions (0 and 45 degrees angle) were chosen. It was shown that when 'reading' the optical parameters of the exposed glass samples, due to the sensitivity of the dose distribution to energy and position, it is very important to be done on the best possible aligned samples. It is also recommended to make multiple determinations on the same sample and use the mean value. By using a mean value, more precise and more accurate values can be obtained, as well as a better evaluation of the associated budget of uncertainties.
Article no. 804: PDF 
Physical degradation detection on artwork surface polychromies using deep learning models
L.M. ANGHELUTA, A. CHIROSCA
Rom. Rep. Phys. 72, 805 (2020)
Abstract. This paper presents the application of a Deep Learning algorithm for a classified accurate detection of different types of physical damages in artwork polychrome surfaces. The algorithm was trained for the automated detection of three classes of typical surface deteriorations: cracks, blisters and detachments (losses). The image sets used in this study were previously recorded for the purpose of detailed surface 3D reconstruction by the means of macro-photogrammetry of a wood painting. These high-resolution images were captured using 2:1 optical macro magnification with a generous overlapping, following the 3D reconstruction methodology, and provided high quality details of the surface features to be classified. Specific activation maps are used to visually emphasize the detected potential deteriorated areas. The purpose of this work was on one hand to validate a process of reusing photogrammetry image data sets, used 3D reconstruction, for machine learning feature detection training and on the other hand to provide a starting point for the development of an affordable real-time surface damage assessment system.
Article no. 805: PDF 
Fourier transform infrared spectroscopic characterization of thermal treated kaolin
R. DEJU, C. MAZILU, I. STANCULESCU, C. TUCA
Rom. Rep. Phys. 72, 806 (2020)
Abstract. The present paper assesses the chemical and microstructural characteristics of the kaolin used as admixture in the mortars for the radioactive waste immobilization. For this purpose, there were used X-ray fluorescence spectroscopy (XRF) methodology as well as the scanning electron microscopy (SEM) coupled with EDS probe. The optimal values of the calcination parameters such as temperature and heating plateau that ensure the complete transformation of the kaolin into metakaolin have been identified by infrared spectroscopy (FTIR). The goal is to increase the mortar performance by reducing the leaching of the immobilized radionuclides in the cementitious matrix obtained by recycling of the radioactive concrete resulted from decommissioning of a VVR-S type nuclear research reactor.
Article no. 806: PDF 
 
PHYSICS EDUCATION
 
Dynamic study of torsion using Tracker software
FABIOLA SANDA CHIRIACESCU, B. CHIRIACESCU, CRISTINA MIRON, C. BERLIC, V. BARNA
Rom. Rep. Phys. 72, 904 (2020)
Abstract. The paper presents an experimental approach that familiarizes students with the video analysis technique. Herein we investigate the dynamic study of the torsion for a metal wire by means of video analysis method with Tracker software and a high-speed camera for data acquisition. The obtained results are in very good agreement with the theoretical calculations for the employed experimental setup.
Article no. 904: PDF 

This is an electronic version of Volume 72 Number 3 2020
 
   
 
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