Volume 74, Number 1, 2022
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS
 
Open quantum dynamics of Gaussian Hilbert-Schmidt geometric discord
ALINA DOBRE, AURELIAN ISAR
Rom. Rep. Phys. 74, 101 (2022)
Abstract. The Gaussian geometric quantum discord is studied for a system composed of two resonant bosonic modes embedded in a squeezed thermal bath. The description of the evolution of the geometric discord is performed in the framework of the theory of open systems, based on completely positive quantum dynamical semigroups, by using a geometric quantification of the total non-classical correlations of the Gaussian states. We take initial squeezed thermal states and use the Hilbert-Schmidt metric to derive the geometric quantum discord. We show that the time evolution of the geometric discord strongly depends on the parameters characterising the initial state of the system (squeezing parameter and the average thermal photon numbers of the two modes) and the parameters of the squeezed thermal reservoir (temperature, squeezing and phase). The geometric discord evolves non-monotonically in time, decreasing asymptotically to zero in the limit of large times, due to the interaction with the squeezed thermal bath.
Article no. 101: PDF 
Novel solutions to the undamped and damped KdV-Burgers-Kuramoto equations and modeling the dissipative nonlinear structures in nonlinear media
NOUFE H. ALJAHDALY, S. A. EL-TANTAWY, ABDUL-MAJID WAZWAZ, H. A. ASHI
Rom. Rep. Phys. 74, 102 (2022)
Abstract. In this paper two approaches including the Tanh-expansion method and G'/G2-expansion method are introduced to find a hierarchy of traveling wave solutions to the integrable KdV-Burgers-Kuramoto equation (KBKE). The proposed methods offer a large number of new exact analytical solutions. But the most important motive in this study is to obtain a general solution to the non-integrable damped KBKE. As is well-known, the later equation does not have any exact analytical solution due to the presence of the damping term. Accordingly, we will find a general semi-analytical solution to this equation using a new ansatz and with the help of the exact solutions of the integrable KBKE. Also, we will check the accuracy of the semi-analytical solution to ensure its efficiency and suitability for describing many natural phenomena. The most important characteristic of the general solution is its ability to explain the mechanism of the propagation of non-stationary dissipative waves, which can be described by the non-integrable damped KBKE such as dissipative solitons, dissipative cnoidal waves, dissipative periodic waves, dissipative shock waves, etc. Also, the obtained solutions serve a large sector of science, especially the nonlinear structures that propagate in plasma physics, seas, oceans, mechanical fluids, optical fibers, and Bose-Einstein condensates.
Article no. 102: PDF 
Analytical simulation for the mutual influence of temporal and spatial Caputo-derivatives embedded in some physical models
MOHAMMED AL-DOLAT, MARWAN ALQURAN, IMAD JARADAT, MOHAMMED ALI
Rom. Rep. Phys. 74, 103 (2022)
Abstract. In this paper, we dilated the residual power series method (RPSM) into higher dimensional fractional space to explore the mutual influence of temporal and spatial Caputo-derivatives. Our dilation method has been reinforced by convergence and error analysis. We displayed the (α,β)-fractional embedding of several well-known physical models and presented their solutions analytically by means of a rapidly convergent (α,β)-Maclaurin series with integer variable coefficients. For validation and comparison purposes, the set of the obtained (α,β)-Maclaurin solutions are viewed in lower fractional/integer space by forcing one or both the fractional derivative parameters to be integers and matching them up with the previously obtained results. Altogether, the technique exhibited great potentiality and influence in solving (non)linear physical models equipped with time and space fractional derivatives.
Article no. 103: PDF 
Localized excitations and their collisional dynamics in (2+1)-dimensional Broer-Kaup-Kupershmidt equation
R. RADHA, C. SENTHIL KUMAR
Rom. Rep. Phys. 74, 104 (2022)
Abstract. In this paper, we investigate the (2+1)-dimensional Broer-Kaup-Kupershmidt equation employing the truncated Painlevé approach and we generate localized solutions like dromions, lumps, and rogue waves. The collisional dynamics of the localized solutions is then studied. While the dromions are found to undergo inelastic collision exchanging energy among them, the lumps are found to be noninteracting. We also bring out the unstable nature of rogue waves.
Article no. 104: PDF 
On the selection of models for the high-frequency quasiperiodic oscillations of black holes: the mass problem
IVAN ZH. STEFANOV, RADOSTINA P. TASHEVA
Rom. Rep. Phys. 74, 105 (2022)
Abstract. High-frequency quasiperiodic oscillations of the X-ray flux comming from black-hole binaries have the potential to provide precise estimates of the mass and the spin of the central black hole, if an adequate model for them was available. There are several models in the literature but none of them is commonly accepted. One way to test the available models is to confront their predictions for the masses of black holes with results obtained through other methods. Here, we study the mass bounds that nine of the most commonly used models provide for three microquasars with known masses GRS 1915+105, GRO 1655-40 and XTE 1550-564 which display high-frequency quasiperiodic oscillations in their X-ray spectra. We also propose a statistical method for the assessment of the average success of the models. The results allow us to discard five of them. Here, "the mass problem" designates the conflict between their predictions and the reference masses.
Article no. 105: PDF 
Families of exact soliton solutions to the AB nonlinear system
LAZHAR BOUGOFFA, ABDELAZIZ MENNOUNI, ABDUL-MAJID WAZWAZ
Rom. Rep. Phys. 74, 106 (2022)
Abstract. In this paper, the exact solutions to the AB nonlinear system are investigated. This system is reduced via two different transformations to a sine-Gordon equation and a quasilinear equation for a new dependent variable φ. Solutions to a sine- Gordon equation and a quasilinear equation are found. Hence, the original system can well be solved for such φ. Also, a similar approach is proposed to solve analytically an eventual extension system for the case of variable coefficients.
Article no. 106: PDF 
Asymptotic analysis for a diffusion problem in thin filtering materials
RENATA BUNOIU, CLAUDIA TIMOFTE
Rom. Rep. Phys. 74, 107 (2022)
Abstract. The homogenization of a diffusion problem in a thin periodic heterogeneous composite medium made up of two materials separated by an imperfect interface is studied. This mathematical model might have applications in the analysis of various filtering materials, such as textiles, paper, or biological tissues.
Article no. 107: PDF 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
Role of octupole distortions of the Fermi surface on electric isoscalar collective modes
Ş. MIŞICU
Rom. Rep. Phys. 74, 201 (2022)
Abstract. The purpose of this work is to inquire on the continuum mechanical features of a system of strongly interacting fermions using the framework of Fermi liquids. The Landau equation for the Fermi distribution function is transformed into a set of coupled fluid-dynamical equations for multipole distortions of the Fermi surface up to l = 3. The set of fluid-dynamical equations for a one-component nuclear Fermi system is applied to the propagation of wave disturbances in infinite nuclear matter and electric isoscalar giant resonances in spherical nuclei.
Article no. 201: PDF 
 
OPTICS AND PHOTONICS, PLASMAS, LASER AND BEAM PHYSICS
 
Three-dimensional few cycle optical pulses in optically anisotropic photonic carbon nanotube based crystals including nonlinear absorption
Y.V. DVUZHILOVA, I.S. DVUZHILOV, I.V. ZAPOROTSKOVA, E.N. GALKINA, M.B. BELONENKO
Rom. Rep. Phys. 74, 401 (2022)
Abstract. This paper considers the propagation of three-dimensional few cycle optical pulses (light bullets) in an optically anisotropic semiconductor carbon nanotubebased spatially-variable refractive index medium (anisotropic photonic crystal). The nonlinear absorption that is described phenomenologically using experimental data as well as the external exciting field are introduced. The pulse shows stable propagation in such a medium and is keeping its energy localized in a limited area. The photonic crystal characteristics (refractive index modulation period and depth) and anisotropy (different velocity components and angle between pulse electric field and carbon nanotube axis) are shown to impact the three-dimensional few cycle optical pulse dynamics.
Article no. 401: PDF 
Monitoring droplet evaporation via real-time digital holographic interferometry using a phase only spatial light modulator
A. SIMA, P. C. LOGOFĂTU, M. L. PASCU, I. NICOLAE
Rom. Rep. Phys. 74, 402 (2022)
Abstract. A previous attempt to use interferometry to investigate the modifications in shape and refractive index within a water droplet using a plane-parallel light wave has failed. We report success, however, when using a divergent wave. Additional advantages are derived from the use of a dynamic digital holographic arrangement that can perform real-time observation of the optical path modifications induced by the droplet evaporation. Holograms are recorded on a digital camera sensor, subtracted from the initial hologram and displayed on a spatial light modulator that, under illumination, performs the optical reconstruction of a real-time holographic interferometry "motion picture". For comparison and fitting the phenomenon was mathematically modelled in the geometric approximation. Qualitative agreement was demonstrated. The extension of the technique to the measurement of more complex phenomena, such as the perturbation of the droplet by inelastic or elastic interaction with a pulsed laser is straightforward.
Article no. 402: PDF 
 
CONDENSED AND SOFT MATTER PHYSICS
 
Reminiscent rare-earth cobalt magnetic couplings above the Curie temperature and spin fluctuations in RCo2 compounds
E. BURZO, L. CHIONCEL
Rom. Rep. Phys. 74, 501 (2022)
Abstract. The complex and interdependent exchange interactions in RCo2 compounds with heavy rare-earths are analysed. Reminiscent R5d-Co3d magnetic couplings are still present above the Curie temperatures in a fairly large temperature range Tc < T < T1 with T1 ≈ Tc +300 K. In this temperature range paramagnetic entities of R moments couple antiparallely to those of neighbouring cobalt atoms. The ratio of rare-earth and cobalt moments projected along the field direction (MR/MCo) is not dependent on the external applied fields nor on temperature. At temperatures higher than T>T1 the rare-earths and cobalt moments decouple, and the cobalt magnetic susceptibilities increase with temperature as predicted by the spin fluctuations model. The saturated effective cobalt moments decrease when the internal mean-field at the cobalt positions increases, a behaviour connected with partial quenching of spin fluctuations.
Article no. 501: PDF 
The role of deformation and temperature fields in the distribution of dot defects and modification of the band structure of ZnO caused by pulsed laser irradiation
O. KUZYK, O. DAN'KIV, R. PELESHCHAK, I. STOLYARCHUK
Rom. Rep. Phys. 74, 502 (2022)
Abstract. The model of self-consistent spatial redistribution of the interstitial zinc and the oxygen vacancies in the ZnO semiconductor under the influence of pulsed laser irradiation in deformation and temperature fields is constructed. The proposed model takes into account the diffusion of dot defects in the nonuniform deformation field created by its own dot defects and temperature gradient, as well as the nonlocal interaction of the interstitial zinc and the oxygen vacancies with atoms of the ZnO crystal lattice. The regularities of spatial redistribution of defects depending on the intensity of laser irradiation, substrate temperature and depth of radiation absorption by the semiconductor are established. Within the proposed model with use of the method of deformation potential the regularities of local shift of edge of the band of conductivity in ZnO under the influence of pulse irradiation are established.
Article no. 502: PDF 
 
BIOPHYSICS AND MEDICAL PHYSICS
 
Bio-nanoplatinum phyto-developed from grape berries and nettle leaves: potential adjuvants in osteosarcoma treatment
M. E. BARBINTA-PATRASCU, M. BACALUM, V.A. ANTOHE, S. IFTIMIE, S. ANTOHE
Rom. Rep. Phys. 74, 601 (2022)
Abstract. Cancer remains the leading cause of millions of deaths annually, worldwide. Every year many people are diagnosed with osteosarcoma, the most common type of cancer starting in the bones. Recent advances in Green Nanotechnology are trying to fight against this disease. Thus, a special interest has been given to noble metal nanoparticles. In this study, bio-platinum nanoparticles (bio-PtNPs) were generated through a "green" bottom-up approach, from an aqueous extract of a mixture of nettle leaves and grape berries. The obtained bio-PtNPs were analyzed by UV-Vis absorption spectroscopy, as well as by Scanning Electron Microscopy (SEM). These bio-PtNPs presented antiproliferative activity against MG-63 osteosarcoma cells, in a dosedependent manner. The morphology of MG-63 cells treated with various doses of bio- PtNPs was studied by epifluorescence microscopy. These findings could be exploited in the development of novel biohybrid systems to be used in osteosarcoma therapy.
Article no. 601: PDF 
End-to-end IMRT evaluation using semi-anthropomorphic thorax phantom
ANDREEA A. UDREA, MIHAI T. DUMITRACHE, ALINA DUMITRACHE, MARIA VLĂSCEANU, AUREL I. POPESCU
Rom. Rep. Phys. 74, 602 (2022)
Abstract. The purpose of this study was to evaluate the intensity modulated radiation therapy (IMRT) workflow using the "end-to-end" approach, i.e. following, with the aid of a semi-anthropomorphic thorax phantom, the pathway of a real patient, from imaging to dose delivery. Patient-specific quality assurance (PSQA) measurements were performed with a 2D array, followed by point dose measurements with an ionization chamber in different locations into the phantom: the planning target volume (PTV) and organs at risk (OARs). The combined standard uncertainties associated with point dose measurements were calculated. The results revealed a high quality of IMRT clinical implementation.
Article no. 602: PDF 
 
ENVIRONMENTAL AND EARTH PHYSICS
 
Low-thermal microwave effects on the enzyme activity in the cellulolytic fungus Phanerochaete Chrysosporium
L. OPRICA, S. MICLAUS, G. VOCHITA, D. CREANGA, E. UNGUREANU
Rom. Rep. Phys. 74, 701 (2022)
Abstract. Low thermal microwave bioeffects are subject of multidisciplinary research with biomedical and environmental issues. In this study some of such effects, with focus enzyme activity changes in Phanerochaete chrysosporium fungus were assayed, with addressing to microwave exposure risks. Very low thermal microwaves (Specific Absorption Rate=2.32 W/kg) have induced non-linear variation in the antioxidant biochemical indicators with significantly increased for 1 hour exposure time while low thermal microwaves (Specific Absorption Rate=8.61 W/kg) elicited linear increasing with exposure times. Lignin peroxidase activity was found to decrease remarkably with more than 30%, indicating the impairing of specific metabolic functions of the environmental fungus. The results sustain the hypothesis of reactive oxygen species generation and lipid peroxidation triggered by microwave absorption with consequences on the fungus ability to degrade lignin from wood waste.
Article no. 701: PDF 
Seismic source and earthquake parameters from local seismic recordings. Earthquakes of 28.10.2018 and 23.09.2016, Vrancea, Romania
B. F. APOSTOL, F. BORLEANU, L. C. CUNE
Rom. Rep. Phys. 74, 702 (2022)
Abstract. A direct, practical and operative procedure is described for deriving the parameters of the seismic source and earthquakes from the ground displacement of the P and S waves recorded at a local site on Earth's surface. The procedure gives the seismic-moment tensor, the earthquake energy and magnitude, the orientation of the fault and the direction of the tectonic slip, the duration of the focal seismic activity and the dimension of the focal region (fault). The (previously published) theory underlying this procedure is briefly discussed. The aim of this paper is to provide a detailed description of how this theory can be used for practical purposes. Two specific examples of Vrancea earthquakes (October 10, 2018 and September 23, 2016) are presented.
Article no. 702: PDF 
 
PHYSICS EDUCATION
 
Plasma speaker as an example for work with gifted students
B. RADULOVIĆ, I. KRSTIĆ
Rom. Rep. Phys. 74, 901 (2022)
Abstract. Work with gifted students implies the use of additional activities that correspond to their needs and potentials. The paper presents an example of how physics syllabus can be extended when teaching gifted students.
Article no. 901: PDF 
Study case of potable water from wells in the metropolitan Bucharest area. Influences on human health - interdisciplinary lab
SANDA VOINEA, CORNELIA NICHITA, ELIZA BURCHIU, CORNELIA DIAC, IULIA ARMEANU
Rom. Rep. Phys. 74, 902 (2022)
Abstract. The quality of drinking water has a special importance on human health. This paper presents an interdisciplinary experimental lab for students to determine the water quality. The case study is focused on the water coming from wells situated in the Bucharest metropolitan area, its quality may severely influence the health of the population living here. The experimental works measured the pH, electrical conductivity, nitrate and metals concentration in the water samples. The results showed an important exceedance of the legal nitrate concentration value for drinking water in the northern neighborhood of Bucharest. At the same time, exceedances of the maximum allowed concentration for Cu in the Snagov area were identified. Further studies are needed in these areas related to the health of the inhabitants, taking into account the effects of the presence of nitrates and metals in drinking water.
Article no. 902: PDF 
The dog-and-rabbit chase problem
R. A. GUŢOIU, T. O. CHECHE
Rom. Rep. Phys. 74, 903 (2022)
Abstract. The dog-and-rabbit chase problem is a classical problem that illustrates the concepts of elementary kinematics and, therefore, can be used in introductory mechanics teaching. By dealing with the relative motion, the problem naturally requires solving elementary differential equations and stimulates students to learn mathematics. The efficiency of the approach we adopt is emphasized by extending the class of problems that can be solved by applying it.
Article no. 903: PDF 

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