Volume 73, Number 4, 2021
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS. HISTORY AND PHILOSOPHY OF PHYSICS
 
Horia Hulubei: The rise to fame. Archival fragments
G.T. PANĂ, D. AVRAMESCU, A.E. CRISTACHE, M.C. RAPORTARU, S. ZGURĂ, V. BĂRAN, A.I. NICOLIN
Rom. Rep. Phys. 73, 124 (2021)
Abstract. In celebration of the 125 years that have passed since the birth of Horia Hulubei, the founder of the Romanian schools of atomic and nuclear physics, we present some historical documents concerning his activity around and during the Second World War. Part of these documents come from the recently established Horia Hulubei Archive (see http://horiahulubei.ro) at University of Bucharest, where he was Professor (1940-1967) and Rector (1941-1944), while others originate from the archive of Monitorul Oficial, the Official Journal of Romania, where all laws and other deeds are published, and which is now available online through Biblioteca Digitală a Bucureştilor.
Article no. 124: PDF 
Self-similar solutions for a generalized nonlinear Schrödinger equation with higher-order varying dispersions and nonlinearities
WEN-XUAN HAO, YAN WANG, LU LI
Rom. Rep. Phys. 73, 125 (2021)
Abstract. In this paper, a generalized nonlinear Schrödinger equation with varying second-, third-, fourth-, fifth-, and sixth-order dispersions, cubic-quintic-septic nonlinearity, and gain/loss is investigated. By means of the similarity transformation, exact self-similar soliton solutions, including bright and dark soliton solutions, are constructed. Based on the exact soliton solutions, we study the corresponding propagation dynamics in a periodically modulated fiber system. The results show that in the absence of gain/loss, the soliton solutions exhibit a periodic oscillatory evolution behavior, and with the periodic modulation of the gain/loss, the dark soliton switch can be implemented. Finally, the stability of the self-similar solutions against the constraint deviations and the initial perturbations are also investigated by employing direct numerical simulations.
Article no. 125: PDF 
Two-dimensional doubly localized rogue waves in the Davey-Stewartson III equation
JING LIANG, CHENZHI RUAN
Rom. Rep. Phys. 73, 126 (2021)
Abstract. This paper focuses on the two-dimensional doubly localized rogue waves on a background of dark line solitons in the third type of Davey-Stewartson (DS III) equation. We obtain a novel family of semi-rational solutions that are constructed by using the Kadomtsev-Petviashvili (KP) hierarchy reduction method combined with Hirota's bilinear technique. These solitary waves are localized in time as well as in the two-dimensional space and can be applied to model two-dimensional rogue waves in many physical settings, such as oceanic rogue waves; thus, they are termed twodimensional doubly localized rogue waves. We find two types of doubly localized rogue waves in the DS III equation: one type that is termed line segment rogue wave, which arises from the background, and has a profile of finite length and then rapidly decays back to the same background; the other type, which is defined as lump-type rogue wave, appears and disappears in the same background and has a profiles of a lump-shaped wave. These key characteristics are similar to those of certain oceanic surface waves.
Article no. 126: PDF 
Soliton, multiple-lump, and hybrid solutions for a (3+1)-dimensional generalized Konopelchenko-Dubrovsky-Kaup-Kupershmidt equation in plasma physics, fluid mechanics, and ocean dynamics
MENG WANG, BO TIAN
Rom. Rep. Phys. 73, 127 (2021)
Abstract. In this paper, we investigate a (3+1)-dimensional generalized Konopelchenko- Dubrovsky-Kaup-Kupershmidt equation in plasma physics, fluid mechanics, and ocean dynamics. Based on the existing bilinear form, we construct the N-soliton solutions, where N is a positive integer. Besides, we obtain the M-lump solutions via the long-wave limit to the N-soliton solutions, where M is a positive integer. Dark one-lump solutions are derived. Moreover, we take M = 2 and M = 3 to derive the two- and three-lump solutions, respectively. We find that the shapes and amplitudes of the dark one-, two-, and three-lump waves remain unchanged during propagation. Finally, three types of hybrid solutions are discussed, namely, the one-lump wave and one-soliton wave, the one-lump wave and two-soliton waves, and the two-lump waves and one-soliton wave.
Article no. 127: PDF 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
New results on 0+ states in the nucleus 156Gd using the (p;t) reaction
A. IONESCU, S. PASCU, O. SIMA, T. FAESTERMANN, R. HERTENBERGER, C. MIHAI, R. MIHAI, C. NITA, A. TURTURICA, H.-F. WIRTH
Rom. Rep. Phys. 73, 202 (2021)
Abstract. The structure of 156Gd was investigated with the Q3D magnetic spectrograph and the (p,t) transfer reaction at an incident energy of 23 MeV. Excitation energies in 156Gd were extracted following a calibration procedure using the 154Gd(p,t) and 172Yb(p,t) reactions measured under the same magnetic conditions. This study is concentrated on revealing the 0+ excited states, which are some of the least understood excitations in the low-energy structure of atomic nuclei. These excitations are well revealed in the (p,t) transfer reaction, which is known to provide an almost complete spectroscopy of low-spin states. Spin assignments were obtained by measuring angular distributions with a good energy resolution and comparing them with the calculations made using the Distorted Wave Born Approximation (DWBA). Many states with different spins in the energy interval between 0 to 3500 keV were identified. The aim of this paper is to present the results for 0+ states; we obtained 18 excited 0+ states, of which 12 have not been previously observed in (p,t) reactions and 6 are confirmed. The high number of 0+ states observed in this work provides an opportunity to test the theoretical models.
Article no. 202: PDF 
Photon luminescence studies of tetrahydrofuran following trihydrogen cations impact in the 20-1000 eV energy range
TOMASZ J. WASOWICZ
Rom. Rep. Phys. 73, 203 (2021)
Abstract. Photon emission arising during tetrahydrofuran (C4H8O,THF) fragmentation initiated by H3+ ion impact has been studied experimentally. Luminescence fragmentation spectra and the relative emission cross-sections of the excited fragments have been measured using collision-induced emission spectroscopy in the 20-1000 eV energy range. The main features in the spectra are the H Balmer series lines, whose intensities decrease with increasing principal quantum number n more quickly than predicted by quantum theory. Optical spectra also display weak emission of vibrationally and rotationally excited diatomic CH fragments. The possible mechanisms leading to the observed products are discussed.
Article no. 203: PDF 
 
OPTICS AND PHOTONICS, PLASMAS, LASER AND BEAM PHYSICS
 
Theoretical study of the behavior of a DBR laser subject to external optical feedback
VASILE TRONCIU, NILS WERNER, HANS WENZEL, HANS JÜRGEN WÜNSCHE
Rom. Rep. Phys. 73, 408 (2021)
Abstract. We report results of the theoretical study of the dynamic properties of distributed Bragg reflector (DBR) lasers subject to an external optical feedback provided by a long-distance mirror. We adapt the Lang-Kobayashi (LK) model to the considered device. The adapted parameters Henry factor, photon life time, feedback strength, and modal group index entering the LK model depend strongly on the lasing wavelength of the solitary laser. The stationary states computed by the full and adapted LK models show good agreement. We consider the external reflectivity and phase and the solitary laser wavelength as a bifurcation parameters. Thus, we investigate the impact of these parameters on the stability of the stationary states.
Article no. 408: PDF 
 
CONDENSED AND SOFT MATTER PHYSICS
 
Optical properties of tungsten oxide (WOx) thin film prepared by pulsed laser deposition (PLD)
VALENTIN ION, ANDREEA ANDREI, MIHAELA FILIPESCU, FLORIN ANDREI, NICOLETA ENEA, NICU DOINEL SCARISOREANU, MARIA DINESCU
Rom. Rep. Phys. 73, 507 (2021)
Abstract. The enormous interest of this material is their optical and electrical properties which are useful for development of advanced technological applications (sensors, photovoltaic cells). The aim of this study is the control of the optical properties of the WO3 thin films prepared by PLD with variation of the deposition parameters.
Article no. 507: PDF 
 
BIOPHYSICS AND MEDICAL PHYSICS
 
Study of structural changes in biocompatible fluid by the acoustic spectroscopy
S. HARDON, J. KUDELCIK, M. RAJNAK, M. KUBOVCIKOVA
Rom. Rep. Phys. 73, 603 (2021)
Abstract. Magnetic fluids with nanoparticles offer some attractive applications in biomedicine. Biocompatible magnetic fluids are used for diagnostics and therapy in medical applications, in pharmacy, and biosensors. These fluids are used as a delivery system for anticancer agents in a locoregional tumor therapy-magnetic drug targeting and hyperthermia. For the study of the influence of an external magnetic field on the aggregation processes of magnetic nanoparticles in biocompatible magnetic fluids, acoustic spectroscopy was used. The jump changes of the magnetic flux density to the values 100, 200 and 300 mT at various temperatures were applied to the investigated fluid. The measured changes of the acoustic attenuation by the presence of the magnetic fields were the results of nanoparticle aggregations into new structures.
Article no. 603: PDF 
Finding specific spectral features for surface-enhanced Raman response of Enterococcus faecalis assisted by multivariate analysis when using common silver sols
L. STANCIOIU, A.M.R. GHERMAN, N.E. DINA
Rom. Rep. Phys. 73, 604 (2021)
Abstract. Surface-enhanced Raman scattering (SERS) was employed for Enterococcus faecalis detection when using three common silver-based SERS-active sols. The SERS spectra obtained for the same species were compared in terms of bands' intensities and Raman shifting. By using multivariate analysis, the spectral data were classified depending on the sample preparation protocol.
Article no. 604: PDF 
 
ENVIRONMENTAL AND EARTH PHYSICS
 
The dormancy overcoming and affection of early growth of alfalfa (Medicago Sativa L.) seeds by non-thermal plasma and plasma activated water
JANA JIRESOVA, BOZENA SERA, VLADIMIR SCHOLTZ, JOSEF KHUN, MICHAL SERY
Rom. Rep. Phys. 73, 711 (2021)
Abstract. The effect of non-thermal plasma (NTP) and plasma activated water (PAW) on the dormancy and early growth of commercial and wild-type seeds of alfalfa (Medicago sativa) were studied. The seeds were exposed to NTP and irrigated by PAW, and the factorial ANOVA statistics confirmed that factors of plant species plasma treatment and treatment time had high importance for early growth of seedlings. The germination of wild seeds increased from 21% to 30-34% after plasma treatment together with PAW irrigation NTP technology having a high potential in break down dormancy in seeds in comparison with mechanical type of dormancy.
Article no. 711: PDF 
Effects of non-thermal postharvest irradiation of dried mushrooms on their antioxidant content and activity
S. OANCEA, F.M. POPA-VECERDEA, M. RACUCIU
Rom. Rep. Phys. 73, 712 (2021)
Abstract. This study presents the effects of non-thermal physical treatment of Boletus mushroom on its antioxidants. A slight increase of their content was noticed after 30 min of UV-C postharvest exposure at 20 cm. Instead, a low polyphenols degradation occurred at shorter exposure distance, characterized by kinetic parameters (k=2.80x10-3 min-1, t1/2=247.50 min). The UV-C had a significant positive effect on the antioxidant activity. The ATR-FTIR spectra confirmed the results on the changes induced by UV-C light. A weak positive effect on antioxidants was found in dried mushrooms exposed to 50 Hz magnetic field of 3 mT.
Article no. 712: PDF 
 
APPLIED AND INTERDISCIPLINARY PHYSICS
 
Vision of plasmonics from microwave and optical ranges
L. NICKELSON, D. PLONIS
Rom. Rep. Phys. 73, 804 (2021)
Abstract. This article analyzes the various traditions that are applied in electromagnetic field theory by experts from different branches of physics, the same results of the study may look different. Here is compared the style of presentation of dispersion characteristics and also the frequency measurement units that may not match entirely in microwave and optical ranges. We explain the causes and logic of such discrepancies. Time-dependent and position-dependent solutions of the Helmholtz equation are often with opposite signs found in literature on microwave electrodynamics and optics including plasmonics. As a result, the intermediate and final expressions may contain opposite signs. A detailed solution to the wave equation and the reasons for the appearance of opposite signs has been made here.
Article no. 804: PDF 
Atmospheric topographic analysis of a part of Mars
F.M. HOWARI, M. SHARMA, Y. NAZZAL, A. BARBULESCU, F. ALAYDAROOS, C.M. XAVIER
Rom. Rep. Phys. 73, 805 (2021)
Abstract. Satellites launched from various countries provide excellent pavement to understand activities and processes taking place in the Martian environment. This paper is brought out with detailed analyses of the atmosphere and topography of around 9 million square kilometers area on Mars near the Landing site of Viking 2 and Mars Science Laboratory (MSL) from Martian satellite datasets which would help in providing new opportunities for future explorations.
Article no. 805: PDF 
 
PHYSICS EDUCATION
 
Lambert W function and different forms of Wien's displacement law
LJILJANA KOSTIC, IVAN MANCEV
Rom. Rep. Phys. 73, 906 (2021)
Abstract. We shall use the standard physics problem of spectral distribution functions of blackbody radiation from standard physics textbooks that many students meet in their education, and we shall express solutions of transcendental equations in terms of Lambert W functions. Finding various forms of Wien's displacement law from spectral distribution functions requires solving transcendental equations. Using the Lambert W function, we derive closed-form analytical expressions for the wavelengths where maxima occur in the different spectral distributions of blackbody radiation. Transcendental equations can be solved by means of numerical methods but the possibility of obtaining the exact analytical solution of such equation e.g. through the Lambert W function is appealing. The reason is that a closed, analytical form of a function is very important as it provides the necessary asymptotic forms both at small and large values of the independent variable. In principle, exact analytical solutions to physics problems are always desirable and preferable to numerical ones. Our method is illustrated in a pedagogical manner for the benefit of students at the undergraduate level.
Article no. 906: PDF 
Employing imageJ software as a measurement tool for optics experiments in the didactic laboratory
ADRIANA RADU, M. V. POPESCU, C. BERLIC, CRISTINA MIRON, V. BARNA
Rom. Rep. Phys. 73, 907 (2021)
Abstract. In this paper, we employed ImageJ as an image processing software for the analysis of the data obtained from experiments in the optics physics laboratory. We used the software to investigate the interference and diffraction patterns obtained from Newton's rings, Fresnel biprism, and the diffraction patterns acquired by diffraction gratings. ImageJ is a free software that is extensively used in scientific research for measurement and inquiry. The program is easy to use and merely demands computational hardware resources that can be found on usual computers. It is also easy to understand by most of the students while being very efficient and accurate. This tool is extremely useful and precise, helping the students to focus on understanding the concepts. It can be also adapted to many laboratories assisting to improve their educational aptitudes.
Article no. 907: PDF 
Mud thrown from a wheel
S. GALIN, T. O. CHECHE
Rom. Rep. Phys. 73, 908 (2021)
Abstract. The mud thrown from a rolling wheel problem is a classical, yet very instructive one. By revisiting this problem we find a pedagogical way to connect basic concepts of kinematics in a more quantitative correlation, suitable for teaching in the mechanics class. Two equivalent approaches, one based on a relation between the velocities of two points fixed on a rigid body, the other strengthening the versatility of cycloidal motion, are introduced and compared.
Article no. 908: PDF 

This is an electronic version of Volume 73 Number 4 2021
 


 
   
 
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