Volume 71, Number 2, 2019
 
THEORETICAL, MATHEMATICAL, AND COMPUTATIONAL PHYSICS
 
Dark solitons for an extended quintic nonlinear Schrödinger equation: application to water waves at kh = 1.363
F. TSITOURA, T.P. HORIKIS, D.J. FRANTZESKAKIS
Rom. Rep. Phys. 71, 104 (2019)
Abstract. We study the existence, formation and dynamics of gray solitons for an extended quintic nonlinear Schrödinger (NLS) equation. The considered model finds applications to water waves, when the characteristic parameter kh - where k is the wavenumber and h is the undistorted water's depth - takes the critical value kh = 1.363. It is shown that this model admits approximate dark soliton solutions emerging from an effective Korteweg-de Vries equation and that two types of gray solitons exist: fast and slow, with the latter being almost stationary objects. Analytical results are corroborated by direct numerical simulations.
Article no. 104: PDF 
Dissipative cylindrical magnetosonic solitary waves in a magnetized quantum dusty plasma
E.I. EL-AWADY, S.A. EL-TANTAWY, A. ABDIKIAN
Rom. Rep. Phys. 71, 105 (2019)
Abstract. The propagation of nonlinear magnetosonic wave in electron-ion-dust (complex) plasmas, considering the effects of Bohm potential in the presence of an external magnetic field is reported. By means of the quantum hydrodynamics model and applying the reductive perturbation method, a cylindrical Kadomtsev-Petviashvili-Burgers (CKPB) equation is derived. The CKPB equation can be solved analytically using a suitable coordinate transformation with the tanh technique. The numerical results reveal that the plasma density, the magnetic field strength, and the dust kinematic viscosity strongly affect on the profile of magnetoacoustic shocks. It is found that the shock structures decrease with the increase of electron number density. Moreover, increasing the value of magnetic field intensity, the strength of the cylindrical magnetoacoustic shock diminishes at a specific time and the strength of the shock increases with the enhancement of the dust kinematic viscosity.
Article no. 105: PDF 
PT-symmetric optical modes and spontaneous symmetry breaking in the space-fractional Schrödinger equation
P. LI, J. LI, B. HAN, H. MA, D. MIHALACHE
Rom. Rep. Phys. 71, 106 (2019)
Abstract. We numerically investigate the parity-time (PT) symmetric optical modes in the space-fractional Schrödinger equation. The PT-symmetric optical modes are found below the critical phase-transition points. Beyond the critical phase-transition points, the spontaneous symmetry breaking of the PT-symmetric system occurs for non- PT-symmetric solutions. The diagrams of the eigenvalue spectra of the optical modes are presented as function of the degree of non-Hermiticity of the system. The numerical results reveal that the critical phase-transition point increases monotonously with the increase of the Levy index.
Article no. 106: PDF 
 
ATOMIC, MOLECULAR, AND NUCLEAR PHYSICS
 
Energy distribution of ejected photoelectrons in K-2V process
K.I. ISAKOVIC, V. M. PETROVIC, H. S. DELIBASIC
Rom. Rep. Phys. 71, 203 (2019)
Abstract. In the last few years, a great deal of attention has been devoted to Double-Core-Hole states, and especially those involving K-shells, K-2 states, as well as, K-2V states, which include simultaneous core ionization and core-excitation. In this paper we gave a theoretical framework that enables prediction of the energy electron distribution in K-2V process in linearly polarized laser field. In order to achieve this, we obtained a formula for the transition rate taking into account the channels of sequential, nonsequential and ionization with ionic core excitation. We started with the K-2V process in helium like atoms. We showed that inclusion of mentioned additional processes significantly influences the transition rate and, at the same time, the energy distribution of the ejected photoelectrons. This is related especially to the energy range of the ejected photoelectrons bringing us to the energy range of low energy electrons which has a significant role in biodamage.
Article no. 203: PDF 
Ion beam optic simulations at the 1 MV TANDETRONTM from IFIN-HH Bucharest
D. PACESILA, D. GHITA, T. SAVA, M. STRATICIUC, V. MOSU, A. ROTARU, A. STATE, O. GAZA, G. CATA-DANIL
Rom. Rep. Phys. 71, 204 (2019)
Abstract. The RO-AMS facility was commissioned in 2012 and it has been dedicated to the analysis of several radionuclides, such as: 10Be, 14C, 26Al and 129I. A significant improvement in the operation and setup change of this machine is done by developing an analytical tool for beam diagnostics by using the SIMION simulation code. Precise ion beam traceability conveys to higher detection sensitivity that is critical in the accelerator mass spectrometry applications. Furthermore, these simulations allow the analysis of various modifications in the ion beam optics of the accelerator by adding, removing or replacing components or changing their relative positions.
Article no. 204: PDF 
Dosimetric comparision for radiation quality in high energy photon beams
EUGENIA BADITA, CATALIN VANCEA, ION CALINA, DANIELA STROE, MIHAELA DUMITRACHE, MIRABELA DUMITRACHE
Rom. Rep. Phys. 71, 205 (2019)
Abstract. The beam quality Q of high energy photon beams produced by a clinical linear accelerator was assessed using the IAEA TRS-398, AAPM's TG-51 and DIN 6800-2 international protocols. The tissue phantom ratio TPR20,10 is the beam quality Q of high energy photons produced by clinical accelerators and is measured at 10 g·cm-2 and 20 g·cm-20 depth in a water phantom with a constant source-phantom surface distance (SSD) of 100 cm and a field size of 10 cm × 10 cm at the plane of the chamber. According to AAPM's TG-51 the specified beam quality % dd(10)x is the percentage depth dose at 10 g·cm-2 in a water phantom due only to photons.
Article no. 205: PDF 
 
OPTICS AND PHOTONICS, PLASMA, LASER AND BEAM PHYSICS
 
Peculiarities of single-sided CW laser beam imaging of small-depth inhomogeneities in highly-scattering media
T. DREISCHUH, L. GURDEV, O. VANKOV, E. TONCHEVA, L. AVRAMOV, D. STOYANOV
Rom. Rep. Phys. 71, 407 (2019)
Abstract. In this paper, we report some seemingly extraordinary features found experimentally and interpreted theoretically of images derived by optical sensing of small-depth characteristic inhomogeneities (inclusions, e.g., ill places in tissues) in homogeneous highly-scattering host media (e.g., healthy tissues), such as dilutions of Intralipid-20% emulsion in distilled water. It is shown experimentally that at a relatively small depth of the inhomogeneities, when they are not yet enveloped entirely by the scattering-widened laser beam, one may observe an inverted or/and double image of an inclusion, depending on the host-medium turbidity and on the inhomogeneity-to-host medium contrast. The effects observed result from some features of the intensity distribution of laser light backscattered from homogeneous liquid tissue-like phantoms of different turbidity. The results obtained would help one to develop optical (cw laser-beam assisted) diagnostics and tomography approaches and to solve the so-called specificity problem by unambiguous interpretation of the captured tissue images.
Article no. 407: PDF 
Interrogation methods for Bragg fiber-based plasmonic sensors
V. A. POPESCU
Rom. Rep. Phys. 71, 408 (2019)
Abstract. The angular and spectral interrogation methods are applied to calculation of the reflectivity, power loss, and spectral and amplitude sensitivities for the TE,TM, and hybrid modes in a Bragg fiber-based plasmonic sensor with four layers. The results are in agreement with the recent studies of the same structure by using another analytical method, where the electromagnetic field is represented by a Bessel function of the first kind in the core region (SiO2), a linear combination of Bessel functions of the first and second kinds in the dielectric interior layer (GaP), a linear combination of the Hankel functions in the gold region, and a modified Bessel function of the second kind in the outermost region (H2O).
Article no. 408: PDF 
Polystyrene surface modification for serum-free cell culture using an atmospheric pressure dielectric barrier discharge
E.C. STANCU, A. QUADE, K.-D. WELTMANN
Rom. Rep. Phys. 71, 409 (2019)
Abstract. Surface treatments that are required to achieve polystyrene surface suitable for cell culture applications were performed using an atmospheric pressure dielectric barrier discharge generated in helium. Short time plasma treatments affected the polystyrene surface hydrophobicity and surface free energy due to insertion of oxygen-containing polar groups such as -OH, -COOH as proofed by X-ray photoelectron spectroscopy. These changes in surface properties were studied in relation to cellular behavior of human keratinocytes (HaCaT) in vitro and in serum-free medium conditions. Plasma treated polystyrene surfaces promoted cell growth in culture, after several hours.
Article no. 409: PDF 
Investigation of the he content within W coatings by using glow discharge optical emission spectrometry
E. GRIGORE, C. RUSET, M. GHERENDI, M. FIRDAOUSS, C. HERNANDEZ
Rom. Rep. Phys. 71, 410 (2019)
Abstract. GDOES (Glow Discharge Optical Emission Spectrometry) technique is able to perform depth profile analysis by measuring the intensities of the emission of the excited atomic species removed from the surface of the investigated samples. W coated samples with He content deposited by CMSII (Combined Magnetron Sputtering and Ion Implantation) were used for GDOES measurements. The morphology of the coatings has been investigated by SEM analysis whereas the He content within the layer has been evidenced by TDS (Thermal Desorption Spectroscopy) measurements. The qualitative elemental depth profile across the coating has been measured by GDOES.
Article no. 410: PDF 
 
CONDENSED AND SOFT MATTER PHYSICS
 
Photo-electrical properties of thin films with Ge nanoparticles embedded in TiO2 matrix
I. STAVARACHE, V.A. MARALOIU
Rom. Rep. Phys. 71, 504 (2019)
Abstract. We present photo-electrical properties of thin films formed of Ge nanoparticles in TiO2 correlated with structure and morphology. The films co-deposited on Si using magnetron sputtering were annealed in conventional oven at 550 ℃C. We performed structure investigations by X-ray diffraction, transmission electron micros- copy and measured current-voltage characteristics in dark and under illumination at different temperatures. We show that the films are formed of cubic Ge nanoparticles in nanostructured anatase TiO2 matrix. Also, (TiGe)O2 with rutile structure was observed. The films have high photosensitivity under white light as the ratio between photo- and dark currents (-1 V) is of ∼ 102.
Article no. 504: PDF 
Photocatalytic activity of TiO2 films deposited by reactive multi pulse HiPIMS at different substrate temperature values
A. BESLEAGA, A. DEMETER, G.B. RUSU, P. DINCA, L. SIRGHI
Rom. Rep. Phys. 71, 505 (2019)
Abstract. Reactive high power impulse magnetron sputtering (HiPIMS) operated in multi-pulse mode was used to grow titanium dioxide (TiO2) thin films on quartz at different substrate temperature values. The films were characterized by X-Ray diffraction, atomic force microscopy, Raman spectroscopy and UV-Vis transmission spectroscopy techniques to investigate the influence of substrate temperature on the microstructure and optical properties of the deposited thin films. In particular, the substrate temperature affected the crystallinity, energy band gap, hydrofilicity induced by UV light irradiation and photocatalytic activity of the deposited films. The photocatalytic activity was evaluated by experiments of degradation under visible light irradiation of the methylene blue molecules in water. It is shown that the photocatalytic activity gradually increases with the value of the substrate temperature used in depositions. By increase of the substrate temperature, the structure of the deposited films changed from amorphous to crystalline anatase phase, while the optical band gap gradually decrease from 3.2 eV to 2.8 eV. These changes in microstructure and optical properties are considered as the main causes of the significant improvement by substrate heating of the visible light photocatalytic activity of the TiO2 thin films.
Article no. 505: PDF 
 
BIOPHYSICS AND MEDICAL PHYSICS
 
High-resolution optical coherence tomography for the diagnosis of actinic keratosis
A.G. PEHOIU, I. POPESCU, C. GIURCANEANU, A.M. FORSEA
Rom. Rep. Phys. 71, 601 (2019)
Abstract. Actinic keratosis (AK) are considered precursors of invasive squamous cell carcinoma and for this reason early correct diagnosis and treatment is necessary. As these lesions often appear in sun exposed areas, mainly the upper body (head, neck, face), minimum or non-invasive diagnosis techniques are preferred, like optical coherence tomography (OCT). The aim of this study is to find typical morphological characteristics of AK using the OCT technique and to guide the clinician to distinguish between AK's and normal skin or from other cutaneous lesions. A total of 25 lesions from 15 patients that clinically and dermoscopically suggested AK were included in this study; OCT using Skintell was performed for all lesions. OCT examination offers morphological information that is helpful in differentiating AK from healthy skin and from its closest clinical imitators. This work brings information about the value of OCT in describing in vivo patterns of AK. These findings can relate and extend previous research on these types of lesions. Further studies on a larger samples of cases, correlated with histopathological results are warranted in this direction.
Article no. 601: PDF 
Bacterial inhibition effect of plasma activated water
I.E. VLAD, C. MARTIN, A.R. TOTH, J. PAPP, S.D. ANGHEL
Rom. Rep. Phys. 71, 602 (2019)
Abstract. The properties of the liquids change at the interaction with electrical discharges. This offers the so activated liquids a variety of possible applications in the biomedical field. The paper investigates the bacterial inhibition effects of plasma activated water on Staphylococcus aureus. Three discharges in He, Ar, respectively air were used for water activation. The effect of the treatment time and liquid storage time were both considered. The plasma activated water proved to be efficient for bacterial inhibition, holding its properties for at least 7 days. Hydrogen peroxide was revealed to be the main inhibition agent generated at the plasma liquid-interaction.
Article no. 602: PDF 
Glucose detection using BSA:PEDOT-PSS as bioactive solute and solid bioactive layer deposited by spin coating
O. BRINCOVEANU, A. IOANID, R. MESTERCA, A. PANTAZI, C. MOISE, M. ENACHESCU, S. IFTIMIE, S. ANTOHE
Rom. Rep. Phys. 71, 603 (2019)
Abstract. The two glucose-protein-polymer composite solutions, Glucose: BSA:PEDOT-PSS [10:1:1] and Glucose/BSA:PEDOT-PSS [1:1], were prepared by mixing protein (BSA), polymer (PEDOT-PSS) and glucose solutions for the first sample and protein-polymer-composite (BSA:PEDOT-PSS [1:1]) and glucose solutions for the second sample with both pH and concentration in biological range values. An analysis of the UV-Vis spectrum of the Glucose/BSA:PEDOT-PSS [1:1] solution to determine the glucose concentration and a comparative study using UV-Vis and ATR/FTIR absorption spectra recorded at room temperature for BSA, PEDOT-PSS, BSA:PEDOT-PSS [1:1] and Glucose:BSA:PEDOT-PSS[10:1:1] were performed. Afterwards, both the Glucose: BSA:PEDOT-PSS [10:1:1] and Glucose/BSA:PEDOT-PSS [1:1] solutions were deposited as solid bioactive layer on silicon (100) coated with a silver thin layer by PLD technique. AFM (topography profiles, electrostatic images, F - z curves) and ATR/FTIR techniques were used to identify morphological and compositional characteristics of the solid bioactive layers surface.
Article no. 603: PDF 
 
ENVIRONMENTAL AND EARTH PHYSICS
 
Spatial distribution of heavy metals in urban soils
R.M. STIRBESCU, C. RADULESCU, C. STIHI, I.D. DULAMA, E.D. CHELARESCU, I.A. BUCURICA, G. PEHOIU
Rom. Rep. Phys. 71, 705 (2019)
Abstract. Heavy metals in the surface soils from 40 points of Targoviste City, were analyzed to assess the industrial and anthropogenic impact on soil pollution. Approximately 700 surface soil samples were collected and analyzed for major heavy metals including Mn, Fe, Ni, Cu, Zn, As, Cd and Pb by using microwave-assisted digestion and inductively coupled plasma–mass spectrometry (ICP-MS). The results indicate that Fe, Cu, Zn, Pb and Cd in the surface soils were primarily derived from industrial and anthropogenic sources, while As content in the surface soils were controlled by both natural and anthropogenic sources. Approximately 10% of the soil samples were polluted from moderately to heavily by these elements.
Article no. 705: PDF 
Antioxidant capacity of some Calendula extracts by EPR spectroscopy
LILIANA LUNGU, CLAUDIA-VALENTINA POPA, MARIA MARINESCU, VICTORITA TECUCEANU, ANDREI FLORIN DANET, VASILE BERCU
Rom. Rep. Phys. 71, 706 (2019)
Abstract. Antioxidant activity of some ethanol extracts of Calendula (marigold) flowers and chloroform fraction of extracts were evaluated. By an optimized electron paramagnetic resonance (EPR) spectroscopy method using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical was determined antioxidant activity of chloroform fraction of each extract. The decrease in time of DPPH concentration in the reaction medium was studied and it was noted that the reaction mechanism is characterized by two different reaction rates. Antioxidant activity of ethanol extracts was determined by spectrophotometric DPPH free radical scavenging activity method and the content of polyphenols in extracts was performed by LC-MS and spectrophotometric analysis methods. Results showed that fat soluble compounds are mainly responsible of the antioxidant activity of extracts. Analyzed extracts showed higher antioxidant activity than BHT (butylated hydroxytoluen), synthetic antioxidant compound.
Article no. 706: PDF 
On some genotoxic effects of UV-C radiation in root meristemes in CUCURBITA PEPO L.
A.VERDES-TEODOR, G. VOCHITA, D. CREANGA
Rom. Rep. Phys. 71, 707 (2019)
Abstract. The influence of high energy ultraviolet rays on radicular meristeme tissues of pumpkin plantlets in early ontogenetic stages was studied in the frame of laboratory experimental arrangement. Cytogenetic analysis was accomplished on adequately prepared single layer cells, colored with fuchsine reagent for chromosome selective visualization. Microscope screening on thousands of cells allowed the evidencing of changes induced by ultraviolet radiation at the levels of mitosis main phase that were comparatively analyzed for two exposure times to UV-C germicidal lamp, revealing dose-response behavior. The percentage of dividing cells as well as the percentage of abnormal divisions were counted and discussed based on tables and graphs generated with average values and standard deviation. Cytotoxicity of ultraviolet ray exposure was emphasized from both those cytogenetic parameters, raising the concern regarding biosphere adaptation to environmental occasional high gradients of radiation background.
Article no. 707: PDF 
Main active faults from Eastern Part of Romania (Dobrogea and Black Sea). Part II: transversal and oblique faults system
M. DIACONESCU, A. CRAIU, I.A. MOLDOVAN, E. G. CONSTANTINESCU, C. GHITA
Rom. Rep. Phys. 71, 708 (2019)
Abstract. The main target of this paper is to established a correlation between the seismicity of the Eastern part of Romania and the active tectonic (faults systems) of the area, the second target is to create a specific database of the faults (ROmanian DAtabase of SEismogenic Faults-RODASEF) in SHARE manner, for seismic hazard assessment process. This paper is a continuation of an article written by the same authors, in which were highlighted the longitudinal faults system from onshore and offshore of the Black Sea coast. To define the active faults, the following elements have been taken into account: Geometrical parameters: length, active length, width and depth of the earthquakes foci; Seismological parameters: strike, dip, rake (slip). In the studied area, there have been identified three fault systems: a longitudinal, transversal and an oblique one. In this paper, we present our results regarding the second and third type, i.e. main faults of the transversal and oblique systems. We present the transversal fault systems, parallel to the Black Sea coast comprising Razelm, Lacul Rosu, and West Midia Faults and the oblique fault systems with a NW-SE direction of the faults, such as Nistru, Odessa and West Crimea.
Article no. 708: PDF 
Interpretation of resonance fundamental frequency for Moldavian and Scythian platforms
E. F. MANEA, A. PREDOIU, C. O. CIOFLAN, M. DIACONESCU
Rom. Rep. Phys. 71, 709 (2019)
Abstract. In this study, we mapped the depth of the fundamental frequency of resonance for the Moldavian and Scythian Platforms using the available data at 18 seismic stations. Each site was investigated through the computation of H/V spectral ratios from three-component single station measurements of ambient vibrations. The observed resonance peaks were interpreted according with the available geological information.
Article no. 709: PDF 
Crustal models assessment in Western Part of Romania employing active seismic and seismologic methods
A. BALA, D. TOMA-DANILA
Rom. Rep. Phys. 71, 710 (2019)
Abstract. In the years 1999-2001 two regional seismic refraction lines were performed within a close cooperation with German partners from University of Karlsruhe. The western part of the line Vrancea 2001, with 420 km total length, crosses part of the Transylvanian Basin. The structure of the crust along the seismic line revealed a very complicated crustal structure beginning with Eastern Carpathians and continuing in the Transylvanian Basin until Medias. As a result of the development of the National Seismic Network in the last ten years, more than 100 permanent broadband stations are now continuously operating in Romania. Complementary to this national dataset, maintained and developed in the National Institute for Earth Physics, new data emerged from the temporary seismologic networks established during the joint projects with European partners in the last decades. The data gathered so far is valuable both for seismology purposes and crustal structure studies, especially for the western part of the country, where this kind of data were sparse until now. Between 2009 and 2011, a new reference model for the Earth's crust and mantle of the European Plate was defined through the NERIES project - EPCrust - from existing data and models. Although the present dataset has its origins in several periods over the last 50 years, the results are made homogeneous and they improve and strengthen our image about the depth of the principal boundaries in the crust. In the last chapter two maps regarding these boundaries are constructed, one for mid-crustal boundary and one for Moho. They were build considering all the punctual information available from different sources in active seismic and seismology which are introduced in the general maps from EPCrust project for Romania. The depths maps in the study region are presented with all their regional peculiarities as they appear, projected on the local tectonic structure for the area under examination. The database gathered from different kind of measurements in Transylvanian Basin and Eastern Pannonian Basin were included in EPCrust and an improved and upgraded model of the Earth crust emerged for Romania.
Article no. 710: PDF 
 
APPLIED AND INTERDISCIPLINARY PHYSICS
 
Advanced Kelvin probe operational methodology for space applications
G. CHIRITOI, E. M. POPESCU, A. A. RADU, A. CARAMETE, L. CARAMETE, A. PAVALAS, M. MARGARITESCU, A. E. ROLEA, T. NECSOIU, A. ENUICA
Rom. Rep. Phys. 71, 801 (2019)
Abstract. We present a novel methodology for the operation of macroscopic Kelvin Probe Instruments. The methodology is based on the use of a harmonic backing potential signal to drive the tip-sample variable capacitance and on a Fourier representation of the tip current, allows for the operation of the instrument under full control and improves its scanning performance by a factor of 60 or more over that of currently available commercial instruments.
Article no. 801: PDF 

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