Volume 56, Number 910, 2011
Theoretical Physics
Chiral Electrons in Static Fields at Finite Temperature MarinaAura Dariescu, Ovidiu Buhucianu, Iordana Astefanoaei Romanian Journal of Physics 56,
10431052 (2011)
With the discovery of graphene, the idea that quantum relativistic effects are minute when studying the planar Halltype evolution of fermions has been revised. Recently, the relativistic counterpart of the integer conventional quantum Hall effect, observed by K. S. Novoselov in graphene mono and bilayers, has led to the conclusion that the quasi particles in this new material are exhibiting the same linear dispersion relation as if they were massless. The present paper starts with the Dirac equation for massless fermions evolving in a constant magnetic field alone, orthogonal to the system plane. The discrete energy levels are in good agreement with the experimentally reported graphene quantized spectrum. By adding a weak electrostatic field, one may employ the perturbation theory to compute the firstorder transition amplitudes and the corresponding current. Finally, within a quantum statistical approach, we derive the partition function and the average energy.
Direct Derivation of Schrödinger Equation from HamiltonJacobi Equation Using Uncertainty Principle Pranab Rudra Sarma Romanian Journal of Physics 56,
10531056 (2011)
In deriving Schrödinger's wave equation the momentum and energy of a particle are taken to be operators acting on a wave function. Here we show that the wave equation can be directly derived from the classical HamiltonJacobi equation, if a basic uncertainty is assumed to be present in the momentum. In this derivation one does not have to assume the momentum and energy to be operators.
Matrix Elements of the Jacobi Group S. Berceanu, A. Gheorghe Romanian Journal of Physics 56,
10571068 (2011)
We calculate the matrix elements of the Jacobi group, the semidirect product of the group SU(1, 1) with the real threedimensional Heisenberg group.
Theoretical Spinodal for Ternary Solution with an Amphiphile Component Using a Generalized WheelerWidom Model Radu P. Lungu, Roberto Sartorio, Florin D. Buzatu Romanian Journal of Physics 56,
10691079 (2011)
The theoretical spinodal for a ternary solution with an amphiphilic solvent is obtained using a generalized WheelerWidom model and a local fitting method applied to every experimental binodal point. This fitting method imposes that the theoretical binodal curve has to pass trough each representative binodal point and that its slope, in each point, must be equal (or as close as possible) to the slope of the corresponding representative experimental binodal. Using the fitting conditions for each experimental binodal, the corresponding theoretical spinodal point is derived, and the theoretical spinodal is constructed as the interpolation curve for the set of theoretical spinodal points. The results are in agreement with an older method where the local fitting between the theoretical model and the experimental data uses the experimental tielines.
Persistent Currents and Dynamic Localization Conditions in LRing Circuits L. Aur, C. Micu, E. Papp Romanian Journal of Physics 56,
10801086 (2011)
Using suitable magnetic flux operators established in terms of discrete derivatives leads to quantummechanical descriptions of LCcircuits with an external time dependent periodic voltage. This leads to second order discrete Schrödinger equations provided by discretization conditions of the electric charge. Neglecting the capacitance leads to a simplified description of the Lring circuit threaded by a related time dependent magnetic flux. The equivalence with electrons moving on one dimensional (1D) lattices under the influence of time dependent electric fields can then be readily established. This opens the way to derive dynamic localization conditions serving to applications in several areas, like the time dependent electron transport in quantum wires or the generation of higher harmonics by 1D conductors. Such conditions, which can be viewed as an exact generalization of the ones derived before by Dunlap and Kenkre [Phys. Rev. B 34, 3625(1986)], proceed in terms of zero values of time averages of related persistent currents over one period.
Elementary Particle Physics
On One Parametrization of KobayashiMaskawa Matrix P. Dita Romanian Journal of Physics 56,
10871093 (2011)
An analysis of Wolfenstein approximation to the KobayashiMaskawa unitary matrix shows that it has a serious flaw: it depends on three independent parameters instead of four as it should be. Because this approximation is currently used in phenomenological analyses from the quark sector, the reliability of many phenomenological results is called in question. Such an example is the PDG fit, [1], page 150, for the KobayashiMaskawa matrix moduli. The parametrization cannot be fixed since even when it is brought to an exact form it has the same flaw and its use leads to many inconsistencies.
[1] C. Amsler et al. [Particle Data Group], Phys.Lett. B 667, 1 (2008).
Nuclear Physics
InBeam Commissioning of a Recoil Mass Spectrometer T.B. Sava, D. Bucurescu, G. CătaDanil, I. CătaDanil, D. Deleanu, D. Filipescu, D. Ghiţă, T. Glodariu, M. Ivaşcu, N. Mărginean, R. Mărginean, C. Mihai, V. Moşu, A. Negreţ, G. Pascovici, S. Pascu, L. Stroe, N. V. Zamfir Romanian Journal of Physics 56,
10941107 (2011)
A review of electromagnetic separation for the lowenergy fusionevaporation recoils produced on a thin ^{12}C target by a 44 MeV beam of ^{19}F delivered by the IFINHH tandem accelerator is presented. The mass, velocity, energy and angular distributions of these recoils were studied using a spectrometer composed of a velocity selector (Wien filter), a 60° analyzing dipole magnet and two magnetic quadrupole doublets. Focal plane secondary beam diagnostic was performed using a 4×2 matrix of photovoltaic SiPIN detectors and a pseudotime of flight (ToF) technique using 5 MHz RF from the beam pulsing system. A complete description of the experiment preparations, running and the results interpretation is made.
Basic Aspects Concerning the Validation of the Measuring Method Using a New Spectrometric Gamma System with HPGe Detector M. A. Saizu, M. R. Calin Romanian Journal of Physics 56,
11081115 (2011)
Because of the major impact of the radioactive materials on the environment, their characterization methods have to be well defined, complete and agreed by the control bodies and the civil society. The paper presents measurements of certified etalon gamma emitting radiation sources, in order to perform the energy and the efficiency calibration of a new HPGe spectrometric system, and to determine different parameters, relevant for the validation of the results and of the measuring method.
PIXE and EDXRF Methods Applied in BiTeSe Thermoelements Study I. Bancuta, I.V.Popescu, A. Chilian, A. Stancu, R. Bancuta, R. Setnescu, V. Cimpoca Romanian Journal of Physics 56,
11161123 (2011)
This paper presents original contributions in the study of BiTeSe thermoelements, using particle induced Xray emission  PIXE and energy dispersive Xray fluorescence – EDXRF techniques. The studied thermoelements are used in micro and optoelectronic systems, as well as in energy recovery applications.
Evaluation of Fuel Channel Behavior (CANDU NPP) for the Long Time Normal Operating Conditions When the Delayed Hydride Cracking Occurs S. Florea, V. Radu, V. Ionescu, M. Pavelescu Romanian Journal of Physics 56,
11241135 (2011)
A critical review of the DHC (Delayed Hydride Cracking) phenomenon in the specific case of the pressure tube subcomponent of the fuel channel assembly of the Cernavoda Nuclear Power Plant (NPP) is presented. For the both stages of DHC – initiation and propagation – the models are discussed and an appropriate numerical assessment was implemented into CANTUP computer code. A first task of the present work is to couple the routines for DHC initiation and propagation steps for better modeling of the characteristics of this damaging phenomenon. Finally, the assessment of DHC rates in the case of various locations of the virtual crack on the CANDU pressure tube is performed. The normal operation conditions for ten years period of time are assumed to consider their influence on the material properties.
Estimation of the Gamma Dose Rate for Homogenous Waste Containers C.N. Dulama, M. Dulama, R. Dobrin, M. Pavelescu Romanian Journal of Physics 56,
11361142 (2011)
Spent ion exchange resins and liquid radioactive wastes are two of the main types of radioactive wastes generated in quasihomogenous batches by the waste streams of a nuclear installation. Transport regulations require, for gamma emitting radioactive waste, that the dose rate in the proximity of the container should stand below a certain threshold. Also, the conditioning technologies for such wastes are based on immobilization of certain quantities of waste in various matrices. The dosage is performed according to the technology prescriptions and to meet the acceptance criteria for transport and final storage. Gamma emitting radionuclides like: Mn54, Co60, Co57, Sb124, Sb125, Zn65, Cs134 and Cs137 are the main contributors to the dose rate produced by the regular radioactive waste from a nuclear installation. A method was developed to optimize the quantity of waste per unit volume of conditioning waste form, based on a mathematical model for dose rate estimation. A computer program was designed to implement this method and computed data were tested against measured values. The paper presents the mathematical model used for dose rate assessment and the results obtained in the validation phase of the method development. A reference test case was, also, considered for a simple geometry, where an analytical solution was calculated and compared with the modeled results.
The LinearNonThreshold Model of the International Commission on Radiological Protection. Comments E. L. Grigorescu, C. Avadanei, F. Ivan, V. Serban Romanian Journal of Physics 56,
11431147 (2011)
The LinearNonThreshold Model (LNT) of the International Commission on Radiological Protection (ICRP) is presented, with arguments supporting it. Arguments against it are presented too. The actions of the “repairing enzymes”, the “suicide” of DNA (DeoxyriboNucleic Acid) and the Tkiller lymphocytes are commented. Deterministic and stochastic effects of radiation are presented, from which important conclusions result. There are strong capabilities of the human body to resist exposure. Unfortunately, the validity of LNT can not be experimentally proved, neither the arguments against it. One may consider that the LNT model is an open question; the dose limits are connected.
Measurements of Beta Ray Emitters in LSC Using Efficiency Tracing CIEMAT/NIST Method R. I. Dobrin, M. Pavelescu, C. N. Dulama Romanian Journal of Physics 56,
11481155 (2011)
The main impediment in liquid scintillation counting (the most suitable technique for the quantitative analysis of the βemitting radionuclides) is the influence of quench phenomenon, which causes a reduction in the counting efficiency. Usually, the correction of the efficiency due to quenching requires the appropriate quenched standards of the same radionuclide whose activity is to be determined, but these might not be readily available. To overcome this difficulty, a relative or tracing method, such as 4πβ Liquid Scintillation Spectrometry Method with ^{3}HStandard Efficiency Tracing (also known as CIEMAT/NIST method) may be used. The paper presents the results obtained in the implementation and validation processes of this method on a Packard TriCarb 2100TR LSA (liquid scintillation analyzer), using as tracer the set of quenched tritium standards supplied along with the analyzer. The influence of quenching degree and level of activity has been studied using samples of known activity and the results were found to agree within ±2% with the beta activity.
Condensed Matter
EPR Study of Free Radicals in Amino Acids Derivatives Irradiated by Gamma Rays M. Aydin, Y. Emre Osmanoglu Romanian Journal of Physics 56,
11561161 (2011)
Exposure of powders forms of DLarginine hydrochloride and glycine hydrochloride to gamma radiation results in the formation of free radicals detected by electron paramagnetic resonance spectroscopy at room temperature. The observed radicals were assigned to be NH_{2}(NH)NHĊHCH_{2}CH_{2}CH(NH_{2})COOH and ( NH_{3}^{+} ) ĊHCOO¯ respectively. The g values and the hyperfine coupling constants of the unpaired electron with the environmental protons and ^{14}N nucleus were determined for these two radicals. These results were compared with the earlier studies on amino acid derivatives.
Identification of Radical Structure in 2,4Dinitrochlorobenzene Single Crystal by EPR Ayhan Usta, Mehmet Zengin, Mehmet Birey Romanian Journal of Physics 56,
11621166 (2011)
The single crystals of the 2,4 dinitrochlorobenzen were grown by slow evaporation of concentrated ethanol solution. Some of these single crystals exposed to ^{60}Cogamma rays with dose rate of 0.880 kGy/h at room temperature for 48 and 72 h. The EPR spectra were recorded as a function of temperature and orientations of the single crystal in the magnetic field. The single crystal irradiated for 72 h was rotated in steps of 10° in three mutually perpendicular planes in the magnetic field. The ESR temperature measurements were performed between 120 K and 440 K. The spectra recorded were found to be dependent on the temperature and the orientations of the crystal. It was also detected that only a radical structure and color centers were occurred after irradiation. The average values of g and hyperfine coupling constants were calculated as follow: a_{Na=Nb}=13.70 G, a_{H1=H2}=8.95 G, a_{H3}=7.06 G, g=2.0039.
Optics
Energy Balance of DC Arc Discharge with Closely Situated Electrodes N. Koprinarov, M. Konstantinova Romanian Journal of Physics 56,
11671172 (2011)
Arc discharge is commonly used for producing carbon nanostructures. Geometry of electrodes, the distance between them and ambient temperature are important factors, which determine the quantity and the variety of the formed carbon structures. Usually, two electrodes of different crosssections (i.e. a thin anode and a thick cathode) are placed far away from each other, allowing a large vapour stream to be obtained, which then creates the nanostructures in the working chamber. However, if the two electrodes were placed closely together, carbon vapour would leave deposits on the cathode. These deposits consist of amorphous carbon and low quantities of carbon nanotubes. The later approach has not been widely studied although it has potential to be used for film depositions. The goal of this study is to understand how the distance between the electrodes influences the temperature and to determine the underlying processes, as well. Energy balance has been determined for two electrodes of equal crosssections of 7.5 mm^{2}. The experimental data needed for the calculation has been obtained for a distance of 0.5 mm between the electrodes.
Biophysics
On the Evaluation of the Parameters of the Basic Stages of the Human Body Growth. I. Analysis of the LowVolume Statistics Data I. Apostol, P. P. Delsanto, R. Dobrescu, A. S. Gliozzi, D. Iordache Romanian Journal of Physics 56,
11731188 (2011)
A comparison of the growth plots of different parameters x (length, height/stature, weight) of the human body in the newly proposed $\left\{ y = \ln( x/x_0 ), \dot{y}\right\}$ representation space with the plots corresponding to the autocatalytic (U0), Gompertz (U1) and West (U2) universality classes was accomplished by means of the growth data given by some lowvolume statistics.
On the Evaluation of the Parameters of the Basic Stages of the Human Body Growth. II. Analysis of the HighVolume Statistics Data I. Apostol, P. P. Delsanto, R. Dobrescu, A. S. Gliozzi, D. Iordache Romanian Journal of Physics 56,
11891198 (2011)
Starting from the results obtained in the frame of the first part of this study, this paper reports the: a) specific features of the existing highvolume statistics growth data, b) proposed criterion of for the evaluation of the compatibility of theoretical models relative to the studied experimental data, c) results obtained by means of the analysis of the highvolume statistics growth data, compared with the results obtained by means of some lowvolume statistics growth data.
Environmental Physics
Considerations about the Presence of Fukushima Radionuclides in the NW Part of Romania C. Cosma, A. R. Iurian, D. C. Niţă, R. Begy, C. Cindea Romanian Journal of Physics 56,
11991207 (2011)
The Fukushima radioactive releases, beginning with March 12, 2011, could be detected in different environmental samples collected from Cluj County and surroundings. All the samples measured between 28^{th} of March  20^{th} of April, showed the presence of radioactive ^{131}I, but in much smaller concentrations that the ones founded in 1986, after the Chernobyl accident. The ordinary measurements made in rainwater give us reasons to believe that the maximum radioiodine activity in the area was reached at the beginning of April, when a value of 1.40±0.21 Bq/l has been found for Arad region. Could be concluded that the registered values due to the Fukushima nuclear events had a minor contribution to the total exposure of public compared to natural radioactivity.
Earth Physics
Studies on the Precursors of an Earthquake as the VLF Electromagnetic Sferics S. S. De, B. K. De, B. Bandyopadhyay, Suman Paul, D. De, S. Barui, Minu Sanfui, Pinaki Pal, T. K. Das Romanian Journal of Physics 56,
12081227 (2011)
The observation and analyses of preseismic VLF electromagnetic (EM) signals recorded by VLF receivers at frequencies 5, 7, 9 and 12 kHz on November 16, 2008 over Kolkata (Lat. 22.56º N, Long. 88.5º E) during the large earthquake at Minahasa, Sulawesi, under Indonesia (Lat. 1.27º N, Long. 122.09º E) will be presented. Spiky variations of signals are observed few days prior to the day of occurrence of the earthquake which continued several days more, then decayed gradually and eventually ceased. These signals are critically examined to delineate their correlation with earthquake. The time variability of natural EM signals in the VLF band is juxtaposed with the preseismic records.
Analytical Solution of Diffusion Equation in Two Dimensions Using Two Forms of Eddy Diffusivities Khaled S. M. Essa, A. N. Mina, Mamdouh Higazy Romanian Journal of Physics 56,
12281240 (2011)
An analytical solution of the twodimensional atmospheric diffusion equation has been developed by the method of Separation of variables. Also Fourier transform and square complement methods has been used to solve the integration. The present model is validated with the data sets obtained at the Northern part of Copenhagen (Gryning and Lyck, 1984) of the tracer sulfur hexafluoride (SF_{6}) in unstable conditions. In this model the vertical eddy diffusivity depends on the downwind distance and is calculated using two methods $K(x) = \gamma Ux$, and $K(x) = K_0 U_* x$. Values of the calculated normalized crosswind concentration are calculated differently, according to the different eddy diffusivities. These values are compared with the observed data graphically and statistically. The proposed method No.1 has performed better than method No.2 with the data from the diffusion experiment considered.
