Showing papers in "Czechoslovak Journal of Physics in 2006"

Fractional hamilton formalism within caputo’s derivative

Abstract: In this paper we develop a fractional Hamiltonian formulation for dynamic systems defined in terms of fractional Caputo derivatives. Expressions for fractional canonical momenta and fractional canonical Hamiltonian are given, and a set of fractional Hamiltonian equations are obtained. Using an example, it is shown that the canonical fractional Hamiltonian and the fractional Euler-Lagrange formulations lead to the same set of equations.

Reinstallation of the COMPASS-D tokamak in IPP ASCR

Abstract: The COMPASS-D tokamak, originally operated by UKAEA at Culham, UK, will be reinstalled at the Institute of Plasma Physics (IPP) AS CR. The COMPASS device was designed as a flexible tokamak in the 1980s mainly to explore the MHD physics. Its operation (with D-shaped vessel) began at the Culham Laboratory of the Association EURATOM/ UKAEA in 1992. The COMPASS-D tokamak will have the following unique features after putting in operation on IPP Prague. It will be the smallest tokamak with a clear H-mode and ITER-relevant geometry. ITER-relevant plasma conditions will be achieved by installation of two neutral beam injection systems (2 × 300 kW), enabling co-and counter-injections. Redeployment of the existing LH system (400 kW) is also envisaged. A comprehensive set of diagnostics focused mainly on the edge plasma will be installed. The scientific programme proposed for the COMPASS-D tokamak installed in IPP Prague will benefit from these unique features of COMPASS-D and consist of two main scientific projects, both highly relevant to ITER-Edge plasma physics (H-mode studies) and Wave-plasma interaction studies. The COMPASS-D tokamak will offer an important research potential as a small, flexible and low-cost facility with ITER-relevant geometry.

A software for optical emission spectroscopy - problem formulation and application to plasma diagnostics

Abstract: The aim of the presented work was to develop a method, which would make possible to identify spectral lines in complicated optical emission spectra. This is an important task for many optical diagnostic methods. It was found out, that the most useful technique combines a manual identification of the lines by the user, according to the developed database of atomic and molecular lines, and an enhanced support of the user by various assistant mechanisms. Therefore, in this work a software for displaying, identification and analysis of the optical emission spectra was developed. Besides the identification, program enables a basic handling of the spectra, corrections of the wavelengths and intensities of the spectra and calculations of some plasma parameters (e. g. calculation of rotational, vibrational and electron temperatures) or other important quantities (e. g. calculation of integrated intensity). The developed software was applied to the study of low pressure RF discharge in neon.

Sequential extraction procedure for determination of uranium, thorium, radium, lead and polonium radionuclides by alpha spectrometry in environmental samples

Abstract: A sequential extraction technique was developed and tested for common naturally-occurring radionuclides. This technique allows the extraction and purification of uranium, thorium, radium, lead, and polonium radionuclides from the same sample. Environmental materials such as water, soil, and biological samples can be analyzed for those radionuclides without matrix interferences in the quality of radioelement purification and in the radiochemical yield. The use of isotopic tracers (232U, 229Th, 224Ra, 209Po, and stable lead carrier) added to the sample in the beginning of the chemical procedure, enables an accurate control of the radiochemical yield for each radioelement. The ion extraction procedure, applied after either complete dissolution of the solid sample with mineral acids or co-precipitation of dissolved radionuclide with MnO2 for aqueous samples, includes the use of commercially available pre-packed columns from Eichrom® and ion exchange columns packed with Bio-Rad resins, in altogether three chromatography columns. All radioactive elements but one are purified and electroplated on stainless steel discs. Polonium is spontaneously plated on a silver disc. The discs are measured using high resolution silicon surface barrier detectors. 210Pb, a beta emitter, can be measured either through the beta emission of 210Bi, or stored for a few months and determined by alpha spectrometry through the in-growth of 210Po. This sequential extraction chromatography technique was tested and validated with the analysis of certified reference materials from the IAEA. Reproducibility was tested through repeated analysis of the same homogeneous material (water sample).

Lorentz-covariant deformed algebra with minimal length

Abstract: TheD-dimensional two-parameter deformed algebra with minimal length introduced by Kempf is generalized to a Lorentz-covariant algebra describing a (D + 1)-dimensional quantized space-time. ForD=3, it includes Snyder algebra as a special case. The deformed Poincare transformations leaving the algebra invariant are identified. Uncertainty relations are studied. In the case ofD=1 and one nonvanishing parameter, the bound-state energy spectrum and wavefunctions of the Dirac oscillator are exactly obtained.

Graded quasi-Lie algebras of Witt type

Abstract: In this article, we introduce a new class of graded algebras called quasi-Lie algebras of Witt type. These algebras can be seen as a generalization of other Witt-type algebras like Lie algebras of Witt type and their colored version, Lie color algebras of Witt type.

Improvement of dye adsorption on synthetic polyester fibers by low temperature plasma pre-treatment

Abstract: Adsorption of the dyes on the surface of the natural and synthetic polymer fibers, or weaved fabrics is created due to the effect of the intermolecular forces between fiber surface and the dye. Such forces are causing relatively strong bonding interaction between dye dipoles and the stained matrix. In the case of polymer and biopolymer materials the number of the dipoles is directly proportional to the number of polar groups in macromolecular side chains. The latter number of present dipoles is possible to be increased by several physico-chemical methods, e.g. fire treatment, chemical etching by strong acids, UV irradiation, corona discharge or low-temperature plasma treatments etc. In this communication the effect of low-temperature plasma treatment of polyester (PES) weaved fabric on dye adsorption to the surface of the studied substrate is discussed. Obtained increased dye selectivity to the stained matrix results in improved tinctorial strength, better economical effectiveness as well as to the improved ecology of the process.

Hybrid gold nanoparticles in molecular imaging and radiotherapy

Abstract: Metallic nanoparticles, because of their size, chemical and physical properties, are particularly attractive as therapeutic probes in treating cancer. Central to any clinical advances in nanoparticulate based therapy will be to produce hybrid nanoparticles that can be targeted to vascular, extracellular or cell surface receptors. Development of hybrid nanoparticles that specifically target cancer vasculature has received considerable attention. Most cancers have leaky vasculature and the defective vascular architecture, created due to the rapid vascularization necessary to serve fast growing cancers, in combination with poor lymphatic drainage allows increased permeation and retention effects. The leaky vasculature, because of higher porosity and permeability, serve as natural high affinity targets to metallic nanoparticles. Another attractive approach toward the application of nanotechnology to nanomedicine is the utility of nanoparticles that display inherent therapeutic properties. For example radioactive gold nanoparticles present attractive prospects in therapy of cancer. The radioactive properties of Au-198 (βmax = 0.96 MeV; t1/2 = 2.7 d) and Au-199 (βmax = 0.46 MeV; t1/2 = 3.14 d) make them ideal candidates for use in radiotherapeutic applications. In addition, they both have imageable gamma emissions for dosimetry and pharmacokinetic studies and Au-199 can be made carrier-free by indirect methods. Gold nanoparticles are of interest for treatment of disease as they can deliver agents directly into cells and cellular components with a higher concentration of radioactivity, e.g. higher dose of radioactivity, to cancerous tumor cells.

Isospectral Hamiltonians from Moyal products

Abstract: Recently Scholtz and Geyer proposed a very efficient method to compute metric operators for non-Hermitian Hamiltonians from Moyal products. We develop these ideas further and suggest to use a more symmetrical definition for the Moyal products, because they lead to simpler differential equations. In addition, we demonstrate how to use this approach to determine the Hermitian counterpart for a pseudo-Hermitian Hamiltonian. We illustrate our suggestions with the explicitly solvable example of the −x 4-potential and the ubiquitous harmonic oscillator in a complex cubic potential.

Erosion of needle electrodes in pulsed corona discharge in water

Abstract: Erosion of needle electrodes in the pulsed corona discharge in water with a pulse energy of ∼ 2÷; 3 J was investigated in dependence on the electrode material (platinum, tungsten and stainless-steel) and the solution conductivity (100 and 500 µS/cm). Erosion of electrodes remarkable increased with the higher solution conductivity for all three tested metals. The highest erosion rates were determined for tungsten while platinum was the least eroded material. In addition to the dominant melting effect, release of anode material by the electrolysis significantly contributed to the total erosion of needle electrodes. The highest contribution of electrolysis was determined for stainless-steel electrodes that released up to 40–50% of eroded metal in the form of iron ions. Peculiar protrusions were observed on the surface of eroded tungsten electrodes.

Uncertainties in the 0 νββ-decay nuclear matrix elements

Abstract: The nuclear matrix elements M 0ν of the neutrinoless double-beta decay (0νβ β) of most nuclei with known 2νββ-decay rates are systematically evaluated using the Quasiparticle Random Phase Approximation (QRPA) and Renormalized QRPA (RQRPA). The experimental 2νβ β-decay rate is used to adjust the most relevant parameter, the strength of the particle-particle interaction. With such procedure the M 0ν values become essentially independent of single-particle basis size, the axial vector quenching factor, etc. Theoretical arguments in favor of the adopted way of determining the interaction parameters are presented. It is suggested that most of the spread among the published M 0ν ’s can be ascribed to the choices of implicit and explicit parameters, inherent to the QRPA method.

Average and recommended half-life values for two-neutrino double-beta decay: Upgrade '05

Abstract: All existing “positive” results on two-neutrino double-beta decay in different nuclei were analyzed. Using the procedure recommended by the Particle Data Group, weighted average values for half-lives of 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 100Mo−100Ru(0 1 + ), 116Cd, 150Nd, 150Nd− 150Sm(0 1 + ) and 238U were obtained. Existing geochemical data were analyzed and recommended values for half-lives of 128Te, 130Te, and 130Ba are proposed. We recommend the use of these results as presently the most precise and reliable values for half-lives.

Gasification of biomass in water/gas-stabilized plasma for syngas production

Abstract: The experimental reactor PLASGAS for plasma pyrolysis and vitrification equipped with the hybrid gas-water stabilized torch was used in the experiments. The plasma torch is characterized by low density, high temperature plasma with very low mass flow rates and high enthalpy. High plasma enthalpy is advantageous for adjustment of higher reaction temperatures with high energy efficiency. Gasification of biomass was experimentally studied using wood as a model substance. The experimental results proved that homogeneous heating of the volume of plasma reactor and proper mixing of plasma with treated material were ensured despite of low plasma mass flow rate and constricted form of plasma jet. The conditions within the reactor ensured complete destruction of tested substance. Syngas with high content of hydrogen and CO was obtained. No presence of complex hydrocarbons or tar was detected, which is very important for possible practical application of the technology.

Effect of indium incorporation on the optical properties of spray pyrolyzed Cd0.22Zn0.78S thin films

Abstract: In this study, effect of indium incorporation on the optical properties is investigated for the spray pyrolyzed onto glass substrates at 275°C substrate temperature undoped and indium doped Cd0.22Zn0.78S thin films. The average optical transmittance of all the films was over 77% in the wavelength range between 450 and 800 nm. The optical band gap energies of the thin films have been investigated by the measurement of the optical absorbance as a function of wavelength. The optical absorption studies reveal that the transitions are direct band gaps of 3.02 and 3.05 eV for undoped and doped indium Cd0.22Zn0.78S thin films, respectively. The Urbach tail parameter and optical constants such as refractive index, extinction coefficient, and dielectric constants were calculated for these films. The dispersion parameters such as single-oscillator energy and dispersive energy were discussed in terms oft he single-oscillator Wemple—DiDomenico model.

Plasma gasification of wood and production of gas with low content of tar

Abstract: The gasification of biomass is a very smart way of its utilization. Tar content in the produced gas always plays an important role because high tar content disables some potentialities of the further treatment of the produced gas. There is a strong effort to produce gas with low tar content from this point of view. High concentrations of hydrogen and carbon monoxide also advance possibilities of the usage of the produced gas. Experiments were carried out in a reactor for plasma gasification equipped with hybrid gas-water stabilized DC torch. They confirmed that the reactor is absolutely suitable for this purpose mainly due to extremely low flow of plasma composed of argon, hydrogen and oxygen and its high inner temperature. The measurements of the tar content, using wood as a treated material, were based on SPE method. The determination of benzene and toluene in a gas phase revealed really low concentrations of tar, mostly below 10 mg/Nm3.

Pic simulations of femtosecond interactions with mass-limited targets

Abstract: Laser interactions with mass-limited targets are studied here via 2D3V relativistic electromagnetic particle-in-cell (PIC) simulations. We also describe our newly developed code that uses novel efficient algorithms. Damping regions have been implemented in order to eliminate spurious reflection of outgoing electromagnetic waves from boundaries of the simulation box. Mass-limited targets limit undesirable spread of absorbed laser energy out of the interaction zone. Mass-limited target, such as droplets, are shown to enhance the achievable fast ion energy significantly.

Non-Hermitian d-dimensional Hamiltonians with position-dependent mass and their η-pseudo-Hermiticity generators

Abstract: A class of non-Hermitian d-dimensional Hamiltonians with position-dependent mass and their η-pseudo-Hermiticity generators is presented Illustrative examples are given in 1D, 2D, and 3D for different position-dependent mass settings

Corona discharge: A simple method of its generation and study of its bactericidal properties

Abstract: The apparatus enabling the generation of low-temperature plasma by DC negative point-to-plane corona discharge at atmospheric pressure in air was developed. The bactericidal effect of plasma was verified on cultures of six non-sporulating aerobic bacterial species, inoculated onto the surface of various semisolid cultivation media. The bactericidal effect was evaluated quantitatively using the area of inhibition zones as its measure.

Krein-space formulation of $$\mathcal{P}\mathcal{T}$$ symmetry, $$\mathcal{C}\mathcal{P}\mathcal{T}$$ -inner products, and pseudo-Hermiticity

Abstract: Emphasizing the physical constraints on the formulation of the quantum theory, based on the standard measurement axiom and the Schrodinger equation, we comment on some conceptual issues arising in the formulation of the $$\mathcal{P}\mathcal{T}$$ -symmetric quantum mechanics. In particular, we elaborate on the requirements of the boundedness of the metric operator and the diagonalizability of the Hamiltonian. We also provide an accessible account of a Krein-space derivation of the $$\mathcal{C}\mathcal{P}\mathcal{T}$$ -inner product, that was widely known to mathematicians since 1950’s. We show how this derivation is linked with the pseudo-Hermitian formulation of the $$\mathcal{P}\mathcal{T}$$ -symmetric quantum mechanics.

A Positive-definite scalar product for free Proca particle

Abstract: We implement recent results of pseudo-Hermitian quantum mechanics to the description of relativistic massive particle with spin-one. We derive a one-parameter family of Lorentz invariant positive-definite scalar products on the space of solutions of Proca equation.

Random matrix theories and exactly solvable models

Abstract: A connection between random-matrix theories and exactly solvable models is discussed here This is done in three parts: firstly, for theWigner—Dyson case; secondly, for the short-range Dyson case; and thirdly, for the pseudo-Hermitian one The exactly solvable models are variants and extensions of Calogero—Sutherland—Moser systems

Crossing scenario for a nonlinear non-Hermitian two-level system

Abstract: The diabolic crossing scenario of two-state quantum systems can be generalized to a non-Hermitian case as well as to a nonlinear one. In the non-Hermitian case two different crossing types appear, distinguished according to the crossing or anticrossing of real parts or imaginary parts of the eigenvalues. In the nonlinear case additional stationary states can emerge, leading to looped structures in the eigenvalues. Here we discuss the basic properties of the most general situation, the combined nonlinear and non-Hermitian system. It is shown that the eigenvalues and eigenstates can be achieved from the real roots of a quartic equation. The corresponding crossing scenario is quite intricate and can be understood as a hybrid of the ones for the nonlinear Hermitian and the linear non-Hermitian systems. In addition, the implications of combined nonlinearity and non-Hermiticity on the system dynamics is studied in terms of a generalized Landau—Zener probability.

RADON LOSS FROM ENCAPSULATED SEDIMENTS IN Ge GAMMA-RAY SPECTROMETRY FOR THE ANNUAL RADIATION DOSE DETERMINATION IN LUMINESCENCE DATING

Abstract: In Ge gamma-ray spectrometry for the annual radiation dose determination in the luminescence dating of sediments, the picture of 226Ra enrichment or depletion (in the 238U decay series) obtained via measurement of its 214Pb and 214Bi daughters may be disturbed by the 222Rn-content of the sample being decreased due to manipulations such as drying and pulverizing. Therefore, it is common practice to start the measurement only about 1 month after encapsulating the material, after which the 226Ra(1600 a)-222Rn(3.82 d) mother-daughter equilibrium is re-established. Evidently, this only holds on condition that no significant escape of Rn occurs out of the sediment after making it up for counting. In order to experimentally investigate this effect, in the present work measurements were carried out with various types of dried and pulverized sediments that were either encapsulated in screw-cap polystyrene vials or in sealed glass containers, or that were mixed with molten wax followed by solidification in a cylindrical geometry. From the results obtained, it could be concluded that preparation and counting of the sediment-wax mixture is the method of choice.

Muon production in extensive air showers and its relation to hadronic interactions

Abstract: In this work, the relation between muon production in extensive air showers and features of hadronic multiparticle production at low energies is studied. Using CORSIKA, we determine typical energies and phase space regions of secondary particles which are important for muon production in extensive air showers and confront the results with existing fixed target measurements. Furthermore possibilities to measure relevant quantities of hadron production in existing and planned accelerator experiments are discussed.

Control of combustion by generation of singlet oxygen molecules in electrical discharge

Abstract: The possibility of the combustion enhancement in a supersonic flow of H2-O2 mixture by activation of molecular oxygen in electrical discharge is analyzed. It is demonstrated that abundance of excited oxygen molecules O2(a 1Δg) and O2(b 1‑ g + ) in the oxygen plasma is responsible for accelerating chain-branching reactions and allows one to arrange the stable combustion in a low temperature supersonic flow at a small discharge energy deposited to the gas.

Radionuclides in produced water from Norwegian oil and gas installations — concentrations and bioavailability

Abstract: Substantial amounts of produced water, containing elevated levels of radionuclides (mainly 226Ra and 228Ra) are discharged to the sea as a result of oil and gas production on the Norwegian Continental Shelf. So far no study has assessed the potential radiological effects on marine biota in connection with radionuclide discharges to the North Sea. The main objective of the project is to establish radiological safe discharge limits for radium, lead and polonium associated with other components in produced water from oil and gas installations on the Norwegian continental shelf. This study reports results indicating that the presence of added chemicals such as scale inhibitors in produced water has a marked influence on the formation of radium and barium sulphates when produced water is mixed with sea water. Thus, the mobility and bioavailability of radium (and barium) will be larger than anticipated. Also, the bioavailability of food-borne radium is shown to increase due to presence of such chemicals.

Nuclear responses for double-beta decays by hadron, photon, and neutrino probes and MOON experiment

Abstract: Neutrino-less double-beta decays (0νββ) with the mass sensitivities of the solar and atmospheric ν masses are of great interest for studying the Majorana nature of neutrinos and the absolute mass spectrum as suggested by recent ν oscillation experiments. Here nuclear responses (nuclear matrix elements) for 0νββ are crucial. They are well studied experimentally by using charge-exchange, photo-nuclear and neutrino reactions. MOON(Mo Observatory Of Neutrinos) is a high sensitivity 0νβ β experiment with the mass sensitivity of an order of 30 meV. Experimental studies of the nuclear responses and the present status of MOON are briefly discussed.

Cylindrically symmetric inhomogeneous cosmological models with viscous fluid and varying Λ

Abstract: Cylindrically symmetric non-static cosmological models representing a bulk viscous fluid distribution have been obtained which are inhomogeneous and anisotropic. Without assuming anyadhoc law, we obtain a cosmological constant as a decreasing function of time. Various physical and geometrical features of the models are also discussed.

Impact of uncertainties in hadron production on air-shower predictions

Abstract: At high energy, cosmic rays can only be studied by measuring the extensive air showers they produce in the atmosphere of the Earth. Although the main features of air showers can be understood within a simple model of successive interactions, detailed simulations and a realistic description of particle production are needed to calculate observables relevant to air shower experiments. Currently hadronic interaction models are the main source of uncertainty of such simulations. We will study the effect of using different hadronic models available in corsika and conex on extensive air shower predictions.

Experimental analysis of a double-spark ignition system

Abstract: The spark that ignites the combustible mixtures is a discharge produced between the electrodes of a spark plug, connected to the secondary of a coil at the high voltage. Optimum combustion requires a steady spark, in a volume as large as is possible, and with maximum energy. We propose a solution to increase the plasma volume and present electrical discharge parameters as a function of inter-electrode distances, pressures in the test-reactor and the width of the electrical pulses of the power supply.