On the logical foundations of the Jauch-Piron approach to quantum physics

We make a critical analysis of the basic concepts of the Jauch-Piron (JP) approach to quantum physics. Then, we exhibit a formalized presentation of the mathematical structure of the JP theory by introducing it as a completely formalized syntactic system, i.e., we construct a formalized languageL _e and formally state the logical-deductive structure of the JP theory by means ofL _e . Finally, we show that the JP syntactic system can be endowed with an intended interpretation, which yields a physical model of the system. A mathematical model endowed with a physical interpretation is given which establishes (in the usual sense of the model theory) the coherence of the JP syntactic system.     

Comparison of Monte Carlo simulations and macroscopic theories of diffusion in systems with non-ideal sources and sinks for vacancies

A new concept of generation and annihilation of vacancies at non-ideal dense sources and sinks for vacancies is incorporated into the standard Monte Carlo model for vacancy-mediated diffusion. This model enables to treat the vacancy wind as well as the deformation of the specimen and the shift of the Kirkendall plane. The Monte Carlo model is used for testing the recent macroscopic theories of diffusion by Darken [Trans. Am. Inst. Min. Eng. 175 184 (1948)], Manning [Phys. Rev. B 4 1111 (1971)] and Moleko et al. [Phil. Mag. A 59 141 (1989)]. The agreement with the self-consistent Moleko et al. theory is excellent. On the other hand, the agreement with the classical Darken theory frequently used in the open literature for the explanation of the Kirkendall effect is rather poor.     

A quasiharmonic model calculation for non-markovian far-infrared spectra of HCl in Kr and Xe liquids

The far-infrared spectra (0–200 cm^?1) of dilute solutions of HCl in liquid Kr and Xe have been calculated by applying of a non-markovian spectral theory called PTOC (partial time ordering cumulants) and by using a quasiharmonic model for the liquid structure recently reported by us (A. Calvo Hernández et al., 1987, J. chem. Phys., 86, 4597) and successfully applied to HCl?Ar solution (Ibid., 86, 4607). The bath correlation functions which appear in the spectral theory involve a reduced set of parameters regarding both the HCl?Kr and HCl?Xe interactions and the liquid structure. From comparison between theoretical and experimental spectra it is possible to deduce quantitative values for the above parameters. The pronounced rotational fine structure of the experimental spectra for HCl in Kr and Xe liquids is quite well explained by the actual model.     

Unification of interactions in a model with composite particles

A model for the unification of interactions with composite quarks, leptons, and Higgs fields is proposed on the basis of the SU(5) group. The model explains in a natural manner the appearance of generations, mixing of cato-quarks, proton decay, and so on. A number of effects are predicted, specifically, the existence of a fourth generation of particles. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 5, 293–298 (10 September 1997)     

A vibronic-structure analysis of optical spectra in ZnO:Ni3+ crystals by localized-vibration simulation

A theoretical study is reported of the vibrations associated with a Ni³⁺ impurity charged with respect to the ZnO lattice. The calculations were made by a recursive method in terms of the shell model for vibrations with different symmetries. The vibronic structure observed in the spectra of d-d intracenter transitions in the Ni³⁺ impurity has been interpreted using model calculations. Fiz. Tverd. Tela (St. Petersburg) 41, 618–622 (April 1999)     

Theoretical study on the static and dynamic first-order hyperpolarisabilities of adenine tautomers

Static and dynamic electronic and vibrational first-order hyperpolarisabilities (β) of the lowest energy neutral adenine tautomers (amine forms A7 and A9) were obtained in gaseous and aqueous phases by using Hartree–Fock, Møller–Plesset second-order and fourth-order perturbation theory (MP2 and MP4-SDQ) and conventional and long-range corrected density functional theory methods with the Dunning's correlation-consistent cc-pVDZ, aug-cc-pVDZ, aug-cc-pVTZ and d-aug-cc-pVDZ basis sets. Frequency-dependent properties were calculated at the characteristic wavelength of the Nd:YAG laser (1064 nm) for the second harmonic generation and electro-optical Pockels effect nonlinear optical processes. Solvent effects were introduced under the polarised continuum model approximation. The electronic β^e values of the investigated isomers are noticeably affected by the theoretical level, basis set and solvation. In vacuum, the static and dynamic β^e values of A9 are greater than the corresponding data of A7, whereas the contribution of the solvent significantly enhances the hyperpolarisabilities of the A7 tautomer, resulting in β^e(A9)/β^e(A7) ratios between 0.5 and 0.6. The vibrational hyperpolarisabilities of the adenine tautomers are quite close to each other.     

Structures responsible for quasisynchronism in second-harmonic generation in BaTiO3:Fe

Second harmonic generation (SHG) of light in iron-doped BaTiO₃ crystals occurs primarily at an angle of about 7° to incident λ=1.06 μm radiation. It is shown that the quasisynchronism is accounted for by a 90° domain structure with a spatial wave vector q∥[011] and a spatial period of about 3 μm. This result may serve as a basis for interpretation of the anomalous SHG enhancement near the phase transition. Fiz. Tverd. Tela (St. Petersburg) 41, 1076–1079 (June 1999)     

Model of current oscillations in a metal-thin insulator-semiconductor structure

A model is proposed for current oscillations in a metal-thin insulator-p-type semiconductor structure which are caused by the self-organization of carrier transport processes via insulator states. Zh. Tekh. Fiz. 68, 93–94 (December 1998)     

Efficient nonlinear-optical frequency conversion in periodic media in the presence of diffraction of the pump and harmonic fields

It has been predicted by Shelton and Shen [Phys. Rev. A 5, 1867 (1972)] and observed by Kajikawa et al. [Jpn. J. Appl. Phys. Lett. 31, L679 (1992)] and Yamada et al. [Appl. Phys. B 60, 485 (1995)] that the efficiency of nonlinear-optical frequency conversion increases significantly in a nonlinear periodic medium and, accordingly, the intensity of the generated harmonic increases as the fourth power of the sample thickness, as opposed to the square law observed in homogeneous media. In this paper it is shown that the same enhancement of the efficiency of nonlinear-optical frequency conversion in a nonlinear periodic medium can be achieved using an ordinary pump wave in the form of a plane wave when both the pump wave and the harmonics are diffracted by the periodic structure of the nonlinear medium. The phenomenon is analyzed quantitatively in the example of second-harmonic generation. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 12, 793–799 (25 December 1999)     

Equation of state for systems of soft diatomic molecules

A new potential that is a modification of the BBL (Bratko, D.,Blum, L., and Luzar, A.,1985, J. chem. Phys., 83, 6367; Blum, L., Vericat, F., and Bratko, D., 1995, J. chem. Phys., 102, 1461) potential and of the one recently solved analytically by Blum and Vericat (BV) (1995, Molec. Phys., 86, 809; 1996, J. phys. Chem., 100, 1197) is studied by Monte Carlo simulation. The main feature of this potential is that it can be solved using only a small number of parameters (3 in the case treated by BV), and therefore produces a substantial simplification of earlier work. The new potential has an orientational octupole–octupole interaction term which is found necessary to reproduce the broad peak of the oxygen–oxygen structure function due to the tetrahedral position of the second nearest neighbour water molecule. This important feature was absent in the original BBL potential. This model agrees also with the experimental pair correlation functions for oxygen–hydrogen and hydrogen–hydrogen, and yields 42·6 kJ mol^-1 for the internal energy of water, also in agreement with experiment. The hard core central repulsion causes the sharpness of the first peaks in all three correlation functions. This is not necessary but convenient for an analytical solution.     

Remarkable effects of uniaxial stress on stimulated far IR emission from hot holes in germanium in crossed electric and magnetic fields

Stimulated far IR emission due to l-h as well as cyclotron transitions of hot holes in uniaxially stressedp-Ge (P H E) was studied. The results obtained showed the significance of intersub-band hole tunnelling for these mechanisms of generation and may be explained by a change in tunnelling produced by the stress. A considerable expansion of the stimulated light hole cyclotron emission band was observed in a stressed crystal. This expansion allows covering (in one sample) of all generation bands in the light hole cyclotron resonance (CR) masers in unstressedp-Ge, reported so far.     

Dynamics of electron-hole plasma in semiconductor opening switches for ultradense currents

A physicomathematical model for calculating the dynamics of the electron-hole plasma in semiconductor opening switches for ultradense currents is developed. The model takes account of the real doping profile of a semiconductor p ⁺-p-n-n ⁺ structure and the following elementary processes in the electron-hole plasma: current-carrier diffusion and drift in high electric fields, recombination on deep impurities and Auger recombination, and collisional ionization in a dense plasma. The electrical pumping circuit of the opening switch is calculated by solving the Kirchhoff equations. The motion of the plasma in the semiconductor structure is analyzed on the basis of the model. It is shown that for ultrahigh pumping levels the interruption of the current in the opening switch occurs in the heavily doped regions of the p ⁺-p-n-n ⁺ structure and is due to saturation of the particle drift velocity in high electric fields. Zh. Tekh. Fiz. 67, 64–70 (October 1997)     

Pulse characteristics of Hg0.8Cd0.2Te n +-p junctions

The pulse characteristics of Hg_0.8Cd_0.2Te n ⁺-p junctions are investigated. It is shown that the shape of the voltage pulse appearing in a junction on passage of a forward (reverse) current is determined by the recombination (generation) of nonequilibrium electrons in the hole region. An increase in the current pulse causes the appearance of an electric field, which draws electrons into the interior of the base region, and leads to variation of their lifetime because of the complex structure of the n ⁺-p junction. Zh. Tekh. Fiz. 67, 130–133 (July 1997     

Chaos game representation walk model for the protein sequences

A new chaos game representation of protein sequences based on the detailed hydrophobic--hydrophilic (HP) model has been proposed by Yu et al (Physica A 337 (2004) 171). A CGR-walk model is proposed based on the new CGR coordinates for the protein sequences from complete genomes in the present paper. The new CGR coordinates based on the detailed HP model are converted into a time series, and a long-memory ARFIMA(p, d, q) model is introduced into the protein sequence analysis. This model is applied to simulating real CGR-walk sequence data of twelve protein sequences. Remarkably long-range correlations are uncovered in the data and the results obtained from these models are reasonably consistent with those available from the ARFIMA(p, d, q) model.     

Mass dependence of nitride sputtering

A molecular dynamics simulation was performed to study the sputtering yield Y for BN, AlN and GaN polycrystals of wurtzite structure as a function of the masses m ₁ of bombarding ions with energies from 200 to 2000 eV. A nonmonotonic behavior of the Y(m ₁) curve was obtained for the irradiation by low-energy ions, the curve having a maximum with a position being dependent on m₂/m₁ (m₂ is the average mass of atoms in a compound). For AlN and GaN the maximum was observed at m₂/m₁ = 2, and for BN at m₂/m₁ = 1. The effect of the mass of bombarding ions on the mean energies and energy spectra of sputtered particles, the depth of sputtering origin, and the generation of emitted atoms for nitrides was also investigated and discussed.     

Design and Analysis of InGaN-GaN Modulation Doped Field-Effect Transistors (MODFETs) for Over 60 GHz Operation

A Modulation-Doped Field-Effect Transistor (MODFET) structure realized in InGaN-GaN material system is presented for the first time. An analytical model predicting the transport characteristics of the proposed MODFET structure is given in detail. Electron energy levels inside and outside the quantum well channel of the MODFET are evaluated. The two-dimensional electron gas (2DEG) density in the channel is calculated by self-consistently solving Schrödinger and Poisson's equations simultaneously. Analytical results of the current-voltage and transconductance characteristics are presented. The unity-current gain cutoff frequency (f _T) of the proposed device is computed as a function of the gate voltage V _G . The results are compared well with experimental f _T value of a GaN/AlGaN HFET device. By scaling the gate length down to 0.25 m the proposed InGaN-GaN MODFET can be operated up to about 80GHz. It is shown in this paper that InGaN-GaN system has small degradation in f _T as the operating temperature is increased from 300°K to 400°K.     

Light scattering by electrons in the excitonic absorption region of GaAs

A study has been made of the effect of the additional generation of photoexcited electrons on the excitonic absorption and luminescence spectra of ultrapure GaAs samples at T=2 K. The observed increase in the absorption coefficient for the ground (n=1) excitonic state is shown to originate from the polariton character of the energy spectrum of this state and to be due to an increase of polariton damping. The increased damping observed under electron generation is caused by polariton scattering from hot electrons as the latter undergo thermalization. As a result, the polaritons are heated. The changes observed in the luminescence spectra are produced by the reverse effect of electron heating and polariton cooling. Fiz. Tverd. Tela (St. Petersburg) 39, 1011–1016 (1997)     

Absorption Spectral Studies Involving 4f–4f Transitions as Structural Probe in Chemical and Biochemical Reactions and Compositional Dependence of Intensity Parameters

Abstract

Absorption spectral studies on lanthanides are described, dealing with 4f–4f transitions as structural probe in chemical and biochemical reactions, and compositional dependence of intensity parameters in order to understand the structure and nature of lanthanide bimolecular interaction. This review is basically addressed to the suitable application of solution absorptional spectral spectroscopy: (i) in probing the binding characteristics and multimetal simultaneous coordination of biomolecules, (ii) following the different steps involved n complex sol-gel processes involving heterometallic alkoxides as precursors fore generation of suitable materials for future computing devices, and (iii) in pursuing the progress of some organic synthesis, specially Meerwin-Ponndorf-Verley reaction and Diels-Alder cycloaddition reaction, homogeneously catalysed by lanthanides. Solution kinetics of interactions of lanthanides involved in the reactions is presented.     

Design and Analysis of InGaN-GaN Modulation-Doped Field-Effect Transistors (MODFETs) for 90 GHz Operations

A Modulation-Doped Field-Effect Transistor (MODFET) structure having quantum wire channel realized in InGaN-GaN material system is presented. This paper presents design and analysis of a novel one-dimensional Modulation-Doped Field-Effect transistor (1D MODFET) in InGaN-GaN material system for microwave and millimeter wave applications. An analytical model predicting the transport characteristics of the proposed MODFET device is also presented. Analytical results of the current-voltage and transconductance characteristics are presented. The unity-current gain cutoff frequency (f _T) of the proposed device is computed as a function of the gate voltage V _G. The results are compared with two-dimensional GaN/AlGaN MODFET and HFET devices. The analytical model also predicts that 0.25 m channel length devices will extend the use of InGaN-GaN MODFETs to above 90GHz.     

Negative Poisson coefficient of fractal structures

On the basis of a fractal model the macroscopic elastic properties of an inhomogeneous medium with random structure have been determined. It is shown that if the ratio of the bulk moduli of the phases K ₂/K ₁→0, then the percolation threshold p _c the Poisson coefficient is equal to 0.2. A study of the behavior of a two-phase medium with negative Poisson coefficient is carried out. Fiz. Tverd. Tela (St. Petersburg) 41, 2147–2153 (December 1999)