Difference scheme for a parabolic problem with changing time direction

Institute of Mathematics and Informatics, Akademijos 4, 2600 Vilnius, Lithuania. Translated from Lietuvos Matematikos Rinkinys, Vol. 35, No. 1, pp. 37–51, January–March, 1995.     

Current-voltage characteristic and parameters of the current filament region of an amorphous gallium telluride-crystalline silicon barrier negistor structure

The transient I-V characteristic of an amorphous GaTe₃-crystalline n-Si barrier negistor structure under negative differential resistance (NDR) conditions is studied. The basic parameters (cross-section radius, current density, and resistivity) of the current filament region in the amorphous layer of the structure are determined. Results obtained are compared with the associated parameters of the current filament in a C-amorphous GaTe₃-C reference barrier-free structure. Under NDR conditions, the conductivity of the filament region in this heterostructure is shown to be governed largely by processes occurring in the crystalline component.     

Treatment of spent NTA-based decontamination solutions

This study deals with potential treatment of spent NTA-containing decontamination solutions for final disposal. The method proposed is based on the degradation of organic substances followed by the separation of radionuclides. The influence of various parameters (pH value, irradiation time, temperature, catalyst amount, type and various combinations of catalysts) on photocatalytic degradation of NTA has been studied. Photo-Fenton reagent (Fe³⁺/H₂O₂) as a homogenous catalyst was found to be much more efficient than the TiO₂-based heterogeneous catalyst Degussa P25. Under optimum conditions NTA in a simulant of a spent decontamination solution without or with hydrazine could be degraded within 5 or 9 hours, respectively. The study of sorption properties of a series of absorbers revealed that radiostrontium and radiosilver can be effectively removed from the simulant of a spent decontamination solution even in the presence of NTA, while total NTA degradation is necessary for effective radiocobalt separation.     

First results for the measurement of double-electron capture of 106Cd in the experiment TGV II

Present status of the experiment TGV II which is devoted to the measurement of double-beta decay of ¹⁰⁶Cd is given. The low background spectrometer TGV II is installed in the Modane Underground Laboratory and has been running from February 2005 with approx 10 grams of ¹⁰⁶Cd enriched at 75%. After an analysis of 3736 hours of experimental data the new improved half-life limit for 2νEC/EC decay of ¹⁰⁶Cd (0 _g.s. ⁺ → 0 _g.s. ⁺ ) is given as T ₁ ^2/2ν > 4.8 × 10¹⁹ years (90% CL). The search for 2νEC/EC decay of ¹⁰⁶Cd to the excited states of ¹⁰⁶Pd allows to determine the limits of the half-lives T ₁ ^2/2ν (0 _g.s. ⁺ → 2 ₁ ⁺ ) > 3.9 × 10¹⁹ years (90% CL) and T ₁ ^2/2ν (0 _g.s. ⁺ → 0 ₁ ⁺ ) > 5.8 × 10¹⁹ years (90% CL). Presented by I. Štekl at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Equipment for measurements of radial profiles of excited species in DC glow discharge

The original experimental device for studying the radial dependences of emitted radiation, generated by the cylindrically symmetric positive column of the DC glow discharge, is proposed. Principle of detection of the radial intensity profiles of the spectral lines by means of the special scanner with two movable conic mirrors is described. The function of the scanner was verified experimentally and by the method of raytracing. As an example, the radial profiles of lines emitted by the positive column of the neon glow discharge are presented. No significant changes were found. This work is a part of the research plan MSM 0021620834, that is financed by the Ministry of Education of the Czech Republic.     

Compatible statistical interpretation of a wave packet

A compatible statistical interpretation of a wave packet is proposed. De Broglian probabilities which unite wave and particle features of quantons are evaluated for free wave packets and Jor a superposition of wave packets. The obtained expressions provide a very plausible and physically appealing explanation of coherence in apparently incoherent beams and of the characteristic modulation of the momentum distribution, found recently in neutron interferometry combined with spectral filtering. Certain conclusions about dualism and objectivity in quantum domain are also derived.     

Transient colour centre in YAG : Nd

Formation of a transient absorption centre is demonstrated in YAG : Nd monocrystals on intensive irradiation in the near UV spectrum region. Spectral distribution has been studied of their absorption coefficient, their decay kinetics was also followed. Activation energy of the decay process was determined from the temperature dependence. The transient absorption centre possessing the character of V-centres exsrcise, in view of the spectral course of their absorption coefficient, a certain amount of influence upon the efficiency of the YAG : Nd laser.     

The 12C + 12C sub-coulomb fusion cross section

The ¹²C + ¹²C fusion cross section has been studied over the energy range 2.46 ≦ E_c.m. ≦ 5.88 MeV. The yields of the γ-rays emitted from the first excited states of ²³Na and ²⁰Ne, following ²⁴Mg compound nucleus decay via proton- and α-emissions, were measured using a Ge(Li) detector. The fusion cross section was obtained by normalizing these yields to previously reported ¹²C(¹²C, p)²³Na and ¹²C(¹²C, α)²⁰Ne cross sections. The data indicate that the cross section below 3.5 MeV is dominated by two or more resonances, and that the average trend in this energy region does not show the absorption-under-the barrier features of the optical model. For astrophysical extrapolations to lower energies, the new results are consistent with the extrapolation proposed by Fowler, Caughlan and Zimmerman.     

Phononless hopping in the mobility gap of amorphous semiconductors

Two different theories are analyzed and shown to yield the same result for the phononless contribution to the dc hopping conductivity due to electrons in localized states (with single-electron energies broadened by the electron-phonon interaction) in the mobility gap of amorphous semiconductors. Numerical estimate is then used to show that this mechanism cannot explain experimental data on elemental covalent amorphous semiconductors.