Ab initio investigation of uranium monochalcogenides

We present ab initio investigation of the electronic structure and magnetic properties of uranium monochal-cogenides: US, USe, UTe. The calculations were performed by using the recently developed LDA+U+SO method in which both Coulomb and spin-orbit interactions have been taken into account in rotationally invariant form. We discuss the problem of choice of the Coulomb interaction value. The calculated [111] easy axes agree with those experimentally observed. The electronic configuration 5f ³ was found for all uranium compounds under investigation.     

Self-referencing measurement of an ultrashort pulse by the standard shear interferometry method

A new method for the self-referencing measurement of the amplitude-phase shape of an ultrashort pulse is proposed. The method uses a two-frequency characteristic of the pulse, which is defined as S(F ₁)S(F ₂), where F is the frequency, S(F) is the complex Fourier spectrum of the pulse, and F ₁ and F ₂ are two independent variables. It is shown that this characteristic can be generated as a two-dimensional polychromatic light wave upon generation of the sum frequency of two crossed spectral decompositions of one and the same pulse, as well as upon space-time Fourier transform of radiation of the noncollinearly generated second harmonic of the pulse. In an orthogonal system of transverse coordinates F ₁ + F ₂ and F ₁ ? F ₂, at any given value of F ₁ + F ₂, the radiation frequency of this wave in the direction of the second coordinate F ₁ ? F ₂ does not change. Therefore, the phase structure of the two-frequency characteristic can be reconstructed by the standard method of lateral shear interferometry in the direction of this coordinate. In the reconstructed two-dimensional phase structure of the two-frequency characteristic, any section by the plane F ₁ = const or F ₂ = const yields the phase structure of the spectrum of the pulse under study. This makes it possible to reconstruct the amplitude-phase shape of the pulse.     

A carbositall electrode modified with a SiO<Subscript>2</Subscript>-hemoglobin-gold film as a promising biosensing element

The analytical prospects of a carbositall electrode modified with a film based on SiO₂, hemoglobin (Hb), and gold nanoparticles (CSE SiO₂-Hb-Au), prepared by deposition with an electrically generated catalyst, are reported. Hemoglobin on the surface of CSE SiO₂-Hb-Au is shown to possess electrocatalytic activity toward dissolved oxygen, giving a rationale for the development of a rapid voltammetric procedure of O₂ quantification with a detection limit of 0.1 mg/L. The inhibition activity of a number of nitrogen-containing organic substances to the catalytic current CSE SiO₂-Hb-Au is studied. A voltammetric procedure is proposed for determination of the anti-flu drug rimantadine, 1-(1-adamantyl)ethylamine hydrochloride, with a detection limit of 0.4 mg/L. The procedure is applicable to the quantification of rimantadine in blood serum and saliva.     

Study of the electro-absorption spectrum of a nickel acceptor exciton in a ZnO:Ni crystal based on a calculation of vibrations associated with a Ni+1 impurity

Localized vibrations in ZnO crystals due to the substitution impurity Ni⁺¹ are modeled. The calculations were performed in the shell model using a recursive method for vibrations with A ₁ and E type symmetry. Numerical calculations allowed us to analyze the vibronic structure in the electro-absorption spectra for nickel acceptor excitons in ZnO:Ni. Fiz. Tverd. Tela (St. Petersburg) 41, 986–990 (June 1999)     

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)     

Spectral holography of pico- and nanosecond optical pulses

Recording and reconstruction of pico- and nanosecond pulses have been accomplished with spectral holography. The development of spectral holography in the nanosecond time-domain was achieved while using high-spectral-resolution equipment based on a Fabry-Perot etalon with a side entrance/exit. The recognition of the shaped nanosecond light pulses was also realized.     

Luminescence of excitons in slightly asymmetric double quantum wells

We report the first studies of exciton luminescence spectra from asymmetric double quantum wells (DQWs) of very similar width. The DQWs were of GaAs/AlGaAs and the differences in widths of the coupled wells were one or two monolayers. The coupled direct and indirect exciton states anticross with a resonance splitting of 1.33 meV. An additional luminescence line appearing at low temperatures is identified as a localized indirect exciton. Fiz. Tverd. Tela (St. Petersburg) 39, 735–739 (April 1997)     

Ab initio calculations of the vibrational spectra of 1/1 approximant of i-AlCuFe quasicrystal

The partial and total densities of vibrational states of the 1/1 crystal approximant of the icosahedral i-AlCuFe quasicrystal are calculated using the method of pseudopotentials in the generalized gradient approximation (to describe the electronic states) and the frozen-phonon method (to determine the dynamic matrix). The results obtained agree well with experimental inelastic neutron scattering data, which indicates that the method of calculations is appropriate and could be used to calculate other crystal approximants.     

Cross talk of wavelength-multiplexed quasi-infinite holograms

The cross talk of wavelength-multiplexed quasi-infinite (written in polychromatic light) holograms is evaluated. Under plausible conditions this cross talk is negligible. The typical information capacity limit of such holograms is evaluated as 10(12) bits for a 1-cm(3) volume.