A class of determining functionals for quasilinear elliptic problems

Conditions providing the uniqueness of the solution to a Dirichlet problem for second order elliptic equations are studied assuming the availability of an information concerning values of functionals determined on solutions     

Metal ion capillary zone electrophoresis with direct UV detection: Comparison of different migration modes for negatively charged chelates

Summary Several migration modes suitable for capillary zone electrophoretic (CZE) separation of metal ions in the form of 8-hydroxyquinoline-5-sulphonic acid complexes are described and compared. Superior analysis time, resolution, efficiency and detectability were achieved using reversed movement of anionic metal complexes (in the anode-to-cathode direction) under the action of the electroosmotic flow. This method allows the CZE analysis of multicomponent mixtures of transition metal ions as well as aluminium within about six minutes.     

Preconcentration and determination of inorganic arsenic using a multisyringe flow injection system and hydride generation-atomic fluorescence spectrometry

A new multisyringe flow injection system for inorganic arsenic determination at trace levels by hydride generation-atomic fluorescence spectrometry (HGAFS) is presented. Preconcentration on a solid-phase was carried out using a column packed with an anion-exchange resin (Amberlite IRA-410). The reagents are dispensed to the system using a multisyringe burette coupled with two multi-port selection valves.

Different parameters were changing in order to make the system as effective as possible. An analytical curve was obtained for arsenic determination between 50 and 2000 ng l⁻¹. This new approach improved five times the sensitivity over a MSFIA–HGAFS technique developed previously by the authors. Detection limit of the proposed technique was (3σ_b/S) of 30 ng l⁻¹. The relative standard deviation (R.S.D.) of As at 1 μg l⁻¹ was 4.8% (n=7). A sample throughput of 10 h⁻¹ has been achieved. The proposed method has been applied to different reference solid and water materials with satisfactory results.     

Effect of ozonation on the composition of crude coal-tar benzene

The effect of ozonation on the composition of crude benzene produced by the coal-tar chemical industry was studied.     

Measurement of the probability of <Superscript>232</Superscript>Th ternary fission induced by fast neutrons

Results obtained by measuring the energy dependence of the probability of ²³²Th ternary fission in the region of vibrational resonances are presented. The measurements were performed by using a double ionization chamber with Frisch grids and a CsI(T1) scintillation detector. The use of digital methods for pulse processing made it possible to obtain highly reliable results. The data analysis reveals that our value of the ternary-fission probability is compatible with existing systematics, which nevertheless need some correction. The results of our measurements unambiguously indicate that local variations in the total kinetic energy of fission fragments in the region of the individual vibrational resonances cannot be explained by corresponding variations in the ternary-fission probability.     

Semiconductor-metal transition in defect lithium cobaltite

The magnetic susceptibility, electrical conductivity, and x-ray photoelectron and x-ray absorption spectra of defect lithium cobaltites of the general formula Li_{1 ? x} CoO₂ are investigated. It is found that, for lithium cobaltites with x > 0.25, the magnetic susceptibility increases abruptly and the conductivity type changes at T ～ 150 K. The assumption is made that the semiconductor-metal transition in defect lithium cobaltite is caused by the increase in the diffusion mobility of lithium ions with an increase in the temperature when there is a correlation between spatial distributions of lithium vacancies and “electron” holes.     

On the choice of expansion functions in the Helmholtz equation least-squares method

This paper examines the performance of Helmholtz equation least-squares (HELS) method in reconstructing acoustic radiation from an arbitrary source by using three different expansions, namely, localized spherical waves (LSW), distributed spherical waves (DSW), and distributed point sources (DPS), under the same set of measurements. The reconstructed acoustic pressures are validated against the benchmark data measured at the same locations as reconstruction points for frequencies up to 3275 Hz. Reconstruction is obtained by using Tikhonov regularization or its modification with the regularization parameter selected by error-free parameter-choice methods. The impact of the number of measurement points on the resultant reconstruction accuracy under different expansion functions is investigated. Results demonstrate that DSW leads to a better-conditioned transfer matrix, yields more accurate reconstruction than both LSW and DPS, and is not affected as much by the change in measurement points. Also, it is possible to obtain optimal locations of the auxiliary sources for DSW, LSW, and DPS by taking an independent layer of measurements. Use of these auxiliary sources and an optimal combination of regularization and error-free parameter choice methods can yield a satisfactory reconstruction of acoustic quantities on the source surfaces as well as in the field in the most cost-effective manner.     

Femtosecond vibrational dynamics of self-trapping in a quasi-one-dimensional system

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.     

Unusual [3+2]-cycloaddition of acrylic acid derivatives to 7-formyl-4,5,6,7-tetrahydro-4,5,7-trimethylpyrrolo[3,2-c]pyridine under Michael reaction conditions

8-Substituted tetrahydropyrido[3,2-e]pyrrolizines are formed in the [3+2]-cycloaddition of 2-formyltetrahydropyrrolo[3,2-c]pyridine and acrolein, acrylonitrile, and methyl acrylate in the presence of trilon B. Russian International Friendship University, 117923 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1670–1675, December, 1998.