Interactions of surface states of copper with transition metals and cesium

The pseudopotential augmented-plane-wave method was used to study the surface structure of thin copper films with monolayers of Co, Ni, and Cs. Local densities of electron states, distributions of charge densities in the layers, and electron energy spectra are analyzed. The effect of adsorbates on the electronic properties of the Cu(001) surface and work function are discussed. Satisfactory agreement with available experimental data has been obtained.     

Reaction of aroyl- and hetaroyltrifluoroacetones with acylhydrazines: Regioselectivity and tautomerism of the condensation products

Acylhydrazines react with 1,3-diketones of the general formula CF₃COCH₂COR (where R is an aryl or hetaryl group) at both carbonyl groups. The reaction at the trifluoroacetyl group is favored by donor substituents in the aromatic ring of the 1,3-diketone or by the 2-furyl and, especially, 2-thienyl group as a hetaryl substituent, as well as by elevated temperature. The condensation products at the carbonyl group contiguous to the aryl or hetaryl ring have the structure of 5-hydroxy-4,5-dihydropyrazoles and do not undergo tautomeric transformations in solution. The condensation products at the trifluoroacetyl group have either 5-hydroxy-4,5-dihydropyrazole or hydrazone structure and give rise to ring-chain tautomeric equilibrium in solution. Electron-withdrawing substituents in the aromatic ring of the 1,3-dicarbonyl fragment and CDCl₃ as solvent favor formation of the cyclic tautomer. The state of the tautomeric equilibrium is weakly sensitive to structural variations in the hydrazine component.     

Circular dichroism spectra of langasite family crystals in the range of electronic transitions of structure defects

The absorption and circular dichroism spectra of langasite family crystals are studied. Wide bands in the range of 285–500 nm that are related to the structure lattice defects are found. For all the crystals, these bands are in approximately the same spectral region, have identical structures, and can be attributed to one type of defects formed by cation vacancies and excess oxygen atoms in the optically active positions.     

Phase Measurement Algorithm in Wavelength Scanned Fizeau Interferometer

Wavelength scanned interferometry allows the simultaneous measurement of top surface shape and optical thickness variation of a transparent object consisting of several parallel surfaces. Interference signals from these surfaces can be separated in frequency space, and their phases are detected by discrete Fourier analysis. However, these signal frequencies are shifted from the detection frequency by the refractive index dispersion of the object and a nonlinearity of the wavelength scanning. The Fourier analysis is sensitive to the detuning of the signal frequency and suffers from the multiple-beam interference noise. Conventional error-compensating algorithms cannot be applied to an object consisting of more than three reflecting surfaces. We derive a new 2N-1 sample error-compensating algorithm, which allows the phase detection of any order of harmonic frequency among the interference signals. The new algorithm suppresses the effect of signal frequency detuning as well as the multiple-beam interference noise and can be applied to the measurement of complex objects consisting of more than three reflecting surfaces.     

Spatial macroscopic structure of a pulsed microsecond discharge in barrier-metal gaps with a nonuniform electric field distribution

Electric and spatial characteristics of a pulse-periodic microsecond barrier discharge are investigated in different geometries—triangular prism, plate, and corrugated electrode—that are in contact with a dielectric plate and form a dihedral angle with it. It is established that, in the space of the dihedral angle, the regions of discharge represent alternating cylindrical layers with the axes lying on the contact line. The first conducting layer is formed at some distance from the contact edge of the electrode. The number of layers and their localization are determined by the angle formed between an electrode and the dielectric plate. A physical model explaining the main features of the structure formation is proposed.     

Specific features of vowel-like signals of white whales

The set of acoustic signals of White-Sea white whales comprises about 70 types of signals. Six of them occur most often and constitute 75% of the total number of signals produced by these animals. According to behavioral reactions, white whales distinguish each other by acoustic signals, which is also typical of other animal species and humans. To investigate this phenomenon, signals perceived as vowel-like sounds of speech, including sounds perceived as a “bleat,” were chosen A sample of 480 signals recorded in June and July, 2000, in the White Sea within a reproductive assemblage of white whales near the Large Solovetskii Island was studied. Signals were recorded on a digital data carrier (a SONY minidisk) in the frequency range of 0.06–20 kHz. The purpose of the study was to reveal the perceptive and acoustic features specific to individual animals. The study was carried out using the methods of structural analysis of vocal speech that are employed in lingual criminalistics to identify a speaking person. It was demonstrated that this approach allows one to group the signals by coincident perceptive and acoustic parameters with assigning individual attributes to single parameters. This provided an opportunity to separate conditionally about 40 different sources of acoustic signals according to the totality of coincidences, which corresponded to the number of white whales observed visually. Thus, the application of this method proves to be very promising for the acoustic identification of white whales and other marine mammals, this possibility being very important for biology.     

L'intégration graphique des équations différentielles ordinaires

In the period which precedes the appearance of computers, needs in calculation of the scientists and engineers led to an important development of graphic methods of integration. To contribute to the study of this little known phenomenon, the article presents techniques and instruments used for the graphic integration of ordinary differential equations, and looks for their historic origins by going back to the beginning of calculus: processes of geometric calculation by the polygonal method or the method of radius of curvature, use of tractional motion for the conception of integraphs, reduction to graphic quadratures in finite or infinite number.