Arc erosion reduction on electrical contacts using transversecurrent injection

Electrical contact lifetime is often directly determined by arc erosion. A method for reducing are erosion was developed consisting of injecting from an external current source an additional electrical current flowing parallel to the contact surface. This method was examined in three are environments using the additional transverse electrical current with a density less than 1 A/mm²: 1) automobile ignition contacts; 2) pulsed air arc; and 3) low pressure (P=100 mTorr) arc in nitrogen, SEM and X-ray examination showed that application of a transverse current in a contact during arcing changed the phase composition and microstructure of the contact surface. Under optimal conditions, the microstructure which is formed is significantly more erosion resistant than without the transverse current injection     

Gain saturation in quantum-well heterostructures

The effect of radiation gain saturation in quantum-well heretostructures was investigated in the system GaAs—AlGaAs with regard to the spectral line broadening and the type of radiation polarization. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 797–800, November–December, 1997.     

Quark models and polarized electroproduction of the Roper resonance

We calculate the recoil polarization observables for neutral pion electroproduction on the proton. In particular, for theN(938)→N ^*(1440) transition, we study these observables for several quark models of the resonant amplitudes. We find that the polarization response functions, unlike the unpolarized cross section, have encouragingly large sensitivity to the presence of the Roper. Furthermore, these observables can clearly reveal the presence of a longitudinal coupling.     

Improved ion-pair high-performance liquid chromatographic method for the quantification of a wide variety of nucleotides and sugar-nucleotides in animal cells.

An improved method including extraction procedures is presented for the analysis of nucleotides in suspension-cultivated animal cells. Quantification was performed by ion-pair high-performance liquid chromatography after perchloric acid extraction. It was found that the amount of perchloric acid taken for extraction influenced the yield and that cell washing procedures caused deterioration of the analysis results for triphosphates. More than thirty nucleotides and sugar-nucleotides were separated within 25 min using a Supelcosil reversed-phase column (3 microns) with tetrabutylammonium hydrogensulphate as pairing agent and methanol-pH gradient elution. Cultivated hybridoma cells showed variations in intracellular nucleotide concentrations as well as relative amounts during different growth phases, which could reflect the physiological state of a cell culture.     

The colloid-structure of semicrystalline low-density polyethylene

The length-distribution of stereoregular sequences in low-density polyethylene (LDPE) is determined by a computer-aided analysis of cp-melting curves within the framework of thermodynamics of eutectoid copolymers. Small-angle x-ray scattering patterns are then described by using the structure data derived. One of the results is that fluctuations of the mean electron-density are increasingly reduced with an increasing degree of crystallinity.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday     

On the possibility of designing interacting semiconductor quantum wells with zero perturbation coupling

The paper describes the possibility of designing matched interacting semiconductor quantum wells. It is shown that for a given eigenstate of a quantum well (QW), it is always possible to find another QW in such a way that the coupling leaves the original eigenstate of the host QW unperturbed irrespective of the strength of interaction. For rectangular QWs, the condition is met with whenever the second QW has appropriate width and depth so that phase travelled by an electron wave through it is an integral multiple of π.     

On non-standard algebras and their representations

To Professor Guillermo Torres on the occasion of his 70^th birthday.     

Combined gas chromatography/tandem mass spectrometry using laser photodissociation

Two fibre-optic interfaces were constructed for laser photodissociation/tandem mass spectrometry using an ion trap spectrometer. These interfaces allow sample introduction from a liquid reservoir, solids probe and gas chromatograph. The laser/ion trap configuration was applied to the analysis of a mixture of alkylbenenes separated by gas chromatography using 573 nm photons.     

Multipliers of Fourier series

New statements are proved regarding multipliers of trigonometric Fourier series in the space C of continuous periodic functions.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 12, pp. 1686–1693, December, 1991.