On edge states in superconductors with time inversion symmetry breaking

The efficiency of conversion of the heat flux into hard x radiation (HXR) is analyzed, via time-dependent two-temperature one-dimensional non-LTE-radiation-hydrodynamic numerical modeling, for a heat-to-radiation flux converter linked to the edge of a low-atomic-number hot Z-pinch. The domain of parameters in this scheme is found where about the same HXR yield can be achieved at values of input energy which are an order of magnitude lower than in the conventional scheme of a radially imploding plasma. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 502–506 (10 April 1997) Published in English in the original Russian Journal. Edited by Steve Torstveit.     

Experimental study of the emission spread at gyrotron cathodes by current-voltage characteristics

A scheme for automated study of current-voltage characteristics of gyroresonance devices is developed. The effective emission spread at the cathodes of powerful gyrotrons is studied by analysis of current-voltage characteristics. Experimental data on the effective emission spread parameter for different modes are given. The permissible emission spread at the cathodes of powerful gyrotrons is estimated, and the dependence of the electron beam parameters on the cathode emission spread is presented. A complex measurement technique showing the contribution of different physical mechanisms to the cathode emission spread is proposed. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 4, pp. 506–516, April, 1997.     

Phase shift moiré studies of processing-induced residual strains in Nickel 200 spot welds

Processing-induced residual strains in solid cylinders of Nickel 200 were investigated using phase shifting moiré interferometry. Two different experimental approaches were used to study the strains produced during Tungsten-inert gas spot welding. A comparison of results for a ‘hot/fast’ and a ‘cool/slow’ weld demonstrate the capabilities of the general approach. Both experimental methods revealed distinct differences in the residual displacement and strain fields between the two types of welds.     

The electronic spectrum of a three-dimensional quasicrystal

The electronic spectrum of an icosahedral quasicrystal with a central-atom decoration of the Amman-Mackay network is investigated in the tight-binding approximation. The quasicrystal is described as a structural limit of the optimal cubic approximants with increasing period. The electronic spectra for the first four optimal cubic approximants do not contain the hierarchical gap structure which is typical for the Cantor set of the spectrum of a one-dimensional quasicrystal. At the same time, as the order of the approximant increases, the spectrum becomes singular throughout the entire energy scale. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 557–562 (25 April 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

The effect of radiofrequency modulation of 57Fe hyperfine interaction by rotating magnetic field

The effect of ⁵⁷Fe hyperfine interaction radiofrequency (rf) modulation by external rotating magnetic field was studied in thin Permalloy foil by means of Mössbauer spectroscopy. The rf effect was investigated as a function of intensity for several rf field frequencies. The experiments show that the external rotating rf field causes considerable changes in the hyperfine pattern. The obtained spectra are in disagreement with those obtained by Perlow [Phys. Rev. 172 (1968) 319]. They also are inconsistent with magnetostriction hypothesis. Proceeding from the Mössbauer spectrum analysis one may conclude that the magnetization of investigated foil changes its direction in a complex manner. However, the undertaken experiments show that the essential number of Mössbauer nuclei experience the rotating magnetic field influence.     

Thermal diffusivity measurements in porous ceramics by photothermal methods

Received: 16 September 1996/Accepted: 6 January 1997     

Novel pattern formation in the collapse process of floating monolayer at the air-water interface

We have observed a remarkable two-armed spiral in the collapse process of a floating monolayer at the air-water interface by phase contrast microscopy. This demonstrates that the floating monolayer as a form of soft condensed matter reorganizes itself due to a certain kind of macroscopic or collective behavior of molecules as it collapses. This pattern formation is caused by the breakdown of a critical dynamical balance between the deformation of solid domain and the applied surface pressure. The fragility as well as the flexibility of the floating monolayer can be associated with the observed pattern growth. There are also observed interesting, periodically arranged collections of molecules in numerous collapsed regions. Received: 8 July 1997 / Accepted: 4 November 1997     

Pseudo-Strong Regularity Around a Set

A generalization of strong regularity around a vertex subset C of a graph Γ, which makes sense even if Γis non-regular, is studied. Such a structure appears, together with a kind of distance-regularity around C , when an spectral bound concerning the so-called predistance polynomial of C is attained. As a main consequence of these results, it is shown that a regular (connected) graph Γwith d + 1 distinct eigenvalues is distance-regular, and its distance- d graph Γ d is strongly regular with parameters a = c , if and only if the number of vertices at distance d from each vertex satisfies an expression which depends only on the order of Γand the different eigenvalues of Γ.