Formation of plasma arc anode spot on the rotating graphite crucible

Formation of anode spots on rotating graphite crucible in the plasma arc furnace was investigated. The size and temperatures of the spots were determined by means of photographs and optical pyrometer. Composition of the plasma in anode spot region has been calculated. Cylindrical crucible of 100 mm in diameter with an axial hole of 40 mm in diameter and 28 mm in depth was rotated with the speed of ~100 rpm. Cylindrical cathode of 50 mm in diameter had an axial channel of 24 mm in diameter. Argon was fed through the channel as plasma forming gas. Crucible and cathode were located in the steel water cooled chamber with a volume of 150 liters. The arc was several centimeters long, arc current was 560-630 A. It was shown experimentally that 23-25 kW argon plasma arc can forms contracted or diffuse anode spot. The current density of contracted spot is 1800 A/cm2, while that of diffuse spot is ~250 A/cm2. Contracted spot formation occurs on a cold crucible and accompanied by intensive evaporation of graphite in a spot region. The carbon vapor decreased ionization potential of plasma near the anode and promoted contraction. A uniform heating of the hole in crucible up to 2700 K is needed for transformation of the contracted spot into diffuse one. Such heating was attained by rotation of crucible. Thermal isolation of crucible also promotes diffuse spot formation. Poisson’s equation was solved, and the voltage falls in space charge zones were calculated for contracted and diffuse spots as 10.7 and 1.5 V respectively. It was assumed that the lesser voltage fall promotes the diffuse spot formation.

The major histocompatibility complex-restricted antigen receptor on T cells. IV. An antiidiotypic antibody predicts both antigen and I-specificity.

In order to prove that a monoclonal antibody, KJ1-26.1, reacted with the idiotypic portion of the receptor for antigen plus major histocompatibility complex product (Ag/MHC) on the T cell hybridoma D0-11.10, 397 independent T cell hybridomas prepared from BALB/c T cells primed with ovalbumin were screened by ELISA for reactivity with the antibody. Of these T cell hybridomas one, 7D0-286, and a subclone of this hybridoma, 7D0-286.2, reacted strongly and consistently with KJ1-26.1. Further analysis revealed that KJ1-26.1 blocked the reaction of 7D0-286 with Ag/MHC, and that 7D0-286 had the same fine specificity both for Ag and MHC as D0-11.10. None of 207 other BALB/c T cell hybridomas specific for ovalbumin shared these fine specificity patterns. Thus, reaction with KJ1-26.1 defined the specificity of a T cell hybridoma both for Ag and MHC, suggesting that KJ1-26.1 reacted with the receptors for Ag/MHC on the T cells in question. KJ1-26.1 precipitated an 85-kdalton molecule from 7D0-286.2 that on reduction ran as a diffuse spot of approximately 43 kdaltons. A similar molecule was precipitated from D0-11.10.

An experimental study of diffuse X-ray reflexion by single crystals

A historical introduction outlines the development of experimental and theoretical interest in the diffuse diffraction of X-rays by single crystals. The present experimental study, illustrated by numerous photographs, has consisted in taking Laue, oscillation and rotation photographs, in many different orientations, of inorganic and organic crystals belonging to various systems, using Cu, Mo and Ag radiations, unfiltered, filtered or monochromatized. Rules are laid down for the indexing of diffuse spots and for the determination of the conditions under which such spots appear. Attention is drawn to the presence of non-radial streaks and to the difference in origin of these and of the more usual radial streaks. The relations of the intensity, shape, size, position and persistence of the diffuse spots to the nature, structure, perfection, orientation and temperature of the crystal examined, to the radiation used and to the conditions of photography, are considered in some detail. The use of diffuse spot patterns as a subsidiary method of crystal structure determination is emphasized. It is pointed out that in reciprocal space each reflecting lattice point is surrounded by a region of diffuse scattering, whose physical significance is open to various theoretical interpretations. These diffusely reflecting regions are not, in general, spherical, but are extended along reciprocal lattice planes and axes.