The structure of atomic nitrogen adsorbed on Fe(100)

Nitrogen atoms adsorbed on a Fe(100) surface cause the formation of an ordered c(2 × 2) overlayer with coverage 0.5. A structure analysis was performed by comparing experimental LEED I–V spectra with the results of multiple scattering model calculations. The N atoms were found to occupy fourfold hollow sites, with their plane 0.27 Å above the plane of the surface Fe atoms. In addition, nitrogen adsorption causes an expansion of the two topmost Fe layers by 10% (= 0.14 Å). The minimum r-factor for this structure analysis is about 0.2 for a total of 16 beams. The resulting atomic arrangement is similar to that in the (002) plane of bulk Fe4N, thus supporting the view of a “surface nitride” and providing a consistent picture of the structural and bonding properties of this surface phase

Modification of H-2 Antigenic Sites by Enzymatic Treatment Influences Virus-Specific Target Cell Lysis

Vaccinia virus-infected cells were treated enzymatically to remove H-2 antigenic sites. The effect of this procedure on virus-specific cell-mediated cytolysis (CMC) and virus-specific antibody-mediated cytolysis (AMC) was tested. Due to the inhibition of cellular proteinsynthesis by the vaccinia virus infection, H-2 antigenic sites were not resynthesized while there was a continuous production of viral surface antigens. These cells with a high concentration of viral surface antigens and decreased H-2 determinants could be used as targets in the virus specific AMC. But they were not lysed in the virus specific CMC which emphasizes the significance of H-2 antigens during recognition of virus-specific determinants by T cells

Witt differentials in the h-topology

Recent important and powerful frameworks for the study of differential forms by Huber-Joerder and Huber-Kebekus-Kelly based on Voevodsky's h-topology have greatly simplified and unified many approaches. This article builds towards the goal of putting Illusie's de Rham-Witt complex in the same framework by exploring the h-sheafification of the rational de Rham-Witt differentials. Assuming resolution of singularities in positive characteristic one recovers a complete cohomological h-descent for all terms of the complex. We also provide unconditional h-descent for the global sections and draw the expected conclusions. The approach is to realize that a certain right Kan extension introduced by Huber-Kebekus-Kelly takes the sheaf of rational de Rham-Witt forms to a qfh-sheaf. As such, we state and prove many results about qfh-sheaves which are of independent interest

Role of early viral surface antigens in cellular immune response to vaccinia virus

Infection of mice with the vaccinia virus strain WR, Elstree or DIs, a conditional lethal mutant of vaccinia virus, resulted in the generation of vaccinia virus-specific sensitized cytolytic T lymphocytes (CTL). It could be shown by cross-reactivity between the three strains and by inhibition experiments with specific antisera that early vaccinia surface antigens are sufficient for the generation of specific CTL in vivo and for the lysis of infected target cells in vitro