Depth of maximum of extensive air showers and cosmic ray composition above 10**17 eV in the geometrical multichain model of nuclei interactions

The depth of maximum for extensive air showers measured by Fly's Eye and Yakutsk experiments is analysed. The analysis depends on the hadronic interaction model that determine cascade development. The novel feature found in the cascading process for nucleus-nucleus collisions at high energies leads to a fast increase of the inelasticity in heavy nuclei interactions without changing the hadron-hadron interaction properties. This effects the development of the extensive air showers initiated by heavy primaries. The detailed calculations were performed using the recently developed geometrical multichain model and the CORSIKA simulation code. The agreement with data on average depth of shower maxima, the falling slope of the maxima distribution, and these distribution widths are found for the very heavy cosmic ray mass spectrum (slightly heavier than expected in the diffusion model at about 3*10**17 eV and similar to the Fly's Eye composition at this energy).Comment: 11pp (9 eps figures

Defects in Crystalline Packings of Twisted Filament Bundles: II. Dislocations and Grain Boundaries

Twisted and rope-like assemblies of filamentous molecules are common and vital structural elements in cells and tissue of living organisms. We study the intrinsic frustration occurring in these materials between the two-dimensional organization of filaments in cross section and out-of-plane interfilament twist in bundles. Using non-linear continuum elasticity theory of columnar materials, we study the favorable coupling of twist-induced stresses to the presence of edge dislocations in the lattice packing of bundles, which leads to a restructuring of the ground-state order of these materials at intermediate twist. The stability of dislocations increases as both the degree of twist and lateral bundle size grow. We show that in ground states of large bundles, multiple dislocations pile up into linear arrays, radial grain boundaries, whose number and length grows with bundle twist, giving rise to a rich class of "polycrystalline" packings.Comment: 10 pages, 7 figure

Dipolar and scalar 3^3He and 129^{129}Xe frequency shifts in mm-sized cells

We describe a $^{3}$He-$^{129}$Xe comagnetometer operating in stemless anodically bonded cells with a 6 mm$^3$ volume and a $^{129}$Xe spin coherence time of 300 sec. We use a $^{87}$Rb pulse-train magnetometer with co-linear pump and probe beams to study the nuclear spin frequency shifts caused by spin polarization of $^{3}$He. By systematically varying the cell geometry in a batch cell fabrication process we can separately measure the cell shape dependent and independent frequency shifts. We find that a certain aspect ratio of the cylindrical cell can cancel the effects of $^3$He magnetization that limit the stability of vapor-cell comagnetometers. Using this control we also observe for the first time a scalar $^{3}$He-$^{129}$Xe collisional frequency shift characterized by an enhancement factor $\kappa_{\text{HeXe}} = -0.011\pm0.001$.Comment: 4 pages, 4 figure