On the measurement of the proton-air cross section using cosmic ray data

Cosmic ray data may allow the determination of the proton-air cross section at ultra-high energy. For example, the distribution of the first interaction point in air showers reflects the particle production cross section. As it is not possible to observe the point of the first interaction $X_{\rm 1}$ of a cosmic ray primary particle directly, other air shower observables must be linked to $X_{\rm 1}$. This introduces an inherent dependence of the derived cross section on the general understanding and modeling of air showers and, therfore, on the hadronic interaction model used for the Monte Carlo simulation. We quantify the uncertainties arising from the model dependence by varying some characteristic features of high-energy hadron production.Comment: Conference proceedings for the Blois07/EDS07 (12th International Conference on Elastic and Diffractive Scattering) Workshop DESY Hambur

Quantum Spin Tomography in Ferromagnet-Normal Conductors

We present a theory for a complete reconstruction of non-local spin correlations in ferromagnet-normal conductors. This quantum spin tomography is based on cross correlation measurements of electric currents into ferromagnetic terminals with controllable magnetization directions. For normal injectors, non-local spin correlations are universal and strong. The correlations are suppressed by spin-flip scattering and, for ferromagnetic injectors, by increasing injector polarization.Comment: 4+ page

From mirco-mechanical properties to tribological performance

Abrasive contacts are still too complex to allow reliable predictions of part performance. There is not a single material model with satisfying generality, yet. However, it should be a combination of the contact body’s relative elastic and plastic properties as well as the loading condition.1 In industry carbide- and boride-reinforced, metal matrix composites are often cladded on a base part with welding processes to counter abrasive wear. These composites generally pose structural features at a multitude of length scales. A millimeter thick coating is reinforced with carbides of 100 µm diameter. Precipitates of 1 to 10 µm decorate the matrix and during the major solidification, a metal-stable carbide-metal eutectic forms with domains widths of 1 µm and 100 – 200 nm lamella spacing. Please click Additional Files below to see the full abstract