Mechanical analysis and optimisation of large and highly-loaded bearing rollers For the "Riesenrad" Ion Gantry

A carbon ion gantry would allow the irradiation of cancer patients with carbon ions from any direction in space best suited for therapy. Till today, such a machine has not been built due to the expected size, mass and cost. A novel design, called "Riesenrad" ion gantry, promises to provide a competitive solution. The central part of the Riesenrad, which can rotate ± 90°, is supported (statically determinate) on pendular bearing units with two rollers each. High precision requirements for the structure rule out any plastic deformations in the area of contact. The present report describes the design of the highly-loaded rollers. In order to achieve a large contact area and a uniform distribution of contact stresses, a "barrel shape" for the rollers is proposed. An analysis using the finite element method (FEM) was performed to optimise the roller design, namely to establish the required crown roll (camber radius)

Towards a physical interpretation for the Stephani Universes

A physicaly reasonable interpretation is provided for the perfect fluid, sphericaly symmetric, conformally flat ``Stephani Universes''. The free parameters of this class of exact solutions are determined so that the ideal gas relation $p=n k T$ is identicaly fulfiled, while the full equation of state of a classical monatomic ideal gas and a matter-radiation mixture holds up to a good approximation in a near dust, matter dominated regime. Only the models having spacelike slices with positive curvature admit a regular evolution domain that avoids an unphysical singularity. In the matter dominated regime these models are dynamicaly and observationaly indistinguishable from ``standard'' FLRW cosmology with a dust source.Comment: 17 pages, 2 figures, LaTeX with revtex style, submitted to General Relativity and Gravitatio

Two conserved domains in PCIF1 mediate interaction with pancreatic transcription factor PDX-1

AbstractPCIF1 is a TRAF and POZ domain containing nuclear factor that interacts with and inhibits transactivation of pancreatic homeodomain transcription factor PDX-1. Here, we demonstrate interaction of endogenous PDX-1 and PCIF1 in MIN6 insulinoma cells. Within PCIF1, the TRAF and POZ domains are both required for physical and functional interaction with the C-terminus of PDX-1, whereas the C-terminal domain of PCIF1 directs its nuclear localization. A human PDX-1 mutation associated with diabetes, E224K, disrupts the ability of PCIF1 to inhibit PDX-1 transactivation, suggesting that the interaction between PDX-1 and PCIF1 is required for normal glucose homeostasis. Inhibition of transactivation occurs by a mechanism distinct from the classical role of POZ domains to recruit co-repressors and histone deacetylases. Understanding the functional roles of PCIF1 domains may have application to therapeutic β-cell replacement strategies involving PDX-1 for the treatment of diabetes

On rigidly rotating perfect fluid cylinders

The gravitational field of a rigidly rotating perfect fluid cylinder with gamma- law equation of state is found analytically. The solution has two parameters and is physically realistic for gamma in the interval (1.41,2]. Closed timelike curves always appear at large distances.Comment: 10 pages, Revtex (galley

An inhomogeneous fractal cosmological model

We present a cosmological model in which the metric allows for an inhomogeneous Universe with no intrinsic symmetries (Stephani models), providing the ideal features to describe a fractal distribution of matter. Constraints on the metric functions are derived using the expansion and redshift relations and allowing for scaling number counts, as expected in a fractal set. The main characteristics of such a cosmological model are discussed.Comment: 11 pages, no figures, accepted for publication on Classical and Quantum Gravit

Birkhoff Theorem and Matter

Birkhoff's theorem for spherically symmetric vacuum spacetimes is a key theorem in studying local systems in general relativity theory. However realistic local systems are only approximately spherically symmetric and only approximately vacuum. In a previous paper, we showed the theorem remains approximately true in an approximately spherically symmetric vacuum space time. In this paper we prove the converse case: the theorem remains approximately true in a spherically symmetric, approximately vacuum space time.Comment: 7 pages, Revtex