Re-Engineering of the GSI Control System

After more than 12 years of operation without substantial revision a modernization of the control system at GSI is overdue. A strategy to adapt the system to future needs is outlined. The system has to support a specific environment of which the main features are described. More flexibility than in the current system can be achieved while still using many parts of the actual system.Comment: ICALEPCS 2001, Talk WEAT002, 3 pages, Late

Acute lower limb ischemia due to thrombo-embolic arterial occlusions in two previously healthy men with markedly elevated Lp(a)

Lipoprotein (a) (Lp(a)) is a well-documented risk factor for atherosclerotic cardiovascular disease. Its role in acute thrombo-embolic occlusions of peripheral arteries is not known. We describe two cases of multiple, acute, peripheral arterial occlusions in two previously healthy men with markedly elevated Lp(a). Both cases had unsatisfactory results after percutaneous and surgical revascularization procedures. Experience yielded in these two cases suggests that when an unfavorable outcome occurs in a peripheral artery disease patient in the absence of the regular risk factors, Lp(a) should be determined and its role investigated

Aspects of Nucleon Chiral Perturbation Theory

I review recent progress made in the calculation of nucleon properties in the framework of heavy baryon CHPT. Topics include: Compton scattering, $\pi N$ scattering, the anatomy of a low-energy constant and the induced pseudoscalar form factor.Comment: plain TeX (macro included), 12pp, lecture delivered at the workshop on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199

Comment on "Anomalies in electrostatic calibration for the measurement of the Casimir force in a sphere-plane geometry"

Recently W. J. Kim, M. Brown-Hayes, D. A. R. Dalvit, J. H. Brownell, and R. Onofrio [Phys. Rev. A, v.78, 036102(R) (2008)] performed electrostatic calibrations for a plane plate above a centimeter-size spherical lens at separations down to 20-30 nm and observed "anomalous behavior". It was found that the gradient of the electrostatic force does not depend on separation as predicted on the basis of a pure Coulombian contribution. Some hypotheses which could potentially explain the deviation from the expected behavior were considered, and qualitative arguments in favor of the influence of patch surface potentials were presented. We demonstrate that for the large lenses at separations of a few tens nanometers from the plate, the electrostatic force law used by the authors is not applicable due to possible deviations of the mechanically polished and ground lens surface from a perfect spherical shape. A model is proposed which explains the observed "anomalous behavior" using the standard Coulombian force.Comment: 9 pages, 3 figure

Surface properties of SmB6 from x-ray photoelectron spectroscopy

We have investigated the properties of cleaved SmB$_6$ single crystals by x-ray photoelectron spectroscopy. At low temperatures and freshly cleaved samples a surface core level shift is observed which vanishes when the temperature is increased. A Sm valence between 2.5 - 2.6 is derived from the relative intensities of the Sm$^{2+}$ and Sm$^{3+}$ multiplets. The B/Sm intensity ratio obtained from the core levels is always larger than the stoichiometric value. Possible reasons for this deviation are discussed. The B $1s$ signal shows an unexpected complexity: an anomalous low energy component appears with increasing temperature and is assigned to the formation of a suboxide at the surface. While several interesting intrinsic and extrinsic properties of the SmB$_6$ surface are elucidated in this manuscript no clear indication of a trivial mechanism for the prominent surface conductivity is found

Dynamo effect in parity-invariant flow with large and moderate separation of scales

It is shown that non-helical (more precisely, parity-invariant) flows capable of sustaining a large-scale dynamo by the negative magnetic eddy diffusivity effect are quite common. This conclusion is based on numerical examination of a large number of randomly selected flows. Few outliers with strongly negative eddy diffusivities are also found, and they are interpreted in terms of the closeness of the control parameter to a critical value for generation of a small-scale magnetic field. Furthermore, it is shown that, for parity-invariant flows, a moderate separation of scales between the basic flow and the magnetic field often significantly reduces the critical magnetic Reynolds number for the onset of dynamo action.Comment: 44 pages,11 figures, significantly revised versio

Flow graphs: interweaving dynamics and structure

The behavior of complex systems is determined not only by the topological organization of their interconnections but also by the dynamical processes taking place among their constituents. A faithful modeling of the dynamics is essential because different dynamical processes may be affected very differently by network topology. A full characterization of such systems thus requires a formalization that encompasses both aspects simultaneously, rather than relying only on the topological adjacency matrix. To achieve this, we introduce the concept of flow graphs, namely weighted networks where dynamical flows are embedded into the link weights. Flow graphs provide an integrated representation of the structure and dynamics of the system, which can then be analyzed with standard tools from network theory. Conversely, a structural network feature of our choice can also be used as the basis for the construction of a flow graph that will then encompass a dynamics biased by such a feature. We illustrate the ideas by focusing on the mathematical properties of generic linear processes on complex networks that can be represented as biased random walks and also explore their dual consensus dynamics.Comment: 4 pages, 1 figur

Rigorous approach to the comparison between experiment and theory in Casimir force measurements

In most experiments on the Casimir force the comparison between measurement data and theory was done using the concept of the root-mean-square deviation, a procedure that has been criticized in literature. Here we propose a special statistical analysis which should be performed separately for the experimental data and for the results of the theoretical computations. In so doing, the random, systematic, and total experimental errors are found as functions of separation, taking into account the distribution laws for each error at 95% confidence. Independently, all theoretical errors are combined to obtain the total theoretical error at the same confidence. Finally, the confidence interval for the differences between theoretical and experimental values is obtained as a function of separation. This rigorous approach is applied to two recent experiments on the Casimir effect.Comment: 10 pages, iopart.cls is used, to appear in J. Phys. A (special issue: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005

Bound-free pair production in ultra-relativistic ion collisions at the LHC collider: Analytic approach to the total and differential cross sections

A theoretical investigation of the bound-free electron-positron pair production in relativistic heavy ion collisions is presented. Special attention is paid to the positrons emitted under large angles with respect to the beam direction. The measurement of these positrons in coincidence with the down--charged ions is in principle feasible by LHC experiments. In order to provide reliable estimates for such measurements, we employ the equivalent photon approximation together with the Sauter approach and derive simple analytic expressions for the differential pair--production cross section, which compare favorably to the results of available numerical calculations. Based on the analytic expressions, detailed calculations are performed for collisions of bare Pb$^{82+}$ ions, taking typical experimental conditions of the LHC experiments into account. We find that the expected count rate strongly depends on the experimental parameters and may be significantly enhanced by increasing the positron-detector acceptance cone.Comment: 10 pages, 4 figure