On a recent attempt to define the interpretation basis in the many worlds interpretation of quantum mechanics

David Deutsch's 1985 algorithm to determine the preferred product structure and basis in the many worlds interpretation is examined. His heuristic argument for the conditions appearing in the algorithm is found wanting. The question of the existence and uniqueness of a final solution to his algorithm is discussed. The algorithm is shown to be inadequate to account for certain types of measurement which are, at least in principle, possible.     

Surface analysis of thick gold films by X-ray fluorescence using the base metal as an internal reference

A procedure has been developed for the determination of the amount of gold clad on a brass base. The method does not require dissolution of the sample and utilizes the presence of copper in the base metal as an internal standard.     

Measuring site-specific cluster-surface bond formation

Recent advances in dynamic force microscopy show that it is possible to measure the forces between atomically sharp tips and particular atomic positions on surfaces as a function of distance. However, on most ionic surfaces, the positive and negative ions can so far not be distinguished. In this paper, we use the CaF2(111) surface, where atomic resolution force microscopy has allowed identification of the positions of the Ca2+ and F- ions in the obtained images, to demonstrate that short-range interaction forces can be measured selectively above chemically identified surface sites. Combining experimental and theoretical results allows a quantification of the strength and distance dependence of the interaction of a tip-terminating cluster with particular surface ions and reveals details of cluster and surface relaxation. Further development of this approach will provide new insight into mechanisms of chemical bond formation between clusters, cluster deposition at surfaces, processes in adhesion and tribology, and single atom manipulation with the force microscope.     

Structural characterization of artificial self-assembling porphyrins that mimic the natural chlorosomal bacteriochlorophylls c, d, and e

We report two crystal structures of a synthetic porphyrin molecule which was programmed for self-assembly. The same groups which ensure that bacteriochlorophylls c, d, and e can self-assemble into the chlorosomal nanorods, the photosynthetic antenna system of some green bacteria, have been engineered into desired positions of the tetrapyrrolic macrocycle. In the case of the 5,15-meso-substituted anchoring groups, depending upon the concentration, by using the same crystallization solvents, either a tetragonal or a layered structure of porphyrin stacks were encountered. Surprisingly, pi-pi interactions combined with extensive dispersive interactions, which also encompass cyclohexane, one of the crystallization solvents, win over putative hydrogen bonding. We are aware that our compounds differ considerably from the natural bacteriochlorophylls, but based upon our findings, we now question the hydrogen-bonding network, previously proposed to organize stacks of bacteriochlorophylls. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS) on various isomeric compounds support our challenge of current models for the chlorosomal antenna as these show structures, astonishingly similar to those of chlorosomes.     

Electroproduction of π0 mesons in the resonance region at q2=1.0 (GeV/c)2

Data are presented for the reaction ep → epπ⁰ at a nominal momentum transfer squared of 1.0 (GeV/c)². The data were obtained using an extracted electron beam from NINA and two magnetic spectrometers for coincidence detection of the electron and proton. Differential cross sections have been measured for isobar masses in the range 1.19–1.73 GeV/c².     

On the blocking process in queue networks

The blocking process in some particular exponential open queue networks is studied. The networks are in the form of two-stage and three-stage queue networks with finite intermediate waitingroom. FIFO scheduling is assumed. Blocking occurs when the flow of units through one queue is momentarily stopped owing to a capacity limitation of another queue have been reached. Exact and approximate bounds for the mean blocking time in these networks are obtained. The condition for stability in the two-stage networks is also derived. Finally the applicability of the results obtained is demonstrated through a case study.