Evidence for static magnetism in the vortex cores of ortho-II YBa2Cu3O6.50

Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories.     

Distributed automated docking of flexible ligands to proteins: Parallel applications of AutoDock 2.4

Summary AutoDock 2.4 predicts the bound conformations of a small, flexible ligand to a nonflexible macromolecular target of known structure. The technique combines simulated annealing for conformation searching with a rapid grid-based method of energy evaluation based on the AMBER force field. AutoDock has been optimized in performance without sacrificing accuracy; it incorporates many enhancements and additions, including an intuitive interface. We have developed a set of tools for launching and analyzing many independent docking jobs in parallel on a heterogeneous network of UNIX-based workstations. This paper describes the current release, and the results of a suite of diverse test systems. We also present the results of a systematic investigation into the effects of varying simulated-annealing parameters on molecular docking. We show that even for ligands with a large number of degrees of freedom, root-mean-square deviations of less than 1 Å from the crystallographic conformation are obtained for the lowest-energy dockings, although fewer dockings find the crystallographic conformation when there are more degrees of freedom.The AutoDock 2.4 suite is written in ANSI C, and is supplied with Makefiles for the following platforms: Convex, DEC Alpha OSF/1, Hewlett-Packard Precision Architecture, Silicon Graphics, and Sun. The AutoDock suite of programs is freely available to the noncommercial scientific community and to educational establishments. Further information, including additional figures and MPEG animations showing all docked conformations for each test system, can be found at the following URL: http://www.scripps.edu/pub/olson-web/doc/autodock.     

Free products of kω-topological groups with normal amalgamation

It is shown in this paper that if A is a closed normal subgroup of k_ω-topological groups G and H, then the free product of G and H with A amalgamated, G1_AH, exists, is Hausdorff and indeed a k_ω-group.     

Polymerization of methyl acrylate in aqueous media

The polymerization of methyl acrylate in water and in dilute, aqueous, soap solutions, initiated by potassium peroxydisulfate, has been investigated, a dilatometric method being used to follow the conversion. It has been shown that small amounts of an anionic soap increase the rate of reaction while a cationic soap has the reverse effect. The change of molecular weight with conversion has also been examined as well as the effect of the exclusion of oxygen from the system.     

Galerkin methods applied to some model equations for non-linear dispersive waves

The application of a dissipative Galerkin scheme to the numerical solution of the Korteweg de Vries (KdV) and Regularised Long Wave (RLW) equations, is investigated. The accuracy and stability of the proposed schemes is derived using a localised Fourier analysis. With cubic splines as basis functions, the errors in the numerical solutions of the KdV equation for different mesh-sizes and different amounts of dissipation is determined. It is shown that the Galerkin scheme for the RLW equation gives rise to much smaller errors (for a given mesh-size), and allows larger steps to be taken for the integrations in time (for a specified error tolerance). Also, the interaction of two solitons is compared for the KdV and RLW equations, and several differences in their behaviour are found.     

The Nasathermionic-Conversion (TEC-Art) Program a Proposed Paper for Presentation at the May 1977 IEEE International Conference on Plasma Science at Rensselaer Polytechnic Institute

The NASA program for applied research and technology (ART) in thermionic energy conversion (TEC) comprises in-house, university-grant, and industrial-contract studies. In a few years this TEC-ART program has produced important results. Although many of these accomplishments are incremental, their integration has yielded performance gains and the knowledge necessary to direct future work. The current emphasis on out-of-core thermionics allows materials and designs previously prohibited by in-core nucleonics and geometrics. The additional degrees of freedom offer new potentialities. But as always high-temperature material effects will determine the level and lifetime of TEC performance: New electrodes must not only raise power outputs but also maintain them regardless of emitter-vapor deposition on collectors. In addition effective electrodes must serve compatibly with hot-shell alloys. Then, of course, space TEC must withstand external and internal high-temperature vaporization problems. And terrestrial TEC must tolerate hot corrosive atmospheres outside and near-vacuum inside. Finally reduction of losses between converter electrodes is essential even though rather demanding geometrics appear to be required for some modes of enhanced operation. In these and other areas from basic material characterizations to possible system definitions, significant progress is being made in the NASA TEC-ART Program.