Radio Observations of 4079 Quasars

Using the NVSS radio catalog, we have searched for radio emission from 4079 quasars taken from the 1996 version of the Veron-Cetty and Veron (1996) quasar catalog. The comparison resulted in the positive detection of radio emission from 799 quasars. Of these, 168 are new radio detections. Examination of the radio luminosities shows a dramatic increase in the fraction of radio-loud quasars from the current epoch to z=0.5 and a gradual decline beyond z=1.0. Inspection of the radio-loud fraction as a function of M_B shows little dependence fainter than M_B=-29.5.Comment: 25 pages, including 9 figures and 1 tabl

Magnetic domain walls in constrained geometries

Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements containing geometrical constrictions by spin-polarized scanning electron microscopy and numerical simulations. By controlling the constriction dimensions, the wall width can be tailored and the wall type modified. In particular, the width of a 180 degree Neel wall can be strongly reduced or increased by the constriction geometry compared with the wall in unconstrained systems.Comment: 4 pages, 6 figure

On a Basis for the Framed Link Vector Space Spanned by Chord Diagrams

In view of the result of Kontsevich, now often called ``the fundamental theorem of Vassiliev theory'', identifying the graded dual of the associated graded vector space to the space of Vassiliev invariants filtered by degree with the linear span of chord diagrams modulo the ``4T-relation'' (and in the unframed case, the ``1T-'' or ``isolated chord relation''), it is a problem of some interest to provide a basis for the space of chord diagrams modulo the 4T-relation. We construct the basis for the vector space spanned by chord diagrams with n chords and m distinguishable link components, modulo 4T relations for n less than or equal to 5.Comment: 25 papers, numerous png figure

Vitamin C and Its Radicals: Tautomerism, Electronic Structure and Properties

The biological importance and activity of ascorbic acid and its radicals are briefly reviewed. The quantum mechanical calculations performed on these remarkable compounds are presented in some detail. Particular attention is devoted to structural and electronic features offered by the semiempirical MINDO/3 and MNDO schemes. By making use of the self-consistent charge (SCC-MO) method, the ESCA spectra of the ascorbic acid tautomers are predicted. It is found that the radical anion is more stable than each of the four AA tautomers. This is of importance because the unusual biological protective property of ascorbate against free radical damage is most likely related to the stability of its radical, Ortgins of the enhanced stability of the radical anion are analyzed by the energy partitioning technique

Generation of spin-wave dark solitons with phase engineering

We generate experimentally spin-wave envelope dark solitons from rectangular high-frequency dark input pulses with externally introduced phase shifts in yttrium-iron garnet magnetic fims. We observe the generation of both odd and even numbers of magnetic dark solitons when the external phase shift varies. The experimental results are in a good qualitative agreement with the theory of the dark-soliton generation in magnetic films developed earlier [Phys. Rev. Lett. 82, 2583 (1999)].Comment: 6 pages, including 7 figures, submitted to Phys. Rev.

Geometric approach to Fletcher's ideal penalty function

Original article can be found at: www.springerlink.com Copyright Springer. [Originally produced as UH Technical Report 280, 1993]In this note, we derive a geometric formulation of an ideal penalty function for equality constrained problems. This differentiable penalty function requires no parameter estimation or adjustment, has numerical conditioning similar to that of the target function from which it is constructed, and also has the desirable property that the strict second-order constrained minima of the target function are precisely those strict second-order unconstrained minima of the penalty function which satisfy the constraints. Such a penalty function can be used to establish termination properties for algorithms which avoid ill-conditioned steps. Numerical values for the penalty function and its derivatives can be calculated efficiently using automatic differentiation techniques.Peer reviewe

Detecting Generalized Synchronization Between Chaotic Signals: A Kernel-based Approach

A unified framework for analyzing generalized synchronization in coupled chaotic systems from data is proposed. The key of the proposed approach is the use of the kernel methods recently developed in the field of machine learning. Several successful applications are presented, which show the capability of the kernel-based approach for detecting generalized synchronization. It is also shown that the dynamical change of the coupling coefficient between two chaotic systems can be captured by the proposed approach.Comment: 20 pages, 15 figures. massively revised as a full paper; issues on the choice of parameters by cross validation, tests by surrogated data, etc. are added as well as additional examples and figure