Magnetic Moments of Baryons with a Heavy Quark

We compute magnetic moments of baryons with a heavy quark in the bound state approach for heavy baryons. In this approach the heavy baryon is considered as a heavy meson bound to a light baryon. The latter is represented as a soliton excitation of light meson fields. We obtain the magnetic moments by sandwiching pertinent components of the electromagnetic current operator between the bound state wave--functions. We extract this current operator from the coupling to the photon field after extending the action to be gauge invariant.Comment: Talk presented by HW at MRST'03 (Joe-Fest), Syracuse, NY, May 2003, 12 pages, uses AIP style files. Ref. adde

Near-BPS Skyrmions: Non-shell configurations and Coulomb effects

The relatively small binding energy in nuclei suggests that they may be well represented by near-BPS Skyrmions since their mass is roughly proportional to the baryon number $A.$ For that purpose, we propose a generalization of the Skyrme model with terms up to order six in derivatives of the pion fields and treat the nonlinear $\sigma$ and Skyrme terms as small perturbations. For our special choice of mass term (or potential) $V$, we obtain well-behaved analytical BPS-type solutions with non-shell configurations for the baryon density, as opposed to the more complex shell-like configurations found in most extensions of the Skyrme model . Along with static and (iso)rotational energies, we add to the mass of the nuclei the often neglected Coulomb energy and isospin breaking term. Fitting the four model parameters, we find a remarkable agreement for the binding energy per nucleon $B/A$ with respect to experimental data. These results support the idea that nuclei could be near-BPS Skyrmions.Comment: Correction of minors errors, references adde

Chiral Quark Model

In this talk I review studies of hadron properties in bosonized chiral quark models for the quark flavor dynamics. Mesons are constructed from Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two--fold Pauli--Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10 pages, proceedings style files include

Autoplot: A browser for scientific data on the web

Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web, usually in the form of a directory containing data files with multiple parameters contained in each file. Data from a data source is abstracted into a common internal data model called QDataSet. Autoplot is built from individually useful components, and can be extended and reused to create specialized data handling and analysis applications and is being used in a variety of science visualization and analysis applications. Although originally developed for viewing heliophysics-related time series and spectrograms, its flexible and generic data representation model makes it potentially useful for the Earth sciences.Comment: 16 page

Direct observation of the potential distribution within organic light emitting diodes under operation

We show the first direct measurement of the potential distribution within organic light emitting diodes (OLEDs) under operation and hereby confirm existing hypotheses about charge transport and accumulation in the layer stack. Using a focused ion beam to mill holes in the diodes we gain access to the cross section of the devices and explore the spatially resolved potential distribution in situ by scanning Kelvin probe microscopy under different bias conditions. In bilayer OLEDs consisting of tris(hydroxyquinolinato) aluminum (Alq_3)/N, N ′-bis(naphthalene-1-yl)-N,N ′-bis(phenyl) benzidine (NPB) the potential exclusively drops across the Alq_3 layer for applied bias between onset voltage and a given transition voltage. These findings are consistent with previously performed capacitance–voltage measurements. The behavior can be attributed to charge accumulation at the interface between the different organic materials. Furthermore, we show the potential distribution of devices with different cathode structures and degraded devices to identify the cathode interface as main culprit for decreased performance