Advances in Atomic Data for Neutron-Capture Elements

Neutron(n)-capture elements (atomic number Z>30), which can be produced in planetary nebula (PN) progenitor stars via s-process nucleosynthesis, have been detected in nearly 100 PNe. This demonstrates that nebular spectroscopy is a potentially powerful tool for studying the production and chemical evolution of trans-iron elements. However, significant challenges must be addressed before this goal can be achieved. One of the most substantial hurdles is the lack of atomic data for n-capture elements, particularly that needed to solve for their ionization equilibrium (and hence to convert ionic abundances to elemental abundances). To address this need, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for the first six ions of Se and Kr. The calculations were benchmarked against experimental photoionization cross section measurements. In addition, we computed charge transfer (CT) rate coefficients for ions of six n-capture elements. These efforts will enable the accurate determination of nebular Se and Kr abundances, allowing robust investigations of s-process enrichments in PNe.Comment: To be published in IAU Symp. 283: Planetary Nebulae, an Eye to the Future; 2 page

Physical properties of solar polar jets: A statistical study with Hinode XRT data

The target of this work is to investigate the physical nature of polar jets in the solar corona and their possible contribution to coronal heating and solar wind flow based on the analysis of X-ray images acquired by the Hinode XRT telescope. We estimate the different forms of energy associated with many of these small-scale eruptions, in particular the kinetic energy and enthalpy. Two Hinode XRT campaign datasets focusing on the two polar coronal holes were selected to analyze the physical properties of coronal jets; the analyzed data were acquired using a series of three XRT filters. Typical kinematical properties (e.g., length, thickness, lifetime, ejection rate, and velocity) of 18 jets are evaluated from the observed sequences, thus providing information on their possible contribution to the fast solar wind flux escaping from coronal holes. Electron temperatures and densities of polar-jet plasmas are also estimated using ratios of the intensities observed in different filters. We find that the largest amount of energy eventually provided to the corona is thermal. The energy due to waves may also be significant, but its value is comparatively uncertain. The kinetic energy is lower than thermal energy, while other forms of energy are comparatively low. Lesser and fainter events seem to be hotter, thus the total contribution by polar jets to the coronal heating could have been underestimated so far. The kinetic energy flux is usually around three times smaller than the enthalpy counterpart, implying that this energy is converted into plasma heating more than in plasma acceleration. This result suggests that the majority of polar jets are most likely not escaping from the Sun and that only cooler ejections could possibly have enough kinetic energy to contribute to the total solar wind flow.Comment: 21 pages, 10 figures, Submitted and accepted for publishing in Astronomy and Astrophysics journa

Single parameter testing Quarterly report

Single parameter testing of ac and dc amplifier

Single parameter testing

Frequency response testing of ac and dc amplifiers, and single parameter testing of X-Y PLOTTE

Single parameter testing Quarterly report

Test signals, AC analysis, transfer function determination, and nonlinear components for single parameter testing of amplifie

Single parameter testing, phase D Final report

Single parameter testing techniques for electronic measuring equipment and other component

U.S. Radio in the 21st Century: Staying the Course in Unknown Territory

This essay examines the development of the radio industry in the United States as it makes its way into the 21st century. Issues of regulation, technology, commerce, and culture are addressed