Evaluation of miniature vacuum ultraviolet lamps for stability and operating characteristics, Lyman-Alpha task

Modifications required to change the near ultraviolet source in the Optical Contamination Monitor to a source with output at or near the Lyman-Alpha hydrogen line are discussed. The effort consisted of selecting, acquiring and testing candidate miniature ultraviolet lamps with significant output in or near 121.6 nm. The effort also included selection of a miniature dc high-voltage power supply capable of operating the lamp. The power supply was required to operate from available primary power supplied by the Optical Effect Module (DEM) and it should be flight qualified or have the ability to be qualified by the user

Turing degrees of limit sets of cellular automata

Cellular automata are discrete dynamical systems and a model of computation. The limit set of a cellular automaton consists of the configurations having an infinite sequence of preimages. It is well known that these always contain a computable point and that any non-trivial property on them is undecidable. We go one step further in this article by giving a full characterization of the sets of Turing degrees of cellular automata: they are the same as the sets of Turing degrees of effectively closed sets containing a computable point

The Wealth and Poverty of Widows: Assets Before and After the Husband's Death

We verify that widows are much more likely than couples to be poor and that they make up a large proportion of the poor elderly; 80 percent are widows or other single individuals. Then we seek to explain why the single elderly are poor, with emphasis on widows. We do this by tracing back over time their financial status, using the Longitudinal Retirement History Survey. The death of the husband very often induces the poverty of the surviving spouse, even though the married couple was not poor. While only about 9 percent of prior couples are poor, approximately 35 percent of the subsequent widows are. A large proportion of the wealth of the couple is lost when the husband dies. In addition we find that: (1) the prior households of poor widows earned and saved less than the prior households of non-poor widows, (2) more of the smaller accumulated wealth was lost at the death of the husband, (3) the absence of survivorship benefits or life insurance insured that the loss in wealth would leave the widow poor thereafter.

Asymmetric field dependence of magnetoresistance in magnetic films

We study an asymmetric in field magnetoresistance that is frequently observed in magnetic films and, in particular, the odd longitudinal voltage peaks that appear during magnetization reversal in ferromagnetic films, with out-of-plane magnetic anisotropy. We argue that the anomalous signals result from small variation of magnetization and Hall resistivity along the sample. Experimental data can be well described by a simple circuit model, the latter being supported by analytic and numerical calculations of current and electric field distribution in films with a gradual variation of the magnetization and Hall resistance.Comment: 7 pages, 5 figures, to be published in Phys. Rev.

Resonant tunneling through a small quantum dot coupled to superconducting leads

We address the problem of non-linear transport through discrete electronic levels in a small quantum dot coupled to superconducting electrodes. In our approach the low temperature I-V characteristics can be calculated including all multiple quasi-particle and Andreev processes. The limit of very weak coupling to the leads and large charging energies is briefly analyzed comparing the calculated lineshapes of the I-V curves with recent experimental results. When the coupling to the leads increases and Coulomb blockade effects can be neglected, the combination of multiple Andreev processes and resonant transmission gives rise to a rich subgap structure which largely differs from the one found in the more studied S-N-S systems. We show how multiple processes can be included within a simple sequential tunneling picture qualitatively explaining the subgap structure. We suggest an experimental set-up where the predicted effects could be observed.Comment: 11 pages, 4 postscript figures, to be published in Phys. Rev. B (rapid communications

Optimized tracking of RF carriers with phase noise, including Pioneer 10 results

The ability to track very weak signals from distant spacecraft is limited by the phase instabilities of the received signal and of the local oscillator employed by the receiver. These instabilities ultimately limit the minimum loop bandwidth that can be used in a phase-coherent receiver, and hence limit the ratio of received carrier power to noise spectral density which can be tracked phase coherently. A method is presented for near real time estimation of the received carrier phase and additive noise spectrum, and optimization of the phase locked loop bandwidth. The method was used with the breadboard Deep Space Network (DSN) Advanced Receiver to optimize tracking of very weak signals from the Pioneer 10 spacecraft, which is now more distant that the edge of the solar system. Tracking with bandwidths of 0.1 Hz to 1.0 Hz reduces tracking signal threshold and increases carrier loop signal to noise ratio (SNR) by 5 dB to 15 dB compared to the 3 Hz bandwidth of the receivers now used operationally in the DSN. This will enable the DSN to track Pioneer 10 until its power sources fails near the end of the century

Leadership Styles of Head NASCAR Executives: A Historical Perspective

This study sought to explore the leadership styles and theories employed throughout the existence of the National Association for Stock Car Auto Racing (NASCAR). The research examines the decision process and subsequent outcomes, exploring how they ultimately affected the business and trajectory of the sport. NASCAR is the product of unique and specific characteristics of racing enthusiasts who turned their passion into an international empire. This illustrates how leadership styles, specifically dictatorial leadership, successfully managed decisions of the business. Through the use of qualitative research to review historical accounts of events, this study strives to explain how leadership guided the business from small beginnings to a worldwide phenomenon. Data collected included document review, observations, and an interview. Synthesis of the data showed that each of the four primary leaders (Bill France Sr., Bill France Jr., Brain France, and Jim France) used the autocratic/dictatorial leadership style as they directed the sport. Historical evidence shows that this style of leadership was required to build the sport and move it to its current recognized level. Recommendation for further study encourage future scholars to revisit the long-term impact of Brian France’s leadership once more time has passed since his negatively charged removal from the leadership position. Researchers would need to also examine the leadership of Jim France because at the time of this study he has been in his leadership position for less than two years