Indestructibility of compact spaces

In this article we investigate which compact spaces remain compact under countably closed forcing. We prove that, assuming the Continuum Hypothesis, the natural generalizations to $\omega_1$-sequences of the selection principle and topological game versions of the Rothberger property are not equivalent, even for compact spaces. We also show that Tall and Usuba's "$\aleph_1$-Borel Conjecture" is equiconsistent with the existence of an inaccessible cardinal.Comment: 18 page

Solving the mystery of the disappearing January blip in state employment data

Frank Berger and Keith Phillips propose a new two-step method of seasonally adjusting state Current Employment Statistics (CES) data produced by the Bureau of Labor Statistics (BLS). This method, first proposed in the July/August 1993 issue of Southwest Economy, recently was adopted by the BLS to seasonally adjust the broadest industry groupings of the state employment series. With this new adjustment procedure, the state employment data should be smoother and better reflect trend-cycle movements than if a more traditional seasonal adjustment method were used. ; The article finds that forty-six states suffer a break in their seasonal pattern toward the end of the data series. The authors explain the reason for the break and describe a procedure to adjust for it. Although the BLS is currently using this procedure for states at the broadest level of industry detail, analysts who want to seasonally adjust the state employment data at a finer level of industry detail should find the authors' description of the process useful. Also, analysts who seek to seasonally adjust the CES data for metropolitan areas may find the two-step method helpful.Employment (Economic theory)

A new quarterly output measure for Texas

Real gross domestic product is one of the most watched indicators of the U.S. business cycle. Yet at the state level, output measures are rarely used to track business conditions. Although the Bureau of Economic Analysis estimates real gross state product (RGSP), the long release lag (usually about two and one-half years after the reporting year) and the annual periodicity of the data severely limit its usefulness. ; In this article, Frank Berger and Keith Phillips find that movements in quarterly personal income and various price measures can accurately explain movements in total Texas RGSP and in eleven broad industry groupings. Based on these findings, Berger and Phillips create quarterly measures of total and industry-specific Texas RGSP that will be available about four months after the reporting quarter. The new series represents a comprehensive measure of economic activity in the state that can be used along with other timely indicators, such as nonfarm employment and the unemployment rate, to gauge current business conditions.Regional economics ; Texas

Two-region model for positive and negative plasma sheaths and its application to Hall thruster metallic anodes.

An asymptotic presheath/sheath model for positive and negative sheaths in front of a conducting electrode, with a continuous parametric transition at the no-sheath case, is presented. Key aspects of the model are as follows: full hydrodynamics of both species in the presheath; a kinetic formulation with a truncated distribution function for the repelled species within the sheath; and the fulfillment of the marginal Bohm condition at the sheath edge, in order to match the two formulations of the repelled species. The sheath regime depends on the ratios of particle fluxes and sound speeds between the two species. The presheath model includes the effect of a magnetic field parallel to the wall on electrons. An asymptotic, parametric study of the anode presheath is carried out in terms of the local ion-to-electron flux ratio and Hall parameter. The drift-diffusive model of magnetized electrons fails in a parametric region that includes parts of the negative sheath regime. In the case of the Hall parameter vanishing near the electrode and a weakly collisional plasma, a quasisonic, quasineutral plateau forms next to the sheath edge

Plasmas generated by ultra-violet light rather than electron impact

We analyze, in both plane and cylindrical geometries, a collisionless plasma consisting of an inner region where generation occurs by UV illumination, and an un-illuminated outer region with no generation. Ions generated in the inner region flow outwards through the outer region and into a wall. We solve for this system's steady state, first in the quasi-neutral regime (where the Debye length ${\lambda}_D$ vanishes and analytic solutions exist) and then in the general case, which we solve numerically. In the general case a double layer forms where the illuminated and un-illuminated regions meet, and an approximately quasi-neutral plasma connects the double layer to the wall sheath; in plane geometry the ions coast through the quasi-neutral section at slightly more than the Bohm speed $c_s$. The system, although simple, therefore has two novel features: a double layer that does not require counter-streaming ions and electrons, and a quasi-neutral plasma where ions travel in straight lines with at least the Bohm speed. We close with a pr\'{e}cis of our asymptotic solutions of this system, and suggest how our theoretical conclusions might be extended and tested in the laboratory.Comment: 10 pages, 3 figures, accepted by Physics of Plasma

Extraordinary sensitivity of the electronic structure and properties of single-walled carbon nanotubes to molecular charge-transfer

Interaction of single-walled carbon nanotubes with electron donor and acceptor molecules causes significant changes in the electronic and Raman spectra, the relative proportion of the metallic species increasing on electron donation through molecular charge transfer, as also verified by electrical resistivity measurements.Comment: 15 pages, 5 figurre

Radio-frequency discharges in Oxygen. Part 1: Modeling

In this series of three papers we present results from a combined experimental and theoretical effort to quantitatively describe capacitively coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo model on which the theoretical description is based will be described in the present paper. It treats space charge fields and transport processes on an equal footing with the most important plasma-chemical reactions. For given external voltage and pressure, the model determines the electric potential within the discharge and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used scattering and reaction cross section data are critically assessed and in some cases modified. To validate our model, we compare the densities in the bulk of the discharge with experimental data and find good agreement, indicating that essential aspects of an oxygen discharge are captured.Comment: 11 pages, 10 figure

Thinning and Harvesting Regimesf or Yellow-Poplar

Grade I yellow-popular logos were recently selling for $150/mbf, three times the price for grade 2 logs in North Carolina. A computerized stand development model was used to examine the profitability of thinning and holding yellow poplar stands for increased diameter and grade. Analyses were done over wide ranges in stand age, site quality, and stocking, at 5% and 10% discount rates. At a 5% discount rate, the maximum net present stumpage value was obtained by thinning in most regimes. Lower stand age, higher initial stocking, and higher site indices favored thin-clearcut regimes over regimes with no initial thinning. At a 10% discount rate, thinning was optimal only at initial age 30 on the highest quality sites at the highest initial stocking. All other combinations of variables favored clearcutting immediately or with a 1O -year delay. Thinning options with net values within 50% of maximum were numerous at a 5% discount rate in younger stands but decrease rapidly as initial age increased. Only a few such options were available at the 10% discount rate. South. J. Appl. For. 14(3):101-103

Flight evaluation of advanced flight control systems and cockpit displays for powered-lift STOL Aircraft

A flight research program was conducted to assess the improvements, in longitudinal path control during a STOL approach and landing, that can be achieved with manual and automatic control system concepts and cockpit displays with various degrees of complexity. NASA-Ames powered-lift Augmentor Wing Research Aircraft was used in the research program. Satisfactory flying qualities were demonstrated for selected stabilization and command augmentation systems and flight director combinations. The ability of the pilot to perform precise landings at low touchdown sink rates with a gentle flare maneuver was also achieved. The path-control improvement is considered to be applicable to other powered-lift aircraft configurations