Advanced NDE research in electromagnetic, thermal, and coherent optics

A new inspection technology called magneto-optic/eddy current imaging was investigated. The magneto-optic imager makes readily visible irregularities and inconsistencies in airframe components. Other research observed in electromagnetics included (1) disbond detection via resonant modal analysis; (2) AC magnetic field frequency dependence of magnetoacoustic emission; and (3) multi-view magneto-optic imaging. Research observed in the thermal group included (1) thermographic detection and characterization of corrosion in aircraft aluminum; (2) a multipurpose infrared imaging system for thermoelastic stress detection; (3) thermal diffusivity imaging of stress induced damage in composites; and (4) detection and measurement of ice formation on the space shuttle main fuel tank. Research observed in the optics group included advancements in optical nondestructive evaluation (NDE)

Risky Income, Life Cycle Consumption, and Precautionary Savings

This paper argues that precautionary savings against uncertain income comprise a large fraction of aggregate savings. A closed-form approximation for life cycle consumption subject to uncertain interest rates and earnings is derived by taking a second-order Taylor-Series approximation of the Euler equations. Using empirical measures of income uncertainty, I find that precautionary savings comprises up to 56 percent of aggregate life cycle savings. The derived expression for n-period optimal consumption is easily implemented for econometric estimation, and accords well with the exact numerical solution. Empirical comparisons of savings patterns among occupational groups using the Consumer Expenditure Survey contradict the predictions of the life cycle model. Riskier occupations, such as the self-employed and salespersons, save less than other occupations, although this finding may in part reflect unobservable differences in risk aversion among occupations.

The Welfare Cost of Uncertain Tax Policy

Frequent shifts in tax policy can increase uncertainty about future net-of-tax wages and interest income. This paper measures the impact of uncertain tax policy on savings, labor supply, and welfare in the United States. A vector autoregression model with six variables was estimated which found the standard error of the one-year-ahead forecast for the wage tax to be 1.8 percentage points, and for the interest income tax 3.3 percentage points. Furthermore, the negative correlation between unanticipated shifts in the real interest rate and changes in the interest income tax amplifies the variability in the real after-tax return. A two-period model of consumption and labor supply is developed that measures the effect of uncertain taxes on savings, work hours, and taxpayer welfare. Using plausible empirical parameters, it is shown that removing all uncertainty about future tax policy can lead to a welfare gain of 0.4 percent of national income, or about 12 billion dollars in 1985.

Outcomes Assessment and Health Care Reform

Argues for the use of outcomes assessment in measuring cost-effectiveness and quality to capture the overall impact of multi-dimensional treatment strategies and to identify healthcare systems that both adopt appropriate technologies and perform well

The Rainbow Site, An Unusual Syrup Mill in Gregg County, Texas

The Rainbow site is a historic archaeological site that was recorded during a cultural resources survey of a proposed Wal-Mart SuperCenter site in Longview, Texas. It was first interpreted as the location of an illegal whiskey still, but testing revealed that the furnace had been part of a sugar cane syrup mill. The early 1900s furnace is unusual when compared to other reported furnaces in that the firebox had been constructed below the original ground level and the flue/pan area had walls that were barely 1.5 ft. above the surrounding ground, whereas most furnaces were constructed on level ground and had waist-high walls where workers could stand upright when processing syrup. In addition, a brick vault had been constructed over the north end of the firebox and no other examples of such a feature have been reported from syrup mill furnaces

Observations of Binary and Single Wolf-Rayet Stars with XMM-Newton and Chandra

We present an overview of recent X-ray observations of Wolf-Rayet (WR) stars with XMM-Newton and Chandra. A new XMM spectrum of the nearby WN8 + OB binary WR 147 shows hard absorbed X-ray emission, including the Fe K-alpha line complex, characteristic of colliding wind shock sources. In contrast, sensitive observations of four of the closest known single WC (carbon-rich) WR stars have yielded only non-detections. These results tentatively suggest that single WC stars are X-ray quiet. The presence of a companion may thus be an essential factor in elevating the X-ray emission of WC + OB stars to detectable levels.Comment: To appear in conf. proceedings: Close Binaries in the 21st Century - New Opportunities and Challenges, eds. A. Gimenez, E. Guinan, P. Niarchos, S. Rucinski; Astrophys. and Space Sci. (special issue), 2006. 4 pages, 2 figure

A Rich Population of X-ray Emitting Wolf-Rayet Stars in the Galactic Starburst Cluster Westerlund 1

Recent optical and IR studies have revealed that the heavily-reddened starburst cluster Westerlund 1 (Wd 1) contains at least 22 Wolf-Rayet (WR) stars, comprising the richest WR population of any galactic cluster. We present results of a senstive Chandra X-ray observation of Wd 1 which detected 12 of the 22 known WR stars and the mysterious emission line star W9. The fraction of detected WN stars is nearly identical to that of WC stars. The WN stars WR-A and WR-B as well as W9 are exceptionally luminous in X-rays and have similar hard heavily-absorbed spectra with strong Si XIII and S XV emission lines. The luminous high-temperature X-ray emission of these three stars is characteristic of colliding wind binary systems but their binary status remains to be determined. Spectral fits of the X-ray bright sources WR-A and W9 with isothermal plane-parallel shock models require high absorption column densities log N$_{H}$ = 22.56 (cm$^{-2}$) and yield characteristic shock temperatures kT_shock ~ 3 keV (T ~ 35 MK).Comment: ApJL, 2006, in press (3 figures, 1 table