Nonelastic nuclear reactions and accompanying gamma radiation

Several aspects of nonelastic nuclear reactions which proceed through the formation of a compound nucleus are dealt with. The full statistical model and the partial statistical model are described and computer programs based on these models are presented along with operating instructions and input and output for sample problems. A theoretical development of the expression for the reaction cross section for the hybrid case which involves a combination of the continuum aspects of the full statistical model with the discrete level aspects of the partial statistical model is presented. Cross sections for level excitation and gamma production by neutron inelastic scattering from the nuclei Al-27, Fe-56, Si-28, and Pb-208 are calculated and compared with avaliable experimental data

The Circumstellar Extinction of Planetary Nebulae

We analyze the dependence of circumstellar extinction on core mass for the brightest planetary nebulae (PNe) in the Magellanic Clouds and M31. We show that in all three galaxies, a statistically significant correlation exists between the two quantities, such that high core mass objects have greater extinction. We model this behavior, and show that the relation is a simple consequence of the greater mass loss and faster evolution times of high mass stars. The relation is important because it provides a natural explanation for the invariance of the [O III] 5007 planetary nebula luminosity function (PNLF) with population age: bright Population I PNe are extinguished below the cutoff of the PNLF. It also explains the counter-intuitive observation that intrinsically luminous Population I PNe often appear fainter than PNe from older, low-mass progenitors.Comment: 12 pages, 2 figures, accepted for ApJ, April 10, 199

The economic value of viewing migratory shorebirds on the Delaware Bay: An application of the single site travel cost model using on-site data

We estimated a count data model of recreation demand using data from an on-site survey of recreational birders who had visited southern Delaware during the month–long annual horseshoe crab/shorebird spring migration in 2008. We analyzed daytrips only. Our estimates from the models ranged from $32 to$142/trip/household or about $131 to$582/season/household (2008$). The variation was due to differences in the value of time. The average household size was 1.66. We found that the valuation results were sensitive to the inclusion of covariates in the model. Our results are useful for damage assessments and benefit–cost analyses where birdwatching is affected.recreational birding, economic value, shorebird migration, onsite sampling, endogenous stratification

Measuring the Recreational Use Value of Migratory Shorebirds on the Delaware Bay

In this article we estimate the recreational use value of household trips to view shorebirds during the annual horseshoe crab/shorebird migration on the Delaware Bay. We use contingent valuation to estimate the value of day and overnight trips separately and use a discrete choice question followed by a payment-card question to generate our valuation data. Our best estimates for the value of a day trip are about $66–$90/household and for an overnight trip about $200–$425/household (2008$). Our data are from the 2008 season, and our average household size is 1.66. For some context, estimates from four other studies report values that vary from$63/trip/person to $442/trip/person. These studies vary in method and specific birding populations studied and mix day and overnight trips.Contingent valuation, discrete choice, bird watching, use value, Environmental Economics and Policy, Public Economics, Research Methods/ Statistical Methods, Q5,

Measuring the recreational use value of migratory shorebirds on the Delaware Bay

In this article we estimate the recreational use value of household trips to view shorebirds during the annual horseshoe crab/shorebird migration on the Delaware Bay. We use contingent valuation to estimate the value of day and overnight trips separately and use a discrete choice question followed by a payment-card question to generate our valuation data. Our best estimates for the value of a day trip are about $66–$90/household and for an overnight trip about $200–$425/household (2008$). Our data are from the 2008 season, and our average household size is 1.66. For some context, estimates from four other studies report values that vary from$63/trip/person to $442/trip/person. These studies vary in method and specific birding populations studied and mix day and overnight trips.Contingent valuation, discrete choice, bird watching, use value

Analysis of Thermal-Protection Systems for Space-Vehicle Cryogenic-Propellant Tanks

Analytical techniques are presented that permit the calculation of heat-transfer rates with various thermal-protection systems for liquid-cryogenic-propellant tanks subjected to on-board, solar, and planetary heat fluxes. The thermal-protection systems considered include using closely spaced reflective surfaces (foils) and widely spaced reflective surfaces (shadow shields), insulation, arrangement of vehicle components, orientation with respect to radiant heating sources, and coatings for the control of solar absorptivity. The effectiveness of these thermal-protection systems in reducing propellant heating is shown both for ideal heat-transfer models and for a simplified hydrogen-oxygen terminal stage on a Mars mission. The proper orientation of a space-vehicle cryogenic tank with respect to the Sun is one of the more beneficial methods of reducing the heating effect of solar flux. Shadow shields can be extremely effective in reducing the propellant heating due to both solar and on-board fluxes. However, low-altitude planet orbits can result in high propellant heating rates due to planetary radiation reflected from the shields. For low-altitude orbits of more than a few days, foils appear to be desirable for all cryogenic-tank surfaces. Foils are also effective in reducing the on-board heating. A choice of shadow shields or foils cannot be made until a particular vehicle and a particular mission are chosen. The thermal conductivity of insulation materials would have to be lower by about two orders of magnitude with no increase in density before insulation could compete with reflective surfaces for use in long-duration thermal protection of cryogenic tanks in space. To demonstrate the application of the methods devised, thermal-protection systems are developed for a hydrogen-oxygen terminal stage for typical Mars missions

Space fusion energy conversion using a field reversed configuration reactor: A new technical approach for space propulsion and power

The fusion energy conversion design approach, the Field Reversed Configuration (FRC) - when burning deuterium and helium-3, offers a new method and concept for space transportation with high energy demanding programs, like the Manned Mars Mission and planetary science outpost missions require. FRC's will increase safety, reduce costs, and enable new missions by providing a high specific power propulsion system from a high performance fusion engine system that can be optimally designed. By using spacecraft powered by FRC's the space program can fulfill High Energy Space Missions (HESM) in a manner not otherwise possible. FRC's can potentially enable the attainment of high payload mass fractions while doing so within shorter flight times

"The Economic Value of Viewing Migratory Shorebirds on the Delaware Bay: An Application of the Single Site Travel Cost Model Using On-Site Data"

Using data from an on-site survey of recreational birders in southern Delaware during the annual horseshoe crab/shorebird spring migration, we estimated four truncated count data models of recreation demand accounting for endogenous stratification due to onsite sampling. We analyzed day-trips only and conducted sensitivity analysis on measurement of the value of time and inclusion of covariates. Our estimates from the models using all covariates were in the range of $40 to$178/trip/household (2008$). The variation is due to differences in the value of time. The average household size is 1.66.Travel-Cost Model, Shorebirds, Valuation

Practical Broad-Band Tuning of Dye Lasers by Solvent Shifting

We have operated a dye laser over a broad wavelength range (593.8-667.0nm) by shifting the dye emission profile with incremental changes of solvent composition. This was accomplished with the laser operating continuously, and only minor adjustment of the laser optics was required. Solvent tuning was facilitated by the critical dependence of the optimum laser wavelength on concentration of the second solvent. Using the known solvent-sensitive laser dye 9-diethylaminobenzo[a]phenoxaz-5-one (DBP), 87% of the tuning range from pure xylenes to pure methanol was covered by cumulative addition of 24 vol. % methanol to the starting xylenes solution. The optimum dye concentration was found to be independent of solvent composition, so that maximum laser power could be maintained by mixing equimolar dye solutions in the two solvents. These results establish the practicality of solvent-tuning as a method of conducting laser experiments over a broad wavelength range