Temporal Reliability of Willingness to Pay from the National Survey of Fishing, Hunting, and Wildlife-Associated Recreation

The U.S. Fish and Wildlife Service's National Survey of Fishing, Hunting, and Wildlife Associated Recreation has been a source of information on wildlife-related recreation since 1955. The contingent valuation method has been used to estimate willingness to pay for recreation trips in the 1980, 1985, 1991, 1996 and 2001 surveys. However, relatively little comparative analysis over time has been performed. Similar value elicitation formats were used in the 1991 and 1996 surveys for bass and trout fishing, deer hunting, and nonconsumptive wildlife recreation. We statistically analyze these data to assess the temporal reliability of the willingness to pay. We control for the effects of trip quality and socioeconomic variables and find that willingness to pay is significantly lower in 1996 for each activity. A subtle, but important, change in the 1996 question format may drive the result of lower willingness to pay.

Storage of Fresh Water in Saline Aquifers Using a Well Field.

The computational procedure presented in this disser­ tation should enable the practicing engineer to design well fields for the storage of fresh water in horizontal saline aquifers in which there is no pre-existing ground-water movement. The recovery efficiency of the injection/storage/ retrieval process can now be reliably computed, thus making possible an economic analysis of the process in any speci­ fied area. An economic comparison of the storage of ap­ proximately one billion gallons in a saline aquifer that underlies the New Orleans area was made with the present most feasible alternate--steel tanks. The results favored the saline aquifer storage project by a factor of more than 50 to 1. The validity of the computational procedure was de­ termined by comparing recovery efficiencies obtained from a laboratory-size miniature aquifer (miniaquifer) with re­ covery efficiencies predicted by the computational pro­ cedure. The computational procedure predicted the experi­ mental data within 10 percent for multiple well systems. The predicted recovery efficiencies were invariably lower than the experimentally determined recovery efficiencies. The aquifer parameters that must be determined before the computational procedure can be used are thickness, permeability, porosity, storativ1ty, longitudinal disper­ sivity coefficient, and viscosity and density of the native fluid. Of the parameters mentioned above the longitudinal dispersivity coefficient is the most difficult to obtain. The procedure used in this investigation to determine the longitudinal dispersivity coefficient for the miniaquifer can be readily adapted to field use. In addition to the aquifer parameters, the well field configuration, the operation schedule of the field, the volume of fresh water to be injected, injection rates, probable duration of storage, production rates, and frac­ ture pressure of the upper confining bed must be known in order to make an economic analysis. When fresh water is injected into a horizontal, homogeneous, saline aquifer which has no pre-existing ground-water movement, the two most important factors which determine the amount of usable water that can be recovered are: (1) mixing of the two fluids due to molecular diffu­ sion and convective dispersion, and (2) gravitational seg­ regation of the two fluids due to density difference

Formation of protonium and positronium in atomic collisions

A minimum-norm method has been developed for solving the coupled integro-differential equations describing the scattering of positrons by one-electron targets in which the rearrangement channels for positronium formation have been explicitly included. The minimum-norm method, applied to this application for the first time in this thesis, is an enhancement of a previously reported least-squares method which has enabled the extension to a significantly larger basis consisting of up to 26 states on the direct centre, including pseudostates, and 3 states on the positronium. The method has been applied here to e+-H and e+-He+ scattering; cross-sections have been produced for the latter over a range of energies up to 250 eV. The basis was found to be large enough to produce smooth cross sections and little evidence of pseudoresonance structure was found. The results are the first converged cross sections to be calculated for e+-He+ scattering using the coupled channel approximation. Results for e+-H scattering compare well with the work of other authors. A highly efficient parallel code was developed for solving the largest coupling cases. The results prove the minimum-norm approach to be an accurate and reliable method for large-scale coupled channel calculations involving rearrangement collisions. Also in this thesis, the capture of slow antiprotons by atomic hydrogen and positronium has been simulated by the Classical Trajectory Monte Carlo (CTMC) method. Statistically accurate cross sections for protonium and antihydrogen formation have been obtained and the energy dependence of the process established. Antihydrogen formation from antiproton collisions with positronium in the presence of a laser has also been simulated with the CTMC method and the effects of laser polarisation, frequency and intensity studied. Enhancements of the antihydrogen formation cross section were observed and it is suggested that more sophisticated calculations should be undertake

Experimental Ca I oscillator strengths for the 4p-5s triplet

Context. Transition lines of neutral calcium are observed in the spectra of stellar and substellar objects. In particular, the abundance of α-elements in metal-poor stars can place important constraints on the galactic chemical evolution. Such stellar abundance analyses rely heavily on accurate values for the oscillator strength of the observable transitions. Theoretical oscillator strengths are available for most neutral calcium lines visible in stellar spectra, but there are a limited number of experimental values in the literature. Aims. We present new and improved experimental oscillator strengths for the optical Ca 

Impact of a Dietary Supplement Containing 1,3-Dimethylamylamine on Blood Pressure and Bloodborne Markers of Health: a 10-Week Intervention Study

Background 1,3-dimethylamylamine is a commonly used ingredient within dietary supplements. Our prior work with this agent indicates a transient increase in blood pressure (systolic in particular) following oral ingestion of a single dosage, but no significant increase in resting blood pressure following chronic ingestion. Moreover, intervention studies involving both two and eight weeks of treatment with finished products containing 1,3-dimethylamylamine indicate minimal or no change in bloodborne markers of health. The present study sought to extend these findings by using a 10 -week intervention trial to determine the change in selected markers of health in a sample of men. Methods 25 healthy men were randomly assigned to either a placebo (n = 13) or to a supplement containing 1,3-dimethylamylamine (n = 12) for a period of 10 weeks. Before and after the intervention, resting blood pressure and heart rate were measured, and blood samples were collected for determination of complete blood count, metabolic panel, and lipid panel. Results No significant differences were noted between conditions for blood pressure ( P > 0.05), although systolic blood pressure increased approximately 6 mmHg with the supplement (diastolic blood pressure decreased approximately 4 mmHg). A main effect for time was noted for heart rate ( P = 0.016), with values decreasing from pre to post intervention. There were significant main effects for time for creatinine (increased from pre to post intervention; P = 0.043) and alkaline phosphatase (decreased from pre to post intervention; P = 0.009), with no condition differences noted ( P > 0.05). There was a significant interaction noted for low density lipoprotein cholesterol (LDL-C) ( P = 0.043), with values decreasing in the supplement group from pre to post intervention approximately 7 mg · dL -1 ( P = 0.034). No other effects of significance were noted for bloodborne variables. Conclusion These data indicate that a dietary supplement containing 1,3-dimethylamylamine does not result in a statistically significant increase in resting heart rate or blood pressure (although systolic blood pressure is increased ~6 mmHg with supplement use). The supplement does not negatively impact bloodborne markers of health. Further study is needed involving a longer intervention period, a larger sample size, and additional measures of health and safety

LaMer's 1950 model of particle formation: a review and critical analysis of its classical nucleation and fluctuation theory basis, of competing models and mechanisms for phase-changes and particle formation, and then of its application to silver halide, semiconductor, metal, and metal-oxide nanoparticles

A review is presented of the pioneering 1950 model (V. K. LaMer, R. H. Dinegar, Theory, Production and Mechanism of Formation of Monodispersed Hydrosols, J. Am. Chem. Soc., 1950, 72, 4847-4854) of how monodisperse particles might possibly be formed. The review begins with a look at the basis of the 1950 model in fluctuation and classical nucleation theories. Presented next are the competing phase-change models and then also chemical mechanisms for particle formation available since the 1950 paper, including a little-cited nucleation mechanism that LaMer insightfully wrote in 1952. This review then takes a critical look at the 164 (similar to 8%) of the 192 total (similar to 10%) out of the 1953 papers (as of March 2019) that cite the 1950 model while also providing at least some discussion, analysis, or additional data bearing on the 1950 model postulating "effectively infinite nucleation" and "diffusion-controlled growth". (The other 28 papers out of the 192 total papers describe S-n sol formation were covered in an earlier, Part I review that is cited.) Those 164 papers are broken down into five tables provided in the Supporting Information and are then covered in separate sections in the main text: first 13 papers on silver halide nanoparticles (Table S1) where the single best evidence in support of the 1950 model has been thought to exist; 26 papers on semiconductor nanoparticles (Table S2); then 69 papers on transition-metal nanoparticle formation (Table S3); 39 papers on oxide-based nanoparticles (Table S4); and 17 papers presenting alternative models or mechanisms in comparison to the 1950 model (Table S5). The review focuses on answering the critical question of: do the concepts of "burst/instantaneous nucleation" and "diffusion-controlled growth" have sound, compelling experimental support in the 70 years since the model first appeared and in the 164 papers examined more closely that do more than just cite the 1950 model? A Conclusions section listing sixteen bullet points is provided, as is a final section entitled "A Look Towards the Future" that discusses evolving areas and suggested emphasis points for facilitating future research in particle formation kinetics, mechanism and associated particle syntheses