An Hedonic Analysis of the Effects of Lake Water Clarity on New Hampshire Lakefront Properties

Policy makers often face the problem of evaluating how water quality affects a region's economic well-being. Using water clarity as a measure of the degree of eutrophication levels (as a lake becomes inundated with nutrients, water clarity decreases markedly), analysis is performed on sales data collected over a six-year period. Our results indicate that water clarity has a significant effect on prices paid for residential properties. Effects of a one-meter change in clarity on property value are also estimated for an average lake in four real estate market areas in New Hampshire, with effects differing substantially by area. Our findings provide state and local policy makers a measure of the cost of water quality degradation as measured by changes in water clarity, and demonstrate that protecting water quality may have a positive effect on property tax revenues.Resource /Energy Economics and Policy,

Studies on growth rates in pigs and the effect of birth weight

End of project reportThe purpose of this study was to assess some environmental and management factors that affect growth performance on commercial pig units. In experiment 1, a survey was carried out on 22 pig units of known growth performance in south-west Ireland to compare management factors between those showing poor and good growth rates. Low growth rate appears to be due to the cumulative effect of a combination of factors. Experiment 2 was conducted to determine the effects of providing an additional feeder on performance of weaned piglets. No benefits were recorded. Feed consumed from the additional feeder was a replacement for feed that otherwise would have been consumed from the control hopper feeder. Experiment 3 was designed to determine if pig performance and efficiency of growth were affected by weight at birth and at weaning. Lightweight pigs showed inferior growth performance up to the finisher period. Although they compensated some of the inferior growth towards the time of slaughter, they never reached the weights of the heavy birth-weight animals. Males were either significantly heavier or tended to be heavier than females throughout. There was no significant difference between the sexes in the number of days to slaughter. Light and heavy pigs did not differ in the levels of IGF-1 in their blood plasma; however lightweight pigs had significantly lower IgG preweaning. Experiment 4 aimed to determine whether piglet birth weight influenced growth performance, plasma IGF-1 concentrations and muscle fibre characteristics at day 42 of life. At slaughter (Day 42) light birth weight pigs were significantly (P < 0.001) lighter. Plasma IGF-1 concentration was lower by 28% (P=0.06) in light pigs. Muscle fibre cross sectional area and total fibre number were not significantly different between groups. This study should be repeated with bigger numbers

Investigation into diagnostic accuracy of common strategies for automated perfusion motion correction

Respiratory motion is a significant obstacle to the use of quantitative perfusion in clinical practice. Increasingly complex motion correction algorithms are being developed to correct for respiratory motion. However, the impact of these improvements on the final diagnosis of ischemic heart disease has not been evaluated. The aim of this study was to compare the performance of four automated correction methods in terms of their impact on diagnostic accuracy. Three strategies for motion correction were used: (1) independent translation correction for all slices, (2) translation correction for the basal slice with transform propagation to the remaining two slices assuming identical motion in the remaining slices, and (3) rigid correction (translation and rotation) for the basal slice. There were no significant differences in diagnostic accuracy between the manual and automatic motion-corrected datasets (p=0.88). The area under the curve values for manual motion correction and automatic motion correction were 0.93 and 0.92, respectively. All of the automated motion correction methods achieved a comparable diagnostic accuracy to manual correction. This suggests that the simplest automated motion correction method (method 2 with translation transform for basal location and transform propagation to the remaining slices) is a sufficiently complex motion correction method for use in quantitative myocardial perfusion

A Composite HST Spectrum of Quasars

We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z > 0.33. The spectrum covers the wavelengths between 350 and 3000 A in the rest frame. There is a significant steepening of the continuum slope around 1050 A. The continuum between 1050 and 2200 A can be modeled as a power law with alpha = -0.99. For the full sample the power-law index in the extreme ultraviolet (EUV) between 350 and 1050 A is alpha = -1.96. The continuum flux in the wavelengths near the Lyman limit shows a depression of about 10 percent. The break in the power-law index and the slight depression of the continuum near the Lyman limit are features expected in Comptonized accretion-disk spectra.Comment: 10 figures To appear in the February 1, 1997, issue of the Ap.