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Ex ante analyses of agricultural practices often examine stated preference data, yet response behavior as a potential source of bias is often disregarded. We use survey data to estimate producers’ willingness to rent public land for rotational grazing in Wisconsin and combine it with information on nonrespondents to control for nonresponse and avidity effects. Previous experience with managed grazing and rental decisions influenced who responded as well as their rental intentions. These effects do not produce discernable bias but still encourage attention to this possibility in other ex ante contexts. Land rental determinants and willingness-to-pay estimates are also related to grazing initiatives.
A series of (HfN)1−x(TaN)x, ceramics with x representing the starting powder blend compositions of 0.0, 18.8, 28.1, and 46.7 at.%, have been fabricated by vacuum plasma spraying. During the plasma spraying, the mixture lost approximately 25 at.% nitrogen facilitating the precipitation of metallic and metal-rich nitride phases. These specimens underwent static air oxidation exposure up to 1700 °C. In general, it was found that the addition of tantalum nitrides to the hafnium nitrides resulted in poorer oxidation behavior. However, the 18.8 at.% specimen deviated from this trend and had the lowest observed mass change. This specimen formed a dark-colored oxide scale, indexed as Hf6Ta2O17, which acted as a passivation layer. Within the scale, hafnium oxynitride phases were observed. A transformation pathway in forming these rhombohedral oxynitride phases is proposed by the filling in of oxygen in the light element interstitial locations of the rhombohedral ε-Hf3N2 and ζ-Hf4N3 structures.
An ecological risk assessment (ERA) may be described as ‘a process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors’ (USEPA 1992, 1998). Arguably the most common stressors are chemical contaminants, and regulatory authorities in many countries around the world use ERA schemes to determine whether chemical contaminants are impacting on ecological systems. The USA, the Netherlands, Canada, Australia, New Zealand and the UK have all spent considerable resources developing ERAs for use under their respective regulatory regimes. But, although each country has developed its ERA schemes for its own specific regulatory needs, the approach taken is broadly similar for all ERAs.
The largest programme of work to develop ERA frameworks is that of the United States Environmental Protection Agency (USEPA), which started in the mid 1980s. Typically, the USEPA ERA follows three basic steps: problem formulation, analysis and risk characterization (USEPA 1998). The ERA process has been further adapted for use at EPA Superfund sites, to include eight specific steps, from screening level evaluations to full site investigations and risk management (USEPA 1999). Marking ten years of use in the United States, the USEPA has recently assessed how well the ERA guidelines have worked, identifying strengths and weaknesses (see Dale et al. 2008; Kapustka 2008; Suter & Cormier 2008).
Seeds vary widely in the sensitivity of germination to oxygen (O2) partial pressure, depending upon the species, temperature, dormancy state and physiological status of the seeds. Most analyses of the O2 sensitivity of germination have focused on final germination percentages and estimated the O2 percentage in air that is required to reduce germination to a given percentage (usually 50%). In contrast, we have applied a population-based threshold model utilizing time courses of germination to quantify three parameters related to seed germination sensitivity to O2 availability: the median base (or threshold) O2 percentage, the standard deviation of O2 thresholds among seeds in the population, and an oxygen–time constant that relates O2 percentage to germination timing. The model fits germination responses accurately across a wide range of O2 concentrations. The response to O2 was logarithmic in all cases, with the O2 percentage required for 50% germination ranging from 21% to as low as 0.005%, depending upon the species, the temperature and the seed dormancy level. Modelling indicated that some seeds can adapt to low O2 percentages and shift their thresholds to lower values over time. Lower temperatures decreased the minimum O2 threshold, as did after-ripening. Seed priming generally reduced the oxygen–time constant and increased the standard deviation of germination responses, but had relatively little effect on the O2 sensitivity per se. The population-based threshold model can be used to quantify the O2 sensitivity of seed germination and to predict germination rates and percentages when O2 availability is limiting.
Nutrigenomics is the study of how constituents of the diet interact with genes, and their products, to alter phenotype and, conversely, how genes and their products metabolise these constituents into nutrients, antinutrients, and bioactive compounds. Results from molecular and genetic epidemiological studies indicate that dietary unbalance can alter gene–nutrient interactions in ways that increase the risk of developing chronic disease. The interplay of human genetic variation and environmental factors will make identifying causative genes and nutrients a formidable, but not intractable, challenge. We provide specific recommendations for how to best meet this challenge and discuss the need for new methodologies and the use of comprehensive analyses of nutrient–genotype interactions involving large and diverse populations. The objective of the present paper is to stimulate discourse and collaboration among nutrigenomic researchers and stakeholders, a process that will lead to an increase in global health and wellness by reducing health disparities in developed and developing countries.
Reduced hippocampal volume is a consistently described structural abnormality in schizophrenia but its cause and timing are not known.
To examine the relationship of duration of schizophrenic illness and treatment effects with hippocampal volumes.
Quantitative 1.5 T magnetic resonance imaging brain scans of young male patients in the early stage of schizophrenic illness were compared with those of chronically ill older patients. Scans were also acquired for controls matched to both patient groups for age and handedness. Duration of illness was recorded and severity of symptoms assessed with the Positive and Negative Syndrome Scale.
The patients with schizophrenia had smaller hippocampal volumes than the controls. The volume reduction was larger in older patients than in young, compared with age-matched controls. In the early illness group atypical antipsychotics rather than haloperidol were associated with larger hippocampal volumes even after controlling for differences in illness severity Conclusions The greater reduction of hippocampal volume in people with chronic v. early illness, after controlling for illness severity and age, supports the hypothesis of progressive hippocampal reduction in males with schizophrenia. Atypical antipsychotics early in illness may protect against this.
We investigate the pricing of 4,989 equity IPOs with offer dates between 1981 and 2000. Approximately three-fourths of these IPOs have integer offer prices. Average initial returns for IPOs with integer offer prices are significantly higher (24.5%) than those priced on the fraction of the dollar (8.1%). This result is robust through time and after conditioning for other effects known to influence initial returns. We hypothesize that integer vs. fractional dollar IPOs are the result of negotiations between the issuing firm and underwriter. Under this negotiation hypothesis, the frequency of integer pricing should be an increasing function of the offer price and the degree of uncertainty surrounding the value of the firm. Empirical evidence, supportive of the negotiation hypothesis, is presented.
We examine the extent to which offer prices reflect public information for 3,325 IPOs over the period 1990–1999. We focus primarily on four variables: share overhang, file range amendments, venture capital backing, and previous issue underpricing. We show that 35%–50% of the variation in IPO underpricing can be predicted using public information known before the offer date and therefore conclude that IPO offer prices underadjust to widely available public information to a much greater extent than previously documented.
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