Hedonic Prices and Implicit Markets: Estimating Marginal Willingness to Pay for Differentiated Products Without Instrumental Variables

The hedonic model of Rosen (1974) has become a workhorse for valuing the characteristics of differentiated products despite a number of well-documented econometric problems. For example, Bartik (1987) and Epple (1987) each describe a source of endogeneity in the second stage of Rosen's procedure that has proven difficult to overcome. In this paper, we propose a new approach for recovering the marginal willingness-to-pay function that altogether avoids these endogeneity problems. Applying this estimator to data on large changes in violent crime rates, we find that marginal willingness-to-pay increases by ten cents with each additional violent crime per 100,000 residents.

Longitudinal Predictors of Weight Fluctuation in Men and Women

Previous literature has indicated that weight loss maintenance represents a major challenge in the management of obesity (Brownell, 1995; Stunkard, 1985). The vast majority of individuals who diet lose and regain weight many times, a pattern often referred to as weight cycling. The present study was a prospective attempt to understand weight maintenance and fluctuation in a general/normal sample of individuals (n = 315) and in a select group of weight loss maintainers (n = 19). Participants were assessed twice, six months apart, and weight change over this period was correlated with several predictors assessed at Time 1. These predictors included weight-related demographics, laboratory stress-induced eating, dieting behaviors, depression, and general life stress. This study also examined factors associated with stress-induced eating in the laboratory and the relationship between depression and weight fluctuation. Results from this study suggest that dietary factors and stress-induced eating are associated with weight fluctuations in men and women. Findings from this study also suggest that proximity to ideal weight and social support for weight loss are related to continued weight loss among weight loss maintainers. In addition, these results indicate that increases in depression are associated with weight gain among weight cyclers but not among those without a weight cycling history. This finding occurred in both the general sample of participants as well as among the weight loss maintainers in this study

In vivo, real-time spectroscopic assessment of contusion-based spinal cord injury in a rat model

The goal of this study was to (1) develop a methodology for real-time, in vivo probing of chemical and physical changes in spinal cords and (2) compare these changes in the immediate aftermath of a localized contusive injury to uninjured spinal cords. Raman spectroscopy images were obtained on in vivo spinal cords that had been surgically exposed between T9 and T10. A total of six rats were studied in two n=3 groups of injured and uninjured control animals. A single 830 nm laser of 100 um round spot size was either spatially scanned across the cord or held at a specified location relative to the injury to improve signal to noise in the Raman spectra and explore effects of injury spread on surrounding tissue. Results show that Raman spectra acquired using our methodology show similar spectra to those acquired previously in our lab and with known literature. Principal component analysis was performed and showed three distinct components assigned to static tissue, cerebrospinal fluid, and plasma. Analysis of the Raman spectra suggest that the tissues underwent changes for both the control and injured animals; however, injured cords display Raman features indicative of changes known in spinal cord injury. Based on this work, use of Raman spectroscopy in the future could facilitate better understanding of in vivo injury in spinal cords

Predictable Feeding in Zoos: Research Methods and Behavioural Effects

The behaviour of zoo animals can come to anticipate temporally predictable feeding times. However, there is a lack of consensus over the effects of such routines on behaviour and welfare. Few studies have been published in this area, perhaps in part due to methodological challenges. The current programme of work therefore aimed to extend knowledge on the effect of predictable feeding routines, and to develop a suitable methodology to overcome challenges. Prior to predictable feeding, tigers showed patterns of increased ‘active’ behaviours such as locomotion and pacing, and decreased inactivity. Geckos also showed increased ‘active’ behaviours such as locomotion and ‘stationary but moving head’ prior to predictable, compared to unpredictable feeding times, with significant differences between conditions (RSS = 0.059 and 0.047, p < .05). However, anticipatory patterns were not demonstrated for meerkats, which highlighted that other environmental factors may affect an animal’s response to temporal predictability (such as obtaining other food during the day, or signalled predictability). Studying patterns of behavioural change over time requires long periods of observation which is often not possible for researchers. The current programme of work argues that a measure which can be reliably used by many, relatively untrained observers is necessary to study predictability. The measure of ‘busyness’, a subjective rating of animal behaviour, was tested for reliability and validity. Busyness ratings showed good inter-observer reliability (ICC > .72) and correlated with traditional measures of behaviour. Busyness ratings demonstrated clear patterns related to feeding time and gave a useful compound measure of behavioural change. The use of multiple observers was extended to a citizen science approach, where useful data on anticipation in fish were obtained from aquarium visitors using a touch screen. The current programme of work successfully investigated the effects of predictable feeding routines on patterns of animal behaviour, alongside the development of suitable methods. The qualitative techniques developed here offer potential to increase the data obtained in future research into predictability and many other topics

25(OH)D Status of Elite Athletes with Spinal Cord Injury Relative to Lifestyle Factors

Background: Due to the potential negative impact of low Vitamin D status on performance-related factors and the higher risk of low Vitamin D status in Spinal Cord Injury (SCI) population, research is warranted to determine whether elite athletes with SCI have sufficient 25(OH)D levels. The purposes of this study were to examine: (1) the seasonal proportion of vitamin D insufficiency among elite athletes with SCI; and (2) to determine whether lifestyle factors, SCI lesion level, and muscle performance/function are related to vitamin D status in athletes with SCI. Methods: Thirty-nine members of the Canadian Wheelchair Sports Association, and the US Olympic Committee Paralympic program from outdoor and indoor sports were recruited for this study. Dietary and lifestyle factors, and serum 25(OH)D concentrations were assessed during the autumn (October) and winter (February/March). An independent t-test was used to assess differences in 25(OH)D status among seasons, and indoor and outdoor sports in the autumn and winter, respectively. Results: Mean ± SD serum 25(OH)D concentration was 69.6 ± 19.7 nmol/L (range from 30 to 107.3 nmol/L) and 67.4 ± 25.5 nmol/L (range from 20 to 117.3 nmol/L) in the autumn and winter, respectively. In the autumn, 15.4% of participants were considered vitamin D deficient (25(OH)D \u3c 50 nmol/L) whereas 51.3% had 25(OH)D concentrations that would be considered insufficient (\u3c80 nmol/L). In the winter, 15.4% were deficient while 41% of all participants were considered vitamin D insufficient. Conclusion: A substantial proportion of elite athletes with SCI have insufficient (41%–51%) and deficient (15.4%) 25(OH)D status in the autumn and winter. Furthermore, a seasonal decline in vitamin D status was not observed in the current study

Book Reviews

Paul Sabin, The Bet: Paul Ehrlich, Julian Simon, and Our Gamble over Earth\u27s Future. James Morton Turner, The Promise of Wilderness: American Environmental Politics Since 1964. Adam Rome, The Genius of Earth Day: How a 1970 Teach-In Unexpectedly Made the First Green Generation. Cindy Ott, Pumpkin: The Curious History of an American Icon Mark Fiege, The Republic of Nature: An Environmental History of the United States. Ted Steinberg, Gotham Unbound: The Ecological History of Greater New Yor

Ventricular endocardial tissue geometry affects stimulus threshold and effective refractory period

Background: Understanding the biophysical processes by which electrical stimuli applied to cardiac tissue may result in local activation is important in both the experimental and clinical electrophysiology laboratory environments, as well as for gaining a more in-depth knowledge of the mechanisms of focal-trigger-induced arrhythmias. Previous computational models have predicted that local myocardial tissue architecture alone may significantly modulate tissue excitability, affecting both the local stimulus current required to excite the tissue and the local effective refractory period (ERP). In this work, we present experimental validation of this structural modulation of local tissue excitability on the endocardial tissue surface, use computational models to provide mechanistic understanding of this phenomena in relation to localized changes in electrotonic loading, and demonstrate its implications for the capture of afterdepolarizations. Methods and Results: Experiments on rabbit ventricular wedge preparations showed that endocardial ridges (surfaces of negative mean curvature) had a stimulus capture threshold that was 0.21 ± 0.03 V less than endocardial grooves (surfaces of positive mean curvature) for pairwise comparison (24% reduction, corresponding to 56.2 ± 6.4% of the energy). When stimulated at the minimal stimulus strength for capture, ridge locations showed a shorter ERP than grooves (n = 6, mean pairwise difference 7.4 ± 4.2 ms). When each site was stimulated with identical-strength stimuli, the difference in ERP was further increased (mean pairwise difference 15.8 ± 5.3 ms). Computational bidomain models of highly idealized cylindrical endocardial structures qualitatively agreed with these findings, showing that such changes in excitability are driven by structural modulation in electrotonic loading, quantifying this relationship as a function of surface curvature. Simulations further showed that capture of delayed afterdepolarizations was more likely in trabecular ridges than grooves, driven by this difference in loading. Conclusions: We have demonstrated experimentally and explained mechanistically in computer simulations that the ability to capture tissue on the endocardial surface depends upon the local tissue architecture. These findings have important implications for deepening our understanding of excitability differences related to anatomical structure during stimulus application that may have important applications in the translation of novel experimental optogenetics pacing strategies. The uncovered preferential vulnerability to capture of afterdepolarizations of endocardial ridges, compared to grooves, provides important insight for understanding the mechanisms of focal-trigger-induced arrhythmias

Estimating the Willingness to Pay to Avoid Violent Crime: A Dynamic Approach

The hedonic model, which has been used extensively in the environmental, urban, and real estate literatures, allows for the estimation of the implicit prices of housing and neighborhood attributes (such as square footage, local crime rates, and school quality), as well as households&apos; demand for these nonmarketed amenities. A recognized drawback of the existing hedonic literature is that the models assume a myopic decision maker, i.e., households do not look to the future when choosing where to live today. In this paper, we apply a dynamic hedonic model of demand to estimate the willingness to pay to avoid violent crime. The existing literature, based on Sherwin Rosen&apos;s seminal 1974 paper, estimates households&apos; willingness to pay for a given amenity by taking advantage of the first-order conditions for utility maximization, i.e., by requiring that the marginal change in price associated with an increase in amenity consumption will be equal to the marginal utility associated with the increase. Given that these first-order conditions are derived from a myopic utility maximization problem (and not the maximization of a lifetime utility function), the traditional model will yield unbiased estimates only under the assumption that households are not forward-looking when they purchase a house. Considering the substantial transaction costs that are present in the real estate market (both monetary and psychological), this assumption is unlikely to hold in most real-world applications. Bishop and Murphy (2011) expand the existing hedonic framework by allowing households to be forward-looking with respect to the ame

DOE PLANT-WIDE ENERGY ASSESSMENT RESULTS RELATED TO THE U. S. AUTOMOTIVE INDUSTRY

Forty-nine plant-wide energy efficiency assessments have been undertaken under sponsorship of the U.S. Department of Industrial Technologies Program. Plant-wide assessments are comprehensive, systematic investigations of plant energy efficiency, including plant utility systems and process operations. Assessments in industrial facilities have highlighted opportunities for implementing best practices in industrial energy management, including the adoption of new, energy-efficient technologies and process and equipment improvements. Total annual savings opportunities of $201 million have been identified from the 40 completed assessments. Many of the participating industrial plants have implemented efficiency-improvement projects and already have realized total cost savings of more than$81 million annually. This paper provides an overview of the assessment efforts undertaken and presents a summary of the major energy and cost savings identified to date. The paper also discusses specific results from assessments conducted at four plants in the automotive manufacturing operations and supporting industries. These particular assessments were conducted at facilities that produce engine castings, plastic films used for glass laminates, forged components, and at a body spray painting plant