Public transit, obesity, and medical costs: Assessing the magnitudes

Objective. This paper assesses the potential benefits of increased walking and reduced obesity associated with taking public transit in terms of dollars of medical costs saved and disability avoided. Methods. I conduct a new analysis of a nationally representative U.S. transportation survey to gauge the net increase in walking associated with public transit usage. I translate minutes spent walking into energy expenditures and reductions in obesity prevalence, estimating the present value of costs and disability that may be avoided. Results. Taking public transit is associated with walking 8.3 more minutes per day on average, or an additional 25.7–39.0 kcal. Hill et al. [Hill, J.O., Wyatt, H.R., Reed, G.W., Peters, J.C., 2003. Obesity and the environment: Where do we go from here? Science 299 (5608), 853–855] estimate that an increase in net expenditure of 100 kcal/day can stop the increase in obesity in 90% of the population. Additional walking associated with public transit could save $5500 per person in present value by reducing obesity related medical costs. Savings in quality-adjusted life years could be even higher. Conclusions. While no silver bullet, walking associated with public transit can have a substantial impact on obesity, costs, and well-being. Further research is warranted on the net impact of transit usage on all behaviors, including caloric intake and other types of exercise, and on whether policies can promote transit usage at acceptable cost

Key Equations in the Tuljapurkar-Lee Model of the Social Security System

N/A

Automated algorithm for CBCT-based dose calculations of prostate radiotherapy with bilateral hip prostheses

ABSTRACTOBJECTIVE:Cone beam CT (CBCT) images contain more scatter than a conventional CT image and therefore provide inaccurate Hounsfield units (HUs). Consequently, CBCT images cannot be used directly for radiotherapy dose calculation. The aim of this study is to enable dose calculations to be performed with the use of CBCT images taken during radiotherapy and evaluate the necessity of replanning.METHODS:A patient with prostate cancer with bilateral metallic prosthetic hip replacements was imaged using both CT and CBCT. The multilevel threshold (MLT) algorithm was used to categorize pixel values in the CBCT images into segments of homogeneous HU. The variation in HU with position in the CBCT images was taken into consideration. This segmentation method relies on the operator dividing the CBCT data into a set of volumes where the variation in the relationship between pixel values and HUs is small. An automated MLT algorithm was developed to reduce the operator time associated with the process. An intensity-modulated radiation therapy plan was generated from CT images of the patient. The plan was then copied to the segmented CBCT (sCBCT) data sets with identical settings, and the doses were recalculated and compared.RESULTS:Gamma evaluation showed that the percentage of points in the rectum with γ < 1 (3%/3 mm) were 98.7% and 97.7% in the sCBCT using MLT and the automated MLT algorithms, respectively. Compared with the planning CT (pCT) plan, the MLT algorithm showed −0.46% dose difference with 8 h operator time while the automated MLT algorithm showed −1.3%, which are both considered to be clinically acceptable, when using collapsed cone algorithm.CONCLUSION:The segmentation of CBCT images using the method in this study can be used for dose calculation. For a patient with prostate cancer with bilateral hip prostheses and the associated issues with CT imaging, the MLT algorithms achieved a sufficient dose calculation accuracy that is clinically acceptable. The automated MLT algorithm reduced the operator time associated with implementing the MLT algorithm to achieve clinically acceptable accuracy. This saved time makes the automated MLT algorithm superior and easier to implement in the clinical setting.ADVANCES IN KNOWLEDGE:The MLT algorithm has been extended to the complex example of a patient with bilateral hip prostheses, which with the introduction of automation is feasible for use in adaptive radiotherapy, as an alternative to obtaining a new pCT and reoutlining the structures

U.S. War Costs: Two Parts Temporary, One Part Permanent

Military spending, fatalities, and the destruction of capital, all of which are immediately felt and are often large, are the most overt costs of war. They are also relatively short-lived. The costs of war borne by combatants and their caretakers, which includes families, communities, and the modern welfare state, tend instead to be lifelong. In this paper I show that a significant component of the public costs associated with U.S. wars are long-lived. One third to one half of the total present value of historical war costs have been absorbed by benefits distributed over the remaining life spans of veterans and their dependents. The half-life of these benefits has averaged more than 30 years following the end of hostilities. Estimates of the value of injuries and deaths, while uncertain, suggest that the private burden of war borne by survivors, namely the uncompensated costs of service-related injuries, are also large and long-lived.

The Cost of Uncertain Life Span

A considerable amount of uncertainty surrounds life expectancy, the average length of life. The standard deviation in adult life span is about 15 years in the U.S., and theory and evidence suggest it is costly. I calibrate a utility-theoretic model of preferences over length of life and show that one less year in standard deviation is worth about half a mean life year. Differences in the standard deviation exacerbate cross-sectional differences in life expectancy between the U.S. and other industrialized countries, between rich and poor countries, and among poor countries. But accounting for the cost of life-span variance also appears to amplify recently discovered patterns of convergence in world average human well-being. This is partly for methodological reasons and partly because unconditional variance in human length of life, primarily the component due to infant mortality, has exhibited even more convergence than life expectancy. Sustained reductions in the standard deviation of adult life span, which have largely ceased among advanced nations, accounted for about 15 percent of the total economic value of gains against mortality in the U.S. prior to 1950 but only about 5 percent since.

Trends in World Inequality in Life Span Since 1970

Previous research has revealed much global convergence over the past several decades in life expectancy at birth and in infant mortality, which are closely linked. But trends in the variance of length of life, and in the variance of length of adult life in particular, are less well understood. I examine life-span inequality in a broad, balanced panel of 180 rich and poor countries observed in 1970 and 2000. Convergence in infant mortality has unambiguously reduced world inequality in total length of life starting from birth, but world inequality in length of adult life has remained stagnant. Underlying both of these trends is a growing share of total inequality that is attributable to between-country variation. Especially among developed countries, the absolute level of between-country inequality has risen over time. The sources of widening inequality in length of life between countries remain unclear, but signs point away from trends in income, leaving patterns of knowledge diffusion as a potential candidate.

A Review of War Costs in Iraq and Afghanistan

As of this writing, the wars in Iraq and Afghanistan are in their eighth and tenth years, having accrued nearly a trillion dollars in direct military costs. I review the history of cost forecasts for these ongoing engagements, highlighting the differences across them in scope and accuracy, assessing the methods and practice of cost forecasting, and exploring the implications of the war costs themselves. Besides the unanticipated length and breadth of the military conflicts themselves, a related and equally important component of costs is the life cycle of costs associated with caring for veterans. The forecasts we have of such costs imply high levels of public spending per veteran and very high levels of costs associated with pain and suffering per veteran, as high as 10 to 25 percent of lifetime wealth. I also discuss the methods and motivations associated with war cost forecasts by comparing them with other types of aggregate forecasts, which are prone to similar types of errors. The history of war cost forecasts suggests that increasing their frequency and transparency may improve their usefulness in guiding policy.

Development of a Maxwell X-57 High Lift Motor Reference Design

NASA's all-electric X-57 airplane will utilize 14 electric motors, of which 12 are exclusively for lift augmentation during takeoff and landing. This report covers the design and development process taken to create an open reference model representative of the 12 lift augmenting motors. A combined worst case scenario was used as the design point, which represents the simultaneously occurring worst case aspects of thermal, static stress, electromagnetic, and rotor dynamic conditions. This work also highlights the tightly coupled nature of aerospace electric motor design, requiring constant iteration between all disciplines involved. Further adding to the uniqueness is the cooling method, which is limited to nacelle skin forced convection cooling only, no internal air flow is permitted. The stator outer diameter limit of 156.45 mm greatly impacts the degree of coupling between the electromagnetic design with the thermal analysis. The permanent magnet synchronous motor developed here operates between 385 V and 538 V, at a peak current of 50 A. Detailed electromagnetic, thermal, static load, and rotordynamic analysis was completed for this electric motor; all of which are required for a full design. The rotordynamic analysis took into consideration the motor housing which is designed specifically for this motor. The final electric motor has a mass of 2.34 kg, produces 24.1 Nm of torque with a specific power of 5.56 kW/kg, and has an efficiency of 96.61% at the combined worst case design point

Historic Farmsteads: Preliminary Character Statement - North East region

This document is one of eight Preliminary Character\ud Statements, which provide information on the\ud characteristics of traditional farm buildings in each\ud Region

Health, Income, and the Timing of Education Among Military Retirees

There is a large and robust correlation between adult health and education, part of which likely reflects causality running from education into health. Less clear is whether education obtained later in life is as valuable for health as are earlier years of schooling, or whether education raises health directly or through income or wealth. In this paper, I examine how the timing of educational attainment is important for adult health outcomes, income, and wealth, in order to illuminate these issues. Among military retirees, a subpopulation with large variation in the final level and timing of educational attainment, the health returns to a year of education are diminishing in age at acquisition, a pattern that is less pronounced for income and wealth. In the full sample, the marginal effects on the probability of fair or poor health at age 55 of a year of schooling acquired before, during, and after a roughly 25-year military career are –0.025, –0.016, and –0.006, revealing a decline of about half a percentage point each decade. These results suggest that education improves health outcomes more through fostering a lifelong accumulation of healthy behaviors and habits, and less through augmenting the flow of income or the stock of physical wealth.