Apparatus for measuring high-flux heat transfer in radiatively heated compact exchangers

An apparatus is described which can deliver uniform heat flux densities of up to 80 W/sq cm over an area 7.8 cm x 15.2 cm for use in measuring the heat transfer and pressure drop in thin (6 mm or less), compact heat exchangers. Helium gas at flow rates of 0 to 40 kg/h and pressures to 6.9 MPa (1000 psi) is the working fluid. The instrumentation used in the apparatus and the methods for analyzing the data is described. The apparatus will be used initially to test the performance of prototype cooling jackets for the engine struts of the National Aerospace Plane (NASP)

Premium Copayments and the Trade-off between Wages and Employer-Provided Health Insurance

This paper estimates the trade-off between salary and health insurance costs using data on Illinois school teachers between 1991 and 2008 that allow us to address several common empirical challenges in this literature. We find no evidence that changes in teachers’ salaries respond to changes in insurance cost, but teachers paid about 17 percent of the cost of individual health insurance and about 46 percent of the cost of their family members’ plans through increased premium copayments. Our results indicate that premium increases were not associated with commensurate increases in teachers’ valuation of their health insurance plans

The Value of Stock Options To Non-Executive Employees

This study empirically investigates the value employees place on stock options using information from the option exercise behavior of individuals. Employees hold options for another period if the value from holding them and reserving the right to exercise them later is higher than the value of exercising them immediately and collecting a profit equal to the stock price minus the exercise price. This simple model implies the hazard describing employee exercise behavior reveals information about the value to employees of holding options another time period. We show the parameters of this model are identified with data on multiple option grants per employee and we apply this model to the disposition of options received in the 1990s by a sample of over 2000 middle-level managers from a large, established firm outside of manufacturing. Exercise behavior is modeled using a random effects probit model of monthly exercise behavior that is estimated using simulated maximum likelihood estimation methods. Our estimates show there is substantial heterogeneity (observed and unobserved) among employees in the value they place on their options. Our estimates show most employees value their options at a value greater than the option’s Black-Scholes value

New Data for Answering Old Questions Regarding Employee Stock Options

This paper is a description and summary of existing questions and sources of data on stock options with an emphasis on two issues; what are the issues surrounding stock options in the national accounts and what value do employees place on stock options? We survey many existing data sources and outline some of the ways these data can be used to answer questions about the use and impact of employee stock options. The data sources include administrative records from individual firms, survey data of employee perceptions, disclosure filings with the SEC and other government, nonprofit, and international sources. We explore ways to investigate the value of options to employees and their cost to the firms using data on employee exercise decisions. Finally, we discuss the implications of our findings for public policy, the reporting of stock options, and how options are considered in the national accounts

Developing Mathematics Enrichment Workshops for Middle School Students: Philosophy and Sample Workshops

This paper describes our approach to organizing enrichment activities using advanced mathematics topics for diverse audiences of middle school students. We discuss our philosophy and approaches for the structure of these workshops, and then provide sample schedules and resource materials. The workshops cover activities on the following topics: Graphing Calculators; The Chaos Game; Statistical Sampling; CT Scans–the reconstruction problem; The Platonic and Archimedean solids; The Shape of Space; Symmetry; The Binary Number System and the game of NIM; Graph Theory: Proof by Counterexample

Employees’ Choice of Method of Pay

Who chooses what type of pay? The costs and benefits of “flexible” and “cafeteria-style” benefit plans have been discussed for some time. Additionally, many papers have considered the potential costs and benefits of certain types of pay plans (e.g. salaries versus piece rates). In this paper, we use detailed data from a specific firm that annually set the total compensation level for each of its employees but then did something extremely unusual. At the start of each pay year, the firm set an exchange rate for the dollar trade-off between cash pay and stock option pay. It then gave every employee nearly complete choice over the fraction of their pay that was contingent (stock options, bonus) versus guaranteed (salary). There are several empirical findings. There is substantial variation in the choice of contingent pay with some workers choosing almost all base pay and others choosing almost entirely stock options. Younger employees, more experienced employees, higher paid employees, and male employees are more likely to allocate a larger fraction of their total compensation to at-risk alternatives. The robustness of these results varies somewhat depending on the empirical specification and set of covariates used

High School Inputs and Labor Market Outcomes for Male Workers in Their Mid-Thirties: New Data and New Estimates from Wisconsin

This study presents new evidence on the relationship between high school inputs measured at the time male respondents attended high school and the earnings of these same individuals when they were in their mid-thirties. To accomplish this task, we matched newly coded data on the characteristics of Wisconsin high schools in 1954–57 to the Wisconsin Longitudinal Survey. Our estimates show a significant relationship between the characteristics of teachers and the earnings of their students 17 years after graduation. Specifically, a 1 percent increase in the average teacher salary in a district increases the earnings of students by 0.33 percent. The magnitude of this effect is larger than estimates reported in previous research and many times larger than the impact of increasing parents’ income by a comparable amount.

An Unusual Cause of Abdominal Ascites.

Abdominal ascites is most commonly caused by portal hypertension from liver cirrhosis. When present, portal hypertension is associated with an elevated serum-ascites albumin gradient (SAAG) ≥1.1 g/dL. In contrast, a SAAG < 1.1 g/dL suggests malignancy, tuberculosis, pancreatitis, or nephrotic syndrome. Here, we present a case of low SAAG ascites caused by epithelioid peritoneal mesothelioma in a woman with no known liver disease. The diagnosis proved elusive until diagnostic laparoscopy with biopsy was performed