A\u27s from Zzzz\u27s? The Causal Effect of School Start Time on the Academic Achievement of Adolescents

Recent sleep research finds that many adolescents are sleep-deprived because of both early school start times and changing sleep patterns during the teen years. This study identifies the causal effect of school start time on academic achievement by using two policy changes in the daily schedule at the US Air Force Academy along with the randomized placement of freshman students to courses and instructors. Results show that starting the school day 50 minutes later has a significant positive effect on student achievement, which is roughly equivalent to raising teacher quality by one standard deviation. (JEL I23, J13

A knowledge-based system design/information tool

The objective of this effort was to develop a Knowledge Capture System (KCS) for the Integrated Test Facility (ITF) at the Dryden Flight Research Facility (DFRF). The DFRF is a NASA Ames Research Center (ARC) facility. This system was used to capture the design and implementation information for NASA's high angle-of-attack research vehicle (HARV), a modified F/A-18A. In particular, the KCS was used to capture specific characteristics of the design of the HARV fly-by-wire (FBW) flight control system (FCS). The KCS utilizes artificial intelligence (AI) knowledge-based system (KBS) technology. The KCS enables the user to capture the following characteristics of automated systems: the system design; the hardware (H/W) design and implementation; the software (S/W) design and implementation; and the utilities (electrical and hydraulic) design and implementation. A generic version of the KCS was developed which can be used to capture the design information for any automated system. The deliverable items for this project consist of the prototype generic KCS and an application, which captures selected design characteristics of the HARV FCS

Evaluating the Long-run Impacts of the 9/11 Terrorist Attacks on US Domestic Airline Travel

Although the US airline industry began 2001 with 24 consecutive profitable quarters, including net profits in 2000 totaling $7.9 billion, the impact of the 9/11 event on the industry was substantial. Whereas the recession that began in early 2001 signaled the end of profitability, the 9/11 terrorist attacks pushed the industry into financial crisis after air travel dropped 20% over the September–December 2001 period compared to the same period in 2000. Given the decline in domestic air travel, an important question is whether the detrimental impact of the attacks was temporary or permanent. That is, did airline travel return to the trend that existed prior to the terrorist attacks? There are theoretical reasons to the believe that it would not. Economists have long viewed travel-mode choices as the outcome of a comparison of opportunity costs and benefits. Thus, anything that permanently raises the opportunity cost of travel, holding benefits constant, should reduce the level of travel volume. To determine whether air travel was permanently reduced, we use econometric and time-series forecasting models to generate a counter-factual forecast of air travel volume in the absence of the terrorist attacks. These dynamic forecasts are compared to actual air travel levels to determine the impact of the terrorist attacks. The findings suggest that domestic air travel did not return to the levels that would have existed in the absence of the attack

Why the median-priced home costs so much

Housing - Prices

Mojave Applied Ecology Notes Fall 2009

USDA working to manage invasive annual grasses, effects of heat and smoke on red brome soil seed bank, how burial depth and substrate affect germination of Sahara mustard and red brome, environmental effects of the southern Nevada groundwater projec

Development of Maize Weevils (Coleoptera: Curculionidae) on Corn Lines Resistant to an Aflatoxin-Producing Fungus

Susceptibility to the maize weevil, Sitophilus zeamais Motschulsky, of corn lines bred for their resistance to the aflatoxin-producing fungus Aspergillus flavus Link ex Fries was determined in the laboratory. Duration of maize weevil development, number of progeny produced, and an index of susceptibility varied with corn line; number of eggs laid and survivorship from egg to adult emergence did not vary with corn line. Soluble carbohydrate, kernel hardness, lipid, soluble nitrogen, free and bound phenolic acids, Kjeldahl protein, and protein/carbohydrate ratio varied with corn line; equilibrium moisture content did not vary with corn line. The only relationship between biological parameters of maize weevils and chemical and physical properties of the stored corn that was predictable was that maize weevil development time increased as lipid content of the corn increased. Susceptibility to A. flavus infection in the field was not correlated with susceptibility to maize weevil population growth or with chemical or physical properties of the stored corn. Predicted weevil population growth over a 180-d period varied 50-fold among the corn lines. Some of the corn lines that are less susceptible to infection by A. flavus in the field were also less susceptible to maize weevils (particularly Mp420 and SC54)

Economic Impacts of Aquatic Vegetation to Angling in Two South Carolina Reservoirs

Angler creel surveys and economic impact models were used to evaluate potential expansion of aquatic vegetation in Lakes Murray and Moultrie, South Carolina. (PDF contains 4 pages.

The Miller Ratio: Is It Really This Simple?

The implication of the study of the Miller Ratio (MR), given the simplicity of its computation, is the possibility of the MR being both a beneficial and easy to use tool for practitioners and regulators to detect for the possibility of earnings management (EM). The previously studied models, particularly the Modified Jones Model (MJM), were not designed to be utilized on a case-by-case basis since they were studied using large samples of firms in an attempt to make generalized statements about the effectiveness of the models. The MR, designed to be utilized on a case-by-case basis, is easily computed. If corporate managers become aware of this simple, easy-to-use tool to detect EM, they may be more cautious about engaging in this activity. Essentially, the MR could assist practitioners and regulators in prioritizing their work load of companies to analyze. It can be another tool in their arsenal to assist them in their regulatory and auditing duties. The simplicity and benefit of the MR is discussed in this study

Upwind MacCormack Euler solver with non-equilibrium chemistry

A computer code, designated UMPIRE, is currently under development to solve the Euler equations in two dimensions with non-equilibrium chemistry. UMPIRE employs an explicit MacCormack algorithm with dissipation introduced via Roe's flux-difference split upwind method. The code also has the capability to employ a point-implicit methodology for flows where stiffness is introduced through the chemical source term. A technique consisting of diagonal sweeps across the computational domain from each corner is presented, which is used to reduce storage and execution requirements. Results depicting one dimensional shock tube flow for both calorically perfect gas and thermally perfect, dissociating nitrogen are presented to verify current capabilities of the program. Also, computational results from a chemical reactor vessel with no fluid dynamic effects are presented to check the chemistry capability and to verify the point implicit strategy