NASA TLA workload analysis support. Volume 1: Detailed task scenarios for general aviation and metering and spacing studies

The techniques required to produce and validate six detailed task timeline scenarios for crew workload studies are described. Specific emphasis is given to: general aviation single pilot instrument flight rules operations in a high density traffic area; fixed path metering and spacing operations; and comparative workload operation between the forward and aft-flight decks of the NASA terminal control vehicle. The validation efforts also provide a cursory examination of the resultant demand workload based on the operating procedures depicted in the detailed task scenarios

The Decline and Rise of Interstate Migration in the United States: Evidence from the IPUMS, 1850-1990

We examine evidence on trends in interstate migration over the past 150 years, using data from the Integrated Public Use Microdata Series of the U.S. Census (IPUMS). Two measures of migration are calculated. The first considers an individual to have moved if she is residing in a state different from her state of birth. The second considers a family to have moved if it is residing in a state different from the state of birth of one of its young children. The latter measure allows us estimate the timing of moves more accurately. Our results suggest that overall migration propensities have followed a U-shaped trend since 1850, falling until around 1900 and then rising until around 1970. We examine variation in the propensity to make an interstate move by age, sex, race, nativity, region of origin, family structure, and education. Counterfactuals based on probit estimates of the propensity to migrate suggest that the rise in migration of families since 1900 is largely attributable to increased educational attainment. The decline of interstate migration in the late nineteenth century remains to be explained.

NASA TLA workload analysis support. Volume 3: FFD autopilot scenario validation data

The data used to validate a seven time line analysis of forward flight deck autopilot mode for the pilot and copilot for NASA B737 terminal configured vehicle are presented. Demand workloads are given in two forms: workload histograms and workload summaries (bar graphs). A report showing task length and task interaction is also presented

NASA TLA workload analysis support. Volume 2: Metering and spacing studies validation data

Four sets of graphic reports--one for each of the metering and spacing scenarios--are presented. The complete data file from which the reports were generated is also given. The data was used to validate the detail task of both the pilot and copilot for four metering and spacing scenarios. The output presents two measures of demand workload and a report showing task length and task interaction

Sex allocation in mound-building ants: The roles of resources and queen replenishment

Social Hymenoptera have become key organisms for tests of sex-ratio theory. We assess the role of resources for explaining sex-ratio variation in a highly male-biased population of the ant Formica exsecta. Key predictions of two of the three leading hypotheses invoking an effect of resource availability on sex ratios in social insects are not upheld. One prediction of the multifaceted parental-investment hypothesis is that colonies with greater brood production will rear a greater proportion of their diploid offspring as reproductive females (gynes), rather than workers, This study shows the positive correlation between female-biased sex ratio and the production of brood by female-producing colonies was not the outcome of a trade-off in the production of workers vs. gynes. The main prediction of the constant-female hypothesis is that investment in gynes should be constant. We found extreme variation among colonies in the number of gynes produced. By contrast, all the predictions of the queen-replenishment hypothesis were supported. The queen-replenishment hypothesis predicts that colonies produce gynes only when queen number is so low that colony production of brood is reduced, or colony survival threatened. We found that, as predicted by this hypothesis, female-producing colonies had fewer queens and produced a lower biomass of brood than male-producing colonies. In contrast, male-producing colonies had lower production per queen, and were more likely to be limited by external resources. This suggests that queen number limits production in female-producing colonies. These data provide evidence of adaptive adjustment of resources to worker, gyne, and male brood

The Sources of Regional Variation in the Severity of the Great Depression: Evidence from U.S. Manufacturing, 1919-1937

The impact of the Great Depression was milder in the South Atlantic states, more severe in the Mountain states, and surprisingly uniform across other regions of the country —despite large diiferences in industrial structure. Employing data on 20 manufacturing industries disaggregated by state, we analyze the relative contributions of industry mix and location to regional variations in economic performance. Industrial composition had a significant impact on employment growth, with regions that concentrated on durable goods or inputs to construction faring worse than others. Long-run trends also mattered, and explain much of the South Atlantic's more favorable performance

Labor-Market Regimes in U.S. Economic History

In much economic analysis it is a convenient fiction to suppose that changes over time in wages and employment are determined by shifts in supply or demand within a more or less competitive market framework Indeed, this framework has been effectively deployed to understand many episodes in American economic history. We argue here, however, that by minimizing the role of labor-market institutions such an approach is incomplete. Drawing on the history of American labor markets over two centuries, we argue that institutions--by which we mean both formal and informal rules that constrain the choices of economic agents--have played a significant role in the determination of wages, employment and other market outcomes over time. The historical evolution of American labor markets can best be characterized as a sequence of relatively stable arrangements punctuated by shifts in institutional regimes. Our narrative emphasizes the importance of understanding the historically contingent role of institutional regimes in conditioning the operation of supply and demand in empirical and policy analysis of the labor market.

What topics of peer interactions correlate with student performance in physics courses?

Research suggests that interacting with more peers about physics course material is correlated with higher student performance. Some studies, however, have demonstrated that different topics of peer interactions may correlate with their performance in different ways, or possibly not at all. In this study, we probe both the peers with whom students interact about their physics course and the particular aspects of the course material about which they interacted in six different introductory physics courses: four lecture courses and two lab courses. Drawing on methods in social network analysis, we replicate prior work demonstrating that, on average, students who interact with more peers in their physics courses have higher final course grades. Expanding on this result, we find that students discuss a wide range of aspects of course material with their peers: concepts, small-group work, assessments, lecture, and homework. We observe that in the lecture courses, interacting with peers about concepts is most strongly correlated with final course grade, with smaller correlations also arising for small-group work and homework. In the lab courses, on the other hand, small-group work is the only interaction topic that significantly correlates with final course grade. We use these findings to discuss how course structures (e.g., grading schemes and weekly course schedules) may shape student interactions and add nuance to prior work by identifying how specific types of student interactions are associated (or not) with performance.Comment: Submitted to European Journal of Physic

Vibronic coupling explains the ultrafast carotenoid-to-bacteriochlorophyll energy transfer in natural and artificial light harvesters

The initial energy transfer in photosynthesis occurs between the light-harvesting pigments and on ultrafast timescales. We analyze the carotenoid to bacteriochlorophyll energy transfer in LH2 Marichromatium purpuratum as well as in an artificial light-harvesting dyad system by using transient grating and two-dimensional electronic spectroscopy with 10 fs time resolution. We find that F\"orster-type models reproduce the experimentally observed 60 fs transfer times, but overestimate coupling constants, which leads to a disagreement with both linear absorption and electronic 2D-spectra. We show that a vibronic model, which treats carotenoid vibrations on both electronic ground and excited state as part of the system's Hamiltonian, reproduces all measured quantities. Importantly, the vibronic model presented here can explain the fast energy transfer rates with only moderate coupling constants, which are in agreement with structure based calculations. Counterintuitively, the vibrational levels on the carotenoid electronic ground state play a central role in the excited state population transfer to bacteriochlorophyll as the resonance between the donor-acceptor energy gap and vibrational ground state energies is the physical basis of the ultrafast energy transfer rates in these systems

The Sources of Regional Variation in the Severity of the Great Depression: Evidence from U.S. Manufacturing, 1919-1937

The severity of the Great Depression in the United States varied by region. Most notably compared with the rest of the country, the South Atlantic states experienced a milder contraction while the Mountain states suffered more severely. The impact of the contraction was more" uniform across other regions of the country--surprisingly so, considering the large regional" differences in industrial structure. We employ data from the biennial Census of Manufactures on" 20 individual manufacturing industries disaggregated by state to analyze the relative" contributions of industry mix and location to regional variations in economic performance during" the period 1919-1937. Industrial composition had a significant impact on regional employment" growth, with regions that concentrated on the production of durable goods or inputs to the" construction sector tending to fare worse than others. Long-run regional trends also played an" important role in regional variation, and explain much of the South Atlantic region's more" favorable performance over the cycle.