Sex Differences in Morbidity and Mortality

Women have worse self-rated health and more hospitalization episodes than men from early adolescence to late middle age, but are less likely to die at each age. We use 14 years of data from the U.S. National Health Interview Survey to examine this paradox. Our results indicate that the difference in self-assessed health between women and men can be entirely explained by differences in the distribution of the chronic conditions they face. Although on average women have worse self-rated health than men, women and men with the same chronic conditions have the same self-rated health. The results for hospital episodes are somewhat different. While the effect of poor health on hospital episodes is the same for men and women, men with respiratory cancer, cardiovascular disease, and bronchitis are more likely to experience hospital episodes than women who suffer from the same chronic conditions, implying that men may experience more severe forms of these conditions. The same is true for mortality. Although the effects of many chronic conditions on the probability of death are the same for women and men, men who report having cardiovascular disease and certain lung disorders are significantly more likely to die than women with these conditions. While some of the gender difference in mortality can be explained by differences in the distribution of chronic conditions, an equally large share can be attributed to the larger adverse effects of these conditions on male mortality. Is smoking the smoking gun? Conditions for which we find excess male hospitalizations and mortality are generally smoking-related.

The Good Old Jackson Car

https://digitalcommons.library.umaine.edu/mmb-vp/1535/thumbnail.jp

The Good Old Jackson Car

https://digitalcommons.library.umaine.edu/mmb-vp/1536/thumbnail.jp

Characterization and Simulation of the Thermoacoustic Instability Behavior of an Advanced, Low Emissions Combustor Prototype

Extensive research is being done toward the development of ultra-low-emissions combustors for aircraft gas turbine engines. However, these combustors have an increased susceptibility to thermoacoustic instabilities. This type of instability was recently observed in an advanced, low emissions combustor prototype installed in a NASA Glenn Research Center test stand. The instability produces pressure oscillations that grow with increasing fuel/air ratio, preventing full power operation. The instability behavior makes the combustor a potentially useful test bed for research into active control methods for combustion instability suppression. The instability behavior was characterized by operating the combustor at various pressures, temperatures, and fuel and air flows representative of operation within an aircraft gas turbine engine. Trends in instability behavior versus operating condition have been identified and documented, and possible explanations for the trends provided. A simulation developed at NASA Glenn captures the observed instability behavior. The physics-based simulation includes the relevant physical features of the combustor and test rig, employs a Sectored 1-D approach, includes simplified reaction equations, and provides time-accurate results. A computationally efficient method is used for area transitions, which decreases run times and allows the simulation to be used for parametric studies, including control method investigations. Simulation results show that the simulation exhibits a self-starting, self-sustained combustion instability and also replicates the experimentally observed instability trends versus operating condition. Future plans are to use the simulation to investigate active control strategies to suppress combustion instabilities and then to experimentally demonstrate active instability suppression with the low emissions combustor prototype, enabling full power, stable operation

Exact results for the Barabasi model of human dynamics

Human activity patterns display a bursty dynamics, with interevent times following a heavy tailed distribution. This behavior has been recently shown to be rooted in the fact that humans assign their active tasks different priorities, a process that can be modeled as a priority queueing system [A.-L. Barabasi, Nature 435, 207 (2005)]. In this work we obtain exact results for the Barabasi model with two tasks, calculating the priority and waiting time distribution of active tasks. We demonstrate that the model has a singular behavior in the extremal dynamics limit, when the highest priority task is selected first. We find that independently of the selection protocol, the average waiting time is smaller or equal to the number of active tasks, and discuss the asymptotic behavior of the waiting time distribution. These results have important implications for understanding complex systems with extremal dynamics.Comment: 4 pages, 4 figures, revte

Branching frequency of Thalassia testudinum (Banks ex K?nig) as an ecological indicator in Florida Bay

The effects of short-shoot density and light availability on rhizome apical meristem density and rhizome branch frequency of Thalassia testudinum were assessed in ten basins in Florida Bay. Core samples for density measurements were obtained from 27-30 stations per basin (over 300 sampling stations total) during the spring 1998 and spring 1999 sampling of the Fish Habitat Assessment Program (FHAP). Rhizome branch frequency (apicals short-shoots-1) was calculated from the core data. Light attenuation, (Kd), estimated from in situ measurements of secchi depths, light profiles of scalar irradiance and Kd values calculated from AVHRR satellite imagery using GIS indicated high light availability and similar optical water quality between the two years. Light attenuation estimates were coupled with USGS bathymetry to determine if there was a significant interaction between light availability and Thalassia densities or rhizome branching. Apical density and short-shoot density were linearly correlated in Florida Bay. Neither apical density nor rhizome branch frequency in 1998 was found to be a good predictor of short-shoot density fluctuations between the spring of 1998 and 1999. Increases in rhizome branch frequencies were only weakly associated with between-year increases in short-shoot densities in this study. Mean rhizome branch frequencies were 0.19 + 0.02, and 0.15 + 0.01, for spring 1998 and spring 1999, respectively. The relatively lower rhizome branching rates observed in Florida Bay in 1998 and 1999 may reflect a density-dependent inhibitory response due to the increase in short-shoot densities following the seagrass die-off from 1990 to 1998 (305 short shoots/m2 in 1990, Durako 1995 versus 590 & 602 short shoots/m2 in this study). There was a positive relationship between percent surface irradiance and short-shoot density. In conclusion, rhizome branch frequency was not a good ecoindicator of light availability or short-shoot density changes in Florida Bay. In contrast, it appears that the effect of short-shoot density, which did respond positively to increasing light availability, may be more important in effecting rhizome branching. Therefore, rhizome branch frequency may be a biological indicator that responds to short-shoot density changes in this non-light limited Bay

Characterization and Simulation of Thermoacoustic Instability in a Low Emissions Combustor Prototype

Extensive research is being done toward the development of ultra-low-emissions combustors for aircraft gas turbine engines. However, these combustors have an increased susceptibility to thermoacoustic instabilities. This type of instability was recently observed in an advanced, low emissions combustor prototype installed in a NASA Glenn Research Center test stand. The instability produces pressure oscillations that grow with increasing fuel/air ratio, preventing full power operation. The instability behavior makes the combustor a potentially useful test bed for research into active control methods for combustion instability suppression. The instability behavior was characterized by operating the combustor at various pressures, temperatures, and fuel and air flows representative of operation within an aircraft gas turbine engine. Trends in instability behavior vs. operating condition have been identified and documented. A simulation developed at NASA Glenn captures the observed instability behavior. The physics-based simulation includes the relevant physical features of the combustor and test rig, employs a Sectored 1-D approach, includes simplified reaction equations, and provides time-accurate results. A computationally efficient method is used for area transitions, which decreases run times and allows the simulation to be used for parametric studies, including control method investigations. Simulation results show that the simulation exhibits a self-starting, self-sustained combustion instability and also replicates the experimentally observed instability trends vs. operating condition. Future plans are to use the simulation to investigate active control strategies to suppress combustion instabilities and then to experimentally demonstrate active instability suppression with the low emissions combustor prototype, enabling full power, stable operation

Pervasive and Personal Learning Environments

This position paper provides some elements about the convergence of institutional and personal learning environments based on Web 2.0 as well as pervasive learning

Long-term power-law fluctuation in Internet traffic

Power-law fluctuation in observed Internet packet flow are discussed. The data is obtained by a multi router traffic grapher (MRTG) system for 9 months. The internet packet flow is analyzed using the detrended fluctuation analysis. By extracting the average daily trend, the data shows clear power-law fluctuations. The exponents of the fluctuation for the incoming and outgoing flow are almost unity. Internet traffic can be understood as a daily periodic flow with power-law fluctuations.Comment: 10 pages, 8 figure