Present Risk, Future Risk Or No Risk - Measuring and Predicting Perceptions of Health Risks of a Hazardous Waste Landfill

Given that perceived risk is multidimensional, the authors seek better understanding by focusing on health risks and, more particularly, on their temporality. In this way, they attempt to measure more meaningfully psychological influences on risk perceptions

Advanced Fuels Modeling: Evaluating the Steady-State Performance of Carbide Fuel in Helium-Cooled Reactors Using FRAPCON 3.4

Uranium carbide (UC) has long been considered a potential alternative to uranium dioxide (UO2) fuel, especially in the context of Gen IV gas-cooled reactors. It has shown promise because of its high uranium density, good irradiation stability, and especially high thermal conductivity. Despite its many benefits, UC is known to swell at a rate twice that of UO2. However, the swelling phenomenon is not well understood, and we are limited to a weak empirical understanding of the swelling mechanism. One suggested cladding for UC is silicon carbide (SiC), a ceramic that demonstrates a number of desirable properties. Among them are an increased corrosion resistance, high mechanical strength, and irradiation stability. However, with increased temperatures, SiC exhibits an extremely brittle nature. The brittle behavior of SiC is not fully understood and thus it is unknown how SiC would respond to the added stress of a swelling UC fuel. To better understand the interaction between these advanced materials, each has been implemented into FRAPCON, the preferred fuel performance code of the Nuclear Regulatory Commission (NRC); additionally, the material properties for a helium coolant have been incorporated. The implementation of UC within FRAPCON required the development of material models that described not only the thermophysical properties of UC, such as thermal conductivity and thermal expansion, but also models for the swelling, densification, and fission gas release associated with the fuel\u27s irradiation behavior. This research is intended to supplement ongoing analysis of the performance and behavior of uranium carbide and silicon carbide in a helium-cooled reactor

Non-Equilibrium Electrons and the Sunyaev-Zel'dovich Effect of Galaxy Clusters

We present high-resolution cosmological hydrodynamic simulations of three galaxy clusters employing a two-temperature model for the intracluster medium. We show that electron temperatures in cluster outskirts are significantly lower than the mean gas temperature, because Coulomb collisions are insufficient to keep electrons and ions in thermal equilibrium. This deviation is larger in more massive and less relaxed systems, ranging from 5% in relaxed clusters to 30% for clusters undergoing major mergers. The presence of non-equilibrium electrons leads to significant suppression of the SZE signal at large cluster-centric radius. The suppression of the electron pressure also leads to an underestimate of the hydrostatic mass. Merger-driven, internal shocks may also generate significant populations of non-equilibrium electrons in the cluster core, leading to a 5% bias on the integrated SZ mass proxy during cluster mergers.Comment: 5 pages, 4 figures, Accepted for publication in ApJ

Research Notes: Pollination study on three varieties of soybeans using honeybees and leafcutter bees

Soybeans are known to exhibit a high degree of flower abortion . Schaik and Probst (1958) noted that a large number of flowers open but drop off without ever forming pods . They also noted definite physical differences between shed ovules and viable ones

AGN heating and dissipative processes in galaxy clusters

Recent X-ray observations reveal growing evidence for heating by active galactic nuclei (AGN) in clusters and groups of galaxies. AGN outflows play a crucial role in explaining the riddle of cooling flows and the entropy problem in clusters. Here we study the effect of AGN on the intra-cluster medium in a cosmological simulation using the adaptive mesh refinement FLASH code. We pay particular attention to the effects of conductivity and viscosity on the dissipation of weak shocks generated by the AGN activity in a realistic galaxy cluster. Our 3D simulations demonstrate that both viscous and conductive dissipation play an important role in distributing the mechanical energy injected by the AGN, offsetting radiative cooling and injecting entropy to the gas. These processes are important even when the transport coefficients are at a level of 10% of the Spitzer value. Provided that both conductivity and viscosity are suppressed by a comparable amount, conductive dissipation is likely to dominate over viscous dissipation. Nevertheless, viscous effects may still affect the dynamics of the gas and contribute a significant amount of dissipation compared to radiative cooling. We also present synthetic Chandra observations. We show that the simulated buoyant bubbles inflated by the AGN, and weak shocks associated with them, are detectable with the Chandra observatory.Comment: accepted to ApJ, minor change

The gap between behavioral risk status and willingness to change behavior among healthcare professionals

Aims: This study explored behavioral health risk factors among healthcare professionals and investigated the at-risk persons' satisfaction with their health habits and ongoing change attempts. Methods: The study was based on a cross-sectional web-based survey directed at the nurses and physicians (N = 1233) in Finnish healthcare. Obesity, low physical activity, smoking, and risky alcohol drinking were used as behavioral health risk factors. Results: In all, 70% of the participants had at least one behavioral risk factor, and a significant number of at-risk persons were satisfied with their health habits and had no ongoing change process. Good self-rated health and good self-rated work ability were significantly associated with whether a participant had a behavioral health risk factor. Conclusion: Overall, unhealthy behaviors and a lack of ongoing change attempts were commonly observed among healthcare professionals. Work in healthcare is demanding, and healthy lifestyles can support coping. Thus, healthy lifestyle programs should also be targeted to healthcare professionals.Peer reviewe

A New Treasure Trove at Special Collections

"A New Treasure Trove at Special Collections" showcases recent acquisitions that strengthen our extraordinary holdings in the areas of radical literature, transportation history, film, rare books, culinary history, Islamic manuscripts, children’s literature, and Judaica.http://deepblue.lib.umich.edu/bitstream/2027.42/120254/7/A_New_Treasure_Trove_16.pd

Evidence for chemical equilibration at RHIC

This contribution focuses on the results of statistical model calculations at RHIC energies, including recently available experimental data. Previous calculations of particle yield ratios showed good agreement with measurements at SPS and lower energies, suggesting that the composite system possesses a high degree of chemical equilibrium at freeze-out. The effect of feeddown contamination on the model parameters is discussed, and the sensitivity of individual ratios to the model parameters ($T$, $\mu_B$) is illustrated.Comment: Talk presented at Strange Quarks in Matter 2001, Frankfurt, September 24-29, 2001. Proceedings to be published by J. Phys. G. 8 pages with 4 figure

Why Do Only Some Galaxy Clusters Have Cool Cores?

Flux-limited X-ray samples indicate that about half of rich galaxy clusters have cool cores. Why do only some clusters have cool cores while others do not? In this paper, cosmological N-body + Eulerian hydrodynamic simulations, including radiative cooling and heating, are used to address this question as we examine the formation and evolution of cool core (CC) and non-cool core (NCC) clusters. These adaptive mesh refinement simulations produce both CC and NCC clusters in the same volume. They have a peak resolution of 15.6 h^{-1} kpc within a (256 h^{-1} Mpc)^3 box. Our simulations suggest that there are important evolutionary differences between CC clusters and their NCC counterparts. Many of the numerical CC clusters accreted mass more slowly over time and grew enhanced cool cores via hierarchical mergers; when late major mergers occurred, the CC's survived the collisions. By contrast, NCC clusters experienced major mergers early in their evolution that destroyed embryonic cool cores and produced conditions that prevented CC re-formation. As a result, our simulations predict observationally testable distinctions in the properties of CC and NCC beyond the core regions in clusters. In particular, we find differences between CC versus NCC clusters in the shapes of X-ray surface brightness profiles, between the temperatures and hardness ratios beyond the cores, between the distribution of masses, and between their supercluster environs. It also appears that CC clusters are no closer to hydrostatic equilibrium than NCC clusters, an issue important for precision cosmology measurements.Comment: 17 emulateapj pages, 17 figures, replaced with version accepted to Ap

Cosmological Shock Waves and Their Role in the Large Scale Structure of the Universe

We study the properties of cosmological shock waves identified in high-resolution, N-body/hydrodynamic simulations of a $\Lambda$CDM universe and their role on thermalization of gas and acceleration of nonthermal, cosmic ray (CR) particles. External shocks form around sheets, filaments and knots of mass distribution when the gas in void regions accretes onto them. Within those nonlinear structures, internal shocks are produced by infall of previously shocked gas to filaments and knots, and during subclump mergers, as well as by chaotic flow motions. Due to the low temperature of the accreting gas, the Mach number of external shocks is high, extending up to $M\sim 100$ or higher. In contrast, internal shocks have mostly low Mach numbers. For all shocks of $M\ge1.5$ the mean distance between shock surfaces over the entire computed volume is $\sim4 h^{-1}$ Mpc at present, or $\sim 1 h^{-1}$ Mpc for internal shocks within nonlinear structures. Identified external shocks are more extensive, with their surface area $\sim2$ times larger than that of identified internal shocks at present. However, especially because of higher preshock densities, but also due to higher shock speeds, internal shocks dissipate more energy. Hence, the internal shocks are mainly responsible for gas thermalization as well as CR acceleration. In fact, internal shocks with 2 \la M \la 4 contribute $\sim 1/2$ of the total dissipation. Using a nonlinear diffusive shock acceleration model for CR protons, we estimate the ratio of CR energy to gas thermal energy dissipated at cosmological shock waves to be $\sim1/2$ through the history of the universe. Our result supports scenarios in which the intracluster medium contains energetically significant populations of CRs.Comment: 25 pages, 8 figures including 1 in color. To appear in ApJ (v593 n2 August 20, 2003). Postscript file with full resolution ftp://canopus.chungnam.ac.kr/ryu/cosmoshock.p