Star Formation Histories of Globular Clusters with Multiple Populations. I. \omega\ Cen, M22, and NGC 1851

There is increasing evidence that some massive globular clusters (GCs) host multiple stellar populations having different heavy element abundances enriched by supernovae. They usually accompany multiple red giant branches (RGBs) in the color-magnitude diagrams (CMDs), and are distinguished from most of the other GCs which display variations only in light element abundances. In order to investigate the star formation histories of these peculiar GCs, we have constructed synthetic CMDs for \omega\ Cen, M22, and NGC 1851. Our models are based on the updated versions of Yonsei-Yale (Y^2) isochrones and horizontal branch (HB) evolutionary tracks which include the cases of enhancements in both helium and the total CNO abundances. To estimate ages and helium abundances of subpopulations in each GC, we have compared our models with the observations on the Hess diagram by employing a \chi^2 minimization technique. We find that metal-rich subpopulations in each of these GCs are also enhanced in helium abundance, and the age differences between the metal-rich and metal-poor subpopulations are fairly small (~0.3-1.7 Gyr), even in the models with the observed variations in the total CNO content. These are required to simultaneously reproduce the observed extended HB and the splits on the main sequence, subgiant branch, and RGB. Our results are consistent with the hypothesis that these GCs are the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.Comment: 40 pages, 16 figures, 4 tables, accepted for publication in Ap

Numerical Investigation of Bubble Movement in Magnetic Nanofluids

Department of Mechanical EngineeringIn this study, the idea to generate electrical energy by using waste heat is suggested. In this idea, the electrical energy can be generated by a magnetic nanofluid and bubble movement. Thus, bubble movement in a magnetic fluid is numerically investigated using the commercial CFD package COMSOL Multiphysics for effective energy generation. The slug characteristics are also investigated because it can be generated by merging each bubble. The level-set method and phase-field method are used to simulate the bubble and slug movement, respectively. For the investigation, EFH1 and EFH3 are selected as working fluidsthey are commercial magnetic fluids manufactured by Ferrotec, and each fluid contains different amounts of magnetic particles. The solvers are validated by comparing the numerical results with previous research studies and experimental data for reliable results. The properties of a fluid can be changed by solid particles if the particles are dispersed in the fluid. These particles can affect the bubble and slug characteristics, such as shape, velocity and wake. Thus, the effect of solid particles is first studied by observing the bubble and slug movement in each magnetic fluid. In the slug investigation, the effects of some parameters are also studied, such as slug length and liquid backflow. The patterns of bubble and slug movement are investigated to predict the effective condition for the energy generation. The effective bubble and slug movements are predicted by evaluating the disturbance of the surrounding magnetic fluid for each flow pattern. A magnetic force can be created, and it can affect any phenomena when the magnetic field is applied to the system. Thus, the effect of the magnetic force is also investigated because the magnetic field should be applied to the system for the electrical energy generation. Finally, the important factor for energy generation is identified by comparing the results.ope

Parton energy loss, saturation, and recombination at BRAHMS

Particle production as observed with the BRAHMS experiment at RHIC is presented. Preliminary baryon/meson ratios and nuclear modification factors at different rapidities will be discussed.Comment: 5 pages, 4 figures, Lake Louise Winter Institute 2005 proceedin

Time-Average Based on Scaling Law in Anomalous Diffusions

To solve the obscureness in measurement brought about from the weak ergodicity breaking appeared in anomalous diffusions we have suggested the time-averaged mean squared displacement (MSD) $\bar{\delta^2 (\tau)}_\tau$ with a integral interval depending linearly on the lag time $\tau$. For the continuous time random walk describing a subdiffusive behavior, we have found that $\bar{\delta^2 (\tau)}_\tau \sim \tau^\gamma$ like that of the ensemble-averaged MSD, which makes it be possible to measure the proper exponent values through time-average in experiments like a single molecule tracking. Also we have found that it is originated from the scaling nature of the MSD at a aging time in anomalous diffusion and confirmed them through numerical results of the other microscopic non-Markovian model showing subdiffusions and superdiffusions with the origin of memory enhancement

Welfare Reform and the Devolution of Decision Making Authority: Changes in Administrative Infrastructure for TANF Implementation

The growing demand for welfare reform represented a devolution of authority from federal administration and enabled state governments to seek ways to improve efficiency and enhance coordination in managing Temporary Assistance for Needy Families (TANF) programs. This shift in authority from the federal government to the state and from the state to county administration empowered interagency collaboration and partnership by expanding organizational linkages between state agencies and local governments, nonprofit, and for-profit agencies for the shared goal of welfare reform.Based on a theoretical framework from New Public Management and governance theories, this research is a small-n comparative case study that explores how the shift in authority emerged at state and local administrative levels, and how states have changed TANF implementation structure in two states: New York and Pennsylvania. It also examines whether the evolution in TANF administrative infrastructure changed the decision making capacity of organizations at state and local welfare jurisdictions and contributed to economic self-sufficiency of TANF clients. The practices of Albany County, New York and Allegheny County, Pennsylvania are examined to explore how county government has implemented TANF programs in partnership with other organizations. This research conducts qualitative, quantitative, and network analysis using data from interviews, surveys, and archival records. It finds that state and county governments in New York and Pennsylvania have not substantially reinvented internal structures, but have expanded the collaboration and partnership with state or county sister agencies and nongovernmental organizations for improving efficiency. The experimentation of New York and Pennsylvania reveals that the involvement of other organizations made a substantial contribution to the decision making capacity of the organizations involved in TANF implementation. It did not yet contribute significantly to an increase in family income for TANF clients. The data also show that a larger proportion of TANF clients left welfare not for employment, but for other reasons. States sought to reduce welfare rolls without a thorough assessment of the impact of participation on the real lives of TANF clients and the reasons why clients left the program until the reauthorization in 2002. TANF clients still face difficult circumstances in becoming economically self-sufficient