The Evolution of Gas Clouds Falling in the Magnetized Galactic Halo: High Velocity Clouds (HVCs) Originated in the Galactic Fountain

In the Galactic fountain scenario, supernovae and/or stellar winds propel material into the Galactic halo. As the material cools, it condenses into clouds. By using FLASH three-dimensional magnetohydrodynamic simulations, we model and study the dynamical evolution of these gas clouds after they form and begin to fall toward the Galactic plane. In our simulations, we assume that the gas clouds form at a height of z=5 kpc above the Galactic midplane, then begin to fall from rest. We investigate how the cloud's evolution, dynamics, and interaction with the interstellar medium (ISM) are affected by the initial mass of the cloud. We find that clouds with sufficiently large initial densities (> 0.1 hydrogen atoms per cc) accelerate sufficiently and maintain sufficiently large column densities as to be observed and identified as high-velocity clouds (HVCs) even if the ISM is weakly magnetized (1.3 micro Gauss). We also investigate the effects of various possible magnetic field configurations. As expected, the ISM's resistance is greatest when the magnetic field is strong and perpendicular to the motion of the cloud. The trajectory of the cloud is guided by the magnetic field lines in cases where the magnetic field is oriented diagonal to the Galactic plane. The model cloud simulations show that the interactions between the cloud and the ISM can be understood via analogy to the shock tube problem which involves shock and rarefaction waves. We also discuss accelerated ambient gas, streamers of material ablated from the clouds, and the cloud's evolution from a sphere-shaped to a disk- or cigar-shaped object.Comment: 46 pages, 16 figures, 3 tables. Accepted for publication in Ap

Fertility, Living Arrangements, Care and Mobility

There are four main interconnecting themes around which the contributions in this book are based. This introductory chapter aims to establish the broad context for the chapters that follow by discussing each of the themes. It does so by setting these themes within the overarching demographic challenge of the twenty-first century – demographic ageing. Each chapter is introduced in the context of the specific theme to which it primarily relates and there is a summary of the data sets used by the contributors to illustrate the wide range of cross-sectional and longitudinal data analysed

The Self-Determination Inventory–Student Report:Confirming the factor structure of a new measure

The Self-Determination Inventory–Student Report (SDI-SR) was developed to address the need in the field for new, theoretically aligned measures of self-determination. The purpose of this study was to establish the most robust and efficient set of items to assess the self-determination of adolescents with and without disabilities on the SDI-SR. Confirmatory factor analysis (CFA), using mean and covariance structures, was used to evaluate the factor structure of the SDI-SR to inform decisions on scale reduction. The items were tested across 20 groups generated by crossing disability (i.e., no disability, learning disability, intellectual disability, autism spectrum disorders, and other health impairment) and race/ethnicity (i.e., White, Black, Hispanic, and Other) groups. A robust set of 21 items that align closely with their associated constructs were identified. These 21 items showed strong measurement properties, including measurement invariance at the item level across the 20 groups. Implications for future research and practice are discussed

The Self-Determination Inventory–Student Report: Confirming the factor structure of a new measure

The Self-Determination Inventory–Student Report (SDI-SR) was developed to address the need in the field for new, theoretically aligned measures of self-determination. The purpose of this study was to establish the most robust and efficient set of items to assess the self-determination of adolescents with and without disabilities on the SDI-SR. Confirmatory factor analysis (CFA), using mean and covariance structures, was used to evaluate the factor structure of the SDI-SR to inform decisions on scale reduction. The items were tested across 20 groups generated by crossing disability (i.e., no disability, learning disability, intellectual disability, autism spectrum disorders, and other health impairment) and race/ethnicity (i.e., White, Black, Hispanic, and Other) groups. A robust set of 21 items that align closely with their associated constructs were identified. These 21 items showed strong measurement properties, including measurement invariance at the item level across the 20 groups. Implications for future research and practice are discussed

The Self-Determination Inventory–Student Report: Confirming the factor structure of a new measure

The Self-Determination Inventory–Student Report (SDI-SR) was developed to address the need in the field for new, theoretically aligned measures of self-determination. The purpose of this study was to establish the most robust and efficient set of items to assess the self-determination of adolescents with and without disabilities on the SDI-SR. Confirmatory factor analysis (CFA), using mean and covariance structures, was used to evaluate the factor structure of the SDI-SR to inform decisions on scale reduction. The items were tested across 20 groups generated by crossing disability (i.e., no disability, learning disability, intellectual disability, autism spectrum disorders, and other health impairment) and race/ethnicity (i.e., White, Black, Hispanic, and Other) groups. A robust set of 21 items that align closely with their associated constructs were identified. These 21 items showed strong measurement properties, including measurement invariance at the item level across the 20 groups. Implications for future research and practice are discussed