Simulations of Evolving or Outbursting Molecular Protostellar Jets

The kinematic and radiative power of molecular jets is expected to change as a protostar undergoes permanent or episodal changes in the rate at which it accretes. We study here the consequences of evolving jet power on the spatial and velocity structure, as well as the fluxes, of molecular emission from the bipolar outflow. We consider a jet of rapidly increasing density and a jet in which the mass input is abruptly cut off. We perform three dimensional hydrodynamic simulations with atomic and molecular cooling and chemistry. In this work, highly collimated and sheared jets are assumed. We find that position-velocity diagrams, velocity-channel maps and the relative H$_2$ and CO fluxes are potentially the best indicators of the evolutionary stage. In particular, the velocity width of the CO lines may prove most reliable although the often-quoted mass-velocity power-law index is probably not. We demonstrate how the relative H$_2$ 1--0 S(1) and CO J=1--0 fluxes evolve and apply this to interpret the phase of several outflows.Comment: 13 pages, 15 figures, Accepted for publication in MNRA

Graph-theoretical conditions for inscribability and Delaunay realizability

We present new graph-theoretical conditions for inscribable polyhedra and Delaunay triangulations. We establish several sufficient conditions of the following general form: if a polyhedron has a sufficiently rich collection of Hamiltonian subgraphs, then it is inscribable. These results have several consequences:All 4-connected polyhedra are inscribable.All simplical polyhedra in which all vertex degrees are between 4 and 6, inclusive, are inscribable.All triangulations without chords or nonfacial triangles are realizable as Delaunay triangulations.We also strengthen some earlier results about matchings in inscribable polyhedra. Specifically, we show that any nonbipartite inscribable polyhedron has a perfect matching containing any specified edge, and that any bipartite inscribable polyhedron has a perfect matching containing any two specified disjoint edges. We give examples showing that these results are best possible

Anticipated and Actual Bequests

This paper uses data on anticipated bequests from two waves of the Health and Retirement Study and the Asset and Health Dynamics of the Oldest Old (AHEAD), and on actual bequests from AHEAD. Actual bequests were measured in exit interviews given by proxy respondents for 774 AHEAD respondents who died between waves 1 and 2. Because the exit interview is representative of the elderly population, the distribution of estate values is quite different from that obtained from estate records, which represent just a wealthy subset of the population. Anticipated bequests were measured by the subjective probability of leaving bequests. Between waves 1 and 2, increases in bequest probabilities were associated with increases in the subjective probability of surviving, increments in household wealth, and widowing while out-of-pocket medical expenses reduced the likelihood of a bequest. By comparing bequest probabilities with baseline wealth we were able to test a main prediction of the life-cycle model, that individuals will dissave at advanced old-age. The AHEAD respondents anticipate substantial dissaving before they die.

The Effects of Subjective Survival on Retirement and Social Security Claiming

According to the life-cycle model, mortality risk will influence both retirement and the desire to annuitize wealth. We estimate the effect of subjective survival probabilities on retirement and on the claiming of Social Security benefits because delayed claiming is equivalent to the purchase of additional Social Security annuities. We find that those with very low subjective probabilities of survival retire earlier and claim earlier than those with higher subjective probabilities, but the effects are not large. The great majority of workers claim as soon as they are eligible.

The Effects of Subjective Survival on Retirement and Social Security Claiming

This research examines the relationship between mortality risk and retirement, and mortality risk and the propensity to take early and reduced Social Security benefits. The main theory for understanding saving behavior is the life-cycle model (LCH). The LCH, however, can be extended to find the optimal retirement age, and can be used to make predictions about the desire to annuitize or equivalently, the desire to delay claiming Social Security benefits. According to the LCH, individuals who expect to be exceptionally long-lived will retire at a later age than individuals who expect to die early because they will need greater wealth to finance more years of retirement. According to almost any model of intertemporal maximization, those who expect to be long lived will see the increase in Social Security benefits that result from retiring at 65 rather than at 62 as being financially advantageous and will, therefore, delay application for benefits until the age of 65. In principle the decision to retire and the decision to take early and reduced benefits are related decisions but not necessarily the same decision. Therefore this study examines both decisions.