1,250 research outputs found

    Retirement Shares Plan: A New Model of Risk Sharing

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    Investment risk and longevity risk are borne by the plan sponsor in a defined benefit (DB) plan or by the plan participant in a defined contribution (DC) plan. By contrast, our proposed Retirement Shares Plan (RSP) allocates the longevity risk to the plan sponsor and investment risk to the plan participant. The RSP allows the participant sufficient control over the investment risk to tailor that risk to his specific circumstances. This allocation of risk provides predictable and stable cost to the plan sponsor with little chance of unfunded liabilities. The retiree receives lifetime income and potential inflation protection

    Observations on Actuarial Assumptions and Models for Defined Benefit Pension Plans

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    The goal of this paper is to review and comment on certain aspects of the Pension Insurance Modeling System (PIMS) and certain actuarial assumptions used by PIMS. The apparent stability of the deficit and funding ratio of the PBGC are partially dependent on a continued stream of premium payments from plan sponsors. However, derisking and other trends among retirement plans may change the pattern of premium income. Deterministic projections that supplement the stochastic simulations may enhance the understanding of the current deficit and the projected net claims over the next ten years

    A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522

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    We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538-522. The broad-band spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at 23.0±0.423.0 \pm 0.4 keV and the iron Kα\alpha line at 6.426±0.0086.426 \pm 0.008 keV, as well as placing limits on the strengths of the iron Kβ\beta line and the iron K edge. We track the evolution of the spectral parameters both in time and in luminosity, notably finding a significant positive correlation between cyclotron line energy and luminosity. A dip and spike in the lightcurve is shown to be associated with an order-of-magnitude increase in column density along the line of sight, as well as significant variation in the underlying continuum, implying the accretion of a overdense region of a clumpy stellar wind. We also present a phase-resolved analysis, with most spectral parameters of interest showing significant variation with phase. Notably, both the cyclotron line energy and the iron Kα\alpha line intensity vary significantly with phase, with the iron line intensity significantly out-of-phase with the pulse profile. We discuss the implications of these findings in the context of recent work in the areas of accretion column physics and cyclotron resonance scattering feature formation.Comment: 15 pages, 8 figures. Accepted to ApJ on 2 July 201

    Probing large-scale wind structures in Vela X-1 using off-states with INTEGRAL

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    Vela X-1 is the prototype of the class of wind-fed accreting pulsars in high mass X-ray binaries hosting a supergiant donor. We have analyzed in a systematic way ten years of INTEGRAL data of Vela X-1 (22-50 keV) and we found that when outside the X-ray eclipse, the source undergoes several luminosity drops where the hard X-rays luminosity goes below 3x10^35 erg/s, becoming undetected by INTEGRAL. These drops in the X-ray flux are usually referred to as "off-states" in the literature. We have investigated the distribution of these off-states along the Vela X-1 ~8.9 d orbit, finding that their orbital occurrence displays an asymmetric distribution, with a higher probability to observe an off-state near the pre-eclipse than during the post-eclipse. This asymmetry can be explained by scattering of hard X-rays in a region of ionized wind, able to reduce the source hard X-ray brightness preferentially near eclipse ingress. We associate this ionized large-scale wind structure with the photoionization wake produced by the interaction of the supergiant wind with the X-ray emission from the neutron star. We emphasize that this observational result could be obtained thanks to the accumulation of a decade of INTEGRAL data, with observations covering the whole orbit several times, allowing us to detect an asymmetric pattern in the orbital distribution of off-states in Vela X-1.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society (5 pages, 3 figures). A few typos fixed to match the published versio

    Best Practices for Preschool Music Education: Supporting Music‑Making Throughout the Day

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    Active engagement in music has numerous academic and social benefits for young children and music-making is included in many early childhood standards and preschool curricula. The purpose of this article is to provide quality resources for classroom teachers to use in providing music-making activities for young children, ages 3–5. Although teachers may use music in their classrooms, we provide resources and suggestions for more intentional and extended integration of music-making. Specifically, we identify best practices for preschool music education based on key standards and research as well as with common music pedagogies. We then turn to concrete examples of how teachers can implement these music best practices throughout the entire preschool day. We provide ideas and resources for whole-group activities, focusing on choice-time/center activities and ways to incorporate music activities in other academic areas as these seem to be of greater need for teachers. Finally, we use the stated best practices to review the alignment of a sample of commercially available preschool music curricula as an additional support for teachers

    Polarization surveys of the Galaxy

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    We report on sensitive 21cm and 11cm polarization surveys of the Galactic plane carried out with the Effelsberg 100-m telescope at arcmin angular resolution and some related work. Highly structured polarized emission is seen along the Galactic plane as well as up to very high Galactic latitudes. These observations reflect Faraday effects in the interstellar medium. Polarized foreground and background components along the line of sight, modified by Faraday rotation and depolarization, add in a complex way. The amplitudes of polarized emission features are highly frequency dependent. Small-scale components decrease in amplitude rapidly with increasing frequency. We stress the need for sensitive absolutely calibrated polarization data. These are essential for baseline setting and a correct interpretation of small-scale structures. Absolutely calibrated data are also needed to estimate the high-frequency polarized background. A recent study of polarized emission observed across the local Taurus-Auriga molecular cloud complexes indicates excessive synchrotron emission within a few hundred parsecs. These results suggest that possibly a large fraction of the Galactic high latitude total intensity and polarized emission is of local origin.Comment: 6 pages with 2 PS figures. To be published in "Astrophysical Polarized Backgrounds", eds. S. Cecchini, S. Cortiglioni, R. Sault and C. Sbarra, AIP Conf. Pro

    A 1.4 GHz radio continuum and polarization survey at medium Galactic latitudes: I. Observation and reduction technique

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    A radio continuum survey at medium Galactic latitudes with the Effelsberg 100-m telescope is being carried out at a centre frequency of 1.4 GHz in total power and linear polarization. Areas up to +/- 20 degree of Galactic latitude are now being observed at a sensitivity of 15 mK TB total intensity and 8 mK TB in linear polarization with an angular resolution of 9'35. This paper describes the observing and reduction technique applied which results in absolutely calibrated maps. The methods are illustrated by examples of images from the survey.Comment: 12 pages, 9 figures, Accepted for publication in Astronomy and Astrophysics Supp. Se
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