Photometry of the Stingray Nebula (V839 Ara) from 1889-2015 Across the Ionization of Its Planetary Nebula

Up until around 1980, the Stingray was an ordinary B1 post-AGB star, but then it suddenly sprouted bright emission lines like in a planetary nebula (PN), and soon after this the Hubble Space Telescope (HST) discovered a small PN around the star, so apparently we have caught a star in the act of ionizing a PN. We report here on a well-sampled light curve from 1889 to 2015, with unique coverage of the prior century plus the entire duration of the PN formation plus three decades of its aftermath. Surprisingly, the star anticipated the 1980's ionization event by declining from B=10.30 in 1889 to B=10.76 in 1980. Starting in 1980, the central star faded fast, at a rate of 0.20 mag/year, reaching B=14.64 in 1996. This fast fading is apparently caused by the central star shrinking in size. From 1994-2015, the V-band light curve is almost entirely from the flux of two bright [OIII] emission lines from the unresolved nebula, and it shows a consistent decline at a rate of 0.090 mag/year. This steady fading (also seen in the radio and infrared) has a time scale equal to that expected for ordinary recombination within the nebula, immediately after a short-duration ionizing event in the 1980s. We are providing the first direct measure of the rapidly changing luminosity of the central star on both sides of a presumed thermal pulse in 1980, with this providing a strong and critical set of constraints, and these are found to sharply disagree with theoretical models of PN evolution.Comment: ApJ accepted, 54 pages, 4 figures, one long data tabl

The impacts of human resource management practices and pay inequality on workers' job satisfaction

In this paper we investigate the relationship between Human Resource Management (HRM) practices and workers' overall job satisfaction and their satisfaction with pay. To investigate these issues we use British data from the 'Changing Employment Relationships, Employment Contracts and the Future of Work Survey' and the 'Workplace Employment Relations Survey'. After controlling for personal, job and firm characteristics, it is shown that several HRM practices raise workers overall job satisfaction and their satisfaction with pay, but these effects are only significant for non-union members. Satisfaction with pay is higher where performance-related pay and seniority-based reward systems are in place. A pay structure that is perceived to be unequal is associated with a substantial reduction in both non-union members' overall job satisfaction and their satisfaction with pay. Although HRM practices can raise worker job satisfaction, if workplace pay inequality widens as a consequence then non-union members may experience reduced job satisfaction.

Loggerhead turtle (Caretta caretta) nest predation at Cape Range National Park

Most of the existing sea turtle populations worldwide are in decline. In particular, loggerhead turtles (Caretta caretta) are listed as endangered and loggerhead nesting populations in Eastern Australia have declined by 86% since the 1970s. However, whilst Eastern Australian loggerhead populations have been extensively studied and monitored, not much is known about the Western Australian nesting population

The Effects of Health Shocks on Employment and Health Insurance: The Role of Employer-Provided Health Insurance

We study how men’s dependence on their own employer for health insurance affects labor supply responses and loss of health insurance coverage when faced with a serious health shock. Men with employment-contingent health insurance (ECHI) are more likely to remain working following some kinds of adverse health shocks, and are more likely to lose insurance. With the passage of health care reform, the tendency of men with ECHI as opposed to other sources of insurance to remain employed following a health shock may be diminished, along with the likelihood of losing health insurance.

Phase-space analysis of bosonic spontaneous emission

We present phase-space techniques for the modelling of spontaneous emission in two-level bosonic atoms. The positive-P representation is shown to give a full and complete description and can be further developed to give exact treatments of the interaction of degenerate bosons with the electromagnetic field in a given experimental situation. The Wigner representation, even when truncated at second order, is shown to need a doubling of the phase-space to allow for a positive-definite diffusion matrix in the appropriate Fokker-Planck equation and still fails to agree with the full quantum results of the positive-P representation. We show that quantum statistics and correlations between the ground and excited states affect the dynamics of the emission process, so that it is in general non-exponential.Comment: 16 pages, 6 figure

Computational fluid dynamics: Transition to design applications

The development of aerospace vehicles, over the years, was an evolutionary process in which engineering progress in the aerospace community was based, generally, on prior experience and data bases obtained through wind tunnel and flight testing. Advances in the fundamental understanding of flow physics, wind tunnel and flight test capability, and mathematical insights into the governing flow equations were translated into improved air vehicle design. The modern day field of Computational Fluid Dynamics (CFD) is a continuation of the growth in analytical capability and the digital mathematics needed to solve the more rigorous form of the flow equations. Some of the technical and managerial challenges that result from rapidly developing CFD capabilites, some of the steps being taken by the Fort Worth Division of General Dynamics to meet these challenges, and some of the specific areas of application for high performance air vehicles are presented