Laser Guide Star Adaptive Optics Integral Field Spectroscopy of a Tightly Collimated Bipolar Jet from the Herbig Ae star LkHa 233

We have used the integral field spectrograph OSIRIS and laser guide star adaptive optics at Keck Observatory to obtain high angular resolution (0.06"), moderate spectral resolution (R ~ 3800) images of the bipolar jet from the Herbig Ae star LkHa 233, seen in near-IR [Fe II] emission at 1.600 & 1.644 microns. This jet is narrow and tightly collimated, with an opening angle of only 9 degrees, and has an average radial velocity of ~ 100 km/s. The jet and counterjet are asymmetric, with the red-shifted jet much clumpier than its counterpart at the angular resolution of our observations. The observed properties are in general similar to jets seen around T Tauri stars, though it has a relatively large mass flux of (1.2e-7 +- 0.3e-7) M_sun/year, near the high end of the observed mass flux range around T Tauri stars. We also spatially resolve an inclined circumstellar disk around LkHa 233, which obscures the star from direct view. By comparison with numerical radiative transfer disk models, we estimate the disk midplane to be inclined i = 65 +- 5 degrees relative to the plane of the sky. Since the star is seen only in scattered light at near-infrared wavelengths, we detect only a small fraction of its intrinsic flux. Because previous estimates of its stellar properties did not account for this, either LkHa 233 must be located closer than the previously believed, or its true luminosity must be greater than previously supposed, consistent with its being a ~4 M_sun star near the stellar birthline.Comment: Accepted for publication in the Ap

Summary of electrical component development for a 400-hertz Brayton energy conversion system

Design, fabrication, and testing of 12-kilowatt inductor alternator, voltage regulator-exciter, and parasitic loading speed controller - summar

Modeling the RXTE light curve of η\eta Carinae from a 3-D SPH simulation of its binary wind collision

The very massive star system $\eta$ Carinae exhibits regular 5.54-year (2024-day) period disruptive events in wavebands ranging from the radio to X-ray. There is a growing consensus that these events likely stem from periastron passage of an (as yet) unseen companion in a highly eccentric ($\epsilon \sim 0.9$) orbit. This paper presents three-dimensional (3-D) Smoothed Particle Hydrodynamics (SPH) simulations of the orbital variation of the binary wind-wind collision, and applies these to modeling the X-ray light curve observed by the Rossi X-ray Timing Explorer (RXTE). By providing a global 3-D model of the phase variation of the density of the interacting winds, the simulations allow computation of the associated variation in X-ray absorption, presumed here to originate from near the apex of the wind-wind interaction cone. We find that the observed RXTE light curve can be readily fit if the observer's line of sight is within this cone along the general direction of apastron. Specifically, the data are well fit by an assumed inclination $i = 45^{\circ}$ for the orbit's polar axis, which is thus consistent with orbital angular momentum being along the inferred polar axis of the Homunculus nebula. The fits also constrain the position angle $\phi$ that an orbital-plane projection makes with the apastron side of the semi-major axis, strongly excluding positions $\phi < 9^{\circ}$ along or to the retrograde side of the axis, with the best fit position given by $\phi = 27^{\circ}$. Overall the results demonstrate the utility of a fully 3-D dynamical model for constraining the geometric and physical properties of this complex colliding-wind binary system.Comment: 5 pages, 4 figures, accepted to MNRAS Letter

Why Do Employees Keep Choosing the Expensive Health Care Plan? An Investigation of the Quality and Logic of Employee Health Care Plan Selections

In 1991, The Dannon Company provided 287 of its employees with a choice of healthcare plans. The new plan was less expensive and designed to fit employees\u27 needs better. Contrary to managerial expectation, three-quarters of employees continued to choose the more expensive plan. To study why this was occurring and to determine if these choices reflected employee mistakes, a cooperative effort was begun between The Dannon Company and Cornell University. This cooperative effort allowed us to investigate this problem using actual employee medical claims. Analysis revealed employees strive not only to minimize costs, but also to avoid risk in their health care plan decisions. Overall, employees with the most significant cost difference chose the plan with the lowest total costs. This effect translated into financial savings for the employees. Employees were better off as a group with the freedom to make their own selections than they would have been if they had been forced into either of the two available health care options. Thus, this study demonstrated that choice is valuable to employees. Implications for Dannon and for future research are discussed

Big Cats Around the Globe: How Communities Around the World Perceive Their Backyard Big Cats

Because of human population growth and activity such as habitat removal, poaching, and anthropogenic climate change, all big cat species populations are on the decline. Conservation of big cats, a group we define as including tigers, lions, mountain lions, jaguars, leopards, snow leopards and cheetahs, is crucial to the health of ecosystems worldwide as these apex predators have an effect on many other species their environment. As human settlements and big cat habitats often overlap, instances of conflict are on the rise, sometimes at the coast of people living near big cats. As such, local acceptance of big cats on the landscape is fundamental to the success of in-situ conservation. Here, we explore this issue by conducting a systematic literature review of local perceptions of big cat species. We searched for articles that quantitatively measured local perceptions of big cats. Our criteria took us from an original database of 1,328 articles, but dwindled to only 45 articles (asking 14,253 locals) that fit our rigorous criteria. We normalized the data in each article to derive overall perceptions of big cats. Generally, we found that locals hold neutral or slightly positive perceptions of big cats. Livestock owners have more negative perceptions of big cats compared to non-livestock owners. Geographically, there are large portions of big cat ranges where no research on local perceptions of big cats exist. This is the first time a systematic literature review of this kind has been done on such a charismatic set of mega-fauna

Motor-starting characteristics of two inductor alternators

Motor starting characteristics of two inductor alternator

Monitoring power-law creep using the failure forecast method

Creep is considered to be the life limiting damage mechanism in many load bearing high temperature components. A range of different parameters determine the creep life of a component, many of which are unlikely to be known to sufficient accuracy to enable satisfactory estimation of remnant life. Instead, the integrity of a component should be established through direct measurement of the response of the component to the operating conditions. Creep deformation is shown to be a positive feedback mechanism; an increase in strain lead s to an increasing strain rate. It has recently been shown that as a consequence of positive feedback the Failure Forecast Method, a generalised framework for predicting time to criticality based on rates of change of damage , may be applied for remnant life calculations. A range of strain rate based assessments have been proposed in the literature but it is proposed that the Failure Forecast Method unifies many of these techniques and provides additional insight into creep behaviour by virtue of the underlying positive feedback. The methodology has been demonstrated using e xperiment data sets that are pertinent to creep in high temperatu re pressure vessels and piping; it is shown that failure times are accurately predicted shortly aft er the minimum creep strain rate