Extended shells around B[e] stars - implications for B[e] star evolution

Aims. The position of B[e] stars in the upper left part of the Hertzsprung-Russell diagram creates a quandary. Are these stars young stars evolving onto the main sequence or old stars that are evolving off of it? Spectral characteristics suggest that B[e] stars can be placed into five subclasses and are not a homogeneous set. Such sub-classification is believed to coincide with varying origins and different evolutions. However, the evolutionary connection of B[e] stars – and notably sgB[e] – to other stars is unclear, particularly to evolved massive stars. We attempt to provide insight into the evolutionary past of B[e] stars. Methods. We performed an Hα narrow-band CCD imaging survey of B[e] stars, in the northern hemisphere. Prior to the current work, no emission-line survey of B[e] stars had yet been made, while only two B[e] stars appeared to have a shell nebula as seen in the Digital Sky Survey. Of nebulae around B[e] stars, only the ring nebula around MWC137 has been previously observed extensively. Results. In this presentation we report the findings from our narrow-band optical imaging survey of the environments of 25 B[e] stars. Of the objects surveyed, 7 show bipolar or uni- polar structures up to 15' across; 5 show faint, large, or filamentary shells; and 2 are compact planetary nebula-type systems. The most spectacular system observed is a large bipolar structure associated with MWC314. Conclusions. The possible links between B[e] stars and other evolved stars, implied by our observations, are investigated

Employer and labour provider perspectives on Eastern European migration to the UK

In a relatively short space of time Eastern Europe has become one of the principal source regions of migrants to the UK and citizens from these states now constitute some of the largest foreign-born populations in the country. This paper focuses on these trends from the perspective of UK employers and labour providers. Three main topics are covered; 1. The function served by East European migrant labour in the UK labour market and how this has changed over time. 2. Employers’ motivations for engaging with East European migrant labour. 3. The migration channels that shape how East European labour is sourced by UK employers. The findings demonstrate how the perspectives and practices of employers and recruiters can play an important role in influencing how East European labour migration flows to the UK are represented and produced

Forms of early walking

Children in the first weeks of independent locomotion display a wide variety of walking forms. The walking forms differ in mechanical strategy and concern with balance. Three extreme walking forms are presented: the Twister, who uses trunk twist, the Faller, who uses gravity, and the Stepper, who remains balanced as much as possible. Each walking form is presented as a ''d-space'', a mathematical format combining continuous and discrete aspects, developed to express the sequence and pattern of a movement without the inappropriate precision of a physical trajectory. The three d-spaces represent analyses of three extreme modes of early walking. They are used to generate the variety of early walking forms and to predict mixtures of mechanical strategies as children mature and converge to more similar walking forms over the first few months of independent locomotion. (C) 1995 Academic Press Limite

The enigmatic young object : Walker 90/V590 Monocerotis

Aims. We assess the evolutionary status of the intriguing object Walker 90/V590 Mon, which is located about 20 arcmin northwest of the Cone Nebula near the center of the open cluster NGC 2264. This object, according to its most recent optical spectral type determination (B7), which we confirmed, is at least 3 mag too faint in V for the cluster distance, but it shows the classical signs of a young pre-main sequence object, such as highly variable H emission, Mg II emission, IR excess, UV continuum, and optical variability. Methods. We analyzed a collection of archival and original data on Walker 90, covering 45 years including photometry, imaging, and spectroscopic data ranging from ultraviolet to near-infrared wavelengths. Results. According to star formation processes, it is expected that, as this object clears its primordial surroundings, it should become optically brighter, show a weakening of its IR excess and present decreasing line emissions. This behavior is supported by our observations and analysis, but timescales are expected to be longer than the one observed here. Based on photometric data secured in 2007, we find Walker 90 at its brightest recorded optical magnitude √(12.47 ± 0.06). We document an evolution in spectral type over the past five decades (from A2/A3 to currently B7 and as early as B4), along with a decrease in the near-infrared K fluxes. From near-infrared VISIR images secured in 2004, Walker 90 appears as a point source placing an upper limit of < 0.1" for its diameter. Evidence of turbulent inflows is found in rapidly changing inverse P-Cygni profiles in the lower Balmer lines, with a broadening of ±400 km s-1 in Hα and a redshifted component in Hβ with a terminal velocity of ~600 km s-1. The measured steep UV continuum fluxes (mimicking a star as early as B4), added to a tentative identification of N V emission, suggest a strong non-photospheric component, typically of fluxes arising from a thermally inhomogeneous accretion disk. We detect a well defined 2200 Å bump, indicative of dense material in the line-of-sight. We conclude that many observational features are explained if W90 is a flared disk system, surrounded by an inclined optically thick accretion disk

The Structural Response and Performance of General Hospitals in a Managed Care Environment

The study purpose is to link hospital structure, represented by each hospital’s professional contingent, service mix, and inpatient capacity; and its environment, characterized by the penetration of managed care enrollees. The secondary purpose is to test the relationship between hospital structural change and subsequent hospital performance. The study employs a non-experimental panel design, with a sample of 1882 community hospitals (service type: general medical and surgical). Environmental variables are measured for the base year 1989. Hospital structural variables are measured for 1989 and 1994, with change variables computed. Performance variables are measured for 1989 and 1995, with change computed for cost measures. Hospital structural change is viewed as a dependent variable related to the environment, as well as an independent variable related to performance. Descriptive data are extracted from the American Hospital Association Annual Survey of Hospitals. Hospital cost performance data are from the Health Care Financing Administration Prospective Payment System Minimum Data Sets. Hospital mortality data for 1989 are from Medicare Hospital Mortality Information. HMO enrollment data are extracted from the Interstudy Edge and aggregated to metropolitan statistical area (MSA) level. Market competition data are from the 1989 Area Resource File. A Herfindahl-Hirschman index (HHI) is calculated for each hospital’s MSA. Analytical hypotheses are tested using ordinary least squares (OLS) technique. Results from Part 1 suggest that where HMO penetration was relatively high, sample hospitals tended to contain growth in their registered nurse (RN) staff between 1989 and 1994. Higher HMO penetration is also associated with more stabilization in occupancy rates, preventive services, and ambulatory workload. In contrast, market competition is associated with changes to a higher Medicare case-mix index (CMI), and increase in ambulatory visits. Results from Part 2 indicate positive associations between increased RN staff and hospital cost growth between 1989 and 1995. Hospitals which did not experience an increased CMI are similarly linked with cost growth. Alternatively, reduction in hospital bedsize is associated with more controlled growth in hospital cost per patient day. Several control variables display noteworthy associations with the variables of interest. Theoretical and management implications for community hospitals are discussed

Variations in Salinity and Temperature on the Flank of an Offshore Louisiana Salt Structure

Sediments located in the vicinity of salt structures in the northern Gulf of Mexico have highly complex structures and fluid dynamics associated with the dissolution and diapirism of salt. Past studies (Lin and Nunn, 1997; Bruno and Hanor, 2003; Richards, 2013) have shown that faults associated with salt structures can act both as migration pathways and barriers to the flow of formation waters. Bruno and Hanor (2003), Steen et al. (2011), and Richards (2013) also demonstrated that lithology was a controlling factor in the flow of formation waters. In this study, two sets of wireline logs, one used in salinity mapping and the other used in temperature mapping, combined with structural interpretations from a 3D seismic volume were used to investigate how faulting and lithology controlled the migration of saline formation waters above a near-shore salt structure in the northern Gulf of Mexico. By using the Revil et al. (1998) method of calculating salinity from continuous digital gamma and resistivity logs, along with other parameters, it was shown that sand-dominated intervals had higher salinity values than shaly intervals. The calculated salinity curves also demonstrate that salinity is much lower in the pore water of the shale-dominated overpressure zone (\u3c100g/L) than in the overlying sand-dominated zone (100-250 g/L). Two areas were identified where faults offset salinity values, suggesting that faults may impede the flow of formation waters in this region and that some faults are younger than brine migration. Temperature and salinity mapping at two depths (6000 and 1000 ft SSTVD) combined with fault interpretations from seismic showed that faulted regions have elevated temperatures and salinities. This suggests that warmer formation waters are migrating upward along the fault from the deeper overpressured zone into the overlying hydrostatically pressured hypersaline zone, as suggested by Lin and Nunn (1997)

More Options, Fewer Students: Joint Physics and Chemistry Courses at Mount Royal University

Mount Royal University is a new University with only a few majors in the sciences. This limits the number of students interested in chemistry and physics courses and makes it difficult to run advanced courses in these areas. We have responded to this problem by designing joint courses in Thermodynamics, Quantum Mechanics, and Solid State that count for credit as either a chemistry course or a physics course. Students in the courses were interviewed in order to determine whether the difficulty level and balance of topics in the courses was appropriate. This short and tweet will discuss the design decisions and problems with a higher-level multidisciplinary course, as well as some feedback gleaned from student interviews. A newer joint course involving both nuclear science and policy studies will also be described briefly

Spacecraft environments interactions: Protecting against the effects of spacecraft charging

The effects of the natural space environments on spacecraft design, development, and operation are the topic of a series of NASA Reference Publications currently being developed by the Electromagnetics and Environments Branch, Systems Analysis and Integration Laboratory, Marshall Space Flight Center. This primer, second in the series, describes the interactions between a spacecraft and the natural space plasma. Under certain environmental/spacecraft conditions, these interactions result in the phenomenon known as spacecraft charging. It is the focus of this publication to describe the phenomenon of spacecraft charging and its possible adverse effects on spacecraft and to present the key elements of a Spacecraft Charging Effects Protection Plan