Absolute energy curves from late B-type supergiants

Energy curves were determined for six late B and early A type supergiants using IUE data and other ultraviolet and ground based photometry. Effective temperatures and angular diameters are presented as well as estimates of the outflow velocity of the wind. All six stars show a strong Balmer continuum in emission; the Ia supergiants also show an infrared excess which reaches into the visible range. Evidence is found for the presence of a warm mantle as well as for wind from the Ia stars

The Origin of Nonradiative Heating/momentum in Hot Stars

The origin of nonradiative heating and momentum in the atmospheres of stars is studied. The similarities and differences between what occurs in the hot stars and what occurs in cool stars are emphasized. Key points in the theory are reviewed. Areas requiring new study are indicated

Attitudes of advanced Australian medical oncology trainees to rural practice

Aim: To identify the views of medical oncology trainees regarding rural training posts and rural practice overall, and to identify factors that may improve recruitment. Methods: A questionnaire was posted to all advanced oncology trainees in Australia in June 2006. The trainees were questioned on the perceived advantages and disadvantages of rural practice, their experience during previous rural rotations and potential incentives and barriers in recruiting trainees and specialist oncologists to regional and rural centers. Results: There was a 60% response rate. Of all participants 58% had considered rural practice. Those with a rural family background were more likely to have considered rural practice. Attitudes based on responses to listed disadvantages and advantages of rural practice were heterogenous. Lifestyle factors seemed to be of particular importance. Although there were perceived deficiencies in opportunities for professional education in rural oncology rotations, 94% felt their rotation had been a positive experience overall and 62% were more likely to consider a rural career following their rural rotation. Improving locum cover for leave was seen as a potential incentive by 97% trainees. Conclusion: Despite positive attitudes towards rural practice, many barriers exist preventing recruitment of medical oncology trainees to rural areas, in particular lifestyle factors that are difficult to modify. Factors that can be improved include improving access to clinical trials, enabling access to locum cover. Educational opportunities for current rural trainees need to be improved. Further study into potential incentives to enhance rural recruitment is required

On Some General Lacunary Interpolation Problems

AbstractThe object of this paper is to give a unified and complete treatment of these related cases of lacunary interpolation whose special cases can be found scattered in the literature. We consider only the case when the nodes are the zeros ofπn(x) whose derivative is −n(n−1)Pn−1(x), the Legendre polynomial of degreen−1. We find the fundamental polynomials and give the convergence results

Three Corner Sat Constellation - New Mexico State University: Communications, LEO Telecommunications Services, Intersatellite Communications, and Ground Stations and Network

The Three Corner Satellite Constellation is part of the AFOSRlDARP A University Nanosatellite program. This project is a joint effort among Arizona State University (ASU), University of Colorado at Boulder (CU), and New Mexico State University (NMSU). The constellation will consist of three identical nanosatellites, that will demonstrate stereo imaging, innovative command and data handling, and formation flying with RF communications and a possibility of cellular phone communications through LEO telecommunications satellites. To achieve mission objectives, the satellites in the constellation and the ground communications network will need to be designed as a cooperative communications and control network that will allow the satellites in the constellation to form a virtual formation. In this paper, we will present the necessary communications and control architecture for the space segment and the ground segment to form this virtual formation that are NMSU\u27s responsibility in the program. Companion papers describe the respective areas of responsibility of the other partners: ASU -Project Management; Electrical Power System; Structures, Mechanisms, Thermal, and Radiation; Attitude/Orbit Determination and Control; Micropropulsion experiment; and • Integration; CU -- Command & Data Handling, Distributed Operations, Stereoscopic Imaging, Science Operations, and Spacecraft Operations

Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths

We present numerical models of the circumstellar disks of Be stars, and we describe the resulting synthetic H-alpha emission lines and maps of the wavelength-integrated emission flux projected onto the sky. We demonstrate that there are monotonic relationships between the emission line equivalent width and the ratio of the angular half-width at half maximum of the projected disk major axis to the radius of the star. These relationships depend mainly upon the temperatures of the disk and star, the inclination of the disk normal to the line of sight, and the adopted outer boundary for the disk radius. We show that the predicted H-alpha disk radii are consistent with those observed directly through long baseline interferometry of nearby Be stars (especially once allowance is made for disk truncation in binaries and for dilution of the observed H-alpha equivalent width by continuum disk flux in the V-band).Comment: 12 pages, 2 figures, ApJL in pres

Narrative-based computational modelling of the Gp130/JAK/STAT signalling pathway.

BACKGROUND: Appropriately formulated quantitative computational models can support researchers in understanding the dynamic behaviour of biological pathways and support hypothesis formulation and selection by "in silico" experimentation. An obstacle to widespread adoption of this approach is the requirement to formulate a biological pathway as machine executable computer code. We have recently proposed a novel, biologically intuitive, narrative-style modelling language for biologists to formulate the pathway which is then automatically translated into an executable format and is, thus, usable for analysis via existing simulation techniques. RESULTS: Here we use a high-level narrative language in designing a computational model of the gp130/JAK/STAT signalling pathway and show that the model reproduces the dynamic behaviour of the pathway derived by biological observation. We then "experiment" on the model by simulation and sensitivity analysis to define those parameters which dominate the dynamic behaviour of the pathway. The model predicts that nuclear compartmentalisation and phosphorylation status of STAT are key determinants of the pathway and that alternative mechanisms of signal attenuation exert their influence on different timescales. CONCLUSION: The described narrative model of the gp130/JAK/STAT pathway represents an interesting case study showing how, by using this approach, researchers can model biological systems without explicitly dealing with formal notations and mathematical expressions (typically used for biochemical modelling), nevertheless being able to obtain simulation and analysis results. We present the model and the sensitivity analysis results we have obtained, that allow us to identify the parameters which are most sensitive to perturbations. The results, which are shown to be in agreement with existing mathematical models of the gp130/JAK/STAT pathway, serve us as a form of validation of the model and of the approach itself

Constraining Disk Parameters of Be Stars using Narrowband H-alpha Interferometry with the NPOI

Interferometric observations of two well-known Be stars, gamma Cas and phi Per, were collected and analyzed to determine the spatial characteristics of their circumstellar regions. The observations were obtained using the Navy Prototype Optical Interferometer equipped with custom-made narrowband filters. The filters isolate the H-alpha emission line from the nearby continuum radiation, which results in an increased contrast between the interferometric signature due to the H-alpha-emitting circumstellar region and the central star. Because the narrowband filters do not significantly attenuate the continuum radiation at wavelengths 50 nm or more away from the line, the interferometric signal in the H-alpha channel is calibrated with respect to the continuum channels. The observations used in this study represent the highest spatial resolution measurements of the H-alpha-emitting regions of Be stars obtained to date. These observations allow us to demonstrate for the first time that the intensity distribution in the circumstellar region of a Be star cannot be represented by uniform disk or ring-like structures, whereas a Gaussian intensity distribution appears to be fully consistent with our observations.Comment: 23 pages, 14 figures, accepted for publication in A

Low Reynolds number hydrodynamics of asymmetric, oscillating dumbbell pairs

Active dumbbell suspensions constitute one of the simplest model system for collective swimming at low Reynolds number. Generalizing recent work, we derive and analyze stroke-averaged equations of motion that capture the effective hydrodynamic far-field interaction between two oscillating, asymmetric dumbbells in three space dimensions. Time-averaged equations of motion, as those presented in this paper, not only yield a considerable speed-up in numerical simulations, they may also serve as a starting point when deriving continuum equations for the macroscopic dynamics of multi-swimmer suspensions. The specific model discussed here appears to be particularly useful in this context, since it allows one to investigate how the collective macroscopic behavior is affected by changes in the microscopic symmetry of individual swimmers.Comment: 10 pages, to appear in EPJ Special Topic

Determining the Physical Properties of the B Stars I. Methodology and First Results

We describe a new approach to fitting the UV-to-optical spectra of B stars to model atmospheres and present initial results. Using a sample of lightly reddened stars, we demonstrate that the Kurucz model atmospheres can produce excellent fits to either combined low dispersion IUE and optical photometry or HST FOS spectrophotometry, as long as the following conditions are fulfilled: 1) an extended grid of Kurucz models is employed, 2) the IUE NEWSIPS data are placed on the FOS absolute flux system using the Massa & Fitzpatrick (1999) transformation, and 3) all of the model parameters and the effects of interstellar extinction are solved for simultaneously. When these steps are taken, the temperatures, gravities, abundances and microturbulence velocities of lightly reddened B0-A0 V stars are determined to high precision. We also demonstrate that the same procedure can be used to fit the energy distributions of stars which are reddened by any UV extinction curve which can be expressed by the Fitzpatrick & Massa (1990) parameterization scheme. We present an initial set of results and verify our approach through comparisons with angular diameter measurements and the parameters derived for an eclipsing B star binary. We demonstrate that the metallicity derived from the ATLAS 9 fits to main sequence B stars is essentially the Fe abundance. We find that a near zero microturbulence velocity provides the best-fit to all but the hottest or most luminous stars (where it may become a surrogate for atmospheric expansion), and that the use of white dwarfs to calibrate UV spectrophotometry is valid.Comment: 17 pages, including 2 pages of Tables and 6 pages of Figures. Astrophysical Jounral, in pres