Specific wavelength colorimeter

A self contained, specific wavelength, single beam colorimeter is described for direct spectrophotometric measurement of the concentration of a given solute in a test sample. An electrical circuit employing a photoconductive cell converts the optical output into a linear, directly readable meter output. The colorimeter is simple to operate and is adapted for use in zero gravity conditions. In a specific application, the colorimeter is designed to analyze the concentration of iodine in potable water carried aboard a space vehicle such as the 4B stage of Skylab

Multicolor Polarimetry of Selected Be Stars: 1995-98

A new polarimeter called AnyPol has been used at Limber Observatory for four years to annually monitor the broadband linear polarization of a sample of bright northern Be stars. This is the fourth report on a program started in 1985 at McDonald Observatory and the first one to come entirely from the new installation. Although no variability was detected at the 3-sigma level during the current reporting period, analysis of the full 13-year data set is beginning to reveal hints of long-term variability that may provide clues for understanding the Be phenomenon.Comment: 25 pages including 17 tables; 17 figures; aaspp4 style; accepted by PAS

Cyclic Variability of the Circumstellar Disc of the Be Star ζ\zeta Tau. II. Testing the 2D Global Disc Oscillation Model

Aims. In this paper we model, in a self-consistent way, polarimetric, photometric, spectrophotometric and interferometric observations of the classical Be star $\zeta$ Tauri. Our primary goal is to conduct a critical quantitative test of the global oscillation scenario. Methods. We have carried out detailed three-dimensional, NLTE radiative transfer calculations using the radiative transfer code HDUST. For the input for the code we have used the most up-to-date research on Be stars to include a physically realistic description for the central star and the circumstellar disc. We adopt a rotationally deformed, gravity darkened central star, surrounded by a disc whose unperturbed state is given by a steady-state viscous decretion disc model. We further assume that disc is in vertical hydrostatic equilibrium. Results. By adopting a viscous decretion disc model for $\zeta$ Tauri and a rigorous solution of the radiative transfer, we have obtained a very good fit of the time-average properties of the disc. This provides strong theoretical evidence that the viscous decretion disc model is the mechanism responsible for disc formation. With the global oscillation model we have successfully fitted spatially resolved VLTI/AMBER observations and the temporal V/R variations of the H$\alpha$ and Br$\gamma$ lines. This result convincingly demonstrates that the oscillation pattern in the disc is a one-armed spiral. Possible model shortcomings, as well as suggestions for future improvements, are also discussed.Comment: 14 pages, 9 figures, accepted to A&

A Search for Intrinsic Polarization in O Stars with Variable Winds

New observations of 9 of the brightest northern O stars have been made with the Breger polarimeter on the 0.9~m telescope at McDonald Observatory and the AnyPol polarimeter on the 0.4~m telescope at Limber Observatory, using the Johnson-Cousins UBVRI broadband filter system. Comparison with earlier measurements shows no clearly defined long-term polarization variability. For all 9 stars the wavelength dependence of the degree of polarization in the optical range can be fit by a normal interstellar polarization law. The polarization position angles are practically constant with wavelength and are consistent with those of neighboring stars. Thus the simplest conclusion is that the polarization of all the program stars is primarily interstellar. The O stars chosen for this study are generally known from ultraviolet and optical spectroscopy to have substantial mass loss rates and variable winds, as well as occasional circumstellar emission. Their lack of intrinsic polarization in comparison with the similar Be stars may be explained by the dominance of radiation as a wind driving force due to higher luminosity, which results in lower density and less rotational flattening in the electron scattering inner envelopes where the polarization is produced. However, time series of polarization measurements taken simultaneously with H-alpha and UV spectroscopy during several coordinated multiwavelength campaigns suggest two cases of possible small-amplitude, periodic short-term polarization variability, and therefore intrinsic polarization, which may be correlated with the more widely recognized spectroscopic variations.Comment: LaTeX2e, 22 pages including 11 tables; 12 separate gif figures; uses aastex.cls preprint package; accepted by The Astronomical Journa

Towards an understanding of the Of?p star HD 191612: optical spectroscopy

We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f?pe-O8fp). The Balmer and HeI lines show strongly variable emission which is highly reproducible on a well-determined 538-d period. Metal lines and HeII absorptions (including many selective emission lines but excluding He II 4686A emission) are essentially constant in line strength, but are variable in velocity, establishing a double-lined binary orbit with P(orb) = 1542d, e=0.45. We conduct a model-atmosphere analysis of the primary, and find that the system is consistent with a O8: giant with a B1: main-sequence secondary. Since the periodic 538-d changes are unrelated to orbital motion, rotational modulation of a magnetically constrained plasma is strongly favoured as the most likely underlying `clock'. An upper limit on the equatorial rotation is consistent with this hypothesis, but is too weak to provide a strong constraint.Comment: Accepted for MNRA

String cavitation formation inside fuel injectors

The formation of vortex or 'string' cavitation has been visualised at pressures up to 2000 bar in an automotive-sized optical diesel fuel injector nozzle. The multi-hole nozzle geometry studied allowed observation of the hole-to-hole vortex interaction and, in particular, that of a bridging vortex in the sac region between the holes. Above a threshold Reynolds number, their formation and appearance during a 2 ms injection event was repeatable and independent of upstream pressure and cavitation number. In addition, two different hole layouts and threedimensional flow simulations have been employed to describe how, the relative positions of adjacent holes influenced the formation and hole-to-hole interaction of the observed string cavitation vortices, with good agreement between the experimental and simulation results being achieved

On the formation of string cavitation inside fuel injectors

The formation of vortex or ‘string’ cavitation has been visualised in the flow upstream of the injection hole inlet of an automotive-sized optical diesel fuel injector nozzle operating at pressures up to 2,000 bar. Three different nozzle geometries and three-dimensional flow simulations have been employed to describe how, for two adjacent nozzle holes, their relative positions influenced the formation and hole-to-hole interaction of the observed string cavitation vortices. Each hole was shown to contain two counter-rotating vortices: the first extending upstream on axis with the nozzle hole into the nozzle sac volume and the second forming a single ‘bridging’ string linked to the adjacent hole. Steady-state and transient fuel injection conditions were shown to produce significantly different nozzle-flow characteristics with regard to the formation and interaction of these vortices in the geometries tested, with good agreement between the experimental and simulation results being achieved. The study further confirms that the visualised vortices do not cavitate themselves but act as carriers of gas-phase components within the injector flow

Long term disc variability in the Be star o Andromedae

We present 18 years of high resolution and S/N H α spectroscopy of the Be shell star o And, obtained between 1985-2002. Spectra taken during late 1985 show a pure photospheric profile, with disc re-formation commencing in 1986; a process that is found to occur over long timescales (103 days). Analysis of the evolution of the properties of the H α shell profile suggest that the disc kinematics are dominated by rotational motion. It has been shown that disc loss in o And occurs "inside out''; we find that the disc also appears to be rebuilt in a similar manner, with disc material gradually diffusing to larger radii. The long timescale for changes in the bulk properties of the disc, domination of rotational over radial velocities and manner of disc loss and formation are all consistent with the predictions of the viscous decretion disc model for Be star discs

Understanding service users’ and therapists’ experiences of pharmacological treatment for sexual preoccupation and/or hypersexuality in incarcerated sex offenders

This research comprises two qualitative studies understanding the experiences of 1) convicted sex offenders voluntarily receiving pharmacological treatment to reduce sexual preoccupation and 2) therapists working with these offenders. The studies form part of a research programme evaluating the use of pharmacological treatment with sexual offenders. In study one, semi-structured interviews were conducted with 13 sexual offenders receiving selective serotonin reuptake inhibitors (SSRIs). In study two, interviews were conducted with eight intervention staff with varying levels of experience of working with offenders taking anti-libidinals. Thematic analysis was used and in study one, two main themes emerged: (i) the impact of the pharmacological treatment on prisoners’ daily functioning; (ii) barriers to compliance/engagement. In study two, three main themes emerged: (i) offenders’ reluctance to engage with pharmacological treatment; (ii) challenges for therapists; (iii) pharmacology: ‘just another piece of the puzzle’. Findings are discussed in relation to practice and future research