The present-day chemical composition of the SMC from UVES spectra of the sharp-lined, B-type dwarf AV 304

High-resolution spectroscopic VLT/UVES observations are presented for the B-type main-sequence star, AV 304, in the Small Magellanic Cloud (SMC). These spectra have been analysed using LTE model-atmosphere techniques, to derive stellar atmospheric parameters and chemical compositions. As AV 304 is located within the hydrogen burning main-sequence band, its chemical composition should reflect that of the SMC interstellar medium (ISM). A detailed line-by-line differential analysis has been undertaken relative to a Galactic comparison star. A general metal deficiency for the a-process elements O, Si & S of -0.43 +/- 0.05 dex is found for AV 304, with iron having a similar underabundance. Oxygen may be relatively over- abundant by similar to0.1 dex and carbon and aluminium underabundant by similar to0.2 dex. A large nitrogen underabundance (of -1.2 dex relative to hydrogen and -0.7 dex relative to iron) is found. This is interpreted in terms of the CNO bi-cycle having been suppressed in the SMC. Furthermore, the large nitrogen deficiency is in excellent agreement with that found for SMC H II regions. Indeed, this represents a first for stellar astrophysics - confirming the low base-line nitrogen composition of the SMC ISM (viz. 12+log(N/H) similar to 6.66 +/- 0.10 dex).

A new look at the pulsating DB white dwarf GD 358: Line-of-sight velocity measurements and constraints on model atmospheres

We report on our findings of the bright, pulsating, helium atmosphere white dwarf GD 358, based on time-resolved optical spectrophotometry. We identify 5 real pulsation modes and at least 6 combination modes at frequencies consistent with those found in previous observations. The measured Doppler shifts from our spectra show variations with amplitudes of up to 5.5 km s-1 at the frequencies inferred from the flux variations. We conclude that these are variations in the line-of-sight velocities associated with the pulsational motion. We use the observed flux and velocity amplitudes and phases to test theoretical predictions within the convective driving framework, and compare these with similar observations of the hydrogen atmosphere white dwarf pulsators (DAVs). The wavelength dependence of the fractional pulsation amplitudes (chromatic amplitudes) allows us to conclude that all five real modes share the same spherical degree, most likely, l=1. This is consistent with previous identifications based solely on photometry. We find that a high signal-to-noise mean spectrum on its own is not enough to determine the atmospheric parameters and that there are small but significant discrepancies between the observations and model atmospheres. The source of these remains to be identified. While we infer Teff =24 kK and log g ~ 8.0 from the mean spectrum, the chromatic amplitudes, which are a measure of the derivative of the flux with respect to the temperature, unambiguously favour a higher effective temperature, 27 kK, which is more in line with independent determinations from ultra-violet spectra.

GD 552: a cataclysmic variable with a brown dwarf companion?

GD 552 is a high proper motion star with the strong, double-peaked emission lines characteristic of the dwarf nova class of cataclysmic variable (CV) star, and yet no outburst has been detected during the past 12yr of monitoring. We present spectroscopy taken with the aim of detecting emission from the mass donor in this system. We fail to do so at a level which allows us to rule out the presence of a near-main-sequence star donor. Given GD 552's orbital period of 103 min, this suggests that it is either a system that has evolved through the ~80-minute orbital period minimum of CV stars and now has a brown dwarf mass donor, or that has formed with a brown dwarf donor in the first place. This model explains the low observed orbital velocity of the white dwarf and GD 552's low luminosity. It is also consistent with the absence of outbursts from the system.

SDSS J150722.30+523039.8: a cataclysmic variable formed directly from a detached white dwarf/brown dwarf binary?

We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J150722.30+523039.8 (hereafter SDSS J1507). This system has an orbital period of 66.61 min, placing it below the observed `period minimum' for cataclysmic variables. We determine the system parameters via a parametrized model of the eclipse fitted to the observed lightcurve by ?2 minimization. We obtain a mass ratio of q = 0.0623 +/- 0.0007 and an orbital inclination . The primary mass is Mw = 0.90 +/- 0.01Msolar. The secondary mass and radius are found to be Mr = 0.056 +/- 0.001Msolar and Rr = 0.096 +/- 0.001Rsolar, respectively. We find a distance to the system of 160 +/- 10pc. The secondary star in SDSS J1507 has a mass substantially below the hydrogen burning limit, making it the second confirmed substellar donor in a cataclysmic variable. The very short orbital period of SDSS J1507 is readily explained if the secondary star is nuclearly evolved, or if SDSS J1507 formed directly from a detached white dwarf/brown dwarf binary. Given the lack of any visible contribution from the secondary star, the very low secondary mass and the low HeI ?6678/Ha emission-line ratio, we argue that SDSS J1507 probably formed directly from a detached white dwarf/brown dwarf binary. If confirmed, SDSS J1507 will be the first such system identified. The implications for binary star evolution, the brown dwarf desert and the common envelope phase are discussed.

A Brown Dwarf Mass Donor in an Accreting Binary

A long-standing and unverified prediction of binary star evolution theory is the existence of a population of white dwarfs accreting from substellar donor stars. Such systems ought to be common, but the difficulty of finding them, combined with the challenge of detecting the donor against the light from accretion, means that no donor star to date has a measured mass below the hydrogen burning limit. We applied a technique that allowed us to reliably measure the mass of the unseen donor star in eclipsing systems. We were able to identify a brown dwarf donor star, with a mass of 0.052 ± 0.002 solar mass. The relatively high mass of the donor star for its orbital period suggests that current evolutionary models may underestimate the radii of brown dwarfs.

Joined Spectral Trees for Scalable SPIHT-Based Multispectral Image Compression

In this paper, the compression of multispectral images is addressed. Such 3-D data are characterized by a high correlation across the spectral components. The efficiency of the state-of-the-art wavelet-based coder 3-D SPIHT is considered. Although the 3-D SPIHT algorithm provides the obvious way to process a multispectral image as a volumetric block and, consequently, maintain the attractive properties exhibited in 2-D (excellent performance, low complexity, and embeddedness of the bit-stream), its 3-D trees structure is shown to be not adequately suited for 3-D wavelet transformed (DWT) multispectral images. The fact that each parent has eight children in the 3-D structure considerably increases the list of insignificant sets (LIS) and the list of insignificant pixels (LIP) since the partitioning of any set produces eight subsets which will be processed similarly during the sorting pass. Thus, a significant portion from the overall bit-budget is wastedly spent to sort insignificant information. Through an investigation based on results analysis, we demonstrate that a straightforward 2-D SPIHT technique, when suitably adjusted to maintain the rate scalability and carried out in the 3-D DWT domain, overcomes this weakness. In addition, a new SPIHT-based scalable multispectral image compression algorithm is used in the initial iterations to exploit the redundancies within each group of two consecutive spectral bands. Numerical experiments on a number of multispectral images have shown that the proposed scheme provides significant improvements over related works.

Fruit and vegetable consumption in older individuals in Northern Ireland: levels and patterns

Low intakes of fruit and vegetables have previously been reported in the older population of Great Britain, particularly among certain socio-demographic groups. Levels and patterns of consumption in the older population of Northern Ireland, however, remain unknown. A representative sample of 1000 members of the older population of Northern Ireland were contacted by telephone to assess average intake of all fruits and vegetables and various demographic details. Data from 426 individuals (representative of the whole population) reported a mean consumption of 4.0 (SD 1-3) and 4.1 (SD 1-3) portions of fruit and vegetables per weekday and per weekend day respectively. Regression analyses revealed greater consumption on weekdays by females (B 0.53; P

The effect of increased dietary fruit and vegetable consumption on endothelial activation, inflammation and oxidative stress in hypertensive volunteers

Background and aims

Public health campaigns recommend increased fruit and vegetable (FV) consumption as an effective means of cardiovascular risk reduction. During an 8 week randomised control trial among hypertensive volunteers, we noted significant improvements in endothelium-dependent vasodilatation with increasing FV consumption. Circulating indices of inflammation, endothelial activation and insulin resistance are often employed as alternative surrogates for systemic arterial health. The responses of several such biomarkers to our previously described FV intervention are reported here.
Methods and results

Hypertensive volunteers were recruited from medical outpatient clinics. After a common 4 week run-in period during which FV consumption was limited to 1 portion per day, participants were randomised to 1, 3 or 6 portions daily for 8 weeks. Venous blood samples for biomarker analyses were collected during the pre and post-intervention vascular assessments. A total of 117 volunteers completed the 12 week study. Intervention-related changes in circulating levels of high sensitivity C-reactive protein (hsCRP), soluble intracellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1) did not differ significantly between FV groups. Similarly, there were no significant between group differences of change in homeostasis model assessment (HOMA) scores.
Conclusions

Despite mediating a significant improvement in acetylcholine induced vasodilatation, increased FV consumption did not affect a calculated measure of insulin resistance or concentrations of the circulating biomarkers measured during this study. Functional indices of arterial health such as endothelium-dependent vasomotion are likely to provide more informative cardiovascular end-points during short-term dietary intervention trials.