The Parkes quarter-Jansky flat-spectrum sample 3. Space density and evolution of QSOs

We analyze the Parkes quarter-Jansky flat-spectrum sample of QSOs in terms of space density, including the redshift distribution, the radio luminosity function, and the evidence for a redshift cutoff. With regard to the luminosity function, we note the strong evolution in space density from the present day to epochs corresponding to redshifts ~ 1. We draw attention to a selection effect due to spread in spectral shape that may have misled other investigators to consider the apparent similarities in shape of luminosity functions in different redshift shells as evidence for luminosity evolution. To examine the evolution at redshifts beyond 3, we develop a model-independent method based on the V_max test using each object to predict expectation densities beyond z=3. With this we show that a diminution in space density at z > 3 is present at a significance level >4 sigma. We identify a severe bias in such determinations from using flux-density measurements at epochs significantly later than that of the finding survey. The form of the diminution is estimated, and is shown to be very similar to that found for QSOs selected in X-ray and optical wavebands. The diminution is also compared with the current estimates of star-formation evolution, with less conclusive results. In summary we suggest that the reionization epoch is little influenced by powerful flat-spectrum QSOs, and that dust obscuration does not play a major role in our view of the QSO population selected at radio, optical or X-ray wavelengths.Comment: 18 pages, 11 figures, accepted 18 Dec 2004, Astron. & Astrophys. The accepted version is expanded to include an analysis of the form of the decline in radio-QSO space density at high redshifts. This is compared with the forms of epoch dependence derived for optically-selected QSOs, for X-ray-selected QSOs, and for star formation rat

The Fallible Phallus: A discourse analysis of male sexuality in a South African men’s interest magazine

This article presents a discourse analysis of the constructions of male sexuality in the South African publication Men’s Health. The focus of the analysis was a series of monthly featured articles on best sexual practices and behaviour. Since the magazine’s content appears to confront men with, on the one hand, the construction of the ideal, potent phallus, and, on the other hand, the fallibility inherent in attempting to live up to this ideal, the overarching discourse in the texts was termed the ‘Fallible Phallus’. By stipulating ideal sexual experiences and then juxtaposing these descriptions with the threat of those moments not occurring, a paradox is created in the texts between the phallic dominance of masculinity and the anxieties and insecurities that may result from sexual failure. The Fallible Phallus discourse is a synthesis of four subsidiary themes derived from the texts, namely the male sexual drive theme, the inadequacies of male sexuality, the rule book of sexual practices, and the problematic nature of female sexuality. In the discussion of these themes, it is suggested that the texts use male sexual performance as a yardstick for assessing level of masculinity

The ASCA spectrum of the z=4.72 blazar, GB 1428+4217

The X-ray luminous quasar GB 1428+4217 at redshift 4.72 has been observed with ASCA. The observed 0.5-10 keV flux is 3.2E-12 erg/s/cm2. We report here on the intrinsic 4-57 keV X-ray spectrum, which is very flat (photon index of 1.29). We find no evidence for flux variability within the ASCA dataset or between it and ROSAT data. We show that the overall spectral energy distribution of GB 1428+4217 is similar to that of lower redshift MeV blazars and present models which fit the available data. The Doppler beaming factor is likely to be at least 8. We speculate on the number density of such high redshift blazars, which must contain rapidly-formed massive black holes.Comment: 5 pages, 3 Postscript figures, to appear in MNRA

VLBI imaging of extremely high redshift quasars at 5 GHz

We present very long baseline interferometry (VLBI) images of ten very high redshift (z>3) quasars at 5 GHz. The sources 0004+139, 0830+101, 0906+041, 0938+119 and 1500+045 were observed in September 1992 using a global VLBI array, while 0046+063, 0243+181, 1338+381, 1428+423 and 1557+032 were observed in October 1996 with the European VLBI Network and Hartebeesthoek, South Africa. Most of the sources are resolved and show asymmetric structure. The sample includes 1428+423, the most distant radio loud quasar known to date (z=4.72). It is barely resolved with an angular resolution of about 2.0*1.4 mas.Comment: Astronomy and Astrophysics, in press, Latex2e, 10 pages, 3 figures (and lots of sub-figures

Magnetism in one-dimensional quantum dot arrays

We employ the density functional Kohn-Sham method in the local spin-density approximation to study the electronic structure and magnetism of quasi one-dimensional periodic arrays of few-electron quantum dots. At small values of the lattice constant, the single dots overlap, forming a non-magnetic quantum wire with nearly homogenous density. As the confinement perpendicular to the wire is increased, i.e. as the wire is squeezed to become more one-dimensional, it undergoes a spin-Peierls transition. Magnetism sets in as the quantum dots are placed further apart. It is determined by the electronic shell filling of the individual quantum dots. At larger values of the lattice constant, the band structure for odd numbers of electrons per dot indicates that the array could support spin-polarized transport and therefore act as a spin filter.Comment: 11 pages, 6 figure

A Synoptic, Multiwavelength Analysis of a Large Quasar Sample

We present variability and multi-wavelength photometric information for the 933 known quasars in the QUEST Variability Survey. These quasars are grouped into variable and non-variable populations based on measured variability confidence levels. In a time-limited synoptic survey, we detect an anti-correlation between redshift and the likelihood of variability. Our comparison of variability likelihood to radio, IR, and X-ray data is consistent with earlier quasar studies. Using already-known quasars as a template, we introduce a light curve morphology algorithm that provides an efficient method for discriminating variable quasars from periodic variable objects in the absence of spectroscopic information. The establishment of statistically robust trends and efficient, non-spectroscopic selection algorithms will aid in quasar identification and categorization in upcoming massive synoptic surveys. Finally, we report on three interesting variable quasars, including variability confirmation of the BL Lac candidate PKS 1222+037.Comment: AJ, accepted for publication 15 Dec 200

Making connections and promoting the profession: social media use by World Federation of Occupational Therapy member organisations

BACKGROUND: World Federation of Occupational Therapists (WFOT) member organisations comprise 77 national occupational therapy organisations across the world. Each national organisation interacts with its members and the public using diverse methods. Increasingly, national organisations are broadening their communication methods. OBJECTIVE: The objective of this study was to examine if and how occupational therapy organisations are using social media for communication, and if so, the types of concerns or barriers they experience and what role they anticipate social media might play in the near future. METHODS: An online survey was developed; 57 of 77 WFOT member organisations responded. FINDINGS: This study identified that WFOT national organisations are using social media, to varying degrees, with or without an individual formally assigned to manage social media. Respondents reported that they used social media to: communicate with members, promote the organisation and promote the profession. Commonly expressed needs included assistance with guide- lines for ethical social media use, developing technical expertise, and recognition of limits of time and competing priorities. Recommendations arising from this research are at the global, national, local and individual levels and incorporate active dissemination and pure diffusion approaches. Taking steps to increase the use of social media could indirectly impact occu- pational therapy practice through enhancing organisations’ abilities to support practitioners to enhance their practice. LIMITATIONS AND RECOMENDATIONS FOR FURTHER RESEARCH: Although 57% of WFOT member organisations returned usable responses, there may be some additional perspectives that were not captured. It would be helpful to contact non-responding organisations to explore their social media use and plans. Further research could examine how future initiatives put in place by WFOT impact social media use by member organisations.Published versio

Testing the validity of twin deficit hypothesis in Pacific island countries: an empirical investigation

Pacific island countries (PICs), since the mid 1990s, have been struggling with current account deficits in their balance of payments. Declining aid inflows and contraction in their traditional exports of primary goods along with growing imports of food, fuel and capital and intermediate goods have been the causes behind current account imbalances. On the fiscal front, stagnation in revenues and rigidities in public expenditures have been responsible for overall budget deficits. Resorting to panel data analysis, this study finds evidence in support of the twin deficit hypothesis in terms of their short-and long-run relationship and suggests suitable policy measures for consideration by decision makers

PMN J0525-3343: soft X-ray spectral flattening in a blazar at z=4.4

We report optical, radio and X-ray observations of a new distant blazar, PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z>4 blazars, GB 1428+4217 (z=4.72) reported by Boller et al and RXJ 1028.6-0844 (z=4.28) by Yuan et al. The spectrum is well fitted by a power-law continuum which is either absorbed or breaks at a few keV. An intrinsic column density corresponding to 2 x 10^23 H-atoms cm-2 at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame UV emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.Comment: 7 pages, 7 figures; MNRAS, in pres