A brief review of long-term X-ray and optical variability in radio-quiet AGN

Long-time-scale X-ray and optical variability is a key characteristic of AGN. Here, we summarise our current understanding of the X-ray and optical continuum variability of radio-quiet AGN and the relation between the two bands. We demonstrate the strong connection between the X-ray variability properties of AGN and the variability of stellar-mass black hole candidates on much shorter time-scales, and discuss the implications of this result for the origins of the variability. The relationship between optical and X-ray variability is complex, with some AGN showing strong X-ray/optical correlations while others show no obvious correlation. We suggest a possible explanation for this variety of behaviour.Comment: 8 pages, invited contribution to the conference 'Stellar mass, Intermediate-mass and Supermassive black holes', October 28-31 2003, Kyoto, Japan (proceedings to be published in Progress of Theoretical Physics

Test-takers’ perspectives on a global test of English: questions of fairness, justice and validity

Although language test-takers have been the focus of much theoretical and empirical work in recent years, this work has been mainly concerned with their attitudes to test preparation and test-taking strategies, giving insufficient attention to their views on broader socio-political and ethical issues. This article examines test-takers’ perceptions and evaluations of the fairness, justice and validity of global tests of English, with a particular focus upon the International English Language Testing System (IELTS). Based on relevant literature and theorizing into such tests, and on self-reported test experience data gathered from test-takers (N = 430) from 49 countries, we demonstrate how test-takers experienced fairness and justice in complex ways that problematized the purported technical excellence and validity of IELTS. Even as there was some evidence of support for the test as a fair measure of students’ English capacity, the extent to which it actually reflected their language capabilities was open to question. At the same time, the participants expressed concerns about whether IELTS was a vehicle for raising revenue and for justifying immigration policies, thus raising questions about the justness of the test. The research foregrounds the importance of focusing attention upon the socio-political and ethical circumstances that currently attend large-scale, standardized English language testing

Direct and indirect influences of intercrops on the coconut defoliator Opisina arenosella

Coconut palm (Cocos nucifera) infestation by Opisina arenosella (Lepidoptera: Oecophoridae) in the Indian sub-continent may occur in November to May each year in the same or adjoining areas of plantations. Parasitoids of O. arenosella may also be consistently present at these times. During other periods, pests and/or parasitoids could be maintained on intercrops that are commonly grown throughout the year. Field surveys of 54 intercrop species in Kerala, India, found that O. arenosella attacks banana, but not others, while laboratory screening showed that O. arenosella can mature on jack fruit, cashew and oil palm. Larvae of 20 lepidopteran species found on intercrops were screened for use by Goniozus nephantidis (Hymenoptera: Bethylidae), a larval parasitoid of O. arenosella, which oviposited on two species but its offspring failed to mature. Thirteen intercrop herbivore species were screened for use by Brachymeria nosatoi (Hymenoptera: Chalcididae), a pupal parasitoid of O. arenosella, which completed development on the pyralids Herculia nigrivita, Syllepte derogata and Psara basalis. Further, connectance trophic webs were compiled using prior field records of coconut, 33 species of intercrops, 58 species of lepidopteran herbivores and 29 species of primary parasitoids. Both laboratory and literature evidence suggests that populations of O. arenosella are unlikely to be maintained by feeding on intercrops or strongly influenced by direct competition with other lepidopterans but are likely to be affected by sharing parasitoids. Intercrop herbivores have clear potential for maintaining parasitoids of O. arenosella and we recommend thirteen plant species as intercrops that should aid in conservation biocontrol

Performative practices and authentic accountabilities: targeting students, targeting learning

This paper critiques recent practices in schooling, particularly efforts to enhance student learning outcomes for more performative purposes. Such practices have become increasingly prevalent as part of a broader trend towards results-oriented accountability practices, with concomitant pressures upon teachers and students to achieve particular outcomes as evidence of improvement-and often in relation to various forms of local, national, and international standardized tests. The research draws upon experiences of teachers in one school in Australia as they grappled with various reform initiatives as part of their overall School Improvement Plan to enhance educational outcomes for students. This paper draws upon theorizing and research into specific practices of performativity, particularly how children, data and teachers' learning processes are all constituted as "targets" for continuous intervention. As well as revealing the problematic effects of more performative accountabilities, the research also shows how alternative more "authentic" forms of accountability were in evidence and enacted by those constituted through these processes. This paper seeks to provide insights into how teachers' work and learning are heavily influenced by performative pressures, but also how teachers might contest the more instrumental and technicist influences of such practices

Performative practices and ‘authentic accountabilities’: Targeting students, targeting learning?

This paper critiques recent practices in schooling, particularly efforts to enhance student learning outcomes for more performative purposes. Such practices have become increasingly prevalent as part of a broader trend towards results-oriented accountability practices, with concomitant pressures upon teachers and students to achieve particular outcomes as evidence of improvement—and often in relation to various forms of local, national, and international standardized tests. The research draws upon experiences of teachers in one school in Australia as they grappled with various reform initiatives as part of their overall School Improvement Plan to enhance educational outcomes for students. This paper draws upon theorizing and research into specific practices of performativity, particularly how children, data and teachers’ learning processes are all constituted as “targets” for continuous intervention. As well as revealing the problematic effects of more performative accountabilities, the research also shows how alternative more “authentic” forms of accountability were in evidence and enacted by those constituted through these processes. This paper seeks to provide insights into how teachers’ work and learning are heavily influenced by performative pressures, but also how teachers might contest the more instrumental and technicist influences of such practices

Action threshold development in cabbage pest management using synthetic and botanical insecticides

As synthetic insecticides can have environmentally detrimental side effects, it is desirable to limit their use while still achieving good marketable yield. One approach is to apply pesticides only when needed, as determined by an action threshold (AT), defined as the number of pests per crop plant or damage intensity at which application is recommended. Another approach is to adopt alternative pesticides, such as botanical biopesticides, which can also be applied according to ATs. Here, ATs are developed in cabbage pest management using both approaches against the moths Plutella xylostella (L.), Helicoverpa armigera (Hübner) and Spodoptera litura (F.) and the aphid Brevicoryne brassicae (L.). Action thresholds were derived using fixed spraying regimes for the synthetic insecticides (imidacloprid and Voliam Flexi) and for azadirachtin, a neem-derived botanical. For synthetics, derived ATs are 40 individuals per plant for B. brassicae, 0.3 larvae for P. xylostella and 0.2 medium-sized larvae for H. armigera and for S. litura. For H. armigera and S. litura, negative relationships between marketable yield and pest were found when larvae were medium or large sized, but not when larvae were small. Compared to synthetics, benefits of using neem formulations include higher action thresholds against P. xylostella (0.6/plant) and H. armigera (0.4/plant) and an oviposition deterrent effect against S. litura. Overall, botanical insecticides were effective alternatives to synthetic pesticides. Although regional limits may apply to the accuracy of any ATs derived, the approach used towards their establishment is simple and transferable to other agricultural regions and crops

Effective "Penetration Depth" in the Vortex State of a d-wave Superconductor

The temperature and field dependence of the effective magnetic penetration depth in the vortex state of a d-wave superconductor, as measured by muon spin rotation experiments, is calculated using a nonlocal London model. We show that at temperatures below T^* \propto \sqrt{B}, the linear T-dependence of the effective penetration depth crosses over to a T^3-dependence. This could provide an explanation for the low temperature flattening of the effective penetration depth curves observed in a recent muon spin rotation experiment.Comment: 4 pages, RevTex, 3 Postscript figure

Leading learning: Theorising principals' support for teacher PD in Ontario

This paper describes and theorizes principals' support for teacher professional development ('PD') during a time of strong provincial pressure for an increased focus upon literacy, numeracy, and improvements in standardized test scores in elementary schools in Ontario, Canada. The paper draws upon semi-structured interviews with 12 principals in one school district to reveal tensions between principals' support for professional development associated with these provincial emphases, and advocacy for professional development relevant to the specific needs of their school sites. To explore these competing priorities, the paper draws upon Pierre Bourdieu's concept of the social world as comprising identifiable and contested social 'fields', each containing individuals and groups with particular and competing socially-inscribed dispositions, or 'habitus'. At the same time, the paper uses principals' responses to validate and extend normative understandings of 'leadership habitus'. While provincial pressures are revealed as having a significant impact upon principals' habitus, an argument is made that the capacity to take local context into account needs to be foregrounded more strongly in current normative conceptions of leadership habitus