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This article considers the problem of testing for an explosive bubble in financial data in the presence of time-varying volatility. We propose a sign-based variant of the Phillips, Shi, and Yu (2015, International Economic Review 56, 1043–1077) test. Unlike the original test, the sign-based test does not require bootstrap-type methods to control size in the presence of time-varying volatility. Under a locally explosive alternative, the sign-based test delivers higher power than the original test for many time-varying volatility and bubble specifications. However, since the original test can still outperform the sign-based one for some specifications, we also propose a union of rejections procedure that combines the original and sign-based tests, employing a wild bootstrap to control size. This is shown to capture most of the power available from the better performing of the two tests. We also show how a sign-based statistic can be used to date the bubble start and end points. An empirical illustration using Bitcoin price data is provided.
The euarthropod Luohuilinella deletres sp. nov. is described from rare material from the Chengjiang biota, Cambrian Series 2, Stage 3, of Yunnan Province, China. Phylogenetic analysis recovers a xandarellid affinity for L. deletres, representing only the fifth described species of this clade. L. deletres possesses a head shield that is about one-fifth of the total body length and a trunk with 30 tergites, the reduced anterior-most tergite and terminal three tergites lacking pleural elongations. Anteriorly situated notches in the head shield are associated with stalked eyes, in contrast to the more posterior, enclosed eye slits present in Xandarella. Posterior to the antennae there are at least 11 pairs of biramous appendages preserved, including three pairs in the head. The morphology of the midline gut of L. deletres, in which lateral, unbranched diverticula are wider towards the front of the body, is a characteristic also found in various trilobites. The dorsoventrally flattened exoskeleton suggests a benthic or nektobenthic mode of life for L. deletres, as for other trilobitomorphs, and it likely used its well-developed anteriorly positioned eyes for searching out food, either to scavenge or to find prey.
The Orion facility at the Atomic Weapons Establishment in the United Kingdom has the capability to operate one of its two 500 J, 500 fs short-pulse petawatt beams at the second harmonic, the principal reason being to increase the temporal contrast of the pulse on target. This is achieved post-compression, using 3 mm thick type-1 potassium dihydrogen phosphate crystals. Since the beam diameter of the compressed pulse is
mm, it is impractical to achieve this over the full aperture due to the unavailability of the large aperture crystals. Frequency doubling was originally achieved on Orion using a circular sub-aperture of 300 mm diameter. The reduction in aperture limited the output energy to 100 J. The second-harmonic capability has been upgraded by taking two square 300 mm
300 mm sub-apertures from the beam and combining them at focus using a single paraboloidal mirror, thus creating a 200 J, 500 fs, i.e., 400 TW facility at the second harmonic.
Little is known about the change processes in gambling disorder-specific cognitive therapy (CT) and exposure therapy (ET). These therapies are underpinned by the cognitive approach (i.e., restructuring gambling cognitions) and the psychobiological approach (i.e., elimination of gambling urges) to treating problem gambling. Here, piecewise-linear modelling is used in a secondary analysis of randomised trial data for a CT group (n = 44) versus an ET group (n = 43) with the aim to open a discourse on how individuals respond to CT and ET relative to theory. Measures were administered between therapy sessions (average = 6.2 per individual) across 18 weeks for gambling urge (GUS) and gambling cognitions (GRCS). Results indicated the ET group had a stronger reduction in GUS (p < .01) in the first 4 weeks of treatment. Between 4–12 weeks, improvement in GUS (p < .01) and GRCS (p = .02) was more rapid in the CT group. Both groups experienced comparable improvements from 12–18 weeks. These findings have implications for further treatment development, including a combined cognitive and exposure approach that is flexibly adapted to the patient. A larger trial is needed to formally establish change processes and identify differences in problem gambler subgroups. This would provide therapists capacity to offer each patient a clear direction and an expedited pathway to their preferred outcome.
We are investigating a complete sample of flat-spectrum extragalactic radio quasars drawn from the Parkes 2.7 GHz survey. The sample is being used to map the space distribution of radio quasars and to determine their luminosity function. Accurate positions are being measured for a selection of the brighter quasars in order to establish an extragalactic position reference frame in the Southern Hemisphere.
We are investigating complete samples of southern hemisphere flat spectrum extra-galactic radio sources drawn from the Parkes 2.7 GHz Survey (see Bolton et al. 1979 and references therein). These samples are being used for a variety of investigations, including a determination of the space distribution and luminosity function of radio QSOs, their radio size distribution, as well as the structures of the individual sources. Accurate positions are being determined, as well, in order to establish an extra-galactic position reference frame in the southern hemisphere.
be a curve of genus three, given as a double cover of a plane conic. Such a curve is hyperelliptic over the algebraic closure of
, but may not have a hyperelliptic model of the usual form over
. We describe an algorithm that computes the local zeta functions of
at all odd primes of good reduction up to a prescribed bound
. The algorithm relies on an adaptation of the ‘accumulating remainder tree’ to matrices with entries in a quadratic field. We report on an implementation and compare its performance to previous algorithms for the ordinary hyperelliptic case.
We have detected a component of sky brightness varying with a frequency of 120 Hertz during high speed photometric observations of 40 Eridani with the 30-cm telescope of the University of British Columbia. The observations were made in 1974, but only recently has their significance to the field of urban illumination been realized. The 120 Hertz component was detected by Fourier analysis of data sets of the star and of the sky alone. We confirmed that the 120 Hertz component was due to urban lighting by direct observation of a “standard source,” a lamp on the campus.
Beyond Marikana, the fifth edition of the New South African Review, continues to present informed, scholarly discussion and debate about key issues animating the South African experience. Produced between January 2014 and May 2015, this particular volume was shaped largely around the contention that there are significant political shifts underway in South Africa today, with several chapters tracing their fault lines to the 2012 massacre by police of striking mineworkers in a place called Marikana.
Although the third volume in the New South African Review series offered an analysis and critique of the various forces immediately implicated in the tragedy associated with Marikana, it could not have anticipated the kinds of political ructions that we have since witnessed, especially from within different parts of the African National Congress (ANC) Alliance. The fifth volume once again, then, consciously draws attention to Marikana, but this time asking what its effects and affects have been, and why it has had such an impact. In this way, Marikana becomes the starting point for a much broader discussion and debate about the potential for new political alliances and forms to emerge in the current context, a discussion that resonates globally in the wake of the political experiments of movements, such as Occupy Tahrir, Occupy Wall Street and the Spanish Indignados, and will hopefully continue in editions to come.
New South African Review 5 also offers close analyses of contemporary developments with regard to other aspects of, and issues affecting, South African society – including corruption, the economy, the Constitution, and uranium poisoning as a by-product of the mining industry.
This volume would not have been possible without the generosity of all its authors, to whom we are extremely grateful. Thanks must also go to the team at Wits University Press who continue to provide excellent guidance, assistance, skill and support to us as editors, and ensure that there is a final product for us to share. Particular thanks to the Dean of Humanities, Professor Ruksana Osman; Head of the School of Social Studies, Professor Shahid Vawda; and the Strategic Planning and Allocation of Resources Committee (Sparc) Fund for their ongoing support of the New South African Review.
This fifth volume in the New South African Review series takes as its starting point the shock wave emanating from the events at Marikana on 16 August 2012 and how it has reverberated throughout politics and society. Some of the chapters in the volume refer directly to Marikana. In others, the infl uence of that fateful day is pervasive if not direct. Marikana has, for instance, made us look differently at the police and at how order is imposed on society. Monique Marks and David Bruce write that the massacre ‘has come to hold a central place in the analysis of policing, and broader political events since 2012’.The chapters highlight a range of current concerns – political, economic and social. David Dickinson’s chapter looks at the life of the poor in a township from within. In contrast, the chapter on foreign policy by Garth le Pere analyses South Africa’s approach to international relations in the Mandela, Mbeki and Zuma eras. Anthony Turton’s account, ‘When gold mining ends’ is a chilling forecast of an impending environmental catastrophe. Both Devan Pillay and Noor Nieftagodien focus attention on the left and, in different ways, ascribe its rise to a new politics in the wake of Marikana.The essays in NSAR 5: Beyond Marikana present a range of topics and perspectives of interest to general readers, but the book will also be a useful work of reference for students and researchers.