Superkicks in ultrarelativistic encounters of spinning black holes

We study ultrarelativistic encounters of two spinning, equal-mass black holes through simulations in full numerical relativity. Two initial data sequences are studied in detail: one that leads to scattering and one that leads to a grazing collision and merger. In all cases, the initial black hole spins lie in the orbital plane, a configuration that leads to the so-called "superkicks". In astrophysical, quasicircular inspirals, such kicks can be as large as ~3,000 km/s; here, we find configurations that exceed ~15,000 km/s. We find that the maximum recoil is to a good approximation proportional to the total amount of energy radiated in gravitational waves, but largely independent of whether a merger occurs or not. This shows that the mechanism predominantly responsible for the superkick is not related to merger dynamics. Rather, a consistent explanation is that the "bobbing" motion of the orbit causes an asymmetric beaming of the radiation produced by the in-plane orbital motion of the binary, and the net asymmetry is balanced by a recoil. We use our results to formulate some conjectures on the ultimate kick achievable in any black hole encounter.Comment: 10 pages, 6 figures, 2 table

Familicide from a clinical-community psychology perspective

In this article familicide and homicide-suicide acts in South Africa and elsewhere are discussed. Issues that are considered include the following: the definition of familicide, the incidence of cases, population groups involved, the role of suicide, the role of psychopathology, familial versus nonfamilial murderers, the influence of stress, male proprietariness in combination with an exaggerated sense of responsibility, age and gender, and sociopolitical influences. A n attempt is made to integrate the personal and societal factors of familicide from a clinical-community psychology perspective, relying specifically on the theories of Frantz Fanon and Hussein Bulhan. It is proposed that an understanding of the oppressor-oppressed relationship, as well as threats to that relationship, may shed light on the current high rate of familicide that occurs mostly among white Afrikaner, South African males, and their families

Personality traits, brie' recurrent depression and attempted suicide

This study investigated the relationship between attempted suicide, personality factors and brief recurrent depression. Over a period of 1 year, the demographic and psychiatric factors of 307 patients who had attempted suicide and subsequently been hospitalised at H. F. Verwoerd Hospital and referred to its Department of Psychiatry were recorded. Their personality traits were evaluated clinically. After 5 years, 205 respondents were traced to complete a follow-up questionnaire and, where possible, a personality assessment was completed on clinical grounds. They were also evaluated for brief recurrent depression. Among the men, antisocial, dependent and histrionic personality traits, in that order, were most commonly noted and among the women, histrionic, dependent and antisocial traits. A clear relationship between suicidal behaviour and the syndrome of brief recurrent depression was established. The latter was also found to be related to histrionic personality traits in women. This underscores the relationship between suicide attempts and histrionic personality traits

Die literariteit van die sogenaamde ‘verhalende element’ in tradisionele heroïese Sothopoësie – ’n intertekstuele ondersoek

The literariness of the so-called “narrative element” in traditional heroic Sotho poetry – an intertextual analysis This article focuses on the “literariness” of the so-called narrative lines that feature prominently in traditional Sotho heroic poetry, better known as dithoko. By means of some intertextual references it has been illustrated that these lines do not merely convey historical detail by means of “ordinary informative” language. The recalling of historical events, is rather characterised by a reconstruction of activities in a poetic context, based on certain referential codes dominated by a specific cultural tradition. The poetic nature of these lines is not only created by the use of wellknown poetic devices such as imagery and rhythm, but also by the selective use of allusion which defamiliarizes communicative language usage. By alluding to historical actions, the traditional poet attempts to create a specific aesthetic convention rather than a mere factual one. Real events in these narrative lines are often camouflaged by defamiliarized language and the presentation of fictional creations. The analysis of a few examples from dithoko that are related to certain historical events clearly indicates that these narrative lines should be evaluated against the background of specific literary conventions and literary codes

Black Hole Mergers and Unstable Circular Orbits

We describe recent numerical simulations of the merger of a class of equal mass, non-spinning, eccentric binary black hole systems in general relativity. We show that with appropriate fine-tuning of the initial conditions to a region of parameter space we denote the threshold of immediate merger, the binary enters a phase of close interaction in a near-circular orbit, stays there for an amount of time proportional to logarithmic distance from the threshold in parameter space, then either separates or merges to form a single Kerr black hole. To gain a better understanding of this phenomena we study an analogous problem in the evolution of equatorial geodesics about a central Kerr black hole. A similar threshold of capture exists for appropriate classes of initial conditions, and tuning to threshold the geodesics approach one of the unstable circular geodesics of the Kerr spacetime. Remarkably, with a natural mapping of the parameters of the geodesic to that of the equal mass system, the scaling exponent describing the whirl phase of each system turns out to be quite similar. Armed with this lone piece of evidence that an approximate correspondence might exist between near-threshold evolution of geodesics and generic binary mergers, we illustrate how this information can be used to estimate the cross section and energy emitted in the ultra relativistic black hole scattering problem. This could eventually be of use in providing estimates for the related problem of parton collisions at the Large Hadron Collider in extra dimension scenarios where black holes are produced.Comment: 16 pages, 12 figures; updated to coincide with journal versio

Planning and monitoring tool to control profitability in a manufacturing concern : a case study at C Chemicals

The aim of this paper is to analyse the key profit drivers in a manufacturing concern, and develop a decision tool based on optimisation techniques. The aim is planning and managing these profit drivers so that the target revenue and profit are realised during an operating period. This was done through developing a forecasting tool based on Visual Basic that was used by the organisation to project the future demand of its products. This tool was linked to a database that had details on past product performance. Planning software was developed using linear programming, which identified the optimum product mix and the sales outlets locations to maximise revenue and profi

Inspiral, merger and ring-down of equal-mass black-hole binaries

We investigate the dynamics and gravitational-wave (GW) emission in the binary merger of equal-mass black holes as obtained from numerical relativity simulations. Results from the evolution of three sets of initial data are explored in detail, corresponding to different initial separations of the black holes. We find that to a good approximation the inspiral phase of the evolution is quasi-circular, followed by a "blurred, quasi-circular plunge", then merger and ring down. We present first-order comparisons between analytical models of the various stages of the merger and the numerical results. We provide comparisons between the numerical results and analytical predictions based on the adiabatic Newtonain, post-Newtonian (PN), and non-adiabatic resummed-PN models. From the ring-down portion of the GW we extract the fundamental quasi-normal mode and several of the overtones. Finally, we estimate the optimal signal-to-noise ratio for typical binaries detectable by GW experiments.Comment: 47 pages, 34 figures, full abstract in paper, revtex4, accepted by PRD, miscellaneous revisions throughout pape

Poesie van E.A.S. Lesoro : 'n studie oor digsoorte en -tradisies

Abstracts in Afrikaans and EnglishIn die verhandeling word die interaksie tussen tradisie en vernuwing in die poesie van die Suid-Sothodigter, EAS Lesoro, ondersoek. Aanvanklik word n teoretiese aanloop tot die begrippe tradisie en vernuwing aange= bied, waarna enkele ontwikkelingstendense in die moderne Suid-Sothopoesie aangetoon word. Lesoro se poesie word in die raamwerk van die bree ont= wikkelingsgang van die Suid-Sothopoesie geplaas. Die irnpak wat die tradi= sionele podic. c.anon op die moderne digter het, is n belangrike aspek wat ter sprake kom. Die 1vyse waarop Lesoro tradisionele poetiese boumiddele in sy moderne poesie ontgin, word ondersoek. Opvallende kenmerke van die tradisionele dLthoRo word aangestip en in sy poesie geidentifiseer. Hul funksies in die moderne gedigte word bepaal. Lesoro se eksperirnentering met 'n verskeidenheid tradisionele Europese digvorrne en digsoorte, en sy Ll'ltegrering van Europese poetiese tegnieke vorrn n integrale deel van die studie.African LanguagesM.A. (Suid-Sotho

Prevalence and clinical characteristics of obsessive-compulsive disorder and obsessive compulsive symptoms in Afrikaner schizophrenia and schizoaffective disorder patients

Objective: There is evidence of variation in the prevalence of co-morbid obsessive-compulsive disorder in schizophrenia amongst ethnic groups. This study evaluated the lifetime prevalence and clinical characteristics of obsessive-compulsive disorder (OCD)/ obsessive-compulsive symptoms (OCS) in Afrikaner schizophrenic and schizoaffective disorder patients. Method: An ongoing genetic study of schizophrenia is currently being conducted on the Afrikaner founder population. In this cohort of 400 subjects from the original genetic study, we identified 53 subjects with schizophrenia or schizoaffective disorder and co-morbid OCD/OCS (study group). They were matched for gender and age of onset of illness with 59 subjects who do not have OCD/OCS (control group). The diagnostic instrument used in this cohort is the Diagnostic Interview for Genetic Studies (DIGS) version 2, which has been translated into Afrikaans. In addition to the DIGS, information for the relevant clinical characteristics reported in this study was also drawn from a detailed narrative chronological summary report and clinical files. A checklist was completed. Results: The prevalence of co-morbid OCD/OCS amongst 400 subjects with schizophrenia or schizoaffective disorder was 13.2% [n=53] of which 40 were male and 13 female patients. The prevalence of OCD was 10.7% and OCS was 2.5%. Contamination obsessions [n=17] were the most common type of obsession reported, followed by religious obsessions [n=8]. The most prevalent compulsions were repetitive rituals [n=32] followed by checking behaviour [n=22]. Onset of psychotic symptoms was found to be insidious in 86.8% of the study group compared to 24.6% of the control group (