Group classification of the Sachs equations for a radiating axisymmetric, non-rotating, vacuum space-time

We carry out a Lie group analysis of the Sachs equations for a time-dependent axisymmetric non-rotating space-time in which the Ricci tensor vanishes. These equations, which are the first two members of the set of Newman-Penrose equations, define the characteristic initial-value problem for the space-time. We find a particular form for the initial data such that these equations admit a Lie symmetry, and so defines a geometrically special class of such spacetimes. These should additionally be of particular physical interest because of this special geometric feature.Comment: 18 Pages. Submitted to Classical and Quantum Gravit

Document delivery by the Jupiter Library Consortium

The Jupiter library consortium consists of 4 of the leading libraries in the Netherlands. During 1993 Jupiter received 600,000 requests for copies of journal articles, or 70 percent of all external article requests in the Netherlands. Over 90 percent of the requested documents were delivered from a collection of 40,000 current international journal subscriptions. Jupiter and its affiliate libraries are non-profit organizations belonging to, and serving, the scientific and technical research community. The usage of the current journal collection of the libraries was analyzed to improve the cost/benefit ratio

Social Network Analysis to Optimize Tax Enforcement Effort

The tax gap is a phenomenon experienced by revenue collection agencies which describes the difference between the taxes due, as prescribed by legislation, and the actual taxes collected. The tax gap is mostly a result of taxpayer non-compliance, such as the failure to submit a tax return. Recent theories suggest that a taxpayer’s social structure is a significant determinant of a taxpayer’s attitude towards tax compliance. This study explores the proposal that social network analysis through decision support systems can facilitate the objective of revenue collection agencies to minimize the tax gap. The results suggest that an agency’s limited enforcement capacity can achieve a greater impact on tax compliance by focusing on non-compliant social structures as opposed to single instances of non-compliance. The research fills a gap in literature by demonstrating IT’s value proposition towards government financial services

A note on the history of the Faculty of Law of the University of the Free State — NUNC PRO TUNC

From text: The year 2004 is the centenary of the University of the Free State. For any university to have survived for a century is nothing new in Europe or in North Africa, but in Sub-Saharan Africa it is a very impressive feat

Warfarin in non-valvular atrial fibrillation

The development of novel oral anticoagulants that are effective alternatives to warfarin in non-valvular atrial fibrillation (AF) is a welcome advance. However, a variety of unresolved problems with their use, and not least with their cost, make it important to re-evaluate the use of warfarin as it will likely remain the anticoagulant of choice in South African patients with non-valvular AF for the foreseeable future. In this article, we review the correct clinical use of warfarin. Guidance is provided on commencing warfarin treatment, maintenance dosing, the recommended steps when temporary withdrawal of treatment is necessary, the management of bleeding, and the use of warfarin in chronic kidney disease. Techniques for changing from warfarin to one of the new oral anticoagulants and vice versa are included

From Point Cloud to Textured Model, the Zamani Laser Scanning Pipeline in Heritage Documentation

The paper describes the stages of the laser scanning pipeline from data acquisition to the final 3D computer model based on experiences gained during the ongoing creation of data for the African Cultural Heritage Sites and Landscapes database. The various processes are briefly discussed and challenges are highlighted which need to be addressed to develop the full potential of laser scanning. Experiences with fieldwork, scan registration, hole-filling, data cleaning, modelling and texturing are reported. The potential strengths and weaknesses of the emerging tool of “Structure from Motion” are briefly explored for their potential use in combination with laser scanning

\u3cem\u3eTetrahymena thermophila\u3c/em\u3e Lack a Homologue of the Caenorhabditis Elegans Lin-4 miRNA

The netrin family of proteins was first discovered because of their role in axonal guidance during development. Netrin homologues are important developmental signals in organisms ranging from vertebrates to the nematode, Caenorhabditis elegans, and netrin-like proteins have even been found in the ciliated protozoan, Tetrahymena thermophila. Since the lin-4 miRNA regulates netrin signaling in C. elegans, we hypothesized that a lin-4 homologue might exists in Tetrahymena thermophila. In order to test this hypothesis, we purified total miRNA from T. thermophila, used this miRNA to make cDNA, then used RT-PCR to quantitate the amount of lin-4 specific cDNA we obtained. Our sample was positive for total cDNA, but not for the lin-4 cDNA specifically, suggesting that this miRNA may not have a homologue in Tetrahymena

Is there a reentrant glass in binary mixtures?

By employing computer simulations for a model binary mixture, we show that a reentrant glass transition upon adding a second component only occurs if the ratio $\alpha$ of the short-time mobilities between the glass-forming component and the additive is sufficiently small. For $\alpha \approx 1$, there is no reentrant glass, even if the size asymmetry between the two components is large, in accordance with two-component mode coupling theory. For $\alpha \ll 1$, on the other hand, the reentrant glass is observed and reproduced only by an effective one-component mode coupling theory.Comment: 4 pages, 3 figure

Stabilized high-power laser system for the gravitational wave detector advanced LIGO

An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments