Analysis of Flatness Measurement and Form Stability of a Granite Surface Plate

It is rather difficult to compare quantitatively flatness measuring results of one and the same object (e.g. in case of a long-term stability investigation) or the results of a series of products (e.g. from the same machinetool in order to indicate machinetool-influences). An extension of a computerprogram applied to the evaluation of flatness measurement (as described in the CIRP-Annals, vol. 26 (1977), no.1), separates the form deviations of a surface into a geometrical part and a random part.\ud The geometric part consists of a best-fitting non-flat, reference plane, composed of the single curvature of a sphere and the double curvature of a real twisted plane. Three parameters (the dimensionless curvature parameters of sphericity and torsion, together with the direction of the torsionvector) are able to characterize the geometrical part of the surface; a fourth one is a measure for the random part.\ud Advantages of the method are demonstrated with the aid of a long-term investigation into the form stability of a granite surface plate.\ud Another extension of the program makes it now possible to measure surfaces with non-rectangular contours in the same way as it is being done in case of a rectangular surface plate.\u

Permanent Secretary, Department of Welfare, Eastern Cape, and another v Ngxuza and others — Hofreëls vir die voer van ’n groepsgeding?

’n Groepsgeding is ’n prosedure vir die akkomodering van litigasie gebaseer op gemeenskaplike (dieselfde) feite- en/of regsvrae ingestel of verdedig deur ’n verteenwoordiger namens ’n definieerbare groep persone. Groepsgedingvoering was tot voor die inwerkingtreding van die tussentydse Grondwet 200 van 1993 grootliks onbekend aan die Suid-Afrikaanse reg. Die tussentydse Grondwet het die posisie verander deur burgerskap aan groepsgedingvoering te verleen. Dié posisie is ook in artikel 38 (gelykluidend aan artikel 7 van die tussentydse Grondwet) van die finale Grondwet 108 van 1996 oorgeneem. Die aanwending van die prosedure is egter tans alleen beperk tot die beskerming van regte in die Grondwet verskans

Die Class Proceedings Act van Ontario — ’n voorbeeld van wetgewing vir die regulering van Suid-Afrikaanse groepsgedingvoering

In 1995 and 1998 the South African Law Commission proposed the promulgation of legislation to govern class action proceedings. The Class Proceedings Act of Ontario was one of the sources consulted by the Commission. According to the commission this piece of legislation played a valuable role in their recommendations. This contribution discusses this act as an example of legislation which may usefully be consulted in the drafting of a procedure to govern class actions in South Africa

Groepsgedingvoering — die voorstel van die Suid-Afrikaanse Regskommissie vir die sertifisering van ’n groepsgeding

In this contribution the proposals of the South African Law Commission for the certification of a class action are discussed. These proposals are the products of a working paper and a report published in 1995 and 1998 respectively. In both these documents the Commission proposed the promulgation of legislation to provide the necessary framework to govern class actions. The proposals are discussed with reference to the Class Proceedings Act (Ontario) and the Federal Rules of Civil Procedure (United States of America)

Further records of dorylaim species from Botswana (Nematoda: Dorylaimida)

Seven known dorylaim species are recorded from Botswana. Illustrations and brief descriptions are given for Neoactinolaimus thornei Chaturvedi & Khera, 1979; Nygolaimus anneckei Heyns, 1968; Solididens vulgaris (Thorne, 1930) Thorne, 1974; Axodorylaimellus caffrae (Kruger, 1965) Jairajpuri & Ahmad, 1980; Dorylaimellus andrassyi Heyns, 1963; Dorylaimellus directus Heyns, 1963 and Tylencholaìmus dorae Kruger, 1965

Dorylaimida (Nematoda) from Botswana

Thirteen nematode species are recorded from Botswana. Illustrations are given for Ecuménicas monohystera (de Man, 1880) Thome, 1974; Eudorylaimus diadematus (Cobb in Thorne & Swanger, 1936) Andrássy, 1959; Labronema mauritiense Williams, 1959; Disoolaimus brevis Siddiqi, 1964; D. major Thorne, 1939; Aporcelaimellus adriaani Botha & Heyns, 1990; A. micropunctatus Botha & Heyns, 1990; A. papillatus (Bastian, 1965) Baqri & Khera, 1975; A. parapapillatus  Botha & Heyns, 1990 and a specimen belonging to Prodorylaimus or to Laimydorus. Measurements are given for the above-mentioned species as well as for Discolaimium simplex Siddiqi, 1965 and Discolaimoides bulbiferus (Cobb, 1906) Heyns, 1963. A new Mesodorylaimus species viz. M. usitatoides is described. For the first time males are described for A. adriaaniand A. micropunctatus. Discolaimus paramajor Coomans, 1966 is considered a possible synonym of D. major

Emission of reactive oxygen species during degradation of iron gall ink

Iron gall inks are characterised by high contents of acids and transition metals, promoting degradation of cellulose due to hydrolysis and oxidation, respectively. Their chemical interaction with the environment is not well understood, especially in view of emissions of degradation products which could lead to spread of degradation processes. In order to study the emissions, we employed gas chromatography/mass spectrometry following headspace micro-extraction, and liquid chromatography following hydroxyl radical scavenging with appropriate probes. We also studied chemiluminescence of cellulose affected by ink degradation. We show that while the emissions of organic volatile degradation compounds by inks are less intense than those of surrounding paper, ink does promote the degradation of cellulose across big distances (from object to object). We were able to link this to emission of reactive oxygen species, probably hydrogen peroxide. Its emission from ink is considerably more intensive than from paper

International arms deliveries from EU member states to Ukraine:Has something changed?

The unprovoked 2022 Russian attack on Ukraine has led to a sharp increase in arms deliveries to Ukraine by European Union (EU) member states and others. Although international arms trade is not prohibited under international law, it is increasingly regulated and restricted. For EU member states Common Position 2008/944/CFSP on the export of military technology and equipment in particular is relevant as it sets out the criteria for reviewing arms exports. The armed conflict in Ukraine shows that member states enjoy a wide margin of appreciation for applying the criteria even though the delivery of arms to Ukraine is not without risks

Complex maps without invariant densities

We consider complex polynomials $f(z) = z^\ell+c_1$ for $\ell \in 2\N$ and $c_1 \in \R$, and find some combinatorial types and values of $\ell$ such that there is no invariant probability measure equivalent to conformal measure on the Julia set. This holds for particular Fibonacci-like and Feigenbaum combinatorial types when $\ell$ sufficiently large and also for a class of `long-branched' maps of any critical order.Comment: Typos corrected, minor changes, principally to Section