Optimale grondgebruik as doelstelling in die landbou

Veel is in die afgelope tyd gesê oor die beskerming van ons natuurlike hulpbronne. Die term natuurlike hulpbronne het uiteraard verskillende betekenisse vir verskillende persone. ’n Natuurlike hulpbron is enige kwaliteit of kenmerk van die natuur wat die mens ekonomies kan gebruik om aan sy behoeftes te voldoen. Die kenmerke en kwaliteite van natuurlike entiteite is sonder perke — grond, water, plantegroei, minerale, diere en baie meer — die variasie binne elk is ewe groot. Daar was van tyd tot tyd baie belangstelling in inventarisse oor hulpbronne; maar enige inventaris van hulpbronne is nutteloos indien dit nie gekoppel is aan ’n spesifieke ekonomiese gebruik, m.b.v. bekende tegnologie nie

A Comparative Study on the Reactivity of Various Ketohexoses to Furanics in Methanol

The acid-catalysed dehydration of the four 2-ketohexoses (fructose, sorbose, tagatose and psicose) to furanics was studied in methanol (65 gL(-1) substrate concentration, 17 and 34 mm sulfuric acid, 100 degrees C) with Avantium high-throughput technology. Significant differences in the reactivities of the hexoses and yields of 5-hydroxymethylfurfural (HMF) and its methyl ether (MMF) were observed. Psicose and tagatose were the most reactive, and psicose also afforded the highest combined yield of MMF and HMF of approximately 55% at 96% sugar conversion. Hydroxyacetylfuran and its corresponding methyl ether were formed as byproducts, particularly for sorbose and tagatose, with a maximum combined yield of 8% for sorbose. The formation of hydroxyacetylfuran was studied through C-13 NMR spectroscopy with labelled sorbose, which provided new insights into the reaction mechanism

A Simple Standard for Sharing Ontological Mappings (SSSOM).

Despite progress in the development of standards for describing and exchanging scientific information, the lack of easy-to-use standards for mapping between different representations of the same or similar objects in different databases poses a major impediment to data integration and interoperability. Mappings often lack the metadata needed to be correctly interpreted and applied. For example, are two terms equivalent or merely related? Are they narrow or broad matches? Or are they associated in some other way? Such relationships between the mapped terms are often not documented, which leads to incorrect assumptions and makes them hard to use in scenarios that require a high degree of precision (such as diagnostics or risk prediction). Furthermore, the lack of descriptions of how mappings were done makes it hard to combine and reconcile mappings, particularly curated and automated ones. We have developed the Simple Standard for Sharing Ontological Mappings (SSSOM) which addresses these problems by: (i) Introducing a machine-readable and extensible vocabulary to describe metadata that makes imprecision, inaccuracy and incompleteness in mappings explicit. (ii) Defining an easy-to-use simple table-based format that can be integrated into existing data science pipelines without the need to parse or query ontologies, and that integrates seamlessly with Linked Data principles. (iii) Implementing open and community-driven collaborative workflows that are designed to evolve the standard continuously to address changing requirements and mapping practices. (iv) Providing reference tools and software libraries for working with the standard. In this paper, we present the SSSOM standard, describe several use cases in detail and survey some of the existing work on standardizing the exchange of mappings, with the goal of making mappings Findable, Accessible, Interoperable and Reusable (FAIR). The SSSOM specification can be found at http://w3id.org/sssom/spec. Database URL: http://w3id.org/sssom/spec

A Simple Standard for Sharing Ontological Mappings (SSSOM)

Despite progress in the development of standards for describing and exchanging scientific information, the lack of easy-to-use standards for mapping between different representations of the same or similar objects in different databases poses a major impediment to data integration and interoperability. Mappings often lack the metadata needed to be correctly interpreted and applied. For example, are two terms equivalent or merely related? Are they narrow or broad matches? Or are they associated in some other way? Such relationships between the mapped terms are often not documented, which leads to incorrect assumptions and makes them hard to use in scenarios that require a high degree of precision (such as diagnostics or risk prediction). Furthermore, the lack of descriptions of how mappings were done makes it hard to combine and reconcile mappings, particularly curated and automated ones. We have developed the Simple Standard for Sharing Ontological Mappings (SSSOM) which addresses these problems by: (i) Introducing a machine-readable and extensible vocabulary to describe metadata that makes imprecision, inaccuracy and incompleteness in mappings explicit. (ii) Defining an easy-to-use simple table-based format that can be integrated into existing data science pipelines without the need to parse or query ontologies, and that integrates seamlessly with Linked Data principles. (iii) Implementing open and community-driven collaborative workflows that are designed to evolve the standard continuously to address changing requirements and mapping practices. (iv) Providing reference tools and software libraries for working with the standard. In this paper, we present the SSSOM standard, describe several use cases in detail and survey some of the existing work on standardizing the exchange of mappings, with the goal of making mappings Findable, Accessible, Interoperable and Reusable (FAIR). The SSSOM specification can be found at http://w3id.org/sssom/spec

Amide-controlled, one-pot synthesis of tri-substituted purines generates structural diversity and analogues with trypanocidal activity

Anovel one-pot synthesis of tri-substituted purines and the discovery of purine analogues with trypanocidal activity are reported. The reaction is initiated by a metal-free oxidative coupling of primary alkoxides and diaminopyrimidines with Schiff base formation and subsequent annulation in the presence of large N,N-dimethylamides (e.g.N,N-dimethylpropanamide or larger). This synthetic route is in competition with a reaction previously-reported by our group1, allowing the generation of a combinatorial library of tri-substituted purines by the simple modification of the amide and the alkoxide employed. Among the variety of structures generated, two purine analogues displayed trypanocidal activity against the protozoan parasite Trypanosoma brucei with IC50 , 5 mM, being each of those compounds obtained through each of the synthetic pathways.J.J.D.M. thanks Spanish Ministerio de Economı´a y Competitividad for a Ramon y Cajal Fellowship. A.U.B. thanks MRC IGMM for an academic fellowship. This work was partially supported by Grant SAF2011-30528 to J.A.G.S.

A Proposed Procedure for the Identification of Dispersive Soils

The piping failure of the Senekal dam and many other small dams in South Africa, despite the use of apparently sound material and good control during construction, emphasizes the need for a method to unambiguously identify dispersive soils. Physical and chemical tests of one hundred and seventy soil samples were evaluated against the double hydrometer method, after removal of free salts. The chemical methods based on characterization of the exchange complex (CEC and ESP) gave consistently more reliable results than the physical tests, such as the pinhole, crumb and sticky point tests and even the double hydrometer test when free salts are not removed

A COMPARISON OF THE CAPITAL STRUCTURES OF THE TOP 40MULTINATIONAL ENTITIES AND THE TOP 40 JSE-LISTED ENTITIES

The strategies and policies of multinational entities (MNEs)centre onthe focalgoal of any company, which isto maximise profits and shareholder wealth.Management aims for an optimum ownership structure by implementing variousstrategies. One of these strategies is the debt-to-equity ratio (the capital structure).Previous studiesconductedonvariouscountries’locally-listed entities confirmthat the capital structure of an entity has an impact on the value ofthat entity.Thisthen raisesan interesting question as to whetherthecapital structures ofthetop 40Johannesburg Stock Exchange (JSE)-listedentitiesare similar to those ofthe top40 global MNEs.Based on market capitalisation on 31December2014, this studysought to compare the capital structures,using the debt-to-equity ratio,ofthe top40JSE-listed entitieswith those ofthe top 40globalMNEs on the Fortune 500list.Independent t-testswere performed on thedebt-to-equity ratios of thetop 40JSE-listed entities and the top 40globalMNEsas a group.Both independent t-tests and the Mann-Whitney testswereperformedonthedebt-to-equity ratiosofapplicable entities of the group divided into threeselectedindustries. The resultsof theindependent t-testindicateastatistical andpractically significant differencebetween the top 40 JSE-listed entities and the top 40 global MNEs’ capitalstructures.The resultsof the Mann-Whitney testsindicatethat if the financialindustry is excluded,there isnostatistical orpractically significant differencebetween the capital structures of the top 40 JSE-listed entities and the top 40MNEs.However, based on the effect size there is a practical visible difference

Marxisme en skoolkadette in Suid-Afrikaanse konteks : 'n studie in die fundamentele opvoedkunde

Proefskrif (M. Ed.) -- Universiteit van Stellenbosch, 1088.Full text to be digitised and attached to bibliographic record