Molecular electronics based on bottom-up electronic circuit design is a potential solution to meet the continuous need to miniaturize electronic devices. The development of highly conductive molecular wires, especially for long distance charge transfer, is a major milestone in the molecular electronics roadmap. A challenge presented by single molecule conductance is to define the relative influence of the molecular "core" and the molecular "interconnects" on the observed currents. Much focus has been placed on designing conductive, conjugated molecules. However, the electrode-molecule contacts can dominate the responses of metal-molecule-metal devices. We have experimentally and theoretically probed charge transfer through single phenyleneethynylene molecules terminated with thiol and carbodithioate linkers, using STM break-junction and non-equilibrium Green's function methods. The STM break-junction method utilizes repeatedly formed circuits where one or a few molecules are trapped between two electrodes, at least one of which has nanoscale dimensions. The statistical analysis of thousands of measurements yields the conductance of single molecules. Experimental data demonstrate that the carbodithioate linker not only augments electronic coupling to the metal electrode relative to thiol, but reduces the barrier to charge injection into the phenyleneethynylene bridge. The theoretical analysis shows that sulfur hybridization provides the genesis for the order-of-magnitude increased conductance in carbodithioate-terminated systems relative to those that feature the thiol linker. Collectively, these data emphasize the promising role for carbodithioate-based connectivity in molecular electronics applications involving metallic and semi-conducting electrodes. One of the strategies for building molecular wires that can transfer charge over long distance is to incorporate metal ions into the conductive molecular core. Peptide nucleic acid (PNA) is a great candidate for this purpose. Studying the conductivity of PNA can not only contribute to a better understanding of charge transfer through biomolecules, but can also help develop better molecular wires and other building blocks of molecular electronics. We study the charge transfer of PNA molecules using the STM break-junction technique and compare with traditional macroscopic voltammetric measurements. By measuring the resistance of different PNA molecules, we hope to develop a deep understanding of how charge transport though PNA is affected by factors such as the number and type of natural and artificial bases, embedded metal ions, pH, etc. Self-assembled monolayers (SAMs) of porphyrins are of great interest due to their diverse applications, including molecular devices, nano-templates, electrocatalysis, solar cells, and photosynthesis. We combined a molecular level study of the redox reactions using electrochemical scanning tunneling microscopy (EC-STM) with a macroscopic electrochemical technique, cyclic voltammetry (CV), to study two redox active porphyrin molecules, TPyP (5,10,15,20-Tetra(4-Pyridyl)-21H,23H-Porphine) and 5, 10, 15, 20-tetrakis (4-carboxylphenyl)-21H, 23H-porphine (TCPP). We showed that the adsorbed oxidized TPyP molecules slowly change to brighter contrast, consistent with the appearance of the reduced form of TPyP, under reduction condition (0.0VSCE). The time scale of the slow reduction is in the order of tens of minutes at 0.0VSCE, but accelerates at more negative potentials. We propose that protonation and deprotonation processes play an important role in the surface redox reaction due to geometric restriction of the molecules adsorbed on the surface. EC-STM and CV experiments were performed at various pH values to investigate the mechanism of this anomalously slow redox reaction. Our results show that the increased concentration of H+ hinders the reduction of porphyrins, a feature that has not been reported preciously. This provides insight into the details of the surface redox reaction. / Chemistry

Le 36Cl est utilisé dans les études hydrologiques en raison de son caractère conservatif. Il apparaît cependant que le Cl- participe à un cycle biogéochimique complexe associé au turnover de la matière organique. Le flux de 36Cl atmosphérique a été déterminé (suivi mensuel des eaux de pluie sur deux ans) et varie saisonnièrement avec des valeurs accrues au printemps - été. L'importance de la période d'échantillonnage a été mise en évidence indiquant qu'une période de 6 mois est recommandée afin de lisser les variations saisonnières et les pics sporadiques du flux de 36Cl. Le flux atmosphérique moyen du 36Cl à notre site, constituant le flux d'entrée majoritaire dans son cycle biogéochimique, est de (75±6) atoms.m-2.s-1.La distribution du Cl et du 36Cl a été étudiée dans l’écosystème forestier grâce au développement des protocoles adéquats. 72% du Cl et 80% du 36Cl sont présents sous forme organique dans le sol alors qu'ils sont principalement sous forme inorganique dans la végétation. Les rapports mesurés dans la végétation (~ 200 x 10-15 at.at-1) sont similaires à ceux provenant des apports atmosphériques (~ 180 x 10-15 at.at-1) et ceux mesurés dans le sol sont un ordre de grandeur supérieur. Ces derniers augmentent significativement à 5-15 cm dans la fraction organique du profil de sol alors que dans la fraction inorganique une faible augmentation apparaît à 15-30 cm. Nous attribuons ces observations au recyclage du 36Cl du pic nucléaire des années 1950-1960. Ces résultats indiquent que la distribution du 36Cl diffère de celle du Cl suggérant des processus dynamiques d’immobilisation et de remobilisation du 36Cl liés au renouvellement de la matière organique. / 36Cl is widely used in hydrological studies since it is considered as a conservative tracer. However it appears that Cl- participates in a complex biogeochemical cycle linked to the organic matter turnover. The 36Cl atmospheric fallout rate has been determined (monthly record of rainwater samples during two years) and varies seasonally with higher values during spring – summer. The sampling period should at least span 6 months to avoid any biais in the fallout rate determination due to the monthly variations or any sporadic bursts of 36Cl. The mean 36Cl fallout rate at our site, corresponding to the main input of its biogeochemical cycle, equals (75±6) atoms.m-2.s-1. The distribution of Cl and 36Cl has been studied into the ecosystem thanks to the development of appropriate protocols.72% of the Cl and 80% of the 36Cl are contained in the organic fraction in soil while they are mainly in inorganic form in the vegetation. 36Cl/Cl measured in vegetation (~200 x 10-15 at.at-1) are within the range of the ones measured in the rainwater samples (~180 x 10-15 at.at-1), while the 36Cl/Cl ratios are 10 times higher in soil. 36Cl/Cl in soil increase significantly at a depth of 5-15 cm in the organic fraction while a slight increase is observed in the inorganic fraction at 15-30 cm deep. This suggests that 36Cl originating from the massive input of 36Cl introduced in the atmosphere more than 50 years as a consequence of nuclear tests, might still be recycling.These results emphasize that the distribution of 36Cl and Cl are not similar suggesting a possible occurrence of dynamic processes of 36Cl accumulation and release associated with the turnover of the organic matter.

Self-assembled monolayers (SAMs) provide well-defined and ordered films of molecules spontaneously chemisorbed on a surface. By designing molecules with desired functionalities, such molecular film can be interesting for a range of applications from molecular electronics to catalysis. Important parameters for SAM applications are the film structure and quality, which are dependent on the structure of molecular constituents, the substrate, and the self-assembly process. In this work, SAMs on Au(111) of a variety of functionalized molecules, with thiol and silane headgroups, have been studied using high-resolution X-ray photoemission spectroscopy (HRXPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, Infrared reflection absorption spectroscopy (IRRAS), contact angle measurements and Kelvin probe measurements. In particular, the effects of varying the size of the backbone, varying the headgroup, inclusion of a porphyrin tailgroup, different ways of deprotection of the headgroups, and mixed molecular layers have been investigated. The first part of thesis work is focused on SAMs of oligo(phenyleneethynylene) (OPE) derivatives. First the effect of the extent of the conjugated system on the structure of SAM was investigated. As the lateral π-system in the OPE backbone increases, molecular surface densities become lower and molecular inclinations larger. Subsequently, a bulky porphyrin tailgroup was added onto the OPE molecule. Porphyrin-functionalized OPE with several headgroups were compared and the thioacetyl anchor group was found to form a high quality SAM. In the second part of the work, the molecular orientation of thiol-derivatized tetraphenylporphyrin layers was studied. The geometry of the molecular layer and the number of linkers that bind to the gold surface depend strongly on preparation schemes, i.e. whether or not the acetyl protection groups on the thiol were removed before adsorption. Finally, mixed SAMs of a ferrocene-terminated alkanethiol and alkanethiols were studied. By diluting the ferrocene-functionalized molecules in unfunctionalized alkanethiols, the orientational order and the packing density improved. The geometrical structure and the fraction of the ferrocene-terminated molecules can be tuned by controlling the parameters in the preparation scheme.

The VAT treatment of over-allowances in the motor retail industry has proved contentious for South African Revenue Services (“SARS”). VAT legislation dictates that notional VAT may be claimed on the lower of the open market value and the consideration paid. The industry, however, claims notional VAT on the actual consideration paid for a used vehicle on the basis that a higher output VAT will be declared on the consequent sale of the new vehicle. This is because the over-allowance is offset against the lower discount granted. SARS allows this practice on account of SARS’ own issuance of a binding general ruling, provided certain criteria are met. This ruling is contained in the VAT Guide to Motor Dealers. This study performs an analysis of the current practice by South African motor retailers pertaining to over-allowances. The aim of the study is to determine the impact on the industry of the issuance of the Guide, both practically and from the perspective of compliance, focussing on VAT legislation and Competition Commission legislation. The study discusses the requirements contained in the Guide in the light of the Competitions Act and the practical benefits, and concludes that the industry is satisfied with the issuance of the Guide, despite its silence on the interpretation of certain key criteria. The industry has chosen to assume that, as SARS has acted reasonably in the issuance of the Guide, it would not expect the industry to deviate from any other legislation, including the Competitions Act. If SARS is not satisfied with this interpretation, the Guide will have to be amended to include definitions of terms such as “permissible discount”. AFRIKAANS : Die hantering van die toelating van oormatige BTW in die motorvoertuig-kleinhandelsindustrie is, insover dit die Suid-Afrikaanse Inkomstediens (“SAID”) betref, omstrede. BTW-wetgewing bepaal dat geagte BTW gehef mag word op die laagste van ope markwaarde en die werklike bedrag betaal. In die motorvoertuigindustrie word BTW egter altyd gehef op die werklike bedrag betaal vir ‘n gebruikte voertuig met die veronderstelling dat hoër uitset BTW verklaar gaan word met die verkoop van ‘n nuwe voertuig wat die inruiltransaksie tot gevolg gaan hê. Daar word geredeneer dat die oortoelating van BTW uitgekanselleer gaan word deur ‘n laer afslag op die nuwe verkope. As gevolg van bindende bepalings in die BTW Handleiding vir Motorhandelaars, wat uitgereik is deur die SAID en die nakoming van sekere voorwaardes deur die motorhandelaars, laat die SAID hierdie praktyk toe. In hierdie mini-verhandeling word die vereistes wat in die Handleiding vervat is teen die agtergrond van die Wet op Mededinging en die praktiese voordele daarvan bespreek. Die gevolgtrekking is dat die motorvoertuigindustrie tevrede is met die uitreiking van die Handleiding vir motorhandelaars ongeag die feit dat sekere sleutel aspekte nie in die Handleiding voldoende toegelig word nie. Die motorindustrie het die aanname gemaak dat SAID redelikerwys opgetree het deur die Handleiding uit te reik en sal daarom nie verwag dat die industrie van enige ander wetgewing sal afwyk nie, insluitende die Wet op Mededinging. As die SAID nie tevrede is met hierdie interpretasie nie sal dit beteken dat die Handleiding aangepas sal moet word om ander relevante terminologieë soos “toelaatbare afslag” beter te omskryf en te verduidelik. Copyright 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Coventry, MA 2011, A critical analysis of the VAT implications of over-allowances in the South African motor retail industry, MCom dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-03092012-112915 / > F12/4/77/gm / Dissertation (MCom)--University of Pretoria, 2012. / Taxation / unrestricted

With six major truck companies holding similar market shares in Europe, advancements and improvements are crucial to avoid falling behind. However, knowing what aspects to improve is paramount, as focusing on the wrong areas can lead to wasted resources and time. At the operational level, collecting accurate data and utilizing it effectively is essential for learning and progress. One effective method is to gather data on process losses and measure effectiveness accordingly. Overall equipment effectiveness (OEE) and overall process effectiveness (OPE), originating from total productive maintenance (TPM), are commonly used metrics for this purpose.   To ensure comprehensive assessment, three main effectiveness measurements are necessary. OEE evaluates machine effectiveness, total effective equipment performance (TEEP) considers planned maintenance, and OPE encompasses all losses, internal and external.   In this thesis, all three effectiveness measurements are applied to Scania's pallet disassembly process. Due to its high variability, traditional TPM methods cannot be directly applied. Therefore, adaptations were made. Time became the common factor for measurement, eliminating the need for cycle times and unit outcomes. Additionally, the aspect of quality was excluded, given the nature of the disassembly process and its minimal quality loss.   The implemented method involves two solutions: one currently in use and one proposed for the future. The current approach involves data entry by an operator into an Excel sheet at the end of each shift. This data is then transformed into OEE, TEEP, and OPE pie charts, allowing for weekly analysis of shift, day, and week effectiveness. As for future recommendations, replacing the programmable logic controller (PLC) would enable real-time effectiveness monitoring and process simulations.

I en hårdnande marknad för tillverkande industrier krävs det att förbättringar och effektiviseringar av produktionen hela tiden prioriteras, det gäller även Scanias växellådstillverkning. I takt med att antalet växellådsvarianter ökar, ökar utmaningarna kopplat till styrning och planering av produktion. Denna studie syftar till att ta fram ett förslag på det bästa sättet att styra produktionsflödet genom testningen av växellådor i de testriggar som finns samt att ge ett förslag på hur uppföljningen av produktionen ska gå till. Syftet mynnade ut i en teoretisk och en praktisk frågeställning. Den teoretiska frågeställningen behandlar sekvenseringen, vilka mätetal som ska användas i produktionen och hur de ska presenteras samt om takttid eller cykeltid ska användas som styrningsmetod vid testriggarna. Den praktiska formuleringen behandlade de praktiska hinder som uppstår vid de existerande systemen på grund av de nya förslagen. Studien avgränsade sig från implementering av förslagen. För att uppfylla syftet och besvara frågeställningarna skapades två simuleringsprogram i Python som undersökte sekvenseringen och jämförde takttid och cykeltid som styrningsmetod för testriggarna. Verklig data från produktionen användes för att kunna simulera skillnaderna mellan styrningsförslagen på ett tillförlitligt sätt. I testriggarna utförs arbetet av maskin och operatör parallellt med varandra. Simuleringsprogrammen fokuserade främst på maskinarbetet, därför utfördes kompletterande tidsstudier över operatörsarbetet vid testriggarna. För att få ytterligare perspektiv gjordes dessutom två benchmark i form av besök vid motortillverkningen och bearbetningen av pinjonger och kronhjul på Scania i Södertälje. Studien visade att cykeltidsstyrning är att föredra framför takttidsstyrning vid testriggarna. Vid en övergång från takttidsstyrning till cykeltidsstyrning kommer kapaciteten att förbättras och stopptidsmätningarna bli mer tillförlitliga. De fördelar som annars finns vid en takttidsstyrning fungerar inte vid testriggarna på grund av hur de är utformade. Den stora variationen i cykeltider vid testriggarna medför stora problem vid en takttidsstyrning. Från operatörstidmätningen framgick att det går att förbättra arbetet med standardiserat arbetssätt. Simuleringsprogrammet för sekvenseringen visade att en förbättrad sekvens inte ger något i nuläget, men att det kan komma att förändras framöver. Nya mätetal definierades, både i den dagliga produktionen och för vidare analys i ett IT-system. Framförallt utvecklades mätetal för stopptid som även visar vad för typ av stopptid som uppkommer.

This research project examined the psychometric properties of the adult learner self-directedness scale (ALSDS). The study assessed the construct validity and reliability of the scale as a measure of adult learner self-directedness for diverse groups of adult learners in the South African open, distance and e-learning higher education (ODeLHE) context. The study also assessed whether the factorial structure of the ALSDS was equivalent for adult learners across gender, race and age groups. Furthermore, the study assessed whether the various socio-demographic groups differed significantly on the sub-scale dimensions of the ALSDS; and explored whether a range of socio-biographical factors predicted adult learner self-directedness. This doctoral study has extended the student’s initial exploratory master’s study on the development and factorial structure of the ALSDS that involved a stratified random sample (N = 1 102) of ODeLHE adult learners. The secondary data set involved a random subsample of n = 747 of the original master’s sample data set. Exploratory structural equation modelling (ESEM), exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) revealed a three-factor solution for the ALSDS, with 15 items loading onto the three factors. The results provided evidence of the construct (convergent and discriminant) validity and internal consistency reliability of the three-factor ALSDS, including the construct equivalence of the scale’s factorial structure across the gender, race and age groups. Significant differences between age, race and gender groups were observed regarding the scale sub-dimensions. The study advances theory on adult learner self-directedness in ODeLHE contexts and contributed evidence of the validity and reliability of a shortened version of the ALSDS as a useful measure of adult learner self-directedness. Psychometric shortcomings to be addressed in future research were also directedness. Psychometric shortcomings to be addressed in future research were also highlighted. Practically, the study highlighted assessing adult learners’ success orientation in ODeLHE, active academic activity and strategic utilisation of resources as aspects of enhancing their self-directedness. Support practices should be considered for especially females, black Africans and younger learner cohorts. ODeLHE practices should also consider learners’ mark for English, gender, access to library, number of modules and who students support financially as factors influencing learners’ level of self-directedness. / Abstract/summary in English, Afrikaans and isiZulu / Die navorsingsprojek het die psigometriese eienskappe van die selfgerigtheidskaal vir die volwasse leerder (ALSDS) ondersoek. Die studie het die konstruk-geldigheid en -betroubaarheid van die skaal geassesseer as 'n maatstaf van selfgerigtheid by volwasse leerders vir diverse groepe van volwasse leerders in die Suid-Afrikaanse ope, afstands- en e-leer-hoëronderwyskonteks (ODeLHE). Die studie het ook geassesseer of die fakulteitstruktuur van die ALSDS gelykstaande was vir volwasse leerders oor geslags-, rasse- en ouderdomsgroepe heen. Verder het die studie geassesseer of die verskeie sosiodemografiese groepe beduidend verskil het op die subskaal-dimensies van die ALSDS en ondersoek of 'n reeks sosiobiografiese faktore selfgerigtheid by volwasse leerders voorspel het. Hierdie doktorale studie het uitgebrei op die student se aanvanklike verkennende meesterstudie oor die ontwikkeling en fakulteitstruktuur van die ALSDS wat 'n gestratifiseerde ewekansige steekproef van ODeLHE-volwasse leerders behels het (N = 1 102). Die sekondêre datastel het 'n ewekansige substeekproef behels van n = 747 van die oorspronklike meestersteekproef-datastel. Verkennende strukturele vergelykingsmodellering, verkennende faktorontleding en bekragtigende faktorontleding het 'n driefaktor-oplossing vir die ALSDS onthul, met 15 items wat op die drie faktore gelaai is. Die resultate verskaf bewyse van die konstruk (konvergerende en diskriminerende) geldigheid en interne konsekwentheid en betroubaarheid van die driefaktor-ALSDS, insluitende die konstruk-ekwivalensie van die skaal se fakulteitstruktuur oor die geslags, rasse- en ouderdomsgroepe heen. Beduidende verskille tussen ouderdoms-, rasse- en geslagsgroepe is waargeneem rakende die skaalsubdimensies. Die studie bevorder teorie oor selfgerigtheid by volwasse leerders in ODeLHE-kontekste en dra bewyse van die geldigheid en betroubaarheid van 'n verkorte weergawe van die ALSDS as 'n nuttige maatstaf van selfgerigtheid by volwasse leerders. Psigometriese tekortkomings wat in toekomstige navorsing hanteer kan word, is ook beklemtoon. Prakties gesproke beklemtoon die studie die assessering van volwasse leerders se sukses-oriëntering in ODeLHE, aktiewe akademiese aktiwiteit en strategiese gebruik van hulpbronne as aspekte om hul selfgerigtheid te bevorder. Ondersteuningspraktyke moet oorweeg word vir veral vroue, swart Afrikaners en jonger leerderkohorte. ODeLHE-praktyke moet ook leerders se punt vir Engels, geslag, toegang tot 'n biblioteek, aantal modules en wie studente finansieel ondersteun, oorweeg as faktore wat leerders se vlak van selfgerigtheid beïnvloed. / Le projekthi yocwaningo, ihlola ama-psychometric properties of the adult learner self-directedness scale (ALSDS). Ucwaningo luhlola i-construct validity nokuthembeka kwe-scale njengendlela yokukala i-adult self-directedness kumaqembu ehlukene abafundi abadala kwisimo semfundo evulekile lapho abantu abafunda bekude esibizwa nge-South African open, distance and e-learning higher education (ODeLHE). Ucwaningo lubuye lwahlola nokuthi ngabe isimo ngamaqiniso e-ALSDS siyalingana yini kubafundi abadala kumaqembu obubili, bezinhlanga ezehlukene ngokwebala kanye nabantu beminyaka ehlukene. Kanti futhi okunye, ucwaningo, luhlola ukuthi ngabe amaqembu emikhakha ehlukene ngokwe-sociodemographic ehlukene kakhulu maqondana nama-dimention e-ALSDS acutshungulwayo ukuthi ngabe ama-range emibandela yama-sociodemographic abonelela noma aqagela inqubo ye-adult leaner self-directedness. Lolu cwaningo lweziqu ze-doctoral study lubheke nocwaningo lokuqala lwabafundi be-masters ngentuthuko yesakhiwo se-factoral structure ye-ALSDS ebandakanye amasampuli akhethwe nje ngaphandle kokukhetha noma ukubeka imibandela ethize, okwaziwa nge-stratified random sample ye (N = 1 102) yabafundi abadala be-ODeLHE. Isethi ye-data yesekondari yona ibandakanya i-random subsample of n = 747 yesethi ye-data yabafundi bokuqala be-masters. I-Exploratory structural equation modelling, i-exploratory factor analysis kanye ne-confirmatory factor analysis eziveze izixazululo ezintathu ngama-ALSDS kuma-ayithemu angu 15 afakelwe kuma-factor amathathu. Imiphumela iveza ubufakazi be-construct (i-convergent and discriminant) validity kanye ne-internal consistency reliability yama-factor amathathu e-ALSDS abandakanya i- ix construct equivalence ye-scale's factorial structure, ukunqamuleza kumaqembu ngobulili, izinhlanga ezehlukene ngokwebala kanye neminyaka yobudala ehlukene. Umehluko osemqoka phakathi kweminyaka yobudala, izinhlanga ezehlukene ngokwebala kanye namaqembu eminyaka ehlukene uye wabonakaka maqondana ne-scale sub-dimensions. Ucwaningo luqhubela phambili ithiyori kwizimo zabafundi zokuziqhuba ngokufunda ezibizwa i-adult learner self-directedness kwi-ODeLHE, kanti futhi ithela esivivaneni kwi-reliability ye-version efinyeziwe ye-ALSDS njengesikali esiwusizo kwi-adult learner self-directedness. Okuyizihibe nge-psychometric okufanele kubhekwane nakho ngocwaningo lwangekusasa, kuye kwavezwa kwagqanyiswa. Ngokubonakala ngendlela ebambekayo, ucwaningo lugqamise ukuhlolwa kwempumelelo yabafundi abadala kwi-ODeLHE, umsebenzi omatasatasa we-akhademiki kanye nokusetshenziswa ngendlela yamasu abambekayo kwemithombo njengengxenye yokuthuthukisa i-self-directedness. Izinkambiso zokusekela kumele zibonelelwe, ikakhulukazi kwabesimame, abamnyama bama-Afrika kanye nabafundi abasebasha. Izinkambiso ze-ODeLHE kumele zibonelele namamaki abafundi olimi lwesiNgisi (i-English), ubulili, ukufinyelela emalayibhrari, inani lama-module kanye nokuthi ngabe abafundi bondla obani ngokwezimali njengemibandela enomthelela kwinqubo yokuthi abafundi bakwazi ukuziqhubela phambili ngokwenqubo ye-self-directedness. / Business Management / D.Com. (Business Management)