M. Tech. Business Administration / The study assesses the dimensions of service quality within a Jaguar Land Rover dealership in Gauteng. The first objective is to determine the importance of each service quality and the second is to measure the effect of the service quality at the dealerships.

The ever-increasing complexity of software systems makes them hard to comprehend, predict and tune due to emergent properties and non-deterministic behaviour. Complexity arises from the size of software systems and the wide variety of possible operating environments: the increasing choice of platforms and communication policies leads to ever more complex performance characteristics. In addition, software systems exhibit different behaviour under different workloads. Many software systems are designed to be configurable so that policies (e.g. communication, concurrency and recovery strategies) can be chosen to meet the needs of various stakeholders. For complex software systems it can be difficult to accurately predict the effects of a change and to know which configuration is most appropriate. This thesis demonstrates that it is useful to run automated experiments that measure a selection of system configurations. Experiments can find configurations that meet the stakeholders' needs, find interesting behavioural characteristics, and help produce predictive models of the system's behaviour. The design and use of ACT (Automated Configuration Tool) for running such experiments is described, in combination a number of search strategies for deciding on the configurations to measure. Design Of Experiments (DOE) is discussed, with emphasis on Taguchi Methods. These statistical methods have been used extensively in manufacturing, but have not previously been used for configuring software systems. The novel contribution here is an industrial case study, applying the combination of ACT and Taguchi Methods to DC-Directory, a product from Data Connection Ltd (DCL). The case study investigated the applicability of Taguchi Methods for configuring complex software systems. Taguchi Methods were found to be useful for modelling and configuring DC-Directory, making them a valuable addition to the techniques available to system administrators and developers.

Mortality statistics are much used although their accuracy is often questioned. Producers of mortality statistics check for errors in death certification but current methods only capture obvious mistakes. This thesis investigates whether non-obvious errors can be found by linking death certificates to hospital discharge data. Data: 69,818 deaths in Sweden 1995. Paper I: Analysing differences between the underlying cause of death from the death certificate (UC) and the main discharge condition from the patient’s last hospitalization (MDC). Paper II: Testing whether differences can be explained by ICD definitions of UC and MDC. Paper III: Surveying methods in 44 current studies on the accuracy of death certificates. Paper IV: Checking death certificates against case summaries for: i) 573 deaths where UC and MDC were the same or the difference could be explained; ii) 562 deaths where the difference could not be explained. Results: In 54% of deaths the MDC differed from the UC. Almost two-thirds of the differences were medically compatible since the MDC might have developed as a complication of the UC. Of 44 recent evaluation studies, only 8 describe the methods in such detail that the study could be replicated. Incompatibility between MDC and UC indicates a four-fold risk that the death certificate is inaccurate. For some diagnostic groups, however, death certificates are often inaccurate even when the UC and MDC are compatible. Conclusion: Producers of official mortality statistics could reduce the number of non-obvious errors in the statistics by collecting additional information on incompatible deaths and on deaths in high-risk diagnostic groups. ICD conventions contribute to the quality problem since they presuppose that all deaths are due to a single underlying cause. However, in an ageing population an increasing number of deaths are due to an accumulation of etiologically unrelated conditions.

Plastic injection moulding machines are a positive example of the possibilities in terms of performance and energy efficiency of modern hydraulic drives technology. In addition to the performance and energy efficiency of the machines, the quality of the plastic mouldings and an easy to use machines control is the focus. To ensure a constant plastics part quality the set process parameters of the injection moulding machines are kept constant by appropriate closed loop control strategies today. Assuming a constant quality of the processed plastic raw material, this strategy is effective. If it comes to a qualitative variation in the processed plastics, which often leads to a change in viscosity of the plastics melt, keeping processing parameters constant will not lead to a constant quality of the moulded parts. The deviations in the plastics viscosity have such a great influence on the moulding process that the relevant process parameters have to be adjusted manually in many cases. Often the stroke of the reciprocating screw system has to be adapted to reach a constant filling volume of the cavity and therefore avoid burr formation or short shots. In this paper an approach for adaptive process control is introduced. This control loop is able to correct the set points of specific machines parameters online within the production cycle and therefore is able to avoid changes in the produced parts quality.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Introduction: Quality assurance in Nuclear Medicine is of utmost importance in order to ensure optimal scintigraphic results and correct patient management. A customised Quality Management System (QMS) should be documented and implemented by following the international guidelines set by the International Standardisation Organization (ISO). Materials & Methods: A Quality Control Manual (QCM), defining the departmental quality policy, mission, vision and objectives was customised following the framework of a tried and tested design. As ISO focuses on client satisfaction and staff harmony, the following departmental objectives were audited in working towards the accreditation of the Nuclear Medicine Department of Tygerberg Hospital: referring physician satisfaction, patient satisfaction as well as staff satisfaction and harmony. Information was collected by means of questionnaires completed by referring physicians and staff members. One-on-one interviews were executed on patients. An international ISO accredited Nuclear Medicine department was visited to establish the suggested path to follow en route to successful ISO accreditation and certification. Results: Referring physicians indicated overall satisfaction with service provision, but a need for electronic report and image transfers seemed too dominant. The patient satisfaction survey resulted into overall satisfaction with personal service providing, but the provision of written and understandable information, long waiting times and t equipment must receive attention. Staff questionnaires indicated a general lack of communication between different professional groups and the need for interpersonal loyalty and team building. Improvement measures were identified to ensure the continuous improvement of the QMS by focusing on these quality parameters. Conclusion: The department has QA procedures in place, but does not meet all criteria for external accreditation. In order to ensure departmental harmony and sustainability of client and staff satisfaction, the departmental objectives in measured and improved where needed. The successful implementation and continuous improvement of a customised QMS, following the guidelines outlined in the QCM will lead to successful accreditation. / AFRIKAANSE OPSOMMING: Inleiding: Die belangrikheid van kwaliteit versekering in Kerngeneeskunde vir die versekering van optimale flikkergrafiese resultate en korrekte pasient handtering kan nie onderskat word me. 'n Klantgerigte Kwaliteitsbeheersisteem (KBS) moet gedokumenteer en geimplimenteer word vir die Kerngeneeskunde Departement deur die riglyne te volg soos uiteengesit deur die Internationale Standardiserings Organisasie (ISO). Materiale & Metodes: 'n Kwaliteitskontrol handleiding (KB), wat die departementele kwaliteitsbeleid, die missie en visie asook die departementele doelwitte definieer is ontwerp en saamgestel vir die Kerngeneeskunde departement van Tygerberg Hospitaal. Hierdie ontwerp is gebaseer op die raamwerk van 'n aanvaarde kwalteitsbeheersisteem. ISO fokus op klante tevredenheid asook personeel harmonie en tevredenheid. Vir hierdie rede is daar 'n tevredenheidpeiling uitgevoer op die klante en personeel in die strewe na ISO akkreditasie en sertifikasie. Inligting was versamel deur vraelyste wat ingevul was deur die verwysende geneeshere, pasiente en personeel. Resultate: 'n Kwaliteitskontrole handleiding was saamgestel VIr gebruik in die Kerngeneeskunde department. Die interne audit resultate het aangedui dat die verwysende geneeshere tevrede is met die algehele dienslewering. Die behoefde aan elektronies versende verlae en beelde was dominerend. Die pasient tevredenheidspeiling het bevestig dat die pasiente tevrede is met persoonlike dienslewering, maar 'n tekort aan verstaanbare en geskrewe inligting was geidentifiseer. Die lang wagtye en stukkende apparaat is ook gebiede wat verbertering benodig. Algemene gebrek aan komminukasie tussen die verskillende beroepsgroepe, die behoefte aan interpersoonlike lojaliteit en span werk was die hoof bevindinge van die personeel tevredenheidspeiling. Verbeterings maatreels, gefokus op hierdie departementele doelwitte, was geidentifiseer ten eide te verseker dat die KBS voordurend verbeter en in stand gehou word. Samevatting: Alhoewel die departement wel KB prosedures in plek het, voldoen dit nie aan al die criteria vir eksterne akkreditasie nie. Ten einde departementele harmonie en kliente tevredenheid te verseker, met die oog op ISO sertifikasie, moet die departmenteIe doelwitte deurlopend gemeet en verbeter word.

Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Manufacturers can gain a competitive advantage through lower production cost, better quality, better efficiencies and being more flexible and dependable than its competitors. Lower production cost can be a result of first-time-right quality products and efficient production processes in terms of throughput. Low production cost is not a destination but a journey where the goalpost will always move as competitors will continuously come up with ideas to lower prices and margins have to be cut in order to stay competitive. This is where manufacturers must come up with initiatives to continuously drive its operational metrics to remain competitive. This research report will explain how Distell's biggest bottling plant, Green Park, successfully introduced Process Control to increase its quality operational metric and a Six Sigma project to reduce downtime to increase its efficiency operational metric to drive its operational costs down. Process Control was introduced as a TOM initiative with a subsequent reduction in rework due to poor quality (thousands) from R1 585 to R484. This contributed to 'first-time-right' production, better efficiencies and not tying up valuable production time with reworks. The Six Sigma principles were used on a production line to introduce initiatives to reduce changeovers and unplanned downtime to improve its GEE. This initiative has a projected benefit of R687 (thousands). The report also indicated that a 1% increase in Green Park's overall GEE will result in 1% saving of production hours resulting in a 1% saving of variable cost. This will result in an OEE of 63% that will save 226 hours and R410(thousands). / AFRIKAANSE OPSOMMING: Vervaardigers kan 'n kompeterende voorsprong verkry deur laer produksiekoste, beter gehalte en groter doeltreffendheid te bewerkstellig en deur meer buigbaar en betroubaar as hul teestanders te wees. Goeie gehalte produkte wat die eerste keer reg is en doeltreffende produksieprosesse vir verwerkingskapasiteit kan laer produksiekoste tot gevolg het. Lae produksiekoste is nie 'n bestemming nie, maar 'n reis waartydens die doelpale sal skuif met teestanders wat deurgaans met idees om pryse te verjaag, vorendag sal kom. Winsgrense sal moet verklein word om kompeterend te bly. Hier moet vervaardigers inisiatief aan die dag lê om hul operasionele meetbares te dryf om kompeterend te bly. Hierdie navorsingsverslag sal verduidelik hoe Distell se grootste botterings aanleg, Green Park, prosesbeheer (Process Control) suksesvol in werking gestel het om sy meetbares wat operasionele gehalte betref, te verhoog, en 'n Six Sigma-projek ingestel het om staantyd te verminder sodat sy meetbares wat operasionele doeltreffendheid betref, kan verhoog en sy operasionele koste sodoende besnoei word. Prosesbeheer is as algehele gehaltebestuursinisiatief ingestel met 'n gevolglike vermindering van herverwerking weens swak gehalte (duisende) van R1 585 na R484. Dit het bygedra tot groter doeltreffendheid met produksie wat uit die staanspoor reg is, en verhoed dat kosbare produksietyd op herverwerking gespandeer word. Die Six Sigma-beginsels is in 'n produksielyn gebruik om inisiatiewe in werking te stel om oorskakelings en onbeplande staantyd ter verbetering van die algehele toerustingsdoeltreffendheid (OEE), te verminder. Hierdie inisiatief hou 'n geprojekteerde voordeel van R687 (duisende) in. Die verslag dui verder aan dat 'n 1%-verhoging in Green Park se algehele OEE sal lei tot 'n 1% besparing in produksie-ure, wat 'n 1% besparing op veranderlike koste tot gevolg het. Dit sal tot 'n OEE van 63% lei, wat 226 uur en R410 (duisende) sal spaar.

Thesis (MBA)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: With globalisation and the accompanying increase in international trade there is a great drive towards performing risk assessments on the quality of products. Such assessments are of particular importance within the food and drug industry, so much that this approach is also being adapted by the FDA in their analysis of the quality of products and probable risks to it. The pharmaceutical industry is heavily regulated to reduce or eliminate the production and distribution of poor quality products. Pharmaceuticals have to be of high quality as people's lives depend on it. Many pharmaceutical companies import raw materials from international manufacturers or international agents. In most cases the raw material or the products have to go through a long and complicated supply chain. The more parties involved in the supply chain, the greater the risk to product quality. Supply chain partnerships have therefore become critical to manage these risks to product quality throughout the supply chain. In order to manage risks to product quality, it has become vital to perform product quality risk assessments, especially through the supply chain. In this study the Failure Mode Effect Analysis (FMEA) is used to perform a risk assessment of risks to product quality throughout the supply chain. To obtain the criticality of the risks the Failure Mode Effect and Criticality Analysis (FMCEA) is applied. Quality improvement systems which contribute towards managing the risks to product quality are also discussed in this report. By managing quality risks to pharmaceutical products along with using quality as a strategy, the pharmaceutical company contributes towards improved health for patients as well as customer satisfaction, business success and excellence. / AFRIKAANSE OPSOMMING: Die toepassing van die analise van die risiko op produkte is vinnig besig om te vermeerder. Die FDA gaan dit toepas in hulle analise van die kwaliteit van produkte en die risiko wat daarmee gepaard gaan, in die voedsel en medisyne bedryf. Die farmaseutiese industrie word baie streng gereguleer om te verhoed dat die produksie en distribusie van swak kwaliteit produkte ervaar word. Farmaseutiese produkte moet van hoë gehalte wees, omdat die gesondheid van pasiënte daarvan afhang. Baie farmaseutiese maatskappye bestel rou materiale van oorsese makelaars en in baie gevalle moet die rou materiale deur 'n lang en gekompliseerde voorsieningsketting gaan. Hoe meer agente betrokke is, hoe hoër word die risiko met respek tot die kwaliteit van die produk. Die voorsieningsketting speel 'n kritiese rol om te verseker dat risikos beheer kan word, omdat elke party verantwoordelik is vir die lewering van kwaliteitsprodukkte. Om te verseker dat risikos beheer word, het dit belangrik geword om risiko analise te doen op die kwaliteit van produkte, veral wanneer in die voorsieningsketting. In hierdie studie word die "Failure Mode Effect Analysis (FMEAJ' gebruik om 'n risiko analise te doen met betrekking tot risikos op 'n produk se kwaliteit wanneer in die voorsieningsketting. Die "Failure Mode Effect, and Criticality Analysis (FMECAJ', word ook toegepas om te bereken hoe krities die risiko is. Verbeteringstelsels wat bydra tot die beheer en kontrole van risikos vir produk kwaliteit word ook in hierdie studie bespreek. Deur die risikos te beheer op die kwaliteit van produkte, dra die farmaseutiese maatskappy by tot beter gesondheid vir pasiente, en verseker klient satisfaksie en suksesvolle besigheid.

Thesis (MScAgric)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Wine cellars are diverse in terms of equipment types and process configurations. Whilst other food production processes have, in many cases, been properly analysed and modelled, this process diversity has resulted in an absence of process analyses in the wine industry. Each wine cellar is unique and represents a fully integrated agro-business, starting with a raw material (grapes) and extending to marketing and selling of the final product (wine). This makes the wine industry unique in this context. This study is the first attempt to analyse winemaking procedures in the form of a process audit. The study was approached in the following manner: • A questionnaire was developed to assess cellar configurations and conditions. This questionnaire was submitted to a statistically significant number of cellars, and a statistically significant number of questionnaires were returned. • The data collected from the questionnaire were statistically analysed and associations between equipment or procedures and wine faults were identified. • Three cellars were studied in depth. These three cellars had their processes audited and their effluent characterised. Additional data were obtained from current sampling projects and these data were analysed to complement the data obtained from the questionnaire • A preliminary input/output model was developed. The major results of this study are: • It was found that certain faults that appear in wine might be associated with equipment and/or process faults. These associations are statistically significant and they show that cellar hygiene is of critical importance when assessing these wine faults. The most important of these faults are VA, microbial contamination of the wine, sluggish and stuck fermentations. A risk hierarchy was derived to indicate which events are associated with others most strongly. • It was found that few wineries measure water consumption and even fewer wineries measure the quantity of effluent produced. • Correlations have been developed to predict winery parameters in terms of tons of grapes pressed per annum. These parameters include water and electricity consumed, wine produced and the quantity of effluent produced. Effluent characteristics have also been correlated to the tons of grapes pressed per annum. These characteristics include chemical oxygen demand, sodium absorption ratio and total dissolved solids in solution. Chemical oxygen demand was identified as the most important contributing factor in winery effluent. It was shown that all variables rise with an increase in cellar size, but the rise is not linear. This implies that large cellars have greater quantities of effluent of lower quality than small cellars. Most cellars have effluent concentrations that require some form of effluent treatment. The characterisation of effluent shows that the most widely used disposal practice is irrigation, and that the effluent disposed in this manner does not meet legislative requirements. • A preliminary input/output model was developed in order to enable wineries that have not measured the relevant parameters to predict the abovementioned variations. The resolution of these predictions is low but the model serves to provide an initial estimate if there are no data available. The model will give industrial averages for any given cellar size. • An economic balance was performed using this preliminary model. It was shown that if cellars were to lower the consumption of utilities and to reduce the strength of their effluent (using cleaner practices and not dilution) the reduction of operating costs could be reduced by 14% for smaller cellars to 17% for larger cellars. This study has shown that it is possible to make wine in a more environmentally friendly manner, producing better quality wines, without incurring extra costs. / AFRIKAANSE OPSOMMING: Wynkelders is diverse eenhede ten opsigte van die tipe toerusting en prosesse wat gebruik word. Terwyl ander prosesse rondom voedselproduksie in baie gevalle reeds geanaliseer en gemodelleer is, het die diversiteit in die wynindustrie gelei tot 'n afwesigheid van prosesanalises. Elke wynkelder is uniek en verteenwoordig 'n ten voile geintegreerde agro-besigheid wat begin met die rou materiaal (druiwe) en lei tot die bemarking en verkope van die finale produk (wyn), 'n eienskap wat die wynindustrie uniek maak in hierdie verband. Hierdie studie is die eerste poging om die wynmaakproses in die vorm van ‘n proses-oudit te analiseer. Die studie is soos volg aangepak: • ‘n Vraelys is ontwikkel om kelderkonfigurasies en -toestande te ondersoek. Die vraelys is aan ‘n statisties betekenisvolle aantal kelders voorgele, en ‘n statisties betekenisvolle aantal vraelyste is terugontvang. • Die data wat uit die vraelyste ontvang is, is statisties ontleed en verwantskappe tussen toerusting of prosesse en wyngebreke is geidentifiseer. • Drie kelders is in diepte bestudeer. Hierdie drie kelders se prosesse is geoudit en die afvloeiwater is gekarakteriseer. Addisionele data is verkry van huidige projekte en hierdie data is ge-analiseer om die data van die vraelys aan te vul. • ‘n Voorlopige inset / uitset model is ontwikkel. Die belangrikste resultate van hierdie studie is: • Dit is bevind dat sekere gebreke wat in wyn voorkom geassosieer kan word met tekortkominge in toerusting en/of prosesse in die kelder. Hierdie assosiasies is statisties betekenisvol en toon dat kelderhigtene van kritiese belang is wanneer gebreke in wyn ondersoek word. Die mees belangrike gebreke wat voorkom is vlugtige suur, mikrobiese kontaminasie van wyn, slepende en gestaakte fermentasie. ‘n Risikohierargie is afgelei om die gebeure te toon wat die sterktste met mekaar geassosieer word. • Dit is gevind dat min wynkelders waterverbruik meet. Selfs minder kelders meet die hoeveelheid afvloeiwater wat geproduseer word. • Korrelasies is ontwikkel om kelderparameters te voorspel in terme van ton druiwe gepars per jaar. Hierdie parameters sluit in water- en elektrisiteitsverbruik, wyn geprosuseer en hoeveelheid afvloeiwater geproduseer. Eienskappe van afvloeiwater is ook gekorreleer met die ton druiwe wat per jaar gepars word. Hierdie eienskappe sluit in chemiese suurstofbehoeftes, natrium absorpsieverhoudings en totale opgeloste soliede materiaal in oplossing. Chemiese suurstofbehoeftes is geidentifiseer as die mees belangrike bydraende faktor tot afvloeiwater in kelders. Dit is getoon dat alle veranderlikes verhoog hoe groter die kelder, maar hierdie verhoging is nie lineer nie. Dit impliseer dat groter kelder meer afvloeiwater van ‘n laer kwaliteit produseer. Die meeste kelders produseer afvloeiwater van sodanige konsentrasies dat behandeling daarvan nodig is. Die ondersoek van hierdie afvloeiwater toon dat die mees algemene wyse van wegdoening van afvloeiwater besproeiing is, en dat afvloeiwater wat op hierdie manier weggedoen word, nie voldoen aan die wetgewing se vereistes nie. • 'n Voorlopige inset/uitset model is ontwikkel om kelders wat nie die toepaslike parameters gemeet het nie in staat te stel om hierdie parameters te voorspel. Die akuraatheid van hierdie voorspellings is nie hoog nie, maar die model verskaf ‘n aanvanklike skatting waar daar geen data beskikbaar is nie. Die model verskaf industriele gemiddeldes aan kelders van enige grootte. • ‘n Ekonomiese balans is uitgevoer deur van hierdie model gebruik te maak. Dit is getoon dat indien kelders die gebruik van water en elektrisiteit verminder en die konsentrasie van afvloeiwater verlaag (deur van skoner paktyke gebruik te maak, en nie verdunning nie) die bestuurskoste met 14% vir kleiner kelders tot 17% vir groter kelders verlaag kan word. Die studie het getoon dat dit moontlik is om wyn te maak op ‘n meer omgewingsvriendelike wyse, en sodoende beter kwaliteit wyn te produseer sonder addisionele kostes.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Nitrogen composition of grape must is highly variable and impacts on the health of the fermenting yeast population as well as the formation of aroma and flavour compounds in wine. Insufficient yeast assimilable nitrogen (YAN), mostly consisting of amino acids and ammonium, can lead to stuck or sluggish fermentations as well as the formation of undesirable compounds such as H2S. Furthermore, it is well established that the total concentration of YAN and the specific amino acid composition have a significant impact on the final aroma and flavour of wines. However, the impact of individual amino acids and of specific amino acid compositions on fermentation kinetics and on the production of aroma and flavour impact compounds under winemaking conditions is not well understood. The first goal of this study was to evaluate the effect of single amino acids on growth kinetics and major volatile production of two industrial wine yeast strains under conditions resembling wine fermentations. To facilitate these fermentation conditions while also allowing for easy reproducibility and manipulation of the initial components, a synthetic grape media was utilized. Biomass formation, exponential growth rate, lag phase, and fermentation duration were utilized to evaluate the efficiency of single amino acids. The data show that previously observed trends in laboratory strains mostly apply to these conditions and strains. In general, the efficiency of amino acids to be used as nitrogen sources and the production of major volatiles due to their presence followed the same patterns for both industrial yeast strains. However, the production of the secondary metabolites butanol, propanol, acetic acid, and ethyl acetate were found to be produced in different final concentrations dependent upon the yeast strain. The branched-chained and aromatic amino acids (BCAAs) treatments were observed to have the most dramatic effects on major volatile production. Investigating the relationships between the initial concentration of the BCAAs and the final concentrations of major volatile compounds, it was found that the production of fusel alcohols and fusel acids due to the degradation of BCAAs by S. cerevisiae could be predicted from the initial concentration of BCAAs. While under simple nitrogen conditions the production of several other secondary metabolites such as butanol, propionic acid, valeric acid, decanoic acid and 2-phenylethyl acetate were found to be correlated to the initial concentration of BCAAs in the media. Future studies should focus on the validation of these trends in aroma production in real grape musts under various fermentation temperatures for a number of industrial wine yeast strains. / AFRIKAANSE OPSOMMING: Die stikstof samestelling van druiwemos is hoogs veranderlik en impakteer op die kerngesondheid van die fermenterende gis populasie asook die produksie van aroma- en geurverbindings in wyn. Onvoldoende assimileerbare stikstof (ook genoem “yeast assimilable nitrogen” (YAN)), wat meestal bestaan uit aminosure en ammonium, kan aanleiding gee tot steek- of slepende fermentasies, asook die vorming van ongewensde verbindings soos H2S. Dit is alombekend dat die totale konsentrasie van YAN en dan ook die spesifieke aminosuur samestelling ‘n noemenswaardige impak op die finale aroma en smaak van wyn het. Die invloed van individuele am inosure en spesifieke aminosuur samestellings op die fermentasie kinetika, asook die produksie van verbindings met ‘n impak op die wyn aroma en smaak, word egter nie deeglik verstaan nie. Die eerste doelwit van die studie was om twee industriële gisrasse te gebruik om die effek van enkel aminosure op die groei-kinetika en produksie van die vername vlugtige verbindings onder wynmaak toestande te bepaal. Kunsmatige, gedefinieerde druiwermosmedium is gebruik om wynmaak toestande te simuleer en ook herhaalbaarheid en manipulering van die aanvanklike samestelling van die medium te verseker. Die studie het vorige tendense wat opgemerk is in die evaluasie van laboratorium rasse onder soortgelyke toestande bevestig. Die doeltreffendheid waarmee aminosure oor die algemeen gebruik word as stikstofbron, asook die produksie van die vernaamste vlugtige verbindings wat gekoppel is aan hulle teenwoordigheid, het ‘n vergelykbare patroon vir beide rasse gevolg. Die sekondêre metaboliete butanol, propanol, asetaat en etiel-asetaat is egter wel in verskillende eindkonsentrasies geproduseer deur die verskillende gisrasse. Die vertakte-ketting en aromatiese aminosuur (“branched-chained and aromatic amino acids” (BCAAs)) behandelings het die mees dramatiese effek op die produksie van die vernaamste vlugtige komponente gehad. Ondersoek na die verwantskap tussen die aanvanklike konsentraies van die BCAAs en die finale konsentrasies van dié verbindings het aangedui dat die produksie van hoër alkohole en sure, as gevolg van die afbraak van BCAAs deur S. cerevisiae, met behulp van die aanvanklike konsentrasie van die BCAAs voorspel kon word. Terselfdertyd is gevind dat onder eenvoudige stikstoftoestande, verskeie ander sekondêre metaboliete soos butanol, propionaat, valeriaat, dekanoësuur en 2-fenieletielasetaat, gekorreleer kan word met die aanvanklike BCAAs in die media. Verdere studies moet poog om hierdie tendense ten opsigte van aromaproduksie te bevestig en wel deur gebruik te maak van ware druiwemos, verskeie fermentasietemperature, asook ’n verskeidenheid van wyngisrasse.

Η απεικόνιση μαγνητικού συντονισμού (MRI) βασίζεται στο φυσικό φαινόμενο του πυρηνικού μαγνητικού συντονισμού (NMR). Ενώ το φαινόμενο αυτό είναι γνωστό από το 1950, η πρώτη μαγνητική τομογραφία σε άνθρωπο διενεργήθηκε μόλις το 1977. Η δεκαετία του '80 ήταν η δεκαετία που τα συστήματα MRI άρχισαν να εξελίσσονται ταχύτατα και η εξέλιξη αυτή συνεχίζεται ακόμη και σήμερα. Στις μέρες μας, τα σύγχρονα συστήματα MRI κάνουν πολύ περισσότερα από απλή απεικόνιση, με τη μαγνητική τομογραφία διάχυσης, τη φασματοσκοπία και τη λειτουργική μαγνητική τομογραφία να αποτελούν νέες και πολλά υποσχόμενες εφαρμογές. Τα συστήματα MRI δεν χρησιμοποιούν ιοντίζουσα ακτινοβολία, αλλά μαγνητικά πεδία και ηλεκτρομαγνητικά κύματα στην περιοχή των ραδιοσυχνοτήτων. Αυτός είναι πιθανώς ο λόγος για τον οποίο τα συστήματα MRI δεν είχαν τύχει τόσης προσοχής όπως τα συστήματα υπολογιστικής τομογραφίας, όσον αφορά τους κανονισμούς που διέπουν την ασφάλεια της χρήσης τους για χρήση σε εξετάσεις ασθενών. Ωστόσο, δεδομένου ότι η απεικόνιση χρησιμοποιείται για τη διάγνωση και μια λανθασμένη διάγνωση μπορεί να οδηγήσει σε λανθασμένη θεραπεία ή την απουσία θεραπείας, τα οποία με τη σειρά τους μπορεί να οδηγήσουν σε μη αναστρέψιμη βλάβη για την υγεία των ασθενών ή ακόμα και στο θάνατο, η Αμερικανική Ένωση Φυσικών Ιατρικής (AAPM) είχε προτείνει μεθόδους για τον έλεγχο της ποιότητας εικόνας από τις αρχές της δεκαετίας του 1990. Το Αμερικανικό Κολλέγιο Ακτινολογίας (ACR), είχε επίσης συμβάλει στην προσπάθεια αυτή από την αρχή της νέας χιλιετίας, προτείνοντας μεθόδους ελέγχου της ποιότητας εικόνας για τη δημιουργία ενός προγράμματος πιστοποίησης για τις εγκαταστάσεις MRI. Το 2010 η AAPM δημοσίευσε μια έκθεση (AAPM report No. 100) με τίτλο «Έλεγχοι αποδοχής και διαδικασίες διασφάλισης ποιότητας για εγκαταστάσεις απεικόνισης μαγνητικής τομογραφίας», το οποίο περιγράφει τις διαδικασίες για τον έλεγχο της απόδοσης των μαγνητικών τομογράφων, αλλά και τις διαδικασίες που αφορούν άλλα ζητήματα ασφάλειας για τους ασθενείς και το προσωπικό. Στην Ελλάδα μέχρι πρόσφατα, οι εγκαταστάσεις MRI - σε αντίθεση με τους υπολογιστικούς τομογράφους και όλα τα άλλα ακτινολογικά συστήματα - ήταν εκτός της εποπτείας της Ελληνικής Επιτροπής Ατομικής Ενέργειας (Ε.Ε.Α.Ε.) και της Ένωσης Φυσικών Ιατρικής Ελλάδος (Ε.Φ.Ι.Ε.). Ωστόσο, από τις αρχές του 2013, η E.E.A.E. έχει προτείνει ένα πρόγραμμα διαπίστευσης (με βάση την έκθεση AAPM Νο. 100) που πρέπει να εφαρμόζεται σε όλες τις καινούριες εγκαταστάσεις MRI. Αυτό το πρόγραμμα πιστοποίησης σταδιακά θα εφαρμοστεί και σε παλαιότερες εγκαταστάσεις. Ο στόχος είναι μέσα σε 5 χρόνια το πολύ, όλες οι εγκαταστάσεις MRI να είναι διαπιστευμένες όπως ισχύει εδώ και πολλά χρόνια για τις εγκαταστάσεις υπολογιστικής τομογραφίας. Ο σκοπός αυτής της διπλωματικής εργασίας είναι να συνοψίσει το βασικό θεωρητικό υπόβαθρο πάνω στο οποίο στηρίζεται η απεικόνιση μαγνητικού συντονισμού, για να βοηθήσει τους Φυσικούς Ιατρικής οι οποίοι δεν έχουν εξειδικευτεί στα συστήματα αυτά, να κατανοήσουν τις αρχές της λειτουργίας τους, ιδίως εκείνες που σχετίζονται με τον τρόπο δημιουργίας των διαγνωστικών εικόνων. Στο επόμενο κεφάλαιο, παρουσιάζεται η AAPM report No. 100 (μεταφρασμένη στα Ελληνικά), προκειμένου να θέσει τις βάσεις για την κατανόηση των διαδικασιών που χρησιμοποιούνται για τους ποιοτικούς ελέγχους (QC), αλλά και άλλα θέματα που αφορούν στην ασφάλεια λειτουργίας των συστημάτων MRI. Στο τελευταίο κεφάλαιο, παρουσιάζεται η εφαρμογή αυτών των διαδικασιών σε μια υπάρχουσα εγκατάσταση MRI, ως ένα παράδειγμα του τρόπου με τον οποίο εκτελούνται οι διαδικασίες QC και του τρόπου με τον οποίο οι εικόνες που προκύπτουν αξιολογούνται προκειμένου να εξαχθούν μετρήσιμες ποσότητες. Αυτές οι ποσότητες χρησιμοποιούνται ως δείκτες απόδοσης και ο Φυσικός Ιατρικής συγκρίνοντάς τις με καθορισμένα όρια, μπορεί να διαπιστώσει εάν το ελεγχόμενο σύστημα MRI πληροί τα καθορισμένα κριτήρια (κάτι που υποδηλώνει μια ικανοποιητική λειτουργία και ποιότητα απεικόνισης) ή εάν υπάρχουν ένα ή περισσότερα προβλήματα που οδηγούν σε μη αποδεκτή ποιότητα απεικόνισης και ως εκ τούτου απαιτούνται διορθωτικές ενέργειες. Στην τελευταία περίπτωση, ο έλεγχος που ανέδειξε το πρόβλημα θα πρέπει να επαναλαμβάνεται μετά από την όποια επισκευή, προκειμένου να διαπιστωθεί εάν το σύστημα MRI είναι κατάλληλο να χρησιμοποιηθεί για διάγνωση. / Magnetic Resonance Imaging (MRI) is based on the physical phenomenon of Nuclear Magnetic Resonance (NMR). While this phenomenon has been known since the 1950s, the first MRI scan was performed on a human being just in 1977. The 80’s was the decade that MRI systems started to evolve rapidly and this evolution still goes on. Nowadays, modern MRI systems do so much more than simple imaging, with diffusion MRI, MRI spectroscopy and functional MRI being the new promising applications. MRI scanners do not use ionizing radiation but magnetic fields and electromagnetic waves in the range of radiofrequencies. This is probably the reason why the MRI scanners did not attract so mach attention as CT scanners did, in terms of regulations regarding the safety of their use for patient scanning. However, since imaging is used for diagnosis and a wrong diagnosis can result to a wrong therapy or no therapy at all, which in turn may result to irreversible damage in the patient health or even to death, the American Association of Physicists in Medicine (AAPM) had proposed methods for testing the image quality from the early 1990s , . The American College of Radiology (ACR) has also contributed to this effort in the beginning of the new millennium, proposing image quality control methods to establish an accreditation program for MRI facilities , . In 2010 the AAPM published a report (AAPM REPORT NO. 100) with title “Acceptance Testing and Quality Assurance Procedures for Magnetic Resonance Imaging Facilities”, which describes procedures for testing the performance of MRI scanners, but also procedures concerning other safety issues for the patients and the personnel. In Greece until recently, MRI facilities – in contrast to CT scanners and all the other radiological equipment - were beyond the supervision of the Greek Atomic Energy Commission (Ε.Ε.Α.Ε.) and the Greek Association of Physicist in Medicine (Ε.Φ.Ι.Ε.). However, from the beginning of 2013, E.E.A.E. has proposed an accreditation program (based on the AAPM report No. 100) to be applied in all new MRI facilities. This accreditation program will progressively applied in older MRI facilities as well. The goal is within 5 years at most, all MRI facilities be accredited in the same way that CT scanners are. The purpose of this MSc thesis was to review the basics of MRI theory, to help Medical Physicists which are not experts in MRI, understand the principles of its operation, especially those related to the production of diagnostic images. In the next chapter the AAPM No. 100 report is presented (translated in Greek), in order to set the foundations for understanding the procedures used for quality control (QC) purposes but also other MRI operation safety issues. In the last chapter, an application of these procedures to an existing MRI installation is presented, as an example of the way that QC procedures are performed and the way that the resulting images are evaluated to result to measurable quantities. These quantities are used as performance indices and when compared to established limits, may inform the Medical Physicist whether the tested MRI systems satisfies the established criteria indicating an acceptable performance or whether one or more problems exist that result to suboptimal image quality and therefore corrective actions should be taken. In the latter case the failed test should be repeated after the field service engineers have corrected the problem, in order to ascertain that the MRI system is eligible to be used for medical diagnosis.