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Comprehensive two-dimensional liquid chromatographic analysis of anthocyaninsWillemse, Chandre Monique 04 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Anthocyanins are naturally occurring pigments responsible for the colour of many natural products,
including grapes and wine. These pigments are important to the food industry and have been
recognised for their nutritional value since they play an important role in the reduced risk of various
chronic diseases in humans. Anthocyanins also play an important role in the aesthetic perception and
quality of red wine. However, due to the large structural diversity of grape-derived anthocyanins and
the many derivatives formed from these during wine ageing, the accurate analysis of wine pigments
is extremely challenging. Reversed-phase liquid chromatography (RP-LC) is mostly used for
anthocyanin analysis, although the technique often provides insufficient resolving power for complex
mixtures of anthocyanins. In addition, the lack of commercially available standards and identical
mass spectral characteristics hampers identification of these compounds. The coupling of multiple
orthogonal separation systems in comprehensive 2-dimensional liquid chromatography (LC×LC)
offers a more powerful approach for the separation of complex mixtures. The current work therefore
focussed on exploring the potential of LC×LC for the improved analysis of anthocyanins and derived
pigments in natural products and wine.
The first part of this work focussed on developing a hydrophilic interaction chromatography (HILIC)
method as an alternative to RP-LC for the anthocyanin analysis. Following extensive optimisation,
the method proved suitable for the analysis of a diverse range of anthocyanins in natural products.
Significantly, it also showed alternative selectivity compared to RP-LC. The optimised HILIC
method was then used in combination with RP-LC to develop an off-line LC×LC approach for
anthocyanins. For this purpose, half-minute fractions of the HILIC effluent were collected and reinjected
onto a RP-LC column. The off-line HILIC×RP-LC method demonstrated exceptionally high
resolving power, as measured in terms of the practical peak capacity, with many compounds separated
in two dimensions that co-eluted in 1-dimensional HPLC. Interestingly, group-type separation was
also observed based on the degree and/or nature of glycosylation and acylation of anthocyanins. In the final part of the work, a systematic approach was used for the development and optimisation of
and on-line HILIC×RP-LC method by using a 10-port switching valve to automatically transfer
fractions between the two columns. This method was then coupled to high resolution mass
spectrometry (MS) to allow the detailed investigation of anthocyanins and derived products in wine.
Ninety four pigments were identified in one- and six-year old Pinotage wines based on HILIC×RPLC
separation in combination with accurate mass MS data and fragmentation information. Significant
differences in especially the content of derived pigments were observed between the wines.
In summary, the methods developed in this work provide the means to improve anthocyanin analysis,
and therefore also show promise for the detailed investigation of these important compounds and their
alteration in natural products and their derived commodities. / AFRIKAANSE OPSOMMING: Antosianiene is natuurlike pigmente wat verantwoordelik is vir die kleur van baie natuurlike
produkte, insluitende dié van druiwe en wyn. Hierdie pigmente is belangrik vir die voedsel industrie
en word gereken vir hul voedingswaarde aangesien hulle 'n belangrike rol speel in die verlaagde risiko
van verskeie chroniese siektes onder die mens. Antosianiene speel ook 'n belangrike rol in die
estetiese persepsie en kwaliteit van rooiwyn. Desnieteenstaande, as gevolg van die groot strukturele
diversiteit van druifgeproduseerde antosianiene en die vele chemiese afgeleides wat uit hulle gevorm
kan word tydens wyn bereiding en veroudering, is die akkurate analise van natuurlike wyn-pigmente
uiters uitdagend. Omgekeerde-fase vloeistofchromatografie (RP-LC) word meestal gebruik vir die
analise van antosianiene. Dié tegniek bied egter dikwels onvoldoende skeidingsvermoë vir komplekse
mengsels van antosianiene en verwante molekules. Verder belemmer die onbeskikbaarheid van
kommersiële standaarde en identiese massa spektrale eienskappe die identifikasie van hierdie
verbindings. Die kombinasie van verskillende ortogonale skeidings meganismes in omvattende 2-
dimensionele vloeistofchromatografie (LC×LC) bied egter 'n baie kragtiger benadering vir die
skeiding van komplekse mengsels. Die huidige werk fokus dus op die ontginning van die potensiaal
van LC×LC vir die verbeterde ontleding van antosianiene en verwante afgeleide pigmente in
natuurlike produkte en wyn.
Die eerste deel van hierdie werk het gefokus op die ontwikkeling van 'n hidrofiliese interaksie
chromatografiese (HILIC) metode as ʼn alternatief vir RP-LC analise van antosianiene. Na uitgebreide
optimisering, is gevind dat die metode geskik is vir die ontleding van 'n verskeidenheid van
antosianiene in natuurlike produkte. Van groot belang is dat dit ook alternatiewe selektiwiteit in
vergelyking met RP-LC demonstreer. Hierdie geoptimiseerde HILIC metode word dan voorts gebruik
in kombinasie met RP-LC vir die ontwikkeling van ʼn af-lyn LC×LC benadering vir die analise van
antosianiene. Hiervoor is half-minuut fraksies van die HILIC uitvloei opgevang en her-ingespuit op
'n RP-LC kolom. Dié af-lyn HILIC×RP-LC metode toon buitengewoon hoë skeidingsvermoë, gemeet
in terme van die bereikbare praktiese piek kapasiteit, met baie verbindings wat geskei is in die twee
dimensies wat saam elueer in 1-dimensionele HPLC. Interessant genoeg is groep-tipe skeiding ook
waargeneem gebaseer op die graad en / of aard van glukosilasie en asilering van die antosianiene. In
die laaste deel van die werk, is 'n sistematiese benadering gevolg vir die ontwikkeling en optimisering
van ʼn aan-lyn HILIC×RP-LC deur gebruik te maak van 'n 10-poort oorskakelingsklep wat fraksies
outomaties oordra tussen die twee kolomme. Die bogenoemde metode is ook verder gekoppel aan
hoë resolusie massaspektrometrie (HR-MS) om ʼn gedetailleerde ondersoek van antosianiene en hulle
afgeleide verbindings in wyn moontlik te maak. Vier en negentig pigmente is in een- en ses jaar oue
Pinotage wyne geïdentifiseer gebaseer op HILIC×RP-LC skeiding in kombinasie met akkurate massa
MS data en fragmentasie inligting. Beduidende verskille in veral die inhoud van antosianien-afgeleide
pigmente is tussen die wyne waargeneem.
Ter samevatting, die metodes ontwikkel in hierdie werk baan die weg om antosianien ontleding te
verbeter en stel gevolglik die moontlikheid van selfs meer gedetailleerde studies van hierdie
belangrike verbindings in natuurlike produkte in die vooruitsig.
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Colour dynamics in LeucadendronSchmeisser, Michael 12 1900 (has links)
Thesis (PhD(Agric)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The bright colouration of involucral leaves in Leucadendron is unfortunately transient in nature. Undesirable colour changes render this cut flower unmarketable, resulting in a considerable loss of profit. A deeper understanding of the mechanism leading to colour change is needed to form the framework on which future manipulation strategies can be built.
Yellow Leucadendron possess the ability to degreen and regreen naturally, a phenomenon linked to the controlled degradation of chlorophyll and the lesser degradation of carotenoids, which then impart the yellow colour. This colour change is directly linked to the development of the inflorescence. Involucral leaves degreen towards anthesis and are entirely yellow at full bloom. They begin to regreen again when the last florets on the cone have wilted. Deconing before flowering completely inhibits the colour change. Deconing at full bloom, results in leaves regreening sooner. Therefore the inflorescence appears to be the origin of the cue for colour change. Any factor that expedites the death of the florets, results in sooner regreening of involucral leaves. Ultra-structurally, the degreening and regreening resulted from a transdifferentiation of mature chloroplasts to gerontoplast-like plastids, which upon regreening completely redifferentiated into fully functional chloroplasts.
In the red Leucadendron cultivar Safari Sunset, the photosynthetic pigment degradation pattern is identical to that of yellow cultivars. However, colour expression is complexed by the presence of anthocyanins. Anthocyanin concentration was shown to be directly related to the opening of the flower head rather than to the phenological development of the inflorescence. With opening, the previously shaded inner involucral leaf surfaces are exposed to higher levels of irradiance and respond by turning red, presumably for photoprotection. Similar to yellow cultivars, any factor leading to the death of the florets before flowering, not only prevents the degreening of involucral leaves, but also prevents the opening of the flower head and therefore the associated change in anthocyanin levels. The ecological significance of regreening was also investigated. What does a female Leucadendron plant stand to gain by regreening rather than discarding the involucral leaves? Regreened involucral leaves were shown not to play a significant role in providing photosynthates for the developing cone. Although the presence of regreened involucral leaves were shown to provide protection against high irradiance and radiant heating of the cone, they were not essential to ensure survival of the cone. The small floral bracts were shown to be very capable of adaptation. The most plausible reason for regreening is therefore assumed to be based on a cost-benefit relationship. As most Leucadendron are adapted to grow on very nutrient poor soils, the question should maybe be rephrased. Why waste valuable resources? Sclerophyllous leaves, like the involucral leaves, are costly to make and therefore reusing, rather than discarding them does seem a sensible strategy for survival. / AFRIKAANSE OPSOMMING: Leucadendron snyblomme word gekenmerk deur die helder kleure van hul omwindselblare. Die helder kleure is egter slegs vir 'n kort periode aanwesig waarna die snyblomme onbemarkbaar word, met aansienlike verlies aan potensiele inkomste. Die ontwikkeling van manipulasies ten einde die bemarkbare periode van Leucadendron te verleng, berus op die verkryging van 'n dieper insig in die meganisme van kleurverandering.
Die kleurveranderinge van geel Leucadendron omwindselblare is te wyte aan 'n unieke vermoë tot die gereguleerde degradasie en heropbou van chlorofiele en karotenoiede onder direkte beheer van die ontwikkelende bloeiwyse. Met die aanvang van blom, lei groter proporsionele degradasie van chlorofiele tot geleidelike vergeling van omwindselblare. Die hele blomhofie verkry uiteindelik met volblom 'n helder geel kleur. Sodra die laaste blommetjies doodgaan, neem chlorofiel- en karotenoiedsintese weer in aanvang en binnekort is die omwindselblare weer net so groen soos voor die aanvang van blom. Die geel verkleuring kan verhoed word deur die keël voor blom uit te breek. Enige faktor wat die dood van die blommetjies versnel, asook die uitbreek van keël tydens volblom, lei tot die vroeëre aanvang van vergroening. Die degradasie van plastiedpigmente hang nou saam met die differensiasie van volwasse chloroplaste tot gerontoplast-agtige plastiede wat op hul beurt weer tydens vergroening tot volkome funksionele chloroplaste herdifferensieer.
Soortgelyk aan geel Leucadendron kultivars, vind die veranderinge in plastiedpigmente ook plaas tydens blom van die rooi kultivar, Safari Sunset. Kleurveranderinge in 'Safari Sunset' is egter meer ingewikkeld vanweë die aanwesigheid van variërende konsentrasies antosianiene. Antosianienkonsentrasies en rooi kleur neem toe tydens blom vanwee die blootstelling van die beskutte adaksiale binnekante van omwindselblare aan hoe irradiasie met die oopvou van die blomhofie. Die akkumulasie van antosianiene het moontlik 'n fotobeskermende funksie. Kleurveranderinge in 'Safari Sunset' kan, soos in geel kultivars, voorkom word deur blom te verhoed. Antosianiensintese word voorkom deurdat die blomhofie geslote bly en is nie direk gekoppel aan blom soos wat met plastiedpigmente die geval is nie.
Die belang van vergroening is ondersoek na aanleiding van die vraag oor wat dit 'n vroulike Leucadendron baat om omwindselblare te behou na die afloop van blom? Die bydrae van foto-assimilasie deur omwindselblare tot die ontwikkeling van keels is beperk. Alhoewel omwindselblare wel keels teen hoe irradiasie en stralingsverhitting beskerm, is die blomskutblare in staat om aan te pas by hierdie kondisies. Die mees waarskynlike verklaring vir die behoud van die omwindselblare na blom berus moontlik op 'n koste-voordele verwantskap. Alhoewel nie essensieel nie, is die beperkte bydrae van die omwindselblare na die afloop van blom tot die oorlewing en welstand van die keel waarskynlik genoegsaam om hul behoud te regverdig. Verskeie Leucadendron spesies groei in gronde wat baie arm is aan nutriente. Sklerefiele blare, soos die van Leucadendron, is verder duur om te vervaardig. Dit maak dus sin om hulle vir meer as een funksie te herontplooi eerder as om hulpbronne te belê in meer gespesialiseerde en minder durende blombykomstighede. Dus dui die behoud van omwindselblare dalk op 'n strategie wat gemik is op die behoud en besparing van beperkte hulpbronne.
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Design, implementation and performance evaluation of robust and secure watermarking techniques for digital coloured images : designing new adaptive and robust imaging techniques for embedding and extracting 2D watermarks in the spatial and transform domain using imaging and signal processing techniquesAl-Nu'aimi, Abdallah Saleem Na January 2009 (has links)
The tremendous spreading of multimedia via Internet motivates the watermarking as a new promising technology for copyright protection. This work is concerned with the design and development of novel algorithms in the spatial and transform domains for robust and secure watermarking of coloured images. These algorithms are adaptive, content-dependent and compatible with the Human Visual System (HVS). The host channels have the ability to host a large information payload. Furthermore, it has enough capacity to accept multiple watermarks. Abstract This work achieves several contributions in the area of coloured images watermarking. The most challenging problem is to get a robust algorithm that can overcome geometric attacks, which is solved in this work. Also, the search for a very secure algorithm has been achieved via using double secret keys. In addition, the problem of multiple claims of ownership is solved here using an unusual approach. Furthermore, this work differentiates between terms, which are usually confusing the researchers and lead to misunderstanding in most of the previous algorithms. One of the drawbacks in most of the previous algorithms is that the watermark consists of a small numbers of bits without strict meaning. This work overcomes this weakness III in using meaningful images and text with large amounts of data. Contrary to what is found in literature, this work shows that the green-channel is better than the blue-channel to host the watermarks. A more general and comprehensive test bed besides a broad band of performance evaluation is used to fairly judge the algorithms.
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Influence of colour on the consumer behaviour of Generation Y students in the Vaal Triangle / Re-an MullerMüller, Re-an January 2011 (has links)
Colour influences the human mind and body through physical as well as psychological reactions to specific colours. These reactions are conditioned by previous experiences leading to certain preferences, associations and perceptions regarding certain colours. There are various aspects within a firm where colour may be utilised to the benefit of its marketing efforts. Marketers must realise that colour may be very influential and it is important to pay close attention to the associations and preferences of the firm’s target market(s) the influence of colour on human perceptions has been widely studied in many research fields. Most marketers recognise the importance of colour within the marketing environment (Section 1.1). Colour has different meanings for different people and these differences need to be acknowledged to ensure success in marketing efforts. If colour is used strategically within the marketing mix (product, place and promotion) of a firm, it may influence consumers positively (Section 1.2). This study endeavoured to determine the colour preferences, associations and perceptions of Generation Y students in South Africa. The findings of this study will be of value to those marketers who target this cohort and may utilised by them to use colour more effectively within their marketing mix. The purpose of this study was to determine the influence of colour on the consumer behaviour of Generation Y students in the South African market. The research study investigated the following aspects: • The colour preferences of Generation Y students. • Emotions Generation Y students associate with different colours. • How Generation Y students perceive various colours. • Product colour and product packaging colour preferences of Generation Y students. • Consumer behaviour patterns of Generation Y students regarding specified products. For this study, the target population comprised of Generation Y students registered at South Africa’s public higher education institutions (HEIs). The sampling frame consisted of a list of South Africa’s 23 public HEIs, as stipulated by the Department of Higher Education and Training (2011). This study made use of a non-probability convenience sample of two HEI campuses located in the Vaal Triangle region of South Africa’s Gauteng province that was drawn from the sampling frame. Thereafter, a convenience sample of 500 under-graduate students was drawn from these HEI campuses - 250 students per campus. A structure self-administered questionnaire was distributed to the respondents. The questionnaire requested respondents to rank colours according to preferences, on a four- and seven-point Likert scales were used respectively to determine colour associations and perceptions. The questionnaire also contained questions using a four-point Likert scale designed to determine product colour and product-package colour preferences as well as questions designed to determine consumer behaviour patterns of Generation Y students regarding certain products. In addition, the respondents were asked to provide certain demographic data. The findings indicate that Generation Y students have distinctive colour preferences, associations and perceptions. The respondents also indicated a number of notable product and product package preferences as well as particular consumer behaviour traits. When comparing male and female respondents as well as black and white respondents respectively, the results depicted various statistical significant differences (p < 0.05). Cohen’s D statistic was computed to determine the level of practical significance of these differences. From this, it is evident that colour do influence Generation Y students’ consumer behaviour and perceptions to some extent. Colour is present in every aspect of marketing. If used strategically, colour may be used by marketers to influence their target market’s perceptions and preferences. The findings emanating from this study should be used as a guideline to incorporate colour into the design of the marketing mix (colour) in such a way as to appeal to Generation Y students. / MCom, Marketing Management, North-West University, Vaal Triangle Campus, 2012
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Wearing identity : colour and costume in Meliador and Sir Gawain and the Green KnightMeredith, Elysse Taillon January 2012 (has links)
Worn items are a crucial part of non-verbal social interaction that simultaneously exhibits communal, cultural, and political structures and individual preferences. This thesis examines the role of fictional costume and colour in constructing identities within two fourteenth-century Arthurian verse narratives: Froissart’s Middle French Meliador and the anonymous Middle English Sir Gawain and the Green Knight. To emphasise the imaginative value of material cultures and discuss the potential reception of fictional objects, the argument draws on illuminations from nine manuscripts of prose Arthurian stories. Particularly stressing the role of colour in garments, the first chapter examines the issues of analysing literary costume, reviews the provenances of the texts and illuminations, and establishes the relevant historical background concerning fashion, symbolism, and materials of construction (such as fabric, dyes, and decorations). This is followed by two chapters on men’s items. First, the use of courtly clothes and colour-related epithets in manipulating perception and deceiving internal and external audiences is explored. Second, the symbolic value of arms and armour in tournament society is evaluated alongside the tensions between war and armed games that such tools reveal. Chapter four expands on the preceding chapters by discussing the application of heraldry as a malleable identifier. Chapter five considers how ladies’ garments, bodies, and character are coalesced and separated through adoption or rejection of literary techniques, thereby creating conflict between noblewomen as social commodities and as persons with narrative agency. The final chapter analyses the employment of wearable items as gifts and commodities and how such objects can alter interpersonal relationships. Colour and costume are a means by which narratives can explore, accept, or reject literary topoi. Their myriad functions allow the active manipulation of identity, relationships, and internal and external audiences. By focusing on the pluralities and ambiguities of meaning connected to colour and costume, this thesis explores how these materials mediate between conflicting connotations to create new meanings within the narratives.
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Bio-inspired optical systemsLethbridge, Alfred John January 2013 (has links)
This thesis presents an investigation into some of the structural colours that are produced in nature. There are many animals and plants that produce structural colour, with a particularly high structural colour diversity in insects. Of the species that exhibit structural colours, three species are the subjects for investigation of this thesis. Those comprise a group of beetles from South-East Asia, Torynorrhina flammea, a buttery, Parides sesostris and a fruit, Margaritaria nobilis, both from South American rainforests. The structures that produce the vivid colours of these species were analysed using electron microscopy. This information aided the design and creation of three inorganic, synthetic replicas of the natural structures. The fruit of Margaritaria nobilis was structurally analysed, yielding the discovery of a novel multilayer fibre. These fibres were cylindrical in design and were found to be layered together producing the epidermis of the fruit. The multilayer structure produced a vivid blue colour appearance, which is believed to offer a selective advantage because the colour deceives birds into thinking that the fruit contains nutritious flesh. This selective advantage earns M. nobilis the label of mimetic fruit. The structure found within the M. nobilis fruit epidermis inspired the synthesis of a structure which comprises single cylindrical multilayer fibres. The synthetic fibres were manufactured from elastic materials which allow the structure to be deformed under strain and, therefore, a change in colour can be observed. As the structure was stretched, this made the layers get thinner and, therefore, the colour of the fibre blue-shifted. The fibre was able to be stretched to over twice its original length which yields a shift in peak reflected wavelength of over 200 nm. Four beetles from the Torynorrhina flammea species were investigated with the aim of replicating the nanostructures responsible for their colour appearance. The initial interest in the beetles came from their strikingly vivid colour appearances. The structure responsible for the vivid colours in all four of the subspecies is a multilayer with high structural order and over 100 laminae. Both of these attributes contribute to the saturation of the colours exhibited. The multilayer was found to be intersected by an array of rods, the long axis of which is orthogonal to the surface. The rods are believed to be the cause of an interesting diffraction phenomenon exhibited by the beetles. Using imaging scatterometry, the structure was found to diffract the colour produced by the multilayers into an annulus around a specularly reflected white spot. This inspired the synthesis of a multilayer permeated with an array of holes with the aim of replicating a system that could reproduce the annular pattern of colour reflection. The initial synthesised system comprised a quarter-wave stack with a perfectly ordered hexagonal array of holes permeating the surface orthogonally. The sample displayed the scattering characteristics of a hexagonal array, and the reflection spectra of the multilayer stack. When disordered hexagonal arrays were milled into the structure with a focussed ion beam, the scattering pattern started to show more of the green colour from the multilayer and less of the ordered scattering pattern. The highly disordered, synthesised structure displayed no hexagonal scattering pattern, but instead it showed a highly scattered bluish-green colouration. One sample was created by directly mapping out the array of holes using an image of the original array from one of the beetle samples. This sample was expected the same annular diffraction pattern as the beetles, however, the sample instead exhibited the same scattering pattern as the highly disordered array. Some structurally coloured systems in nature have more than one light scattering structure, all of which contribute to the overall colour of the system. For complicated systems such as this, it is necessary to devise a technique to characterise the individual scattering structures separately. One such species that displays a complex, multicomponent system is Parides sesostris. The male of the species displays bright green patches on the dorsal side of the forewings which are made up of thousands of green wing scales. These green scales contain a 3D gyroid poly-crystal at centre with a membrane layer surrounding the underside of each scale and a scattering structure on top. Using focussed ion beam milling techniques allowed the individual characterisation of each of these structures. The gyroid poly-crystal was found to reflect not green but blue wavelengths. This led to the discovery by another group [1] that the scales contain at least one type of fluorophore. The removal of the membrane structure and some of the gyroid poly-crystal from the base of the scale resulted in the change of the overall scale structure from green to cyan. This suggests that the membrane maybe a significant source of fluorescence. Computational modelling, without fluorescence, suggests that the addition of the membrane layer to the gyroid does not shift the band-gap wavelengths; however, the overall reflection intensity does increase. The scattering structure on the top side of each scale is comprised a bi-grating which sits on top of the 3D gyroid structure. The long periodicity of the bi-grating protrudes above the surface, resulting in the very top layer of the scale to be a mono-grating. This whole structure decreases the angular-dependence of the colour by efficiently scattering the incident light into the gyroid and also scattering the reflected light from the gyroid, resulting in a double-scattering. FIB-milling was used to isolate the scattering part of the structure. Analysis of this component of the structure revealed that it was not a source of the green colour itself; however, it did show the characteristic scattering pattern of a mono-grating. The small periodicity of the bi-grating did not produce a scattering pattern since the periodicity is too small to produce optical diffraction at normal incidence. To characterise the effect of the fluorophores, the whole scale structure was photo-bleached using ultra-violet radiation for two months with the aim of destroying the fluorophores contained within the structure. The expected result occurred which was the blue-shifting of the peak reflected wavelengths. However, it could not be confirmed whether or not the photo-bleaching reduced the physical size of the light scattering structures which would, in theory, result in a blue-shift of the peak reflected wavelengths. The male P. sesostris green wing scales were also the subject for investigation for trying to make inorganic replicas of the gyroid-polycrystal. A surface sol-gel coating process was utilised to coat the green wing scales with titania. This coating process was performed using a few different methods. Half of the samples were coated with TiO2 and the other half with tin-doped TiO2. Half of each of these samples had their surfaces dendritically amplified before the coating processes and the other half were left untreated. The samples were coated with 25 surface sol-gel (SSG) cycles of each treatment at a time. After each 25 cycle treatment the samples were optically characterised. The total number of cycles applied to the samples at the end was 150. The addition of layers of titania resulted in a general red-shift that was higher for the tin-doped titania samples than for the titania samples. Another general trend found was that the samples that had their surfaces dendritically amplified, produced a lower red-shift in peak wavelength. This was contrary to the hypothesis that the amplification process was supposed to aid the SSG coating process and, therefore, increases the red-shift in peak wavelength.
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Etude de pigments thermochromes autour du cobalt II / Synthesis and characterization of new irreversible cobalt doped thermochromic pigmentsRobertson, Lionel 09 December 2010 (has links)
Ce travail porte sur la synthèse et la caractérisation de nouveaux pigments thermochromes irréversibles avec le cobalt divalent pour chromophore principal en vue de les intégrer à une peinture thermosensible commerciale.Le travail a été réalisé en suivant trois phases. La première phase a consisté en l’identification de matrices thermosensibles présentant des évolutions structurales irréversibles en température dues à des transitions de phase du premier ordre ou des dégradations chimiques. Puis la synthèse de ces matrices a été effectuée par des voies compatibles avec les méthodes d’élaboration industrielle et permettant un dopage au cobalt. Enfin la troisième et dernière étape est l’étude in-situ et ex-situ des propriétés thermosensibles des pigments synthétisés à l’aide de techniques comme la diffraction des rayons X et des neutrons en température, l’analyse thermogravimétrique et la réflexion diffuse en température.À l’issue de ce travail de recherche, les solutions les plus efficaces ont été synthétisées à l’échelle industrielle puis intégrées à une peinture commerciale en phase aqueuse. / This work deals with the development of new thermochromic pigment which will be the active part of an irreversible thermochromic paint.The studies moved towards three steps. Firstly, an identification of crystalline matrix offering structural rearrangement in temperature because of first order phase transition or chemical degradation were performed. Then the identified matrix were synthesised thanks to synthesis routes compatible with industrial procedures. The third and last step consisted in the in-situ and ex-situ characterization of thermochromic properties of the synthesized compounds with technics like temperature coupled X-ray and neutrons diffraction, thermogravimetric analysis and temperature coupled diffuse reflectance analysis.The most efficient compounds were then industrially synthesized and integrated to a commercial aqueous paint.
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Färg och ljus i Låt den rätte komma in och Let Me In : En jämförande analysSchönbeck, Lex, Symeonidis, Athanasios January 2017 (has links)
This thesis analyses and compares colour and light in the movies Låt den rätte komma in (2008) and Let Me In (2010). Under the analysis have earlier texts about colour and light been used to distinguish and interpret the material. The result of the analysis shows that there is a big difference between the movies. Why there is such a big difference between two adaptation of the same book have been discussed from a neoformalist perspective and through a cognitive approach. The difference between the colour and the lighting in the movies may be because they are made in two different countries for spectators that interpret the content in movies differently.
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Visual perception of gradients : a psychophysical study of the mechanisms of detection and discrimination of achromatic and chromatic gradientsGarcia-Suarez, Luis January 2009 (has links)
No description available.
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Sociální a politické změny v Jihoafrické republice během apartheidu a po něm zachycené v románech od P. Jooste a J. M. Coetzee / Depiction of social and political changes in apartheid and post-apartheid South Africa in novels by P. Jooste and J. M. CoetzeeLaubová, Kristýna January 2015 (has links)
The aim of this thesis is to depict the social and political state of South Africa during the apartheid and after in two novels, Dance with a Poor Man's Daughter (1998) by Pamela Jooste and Disgrace (1999) by J. M. Coetzee. The Theoretical Part analyses the apartheid as a political ideology which is based on racial segregation and its projection in ordinary life. The Practical Part shows concrete features of apartheid and post-apartheid in the aforementioned novels.
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