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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Barrier properties of water-borne polymeric coatings and corrosion protection

Tay, Hwee Koon January 1997 (has links)
No description available.
102

Location of the Carotenoid Pigments of Corynebacterium Species Strain 7E1C

Wilkinson, Joanne C. 08 1900 (has links)
The purpose of this investigation was to determine the site of the carotenoid pigments in C. spp. strain 7E1C as a step towards resolving the role of the pigment in the cell.
103

Elaboration d’un protocole de caractérisation des matériaux goniochromes / Development of a protocol for characterizing goniochromism

Ammar El Ghoul, Chiraz 15 November 2012 (has links)
Les matériaux iridescents changent de couleur avec la géométrie d’éclairage et d’observation de l’objet. La croissance de leur utilisation dans des domaines comme la peinture automobile et la cosmétique fait du contrôle de leur apparence un enjeu. L’objectif de ce travail est de mettre en place un protocole de caractérisation qui permettrait d’évaluer les grandeurs caractéristiques de la perception du goniochromisme. Une caractérisation instrumentale et une autre sensorielle ont permis de recenser les attributs physiques et sensoriels qui caractérisent ces matériaux. Une confrontation des résultats de ces deux évaluations a été réalisée afin de chercher à exprimer les grandeurs sensorielles caractéristiques des matériaux goniochromes en fonction de grandeurs mesurables instrumentalement. / Iridescent materials change their colour with the geometry of illumination and observation. The growth of their use in domains like automotive painting and cosmetics constitutes an important issue for appearance control. The aim of this work is to develop a protocol for evaluating the characteristics of goniochromism perception. Both instrumental and sensory measurements allowed us to determine the relevant physical and sensorial attributes characterising these materials. A confrontation of the results of both evaluations was carried out in order to express the sensory characteristics of the goniochromic materials according to instrumentally measurable quantities.
104

Establishment of cell culture and characterization of seed coat pigments of vigna sinensis.

January 2000 (has links)
Yip Mei-kuen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 93-102). / Abstracts in English and Chinese. / Acknowledgments --- p.i / List of abbreviations --- p.ii / Abstract --- p.iii / Table of Contents --- p.vi / List of tables --- p.x / List of figures --- p.xii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Plant of interest --- p.1 / Chapter 1.2 --- Literature review --- p.2 / Chapter 1.2.1 --- Anthocyanins-natural pigments in plants --- p.2 / Chapter 1.2.1.1 --- Sources and biosynthesis --- p.2 / Chapter 1.2.1.2 --- Chemical properties --- p.2 / Chapter 1.2.1.3 --- Biological effects --- p.3 / Chapter 1.2.2 --- Characterization of anthocyanins --- p.4 / Chapter 1.2.3 --- Plant tissue and cell cultures --- p.6 / Chapter 1.2.4 --- Induction of anthocyanins in plant tissue culture --- p.7 / Chapter 1.2.5 --- Factors affecting anthocyanin production --- p.8 / Chapter 1.2.5.1 --- Plant hormones --- p.8 / Chapter 1.2.5.2 --- Nutrients --- p.9 / Chapter 1.2.5.2.1 --- Phosphate --- p.9 / Chapter 1.2.5.2.2 --- Nitrogen --- p.9 / Chapter 1.2.5.3 --- Osmoticums --- p.10 / Chapter 1.2.5.3.1 --- Sucrose --- p.10 / Chapter 1.2.5.3.2 --- Other factors --- p.10 / Chapter 1.3 --- Research objectives --- p.12 / Chapter 2. --- Materials and methods --- p.16 / Chapter 2.1 --- Plant materials --- p.16 / Chapter 2.2 --- Study of pigment formation at different developmental stages --- p.16 / Chapter 2.2.1 --- Cultivation of Vigna sinensis --- p.16 / Chapter 2.2.2 --- Sample collection --- p.16 / Chapter 2.2.3 --- HPLC analysis of pigmented vegetative tissues --- p.16 / Chapter 2.2.4 --- HPLC analysis of seed coats at different developmental stages --- p.17 / Chapter 2.3 --- Characterization of seed coat pigments --- p.17 / Chapter 2.3.1 --- Extraction of seed coats pigments --- p.17 / Chapter 2.3.2 --- Acid hydrolysis of anthocyanins --- p.17 / Chapter 2.3.3 --- High performance liquid chromatography --- p.18 / Chapter 2.3.3.1 --- HPLC system --- p.18 / Chapter 2.3.3.2 --- Analytical conditions --- p.18 / Chapter 2.4 --- Establishment of tissue culture system --- p.19 / Chapter 2.4.1 --- Aseptic plant stocks --- p.19 / Chapter 2.4.2 --- Shoot-tip cultures --- p.19 / Chapter 2.4.3 --- Callus initiation --- p.19 / Chapter 2.4.3.1 --- From seed coats --- p.20 / Chapter 2.4.3.2 --- From vegetative tissues --- p.20 / Chapter 2.4.3.3 --- Light and dark --- p.20 / Chapter 2.4.4 --- Optimization of callus growth --- p.21 / Chapter 2.4.4.1 --- Basal medium --- p.21 / Chapter 2.4.4.2 --- Combination of various plant hormones --- p.21 / Chapter 2.4.4.3 --- Basal salt --- p.21 / Chapter 2.5 --- Studies of anthocyanin production in hypocotyl callus cultures --- p.22 / Chapter 2.5.1 --- Effects of nutrients --- p.22 / Chapter 2.5.1.1 --- Nitrogen --- p.22 / Chapter 2.5.1.2 --- Phosphate --- p.22 / Chapter 2.5.2 --- Osmotic stress --- p.22 / Chapter 2.5.2.1 --- Sucrose --- p.22 / Chapter 2.5.2.2 --- Mannitol --- p.23 / Chapter 2.5.2.3 --- Sodium chloride --- p.23 / Chapter 2.5.2.4 --- Polyethylene glycol --- p.23 / Chapter 2.6 --- Studies of anthocyanin production in cell suspension cultures --- p.23 / Chapter 2.6.1 --- Effects of nutrients --- p.24 / Chapter 2.6.1.1 --- Nitrogen --- p.24 / Chapter 2.6.1.2 --- Phosphate --- p.24 / Chapter 2.6.2 --- Osmotic stress --- p.25 / Chapter 2.6.2.1 --- Sucrose --- p.25 / Chapter 2.6.2.2 --- Polyethylene glycol --- p.25 / Chapter 2.6.3 --- Effects of other factors --- p.25 / Chapter 2.6.3.1 --- Riboflavin --- p.25 / Chapter 2.6.3.2 --- pH --- p.26 / Chapter 2.7 --- Measurement of cell growth --- p.26 / Chapter 2.8 --- Estimation of anthocyanins --- p.26 / Chapter 2.9 --- Statistical analysis --- p.27 / Chapter 3. --- Results --- p.30 / Chapter 3.1 --- Study of pigment formation at different developmental stages --- p.30 / Chapter 3.1.1 --- General description --- p.30 / Chapter 3.1.2 --- HPLC analysis of developing seed coats and other vegetative tissues --- p.30 / Chapter 3.1.3 --- The relationship between pigment formation and seed development --- p.30 / Chapter 3.2 --- Characterization of seed coat pigments --- p.31 / Chapter 3.3 --- Establishment of tissue culture system --- p.43 / Chapter 3.3.1 --- Callus initiations from seed coats --- p.43 / Chapter 3.3.2 --- Callus initiations from vegetative tissues --- p.43 / Chapter 3.3.3 --- Optimization of callus growth --- p.43 / Chapter 3.3.3.1 --- Effects of NAA and BA --- p.43 / Chapter 3.3.3.2 --- Effects of basal medium and combinations of plant hormones --- p.44 / Chapter 3.3.3.3 --- Effects of basal salt --- p.44 / Chapter 3.4 --- Studies of anthocyanin production in hypocotyl callus culture --- p.54 / Chapter 3.4.1 --- Effects of nutrients --- p.54 / Chapter 3.4.1.1 --- Effects of total nitrogen --- p.54 / Chapter 3.4.1.2 --- Effects of phosphate --- p.54 / Chapter 3.4.2 --- Effects of plant hormones --- p.55 / Chapter 3.4.3 --- Osmotic stress --- p.55 / Chapter 3.5 --- Establishment of suspension culture system --- p.64 / Chapter 3.6 --- Studies of anthocyanin production in seed coat suspension cultures --- p.64 / Chapter 3.6.1 --- Nutrient effects on suspension cultures --- p.64 / Chapter 3.6.2 --- Osmotic stress on suspension cultures --- p.65 / Chapter 3.6.3 --- Effects of phosphate with high nitrogen --- p.65 / Chapter 3.6.4 --- Effects of riboflavin with high nitrogen --- p.66 / Chapter 3.6.5 --- Influence of pH with high nitrogen --- p.66 / Chapter 4. --- Discussion --- p.79 / Chapter 4.1 --- Anthocyanin in vegetative tissues and seed coats of Vigna sinensis --- p.79 / Chapter 4.2 --- Factors affecting callus initiation in Vigna sinensis --- p.81 / Chapter 4.2.1 --- Explant types --- p.81 / Chapter 4.2.2 --- Plant hormones --- p.82 / Chapter 4.2.3 --- Basal medium --- p.82 / Chapter 4.3 --- Factors affecting anthocyanin production in callus cultures derived from hypocotyls --- p.83 / Chapter 4.3.1 --- Nutrients --- p.83 / Chapter 4.3.2 --- Osmotic stress --- p.85 / Chapter 4.4 --- Factors affecting anthocyanin production in suspension culture derived from seed coats --- p.86 / Chapter 4.4.1 --- Nutrients --- p.86 / Chapter 4.4.2 --- Osmotic stress --- p.87 / Chapter 4.5 --- Comparison of anthocyanin production from natural source and plant tissue cultures of V.sinensis --- p.89 / Chapter 4.6 --- Further studies --- p.89 / Chapter 5. --- Conclusions --- p.91 / References --- p.93
105

Characterization and potential applications of pigment from castanea mollissima shells.

January 2004 (has links)
Yeung Kit Ying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 98-106). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / List of Abbreviations --- p.iv / List of Tables --- p.v / List of Figures --- p.vi / Chapter 1 --- Introduction / Chapter 1.1 --- Botany --- p.1 / Chapter 1.2 --- Food additives and food preservation --- p.2 / Chapter 1.2.1 --- Lipid peroxidation --- p.2 / Chapter 1.2.2 --- Role of food antioxidant --- p.4 / Chapter 1.2.3 --- Microbial spoilage --- p.5 / Chapter 1.2.4 --- Additives in future --- p.6 / Chapter 1.3 --- Antioxidant and health benefits effects --- p.7 / Chapter 1.4 --- Measurement of antioxidants --- p.7 / Chapter 1.4.1 --- Trolox equivalent antioxidant capacity (TEAC) assay --- p.8 / Chapter 1.4.2 --- DPPH radical scavenging assay --- p.9 / Chapter 1.4.3 --- β-carotene bleaching assay --- p.9 / Chapter 1.4.4 --- Assay for erythrocyte hemolysis mediated by peroxyl free radicals --- p.10 / Chapter 1.4.5 --- Measurement of lipid peroxidation in foods --- p.10 / Chapter 1.5 --- Antiproloiferative studies --- p.12 / Chapter 1.5.1 --- MTT assay --- p.12 / Chapter 1.5.2 --- Cell Proliferation ELISA-BrdU (chemiluminescence) assay --- p.13 / Chapter 1.5.3 --- Cytotoxicity detection assay (LDH) --- p.13 / Chapter 1.6 --- Characterization of phenolic compounds --- p.14 / Chapter 1.6.1 --- Sephadex column chromatography --- p.14 / Chapter 1.6.2 --- Folin and Ciocalteu's assay --- p.15 / Chapter 1.7 --- Research objectives --- p.15 / Chapter 2 --- Materials and Methods / Chapter 2.1 --- Standards and reagents --- p.22 / Chapter 2.2 --- Plant materials --- p.23 / Chapter 2.3 --- Pigment preparation --- p.23 / Chapter 2.4 --- Determination of antioxidant activity --- p.25 / Chapter 2.4.1 --- Trolox equivalent antioxidant capacity (TEAC) assay --- p.25 / Chapter 2.4.2 --- DPPH. radical scavenging assay --- p.26 / Chapter 2.4.3 --- β-carotene bleaching assay --- p.26 / Chapter 2.4.4 --- Assay for erythrocyte hemolysis mediated by peroxyl free radicals --- p.27 / Chapter 2.4.4.1 --- Determination of IC50 --- p.28 / Chapter 2.5 --- Evaluation of CP as antioxidant in various food models --- p.28 / Chapter 2.5.1 --- Preparation of food samples --- p.28 / Chapter 2.5.2 --- Butter cookies --- p.29 / Chapter 2.5.3 --- Salad dressing --- p.29 / Chapter 2.5.4 --- Fried potato chips --- p.29 / Chapter 2.5.5 --- PeroXOquant´ёØ quantitative peroxide assay --- p.29 / Chapter 2.5.6 --- Statistical analysis --- p.30 / Chapter 2.6 --- Determination of antimicrobial activity --- p.31 / Chapter 2.6.1 --- Determination of antimicrobial activity --- p.31 / Chapter 2.6.1.1 --- Bacterial stock --- p.31 / Chapter 2.6.1.2 --- Preparation of nutrient agar plate --- p.31 / Chapter 2.6.1.3 --- Minimal inhibiting concentration (MIC) --- p.31 / Chapter 2.6.2 --- Determination of antifungal activity --- p.32 / Chapter 2.6.2.1 --- Fungi stock --- p.32 / Chapter 2.6.2.2 --- Preparation of potato dextrose agar plates --- p.32 / Chapter 2.6.2.3 --- Growth inhibition effect --- p.32 / Chapter 2.6.3 --- Statistical analysis --- p.33 / Chapter 2.7 --- In vitro effect on human cell lines --- p.34 / Chapter 2.7.1 --- Cell lines --- p.34 / Chapter 2.7.2 --- Maintenance of cell lines --- p.34 / Chapter 2.7.3 --- MTT assay --- p.35 / Chapter 2.7.4 --- Cell Proliferation ELISA-BrdU (chemiluminescence) assay --- p.36 / Chapter 2.7.5 --- Determination of IC50 --- p.37 / Chapter 2.7.6 --- Cytotoxicity detection assay --- p.37 / Chapter 2.7.6.1 --- Optimal cell concentration --- p.37 / Chapter 2.7.6.2 --- LDH detection assay --- p.38 / Chapter 2.7.7 --- Statistical analysis --- p.39 / Chapter 2.8 --- Fractionation and characterization --- p.40 / Chapter 2.8.1 --- Sephadex column chromatography --- p.40 / Chapter 2.8.2 --- Fourier transform infrared (FT-IR) spectra --- p.40 / Chapter 2.8.3 --- Folin and Ciocalteu's assay --- p.40 / Chapter 2.8.4 --- Statistical analysis --- p.41 / Chapter 3 --- Results / Chapter 3.1 --- Determination of antioxidant activity --- p.43 / Chapter 3.1.1 --- Trolox equivalent antioxidant capacity (TEAC) assay --- p.43 / Chapter 3.1.2 --- DPPH.radical scavenging assay --- p.43 / Chapter 3.1.3 --- β-carotene bleaching assay --- p.44 / Chapter 3.1.4 --- Assay for erythrocyte hemolysis mediated by peroxyl free radicals --- p.44 / Chapter 3.2 --- Potential application as food antioxidant --- p.45 / Chapter 3.2.1 --- Peroxide standard curve --- p.45 / Chapter 3.2.2 --- Inhibition of lipid peroxidation in different food items --- p.45 / Chapter 3.3 --- Potential application as food preservative --- p.46 / Chapter 3.3.1 --- Antibacterial activity --- p.46 / Chapter 3.3.2 --- Antifungal activity --- p.46 / Chapter 3.4 --- In vitro effect on human cell lines --- p.47 / Chapter 3.4.1 --- Effect on the growth of human cancer cells --- p.47 / Chapter 3.4.2 --- Antiproliferative effect on selected human cancer cells --- p.48 / Chapter 3.4.3 --- Cytotoxicity effect on selected human cancer cells and normal fibroblast --- p.48 / Chapter 3.4.3.1 --- Optimal cell density for cytotoxicity determined assay --- p.48 / Chapter 3.4.3.2 --- Cytotoxic effect --- p.48 / Chapter 3.5 --- Fractionation and characterization --- p.49 / Chapter 3.5.1 --- Percentage of yield --- p.49 / Chapter 3.5.2 --- Fourier transform infrared (FT-IR) spectra --- p.49 / Chapter 3.5.3 --- Determination of total phenolic content --- p.49 / Chapter 3.5.4 --- Determination of antioxidant activity --- p.50 / Chapter 3.5.5 --- Relationship between total phenolics and antioxidant activity --- p.50 / Chapter 3.5.6 --- Antiproliferative effect on cancer cell --- p.50 / Chapter 3.5.7 --- Cytotoxic effect --- p.51 / Chapter 3.5.7.1 --- HepG2 human cancer cell line --- p.51 / Chapter 3.5.7.2 --- Hs68 human normal fibroblast --- p.51 / Chapter 4 --- Discussion / Chapter 4.1 --- Application of CP as a natural food additive with multi-functions --- p.87 / Chapter 4.1.1 --- CP as a natural food antioxidant --- p.88 / Chapter 4.1.2 --- CP as a natural food preservative --- p.90 / Chapter 4.2 --- Potential health-beneficial --- p.91 / Chapter 4.2.1 --- CP as dietary antioxidant --- p.91 / Chapter 4.2.2 --- Antiproliferative activity of CP --- p.92 / Chapter 4.3 --- Further characterization of CP --- p.94 / Chapter 4.4 --- Future perspectives --- p.96 / Chapter 5 --- Conclusion --- p.97 / References --- p.98
106

Interaction of polymeric dispersants with Titania pigment particles

Farrokhpay, Saeed January 2004 (has links)
The aim of the research presented in this thesis was to increase the understanding of the interaction between polymeric dispersants and titania pigment particles. In particular, the effects of dispersants of varied functionalities on the pigment dispersion behaviour in both aqueous suspension and dry paint film were investigated. / thesis (PhDEng(MineralsandMaterials))--University of South Australia, 2004.
107

Copigmentation and its impact on the stabilisation of red wine pigments / by Stephanie Green Lambert.

Lambert, Stephanie Green January 2002 (has links)
"October 2002" / Includes bibliographical references (leaves 172-183) / x, 183 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002
108

Oxylipins from temperate marine algae and a photoprotective sheath pigment from blue-green algae

Proteau, Philip J. 13 August 1993 (has links)
Graduation date: 1994
109

Physicochemical properties and phenolic composition of selected Saskatchewan fruits : buffaloberry, chokecherry and sea buckthorn

Green, Richard Christopher 31 July 2007
There is increasing interest in the commericalization of native fruits for utilization as foods and medicinal extracts. This study was undertaken to determine the physicochemical properties and phenolic composition of selected Saskatchewan native fruits, including buffaloberry (<i>Shepherdia argentea</i> Nutt.), chokecherry (<i>Prunus virginiana</i> L.) and sea buckthorn (<i>Hippophae rhamnoides</i> L.). The physicochemical analyses included carbohydrate content, CIELAB colour values, organic acid composition, phenolic content, % seed, soluble solids, pH, total solids, total titratable acidity and proximate composition. Fruit samples were collected and analyzed over four crop years. The proanthocyanidin content was also determined photometrically after acid depolymerization in acid-butanol. Buffaloberry contained a proanthocyanidin concentration of 505 ± 32 mg/100 g fresh fruit and this level was 10 fold higher than that of chokecherry and sea buckthorn. Chokecherry was found to contain an anthocyanin concentration of 255 ± 35 mg/100 g fresh fruit, as determined using the pH differential method. Two high performance liquid chromatography (HPLC) methods were developed for simultaneous determination of seven phenolic classes, including anthocyanins, hydroxybenzoic acids, hydroxycinnamic acids, flavanols, flavanones, flavones and flavonols in aqueous methanol extracts. Based on the semi-quantitative analysis of the total phenolic chromatographic index (TPCI), chokecherry contained the highest levels of phenolic compounds with a concentration of 3,327 ± 469 µg/g fresh fruit followed by buffaloberry (578 ± 73 µg/g fresh fruit) and sea buckthorn (477 ± µg/g fresh fruit). The antioxdant activity of the fruit extracts was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2´-azinobis-3-ethylbenzthiazoline-sulphonic acid (ABTS) radical scavenging assays. Buffaloberry and chokecherry produced the highest radical scavenging activity and were at least five fold greater than that of sea buckthorn. The major radical scavenging compounds in buffaloberry were ascorbic acid and proanthocyanidins. Radical scavenging activity of chokecherry fruit was largely attributable to its anthocyanins, flavonols and hydroxycinnamic acids. Prominent antioxidants in sea buckthorn included ascorbic acid, proanthocyanidins and flavonols. Certain individual compounds in the phenolic extracts were identified by HPLC-photodiode array and HPLC-mass spectrometry. Rutin was found in all of the extracts. Other phenolic compounds identified included catechin in sea buckthorn, and chlorogenic acid and quercetin in chokecherry. The chokecherry fruit pigments were comprised of two major anthocyanins and these were identified as cyanidin 3-glucoside and cyanidin 3-rutinoside. A preparative scale purification method for these anthocyanins using centrifugal partition chromatography (CPC) was determined. Under the CPC conditions employed, cyanidin 3-glucoside and cyanidin 3-rutinoside were purified to concentrations of 84 and 90%, respectively.
110

Estudi, anàlisi, disseny i implementació de tècniques de reconeixement d'espectres Raman. Aplicació a la identificació de materials pictòrics.

Castanys Tutzó, Mireia 24 April 2009 (has links)
L'espectroscòpia Raman és una tècnica fotònica molt emprada per l'anàlisi i la caracterització de materials. Entre les seves aplicacions destaca el seu ús en l'estudi del patrimoni cultural, on s'aplica per exemple en l'estudi de peces arqueològiques o en la identificació de pigments artístics. La seva popularitat es deu principalment a la seva capacitat d'identificar inequívocament qualsevol material i per ser una tècnica (1) no destructiva, (2) altament específica i (3) que permet realitzar les anàlisis sense que sigui necessària cap preparació del material o extracció d'una mostra. Un espectre Raman consisteix en la representació de part la radiació dispersada per la mostra (intensitat Raman) en funció dels números d'ona (unitat proporcional a l'energia de la radiació, definida en cm-1). Així un espectre Raman es caracteritza per una sèrie de bandes espectrals específiques de la composició molecular del material analitzat.La manera més senzilla d'identificar un material desconegut mitjançant el seu espectre Raman és comparant-lo amb espectres Raman coneguts (patrons), buscant quin de tots ells se li assembla més. Aquesta comparació visual resulta molt intuïtiva, però a l'hora és subjectiva i el seu èxit depèn en gran mesura de l'experiència de qui la dur a terme. A més a més, segons el número d'espectres a comparar i la seva complexitat pot resultar una tasca llarga i complicada, i en conseqüència suposar certes dificultats per persones no expertes en espectroscopia Raman. Aquesta comparació es pot encarar seguint dues estratègies diferents. Una consisteix en provar d'identificar l'espectre Raman desconegut comparant la posició de les seves bandes Raman amb la posició de les dels patrons. L'altre mètode consisteix en tenir en compte tota la forma dels espectres, és a dir, valorar de forma com d'iguals o diferents són els espectres.Totes dues opcions són valides, però comparar de forma global els espectres pot resultar més apropiada quan els espectres contenen moltes bandes i/o en quan comparteixen moltes d'elles. Aquest últim cas correspon per exemple a pigments orgànics d' estructura molecular complicada que es sol traduir en un alt número de bandes Raman.En aquesta tesi es proposa un sistema que identifiqui espectres Raman modelant de manera automàtica el procés de comparació visual dut a terme pels analistes. Amb aquesta opció s'assegura que el resultat sigui el més objectiu possible i no es fa necessària la intervenció d'un especialista. Per tal de tenir en consideració tota la informació continguda en els espectros comparats, com ara el número de bandes, les seves intensitats i els amples de banda es valora la seva semblança en base a la coincidència de les seves formes. Aplicant aquesta estratègia es facilita la identificació de qualsevol espectre Raman, sense tenir en compte la seva complexitat (número de bandes).Un espectre Raman pot ser interpretat com un vector definit per un alt número de punts,típicament entre 1000 i 2000. Així, emmagatzemar tots els espectres Raman representa un gran volum de dades, i implementar les comparacions pot suposar una considerable càrrega computacional. En aquest sentit, s'ha considerat oportú, previ a la comparació, destinar una etapa del sistema al tractament dels espectres aplicant la tècnica de reducció dimensional coneguda com Anàlisi per Components Principals (ACP). Amb aquesta etapa tots els espectros Raman s'expressen amb un número reduït de coordenades sense que es perdi informació rellevant.Per quantificar objectivament la similitud en la forma dels dos espectres Raman s'han escollit dos dels operadors matemàtics més habituals en processat de senyal: la distància euclidiana i els coeficients de correlació o de Pearson. A partir d'uns llindars, Dminbase i Cmaxbase, el sistema selecciona els patrons que tenen més probabilitat de correspondre a l'espectre incògnita. Aquests patrons escollits són anomenats candidats. Un espectre Raman està inevitablement contaminat per soroll inherent al seu procés de mesura, de manera que dos espectres provinents del mateix material són lleugerament diferents. Així, les mesures de similitud obtingudes no són sempre directament interpretables. Per tal de tractar aquesta ambigüitat intrínseca a les dades, l'última etapa del sistema és un sistema de lògica fuzzy que permet decidir quin dels candidats és el més semblant al desconegut i com de fiable és aquesta identificació.En resum, aquesta tesi proposa una eina pel reconeixement automàtic d'espectres Raman que guia al seu usuari en el procés d'identificació del material analitzat, pigments artístics en aquest cas.

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