Non-invasive methods to evaluate skeletal muscle oxidative capacity have beenemerging as a viable substitute for invasive methods in recent years. One ofthose methods utilises near-infrared spectroscopy (NIRS) to calculate V O2mrecovery off-kinetics following an exercise. The data analysis of the measuredsignals from the NIRS is still done manually in a time-consuming and dauntingprocess. The present thesis aimed to develop software, associated with theNIRS method, capable of analysing the recovery from a repeated arterialocclusion protocol following an exercise to assess muscle oxidative capacity.Additionally, to analyse the recovery from ischemic preconditioning as a singletest to assess muscle oxidative capacity. A method that has never been utilisedbefore.11 active, healthy subjects were analysed to calculate their recovery rate.Subjects underwent ischemic preconditioning before exercising for 6 minutesat 80% of gas exchange threshold. A repeated arterial occlusion protocol wascarried out after the exercise. A software was developed in R that utilised linearregression as well as exponential fitting to calculate the recovery rate of eachsubject during both the ischemic preconditioning and the occlusion protocol.The calculated results were compared to predetermined recovery rate results ofeach subject. The calculated results of the repeated arterial occlusion protocolgave similar results to the predetermined ones and even more data on eachsubject’s recovery from an exercise. The calculated results of the ischemicpreconditioning were promising and implied that ischemic preconditioning asa single test can be utilised as a method to assess muscle oxidative capacity.However, further research is required to confirm it. / Icke-invasiva metoder för att utvärdera skelettmuskulaturens oxidativa förmågahar på senare år blivit en användbar ersättning för invasiva metoder. Nearinfrared spectroscopy (NIRS) är en utav dessa metoder och har använts föratt beräkna V O2m återhämtning off-kinetics efter träning. Dataanalysen av deuppmätta signalerna från NIRS görs fortfarande manuellt i en tidskrävandeoch felbenägen process. Syftet med den här uppsatsen var att utveckla enprogramvara som kopplad till NIRS metoden, kan analysera återhämtningenfrån ett protokoll med upprepade arteriella ocklusioner efter träning för attutvärdera skelettmuskulaturens oxidativa förmåga. Dessutom att analyseraåterhämtningen från ischemic preconditioning som ett enda test för att utvärderaskelettmuskulaturens oxidativa förmåga. En metod som aldrig tidigare använts.11 aktiva, friska försökspersoner analyserades för att beräkna deras återhämtningshastighet.Försökspersonerna genomgick ischemic preconditioning innan de tränadei 6 minuter med 80% av gasutbyteströskeln. Ett protokoll med upprepadearteriella ocklusioner genomfördes efter träningen. En programvara utveckladesi R som använde sig av linjär regression och monoexponentiell funktionsanpassningför att beräkna återhämtningshastigheten för varje försöksperson under bådeichemic preconditioning och ocklusionprotokollet. De beräknade resultatenjämfördes med förutbestämda resultat av återhämtningshastigheten för varjeförsöksperson. De beräknade resultaten av ocklusionprotokollet gav liknanderesultat som de förutbestämda och gav ännu fler uppgifter om varje försökspersonåterhämtning efter träning. De beräknade resultaten av ischemic preconditioningvar lovande och indikerade att ischemic preconditioning som ett enda testkan användas som en metod för att utvärdera skelettmuskulaturens oxidativaförmåga. Det krävs dock ytterligare forskning för att bekräfta detta.

Die intratracheale Applikation von Perfluorcarbonen (PFC) in ungeschädigte Lungen, z.B. als Röntgenkontrastmittel und zur PFC-induzierten cerebralen Kühlung, wird derzeit diskutiert. Ob es aufgrund der Dichte und Sauerstofflöslichkeit der PFC zu einer Beeinflussung der cerebralen Oxygenierung und Hämodynamik durch die pulmonale PFC Applikation kommt, ist bisher unbekannt. Änderungen der Konzentration von cerebralem oxygeniertem und totalem Hb koennen mittels Near-infrared Spectroscopy gemessen werden. I.) Effekt durch die PFC-Applikation in gesunde Lungen neugeborener Ferkel: Es wurden zwei verschiedene Applikationsgeschwindigkeiten (30 ml PFC pro kg Körpergewicht als Bolusgabe versus 1,5 ml/min pro kg) und zwei Füllvolumen (30 versus 10 ml/kg) verglichen. Die Bolusgabe bewirkt einen sofortigen Abfall des PaO2 und der cerebralen Oxygenierung, bei langsamer Gabe des gleichen Volumens ist dies weniger ausgeprägt. Mit 10 ml/kg PFC fand sich nahezu keine Beeinflussung der Parameter. II.) Effekte der Änderung der FiO2 in PFC-gefüllten Lungen: Hierfür wurden Änderungen der FiO2 unter konventioneller Druckbeatmung vor PFC-Applikation und unter PFC-Füllung (30 oder 10 ml/kg PFC) verglichen. Beide PFC-Volumen (mit FiO2 1,0) bedingten PaO2-Werte wie unter CMV mit FiO2 von 0,5. Mit 30 ml/kg PFC kam es unter FiO2 von 0,5 zur Abnahme des cerebralen oxygenierten Hb. Zusammenfassend ergibt sich, dass die Applikation von 10 ml PFC/kg bevorzugt werden sollte. Bei kompletter Füllung der Lungen werden durch langsame Applikation cerebrale Nebenwirkungen minimiert. In PFC-gefüllten gesunden Lungen ist zum Erhalt der systemischen und cerebralen Oxygenierung die FiO2 zu erhöhen. / Intratracheal administration of perfluorochemicals (PFC) has been suggested for reasons other than respiratory insufficiency, such as pulmonary imaging and PFC-associated brain cooling. Due to their high density and oxygen solubility, PFC application has been described to affect systemic hemodynamics and oxygenation during liquid ventilation. Whether the PFC application into healthy lungs or changes in inspired oxygen fraction (FiO2) in PFC-filled healthy lungs affects cerebral hemodynamics is not known. Changes in the concentration of cerebral oxygenated and total Hb can be measured by near-infrared spectroscopy (NIRS). I.) Initial effects of PFC application into healthy lungs of newborn piglets: Two different filling modes (rapid versus slow) and two different filling volumes (slow filling of 30 versus 10 ml PFC/kg body weight) were compared. Rapid filling caused an immediate drop of systemic and cerebrale oxygenation, which was less prominent by filling 30 ml/kg PFC slowly. Almost no changes for all parameters were found with 10 ml kg/PFC. II.) Effects of variations in FiO2 in the PFC filled lungs of healthy piglets: Changes in FiO2 during conventional mechanical ventilation (CMV) prior to PFC-application and in the PFC-filled lungs (30 ml/kg or 10 ml/kg PFC) were compared. Both PFC-volumes (at a FiO2 of 1.0) caused PaO2-values that were similar to CMV with FiO2 of 0.5. In the 30 ml/kg PFC group a reduction of cerebral oxygenated Hb was found at FiO2 of 0.5. According to the data application of 10 ml/kg PFC should be preferred. If complete filling of the lung is needed, the slow administration of PFC minimizes cerebral side effects. In PFC- filled healthy lungs an increase in FiO2 is necessary to maintain systemic and cerebral oxygenation.

Doctor of Philosophy / Department of Physics / Kristan L. Corwin / Current portable near-infrared optical frequency references offer modest accuracy and instability compared to laboratory references. Low pressure reference cells are necessary to realize features narrower than the Doppler broadened overtone transitions, and most setups to date have occurred in free-space. Hollow-core photonic crystal fibers offer a potential alternative to free-space setups through their small cores (~10’s of µm) and low-loss guidance. Furthermore, HC-PCF can be made into fiber cells that could be directly integrated into existing telecommunications networks. Efforts were made to fabricate these fiber cells with a low pressure of molecules trapped inside, but this has proven to be quite challenging. Therefore, investigation of these fibers is conducted by placing the ends of the fiber inside vacuum chambers loaded with acetylene (12C2H2). The linewidths of several P branch transitions (near 1.5 µm) are investigated as a function of acetylene pressure and optical pump power in three different HC-PCFs. Frequency modulation spectroscopy is then implemented on the acetylene-filled HC-PCF to generate sub-Doppler dispersion features that are useful for frequency stabilization using standard servo electronics. Instability and accuracy of this near-IR optical reference were then determined by analysis of heterodyne experiments conducted with frequency combs referenced to a GPS-disciplined rubidium oscillator. The instability and accuracy of this HC-PCF reference are within an order of magnitude of free-space experiments, as expected based on the ratio of linewidths observed in the two experiments. Therefore, HC-PCF has been shown to be suitable for potential frequency references. Further work is necessary to fabricate gas fiber cells with high optical transmission and low molecular contamination.

Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Near infrared reflectance spectroscopy (NIRS) was evaluated as a tool to predict the chemical composition of ostrich meat, mutton and feedstuffs. Seventy-three calibrations were developed. NIRS analyses were conducted on an InfraAlyzer 500 spectrophotometer between 1100 and 2500 nm wavelengths. Near infrared reflectance calibrations were developed for (i) the proximate chemical composition of ostrich meat; (ii) the proximate chemical and mineral composition of mutton; (iii) the chemical composition and digestibility of lupins, full-fat canola and the determination of alkaloids in lupins; (iv) the chemical composition and digestibility of winter grains and maize; (v) the chemical composition and digestibility of cereal hay, cereal straw, wheat stubble and alfalfa-grass/hay mixtures. The chemical composition of different types of winter grain produced in the Western Cape area of South Africa, as well as the chemical composition and digestibility of winter grain hay and straw produced in a Mediterranean rainfall area were also determined. Near infrared reflectance spectrometry proved to be successful for the prediction of crude protein (CP) and fat in both animal species, as well as for ash and dry matter (DM) in freeze-dried mutton. Accurate calibrations were also developed for certain minerals (K, P, Na, Mg, Fe and Zn). Calibrations proved to be accurate for all the relevant chemical constituents in lupins, as well as the DM, CP and fat calibrations in full-fat canola. The alkaloid calibration showed potential although more samples should be included for a more accurate calibration. Winter grain calibrations were accurate for fat, acid detergent fibre (ADF), in vitro organic matter digestibility (IVOMD), lysine and methionine. All chemical composition calibrations of maize, except for ash, were accurate for future prediction. Chemical composition calibrations of wheat stubble and alfalfa-grass hay mixtures resulted in prediction with similar or slightly higher accuracy than calibrations reported in the literature. The calibrations developed for cereal hay and straw were not suitable for prediction purposes. Possible reasons were discussed to explain these inaccurate calibrations. Variation shown between different types of cereal grain (2-row barley, 6-row barley, oats, wheat and triticale) accentuated the need for the analysis of different batches of grain produced under different conditions for use in animal feed. The chemical composition and digestibility of winter grain straw and hay were also obtained. These values provide a database for calculation of inclusion levels of these feedstuffs in animal diets. These investigations showed the NIRS to be a successful and rapid tool for the prediction of the chemical composition of ostrich and lamb meat and locally produced feedstuffs. / AFRIKAANSE OPSOMMING: Naby infrarooi refleksie spektroskopie (NIRS) is geëvalueer as 'n metode om die chemiese samestelling van volstruis- en skaapvleis, asook voedingsgewasse te voorspel. Drie en sewentig kalibrasies is ontwikkel. NIRS ontledings is gedoen met ‘n InfraAlyzer 500 spektrofotometer tussen die golflengtes 1100 en 2500 nm. Naby infrarooi refleksie kalibrasies is ontwikkel vir (i) die basiese chemiese samestelling van volstruisvleis; (ii) die basiese chemiese en minerale samestelling van lamsvleis; (iii) die chemiese samestelling en verteerbaarheid van lupiene en volvet kanola en die bepaling van alkaloïede in lupiene; (iv) die chemiese samestelling en verteerbaarheid van wintergrane en mielies; (v) die chemiese samestelling en verteerbaarheid van graanhooie, graanstrooie, koringstoppels and lusern-gras/hooi mengsels. Die chemiese samestelling van verskillende tipes wintergrane wat in die Wes-Kaap omgewing van Suid-Afrika geproduseer word, sowel as die chemiese samestelling en verteerbaarheid van wintergraanhooi en –strooi wat geproduseer word in ‘n Mediterreënse reënval omgewing, is ook bepaal. Naby infrarooi refleksie spektrofotometrie was suksesvol in die voorspelling van ru-proteïen (RP) en vet in beide dierspesies, sowel as vir die bepaling van as en droë materiaal (DM) in gevriesdroogde lamsvleis. Akkurate kalibrasies is ook ontwikkel vir sekere minerale (K, P, Na, Mg, Fe en Zn). Kalibrasies ontwikkel vir die chemiese samestellings komponente in lupiene is reg deur die bank akkuraat, sowel as die DM, RP en vet kalibrasies vir volvet kanola. Die alkaloïed kalibrasie het goeie potensiaal getoon, alhoewel meer alkaloïedmonsters benodig word vir ‘n akkurate kalibrasie. Wintergraan kalibrasies was akkuraat vir vet, suurbestande vesels (SBV), in vitro organiese materiaal verteerbaarheid (IVOMV), lisien en metionien. Al die chemiese komponent kalibrasies vir mielies, behalwe die een vir as, was akkuraat vir toekomstige bepalings. Chemiese komponent kalibrasies vir koring stoppels en luserngras/ hooi mengsels het akkuraatheid getoon wat gelyk, of effe beter, is as kalibrasies wat in die literatuur opgeteken is. Kalibrasies ontwikkel vir graanhooie en graanstrooie was nie geskik vir voorspellingsdoeleindes nie. Moontlike redes vir die onakkurate kalibrasies is volledig bespreek. Variasie gevind tussen verskillende tipes wintergrane (2-ry gars, 6-ry gars, hawer, koring en korog) het die behoefte beklemtoon vir ontledings van grane geproduseer onder verskillende omgewingstoestande vir gebruik in dierevoeding. Die chemiese samestelling en verteerbaarheid van wintergraanstrooi en –hooi is ook bepaal. Hierdie waardes verskaf ‘n databasis vir berekening by insluiting van hierdie voergewasse in diererantsoene. Hierdie ondersoek het bewys dat NIRS ‘n suksesvolle en vinnige metode is vir die voorspelling van die chemiese samestelling van volstruis- en lamsvleis en plaaslik geproduseerde voergewasse.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Maize (Zea mays L.) is used for human and animal consumption in diverse forms, from specialised foods in developed countries, to staple food in developing countries. Unfortunately, maize is prone to infection by different Fusarium species that can produce harmful mycotoxins. Fusarium verticillioides is capable of asymptomatic infection, where infected kernels show no sign of fungal growth, but are contaminated with mycotoxins. If fungal contamination is not detected early on, mycotoxins can enter the food chain. Rapid and accurate methods are required to detect, identify and distinguish between pathogens to enable swift decisions regarding the fate of a batch or consignment of cereal. Near infrared (NIR) hyperspectral imaging and multivariate image analysis (MIA) were evaluated to investigate the fungal development in maize kernels over time. When plotting principal component (PC) 4 against PC5, with percentages sum of squares (%SS) 0.49% and 0.34%, three distinct clusters were apparent in the score plot and this was associated with degree of infection. Prominent peaks at 1900 nm and 2136 nm confirmed that the source of variation was due to changes in starch and protein. Variable importance plots (VIP) confirmed the peaks observed in the PCA loading line plots. Early detection of fungal contamination and activity (20 h after inoculation) was possible before visual symptoms of infection appeared. Using NIR hyperspectral imaging and MIA it was possible to differentiate between species of Fusarium associated with maize. It was additionally applied to examine the fungal growth kinetics on culture media. Partial least squares discriminant analysis (PLS-DA) prediction results showed that it was possible to discriminate between species, with F. verticillioides the least correctly predicted (between 16-47% pixels correctly predicted). For F. subglutinans 78-100% and for F. proliferatum 60-80% pixels were correctly predicted. Three prominent bands at 1166, 1380 and 1918 nm were considered to be responsible for the differences between the growth zones. Variations in the bands at 1166 and 1380 nm were correlated with the depletion of carbohydrates as the fungus grew while the band at 1918 nm was a possible indication of spore and new mycelial formation. By plotting the pixels from the individual growth zones as a function of time, it was possible to visualise the emergence and interaction of the growth zones as separate growth profiles. The microstructure of fungal infected maize kernels was studied over time using high resolution X-ray micro-computed tomography (μCT). The presence of voids and airspaces could be seen in two dimensional (2D) X-ray transmission images and in the three dimensional (3D) tomograms. Clear differences were detected between kernels imaged after 20 and 596 h of inoculation. This difference in voids as the fungus progressed showed the effect of fungal damage on the microstructure of the maize kernels. Imaging techniques are important for rapid, accurate and objective evaluation of products for quality and safety. NIR hyperspectral imaging offers rapid chemical evaluation of samples in 2D images while μCT offers 3D microstructural information. By combining these image techniques more value was added and this led to a comprehensive evaluation of Fusarium infection in maize. / AFRIKAANSE OPSOMMING: Mielies (Zea mays L.) word in verskeie vorms deur mens en dier verbruik, van gespesialiseerde voedsel in ontwikkelde lande, tot stapelvoedsel in ontwikkelende lande. Ongelukkig is mielies onderhewig aan besmetting deur verskeie Fusarium spesies wat skadelike mikotoksiene kan produseer. Fusarium verticilloioides is in staat tot asimptomatiese infeksie waar die besmette pit geen teken van fungusgroei toon nie, maar (reeds) met mikotoksiene besmet is. Indien fungusbesmetting nie vroegtydig opgespoor word nie, kan mikotoksiene die voedselketting betree. Vinnige en akkurate metodes word benodig om patogene op te spoor, te identifiseer en ook om onderskeid tussen patogene te tref om sodoende (effektiewe) besluite aangaande die gebruik van ‘n lot of besending graan te neem. Naby-infrarooi (NIR) hiperspektrale beelding en meerveranderlike beeld ontleding (MIA) is geëvalueer om fungusontwikkeling in mieliepitte oor tyd te ondersoek. Wanneer hoofkomponent (PC) 4 teenoor PC5 gestip word, met persentasies som van kwadrate (%SS) 0.49% en 0/34%, is drie afsonderlike groepein die telling grafiek waargeneem. Dit is geassosieer met die graad van besmetting. Prominente pieke by 1900 nm en 2136 nm het bevestig dat veranderinge in stysel en proteïene die bron van die variasie was. Veranderlike belangrikheidsgrafieke (VIP) het die pieke wat in die PCA beladingslyngrafieke waargeneem is, bevestig. Vroegtydige opsporing (bespeuring) van fungusbesmetting en aktiwiteit (20 h na inokulasie) was moontlik voor visuele besmettingsimptome verskyn het. Onderskeid tussen Fusarium spesies wat met mielies geassosieer word, was moontlik deur gebruik te maak van NIR hiperspektrale beelding en MIA. Dit is bykomend toegepas om fungusgroeikinetika op kwekingsmedia te bestudeer. Parsiële kleinste kwadrate diskriminantanalise (PLS-DA) voorspellingsresultate het getoon dat dit moontlik was om tussen spesies te onderskei, met F. verticillioides die minste korrek voorspel (tussen 19-47% beeldelemente korrek voorspel). Vir F. subglutinans is 78-100% en vir F. proliferatum is 60-80% beeldelemente korrek voorspel. Drie prominente bande by 1166, 1380 en 1918 nm is oorweeg as oorsaak vir die verskille tussen die groeisones. Variasies in die bande by 1166 en 1380 nm is gekorreleer met die vermindering van koolhidrate soos die fungus groei, terwyl die band by 1918 nm ‘n moontlike aanduiding van spoor en nuwe miseliale vorming is. Deur die beeldelemente van die individuele groeisones as ‘n funksie van tyd te stip, was dit moontlik om die verskyning en interaksie van die groeisones as aparte groeiprofiele te visualiseer. Hoë-resolusie X-straal mikro-berekende tomografie (μCT) is gebruik om die mikrostruktuur van fungusbesmette mieliepitte oor tyd te ondersoek. Die voorkoms van leemtes en lugruimtes kon in die twee-dimensionele (2D) X-straal transmissie beelde en in die drie-dimensionele (3D) tomogramme gesien word. Duidelike verskille is waargeneem tussen pitte wat na 20 en 596 h na inokulasie verbeeld is. Hierdie verskil in leemtes soos die fungus vorder, het die effek van fungusskade op die mikrostruktuur van mieliepitte getoon. Beeldingstegnieke is belangrik vir vinnige, akkurate en objektiewe evaluasie van produkte vir kwaliteit en veiligheid. NIR hiperspektrale beelding bied vinnige chemiese evaluering van monsters in 2D beelde, terwyl μCT 3D mikrostrukturele inligting gee. Meer waarde is toegevoeg deur hierdie beeldingstegnieke te kombineer en dit het gelei tot ‘n omvangryke evaluering van Fusarium besmetting in mielies.

La digestion anaérobie est un moyen de traitement des déchets solides produisant de l'énergie sous forme de biogaz (méthane et dioxyde de carbone). L'optimisation de la production de méthane passe par une sélection des déchets à fort potentiel méthane. Actuellement, la mesure du potentiel méthane est réalisée par le test BMP (Biochemical Methane Potential), qui repose sur une fermentation pouvant durer plus de 30 jours, ce qui est trop long pour une installation industrielle. Une méthode rapide de détermination du potentiel méthane est donc nécessaire. Le BMP est lié uniquement à la quantité et à la qualité de la matière organique. Cette méthode doit donc réaliser une analyse globale et rapide de la matière organique. L'objectif de la thèse a été d'identifier et d'étudier une méthode rapide d'analyse de la matière organique de déchets solides permettent de prédire le potentiel méthane. Suite au travail bibliographique, la spectroscopie proche infrarouge s'est révélée la méthode la plus appropriée: analyse globale et rapide, non destructive, préparation d'échantillon réduite, possibilité d'utiliser des fibres optiques pour déporter la mesure. Nous avons ensuite étudié des étalonnages pour prédire le potentiel méthane d'un ensemble homogène de 74 déchets. Un coefficient de corrélation de 0,76 et un écart standard de prédiction (RMSEP) de 28 ml CH4.g-1 MV ont été obtenus. Ensuite, les coefficients du modèle ont été analysés par rapport aux molécules présentes et rapprochés des variables sélectionnées par algorithme génétique afin de valider ce modèle d'un point de vue chimique. Enfin, la robustesse de ce modèle vis à vis de l'origine des échantillons et de l'humidité a été testée. Les résultats montrent clairement le fort potentiel de la spectroscopie proche infrarouge pour la prédiction du potentiel méthane. Pour une utilisation industrielle, il ressort qu'une attention particulière doit être portée sur l'ensemble d'étalonnage, qui doit être le plus exhaustif possible. / Anaerobic digestion is a solution to process solid waste, while producing energy by biogas production (methane and carbon dioxide). Methane production could be optimized by selecting only wastes with high methane potential. Currently, the BMP (Biochemical Methane Potential) test is conducted to predict the methane potential. This test is based on a fermentation process. It is time consuming, sometimes, lasting over 30 days, which is too long from an industrial point of view. A rapid method for determining the methane potential is therefore urgently needed. The BMP value depends only on the quantity and the quality of the organic matter, so a method capable of determining the quality and quantity of organic matter is searched for. The objective of this thesis was to identify and study such a method. First, a bibliographic study led us to chose the near infrared (NIR) spectroscopy method: fast and global analysis of the organic matter, non-destructive method, few or no sample preparation, and remote monitoring by use of fiber optics. Second, a calibration for predicting the BMP of and homogenous sample set has been built based on a 74-waste sample set. A correlation coefficient of R² = 0,76 and a standard error of prediction (RMSEP = 28 ml CH4.g-1 VS). Then, the regression coefficients (called b coefficients) were analysed with regard to the molecules in the waste and were compared to the variables selected from the spectrum, in order to validate the model from a chemical point of view. Finally, the robustness of the model, regarding the waste origins and the moisture was tested with heterogeneous samples set. Results show the potential of the near infrared spectroscopy to predict the methane potential quickly, but attention must be paid on the calibration data set when an industrial implementation is dealt with..

Les naines brunes sont des astres incapables de déclencher et soutenir des réactions nucléaires dans leur cœur. En l’absence de cette source d’énergie, leur luminosité diminue avec le temps jusqu’à leur extinction complète. Leur flux aux longueurs d’onde de 0,8 à 2,35 μm est particulièrement altéré par l’humidité contenue dans l’atmosphère terrestre, ce qui complique l’étude de ces astres. Le but de la présente recherche est de vérifier si la division par un spectre d’étoile A0 est un moyen de corriger l’altération causée par l’atmosphère terrestre sur cette partie de leur spectre. Tout d’abord, des notions, pertinentes à la compréhension de ce travail, sont abordées. L’introduction présente quelques notions sur les naines brunes et sur l’atmosphère terrestre. Le deuxième chapitre concerne le traitement des données. Il traite de la calibration, de la mise en évidence du problème de non-répétabilité de la position de la fente du spectromètre SIMON ainsi que de ses causes. Il porte aussi sur l’uniformisation de la réponse des pixels et de la soustraction du ciel pour extraire les spectres. La méthode employée pour étudier l’effet de l’atmosphère terrestre sur les spectres de naines brunes y est présentée. Le troisième chapitre analyse les résultats obtenus par l’utilisation de l’étoile de référence de type A0 comme calibration pour corriger le spectre de naine brune, en assumant un même effet de l’atmosphère terrestre sur les deux types d’astres. Nous ne pouvons conclure, avec certitude, que l’absorption tellurique affecte de la même façon les deux spectres ni de quelle façon exactement ils sont affectés. Une recherche supplémentaire nécessitant de nouvelles prises de données à des masses d’air et à des taux d’humidité variés est requise. / Brown dwarfs are celestial bodies unable to sustain nuclear reactions. For this reason their luminosity declines until complete extinction. Their flux, particularly in the band between 0,8 and 2,35 μm, is absorbed by the water vapor in the terrestrial atmosphere. The goal of this research is to find a way to correct this part of their spectra affected by this effect. First, general notions needed to understand the project are exposed. The second chapter concerns the data reduction. The calibration, the problem of the position repeatability of the slit of the spectrometer SIMON and his cause are exposed. It discusses techniques to even up the pixels’ response and the substraction of the sky from the spectra. The method used to study the atmosphere effect on brown dwarf spectra is presented. The third chapter analyses the results that use the A0 reference star to correct the brown dwarf spectrum. We cannot conclude that the A0 spectrum is affected in the same way as the brown dwarf spectrum by the terrestrial atmosphere. The data from a single night do not allow a good analysis of this effect as a function of air mass and humidity level. Others missions are needed.

L'UMR ITAP d'IRSTEA à Montpellier et la société Pellenc SA souhaitent développer un système de mesure par spectrométrie visible - proche infrarouge permettant d'évaluer la qualité des olives et d'en suivre la maturité. La mesure doit être effectuée sur une seule olive et de manière non destructive. Les critères de maturité retenus pour une première phase d'étude sont les teneurs en eau et en huile. L'objectif de ces travaux est d'optimiser la mesure des critères de maturité par spectrométrie portable, en s'adaptant aux contraintes induites par l'objet d'étude et en levant des verrous imposés par la technologie retenue. En lien avec les objectifs industriels, trois questions scientifiques ont été soulevées :QS1 : Comment obtenir les valeurs de référence des critères de maturité à partir d'une seule olive ?QS2 : Comment mesurer le spectre d'une olive ? Quelle configuration optique est la plus adaptée à l'objet mesuré ? Quel volume de l'olive est interrogé lors de la mesure spectrale ? Le noyau intervient-il dans cette mesure ?QS3 : Comment étalonner la mesure spectrale ? Les modèles de prédiction sont-ils robustes au regard d'une variété non incluse dans leur étalonnage ? Comment inclure la masse du noyau dans les valeurs prédites ?Afin de répondre à ces questions, des études expérimentales et comparatives ont été menées. Pour la détermination de la teneur en huile (QS1) deux méthodes ont été évaluée, la résonance magnétique nucléaire (RMN) et l'extraction à l'hexane, lorsqu'elles sont appliquées à la pulpe d'une olive unique. L'étude sur les différentes configurations optiques (QS2) a permis de mettre en évidence l'impact de chacune sur la mesure spectrale et ainsi déterminer si l'ensemble de ces configurations proposées (transmission, réflexion diffuse avec propagation guidée de la lumière au moyen d'une sphère, réflexion diffuse avec propagation libre de la lumière et rétrodiffusion) sont envisageables pour la mesure sur une seule olive. De plus, ces travaux se sont intéressés au volume de peau et de pulpe réellement interrogé lors de la mesure spectrale par une étude de la perte de lumière transmise à travers la peau et la pulpe. Le questionnement de l'étalonnage des mesures spectrales (QS3) a consisté en une analyse fine des modèles construits mais aussi en une étude de la robustesse et des différentes méthodes envisageables pour l'améliorer (sélection de longueurs d'onde, mise à jour des modèles, correction “biais-pente”, méthode DOP). Le dernier point traité par ces travaux de thèse est la prise en compte de la masse du noyau dans les valeurs prédites et l'évaluation des différentes méthodes pour réaliser cette correction.L'ensemble des résultats obtenus au cours de cette thèse ont servi à fournir des éléments pour guider la conception d'un outil portable de mesures par spectrométrie sur olives individuelles. / ITAP Research Unit of IRSTEA and Pellenc SA company want to developa visible - near infrared spectroscopy measurement system in order to assess the quality of olives and monitor their ripeness. The measurement has to be non-destructive and performed on a single olive. The ripeness criteria selected are water and oil content. The main objective of this work is to optimize the measurement of these criteria, recorded by a portable spectrometer, by taking into account the constraints linked to the studied object and by overcoming the obstacles imposed by the technology used. In relation to the industrial objectives, three scientific questions were raised :SQ1 : How to get the reference values of the ripeness criteria from a single olive ?SQ2 : How to measure the spectrum of one olive ? Which optical configuration isbest suited for an olive ? Which volume of the olive is actually analyzed during thespectral measurement ? Does the spectrum contain information about the kernel ?SQ3 : How to calibrate the spectral measurement ? Are the prediction models robustregarding a variety not used for the calibration step ? How to include the kernel mass in the predicted values ?In order to answer those questions, experimental and comparative studies have been led. As the determination of water content is easily transposable to a single olive, only the measurement of oil content is studied (SQ1). Two existing methods nuclear magnetic resonance and hexane extraction have been characterized end evaluated when they are applied to the pulp of a single olive.The comparative study conducted on different optical configurations(SQ2) has high-lighted the impact of each configuration (transmission, diffuse reflectance with guidedpropagation of light through a sphere, diffuse reflectance with free propagation of light and interactance) on the spectral measurement. This study has also determined if all of these configurations are suitable for the whole olive measurements. Furthermore, the real volume analyzed during the spectral measurement has been investigated by studying the loss of transmitted light through the skin and the pulp.In order to answer SQ3, the present work provides optimized models for prediction ofwater content on the one hand and oil content on the other hand. The robustness study leads us to consider different methods (Model Update, Biais and Slope, DOP, wavelength selection) depending on the correction set used and therefore the finality of the future device. Concerning the introduction of kernel mass in predicted values, it has be done using various methods which are more or less destructive. The choice of one of these methods has been be determined by the technical possibilities of the device and the minimum expected accuracy of water and oil content predictions.Therefore, the results of this thesis provide some elements to guide the development of a portable spectrometer for measurements on individual olive fruits.

The manipulation of photons, especially the control of spontaneous emission, has become a core area of photonics research in the 21st century. One of the key challenges is the control of the broadband emission profile of thermal emitters. Recently, attention has focused on resonant nanophotonic structures to control the thermal emission with most of the work concentrating on the mid-infrared wavelength range and/or based on metallic nanostructures. However, the realisation of a high temperature, single wavelength, narrowband and efficient thermal source, remains a challenge. In this project, four individual nanophotonic resonant structures are presented for the control of thermal emission, all operating in the near-infrared (≈ 1.5 μm) wavelength range. The work is split over two different emission materials; gold and doped silicon. While I present two successful designs of narrowband thermal emitters from gold, the main backbone of the research is concentrated on doped silicon as the emission material. By combining the weak broadband absorption of doped silicon with a photonic crystal resonator, resonantly enhanced narrowband absorption is achieved. Using Kirchhoff's law of thermal radiation which equates the absorptivity and emissivity, narrowband absorption leads to narrowband emission, which is the underlying principle used throughout the work presented in this thesis to achieve narrowband thermal emission. One common oversight in many of the presented thermal emitter designs is the angular emission dependence, i.e. how the emission wavelength behaves away from surface normal. Typically, since the majority of the devices are based on periodic structures, the resonant emission wavelength changes with emission angle, which is not ideal. Here, the angular sensitivity is considered and addressed, by constructing a device that is based on localised confined resonances and not on propagating resonances, it is possible to achieve a truly monochromatic source i.e. one with the same emission wavelength in all directions, all the way up to an angle of 90°. Finally, the devices presented here demonstrate that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission away from the resonant wavelength.

L’étude des propriétés fractales des séries biologiques fait l’objet d’un intérêt croissant. Néanmoins la littérature met en évidence une ambiguïté quand à l’explication causale de la présence de ces séries temporelles ne permettant pas de distinguer entre l’adaptation effective réalisée par un sujet ou ses capacités d’adaptabilité globales. La présente thèse a pour objectif de décorréler ces deux notions, notamment en liant le niveau comportemental au niveau cérébral. Notre première étude a permise de mettre en évidence que les propriétés mono-fractales pourraient refléter l’adaptabilité des sujets tandis que les propriétés multifractales seraient liées à l’adaptation effective réalisée au cours de la tâche. La seconde étude à mise en évidence une corrélation entre les propriétés multifractales et le nombre de réseaux cérébraux mis en oeuvre au cours de la tâche, reflétant l’adaptation effective aux contraintes expérimentales imposées. Les résultats de ces travaux de thèse nous ont permis de mieux comprendre la signification fonctionnelle des analyses fractales en terme d’adaptation effective et d’adaptabilité. / The study of fractal properties in biological time series is of increasing interest. Nevertheless, the literature highlights an ambiguity on the causal explanation of the presence of these time series which does not make it possible to distinguish between the effective adaptation made by a subject or his overall adaptability capacities. The aim of this dissertation is to decorrelate these two notions, notably by linking the behavioral level to the cerebral level. Our first study allowed to highlight that the mono-fractal properties could reflect the adaptability of the subjects whereas the multifractal properties would be related to the effective adaptation carried out during the task. The second study showed a correlation between the multifractal properties and the number of brain networks implemented during the task, reflecting the effective adaptation to the experimental constraints imposed. The results of this work have allowed us to better understand the functional meaning of fractal analyzes in terms of effective adaptation and adaptability.