Dissolved organic matter (DOM) plays a vital role in biogeochemical processes and can flux CO2 to the atmosphere when labile fractions are degraded, hence DOM degradation is increasingly studied. Some studies have suggested that fluorescence-derived substrate characteristics are useful metrics for estimating bioavailability (as prerequisite condition for biodegradability), however, recent findings on soil organic matter emphasize the importance of ecosystem scale factors such as physical separation of substrate from soil microbial communities and soil physiochemical cycles driving organic matter stability. I extend this principle to soil derived DOM and hypothesize that such environmental conditions, covariant with season, land use and landscape position, impact the composition of soil DOM and activity and abundance of the microbial community, which together govern DOM biodegradability. As a result, DOM bioavailability may not reliably be predicted using substrate characteristics alone. To test these hypotheses, I assessed aqueous soil extracts for water extractable organic carbon (WEOC) content, biodegradability, microbial biomass and fluorescence spectroscopy on water extractable organic matter (WEOM) across a range of environmental conditions in northern Vermont, USA. My results indicate that changes in environmental conditions affect composition, quantity, and biodegradability of DOM. WEOC concentrations were highest in the fall and lowest in the summer, while no significant differences were found between land covers or landscape position, however, DOM biodegradability was significantly higher in the agricultural (AG) site across seasons. Despite a shift in utilized substrate from less aromatic DOM in summer to more aromatic DOM in winter, biodegradability was similar for all seasons. The only exception were cold temperature incubations where microbial activity was depressed, and processing was halted. These results indicate that bioavailability cannot be reliably predicted based on fluorescence-based metric alone, rather, my core findings illustrate a complex picture of how environmental conditions, landscape characteristics, and substrate composition interact to drive the biodegradability of labile carbon pools in the soil environment. This thesis includes i) a background and comprehensive review of literature to inform the reader of any relevant topics, ii) a paper submitted for publication to Biogeochemistry (Chapter 2), and iii) supplemental information containing figures and tables pertinent to the paper.

No description available.

Les professionnels de la filière vin sont à la recherche de méthodes globales pour suivre la maturité du raisin et ainsi en déterminer la qualité à la vendange pour l'élaboration de leurs vins. Dans ce contexte, le principal objectif de ce travail est de rechercher des méthodes sensorielle et instrumentales innovantes pour suivre globalement la maturation des baies de raisin de Cabernet franc. La spectroscopie VisNIR et l'analyse sensorielle des baies de raisin apparaissent comme les méthodes les plus prometteuses en terme de suivi de maturation pour la filière vin. La technique de double compression à 20 % n'est en revanche pas appropriée pour suivre la maturité « texturale ». D'autres techniques mécaniques destructives pourraient cependant être envisagées comme la pénétrométrie. La spectroscopie de fluorescence a permis de suivre la maturité phénolique du raisin. Mais, cette méthode doit être optimisée pour gagner en précision. Une méthode capable de caractériser la qualité globale du raisin a également été recherchée. La spectroscopie VisNIR et les descripteurs sensoriels permettent de caractériser les différents aspects de la qualité globale du raisin pendant sa maturation. Ces deux techniques permettent en effet une caractérisation en termes de maturités technologique, phénolique, aromatique et « texturale ». La méthode d'analyse sensorielle des baies de raisin est en cours de transfert vers les professionnels de la filière afin d'obtenir un outil d'aide à la décision pour déterminer la date de vendange. La mise au point d'un appareil portable de spectroscopie VisNIR pourrait quant à elle être envisagé afin de réaliser des mesures directes dans les parcelles.

Les matrices d'excitation et d'émission de fluorescence (MEEF) sont utilisées pour caractériser la matière organique naturelle (MON). Afin de mieux exploiter ces informations, un algorithme trilinéaire, PARAFAC, est employé. Après l'élimination des diffusions Rayleigh et Raman et la correction de l'effet d'écran, cette méthode permet de séparer les composants spectraux présents dans les MEEF.Ce travail présente deux études : la qualification et la quantification de la MON selon son origine environnementale et le calcul des constantes de complexation de la MON et du cuivre sous forme ionique.Les composants spectraux et leurs intensités relatives sont calculés par PARAFAC à partir 1146 échantillons regroupés suivant les missions, leur type de milieu, ou le niveau de salinité. Pour étudier ces composants, une nouvelle représentation spectrale est proposée afin de mettre en évidence leur variabilité spectrale. Les résultats montrent que le regroupement d'échantillons d'origine diverse conserve le recouvrement spectral global et les intensités relatives. Sur l'ensemble du domaine spectral, les zones correspondant aux substances humiques sont peu variables, comparées à la zone protéinique.La complexation des métaux par la MON est analysée par une technique combinant quatre outils : l'ajout logarithmique d'ions métalliques, la mesure de MEEF, la méthode PARAFAC et l'algorithme PROSECE. La mesure du quenching de fluorescence ne se limite pas seulement à la modélisation d'une intensité de fluorescence mais à celle de l'intensité relative de chaque composant PARAFAC surpassant ainsi les méthodes utilisées jusqu'à présent. Finalement, l'application de cette technique originale permet de quantifier les propriétés de complexation de la MON à l'aide d'un modèle de complexation utilisant 2 sites de complexation par composant en utilisant la totalité du signal de fluorescence.

De par leur diversité et leur large gamme d'applications, les polymères se sont imposés dans notre environnement. Dans le cas d'applications techniques ces matériaux peuvent être exposés à des environnements agressifs conduisant à une altération de leurs propriétés. Les effets de cette dégradation sont reliés à la notion de durée de vie, c'est-à-dire au temps nécessaire pour qu'une propriété atteigne un seuil en dessous duquel le matériau devient inutilisable. Le suivi du vieillissement des matériaux polymères présente donc des enjeux importants. La spectroscopie de fluorescence est une technique qui permet d'apporter certaines réponses à ce problème. Dans le cadre de cette étude, l'accent a été porté sur l'utilisation de la spectroscopie de fluorescence pour l'étude des phénomènes intervenant lors de l'irradiation UV ou de la sollicitation mécanique d'un polymère. Dans le cas du polyéthylène haute densité, l'absence de signal fluorescent intrinsèque impose l'ajout d'un colorant. Ce colorant donnant une réponse en fluorescence dépendant de son microenvironnement, toutes modifications des chaînes du polymère engendrent un déplacement du pic de fluorescence de la sonde. Ce travail peut être séparé en deux grandes parties indépendantes, d'un coté l'influence du vieillissement UV sur la réponse fluorescente et de l'autre l'influence d'une sollicitation mécanique. Dans la première partie, l'utilisation de techniques complémentaires telles que l'IRTF ou l'AED a permis de corréler les différents résultats avec les mécanismes de vieillissement connus du polyéthylène. Les résultats obtenus dans cette partie montrent la grande sensibilité de la spectroscopie de fluorescence aux réarrangements microstructuraux intervenant dans le matériau. Dans la seconde partie, la dépendance entre la contrainte appliquée au matériau et la longueur d'onde de fluorescence a permis a partir de modèles simples d'évaluer les contraintes internes qui se développent au cours d'une sollicitation cyclique.

<p>This thesis describes the research I have done, and partly will do, during my time as a PhD student in the laboratory of Applied Optics at Linköping University. Due to circumstances beyond the scope of this book, this incorporates three quite different projects. The first two, involving gas sensing and measuring on paper with ellipsometry, have been discontinued, whereas the third one, measuring fluorescence with a computer screen and web camera, is in full progress and will be until I complete my studies.</p><p>Thus the purpose of this work also has several aspects. Partly, it describes performed research and its results, as well as theoretical background. On the other hand, it provides practical and theoretical background necessary for future work. While the three projects are truly quite different, each of them has certain things in common with each of the other. This is certainly also true for the necessary theory. Two of them involve spectroscopic ellipsometry, for example, while another pair needs knowledge of color theory, etc. This makes it impossible to separate the projects, despite of their differences. Hopefully, these links between the different projects, connecting the different chapters, will make this work whole and consistent in its own way.</p> / Report code: LiU-TEK-LIC-200 4-19. On the day of the public defence the status of article I was: In press and the status of article III was: Manuscript and has a new title. The old title was Computer screen photo-assisted spectroscopic fluorimetry.

<p>Lévy flights and Lévy walks are two mathematical models used to describe anomalous diffusion(i.e. those having mean square displacements nonlinearly related to time (as opposed to Brownian motion)). Lévy flights follow probability distributions p(|<strong>r</strong>|) yielding infinite mean square displacements since some rare steps are very long. Lévy walks, however, have coupled space-time probability distributions penalising very long steps. Both Lévy flights and Lévy walks are dominated by a few long steps, but most steps are much, much smaller. The semi-experimental part ofthis work dealt with how fluorescent probes moved in systems of cationic starch and latex/solutions of dodecyl trimethyl ammonium bromide, respectively. Visually, no Lévy walks couldbe detected. However, mathematical regression suggested enhanced diffusion and subdiffusion. Moreover, time-dependent diffusion coefficients were calculated. Also examined was how Microsoft Excel could be used to generate normal diffusion as well as anomalous diffusion.</p> / <p>Lévyflygningar och Lévypromenader är matematiska modeller som används för att beskriva anomal diffusion (i.e. dessa då medelvärdet av kvadratförflyttningarna är icke-linjärt relaterat tilltiden (till skillnad från Brownsk rörelse)). Lévyflygningar följer sannolikhetsfördelningar p(|<strong>r</strong>|)som ger oändliga medelkvadratförflyttningar eftersom vissa steg är väldigt långa. Lévypromenader,å andra sidan, har kopplade rum-tid-sannolikhetsfördelningar som kraftigt reducerar demycket långa stegen. Både Lévyflygningar och -promenader domineras av ett fåtal långa steg ävenom de flesta steg är mycket, mycket mindre. Den semiexperimentella delen av detta arbetestuderade hur fluorescerande prober rör sig i katjonisk stärkelse respektive latex/lösningar avdodecyltrimetylammoniumbromid. Inga Lévypromenader kunde ses. Emellertid taladematematisk regression för att superdiffusion och subdiffusion förelåg. Tidsberoende diffusionskoefficienter beräknades också. I detta arbete undersöktes även hur Microsoft Excel kan användas för att generera både normal och anomal diffusion.</p>

Molecular assemblies capable of harvesting light and using the absorbed energy have attracted great interest in recent years because of their applicability in such domains as light emitting diodes, fluorescent labelling of biological molecules, and photonic devices. Nature has also developed in plants and photosynthetic bacteria several examples of photonic nanostructures which guide light over small distances and harvest light energy, using resonance energy transfer (RET). For some time, researchers have tried to mimic the spatial arrangements of high energy transfer efficiency found in Nature. Recent progress in the application, creation and manipulation of individual or small groups of molecules are opening new perspectives for further developments in this field. These recent advances are commonly considered to lie at the root of what is being called "Nanotechnology". Although the definitions of nanotechnology are diverse, it is commonly admitted that this new domain of Science draws ideas and concepts from disciplines including engineering, physics, chemistry, biology, mathematics and computer science. The central dogma of the “bottom up” version of nanotechnology is the notion of self-assembly, which is the spontaneous assembly of materials into predetermined ordered structures or complexes. Presented here is an example from a field of nanotechnology that utilizes self-assembly onto nano-patterned surfaces to generate nano-structured systems and devices. More precisely, in the present case we target photo-active devices based on Fluorescence Resonance Energy Transfer (FRET), taking inspiration from photosynthetic light harvesting systems, where concentric nanometric rings of chromophores funnel light energy to a reaction center. Here, we synthesize nano-patterned chromophore surfaces which are able to collect light energy over a large surface and funnel it in regions of ~100 nm size. Our results indicate that an efficient collection and transfer of light energy can be performed by properly nano-designed surfaces, which may have practical consequences for the fabrication of light-powered active nano-devices.

Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the _rst pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (_ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy singlepulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 _J and an excitation laser pulse energy of 8 _J. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the e_ect of detector gain, the gate delay and the gate width were studied. In this thesis LIBS and LA-LIF were also used to analyze ultralow volumes of analyte in liquids in microuidic geometries. LIBS was applied for the detection of Na in liquid droplets in a microuidic system. The detection of Na as low as 360 femtograms was demonstrated for 100 shots integrated in this system. An LOD of 7 ppm for Pb for 100 shot accumulation was demonstrated using the LA-LIF technique on an 18 _m diameter microdroplet. To study the laser interaction with the water targets the MEDUSA one dimensional hydrocode was used. The propagation of the shockwave and plume dynamics were studied using this modeling code. The expansion of the plume was studied and compared to experimentally measured values and to physical models for blast wave expansion and stagnation. Two preconcentration techniques were also studied, one of which used a wood-chip as a substrate to absorb the analyte liquid and wick the salt on to the surface for analysis and the other used an electroplating technique to plate the analyte metal as a thin _lm on a substrate metal used as a cathode. The electroplating method for preconcentration was also studied using a microchip laser and a LOD of 6.4 ppb for Pb in water was obtained for an accumalation of 200,000 shots. / Photonics and Plasmas

The main focus of this dissertation is to develop a multispectral imaging system with spectral zooming capability and also successfully demonstrate its promising medical applications through combining this technique with microscope system. The realization of the multispectral imaging method in this dissertation is based on the 4-f spatial filtering principle. When a collimated light is dispersed by the grating, there exists a clear linear distribution spectral line or spectrum at the Fourier plane of the Fourier transform lens group base on the Abbe imaging theory and optics Fourier Transform principle. The optical images, not the collimated light, are applied into this setup and the spectrum distribution still keeps linear relationship with the spatial positions at Fourier plane, even through there exists additional spectral crosstalk or overlap. The spatial filter or dynamic electrical filters used at the Fourier plane will facilitate randomly access the desired spectral waveband and agilely adjust the passband width. It offers the multispectral imaging functionality with spectral zooming capability. The system is flexible and efficiency. A dual-channel spectral imaging system based on the multispectral imaging method and acousto-optical tunable filter (AOTF) is proposed in the dissertation. The multispectral imaging method and the AOTF will form spate imaging channels and the two spectral channels work together to enhance the system efficiency. The AOTF retro reflection design is explored in the dissertation and experimental results demonstrate this design could effectively improve the spectral resolution of the passband. Moreover, a field lens is introduced into the multispectral imaging system to enhance the field of view of the system detection range. The application of field lens also improves the system spectral resolution, image quality and minimizes the system size. This spectral imaging system can be used for many applications. The compact prototype multispectral imaging system has been built and many outdoor remote spectral imaging tests have been performed. The spectral imaging design has also been successfully applied into microscope imaging. The prototype multispectral microscopy system shows excellent capability for normal optical detection of medical specimen and fluorescent emission imaging/diagnosis. Experiment results have demonstrated this design could realize both spectral zoom and optical zoom at the same time. This design facilitates fast spectral waveband adjustment as well as increasing speed, flexibility, and reduced cost.