Dissertations / Theses on the topic 'ENHANCED CORRELATION'

Magnesium is the lightest metal with a very high specific strength. However, its practical applicability is limited by its toughness and reliability. Mg, being HCP has low ductility. This makes the improvement of toughness a grand challenge in Mg alloys. Friction stir processing (FSP) is a thermomechanical technique used to effect microstructural modification. Here, FSP was utilized to affect the toughness of WE43 sheets through microstructural modification. Room temperature Kahn-type tests were conducted to measure the toughness of WE43 sheets. Microscopic techniques (SEM, TEM) was utilized to study the effect of various microstructural factors like grain size, texture, constituent particles, precipitates on crack initiation and propagation. Tensile properties were evaluated by mini-tensile tests. Crack growth in WE43 sheets was also affected by mechanics and digital image correlation (DIC) was utilized to study the plastic zone size. The underlying mechanisms affecting toughness of these sheets were understood which will help in formulating ways in improving it. WE43 nanocomposites were fabricated via FSP. Uniform distribution of reinforcements was obtained in the composites. Improved mechanical properties like that of enhanced strength, increased hardness and stiffness were obtained. But contrary to other metal matrix composites which show reduction in ductility with incorporation of ceramic reinforcements, the nanocomposites showed good strength-ductility combination. The composites were precisely characterized and mechanisms governing this property were studied. The nano-length of the reinforcements was observed to be the main criteria and the dislocation-particle interaction, the main reason behind the strength-ductility property.

Sequence stratigraphy relates changes in vertical and lateral facies distribution to relative changes in sea level. These relative changes in carbonates effect early diagenesis, types of pores, cementation and dissolution patterns. As a result, in carbonates, relative changes in sea level significantly impact the lithology, porosity, diagenesis, bed and bounding surfaces which are all factors that control fracture patterns. This study explores these relationships by integrating stratigraphy with fracture analysis and petrophysical properties. A special focus is given to the relationship between mechanical boundaries and sequence stratigraphic boundaries in three different settings: 1) Mississippian strata in Sheep Mountain Anticline, Wyoming, 2) Mississippian limestones in St. Louis, Missouri, and 3) Pennsylvanian limestones intermixed with clastics in the Paradox Basin, Utah. The analysis of these sections demonstrate that a fracture hierarchy exists in relation to the sequence stratigraphic hierarchy. The majority of fractures (80%) terminate at genetic unit boundaries or the internal flooding surface that separates the transgressive from regressive hemicycle. Fractures (20%) that do not terminate at genetic unit boundaries or their internal flooding surface terminate at lower order sequence stratigraphic boundaries or their internal flooding surfaces. Secondly, the fracture spacing relates well to bed thickness in mechanical units no greater than 0.5m in thickness but with increasing bed thickness a scatter from the linear trend is observed. In the Paradox Basin the influence of strain on fracture density is illustrated by two sections measured in different strain regimes. The folded strata at Raplee Anticline has higher fracture densities than the flat-lying beds at the Honaker Trail. Cemented low porosity rocks in the Paradox Basin do not show a correlation between fracture pattern and porosity. However velocity and rock stiffness moduli's display a slight correlation to fracture spacing. Furthermore, bed thickness is found to be only one factor in determining fracture density but with increasing strain, internal bedforms and rock petrophysical heterogeneities influence fracture density patterns. This study illustrates how integrating sedimentologic and sequence stratigraphic interpretations with data on structural kinematics can lead to refined predictive understanding of fracture attributes.

La spectroscopie de fluorescence de molécule individuelle a révolutionné le domaine des sciences biophysiques, en permettant la visualisation des interactions moléculaires dynamiques et des caractéristiques nanoscopiques avec une haute résolution spatio-temporelle. Le contrôle des réactions enzymatiques et l'étude de la dynamique de diffusion de molécules individuelles permet de comprendre l'influence et le contrôle de ces entités nanoscopiques sur plusieurs processus biophysiques. La nanophotonique basée sur la plasmonique offre des nouvelles opportunités de suivi d'évènements à molécule unique, puisque il est possible de confiner des champs électromagnétiques dans les hotspots à nano-échelle, à dimensions spatiales comparables à une molécule unique. Dans ce projet de thèse, nous explorons plusieurs plateformes de nanoantennas photoniques avec des hotspots, et nous avons démontré les applications dans l'amélioration de la spectroscopie de fluorescence de molécule individuelle. En utilisant la fluorescence burst analysis, l'analyse de fluctuations temporelle de fluorescence,TCSPC, nous quantifions les facteurs d'amélioration de fluorescence, les volumes de détection de nanoantennas; ainsi, nous discutons l'accélération de fluorescence photo dynamique. En alternative aux structures plasmoniques, des antennes diélectriques basées sur les dimères en silicone ont aussi démontré d'améliorer la détection de fluorescence à molécule unique, pour des concentrations micro molaires physiologiquement pertinentes. En outre, nous explorons des systèmes planaires antennas in box pour l'investigation de la dynamique de diffusion de la PE et de la SM dans les membranes des cellules vivantes
Single-molecule fluorescence spectroscopy has revolutionized the field of biophysical sciences by enabling visualization of dynamic molecular interactions and nanoscopic features with high spatiotemporal resolution. Monitoring enzymatic reactions and studying diffusion dynamics of individual molecules help us understand how these nanoscopic entities influence and control various biochemical processes. Nanophotonic antennas can efficiently localize electromagnetic radiation into nanoscale spatial dimensions comparable to single bio-molecules. These confined illumination hotspots there by offer the opportunity to follow single-molecule events at physiological expression levels. In this thesis, we explore various photonic nanoantenna platforms and demonstrate their application in enhanced single-molecule fluorescence detection. Using fluorescence burst analysis, fluorescence correlation spectroscopy (FCS), time-correlated TCSPC measurements, and near field simulations, we quantify nanoantenna detection volumes, fluorescence enhancement factors and discuss the fluorescence photodynamic accelerations mediated by optical antennas. Further, using resonant planar antenna-in-box devices we investigate the diffusion dynamics of phosphoethanolamine and sphingomyelin on the plasma membrane of living cells and discuss the results in the context of lipid rafts. Together with cholesterol depletion experiments, we provide evidence of cholesterol-induced nanodomain partitioning within less than 10~nm diameters and characteristic times being ~100 microseconds

Owing to its ability to capture a systemic and temporal metabolic description of an organism’s response to a treatment, metabonomics is a well-established and valuable approach in elucidating the effects and mechanisms of a given perturbation. However, to optimise information recovery from the complex datasets generated, chemometric methods are essential. The work presented in this thesis focuses on the development of novel methods, and the use of existing methods in new applications to ease data interpretation and enhance information recovery from 1H Nuclear Magnetic Resonance (NMR) metabonomic datasets using correlation based methods. Although the methods here are largely applied to toxicological data, they could be equally valuable in the analysis of any metabonomic dataset, and indeed potentially to other ‘omics’ data presenting similar analytical challenges. The first two methodological approaches relate to novel extensions of Statistical Total Correlation Spectroscopy (STOCSY), a valuable tool in elucidation of both inter- and intra-metabolite spectral intensity correlations in NMR metabonomic datasets. In the first, STOCSY is utilised in STOCSY-editing, a method for the selective identification and downscaling of the peaks from unwanted metabolites such as those arising from xenobiotics. Structurally correlated peaks from drug metabolites are first identified using STOCSY, and the returned correlation information utilised to scale the spectra across these regions, producing a modified set of spectra in which drug metabolite contributions are reduced, endogenous peaks reconstructed and thus, analysis by pattern recognition methods without drug metabolite interferences facilitated. In the second, the STOCSY approach is extended in Iterative-STOCSY, where metabolic associations are followed over several rounds of STOCSY through calculation of correlation coefficients initially from a driver spectral peak of interest, and subsequently from all peaks identified as correlating above a set threshold to peaks picked in the previous round. The condensation of putatively structurally related peaks into single nodes, and representation of the otherwise complex network in a fully interactive plot of node-to-node connections and corresponding spectral data, allows the ready exploration of both inter- and intrametabolite relationships and a more directed approach to the identification of biomarkers of the studied perturbation. Finally various clustering methods are investigated with the aim of providing improved structural (intra-metabolite) versus non-structural (inter-metabolite) assignment. Thus, this thesis presents a framework for the enhanced identification, recovery and characterisation of inter- and intrametabolite relationships and how these are affected by metabonomic perturbation.

The need for high speed and cost efficient inspection in manufacturing lineshas led to a vast usage of camera-based vision systems. The performance ofthese systems is sufficient to determine shape and size, but hardly to an accuracylevel comparable with traditional metrology tools. To achieve highprecision shape/position/defect measurements, the camera techniques haveto be combined with high performance image metrology techniques whichare developed and adapted to the manufactured components. The focus ofthis thesis is the application of enhanced image analysis as a tool for highprecision metrology. Dedicated algorithms have been developed, tested andevaluated in three practical cases ranging from micro manufacturing at submicronprecision to meter sized aerospace components with precision requirementsin the 10 μm range.The latter measurement challenge was solved by low cost standard consumerproducts, i.e. digital cameras in a stereo configuration and structured lightfrom a gobo-projector. Combined with high-precision image analysis and anew approach in camera calibration and 3D reconstruction for precise 3Dshape measurement of meter sized surfaces, the achievement was fulfilledand verified by two conventional measurement systems; a high precisioncoordinate measurement machine and a laser scanner.The sub-micron challenge was the implementation of image metrology forverification of micro manufacturing installations within a joint Europeaninfrastructure network, EUMINAfab. The results were an unpleasant surprisefor some of the participating laboratories, but became a big step forwardto improve the dimensional accuracy of the investigated laser micromachining, micro milling and micro-printing systems, since the accuracy ofthese techniques are very difficult to assess.The third high precision metrology challenge was the measurement of longrange,low-amplitude topographic structures on specular (shiny) aerodynamicsurfaces. In this case Fringe Reflection Technique (FRT) was appliedand image analysis algorithms were used to evaluate the fringe deformationas a measure of the surface slopes to obtain high resolution data. The resultwas compared with an interferometric analysis showing height deviation inthe range of tens of micrometers over a lateral extension of several cm.

QC 20170523

LOCOMACHS
EUMINAfab
Cleansky

Single-molecule fluorescence spectroscopy has revolutionized the field of biophysical sciences by enabling visualization of dynamic molecular interactions and nanoscopic features with high spatiotemporal resolution. Monitoring enzymatic reactions and studying diffusion dynamics of individual molecules (such as lipids and proteins) help us understand how these nanoscopic entities influence and control various biochemical processes. Nanophotonic antennas can efficiently localize electromagnetic radiation into nanoscale spatial dimensions comparable to single bio-molecules (<10 nm). These ultra-confined illumination hotspots thereby offer opportunity to follow single-molecule events at physiological expression levels. In this thesis, we explore various photonic nanoantenna platforms (double nanohole apertures, dimer nanogap antennas and planar "antenna-in-box'') and demonstrate their application in enhanced single-molecule fluorescence detection. Using fluorescence burst analysis, fluorescence correlation spectroscopy (FCS), time-correlated TCSPC measurements, and near field simulations, we quantify nanoantenna detection volumes, fluorescence enhancement factors and discuss the fluorescence photodynamic accelerations mediated by optical nanoantennas. An alternative to plasmonic structures, all-dielectric nanoantenna based on silicon nanogap is also demonstrated to enhance the fluorescence detection of single molecules diffusing in concentrated solutions. Further, using resonant planar "antenna-in-box'' devices we investigate the diffusion dynamics of phosphoethanolamine and sphingomyelin on the plasma membrane of living cells and discuss the results in the context of lipid rafts. Together with cholesterol depletion experiments, we provide evidence of cholesterol-induced nanodomain partitioning within less than 10 nm diameters and characteristic times being ~100 microseconds
La espectroscopia de fluorescencia de una sola molecula ha revolucionado el campo de las ciencias biofisicas, permitiendo la visualizacion de interacciones moleculares dinamicas y caracteristicas nanoscopicas con alta resolucion espaciotemporal. La monitorizacion de las reacciones enzimaticas y el analisis de la dinamica de difusion de moleculas individuales (como lipidos y proteinas) nos ayudan a comprender como estas entidades nanoscopicas influyen y controlan diversos procesos bioquimicos. Las antenas nanofotonicas pueden localizar eficientemente la radiacion electromagnetica en dimensiones espaciales en nanoescala, comparables a biomoleculas unicas (<10 nm). Estos hotspots de iluminacion ultra configurados ofrecen de este modo la oportunidad de monitorizar eventos de molecula unica a niveles de expresion fisiologica. En esta tesis, exploramos varias plataformas fotonicas de nanoantenas (double nanohole aperture, dimero nanogap antenas y "antenna-in-box" planares) y demostramos su aplicacion en la mejora de la deteccion una sola molecula de fluorescencia. Utilizando el analisis por explosion de fluorescencia, espectroscopia de correlacion de fluorescencia (FCS), medidas TCSPC correlacionadas en el tiempo y simulaciones de campo cercano, cuantificamos volumenes de deteccion de nanoantenas, factores de mejora de fluorescencia y discutimos las aceleraciones fotodinámicas de fluorescencia mediada por nanoantennas opticas. Las nanoantennas dielectricas basadas en nanogaps de silico se han propuesto como una alternativa en el realce de la deteccion de fluorescencia de difusion de moleculas unicas en soluciones concentradas. Ademas, utilizando dispositivos resonantes planares de "antenna-in-box", investigamos la dinamica de difusion de la fosfoetanolamina y la esfingomielina en la membrana plasmatica de las celulas vivas y discutimos los resultados en el contexto de las balsas lipidicas. Junto con experimentos de dismincion de colesterol, proporcionamos pruebas de division inducida por colesterol en el nanodominio dentro de diametros menors de 10 nm y con tiempos caracteristicos de ~100 microsegundos.
La spectroscopie de fluorescence d'une seule molécule a révolutionné le domaine des sciences biophysiques, permettant la visualisation d'interactions moléculaires dynamiques et de caractéristiques nanoscopiques à haute résolution spatio-temporelle. Le suivi des réactions enzymatiques et l'analyse de la dynamique de diffusion des molécules individuelles (telles que les lipides et les protéines) nous aident à comprendre comment ces entités nanoscopiques influencent et contrôlent divers processus biochimiques. Les antennes nanophotoniques peuvent localiser efficacement le rayonnement électromagnétique à des dimensions spatiales nanométriques, comparables à des biomolécules uniques (<10 nm). Ces hotspots d'éclairage ultra-configurés offrent la possibilité de surveiller les événements de molécules uniques à des niveaux d'expression physiologiques. Dans ce mémoire, nous examinons plusieurs plates-formes photoniques nanoantennas (nanotrou à double ouverture, I antennes Dimer nanoespace et plane « antenne-in-box ») et de démontrer son application dans l'amélioration de la détection d'une fluorescence seule molécule. Utilisation de l'analyse par spectroscopie de fluorescence d'explosion corrélation de fluorescence (FCS), les mesures TCSPC corrélées dans le temps et proches des simulations champ quantifier les volumes de détection de nanoantennas, les facteurs d'amélioration fluorescence et discuter des accélérations photodynamiques fluorescence médiée nanoantennas opticas. Des nanoantennas diélectriques à base de nanogap silico ont été proposées comme alternative dans l'amélioration de la détection par fluorescence de la diffusion de molécules uniques dans des solutions concentrées. En outre, l'utilisation de "plan d'antenne-in-box" dispositifs de résonance, nous étudions la dynamique de diffusion de phosphoéthanolamine et sphingomyéline dans la membrane plasmique des cellules vivantes et de discuter des résultats dans le contexte des radeaux lipidiques. Conjointement avec des expériences de réduction du cholestérol, nous fournissons des tests de division induits par le cholestérol dans le nanodomaine dans des diamètres plus petits de 10 nm et avec des temps caractéristiques de ~ 100 microsecondes.

Les techniques de fluorescence de molécule individuelle permettent de suivre la dynamique moléculaire et les interactions dans les processus biologiques. Maintenant, la dynamique moléculaire des protéines est principalement accompagnée du marquage fluorescent externe. Cependant, une molécule attachée peut perturber la dynamique de protéines. Heureusement, la majorité des protéines contiennent le tryptophane ou la tyrosine qui absorbent et émettent la lumière dans le domaine spectral d'UV entre 260 nm et 400 nm. Ces acides aminés ont de basses efficacités quantiques, photostabilisées dans l'UV et la section efficace d'absorption, qui gênent la détection des protéines individuelles. Afin d'atteindre la sensitivité de l'auto fluorescence UV des protéines individuelles, nous développons un microscope confocal UV à la résolution temporelle avec les lasers de 266 nm et 295 nm. Nous quantifions la sensitivité de détection et l'effet des techniques de photostabilisation sur l'autofluorescence des protéines. La spectroscopie de corrélation de fluorescence (SCF) et les mesures de time-correlated single photon counting (TCSPC) fournissent des informations quantitatives du volume de détection, de l'amélioration de fluorescence (AF), et de la photokinétique accélérée des molécules émettant à la présence et à l'absence des nanostructures d'aluminium (Al). En utilisant le p-terphenyl, nous optimisons les nanostructures plasmoniques d'Al afin d'améliorer la fluorescence. Sous certaines conditions, le confinement de la lumière et l'AF dans les structures d'Al permettent d'appliquer la plasmonique UV pour la détection des protéines individuelles de beta-galactosidase sans marquage
Single molecule fluorescence techniques enable to monitor the molecular dynamics and interactions in the biological processes. Nowadays, the molecular dynamics of proteins is principally accompanied by external fluorescent labeling. However, an attached molecule might perturb the protein dynamics. Fortunately, a vast majority of proteins contain tryptophan and tyrosine that absorb and emit light in the UV range of 260-400 nm. These intrinsically fluorescent amino acids yield limited absorption cross-section, quantum yield, and photostability in the UV range, which hampers single protein UV autofluorescence detection. In order to reach single molecule sensitivity of protein UV autofluorescence, we develop a time-resolved UV confocal microscope with 266 nm and 295 nm excitations and the detection optics in the near UV. Based on the total fluorescence time traces, we quantify the single molecule sensitivity, the effect of photostabilization techniques on the protein autofluorescence. Fluorescence correlation spectroscopy (FCS) and time-correlated single photon counting (TCSPC) measurements provide quantitative information on the detection volume, the fluorescence enhancement factors, and the accelerated photokinetics of the UV emitting molecules in the presence and absence of the aluminum (Al) nanostructures. Using p-terphenyl as a bright UV emitting molecule, we optimize the Al plasmonic nanostructures to enhance the single molecule fluorescence. Under certain conditions, the light confinement and fluorescence enhancement in the aluminum nanostructures enable to apply the UV plasmonics for the single molecule detection of label-free beta-galactosidase protein

Des opérations de renforcement ou réparation sont souvent nécessaires pour garantir l’intégrité des structures en Béton Armé (BA) vis-à-vis du risque sismique. Dans ce cadre, le Polymère Renforcé de Fibres (PRF) stratifié au contact a démontré son efficacité pour améliorer le comportement en flexion des éléments de structures tant en termes de résistance que de ductilité. Afin d’en améliorer la liaison en proximité des jonctions, les ancrages noyés dans le béton représentent une solution avantageuse en termes de performances et de facilité de mise en place. Néanmoins, leur comportement mécanique est fréquemment associé à des mécanismes locaux de déformation qui peuvent affecter la réponse globale de la structure. Un nouveau montage expérimental a été donc conçu pour réaliser des essais de flexion in-situ sur des poutres renforcées de petite échelle avec l’utilisation de la tomographie 3D et étudier l’interaction entre le béton et les ancrages. L’objectif principal est de suivre grâce à la Corrélation d’Images Volumiques (CIV) l’évolution de la dégradation du matériau pendant le chargement et de reconstruire la cinématique de la zone renforcée. D’un point de vue numérique, un modèle éléments finis enrichis inspiré par la Méthode des Discontinuités Fortes (SDA) a été développé dans le but d’améliorer la représentation de l’interface. De cette façon, des comportements mécaniques complexes comme les phénomènes d’arrachement peuvent être facilement reproduits, en limitant en même temps le coût de calcul. La calibration du comportement d’interface est faite enfin grâce aux résultats des essais in-situ qui permettent de valider le modèle dans le cas de problèmes non-linéaires
Strengthening and retrofitting techniques are often required for guaranteeing the integrity of Reinforced Concrete (RC) structures to prevent seismic risk. In such a framework, Externally Bonded (EB) FRP strengthening systems have proven their effectiveness in enhancing the flexural performances of structural members both in terms of bearing capacity and ductility. In order to improve the bond in the vicinity of RC joints, embedded anchors represent an attractive solution in terms of both performances and ease of installation. Nevertheless, their mechanical behaviour is often associated with localised deformation mechanisms that can strongly affect the overall structural response. A novel experimental apparatus has therefore been designed in order to carry out in-situ bending tests on small-scale strengthened beams in conjunction with 3D tomography and study the interaction between concrete and anchors. The main goal is to track the evolution of material degradation over the entire loading history by means of Digital Volume Correlation (DVC) and to reconstruct the kinematics of the strengthened region. From a numerical point of view, an enriched finite element model inspired by the Strong Discontinuity Approach (SDA) has been developed with the aim of improving the interface representation. By means of a kinematic enrichment, this strategy allows, on the one hand, to account for complex mechanical behaviours such as pull-out deformation modes and debonding mechanisms, on the other hand, to limit the computational effort. The calibration of the interfacial behaviour is then realised by means of the in-situ experimental results which allow to validate the model in the case of non-linear problems

The foundational theory of quantum enhanced metrology for parameter estimation is of fundamental importance to the progression of science and technology as the scientific method is built upon empirical evidence, the acquisition of which is entirely reliant on measurement. Quantum mechanical properties can be exploited to yield measurement results to a greater precision (lesser uncertainty) than that which is permitted by classical methods. This has been mathematically demonstrated by the derivation of theoretical bounds which place a fundamental limit on the uncertainty of a measurement. Furthermore, quantum metrology is of immediate interest in the application of quantum technologies since measurement plays a central role. This thesis focuses on the role of quantum correlations and uncertainty relations which govern the precision bounds. We show how correlations can be distributed amongst limited resources in realistic scenarios, as permitted by current experimental capabilities, to achieve higher precision measurements than current approaches. This is extended to the setting of multiparameter estimation in which we demonstrate a more technologically feasible method of correlation distribution than those previously posited which perform as well as, or worse than, our scheme. Furthermore, a quantum metrology protocol is typically comprised of three stages: probe state preparation, sensing and then readout, where the time required for the first and last stages is usually neglected. We consider the more realistic sensing scenario of time being a limited resource which is divided amongst the three stages and demonstrate the most efficient use of this resource. Additionally, we take an information theoretic approach to quantum mechanical uncertainty relations and derive a one-parameter class of uncertainty relations which supplies more information about the quantum mechanical system of interest than conventional uncertainty relations. Finally, we demonstrate how we can use this class of uncertainty relations to reconstruct information of the state of the quantum mechanical system.

Dans un contexte de vieillissement de la population et d’accroissement des maladies chroniques liées à l’âge, l’étude de la glycation non-enzymatique des protéines constitue un axe de recherche d’actualité. En effet, les produits de glycation avancée (AGE) jouent un rôle important dans la complication des maladies liées à l’âge comme le diabète. La compréhension des mécanismes de glycation est complexe du fait de la variété importante d’AGE formés. L’objectif de cette thèse est d’étudier in vitro la glycation des protéines, le collagène de type I en particulier, au moyen de cette technique de microscopie photonique. Deux AGE, la carboxyméthyllysine et la pentosidine, ont été ciblés. L’exploitation des spectres Raman a nécessité des adaptations chimiométriques originales. En effet, une approche couplant l’analyse en composantes principales aux indices de validité a été développée pour déterminer le type de normalisation à appliquer aux données spectrales. De plus, la régression Lasso a été utilisée pour identifier des marqueurs Raman associés au processus de glycation. Ces investigations ont été menées en réalisant des réactions de glycation sous diverses conditions expérimentales et en considérant les dosages en AGE par chromatographie liquide couplée à la spectrométrie de masse en tandem comme références. Ces travaux permettent de positionner l’apport et les limitations analytiques de la microspectroscopie Raman dans l’étude moléculaire de la glycation non-enzymatique des protéines
In the context of an aging population and an increase in age-related chronic diseases, the study of protein non-enzymatic glycation constitutes a topical research axis. Indeed, the advanced glycation products (AGE) play an important role in the complication of age-related diseases such as diabetes. Understanding the mechanisms of glycation is complex due to the large variety of AGE formed. The objective of this work is to study protein glycation in vitro, especially type I collagen, using this biophotonic technique. Two AGE, carboxymethyllysine and pentosidine, were targeted. The exploitation of Raman spectra required original chemometric adaptation. Indeed, an approach coupling principal component analysis to validity indices has been developed to determine the type of normalization to apply to spectral data. Additionally, Lasso regression was used to identify Raman markers associated with glycation process. These investigations were carried out by performing chemical reactions to induce glycation under various experimental conditions and by considering the AGE assays by liquid chromatography coupled to tandem mass spectrometry as references. This work makes it possible to position the contribution and the analytical limitations of Raman microspectroscopy in the molecular study of the non-enzymatic glycation of proteins

Quatre huiles (boscan, cerro negro, nordhorn et pematang) sont pyrolysees en milieu ferme. Les produits de reaction sont analyses et leur formation est correlee a la composition chimique des huiles de depart. Des experiences de pyrolyse sont realisees avec les memes huiles en presence de matrices minerales telles que le quartz, la kaolinite et l'ellite. Les resultats montrent que les mineraux argileux favorisent es reactions de cokefaction. Un essai de deplacement du front de combustion est realise avec l'huile de cerro negro afin de determiner des methodologies d'etude des transformations thermiques de l'huile au cours de la combustion in situ

This thesis describes the development of a tip-enhanced fluorescence microscope, based upon combining confocal fluorescence methods with a commercially-available atomic force microscope (AFM). A microscope which is capable of simultaneous fluorescence and atomic force measurements has been realised. This has been achieved by mounting an AFM onto an inverted optical microscope, allowing the sample to be fluorescently excited from underneath. The incident position of the excitation spot at the sample can be controlled by a 2D galvanometer present in the excitation beam path. A program has been developed which aligns the laser spot with the AFM-tip by correlating sample features, and then applying a corresponding voltage to the galvanometer, in order to translate the beam towards the AFM-tip. A result of this process is that the fields-of-view of the fluorescence and atomic force images are also aligned, enabling simultaneous correlative microscopy. The benefits of performing these techniques simultaneously include eliminating the need to image over large areas with both techniques to ensure overlapping fields-of-view (as would be required if these measurements were being performed consecutively). It also unlocks the potential to track the mechanical changes of a known structure over time. Moreover, elements of the alignment program may be useful for general applications in correlative microscopy, providing an automated tool for overlaying images which have been obtained using different techniques. Alongside simultaneous imaging, this alignment method is also a potential technique for introducing a tip-enhancement effect into this particular instrument. A method has been developed which acquires data from a single photon counting module (SPCM) and the AFM using a LabVIEW field programmable gate array (FPGA), and subsequently correlates the number of detected photons from the sample with the position of the AFM-tip at that time. Although fluorescence enhancement was not detected using this instrument, the method was sufficient enough to detect scatter as the AFM-tip made contact with the sample; this is evidence that the method can successfully measure the number of photons detected with respect to tip-sample separation and should be able to also detect an increase in photons due to enhancement, if the effect can be optimised.

Previously studies used correlation of DNase I hypersensitivity sites sequencing (DNase-seq) experiments to predict interactions between enhancers and its target promoter gene. We investigate the correlation methods Pearson’s correlation and Mutual Information, using DNase-seq data for 100 cell-types in regions on chromosome one. To assess the performances, we compared our results of correlation scores to Hi-C data from Jin et al. 2013. We showed that the performances are low when comparing it to the Hi-C data, and there is a need of improved correlation metrics. We also demonstrate that the use of Hi-C data as a gold standard is limited, because of its low resolution, and we suggest using another gold standard in further studies.

Quatre huiles (boscan, cerro negro, nordhorn et pematang) sont pyrolyses en milieu fermé. Les produits de réaction sont analysés et leur formation est corrélée à la composition chimique des huiles de départ. Des expériences de pyrolyse sont réalisées avec les mêmes huiles en présence de matrices minérales telles que le quartz, la kaolinite et l'ellite. Les résultats montrent que les minéraux argileux favorisent les réactions de cokéfaction. Un essai de déplacement du front de combustion est réalisé avec l'huile de Cerro negro afin de déterminer des méthodologies d'étude des transformations thermiques de l'huile au cours de la combustion in situ.

Thesis (M.S.)--State University of New York at Buffalo, 2006.
Title from PDF title page (viewed on Mar. 16, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Fam, Adly T. , Kondi, Lisimachos P.

碩士
國立臺灣大學
物理研究所
98
Second order correlation of photons provides more properties and information of light. Recent years, people pay much attention to research about second order correlation of light, giving rise to applications of quantum and classical “ghost image” which retrieves more information by way of comparing photons experiencing different process. In this thesis, we extend the concept of “ghost image” and then bring up whole new idea through mixing random light and modulated light from the identical chaotic source, and furthermore revealing images bearing messages by statistical mechanism of second order correlation via computer simulation and optical experiment.

碩士
東海大學
環境科學與工程學系
98
Application of photocatalysis in the air pollution reduction of indoor has been focus of study during last years. In this study of point was the correlation between film structures and their photocatalytic activity. To preparation of ZnO photocatalyst by plasma enhanced- chemical vapor deposition (PE-CVD) and template synthesis method. The diethyl zinc (DEZn) has been the precursor of ZnO photocatalyst, and substrate was anodic alumina oxide (AAO). To synthesize ZnO film with different structures on AAO membrane, and using the different parameters of deposit membranes to do the photocatalytic activity test and film structure analysis. Analysis of photocatalysis for chemical and physical property, and using Isopropyl alcohol for pollution on UV light irradiation to do the photocatalytic activity test. By photocatalytic activity to obtain the pollution of dissolution efficiency. Efficiency of photocatalytic activity test, the structure of the ZnO photocatalysts are more important than the quantity in their photocatalytic activity.

Piezoelectric materials find use as actuators and sensors in automotive, aerospace and other related industries. Automotive applications such as fuel injection nozzles and engine health monitoring systems require operating temperatures as high as 300-500 oC. The commercially used piezoelectric material PbZr1-xTixO3 (PZT) is limited to operating temperatures as low as 200 oC due to the temperature induced depolarization effects. PZT, in the undoped state exhibits a piezoelectric coefficient (d33) of 223 pC/N and ferroelectric-paraelectric transition temperature (Tc) of 386 oC. The enhanced properties of PZT occur at a region between the tetragonal and rhombohedral phases, called the Morphotropic Phase Boundary (MPB). Therefore, search for new materials with higher thermal stability and better sensing capabilities were focused on systems that exhibit a PZT-like MPB. This led to the discovery of (x)BiScO3-(1-x)PbTiO3 (BSPT), which exhibits an MPB with enhanced Tc (450 oC) and exceptionally high piezoelectric response (d33 = 460 pC/N). Theoretical studies have shown that the mechanism of enhanced piezoresponse in ferroelectric systems is related to the anisotropic flattening of the free energy profiles. An alternative view point attributes the anomalous piezoelectric response to the presence of high density of low energy domain walls near an inter-ferroelectric transition. Diffraction is a versatile tool to study the structural and microstructural changes of ferroelectric systems upon application of electric field. However, characterization of electric field induced structural and microstructural changes is not a trivial task, since in situ electric field dependent diffraction studies almost invariably give diffraction patterns laden with strong preferred orientation effects, due to the tendency of the ferroelectric/ferroelastic domains to align along the field direction. Additionally, diffraction profiles of MPB compositions exhibit severe overlap of Bragg peaks of the coexisting phases, and hence, it is difficult to ascertain with certainty, if the alteration in the intensity profiles upon application of electric field is due to change in phase fraction of the coexisting phases or due to preferred orientation induced in the different phases by the electric field. The characterization of electric field induced phase transformation in MPB systems, has therefore eluded researchers and has been considered of secondary importance, presumably due to the difficulties in unambiguously establishing the structural changes upon application of electric field. In fact, majority of the in situ electric field dependent diffraction studies have been carried out on compositions just outside the MPB range, i.e. on single phase compositions. In such studies, the focus has been mainly on explaining the piezoelectric response in terms of motions of the non-180° domain walls and field induced lattice strains. In this dissertation, the BSPT system has been systematically investigated with the view to understand the role of different contributing factors to the anomalous piezoelectric response of compositions close to the MPB. Using a comparative in situ electric field dependent diffraction study on a core MPB composition exhibiting highest piezoelectric response and a single phase monoclinic (pseudo-rhombohedral) composition just outside the MPB, it is demonstrated that, inspite of the significantly large domain switching and lattice strain (obtained from peak shifts) in the single phase composition, as compared to the MPB composition, the single phase composition shows considerably low piezoelectric response. This result clearly revealed that the anomalous piezoelectric response of the MPB composition is primarily associated with field induced inter-ferroelectric transformation and the corresponding field induced interphase boundary motion. A simple strategy has been employed to establish the field induced structural transformation for the MPB compositions, by overcoming the experimental limitation of in situ electric field dependent diffraction studies. The idea stemmed from the fact that, if the specimens for diffraction study can be used in powder form instead of pellet, the problems associated with preferred orientation effects can be eliminated, and the nature of field induced structural changes can be accurately determined. A comparative study of the diffraction profiles from poled (after subjecting the specimen to electric field) and unpoled (before subjecting the specimen to electric field) powders could precisely establish the nature of electric field induced phase transformation for the MPB compositions of BSPT and provided a direct correlation between the electric field induced structural changes and the enhanced piezoelectric response. A new ‘powder poling’ technique was devised, which involves application of electric field to powder form of the specimen. Using this technique, it was possible to study separately, the effect of stress and electric field on the nature of structural transformation. A unique outcome of this study was, it could demonstrate for the first time, analogous nature of the stress and electric field induced structural transformation. A comparative study of the dielectric response of poled and unpoled samples was used to show a counterintuitive phenomenon of field induced decrease in polarization coherence for the MPB compositions. This approach was used to suggest that the criticality associated with the MPB extends beyond the composition boundary conventionally reported in literature based on bulk diffraction techniques (x-ray and neutron powder diffraction). The layout of the dissertation is as follows: Chapter 1 gives a brief introduction of the fundamental concepts related to ferroelectric materials. The theories that explain the enhanced piezoresponse of MPB based ferroelectric systems have been outlined. Detailed information of the existing literature is presented in the relevant chapters. Chapter 2 presents the details of the solid state synthesis of BSPT compositions and structural analysis using diffraction studies. The dielectric measurements were used to establish the Tc for the different compositions. The enhanced ferroelectric and piezoelectric properties were observed for the MPB compositions, which were shown to exhibit coexistence of tetragonal and monoclinic phases from structural studies. The critical MPB composition exhibiting highest piezoelectric and ferroelectric properties was established to be x = 0.3725. The thermal stability of the critical MPB composition was established to be 400 oC using ex situ thermal depolarization studies. The common approach of structural analysis in the unpoled state failed to provide a unique relationship between the anomalous piezoelectric response and the structural factors at the MPB, emphasizing the need to characterize these system using electric field dependent structural studies. Chapter 3 presents the results of in situ electric field dependent diffraction measurements carried out at Argonne National Laboratory, USA. The quasi-static field measurements could successfully quantify the non-180o domain switching fractions and the field induced lattice strains. The changes in the integrated intensities were used to obtain the non-180o domain switching fraction and the shift in peak positions were used to quantify the field induced lattice strains. The in situ studies could successfully explain the macroscopic strain response for the single phase pseudo-rhombohedral (monoclinic) composition on the basis of domain switching mechanisms and field induced lattice strains. The MPB compositions were shown to have additional contributions from interphase boundary motion, resulting from change in phase fraction of the coexisting phases. The results emphasized the need to investigate the electric field induced transformation for MPB compositions, in order to give a comprehensive picture of the various contributions to the macroscopic piezoreponse. While Rietveld analysis could be used to investigate the phase transformation behaviour upon application of electric field, textured diffraction profiles obtained using in situ studies, in addition to the severely overlapping Bragg reflections of the coexisting phases for the MPB compositions hindered reliable estimation of the structural parameters. An alternate approach to investigate the field induced phase transformation is presented in Chapter 4. The stroboscopic measurements on the MPB composition showed evidence of non-180o domain wall motion even at sub-coercive field amplitudes as low as 0.1 kV/mm. Chapter 4 presents the results of the ex situ electric field dependent structural study, wherein the diffraction profiles collected from poled powders is compared to that of unpoled powders. The diffraction profiles from the poled powders did not exhibit any field induced crystallographic texture and could successfully be analyzed using Rietveld analysis. High resolution synchrotron diffraction studies (ESRF, France) carried out on closely spaced compositions revealed that, the composition exhibiting the highest piezoelectric response is the one, which exhibits significantly enhanced lattice polarizability of both the coexisting (monoclinic and tetragonal) phases. The enhanced lattice polarizability manifests as significant fraction of the monoclinic phase transforming irreversibly to the tetragonal phase after electric poling. The monoclinic to tetragonal transformation suggested the existence of a low energy polarization rotation pathway towards the [001]pc direction in the (1 1 0)pc pseudocubic plane of the monoclinic phase. The results are discussed on the basis of the existing theories that explain piezoresponse in MPB systems and are in support of the Polarization rotation model, in favor of a genuine monoclinic phase. Chapter 5 discusses the ferroelectric-ferroelectric stability of the MPB compositions in response to externally applied stress and electric field independently. Using the newly developed ‘powder poling’ technique, which is based on the concept of exploiting the irreversible structural changes that occur after application of electric field and stress independently, it was possible to ascertain that, both moderate stress and electric field induce identical structural transformation - a fraction of the monoclinic phase transforms irreversibly to the tetragonal phase. The powder poling technique was also used to demonstrate field induced inter-ferroelectric transformation at sub-coercive field amplitudes. In addition, the analysis of the dielectric response before and after poling revealed a counterintuitive phenomenon of poling induced decrease in the spatial coherence of polarization for compositions around the MPB and not so for compositions far away from the MPB range. Exploiting the greater sensitivity of this technique, it was demonstrated that, the criticality associated with the inter-ferroelectric transition spans a wider composition range than what is conventionally reported in the literature based on bulk x-ray/neutron powder diffraction techniques. Chapter 6 presents the closure and important conclusions from the present work and summarizes the key results, highlighting the proposed mechanism of enhanced piezoresponse in BSPT. The last part of the chapter deals with suggestions for future work from the ideas evolved in the present study. vi

Piezoelectric materials find use as actuators and sensors in automotive, aerospace and other related industries. Automotive applications such as fuel injection nozzles and engine health monitoring systems require operating temperatures as high as 300-500 oC. The commercially used piezoelectric material PbZr1-xTixO3 (PZT) is limited to operating temperatures as low as 200 oC due to the temperature induced depolarization effects. PZT, in the undoped state exhibits a piezoelectric coefficient (d33) of 223 pC/N and ferroelectric-paraelectric transition temperature (Tc) of 386 oC. The enhanced properties of PZT occur at a region between the tetragonal and rhombohedral phases, called the Morphotropic Phase Boundary (MPB). Therefore, search for new materials with higher thermal stability and better sensing capabilities were focused on systems that exhibit a PZT-like MPB. This led to the discovery of (x)BiScO3-(1-x)PbTiO3 (BSPT), which exhibits an MPB with enhanced Tc (450 oC) and exceptionally high piezoelectric response (d33 = 460 pC/N). Theoretical studies have shown that the mechanism of enhanced piezoresponse in ferroelectric systems is related to the anisotropic flattening of the free energy profiles. An alternative view point attributes the anomalous piezoelectric response to the presence of high density of low energy domain walls near an inter-ferroelectric transition. Diffraction is a versatile tool to study the structural and microstructural changes of ferroelectric systems upon application of electric field. However, characterization of electric field induced structural and microstructural changes is not a trivial task, since in situ electric field dependent diffraction studies almost invariably give diffraction patterns laden with strong preferred orientation effects, due to the tendency of the ferroelectric/ferroelastic domains to align along the field direction. Additionally, diffraction profiles of MPB compositions exhibit severe overlap of Bragg peaks of the coexisting phases, and hence, it is difficult to ascertain with certainty, if the alteration in the intensity profiles upon application of electric field is due to change in phase fraction of the coexisting phases or due to preferred orientation induced in the different phases by the electric field. The characterization of electric field induced phase transformation in MPB systems, has therefore eluded researchers and has been considered of secondary importance, presumably due to the difficulties in unambiguously establishing the structural changes upon application of electric field. In fact, majority of the in situ electric field dependent diffraction studies have been carried out on compositions just outside the MPB range, i.e. on single phase compositions. In such studies, the focus has been mainly on explaining the piezoelectric response in terms of motions of the non-180° domain walls and field induced lattice strains. In this dissertation, the BSPT system has been systematically investigated with the view to understand the role of different contributing factors to the anomalous piezoelectric response of compositions close to the MPB. Using a comparative in situ electric field dependent diffraction study on a core MPB composition exhibiting highest piezoelectric response and a single phase monoclinic (pseudo-rhombohedral) composition just outside the MPB, it is demonstrated that, inspite of the significantly large domain switching and lattice strain (obtained from peak shifts) in the single phase composition, as compared to the MPB composition, the single phase composition shows considerably low piezoelectric response. This result clearly revealed that the anomalous piezoelectric response of the MPB composition is primarily associated with field induced inter-ferroelectric transformation and the corresponding field induced interphase boundary motion. A simple strategy has been employed to establish the field induced structural transformation for the MPB compositions, by overcoming the experimental limitation of in situ electric field dependent diffraction studies. The idea stemmed from the fact that, if the specimens for diffraction study can be used in powder form instead of pellet, the problems associated with preferred orientation effects can be eliminated, and the nature of field induced structural changes can be accurately determined. A comparative study of the diffraction profiles from poled (after subjecting the specimen to electric field) and unpoled (before subjecting the specimen to electric field) powders could precisely establish the nature of electric field induced phase transformation for the MPB compositions of BSPT and provided a direct correlation between the electric field induced structural changes and the enhanced piezoelectric response. A new ‘powder poling’ technique was devised, which involves application of electric field to powder form of the specimen. Using this technique, it was possible to study separately, the effect of stress and electric field on the nature of structural transformation. A unique outcome of this study was, it could demonstrate for the first time, analogous nature of the stress and electric field induced structural transformation. A comparative study of the dielectric response of poled and unpoled samples was used to show a counterintuitive phenomenon of field induced decrease in polarization coherence for the MPB compositions. This approach was used to suggest that the criticality associated with the MPB extends beyond the composition boundary conventionally reported in literature based on bulk diffraction techniques (x-ray and neutron powder diffraction). The layout of the dissertation is as follows: Chapter 1 gives a brief introduction of the fundamental concepts related to ferroelectric materials. The theories that explain the enhanced piezoresponse of MPB based ferroelectric systems have been outlined. Detailed information of the existing literature is presented in the relevant chapters. Chapter 2 presents the details of the solid state synthesis of BSPT compositions and structural analysis using diffraction studies. The dielectric measurements were used to establish the Tc for the different compositions. The enhanced ferroelectric and piezoelectric properties were observed for the MPB compositions, which were shown to exhibit coexistence of tetragonal and monoclinic phases from structural studies. The critical MPB composition exhibiting highest piezoelectric and ferroelectric properties was established to be x = 0.3725. The thermal stability of the critical MPB composition was established to be 400 oC using ex situ thermal depolarization studies. The common approach of structural analysis in the unpoled state failed to provide a unique relationship between the anomalous piezoelectric response and the structural factors at the MPB, emphasizing the need to characterize these system using electric field dependent structural studies. Chapter 3 presents the results of in situ electric field dependent diffraction measurements carried out at Argonne National Laboratory, USA. The quasi-static field measurements could successfully quantify the non-180o domain switching fractions and the field induced lattice strains. The changes in the integrated intensities were used to obtain the non-180o domain switching fraction and the shift in peak positions were used to quantify the field induced lattice strains. The in situ studies could successfully explain the macroscopic strain response for the single phase pseudo-rhombohedral (monoclinic) composition on the basis of domain switching mechanisms and field induced lattice strains. The MPB compositions were shown to have additional contributions from interphase boundary motion, resulting from change in phase fraction of the coexisting phases. The results emphasized the need to investigate the electric field induced transformation for MPB compositions, in order to give a comprehensive picture of the various contributions to the macroscopic piezoreponse. While Rietveld analysis could be used to investigate the phase transformation behaviour upon application of electric field, textured diffraction profiles obtained using in situ studies, in addition to the severely overlapping Bragg reflections of the coexisting phases for the MPB compositions hindered reliable estimation of the structural parameters. An alternate approach to investigate the field induced phase transformation is presented in Chapter 4. The stroboscopic measurements on the MPB composition showed evidence of non-180o domain wall motion even at sub-coercive field amplitudes as low as 0.1 kV/mm. Chapter 4 presents the results of the ex situ electric field dependent structural study, wherein the diffraction profiles collected from poled powders is compared to that of unpoled powders. The diffraction profiles from the poled powders did not exhibit any field induced crystallographic texture and could successfully be analyzed using Rietveld analysis. High resolution synchrotron diffraction studies (ESRF, France) carried out on closely spaced compositions revealed that, the composition exhibiting the highest piezoelectric response is the one, which exhibits significantly enhanced lattice polarizability of both the coexisting (monoclinic and tetragonal) phases. The enhanced lattice polarizability manifests as significant fraction of the monoclinic phase transforming irreversibly to the tetragonal phase after electric poling. The monoclinic to tetragonal transformation suggested the existence of a low energy polarization rotation pathway towards the [001]pc direction in the (1 1 0)pc pseudocubic plane of the monoclinic phase. The results are discussed on the basis of the existing theories that explain piezoresponse in MPB systems and are in support of the Polarization rotation model, in favor of a genuine monoclinic phase. Chapter 5 discusses the ferroelectric-ferroelectric stability of the MPB compositions in response to externally applied stress and electric field independently. Using the newly developed ‘powder poling’ technique, which is based on the concept of exploiting the irreversible structural changes that occur after application of electric field and stress independently, it was possible to ascertain that, both moderate stress and electric field induce identical structural transformation - a fraction of the monoclinic phase transforms irreversibly to the tetragonal phase. The powder poling technique was also used to demonstrate field induced inter-ferroelectric transformation at sub-coercive field amplitudes. In addition, the analysis of the dielectric response before and after poling revealed a counterintuitive phenomenon of poling induced decrease in the spatial coherence of polarization for compositions around the MPB and not so for compositions far away from the MPB range. Exploiting the greater sensitivity of this technique, it was demonstrated that, the criticality associated with the inter-ferroelectric transition spans a wider composition range than what is conventionally reported in the literature based on bulk x-ray/neutron powder diffraction techniques. Chapter 6 presents the closure and important conclusions from the present work and summarizes the key results, highlighting the proposed mechanism of enhanced piezoresponse in BSPT. The last part of the chapter deals with suggestions for future work from the ideas evolved in the present study. vi

Idiopathic pulmonary fibrosis (IPF) is an irreversible disease of unknown etiology that involves progressive scarring of the lung tissue, leading to respiratory failure and death.1 IPF is thought to develop from repetitive lung injury and aberrant wound healing that leads to the generation of fibrous tissue rather than restoration of normal tissue.2 It has been suggested in mice that vascular leak after lung injury contributes to the development of lung fibrosis.2,3 Gadofosveset is an intravascular enhancing, gadolinium-based contrast agent used with magnetic resonance imaging (MRI) to assess a variety of biological processes in vivo because it can reversibly bind to albumin.13-14 Gadofosveset has been used to assess endothelial permeability and function, as it diffuses through the vessel walls via leaky neovessels and damaged endothelium.15 Our research group has developed a new method to assess disease activity in IPF patients using gadofosveset-enhanced lung MRI. In unpublished work, we have demonstrated that this technique can be used to generate an albumin extravasation index (AEI), and we have found that this is significantly and diffusely increased in the lung of patients with idiopathic pulmonary fibrosis compared to healthy controls.16 The AEI is a measure of the change in signal intensity post-contrast minus pre-contrast in predefined regions of interest (ROIs) in the lung parenchyma divided by post- minus pre-contrast signal intensity in the ROI in the aorta. In this study, we compared the AEI in patients with IPF to healthy control (HC) subjects and evaluated the correlation between the AEI and high-resolution computed tomography (HRCT) and pulmonary function testing (PFT). We found that IPF subjects had increased AEI values compared with HC subjects. While not statistically significant, AEI was more strongly correlated with fibrosis (interstitial abnormalities) than ground-glass (alveolar abnormalities) on HRCT. Furthermore, there was a possible correlation between AEI and change in percent predicted forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), and diffusion capacity of carbon monoxide adjusted for hemoglobin (DLCO) [Hb]. Our results demonstrate that AEI calculations from gadofosveset-enhanced lung MRI are a surrogate measure of vascular leak and can potentially serve as an alternative method for predicting the clinical course and severity of IPF through its correlation with fibrosis on HRCT and pulmonary function.

Detection of explosives has always been a challenging issue all over the world. Different analytical techniques and instrumentation methods have been explored to obtain a 100% fail proof detector. Some technologies have matured and have been deployed in the field already. However, active research is still being pursued to make the ultimate explosive detection device. The present thesis broadly addresses the development of Raman spectroscopy based techniques for the detection of explosives. Although Raman spectroscopy has technologically developed and has become a regular tool for chemical identification, its use in the field of detection of explosives has been limited. Two aspects of detection were addressed in this thesis. The first part consists of the detection of minute quantities or traces of explosives using a Raman based method. In order to approach this problem, surface enhanced Raman spectroscopy (SERS), an offshoot of Raman spectroscopy was explored. Chapters 2-4 deal with developing efficient SERS substrates. In this endeavour, the first and the most obvious choice as SERS substrates were silver (Ag) nanoparticles (NPs). However, we were exploring methods that could be simple one-pot synthesis methods, cost-effective and without employing strong reducing agents (green). Therefore, Ag NPs were synthesized using biosynthetic route. These nanoparticles were used to study their SERS efficiency. Sub-nano molar concentration of dye as well explosive like trinitrotoluene (TNT) and hexanitrohexaazaisowurtzitane (CL-20) could be obtained for both the clove reduced as well as pepper Ag nanoparticles. Hence Ag NPs are very efficient SERS substrates. In the second part of the work on SERS, bimetallic nanoparticles with core-shell (Agcore-Aushell) architecture were synthesized, characterized and tested for SERS activity. After successful synthesis and characterization of the bimetallic nanoparticles, these were tested for their SERS activities using a dye molecule and an explosive molecule. SERS spectra could be obtained for the bimetallic nanoparticles. It was observed that the sensitivity of these NPs were almost at par with the mono-metallic Ag NPs. In order to bring SERS from laboratory to field, a more practical approach was to prepare solid SERS substrates or SERS substrates on solid platform. In the next chapter, we ventured into the most abundant material which forms the backbone of the organic world, carbon. Various carbonaceous materials ranging from chemically synthesized graphene, graphene oxide, multi-walled carbon nanotube (MWCNT), graphite and activated charcoal were explored as potential substrates for surface enhanced Raman spectroscopic applications. The analytes chosen for this particular study were some fluorescent molecules such as rhodamine B (RB), rhodamine 6G (R6G), crystal violet (CV), Nile blue A (NBA) and a non-fluorescent molecule acetaminophen, commonly known as paracetamol. Enhanced Raman signals were observed for the fluorescent molecules, especially for the molecules whose absorbance maxima are near the excitation wavelength of the laser (514.5 nm). The most interesting outcome of this work was obtaining enhanced Raman signals of nanomolar concentration of R6G on activated charcoal. However, for the non-fluorescent molecule, paracetamol, Raman spectra could not be observed beyond -5 10M concentration for all the carbon substrates including chemically synthesized graphene and MWCNT. This study was crucial in our quest for an ideal SERS substrate. Our observations let us to conclude that chemically synthesized graphene was not the only candidate for the preparation of SERS substrates. Since carbon materials efficiently adsorb and also provide a separate channel for energy decay (fluorescence quenching), even activated charcoal could be employed as a SERS platform. However, carbon alone could not provide an effective solution for the preparation of SERS substrates. Therefore, combining the plasmonic effect of the metal nanoparticles with the efficient adsorption and fluorescence quenching of carbon materials would be ideal. In the next part of the carbon studies, graphene-Ag composites which were either prepared by in situ reduction process or physically mixed were studied for SERS activity. An ideal SERS substrate should possess the following properties: (i) Support plasmon, thereby provide SERS enhancement (ii) Easy to fabricate or synthesize (large scale/bulk) (iii) Ensure high reproducibility and sensitivity (iv) Low false alarm from matrix chemicals (v) Cost effective (vi) Solid substrate (in the form of chip, pellet, slide etc.) Hence, as a final study, carbon silver based composites were explored. R6G was chosen as an analyte again and SERS experiments were conducted. Raman signals at low concentration could be obtained for the carbon-Ag composites as well. In addition, feasibility experiments were also conducted for an explosive molecule, FOX-7. From these preliminary experiments we observed that carbon-metal NP composites can be efficient, cost-effective SERS substrates that will overcome the current issue. The previous chapters dealt with the trace detection of explosives. The next part of the thesis deals with the development of the Raman spectroscopic methods for non-invasive detection of concealed objects. Chapters 4 and 5 primarily focus on explosives detection. Spatially offset Raman spectroscopy (SORS) instrumentation was developed in the laboratory for non-invasive detection solid and liquid explosives. Several experiments were carried out to detect concealed materials inside high density polyethylene (HDPE) containers, coloured glass bottles, envelopes etc. with this technique, Raman signals of materials could be retrieved even within 4 mm thick outer-layer. SORS imaging experiments were also performed on bilayered compounds, tablets etc. However, while performing the SORS experiments, it was observed that due to the restriction in geometry imposed by the method, the signals from the inner-layers could be obtained only up to a certain depth. This posed a serious limitation of SORS for practical scenarios, where the thickness of the outer layer may be tens of mm. In such situation, SORS may not be an effective method. We then performed Raman experiments using a transmission geometry using a series of samples. The transmission Raman (TR) experiments yielded better SNR for the inner (concealed) material as compared to the outer material. Although transmission Raman experiments yielded better signal but these experiments were again geometry dependent, hence, less flexible and TR experiments did not provide information about the position of the underlying materials. In order to obtain complete information, it was necessary to understand photon migration in a multiple scattering medium. It is known that a photon in a multiple scattering medium may be approximated to undergo a random-walk. Statistically, the photon that undergoes multiple scattering in a medium loses its sense of origin (direction), hence, there is a finite probability to observe the exiting photon in any direction. Rayleigh and NIR based imaging modalities have been conducted using this model. Diffuse optical tomographic (DOT) measurements also deal with measuring the photons that have exited the sample after undergoing multiple scattering in a turbid medium. If it was possible to collect the Rayleigh photons or the diffuse photons in DOT experiments, in principle, Raman photons could also be collected from several directions. It was then proposed that if Rayleigh scattered photons can exit at 4π solid angle from a sample, then it can be assumed that some Rayleigh photons may convert to Raman photons, which in turn, shall have a finite probability to exit the sample from all the sides (4π solid angles). This idea of collecting Raman photons has never been discussed before! Thus, as expected based on the above principles, we were able to record Raman scattered photons at all angles and on all sides. This new technique has been termed as ‘Universal Multiple Angle Raman Spectroscopy (UMARS)’. Monte Carlo simulation studies were also performed to understand the distribution of photons in a multiple scattering medium. Simulation studies also revealed that Raman photons exited from all sides of the medium at varying percentages. Hence, several fiber optic probes were designed for illumination and collection to perform the UMARS experiments for samples concealed at depths beyond 20 mm. UMARS was not only applied successfully for the detection of concealed explosives, but also for biologically relevant samples as well. In fact a pharmaceutical tablet as thick as 7 mm was also tested with UMARS and signals could be successfully obtained. Since the UMARS signals were obtained from all possible angles, imaging experiments were also conducted to obtain sample specific information. Frequency-specific images of bilayer materials could be obtained. In the case where one material was concealed within another, the reconstruction of the frequency-specific intensities in a contour plot revealed the position of the concealed layer. One of the most challenging and exciting studies that was conducted was to use UMARS to obtain shapes of hidden materials. Several shapes such as dumbbell, ellipsoid etc were fabricated (made of glass) and were filled with a test chemical, trans-stilbene (TS). This shape was placed inside an outer material like ammonium nitrate (AN) that was taken in a glass beaker. The diameter of the beaker was varied from 25 mm to 60 mm. A series of UMARS measurement was carried out with 10 collection fiber optic probes. The spatial resolution (vertical) was varied from 200 μm to 1 mm. Series of UMARS images were obtained which were then processed and the intensity of the individual fibers were averaged (CCD row pixels) based on the image of the individual fiber on the CCD. The frequency specific intensity of the materials was utilized to reconstruct 2D or a 3D shape. The shapes of the objects could be clearly discerned using UMARS imaging. This marks a major step for the development of UMARS as a 3D imaging modality. UMARS experiments conducted so far have affirmed our belief that this technology can be used as an effective technique for screening solid and liquid samples at airports, railway stations and other entry points. 3D imaging for biomedical diagnostics will provide molecular information in addition to the location and shape of an object inside a tissue such as calcified masses and bones. In the final part of the thesis, 2D Raman correlation spectroscopic method was applied to understand the dynamics of a system that was subjected to external perturbation. In the field of explosive processing and formulations, large batches are generally prepared. However, it is very difficult to ascertain the molecular or structural changes that occur during the processing of these formulations in situ. Analytical methods to monitor the changes online are limited. Raman spectroscopy can be an effective technique for such measurements. This process however, generates a large number of spectra. In such cases, it becomes cumbersome to handle such large number of data and obtain meaningful information. 2D correlation spectroscopy can be applied under such situations. 2D correlation analysis generates essentially two maps, synchronous and asynchronous. In this study, 2D Raman correlation spectroscopy was applied to ammonium nitrate that was subjected to temperature variations. 2D maps were constructed to obtain information about the structural changes associated with temperature. The synchronous map reveals the overall similarity of the intensity changes. Whereas, the 2D asynchronous maps provide the sequence of changes that occur. Based on the set of well defined rules proposed by Isao Noda, the synchronous and the asynchronous correlation maps were analysed. Hence, generalized 2D correlation spectroscopy can be extended to any kind of perturbation and will prove useful in understanding the structural dynamics. The objective of the thesis was to explore various facets of Raman spectroscopy that would be useful in the field of high energy materials specifically in the detection of explosives. Attempts were made for the development of trace detection of explosives using Raman based technique, SERS. In addition, bulk detection of concealed explosives was performed non-invasively using SORS and UMARS. In the field of high energy materials, these techniques will find immense applications. Raman spectroscopy, as we saw is a very important technique that can be used as a stand-alone method and can also be interfaced with other analytical or imaging modalities. This treatise is an example where the strength of this powerful spectroscopic method has been explored to some extent.

Detection of explosives has always been a challenging issue all over the world. Different analytical techniques and instrumentation methods have been explored to obtain a 100% fail proof detector. Some technologies have matured and have been deployed in the field already. However, active research is still being pursued to make the ultimate explosive detection device. The present thesis broadly addresses the development of Raman spectroscopy based techniques for the detection of explosives. Although Raman spectroscopy has technologically developed and has become a regular tool for chemical identification, its use in the field of detection of explosives has been limited. Two aspects of detection were addressed in this thesis. The first part consists of the detection of minute quantities or traces of explosives using a Raman based method. In order to approach this problem, surface enhanced Raman spectroscopy (SERS), an offshoot of Raman spectroscopy was explored. Chapters 2-4 deal with developing efficient SERS substrates. In this endeavour, the first and the most obvious choice as SERS substrates were silver (Ag) nanoparticles (NPs). However, we were exploring methods that could be simple one-pot synthesis methods, cost-effective and without employing strong reducing agents (green). Therefore, Ag NPs were synthesized using biosynthetic route. These nanoparticles were used to study their SERS efficiency. Sub-nano molar concentration of dye as well explosive like trinitrotoluene (TNT) and hexanitrohexaazaisowurtzitane (CL-20) could be obtained for both the clove reduced as well as pepper Ag nanoparticles. Hence Ag NPs are very efficient SERS substrates. In the second part of the work on SERS, bimetallic nanoparticles with core-shell (Agcore-Aushell) architecture were synthesized, characterized and tested for SERS activity. After successful synthesis and characterization of the bimetallic nanoparticles, these were tested for their SERS activities using a dye molecule and an explosive molecule. SERS spectra could be obtained for the bimetallic nanoparticles. It was observed that the sensitivity of these NPs were almost at par with the mono-metallic Ag NPs. In order to bring SERS from laboratory to field, a more practical approach was to prepare solid SERS substrates or SERS substrates on solid platform. In the next chapter, we ventured into the most abundant material which forms the backbone of the organic world, carbon. Various carbonaceous materials ranging from chemically synthesized graphene, graphene oxide, multi-walled carbon nanotube (MWCNT), graphite and activated charcoal were explored as potential substrates for surface enhanced Raman spectroscopic applications. The analytes chosen for this particular study were some fluorescent molecules such as rhodamine B (RB), rhodamine 6G (R6G), crystal violet (CV), Nile blue A (NBA) and a non-fluorescent molecule acetaminophen, commonly known as paracetamol. Enhanced Raman signals were observed for the fluorescent molecules, especially for the molecules whose absorbance maxima are near the excitation wavelength of the laser (514.5 nm). The most interesting outcome of this work was obtaining enhanced Raman signals of nanomolar concentration of R6G on activated charcoal. However, for the non-fluorescent molecule, paracetamol, Raman spectra could not be observed beyond -5 10M concentration for all the carbon substrates including chemically synthesized graphene and MWCNT. This study was crucial in our quest for an ideal SERS substrate. Our observations let us to conclude that chemically synthesized graphene was not the only candidate for the preparation of SERS substrates. Since carbon materials efficiently adsorb and also provide a separate channel for energy decay (fluorescence quenching), even activated charcoal could be employed as a SERS platform. However, carbon alone could not provide an effective solution for the preparation of SERS substrates. Therefore, combining the plasmonic effect of the metal nanoparticles with the efficient adsorption and fluorescence quenching of carbon materials would be ideal. In the next part of the carbon studies, graphene-Ag composites which were either prepared by in situ reduction process or physically mixed were studied for SERS activity. An ideal SERS substrate should possess the following properties: (i) Support plasmon, thereby provide SERS enhancement (ii) Easy to fabricate or synthesize (large scale/bulk) (iii) Ensure high reproducibility and sensitivity (iv) Low false alarm from matrix chemicals (v) Cost effective (vi) Solid substrate (in the form of chip, pellet, slide etc.) Hence, as a final study, carbon silver based composites were explored. R6G was chosen as an analyte again and SERS experiments were conducted. Raman signals at low concentration could be obtained for the carbon-Ag composites as well. In addition, feasibility experiments were also conducted for an explosive molecule, FOX-7. From these preliminary experiments we observed that carbon-metal NP composites can be efficient, cost-effective SERS substrates that will overcome the current issue. The previous chapters dealt with the trace detection of explosives. The next part of the thesis deals with the development of the Raman spectroscopic methods for non-invasive detection of concealed objects. Chapters 4 and 5 primarily focus on explosives detection. Spatially offset Raman spectroscopy (SORS) instrumentation was developed in the laboratory for non-invasive detection solid and liquid explosives. Several experiments were carried out to detect concealed materials inside high density polyethylene (HDPE) containers, coloured glass bottles, envelopes etc. with this technique, Raman signals of materials could be retrieved even within 4 mm thick outer-layer. SORS imaging experiments were also performed on bilayered compounds, tablets etc. However, while performing the SORS experiments, it was observed that due to the restriction in geometry imposed by the method, the signals from the inner-layers could be obtained only up to a certain depth. This posed a serious limitation of SORS for practical scenarios, where the thickness of the outer layer may be tens of mm. In such situation, SORS may not be an effective method. We then performed Raman experiments using a transmission geometry using a series of samples. The transmission Raman (TR) experiments yielded better SNR for the inner (concealed) material as compared to the outer material. Although transmission Raman experiments yielded better signal but these experiments were again geometry dependent, hence, less flexible and TR experiments did not provide information about the position of the underlying materials. In order to obtain complete information, it was necessary to understand photon migration in a multiple scattering medium. It is known that a photon in a multiple scattering medium may be approximated to undergo a random-walk. Statistically, the photon that undergoes multiple scattering in a medium loses its sense of origin (direction), hence, there is a finite probability to observe the exiting photon in any direction. Rayleigh and NIR based imaging modalities have been conducted using this model. Diffuse optical tomographic (DOT) measurements also deal with measuring the photons that have exited the sample after undergoing multiple scattering in a turbid medium. If it was possible to collect the Rayleigh photons or the diffuse photons in DOT experiments, in principle, Raman photons could also be collected from several directions. It was then proposed that if Rayleigh scattered photons can exit at 4π solid angle from a sample, then it can be assumed that some Rayleigh photons may convert to Raman photons, which in turn, shall have a finite probability to exit the sample from all the sides (4π solid angles). This idea of collecting Raman photons has never been discussed before! Thus, as expected based on the above principles, we were able to record Raman scattered photons at all angles and on all sides. This new technique has been termed as ‘Universal Multiple Angle Raman Spectroscopy (UMARS)’. Monte Carlo simulation studies were also performed to understand the distribution of photons in a multiple scattering medium. Simulation studies also revealed that Raman photons exited from all sides of the medium at varying percentages. Hence, several fiber optic probes were designed for illumination and collection to perform the UMARS experiments for samples concealed at depths beyond 20 mm. UMARS was not only applied successfully for the detection of concealed explosives, but also for biologically relevant samples as well. In fact a pharmaceutical tablet as thick as 7 mm was also tested with UMARS and signals could be successfully obtained. Since the UMARS signals were obtained from all possible angles, imaging experiments were also conducted to obtain sample specific information. Frequency-specific images of bilayer materials could be obtained. In the case where one material was concealed within another, the reconstruction of the frequency-specific intensities in a contour plot revealed the position of the concealed layer. One of the most challenging and exciting studies that was conducted was to use UMARS to obtain shapes of hidden materials. Several shapes such as dumbbell, ellipsoid etc were fabricated (made of glass) and were filled with a test chemical, trans-stilbene (TS). This shape was placed inside an outer material like ammonium nitrate (AN) that was taken in a glass beaker. The diameter of the beaker was varied from 25 mm to 60 mm. A series of UMARS measurement was carried out with 10 collection fiber optic probes. The spatial resolution (vertical) was varied from 200 μm to 1 mm. Series of UMARS images were obtained which were then processed and the intensity of the individual fibers were averaged (CCD row pixels) based on the image of the individual fiber on the CCD. The frequency specific intensity of the materials was utilized to reconstruct 2D or a 3D shape. The shapes of the objects could be clearly discerned using UMARS imaging. This marks a major step for the development of UMARS as a 3D imaging modality. UMARS experiments conducted so far have affirmed our belief that this technology can be used as an effective technique for screening solid and liquid samples at airports, railway stations and other entry points. 3D imaging for biomedical diagnostics will provide molecular information in addition to the location and shape of an object inside a tissue such as calcified masses and bones. In the final part of the thesis, 2D Raman correlation spectroscopic method was applied to understand the dynamics of a system that was subjected to external perturbation. In the field of explosive processing and formulations, large batches are generally prepared. However, it is very difficult to ascertain the molecular or structural changes that occur during the processing of these formulations in situ. Analytical methods to monitor the changes online are limited. Raman spectroscopy can be an effective technique for such measurements. This process however, generates a large number of spectra. In such cases, it becomes cumbersome to handle such large number of data and obtain meaningful information. 2D correlation spectroscopy can be applied under such situations. 2D correlation analysis generates essentially two maps, synchronous and asynchronous. In this study, 2D Raman correlation spectroscopy was applied to ammonium nitrate that was subjected to temperature variations. 2D maps were constructed to obtain information about the structural changes associated with temperature. The synchronous map reveals the overall similarity of the intensity changes. Whereas, the 2D asynchronous maps provide the sequence of changes that occur. Based on the set of well defined rules proposed by Isao Noda, the synchronous and the asynchronous correlation maps were analysed. Hence, generalized 2D correlation spectroscopy can be extended to any kind of perturbation and will prove useful in understanding the structural dynamics. The objective of the thesis was to explore various facets of Raman spectroscopy that would be useful in the field of high energy materials specifically in the detection of explosives. Attempts were made for the development of trace detection of explosives using Raman based technique, SERS. In addition, bulk detection of concealed explosives was performed non-invasively using SORS and UMARS. In the field of high energy materials, these techniques will find immense applications. Raman spectroscopy, as we saw is a very important technique that can be used as a stand-alone method and can also be interfaced with other analytical or imaging modalities. This treatise is an example where the strength of this powerful spectroscopic method has been explored to some extent.

Light entering the eye is transformed by the retina into electrical signals. Extensive processing takes place in the retina before these signals are transmitted to the brain. Beginning in the outer retina, light-evoked electrical signals are distributed into parallel pathways specialized for different visual tasks, such as the detection of dark vs. bright ambient light, the onset or offset of light, and the direction of stimulus motion. Pathway diversity is a consequence of cell type diversity, differential cell connectivity, synapse organization, receptor expression, or any combination thereof. Cell connectivity itself can be accomplished through excitatory or inhibitory chemical synapses, or electrical coupling via gap junctions. Gap junctions are further specialized based on the expression of different connexin subunit isoforms. In aggregate, this diversity gives rise to ganglion cells with highly specialized functions, including ON and/or OFF responses, contrast-tuning and direction-selectivity (DS). The directionally-selective circuit, a circuit specialized for the encoding of stimulus motion, makes use of many of these circuit specializations. Bipolar cells, in response to glutamate release from cone photoreceptors, provide highly-sensitive glutamatergic input to amacrine cells and DS ganglion cells (DSGCs) in this circuit, while amacrine cells provide cholinergic and directionally-tuned GABAergic input to DSGCs. One population of DSGCs also transmit signals laterally to one another via gap junctions. Thus numerous specializations in bipolar cells, amacrine cells and ganglion cells endow DSGCs with their unique encoding abilities. In Chapters 2 and 3 of this dissertation I focus on synchronized firing between gap junction-coupled DSGCs. sDSGCs exhibit fine-scale correlations, with action potentials in an sDSGC more likely within ~2ms of action potential firing in a coupled neighbour. I first characterize electrical coupling of DSGCs through the identification of the molecular composition of DSGC gap junctions (Chapter 2). Physiological and immunohistochemical methods allowed me to demonstrate an important role for connexin 36 subunits in DSGC electrical coupling. Next (Chapter 3) I investigate the sub-cellular mechanisms underlying neuronal correlations between electrically coupled DSGCs. Using paired recordings, I show that chemical input (from bipolar cells and amacrine cells), electrical input (from gap junctions), and Na+ channel activity in DSGC dendrites underlie the generation of correlated spiking activity. While a common feature of electrically coupled networks, the mechanisms underlying correlations were previously unclear. In Chapter 4 I focus on the mechanisms within the DS circuit that endow these neurons with impressive sensitivity to stimulus contrast. Using physiological and pharmacological methods I first assess the relative contrast sensitivity of ganglion cells and starburst amacrine cells (SACs) in the DS circuit. The sensitivity of DSGC and SAC excitatory currents to antagonists of Na+ channels suggests an important role for these channels in amplifying low contrast responses and other weak inputs to the circuit. This role is later attributed to the differential expression of voltage-gated Na+ channels in specific bipolar cell populations. In aggregate, this dissertation describes several novel circuit mechanisms within the well-studied DS circuit. I also provide specific roles for such specializations in visual coding.
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