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Li, Yun-Thai. "Tip-enhanced Raman spectroscopy." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609992.
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Lee, Nam-Heui. "Extending Raman spectroscopy to the nanoscale." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1172680006.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2007."May, 2007." Title from electronic dissertation title page (viewed 04/07/2008) Advisor, Mark D. Foster; Committee members, Alexei P. Sokolov, Darrell H. Reneker, Ali Dhinojwala, Rex D. Ramsier; Department Chair, Mark D. Foster; Dean of the College, George R. Newkome; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Touzalin, Thomas. "Tip-enhanced Raman spectroscopy on electrochemical systems." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS364.
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L'analyse in situ d'interfaces électrochimiques à l'échelle nanométriques est un enjeu majeur pour la compréhension des mécanismes de transferts de charges et d'électrons dans les domaines du stockage d'énergie ou de l'électrocatalyse. Ce travail a permis le développement de la spectroscopie Raman exaltée de pointe (TERS) en milieu liquide et en conditions électrochimiques. Le TERS permet l'analyse de la structure de molécules ou de matériaux à l'échelle nanométrique du fait de l'exaltation localisée du champ électrique à l'extrémité d'une sonde de microscope à effet tunnel (STM) en or ou en argent. Un dispositif reposant sur l'illumination d'une pointe au travers d'un solvant organique a démontré la possibilité d'imager les inhomogénéités d'une monocouche auto-assemblée sur or. Une seconde approche reposant sur l'exaltation du signal Raman à l'apex d'une pointe de taille nanométrique utilisée comme microélectrode (spectroscopie Raman exaltée de surface de pointe, tip SERS) a permis de suivre la réduction d'une monocouche auto-assemblée et d'améliorer la compréhension de son mécanisme. Afin d'imager la surface d'une électrode polarisée, le couplage d'un STM utilisant une pointe TERS en conditions électrochimiques a montré une résolution latérale de moins de 8 nm pour sonder de variations locales de l'exaltation du champ électromagnétique induites par des singularités géométriques de surface. Par ailleurs, l'analyse TERS de couches organiques formées à partir de sels d'aryldiazoniums a permis de montrer des différences de structures selon type de greffage. Ce travail constitue donc une avancée majeure pour l'analyse locale de surfaces modifiéesThe in situ investigation of electrochemical interfaces structures at the nanoscale is a key element in the understanding of charge and electron transfer mechanisms e.g. in the fields of energy storage or electrocatalysis. This thesis introduces the implementation of tip-enhanced Raman spectroscopy (TERS) in liquid and in electrochemical conditions enabling the nanoscale analysis of electrified solid/liquid interfaces through the strong and local electric field enhancement at gold or silver scanning tunneling microscopy (STM) probes. The ability of TERS to image inhomogeneities in the coverage density of a self-assembled monolayer (SAM) through a layer of organic solvent on gold was demonstrated. A TERS-inspired analytical tool was also developed, based on a TERS tip used simultaneously as a single-hot spot surface-enhanced Raman spectroscopy (SERS) platform and as a microelectrode (EC tip SERS). The reduction of an electroactive SAM could then be monitored by electrochemical and in situ SERS measurements. In situ electrochemical STM-TERS was also evidenced through the imaging of local variations of the electric field enhancement on peculiar sites of a gold electrode with a lateral resolution lower than 8 nm. Finally TERS also demonstrated to be efficient in investigating the structure of organic layers grafted either by electrochemical reduction or spontaneously. This work is therefore a major advance for the analysis of functionalized surfaces
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Lloyd, Jonathan S. "The development of tip enhanced raman spectroscopy." Thesis, Swansea University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678427.
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Beaman, R. A. "Two beam coherent spectroscopy." Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379609.
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Zhang, Weihua. "Tip-enhanced Raman spectroscopy : theory, practice and applications /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17564.
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Williams, Craig Miles. "A tip-enhanced raman microscope: development and application." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492591.
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Tip-enhanced Raman microscopy is a powerful technique that combines the high spatial resolution of a scanning probe microscope with the chemical sensitivity of Raman spectroscopy to yield sub-diflfraction limited resolution.
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Gryspolakis, Nikolaos. "Theoretical analysis of two-stage discrete fibre Raman amplifiers." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80017.
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A methodical analysis of two-stage Discrete Fibre Raman Amplifiers (DFRA) for DWDM transmission systems is presented in this thesis. Combinations of both unclamped and gain-clamped stages are investigated. A full numerical model was developed to simulate and fully illustrate the performance and properties of both single-stage and two-stage DFRAs.In particular we concentrate on two configurations of two-stage DFRAs. One that consists of two non gain-clamped stages and one that consists of one gain-clamped followed by an unclamped stage and the inverse. The gain-clamping is attained by placing two fibre Bragg gratings in the two sides of the stage that we desire to gain-clamp; and thus creating a fibre laser in either the first or the second stage of the two-stage FRA.
The conclusions we draw from our simulations, are the following: (1) a good gain-clamping effect can be achieved by partially gain-clamped configurations in which only one stage (first or second) is truly clamped; (2) an inherent low noise figure can also be obtained when the second stage is clamped; (3) the selection of feedback wavelengths and feedback levels are critical for obtaining a flat gain spectrum and low noise performance.
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O, Suilleabhain Liam Colman. "Raman studies of plasmons in two-dimensional electron gases." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318467.
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McDearmid, Jonathan R. "Noradrenergic control of spinal motor circuitry in two related amphibian species, Xenopus laevis and Rama temporaria." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/15058.
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1. The role of the catecholamine noradrenaline (NA) was examined during fictive swimming in Xenopus laevis tadpoles. 2. The primary effects of the amine in both embryonic and larval Xenopus was to markedly decrease motor frequency whilst simultaneously reducing rostrocaudal delays during swimming. 3. The NA-mediated modulation of swimming activity in Xenopus larvae can be reversed with phentolamine, a non-selective an adrenergic receptor antagonist, suggesting that NA may be acting through either ?1 or ?2 receptors, or a combination of both. 4. Intracellular recordings made from embryo spinal motorneurones revealed that reciprocal inhibitory glycinergic potentials are enhanced by NA. This effect is most prominent in caudal regions of the spinal cord where inhibitory synaptic drive is generally weaker. 5. NA was also found to enhance glycinergic reciprocal inhibition during swimming in larval spinal cord motomeurones. 6. Intracellular recordings, under tetrodotoxin, reveal that NA enhances the occurrence of spontaneous glycinergic inhibitory post synaptic potentials arising from the terminals of inhibitory intemeurones, suggesting that the amine is acting presynaptically to enhance evoked release of glycine during swimming. 7. The effects of NA on swimming frequency and rostrocaudal delay appear to be largely mediated through an enhancement of glycinergic reciprocal inhibition as blockade of glycine receptors with strychnine weakens the ability of the amine affect these parameters of motor output. 8. The effects of NA on motor output were also examined in embryos of the amphibian Rana temporaria. Whilst NA did not obviously affect swimming activity, the amine induced a non-rhythmic pattern of motor activity. 9. The free radical gas, nitric oxide also induced a non-rhythmic pattern of motor discharge that was remarkably similar to that elicited by NA, indicating that this neural messenger may be important for motor control.
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Schambach, Philip [Verfasser]. "Tip-enhanced Raman spectroscopy in ultra-high vacuum / Philip Schambach." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/104348079X/34.
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Sheremet, E., A. G. Milekhin, R. D. Rodriguez, T. Weiss, M. Nesterov, E. E. Rodyakina, O. D. Gordan, et al. "Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-161500.
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Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 103 was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 104. This is an important step towards the detection of the phonon spectrum from a single QDDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Mehtani, Disha. "Development and Optimization of Scanning nano-Raman Spectroscopy." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1152212506.
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Boone, Kenneth P. "Photodissociation of (DMSO)₂Fe(II)TPP, (TMSO)₂Fe(II)TPP, and (PSO)₂Fe(II)TPP to form a transient five-coordinate complex as studied using transient resonance Raman spectroscopy /." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1229660779.
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Thesis (M.S.)--University of Toledo, 2008.Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science Degree in Chemistry." "A thesis entitled"--at head of title. Bibliography: leaves 58-62.
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Boone, Kenneth Patrick. "Photodissociation of (DMSO)2Fe(II)TPP, (TMSO)2Fe(II)TPP, and (PSO)2Fe(II)TPP to form a transient Five-Coordinate Complex as Studied Using Transient Resonance Raman Spectroscopy." University of Toledo / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1229660779.
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Domke, Katrin F. "Tip enhanced Raman spectroscopy topographic and chemical information on the nanoscale /." [S.l.] : [s.n.], 2006. http://www.diss.fu-berlin.de/2006/656/index.html.
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Martín, Sabanés Natalia [Verfasser]. "Electrochemical tip-enhanced Raman spectroscopy : development and applications / Natalia Martín Sabanés." Mainz : Universitätsbibliothek Mainz, 2018. http://d-nb.info/115869282X/34.
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Scherger, Jacob D. "Expanding Tip Enhanced Raman Spectroscopy: Blinking Measurements and Alternative Probe Materials." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510657402180872.
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De, Sanctis Adolfo. "Manipulating light in two-dimensional layered materials." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/27414.
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Graphene and layered two-dimensional (2D) materials have set a new paradigm in modern solid-state physics and technology. In particular their exceptional optical and electronic properties have shown great promise for novel applications in light detection. However, several challenges remain to fully exploit such properties in commercial devices. Such challenges include the limited linear dynamic range (LDR) of graphene-based photodetectors (PDs), the efficient extraction of photoexcited charges and ultimately the environmental stability of such atomically-thin materials. In order to overcome the aforementioned limits, novel approaches to tune the properties of graphene and semiconducting \ce{HfS2} are explored in this work, using chemical functionalisation and laser-irradiation. Intercalation of graphene with \ce{FeCl3} is shown to lead to a highly tunable material, with unprecedented stability in ambient conditions. This material is used to define photo-active junctions with an unprecedented LDR via laser-irradiation. Intercalation with \ce{FeCl3} is also used to demonstrate the first all-graphene position-sensitive photodetector (PSD) promising for novel sensing applications. Finally, laser-irradiation is employed, to perform controlled oxidation of ultra-thin \ce{HfS2}, which leads to induced strain in the material and a consequent spatially-varying bandgap. Such structure is used to demonstrate, for the first time, efficient extraction of photogenerated carriers trough the so-called ``charge-funnel'' effect, paving the way to the development of ultra-thin straintronic devices.
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Rickman, Robert. "The development of tip-enhanced Raman spectroscopy for defect characterisation in graphene." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42581.
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Tip-enhanced Raman spectroscopy (TERS) is a scanning probe technique that utiHscs a confined, ovanescent field at the tip apex to conduct optical characterisation of a surface at length-scales below the diffraction limit. This thesis details the development of a new TER.S system based upon a shear-force scanning probe microscope (SPM) which sits atop an inverted microscope configured for bottom illumination geometry and coupled to a Raman spectrometer. The system has been optimised for use with solid silver probes and 532 nm illumination. Measurement procedures, automated scripts and data analysis software have been developed that allow reliable alignment of the tip; complex automated mapped measurements; and post processing which produces visual summary sheets to facilitate rapid review of a TERS experiment. Enhanced TERS spectra have been demonstrated on ultra-thin Rhodamine 6G films, self assembled monolayers (SAM) of thiophenole molecules, ultra-thin graphitic films and on multilayered graphene. Improvements in fabrication and alignment procedures have reduced the setup time between fabrication and approach to 20 minutes and improved the reliability of TERS tips with ~ 50% of tips demonstrating TERS activity. Using TERS, heightened defect sensitivity was observed on graphene edges, folds and overlapping regions. The TERS contrast of the defect induced D band was ~ 7.5 times the contrast of the graphene G band. Calculations show that the phonons correlating to the D and G bands interact differently with the enhanced TERS field and that the for certain defect types the D band experiences greater enhancement. Defects play an important role in tailoring the electronic and chemical properties of graphene which is key to the development of graphene based devices. The localised structural and spectral information makes TERS a highly promising tool for the characterisation of defects in graphene. This work demonstrates the potential of TERS for this exciting and important application.
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Najjar, Samar. "Couplage AFM/Raman et spectroscopie Raman exaltée par effet de pointe de nanostructures." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00869044.
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Pour mieux comprendre leurs propriétés, diverses nanostructures individuelles ont été étudiées à l'aide d'une technique couplant microscopie à force atomique et spectroscopie Raman confocale. Sous excitation lumineuse polarisée, la composition chimique, la structure et la présence de défauts a pu être précisée dans des nanobâtonnets d'oxydes métalliques (ZnO et α-Fe2O3). Sous irradiation laser résonnante, les spectres de nanotubes de carbone monoparoi enrobés de polymères ont révélé notamment l'absence de transfert de charge polymère-nanotube et un effet de désolvatation. Finalement, des feuillets de graphène oxydé et des ADNs double-brin peignés ont pu être préparés et caractérisés par spectroscopie Raman exaltée par effet de pointe en atteignant une résolution spatiale latérale voisine du rayon de courbure de l'apex de la pointe utilisée (12 nm), bien plus faible que la limite de diffraction, ce qui ouvre la voie à de nouveaux travaux spectroscopiques à l'échelle nanométrique.
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Rodriguez, Raul D., Evgeniya Sheremet, Tanja Deckert-Gaudig, Corinne Chaneac, Michael Hietschold, Volker Deckert, and Dietrich R. T. Zahn. "Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-168045.
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Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm−1 attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal–nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically inducedDieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Gorman, Thomas Andrew. "Ecology of Two Rare Amphibians of the Gulf Coastal Plain." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26780.
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Globally, amphibian species have been in decline and a wide range of factors have been purported to be driving the decline. The Gulf Coastal Plain of Florida has a high degree of endemism and rarity and the biodiversity in the region includes a diverse suite of amphibian species. Degradation of habitat has been considered by many to be a major part of amphibian declines, however amphibian declines are complex and in many cases multiple factors are occurring in concert. My dissertation research examined aspects of habitat ecology and occupancy for two rare amphibians, Florida Bog Frog (Rana okaloosae) (Chapter 1, 2, and 3) and Reticulated Flatwoods Salamander (Ambystoma bishopi) (Chapter 5), that are both restricted to the Northern Gulf Coastal Plain. Further, for R. okaloosae I examined the influence of a sympatric congener, Bronze Frog (R. clamitans clamitans), on microhabitat selection (Chapter 1) and growth of tadpoles (Chapter 4). My overall goal was to be able to elucidate factors that limit the geographic range of R. okaloosae and A. bishopi and to identify habitat characteristics that managers could maintain or create to conserve or increase populations of these species.
My first chapter examined the microhabitat relationships between R. okaloosae and R. c. clamitans. Rana okaloosae is endemic to northwestern Florida and is sympatric with R. c. clamitans, a more common and widely distributed congener. Further, the two species appeared to be syntopic, have overlapping breeding seasons, and are known to hybridize. The objectives of this chapter were to assess the microhabitat selection of both species and to assess differences in microhabitat use of males of both species during the breeding season. My modeling of habitat selection and comparison of variables used by each species suggests that males of these species select different resources when calling. Therefore, these sympatric ranids select for different resources at a fine scale, however there does appear to be some overlap among some selected habitat characteristics.
In Chapter 2, I assessed the habitat use of R. okaloosae at multiple spatial scales. I surveyed for R. okaloosae and evaluated habitat characteristics at used sites and sites where I had no detections to develop among- and within-stream habitat models for R. okaloosae. Rana okaloosae used habitats with high amounts of emergent vegetation at both the among-stream scale and the within-stream scale. Emergent vegetation appears frequently in models of anuran habitat selection, particularly those that occur in fire-dominated landscapes. Further understanding the habitat requirements of R. okaloosae will allow land managers to use appropriate management activities (e.g., prescribed fire) that will increase emergent vegetation and potentially restore habitat that may help increase populations of R. okaloosae.
In Chapter 3, I conducted aural surveys for R. okaloosae at two different spatial scales: range-wide and stream-level scales to understand how occupancy and colonization of R. okaloosae may be influenced by scale. My results suggest that at both spatial scales occupancy of R. okaloosae was best described by the presence of mixed forest wetlands at survey sites. At the range-wide scale, colonization and detection were constant across years, however, at the stream-level scale, colonization was predicted by the number of years since last fire and detection was best predicted by the additive combination of relative humidity and temperature. Occupancy of R. okaloosae was patchy at the range-wide and at the stream-level scales and colonization was low at both scales, while derived estimates of local extinction were moderately high. While R. okaloosae still occur in 3 watersheds where they were initially observed in the 1980â s, one of the three watersheds appears to be very isolated and detections there are becoming very infrequent.
In Chapter 4, I experimentally evaluated the effects of R. c. clamitans tadpoles on R. okaloosae tadpoles. My results suggest that there was limited influence of R. c. clamitans on R. okaloosae. Conversely, it appeared that Rana c. clamitans was more susceptible to intraspecific competition than interspecific competition. The lack of a strong competitive effect of Rana c. clamitans on Rana okaloosae suggests that competitive interactions among tadpoles may have a limited effect at the densities I examined.
In Chapter 5, our objectives were to evaluate a suite of within-pool factors (i.e., vegetation structure, water level, and an index to presence of fish) that could influence occupancy of breeding wetlands by larval flatwoods salamanders on Eglin Air Force Base in Florida, USA. Site occupancy over a 4 year period was best described by a model that incorporated high herbaceous vegetation cover and open canopy cover. Detection probability was assessed, but it varied among years and was not included in the model. Our study suggests that managing the breeding habitat of flatwoods salamander for open canopies and dense herbaceous vegetation may contribute to this speciesâ recovery.
In conclusion, Chapters 1-3 of my dissertation contribute to a growing understanding about the habitat ecology of R. okaloosae. I have evaluated habitat use of R. okaloosae at multiple spatial scales. At the finest spatial scale R. okaloosae selected for sites that had an abundance of cover probably decreasing their risk of predation (Chapter 1). Similarly, in Chapter 2 at two spatial scales, among and within-streams, R. okaloosae selected for emergent vegetation. Finally, at the broadest spatial scale, range-wide, R. okaloosae were found to be associated with mixed forest wetlands (Chapter 3). I did not find strong support for competition between R. okaloosae and R. c. clamitans tadpoles, although there was some evidence of asymmetric competition (Chapter 4). Further, adult males of each species did not select the same habitat characteristics for calling sites, so there appeared to be some resource partitioning (Chapter 1). Finally, the presence of A. bishopi larvae was found to be associated with herbaceous vegetation and moderate amounts of canopy cover (Chapter 5). Results from Chapter 2 and 5 suggest that both R. okaloosae and A. bishopi are associated with habitat conditions that are likely a result of fire penetrating wetland areas.Ph. D.
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Driessen, Leonie [Verfasser]. "Development of a tip-enhanced Raman spectrometer to investigate solid-liquid interfaces / Leonie Driessen." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1177305259/34.
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Böhme, René, Msau Mkandawire, Udo Krause-Buchholz, Petra Rösch, Gerhard Rödel, Jürgen Popp, and Volker Deckert. "Characterizing cytochrome c states – TERS studies of whole mitochondria." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138679.
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Protein structures (cytochrome c) were visualized by TERS measurements on whole mitochondria referring to specific spectral features describing the electronic state of the heme moietyDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Baniasadi, Fazel. "Structure Characterization and Electronic Properties Investigation of Two-Dimensional Materials." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103904.
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This dissertation will have three chapters. In chapter one, a comprehensive review on defects in two dimensional materials will be presented. The aim of this review is to elaborate on different types of defects in two dimensional (2D) materials like graphene and transition metal dichalcogenides (TMDs). First, different types of point and line defects, e.g. vacancies, anti-sites, guest elements, adatoms, vacancy clusters, grain boundaries, and edges, in these materials are categorized in terms of structure. Second, interactions among defects are discussed in terms of their rearrangement for low-energy configurations. Before studying the electronic and magnetic properties of defective 2D materials, some of the structures are considered in order to see how defect structure evolves to a stable defect configuration. Next, the influence of defects on electronic and magnetic properties of 2D materials is discussed. Finally, the dynamic behavior of defects and 2D structures under conditions such as electron beam irradiation, heat treatment, and ambient conditions, is discussed. Later as a case study, defects in a two dimensional transition metal dichalcogenide will be presented. Among two-dimensional (2D) transition metal dichalcogenides (TMDs), platinum diselenide (PtSe2) stands at a unique place in the sense that it undergoes a phase transition from type-II Dirac semimetal to indirect-gap semiconductor as thickness decreases. Defects in 2D TMDs are ubiquitous and play crucial roles in understanding and tuning electronic, optical, and magnetic properties. Here intrinsic point defects in ultrathin 1T-PtSe2 layers grown on mica were investigated through the chemical vapor transport (CVT) method, using scanning tunneling microscopy and spectroscopy (STM/STS) and first-principles calculations. Five types of distinct defects were observed from STM topography images and the local density of states of the defects were obtained. By combining the STM results with first-principles calculations, the types and characteristics of these defects were identified, which are Pt vacancies at the topmost and next monolayers, Se vacancies in the topmost monolayer, and Se antisites at Pt sites within the topmost monolayer. Our study shows that the Se antisite defects are the most abundant with the lowest formation energy in a Se-rich growth condition, in contrast to cases of 2D molybdenum disulfide (MoS2) family. Our findings would provide critical insight into tuning of carrier mobility, charge carrier relaxation, and electron-hole recombination rates by defect engineering or varying growth condition in few-layer 1T-PtSe2 and other related 2D materials. Also, in order to investigate the layer dependency of vibrational and electronic properties of two dimensional materials, 2M-WS2 material was selected. Raman spectroscopy and DFT calculation proved that all Raman active modes have a downshift when material is thinned to few layers (less than 5 layers). It was proven that there is a strong interaction between layers such that by decreasing the number of layers, the downshift in Raman active modes is mostly for the ones which belong to out-of-plane atomic movements and the most downshift is for the Ag2 Raman active mode. Also, I investigated the effect of number of layers on the band structure and electronic properties of this material. As the number of layers decreases, band gap does not change until the materials is thinned down to only a single monolayer. For a single monolayer of 2M-WS2, there is an indirect band gap of 0.05eV; however, with applying in-plane strain to this monolayer, the material takes a metallic behavior as the strain goes beyond ±1%.Doctor of Philosophy
Graphite (consisting of graphene as building blocks) and TMDS in bulk form are layered and with exfoliation one can reach to few layers which is called two-dimension. Two dimensional materials like graphene have been used in researches vastly due to their unique properties, e.g. high carrier mobility, and tunable electronic properties. Transition metal dichalcogenides (TMDs) with a general formula of MX2, where M represents transition metal elements (groups 4-10) and X represents chalcogen elements (S, Se or Te), are another family of two-dimensional materials which have been extensively studied in the past few years. Besides exfoliation, there are also synthesis methods to produce two dimensional materials, e.g. chemical vapor deposition and chemical vapor transport. Normally, after synthesizing these materials, researchers investigate structure and electronic properties of these materials. There might be some atoms which no longer exist in the structure; hence, those are replaced by either vacancies or other elements which all of them are called defects. In chapter 1, defects in graphene and transition metal dichacolgenides were investigated, carefully. Later, dynamic behavior of defects in these materials were investigated and finally, the effect of defects on the electronic properties of the two dimensional materials were investigated. Chapter two talks about a case study which is two dimensional 1T-PtSe2. In this chapter, 5 different kinds of defects were studied using scanning tunneling microscopy and spectroscopy investigations and density functional theory was used to prove our assumptions of the origin of defects. Also, another thing which is investigated by researcher is that how atoms in two dimensional materials vibrate and how the number of layers in the two dimensional material influences vibrations of atoms. Other than this, electronic properties of these materials is dependent upon the number of layers. When these materials are synthesized, there is a stress applied to the material due the mismatch between the material and its substrate, so it is worth investigating the effect of stress (strain) on the structure, and electronic properties of the material of interest. For this purpose, 2M-WS2 was exfoliated on Si/SiO2 substrate and the layer dependency of its vibrational modes was investigated using Raman spectroscopy and density functional theory calculation. Also, in order to investigate the influence of stress (strain) on the electronic properties of two dimensional 2M-WS2, a single monolayer of this materials underwent a series of strains in density functional theory calculations and the effect of strain on the electronic properties of this material was investigated.
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Eschimese, Damien. "Design, fabrication, and characterization of TIP-enhanced Raman spectroscopy probes based on metallic nano-antennas." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I020/document.
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Depuis les années 2000, le développement de la spectroscopie Raman à exaltation de pointe (TERS) a permis l’accès de manière extrêmement localisée aux propriétés structurales et moléculaires à la surface de la matière et à des analyses physico-chimiques combinées. La technologie TERS associe les techniques de microscopie à sonde locale - ici le microscope à force atomique (AFM) - avec le champ proche optique. Elle bénéficie en particulier de la génération, à la surface métaux nobles, de plasmons de surface à l’origine d’exaltation d’ondes électromagnétiques pouvant être confinées dans un volume sub-longueur d'onde à l'extrémité des sondes AFM-TERS. Aujourd'hui le principal verrou technologique en TERS est la conception des sondes AFM en termes de reproductibilité à échelle nanométrique, et de fabrication en série. Ce travail de thèse effectué dans le cadre d’une thèse CIFRE (HORIBA Scientific) a eu pour but de concevoir un nouveau type de sonde AFM-TERS répondant aux exigences de performances et de fabrication actuelles. Pour atteindre cet objectif, une étude de simulation numérique a conduit à proposer une nanostructuration métallique de l’extrémité d’un levier AFM, afin de conduire à une exaltation électromagnétique optimisée. Un procédé de nano- et micro-fabrication a été développé au sein de la plateforme de micro et nano-fabrication de l'IEMN, combinant lithographie électronique et optique, évaporation métallique et gravure sur wafers silicium. Il permet la réalisation en série de sondes AFM dont chaque extrémité est composée d'une nano-antenne métallique de taille sub-longueur d'onde, composée d'un nanodisque supportant un nanocône. La méthode de fabrication proposée permet un contrôle des réponses plasmoniques en termes d’amplification du champ et d’accordabilité de la résonance, qui sont la clé des performances en spectroscopie Raman à exaltation de pointe. Une étude sur l’évaporation inclinée lors du procédé de nano-fabrication développé par lithographie électronique a également été réalisé dans le but de contrôler la forme des nanoparticules – de forme conique à cylindrique avec des parois poreuses -- isolées ou en réseaux denses. Les simulations numériques suggèrent que de tels objets peuvent être des candidats potentiels pour le TERS ou le SERS (spectroscopie Raman à exaltation de surface)Since the start of the 2000s the evolution of tip-enhanced Raman spectroscopy (TERS) has enabled the simultaneous measurement of localized structural, molecular, and physicochemical properties. TERS technology combines scanning probe microscopy -- atomic force microscopy (AFM) -- with near field optical microscopy. The combined technique is referred to as AFM-TERS. The technique harnesses and exploits the generation of surface plasmons on metal surfaces. These plasmons lead to the generation of confined electromagnetic waves in a sub-wavelength volume at the very tip of the AFM-TERS probe. The main technological challenge today is the design and optimization of an AFM-TERS probe having nanometer-sized dimensions -- and the controlled, reproducible batch fabrication of such structures. The objective of the work presented in this PhD thesis was to design, fabricate, and characterize a new type of AFM probe capable of bettering the current state-of-the-art performances. The PhD was carried out in collaboration with HORIBA and funded partly by a French ‘CIFRE’ grant. In order to meet these objects, comprehensive numerical modelling led to the design of an optimized metal nanostructuring having maximum electromagnetic exaltation -- placed at the extremity of a silicon-based AFM cantilever. A new combined micro and nano fabrication process was developed to achieve this -- to be performed using the existing equipment found in the IEMN cleanroom. The process encompasses techniques such as masking using electron beam (ebeam) lithography and UV photolithography, thermal evaporation of metals and ‘lift-off’ techniques, and highly-controlled dry etching of small silicon mesas structures and deep etching for MEMS cantilever releasing. The process enables the batch-fabrication manufacture of AFM-TERS probes containing matter on the millimeter scale (the silicon probe support), the micrometer scale (the silicon cantilever), and the nanometer scale (the combined metallic disk and cone having sub-wavelength dimensions). This method allows nanostructuring on the optical/plasmonic behavior of TERS probes, the key factor which will lead to higher performance in TERS. Finally, a further study concerning the inclined evaporation of metallic nanostructures via an ebeam-derived lithographic shadow mask was performed in order to control the size and shape of the nanostructuring. The study proved this approach to be feasible. Furthermore, numerical modelling of such structures suggests that they are potential original candidates for both TERS and SERS (surface-enhanced Raman spectroscopy)
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Spencer, Joseph. "Vibrational and electronic excitations of two atom diameter mercury telluride nanowires studied by resonance Raman spectroscopy." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/409712/.
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This thesis presents the results from a temperature dependant resonance Raman spectroscopy study of HgTe extreme nanowires embedded within SWCNTs. Extreme nanowires are nanowires at the absolute limits of the nanoscale, in this case, just 1-2 atoms in diameter. This work demonstrates that due to the effect of quantum confinement on the electronic wavefunction and the reordering of atoms creating a new allotrope of HgTe never previously measured, new physics of 1D materials is observed. In this body of work we perform resonance Raman spectroscopy experiments with excitation photon energies of 1.65eV to 1.90eV and sample temperatures between 4-300K on an ensemble of HgTe filled single-walled carbon nanotubes. The Raman spectra are analysed and show that 1D HgTe within a SWCNT exhibits new Raman peaks not associated with modification of the bulk material. We couple the Raman results with HRTEM and utilise symmetry arguments to propose two of the fundamental vibrational modes at 47cm⁻¹ and 52cm⁻¹ are associated with vibrations with Bg and Ag symmetry respectively. Most strikingly, our results indicate a decrease in the rate of Raman scattering as a function of increasing temperature, not clearly in-line with the expected behaviour of Raman scattering due to an increase in the thermal phonon population. Through detailed analysis of temperature dependent resonance Raman data we can understand this effect in terms of broadening of the linewidth of the optical transition. We set out the evidence that this result can be understood by a model in which the resonance’s broadening is dominated by the coherence lifetime broadening. This allows us to determine the coherence lifetime of the underlying optical transition: 9fs at 295K and 18fs at 50K. The results are compared with similar results on carbon nanotubes which suggests that the optical transitions responsible for the Raman resonances are excitonic and is likely general to small diameter nanowires. A review of existing and comparable Raman measurements on such nanowires is presented and the implications of the main results in this thesis are discussed in terms of a general interest to the wider physics community.
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Jo, Ju-Yeon. "Full molecular dynamics simulations of molecular liquids for single-beam spectrally controlled two-dimensional Raman spectroscopy." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263491.
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Böhme, René, Msau Mkandawire, Udo Krause-Buchholz, Petra Rösch, Gerhard Rödel, Jürgen Popp, and Volker Deckert. "Characterizing cytochrome c states – TERS studies of whole mitochondria." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27770.
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Protein structures (cytochrome c) were visualized by TERS measurements on whole mitochondria referring to specific spectral features describing the electronic state of the heme moiety.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Lima, Kellen Cristina Vilhena. "Qualidade de gasolinas automotivas através de Espectroscopia Vibracional FT-Raman, combinada com correlação 2D generalizada." reponame:Repositório Institucional da UFC, 2005. http://www.repositorio.ufc.br/handle/riufc/12469.
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LIMA, Kellen Cristina Vilhena. Qualidade de gasolinas automotivas através de Espectroscopia Vibracional FT-Raman, combinada com correlação 2D generalizada. 2005. 305 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2005.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-25T22:26:07Z No. of bitstreams: 1 2005_tese_kcvlima.pdf: 10475763 bytes, checksum: e618c6deda94d946c15be6e420912ad1 (MD5)
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It is reported the use of Generalized Two-Dimensional FT-Raman Correlation Spectroscopy (2DCOS-FT-Raman) method to monitor the quality of automotive gasoline in the gas stations. It is presented a procedure to identify the adulteration of automotive gasoline by the illicit addition of ethanol, methanol, aromatic and paraphinic compounds through the analysis of the Raman spectra obtained for different compositions of adulterants added to gasoline “A” type and to gasoline “A” type plus ethanol samples. It is discussed the data preconditioning step, the application of 2DCOS method, and the calibration curves that correlates the integrated intensities of the Raman bands of a given adulterant with its percentage in a given gasoline sample. It shown the protocol for using the 2DCOS-FT-Raman method to verify the adulteration in a given gasoline sample compared with a specific standard. This work emphasizes the flexibility and viability of using this method to have a specific standard for each gasoline distribution firm and also for each new gasoline derived from the refinery.
Relata a utilização da espectroscopia FT-Raman combinada com Correlação 2D Generalizada como método alternativo para a realização do controle de qualidade de Gasolinas automotivas diretamente nos postos de combustível. Apresenta os procedimentos para identificar a adulteração da Gasolina automotiva pela adição irregular de Etanol, Metanol e compostos aromáticos e parafínicos, através da análise dos espectros Raman obtidos para os diferentes adulterantes separadamente, misturados à Gasolina A e misturados à Gasolina A e ao Etanol. Descreve os procedimentos de pré-tratamento sobre os espectros Raman, a aplicação do método de Correlação 2D Generalizada aos sistemas estudados e a determinação das curvas de calibração que relacionam as intensidades integradas das bandas Raman com o teor de adulterante na Gasolina. Apresenta a praticidade de aplicação do método, que possibilita verificar a adulteração da Gasolina automotiva através da comparação entre o espectro Raman da amostra cuja conformidade se deseja verificar com o espectro da amostra padrão. Enfatiza a flexibilidade e a viabilidade de se ter um padrão específico para cada distribuidora, ou até mesmo para cada nova produção de Gasolina da refinaria.
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Davies, Heather. "Mucins in the alimentary canal : their structure and interactions with polyphenols." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/mucins-in-the-alimentary-canal-their-structure-and-interactions-with-polyphenols(76aaa531-bf78-4be1-94a7-c8b4db9114bb).html.
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The polymeric gel-forming mucins provide the structural framework of saliva and the mucus barriers that cover the mucosal surfaces of the alimentary canal. Dietary compounds may influence the barrier properties of these protective layers. The effects of green tea polyphenols, which have many health benefits but have low bioavailability and contribute to the astringency of green tea, on the structural properties of the mucins in the alimentary canal are investigated here. Using well characterised, highly purified salivary mucins MUC5B and MUC7, and porcine gastric mucins, the effects of the green tea polyphenol epigallocatechin-3-gallate (EGCG) on mucins were studied here. Using rate-zonal centrifugation coupled to agarose gel electrophoresis, atomic force microscopy and particle tracking microrheology, EGCG, at concentrations found in a cup of green tea, caused increased aggregation of MUC5B in human whole saliva, and increased aggregation and viscosity of purified MUC5B. It was revealed using recombinant proteins of the N- and C-terminal regions of MUC5B that EGCG had these effects by aggregating the terminal globular protein domains of MUC5B. In contrast, MUC5B trypsin-resistant high molecular weight glycopeptides were not aggregated by EGCG, demonstrating that the oligosaccharide-rich, highly-glycosylated regions of mucins are not involved in the EGCG-induced aggregation of mucins. EGCG also caused the majority of MUC7 in human whole saliva to aggregate, and purified MUC7 also showed substantial aggregation in the presence of EGCG.Porcine gastric mucins were also used in order to model human gastric mucins. First, the identity of the porcine gastric mucins was explored using tandem mass spectrometry and immunohistochemistry. This revealed that Muc5ac was expressed by the surface epithelium and was the prominent mucin in porcine gastric mucus. Muc6 was expressed by gastric submucosal glands, but was not a major component of the secreted mucus barrier. Porcine Muc5ac and Muc6 were shown to be aggregated by EGCG. These data demonstrate that mucins from both saliva and the stomach are substantially altered by EGCG. This may contribute to the astringency and low bioavailability of EGCG. In contrast, the green tea polyphenol epicatechin (EC) did not cause aggregation of salivary mucins or porcine gastric mucins, suggesting that the galloyl ring of EGCG (which is absent in EC) is important for its aggregation of mucins, and that EC has different mechanisms of astringency. The structure of the mucins in the alimentary canal was studied using Raman spectroscopy, Raman optical activity (ROA) and Tip-enhanced Raman spectroscopy (TERS). The secondary structure of the oligosaccharide-rich regions of mucins was shown to be largely disordered, with some contribution of poly-proline II helix. The N- and C-terminal regions of MUC5B were largely β-sheet in structure, with some disordered structure also present in the C-terminal region. Raman spectroscopy could reliably distinguish between MUC5B glycoforms, demonstrating the sensitivity of this technique to mucin glycosylation and secondary structure. The first TERS spectra along the length of a MUC5B chain are reported, and suggest that patterns may exist in the glycosylation of MUC5B. Therefore, Raman spectroscopies are novel tools that shed new light on mucin structure and in future may be useful for studying the changes to mucin structure during interactions, such as those with polyphenols.
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Le, Nader Victor. "Approche expérimentale et théorique de la diffusion Raman exaltée : résonance des plasmons de surface et effet de pointe." Phd thesis, Université de Nantes, 2010. http://tel.archives-ouvertes.fr/tel-00559365.
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Ce travail de thèse s'articule autour des phénomènes d'exaltation de la diffusion Raman grâce aux propriétés optiques des métaux nobles (Or et Argent). Des expériences de Spectroscopie Raman Exaltée de Surface (SERS : Surface Enhanced Raman Spectroscopy) et de Spectroscopie Raman Exaltée par sonde locale (TERS : Tip Enhanced Raman Spectroscopy) ont permis l'exploration des ces phénomènes. Le premier volet de ce travail a consisté en la préparation de substrats « SERS-actifs » et en l'analyse de leurs pouvoir exaltant. Trois types de substrats ont été élaborés au laboratoire afin d'étudier les paramètres d'influence (structuration de la surface, longueur d'onde et polarisation de la lumière incidente, nature du métal, etc...). Le second volet du travail a été consacré à la mise en place d'un dispositif TERS. La conception des pointes métalliques a fait l'objet d'une attention particulière. De plus, un module a été élaboré afin d'associer un système de nano-positionnement de la pointe à un Raman confoncal commercial. Ce module a aussi été conçu pour permettre de focaliser le faisceau laser à l'extrémité de la nano-sonde métallique. La conception des outils ainsi que la compréhension des résultats expérimentaux sont corrélés à une analyse numérique. Les sources électromagnétiques (plasmons de surface et effet de pointe) de l'amplification de la diffusion Raman sont étudiées avec l'appui de simulations numériques par la méthode des éléments finis. Enfin les aspects chimiques des phénomènes d'exaltation sont abordés par DFT (Density Functiunal Theory).
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Lin, Xiu-Mei [Verfasser], Volker [Akademischer Betreuer] Deckert, and Wolfgang [Akademischer Betreuer] Weigand. "Tip-enhanced Raman Spectroscopy (TERS) for Biomolecular Analyses at Nanometer / Xiu-Mei Lin. Gutachter: Volker Deckert ; Wolfgang Weigand." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2014. http://d-nb.info/1047579073/34.
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Lima, Kellen Cristina Vilhena. "The use of Generalized Two-Dimensional FT-Raman Correlation Spectroscopy method to monitor the quality of automotive gasoline." Universidade Federal do CearÃ, 2005. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=115.
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Relata a utilizaÃÃo da espectroscopia FT-Raman combinada com CorrelaÃÃo 2D Generalizada como mÃtodo alternativo para a realizaÃÃo do controle de qualidade de Gasolinas automotivas diretamente nos postos de combustÃvel. Apresenta os procedimentos para identificar a adulteraÃÃo da Gasolina automotiva pela adiÃÃo irregular de Etanol, Metanol e compostos aromÃticos e parafÃnicos, atravÃs da anÃlise dos espectros Raman obtidos para os diferentes adulterantes separadamente, misturados à Gasolina A e misturados à Gasolina A e ao Etanol. Descreve os procedimentos de prÃ-tratamento sobre os espectros Raman, a aplicaÃÃo do mÃtodo de CorrelaÃÃo 2D Generalizada aos sistemas estudados e a determinaÃÃo das curvas de calibraÃÃo que relacionam as intensidades integradas das bandas Raman com o teor de adulterante na Gasolina. Apresenta a praticidade de aplicaÃÃo do mÃtodo, que possibilita verificar a adulteraÃÃo da Gasolina automotiva atravÃs da comparaÃÃo entre o espectro Raman da amostra cuja conformidade se deseja verificar com o espectro da amostra padrÃo. Enfatiza a flexibilidade e a viabilidade de se ter um padrÃo especÃfico para cada distribuidora, ou atà mesmo para cada nova produÃÃo de Gasolina da refinaria.It is reported the use of Generalized Two-Dimensional FT-Raman Correlation Spectroscopy (2DCOS-FT-Raman) method to monitor the quality of automotive gasoline in the gas stations. It is presented a procedure to identify the adulteration of automotive gasoline by the illicit addition of ethanol, methanol, aromatic and paraphinic compounds through the analysis of the Raman spectra obtained for different compositions of adulterants added to gasoline âAâ type and to gasoline âAâ type plus ethanol samples. It is discussed the data preconditioning step, the application of 2DCOS method, and the calibration curves that correlates the integrated intensities of the Raman bands of a given adulterant with its percentage in a given gasoline sample. It shown the protocol for using the 2DCOS-FT-Raman method to verify the adulteration in a given gasoline sample compared with a specific standard. This work emphasizes the flexibility and viability of using this method to have a specific standard for each gasoline distribution firm and also for each new gasoline derived from the refinery.
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Lin, Xiu-Mei [Verfasser], Volker Akademischer Betreuer] Deckert, and Wolfgang [Akademischer Betreuer] [Weigand. "Tip-enhanced Raman Spectroscopy (TERS) for Biomolecular Analyses at Nanometer / Xiu-Mei Lin. Gutachter: Volker Deckert ; Wolfgang Weigand." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2014. http://nbn-resolving.de/urn:nbn:de:gbv:27-20140210-112607-2.
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Silva, Michelle Moura da. "ProteÃnas do plasma seminal de touros Bos Indicus e associaÃÃes com parÃmetros seminais." Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=6610.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoA realizaÃÃo desta pesquisa teve por objetivos a descriÃÃo do mapa eletroforÃtico bidimensional do plasma seminal de touros adultos Bos indicus, raÃa Brahman, bem como a determinaÃÃo das associaÃÃes estatÃsticas entre proteÃnas do plasma seminal e parÃmetros seminais destes touros. Amostras de sÃmen de 56 touros foram coletadas e o plasma seminal foi obtido atravÃs de centrifugaÃÃo e submetido à eletroforese bidimensional. Os gÃis foram corados com Coomassie coloidal, digitalizados e analisados por meio do aplicativo PDQuest. Os touros foram divididos em grupos de alta e baixa motilidade espermÃtica e alto e baixo percentual de cÃlulas espermÃticas morfologicamente normais. As proteÃnas mais abundantes no plasma seminal dos touros Bos indicus e detectadas em todos os 56 gÃis apresentaram semelhanÃa com espermadesinas e BSPs. A expressÃo de spots com valores de kDa e pI equivalentes aos das proteÃnas aSFP, BSPs, clusterina , albumina e osteopontina foram estatisticamente diferentes entre os grupos de animais com parÃmetros contrastantes de motilidade e morfologia espermÃticas. As associaÃÃes encontradas entre tais spots protÃicos e os parÃmetros seminais sugerem a possibilidade do uso destes como marcadores moleculares da fertilidade potencial dos animais.
This research aimed to describe the two-dimensional electrophoresis map of bull seminal plasma of adult Bos indicus, Brahman, and the determination of statistical associations between proteins of seminal plasma and semen parameters of these bulls. Semen samples from 56 bulls were collected and seminal plasma was obtained by centrifugation and subjected to two-dimensional electrophoresis. The gels were stained with colloidal Coomassie, scanned and analyzed using PDQuest application. The bulls were divided into groups of high and low sperm motility and high and low percentage of morphologically normal sperm cells. The most abundant proteins in seminal plasma of bulls Bos indicus and detected in all 56 gels showed similarity to espermadesinas and BSPs. The expression of spots with pI values kDa protein equivalent to aSFP, BSPs, clusterin, albumin and osteopontin were significantly different between groups of animals with contrasting parameters of sperm motility and morphology. The associations found between such protein spots and semen parameters suggest the possibility of their use as molecular markers of potential fertility of animals.
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Xu, Yunnan. "Statistical Methods for In-session Hemodialysis Monitoring." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99037.
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Motivated by real-time monitoring of dialysis, we aim at detecting difference between groups of Raman spectra generated from dialyzates at different time in one session. Baseline correction being a critical procedure in use of Raman Spectra, existing methods may not perform well on dialysis spectra due to nature of dialyzates, which contain numerous chemicals compounds. We first developed a new baseline correction method, Iterative Smoothing-spline with Root Error Adjustment (ISREA), which automatically adjusts intensities and employs smoothing-spline to produce a baseline in each iteration, providing better performance on dialysis spectra than a popular method Goldindec, and better accuracy regardless of types of samples. We proposed a two sample hypothesis testing on groups of baseline-corrected Raman spectra with ISREA. The uniqueness of the test lies in nature of the tested data. Instead of using Raman spectra as curves, we also consider a vector whose elements are peak intensities of biomarkers, meaning the data is regarded as mixed data and that a spectrum curve and a vector compose one observation. Our method tests on equality of the means of the two groups of mixed data. This method is based on asymptotic properties of the covariance of mixed data and FPCA. Simulation studies shows that our method is applicable to small sample size with proper power and size control. Meanwhile, to locate regions that contribute most to significant difference between two groups of univariate functional data, we developed a method to estimate the a sparse coefficient function by using a L1 norm penalty in functional logistic regression, and compared its performance with other methods.Doctor of Philosophy
In U.S., there are more than 709,501 patients with End-Stage Renal Disease (ESRD). For those patients, dialysis is a standard treatment. While dialysis is time-consuming, expensive, and uncomfortable, it requires patients to take three sessions every week in facilities, and each session lasts for four hours regardless of patients' condition. An affordable, fast, and widely-applied technique called Raman spectroscopy draws attention. Spectral data from used dialysate samples collected at different time in one session can give information on the dialysis process and thus make real-time monitoring possible. With spectral data, we want to develop a statistical method that helps real-time monitoring on dialysis. This method can provide physicians with statistical evidence on dialysis process to improve their decision making, therefore increases efficiency of dialysis and better serve patients. On the other hand, Raman spectroscopy demands preprocessing called baseline correction on the raw spectra. A baseline is generated because of the nature of Raman technique and its instrumentation, which adds complexity to the spectra and interfere with analysis. Despite popularity of this technique and many existing baseline correction method, we found performance on dialysate spectra under expectation. Hence, we proposed a baseline correction method called Iterative Smoothing-spline with Root Error Adjustment (ISREA) and ISREA can provide better performance than existing methods. In addition, we come up with a method that is able to detect difference between the two groups of ISREA baseline-corrected spectra from dialysate collected at different time. Furthermore, we proposed and applied sparse functional logistic regression on two groups to locate regions where the significant difference comes from.
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Itasaka, Hiroki. "Area-selective electroless deposition of gold nanostructures on silicon." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215550.
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Wang, Yejiao. "Fabrication of Cu2ZnSnSe4 Thin-film Solar Cells by a Two-stage Process." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6154.
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Copper zinc tin selenide (Cu2ZnSnSe4 or CZTSe) is a quaternary compound semiconductor material that has attained more and more attention for thin film photovoltaic applications. CZTSe is only comprised of abundant and non-toxic elements. People have concerns about availability and cost of indium from CIGS and tellurium from CdTe, also about cadmium’s toxicity. These concerns have promoted CZTSe as an alternative thin film solar cell material. The major issues about CZTSe absorber fabrication are: tin loss during selenization process and existence of secondary phases. Recent improvements of CZTSe absorber have increased the efficiency of CZTSe thin film solar cell to 9.7% in laboratory, and this was accomplished by using H2Se as selenium source in a “two-stage” process. [1] However “one-stage” vacuum co-evaporation technique is still the most popular technique for CZTSe thin-film solar cells fabrication.
In this research, Cu2ZnSnSe4 thin-film solar cells have been fabricated by using a two-step rapid thermal selenization process. The first step selenization is operated at 375℃, a relatively low annealing temperature, which helps avoiding the most common issue of tin loss. The second step selenization is carried out at a higher annealing temperature, 400℃ to 500℃, at where the formation of CZTSe quaternary compound can be completed, and fewer secondary phases remain in the CZTSe absorber bulk. A specially designed metallic precursor stacks deposition order has been developed to inhibit tin loss and zinc loss during selenization. Vacuum co-evaporation technique is not feasible to mass production, due to facility difficulty and bad uniformity. And H2Se is toxic and dangerous. We have developed these metallic precursor stacks vacuum deposition process and two-step selenium vapor selenization process. We believe this technique is more suitable for potential mass production in future.
The properties of CZTSe thin-films and the performance of CZTSe thin-film solar cells have been characterized using techniques, including J-V, Raman spectroscopy, spectral response, and SEM/EDS. The best performance CZTSe thin-film solar cell that have been accomplished, has an open circuit voltage of 0.42 volt, shirt circuit current densities of 14.5 mA/cm2, fill factor of 47%, and efficiency of 2.86%.
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Mikoliunaite, Lina, Raul D. Rodriguez, Evgeniya Sheremet, Vladimir Kolchuzhin, Jan Mehner, Arunas Ramanavicius, and Dietrich R. T. Zahn. "The substrate matters in the Raman spectroscopy analysis of cells." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-178060.
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Raman spectroscopy is a powerful analytical method that allows deposited and/or immobilized cells to be evaluated without complex sample preparation or labeling. However, a main limitation of Raman spectroscopy in cell analysis is the extremely weak Raman intensity that results in low signal to noise ratios. Therefore, it is important to seize any opportunity that increases the intensity of the Raman signal and to understand whether and how the signal enhancement changes with respect to the substrate used. Our experimental results show clear differences in the spectroscopic response from cells on different surfaces. This result is partly due to the difference in spatial distribution of electric field at the substrate/cell interface as shown by numerical simulations. We found that the substrate also changes the spatial location of maximum field enhancement around the cells. Moreover, beyond conventional flat surfaces, we introduce an efficient nanostructured silver substrate that largely enhances the Raman signal intensity from a single yeast cell. This work contributes to the field of vibrational spectroscopy analysis by providing a fresh look at the significance of the substrate for Raman investigations in cell research.
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Picardi, Gennaro. "Raman spectroscopy and light emission at metal surfaces enhanced by the optical near field of a scanning tunneling tip." [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/191/index.html.
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Kalbacova, Jana [Verfasser]. "Micro- and tip-enhanced Raman spectroscopy of single-wall carbon nanotubes: from material studies to device applications / Jana Kalbacova." Chemnitz : Technische Universität Chemnitz, 2018. http://d-nb.info/1215909136/34.
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Brachmi, Rhizlane. "Congestion Mitigation Strategy:Modeling the Effect of Different Geometric Configurations of a Two-Lane On-Ramp on Capacity Using VISSIM." Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560189783503486.
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Liu, Kai. "Theoretical Characterization of Optical Processes in Modecular Complexes." Doctoral thesis, Stockholm : Bioteknologi, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4629.
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Sheremet, Evgeniya. "Micro- and Nano-Raman Characterization of Organic and Inorganic Materials." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-188175.
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Die Raman-Spektroskopie ist eine der nützlichsten optischen Methoden zur Untersuchung der Phononen organischer und anorganischer Materialien. Mit der fortschreitenden Miniaturisierung von elektronischen Bauelementen und der damit einhergehenden Verkleinerung der Strukturen von der Mikrometer- zur Nanometerskala nehmen das Streuvolumen und somit auch das Raman-Signal drastisch ab. Daher werden neue Herangehensweisen benötigt um sie mit optischer Spektroskopie zu untersuchen. Ein häufig genutzter Ansatz um die Signalintensität zu erhöhen ist die Verwendung von Resonanz-Raman-Streuung, das heißt dass die Anregungsenergie an die Energie eines optischen Überganges in der Struktur angepasst wird. In dieser Arbeit wurden InAs/Al(Ga)As-basierte Multilagen mit einer Periodizität unterhalb des Beugungslimits mittels Resonanz-Mikro-Raman-Spektroskopie und Raster-Kraft-Mikroskopie (AFM) den jeweiligen Schichten zugeordnet.
Ein effizienterer Weg um die Raman-Sensitivität zu erhöhen ist die Verwendung der oberflächenverstärkten Raman-Streuung (SERS). Sie beruht hauptsächlich auf der Verstärkung der elektromagnetischen Strahlung aufgrund von lokalisierten Oberflächenplasmonenresonanzen in Metallnanostrukturen.
Beide oben genannten Signalverstärkungsmethoden wurden in dieser Arbeit zur oberflächenverstärkten Resonanz-Raman-Streuung kombiniert um geringe Mengen organischer und anorganischer Materialien (ultradünne Cobalt-Phthalocyanin-Schichten (CoPc), CuS und CdSe Nanokristalle) zu untersuchen. Damit wurden in beiden Fällen Verstärkungsfaktoren in der Größenordnung 103 bis 104 erreicht, wobei bewiesen werden konnte, dass der dominante Verstärkungsmechanismus die elektromagnetische Verstärkung ist.
Spitzenverstärkte Raman-Spektroskopie (TERS) ist ein Spezialfall von SERS, bei dem das Auflösungsvermögen von Licht unterschritten werden kann, was zu einer drastischen Verbesserung der lateralen Auflösung gegenüber der konventionellen Mikro-Raman-Spektroskopie führt. Dies konnte mit Hilfe einer Spitze erreicht werden, die als einzelner plasmonischer Streuer wirkt. Dabei wird die Spitze in einer kontrollierten Weise gegenüber der Probe bewegt. Die Anwendung von TERS erforderte zunächst die Entwicklung und Optimierung eines AFM-basierten TERS-Aufbaus und TERS-aktiver Spitzen, welche Gegenstand dieser Arbeit war. TERS-Bilder mit Auflösungen unter 15 nm konnten auf einer Testprobe mit kohlenstoffhaltigen Verbindungen realisiert werden. Die TERS-Verstärkung und ihre Abhängigkeit vom Substratmaterial, der Substratmorphologie sowie der AFM-Betriebsart wurden anhand der CoPc-Schichten, die auf nanostrukturierten Goldsubstraten abgeschieden wurden, evaluiert. Weiterhin konnte gezeigt werden, dass die hohe örtliche Auflösung der TERS-Verstärkung die selektive Detektion des Signals weniger CdSe-Nanokristalle möglich macht.
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KESNER, LORI ANN. "KRISHNA MEETS PAN: INDIAN-WESTERN FUSION IN TWO WORKS FOR FLUTE AND HARP BY RAVI SHANKAR AND JOHN MAYER." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154446863.
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Braun, Kai [Verfasser], and Alfred J. [Akademischer Betreuer] Meixner. "Multimodal Tip Enhanced Raman Microscopy with a Cylindrical Vector Beam Focused by a Parabolic Mirror / Kai Braun ; Betreuer: Alfred J. Meixner." Tübingen : Universitätsbibliothek Tübingen, 2014. http://d-nb.info/1162970758/34.
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Martina, Manuel [Verfasser], and Monika [Akademischer Betreuer] Fleischer. "Large-area fabrication of pyramidal plasmonic nanoprobes and their characterisation in tip-enhanced Raman spectroscopy applications / Manuel Martina ; Betreuer: Monika Fleischer." Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1167246802/34.
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Nishizawa, Norihiko, Ryuji Okamura, and Toshio Goto. "Simultaneous generation of wavelength tunable two-colored femtosecond soliton pulses using optical fibers." IEEE, 1999. http://hdl.handle.net/2237/6771.
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