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Ramani, Anand [Verfasser], Jay [Akademischer Betreuer] Gopalakrishnan und Thomas [Akademischer Betreuer] Klein. „Role of Sas-4/CPAP in building functional centrosomes and cilia / Anand Ramani ; Jay Gopalakrishnan, Thomas Klein“. Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2019. http://d-nb.info/1200207106/34.
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Ramani, Mohan Ramkumar [Verfasser], Jan [Gutachter] Hansmann, Franz [Gutachter] Jakob und Heike [Gutachter] Walles. „Effect of Mechanical Stress On Stem Cells to Improve Better Bone Regeneration / Ramkumar Ramani Mohan ; Gutachter: Jan Hansmann, Franz Jakob, Heike Walles“. Würzburg : Universität Würzburg, 2021. http://d-nb.info/1236503643/34.
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Begam, Gulnahar. „Prachin bangalir ramanir besh o bhushan : adikal theke 1200 প্রাচীন বাঙালির রমণীর বেশ ও ভূষণ : আদিকাল থেকে ১২০০ খ্রীস্টাব্দ পর্যন্ত“. Thesis, Rajshahi University, 1996. http://hdl.handle.net/123456789/1708.
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Ali, Momenpour. „Raman Biosensors“. Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36468.
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This PhD thesis focuses on improving the limit of detection (LOD) of Raman biosensors by using surface enhanced Raman scattering (SERS) and/or hollow core photonic crystal fibers (HC-PCF), in conjunction with statistical methods. Raman spectroscopy is a multivariate phenomenon that requires statistical analysis to identify the relationship between recorded spectra and the property of interest. The objective of this research is to improve the performance of Raman biosensors using SERS techniques and/or HC-PCF, by applying partial least squares (PLS) regression and principal component analysis (PCA).
I began my research using Raman spectroscopy, PLS analysis and two different validation methods to monitor heparin, an important blood anti-coagulant, in serum at clinical levels. I achieved lower LOD of heparin in serum using the Test Set Validation (TSV) method. The PLS analysis allowed me to distinguish between weak Raman signals of heparin in serum and background noise.
I then focused on using SERS to further improve the LOD of analytes, and accomplished simultaneous detection of GLU-GABA in serum at clinical levels using the SERS and PLS models. This work demonstrated the applicability of using SERS in conjunction with PLS to measure properties of samples in blood serum. I also used SERS with HC-PCF configuration to detect leukemia cells, one of the most recurrent types of pediatric cancers. This was achieved by applying PLS regression and PCA techniques.
Improving LOD was the next objective, and I was able to achieve this by improving the PLS model to decrease errors and remove outliers or unnecessary variables. The results of the final optimized models were evaluated by comparing them with the results of previous models of Heparin and Leukemia cell detection in previous sections.
Finally, as a clinical application of Raman biosensors, I applied the enhanced Raman technique to detect polycystic ovary syndrome (PCOS) disease, and to determine the role of chemerin in this disease. I used SERS in conjunction with PCA to differentiate between PCOS and non-PCOS patients. I also confirmed the role of chemerin in PCOS disease, measured the level of chemerin, a chemoattractant protein, in PCOS and non-PCOS patients using PLS, and further improved LOD with the PLS regression model, as proposed in previous section.
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Razmutė-Razmė, Inga. „Vibrational spectroscopic studies on the structure and interaction with solution components of bifunctional organic compounds adsorbed at metal electrodes“. Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091215_091605-81688.
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The indole and phenole rings comprise the main part of tryptophan and tyrosine side chains in proteins and play an important role in the stabilization of tertiary structure, interaction with active centers in biomolecules, and electron transfer phenomena. To get better insight into the interactions of these functional groups, the artificial monomolecular structures have been constructed from the synthesized bifuncional compounds with thiol and indole or phenole ring functional groups able to form self-assembled monolayers on gold, silver and copper electrodes. Properties of these monolayers were studied by Raman, infrared, and sum-frequency generation spectroscopies.
The main tasks of this work were to assess the adsorption peculiarities of the bifunctional thiols at the initial stage of the monolayer formation, to determine the influence of the electrode nature on the monolayer structure, and to establish the potential influence on the properties of the terminal functional groups.
It was demonstrated for the first time that at the initial stage of monolayer formation the methylene groups interact with the metal surface. Evidence for the metal-induced lowering of the CH stretching mode frequency down to 2820 cm-1 was provided. It was demonstrated that indole ring interacts with the Ag electrode surface at sufficiently negative potentials and this interaction can be recognized from the downshift of the W16 mode from ~ 1010 cm-1 to ~ 1001 cm-1. Investigations of indole... [to full text]Triptofano ir tirozino aminorūgščių funkcinės grupės – indolo ir fenolio žiedai, stabilizuoja baltymų tretinę struktūrą, sąveikauja su aktyviais centrais biomolekulėse, dalyvauja elektronų pernašos procesuose. Siekiant giliau suprasti kaip šios grupės sąveikauja, buvo sukonstruotos dirbtinės monosluoksninės struktūros, sudarytos iš susintetintų bifunkcinių junginių, turinčių galines tiolio ir indolo žiedo arba fenolio žiedo grupes ir gebančių formuoti savitvarkius monosluoksnius ant aukso, sidabro ir vario elektrodų. Jų savybės ištirtos Ramano, infraraudonosios ir suminio dažnio generacijos spektroskopijų metodais. Pagrindiniai darbo tikslai buvo nustatyti bifunkcinių alkantiolių struktūrą ir adsorbcijos ypatumus pradinėje monosluoksnio formavimosi stadijoje, elektrodo prigimties įtaką monosluoksnių struktūrai ir potencialo įtaką galinių funkcinių grupių savybėms. Paviršiaus sustiprintos Ramano spektroskopijos metodu pirmą kartą parodyta, kad pradinėse monosluoksnių formavimo stadijose metileno grupės sąveikauja su metalo paviršiumi. Darbe įrodyta, kad dėl sąveikos su metalu spektruose atsiranda žemesnio dažnio („minkšta“) CH juosta ties 2820 cm-1. Pirmą kartą parodyta, kad indolo žiedas sąveikauja su Ag paviršiumi, esant pakankamai neigiamiems potencialams ir tą sąveiką galima spektriškai atpažinti pagal W16 modos ties ~1010 cm-1 dažnio sumažėjimu iki ~ 1001 cm-1. Tiriant indolo žiedu terminuotus ir mišrius monosluoksnius su įterptomis oktadekantiolio molekulėmis nustatytas... [toliau žr. visą tekstą]
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Razmutė-Razmė, Inga. „Bifunkcinių organinių junginių adsorbuotų ant metalinių elektrodų, struktūros ir sąveikos su tirpalo komponentais tyrimas virpesių spektroskopijos metodais“. Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091215_091625-86896.
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Triptofano ir tirozino aminorūgščių funkcinės grupės – indolo ir fenolio žiedai, stabilizuoja baltymų tretinę struktūrą, sąveikauja su aktyviais centrais biomolekulėse, dalyvauja elektronų pernašos procesuose. Siekiant giliau suprasti kaip šios grupės sąveikauja, buvo sukonstruotos dirbtinės monosluoksninės struktūros, sudarytos iš susintetintų bifunkcinių junginių, turinčių galines tiolio ir indolo žiedo arba fenolio žiedo grupes ir gebančių formuoti savitvarkius monosluoksnius ant aukso, sidabro ir vario elektrodų. Jų savybės ištirtos Ramano, infraraudonosios ir suminio dažnio generacijos spektroskopijų metodais.
Pagrindiniai darbo tikslai buvo nustatyti bifunkcinių alkantiolių struktūrą ir adsorbcijos ypatumus pradinėje monosluoksnio formavimosi stadijoje, elektrodo prigimties įtaką monosluoksnių struktūrai ir potencialo įtaką galinių funkcinių grupių savybėms.
Paviršiaus sustiprintos Ramano spektroskopijos metodu pirmą kartą parodyta, kad pradinėse monosluoksnių formavimo stadijose metileno grupės sąveikauja su metalo paviršiumi. Darbe įrodyta, kad dėl sąveikos su metalu spektruose atsiranda žemesnio dažnio („minkšta“) CH juosta ties 2820 cm-1. Pirmą kartą parodyta, kad indolo žiedas sąveikauja su Ag paviršiumi, esant pakankamai neigiamiems potencialams ir tą sąveiką galima spektriškai atpažinti pagal W16 modos ties ~1010 cm-1 dažnio sumažėjimu iki ~ 1001 cm-1. Tiriant indolo žiedu terminuotus ir mišrius monosluoksnius su įterptomis oktadekantiolio molekulėmis nustatytas... [toliau žr. visą tekstą]The indole and phenole rings comprise the main part of tryptophan and tyrosine side chains in proteins and play an important role in the stabilization of tertiary structure, interaction with active centers in biomolecules, and electron transfer phenomena. To get better insight into the interactions of these functional groups, the artificial monomolecular structures have been constructed from the synthesized bifuncional compounds with thiol and indole or phenole ring functional groups able to form self-assembled monolayers on gold, silver and copper electrodes. Properties of these monolayers were studied by Raman, infrared, and sum-frequency generation spectroscopies. The main tasks of this work were to assess the adsorption peculiarities of the bifunctional thiols at the initial stage of the monolayer formation, to determine the influence of the electrode nature on the monolayer structure, and to establish the potential influence on the properties of the terminal functional groups. It was demonstrated for the first time that at the initial stage of monolayer formation the methylene groups interact with the metal surface. Evidence for the metal-induced lowering of the C−H stretching mode frequency down to 2820 cm-1 was provided. It was demonstrated that indole ring interacts with the Ag electrode surface at sufficiently negative potentials and this interaction can be recognized from the downshift of the W16 mode from ~ 1010 cm-1 to ~ 1001 cm-1. Investigations of indole ring... [to full text]
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Verma, Tarishi. „The Legitimacy of Online Feminist Activism: Subversion of Shame in Sexual Assault by Reporting it on Social Media“. Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1617396334881314.
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Kunarajah, Enoch Arumaishanth. „Distributed Raman amplifiers“. Thesis, University of Essex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399979.
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Nash, J. „Time resolved Raman scattering in liquid crystals using a Raman microprobe“. Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356443.
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Tanaka, Tomoyoshi. „Resonance raman and surface enhanced raman studies of hemeproteins and model compounds“. Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/27678.
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Delhaye, Caroline. „Spectroscopie Raman et microfluidique : application à la diffusion Raman exaltée de surface“. Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13927/document.
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Ce mémoire porte sur la mise au point de plateforme microfluidique couplée à la microscopie Raman confocale, utilisée dans des conditions d’excitation de la diffusion Raman (diffusion Raman exaltée de surface), dans le but d’obtenir une détection de très haute sensibilité d’espèces moléculaires sous écoulement dans des canaux de dimensions micrométriques. Ce travail a pour ambition de démontrer la faisabilité d’un couplage microscopie Raman/microfluidique en vue de la caractérisation in-situ et locale, des espèces et des réactions mises en jeu dans les fluides en écoulement dans les microcanaux. Nous avons utilisé un microcanal de géométrie T, fabriqué par lithographie douce, dans lequel sont injectées, à vitesse constante, des nanoparticules métalliques d’or ou d’argent dans une des deux branches du canal et une solution de pyridine ou de péfloxacine dans l’autre branche. La laminarité et la stationnarité du processus nous ont permis de cartographier la zone de mélange et de mettre en évidence l’exaltation du signal de diffusion Raman de la pyridine et de la péfloxacine, obtenue grâce aux nanoparticules métalliques, dans cette zone d’interdiffusion. L’enregistrement successif de la bande d’absorption des nanoparticules d’argent (bande plasmon) et du signal de diffusion Raman de la péfloxacine, en écoulement dans un microcanal, nous a permis d’établir un lien entre la morphologie des nanostructures métalliques, et plus précisément l’état d’agrégation des nanoparticules d’argent, et l’exaltation du signal Raman de la péfloxacine observé. Nous avons alors modifié la géométrie du canal afin d’y introduire une solution d’électrolyte (NaCl et NaNO3) et de modifier localement la charge de surface des colloïdes d’argent en écoulement. Nous avons ainsi confirmé que la modification de l’état d’agrégation des nanoparticules d’argent, induite par l’ajout contrôlé de solutions d’électrolytes, permet d’amplifier le signal SERS de la péfloxacine et d’optimiser la détection en microfluidique. Enfin, nous avons développé une seconde approche qui consistait à mettre en place une structuration métallisée des parois d’un microcanal. Nous avons ainsi démontré que la fonctionnalisation chimique de surface via un organosilane (APTES) permettait de tapisser le canal avec des nanoparticules d’argent et d’amplifier le signal Raman des espèces en écoulement dans ce même microcanalThis thesis focuses on the development of a microfluidic platform coupled with confocal Raman microscopy, used in excitation conditions of Raman scattering (Surface enhanced Raman scattering, SERS) in order to gain in the detection sensitivity of molecular species flowing in channels of micrometer dimensions. This work aims to demonstrate the feasibility of coupling Raman microscopy / microfluidics for the in situ and local characterization of species and reactions taking place in the fluid flowing in microchannels. We used a T-shaped microchannel, made by soft lithography, in which gold or silver nanoparticles injected at constant speed, in one of the two branches of the channel and a solution of pyridine or pefloxacin in the other one. The laminar flow and the stationarity of the process allowed us to map the mixing zone and highlight the enhancement of the Raman signal of pyridine and pefloxacin, due to the metallic nanoparticles, in the interdiffusion zone. The recording of the both absorption band of the silver nanoparticles (plasmon band) and the Raman signal of pefloxacin, flowing in microchannel, allowed us to establish a link between the shape of the metallic nanostructure, and more precisely the silver nanoparticle aggregation state, and the enhancement of the Raman signal of pefloxacin observed. We then changed the channel geometry to introduce an electrolyte solution (NaCl and NaNO3) and locally modify the surface charge of the colloids. We have put in evidence that the change of the silver nanoparticle aggregation state, induced by the controlled addition of electrolyte solutions, could amplify the SERS signal of pefloxacin and thus optimizing the detection in microfluidics. At last, we established second a approach that consists in the metallic structuring of microchannel walls. This has shown that the surface chemical functionalization through organosilanes (APTES) allowed the pasting of the channel with silver nanoparticles, thus amplifying the Raman signal of the species flowing within the same microchannel
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Cazayous, Maximilien. „Interférences Raman et Nanostructures“. Phd thesis, Université Paul Sabatier - Toulouse III, 2002. http://tel.archives-ouvertes.fr/tel-00001850.
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Les structurations de la matière à l'échelle nanométrique ont ouvert de larges champs d'étude. L'analyse des propriétés structurales des nanostructures, de leur degré d'organisation ainsi que leur influence sur les propriétés électroniques représentent actuellement un défi de première importance. Pour accéder à ces informations, il est souvent nécessaire de faire appel à un ensemble de techniques expérimentales et numériques souvent complexes dans leur mise en oeuvre. Dans cette contribution, nous étudions l'organisation et le confinement électronique dans des multiplans de boîtes quantiques, en nous appuyant à la fois sur une étude expérimentale et un travail de modélisation. Les interférences Raman, observées dans la gamme des phonons acoustiques, résultent de l'interaction entre ces derniers et les états électroniques localisés dans les nanostructures. Parce qu'ils explorent une gamme allant de quelques nanomètres à plusieurs centaines de nanomètres, les phonons acoustiques représentent une sonde particulièrement efficace pour l'étude des nanosystèmes. Les interférences Raman utilisent leur sensibilité pour la mesure des propriétés structurales et électroniques. Elles permettent de mesurer les effets de corrélation verticale et latérale dans les multiplans de boîtes quantiques. Nous avons développé un modèle général dont le domaine d'application s'étend des systèmes contenant quelques plans au super-réseaux. En utilisant l'analyse de Fourier des interférences, on détermine la fonction d'auto-corrélation de la densité de probabilité électronique selon l'axe de croissance. Sensible à la taille et à la forme de la densité électronique, les interférences Raman ouvrent la voie à une imagerie optique de la densité électronique.
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Wiley, James Hugh. „Raman spectra of celluloses“. Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5748.
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Hagen, Johannes. „Spektral beherrschter Raman-Faserlaser /“. Aachen : Shaker, 2008. http://d-nb.info/988549115/04.
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Grantier, David Raymond. „Chemically induced raman scattering“. Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30321.
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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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Patil, Raj. „Deep UV Raman Spectroscopy“. Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/613378.
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This thesis examines the performance of a custom built deep UV laser (257.5nm) for Raman spectroscopy and the advantages of Raman spectroscopy with a laser in the deep UV over a laser in the visible range (532 nm). It describes the theory of resonance Raman scattering, the experimental setup for Raman spectroscopy and a few Raman spectroscopy measurements. The measurements were performed on biological samples oak tree leaf and lactobacillus acidophilus and bifidobacteria from probotioc medicinal capsules. Fluorescence free Raman spectra were acquired for the two samples with 257.5 nm laser. The Raman spectra for the two samples with a 532nm laser was masked with fluorescence. Raman measurements for an inorganic salt sodium nitrate showed a resonance Raman effect with 257.5 nm laser which led to enhancement in the Raman intensity as compared to that with 532 nm laser. Therefore we were able to demonstrate two advantages of deep UV Raman spectroscopy. First one is the possibility of acquiring fluorescence free spectra for biological samples. Second is the possibility of gaining enhancement in Raman intensity due to resonance Raman effect. It was observed that 257.5 nm laser requires optimization to reduce the bandwidth of the laser to get better resolution. The 257.5 nm laser also needs to be optimized to obtain higher power to get better signal to noise ratio. The experimental setup can also be further improved to obtain better resolution. If the improvements required in the setup are implemented, the deep UV Raman setup will become an important tool for spectroscopy.
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Nathaniel, Todd. „Spatial heterodyne Raman spectroscopy“. Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/810642/.
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Céreyon, Arnaud. „Amplification Raman et nanostructures“. Lyon 1, 2008. http://www.theses.fr/2008LYO10133.
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Maher, Robert Christopher. „Surface enhanced Raman scattering“. Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/7843.
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Petrak, Benjamin James. „Microcavity Enhanced Raman Scattering“. Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6354.
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Raman scattering can accurately identify molecules by their intrinsic vibrational frequencies, but its notoriously weak scattering efficiency for gases presents a major obstacle to its practical application in gas sensing and analysis. This work explores the use of high finesse (50 000) Fabry-Pérot microcavities as a means to enhance Raman scattering from gases. A recently demonstrated laser ablation method, which carves out a micromirror template on fused silica--either on a fiber tip or bulk substrates-- was implemented, characterized, and optimized to fabricate concave micromirror templates ~10 µm diameter and radius of curvature. The fabricated templates were coated with a high-reflectivity dielectric coating by ion-beam sputtering and were assembled into microcavities ~10 µm long and with a mode volume ~100 µm3. A novel gas sensing technique that we refer to as Purcell enhanced Raman scattering (PERS) was demonstrated using the assembled microcavities. PERS works by enhancing the pump laser's intensity through resonant recirculation at one longitudinal mode, while simultaneously, at a second mode at the Stokes frequency, the Purcell effect increases the rate of spontaneous Raman scattering by a change to the intra-cavity photon density of states. PERS was shown to enhance the rate of spontaneous Raman scattering by a factor of 107 compared to the same volume of sample gas in free space scattered into the same solid angle subtended by the cavity. PERS was also shown capable of resolving several Raman bands from different isotopes of CO2 gas for application to isotopic analysis. Finally, the use of the microcavity to enhance coherent anti-Stokes Raman scattering (CARS) from CO2 gas was demonstrated.
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Calizo, Irene Gonzales. „Raman nanometrology of graphene“. Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359892.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 8, 2010). Includes bibliographical references (p. 59-64). Also issued in print.
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Bergqvist, Saga. „Raman spectroscopy in neurosurgery“. Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-78665.
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Brain tumors or brain cancer is a disease than affects people of all ages. The median age of a person living with a brain tumor is 60 years, it is however a disease that affects children and young adults in high grade. Brain cancer is the second most common type of cancer among children and is also the most common cause of cancer related death among this group. To ensure that the damages on the brain is as small as possible, it is important that a tumor can be diagnosed and removed as early as possible. Previous methods of diagnosis is based on biopsy where a part of the tumor is removed and examinated by a pathologist. This is a time consuming process that also is biased by the human factor, there is therefore a need for a method that can be used \textit{in situ} with an unbiased result. One method that have shown great promise is photensitation with 5-Aminolevoluic acid (5-ALA). However, this method have shown to only work properly on tumors of high malignancy in adults. As a comlpiment to photosentisation, Raman spectroscopy have shown good promise in previous studies. This study was conducted to investigate the use of Raman spectroscopy as a tool for \textit{in situ} brain tumor diagnostics. The use of Raman spectroscopy was tested by comparing two previously performed studies, where they looked at a number of Raman bands from biological markers that are known to change in cancerous tissue as well as the intensity ratio between some Raman bands. A measurement system for Raman spectroscopy was designed and built at Luleå University of Technology where the system were evaluated on tissue samples from conventional meat i.e. pork and beef to ensure that is was possible to achieve spectroscopic information of protein and lipid content in tissue. The measurement system was then transported to Linköpings University where the measurements on six brain tissue samples where performed. The samples came from five different tumors of which one tumor was thought to come from a high malignant tumor based on preliminary histopathological analysis and four from low malignant or benign tumors. Two samples where obtained from the high malignant tumor that was photosentisized with 5-Aminolevoluic acid and one of the samples where illuminated with blue light prior to the Raman spectroscopic measurements. The spectroscopic data was pre-processed before analysis using conventional methods. The analysed spectra from the brain tissue samples showed presence of the Raman bands associated with brain tissue. It was also possible to see Raman bands associated with 5-ALA in the samples that had been photosentisized, however when the tissue had been illuminated with blue light it was also possible to see distinct Raman bands associated with brain tissue. One tissue sample also showed presence of reduced Neuroglobin (NGB). The composition of NGB is also known to change in tumorous tissue and could therefore be used in future work as a biological marker for brain tumors. When comparing the results obtained in this study with the two previously performed, one of the studies showed that two samples were from a tumor of high malignancy and the other from low malignant or benign tumors. This result was in accordance with the preliminary histopathological assessment of the brain tissue samples. When comparing the results to the other study, the results where contradictory and indicated that all tissue samples where from low malignant or benign tumors. The conclusion of this work is that Raman spectroscopy is possible to use as a tool for brain tumor diagnostics. It would be desirable to use this method in combination with 5-ALA staining since the Raman bands from brain tissue could be resolved when the tissue had been illuminated with blue light.Hjärntumörer kan drabba människor i alla åldrar, medelåldern för människor som lever med en hjärntumör är 60 år, men det är ett tillstånd som även drabbar barn och unga i stor utsträckning. Hjärntumörer är den näst vanligaste cancerformen hos barn och är även den främsta orsaken till cancerrelaterad död i den åldergruppen. För att minimera skadorna på hjärnan är det viktigt att en tumör kan lokaliseras och tas bort så tidigt som möjligt. De metoder som används idag bygger framför allt på biopsi, där en del av tumören tas bort och undersöks av en histopatalog. Det är en process som tar lång tid och även påverkas av den mänskliga faktorn, det finns därmed ett behov av en metod som kan avändas \textit{in situ} som ger ett resultat som inte påverkas av den mänskliga faktorn. En metod som har visat lovande resultat är fotosensibilisering med 5-Aminolevulinsyra (5-ALA). Desvärre har den metoden bara visat sig fungera bra för högmaligna tumörer hos vuxna. Som ett komplement till fotosensibilisering har Ramanspektroskopi visat lovande resultat i tidigare genomförda studier. Det här arbetet genomfördes för att undersöka användningen av Ramanspektroskopi som ett verktyg för diagnostisering av hjärntumörer. Som grund användes två tidigare genomförda studier där de undersökte Ramanband från biologiska markörer i hjärnvävnad som ändras i cancerogen vävnad. De undersökte även hur den biokemiska sammansättningen av hjärnvävnaden ändrades genom att jämföra intensiteten av olika Ramanband. Ett mätsystem för Ramanspektroskopi designades och byggdes upp på Luleå Tekniska Universitet där det även testades på vävnad från kött (fläsk och biff). Därefter transporterades mätsystemet till Linköpings Universitet för att genomföra mätningar på sex olika vävnadsprov från fem hjärntumörer av olika malignitet. Baserat på en preliminär histopatalogisk bedömning var en av tumörerna högmalignt och de fyra andra tumörerna var antingen lågmalignta eller benigna. Två av proverna som undersöktes kom från den högmalignta tumören som även var fotosensibilierad med 5-Aminolevulinsyra, varav ett av proverna var belyst med blått ljus innan de Ramanspektroskopiska mätningarna genomfördes. Innan resultatet från Ramanspektroskopiska mätningarna analyserades behandlades datan med konventionella metoder i MatLab. I de resulterade spektrumen gick det att se tydliga Ramanband associerade med hjärnvävnad. Det gick även att se Ramanband associerade med 5-ALA i de två prover som var fotosensibiliserade och i det provet som var belyst med blått ljus innan de spektroskopiska mätningarna gjordes gick det även att se tydliga Ramanband associerade med hjärnvävnad. När resultatet analyserades gick det även att se spektra associerat med reducerat Neuroglobin (NGB) i ett av proverna. Sammansättningen av NGB är också någonting som ändras i cancerogen vävnad och skulle därför också kunna användas som en bilogisk markör för hjärntumörer i framtida studier. När resultaten från den här studien jämfördes med de tidigare studierna indikerade den ena studien att två av vävnadsproverna kom från en högmalignt tumör och att de resterande fyra från lågmaligna eller benigna tumörer, vilket stämmer överens med den preliminära diagnosticeringen av tumörerna. När resultatet istället jämfördes med den andra studien stämde inte resultatet lika bra med den preliminära diagnosticeringen av tumörerna. Metoden presenterad av Zhou m.fl. indikerade att alla tumörer kom från lågmaligna eller benigna tumörer. Slutsaten av det här arbetet är att Ramanspektroskopi skulle kunna användas som en metod för diagnosticering av hjärntumörer. Metoden skulle även fungera bra som ett komplement till fotosensibilisering med 5-ALA eftersom att det var möjligt att se Ramanband associerade med hjärnvävnad när vävnaden hade belysts med blått ljus.
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Cancado, Luiz Gustavo de Oliveira Lopes. „Raman spectroscopy of nanographites“. Universidade Federal de Minas Gerais, 2006. http://hdl.handle.net/1843/IACO-6W8NYM.
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This work presents the application of the Raman spectroscopy for the study and characterization of nanographite systems. We report the ¯rst detection of nanographite ribbons on a highly oriented pyrolytic graphite substrate by Raman spectroscopy. We found a way to di®erentiate the Raman signal of the ribbon from that of the substrate, the Raman signal of the ribbon having the same order of magnitude as the one of the substrate, despite the much smaller number of illuminated carbon atoms (»10¡3). The results show that these structures present van Hove singularities in the electronic density of states due to quantum con¯nement into their 1D structure. In another experiment, we use micro-Raman scattering to determine the arrangement of carbon atoms in a graphite edge. Theedge of a semi-in¯nite plane can be considered as a one-dimensional defect, leading to unusual defect-induced Raman scattering that turns out to be structurally selective. In this case, Raman scattering can be used to de¯ne the orientation of the carbon hexagons with respect to the edge of a graphite plane, in the so called armchair and zigzag arrange-ments. These two experiments involve the ¯rst detection of the anisotropy in the optical absorption of graphite, giving strong support to previous theoretical predictions. We also present a systematic study of the ratio between the integrated intensities of the disorder-
induced D band and the ¯rst-order allowed G band (ID=IG) in the Raman spectra of nanographite samples with di®erent crystallite sizes (La) and using di®erent excitation laser energies (wavelengths). The crystallite size La of the nanographite samples were obtained both by X-ray di®raction using synchrotron radiation and directly from scan-
ning tunneling microscopy images. A general equation for the determination of La using any laser energy in the visible range is obtained. Moreover, we performed measurements
of the absolute intensities of individual features in the Raman spectra of nanographites,showing the dependence of these features on the excitation laser energy and crystallite size.Resumo: No presente trabalho investigamos alguns efeitos físicos que acontecem na estrutura e evolução estelar. Focalizamos nossa atenção em estrelas de baixa massa na pré-sequência principal. Incluímos alguns efeitos físicos no código de estrutura e evolução estelar ATON2.3, escrito pelo Dr. Ítalo Mazzitelli (1989) e posteriormente modificado pelo Dr. Luiz Themystokliz Sanctos Mendes (1999b) para adicionar os efeitos de rotação e redistribuição interna de momento angular. Com o objetivo de economizar tempo computacional, introduzimos o mecanismo de parada de controle (checkpoint), que permite iniciar uma dada execução em um estágio de evolução intermideário, desde que os passos iniciais tenham sido devidamente registrados. Essas modificações foram feitas juntamente com um controle completo de variáveis não inicializadas, precisão e reestruturação do programa, visando futuramente paralelizar o código. Introduzimos efeitos combinados de rotação e forças de maré na configuração de equilíbrio das estrelas. Estes efeitos perturbadores, contidos na função potencial total, desviam a forma da estrela da aproximação esfericamente simétrica. Usamos o método de Kippenhahn & Thomas (1970), posteriormente aperfeiçoado por Enda & Sofia (1976). À função potencial obtida por estes autores, adicionamos termosrelacionados à forças de maré e àqueles relacionados à parte não simétrica do potencial gravitacional devido à distorção que tais forças causam na figura da estrela. Seguindo esta aproximação, corrigimos as equações constitutivas a fim de obter uma configuração estrutural de uma estrela distorcida. Cálculos de constantes de estrutura interna e raios de giração foram incluídos no código. Várias trilhas evolutivas foram geradas com os novos modelos, incluindo as quantidades mencionadas acima. Os novos modelos foram testados através de dados observacionais das dimensões absolutas, taxa de movimento apsidal e abundância de lítio das componentes do sistema binário eclipsante EK Cephei. No presente trabalho, também apresentamos estimativas teóricas do convective turnover time, Tc e Números de Rossby, Ro, para estrelas com massas semelhantes à massa solar, com rotação e na pré-sequência principal. Ro está relacionado com a força magnética na teoria do dínamo e, pelo menos para estrelas na seqüência principal, observa-se uma correlação entre rotação e atividade estelar. Incluímos também a possibilidade de utilizar modelos de atmosferas não cinza, com o objetivo de seguir a evolução estelar de estrelas de baixa massa desde estágiosbem iniciais, caracterizados por baixa gravidade. Adotamos os modelos NextGen e ATLAS9 de atmosferas estelares. Usando os nossos novos modelos não-cinza, geramos vários conjuntos de trilhas evolutivas, partindo da pré-sequência principal. Tais trilhas foram usadas para investigar algumas propriedades físicas e rotacionais de estrelas jovens na Nebulosa de Orion. Comparações entre resultados teóricos e dados observacionais, permitiram-nos obter informações sobre esta classe de objetos, principalmente no que diz respeito à distribuição inicial de momento angular. A interpretação dos dados depende fortemente das considerações físicas feitas no modelos, sendo a eficiência da convecção a mais importante. Nossa análise indica que um segundo parâmentro é necessário para descrever a convecção na pré-sequência principal. Tal parâmetro está possivelmente relacionado ao efeito estrutural de um campo magnético gerado por efeito dínamo.
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SPEISER, EUGEN. „Raman spectroscopy on nanostructures“. Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/566.
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One of the most current and also most promising fields of research in solid state physics is that of nano-structured materials. In particular, there is a great interest in nanostructured semiconductors, thanks to the latest developments in preparation techniques. These techniques allow to prepare nano-sized semiconductors with excellent crystalline structure and most often also with epitaxially determined orientations with respect to a template.
The interest in nano-structures is triggered by the discovery that their physical properties (electronic, optical, thermodynamical) are different from those of the corresponding bulk material due to confinement. Consequently, the size becomes a new design parameter for new electronic and optoelectronic devices, for example.
The goal of this work is to study nano-structures by optical methods, especially by Raman spectroscopy. 1-dimensional nano-structures are the main focus because of their recently intensively investigated and improved growth mechanisms. This research enables the synthesis of nano-materials of high crystalline quality, controlled orientation and size.
To obtain measurements from 1- dimensional (quantum wires, nanorods, nanotubes) and 0-dimensional nanostructures (quantum dots)—in contrast to well-investigated 2- dimensional quantum wells—an additional requirement for the measurement technique is that the probe must provide lateral resolution in the nanometer range. This requirement excludes or limits many of the standard surface science techniques and is especially true for the standard optical tools with diffraction limited spatial resolution in the sub-micrometer range. If possible, samples with modified growth process parameters are chosen in order to reduce the spatial density of the nanostructures in a way that only one structure is contained in the probing area. The goal is to exclude averaging of their properties by summing contributions from different structures. This is achieved also by using confocal microscopy spectroscopy providing diffraction limited spatial resolution in the micrometer range (~ 1μm). Confocal micro Raman measurements are performed on low dimensional semiconductor structures such as Si, GaAs, AlGaAs, SnO2 and ZnO nanowires.
Another important goal of this work is to design and build a new experimental set-up in order to extend the spatial resolution to the nanometer range, exploiting near field optics in combination with scanning probe microscopy (Scanning Tunnelling Microscopy and Atomic Force Microscopy). This enables simultaneous measurements of topography and spectroscopy, thus permitting direct correlation of morphological and optical properties. Moreover the internal structure of nano-samples can be made accessible by optical spectroscopy. For this purpose an apertureless scanning near field optical microscope (a-SNOM) set-up was developed. Scanning Probe Microscopy (SPM) equipment was integrated into a confocal Raman spectroscopy apparatus and preliminary test measurements are performed.
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Dragomir, Fatu Ramona. „Étude et modélisation de la lubrification mixte et des modes d'avaries associés dans les paliers moteur“. Poitiers, 2009. http://theses.edel.univ-poitiers.fr/theses/2009/Dragomir-Fatu-Ramona/2009-Dragomir-Fatu-Ramona-These.pdf.
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La maîtrise des conditions de lubrification mixte est un challenge complexe à relever puisqu'elle nécessite d'appréhender plusieurs phénomènes couplés: écoulement du fluide entre les rugosités, déformations élastoplastiques des aspérités, usure des surfaces. Le but de cette étude est de proposer une approche des phénomènes de lubrification mixte dans le contexte des paliers moteur. Le premier chapitre donne un aperçu des principales études théoriques et modélisations numériques dédiées à l'analyse du comportement des paliers. Le deuxième chapitre est dédié au phénomène d'écoulement du fluide entre deux surfaces rugueuses. En partant du modèle proposé par Patir et Cheng, une nouvelle définition des facteurs d'écoulement est proposée. Ce modèle prend en compte la direction des textures de surface. Plusieurs calculs paramétriques ont permis de définir des critères de choix pour les surfaces de calcul utilisées pour déterminer les facteurs d'écoulement. Le but de chapitre 3 est de détailler trois principaux modèles de contact existants, de les comparer afin d'extraire les avantages et les inconvénients de chaque modèle et surtout de voir leurs applications dans l'étude de la lubrification mixte des paliers de moteurs. Afin de mieux comprendre leurs limites, les modèles statistiques ont été comparés à un modèle déterministe, en éléments finis. Le chapitre 4 est dédié à l'étude de l’usure. Trois modèles d'usure basés sur la loi d'Archard sont présentés. Les différents modèles d'écoulement, de contact et d'usure sont finalement intégrés dans un programme de calcul numérique et utilisés pour prédire le comportement d'un palier de tête de bielleControl of mixed lubrication conditions is a complex challenge to meet since it requires understanding of several coupled phenomena: fluid flow between rough surfaces, elasto-plastic deformation of asperities, surface wear. The goal of this study is to propose an approach of mixed lubrication conditions in the context of ICE bearings. The first part gives an overview of key theoretical and numerical modeling dedicated to the analysis of bearings in hydrodynamic and mixed conditions. The second chapter is dedicated to the phenomenon of flow between two rough surfaces. Starting from the model proposed by Cheng and Patir, a new definition of flow factors is proposed. This model takes into account the direction of surface textures. Several parametric calculations have identified selection criteria for rough surfaces used to determine the new flow factors coefficients. The purpose of Chapter 3 is to detail three existing statistical contact models of rough interface asperities. Several comparisons permit to extract the advantages and disadvantages of each model and especially to see their applications in the study of mixed lubrication in ICE bearings. To a better understanding of their limits, the statistical models were compared to a deterministic finite element model. Chapter 4 is dedicated to the study of wear. Three wear models based on Archard's law are detailed. Finally, the different flow, contact and wear models are integrated in a numerical prediction tool and used to simulate the behavior of a big-end connecting rod bearing
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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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Gühlke, Marina. „Oberflächenverstärkte Hyper-Raman-Streuung (SEHRS) und oberflächenverstärkte Raman-Streuung (SERS) für analytische Anwendungen“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17570.
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Hyper-Raman-Streuung folgt anderen Symmetrieauswahlregeln als Raman-Streuung und profitiert als nicht-linearer Zweiphotonenprozess noch mehr von verstärkten elektromagnetischen Feldern an der Oberfläche plasmonischer Nanostrukturen. Damit könnte die oberflächenverstärkte Hyper-Raman-Streuung (SEHRS) praktische Bedeutung in der Spektroskopie erlangen. Durch die Kombination von SEHRS und oberflächenverstärkter Raman-Streuung (SERS) können komplementäre Strukturinformationen erhalten werden. Diese eignen sich aufgrund der Lokalisierung der Verstärkung auf die unmittelbare Umgebung der Nanostrukturen besonders für die Charakterisierung der Wechselwirkung zwischen Molekülen und Metalloberflächen. Ziel dieser Arbeit war es, ein tieferes Verständnis des SEHRS-Effekts zu erlangen und dessen Anwendbarkeit für analytische Fragestellungen einzuschätzen. Dazu wurden SEHRS-Experimente mit Anregung bei 1064 nm und SERS-Experimente mit Anregung bei derselben Wellenlänge sowie mit Anregung bei 532 nm - für eine Detektion von SEHRS und SERS im gleichen Spektralbereich - durchgeführt. Als Beispiel für nicht-resonante Anregung wurden die vom pH-Wert abhängigen SEHRS- und SERS-Spektren von para-Mercaptobenzoesäure untersucht. Mit diesen Spektren wurde die Wechselwirkung verschiedener Silbernanostrukturen mit den Molekülen charakterisiert. Anhand von beta-Carotin wurden Einflüsse von Resonanzverstärkung im SEHRS-Experiment durch die gleichzeitige Anregung eines molekularen elektronischen Übergangs untersucht. Dabei wurde durch eine Thiolfunktionalisierung des Carotins eine intensivere Wechselwirkung mit der Silberoberfläche erzielt, sodass nicht nur resonante SEHRS- und SERS-Spektren, sondern auch nicht-resonante SERS-Spektren von Carotin erhalten werden konnten. Die Anwendbarkeit von SEHRS für hyperspektrale Kartierung in Verbindung mit Mikrospektroskopie wurde durch die Untersuchung von Verteilungen verschiedener Farbstoffe auf strukturierten plasmonischen Oberflächen demonstriert.Hyper-Raman scattering follows different symmetry selection rules than Raman scattering and, as a non-linear two-photon process, profits even more than Raman scattering from enhanced electromagnetic fields at the surface of plasmonic nanostructures. Surface-enhanced hyper-Raman scattering (SEHRS) could thus gain practical importance for spectroscopy. The combination of SEHRS and surface-enhanced Raman scattering (SERS) offers complementary structural information. Specifically, due to the localization of the enhancement to the close proximity of the nanostructures, this information can be utilized for the characterization of the interaction between molecules and metal surfaces. The aim of this work was to increase the understanding of the SEHRS effect and to assess its applicability to answer analytical questions. For that purpose, SEHRS experiments with excitation at 1064 nm and SERS experiments with excitation at the same wavelength, as well as with excitation at 532 nm - to detect SEHRS and SERS in the same spectral region - were conducted. As an example for non-resonant excitation, pH-dependent SEHRS and SERS spectra of para-mercaptobenzoic acid were examined. Based on these spectra, the interaction of different silver nanostructures with the molecules was characterized. beta-Carotene was used to study the influence of resonance enhancement by the excitation of a molecular electronic transition during SEHRS experiments. By the thiol-functionalization of carotene, a more intense interaction with the silver surface was achieved, which enables to obtain not only resonant SEHRS and SERS but also non-resonant SERS spectra of carotene. Hyperspectral SEHRS imaging in combination with microspectroscopy was demonstrated by analyzing the distribution of different dyes on structured plasmonic surfaces.
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Guo, Yu. „RAMAN SPECTROSCOPY OF GLASSESWITH HIGH AND BROAD RAMAN GAIN IN THE BOSON PEAK REGION“. Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4275.
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This thesis investigates Raman spectra of novel glasses and their correlation with structure for Raman gain applications. Raman gain for all-optical amplification by fibers depends significantly on the cross section for spontaneous Raman scattering allowing to compare signal strength and spectral coverage. We also investigate the relationship between glass structure and the Boson peak (enhancement of the low-frequency vibrational density of states) and report new inelastic neutron scattering spectra for niobium-phosphate glasses. Polarization resolved Raman spectra of glasses based on tellurite and phosphate formers have been measured from 6 – 1500 cm-1 using an excitation wavelength of 514 nm. The Tellurite glasses exhibit Raman Spectra at least 10 times more intense, are more spectrally uniform and possess spectral bandwidths more than a factor of two wider than fused silica. Assignments of the vibrational bands are presented and the compositional dependence of the spectra is discussed with respect to the molecular structure. Significantly high Boson peaks were found in the frequency range from 30-100 cm-1. The Raman gain curves were calculated from the polarized spontaneous Raman spectra. In particular, they show broad and flat band in the low frequency region (50-400 cm-1) suggesting that these glasses may be useful for Raman gain applications extending to very low frequencies. The inelastic neutron scattering spectra of the niobium-phosphate glasses display a pronounced low-frequency enhancement of the vibrational density of states. By averaging over the full accessible wavevector range we obtain an approximate spectral distribution of the vibrational modes. Through direct comparison with the Raman spectra we determine the Raman coupling function which shows a linear behavior near the Boson peak maximum. Possible mechanisms contributing to the low frequency Raman band such as disorder-induced irregular vibrational states are discussed.Ph.D.
Department of Physics
Sciences
Physics
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Ulrichs, Edzard. „Raman-Spektroskopie an niedrigdimensionalen Elektronensystemen“. [S.l. : s.n.], 2000. http://www.sub.uni-hamburg.de/disse/123/DISS.pdf.
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Mohammed, Abdelsalam. „Theoretical Studies of Raman Scattering“. Doctoral thesis, KTH, Teoretisk kemi (stängd 20110512), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28332.
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Different theoretical approaches have been presented in this thesis to study the Raman scattering effect. The first one is response theory applied up to third order of polarization, where the determination of α, β and γ is used to calculate linear Raman scattering (resonance Raman scattering (RRS) and normal Raman scattering (NRS)), hyper Raman scattering (HRS) and coherent anti-Stokes Raman scattering (CARS), respectively. The response theory refers to adiabatic time-dependent density functional theory in the complex domain with applications on RRS and NRS, and to a recently developed methodology (Thorvaldsen et al. [105, 106]) for the analytic calculation of frequency-dependentpolarizability gradients of arbitrary order, here with applications on CARSand HRS. Various systems have been studied with the response theory, such as explosive substances (DNT, TNT, RDX and H2O2), optical power limiting materials (platinum(II) acetylide molecules), DNA bases (methylguanine-methylcytosine) and other systems (Trans-1,3,5-hexatriene and Pyridine). We have explored the dependency of the calculated spectra on parametrization in terms of exchange-correlation functionals and basis sets, and on geometrica loptimization. The second approach refers to time-dependent wave packet methodology for RRS and its time-independent counterpart in the Kramers-Heisenberg equation for the scattering cross section, which reduces the calculation of the RRS amplitude to computation of matrix elements of transition dipole moments between vibrational wave functions. The time-dependent theory has been used to examine RRS as a dynamical process where particular attention is paid to the notion of fast scattering in which the choice of photon frequency controls the scattering time and the nuclear dynamics. It is shown that a detuning from resonance causes a depletion of the RRS spectrum from overtones and combination bands, a situation which is verified in experimental spectra. The cross section of NRS has been predicted for the studied molecules to be in the order of 10−30 cm2/sr. A further increase in sensitivity with a signal enhancement up to 104 to 105 is predicted for the RRS technique, while CARS conditions imply an overall increase of the intensity by several orders of magnitude over NRS. In contrast to RRS and CARS, the HRS intensity is predicted to be considerably weaker than NRS, by about four orders of magnitude. However, silent modes in NRS can be detected by HRS which in turncan provide essential spectroscopic information and become complementary to NRS scattering. With the above mention methodological development for NRS, RRS, CARS and HRS, we have at our disposal a powerful set of modelling tools for the four different Raman techniques. They have complementary merits and limitations which facilitate the use of these spectroscopes in applications of Raman scattering for practical applications, for instance stand-off detection of foreign substances.QC 20110112
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Souza, Marcelo Abreu de. „Espectroscopia Raman de altos explosivos“. Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-09022007-150540/.
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Alguns altos explosivos foram caracterizados por espectroscopia Raman e no Infravermelho, e o efeito da temperatura sobre os espectros Raman foi medido in-situ. Foram estudados os produtos comerciais TNT, HMX, RDX e PETN, os quais, com exceção do HMX e RDX, pertencem a classes químicas distintas e também foi investigado o TATP sintetizado no laboratório. As amostras foram inicialmente caracterizadas por FT-IR, FT-IR/ATR e espectroscopia Raman com excitação no visível (632,8 nm) e no NIR (1064 nm) visando determinar se a técnica de amostragem exercia algum efeito, especificamente transições de fase e degradação, sobre os espectros. ATR e FT-Raman forneceram os espectros a partir dos quais foi feita a atribuição de bandas, a qual foi suportada por simulações teóricas (DFT, B3PW91). Cada amostra foi aquecida até uma temperatura abaixo do ponto de fusão, na qual o comportamento do espectro com o aquecimento era reversível. No caso do PETN e TNT esse valor foi bem próximo do ponto de fusão e no caso do HMX e RDX, foi substancialmente inferior. As bandas mais afetadas pela temperatura devem ser aquelas envolvidas nas rotas de relaxação de energia em explosivos. Os resultados obtidos sugerem que o PETN sofra decomposição térmica através da ruptura da ligação C-ONO2, enquanto que no HMX e RDX a ligação N-N deve ser rompida. As mudanças no espectro do TNT indicam que vibrações envolvendo os grupos NO2 e a ligação C-N são as mais sensíveis à temperatura. TATP sublima à temperatura de 70°C e até essa temperatura o espectro não é afetado pelo calor. Provavelmente a energia é utilizada no processo de sublimação.Selected high explosives were characterized by Raman and Infrared spectroscopies and the effect of temperature was followed in-situ by Raman spectroscopy. TNT, HMX, RDX, PETN (commercial products) and TATP belong to distinct chemical families (except HMX and RDX) and their response to heating was evaluated. The samples were first characterized by FT-IR, FT-IR/ATR and Raman with excitation in the visible (632.8 nm) and in the NIR (1064 nm) aiming at the detection of sampling effects in the obtained spectra, specifically phase transitions and degradation. ATR and FT-Raman were the techniques of choice to provide the spectra for band assignment, which was assisted by theoretical simulations (DFT). Each sample was heated up to a temperature well below its melting point, in order to avoid thermal decomposition. The bands most affected by temperature were taken as the routes for energy relaxation in explosives. The obtained results lead to the conclusion that PETN decomposes through the rupture of the C-ONO2 bond, whereas in HMX and RDX the N-N bond is broken. TNT spectra indicates that the NO2 and C-N vibrations are the most sensitive to temperature and TATP sublimated at 70°C and no bands were affected by temperature. The results are agreement with the literature or theoretical simulations.
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McGoverin, Cushla Maree, und n/a. „Raman spectroscopy of complex mixtures“. University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081103.112612.
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This thesis presents several Raman spectroscopic studies of bovine milk-derived products (skim and whole milk powder, anhydrous milk fat, processed cheese and soy cheese made from milk protein). Raman spectroscopy, unlike infrared spectroscopy (both mid- and near-infrared), has not been widely used as an analytical tool within the dairy industry. The purpose of this project was to assess the utility of Raman spectroscopy in several dairy industry relevant problems. FT-Raman spectroscopy coupled with partial least squares (PLS) reliably predicted the concentration of fat and protein within whole milk and protein within skim milk powders as evidenced by ratios of prediction to deviation in excess of three. It was shown that sample geometry did not significantly affect the calculated predictive models, thereby allowing the simplest, quickest method of sample presentation to be utilised without harming quantification model efficacy.
The fat fraction of milk was further investigated, and it was shown that Raman spectra collected from anhydrous milk fat samples were a good basis for solid fat content (SFC) determination. Such spectra were collected when the samples were held at 40 �C, pretreated by baselining and area normalisation, and analysed using PLS with modified jack-knifing (PLS1-JK). Triacylglycerol class concentrations were also well predicted by PLS1-JK models developed from Raman spectroscopic data. Resonance enhancement of β-carotene within fat was shown to have little effect on the reliability of the optimal prediction model when compared to SFC Raman quantification.
Raman microscopic mapping for heterogeneity description of processed cheese and soy cheese mimics was examined. The FT-Raman milk powder constituents study had shown fat and protein Raman spectra within complex dairy mixtures could be distinguished, hence this utility was applied to mapping of cheese systems. Univariate, principal components analysis and multivariate curve resolution methods of analyses were compared; as expected the more complex samples required multivariate methods of analyses. Raman microscopic mapping was not a time efficient method in comparison to the standard method of confocal laser scanning microscopy. However, Raman spectroscopic mapping is a more universal technique which allowed the presence of an unexpected localised constituent within the soy cheese mimics to be observed. It was proposed that this constituent was a crystalline form of a short saturated fatty acid.
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Liu, Xiaohua. „Resonance raman studies of hemoproteins“. Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/27170.
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Castillo, Carolina Graciela. „Biological applications of raman spectroscopy“. Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30414.
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Lewis, Steffan A. E. „Fibre Raman amplifiers for telecommunications“. Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288385.
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Parr, Andrea Ann. „Raman microscopy studies of polysilicon“. Thesis, Northumbria University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324468.
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Thomas, Chapman. „Autoresonance in Stimulated Raman Scattering“. Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00674111.
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La diffusion Raman Stimulée (DRS) est étudiée dans le contexte des plasmas qui sont pertinents pour la Fusion par Confinement Inertielle (FCI). Dans un plasma inhomogène le processus d'auto-résonance de l'onde Langmuir, générée par DRS, peut se produire dans le régime cinétique (k_L*lambda_D>0.25) et conduire à des amplitudes au delà du niveau de l'amplification attendue due à l'inhomogénéité selon Rosenbluth [M. N. Rosenbluth, Phys. Rev. Lett. 29, 565 (1972)]. On démontre que des effets cinétiques faibles, comme le piégeage d'électrons donnent lieu à un décalage de fréquence non-linéaire (dépendant de l'amplitude), et peuvent compenser le déphasage de la résonance de DRS des trois ondes, observé dans les plasmas inhomogènes. Un modèle analytique du processus d'auto-résonance décrivant à la fois la croissance, la saturation et la phase des ondes de Langmuir a été développé. Ce modèle est en excellent accord avec les résultats des simulations cinétiques (particle-in-cell) pour des paramètres proches des conditions des plasmas des expériences de la fusion laser (Laser Mégajoule, National Ignition Facility). Une application possible de l'autorésonance est proposée sous la forme d'un amplificateur de Raman.
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O'Grady, Noelle Antoinette. „Raman spectroscopy of fluorescent samples“. Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246542.
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Russell, K. T. „Raman spectroscopic studies of asbestos“. Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355239.
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Zugic, Minjas. „Raman spectra of clathrate hydrates“. Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271176.
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Narula, Rohit. „Resonant Raman scattering in graphene“. Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/118567.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 131-144).
In this thesis we encounter the formulation of a rigorous theory of resonant Raman scattering in graphene, the calculation of the so-obtained Raman matrix element K2f,1o for the 2D Raman mode with the full inclusion of the matrix elements and a physically appealing bridge between theory and experiment by eschewing the problematic ascription of graphene with a finite thickness. Finally, we elucidate an experimental study of the Raman D and G modes of graphene and highly-defected pencil graphite over the visible range of laser radiation. Marking a departure from the usual practice for light scattering in semiconductors of including only the dynamics of the electrons and holes separately, we show via fourth-order quantum mechanical perturbation theory using a Fock state basis that for resonant Raman scattering in graphene the processes to leading order are those that involve the simultaneous action of the electrons and holes. Such processes are indeed an order of magnitude stronger than those prevalent in the literature under the double resonance [1, 2, 3] moniker. We translate our perturbation theoretic analysis into simple rules for constructing Feynman diagrams for processes to leading order and we thereby enumerate the 2D and D modes. Using expressions for the terms to leading order obtained from our theoretical treatment we proceed to evaluate the Raman matrix element [4] for the Raman 2D mode by using state-of-the-art electronic [5] and iTO phonon dispersions [6] fit to ab initio GW calculations. For the first time in the literature we include the variation of the light-matter and electron-phonon interaction matrix elements calculated via an ab initio density functional theory (DFT) calculation under the local density approximation (LDA) for the electronic wavefunctions. Our results for the peak structure, position and intensity dependence are in excellent agreement with experiments [7, 8, 9, 10]. Strikingly, our results show that depending on the combination of the input (polarizer) and output (analyzer) polarization of the laser radiation, very different regions of the phonon dispersion are accessed. This has a direct impact on the dominant electronic transitions according to the pseudo-momentum conservation condition satisfied by the scattering of an electron by a phonon ki = kf + q. Using sample substitution [11] we deconvolve the highly wavelength dependent response of the spectrometer from the Raman spectra of graphene suspended on an SiO2 - Si substrate and graphite for the D and G modes in the visible range. We derive a model that considers graphene suspended on an arbitrary stratified medium while sidestepping its problematic ascription as an object of finite thickness and calculate the absolute Raman response of graphene (and graphite) via its explicitly frequency independent Raman matrix element [K'2f10]2 vs. laser frequency. For both graphene and graphite the [K'2f10]2 per graphene layer vs. laser frequency rises rapidly for the G mode and less so for the D mode over the visible range. We find a dispersion of the D mode position with laser frequency for both graphene and graphite of 41 cm-YeV and 35 cm-YeV respectively, in good agreement with Narula and Reich 131 assuming constant matrix elements, the observed intensity follows the joint density states of the electronic bands of graphene. Finally, we show the sensitivity of our calculation to the variation in thickness of the underlying SiO2 layer for graphene.
by Rohit Narula.
Ph. D.
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Danilovic, Borka. „Étude Raman des supraconducteurs organiques“. Mémoire, Université de Sherbrooke, 1999. http://savoirs.usherbrooke.ca/handle/11143/4459.
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On a étudié des spectres Raman des supraconducteurs organiques ?-(ET) 2 Cu[N(CN) 2 ]Cl et ?-(ET) 2 Cu[N(CN) 2 ]Br .5 Cl .5 sous pression en fonction de la température et comparé nos résultats avec ceux obtenus précédemment dans le composé ?-(ET) 2 Cu[N(CN) 2 ]Br. Les vibrations C=C et CH 2 sont analysées avant et après les transitions de phase structurale et supraconductrice. Dans le composé ?-(ET) 2 Cu[N(CN) 2 ]Cl nous avons démontré la sensibilité du mode CH 2 au changement structurel autour de 80 K et à la possible formation de super réseau autour de 160 K. L'influence de la transition de phase supraconductrice sur le mode C=C ? 2 (Ag) a été mise en évidence et le transfert de charge a été estimé à ? =.5 e pour les deux composés. Ce travail s'insère dans l'effort global du laboratoire voulant établir un lien entre les supraconducteurs organiques et les composés d'oxydes de cuivre supraconducteurs à température critique élevée de type YBa 2 Cu 3 O 7-x et Nd 2-x Ce x CuO 4.
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Rodrigues, Pedro Augusto Matos. „Espalhamento Raman por semicondutores mesoscópicos“. [s.n.], 1988. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277696.
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Orientador: Fernando CerdeiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nós desenvolvemos um modelo para o espectro Raman de semicondutores microcristalinos. Neste modelo o confinamento dos fonons tem dois efeitos: a) produz uma relaxação da lei de conservação do momento cristalino; b) limita as vibrações óticas permitidas àquelas que satisfaçam a condição de onda estacionária. Estas modificações em relação a um cristal macroscópico resultam em um espectro Raman composto de vários picos que é claramente distinto daquele de um cristal macroscópico mesmo no caso em que o tamanho dos microcristais não é constante em toda a amostra. Nossos resultados são utilizados para caracterizar amostras de CdSe microcristalino obtido por deposição química
Abstract: We developed a model for the Raman spectrum of small semiconductors crystallites. In this model phonon confinement has two effects: a) it produces a relaxation of the k conservation rule. b) it limits the amount of allowed optical vibrations to those which obey the stationary wave condition. These modifications with respect to macroscopic crystal result in a Raman spectrum containing several peaks which is clearly distinguished from that of bulk materials even in the case where the crystallite size is not constant throughout the sample. Our results are used to characterize microcrystalline samples of CdSe obtained by chemical deposition
Mestrado
Física
Mestre em Física
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Moreira, Alessandro Ferreira Lisboa. „Espalhamento Raman em perovskitas duplas“. [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277693.
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Orientador: Eduardo Granado Monteiro da SilvaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Nesse trabalho foram realizados estudos em duas famílias de compostos de perovskitas duplas Ba2FeReO6 e S r2UO6 (B'= Co, Ni) por espectroscopia Raman e difração de raios-X com luz síncrotron. No primeiro composto há uma transição de uma estrutura cúbica Fm3m paramagnética para uma tetragonal I4/mmm ferrimagnética abaixo de TC~305 K. O mecanismo de acoplamento magnético neste material ainda permanece uma incógnita. Dois grupos de medidas de espalhamento Raman foram realizados em regiões distintas da amostra à base de FeRe. Foi verificado que o fônon associado às vibrações de estiramento dos oxigênios nos octaedros sofre um desvio na freqüência em relação ao comportamento convencional abaixo de TC nos dois grupos de medidas. Isso pode ser associado a dois possíveis mecanismos: acoplamento spin-fônon gigante e acoplamento órbita-spin-fônon. Na segunda família de compostos contendo urânio, os compostos estudados apresentam uma estrutura cristalina monoclínica com grupo espacial P 21/n e um ordenamento antiferromagnético abaixo de TN~21 K para B" = Ni e TN~10 K para B" = Co. A partir dos espectros Raman desses compostos observa-se que a área integrada do modo de estiramento do oxigênio sofre um decréscimo anômalo sob aquecimento até T*~300 K. Além disso, este modo sofre um endurecimento anômalo de ~1 cm -1 sob aquecimento até T*. Para verificar a hipótese de que T* poderia estar associada a uma transição estrutural nesta família, medidas de difração de raios-X de pó com luz síncrotron foram realizadas no LNLS. A análise estrutural de ambos os compostos não mostraram nenhum grau observável de desordem de antisítios entre B' e U e tampouco uma transição de fase ou comportamento anômalo dos parâmetros de rede foi encontrada em torno de T*. Portanto, as anomalias encontradas em espectroscopia Raman nestes materiais são de origem eletrônica
Abstract: In this work, studies on two families of double perovskite compounds Ba2FeReO6and Sr2B'U O6(B' = Ni, Co) were carried out by Raman spectroscopy and synchrotron X-ray diffraction. In the first compound, a transition from a cubic Fm3m paramagnetic to a tetragonal ferromagnetic structure takes place below TC ~305 K. The magnetic coupling mechanism in this material remains unknown. Two groups of Raman scattering measurements were performed in distinct regions of the FeRe-based sample. It was verified that the phonon associated to stretching vibrations of oxygen octahedra shows a frequency shift with respect to the conventional behavior below TC, in both groups of measurements. This may be associated with two possible mechanisms: giant spin-phonon coupling and orbit-spin-phonon coupling. In the second family of compounds with uranium, the studied compounds present a monoclinic crystal structure with space group P21/n and an antiferromagnetic ordering below TN~21 K for B'' = Ni and TN ~10 K for B'' = Co. From the Raman spectra of these compounds, an anomalous decrease of the integrated area of the oxygen stretching mode was observed upon heating up to T*~300 K. Also, this mode shows an anomalous hardening of ~1 cm -1 under heating up to T*. In order to verify the hypothesis that T* could be associated to a structural transition in this family, powder x-ray diffraction measurements with synchrotron light were perfomed at LNLS. The structural analysis of both compounds did not show any observable degree of antisite disorder between B' and U, and no phase transition or anomalous behavior of lattice parameters was found close to T*. Therefore, the anomalies found by Raman spectroscopy in these materials are electronic in origin
Mestrado
Física da Matéria Condensada
Mestre em Física
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Ribeiro, Henrique Bücker. „Espectroscopia raman em materiais bidimensionais“. Universidade Presbiteriana Mackenzie, 2017. http://tede.mackenzie.br/jspui/handle/tede/3485.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Fundação de Amparo a Pesquisa do Estado de São Paulo
Fundo Mackenzie de Pesquisa
In this thesis, the properties of four kinds of layered materials were investigated: twisted bilayer graphene, black phosphorus, germanium selenide (GeSe) and germanium sulfide (GeS) (group IV monochalcogenides) by means of Raman spectroscopy. The Raman spectrum of different twisted bilayer graphene samples rotated by different angles ranging from 0 to 30 was measured using three lasers with wavelengths of 488 nm, 532 nm, and 633 nm. The electronic structure of the investigated samples was mapped and the energy in which the resonances take place were attributed to the presence of van Hove singularities that are related to the size of Moiré cell. Angular dependence measurements of the Raman spectrum on black phosphorus (BP) samples were also performed and it was demonstrated that the angular dependence of the Raman band intensities presents an unusual behavior. In order to explain such behavior, one must consider the complex nature of the Raman tensors. Furthermore, the atomic structure and phonon behavior in the vicinity of the BP sample edges were also studied using polarized Raman spectroscopy and the experimental results were explained by using density functional theory calculations. Polarized Raman spectra showed the appearance of some modes at the edges of the samples prohibited by symmetry selection rules. Theoretical simulations confirm that this symmetry breaking originates from an atomic rearrangement at the edges of the crystal. A similar behavior was also observed for GeS and GeSe samples and the appearance of Raman modes of the edges was attributed to the reorganization of the atoms of the crystal edges, since their crystal structure are similar to that of BP crystals.
Nesta tese investigamos as propriedades de quatro tipos de materiais bidimensionais: grafeno bicamada rodado(empilhamento de duas camadas com diferentes ângulos de rotação entre camadas), fósforo negro, seleneto de germânio e sulfeto de germânio (monocalcogenetos do grupo IV) por meio de espectroscopia Raman. O espectro Raman de diferentes amostras de grafeno rodado com diferentes ângulos de rotação entre as camadas, variando entre 0_ a 30_ foram medidos utilizando lasers com comprimentos de onda de 488nm, 532nm e 633nm. As estruturas eletrônicas das amostras investigadas foram mapeadas e a energia em que as ressonâncias acontecem foram atribuídas às singularidades de van Hove que estão relacionadas com o tamanho da célula de Moiré obtida pela rotação de uma camada em relação a outra. Medidas de dependência angular do espectro Raman em amostras de fósforo negro(BP) foram também realizadas e foi demonstrado que a dependência angular dos espectros Raman apresenta um comportamento não usual. Para explicar tal comportamento foi mostrado que deve-se sempre considerar a natureza complexa dos elementos do tensor Raman. A estrutura atômica e comportamento de fônons nas proximidades da borda de amostra de BP foi também estudada experimentalmente usando espectroscopia Raman polarizada e explicada teoricamente usando cálculos baseados na teoria do funcional da densidade. Os espectros Raman polarizados mostraram o aparecimento de modos nas bordas das amostras, normalmente proibidos por regras de seleção de simetria da fase bulk. As simulações teóricas confirmaram que a quebra de simetria se origina de uma reorganização atômica nas bordas do cristal. Esse mesmo fenômeno foi também observado em amostras de GeS e GeSe que apresentam uma estrutura cristalina similar à de cristais de BP.
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Bonhomme, Frédéric. „Spectroélectrochimie par microspectroscopie Raman confocale“. Bordeaux 1, 2000. http://www.theses.fr/2000BOR10526.
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La microspectroscopie raman confocale (mrc) a ete couplee a des experiences d'electrochimie afin d'analyser, avec une resolution de l'ordre du micrometre cube et en temps reel, les phenomenes qui se produisent aux electrodes ou pres des electrodes en cours de polarisation. Apres avoir discute les avantages et les limites de cette approche spectroelectrochimique, deux exemples d'application sont presentes : le premier concerne la cartographie tridimensionnelle des especes electroactives au voisinage d'une ultramicroelectrode et la mise en evidence directe d'une reaction chimique secondaire de conproportionation. Le second porte sur la caracterisation des mecanismes de stockage electrostatique dans un supercondensateur.
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Li, Zheng Ph D. Massachusetts Institute of Technology. „Computational Raman imaging and thermography“. Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130673.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February, 2021Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 185-201).
Thermography tools that perform accurate temperature measurements with nanoscale resolution are highly desired in our modern society. Although researchers have put extensive efforts in developing nanoscale thermography for more than three decades and a significant amount of achievements have been made in this field, the mainstream thermography tools have not fully met the requirements from the industry and the academia. In this thesis, we present our home-built Raman microscope for Raman imaging and thermography. The performance of this instrument is enhanced by computational approaches. The body of the thesis will be divided into three parts. First, the instrumentation of our setup are introduced. Second, we present the results of Raman imaging with computational super-resolution techniques. Third, this instrument is used as a thermography tool to map the temperature profile of a nanowire device. These results provide insights in combining advanced instrumentation and computational methods in Raman imaging and Raman thermography for the applications in modern nano-technology.
by Zheng Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
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Nemeth, Amanda. „Raman Signature of Molecular Charging“. Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1609258734249143.
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Raghunathan, Varun. „Raman-based silicon photonic devices“. Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1481677321&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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