Dissertations / Theses on the topic 'Ultraviolet and visible spectroscopy'
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Fish, Deborah Jane. "Measurement of stratospheric composition using ultraviolet and visible spectroscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360887.
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Adamopoulos, Georges. "Visible and ultraviolet Raman spectroscopy of diamond-like carbon." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621148.
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O'Shay, Joseph Fred. "Time-resolved visible and extreme ultraviolet spectroscopy of laser-produced tin plasma." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3264604.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed August 7, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 248-255).
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George, Ronie. "Early Ovarian Cancer Detection Using Fluorescence Spectroscopy in the Ultraviolet-C through Visible." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301694.
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We evaluate the changes in fluorescence from endogenous fluorophores such as amino acids, structural proteins and enzymatic co-factors to predict malignancy and risk of developing ovarian cancer. 249 ovarian biopsies of the surface epithelium were interrogated in vitro, over 270-550 nm excitation, and fluorescence was collected from 290-700nm. Spectroscopic data was analyzed using parallel factor analysis (PARAFAC) to determine excitation and emission spectra of the underlying fluorophores that contribute to the total detected fluorescence intensity. Using multivariate normal distribution fits and cross-validation techniques, sensitivity (SN) and specificity (SP) of 88 and 93 percent, respectively, were achieved when classifying malignant samples versus others, while 88 and 80 percent, respectively, were achieved when classifying normal post menopausal patients as being either at low- or high-risk of developing ovarian cancer based on their personal and family history of cancer. Also, the performance of classifying cancer increases when the normal group excludes benign neoplasm and endometriosis samples, while the performance of low- v. high-risk decreases when both pre- and post-menopausal samples are included. These results could potentially be useful in screening women at increased risk of developing ovarian cancer. This motivated our study to investigate similar changes in ovarian autofluorescence in vivo. 40 patients were recruited and a total of 189 samples were imaged using a fiber optic bundle and biopsied. Using PARAFAC, the factors computed from in vitro data analysis and in vitro data as a training set; pathology from each in vivo site biopsied was compared to calibrated tissue-fluorescence. It resulted in a SN and SP of 100 and 94 percent, respectively, for classifying normal versus malignant. In the case of risk assessment, cross validated in vivo data gave a SN and SP of 68 and 93%. Results obtained were consistent with those obtained in vitro, except for the presence of blood absorption peaks which affected risk assessment. Assessing endogenous fluorescence has diagnostic potential and if adapted to trans-vaginal access, would make the screening procedure less costly and less invasive, and would be most useful and economical in women at increased risk of developing ovarian cancer and might determine the ideal time to undergo an oophorectomy.
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RAMSEY-BELL, DEBBY COLLEEN. "PHOTOACOUSTIC MEASUREMENTS OF ATMOSPHERIC AEROSOL ABSORPTION COEFFICIENTS AT ULTRAVIOLET, VISIBLE, AND INFRARED WAVELENGTHS." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184139.
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A photoacoustic spectrometer was developed and built for measuring absorption of light by collected particles. Major advantages of the photoacoustic method are that it measures absorption directly, it is insensitive to scattered light, and it is readily used at different wavelengths. To evaluate the performance of the spectrometer, comparisons were made between photoacoustic absorption spectra and spectra calculated with Mie thoery. Pure powders with varied optical properties were used in the comparison, including carbon, hematite, and others. Results were reasonable in both absolute magnitude and spectral shape. Aerosol particles were collected in different environments in southern Arizona under background conditions in the mid-troposphere, and in a moderately polluted city. Results for the two locations, and two size ranges, are compared and contrasted in this thesis. Absolute magnitudes of absorption coefficients, measured at green wavelengths, are used to summarize many important results. Absorption by fine urban aerosol was 6 ± 4 x 10⁻⁷ m⁻¹, and four times larger than absorption by coarse urban aerosol. Normalized photoacoustic absorption spectra for urban aerosol are uniform with wavelength; background aerosol spectra have a relative increase in absorption at near UV wavelengths compared to near IR wavelengths. Urban aerosol absorption can be attributed to carbon particles larger than approximately 0.1 micron. Absorption by hematite (alpha iron oxide) particles in more strongly wavelength dependent than absorption by carbon particles, of the same size. This wavelength dependence is still not great enough to be attributed to hematite alone--although submicron hematite particles may be the dominant absorber in coarse background aerosol. (Abstract shortened with permission of author.)
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Gratien, Aline Orphal Johannes Picquet-Varrault Bénédicte. "Spectroscopie ultraviolet-visible et infrarouge de molécules clés atmosphériques." S. l. : Paris Est, 2008. http://doxa.scd.univ-paris12.fr:80/theses/th0494573.pdf.
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Gratien, Aline. "Spectroscopie ultraviolet-visible et infrarouge de molécules clés atmosphériques." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00846616.
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Les mesures des constituants mineurs de l'atmosphère sont souvent réalisées à partir du sol, d'avions, de ballons ou encore par les satellites. Celles-ci sont effectuées régulièrement par des spectromètres fonctionnant dans des régions spectrales différentes, en particulier dans les domaines UV-visible et infrarouge. Or, l'analyse et l'interprétation des spectres atmosphériques requièrent une bonne connaissance des paramètres spectroscopiques. Cependant, les mesures de ces paramètres sont généralement effectuées dans un domaine spectral donné (IR ou UV) et peu d'études de laboratoire ont vérifié la cohérence entre les sections efficaces UV et IR. Il est alors difficile de comparer des profils atmosphériques déduits de mesures effectuées dans différents domaines. Le but de cette étude est donc d'intercalibrer les spectres UV et IR de composés atmosphériques en déterminant et/ou e vérifiant la cohérence des sections efficaces publiées dans la littérature. Ces expériences ont été effectuées dans la chambre de simulation du LISA, en acquérant simultanément des spectres UV et IR à température ambiante et à pression atmosphérique au sein d'une cellule optique commune. Ce travail a porté sur trois molécules clés atmosphériques : le formaldéhyde (et ses isotopes), l'ozone et l'acide nitreux. Ces composés jouent un rôle fondamental dans la physico-chimie atmosphérique puisqu'ils constituent les sources du principal oxydant de l'atmosphère : le radical hydroxyle. Ce travail de laboratoire a permis ainsi d'obtenir des spectres précis et cohérents de l'ozone, du formaldéhyde et de l'acide nitreux dans le moyen infrarouge et l'UV-visible afin d'améliorer la précision de leurs mesures.
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Bloch, Jonathan C. (Jonathan Craig). "Extending frequency modulation spectroscopy : sensitive and selective high resolution laser absorption in the visible and ultraviolet." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10861.
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Wang, Xuzhu. "Beam-folding ultraviolet-visible Fourier transform spectrometry and underwater cytometry for in situ measurement of marine phytoplankton." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/814.
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Van, der Horst Charlton. "Development of a bismuth-silver nanofilm sensor for the determination of platinum group metals in environmental samples." University of the Western Cape, 2015. http://hdl.handle.net/11394/4451.
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Philosophiae Doctor - PhDNowadays, the pollution of surface waters with chemical contaminants is one of the most crucial environmental problems. These chemical contaminants enter rivers and streams resulting in tremendous amount of destruction, so the detection and monitoring of these chemical contaminants results in an ever-increasing demand. This thesis describes the search for a suitable method for the determination of platinum group metals (PGMs) in environmental samples due to the toxicity of mercury films and the limitations with methods other than electroanalytical methods. This study focuses on the development of a novel bismuth-silver bimetallic nanosensor for the determination of PGMs in roadside dust and soil samples. Firstly, individual silver, bismuth and novel bismuth-silver bimetallic nanoparticles were chemically synthesised. The synthesised nanoparticles was compared and characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM) analysis to interrogate the electrochemical, optical, structural, and morphological properties of the nanomaterials. The individual silver, bismuth, and bismuth-silver bimetallic nanoparticles in the high resolution transmission electron microscopy results exhibited an average particle size of 10-30 nm. The electrochemical results obtained have shown that the bismuth-silver bimetallic nanoparticles exhibit good electro-catalytic activity that can be harnessed for sensor construction and related applications. The ultraviolet-visible spectroscopy, Fourier-transformed infrared spectroscopy, and Raman spectroscopy results confirmed the structural properties of the novel bismuth-silver bimetallic nanoparticles. In addition the transmission electron microscopy and selected area electron diffraction morphological characterisation confirmed the nanoscale nature of the bismuth-silver bimetallic nanoparticles. Secondly, a sensitive adsorptive stripping voltammetric procedure for palladium, platinum and rhodium determination was developed in the presence of dimethylglyoxime (DMG) as the chelating agent at a glassy carbon electrode coated with a bismuth-silver bimetallic nanofilm. The nanosensor further allowed the adsorptive stripping voltammetric detection of PGMs without oxygen removal in solution. In this study the factors that influence the stripping performance such as composition of supporting electrolyte, DMG concentration, deposition potential and time studies, and pH have been investigated and optimised. The bismuth-silver bimetallic nanosensor was used as the working electrode with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. The differential pulse adsorptive stripping peak current signal was linear from 0.2 to 1.0 ng/L range (60 s deposition), with limit of detections for Pd (0.19 ng/L), Pt (0.20 ng/L), Rh (0.22 ng/L), respectively. Good precision for the sensor application was also obtained with a reproducibility of 4.61% for Pd(II), 5.16% for Pt(II) and 5.27% for Rh(III), for three measurements. Investigations of the possible interferences from co-existing ions with PGMs were also done in this study. The results obtained for the study of interferences have shown that Ni(II) and Co(II) interfere with Pd(II), Pt(II) and Rh(III) at high concentrations. The interference studies of Cd(II), Pb(II), Cu(II) and Fe(III) showed that these metal ions only interfere with Pd(II) and Pt(II) at high concentrations, with no interferences observed for Rh(III). Phosphate and sulphate only interfere at high concentrations with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) solution as the supporting electrolyte. Based on the experimental results, this bismuth-silver bimetallic nanosensor can be considered as an alternative to common mercury electrodes, carbon paste and bismuth film electrodes for electrochemical detection of PGMs in environmental samples. Thirdly, this study dealt with the development of a bismuth-silver bimetallic nanosensor for differential pulse adsorptive stripping voltammetry (DPAdSV) of PGMs in environmental samples. The nanosensor was fabricated by drop coating a thin bismuth-silver bimetallic film onto the active area of the SPCEs. Optimisation parameters such as pH, DMG concentration, deposition potential and deposition time, stability test and interferences were also studied. In 0.2 M acetate buffer (pH = 4.7) solution and DMG as the chelating agent, the reduction signal for PGMs ranged from 0.2 to 1.0 ng/L. The detection limit for Pd(II), Pt(II) and Rh(III) was found to be 0.07 ng/L, 0.06 ng/L and 0.2 ng/L, respectively. Good precision for the sensor application was also obtained with a reproducibility of 7.58% for Pd(II), 6.31% for Pt(II) and 5.37% for Rh(III), for three measurements. In the study of possible interferences, the results have shown that Ni(II), Co(II), Fe(III), Na+, SO42- and PO43- does not interfere with Pd(II) in the presence of DMG with sodium acetate buffer as the supporting electrolyte solution. These possible interference ions only interfere with Pt(II) and Rh(III) in the presence of DMG with 0.2 M acetate buffer (pH = 4.7) as the supporting electrolyte solution.
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Rives, Patrick. "Étude spectroscopique et cinétique des mélanges Xe-HCl dans le proche ultraviolet et le visible." Toulouse 3, 1993. http://www.theses.fr/1993TOU30109.
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On etudie dans le proche uv et le visible un melange de xenon et de chlorure d'hydrogene excite par des particules alpha. La pression est inferieure a l'atmosphere et la teneur en chlorure d'hydrogene n'excede pas 2%. L'etude spectroscopique permet d'observer le troisieme continuum du xenon et les emissions xecl(bx), xecl(ca)+xecl(ba) et xe#2cl(4#21#2) centrees respectivement a 308, 345 et 470 nm. L'emission de xe#2cl n'est presente que lorsque le chlorure d'hydrogene est a l'etat de traces et lorsque la pression de xenon est superieure a 200 torr. Les emissions de xecl* sont competitives avec celle du troisieme continuum. Les ions xe** et xe#2** sont donc impliques dans les processus responsables des trois emissions. L'etude cinetique des emissions centrees a 308 et 345 nm permet de mettre en evidence un couplage collisionnel par le xenon des etats b et c de xecl. Des constantes de vitesse correspondantes, on en deduit l'ecart energetique entre les deux etats. Il vaut 119 cm##1. On mesure egalement des constantes de vitesse de processus de destruction de la molecule xecl(b, c) par des collisions binaires (avec un atome de xenon ou une molecule hcl) ou ternaires (avec deux atomes de xenon ou un atome de xenon et une molecule hcl)
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Chailleux, Yohann. "Observation satellitaire de la pollution à l’ozone par synergie multispectrale à trois bandes Ultraviolet+Visible+Infrarouge." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1033/document.
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La qualité de l’air est un enjeu environnemental majeur de notre société. Cette thèse se focalise sur l’observation depuis l’espace du polluant gazeux majeur, l’ozone troposphérique. Les instruments satellitaires de nouvelle génération permettent de le mesurer journalièrement aux échelles régionales à globale. Cependant, les mesures d’un seul domaine spectral n’amène pas d’information suffisante pour quantifier les concentrations de l’ozone dans la couche limite atmosphérique, où se situe l’air que nous respirons. Le couplage des mesures de multiples domaines spectraux offre un fort potentiel pour mieux caractériser la pollution à l’ozone. La première approche multispectrale à 2 bandes combinant les mesures de l’infrarouge (IR) de IASI et l’ultraviolet (UV) de GOME-2 a été développée au laboratoire LISA, que j’ai intégré dans le cadre de ma thèse. L’objectif de mon travail de thèse est de franchir un pas supplémentaire dans la quantification de la pollution à l’ozone en incluant la bande visible (VIS) de Chappuis, afin de développer un couplage multispectral inédit à trois bandes spectrales UV+VIS+IR. Premièrement, j’ai mis au point une approche pour extraire l’information sur l’ozone des spectres VIS de GOME-2, en sélectionnant les longueurs d’onde affectées majoritairement par l’absorption à l’ozone et rejetant celles avec des absorptions d’autres gaz, ainsi que déterminant les variables d’ajustement conjoint de l’approche (profil vertical d’ozone, albédo de surface, shifts spectraux, etc) et les bases de données nécessaires pour simuler les spectres VIS (albédo de surface, spectroscopie).Ensuite, j’ai mis en œuvre la méthode multispectrale à trois bandes UV+VIS+IR, premièrement sur des observations simulées défilantes de IASI et GOME-2 et géostationnaires de MAGEAQ afin d’estimer l’amélioration en terme de sensibilité et précision, par rapport aux méthodes existantes. Dernièrement, j’ai appliqué l’approche multispectrale à 3 bandes à des observations satellitaires réelles de IASI et GOME-2. Des comparaisons avec d’autres données montrent des meilleures performances des nouvelles observations UV+VIS+IR pour caractériser des évènements de pollution à l’ozone, par rapport à l’approche à 2 bandesAir quality is a major environmental issue for our society. This PhD thesis focuses on space borne observation of the major gaseous pollutant. Tropospheric ozone. New generation satellite instruments allow measuring it daily at regional to global scales. However, single spectral domain measurements do not provide enough information for quantifying ozone concentrations at the atmospheric boundary layer, where the air we breathe is located. Synergism of measurements from multiple spectral domains offers a great potential for better characterizing ozone pollution. The first 2-band multispectral approach combining infrared (IR) measurements of IASI and the ultraviolet (UV) of GOME-2 was developed at LISA laboratory, where I conducted my thesis. The goal of my thesis is to go a step further in the quantification of ozone pollution by including the visible (VIS) Chappuis band, in order to develop an unprecedented 3-band multispectral synergism UV+VIS+IR. First, I developed a approach for extracting ozone information from GOME-2 VIS spectra, by selecting the wavelengths mostly affected by ozone absorption and rejecting those with absorptions from other gases, as well as determining the joint adjustment variables of the approach (vertical ozone profile, surface albedo, spectral shifts, etc) and the databases needed to simulate the spectra VIS (surface albedo, spectroscopy).Then, I implemented the multispectral method with three bands UV+VIS+IR, first on simulated low-orbit and geostationary observations from respectively IASI and GOME-2 and MAGEAQ to estimate the improvement in terms of sensitivity and precision, as compared to existing methods. Last, I applied the 3-band multispectral approach to real satellite observations of IASI and GOME-2. Comparisons with other data shows enhanced performances of the new UV+VIS+IR observations to characterize ozone pollution events, with respect to the 2-band approach
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Selig-Parthey, Ulrike [Verfasser], and Tobias [Akademischer Betreuer] Brixner. "Methods of Nonlinear Femtosecond Spectroscopy in the Visible and Ultraviolet Regime and their Application to Coupled Multichromophore Systems / Ulrike Selig-Parthey. Betreuer: Tobias Brixner." Würzburg : Universitätsbibliothek der Universität Würzburg, 2012. http://d-nb.info/1029661766/34.
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Hebrard, Guillaume. "L'ABONDANCE DU DEUTÉRIUM, DE L'ULTRAVIOLET AU VISIBLE." Phd thesis, Université Paris-Diderot - Paris VII, 2000. http://tel.archives-ouvertes.fr/tel-00002333.
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Dans le cadre du modèle standard du Big Bang, le deutérium est l'élément dont l'abondance primordiale est la plus sensible à la densité baryonique de l'Univers. Cet élément est uniquement créé lors de la nucléosynthèse primordiale, quelques minutes après le Big Bang ; aucune théorie standard n'en prédit actuellement d'autres sources significatives. Au contraire, étant brûlé dans les étoiles, son abondance D/H décroît au cours de l'évolution cosmique. Les mesures de D/H apportent ainsi des contraintes sur les modèles de Big Bang et d'évolution chimique des galaxies. On peut distinguer trois types de mesures de D/H : les abondances primordiale, proto-solaire et interstellaire, respectivement représentatives de l'Univers il y a environ 15 milliards d'années, 4.5 milliards d'années et à l'époque actuelle. Si l'évolution du deutérium semble qualitativement claire, les résultats concernant ces trois types d'abondance ne convergent pas pour l'instant vers trois valeurs bien définies. Les travaux entrepris durant cette thèse sont reliés à la mesure de l'abondance interstellaire du deutérium. Celle-ci s'obtient habituellement par l'observation spectroscopique en absorption des séries de Lyman de l'hydrogène et du deutérium. Ces observations se font dans le domaine ultraviolet, au moyen d'observatoires spatiaux. Les résultats présentés ici ont été obtenus avec le Télescope spatial Hubble puis le satellite FUSE, récemment mis en orbite. D'autre part, une nouvelle méthode d'observation du deutérium a été proposée, dans le domaine visible à partir de télescopes au sol. Ce travail a mené aux premières détections et à l'identification de la série de Balmer du deutérium, observée en émission dans des régions HII avec le Télescope Canada-France-Hawaii et le Very Large Telescope.
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Lai, Sin Pin. "Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2342.
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An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
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Lefez, Benoît. "Caractérisation d'oxydes de cuivre par photoluminescence." Rouen, 1991. http://www.theses.fr/1991ROUES047.
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La caractérisation d'oxydes de cuivre par photoluminescence a nécessité le développement d'un spectrofluorimètre. La sensibilité de la méthode a été testée sur des échantillons non-stoichiométriques. La corrélation de données obtenues par différentes méthodes optiques (spectroscopie de réflexion dans l'ultraviolet proche infrarouge, photoluminescence) a permis de préciser les domaines énergétiques mis en jeu lors des transferts radiatifs. La structure et la composition d'un film d'oxydation multicouches ont été établies (spectroscopie dans l'infrarouge, microsonde de Castaing). Un oxyde de cuivre(i), de composition Cu302, a été caractérisé. Différentes applications de la photoluminescence ont été proposées telles que l'aide à l'analyse de la corrosion d'un laiton ou la mise en évidence d'une étape de l'absorption dissociative de l'oxygène
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Venumuddala, Hareesha Reddy. "Study of Drug Delivery Behavior Through Biomembranes Using Thermal And Bioanalytical Techniques." Cleveland State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1295472144.
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Lai, Sin Pin. "Furan measurement in transformer oil by UV-Vis spectroscopy using fuzzy logic approach." Curtin University of Technology, Department of Electrical and Computer Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=128452.
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An Ultraviolet to Visible (UV-Vis) spectroscopic analysis based on fuzzy logic approach has been developed for furan content measurement in transformer oil. Following the successful identification and quantification of furan derivatives in transformer oil by ASTM D5837 standard, the new approach is able to approximate the furan content more conveniently and economically. As furan concentration level would determine the absorption intensity in UV-Vis spectral range, the fuzzy logic software model developed would exploit this characteristic to aggregate the furans content level in transformer oil. The UV-Vis spectral response at other ambient temperature is also studied. The proposed technique provides a convenient alternative to conventional method of furan measurement by High Performance Liquid Chromatography (HPLC) or Gas Chromatography Mass Spectrometry (GC/MS) in ASTM D5837 Standard.
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Kherde, Yogesh A. "Green Synthesis and Evaluation of Catalytic Activity of Sugar Capped Gold Nanoparticles." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1388.
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Owing to the importance of gold nanoparticles in catalysis, designing of them has become a major focus of the researchers. Most of the current methods available for the synthesis of gold nanoaprticles (GNPs) suffer from the challenges of polydispersity, stability and use of toxic and harmful chemicals. To overcome these limitations of conventional methods, in our present study, we made an attempt to design a method for the green synthesis of monodispersed and stable gold nanoparticles by sugars which act as reducing and stabilizing agent. Characterization of synthesized nanoparticles was done by using various analytical techniques such as transmission electron microscope (TEM), dynamic light scattering spectroscopy (DLS), UV-Vis spectroscopy, scanning electron microscopy and electron dispersion spectroscopy. The synthesized sugar GNPs (S-GNPs) were spherical in shape and in the size range of 10 ± 5 nm. p-Nitrophenol reduction assay was used as a model system to determine the catalytic reduction activity of various sugar capped GNPs, monosaccharides (fructose), disaccharide (sucrose) and trisaccharide (raffinose) GNPs. The effect of temperature and the size of ligand on catalytic activity was also evaluated at different temperature using UV-Vis spectrometer. Using the spectroscopic data, rate constant (k) for three sugar capped GNPs was determined followed by its activation energy (Ea) and exponential (A) factor.
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Åhlund, John. "Electronic and Geometrical Structure of Phthalocyanines on Surfaces : An Electron Spectroscopy and Scanning Tunneling Microscopy Study." Doctoral thesis, Uppsala universitet, Fysiska institutionen, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7802.
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Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields. Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films. We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature. Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K.
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Höger, Geralin. "Self-Organization of β-Peptide Nucleic Acid Helices for Membrane Scaffolding." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0003-C187-A.
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Mazet, Jean-François. "Couleur et qualité des placages de chêne et étude de leur comportement photochimique." Nancy 1, 1988. http://www.theses.fr/1988NAN10393.
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Dans la première partie, on a cherché à traduire par des mesures objectives l'appréciation professionnelle de la qualité de l'aspect des placages de chêne. Dans la seconde partie, on s'attache à mieux comprendre les mécanismes d'altération de la couleur des placages au cours de l'exposition à la lumière du jour, tout en s'intéressant à quelques moyens possibles de protection
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Shreepathi, Subrahmanya, Hung Van Hoang, and Rudolf Holze. "Corrosion Protection Performance and Spectroscopic Investigations of Soluble Conducting Polyaniline-Dodecylbenzenesulfonate Synthesized via Inverse Emulsion Procedure." Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200900775.
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Corrosion protection performance of a completely soluble polyaniline-dodecylbenzenesulfonic acid salt (PANI-DBSA) on C45 steel has been studied with electrochemical impedance and potentiodynamic measurements. Chloroform is the most suitable solvent to process the pristine PANI-DBSA because of negligible interaction of the solvent with the polyaniline (PANI) backbone. An anodic shift in the corrosion potential (
E=~70 mV), a decrease in the corrosion current and a significant increase in the charge transfer resistance indicate a significant anti-corrosion performance of the soluble PANI deposited on the protected steel surface. Corrosion protection follows the mechanism of formation of a passive oxide layer on the surface of C45 steel. In situ UV-Vis spectroscopy was used to investigate the differences in permeability of aqueous anions into PANI-DBSA. Preliminary results of electron diffraction studies show that PANI-DBSA possesses an orthorhombic type of crystal structure. An increase in the feed ratio of DBSA to aniline increases the tendency of aggregation of spherical particles of PANI obvious in transmission electron microscopy. PANI-DBSA slowly loses its electrochemical activity in acid free electrolyte without undergoing degradation.
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Beucher, Eric. "Etude de l'oxydabilité de cuivre désoxygéné au phosphore et de laitons monophasés alpha par spectroscopies optiques et par spectrométrie de masse des ions secondaires." Rouen, 1992. http://www.theses.fr/1992ROUE5003.
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Cette étude a permis la caractérisation, lors des dernières étapes industrielles, en surface des cuivres désoxygénés au phosphore, de métaphosphate de cuivre i (CuPo#3) pouvant inhiber par la suite une corrosion éventuelle du matériau. Néanmoins, lors du développement de couches d'oxydes importantes, le métaphosphate de cuivre se retrouve localisé à l'interface oxyde-métal formant ainsi une barrière de potentiel ralentissant la diffusion des espèces cationiques. Quant aux laitons, la préparation de surface avant oxydation (polissage mécanique ou décapage chimique) influe sur la nature des oxydes formés. Dans le cas d'un décapage chimique, les mécanismes de corrosion conduisent à l'obtention d'une structure bicouche avec les oxydes de cuivre en surface et l'oxyde de zinc à l'interface oxyde-métal. La croissance de l'oxyde de zinc est alors considérée comme un phénomène d'oxydation interne. Dans le cas d'un polissage mécanique, les oxydes de cuivre disparaissent de la surface de la couche de corrosion. Cependant, une importante diffusion de cuivre a lieu à l'interface oxyde de zinc-métal. La formation de l'oxyde de zinc apparaît dès lors comme le paramètre conditionnant les mécanismes de corrosion d'un laiton monophasé alpha
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Bertaut, Éléonore. "Développement de nouvelles méthodologies pour la calorimétrie de titration isotherme : Applications aux domaines de l'environnement et de la santé." Thesis, Littoral, 2016. http://www.theses.fr/2016DUNK0424/document.
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Ce travail de thèse a été consacré au développement de nouvelles méthodologies de caractérisation des affinités intermoléculaires par le biais de la calorimétrie de titration isotherme (ITC), après validation de systèmes modèles par l'intermédiaire des spectroscopies UV-visible, RMN et de l'électrophorèse capillaire. Nous avons en particulier montré que la mise en place et le couplage d'expériences non conventionnelles avec les protocoles classiques permettait d'améliorer la caractérisation calorimétrique, avec notamment une diminution parfois spectaculaire des incertitudes liées aux paramètres thermodynamiques. Ce potentiel de l'analyse globale d'expériences différenciées a été évalué sur un plan théorique, permettant ainsi la définition et l'optimisation des expériences à mettre en oeuvre en fonction du type de complexe étudié. L'exploitation expérimentale de ces stratégies a également permis l'étude de complexations problématiques sur le plan analytique, dans le cadre de complexes impliquant des molécules telles que les cyclodextrines ou l'albumine, et s'inscrivant dans des applications liés aux domaines de l'environnement et de la santé. Ainsi, nos stratégies ont levé les difficultés liées aux complexes athermiques, aux complexes de faibles affinités, aux équilibres multiples et aux faibles solubilités de l'un ou l'autre des partenaires de la complexation. Enfin, l'évaluation d'un nouveau modèle de traitement thermo-cinétique du thermogramme ITC a été réalisée, accroissant encore le potentiel de cette technique vis-à-vis de la caractérisation des interactions moléculairesThis work was dedicated to the development of new isothermal titration calorimetry (ITC) methodologies for the characterization of intramolecula affinities, after validation of model system via capillary electrophoresis, UV-visible and NMR spectroscopy. We have demonstrated that the coupling of unconventional experiments with the conventional protocols generally improves the calorimetric characterization, with a dramatic decrease of the uncertainties on thermodynamic parameters. The potential of global analysis applied to differentiated experiments was evaluated on a theoretical level, allowing the definition of optimal experiments, depending on the type of studied complex. These strategies also enabled, on a experimental point of view, the study of complexations which cannot be analyzed by conventional approaches, in the case of complexes involving cyclodextrins or albumin. Indeed, our strategies overcomes the difficulties associated with athermic complexes, with complexes of low affinity, with multiple equilibria and with the low solubility of interacting partners. Finally, the evaluation of a new thermo-kinetic treatment of ITC thermograms has been achieved, further increasing the potential of this technique in the characterization of molecular interactions
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Roberge, Aki. "Ultraviolet spectroscopy of circumstellar disks." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068203.
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Gong, Yun. "Structure-property relationships of dyes as applied to dye-sensitized solar cells." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275007.
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This work investigates the correlation of structural and photovoltaic properties of dyes used in dye-sensitized solar cells. Experimental methods, including ultraviolet-visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy are employed to study optical and electrochemical properties of dye molecules. Computational methods, including density functional theory and time-dependent density functional theory, are used to validate and predict the optical and electronic properties of dye molecules, in their isolated state and once embedded into a working electrode device environment that comprises a dye...TiO2 interface. The results chapters begin with the presentation of a series of quinodimethene dyes that are experimentally validated for their photovoltaic application, and associated computational studies reveal that an inner structural factor - a phenyl ring rotation occurring during the optical excitation process - leads to the competitive photovoltaic device performance of these dyes. Carbazole-based dyes are then systematically studied by computation, especially considering charge transfer paths and binding modes of these dyes on a titania surface. The theoretical models for the basic building block of this chemical family of dyes, known as MK-44, successfully support and explain structural discoveries from X-ray diffraction and reflectometry that impact of their function. A benzothiadiazole-based dye, RK-1, is then systematically studied by both experimental and computational methods, and the results show that the π-bridge composed of thiophene, benzothiadiazole and benzene rings leads to excellent charge separation; and the rotation of these rings during the optical excitation process may well be consistent with the fluorescence spectrum. Finally, the well-known ruthenium-based dyes are theoretically studied to determine the properties of different ligands connected to the metal core of the complex. Conformations with different NCS ligands are calculated in terms of energy and explain well the corresponding results from X-ray diffraction. Acid-base properties of carboxyl groups connected to pyridine ligands in N3 and N749 are theoretically calculated based on thermodynamics and density functional theory. Implicit and explicit models are both adopted to predict these acid dissociative constant values, which are generally in a good agreement with the reported experimental data. The thesis concludes with conclusions and a future outlook.
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Gianola, Adam J. "Ultraviolet photoelectron spectroscopy of organic anions." Diss., Connect to online resource, 2006. 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:3219005.
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Zhang, Feifei. "Fabrication of Aluminium Nanostructure for Visible to Ultraviolet Plasmonics." Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0011.
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L'aluminium (Al) est à ce jour largement considéré comme l'un des métaux les plus prometteurs pour pousser les limites spectrales de la plasmonique vers l'ultraviolet. De plus, l’Al est bon marché, abondant, non toxique et compatible avec la technologie métal-oxyde-semi-conducteur. Dans cette thèse, nous étudions numériquement et expérimentalement l'influence de divers paramètres clés sur les propriétés optiques des nanostructures d’Al. Dans un premier temps, nous étudions la stabilité naturelle des nanoparticules d'aluminium, qui montrent une stabilité d'environ 90 jours lorsqu'elles sont exposées à l'air ambiant. Deuxièmement, nous étudions l'influence du recuit thermique rapide sur les propriétés plasmoniques des nanostructures d'Al. En raison de la réduction du nombre de joints de grains à l'intérieur du métal, une amélioration du facteur de qualité des résonances plasmoniques est trouvée avec un recuit dans des conditions optimales. Troisièmement, nous dévoilons l'effet crucial de la rugosité de surface présente sur les nanostructures lithographiées d’Al. Entres autres, La rugosité de surface provoque la disparition du mode quadripolaire induit par le substrat et l'affaiblissement du mode dipolaire plasmonique. Enfin, nous étudions l'effet de trois types de désordre uniforme (déplacement, taille et rotation sur des structures de types nano-bâtonnets) sur les propriétés plasmoniques de réseaux de nanoparticules d'aluminium. La possibilité d'ajuster leurs propriétés plasmoniques dans le visible et le proche ultraviolet en contrôlant le désordre est étudiéAluminum (Al) is now widely regarded as one of the most promising metals for pushing the spectral limits of plasmonics towards the ultraviolet range. Additionally, Al is cheap, abundant, non-toxic, and compatible with the complementary metal-oxide-semiconductor technology. In this thesis, we investigate numerically and experimentally the influence of various key parameters on the optical properties of Al nanostructures. Firstly, we study the natural stability of Al nanoparticles, which show about 90-days stability when totally exposed to the ambient air. Secondly, we study the influence of rapid thermal annealing on the plasmonic properties of Al nanostructures. Due to the reduction of the number of grain boundaries inside the metal, an improvement of the plasmonic resonances quality factor is found with annealing at optimal conditions. Thirdly, we unveil the crucial effect of the surface roughness of Al lithographed nanostructures. The surface roughness is found to cause the disappearance of the substrate-induced quadrupolar mode and the weakening of the plasmonic dipolar mode. Finally, we investigate the effect of three kinds of uniform disorder (displacement disorder, size disorder, and rotation disorder) on the plasmonic resonances of Al nanoparticle arrays. The possibility to tune their plasmonic properties in the visible and near ultraviolet range by controlling the disorder is studied
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Kalusniak, Sascha. "Ultraviolet and visible semiconductor lasers based on ZnO heterostructures." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16898.
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Im Rahmen dieser Arbeit wurden die optischen Eigenschaften von auf ZnO-basierenden Heterostrukturen untersucht. Besonderes Augenmerk lag hierbei auf ihrer Eignung als aktives Material in Laserdioden für den ultravioletten und sichtbaren Spektralbereich. Es wurde gezeigt, dass ZnO und seine ternären Mischkristalle ZnCdO und ZnMgO erstaunlich vielfältige Anwendungen ermöglichen. Mit diesem Materialsystem lässt sich sowohl ein sehr großer Spektralbereich für Lasertätigkeit abdecken als auch eine Vielzahl von Laseranordnungen realisieren. Im Detail wurde demonstriert, dass sich die Lasertätigkeit von ZnCdO/ZnO Quantengraben-Strukturen vom violetten bis in den grünen Spektralbereich verschieben lässt. Obwohl diese Strukturen starke interne elektrische Felder aufweisen, konnte optisch gepumpte Lasertätigkeit bei Zimmertemperatur bis zu einer Wellenlänge von 510 nm gezeigt werden. Die für die Lasertätigkeit nötige optische Rückkopplung wird durch makroskopische Defekte der Probe verursacht und die Proben fungieren somit als Zufallslaser. Die Herstellung von Mikroresonatoren ermöglichte die Untersuchung des Zusammenspiels von Fabry-Perot- und Zufalls-Rückkopplung. Die experimentellen und theoretischen Ergebnisse zeigen, dass der Schwellengewinn eines Zufallslasers in der Regel größer ist als der des Fabry-Perot-Lasers. Des Weiteren wurde gezeigt, dass hoch reflektierende Braggreflektoren für den ultravioletten und blau/grünen Spektralbereich aus ZnO- und ZnMgO-Schichten hergestellt werden können. Ferner wurden die teils unbekannten Brechungsindexverläufe der verwendeten ternären Materialen erarbeitet und Mikrokavitäten mit ZnO/ZnMgO Quantengraben Strukturen als aktive Schichten realisiert. An diesen Kavitäten konnte bei Temperaturen bis zu 150 K starke Kopplung zwischen Exzitonen und Photonen nachgewiesen werden. Bei Zimmertemperatur konnte vertikal-emittierende Lasertätigkeit im nahen ultravioletten Spektralbereich demonstriert werden.In the framework of this thesis, the optical properties of ZnO-based heterostructures fabricated by molecular beam epitaxy have been investigated, particularly with regard to their suitability for semiconductor laser devices operating in the ultraviolet and visible spectral range. It turned out that ZnO and its ternary alloys ZnMgO and ZnCdO are extremely versatile. They allow to tune the laser emission in a wide spectral range as well as to realize various laser geometries. In detail, it was shown that the laser emission of ZnCdO/ZnO multiple quantum wells can cover a spectral range from violet to green wavelengths. Although these structures suffer from large built-in electric fields, room temperature laser action under optical pumping was demonstrated up to a wavelength of 510. The optical feedback for lasing is provided by growth imperfections on a macroscopic length scale turning these structures into random lasers. The fabrication of micro-resonators allowed to study the interplay between random and Fabry-Perot feedback. The experimental and theoretical analysis shows that random feedback generally requires a larger gain than under Fabry-Perot feedback. Further, this work demonstrates that ZnO- and ZnMgO-layers can be used to fabricate highly reflective distributed Bragg reflectors for applications in the ultraviolet and blue/green spectral range. The partly unknown dispersion curves of the index of refraction of the employed ternary alloys have been elaborated. This enabled the realization of all monolithic microcavities with ZnO/ZnMgO quantum wells as active zone. For temperatures below 150 K strong exciton-photon coupling is observed in such microcavities. At room temperature, vertical cavity surface emitting laser action in the near UV spectral range is demonstrated for appropriately designed microcavities.
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West, Gavin N. (Gavin Neal). "Visible and ultraviolet integrated photonics for addressing atomic systems." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122915.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 117-129).
In the wake of many technological successes in integrated photonics based on silicon, attention has been given to applications in the visible light regime. This thesis is concerned with furthering the development of integrated photonics for controlling atomic systems, in particular individual trapped atomic ions. Nature places strict constraints on the frequency of the lasers used to address these atoms, typically spanning from the ultraviolet into the near infrared, and on the sensitivity to accidental perturbations from the control hardware. A platform for broadband integrated photonics, using amorphous aluminum oxide as the patterned material, is developed and exhibits suitable performance in the visible and ultraviolet. The waveguide loss and resonator quality factors are the best which have been reported to date, for wavelengths shorter than 500 nm. Next, a theory is developed which proposes laser frequency noise as a limiting factor for the extinction ratio of common integrated modulator designs. Understanding of this limit, and possible methods to suppress its effects, is important due to the fragile nature of single-photon-sensitive quantum systems. Finally, the application of technology developed here is applied to the analysis of trapped-ion-based optical atomic clocks. Justification for such integration of clocks and the impacts that result -- both good and bad -- are discussed from the perspective of a hardware designer.
by Gavin N. West.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Miller, Bradley E. "Vacuum ultraviolet laser spectroscopy of small molecules." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27891.
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Morton, Lynne G. "Visible and ultraviolet vertical external cavity surface emitting semiconductor lasers." Thesis, University of Strathclyde, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487870.
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Vertical External Cavity Surface Emitting Lasers (VECSELs) are an amalgamation of solid state laser and semiconductor laser technologies. They combine the high power and excellent beam quality associated with solid state laser design with the compactness and wavelength flexibility of semiconductor lasers. This thesis will report on the first red VECSEL which was used to demonstrate a novel VECSEL array and the first UV VECSEL using an AlGahiP gain region.
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Zhang, Yun. "Fabrication and characterization of GaN visible-blind ultraviolet avalanche photodiodes." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29604.
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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Shen, Shyh-Chiang; Committee Member: Doolittle, William A.; Committee Member: Dupuis, Russell Dean. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Scully, Shane William James. "Negative photoion spectroscopy in the extreme ultraviolet." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484323.
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Del, Zanna Giulio. "Extreme ultraviolet spectroscopy of the solar corona." Thesis, University of Central Lancashire, 1999. http://clok.uclan.ac.uk/7916/.
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New Extreme Ultra-Violet (EUV) observations of the solar corona, obtained by the Coronal Diagnostic Spectrometer (CDS) instrument on board the NASA/ESA Solar and Heliospheric Observatory (SOHO) are presented. The CDS instrument for the first time has provided the opportunity of observing a large number of emission lines from a wide range of ions of different elements. The spectral and spatial resolution of the CDS instrument has allowed the simultaneous application of a wide range of spectroscopic diagnostic techniques to determine the temperature distribution, densities and elemental abundances in the solar plasma. A differential emission measure (DEM) diagnostic technique has been used to infer the temperature structure and the element abundances. The importance of including DEM effects in the element abundance analysis is demonstrated. A complete in-flight cross-calibration between all the CDS detectors (NIS and €115, 150-785 A), is presented here for the first time. The level of accuracy and completeness of the CHIANTI atomic database, used throughout this thesis, has allowed the identification of the many hundreds of spectral lines observed in the CDS spectra, resulting in several new line identifications. An assessment of the €115 solar spectra is presented, showing that, in spite of complexities, €115 spectra are useful for diagnostic analyses. Many discrepancies (in particular with the Li-like ions) between theory and CDS observations are highlighted. It is shown that some of these may be explained by inaccurate ionization equilibrium calculations. Coronal hole densities, temperatures, DEMs, and relative element abundances from both off-limb (plume and inter-plume regions) and on-disc observations are derived and compared with quiet sun values. These included (August 1996) a large equatorial hole, the Elephant's Trunk, probably the best example of a coronal hole observed by SOHO. Coronal hole densities in both coronal (N 1x10 8 cm 3 ) and transition region (Ne = lxlO'° cm 3 ) plasma were found to be about a factor of 2 lower than in the quiet sun, with much lower emission measures at temperatures above 106 K. Moreover, in the transition region, the cell-centres in both coronal holes and quiet sun regions show consistently higher densities (factor of 2) compared to those in the network. Relative element abundances show approximately photospheric values for the coronal holes, with an indication of element abundance variation .(neon in particular) with the supergranular structure. On-disc EUV observations of coronal hole plumes have been performed. This allowed a spectroscopic characterisation of plumes to be obtained for the first time, leading to the first identification of a low-latitude plume near sun-centre. Plumes are shown to be quasi-isothermal structures, with temperatures T 7 - 8x10 5 K. Abundance analyses (using transition region lines) reveal a small FIP effect in these plumes, together with a decreased Ne/O abundance ratio (compared to photospheric).
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Millar, Sean Charles. "Ultraviolet photoelectron spectroscopy of metals and alloys." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328146.
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Coulomb, Bruno. "Spectrophotométrie U. V. -visible avancée pour l'analyse en continu d'éléments métalliques dans les eaux." Aix-Marseille 1, 2000. http://www.theses.fr/2000AIX11030.
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L'evolution constante des normes de qualite de l'eau et les nouvelles pratiques industrielles impliquent le developpement de procedures simples et rapides, adaptees aux techniques d'analyse en continu. Les metaux presentent, parmi les nombreux polluants rejetes dans le milieu naturel, un risque sanitaire important et leur concentration doit etre controlee frequemment dans les eaux naturelles et les effluents, sur site, afin de permettre une prise de decision rapide en cas de pollution accidentelle. Cependant, les methodes usuelles pour l'analyse des metaux sont couteuses et complexes, et ne permettent pas leur determination sur site. L'objectif de cette etude est donc de developper une procedure analytique simple et rapide pour l'analyse de 6 metaux (cu, fe, hg, ni, pb, zn) dans les eaux, adaptable a un analyseur en continu, par l'utilisation d'une separation complexometrique couplee a une detection u. V. Visible robuste, apres une etape rapide de photo-oxydation des echantillons. Dans un premier temps, differents reactifs ont ete elabores pour etre specifiques aux elements metalliques etudies. Pour chaque reactif, chaque complexe metallique forme presente une absorptivite differente des autres complexes et des ligands sous forme libre, permettant ainsi la differenciation des differents complexes metalliques et la quantification des metaux etudies par l'utilisation d'un calcul de deconvolution spectrale, realise sur des fenetres de longueurs d'onde dependant des metaux etudies et des reactifs utilises. La procedure proposee montre des resultats satisfaisants en comparaison avec la methode de reference d'analyse des metaux, et permet la determination quasi-simultanee de 6 metaux dans les eaux naturelles et les effluents industriels.
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Shen, Tiehan. "Optical properties of layered materials in the visible and vacuum ultraviolet." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330253.
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Lawrence, Karl Perry. "Photoprotection from ultraviolet and visible radiation induced damage to the skin." Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/photoprotection-from-ultraviolet-and-visible-radiation-induced-damage-to-the-skin(b2735cfd-f448-4fe6-837a-21ad5eb12311).html.
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Solar radiation has numerous effects on the skin. Some are beneficial, however the majority are negative and contribute to development of skin cancer. Most studies have focused on ultra violet radiation (UVR ~290-400nm), however there is growing evidence to suggest that visible light (400-700nm) also causes skin damage. The main way of preventing solar damage is with the use of sunscreens, however these absorb in the UVR region with poor protection in the UVA/visible boundary waveband. There is growing evidence to suggest that synthetic UVR filters damage fragile marine environments, causing bleaching of corals and hormonal changes in fish. There is also evidence that some filters may damage human health, acting as exogenous oestrogens and inducing oxidative stress. The aim of this thesis was to assess biomarkers of skin damage with a range of in vitro and in vivo endpoints: DNA photodamage, inflammation/ immunoregulation, photoageing, oxidative stress and pigmentation. The focus was on broadband solar simulated UVR and its boundary with visible radiation (385-405nm). It was determined whether current sunscreen formulations provided adequate protection in this region, and if the addition of a new synthetic filter, could improve photoprotection. Furthermore, the ability of naturally occurring marine UVR filters, mycosporine-like amino acids (MAAs) was assessed, with a view to the development of a new generation of biocompatible alternatives to eco-toxic synthetic UVR filters. The results demonstrate that there is substantial damage in the UVR/visible boundary region for all biomarkers tested, and sunscreens using currently available filters do not provide sufficient protection; however the addition of the new filter significantly improved the protection offered. The MAA provided significant protection against all endpoints induced by solar simulated UVR. Furthermore, it demonstrated anti-oxidant capacity when added post UVR exposure. These results demonstrate that further investigation into the effects of visible radiation on the skin is required and the importance of improving sunscreens from an efficacy and environmental standpoint.
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Carlson, David R. "Frequency Combs for Spectroscopy in the Vacuum Ultraviolet." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/612874.
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This dissertation explores frequency comb spectroscopy and, in particular, its extension to the vacuum-ultraviolet (VUV) and extreme-ultraviolet (XUV) wavelength regimes through a technique called intracavity high harmonic generation (IHHG). By combining the techniques of passive pulse amplification in an enhancement cavity with high harmonic generation, IHHG enables the direct conversion of near-infrared radiation to the VUV/XUV while still maintaining the underlying comb structure .As part of this work, a series of numerical simulations was performed to investigate the plasma that is formed in the IHHG process and its implications for the resulting VUV comb. It was demonstrated that a fundamental limitation to the performance of IHHG experiments is due to the single-pass ionization phase shift acquired by the pulse circulating in the enhancement cavity. Furthermore, we showed that a static background plasma accumulates between pulses and complicates cavity stabilization. Insights gained from the simulations led to the development of a novel pump-probe technique using the enhancement cavity that allowed a direct measurement of the intracavity plasma and its decay dynamics in real-time. Because the plasma lifetime plays such a crucial role in the operation of these cavities, it was important to have a method to test ways of reducing it. To build on our initial IHHG results showing record-level powers in the XUV, we implemented a fully phase-coherent dual comb spectrometer consisting of two identical IHHG systems operating in parallel. The system is designed for precision spectroscopy in the VUV and is based on a pair of homemade ytterbium fiber lasers that use a parabolic amplification scheme to achieve 80 fs pulses after amplification to 50 W of average power. Initial dual comb data showing system performance at the fundamental frequency and third harmonic are presented.
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Richmond, A. M. "Vacuum ultraviolet discharge excited lasers." Thesis, University of Oxford, 1987. http://ora.ox.ac.uk/objects/uuid:3a09736b-bffb-4ac9-b57c-fb9daa1c8484.
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The thesis concerns experimental studies of discharge excited lasers operating in the vacuum ultraviolet (VUV) region of the spectrum. The known molecular fluorine laser operating at 157nm, on a bound- to-bound transition of the F2 molecule was selected for initial study. As a result of the work reported here the energy per pulse was increased by a factor of five (10mJ to 50mJ) from that of earlier F2 lasers. Similary the working lifetime of the gas mixture was increased from a few shots to several thousand by the application of cryogenic gas purification techniques. These improvements have resulted in the development of a practical commercial F2 laser. The performance characteristics of the fluorine laser and their relationship to the physical mechanisms are discussed. With the objective of achieving laser action in the 110 to 130nm region of the VUV a novel scheme is investigated. The scheme involves the production of a population inversion between the v'=1 level of the b1πu state of molecular nitrogen and high lying levels of the X1Σg ground state. The excitation of the upper laser level involves production of N2 molecules in the a1πg state by means of a pulsed discharge. Transfer of population from this intermediate 'a' state to the upper level is accomplished by absorption of radiation at 308nm from a discharge excited xenon chloride laser. The practicality of this scheme has been investigated to the extent that populations of the order of 1013 molecules per cm3 have been produced in the 'a' state and laser induced fluorescence on the 'b' to 'X' band has been observed. Under the conditions of "the present experiments the potential VUV gain is too small (10-4cm-1>/sup>) to reach laser threshold. The problems of increasing the gain to reach threshold for a practical device are discussed.
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Posavec, Tony. "An Investigation into the Fluorescence of Polymers." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1499353221343727.
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HUTH, THOMAS CARL. "ANALYTICAL MASS SPECTROMETRY WITH A SELECTIVE VACUUM ULTRAVIOLET PHOTOIONIZATION SOURCE." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183916.
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The vacuum ultraviolet molecular hydrogen laser is evaluated as a selective ion source for analytical mass spectrometry of easily-ionized compounds. The types of compounds ionized below the photon energy of 7.8 eV include polynuclear aromatic hydrocarbons, and many amines and nitrogen-containing heterocycles. The latter two categories encompass a large number of pharmaceuticals and drugs of abuse. H₂ laser photoionization produces parent molecular ions only, for all compounds studied thus far. Selectivity of the threshold photoionization process is very high, as compounds within as little as 0.2 eV above the threshold are completely rejected. The ability of the technique to discriminate against interfering matrix components is demonstrated for both simple synthetic and complex "real world" mixtures. Easily interpreted spectra are obtained from simple extracts of spiked coffee, beer, soy sauce, urine and blood serum. The most important interference is shown to be electron impact ionization arising from acceleration of stray electrons in the ion source. Most of this ionization is caused by low-energy secondaries generated when stray primaries are collected by the ion source electrodes. The primaries are produced mainly by interaction of scattered laser radiation with metal surfaces. This interference can be controlled through proper instrumental design.
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Aguilar, Lara Karla. "Effect of ultraviolet/visible radiation processing on the quality of fruit juices." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/405804.
Full textAbstract:
Aquest treball va estudiar la irradiació ultraviolada-visible (UV-Vis) com una alternativa per a la pasteurització de sucs. Els resultats van mostrar que la irradiació ultraviolada no produeix hidroximetilfurfural i es capaç de degradar-lo. Es va proposar un mecanisme de foto-degradació i es van usar diferents models cinètics per descriure la reacció. La foto-degradació de la vitamina C va ser insignificant usant una làmpada d’emissió múltiple. A més, el processament d’UV-Vis va ser efectiu inactivant els enzims polifenoloxidasa i peroxidasa; a major temperatura major inactivació. Mentrestant, la majoria dels paràmetres fisicoquímics van ser pràcticament inalterats i la quantitat inicial de pigments es va reduir. Per tant, el processament d’UV-Vis combinat amb lleu escalfament és una alternativa viable per a la pasteurització de sucs.Este trabajo estudió la irradiación ultravioleta-visible (UV-Vis) como una alternativa para la pasteurización de zumos. Los resultados demostraron que la irradiación ultravioleta no produce hidroximetilfurfural y es capaz de degradarlo. Se propuso un mecanismo de foto-degradación y se usaron diferentes modelos cinéticos para describir la reacción. Por el contrario, la foto-degradación de la vitamina C fue insignificante usando una lámpara de emisión múltiple. Además, el procesamiento UV-Vis fue efectivo inactivando las enzimas polifenoloxidasa y peroxidasa en zumos; a mayor temperatura, mayor inactivación. Mientras tanto, la mayoría de los parámetros fisicoquímicos fueron prácticamente inalterados y la cantidad inicial de pigmentos fue reducida. Por lo tanto, el procesamiento UV-Vis combinado con un calentamiento suave representa una alternativa viable para la pasteurización de zumos.
This work studied the ultraviolet-visible (UV-Vis) irradiation as an alternative for fruit juice pasteurisation. The results showed that ultraviolet irradiation does not produce hydroxymethylfurfural and is capable of degrade it. A mechanism of photo-degradation was proposed and different kinetic models were used to describe the reaction. On the contrary, the photo-degradation of vitamin C was insignificant using a multi-wavelength emitting lamp. Moreover, the UV-Vis processing was effective inactivating the enzymes polyphenoloxidase and peroxidase in fruit juices. The higher the temperature the higher the inactivation. Meanwhile, most physicochemical parameters were practically unaltered and the initial quantity of pigments was reduced. Therefore, the UV-Vis processing combined with a mild-heating represents a viable alternative for fruit juice pasteurisation.
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Cates, Ezra Lucas Hoyt. "Development of visible-to-ultraviolet upconversion phosphors for light-activated antimicrobial surfaces." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47619.
Full textAbstract:
A new form of antimicrobial surface was developed, which relies on an optical mechanism rather than chemical inactivation of microorganisms. Through the photoluminescence process of upconversion, low energy photons can be amplified into higher energy photons, and in this case, phosphors capable of converting visible light into germicidal UVC radiation were synthesized. Host crystals were doped with a praseodymium activator ion and shown to emit UVC photons upon excitation by blue or violet light. Surface coatings were prepared and proof-of-concept experiments demonstrated that, under exposure to a household fluorescent lamp, sufficient UVC radiation was emitted from the surfaces to achieve observable inactivation of surface bacterial spores and inhibition of biofilm growth. Material engineering was conducted to achieve higher optical conversion efficiency, wherein lithium codoping and development of alternative oxyfluoride host crystals were found to significantly improve upconversion emission. Implications of polychromatic excitation were investigated by conducting photoluminescence spectroscopy under combined laser beam excitation, while the effects of other application parameters are also discussed. These findings show that upconversion-based antimicrobial materials have strong potential for offering sustainable and effective technology for the prevention of diseases.
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Eichert, James J., James F. Carbary, Priscilla L. McKerracher, and Lora L. Suther. "Ultraviolet and Visible Imaging and Spectrographic Imaging (UVISI) Data Processing Center (DPC)." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/608394.
Full textAbstract:
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThe nine sensors and one image processor of the Ultraviolet and Visible Imaging and Spectrographic Imaging (UVISI) instrument aboard the Midcourse Space Experiment (MSX) satellite can potentially generate up to three gigabytes of data of data per day. The UVISI Data Processing Center (DPC) must execute a multitude of complex processing functions in a 24-hour operational window, verify the UVISI data and also provide a compact, quantified record of the verification. The Center additionally must support higher-level data analysis functions. Data processing functions are divided into pipeline processing and data conversion processing. Pipeline processing, which consists of the main pipeline process, Pipeline, and several auxiliary processes is responsible for generating Data Quality Indices (DQI) that summarize sensor performance and Data Measurement Indices (DMI) that summarize sensor measurements. Both sets of indices provide scientists and engineers with a compact, easily-reviewed record of instrument performance. The conversion process, Convert, supports data analysis by converting raw telemetry into scientific/engineering units. On a pixel-by-pixel basis, Convert provides functions for dark-correction, flat-fielding, gain and gate adjustment, non-linearity correction, and count-to-photon conversion. Operating in conjunction with Convert, a pointing utility, Point, is used to determine the locations of selected objects in inertial space. The accomplishment of these myriad tasks relies on a state-of-the-art computer network using multiple workstations. Normal DPC operations are fully automated but remain flexible enough to allow prompt intervention by the UVISI Performance Assessment Team (PAT).
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Zhang, Zhipeng, Wenckstern Holger von, Jörg Lenzner, Michael Lorenz, and Marius Grundmann. "Visible-blind and solar-blind ultraviolet photodiodes based on (InxGa1-x)2O3." American Institute of Physics, 2016. https://ul.qucosa.de/id/qucosa%3A23547.
Full textAbstract:
UV and deep-UV selective photodiodes from visible-blind to solar-blind were realized based on a
Si-doped (InxGa1–x)2O3 thin film with a monotonic lateral variation of 0.0035
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Henderson, Angus. "Studies of optical parametric oscillators for the ultraviolet and visible spectral regions." Thesis, University of St Andrews, 1993. http://hdl.handle.net/10023/14951.
Full textAbstract:
The work described herein concerns the characterisation and development of optical parametric oscillators (OPOs) tunable in the ultraviolet, visible and near infrared regions. These devices were pumped by the 308nm output from line-narrowed Xenon Chloride excimer lasers of pulse energy up to 150mJ. The behaviour of Type 2 phase-matched Urea, and Type 1 phase-matched Barium Borate OPOs in terms of oscillation threshold and conversion efficiency, has been explored. The detrimental effects of pump beam walkoff on the threshold of the critically phase-matched Barium Borate OPO have been quantified. It was found that minimum 17ns pulse energies of 5mJ were required to reach threshold in a device based on a crystal of 20mm length. By contrast, noncritically phase-matched Urea OPOs using crystal lengths of 25mm were operated with as little as 0.6mJ pump energy. A deterioration in performance was observed in both cases with decreasing pump beam waist. Maximum pump depletions of 72% and 64% were observed in Urea and BBO respectively. The useful output from the urea device reached 65%, while higher absorption/scattering losses meant that the useful fraction in BBO was very much lower. Two different types of noncollinear phase-matching were studied in the BBO-OPO. The first recorded observation of operation of a Type 1 OPO at crystal angles beyond the degenerate wavelength point was made. The output took the form of two concentric rings and was attributed to simultaneous singly and doubly resonant operation. Finally, single longitudinal mode operation of the BBO-OPO was demonstrated using a dispersive cavity arrangement. The widely varying inherent linewidth of the device required that different strategies be adopted over different wavelength ranges. Encouraging performance in terms of threshold was observed using the dispersive cavity, and the feasibility of using this device as a low-power first stage for an oscillator/amplifier set-up was studied.
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Glass, Fenton John, and f. glass@fz-juelich de. "Tomographic Visible Spectroscopy of Plasma Emissivity and Ion Temperatures." The Australian National University. Research School of Physical Sciences and Engineering, 2004. http://thesis.anu.edu.au./public/adt-ANU20051028.002110.
Full textAbstract:
Extending the use of Doppler spectroscopy as an important plasma diagnostic -- by developing a multi-channel system capable of tomography -- is the foundation of this thesis. A system which can simultaneously measure the emissivity, temperature and flow velocity of plasma ions has been installed, calibrated and operated on the H-1NF heliac, yielding comprehensive and interesting results. The measurements are time-resolved, made from a large range of viewing positions and, using scalar tomographic inversion methods, can be
unfolded to give two-dimensional images of ion emissivity and temperature. The flow velocity profiles, while not inverted, nevertheless lead to a greater understanding of the plasma behaviour.¶
Fifty-five lens-coupled optical fibres, mounted on a large rotatable stainless steel ring, encircle the plasma poloidally and transport light to a multi-channel Fourier-transform spectrometer. This
`coherence-imaging' spectrometer employs an electro-optically modulated birefringent crystal plate to monitor the coherence of an
isolated spectral line. Measurement of the intensity, fringe visibility and phase of the resulting interferogram leads to values
for the emissivity, ion temperature and flow velocity. Using a multi-anode photomultiplier assembly, allows the time-resolved detection of all optical channels simultaneously.¶
The system has been fully calibrated, including a measurement of the spatial response of each line-of-sight. The calibration procedure accounts for the relative channel sensitivities, the response of the line filter and the removal of detector cross-talk. In situ light sources are installed provide routine and accurate relative
intensity calibration of the system.¶
Methods of tomography provide the unfolding of the measured plasma
parameters to construct two-dimensional images of ion temperature and emissivity. Methods of inversion include the iterative ART routine -- using projection data gathered with the light-collecting optics rotated to different viewing positions -- and linear composition of Fourier-Bessel basis functions -- with the data obtained from a
single unrotated viewing position. ART reconstructions of the emissivity are performed without the need for a priori information while those of the ion temperature are computed using regularising functions to help stabilise the
inversion.¶
This new system -- named ToMOSS for Tomographic Modulated Optical
Solid-state Spectrometer -- enables a more detailed study of various plasma
phenomena observed in H-1NF. Among other results, this thesis presents the first tomographic reconstructions of emissivity and temperature fluctuations associated with a large-scale coherent instability.