To see the other types of publications on this topic, follow the link: Spectroscopic and physicochemical techniques.
Dissertations / Theses on the topic 'Spectroscopic and physicochemical techniques'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Spectroscopic and physicochemical techniques.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
VALENTE, VANESSA SOUZA BREDER. "PHYSICOCHEMICAL CHARACTERIZATION OF COMMERCIAL BIODIESEL/DIESEL BLENDS AND POTENTIALITY EVALUATION OF UNCONVENTIONAL SPECTROSCOPIC VIBRATIONAL TECHNIQUES IN MONITORING THEIR OXIDATION AND HYDROLYSIS DURING STORAGE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29804@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Uma série de ensaios físico-químicos realizados em misturas comerciais Bx (0 por cento, 7 por cento, 20 por cento, e 100 por cento de biodiesel soja/sebo) em óleo diesel S10 e S500, bem como o desempenho de duas técnicas rápidas e ainda pouco exploradas, denominadas, espectroscopia FTIR-HATR e Raman, foram utilizadas para avaliar a estabilidade oxidativa e a hidrólise destas misturas. A adição de biodiesel ao diesel afeta negativamente a resistência ao envelhecimento das misturas resultantes. Misturas S500 são mais ácidas do que misturas S10, em concordância com o teor de água mais elevado da primeira. Testes de estabilidade oxidativa acelerada por Rancimat mostraram que os tempos de indução das amostras de B7 e B20 são maiores do que os de B100, independente do teor de enxofre do diesel. O uso prático de FTIR-HATR para caracterizar o estágio de degradação das misturas é condicionado pelo fato de existirem duas contribuições químicas para cada uma das bandas estudadas. Por outro lado, a espectroscopia Raman representa uma técnica espectroscópica muito adequada para detectar presença de insaturações das cadeias de ácidos graxos do biodiesel. Uma vez que as espectroscopias FTIR-HATR e Raman não necessitam de preparação de amostras, são técnicas rápidas e de baixo custo, e causam baixo impacto ao meio ambiente, mais atenção pode ser dada a elas.
A series of physicochemical studies performed on Brazilian commercial Bx (0 per cent, 7 per cent, 20 per cent, and 100 per cent soybean/tallow biodiesel) mixtures in S10 and S500 oil diesel, as well as the performance of two rapid and still underexplored techniques, namely, FTIR-HATR and Raman spectroscopies, to evaluate the hydrolysis and oxidative stability of these blends are reported. The addition of biodiesel to diesel affects negatively the aging resistance of the resulting blends. S500 blends are more acidic then S10 blends, in accordance with the higher water content of the former. Rancimat accelerated oxidative stability tests showed that the induction times of B7 and B20 samples are greater than that of B100, independent of the sulfur content of the diesel. The practical use of FTIR-HATR to characterize the mixtures degradation stage is conditioned by the fact that there are two chemical contributions for each of the studied bands. On the other hand, Raman spectroscopy represents a very suitable spectroscopic technique to detect the presence of unsaturations in the fatty acids chains of biodiesel. Since FTIR-HATR and Raman spectroscopies do not require sample preparation, are fast and quite low cost techniques, and cause low impact to the environment, further attention may be paid to them.
2
Saha, Subhadeep. "Study to explore the formation of host - guest inclusion complexes of cyclodextrins with biologically active moleculars and crown ethers with ionic liquids by spectroscopic and physicochemical techniques." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2648.
Full text
3
Kumar, Pushpendra. "Impact of 14/28nm FDSOI high-k metal gate stack processes on reliability and electrostatic control through combined electrical and physicochemical characterization techniques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT114/document.
Full textAbstract:
Cette thèse concerne l’étude des procédés de fabrication des grilles HKMG des technologies FDSOI 14 et 28 nm sur les performances électriques des transistors MOS. Elle a porté spécifiquement sur l'aspect fiabilité et la maîtrise du travail de sortie effectif (WFeff), au travers de la diffusion des additifs comme le lanthane (La) et l’aluminium (Al). Ce travail combine des techniques de caractérisation électriques et physico-chimiques et leur développement. L'effet de l'incorporation de ces additifs sur la fiabilité et la durée de vie du dispositif a été étudié. Le lanthane dégrade les performances de claquage TDDB et de dérives suite aux tests aux tensions négatives. L’introduction d’aluminium améliore le claquage TDDB, mais dégrade les dérives aux tensions positives. Ces comportements ont été reliés à des mécanismes physiques. Par ailleurs, la diffusion de ces additifs dans l’empilement de grille a été étudiée pour différents matériaux high-k en fonction de la température et de la durée de recuit de diffusion. Les doses d’additifs ont pu être ainsi mesurées, comparées et corrélées au décalage de travail de sortie effectif de grille. On a également étudié, les influences des paramètres du procédé de dépôt de grille TiN sur leur microstructure et les propriétés électriques du dispositif, identifiant certaines conditions à même de réduire la taille de grain ou la dispersion d’orientation cristalline. Toutefois, les modulations obtenues sur le travail de sortie effectif de grille dépendent plus du ratio Ti/N, suggérant un changement du dipôle à l'interface SiO2 / high-k. Enfin, une technique éprouvée de mesure de spectroscopie à rayon X sous tension a pu être mise en place grâce des dispositifs spécifiques et une méthodologie adaptée. Elle permet de mesurer les positions relatives des bandes d’énergie à l'intérieur de l’empilement de grille. Cette technique a démontré que le décalage du travail de sortie effectif induits par des additifs (La or Al) ou par des variations d'épaisseur de grille métallique TiN provient de modifications du dipôle à l'interface SiO2/ high-kThis Ph.D. thesis is focused on the impact of the 14 and 28 nm FDSOI technologies HKMG stack processes on the electrical performance of MOS transistors. It concerns specifically the reliability aspect and the engineering of effective workfunction (WFeff ), through diffusion of lanthanum (La) and aluminum (Al) additives. This work combines electrical and physicochemical characterization techniques, and their development. The impact of La and Al incorporation, in the MOS gate stack, on reliability and device lifetime has been studied. La addition has a significant negative impact on device lifetime related to both NBTI and TDDB degradations. Addition of Al has a significant negative impact on lifetime related to PBTI, but on the contrary improves the lifetime for TDDB degradation. These impacts on device lifetime have been well correlated to the material changes inside the gate oxides. Moreover, diffusion of these additives into the HKMG stack with annealing temperature and time has been studied on different high-k materials. The diffused dose has been compared with the resulting shift in effective workfunction (WFeff), evidencing clear correlation. In addition, impact of TiN metal gate RF-PVD parameters on its crystal size and orientation, and device electrical properties has been studied. XRD technique has been used to obtain the crystal size and orientation information. These properties are significantly modulated by TiN process, with a low grain size and a unique crystal orientation obtained in some conditions. However, the WFeff modulations are rather correlated to the Ti/N ratio change, suggesting a change in the dipole at SiO2/high-k interface. Lastly, using specific test structures and a new test methodology, a robust and accurate XPS under bias technique has been developed to determine the relative band energy positions inside the HKMG stack of MOS devices. Using this technique, we demonstrated that WFeff shift induced by La and Al or by variations in gate thickness originates due to modifications of the dipole at SiO2/high-k interface
4
Pell, Wendy. "Zinc/bromine battery electrolytes: Electrochemical, physicochemical and spectroscopic studies." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9521.
Full textAbstract:
The zinc/bromine battery is a flowing electrolyte battery operating at ambient temperatures, and having both stationary and mobile applications. It is characterized by a flat voltage discharge profile, can be deeply discharged without adverse effects, and is made from low cost materials which can be recycled at the end of the battery's life. The electrochemically active materials are stored externally to the electrode assembly in two reservoirs, and are pumped to the electrodes during operation. The electrolyte typically includes aqueous zinc bromide and quaternary ammonium salts, such as methyl ethyl pyrrolidinium bromide (MEPBr) and methyl ethyl morpholinium bromide (MEMBr) which complex bromine and reduce self-discharge losses. Modification of the low temperature behaviour of the usual electrolyte, which freezes between $-$5 and 5$\sp\circ$C, is required if the battery is to perform successfully at low temperatures. This project identified electrochemical and physical chemical techniques to study zinc deposition and bromine production at glassy carbon electrodes as a method to gain quantitative and qualitative information from the electrolyte system. Electrochemical response, chemical species distribution, conductivity and phase change data were obtained for battery electrolytes at low temperatures and used to identify candidate electrolytes for low temperature applications. The effect of the quaternary ammonium bromide salt on zinc species distribution and zinc deposition has not previously been studied. Spectroscopic and electrochemical studies indicated that the distribution of zinc/bromine complexes in solutions, and zinc deposition at glassy carbon were unaffected by the addition of quaternary ammonium bromides. The distribution of zinc/bromine complexes was significantly affected by temperature and state-of-charge or concentration of the electrolyte. Several organic compounds, including propan-2-ol, ethylene dichloride, propylene glycol and ethylene glycol, were evaluated as additives to the aqueous electrolyte for low temperature applications using techniques of cyclic voltammetry, chronoamperometry, conductivity, and freezing point determination. Ethylene glycol was also selected on the basis of electrochemical and physical chemical data, to be tested in the single cell battery. Due to reduced conductivity of the electrolyte (higher solution resistance in the battery), the voltaic and energy efficiencies were expected to be lower than those of a standard electrolyte battery. Electrochemical experiments showed that neither bromide oxidation nor zinc cation reduction reactions were significantly affected by the presence of ethylene glycol. (Abstract shortened by UMI.)
5
Chakraborty, Moumita. "PHYSICOCHEMICAL INVESTIGATIONS ON MICROHETEROGENOUS SYSTEMS WITH SPECIAL REFERENCE TO SPECTROSCOPIC STUDIES." Thesis, University of North Bengal, 2013. http://hdl.handle.net/123456789/974.
Full text
6
Hargreaves, Elaine Carol. "Applications of surface vibrational spectroscopic techniques." Thesis, University of Nottingham, 1997. http://eprints.nottingham.ac.uk/28593/.
Full textAbstract:
An advanced Electron Energy Loss Spectrometer has been used to study the formation of 3,3,3-trifluoropropylidyne on Pt (111). This has been compared to the results from the same system using the complementary vibrational spectroscopic technique of Reflection Absorption Infrared Spectroscopy (RAIRS). This study demonstrates the improved resolution of the new spectrometer. The thermal decomposition products, CF3 and CF2 have been detected in the Electron Energy Loss (EEL) spectra. The RAIR spectra of carbon monoxide on Cu (111) have been recorded using synchrotron radiation. An optical accessory has been used to record the RAIR spectra at an incident angle of 20°. The results have been compared to an incident angle of 87°. At 20° no conventional absorption band at 339 cm-l was observed and an anti absorption band at 274 em-l of similar magnitude to that at 87° was seen. This has confirmed the involvement of the parallel electric field in the observation of antiabsorption bands. The EEL spectra of hydrogen and deuterium adsorbed on Pt (111) at 160 K have been recorded. The data has been interpreted using the Nearest Neighbour Central Force Constant (NNCFC) model in terms of 3- fold and 2-fold bridging sites. It is the 2-fold site which offers the more complete assignment of the vibrational bands observed.
7
Zadrozny, Andrew. "Spectroscopic techniques and observations in infrared astronomy." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46625.
Full text
8
Santerne, A., J. P. Beaulieu, Ayala B. Rojas, I. Boisse, E. Schlawin, J. M. Almenara, V. Batista, et al. "Spectroscopic characterisation of microlensing events." EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/622445.
Full textAbstract:
The microlensing event OGLE-2011-BLG-0417 is an exceptionally bright lens binary that was predicted to present radial velocity variation at the level of several km s(-1). Pioneer radial velocity follow-up observations with the UVES spectrograph at the ESO-VLT of this system clearly ruled out the large radial velocity variation, leaving a discrepancy between the observation and the prediction. In this paper, we further characterise the microlensing system by analysing its spectral energy distribution (SED) derived using the UVES spectrum and new observations with the ARCoIRIS (CTIO) near-infrared spectrograph and the Keck adaptive optics instrument NIRC2 in the J, H, and Ks-bands. We determine the mass and distance of the stars independently from the microlensing modelling. We find that the SED is compatible with a giant star in the Galactic bulge and a foreground star with a mass of 0.94 +/- 0.09 M-circle dot at a distance of 1.07 +/- 0.24 kpc. We find that this foreground star is likely the lens. Its parameters are not compatible with the ones previously reported in the literature (0.52 +/- 0.04 M-circle dot at 0.95 +/- 0.06 kpc), based on the microlensing light curve. A thoughtful re-analysis of the microlensing event is mandatory to fully understand the reason of this new discrepancy. More importantly, this paper demonstrates that spectroscopic follow-up observations of microlensing events are possible and provide independent constraints on the parameters of the lens and source stars, hence breaking some degeneracies in the analysis. UV-to-NIR low-resolution spectrographs like X-shooter (ESO VLT) could substantially contribute to this follow-up efforts, with magnitude limits above all microlensing events detected so far.
9
Haines, Emma Sara. "The application of chemometric techniques to spectroscopic data." Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301636.
Full text
10
Dallin, Paul Howard. "Novel spectroscopic techniques applied to metal cluster compounds." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291953.
Full text
11
Knowles, S. J. "Quantitative analysis of agrochemicals by multivariate spectroscopic techniques." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394518.
Full text
12
Allen, James Thomas. "Application of novel techniques to large spectroscopic surveys." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609709.
Full text
13
Neil, Simon R. T. "Condensed-phase applications of cavity-based spectroscopic techniques." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:4431e46e-1226-4950-aa5d-ce22e0309ba9.
Full textAbstract:
This thesis describes the development and application of condensed-phase cavity-based spectroscopic techniques - namely cavity ring-down spectroscopy (CRDS); cavity enhanced absorption spectroscopy (CEAS); broadband cavity enhanced absorption spectroscopy (BBCEAS) and evanescent wave (EW) variants of all three. The recently-developed cavity technique of EW-broadband cavity enhanced absorption spectroscopy (EW-BBCEAS) has been used—in combination with a supercontinuum source (SC) and a sensitive, fast readout CCD detector—to record of the full visible spectrum (400–700 nm) of a silica-liquid interfacial layer (with an effective thickness ca. 1 µm), at rapid acquisition rates (> 600 Hz) that are sufficient to follow fast kinetics in the condensed phase, in real time. The sensitivity achieved (Amin= 3.9 x 10-5) is comparable with previous EW-CRDS and EW-CEAS studies, but the spectral region accessed in this broadband variant is much larger. The study of liquid|air interfaces using EW cavity-based techniques is also illustrated for the first time. The first application of BBCEAS to the analysis of microfluidic samples, flowing through a microfluidic chip, is illustrated. Proof-of-principle experiments are presented, demonstrating the technique’s ability to provide full visible broadband spectral measurements of flowing microfluidic droplets, with both high detection sensitivity (αmin < 10-2 cm-1) and excellent spatial and temporal resolution: an SC light source and sensitive, fast readout CCD allowed measurement repetition rates of 273 Hz, whilst probing a very small sample volume (ca. 90 nL). A significant portion of this thesis is devoted to demonstrating the powerful capabilities of CEAS, CRDS and BBCEAS in monitoring radical recombination reactions and associated magnetic field effects (MFEs) in solution. The efficacy of CEAS as a high-sensitivity MFE detection method has been established in a proof-of-principle study, using narrow band CEAS in combination with phase-sensitive detection: MFE-induced absorbance changes of ca. 10-6 could be detected using the modulated CEAS technique and the data are shown to be superior to those obtained using conventional transient absorption (TA) methods typically employed for MFE measurements. The powerful capabilities of CRDS in monitoring radical recombination reactions and associated MFEs are also demonstrated. In particular, a pump-probe CRDS variant allows not only high sensitivity (Amin on the order 10-6), but also sub-microsecond time-resolution. Combined, these features represent significant advantages over TA. Finally, SC-BBCEAS is used to measure full visible spectra of photoinduced reactions and their MFEs. The applicability of this approach to in vitro MFE studies of Drosophila cryptochrome is demonstrated—the results mark the first in vitro observation of a magnetic field response in an animal cryptochrome, a key result supporting the hypothesis that cryptochromes are involved in the magnetic sense in animals.
14
Playez, Mickaël. "Titan atmosphere plasma characterization using spectroscopic measurement techniques." Châtenay-Malabry, Ecole centrale de Paris, 2006. http://www.theses.fr/2006ECAP1007.
Full textAbstract:
Lors des manoeuvres d'entrée ou d'aérocapture dans l'atmosphère de Titan, une quantité importante d'énergie est émise sous forme de radiation dans la couche de choc présente autour du véhicule spatial. Le dimensionnement du bouclier thermique du véhicule demande une évaluation précise de la quantité d'énergie qu'il reçoit sous forme radiative. Nous proposons dans cette étude une analyse du rayonnement émis par un plasma dont la composition est représentative de l'atmosphère de Titan, et ceci dans l'intervalle de longueur d'onde compris entre 350 et 1000 nm. Le plasma analysé est produit dans un tunnel plasma à couplage inductif (ICP). Des mesures par spectroscopie d'émission sont effectuées pour deux pressions différentes, 300 et 23 mbar. Le cas à haute pression favorise l'équilibre thermodynamique local dans l'écoulement, tandis que le cas à basse pression permet d'étudier un plasma hors équilibre. La modélisation de l'émission radiative du plasma est effectuée pour des conditions d'équilibre thermodynamique et montre un bon accord, sur une échelle absolue de l'émission, avec le spectre mesuré à haute pression. L'application du modèle développé à l'analyse du cas basse pression démontre l'obtention de conditions hors équilibre thermique. Des limitations liées à l'implémentation des mesures sont néanmoins observées. Elles sont liées aux fluctuations du plasma étudiéDuring entry or aero-capture in the atmosphere of the Saturn’s satellite Titan, largeamounts of radiation are produced in the shock layer of a spacecraft. The design of theheat shield of this vehicle requires a precise assessment of the radiative heat flux impingingon it. We propose in this study an analysis of the radiation emitted in the spectral range350-1000 nm by a high temperature gas mixture with a composition representative of theTitan atmosphere composition. The plasma is produced in an Inductively Coupled Plasmawind tunnel. Emission spectroscopy measurements are performed for two different pressureconditions, 300 and 23 mbar, in order to produce equilibrium and non-equilibrium plasmas. The modelling of the plasma emission at equilibrium is performed and shown to agree tothe measured spectra on a absolute scale for the high-pressure case. The use of the samemodel for the analysis of the low-pressure case provides evidence of departure from equilibrium. Limitations of the implemented procedure are observed. They are due to unresolved fluctuations of the plasma source
15
Huong, Audrey Kah Ching. "Spectroscopic analysis of scattering media via different quantification techniques." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12464/.
Full textAbstract:
This thesis outlines problems in the estimation of concentration value of an absorber present in a medium that is scattering and shortcomings of using the currently available techniques for the characterisation of such a scattering medium. The work describes experiment and analytic techniques used to overcome these problems. This thesis explored experimentally the practicality of using polarisation subtraction technique to minimise the effects of scattering components on the measured data. This work also considered the case when this technique has not been used owing to its limited application, and to that end, the improved linear equation and nonlinear fitting models, and gradient processing method were developed on the basis of the assumed behaviour of how a medium’s scattering coefficient changes with wavelength to provide information about the fractional concentration value of an absorber. The performance of these techniques evaluated via simulation showed that linear equation model has the fastest processing speed, nonlinear fitting method is robust to system noise and is able to provide an overall more accurate estimate of value with mean of errors of less than ±1%. The gradient processing method has intermediate performances with accuracy of its estimated value improved by about 30% with an increase in the spectral resolution from 1 nm to 0.5 nm. This work concludes that gradient processing method would be employed if accuracy of estimated value, noise robustness and computing time are of concern. However, nonlinear fitting method would be chosen in case high accuracy of the estimated value is required. Both of these methods can be suitably used as complementary techniques to clinical assessment of skin grafts and burnt skin. The simultaneous solution of linear equation model works well if all the measurement parameters are known.
16
Romans, James Alexander. "Multivariate Calibration Techniques for Spectroscopic Characterisation of Crude Oils." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506561.
Full text
17
Lizio, Maria Giovanna. "Exploring peptide foldamer-membrane interactions using optical spectroscopic techniques." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/exploring-peptide-foldamermembrane-interactions-using-optical-spectroscopic-techniques(694db937-1fb6-430d-98af-ba147c857e6e).html.
Full textAbstract:
The evolution of drug resistant pathogens creates the need for the introduction of new antimicrobial drugs. Peptaibols, a class of naturally occurring peptides, contain large amounts of alpha aminoisobutyric acid (Aib). They are known to exhibit their antimicrobial activity by perturbing the membranes of pathogens. However, a comprehensive model of action for these peptides has not yet been identified. Aib residues support the formation of 310-helix conformation and it is thought that this secondary structure is important for their antimicrobial activity. It is possible to design small synthetic peptides, known as foldamers, endowed with specific properties; in particular, Aib-rich foldamers are used as a model for the understanding of the folding and membrane interaction of the naturally occurring species. The aim of this thesis is to investigate the conformational preference of monodisperse Aib-oligomers as well as understanding their interaction with bilayer membranes. A large set of spectroscopic techniques have been used to establish the conformation of Aib-rich foldamers both in solution and when bound to membranes. In particular: Raman, Raman Optical Activity (ROA), Infrared (IR), Vibrational Circular Dichroism (VCD), Linear Dichroism (LD) and Neutron Scattering (NR) were employed to provide new structural insights. These vibrational analysis (VA) and vibrational optical analysis (VOA) investigations in solution were focused on the identification of spectral features for 310-helix conformation, particularly with Raman and Raman Optical Activity spectroscopies. Spectroscopic markers for this conformation in the amide I region were successfully identified. Moreover, it is known that chiral Aib-rich peptides can show a right or left handed screw-preference based on the primary sequence. VOA studies successfully distinguished between peptides with opposite helicity. VCD, ROA, LD and NR of Aib-foldamers bound to membranes were shown to be useful for identification of conformational preferences of the peptides within the membrane as well as for determining their orientation in the bilayer, and ultimately the effect of the peptides on the membrane structure.
18
Perera, Mahakumarage Suchithranga, and Mahakumarage Suchithranga Perera. "Investigation of Rhodopsin Activation Using Spectroscopic and Scattering Techniques." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/622975.
Full textAbstract:
G-protein–coupled receptors are the largest superfamily in the human genome, and involved in critical cellular signaling processes in living cells. Protein structural fluctuations are the key for GPCR function that is driven and modulated by a variety of factors that are not well understood. This dissertation focusses on understanding the activation of GPCRs using the visual receptor, rhodopsin as the prototype. Rhodopsin is an ideal candidate for this study, as it represents the largest class of GPCRs, and is known to demonstrate more noticeable structural changes upon activation compared to the other GPCRs. What structural fluctuations occur, the role of water, and how the retinal cofactor regulates the protein dynamics during rhodopsin activation are specific research problems addressed in this work. Hypothesizing an ensemble activation mechanism, experiments were conducted using a variety of techniques to probe structural and dynamical fluctuations of rhodopsin in native membranes, as well as in membrane mimetics such as detergent micelles. Time-resolved wide-angle X-ray scattering (TR-WAXS), small-angle neutron scattering (SANS), quasielastic neutron scattering (QENS), and electronic spectroscopy are among the prominent techniques used to gain insights into the photo-intermediates that are key to understanding the rhodopsin activation process. The small-angle neutron scattering (SANS) experiments revealed a volumetric expansion of the protein molecule upon photoactivation of rhodopsin. Electronic spectroscopy together with the differential hydration study revealed the crucial role of water in rhodopsin signaling process and signal amplification by water. The quasielastic neutron scattering study conducted on powdered rhodopsin probed the changes in the local dynamics that are regulated by the retinal cofactor of the rhodopsin molecule. The increased local steric crowding in the ligand-free opsin is consistent with collapsing of the apoprotein structure in the absence of the retinal chromophore leading to inactive opsin conformation. Finally, a time-resolved wide-angle X-ray scattering study was conducted using the X-ray free electron laser at the SLAC national laboratory to probe the early structural fluctuations in rhodopsin photoactivation. The preliminary pump-probe experiments conducted on rhodopsin in CHAPS detergent micelles revealed a light-triggered protein quake that occurs during the early activation stages of rhodopsin photoactivation. Thus the protein fluctuations underlying the GPCR function are revealed by neutrons, X-rays, and other photons in a combined implementation of both spectroscopic and scattering techniques as applied to the investigation of rhodopsin activation.
19
Appadoo, Dominique R. T. (Dominique Rupert Thierry) 1964. "Spectral simplification techniques for high resolution fourier transform spectroscopic studies." Monash University, School of Chemistry, 2002. http://arrow.monash.edu.au/hdl/1959.1/7746.
Full text
20
Jakubowska, Katarzyna. "Development of visible spectroscopic techniques for applications in plasma diagnostics." Licentiate thesis, Stockholm : KTH Physics, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4252.
Full text
21
Mann, Berenice Ann. "Novel coherent laser spectroscopic techniques for minor species combustion diagnostics." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304258.
Full text
22
Whittaker, Kimberley Elaine. "Development and application of spectroscopic techniques in the mid-infrared." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:3fe68179-e217-431b-81d6-37ebbfa0b361.
Full textAbstract:
Applications of laser absorption spectroscopy for trace gas detection are many and diverse, ranging from the environmental and atmospheric to the medical and industrial. The aim of creating a spectrometer which combines high sensitivities and selectivities (in order to measure small amounts of absorbers or species that are only weakly absorbing, in a complex background matrix) with a wide spectral coverage (to allow broadband absorbers or multi-component samples to be studied) can be realised by implementing three separate concepts: the exploitation of the strong, fundamental transitions of the mid-infrared; the use of sensitive spectroscopic techniques; and the selection of a widely tunable laser source. In this thesis, these ideas are investigated individually and in combination in order to achieve such a goal. Laser spectroscopic techniques based on optical cavities are used to build a high resolution spectrometer covering a large spectral range capable of selectively detecting low levels of gaseous compounds of interest, especially those of medical or environmental significance. Work in both the near- and mid-infrared is presented, including much of the initial, developmental work which was conducted in the former region. The thesis begins with an overview of both narrowband and broadband near-infrared radiation sources, with a particular emphasis on commonly available diode lasers (DLs). A novel laser source, the digital supermode distributed Bragg reector (DS-DBR) laser, is introduced as a useful laser source for spectroscopy, combining the usual benefits of telecom DLs with a wide tunability (1563 – 1613 nm). The laser can be operated in an internal or external ramping mode, allowing the output wavelength to be scanned or stepped across a desired region. The observation of mode-hopping during the application of the scanning methodology is examined and rationalised. The ability of the DS-DBR laser to perform high resolution spectroscopy over its entire spectral coverage is demonstrated by recording spectra of carbon dioxide (CO2) over this range, covering transitions from two of the four Fermi resonance components of the 3ν1 + ν3 combination band. The results of conducting wavelength modulation spectroscopy on CO2 are also reported. A system developed for performing cavity ring-down spectroscopy (CRDS), capable of the real-time retrieval of ring-down times (RDTs), is presented and discussed. The outcomes of initial tests performed with a conventional DL at 1557 nm, to study a calibrated mixture of CO2 in air at various pressures, are given. In addition, the results of combining this system with the DS-DBR laser are discussed. The bandwidth of the DS-DBR laser was found to be larger than that of a standard DFB DL, resulting in the presence of noisy cavity modes. Despite this, the acquisition of reproducible RDTs is demonstrated, with single wavelength studies of an evacuated cavity at 1605.5 nm yielding a RDT of 24.54 ± 0.04 µs and Allan variance calculations signalling an attainable minimum detectable absorption coefficient, αmin, of 2.8 x 10-10 cm-1 over 20 s. The ability to perform CRDS across the whole DSDBR laser wavelength range without the need for cavity re-alignment is illustrated, and studies conducted on CO2 in air, calibrated mixtures and breath are reported. Investigations are also described into the accurate determination of the 13C/12C ratio in exhaled CO2 undertaken using CRDS and cavity enhanced absorption spectroscopy (CEAS) on CO2 isotopologues, an approach which can be utilised as a diagnostic aid in determining Helicobacter pylori infection. The focus of the thesis then moves to the mid-infrared, to describe quasi phase matching difference frequency generation (QPM-DFG) and its use to generate laser light at 3 µm by optically mixing near-infrared DLs. The theory behind this non-linear optical interaction is outlined, and the construction of a free-space QPM-DFG system using periodically poled lithium niobate is detailed and characterised. This DL-based QPM-DFG arrangement has been coupled with the CRDS system developed to create a mid-infrared CRD spectrometer. The results of single wavelength studies indicate RDTs of ~ 6 µs and an achievable αmin of 2.9 x 10-9 cm-1 over 44 s for an evacuated cavity. Spectroscopic investigations carried out on methane (CH4), acetone and deuterium are documented; for the latter species, Dicke narrowing of the electric quadrupole ν(1←0) Q(2) transition at 2987.29 cm-1 is observed and the integrated absorption cross-section for the same transition measured as 2.29 ± 0.03 x 10-27 cm2cm-1molec-1. The results of modifications made to the system, namely the use of a more powerful Nd:YAG laser as the pump radiation source, as well as a faster detector combined with a variable amplifier, are presented; these include the observation of an improved optimal αmin of 6.4 x 10-10 cm-1 over 151 s for an empty cavity. Finally, work utilising the DS-DBR laser as one of the near-infrared sources for the QPM-DFG set-up is presented. This configuration generates radiation covering a wide mid-infrared range (3130 – 3330 nm) and has been used to perform direct absorption and wavelength modulation spectroscopy on ro-vibrational transitions within the fundamental ν3 (F2) band of CH4. The spectrum of methanethiol (CH3SH) over this region has also been investigated, with preliminary studies identifying a feature at 3040 cm-1 as a potential indicator for monitoring this biomarker in breath. The results of coupling this mid-infrared radiation with an optical cavity to perform CEAS combined with phase sensitive detection are subsequently reported. Studies were conducted on calibrated CH4 mixtures and ambient air to examine two transitions of the fundamental ν3 (F2) band of CH4 in order to characterise the system: effective path lengths of ~ 700 m and αmin of 6.2 x 10-8 cm-1 over 8 s were found. The RQ4 CH3SH absorption feature at 3040 cm-1 was also further studied with this system using prepared samples of CH3SH in N2 at different concentrations, yielding a CH3SH detection limit of 2.4 ppm at 19 Torr. The potential of such a cavity-based, DS-DBR sourced, QPM-DFG mid-infrared spectrometer for trace gas sensing having thus been demonstrated, possible improvements that could be implemented to increase the sensitivity of the system are then discussed.
23
Banfield, Beulah. "Human serum albumin characterisation and binding studies by spectroscopic techniques." Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/human-serum-albumin-characterisation-and-binding-studies-by-spectroscopic-techniques(1cae0d90-d540-46c9-8169-3b8ab2249acb).html.
Full textAbstract:
Human Serum Albumin (HSA) is a plasma protein of great significance with an ability to bind numerous endogenous and exogenous ligands, having a single polypeptide chain of 585 amino acids constructed in three domains of relatively equal size. Although HSA's existence has been known for many years, its characterisation and ability to bind ligands still remain enigmatic. Only in 1992 was the crystal structure of HSA reported (Carter and Ho, 1992). Effective crystallisation and the determination of meaningful crystallographic data and structure had proven difficult. The 1992 report concerned HSA crystals grown using zero gravity conditions. The objective of this project is the characterisation of recombinant and native HSA using Ultraviolet (UV) & circular dichroism spectroscopy (CD) and involved HSA conformational changes, which altered the ability to bind or off-load ligands. Changing environment, together with the use of characteristic "marker ligands," influences binding to provide a handle that can be utilised and monitored. This enables the assignment of binding sites and the study of perturbating conditions. Changing conditions such as pH, temperature, ionic strength and solvents in the presence and absence of ligands were employed to extract further information on this elusive protein. Fragments of recombinant HSA were also used (namely domain I and domain I + II) under identical conditions as the whole protein in order to help elucidate and assign binding sites.
24
Dixon, Daniel Wayne. "Characterization of Commercial Pectin Preparations by Spectroscopic and Chromatographic Techniques." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etd/1910.
Full textAbstract:
Pectin has a long history as a food additive. However, elucidation of its fine structural and property relationships remains elusive. Recent research has focused on pectin's ability to complex with divalent heavy metals to aid in characterizing it. Commercial pectins of unknown composition were obtained from local grocers. Purified pectin samples from orange peel, lemon peel, and apple pomace, each of low and high levels of methyl esterification and of unknown distribution pattern were also purchased. Instead of metal complexation, several highly absorbing dyes such as Ruthenium Red, Nile Blue, and Acridine Orange were used to complex with the pectins and their resulting UV-Vis spectral patterns were employed to determine if one can characterize the different pectins. Chemometric methods are also included to aid in distinguishing them apart.
25
Bawazeer, Tahani Mohammad. "Developments of new techniques for studies of coupled diffusional and interfacial physicochemical processes." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56925/.
Full textAbstract:
This study is concerned with the development and application of electrochemical techniques combined with confocal laser scanning microscopy (CLSM) as a probe of the kinetics of electrochemical and surface reactions at different interfaces. A CLSM set up has been designed which combines electrochemical and microscopic techniques to extend the applications of CLSM in a new research fields. This methodology has been applied to various electrochemical systems in this thesis. The electrochemical activity of ultramicroelectrodes (UMEs) has been quantified using CLSM. A special optically transparent electrode, comprising a thin film of carbon nanotube network has been developed for these studies. The methodology comprises of tracking the dynamic, reversible concentration profiles of electroactive and photoactive tris(2,2'- bipyridine)ruthenium(II) species in aqueous solutions during cyclic voltammetry experiments. A decrease of the solution intensity is recorded at and around the UME surface during the oxidation of luminescent Ru(bpy)3 2+ to non-luminescent Ru(bpy)3 3+, followed by an increase of the intensity signal in the reverse scan direction as the oxidized Ru(bpy)3 3+ is consumed at the electrode surface. A three dimensional map of the concentration gradients of Ru(bpy)3 2+ is constructed by collecting sections of the object across the normal to the electrode plane at the steady state current regime. The first use of CLSM coupled with scanning electrochemical microscopy (SECM) has been introduced as a means of time dependent visualisation and measurement of proton dispersion at dental enamel surfaces and the effectiveness of inhibitors on substrates. This new technique provides an analytical method with high spatial and temporal resolution permitting sub-second analysis of treatment effects on enamel substrates. In this case the UME tip of SECM is used to generate protons galvanostatically in a controlled manner and the resulting proton fields were quantified by CLSM using a pH sensitive fluorophore. Given the advantage of SECM to deliver high controllable, and local acid challenges in a defined way, and the high temporal and spatial resolution in the millisecond and micrometer range, respectively, in CLSM allows the surface kinetics of dissolution and the effect of barriers on the enamel surfaces to be evaluated. Finite element model has been used to describe the dissolution process, which allows the kinetics to be evaluated quantitatively, simply by measuring the size of pH profiles over time. Fluoride and zinc were used as treatments for enamel surfaces to investigate the effect of inhibitors on proton distribution, since they are generally considered to impede the dissolution process. Proton lateral diffusion at modified surfaces was also investigated using CLSM and SECM to validate the use of these techniques. A disc UME was brought close to the membrane and the oxidation of water was induced. Proton lateral diffusion was observed as a change in pH along the membrane. Different electrostatic interactions were investigated by functionalising the surface with different phospholipid head group and polypeptide multilayer films, since they are thought to have an effect on facilitate or retreat the process. Anionic lipids head groups share protons as acid-anion dimmers and thus trap and conduct protons along the head group domain of bilayers that contain such anionic lipids. The results also indicate the rate and mobility of proton diffusion along membrane are largely determined by the local structure of the bilayer interface.
26
Ren, Deqing. "New techniques of multiple integral field spectroscopy." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3800/.
Full textAbstract:
The work of this thesis is to investigate new techniques for Integral Field Spectroscopy (IPS) to make the most efficient use of modem large telescopes. Most of the work described is aimed at the FMOS for the SUBARU 8m telescope. Although this is primarily a system for Multiple Object Spectroscopy (MOS) employing single fibres, there is an option to include a multiple-IFS (MIPS) system. Much of this thesis is therefore aimed at the design and prototyping of critical systems for both the IPS and MOS modes of this instrument. The basic theory of IFU design is discussed first. Some particular problems are described and their soludons presented. The design of the MIPS system is described together with the construction and testing of a prototype deployable IFU. The assembly of the pickoff/fore-optics, microlens array and fibre bundle and their testing are described in detail. The estimated performance of the complete module is presented together with suggestions for improving the system efficiency which is currently limited by the performance of the microlens array. The prototyping of the MIPS system is supported by an extensive programme of testing of candidate microlens arrays. Another critical aspect of the instrument is the ability to disconnect the (IPS and MOS) fibre input which is installed on a removable prime focus top-end ring from the spectrographs which are mounted elsewhere on the telescope. This requires high-performance multiple fibre connectors. The designs of connectors for the MOS and IPS modes are described. Results from the testing of a prototype for the MOS mode are presented. This work is supported by a mathematical model of the coupling efficiency which takes into account optical aberrations and alignment errors. The final critical aspect of FMOS which has been investigated is the design of the spectrographs. The baseline system operates in the near-infrared (NIR) but an additional visible channel is an option. Efficient designs for both the visible and NIR systems are presented. The design of the NIR spectrograph presents challenges in the choice of materials for the doublet and triplet lenses employed. The choice of material and the combinations in which they can be used are described. This thesis shows that all these critical aspects of FMOS have good solutions that will result in good performance of the whole instrument. For the multiple IFU system, the prototype demonstrates acceptable performance which can be made excellent by the use of a better microlens array. The multiple fibre connector prototype already indicates excellent performance. Finally, the spectrograph designs presented should result in high efficiency and good image quality.
27
Stafford, Hannah. "Mapping portuguese soils using spectroscopic techniques with a machine learning approach." Master's thesis, Instituto Superior de Ciências da Saúde Egas Moniz, 2014. http://hdl.handle.net/10400.26/6712.
Full textAbstract:
Dissertação de mestrado Erasmus Mundus para obtenção do grau de mestre em Técnicas Laboratoriais ForensesSoil analysis is an important part of forensic science as it can provide vital links between a suspect and a crime scene based on its characteristics. The use of soil in a forensic context can be characterised into two categories: intelligence purposes or court purposes. The core basis of the comparison of sites to determine the provenance is that soil composition, type etc. vary from one place to another. The aim of this project is to ‘map’ soils and predict the location of a sample of unknown origin based on the chemometric profiles of Fourier transform infrared (FTIR) spectra, micro x-ray fluorescence profiles and visible spectra. Thirty one samples were collected in triplicate from Monsanto Park in Lisbon for each predetermined collection point on a defined grid. Full FTIR spectra (400-4000cm-1), Visible (1100-401cm-1) spectra, UV (400-200cm-1) spectra and μXRF profiles were collected for all samples. A subset of 43 discriminant features was selected from a total of 1430 using the Boruta feature selection algorithm from the FTIR, μXRF and visible spectra. These discriminant features acted as input data that was used to create a neural network which allowed the prediction of Cartesian co-ordinates (or location) of the samples with a high degree of accuracy (86%) and has shown to be a very useful approach to predict soil location.
28
Mäkinen, A. (Ari ). "Experimental spectroscopic studies of metals with electron, ion, and optical techniques." Doctoral thesis, University of Oulu, 2014. http://urn.fi/urn:isbn:9789526203149.
Full textAbstract:
Abstract
In this thesis, different spectroscopic methods are used for studying metals. Electron spectroscopy is applied for the study of binding energy shifts between atomic vapor and solid metals. Photoionization and Auger decay of high temperature aluminum vapors are investigated. Ionization of atomic chromium metal vapor by light absorption is studied with synchrotron radiation and time-of-flight ion mass spectroscopy. Optical spectroscopy is used for studying light emission from electric arc furnace plasma in experimental apparatuses developed during this work. Experimental techniques and sample preparation methods are presented.
29
Ramsey, E. D. "Studies of pharmaceutical products and peptides by chromatographic and spectroscopic techniques." Thesis, Cardiff Metropolitan University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482906.
Full text
30
Green, Anthony. "Applications of Molecular Dynamics Techniques and Spectroscopic Theories to Aqueous Interfaces." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3457.
Full textAbstract:
The primary goal of spectroscopy is to obtain molecularly detailed information about the system under study. Sum frequency generation (SFG) vibrational spectroscopy is a nonlinear optical technique that is highly interface specific, and is therefore a powerful tool for understanding interfacial structure and dynamics. SFG is a second order, electronically nonresonant, polarization experiment and is consequently dipole forbidden in isotropic media such as a bulk liquid. Interfaces, however, serve to break the symmetry and produce a signal. Theoretical approximations to vibrational spectra of O-H stretching at aqueous interfaces are constructed using time correlation function (TCF) and instantaneous normal mode (INM) methods. Detailed comparisons of theoretical models and spectra are made with those obtained experimentally in an effort to establish that our molecular dynamics (MD) methods can reliably depict the system of interest. The computational results presented demonstrate the potential of these methods to accurately describe fundamentally important systems on a molecular level.
31
Quinn, Marguerite Claire. "The characterization of olive oils by various chromatographic and spectroscopic techniques." Thesis, University of South Wales, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265732.
Full text
32
Ruslen, Leah M. (Leah Marie) 1973. "Application of sensitive spectroscopic techniques to intramolecular dynamics and combustion kinetics." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8361.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2002.Vita.
Includes bibliographical references.
Modifications of Cavity Ringdown Spectroscopy (CRD) for use in the UV region are discussed. These modifications partially overcome the low sensitivity of CRD in the UV (due to lower mirror reflectivity, R - 0.99) by removal of non-exponential contributions to the ringdown decay. We have also developed a novel fitting algorithm to accurately extract the ringdown decay time from the ringdown signal. The resulting sensitivity is comparable to that achieved in the visible region (10-8 cm-1), where mirror reflectivities are higher (R - 0.9999). Application of this new UV-CRD apparatus and software for acetylene absolute absorption cross section measurements is also discussed. The observation and assignment of high-resolution spectra of the A' A" - X1 A' transition of HCBr and DCBr, recorded using Frequency Modulation Spectroscopy, is described in the second section. The 2 band of HCBr (vo = 11957 cm'l) and the 2' band of DCBr (vo = 12349 cm-1) have been observed for both naturally occurring isotopes of bromine. The presence of several K, subbands indicates that the molecule exhibits bent molecule rotational structure in these vibrational levels. Analysis of the rotational structure that is reported here has required a reassessment of rotational assignments of previous work published for HCBr. The lower singlet state is isolated, i.e. there is no evidence of triplet state perturbations in the vibrationless level of the ground state. Rotational constants derived for the ground state of all naturally occurring bromine isotopomers were used to estimate structural parameters.
(cont.) The barrier to linearity for the A 'A state is also estimated to be - 13600 cm'. Finally, the application of sensitive spectroscopic techniques to measurements of combustion-relevant radical reaction rates is discussed. Unsuccessful attempts to record the spectra of two target radicals, cyclohexadienyl (C6H7) and 2-phenyl ethyl (C6HsC2H5), in the gas phase are described. The radicals are generated via flash photolysis and absorption spectra are recorded in both liquid and gas phase. A specially designed multipass cell (Herriott cell) used for gas phase absorption and kinetic measurements is described. Investigation of the oxidation rate of cyclohexadienyl (C6H7) in liquid phase is also presented.
by Leah M. Ruslen.
Ph.D.
33
Barnsley, Robin. "X-ray spectroscopic diagnostics of magnetically confined plasmas : instrumentation and techniques." Thesis, University of Leicester, 1993. http://hdl.handle.net/2381/35789.
Full textAbstract:
This thesis reports several advances in x-ray crystal spectroscopic techniques for the diagnosis of high-temperature magnetically confined plasmas. Two complementary spectrometers have been developed, and have been demonstrated in a wide range of experiments on the Culham Laboratory DITE and COMPASS tokamaks, and on the Joint European JET tokamak. A Bragg rotor' spectrometer uses a combination of crystals and multilayers to give complete coverage of the spectrum between 1 A and 100 A. Developments were made to extend the coverage from 25 A to 100 A, using multilayer mirrors and organic crystals. The success of the instrument depends largely on the development of a high-rate ( 107 count/s) gas proportional counter system, capable of covering the energy range from 100 eV to 10 keV. A Johann spectrometer uses a novel four-pillar jig to bend' crystals to typically 1 m radius. A large-area cooled x-ray CCD array is used in the focus, resulting in a compact high-resolution instrument. This allows line profile and ratio measurements with a time resolution of ~1 ms. Observations using the Bragg rotor spectrometer include impurity monitoring under various plasma and limiter configurations. Temperature and density sensitive line ratios were measured under known plasma conditions and compared with theory, adding confidence to their use for less well diagnosed plasmas such as those observed in astrophysics. A major application has been the study of a switch (controlled by the refuelling rate) between long and short impurity confinement times in the DITE tokamak. Trace impurities were injected by laser ablation, and their subsequent temporal and spatial behavour studied spectroscopically. Weak lines, due to radiative recombination into excited states of H- and He-like ions, were observed in the outer plasma. The radial profiles of these "radiative recombination lines" were governed by a balance between transport and, recombination, and allowed the effective diffusion coefficient to be measured locally. It was shown that the transport changes occurred in the outer half of the plasma, and that conditions in the core were unchanged. The suitability of Bragg spectroscopy for a reactor-relevant plasma was demonstrated during the JET preliminary tritium experiment (PTE). A double- reflection instrument was used, with a tritium-compatible radiation-shielded beamline. Based on this operational experience, a soft x-ray spectroscopy system for a next-step device such as ITER is proposed.
34
Li, Jing. "Applications of optical-cavity-based spectroscopic techniques in the condensed phase." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d6a0c476-e67f-4390-a63a-e3cb9e60bf2c.
Full textAbstract:
Cavity ring-down spectroscopy (CRDS) and cavity enhanced absorption spectroscopy (CEAS) are two well-established absorption spectroscopic techniques originally developed for gas-phase samples. Condensed-phase applications of these techniques still remain rare, complicated as they are by additional background losses induced by condensed-phase samples as well as the intracavity components in which the sample is constrained. This thesis is concerned with the development and application of optical-cavity-based techniques in the condensed phase. Polarization-dependent evanescent wave CRDS (EW-CRDS) has been used to study the molecular orientation at the solid/air and solid/liquid interfaces. An increase in average orientation angle with respect to the surface normal has been observed for both methylene blue and coumarin molecules as a function of coverage at the fused silica/air interface. An orientation-angle-dependent photobleaching of pyridin molecules at the fused silica/methanol interface have also been observed. EW-CRDS has also been used to monitor slow in situ photobleaching of thin dye films deposited on the prism surface. The photobleaching dynamics is interpreted as a combination of first- and second-order processes. A significant fraction of this thesis has been devoted to studying magnetic field effects (MFEs) on the kinetics of the radical pair (RP) reactions in solution, in an effort to understand the ability of animals to sense the geomagnetic field. Two novel optical-cavity-based techniques – broadband CEAS (BBCEAS) and CRDS have been developed for this purpose. BBCEAS uses a supercontinuum (SC) source as the cavity light source and a CCD camera as photodetector, enabling simultaneous acquisition of absorption spectrum across the whole visible region (400 – 800 nm). In CRDS, a tunable optical parametric oscillator has been used as the cavity light source. Combined with the switching of external magnetic field (SEMF) method, this technique allows the decay kinetics of the geminate RPs to be monitored, with nanosecond resolution. Both BBCEAS and CRDS provide sensitivity superior to single-pass transient absorption (TA), a technique traditionally used in the MFE studies. A series of photochemical systems have been studied by BBCEAS and CRDS, respectively, among which, the MFEs of drosophila melanogaster cryptochrome has been observed. Importantly, this is the first time an MFE has been observed in an animal cryptochrome, and provides key supporting evidence for the cryptochrome hypothesis of magnetoreception in animals. Besides the optical-cavity-based techniques, a novel fluorescence detection method of MFEs has also been demonstrated. This technique proved ultrahigh sensitivity when applicable.
35
Ferguson, Leesa Susanne. "Analysis of the composition of latent fingermarks by spectroscopic imaging techniques." Thesis, Sheffield Hallam University, 2013. http://shura.shu.ac.uk/19645/.
Full textAbstract:
Despite the success of DNA fingerprinting, fingermarks remain an efficient means of ascertaining the identity of an individual at many crime scenes. There are numerous enhancement techniques used to develop fingermarks on a range of deposition surfaces. Despite this, there is a need for further intelligence to be gained in situations where fingermarks retrieved at crime scenes do not yield identification. The majority of the work presented in this thesis utilises MALDI mass spectrometry in profiling and imaging mode to investigate latent fingermarks, with SERS and ATR-FTIR used as complementary techniques. One of the major issues of using analytical techniques to investigate latent fingermarks is their inadequate application to real crime scene scenarios. Presented within this thesis is a new method of matrix application that makes MALDI-MSI forensically applicable and enables the distribution of various endogenous lipids and exogenous compounds within fingermarks to be visualised. The work is extended to include detection of various antimicrobial peptides and small proteins in the fingermarks of a cohort of 80 donors using MALDI mass spectrometry profiling followed by multivariate statistical analysis in an attempt to differentiate donors based on their sex. Chemical imaging of latent fingermarks by SERS and ATR-FTIR is also demonstrated, which could potentially lead to a three step multi-informative analytical approach for chemical characterisation of fingermark residue.
36
Mahrous, Engy Abdelhameed. "The use of spectroscopic techniques in the characterization of mycobacterial metabolites." View the abstract Download the full-text PDF version, 2009. http://etd.utmem.edu/ABSTRACTS/2009-020-Mahrous-Index.htm.
Full textAbstract:
Thesis (Ph.D.)--University of Tennessee Health Science Center, 2009.Title from title page screen (viewed on August 27, 2009). Research advisor: Richard E. Lee, Ph.D. Document formatted into pages (xvi, 2003 p. : ill.). Vita. Abstract. Includes bibliographical references (p.140-167).
37
Kristova, Petra. "Spectroscopic techniques for monitoring carbonation reactions and quantification of their products." Thesis, University of Brighton, 2016. https://research.brighton.ac.uk/en/studentTheses/416cf26e-b0d4-4edb-ac4c-8b38a0fb59d6.
Full textAbstract:
Synthetic and naturally occurring calcium and magnesium carbonate minerals are widely used in a range of industrial and environmental applications where the mineral quality and purity is often critical for their intended use. Hence accurate characterisation of the mineral assemblages is essential. Equally important is an understanding of the chemical and physical pathways leading to mineral formation and their roles in carbon sequestration from greenhouse gases. This study investigates the application of Raman and infrared spectroscopies to Ca-Mg carbonate analysis. A full quantitative calibration has been achieved for quaternary mixtures by Raman spectroscopy (RS) employing monovariable and multivariable methods. The method was validated by X-ray powder diffraction (XRD). The lowest error on component values was obtained by Principal Component Regression with application of Standard Normal Variate. The quantifications show that RS is comparable to XRD. The effect of particle size on the fundamental vibrations of the [CO32-] anion in calcite is investigated by mid-infrared and RS. While the effect of particle size on the infrared signature of internal modes of the [CO32-] anion is well documented, this thesis documents associated changes in Raman spectra as a function of particle size. With decreasing size spectral contrast diminishes and changes in the relative ratios of the internal modes occur. For RS the turnaround from optically thick to thin material occurs in the 42-59 μm size range with further changes occurring at ≤ 5 μm. RS was also utilized to monitor carbonate reaction kinetics after dissolution of [Mg(OH)2] by CO2 sparging in the presence of calcium salts at 35 °C, 30 days duration. Four experiments employing different calcium salts, Ca:Mg ratios and effect of hydromagnesite [Mg5(CO3)4(OH)2.xH2O] seeding were examined utilizing vibrational spectroscopies, XRD and SEM. Results suggest that carbonate mineral paragenesis is driven by geochemical feedback between a range of calcium and magnesium carbonate dissolution-precipitation events where decomposition of nesquehonite [Mg(HCO3,OH)∙2H2O] leads to formation of magnesium carbonate hydrates [Mg5(CO3)4(OH)2.xH2O]. XRD confirmed that these hydrated phases contain 8 and/or 5 molecules of crystalline water. However, RS cannot distinguish these phases. Traces of barringtonite [Mg(CO3)∙2H2O] found at the end of experiments were interpreted as an indicator of incongruent dissolution of nesquehonite. Findings suggest that the Raman active ν1 mode of barringtonite is situated at ca. 1094-1095 cm-1. The limitations of Raman analysis in the context of mineral assemblage quantification, short range ordering and particle size effects are discussed in the context of these findings.
38
Mäkinen, A. (Ari). "Experimental spectroscopic studies of metals with electron, ion, and optical techniques." Doctoral thesis, University of Oulu, 2014. http://urn.fi/urn:isbn:9789526203140.
Full textAbstract:
Abstract In this thesis, different spectroscopic methods are used for studying metals. Electron spectroscopy is applied for the study of binding energy shifts between atomic vapor and solid metals. Photoionization and Auger decay of high temperature aluminum vapors are investigated. Ionization of atomic chromium metal vapor by light absorption is studied with synchrotron radiation and time-of-flight ion mass spectroscopy. Optical spectroscopy is used for studying light emission from electric arc furnace plasma in experimental apparatuses developed during this work. Experimental techniques and sample preparation methods are presentedOriginal papers The original publications are not included in the electronic version of the dissertation. Huttula, M., Jänkälä, K., Mäkinen, A., Aksela, H., & Aksela, S. (2008). Core shell electron spectroscopy on high temperature vapors: 2s photoionization and Auger decay of atomic aluminium. New Journal of Physics, 10(1), 13009. https://doi.org/10.1088/1367-2630/10/1/013009 Huttula, M., Partanen, L., Mäkinen, A., Kantia, T., Aksela, H., & Aksela, S. (2009). KLL Auger decay in free aluminum atoms. Physical Review A, 79(2). https://doi.org/10.1103/physreva.79.023412 Aksela, S., Kantia, T., Patanen, M., Mäkinen, A., Urpelainen, S., & Aksela, H. (2012). Accurate free atom–solid binding energy shifts for Au and Ag. Journal of Electron Spectroscopy and Related Phenomena, 185(8–9), 273–277. https://doi.org/10.1016/j.elspec.2012.05.007 Mäkinen, A., Patanen, M., Aksela, S., & Aksela, H. (2012). Atom-solid 3p level binding energy shift of transition metals Cr, Mn, Fe, Co, and Ni. Journal of Electron Spectroscopy and Related Phenomena, 185(12), 573–577. https://doi.org/10.1016/j.elspec.2012.12.006 Mäkinen, A., Niskanen, J., & Aksela, H. (2012). Relative photoionization cross section of Cr atoms in the valence region. Physical Review A, 85(5). https://doi.org/10.1103/physreva.85.053411 Mäkinen, A., Niskanen, J., Tikkala, H., & Aksela, H. (2013). Optical emission from a small scale model electric arc furnace in 250–600 nm region. Review of Scientific Instruments, 84(4), 43111. https://doi.org/10.1063/1.4802833
39
TARIS, ALESSANDRA. "Multivariate techniques applied on spectroscopic data for process analysis and monitoring." Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/249570.
Full textAbstract:
L’analisi e il monitoraggio di processo sono diventati di fondamentale importanza per garantire le prestazioni del processo e mantenere la qualità del prodotto. A tal scopo, la spettroscopia rappresenta uno strumento innovativo che permette di superare le problematiche che si incontrano con le tecniche analitiche convenzionali (per esempio, la gas cromatografia), poichè è veloce e non distruttiva e può fornire informazioni sullo stato chimico del processo in tempo reale. Tuttavia, a causa della grande quantità di informazioni presenti nelle misure raccolte, l’interpretazione e l’estrazione di informazione non è un compito semplice. A tal proposito, le tecniche multivariate agevolano significativamente il trattamento dei dati e permettono di inferire informazioni sul sistema analizzato.
In questa tesi, quattro sistemi sono indagati mediante misure spettroscopiche per mostrare la varietà di problemi che possono sorgere quando si trattano dati complessi e altamente informativi provenienti da differenti tecniche spettroscopiche. Per questo motivo, sono state esplorate differenti tecniche multivariate e sono mostrate le loro potenzialità e limitazioni: (i) si suggeriscono strategie basate sulla Principal Component Analysis e Partial Least Squares Regression per un migliore e più robusto monitoraggio di qualità dei detergenti commerciali liquidi; (ii) la Moving Window Principal Component Analysis è proposta per il monitoraggio di processi che si evolvono come la cristallizzazione di un Ingrediente Farmaceutico Attivo per identificare la nucleazione; (iii) la Time Window Statistical Total Correlation Spectroscopy insieme alla Multivariate Curve Resolution sono proposte per indagare la reazione di formazione di un materiale cementizio; (iv) la Multivariate Curve Resolution è utilizzata per ottenere informazioni sulla dissoluzione nello spazio e nel tempo di una pasta costituita da tensioattivi a partire da dati iperspettrali .
Perciò, le tecniche multivariate applicate a dati spettroscopici si dimostrano capaci di raggiungere i seguenti risultati:
a) Nel caso di detergenti commerciali, le osservazioni che non rispecchiano le condizioni di riferimento sono classificate correttamente. Inoltre, l’approccio proposto identifica quando la stima della concentrazione dei composti non può essere considerata accurata;
b) Riguardo la cristallizzazione dell’ingrediente farmaceutico, la nucleazione è stata individuata in modo accurato;
c) Gli spettri e la concentrazione dei composti coinvolti nella reazione di presa di un materiale cementizio sono stati stimati e l’evoluzione temporale del processo può essere seguita;
d) La velocità di dissoluzione dei tensioattivi presenti nella pasta è stata valutata.
Di conseguenza, i metodi multivariati implementati su misure spettroscopiche si rivelano essenziali per trattare i dati e agevolare la comprensione e il monitoraggio di processo.Process analysis and monitoring has become essential in industry to ensure improvement of the process performances and to maintain a specific product quality. To this aim, spectroscopy represents an innovative tool that allows to overcome the issues encountered with conventional analytical techniques (e.g. gas chromatography), since it is fast and non-destructive and can give information about the chemical state of the process in real time. Nevertheless, due to the huge amount of information present in the collected data, the interpretation and information extraction is not a straightforward task. For this purpose, multivariate techniques significantly aid the treatment of the data and allow to infer information about the system analyzed. In this thesis, four systems are investigated by means of spectroscopy to show the variety of problems that may arise when dealing with complex and highly informative data coming from different spectroscopic techniques. To this aim, different multivariate techniques are explored and their potentialities and limitations are shown: (i) Strategies based on Principal Component Analysis and Partial Least Squares Regression are suggested for an improved and more robust quality monitoring of liquid commercial detergents; (ii) Moving Window Principal Component Analysis is proposed for the monitoring of an evolving process like the crystallization of an Active Pharmaceutical Ingredient in order to detect the nucleation; (iii) Time Window Statistical Total Correlation Spectroscopy combined with Multivariate Curve Resolution are proposed to investigate the setting reaction of a cementing material; (iv) Multivariate Curve Resolution is employed to infer information from hyperspectral data about the dissolution of a surfactants paste. Therefore, multivariate techniques applied to spectroscopic data demonstrate capable of achieving the following results: a) in case of commercial detergents, they correctly classify observations that do not agree with the reference conditions. Moreover, the approach proposed is able to assess when the estimation of the compounds concentration cannot be considered accurate, this scenario may occur when the deviations of one compound is not taken into account during model calibration; b) for the crystallization of the pharmaceutical ingredient, the nucleation is accurately detected; c) spectra and concentration of the compounds involved in the setting reaction of a cementing material are estimated and time evolution of the process can be tracked; d) the dissolution rate of the surfactants present in the paste is estimated. As a result, multivariate methods applied to spectroscopic data reveal essential to treat data and aid process understanding and monitoring.
40
Agyemang, Perpetual O. "Modeling the Preference of Wine Quality Using Logistic Regression Techniques Based on Physicochemical Properties." Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1298055470.
Full text
41
Degaga, Gemechis D. "Physicochemical, Spectroscopic Properties, and Diffusion Mechanisms of Small Hydrocarbon Molecules in MOF-74-Mg/Zn| A Quantum Chemical Investigation." Thesis, Michigan Technological University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791501.
Full textAbstract:
In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic bricks connected by organic linkers. From a crystal engineering stand point, MOFs are advantageous in creating a range of microporous (0.2–2.0 nm) to mesoporous (>50 nm) void cavities, presenting unique opportunities for the functionalization of both the organic linkers and the void. Of significant importance is the MOF-74-M family (M = metal), characterized by a high density of open metal sites, that is not fully coordinated metal centers. This family of MOF is also known as CPO-27-M. MOF-74 have demonstrated more separation potential than other known MOFs and zeolites. Density functional theory (DFT), as implemented within a linear combination of atomic orbital (LCAO) approach, has been used to investigate the selective sorption of C1-C4 hydrocarbons in MOF-74-Mg/Zn. The study was first implemented by adopting a molecular cluster approach, and later by applying periodic boundary conditions (PBC). While both modellistic approaches agree in showing significant differences in binding energies between olefins and paraffins adsorbed at the MOFs’ open metal sites, results reported at the molecular cluster level show underestimation when compared to those obtained at the PBC level. The use of PBC models allow for the correcting of binding energies for basis set superposition error (BSSE), molecular lateral interaction (LI), zero-point energy (ZPE), and thermal energy (TE) contributions. As such, results obtained at the PBC level are directly comparable to experimental calorimetric values (i.e., heat of adsorptions). This work discusses, for the first time, the origin of the fictitious agreement between binding energies obtained with molecular clusters and experimental heats of adsorption, identifying its origin as due to compensation of errors. Spectroscopy studies based on the intensities and frequency shifts with respect to the molecules in the gas phase are presented as a further investigation of the interaction of the small hydrocarbons (C1-C 2) with the open metal sites in MOF-74-Mg. In an attempt to provide a more comprehensive description of the behavior of the hydrocarbon molecules, results from diffusion mechanism studies are also presented. The investigations of the diffusion mechanisms are based on the use of climbing-image nudge elastic band (CI-NEB) simulations, coupled with van der Waals functional (vdW-DF) and ultra-soft pseudopotentials as implemented within the plane-wave (PW) DFT approach. The CI-NEB studies showed that paraffin molecules are more energetically favored to diffuse within and along the cavity of MOF-74-Mg with respect to their olefin counterparts.
42
Bhattacharjee, Sushmita. "Organatin (iv) complexes of Schiff boses derived from Glycicne : synthesis and structural studies using spectroscopic techniques." Thesis, University of North Bengal, 2001. http://hdl.handle.net/123456789/732.
Full text
43
Choudhury, Subhankar. "Physicochemical study of diverse interactions of ionic liquids and biologically active solutes prevailing in liquid environments." Thesis, University of North Bengal, 2016. http://ir.nbu.ac.in/handle/123456789/2763.
Full text
44
Olander, Petra. "Quantitative Analysis of TiWCN in Cemented Carbide : A Comparison of Spectroscopic Techniques." Thesis, Uppsala universitet, Institutionen för materialkemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-143490.
Full textAbstract:
The aim of this master thesis was to compare EELS in TEM with TEM-EDS and WDS-EPMA for quantitative analysis of γ-phase in cemented carbide. Especially, the quantification of the light elements nitrogen and carbon in compounds like TiCxN1-x is interesting, since this is problematic. The techniques were compared by acquiring spectra for quantification of two samples of cemented carbide containing γ-phase (Tix,W1-x)(CyN1-y) with different nitrogen and tungsten content. Also, a rigorous evaluation about how EELS spectra best is acquired and processed was performed in order to enable the comparison. Experimental results show that EELS gives satisfying results for TiC0.7N0.3 and that EELS is comparable with WDS-EPMA for quantification of nitrogen, carbon and titanium in (Tix,W1-x)(CyN1-y) when the atomic concentration of nitrogen is around 20%. However, EELS was not used for quantification of tungsten. Concluded is also that EELS and WDS should be considered as complementary rather than competing techniques.
45
Lopatik, Dmitry [Verfasser]. "On aspects of plasma surface interactions studied by spectroscopic techniques / Dmitry Lopatik." Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1043667679/34.
Full text
46
Tani, Akiko. "Distinguishing between single- and double-stranded DNA : votammetric and muon spectroscopic techniques." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249775.
Full text
47
Grose, Richard Ian. "Molecular spectroscopic techniques in the characterisation and structural determination of novel systems." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239959.
Full text
48
Boulet-Audet, Maxime. "Why and how is silk spun? : integrating rheology with advanced spectroscopic techniques." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8c1536ee-1d49-4f2b-98df-1fff0dcc24e0.
Full textAbstract:
This thesis investigates the mechanisms behind natural silk spinning by integrating rheology, spectroscopy and small angle scattering to better understand this process and to guide our efforts towards mimicking Nature’s ways of producing high performance fibres. As a result of natural selection, arthropods such as spiders and moths have evolved the ability to excrete silk proteins in a highly controlled manner. Spun from liquid feedstocks, silk fibres are used ex vivo to build structures with mechanical properties currently unmatched by industrial filaments. As yet, relatively little attention has been directed to the investigation of spinning under biologically relevant conditions. To better understand how and why silk is spun, this thesis bridges the gap between liquid silk flow properties and structure development. To directly connect the two, I have developed and deployed novel experimental platforms that combine infrared spectroscopy and small angle scattering with rheology. This approach has clarified long-standing ambiguities on the structural root of silk’s apparently complex flow properties. Small angle scattering revealed the length scales involved in the flow induced solidification under a range of spinning conditions. Mo reover, infrared spectroscopy offered a unique perspective into silk’s formation process immediately after excretion. In a similar manner to the post-extrusion tuning of the properties of partly solidified spider silk filaments, this thesis has revealed that silkworm silk fibres are far from completely formed once excreted. One might describe the filaments of mulberry silkworm as seeded molten polymers that form its hydrogen bonding network and crystallises slowly on site. Consequently, it enlightens that post-spinning conditions are equally paramount for silkworm silk, giving an explanation for the relatively poorer mechanical properties. The comparison of silks from a range of species, allowed this hypothesis to be extended to wild silkworm silk. My insights into spinning had the fortuitous repercussion of facilitating silk fibre solubilisation leading to the development of better artificial silk feedstocks flowing like native silks. With these findings, I believe we are now in an improved position to conceive artificial fibres with properties rivalling those of Nature.
49
Zhao, Ming. "In situ reflection absorption spectroscopic techniques for the study of electrogenerated species." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057154581.
Full text
50
Sandifer, Marnita Elizabeth. "Application of in-situ spectroscopic techniques to the study of electrochemical processes." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1057236338.
Full text