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Jelzow, Alexander [Verfasser], Rainer Akademischer Betreuer] Macdonald, Ulrike [Akademischer Betreuer] [Woggon, and Jens [Akademischer Betreuer] Steinbrink. "In vivo quantification of absorption changes in the human brain by time-domain diffuse near-infrared spectroscopy / Alexander Jelzow. Gutachter: Rainer Macdonald ; Ulrike Woggon ; Jens Steinbrink. Betreuer: Rainer Macdonald." Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1067385398/34.
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Jelzow, Alexander Verfasser], Rainer [Akademischer Betreuer] Macdonald, Ulrike [Akademischer Betreuer] [Woggon, and Jens [Akademischer Betreuer] Steinbrink. "In vivo quantification of absorption changes in the human brain by time-domain diffuse near-infrared spectroscopy / Alexander Jelzow. Gutachter: Rainer Macdonald ; Ulrike Woggon ; Jens Steinbrink. Betreuer: Rainer Macdonald." Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1067385398/34.
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Hani, Umama. "Regulation of cyclic and pseudocyclic electron transport." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASB044.
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La photosynthèse, principale voie de production d'énergie dans les environnements naturels, repose sur des flux d'électrons intervenant dans plusieurs complexes dans la membrane des thylakoïdes des organismes photosynthétiques. Le flux principal est le transport « linéaire » des électrons qui implique leur transfert de l'eau au NADP⁺, le tout couplé à la synthèse d'ATP. L'oxydation de l'eau photosynthétique est catalysée par les clusters de manganèse (Mn₄CaO₅) au niveau du photosystème II (PSII). Pour assurer un équilibre optimal entre la quantité d'énergie produite et consommée, les organismes photosynthétiques détournent une partie de l'énergie lumineuse récoltée des voies de transport d'électrons "linéaires" vers des voies "alternatives". Parmi ces voies, on trouve les transports cyclique et pseudocyclique des électrons autour du photosystème I (PSI), qui fournit de l'ATP supplémentaire pour répondre aux besoins métaboliques. En outre, des systèmes redox spécialisés appelés "thiorédoxines" sont responsables du maintien de l'état redox et de l'acclimatation rapide des plantes à un environnement changeant. Dans le cas contraire, cela peut conduire à des niveaux toxiques d'espèces réactives de l'oxygène (ROS) dans les cellules. Nous avons étudié les effets de l'excès et de la carence en manganèse (Mn) sur le transport des électrons au cours de la photosynthèse chez l'hépatique Marchantia polymorpha. Nous avons montré que l'homéostasie du Mn a un effet sur le métabolisme mais aussi sur la photosynthèse. De plus, nous avons étudié les changements redox in vivo du P700 et du la plastocyanine (PC) en utilisant le spectrophotomètre KLAS-NIR. Il semble que la carence en Mn permet une augmentation du transport cyclique des électrons (TCE) ce qui indique la présence de supercomplexes contenant le PSI et le complexe du cytochrome b6f. Dans un second temps, nous nous sommes concentrées sur la régulation redox de la réduction de l'oxygène (transport d'électrons pseudocyclique) du côté de l'accepteur du PSI. En utilisant la spectroscopie RPE par piégeage indirect de spin, nous avons montré que des plantes sauvages d'Arabidopsis thaliana génèrent plus de ROS en photopériode de jour court (JC) qu'en photopériode de jour long (JL). En outre, nous avons mis en évidence le rôle de plusieurs acteurs, y compris les thiorédoxines et plusieurs protéines du lumen et du stroma dans la régulation redox. De plus, j'ai découvert que le transfert du pouvoir réducteur du stroma au lumen est médié par une protéine appelée CCDA. Par ailleurs, l'attachement réversible de Trxm à la membrane des thylakoïdes agit comme une force motrice pour l’accumulation des ROS en JC. Dans l'ensemble, les résultats établissent un lien étroit entre le transport cyclique et pseudocyclique des électrons en termes de régulations redox médiées par les thiorédoxines. Une voie est également ouverte quant à une exploration plus approfondie du TCE dans différentes conditions de stressPhotosynthesis acts as the main gateway for energy production in natural environments and relies on the electron flow via several complexes in the thylakoid membrane of photosynthetic organisms. The major flux is “linear” electron transport, which involves the transfer of electrons from water to NADP⁺, coupled with the ATP synthesis. Photosynthetic water oxidation is catalyzed by manganese cluster (Mn₄CaO₅) at photosystem II (PSII). To ensure an optimal balance between the amount of energy produced and consumed, photosynthetic organisms divert part of the harvested light energy from “linear” to “alternative” electron transport pathways. Among those pathways are cyclic and pseudocyclic electron transport around Photosystem I (PSI), which supplies extra ATP to meet metabolic demands. Moreover, specialized redox systems, called " thioredoxins " are responsible for maintaining the redox status and fast acclimation of plants to constantly fluctuating environments, which could otherwise lead to toxic levels of reactive oxygen species (ROS) production. We studied the effects of manganese (Mn) excess and deficiency on photosynthetic electron transport in the liverwort Marchantia polymorpha. We have shown that Mn homeostasis has an effect at both metabolic and photosynthetic levels. Moreover, we have studied the in vivo redox changes of P700 and PC using KLAS-NIR spectrophotometer and have shown that Mn deficiency seems to enhance cyclic electron transport (CET), that may indicate the presence of supercomplexes containing PSI and cytochrome b6f complex. The second part of this PhD focused on the redox regulation of oxygen reduction (pseudocyclic electron transport) at the PSI acceptor side. By using indirect spin trapping EPR spectroscopy, we have shown that Arabidopsis thaliana wild type plants generate more ROS in short day (SD) photoperiod than in long day (LD) photoperiod. Further, the current study highlighted the role of several players in redox regulation; including thioredoxins and several other lumenal and stromal proteins. Moreover, I explored that the transfer of reducing powers from stroma to lumen is mediated by a protein called CCDA and that reversible attachment of Trxm to the thylakoid membrane acts as the driving force for higher ROS under the SD light regime. Overall, this research establishes a strong connection between cyclic and pseudocyclic electron transport in terms of thioredoxins mediated redox regulations and also paves the way to further explore CET under different stress conditions
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Wirth, Adrian. "Attosecond transient absorption spectroscopy." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-140120.
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Arita, Yoshihiko. "Multi-mode absorption spectroscopy." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489407.
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A novel approach to absorption spectroscopy is presented which achieves, simultaneously, wide spectral coverage and high spectral resolution. The principle of the technique - dubbed multi-mode absorption spectroscopy (MUMAS) - is described, and demonstrations of the principle are reported using two multi-mode sources: diode lasers and micro-cavity solid state lasers. The technique is shown to have potential for the detection of multiple species and multiple parameters using a single laser and a single detector.
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Hageman, Stephen James. "Complex Attosecond Transient-absorption Spectroscopy." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1608050018545904.
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Durrant, James Robert. "Transient absorption spectroscopy of photosystem two." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/11455.
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Davidson, Stephen John. "Absorption spectroscopy in near LTE plasmas." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241501.
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Fiedler, Sven E. "Incoherent broad band cavity enhanced absorption spectroscopy." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97431966X.
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Howard, John Brooks. "Double point contact single molecule absorption spectroscopy." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31648.
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Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2010.Committee Chair: Marchenkov, Alexei; Committee Member: Davidovic, Dragomir; Committee Member: Gole, James; Committee Member: Hunt, William; Committee Member: Reido, Elisa. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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McCarthy, Richard Ivor. "GUSTO : a differential UV absorption spectroscopy instrument." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430743.
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Griffiths, T. R. "Development studies of concentration modulated absorption spectroscopy." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637100.
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The development of the concentration modulated absorption spectroscopy (C.O.M.A.S.) is detailed from 1986-1989. The theory has been developed which allows excited state lifetimes to be measured in the range 50ps to 100ns, using dye lasers mode locked at 82 MHz. Lifetimes in the range 10ns to 10ms can be measured using the C.O.M.A.S. technique and continuous wave (c.w.) lasers. A boule of synthetic Ruby has been analysed, using the C.O.M.A.S. technique. The lifetime of the 2E state has been measured, and the concentration of the Chromium ions within the matrix determined. Both values were found to be in agreement with literature values. The study of solutions of transition metal complexes (Iron and Chromium), was complicated by the effects of sample diffusion. The C.O.M.A.S. theory (for c.w. lasers) has been extended to include these effects. Comparison of the theoretical and experimental results is made. Both pulsed and c.w. lasers have been used to investigate the d.c. discharge generated by an Iron Neon hollow cathode lamp. The lifetimes of a number of excited states within Neon have been measured. The concentration of the excited states has been determined with good spatial resolution. The concentration measurements have allowed excitation and de excitation rates for the discharge to be evaluated.
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Shiwai, B. A. "X-ray absorption spectroscopy of dense plasmas." Thesis, University of Essex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235244.
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Simpson, Emma. "Attosecond transient absorption spectroscopy in atomic species." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44970.
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When high intensity laser light is focused into a gaseous target, high energy photons can be produced through the strongly nonlinear effect of high order harmonic generation. For a 30 fs, 800 nm or 1400 nm wavelength laser pulse, the result is a train of attosecond pulses produced at odd harmonic frequencies of the driving laser field, spanning energy ranges into the 100s eV. These attosecond pulses can access timescales characteristic to the movement of electrons in atoms, and by exploiting their properties as an ultrafast probe, electron dynamics in evolving atomic systems can be observed. This thesis presents the development of a pump-probe beamline capable of performing transient absorption spectroscopy experiments with resolution better than 150 as. Accompanying a full description of the experimental setup and methods, investigations are made into the attosecond transient absorption from strong field dressed helium and krypton atoms around their first ionisation edge, and 3d ionisation edge respectively. The result of the delay dependent transient absorption measurement is modulations to the recorded absorption amplitude for the harmonic orders around the respective ionisation thresholds. We investigated intensity regimes with an 800 nm laser field approaching the strong field ionisation threshold in helium. Experimental results are presented considering first the response of strong field dressed helium using an 800 nm laser field, and second the response of strong field dressed helium and krypton using a 1400 nm laser field. The use of the longer 1400 nm wavelength allows access to higher energy probe harmonics, enabling laser dressed krypton core to continuum, and core to Rydberg state transitions to be studied. By comparing the effect to the delay dependent absorption modulation as additional parameters are varied, information can be gained about the behaviour of the electrons. The parameters studied as a function of delay include: the dressing field intensity, target backing pressure and dressing field relative linear polarisation, aligned both parallel and perpendicular with respect to the probing harmonic pulse train. Key results include a strong suppression of the modulation amplitude for the above ionisation threshold harmonic orders when the dressing field linear polarisation is changed from parallel to perpendicular in the helium target. This is reproduced at both 800 nm and 1400 nm driving wavelengths.
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Erni, Peter. "Early nucleosynthesis studies with quasar absorption line spectroscopy." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983739854.
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Ma, Tongmei, and 馬彤梅. "Cavity ringdown laser absorption spectroscopy of free radicals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30137342.
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Stringer, M. R. "Laser-induced transient absorption spectroscopy of phthalocyanine dyes." Thesis, Open University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354989.
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Aliwell, Simon Richard. "Measurement of atmospheric trace gases by absorption spectroscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388668.
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Foo, James. "Laser absorption spectroscopy and tomography of gas flows." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/laser-absorption-spectroscopy-and-tomography-of-gas-flows(47a30c34-4290-4b28-bcb4-bbfa94cc5859).html.
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This research focuses on developing optical sensing systems for 2D and 3D spatial monitoring of temperature and concentration distribution profiles of complex or reacting gas flows. Non-invasive, species specific and sensitive nature of monitoring allows spatial information to be extracted from harsh environments with poor physical access, allowing validation of computational models or process monitoring. This is suitable for processes like combustion engines or sealed atmospheric cloud chambers. A novel line-of-sight (LOS) Tunable Diode Laser Absorption Spectroscopy(TDLAS) system using a preselected laser diode centred at 7212.88 cm-1 was first designed to monitor the change of relative humidity (water vapour concentration) during an expansion process within the Manchester Ice Cloud Chamber (MICC), operating from atmospheric pressure, down to 0.7 atm. The experimental results were validated with an Aerosol Cloud Precipitation Interaction Model (ACPIM) simulation, feasible for tomography applications. The MICC shares similar combustion monitoring challenges such as minimal optical access or reactive gas flows. The TDLAS system developed for the MICC was then used as a foundation design for a TDLAS tomography setup capable of conducting temporal two-dimensional (2D) and three-dimensional (3D) concentration and temperature imaging. This system uses the principle of two-line thermometry, centred within the near infrared (NIR) region of 7181.93cm-1 and 7179.8 cm-1. The laser was divided into 4 simultaneous parallel beams using a 1 × 4 fiber coupler (4 LOS). Using a motorised platform, the beams were projected at 0.5° interval, from 0° to 179° angle within 3.6 s, around the exhaust of two asymmetrical shaped flame burners. A total of 360 projection slices comprised of 1440 integrated absorbance data were used per tomogram reconstruction. By solving for the spatial distribution of temperature first, the concentration distribution of water vapour could be then calculated. Reconstruction algorithms (Filtered Back Projection, Fourier Slice Reconstruction and Direct Fourier Reconstruction (DFR)) were compared using a range of criteria. The DFR method was selected as the best method at 700 zero padding, with a spatial in-plane resolution of 1-2 lp/cm, pixel resolution of 128 by 128, thermocouple temperature validations of ±5°C and a relative mean error performance of 8.12%. The concentration could not be validated due to the lack of a mass spectrometer.3D volumetric monitoring results took 36 seconds to complete, and was constructed using 10 interpolated parallel, 1 cm height interval spaced tomograms. Independent vertical slices along the x-axis and y-axis could also be extracted. The temporal results were also successfully conducted and consisted of a quick succession of 16 experiments at a temporal resolution of 0.28 frames per second. A tomographic system that performs 3D and 2D temporal sensing was successfully developed and validated. Although 3D work was conducted using planar imaging or hyperspectral tomography, no work has been conducted so far using NIR TDLAS systems to date.
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Lewis, Thomas Robert. "Time-resolved absorption spectroscopy applied to tropospheric chemistry." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18122/.
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A Time-Resolved UV-Vis Absorption Spectrometer (TRUVAS) has been constructed with the ability to record time-resolved absorption spectra between ~250-800 nm, with a maximum time-resolution of 0.78 ms. The rate of reaction of the C1 Criegee Intermediate (formaldehyde oxide) with water vapour has been studied. The removal rate constant shows a quadratic dependence on [H2O], implying reaction with the water dimer, (H2O)2. The removal rate of the Criegee intermediate via. reaction with the water dimer ((H2O)2) was discovered to be 4.0 ± 1.2 × 10−12 cm3 molecule−1 s−1, and sufficiently fast to dominate the species’ removal in the troposphere. This result was published in PCCP3. The primary motivation for building the TRUVAS instrument was to measure the absorption cross-sections of isoprene-derived peroxy radicals in the actinic region, with a view to calculating the total atmospheric photolysis rates. The total atmospheric photolysis rates of the isoprene, 2,3-dimethylbutadiene and butadiene hydroxyperoxy (HP) radicals were calculated at noon in Borneo, and were found to be 1.27, 1.81 and 1.01 × 10-3 s-1 respectively. The absorption spectra of ethylene, but-2-ene and 2,3-dimethylbut-2-ene (TetraMethyl Ethylene – TME) HP radicals were measured. The measured absorption spectra show a marked broadening effect, with the Gaussian width increasing 11% from ethylene to but-2-ene HP radical absorption spectrum, and 26% to the TME HP radical, which translate to atmospheric photolysis rates of 0.552, 1.21 and 1.68 × 10-3 s-1. The absorption spectra of the methyl, tertiary-butyl and cyclohexyl peroxy radicals are presented. The methyl peroxy absorption spectrum measured in this study largely agree with the numerous existing studies. Atmospheric photolysis of methyl peroxy radicals comprises around 1% of the species’ removal in the marine boundary layer.
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Zhang, Siyuan. "Absorption spectroscopy and atomistic modelling on nitride semiconductors." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/283955.
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Shokry, Dina. "Predicting human intestinal absorption using chromatography and spectroscopy." Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34142/.
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New drug entities (NDE) are constantly being developed with most of them intended for oral administration. For this reason, there is a need to estimate their absorption in order to save time and money that would be lost if the drug enters the clinical stage and is then found to exhibit poor absorption. For many years, the use of animals was the most abundant method for studying pharmacokinetics to predict parameters such as intestinal absorption. However, these methods are time consuming, and expensive as well as being ethically unfavourable. As a result, developing other methods to evaluate a drug’s pharmacokinetics is crucial. The aim of this work was to develop in vitro methods for estimation of human intestinal absorption (%HIA) to replace the use of the aforementioned, less favourable methods involving the use of animals. Among the developed methods in this thesis is a unique type of chromatography known as micellar liquid chromatography (MLC) using biosurfactants such as bile salts as a mobile phase. Furthermore, studies investigated the effect of a change in the stationary phase in addition to investigating the effect of the change in temperature on the elution of the analysed compounds. It was found that R2PRED for the developed MLC methods was in the range of 43.3 % - 91.12 %. Another developed method was a spectrophotometric method based on the use of the solubilising effects of bile salts, as well as their binding to compounds. Therefore, two spectrophotometric methods were developed, a solubilisation method and a double reciprocal method, and used in the prediction of %HIA. It was found that the solubilisation method had a better predictability for %HIA than that of the double reciprocal method where R2PRED was found to be 82.32 % and 61.90 % respectively. Finally, a permeation method was developed using the ability of NaDC to form a hydrogel under specific conditions and applying the investigated drugs in an infinite dose to the prepared hydrogels. This facilitated the determination of permeability coefficients (Kp) that were then used in the prediction of %HIA using the obtained model. The two developed permeation methods were found to have close values of R2PRED for % HIA where R2PRED of the permeation method using flow through cells was found to be 79.8 % while that of the permeation method using Franz cells was found to be 79.67 %. In summary, this work reports several unique models for the in vitro prediction of human intestinal absorption, potentially removing the need for animal testing to predict %HIA.
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Smila-Castro, Ornella. "X-ray absorption spectroscopy studies of electrochemical processes." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3766/.
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Electron transfer is a key part of many chemical, biological and physical processes, that is commonly studied by electrochemical methods, which give insight into reaction mechanisms but no structural information. It is necessary to combine electroanalysis with another technique to gain essential knowledge of metal-ligand bond length and oxidation states. X-ray absorption spectroscopy (XAS) can provide these data for species in dilute solution and, if combined with electrochemistry, could potentially provide powerful insight into electron transfer reactions. This dissertation describes the development and application of techniques for the study of electrochemical intermediates by XAS. Chapters 2 and 3 introduce the theory and practice of electrochemistry and spectroscopy with emphasis on XAS. Chapter 4 describes the development of variable-temperature spectroelectrolysis cells for the study of electrochemical intermediates. In Chapter 5, the electrochemical behaviour of Cp\( \ast \)Rh(CO)\(_2\), is investigated as an organometallic compound representative of the redox chemistry studied in this thesis. Chapter 6 describes a new approach to the study of electrochemical intermediates in which a miniature electrolysis cell is combined with a microdispenser so that electrochemical intermediates can be generated and then dispensed, quenched at low temperature prior to study by XAS. Chapter 7 contains final conclusions.
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Lee, Jonathan Richard Ian. "X-ray absorption spectroscopy studies of electrode surfaces." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615888.
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Chadwick, Alan V., and Shelley L. P. Savin. "X-Ray absorption spectroscopy measurements on nanocrystalline materials." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186608.
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Bergin, Ann G. V. "Applications of optical-feedback cavity-enhanced absorption spectroscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:26ecc3d0-2aa1-4d21-a698-dc362956280b.
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This thesis presents two contrasting implementations of the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique. OF-CEAS com- bines passive optical-feedback locking of semiconductor lasers with cavity-enhanced absorption spectroscopy, and is well suited to sensitive detection of pressure- broadened trace gases. Chapters 1 and 2 set the work in this thesis in context, by describing the theory and discussing the motivations behind trace gas sensing by tuneable laser spectroscopy in the near- and mid-IR. Chapter 3 reviews the theory of OF-CEAS, prior to presenting the results of an experimental implementation based on a near-IR DFB diode laser setup following the traditional V-cavity methodology to spatially decouple the optical- feedback beam from the direct back reflection. The capabilities of the system are demonstrated by accurate determination of a self-broadened half-width at half- maximum of a CO 2 transition, and by detection of acetylene in a car exhaust sample. Chapter 4 describes the design and implementation of the linear cavity method- ology for QCL OF-CEAS, which is the significant contribution of this work. Successful OF-CEAS locking with the linear cavity is shown for two different DFB-QCLs, with close operating wavelengths (5.5 and 5.2 µm) but quite different operating powers and facet size. Chapter 5 presents quantitative spectroscopic results from the linear cavity OF-CEAS instrument, using both lasers. Spec- troscopy on mixes of N 2 O and NO returned sensitivities, quantified by the α min , of 2.7 × 10 −8 cm −1 in 1 s at 0.28 atm and 2.4 × 10 −8 cm −1 in 1 s at 0.19 atm respectively. Limited by etalon fringing on the baseline, the α min compared well with those obtained with V-cavity QCL OF-CEAS instruments. The temporal stability was investigated by Allan variance calculations and the best minimum detectable concentrations for the linear QCL OF-CEAS instrument were 32 ppm for N 2 O (35 s) and 5 ppb for NO (2 s). For NO, this detection limit compares favourably with other mid-IR QCL-based NO sensors, and is sufficient for mon- itoring NO in polluted urban environments. With the Maxion DFB-QCL, mon- itoring of NO in air outside the laboratory was attempted, and an air sample drying system benchmarked. Although this experiment proved unsuccessful, it was possible detect trace amounts of NO desorbing from the walls of the gas cell. Over the course of one hour the concentration rose from 3.8 ± 0.7 ppb to 28.4 ± 0.2 ppb, leading to a rate of desorption of 6.76 ± 0.01 × 10 −3 ppb s −1 . The sensitivity (α min ) of these spectra was 7.0 × 10 −9 cm −1 in 1 s, improved due to the higher mirror reflectivity at the lasing wavelength of the Maxion DFB-QCL, although still limited by etalon fringing.
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Chadwick, Alan V., and Shelley L. P. Savin. "X-Ray absorption spectroscopy measurements on nanocrystalline materials." Diffusion fundamentals 12 (2010) 17, 2010. https://ul.qucosa.de/id/qucosa%3A12819.
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Leal, Luis Carlos Avila. "Intracavity absorption spectroscopy with Er3+-doped fiber lasers." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7371.
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Mestrado em Engenharia FísicaEspectroscopia de absorção de intracavidade com um laser de banda larga de fibra dopada com Er3+ é aplicada para medidas resolvidas no tempo de moléculas de CO2 revelando informações quantitativas sobre a concentração do gás exalado na respiração humana. A gama espectral das medições estende-se de 1.52 μm – 1.61 μm através da deslocação da lente de intracavidade. Com um laser pulsado aplicado nesta experiência, a sensibilidade à absorção corresponde a um comprimento do percurso de absorção efectiva de 6 km assumindo que a cavidade está completamente preenchida com a amostra. O aumento da sensibilidade é alcançada através da construção de um laser de configuração em anel unidirecional. O comprimento do percurso de absorção efectiva é aumentado por um factor de três comparando com uma configuração linear com o mesmo comprimento da cavidade.
Intracavity absorption spectroscopy with a broadband Er3+-doped fiber laser is applied for time-resolved measurements of CO2 molecules revealing quantitative information about the gas concentration in exhaled human breath. The spectral range of measurements extends from 1.52 to 1.61 μm by moving an intracavity lens. With a pulsed laser applied in this experiment, the sensitivity to absorption corresponds to an effective absorption path length of 6 km assuming the cavity is completely filled with the sample. Sensitivity enhancement is achieved by employing an unidirectional ring laser. The effective absorption path length is enhanced by a factor of three compared to a linear configuration with the same cavity length.
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Göktaş, Oktay Güneş Mehmet. "Subgap Absorption Spectroscopy In Microcrystalline Silicon Thin Films/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/fizik/T000461.pdf.
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Cocola, Lorenzo. "Tunable diode laser absorption spectroscopy for oxygen detection." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422063.
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The evolution of diode laser sources for optical communications during the last years led to commercial availability of devices which are suitable for gas absorption spectroscopy in the near and mid infrared. In this work it is shown
how the traditional limits of Tunable Diode Laser Absorption Spectroscopy are addressed with digital signal processing techniques and careful optical design towards the realization of gas sensing instruments with the stability, robustness and reliability that are required in an industrial environment. Being one of the most challenging gases to be sensed with this technique, oxygen was considered under many measurement aspects such as:
• Non invasive monitoring;
• Gas in scattering media sensing;
• Sensing with back-scattering targets;
• Pressure measurement techniques for weak absorption signals;
• Time resolved, dynamic sensing;
• Temperature measurement through absorption spectroscopy.
Many of these aspects were considered together, leading to the developement of instruments tailored for real life industrial applications such as:
• Oxygen sensing in partially transparent containers such as wine or soft
drink bottles;
• Monitoring of double glazing insulating glass gas filling machines;
• Oxygen sensing in containers with backscattering targets such as food
packagings.
Other applications for the technique and experiments involving Gas in Scattering Media Absorption Spectroscopy were explored during a 6 months period at the Lunds Universitet - Lunds Tekniska Högskola - Atomfysik (Sweden) under the supervision of Prof. S. Svanberg:
• Gas probing into porous fruit samples;
• Gas sensing inside the human body as a medical diagnosis technique;
• Oxygen measurement in fully scattering food containers;
• Multi-line absorption spectroscopy as a temperature measurement.L’evoluzione delle sorgenti laser a diodo per le comunicazioni ottiche negli ultimi anni ha portato ad una disponibilità commerciale di dispositivi che si prestano alla spettroscopia di assorbimento di gas nel vicino e medio infrarosso. In questo lavoro si mostra come i limiti tradizionali della spettroscopia di assorbimento a diodi laser sintonizzabili vengano affrontati con tecniche di elaborazione numerica di segnali ed una attenta progettazione ottica rivolta alla realizzazione di strumenti per il rilevamento di gas caratterizzati dalla stabilità, robustezza ed affidabilità necessari per un ambiente industriale. Trattandosi di uno dei gas più critici per il rilevamento con questa tecnica, l’ossigeno è stato affrontato sotto molteplici aspetti di misura come: • Monitoraggio non invasivo; • Rilevazione di gas in mezzi diffondenti; • Rilevazione tramite bersagli retrodiffondenti; • Tecniche di misura di pressione per deboli segnali di assorbimento; • Rilevazione dinamica con risoluzione temporale; • Misure di temperatura attraverso spettroscopia di assorbimento. Molti di questi aspetti sono stati considerati simultaneamente portando allo sviluppo di strumenti appropriati ad un uso nel mondo reale in applicazioni industriali quali: • Rilevazione di ossigeno in contenitori parzialmente trasparenti come bottiglie di vino e bibite; • Controllo di macchine per il riempimento di pannelli isolanti in vetrocamera; • Rilevazione di ossigeno in contenitori con bersagli retrodiffondenti, quali confezioni alimentari. Altre applicazioni della tecnica ed esperimenti sulla spettroscopia di assorbimento di gas in mezzi porosi sono stati esplorati durante un periodo di 6 mesi presso Lunds Universitet - Lunds Tekniska Högskola - Atomfysik (Svezia) sotto la supervisione del Prof. S. Svanberg: • Analisi di gas in campioni porosi di frutta; • Rilevazione di gas all’interno del corpo umano come tecnica per la diagnostica medica; • Misura di ossigeno in contenitori completamente diffondenti per alimenti; • Spettroscopia di assorbimento multi-riga come misura di temperatura.
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Newnham, David A. "High vibrational overtone spectroscopy." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278081.
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Harvey, Ewan James. "Femtosecond spectroscopy of conjugated polymers." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389845.
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Trefiak, Nicholas Ronald. "Ringdown spectroscopy in optical waveguides." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/436.
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Cho, Suyeon. "Synthesis and characterization of refractory oxides doped with transition metal ions." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00856580.
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In this study, the oxygen-deficient TiO2, SrTiO3 systems and transition metal ion (Cr or V) doped TiO2, SrTiO3 and SrZrO3 systems have been investigated. We prepared samples as polycrystals, single crystals and thin films for various desires. Their structural, physical and electronic properties were measured by bulk-sensitive techniques (X-Ray Diffraction, SQUID and Electro Paramagnetic Resonance) or surface-sensitive techniques (Photoemission spectroscopy and X-ray absorption spectroscopy). The measurement of SQUID and EPR showed not only their magnetic properties but also the valence state of Cr dopant. We verified the valence state of Cr ions in oxides and found the key parameters of sample synthesis which control the valence state of Cr ions. Segregated phases such as SrCrO4 were formed when the samples were synthesized under O2 rich environment. The surface properties of Cr doped SrZrO3 films are also discussed. We found the synthesis conditions which influence on not only the behavior of Cr ions but also the resistive-switching behaviors. Various resistive-switching behaviors seem to depend on the surface chemistry of films. We found that the accumulation of Cr3+ on film surface provides a clean interface without any non-stoichiometric oxides and that this sharp interface termination results in a good performance of resistive-switching.
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Polshakov, Dmitrii A. "Ultrafast spectroscopy and dynamics of nitrenes and carbenes." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1130968887.
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Bingham, Kathryn Ruth. "In vivo '1'3C spectroscopy at 3 Tesla." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262964.
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Kraft, Robert A. (Robert Arthur) 1970. "In vivo two-dimensional NMR correlation spectroscopy." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85271.
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Inglis, Benjamin Alastair. "In vivo NMR spectroscopy of the brain." Thesis, Queen Mary, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.644797.
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Schiwon, Robert. "Cavity enhanced absorption spectroscopy von dünnen Filmen mit Ferninfrarotstrahlung." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97198235X.
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Wirth, Adrian [Verfasser], and Ferenc [Akademischer Betreuer] Krausz. "Attosecond transient absorption spectroscopy / Adrian Wirth. Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1019930233/34.
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Anselmo, Christophe. "Atmospheric greenhouse gases detection by optical similitude absorption spectroscopy." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1131/document.
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Cette thèse porte sur le développement théorique et expérimental d’une nouvelle méthodologie de détection des gaz à effet de serre basée sur la spectroscopie optique d’absorption. La question posée était : est-il possible d’évaluer de manière univoque la concentration d’un gaz à partir d’une mesure par spectroscopie d’absorption différentielle, dans laquelle l’étendue spectrale de la source lumineuse est plus large que celle d’une ou de plusieurs raies d'absorption de la molécule considérée et que, de plus la détection n’est pas résolue spectralement ? La réponse à cette question permettra d’entrevoir à terme le développer d’un instrument de télédétection de terrain robuste sans contrainte opto-mécanique majeure aussi bien sur la source laser que sur la chaîne de détection.Ces travaux ont donné lieu au développement d’une nouvelle méthodologie que l’on dénomme « Optical Similitude Absorption Spectroscopy » (OSAS) ou spectroscopie d’absorption optique de similitude. Cette méthodologie permet donc de déterminer de manière quantitative une concentration d’un gaz à partir de mesures d’absorption différentielle non résolue spectralement sans procédure de calibration en concentration. Ceci demande alors une connaissance précise de la densité spectrale de la source lumineuse et du système de détection. Ces travaux publiés ont permis de démontrer que cette nouvelle méthodologie est dans le domaine spectral du proche infrarouge peu sensible aux conditions thermodynamiques du gaz observé. D’autre part, ces travaux ont permis de mettre en exergue l’inversion de la Loi de Beer-Lambert non résolue spectralement ce qui donne lieu à la résolution d’un système analytique non linéaire. À cette fin le développement d’un nouvel algorithme d’inversion de ce type de mesures a pu être vérifié expérimentalement en laboratoire sur le méthane, en exploitant aussi bien des sources à large bande spectrale cohérente et non cohérente. La détection de cette molécule dans l’atmosphère a pu être réalisée dans le cadre de ces travaux en couplant judicieusement la méthodologie OSAS et la technique Lidar. Ces travaux ouvrent de nombreuses perspectives sur la détection de gaz à effet de serre dans le domaine spectral infrarouge ainsi que la possibilité de détecter plusieurs molécules d’intérêt atmosphérique simultanémentThis thesis concerns the theoretical and experimental development of a new methodology for greenhouse gases detection based on the optical absorption. The problem relies on the unambiguous retrieval of a gas concentration from differential absorption measurements, in which the spectral width of the light source is wider than one or several absorption lines of the considered target gas given that the detection is not spectrally resolved. This problem could lead to the development of a robust remote sensing instrument dedicated to greenhouse gas observation, without strong technology limitations on the laser source as well as on the detection system. Solving this problem, we could propose a new methodology named: "Optical Similitude Absorption Spectroscopy" (OSAS).This methodology thus allows to determine a quantitative target gas concentration from non-resolved differential absorption measurements avoiding the use of a gas concentration calibration procedure. Thereby, a precise knowledge of the emitted power spectral density of the light source and the efficiency of the detection system are needed.This work that has been recently published could demonstrate that this new methodology applied on the NIR remains accurate even in the presence of strong atmospheric pressure and temperature gradients. Moreover, we show that inverting spectrally integrated measurements which follow the Beer-Lambert law leads to solve a nonlinear system. For this, a new inversion algorithm has been developed. It was experimentally verified in laboratory on methane by using coherent and non-coherent broadband light sources. The detection of methane in the atmosphere could be also realized by coupling the OSAS methodology and the Lidar technique. Outlooks are proposed and especially on the detection of greenhouse gases in the infrared spectral domain as well as the ability to simultaneously detect several atmospheric molecules of interest
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Nadeau, Patrice. "Measurement of residence time distribution by laser absorption spectroscopy." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22666.
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The residence time distribution was measured at ambient temperature and pressure in a tubular reactor with radial injection at very short space times (0.04-0.7 s). A technique using infrared laser absorption spectroscopy was developed and used to provide the required rapid response for concentration measurements. The equipment comprised an infrared He-Ne laser emitting at a wavelength of 3.39$ mu m$ and a lead selenide detector. Methane, which absorbs strongly at the laser wavelength, was used as the tracer. The absorption of the laser light was related to the tracer concentration by Beer-Lambert law. The laser beam passed through the diameter of the reactor at different axial locations. The residence time distributions were obtained from the response to quasi-step inputs. An axial dispersion model was used to describe the reactor.
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O'Grady, C. E. "Fundamental research into aerosols for analytical atomic absorption spectroscopy." Thesis, University of Aberdeen, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377568.
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The material presented in this thesis falls into three main sections: 1) The measurement of nebulizer suction and its applications. Three methods of measurement of nebulizer suction were evaluated. The potential and limitations of each method was assessed. The most reliable and generally applicable method was measurement with a mercury manometer via a T-piece during aspiration, but after correction for suction drops along all the nebulizer capillaries and across connections. The measurement of suction was then applied to practical problems in AAS, i.e. the lack of dependence of signal on sample solution temperature, and to provide immediate warning of drift in aspiration rate. 2) Observations and causes of deposition in spray chambers. The deposition patterns of aerosol lost in the spray chamber was studied using a lithium tracer. Areas of high turbulence were identified and their positions related to the deposition patterns. The nebulizer/spray chamber system was considered to fulfill a sub-sampling role and the dual roles of pneumatic nebulizer as pumps and sub-samplers were critically discussed. 3) Observations on impactors in flame AAS. Five techniques for the evaluation of the effects of impact beads and other impactors were evaluated, i) aerosol droplet size distributions ii) aspiration of dye solutions iii) aerosol sizing with a second species introduced through the bead iv) effects on linear absorbance range v) effects on the extent of chemical interference The advantages and disadvantages of each technique were considered and the value of impactors critically appraised. An assessment was then made of the extent to which an impact cup or bead may be used to regulate sensitivity in flame AAS with a view to increasing the useful working ranges of calibration graphs.
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Toomes, Rachel Louise. "Reflection-absorption infrared spectroscopy of adsorbates on Co{1010}." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362815.
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Witonsky, Scott Kenneth 1975. "Kinetics and dynamics measured using IntraCavity Laser Absorption Spectroscopy." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8045.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2002.Vita.
Includes bibliographical references (p. 133-138).
IntraCavity Laser Absorption Spectroscopy (ICLAS) is a high-resolution, high sensitivity spectroscopic method capable of measuring line positions, linewidths, lineshapes, and absolute line intensities with a sensitivity that far exceeds that of a traditional multiple pass absorption cell or Fourier Transform spectrometer. From the fundamental knowledge obtained through these measurements, information about the underlying spectroscopy, dynamics, and kinetics of the species interrogated can be derived. The construction of an ICLA Spectrometer will be detailed, and the measurements utilizing ICLAS will be discussed, as well as the theory of operation and modifications of the experimental apparatus. Results include: i) Line intensities and collision-broadening coefficients of the A band of oxygen and previously unobserved, high J, rotational transitions of the A band, hot-band transitions, and transitions of isotopically substituted species. ii) High-resolution (0.013 cm-1) spectra of the second overtone of the OH stretch of trans-nitrous acid recorded between 10,230 and 10,350 cm-1. The spectra were analyzed to yield a complete set of rotational parameters and an absolute band intensity, and two groups of anharmonic perturbations were observed and analyzed. These findings are discussed in the context of the contribution of overtone-mediated processes to OH radical production in the lower atmosphere.
(cont.) iii) The implementation of Correlated Double Sampling (CDS) for time-resolved studies of CN fragments generated by the excimer laser photolysis of acrylonitrile. iv) The extension of ICLAS to study the kinetics of a test system. Nitrosyl hydride, HNO, was reacted with oxygen in a flow cell, and the subsequent chemistry was monitored using an electronic transition of HNO. Analysis of the rate equations and time integrated measured signal yielded a preliminary value for the rate constant of the reaction, HNO + 02 [right arrow] products.
by Scott Kenneth Witonsky.
Ph.D.
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Northern, Jonathen Henry. "Multi-species detection using Infrared Multi-mode Absorption Spectroscopy." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:10f3bd62-4c81-4eaf-854d-1f388af73be9.
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This thesis reports work extending the scope of a recently developed gas sensing technique, multi-mode absorption spectroscopy (MUMAS). The ability of MUMAS to simultaneously detect multiple species from a mixture is demonstrated for the first time. The technique is subsequently extended to mid-infrared wavelengths, realising large gains in sensitivity. A solid-state, multi-mode laser has been developed to provide a high-performance comb source for use with MUMAS. This in-house constructed, diode-pumped, Er/Yb:glass laser operates on 10 longitudinal modes, separated by 18 GHz and centred close to 1565 nm. The extensive development and prototyping work leading to this final laser design is described. Multi-species detection with MUMAS is reported for the first time, thus demonstrating the ability of this technique to perform multi-gas sensing using a single laser and simple detection scheme. The previously described Er/Yb multi-mode laser was used to record MUMAS signals from a sample containing CO, C2H2, and N2O. The components of the mixture were detected simultaneously by identifying multiple transitions in each of the species. Temperature- and pressure-dependent modelled spectral fits to the data were used to determine the partial pressures of each species in the mixture with an uncertainty better than +/-2%. Multi-mode radiation has been successfully generated at 3.3 μm using quasi phase matched difference frequency generation (QPM-DFG). A mid-infrared laser comb was produced by optically mixing the near-infrared, multi-mode comb produced by the previously developed Er/Yb:glass laser with the single-mode output of a Nd:YAG laser operating at 1064 nm. This multi-frequency laser source was characterised to verify performance, and subsequently used to perform proof-of-principle MUMAS measurements on the strong transitions found in this spectral region. Spectra were recorded of NH3 and CH4 both individually and as components of a mixture. A minimum detection level for this system was determined to be 4.3 μbar m-1 for CH4, a sensitivity increase of 300 over similar measurements performed in the near-IR.
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Rosen, Gregory Todd. "X-ray Absorption Fine Spectroscopy of Amorphous Selenium Nanowires." Ohio University Honors Tutorial College / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1294448896.
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Ding, Yun. "High sensitivity absorption spectroscopy of molecules of atmospheric interest." Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10123.
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Le spectre d'absorption de molécules d'intérêt atmosphérique a été enregistré et analysé à l'aide de techniques expérimentales de très haute sensibilité : la technique ICLAS (Intracavity laser absorption spectroscopy) près de 1 æm, la spectroscopie par transformée de Fourier et la technique CW-CRDS (Cavity Ring Down Spectroscopy) dans l'infrarouge moyen. L'analyse et l'attribution rovibrationnelles des nombreuses bandes nouvelles 13CO2, ont été réalisées sur la base d'un Hamiltonien rovibrorationnel effectif. Un nouvel ajustement global tenant compte de nos nouvelles données et de toutes les données disponibles dans la littérature a été réalisée pour 13C16O2 et 16O13C18O. L'intensité absolue de sept bandes de 13C16O2 a aussi été mesurée. L'analyse spectroscopique de la structure vibrationnelle de SiHCI3 et rovibrationnelle de bandes de H70GeD3, DOCI and H2S est aussi présentée. Les paramètres rovibrationnels ont pu être déterminés pour les bandes faibles observées et des interactions rovibrationnelles fortes ont été mises en évidence et modéliséesThe present work is devoted to the recording and anlysis of highly excited vibrational state of molecules of atmospheric interest with several high sensitive absorption techniques : intracavity laser absorption spectrometry (ICLAS) based on a Vertical External Cavity Surface Emitting Lasers (VeCSEL) near 1 æm, Fourier transform spectroscopy and cw-Cavity Ring Down Spectroscopy in the mid-infrared region. For 13CO2, the rotational analysis and vibrational assignments of the observed upper states have been performed on the basis of predictions of the effective Hamiltonian. New global fittings of the line positions of by gathering the present line positions with prévious measurements were performed for 13C16O2 and 16O13C18O. The parameters of the reduced effective Hamiltonian were derived. Line intensities of seven 13C16O2 bands were also recorded. The vibrational structure of SiHCI3 and rotational analysis of other molecules (H70GeD3, DOCI and H2S) are also presented. Their rovibrational parameters are obtained and strong interactions are evidenced and analized for most of the studied bands
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Thompson, Alexander W. J. "Multimode absorption spectroscopy of CO and CO₂ gas mixtures." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:ebcb2031-1165-414e-88d8-69465bdaf291.
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The development of multimode absorption spectroscopy (MUMAS) for multi-species detec- tion and its potential for process control or environmental monitoring is reported. The simultaneous detection of CO and CO2 is demonstrated in a proof-of-principle experiment for applications in industrially relevant gas species monitoring. The technique of MUMAS is extended to the near infrared in order to detect these and other industrially relevant species. A laser was designed and constructed to emit a multimode spectrum in the region of 1.57um to take advantage of the spectral overlap of the second vibrational overtone of CO and the combination band 3ν1 + ν3 of CO2. The laser consisted of a semi-confocal cavity employing an Er:Yb glass chip as the gain medium. The laser was pumped by a 1W laser diode at 980nm and emitted up to 30mW in a bandwidth of 180GHz. The laser emitted between 6-10 modes depending upon the selective cavity length. Mode spacings varied between 18GHz to 33GHz with an individual mode linewidth of less than 8MHz. The laser modes were simultaneously scanned using a piezo-electric transducer (PZT) in order to modulate the cavity length at frequencies between 1Hz and 10Hz. A system for linearizing the MUMAS spectra with respect to frequency was devised based on a transmission spectra of a confocal Fabry-Perot etalon. Refinements to the MUMAS fitting code were developed to improve the computational efficiency. An initial demonstration of MUMAS on a known gas mixture of CO and CO2 was per- formed. The ratio of CO:CO2 concentrations in the gas mixture was measured with an accuracy of 0.4% which was within the supplier’s quoted uncertainty. MUMAS is then applied to the detection of CO and CO2 concentrations in exhaust gas produced by a 1.3 litre 4-cylinder turbo-charged spark ignition engine. Relative and absolute concentrations were derived from MUMAS signals and values compared to measurements using a 4-gas analyser. Concentrations of CO and CO2 were measured using MUMAS to a precision of 0.17% and 0.23% respectively compared to less than 0.1% for the 4-gas analyser. Ratios of CO and CO2 were determined with a precision of 0.28 using MUMAS compared to 0.11 with the 4-gas analyser. The detection limit of CO was found to be 1486ppm in these circumstances. Finally a discussion is presented of potential improvements arising from wavelength mod- ulation spectroscopy and cavity enhancement techniques.
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Bobrowski, Nicole. "Volcanic gas studies by Multi Axis Differential Absorption Spectroscopy." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-60521.
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