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Williams, Daffydd Griffin. "Mechanism of action of penetration enhancers." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320625.
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Day, S. "Studies on the interfacial activities of some drug absorption enhancers." Thesis, De Montfort University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233881.
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Pritchard, Kelly. "The effects of some absorption enhancers on the mucociliary clearance mechanism." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289838.
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Tippin, Timothy Kent Thakker Dhiren R. "Novel approaches to assess the efficacy and toxicity of intestinal absorption enhancers." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,691.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the School of Pharmacy." Discipline: Pharmacy; Department/School: Pharmacy.
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Steenekamp, Willem. "The transdermal absorption of 5-Fluorouracil in the presence and absence of terpenes / Wilma Steenekamp." Thesis, North-West University, 2003. http://hdl.handle.net/10394/234.
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The skin is an amazingly resilient and relatively impermeable barrier that provides protective,
perceptive and communication functions to the body (Ramachandran & Fleisher, 2000). The
stratum corneum is widely accepted as the barrier of the skin - limiting the transport of
molecules into and across the skin. One of the bottlenecks in the successful development of
transdermal drug delivery devices is the fact that the skin (more accurately, the stratum corneum
- SC) tends to control the rate of drug transport. This makes it very difficult to influence or
regulate the transdermal drug absorption kinetics from outside, Le. by means of the vehicle. A
possible, and even elegant, solution may be the use of so-called "penetration enhancers",
thereby suppressing the dominant role of the stratum corneum penetration barrier (Bodde et al.,
1990).
For this study 5-fluorouracil (5-FU), a polar hydrophilic drug, was chosen as model drug to study
its penetration through the stratum corneum. Terpenes used as possible penetration enhancers
for 5-FU were menthol, isomenthol, menthone, l3-myrcene, limonene and 1,8-cineole. In
previous studies, terpenes with low skin irritancy and low systemic toxicity, were found to be
effective penetration enhancers for a number of hydrophilic and lipophillic drugs (Cornwell &
Barry, 1994; Cornwell et a/., 1996; Godwin & Michniak, 1999).
The objective of this study was to determine the different flux rates of 5-FU in the absence of
any pre-treatment of the stratum corneum and also through ethanol and selected terpene
pre-treated SC. The effect of each terpene on the penetration of 5-FU was determined. The
penetration of the selected terpenes themselves through the human stratum corneum was also
determined in vitro permeation studies were performed using vertical Franz diffusion cells with human skin
(stratum corneum). A saturated aqueous solution of 5-fluorouracil in the absence and presence
of pre-treatment of the SC was used as the donor phase. Pre-treatment was performed by
applying a 5 % terpene solution or absolute ethanol to the SC half an hour before the saturated
III
solution was applied in the donor compartment. A 50/50 ethanol/water solution was used as the
receptor phase. All the experiments were conducted over a 24 h period. The 37°C
temperature was held constant by means of a water bath. For the analysis of 5-FU flux rates,
samples from the receptor compartment were obtained and were analysed by means of high-pressure
liquid chromatography (HPLC). In order to determine the cumulative percentage of
terpenes penetrated through human stratum corneum, the samples were analysed by gas
chromatography (GC).
In this study, only menthol and isomenthol (both oxygen-containing terpenes) showed a
statistically significant increase on the flux of 5-FU, with flux values of 1.13 +- 0.38 and
1.45 +- 0.68 ug/cm2/h, respectively, compared to untreated skin with a flux value of 0.54 +- 0.23
ug/cm2/h for 5-FU. It was also proved that ethanol itself had an enhancing effect on 5-FU and
showed synergistic effects on the enhancement activities of all the terpenes. It was found that
all the terpenes (applied as a 5 % solution in ethanol) penetrated through the stratum corneum
in the absence of 5-fluorouracil. 5-Fluorouracil had either an increasing or decreasing effect on
the penetration of the terpenes.
From these findings, it could be concluded that oxygen-containing terpenes had the best
penetration enhancing effect on 5-FU and that menthol and isomenthol were the most effective
penetration enhancers, although the extend of penetration enhancement is not large enough for
clinical application. All the terpenes have the ability to penetrate through human stratum
corneum, and 5-FU either had an increasing or decreasing effect on their penetration.Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.
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Pretorius, Mariska Heleen. "Percutaneous delivery of methotrexate in the absence and presence of natural permeation enhancers / Mariska H. Pretorius." Thesis, North-West University, 2003. http://hdl.handle.net/10394/164.
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The transdermal delivery of drugs has a lot of advantages above other routes of delivery,
such as the avoidance of first-pass hepatic and intestinal metabolism, the non-invasive
infusion of drugs, etc. However, the transdermal delivery of drugs, especially hydrophilic
drugs, is limited due to the lipophilic nature of the stratum corneum. Methotrexate is a folic
acid antagonist with antineoplastic activity and is used for the treatment of psoriasis and
Kaposi's sarcoma. The permeation of methotrexate through the skin for systemic use is
however limited due to its high molecular weight, the fact that it is mainty dissociated at
physiological pH and its hydrophilic nature (Alvarez-Figueroa et al.. 2001). Thus the aim
of my study was to enhance the permeation of methotrexate with the use of terpene.
Terpenes are lipophilic in nature and have Log P values of around 2-4 (Godwin &
Michniak, 1999). These characteristics make them excellent candidates as penetration
enhancers. Terpenes are not only used for penetration enhancers, but in a huge number
of other products, such as aromatherapeutic oils. For this reason the permeation of the
terpenes through human skin and the effect of methotrexate on this permeation were also
determined. The following enhancers were used in this study: menthol, menthone.
isomenthol, limonene, B-myrcene, a-pinene and 1,8-cineole
Five different sets of experiments were done in this study: a) a control experiment with
methotrexate in the absence of the terpenes without ethanol; b) a control experiment with
methotrexate in the absence of the terpenes with ethanol: c) experiments with
methotrexate in the presence of the terpenes; d) control experiments with the terpenes in
the absence of methotrexate and e) experiments with tile terpenes in the presence of
methotrexate. For this study only human female abdominal skin was used. A saturated
solution of methotrexate in water:propylene glycol (50:50) with a pH between 4 and 5
(Vaidyanathan et al., 1985) was used as the model drug and the receptor phase was PBS-buffer
(pH=74) and water:ethanol (50:50) for HPLC and GC analysis respectively. The
dilfusion apparatus used consisted of Vertical Franz diffusion cells with a capacity of 2 ml and a diffusion area of 1.075 cm2. The cells were placed in a water bath (+- 37 "C) on
magnetic stirrers for the duration of the experiment. After the receptor phase was placed in
the receptor compartment the cells were equilibrated for an hour before putting 25 ul of a 5% terpene solution in absolute ethanol on the skin in the donor compartment. This was left
for half and hour to allow evaporation of the ethanol. The saturated solution of the
methotrexate was now placed on the skin in the donor compartment. The experiments for
methotrexate stretched over a period of 12 hours and samples were collected every 2
hours. The terpene experiments were performed over a 24-hour period and samples were
taken at 2,4,6,12 and 24 hours. The concentration methotrexate permeated was
determined by using HPLC-analysis and terpenes by using GC-analysis.
The flux (ug/cm2/h), kp(cm/h), lag time (h) and enhancement ratio were calculated to
compare the methotrexate permeation in the control and actual experiments. The results
showed that a-pinene, B-myrcene and isomenthol enhanced the permeation of
methotrexate most, although all the terpenes had an enhancing effect. They produced a 4-
fold increase in the flux values of methotrexate. Due to the fact that the terpene
experiments were only a semi-quantitative evaluation only the percentage terpenes that
permeated was calculated. The experiments were done on all the terpenes except apinene.
All the terpenes permeated the skin with menthol having the highest permeation.
The results also showed that methotrexate did have an effect on the terpene permeation.
Menthone and menthol's permeation was higher in the presence of methotrexate, while the
other terpenes had a higher permeation in the absence of methotrexate. The reason for
this is not clear.
In conclusion, the study revealed that the enhancers used did have an enhancing effect on
methotrexate permeation. This could be due to the extraction or disruption of lipids by the
terpenes (Zhoa & Singh, 2000) or an increase in diffusivity and partitioning. The terpene
experiments also showed that the terpenes do permeate the skin and that methotrexate
does have an effect on this permeation.Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.
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Burch, Charmita P. "The extent of perturbation of skin models by transdermal penetration enhancers investigated by ³¹P NMR and fluorescence spectroscopy." unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-04252007-133030/.
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Thesis (Ph. D.)--Georgia State University, 2007.Title from thesis title screen. Author's name from thesis title screen. Jerry C. Smith, committee chair; Kathryn Grant, Stuart Allison, committee members. Electronic text (148 p. : ill. (some col.)) : digital PDF file. Description based on contents viewed October 5, 2007. Includes bibliographical references (p. 124-148).
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De, Bruyn Tanile. "Nasal delivery of insulin with Pheroid technology / Tanile de Bruyn." Thesis, North-West University, 2006. http://hdl.handle.net/10394/730.
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Approximately 350 million people worldwide suffer from diabetes mellitus (DM) and this
number increases yearly. Since the discovery and clinical application of insulin in 1921,
subcutaneous injections have been the standard treatment for DM. Because insulin is hydrophilic
and has a high molecular weight and low bioavailability, this molecule is poorly absorbed if
administered orally.
The aim of this study is to evaluate nasal delivery systems for insulin, using Sprague Dawley rats
as the nasal absorption model. Pheroid technology and N-trimethyl chitosan chloride (TMC)
with different dosages of insulin (4, 8 and 12 IU/kg bodyweight insulin) was administered in the
left nostril of the rat by using a micropipette. Pheroid technology is a patented (North-West
University) carrier system consisting of a unique oil/water emulsion that actively transports drug
actives through various physiological barriers. These formulations were administered nasally to
rats in a volume of 100 p/kg bodyweight in different types of Pheroids (vesicles, with a size of
1.7 1 - 1.94 pm and microsponges, with a size of 5.7 1 - 8.25 pm).
The systemic absorption of insulin was monitored by measuring arterial blood glucose levels
over a period of 3 hours. The TMC formulation with 4 IU/kg insulin produced clinically relevant
levels of insulin in the blood and as a result also the maximal hypoglycaemic effect. TMC is a
quaternary derivative of chitosan and is able to enhance the absorption of various peptide drugs
by opening tight junctions between epithelial cells. Pheroid formulations were also effective in
lowering blood glucose levels but only at higher doses (8 and 12 IU/kg) of insulin. This study
indicated that Pheroid rnicrosponges had a faster onset of action and a slightly better absorption
of insulin when compared to Pheroid vesicles, but many more studies are needed in this field.
Although the results of this study with absorption enhancers are encouraging, nasal insulin
bioavailability is still very low, and the Pheroid formulations and long-term safety of nasal
insulin therapy have yet to be investigated.Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.
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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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Higgins, Kieran. "Quantum technologies for enhanced sensing and light absorption." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:f21e691a-f83e-4c9f-bc51-d94c4703e16e.
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The counterintuitive properties of quantum mechanics have the potential to produce revolutionary new technology. The applications of these devices are both vital and diverse: the efficient generation of energy from light, sensing and measuring with exquisite precision, and information processing with unparalleled speed. In this thesis, I use the theory of open quantum systems to investigate quantum technologies for enhanced sensing and light absorption. In the first research chapter, we develop a new method for describing qubit dynamics in the Rabi model. We obtain a new expression for the ac Stark shift, which enables practical and precise qubit thermometry of an oscillator. In the second research chapter, we demonstrate that it is possible to invert the phenomenon of Dicke Superradiance using nanostructures and quantum control. This creates the possibility of a new class of quantum light absorption technologies with a super-linear scaling in the absorption rate. In the final research chapter, we investigate another means of enhancing light absorption. We show that phonon assisted transitions to ratchet states in rings allow absorbed excitions to be protected from reemission.
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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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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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Charles, Therese. "Enhanced e-learning engagement using game absorption techniques ELEGANT." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551593.
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The influence of technology on education is significant and growing. In particular, most students in higher education now work in a learning environment that supports electronic access to course materials and perhaps controls aspects of the learning process. Within such an environment, students have greater choice as to when, where and how they study; unfortunately, however, these advantages are often offset by a reduction in student engagement. This is partly due to the quality of the learning content but equally important is the suitability of the learning environment in which that material is studied. This thesis focuses on that environment, considering, in particular, how student engagement might be improved using techniques common in digital games. In general, games succeed by entertaining players in a way that builds on their natural curiosity and competitiveness, thereby encouraging them to continue to play. Similar encouragement seems desirable in education. The thesis examines the hypothesis that student performance in e-learning can be improved by using engagement techniques from digital games. Essentially, this means enhancing technology-oriented learning environments with engaging features that occur in game design. The thesis considers the general requirements of such environments and identifies relevant engagement techniques. From this understanding, a game-oriented learning framework (GOLF) is proposed. The essence of the framework is that a game setting can promote desirable behaviour in terms of completing basic learning tasks and tackling additional challenges, with engagement further encouraged through regular feedback on performance, measured against others in the same class. It was anticipated at the outset that the design of the framework would require significant experimental evaluation and refinement so it has been produced through action research and evolutionary prototyping. A series of case studies in academia has been used in this development process. Results show that the framework can enhance, student engagement leading to improved performance. Also, as might be expected, however, there are significant soft factors involved that can have a significant impact on the benefit of the game approach and indeed determine whether or not it succeeds at all. These factors are discussed, together with suggestions for future work.
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Soltanmoradi, Reyhaneh. "Structured Metallic Films for Enhanced Light Transmission and Absorption." Doctoral thesis, KTH, Optik och Fotonik, OFO, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166706.
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Photonic devices such as light emitters, detectors, solar cells etc. are playing increasingly important roles in modern society. Yet their structures and designs are still under constant improvement, driven mostly by advances in material science and progress in integration techniques. A common challenge in these devices is to precisely manage transmission and absorption of light when it enters or escapes active regions. In certain devices it is even required to have both high optical transmission as well as high electrical conductivity. The current thesis investigates how structured metallic films can be devised to meet these challenges. Our work demonstrates that nanostructured noble metals can be tailored as either transparent or highly absorptive at wavelengths of interest, with or without electrical conductivity.In the first part of this work, metallic photonic crystals in the form of a thin gold film with an array of holes were fabricated with various geometrical parameters (hole size, pitch and metal thickness) on different substrate materials to investigate the impact of each parameter on the transmittance spectra at mid- to long-wave infrared wavelengths. Pitch size is shown to be the dominating factor for the high-transmittance band positions. Fill factor and metal thickness collectively define the selectivity of the pass bands. The selective transmission of infrared light can be used to improve the performance of infrared detectors. In the second part of this work, a thin-film multilayer structure based on two coupled metal-insulator-metal optical resonators was investigated for achieving a transparent conductor at visible wavelength range. The fabricated silver-based sample has a figure of merit (transmissivity-over-resistance) comparable to that of the traditionally used indium tin oxide. Such structures can potentially be used in light-emitting diodes and displays. In the third part of this work, a thin gold nanoparticle layer is obtained from a thermal annealing process. The interplay between this nanoparticle layer and a substrate metal reflector gives rise to broadband extinction of light at the near-infrared wavelength range. Specular and diffuse reflectances were singled out. Samples with high absorption or high diffuse reflection are identified. The structures can potentially be incorporated in solar cells as diffuse back reflectors or as spectrally selective absorbers for solar thermal collectors. In the fourth part of this work, the possibility of using a metal-insulator-metal structure (based on titanium, alumina, and aluminum) for achieving artificial coloration is explored. Through a diffusion-assisted deposition procedure, the dielectric spacer has a laterally varying thickness. Thereby the sample exhibits a continuum of visible colors. The reflectance spectra of the fabricated sample in the visible range were measured, and agreement to theoretical calculation is found to be very good. The artificial colors can be patterned at various geometries. Their potential application, besides functioning as spectrally selective absorbers in optoelectronic devices, can be used for security applications of consumer and artistic products.QC 20150519
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Neupane, Rabin. "Percutaneous absorption and Skin accumulation of ABH Carbopol gel in Porcine Ear Skin." University of Toledo Health Science Campus / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=mco1556641636092785.
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Buskühl, Martin. "Infrarotellipsometrische Untersuchungen zur oberflächenverstärkten Infrarotabsorption (SEIRA, surface enhanced infrared absorption) /." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969092148.
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Barho, Franziska Barbara. "Highly doped semiconductor plasmonic resonators for surface enhanced infrared absorption." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS075/document.
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La détection et l'identification des substances biologiques ou chimiques peuvent être accomplies par des biocapteurs. On exige des biocapteurs d'être simple et rapide à utiliser, d'avoir une taille réduite, et d'être suffisamment sensible afin de pouvoir détecter des molécules en petite quantité. Des dispositifs plasmoniques se sont révélés adaptés pour l'usage en tant qu'élément transducteur des biocapteurs. Les plasmon-polaritons de surface (SPP) sont des oscillations collectives du nuage électronique des métaux, couplées à des ondes électromagnétiques. Leur fréquence de résonance dépend de l'indice de réfraction de leur environnement diélectrique. Ceci permet de sonder de manière efficace la présence des molécules par la modification de l'indice de réfraction engendrée par celles-ci. La technique reposant sur ce principe s'appelle la détection par résonance des plasmons de surface (SPR sensing en anglais). De plus, les SPP confinent le champ électrique incident à des volumes sub-longueurs d'onde et l'exaltent ainsi. Les molécules qui se situent dans ces zones de forte exaltation du champ électrique interagissent plus efficacement avec la lumière incidente par l'intermédiaire du SPP, tel que leur section efficace de l'absorption infrarouge (IR) augmente. La spectroscopie IR est une technique standard d'identification de molécules en quantités suffisantes. Pour améliorer la sensibilité, la spectroscopie vibrationnelle d'absorption exaltée par la surface (SEIRA pour surface enhanced infrared absorption en anglais) est particulièrement bien adaptée.Alors que la plasmonique s'est principalement développée dans le visible via les métaux nobles, les semi-conducteurs III-V fortement dopés présentent une alternative intéressante pour la plasmonique dans le moyen IR. Leur fonction diélectrique ressemble à celle des métaux nobles dans le visible, mais décalée dans le moyen IR. Leur densité de charges moindre que celle de l'or permet de réduire considérablement leurs pertes. La spectroscopie SEIRA utilise des nanoantennes plasmoniques dont les résonances se situent dans l'IR pour couvrir la gamme spectrale des modes vibrationnels moléculaires. L'InAsSb fortement dopé accordé en maille sur un substrat en GaSb présente des propriétés plasmoniques au-delà de 5 µm de longueurs d'onde.Dans ce manuscrit, nous proposons des nanostructures en InAsSb:Si/GaSb pour développer un biocapteur utilisant les techniques de SEIRA et de SPR "sensing". Les nanostructures ont été réalisées soit par photolithographie et gravure chimique humide soit par lithographie interférentielle et gravure par plasma réactif. Les caractérisations optiques ont été effectuées par spectroscopie IR à transformée de Fourier. Des calculs numériques par la méthode des différences finies dans le domaine temporel (FDTD) ont permis d'étudier l'effet des paramètres géométriques sur la réponse optique des structures. Deux types de structure ont été proposés : des réseaux unidimensionnels ainsi que des réseaux bidimensionnels de nanoantennes rectangulaires supportant des résonances de plasmon de surface localisé (LSPR) dans les deux directions de polarisation de la lumière par rapport aux axes de la structure. Ce type de structures permet ainsi une réponse optique ayant des résonances dans deux bandes spectrales différentes. Les techniques de SPR "sensing" et de SEIRA ont été démontrées pour l'ensemble des structures uni- et bidimensionnelles. Différents types d'analytes comme les polymères et le benzaldéhyde vanilline ont servi de systèmes de tests pour les structures plasmoniques. Les sensibilités se situent entre 10² et 10^3 nm/RIU. Les facteurs d'augmentation des signaux vibrationnels obtenus sont compris dans une gamme de 1,2 à 5,7 et les facteurs d'exaltation ont été évalués autour de 10^3 à 10^4 pour les réseaux bidimensionnels de nanoantennes plasmoniquesThe detection and identification of biological and chemical substances can be performed with biosensors. Biosensors are required to be simple and rapid to use, small, and sensitive in order to detect minute amounts of analyte molecules. Plasmonic devices have proven their utility as biosensing transducers. Surface plasmon-polaritons (SPP), collective oscillations of the electron cloud in metallic media coupled to an electromagnetic wave, are sensitive to the refractive index of their environment, providing thus an efficient way to probe the presence of molecules by the refractive index modification. This technique is called surface plasmon resonance (SPR) sensing. Moreover, SPP confine the incident electric field to sub-wavelength dimensions and enhance the field strength. Molecules located in these so-called field hotspots interact more efficiently with incident light due to a coupling mechanism mediated by the SPP, so that their infrared (IR) absorption cross section is increased. While IR spectroscopy is a standard tool for molecular identification, it does not provide sufficient sensitivity for the detection of smallest quantities. Exploiting the surface enhanced IR absorption (SEIRA) due to the plasmonic enhancement enables the detection of small amounts of analyte.While surface plasmons were mainly discovered using noble metals such as gold and silver, nowadays other material systems are also considered which display complementary or improved properties compared to the standard materials in plasmonics, especially to enlarge the spectral range where plasmonic effects can be observed and exploited. Material science enables to tailor the dielectric function of a material and consequently to control the plasmonic properties. Highly doped III-V semiconductors constitute an alternative to gold and silver for mid-IR plasmonics, due to their dielectric function which resembles the one of the noble metals, but shifted to the mid-IR spectral range. Indeed, InAsSb in the IR is even less lossy than gold in the visible. SEIRA using plasmonic resonances spectrally tuned to molecular absorption lines, or resonant SEIRA, requires nanoantenna substrates displaying their resonances in the IR. Highly doped InAsSb grown lattice matched on GaSb substrates is an interesting material system for this task. InAsSb is plasmonic for wavelengths above approximately 5 µm.In this work, we propose InAsSb:Si/GaSb nanostructures as SEIRA and SPR substrates for an application in biosensing devices. InAsSb nanoantennas on GaSb substrates have been prepared using photolithography and wet chemical etching by a citric acid: hydrogen peroxyde solution or alternatively, by interferential lithography and reactive ion etching, especially to reduce the lattice parameter. An optical characterization of the structures was performed by FTIR spectroscopy, supported by numerical finite-difference time-domain (FDTD) calculations which were also applied to study the impact of geometrical parameters on the optical response. Notably, two types of structure designs were proposed: one-dimensional periodic gratings and two-dimensional arrays of rectangular shaped nanoantennas which provide localized surface plasmon resonances (LSPR) in both polarization directions contrary to the gratings and enable hence a dual band optical response. SPR sensing and SEIRA have successfully been demonstrated using both types of structures, with proof-of-concept analytes such as different polymers and the aromatic compound vanillin with absorption features at high IR wavelengths. A bulk sensitivity in the range of 10² to 10^3 nm/RIU was reached. The vibrational signals increased of factors ranging between approximately 1.2-5.7, and the SEIRA enhancement was estimated to be in the range of 10^3 to 10^4 for the rectangular nanoantenna arrays
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Hallensleben, Sebastian. "Enhanced sensitivity and speed in photomultiplier tubes." Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323025.
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Rushworth, Cathy M. "Analysis of small volume liquid samples using cavity enhanced absorption spectroscopies." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:df00e411-4be9-4816-ae46-a1fe948053b6.
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Cavity enhanced absorption spectroscopies have earned themselves a place as one of the methods of choice for sensitive absorption measurements on gas-phase samples, but their application to liquid samples has so far been more limited. Sensitive short pathlength analysis of liquid samples is required for online analysis of microfluidic samples, which are processed in channels with dimensions of tens to hundreds of micrometres. Microfluidics is important for a range of applications including drug discovery and environmental sensing. This thesis explores the application of cavity enhanced absorption spectroscopies to short pathlength (0.010 mm to 2 mm) analysis of sub-microlitre volumes of liquids. Three experimental set-ups have been been examined. Firstly, a single-wavelength cavity ringdown (CRD) spectrometer operating at 532 nm was assembled using two 99.8% reflectivity mirrors. High optical quality flow cells with short pathlengths ranging from 0.1 mm to 2 mm were inserted into this cavity at Brewster’s angle. The detection limit of the set-up with each inserted flow cell was established using a concentration series of aqueous potassium permanganate (KMnO₄) solutions. For the 1 mm flow cell, a detection limit of 29 nM KMnO₄ or 1.4 x 10⁻⁴ cm⁻¹ was established. Several different types of microfluidic devices were also inserted into the cavity, and it was found that the losses arising from the inserted chip were highly dependent on the method of chip manufacture. The CRD set-up with inserted 1 mm flow cell was applied to the detection of two important species, nitrite and iron(II), via analyte-specific colourimetric reactions. Detection limits of 1.9 nM nitrite and 3.8 nM iron(II) were established. The second experimental set-up utilised broadband, supercontinuum light generated in a 20 m length of nonlinear photonic crystal fibre. Broadband mirrors with around 99% reflectivity over the wavelength range from 400 to 800 nm were used to form the cavity, and a miniature spectrometer was used to wavelength-resolve the time-integrated cavity output. Flow cells and microfluidic chips were inserted into the cavity either at normal incidence or at Brewster’s angle. This set-up was employed for reaction analysis of an iron complexation reaction with bathophenanthroline, and for a model organic reaction, the Diels-Alder reaction between anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione. The same broadband set-up was also used for pH measurements using bromocresol green indicator solution. Using dual-wavelength CRD spectroscopy, the pH sensitivity was established to be around a few milli pH units. Finally, an alternative type of cavity, formed from a loop of optical fibre has been investigated. A novel light-coupler was designed and fabricated in 365 μm core diameter multimode optical fibre. Sample designs employing both direct and evanescent wave absorption were investigated in small-core and large-core optical fibres, and the lowest detection limit of 0.11 cm⁻¹ was determined in direct absorption measurements, with a pathlength of 180 μm, using our novel light coupler in 365 μm core diameter optical fibre.
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Cohanoschi, Ion. "THREE-PHOTON ABSORPTION PROCESS IN ORGANIC DYES ENHANCED BY SURFACE PLASMON RESONANCE." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3891.
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Multi-photon absorption processes have received significant attention from the scientific community during the last decade, mainly because of their potential applications in optical limiting, data storage and biomedical fields. Perhaps, one of the most investigated processes studied so far has been two-photon absorption (2PA). These investigations have resulted in successful applications in all the fields mentioned above. However, 2PA present some limitations in the biomedical field when pumping at typical 2PA wavelengths. In order to overcome these limitations, three-photon absorption (3PA) process has been proposed. However, 3PA in organic molecules has a disadvantage, typical values of σ3' are small (10-81 cm6s2/photon2), therefore, 3PA excitation requires high irradiances to induce the promotion of electrons from the ground state to the final excited state. To overcome this obstacle, specific molecules that exhibit large 3PA cross-section must be designed. Thus far, there is a lack of systematic studies that correlate 3PA processes with the molecular structure of organic compounds. In order to fill the existent gap in 3PA molecular engineering, in this dissertation we have investigated the structure/property relationship for a new family of fluorene derivatives with very high three-photon absorption cross-sections. We demonstrated that the symmetric intramolecular charge transfer as well as the -electron conjugation length enhances the 3PA cross-section of fluorene derivatives. In addition, we showed that the withdrawing electron character of the attractor groups in a pull-pull geometry proved greater 3PA cross-section. After looking for alternative ways to enhance the effective σ3' of organic molecules, we investigated the enhancement of two- and three-photon absorption processes by means of Surface Plasmon. We demonstrated an enhancement of the effective two- and three-photon absorption cross-section of an organic compound of 480 and 30 folds, respectively. We proved that the enhancement is a direct consequence of the electric field enhancement at a metal/buffer interface. Next, motivated by the demands for new materials with enhanced nonlinear optical properties, we studied the 3PA of Hematoporphyrin IX and J-aggregate supramolecular systems. As a result, we were able to propose the use of 3PA in photodynamic therapy using Photofrin, the only drug approved by the FDA for PDT.Ph.D.
Other
Optics and Photonics
Optics
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Clark, W. Andrew, Ronald C. Hamdy, P. E. Jr Brown, Reza M. Mohseni, and B. H. Owens. "Efficacy of an Absorption Enhanced Vitamin D3 Supplement for an Aging Population." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/2519.
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Espley-Jones, Robert. "Enhanced absorption of infrared radiation in semiconductor photodetectors using micro-antenna arrays." Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/106551/.
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This thesis is focused on signal-to-noise (S/N) enhancement of III - V semiconductor photodetectors for use in gas sensing applications within a specific frequency band of interest in the mid infrared (MIR) range. The semiconductor photodetectors can be grown as homostructures, but experiments have shown a clear benefit to using heterostructures and the quantum barriers they incorporate to reduce diode leakage. The proposed method of enhancement is the use of waveguide coupling with different resonating materials of different shapes, known as micro-antennas. The antennas were designed to be responsive to an incoherent light source, such as LEDs. State of the art examples were considered to optimise all aspects of the antenna design (i.e. the length, thickness, pitch and the dielectric constant) to reduce surface scattering and enhance coupling. The experimental demonstration requires consideration of maximisation of energy coupling into the intrinsic regions of Al0.05In0.95Sb (Aluminium Indium Antimonide) semiconductor diodes. The theoretical results were generated as a hybrid model to ensure full calibration and accuracy. Measurements of the semiconductor attenuation coefficient were taken externally and applied to sophisticated Electromagnetic (EM) simulation software. The EM simulations were done using Computer Simulation Technology (CSTTM). It was used to verify the expected results for different antenna sizes and to provide confidence for the outcomes of more elaborate design enhancements, including large scale selective removal of the semiconductor. Selective removal capitalises on energy coupling towards a specific position and depth close to the surface. Further work into investigating far field manipulation effects of antenna design applied to isotropically stimulated LEDs was included. Theoretical and experimental studies are reported that show that the antennas needed to be of an appropriate size to resonate at the appropriate wavelength. The variation with the antenna’s dielectric properties as well as the polarisation angle and trajectory angle of the stimulating source are reported. There are numerous shapes to be considered for various intended applications. The antenna design that has suited our specific purpose has an efficient packaging density, is responsive to a non-collimated stimulation source, is made out of low cost conductive materials, is fabricated in a commercially viable way and provides consistent and stable results.
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Langridge, Justin Mohsen. "Development and atmospheric applications of a novel broadband cavity enhanced absorption spectrometer." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612265.
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James, Dean. "Cavity enhanced spectroscopies for small volume liquid analysis." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:0b47d4a1-7f21-4c80-a8d4-496ca1080d52.
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Cavity enhanced spectroscopies (CES) are currently amongst the most sensitive spectroscopic techniques available for probing gas-phase samples, however their application to the liquid-phase has been more limited. Sensitive analysis of submicrolitre liquid samples is highly desirable, as miniaturisation allows for the reaction and analysis of scarce or expensive reagents, produces less waste, and can increase the speed of separations and reactions, whilst having a small footprint and high throughput. Absorption spectroscopy is a particularly desirable technique due to its universal, label-free nature, however its application to small volume liquid samples is hampered by the associated short absorption pathlengths, which limit sensitivity. CES improve sensitivity by trapping light within a confined region, increasing the effective pathlength through the sample. Three distinct types of optical cavity were constructed and evaluated for the purposes of making optical absorption measurements on liquid samples. The first incorporated a high optical quality flow cell into a "macrocavity" formed from two dielectric mirrors separated by 51.3 cm. Cavity losses were minimised by positioning the flow cell at Brewster's angle to the optical axis, and the setup was used to perform a single-wavelength cavity ringdown spectroscopy experiment to detect and quantify nitrite within aqueous samples. The detection limit was determined to be 8.83 nM nitrite in an illuminated volume of only 74.6 nL. Scattering and reflective losses from the flow cell surfaces were found to be the largest barrier to increased sensitivity, leading us to focus on the integration of cavity mirrors within a microfluidic flow system in the work that followed. In the second set of experiments, cavity enhanced absorption spectroscopy (CEAS) measurements were performed on Thymol Blue using custom-made microfluidic chips with integrated cavity mirrors. Unfortunately, due to the plane-parallel configuration of the mirrors and the corresponding difficulty in sustaining stable cavity modes, the results were underwhelming, with a maximum cavity enhancement factor (CEF) of only 2.68. At this point, attention was focussed toward a more well-defined cavity geometry: open-access plano-concave microcavities. The microcavities consist of an array of micron-scale concave mirrors opposed by a planar mirror, with a pathlength that is tunable to sub-nanometer precision using piezoelectric actuators. In contrast to the other experimental setups described, themicrocavities allow for optical measurements to be performed in which we monitor the change of wavelength and/or amplitude of a single well-defined cavity mode in response to a liquid sample introduced between the mirrors. In the first microcavity experiment, we used 10 μm diameter mirrors with cavity lengths from 2.238 μm to 10.318 μm to demonstrate refractive index sensing in glucose solutions with a limit of detection of 3.5 x 10-4 RIU. The total volume of detection in our setup was 54 fL. Thus, at the limit of detection, the setup can detect the change of refractive index that results from the introduction of 900 zeptomoles (500,000 molecules) of glucose into the device. The microcavity sensor was then adapted to enable broadband absorption measurements of methylene blue via CEAS. By recording data simultaneously from multiple cavities of differing lengths, absorption data is obtained at a number of wavelengths. Using 10 μm diameter mirrors with cavity pathlengths from 476 nm to 728 nm, a limit of detection, expressed as minimum detectable absorption per unit pathlength, of 1.71 cm-1 was achieved within a volume of 580 attolitres, corresponding to less than 2000 molecules within the mode volume of the cavity. Finally, a new prototype was developed with improved cavity finesse, a much more intense and stable light source, and improved flow design. Using a single plano-concave microcavity within the array with a cavity pathlength of 839.7 nm, and 4 μm radius of curvature mirror, absorption measurements were performed on Methylene Blue. Analysis of this data indicated a CEF of around 9270, and a limit of detection based on the measured signal-to-noise ratio of 0.0146 cm-1. This corresponds to a minimum detectable concentration of 104 nM Methylene Blue, which given the mode volume of 219 aL, suggests a theoretical minimum detectable number of molecules of 14.
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Benton, A. K. "Studies of trace gases in the troposphere using broadband cavity enhanced absorption spectroscopy." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596582.
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The aim of this Ph.D. was to develop and deploy a broadband cavity enhanced absorption spectrometer for use in the field, to test the instrument in a variety of locations, and to contribute to the body of knowledge both on spectroscopic measurement techniques and on the chemical composition of the troposphere through analysis of datasets from both this instrument and others. The first ship-deployment of the cavity instrument provided challenging conditions but retrieved a detection limit for IO of 20 pptv over 10 min and measurements of NO2 with a detection limit of 0.9 ppbv over 10 min. Additional IO measurements were attempted at a coastal site thought to be a greater IO source but IO was not observed above the detection limit. The final deployment detailed here was for the measurement of the sum of NO3 and N2O3 concentrations on the BT tower at 160m above London. A highly variable, month-long dataset was obtained showing a strong diurnal cycle with very low daytime concentrations measured. The maximum night-time mixing ratio was approximately 800 pptv, with a limit of detection of 2 pptv over 15 s. The results from this campaign were compared with models to aid our understanding of nocturnal processes occurring in this region. It was found that night-time enhancements in NO3 and N2O5 often coincided with air masses containing little NO and moderate O3. Those of low turbulence also favoured the night-time enhancement. N2O3 was found to be very reactive and calculated lifetimes were short. Estimates of the heterogeneous uptake of N2O5 onto water suggest a small contribution of around 8 ppbv per night of HNO3 via this route.
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Baumann, Axel [Verfasser]. "Studies on membrane protein folding by surface enhanced infrared absorption spectroscopy / Axel Baumann." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1159900612/34.
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Liu, Fei. "A sensitivity study of a general circulation model with enhanced shortwave atmospheric absorption." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068182.
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Adams, Thomas John. "Atmospheric measurements of biogenic and anthropogenic emissions by broadband cavity enhanced absorption spectroscopy." Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/37611.
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This thesis describes the quantification of biogenic and anthropogenic trace gases using the highly sensitive spectroscopic technique of broadband cavity enhanced absorption spectroscopy (BBCEAS). This technique uses a high finesse optical cavity to make absorption measurements over extended path lengths within a compact instrument and over wavelength ranges that are sufficiently broad to enable several overlapping absorbers to be quantified simultaneously. Here, BBCEAS was applied to measure I₂ emissions in coastal regions, NO₂ in urban ambient air, and VOC oxidation products during experiments in an atmospheric simulation chamber. Much of the work used a novel, mobile, battery-powered BBCEAS system to measure gas concentrations in very close proximity to their emission sources. The dominant emission source of iodine into the atmosphere in coastal regions comes from intertidal macroalgal beds. Gas-phase iodine chemistry perturbs the HOₓ and NOₓ radical cycles, provides additional sink reactions for tropospheric ozone, and initiates nucleation of new aerosol particles. Results are presented from an extensive laboratory study of I₂ emissions from five species of temperate seaweeds. Time- and species-dependent I₂ emission rates were quantified in studies mimicking the progressive exposure of seaweeds to air around low tide. Seasonal differences in I₂ emission rates were investigated. By deploying the BBCEAS instrument from a boat, I₂ concentrations were also measured directly above Laminaria digitata and Ascophyllum nodosum seaweeds growing in their natural habitat. NOₓ emissions affect urban air quality directly and indirectly (the latter via formation of tropospheric ozone and secondary aerosol). BBCEAS was applied to measure NO₂ and the optical extinction from aerosol particles at locations around the Leicester University campus. BBCEAS results were compared with commercial NOₓ (chemiluminescence) and aerosol instrumentation. The mobile BBCEAS instrument was also deployed to investigate the dispersion of NO₂ from the roadside.
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Dunbar, Ricky. "Using metallic nanostructures to trap light and enhance absorption in organic solar cells." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-142241.
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Gimeno, Furió Alexandra. "On the use of nanofluids to enhance the direct absorption of solar radiation." Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/666638.
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The present thesis evaluates the potential of solar nanofluids as direct absorption solar collectors and to generate steam. Nowadays, as energy consumption continues to rise while conventional energy are close to begin exhausted, there is an increasing demand for renewable energy technologies, especially solar thermal.
Currently, solar thermal energy systems include numerous losses due to the heat transfer processes, thus, nanofluids have been proposed to enhance the solar collectors efficiency through the direct sunlight absorption.
In this work, optical properties of different nanofluids carbon based have been characterised in order to study their suitability as direct absorption solar collectors.La presente tesis trata de evaluar el potencial de los nanofluidos solares para absorber directamente la radiación solar e intentar generar vapor. Como el consumo de energía continúa aumentando y las fuentes de energía convencionales se están agotando, aparece como excelente alternativa, el uso de las energías renovables, concretamente, la energía solar térmica. Los sistemas actuales de energía solar térmica presentan numerosas pérdidas debido a los procesos de transferencia de calor, por ello, se han propuesto los nanofluidos solares como absorbedores de la radiación y fluidos de transferencia de calor y así, mejorar la eficiencia del proceso de generación de vapor en las centrales solares térmicas. En este trabajo, se ha realizado la caracterización de las propiedades ópticas de diferentes nanofluidos solares basados en nanopartículas de carbón para estudiar su idoneidad en la aplicación solar térmica.
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Liu, Kai. "Theoretical Characterization of Optical Processes in Modecular Complexes." Doctoral thesis, Stockholm : Bioteknologi, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4629.
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McLeod, Matthew Wojciech. "Atmospheric studies of NO₃, N₂O₅ and IO using broadband cavity enhanced absorption spectroscopy." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708839.
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Golebiowski, Dariusz. "High resolution FTIR spectroscopy using a femto-OPO laser source and cavity enhanced absorption." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/221150.
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Dans cette thèse, nous améliorons et utilisons le montage expérimental développé au laboratoire nommé femto/OPO-FT-CEAS. Ce montage combine une source laser femto/OPO, une cavité optique haute finesse et un interféromètre à transformée de Fourier. Il permet d'enregistrer des spectres sur un intervalle de 150 cm-1, avec un coefficient d'absorption minimal de 3x10-9 cm-1, à une résolution de 2x10-2 cm-1 et un temps d’acquisition de 2 heures. Un chemin d'absorption de 20 km a été obtenu dans une cellule de 145 cm. Différents miroirs à hauts indices de réflexion permettent d'accéder à deux gamme spectrales dans le domaine de l'infrarouge proche :6200-6700 cm-1 et 7700-8300 cm-1.Le montage femto/OPO-FT-CEAS a été utilisé afin d'enregistrer des spectres à température ambiante. La molécule OCS a été étudiée dans les gammes spectrales de 6200 à 6700 cm-1 et 7700 à 8300 cm-1. Les nouvelles données rovibrationnelles ont été intégrées au modèle global développé par le Prof. Fayt de l'université catholique de Louvain. Un échantillon de CO2 enrichi en oxygène 17 a également été étudié dans la gamme spectrale de 7700 à 8300 cm-1. Les données ont été traitées avec l'aide du Dr. Lyulin l'institut d'optique atmosphérique de Tomsk, Russie.Le montage femto/OPO-FT-CEAS a également été modifié pour enregistrer des spectres de molécules refroidies au sein d'un jet supersonique. Les molécules de N2O, C2H4 et H12C13CH en abondance isotopique naturelle ont été étudiées. Le montage permet de refroidir les molécules étudiées jusqu'à 10 K et un coefficient de 5x10-8 cm-1 a été obtenu. Ce montage a également permis d'enregistrer des spectres CEAS et CRDS de NH3 à des températures de 17 et 14 K respectivement. L'analyse des spectres aété réalisée avec l'aide des Profs. Fusina et Di Lonardo de l'Université de Bologne, Italie.Une cellule de 145 cm pouvant être refroidie à l'aide de réfrigérants liquides a également été développée en vue de remplacer une cellule à température ambiante de 77 cm utilisée dans le montage femto/OPO-FT-CEAS.Enfin, les montages FANTASIO+ et femto/OPO-FT-CEAS ont été utilisés afin afin d'enregistrer des spectres de HCOOH à température ambiante et à 10 K. Les données ont été traitées avec l'aide du Dr. Perrin de l'Université Paris-Créteil, France.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Hamza, Taha Mohamed. "Doped ZnO nanostructures for Mid Infrared plasmonics." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC051/document.
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L'objectif de ce travail est de réaliser des substrats pour l’effet SEIRA (surface enhanced IR absorption) pour mesurer de faibles volumes de gaz ambiants possédant une signature moléculaire de 3,3 μm à 5,1 μm en exploitant la forte amplification de champ électrique due à la résonance plasmon de surface localisés. A cette fin, nous avons démontré la modulation des résonances de plasmon de surface localisées MIR (LSPR) dans les nanocristaux de ZnO dopés (NCs) dopés à Ga ou Al ainsi que dans des nanofils (NWs) de ZnO dopés Ga (GZO) et dans des nanofils coeur/coquille de ZnO/GZO. En ce qui concerne l’accordabilité de MIR LSPR dans les NC, nous avons modulé la résonance plasmon de surface dans des NC de ZnO dopés Ga et Al, de 3 à 5 μm en faisant varier la teneur en Al et en Ga de 3 à 9 at.%. L’incorporation des dopants s’est révélée homogène jusqu’à 6%. Au-delà (9%), l’incorporation était fortement hétérogène, révélant que la limite de solubilité était atteinte. Les NC présentent une faible activation des impuretés. L'activation était aussi faible que 8%. Les LSPR présentaient également un fort élargissement (largeur-à-mi-hauteur FWHM). Pour accroitre l'activation des dopants, nous avons synthétisés les NC dans des conditions pauvres en O et en passivant les NC synthétisés dans des conditions riches en O (en les isolant dans des matrices telles que Al2O3 et SiO2). Nous avons ainsi augmenté l'activation de 8% à 20% pour les deux stratégies. De plus, l'incorporation des NC dans les matrices a réduit l'élargissement spectral de moitié (de 2200 cm-1 pour les NC déposés à 1100 cm-1 pour les NC noyés en matrice). En correspondance, les effets d’auto-assemblage des nanocristaux sur leur LSPR ont été modélisés par simulation FDTD. Cela a fourni des indications quant aux mécanismes responsable de l’élargissement inhomogènes des LSPR de nanocristaux de GZO. Outre les nanoparticules, nous avons étudié des nanofils ZnO dopés Ga (GZO) et coeur/coquille (ZnO/GZO) synthétisés par CVD d’organométalliques . La première conclusion importante est que le gallium produit un fort effet surfacatnt lors de la croissance MOCVD de GZO. Au lieu de former des nanofils de section hexagonale, l’introduction de Ga modifie nettement l’énergie de surface des faces latérales et conduit à al formation de structures de type « sapins de Noël ». Ce constat est aussi valable pour les coquilles de GZO déposées sur coeur de ZnO. Dans ce cas, les coquilles démouillent et forment des structures hiérarchiques en branches. Concernant les propriétés optiques de ces objets, les mesures de FTIR-photo acoustiques ont démontré une signature d’absorption reliée à la présence de Ga et pouvant être accordée selon la teneur en Ga. Cette absorption reproduit le comportement d’une résonance plasmon de surface. Cette résonance a pu être accordée de 1600 à 1900 cm-1The scope of this thesis is about developing SEIRA (surface enhanced IR absorption) platform to probe low volumes of environmental gases that possess molecular signature from 3.3 μm to 5.1 μm leveraging the high field amplification of localised surface plasmon resonance (LSPR). To realise SEIRA, we demonstrated tuning MIR LSPR in Al or Ga doped ZnO nanocrystals (NCs) as well as in GZO or core-shell (ZnO/GZO) nanowires (NWs). Regarding tuning MIR LSPR in NCs, we demonstrated tunable MIR LSPR in Ga and Al doped ZnO NCs from 3 to 5 μm varying the Al or Ga content from 3 to 9 at.%. The incorporation of dopant was homogeneous up to 6%. At 9% dopant concentration, the incorporation was inhomogeneous, revealing the solubility limit has been reached. However, the NCs exhibited low activation of impurities. The activation was as low as 8%. The LSPR were characterised by large broadening as well. In order to enhance the dopant activation, we synthesized the NCs in O-poor conditions as well as passivated the NCs fabricated in O-rich condictions (by isolating and embedding them in matrices such as Al2O3 and SiO2 matrices). Both strategies improved the dopant activation from 8% up to 20%. Moreover, for assemblies of NCs dispersed in matrices, the broadening (FWHM) of the LSPR was reduced by half (from 2200 cm-1 in as-deposited NCs to 1100 cm-1 in embedded NCs). Correspondingly, the effect of the self-assembly of the nanocrystals on their LSPR was modeled by FDTD simulation and provided hindsight into the mechanisms responsible for the heterogeneous broadening of the LSPR. Finally, we have studied Ga-doped ZnO (GZO) and core-shell (ZnO/GZO) NW synthesized by MOCVD. The first important conclusion is that Ga plays a major surfactant role during the MOCVD growth of GZO. Instead of leading to hexagonal NWs, the introduction of Ga during the synthesis led to faceted “Christmas-tree” like architectures. The same observation held for core-shell ZnO-GZO nanowires; in the latter case, the GZO shell resulted in a dewetting branched architecture. Regarding their optical properties, photo-acoustic FTIR measurements revealed an absorption feature related to the Ga content, likely to be assigned to a plasmonic effect. This resonance could be tuned from 1600 to 1900 cm
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Curtin, Benjamin Michael. "Photonic crystal back-reflectors for light management and enhanced absorption in a-Si:H solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468075.
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Devkota, Jagannath. "Enhanced Magnetoimpedance and Microwave Absorption Responses of Soft Ferromagnetic Materials for Biodetection and Energy Sensing." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5862.
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A combination of magnetic sensors with magnetic nanoparticles offers a promising approach for highly sensitive, simple, and rapid detection of cancer cells and biomolecules. The challenge facing the field of magnetic biosensing is the development of low-cost devices capable of superconducting quantum interference device (SQUID)-like field sensitivity at room temperature. In another area of interest, improving the sensitivity of existing electromagnetic field sensors for microwave energy sensing applications is an important and challenging task. In this dissertation, we have explored the excellent magnetoimpedance and microwave absorption responses of soft ferromagnetic amorphous ribbons and microwires for the development of high-performance magnetic biodetectors and microwave energy sensors.
We have developed the effective approaches to improve the magnetoimpedance response of Co65Fe4Ni2Si15B14 amorphous ribbons by tuning their dimension and/or coating them with thin layers of CoFe2O4. Coating amorphous and crystalline CoFe2O4 films on the ribbon surface have opposite impacts on the magnetoimpedance response. Pulsed laser deposition (PLD) is shown to be a novel in-situ annealing and coating method for improving the magnetoimpedance response of the soft ferromagnetic amorphous ribbons for advanced sensor applications. The magnetoimpedance responses are also enhanced in multi-microwire systems relative to their single microwires. We have introduced a new method of combining the magnetoresistance (MR), magnetoreactance (MX), and magnetoimpedance (MI) effects of a soft ferromagnetic amorphous ribbon to develop an integrated biosensor with enhanced sensitivity and tunable frequency. While existing MI biosensors have limited sensitivities, we show that by exploiting the MR and MX effects it is possible to improve the sensitivity of the biosensor by up to 50% and 100%, respectively. The MX-based approach shows the most sensitive detection of superparamagnetic (Fe3O4) nanoparticles at low concentrations, demonstrating a sensitivity level comparable to that of a SQUID-based biosensor. Unlike a SQUID, however, the proposed MX technique is cryogen-free and operates at room temperature, providing a promising avenue to the development of low-cost highly sensitive biosensors. We have further improved the detection sensitivity of the MI and MX biosensors by patterning the sensing (ribbon) surface with nano/micro-sized holes, using the etching or focused ion beam (FIB) technique. These biosensors have been successfully employed to detect and quantify various bioanalytes, such as Curcumin-type anticancer drugs, bovine serum albumen (BSA) proteins, and Lewis lung carcinoma (LLC) cancer cells that have taken up the surface-functionalized Fe3O4 nanoparticles. Since Fe3O4 nanoparticles are widely used as magnetic resonance imaging (MRI) contrast agents, our biosensing technique can also be used as a new, low-cost, fast and easy pre-detection method before MRI. Finally, we have developed a new method of using a soft ferromagnetic glass-coated amorphous microwire as a microwave absorber for fabrication of a fiber Bragg grating-based microwave energy sensor with improved sensitivity and less perturbation of the microwave field. As compared to a similar approach that uses gold to absorb electromagnetic radiation, the microwire yields a device with greater sensitivity (~10 times at f = 3.25 GHz) relative to the perturbation of the microwave field. A correlation between the magnetic softness and microwave absorption in the microwires has been established, paving the way to improve the performance of the microwave energy sensor by tailoring their soft magnetic properties.
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de, Ghellinck d'Elseghem Vaernewijck Xavier. "Instrumental contribution to FTIR spectroscopy using a femto-OPO laser source and cavity enhanced absorption." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209629.
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L'expérience nommée femto-FT-CEAS a été mise en place durant ce travail. Ellecombine une source d'absorption laser femto-opo, une cavité optique haute finesse
et un interféromètre à transformée de Fourier. Ce montage instrumental a permis
d'enregistrer des spectres sur un domaine de 100 cm−1 avec un coefficient d'absorption
minimal détectable de 5 10−10cm−1 pour des paramètres de résolution spectrale de
2 10−2cm−1 et un temps d'enregistrement d'une heure. Le coefficient d'absorption
equivalent par moyenne quadratique par élément spectral correspondant est de 1.2
10−12cm−1 Hz−1/2. Un chemin optique équivalent de 13 km a été obtenu dans une
cellule de 77 cm de long. La gamme spectrale accessible est de 6000 − 6700 cm−1 et
7800 − 8300 cm−1.
Les spectres enregistrés à l'aide du montage femto-FT-CEAS ont permis d'attribuer
plus de 1000 transitions rovibrationelles d'échantillons de CO2 enrichis en 17O,
d'OCS, CS2, H12C13CD, et CH3CCH. Les bandes suivantes ont été enrégistrées :
pour 12C17O2, les bandes 30013e, 30012e, 30011e, 31113e, 31113f, 31112e, 31112f,
et 31111e; pour 17O12C18O, les bandes 30013e, 30012e, et 30011e; pour 16O12C32S,
les bandes 540, 0, 501, 0, 511, 1e, 511, 1f, 601, 0, 460, 0, 421, 0, 431, 1e, 431, 1f,
521, 0, 341, 0, 351, 1e, 351, 1f, 302, 0, 312, 1e, 312, 1f, 402, 0, 322, 2e, et 322, 2f;
pour 16O12C34S, les bandes 501, 0 et 302, 0; pour 16O13C32S, la bande 302, 0 ;pour
16O12C33S, la bande 302, 0; pour 12C32S2, les bandes 0403, 0114, 3003 et 2203; pour
32S12C34S, la bande 3003. Les conventions de notation vibrationelles utilisées ici sont
pour CO2, ν1 ν2 l ν3 n où les bandes vibrationelles perturbées par la résonance de
Fermi ν1 2ν2 sont ordonnées selon n par ordre décroissant d'énergie. Pour l'OCS,
les conventions de notation sont ν1 ν2 ν3, l et pour le CS2, ν1 νl2 ν3. Leur analyse
spectrale a été réalisée, aboutissant à de nouvelles constantes rovibrationelles ou des
constantes améliorées par rapport à celles de la littérature. Les raies rovibrationnelles
attribuées sont données. L'analyse des spectres de H12C13CD et de CH3CCH a étéréalisée par l'équipe du Pr. L. Fusina (Université de Bologne, Italie).
L'expérience a aussi été installée autour d'un jet supersonique, enregistrant les
structures rotationnelles des bandes vibrationelles ν5 + ν9 de C2H4, 3ν3 de N2O et
ν1 + ν3 de H12C13CH en abondance naturelle, toutes avec une température rotationelle
inférieure à 35 K.
Finalement, un programme de simulation de ligne de base a été écrit.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Intarakumhaeng, Rattikorn. "Factors Influencing Percutaneous Absorption:Effects of Solvents, Solute Physicochemical Properties, and Penetration Enhancer." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491316295006087.
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Hollingsworth, Anna Marie. "Quantitative detection of trace gas species in the atmosphere using LED Broadband Cavity Enhanced Absorption Spectroscopy." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/9526.
Full textAbstract:
A broadband version of cavity enhanced absorption spectroscopy (BBCEAS) has been applied to measure the ambient concentrations of reactive trace gases, particularly nitrogen dioxide (NO2) in the polluted urban environment and molecular iodine (I2) in the marine boundary layer. The spectrometer’s light source, a light emitting diode (LED), enables absorption spectra of gas samples to be acquired over 50 nm bandwidths at visible and nearultraviolet wavelengths. Differential optical absorption spectroscopy (DOAS) is then applied to unambiguously identify and quantify the various absorbers present in the samples. Especially difficult operating conditions were encountered during the instrument’s first field deployment onboard the research vessel RRS Discovery. As a result, the instrument did not achieve the I2 detection limits it had demonstrated in laboratory testing and was unable to detect any I2 signal in the mid‐Atlantic Ocean during the Reactive Halogens in the Marine Boundary Layer Experiment. However, iodine was detected around many night‐time low tides during the BIOFLUX II campaign at the Mace Head Atmospheric Research Station in County Galway, Ireland. The maximum I2 concentration of 608 pptv (parts per trillion by volume) correlated with the campaign’s lowest tide, and is three times greater than any previous report of atmospheric I2 concentrations. The BIOFLUX observations support current understanding that coastal I2 derives from seaweed (particularly kelp species) exposed to air around low tide. LED‐BBCEAS measurements of NO2 made on the University campus during the Leicester Air Quality Measurement Project are compared with data from two chemiluminescence instruments. The need to closely co‐locate instruments during comparisons of the various techniques is discussed, and evidence of a possible interference in the chemiluminescence measurements has been found.
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Silander, Isak. "Cavity enhanced optical sensing." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110278.
Full textAbstract:
An optical cavity comprises a set of mirrors between which light can be reflected a number of times. The selectivity and stability of optical cavities make them extremely useful as frequency references or discriminators. With light coupled into the cavity, a sample placed inside a cavity will experience a significantly increased interaction length. Hence, they can be used also as amplifiers for sensing purposes. In the field of laser spectroscopy, some of the most sensitive techniques are therefore built upon optical cavities. In this work optical cavities are used to measure properties of gas samples, i.e. absorption, dispersion, and refractivity, with unprecedented precision. The most sensitive detection technique of all, Doppler-broadened noise-immune cavity enhanced optical heterodyne molecular spectrometry (Db NICE-OHMS), has in this work been developed to an ultra-sensitive spectroscopic technique with unprecedented detection sensitivity. By identifying limiting factors, realizing new experimental setups, and determining optimal detection conditions, the sensitivity of the technique has been improved several orders of magnitude, from 8 × 10-11 to 9 × 10-14 cm-1. The pressure interval in which NICE-OHMS can be applied has been extended by derivation and verification of dispersions equations for so-called Dicke narrowing and speed dependent broadening effects. The theoretical description of NICE-OHMS has been expanded through the development of a formalism that can be applied to the situations when the cavity absorption cannot be considered to be small, which has expanded the dynamic range of the technique. In order to enable analysis of a large number of molecules at their most sensitive transitions (mainly their fundamental CH vibrational transitions) NICE-OHMS instrumentation has also been developed for measurements in the mid-infrared (MIR) region. While it has been difficult to realize this in the past due to a lack of optical modulators in the MIR range, the system has been based on an optical parametric oscillator, which can be modulated in the near-infrared (NIR) range. As the index of refraction can be related to density, it is possible to retrieve gas density from measurements of the index of refraction. Two such instrumentations have been realized. The first one is based on a laser locked to a measurement cavity whose frequency is measured by compassion with an optical frequency comb. The second one is based on two lasers locked to a dual-cavity (i.e. one reference and one measurement cavity). By these methods changes in gas density down to 1 × 10-9 kg/m3 can be detected. All instrumentations presented in this work have pushed forward the limits of what previously has been considered measurable. The knowledge acquired will be of great use for future ultrasensitive cavity-based detection methods.
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Schmidt, Florian. "Laser-based Absorption Spectrometry : Development of NICE-OHMS Towards Ultra-sensitive Trace Species Detection." Doctoral thesis, Umeå : Department of Physics, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1414.
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Krauth, Oliver. "Investigation of the surface enhanced infrared absorption in the case of carbon monoxide on iron thin films." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=961929510.
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Pliutau, Dzianis V. "LIBS and LITE Emission Based Laser Remote Sensing of Chemical Species and Enhanced Modeling of Atmospheric Absorption." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3531.
Full textAbstract:
Laser-Induced Breakdown spectroscopy (LIBS) and Laser-Induced Thermal Emission (LITE) emission based laser remote sensing were investigated with the application to the remote measurements of trace chemical species. In particular, UVvisible LIBS and Mid-IR LITE systems were developed and measurements of remote targets and chemical surfaces were studied. The propagation through the atmosphere of the multi-wavelength backscattered LIBS and LITE optical spectrum with atmospheric absorption effects on the returned lidar signal was investigated. An enhanced model of the atmospheric effects on emission-based laser-remote sensing was developed and found to be consistent and in agreement with our experimental results.
LITE measurements were performed which involved heating a remote hard target and recording the vibrational band emission spectra produced. Sample heating was carried out using a 1.5W cw-CO2 10.6 μm wavelength laser, and a 9W cw-diode laser operating at 809nm. The emission spectra over the wavelength range of 8 to 14 μm was observed which can be potentially used to detect and identify chemical composition of the target. LITE spectra of DMMP and DIMP (chemical agent simulants), paints, and energetic materials on various substrates were measured for the first time.
A LIBS study was carried out with a 1.064 μm Nd:YAG laser (10 ns pulses, 50mJ per pulse) and remote LIBS measurements were performed for aluminum, copper, steel and plastics over the spectral range of 200 – 1000nm. LIBS measurements as a function of range were studied, and compared to a modified lidar equation suitable for emission based lidar remote sensing.
A computer simulation model was developed for emission-based LIDAR remote sensing such as LIBS and LITE. This involved the development and modification of atmospheric transmission modeling programs which use the HITRAN, PNNL and other atmospheric spectral databases to model the transmission of the atmosphere over a wide range of wavelengths from the deep-UV near 200 nm to the mid-IR near 14 microns. A comparison of HITRAN simulations with the PNNL database calculated spectra was carried out and used for the first time for improvements of the HITRAN database line intensities. In addition, a Principal Component Analysis (PCA) of the LIBS and LITE lidar return signal as a function of range was performed. This PCA analysis showed, for the first time, the degradation of the chemical selectivity (i.e. identification capability) of the emission lidar system as the range was increased and the effect of atmospheric absorption spectral lines on the propagated LIBS and LITE lidar multi-wavelength spectral signal.
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Moreshead, William. "Enhanced Two-Photon Absorption in a Squaraine-Fluorene-Squaraine Dye: Design, Synthesis, Photophysical Properties, and Solvatochromic Behavior." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6325.
Full textAbstract:
The discovery of any new technology is usually accompanied by a need for new or improved materials which make that technology useful in practical applications. In the case of two-photon absorption (2PA) this has truly been the case. Since its first demonstration in 1961, there has been an ever increasing quest to understand the relationships between two-photon absorption and the structure of two-photon absorbing materials. This quest has been motivated by the many applications for 2PA which have been reported, including fluorescence bioimaging, 3D microfabrication, 3D optical data storage, upconverted lasing, and photodynamic therapy.
The work presented in this dissertation represents another step in the effort to better understand the structure/property relationships of 2PA. In this work a new, squaraine-fluorene-squaraine molecule, proposed through a joint effort of quantum and synthetic chemists, was synthesized and its photophysical properties were measured. The measurements included linear and two-photon photophysical properties, as well as solvatochromic behavior. Quantum calculations were done to aid in understanding those photophysical and solvatochromic properties. A single squaraine dye was also synthesized and used as a model compound to assist in understanding this new structure.
In Chapter 1 an introduction to 2PA and several of its applications is given. Chapter 2 gives a background of 2PA structure/property relationships that have been reported to date, based on work done with polymethine dyes. Chapter 3 gives a full account of the synthesis, characterization, and detailed quantum chemical analyses of this new squaraine-fluorene-squaraine molecule and the corresponding model compound squaraine dye. Chapter 4 gives some additional work and suggested future directions.Ph.D.
Doctorate
Chemistry
Sciences
Chemistry
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Kennedy, Oliver John. "Development and deployment of a broadband cavity enhanced absorption spectroscopy instrument for airborne measurements of trace gases." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610332.
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Favier, Marine. "Vers un instrument commercial pour la mesure des rapports isotopiques par Optical Feedback Cavity Enhanced Absorption Spectroscopy." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY106.
Full textAbstract:
Les isotopes stables ont permis de faire des découvertes majeures en science, comme, la datation de l'apparition de l'oxygène sur Terre à partir des isotopes du soufre [1] et l'analyse des échanges entre le carbone atmosphérique et celui des autres réservoirs (biosphère, océans) à partir du rapport isotopique 13C/12C [2].Traditionnellement, les rapports isotopiques sont mesurés avec des spectromètres de masse dédiés (IRMS : « isotope ratio mass spectrometer »). Depuis une dizaine d’années, ils sont également remplacés par des spectromètres commerciaux basés sur la spectroscopie infrarouge. Ces nouveaux instruments peuvent quantifier en temps réel et in-situ les rapports isotopiques des petites molécules d’intérêt environnemental en phase gazeuse (notamment l’eau et le dioxyde de carbone). Cependant, dans certains cas, ces instruments sont inadaptés. Ils utilisent soit trop d'échantillon, ou sont trop coûteux, ou ne mesurent pas certains isotopes. C'est en particulier le cas des isotopes du soufre.Nous montrons dans ce travail deux prototypes d’instruments qui mesurent des rapports isotopiques par Optical Feedback Cavity Enhanced Absorption Spectroscopy (OFCEAS). Le premier instrument détermine le rapport 13C/12C dans des échantillons d’air atmosphérique contenant entre 200 et 500 ppmv de CO2. Les concentrations les plus basses de cette gamme sont typiques de celles de l’air atmosphérique datant d’une dizaine de milliers d’années. On retrouve cet air dans les bulles emprisonnées dans les carottes de glace. Les concentrations les plus élevées correspondent à celles de l’air atmosphérique actuel. Pour cet instrument nous avons mis en évidence, grâce à une étude systématique des variables du système, l'impact de la pression, de la température et des franges optiques sur la mesure du rapport 13C/12C. En limitant ces sources de bruit, nous avons obtenu une précision de 0.2‰ en 2 minutes sur la mesure du rapport 13C/12C avec une concentration de CO2 autour de 280 ppmv. Nous avons obtenu une précision de 0.05‰ en référençant alternativement la mesure d'un échantillon à celle d'un gaz standard dans un cycle de mesure d'une durée de 2h par échantillon.Le deuxième prototype est le premier opérant dans le proche infrarouge capable d’analyser les rapports isotopiques 33S/32S et 34S/32S. Pour cela, il utilise la molécule H2S en phase gazeuse. Les composés de soufre, tels que les sulfates, sont en effet facilement convertis en H2S, contrairement au SF6 et au SO2, qui sont les gaz employés par la méthode IRMS conventionnelle. Les performances de l'instrument ont été examinées en réalisant des mesures statique sur trois mélanges de H2S et d'azote, présentant trois enrichissements en soufre différents. Ces trois mélanges ont été synthétisés au laboratoire. Les trois enrichissements relatifs en soufre-34 (0‰, 42.6‰ et 83.6‰) et en soufre-33 (0 ‰, 2.81‰, 5.39‰) ont été rigoureusement calibrés par IRMS. Nos mesures OFCEAS s'accordent à 1‰ près avec les valeurs obtenues par spectrométrie de masse. La précision obtenue en moyennant les résultats de 3 injections comportant 12 minutes de mesure est de 0.08‰ sur les deux rapports isotopiques 33S/32S et 34S/32SThe study of stable isotopes has led to many important advances in science, such as, for example, the determination of the timing of the oxygenation of Earth’s atmosphere using sulfur isotopes [1] and the quantification of the exchanges of carbon between the atmosphere and other reservoirs (biosphere, oceans) from the analysis of the 13C/12C isotope ratio [2].The conventional method to measure such isotopic ratios is by means of isotope ratio mass spectrometry (IRMS). About ten years ago, commercial instruments appeared that enabled the measurement of isotopic ratios using infrared spectroscopy of small molecules in the gas phase of interest for environmental studies (notably water and carbon dioxide). However, for some applications these instruments are not well adapted, for example, because they require too much material, or too expensive, or not able to measure isotopes in question. This is in particular the case for sulfur isotopes.During this work two prototype instruments were developed for the analysis of isotopic ratios by means of Optical Feedback Cavity Enhanced Absorption Spectroscopy (OFCEAS). The first targets the 13C/12C isotopic ratio in atmospheric air samples containing between 200 and 500 ppmv of CO2.The lowest concentration of this range is typical of paleo-air trapped in bubbles in ice cores, whereas the higher concentrations are encountered in modern air samples. For this instrument we have shown, through a detailed and systematic study, the effect of pressure, temperature, and optical interference fringes on the measurement of the isotopic ratio. Mitigating these sources of errors has led to a performance characterized by a precision of 0.2‰ in 2 minutes on measurements at a concentration of about 280 ppmv and a precision of 0.05‰ when alternatingly referencing the sample measurement to that of a standard material in a measurement cycle with duration of 2h for one sample.The second instrument is the first of its kind being able to analyze the 33S/32S and 34S/32S ratios through near-infrared spectroscopy on H2S gas. Sulfur compounds, such as sulfate, are easily converted to H2S, but this is not the case for SF6 or SO2, which are the common gases used in the conventional IRMS method. The instrument was demonstrated by performing static measurements on three isotopically different samples of H2S – nitrogen mixtures. These local standard materials were synthesized by us, and shown to have relative enrichment levels of 0‰, 42.6‰ and 83.6‰ for 34S/32S, and 0 ‰, 2.81‰, and 5.39‰ for 33S/32S by IRMS analyses. Our laser spectrometer measurements agree to within 1‰ with the calibrated IRMS values. The precision obtained after averaging three 12-minute measurements is 0.08‰ for both isotopic ratios
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Rodriguez, Kenneth Ralph. "The extraordinary infrared transmission of metal microarrays for enhanced absorption spectroscopy of monolayers, nanocoatings, and catalytic surface reactions." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189549712.
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Panov, Nikolay A., Daniil E. Shipilo, Vera A. Andreeva, Olga G. Kosareva, Alexander M. Saletsky, Huailiang Xu, and Pavel Polynkin. "Supercontinuum of a 3.9μm filament in air: Formation of a two-octave plateau and nonlinearly enhanced linear absorption." AMER PHYSICAL SOC, 2016. http://hdl.handle.net/10150/621548.
Full textAbstract:
Through numerical simulations we reveal the scenario of 3.9-mu m filament spectrum enrichment in the atmosphere in the cases of linear and circular polarization of the incident pulse. The discrete spectrum of odd harmonics transforms into the two-octave plateau in the case of linear polarization. In contrast, in the case of circular polarization of the incident pulse, the harmonic-free flat supercontinuum appears with the plasma onset, reaching the tenth harmonic of the input radiation. We identify the energy balance specific to the filamentation near 4 mu m: the absorption on CO2 lines in the atmosphere is accelerated by the self-phase modulation in the Kerr nonlinearity early before the plasma channel is formed. This nonlinearly enhanced linear absorption overwhelms the plasma losses and conversion of the input pulse energy to the higher harmonics as well as the plateau.
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Liu, Ping. "Preparation and evaluation of alginate-pectin-poly-/-lysine particulates for drug delivery and evaluation of melittin as a novel absorption enhancer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/MQ42408.pdf.
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Dunbar, Ricky [Verfasser], and Lukas [Akademischer Betreuer] Schmidt-Mende. "Using metallic nanostructures to trap light and enhance absorption in organic solar cells / Ricky Dunbar. Betreuer: Lukas Schmidt-Mende." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1022318829/34.
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