Dissertationen: „Reactive light“

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Myronidi, Despoina. „LIGHT-BEAT: REACTIVE LIGHT FOR THE EMOTIONAL COMFORT OF NEWBORN BABIES“. Thesis, KTH, Ljusdesign, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297961.

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This is a project-based thesis focusing on the investigation of topics related to human newborns and the factors found in their surrounding environment that need to be assessed so as to provide them with a feeling comfort. The objective is to boost their emotional development by the means of light in a close relation to sound so as to provide them with a type of intelligence allowing them to normally interact within a society during their adult life, reassuring social equality and eliminating potential social exclusion due to unexpected behaviours. After researching topics to have a better understanding of the newborn baby and its enclosing environment, a luminaire design solution -functioning with a reactive scheme performed with integrated sound sensors- provided further results to the main topic investigation. The conceptual scheme for the product development was inspired by the connection between the newborn and their life-giver, closely linked to the cross-modality of sensory development before and after birth. Additional results were obtained with light measurement assessments and a parent survey targeting both the intended light quality subjective evaluations and the marketing strength of the designed product. This survey was used -along with other means- as a design evaluation tool at the final stage of the design process. Potential further improvements as well as considerations for a distinct spatial application are discussed in the final part of the thesis. The sustainability aspect covered within this degree project is closely linked to good physical and mental health aspects, clean energy use and efficiency achieved by the integration of input sound sensors and controls, and conscious production and consumption by the proposal of low global footprint materials for the luminaire design. In the conclusions, an overall summary of the thesis outcomes is presented and further research is proposed regarding both the main topic investigation as well as a greater user category that can be related to the light metric assessments that were carried out for this research.

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Kiszka, Mariusz. „Spectroscopic characterisation of reactive species generated by light and ionising radiation in low temperature matrices“. Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366952.

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3

Edwards, Jessica Corinne. „Investigation of Color Removal by Chemical Oxidation for Three Reactive Textile Dyes and Spent Textile Dye Wastewater“. Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34091.

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This research investigated the efficacy of chlorine dioxide (ClO2), ultraviolet (UV) irradiation, UV in combination with chlorine dioxide (UV/ClO2), and UV in combination with hydrogen peroxide (UV/H2O2) for decolorizing three reactive azo dyes (sultan red, indigo blue and cypress green) and treated textile-manufacturing wastewater. The objective was to determine the best treatment for reducing color to the Virginia Pollutant Discharge Elimination System (VPDES) permit level of 300 American Dye Manufacturers Institute (ADMI) units. The effects of the three chemical oxidation treatments provided color reduction for all three dyes. The results suggested UV/H2O2 and UV/ClO2 treatments provided maximum color reduction of the red and blue dyes, and UV/H2O2 was the most effective for maximum reduction of the green dye.

A research goal was to provide predictive models of the wastewater effluent for the treatment processes, including the UV exposure time required to reach the 300 ADMI permit value and the effective ClO2 dose necessary to achieve the 300 units. The results of the investigations regarding the effluent indicated that UV/H2O2 and UV/ClO2 (5 mg/L) provided reduction to 300 units in less than 10 minutes UV exposure when the initial effluent color was less than 500 ADMI units. Without the addition of oxidant, contact times longer than 10 minutes were required for UV to decolorize these effluents to 300 ADMI units. Chlorine dioxide dosages between 10 and 30 mg/L both with and without UV irradiation achieved the same results.
Master of Science

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Fergusson, Stanley MacArthur, und mac fergusson@rmit edu au. „The Effect of Laundry Detergents and Residual Alkali on the Light Fastness of Reactive Dyes on 100% Cotton“. RMIT University. Fashion and Textiles, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081128.162252.

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This study presents findings on the effect of domestic laundry detergents on the fastness to light of selected fibre reactive dyes applied to cotton. The study was carried out to elucidate the reasons for the accelerated colour loss of cotton garments washed under Australian domestic laundering conditions. Cotton fabric dyed with commonly used reactive dyes were laundered with water only, several domestic detergents and a laboratory formulated neutral detergent, and then exposed to light for two hours in the wet state. Quantities of detergent used were in accordance with the manufacturers recommendations. Exposures were repeated fifteen times equivalent to 30 hours exposure. Colour loss and colour difference were measured after 5, 10 and 15 wash cycles and 10, 20 and 30 hours exposure. When the fabric was exposed wet the colour faded more rapidly than when exposed dry to light. Detergents increased the colour loss even when the fabric was not exposed to light. The presence of an oxidizing bleach (sodium perborate) in the detergent increased colour loss during washing and wet exposure to light. Ultraviolet radiation from the light source, heat, moisture, alkali and oxidising bleach during exposure resulted in hydrolysis of the dye-fibre bond causing dye desorption during washing and rinsing. Water alone increased the fading of the dyes most likely due to presence of dissolved oxygen held within the fibre. The combination of ultraviolet radiation and oxidizing bleaches altered the chemistry of the dye and hence its shade. This was particularly evident on the black dye and one of the navy blue dyes.

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Teale, Carson(Carson Arthur). „In-situ depth monitoring for a deep reactive ion etcher using a white light interferometer with active vibration cancellation“. Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121726.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-121).
Standard process development for micro and nanofabrication etching technologies relies on open-loop trial and error testing of recipes to achieve optimal etch depths and uniformities. This strategy is inefficient for research and fabrication of novel devices where one-of-a-kind experiments cannot justify lengthy process development times. This thesis describes the development of an in-situ depth measurement device for real-time feedback of etch depth and uniformity. This device will help facilitate far shorter process development times, potentially enabling the desired etch to be achieved on the first process run. The depth imager consists of a wide-field, white light interferometer with a 12" working distance, capable of imaging across a 1/2" field of view. Active feedback from a co-propagating laser interferometer is used to stabilize the system against vibrations through a feedback loop that controls the position of the reference mirror using a piezo actuator. This scheme ties the accuracy of the white light depth scan to the stability of the laser wavelength, allowing for accurate step sizes without the need for an expensive scanning stage. The well defined sampling period allows for the phase sensitive detection of the white light interference signal, reducing amplitude fluctuations from plasma emissions. This design is able to image deep trenches with optically rough surfaces, etched directly into a silicon substrate with aspect ratios of 10 or more. The device is demonstrated on a custom built deep reactive ion etcher (DRIE), achieving a depth resolution of better than 1 [mu]m in the presence of large vibrations.
by Carson Teale.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

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Lumbala, Jenny Chansa. „Synthesis and characterisation of Au/TiO2 composites for plasmon-enhanced visible light driven photocatalytic degradation of reactive orange 16 dye“. Thesis, Cape Peninsula University of Technology, 2019. http://hdl.handle.net/20.500.11838/2984.

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Thesis (Master of Applied Science in Chemistry)--Cape Peninsula University of Technology, 2019
Photocatalysis is one of the methods that have gained popularity for degradation of organic pollutants in water. Metal oxides, such as ZnO, Fe2O3, and TiO2 are considered to be good and efficient photocatalysts. TiO2, in particular, has been the most investigated because it is naturally abundant, non-toxic and stable. However, the wide band gap of TiO2 (3.2 eV), make TiO2 only to absorb UV light. For this reason, plasmon enhanced-photocatalysis has emerged as one of the appealing processes to achieve visible light utilization by TiO2. This process exploits the Localized Surface Plasmon Resonance (LSPR) of the metal nanoparticles such as gold to harvest the visible light and bring about photocatalytic process. LSPR is the effect of the oscillation of electrons in noble metals when they are in contact with light. Due to the LSPR phenomena, noble metals are able to increase the lifetime of the charge carriers and increase electron/hole generation semiconductors photocatalysts under visible light. In this study, TiO2 was coupled with gold nanoparticles in order to facilitate visible light absorption and to improve the photocatalytic performance. Gold nanoparticles (nanospheres and nanorods) were synthesised using the Turkivich and seed mediated methods. These were characterised by UV-visible spectrophotometry, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) for optical properties, size and morphology. The concentration of the as prepared gold samples was measured using the inductively coupled plasma optical emission spectrometry (ICP-OES). Gold nanospheres and gold nanorods were loaded into TiO2 using the nucleation and growth method to obtain the Au/TiO2 plasmonic composites. To investigate to effect of the gold size, two AuNRs samples with different aspect ratios (1.9 and 3.4) were prepared and used to form the nanocomposites with TiO2. Another Au/TiO2 composite sample was prepared by loading AuNS to compare the behaviour of the two shapes. The characterisation results of these samples from the transmission electron microscopy TEM and SEM confirmed the expected shapes (spheres and rods) and the formation of the nanocomposites. The energy dispersive spectroscopy (EDS) results showed the presence of the all the expected elements in the composites materials, further confirming the successful synthesis of the Au/TiO2 composites. The absorption spectra of the prepared nanocomposites showed the plasmonic peaks of the gold nanoparticles in the visible region, which also confirmed the formation of the composite materials. The photocatalytic performance of the photocatalysts was investigated for the degradation of reactive orange 16. From the results obtained in this study, it was found that the photocatalysts loaded with AuNRs gave higher photodegradation efficiencies compared to the one loaded with AuNS. The photocatalytic efficiency was found to increase with an increase on the aspect ratio of the AuNRs. For AuNRs (1.9) the achieved efficiency was 84.56 % and 86.65 % for AuNRs (3.4). Meanwhile, direct photolysis did not have an effect on the photodegradation of Reactive Orange 16 (RO 16). The combined effect of AuNRs and AuNS showed a drastic improvement on the photocatalytic efficiency and the rates of the process which was attributed to the synergistic effects of the transverse and the longitudinal plasmons peaks of both nanospheres and nanorods. The photocatalyst prepared with the mixed nanospheres and nanorods gave an efficiency of up to 90.15 % for the 1:1 ratio at 60 min reaction time. A number of reaction parameters were investigated for their effect on the photodegradation efficiency including: pH, Au content, and temperature. The photocatalytic degradation of RO 16 was very slow in very acidic (pH 2.5) and very basic conditions (pH 11.5). The highest degradation efficiency was achieved at pH of about 6.7. Furthermore, the rate of degradation also increased with an increase in temperature from 15 oC to 30 oC due to the reduction of the activation energy. The increase in Au loading from 0.1 wt % to 0.2 wt % increased the photocatalytic performance of the catalyst from 56.29 % to 86.65 %. However, further increase in gold loading blocked the light penetration and hence, caused a decrease on the efficiency to 66.35 %.

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Gatlin, DeVonna M. M. S. „Characterization and Photodynamics of Reactive Intermediates for Various Carbonyl-Based Systems: Alkyl Azides, Vinyl Azides, and Beta-Ketoester Moieties“. University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535380770508755.

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Matheus, Luiz Eduardo Mendes. „DYRP-VLC: a dynamic routing protocol for visible light communication networks“. Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/8076.

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Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-11-19T12:44:23Z No. of bitstreams: 1 luizeduardomendesmatheus.pdf: 1606990 bytes, checksum: 2736fa2230ff16ef4aaa41155178b616 (MD5)
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Na última década, o interesse (acadêmico e comercial) em torno da Comunicação por Luz Visível (VLC) aumentou consideravelmente, devido a fatores como a crescente demanda por recursos sem ﬁo na Internet e às vantagens oferecidas pela transmissão de dados através da luz visível. Entretanto, a utilização da luz como meio de comunicação, principalmente em ambientes internos, oferece diversos desaﬁos, como interferência e bloqueios criados por obstáculos. Ao mesmo tempo, este tipo de ambiente oferece uma rica infraestrutura de fontes de luz, que podem ser utilizadas para auxiliar na comunicação através de mecanismos multi-hop. A maioria dos trabalhos presentes na literatura adotam técnicas simples para construção de mecanismos multi-hop em redes VLC, focando principalmente em aumento de distância. Neste trabalho, foi desenvolvido um protocolo de roteamento dinâmico, DYRP-VLC (DynamicRoutingProtocolforVisibleLightCommunication),quetemcomoobjetivo aumentar o desempenho de sistemas VLC em ambientes dinâmicos, enquanto reage à obstáculos construindo rotas alternativas na rede. A avaliação do protocolo foi realizada em um ambiente real, utilizando a plataforma embarcada OpenVLC 1.0 e métricas adotadas para problemas de roteamento. Os resultados obtidos mostram que, usando o DYRP-VLC, a rede foi capaz de se adaptar a mudanças dinâmicas na comunicação, como sombras e obstáculos, com pouca sobrecarga.
In the last decade, the interest in Visible Light Communication (VLC) has increased considerably, from both academic and commercial perspectives, due to factors such as the growing demand for wireless resources and the advantages oﬀered by the transmission of data through visible light. However, the use of light as a communication medium, especially in indoor environments, oﬀers several challenges, which includes shadowing and interference caused by obstacles. At the same time, this type of environment oﬀers a rich infrastructure of light sources, which can be used to aid communication through multi-hop mechanisms. Most of the works present in the literature adopt simple techniques to construct multi-hop mechanisms in VLC networks, focusing mainly on increasing distance. Inthisthesis,wedevelopedDYRP-VLC(DynamicRoutingProtocolforVisibleLight Communication), a reactive routing protocol which aims to increase the performance ofVLCsystemsindynamicenvironments,whilereactingtoobstaclesbyconstructing alternative routes in the network. The evaluation of the protocol was performed in a real environment, using OpenVLC 1.0 embedded platform and adopting metrics for routing problems. The results show that, by using DYRP-VLC, the network was able to adapt to dynamic changes in communication, such as shadows and obstacles, with low overhead.

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Neukermans, Jenny. „Interactions between light, CO2 and oxidative stress in Arabidopsis“. Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112054.

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Au cours de l’évolution, les plantes ont développé des mécanismes pour percevoir et s'adapter aux conditions de stress. Les formes actives de l'oxygène (FAO) sont des facteurs importants de l'état redox cellulaire et sont impliquées dans ces réponses. Le peroxyde d'hydrogène (H2O2), une FAO majeure des voies de signalisation oxydative, peut être produit rapidement dans la photorespiration. Chez Arabidopsis, le H2O2 produit dans la photorespiration est métabolisé notamment par la CATALASE2 (CAT2). Dans le contexte du mutant cat2 déficient pour cette catalase, les réponses au stress oxydatif induit par la production conditionnelle du H2O2 sont fortement dépendante de la photopériode. En particulier, la formation de lésions, accompagnée de réponses similaires à celles d' attaques pathogènes, sont spécifiques des conditions de culture en jours longs (JL). Ces effets ne sont pas observés en jours courts (JC) malgré un stress oxydant qui semble être aussi prononcé qu’en JL. Une approche transcriptomique globale a été utilisée pour explorer les patterns d’expression génique associées à ces effets. Elle a permis de mettre en évidence des interactions entre photopériode et H2O2 ou entre photopériode et CO2. En particulier, la majorité des gènes répondant à l' H2O2 dans le mutant cat2 sont induits lorsque les plantes sont cultivées en JC alors que un plus petit nombre sont induits par l’ H2O2 spécifiquement en JL. De façon générale, ces analyses ont mis en évidence des relations étroites entre les ressources carbonées, la lumière et l'état redox cellulaire dans les réponses aux changements environnementaux. Un gène induit par le H2O2 spécifiquement en JL, l’AZELAIC ACID INDUCED 1 (AZI1), a été sélectionné pour des analyses fonctionnelles à l’aide d’approches génétique, biochimique et transcriptomique. L’analyse de mutants cat2 azi1 a révélé que AZI1 ne semble pas jouer un rôle majeur dans les réponses des plantes à un stress oxydatif durable. Cependant, ce gène semble jouer un rôle important lorsque le stress oxydatif est déclenchée de façon abrupte par le transfert des plantes de conditions de culture en fort CO2 vers l'air ambiant. De plus, cette étude montre que la communication de feuille à feuille est impliquée dans la régulation de l'expansion de la mort cellulaire en réponse a l'H2O2 issue de la photorespiration. Dans la régulation de l'expansion des lésions, nous proposons que AZI1 agirait d'une part localement pour induire la mort cellulaire et d'autre en inhibant la mort cellulaire d'une façon systémique. Dans des fonds génétiques sauvage Col-0 ou mutant cat2, l’analyse comparative de mutants d'insertion ADN-T pour les principaux photochromes (phyA , phyB) et cryptochromes (cry1, cry2) a permis d'étudier les interactions entre les stress et les fonctions des photorécepteurs. Il est apparu que, la mutation des gènes PHY comme CRY conduit a une stimulation de l’accumulation de glutathion H2O2 dépendante. En revanche, dans le fond génétique cat2 contrairement à la perte des fonctions PHY, la mutation des gènes cry conduit a une modulation du profil transcritomique induit par l’ H2O2. De plus, un criblage de conditions de stress sur les simples mutants cry a révélé une plus forte sensibilité de ces génotypes au stress osmotique, a l’ H2O2 et au paraquat. Globalement, ces données indiquent que l’ensemble des photorécepteurs et plus particulièrement les cryptochromes peuvent jouer un rôle dans la réponse à l’ H2O2 intracellulaire suggérant ainsi l’existence d’un réseau complexe permettant l’intégration de conditions environnementales et la détermination de réponses appropriées au stress
During evolution, plants have developed mechanisms to perceive and respond to stress conditions. Reactive oxygen species (ROS) are important components of cell redox state that have been implicated in these responses. H2O2, an important ROS molecule in oxidative signalling, can be produced rapidly in photorespiration. In Arabidopsis, photorespiratory H2O2 is notably metabolized by CATALASE2 (CAT2). Responses to oxidative stress induced conditionally by photorespiratory H2O2 in the catalase-deficient mutant, cat2, are highly determined by growth daylength. In particular, lesion formation, accompanied by induction of a range of pathogenesis responses, is specific to the long day (LD) photoperiod: these responses are not observed in short days (SD), even though oxidative stress seems to be as marked as in LD. A whole-genome transcriptomics approach was used to explore gene expression patterns underlying these effects, and identified interactions between daylength and H2O2 and between daylength and CO2. In particular, the majority of H2O2-responsive genes in cat2 were up-regulated more strongly in SD air, though a subset of H2O2-induced genes showed a LD-specific response. Overall, this analysis indicates close networking between carbon status, light, and redox state in environmental responses. The most strongly H2O2-induced gene in LD was azelaic acid induced 1 (AZI1) and this gene was chosen for functional analysis using a genetic, biochemical and transcript profiling approach. Analysis of cat2 azi1 mutants revealed that AZI1 does not seem to play an important role in the plant response to sustained, continuous oxidative stress, but is influential when oxidative stress is abruptly induced, in this case, by transferring plants from high CO2 to air. Moreover, this study provided evidence that leaf-to-leaf communication is involved in regulating cell death spread in response to photorespiratory H2O2. In the regulation of this lesion spread, it is proposed that AZI1 acts both locally to promote cell death as well as systemically to inhibit it. Using a comparative analysis of T-DNA insertion mutants for the major phytochromes (phyA, phyB) and cryptochromes (cry1, cry2) introduced into the Col-0 or cat2 background, interactions between stress and photoreceptor function were analyzed. A stimulatory effect of both phy and cry mutations on H2O2-triggered glutathione accumulation was apparent. In contrast to loss of PHY function, both cry mutations modulated daylength-dependent H2O2-triggered transcriptome profiles in cat2. In addition, stress screening of single cry mutants revealed effects on osmotic, H2O2 and paraquat sensitivity. Overall, these data show that both kinds of photoreceptor, but particularly cryptochromes, can play a role in the response to intracellular H2O2, suggesting that there is an intricate network allowing integration of environmental information to determine appropriate responses to stress

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Messenger, David James. „Impact of UV light on the plant cell wall, methane emissions and ROS production“. Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4347.

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This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

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Karavadara, Nilesh. „RA-LPEL : a Resource-Aware Light-weight Parallel Execution Layer for reactive stream processing networks on the SCC many-core tiled architecture“. Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17225.

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In computing the available computing power has continuously fallen short of the demanded computing performance. As a consequence, performance improvement has been the main focus of processor design. However, due to the phenomenon called 'Power Wall' it has become infeasible to build faster processors by just increasing the processor's clock speed. One of the resulting trends in hardware design is to integrate several simple and power-efficient cores on the same chip. This design shift poses challenges of its own. In the past, with increasing clock frequency the programs became automatically faster as well without modifications. This is no longer true with many-core architectures. To achieve maximum performance the programs have to run concurrently on more than one core, which forces the general computing paradigm to become increasingly parallel to leverage maximum processing power. In this thesis, we will focus on the Reactive Stream Program (RSP). In stream processing, the system consists of computing nodes, which are connected via communication streams. These streams simplify the concurrency management on modern many-core architectures due to their implicit synchronisation. RSP is a stream processing system that implements the reactive system. The RSPs work in tandem with their environment and the load imposed by the environment may vary over time. This provides a unique opportunity to increase performance per watt. In this thesis the research contribution focuses on the design of the execution layer to run RSPs on tiled many-core architectures, using the Intel's Single-chip Cloud Computer (SCC) processor as a concrete experimentation platform. Further, we have developed a Dynamic Voltage and Frequency Scaling (DVFS) technique for RSP deployed on many-core architectures. In contrast to many other approaches, our DVFS technique does not require the capability of controlling the power settings of individual computing elements, thus making it applicable for modern many-core architectures, with which power can be changed only for power islands. The experimental results confirm that the proposed DVFS technique can effectively improve the energy efficiency, i.e. increase the performance per watt, for RSPs.

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Kasson, Tina Michelle Dreaden. „High light stress in photosynthesis: the role of oxidative post-translational modifications in signaling and repair“. Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45759.

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Oxidative stress is a natural consequence of photosynthetic oxygen evolution and redox enzyme processes. Trp oxidation to N-formylkynurenine (NFK) is a specific, reactive oxygen species (ROS)-mediated reaction. This thesis work describes the identification and functional characterization of NFK in oxygen evolving Photosystem II (PSII). Although proteomics studies have confirmed NFK modifications in many types of proteins, limited knowledge on the biochemical significance exists. In vitro studies in thylakoids and PSII membranes were used to establish a correlation between oxidative stress, NFK formation, and photoinhibition. The in vivo effect of preventing Trp oxidation to NFK was assessed by site-directed mutation in the cyanobacteria Synechocystis sp. PCC 6803. This work provides insight into the role of NFK in photosynthetic oxygen evolution and photoinhibition. Based on the current knowledge of NFK, ROS, and repair, a new model is described. In this modified model for photoinhibition and repair, NFK plays a role in signaling for turnover of damaged proteins. NFK may play a similar role in replacement of damaged proteins in other systems.

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Meßmer, Andreas T. [Verfasser], Jens [Akademischer Betreuer] Bredenbeck und Josef [Akademischer Betreuer] Wachtveitl. „Shedding light on reaction mechanisms : structure determination of reactive intermediates and investigation of protein structural dynamics using 2D-IR spectroscopy / Andreas T. Meßmer. Gutachter: Jens Bredenbeck ; Josef Wachtveitl. Betreuer: Jens Bredenbeck“. Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2013. http://d-nb.info/1044276193/34.

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Meßmer, Andreas Thomas [Verfasser], Jens [Akademischer Betreuer] Bredenbeck und Josef [Akademischer Betreuer] Wachtveitl. „Shedding light on reaction mechanisms : structure determination of reactive intermediates and investigation of protein structural dynamics using 2D-IR spectroscopy / Andreas T. Meßmer. Gutachter: Jens Bredenbeck ; Josef Wachtveitl. Betreuer: Jens Bredenbeck“. Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2013. http://nbn-resolving.de/urn:nbn:de:hebis:30:3-293750.

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Mateo, Alfonso. „Roles of LESIONS SIMULATING DISEASE1 and Salicylic Acid in Acclimation of Plants to Environmental Cues : Redox Homeostasis and physiological processes underlying plants responses to biotic and abiotic challenges“. Doctoral thesis, Stockholm University, Department of Botany, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-698.

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In the natural environment plants are confronted to a multitude of biotic and abiotic stress factors that must be perceived, transduced, integrated and signaled in order to achieve a successful acclimation that will secure survival and reproduction. Plants have to deal with excess excitation energy (EEE) when the amount of absorbed light energy is exceeding that needed for photosynthetic CO2 assimilation. EEE results in ROS formation and can be enhanced in low light intensities by changes in other environmental factors.

The lesions simulating disease resistance (lsd1) mutant of Arabidopsis spontaneously initiates spreading lesions paralleled by ROS production in long day photoperiod and after application of salicylic acid (SA) and SA-analogues that trigger systemic acquired resistance (SAR). Moreover, the mutant fails to limit the boundaries of hypersensitive cell death (HR) after avirulent pathogen infection giving rise to the runaway cell death (rcd) phenotype. This ROS-dependent phenotype pointed towards a putative involvement of the ROS produced during photosynthesis in the initiation and spreading of the lesions.

We report here that the rcd has a ROS-concentration dependent phenotype and that the light-triggered rcd is depending on the redox-state of the PQ pool in the chloroplast. Moreover, the lower stomatal conductance and catalase activity in the mutant suggested LSD1 was required for optimal gas exchange and ROS scavenging during EEE. Through this regulation, LSD1 can influence the effectiveness of photorespiration in dissipating EEE. Moreover, low and high SA levels are strictly correlated to lower and higher foliar H2O2 content, respectively. This implies an essential role of SA in regulating the redox homeostasis of the cell and suggests that SA could trigger rcd in lsd1 by inducing H2O2 production.

LSD1 has been postulated to be a negative regulator of cell death acting as a ROS rheostat. Above a certain threshold, the pro-death pathway would operate leading to PCD. Our data suggest that LSD1 may be subjected to a turnover, enhanced in an oxidizing milieu and slowed down in a reducing environment that could reflect this ROS rheostat property. Finally, the two protein disulphide isomerase boxes (CGHC) present in the protein and the down regulation of the NADPH thioredoxin reductase (NTR) in the mutant connect the rcd to a putative impairment in the reduction of the cytosolic thioredoxin system. We propose that LSD1 suppresses the cell death processes through its control of the oxidation-reduction state of the TRX pool. An integrated model considers the role of LSD1 in both light acclimatory processes and in restricting pathogen-induced cell death.

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Tikhomirova, Anastasiia. „Studies of Photoinduced DNA Damage by Phenanthrene Dihydrodioxin and Light-driven Electron Delocalization in Pyridinium Molecules“. Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1561918589357022.

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17

Arthaut, Louis-David. „Effets de la lumière bleue et du champ magnétique sur la synthèse des ROS par le cryptochrome“. Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS400.

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Les cryptochromes sont des photorécepteurs qui absorbent la lumière bleue. On les trouve chez les animaux et les plantes, ils ont de multiples rôles de signalisation. Ils permettent de réguler la croissance, le développement, les rythmes circadiens ou encore le stress. Leur activation par la lumière bleue se traduit au niveau biochimique par la photoréduction d’un cofacteur qui leur est associé : la flavine, ce qui déclenche ensuite un changement conformationnel du domaine C-terminal qui permettra la liaison des cryptochromes à de multiples partenaires responsables de la signalisation. Aujourd’hui la recherche sur le fonctionnement des cryptochromes s’appuie sur de nouveaux champs d’étude, parmi ceux-ci figurent leur lien avec les ROS ainsi que leur sensibilité aux champs magnétiques. Dans nos travaux nous montrons pour la première fois que les cryptochromes animaux peuvent, à l’instar des cryptochromes de plante, synthétiser directement certains ROS après activation par la lumière bleue, et que cette synthèse a un rôle de signalisation. Enfin nous avons mis en lien leur propriété de magnétoreception avec leur synthèse de ROS chez des modèles cellulaires animaux
Cryptochromes are photoreceptors that absorb blue light, they are found in animals and plants and have multiple signaling roles. In plants they can regulate growth, development, circadian rhythms or stress; in animals they also regulate circadian rhythms and stress responses. Their activation in the presence of blue light is reflected biochemically by the photoreduction of the flavin which is associated with these proteins, this cofactor then triggers a conformational change of the C-terminus domain that will allow the binding of cryptochromes to multiple partners responsible for signaling. Today, research on the functioning of cryptochromes is based on new fields of study, among them are their link with the ROS and their sensitivity to magnetic fields. In our work we show for the first time that animal cryptochromes can also directly synthesize some ROS after activation in blue light, and that this synthesis which is also observed in plants has a signaling role. Finally, we have linked their magnetoreception property with their ROS synthesis in animal cell models

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Apicella, Fernandez Sergio. „Surface energy modification of metal oxide to enhance electron injection in light-emitting devices : charge balance in hybrid OLEDs and OLETs“. Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-25097.

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Organic semiconductors (OSCs) present an electron mobility lower by several orders of magnitude than the hole mobility, giving rise to an electron-hole charge imbalance in organic devices such as organic light-emitting diodes (OLEDs) and organic light-emitting transistors (OLETs). In this thesis project, I tried to achieve an efficient electron transport and injection properties in opto-electronic devices, using inorganic n-type metal oxides (MOs) instead of organic n-type materials and a polyethyleneimine ethoxylated (PEIE) thin layer as electron transport (ETLs) and injection layers (EILs), respectively. In the first part of this thesis, inverted OLEDs were fabricated in order to study the effect of the PEIE layer in-between ZnO and two different emissive layers (EMLs): poly(9,9-dioctylfluorene-alt-benzothiadiazole) polymer (F8BT) and tris(8-hydroxyquinolinato) aluminum small molecule (Alq3), based on a solution and thermal evaporation processes, respectively. Different concentrations (0.80 %, 0.40 %) of PEIE layers were used to further study electron injection capability in OLEDs. After a series of optimizations in the fabrication process, the opto-electrical characterization showed high-performance of devices. The inverted OLEDs reported a maximum luminance over 104 cd m-2 and a maximum external quantum efficiency (EQE) around 1.11 %. The results were attributed to the additional PEIE layer which provided a good electron injection from MOs into EMLs. In the last part of the thesis, OLETs were fabricated and discussed by directly transferring the energy modification layer from OLEDs to OLETs. As metal oxide layer, ZnO:N was employed for OLETs since ZnO:N-based thin film transistors (TFTs) showed better performance than ZnO-based TFTs. Finally, due to their short life-time, OLETs were characterized electrically but not optically.

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Pooam, Marootpong. „The biological effects of applied magnetic fields on cryptochrome and response“. Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS062.

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Cryptochromes (cry) sont des flavoprotéines absorbant la lumière bleue conservées qui ont été liées à perception de stimuli électromagnétiques dans de nombreux organismes. Nous avons principalement étudié le mécanisme d'interaction entre les champs magnétiques (MF) et cry dans le cadre de la théorie des paires de radicaux. Nous avons étudié la réponse d'Arabidopsis cry-1 in vivo à MF. Les activités biologiques du cry ont été renforcées par MF. Les effets des MF ont pu être observés même si MF était donné exclusivement pendant les intervalles d'obscurité entre expositions à la lumière. Cette découverte a indiqué que l'étape de réaction magnétiquement sensible dans photocycle du cry doit se produire pendant la réoxydation des flavines. De plus, nous avons également utilisé la fréquence (RF) stimulée par cry-Arabidopsis comme outils de diagnostic pour confirmer l'hypothèse de la paire de radicaux. Dans l'étude, nous avons trouvé un effet perturbateur des RF sur l'activité du cryptochrome. Notre découverte pourrait confirmer l'apparition du mécanisme de la paire de radicaux et l'implication du cry pour la magnétoréception. De plus, nous avons également montré un effet perturbateur de la condition MF statique de bas niveau (LLF) où les champs magnétiques externes étaient presque éliminés. Le résultat de cette condition était cohérent avec l'effet de l'exposition aux RF. En outre, nous avons également signalé que LLF pourrait augmenter l'expression de certains gènes induits par le PEMF dans dans les les cellules humaines. Cette découverte pourrait fournir des preuves à l'appui de l'effet des champs électriques magnétiques et non induits sur la physiologie humaine
Cryptochromes are highly conserved blue-light-absorbing flavoproteins that have been linked to the perception of electromagnetic stimuli in numerous organisms. We mainly studied the mechanism for the interaction between magnetic fields and cryptochromes in the context of the radical-pair theory. We investigated the response of Arabidopsis cryptochrome-1 in vivo to a static magnetic field. The biological activities of cryptochrome were enhanced by the magnetic field. Interestingly, the effects of the magnetic fields could be observed even the magnetic field was given exclusively during dark intervals between light exposures. This finding indicated that the magnetically sensitive reaction step in the cryptochrome photocycle must occur during flavin reoxidation. Moreover, we also used frequency (RF) stimulated to Arabidopsis cryptochrome as the diagnostic tools to confirm the radical-pair hypothesis. In the study, we found a disruptive effect of RF on the activity of cryptochrome. Our findings could confirm the occurrence of the radical-pair mechanism and the involvement of cryptochrome for magnetoreception. Additionally, we also showed a disruptive effect of the low-level static magnetic field (LLF) condition where the external magnetic fields were almost eliminated. The result of this condition was consistent with the effect of RF exposure. Furthermore, we also reported that LLF could increase the expression of some PEMF-induced genes in human cells. This finding could provide the evidence to support the effect of magnetic, not induced electric fields in human physiology

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Mano, Camila Marinho. „Espécies excitadas tripletes em sistemas biológicos - visita à hipótese de \"fotobioquímica no escuro\" de Giuseppe Cilento“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-20032014-095058/.

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Espécies carbonílicas tripletes formadas quimicamente no escuro, por exemplo, durante a peroxidação de lipídios, têm reatividade química análoga à de radicais alcoxilas. Aventou-se que tais espécies possam estar implicadas na fisiopatologia de doenças degenerativas (\"estresse carbonílico\"). A pesquisa dos efeitos de espécies tripletes sobre algumas biomoléculas e consequentes respostas biológicas, propostas e pesquisadas no período 1970 - 1990 (hipótese de \"fotoquímica sem luz\" dos Profs. G. Cilento, IQUSP, e Emil H. White, Johns Hopkins University), encontrou empecilhos instrumentais e relativamente poucas propostas foram confirmadas. Com o uso de técnicas de alta resolução, tais como EPR, HPLC e MS, este trabalho teve como objetivo analisar intermediários e produtos de tais processos e estudar mecanismos de reação de acetona triplete, produzida quimicamente pela decomposição térmica de 3,3,4,4-tetrametildioxetano (TMD) ou, enzimaticamente, pela oxidação aeróbica de isobutanal (IBAL), catalisada por peroxidase de raiz forte (HRP), na presença de aminoácidos e proteínas. Este trabalho demonstra a formação de um radical acetila, presumidamente formado da clivagem α de acetona triplete, e um radical terciário centrado em carbono, formado pela abstração de hidrogênio do IBAL. Resultados de espectrometria de massas demonstraram a formação de três diferentes adutos entre o radical terciário de IBAL, com L-Trp. Aventou-se que um dos produtos era resultante de alteração no nitrogênio e os outros no carbono 3, ambos no anel indólico. Observou-se também a formação de produto correspondente ao radical hidroxipropionil com L-Trp. Também se observaram dois produtos de L-Trp típicos de sua oxidação por oxigênio singlete, a formilquinurenina, e um aduto de função álcool. A formação de base de Schiff entre o L-Trp estudado e o IBAL também é apresentada. A formação de oxigênio singlete foi evidenciada indiretamente via EPR utilizando o spin trap TEMP e através de um captador de adição-9,10 (tipo Diels-Alder) em derivado de antraceno. Foram realizados, também, experimentos com precursores de melanina e demonstrou-se a formação de espécies excitadas do ácido 5,6-dihidroxi-indol-2-carboxílico (DHICA) que poderiam explicar a formação de produtos de DNA tipicamente resultantes de reação fotoquímica, mas na ausência de luz. Tais resultados corroboram a reação de espécies tripletes com biomoléculas, possibilitando a compreensão de número significativo de eventos biológicos conhecidos, mas teoricamente \"proibidos\" de ocorrer no estado fundamental, em tecidos não expostos à luz
Electronically excited triplet carbonyl species formed as products of some biochemical reactions, such as lipid peroxidation, behave similarly as alcoxyl radicals. It has long been hypothesized that such excited species could have a role in some diseases (\"carbonyl stress\"). Research of chemical lesions of triplet carbonyls over biomolecules and their biological response took place principally from 1970 to 1990 (the \"photochemistry without light\" hypothesis proposed by Profs. G. Cilento, IQUSP, and Emil H. White, Johns Hopkins University), but it suffered from the lack of required instrumentation, and just few cases of photo(bio)chemistry without light were confirmed. The aim of this work, using high resolution techniques (EPR, HPLC, and MS), is to analyze the reaction products of excited triplet acetone with aminoacid and protein targets. Triplet acetone was produced from the thermal decomposition of 3,3,4,4-tetramethyldioxetane (TMD) or from the aerobic oxidation of isobutanal (IBAL) catalyzed by horseradish peroxidase (HRP). We revealed the generation of acetyl radical, putatively originated from α-cleavage of triplet acetone, and a carbon-centered tertiary radical, proposed as an IBAL radical formed by hydrogen abstraction from IBAL. Mass spectrometry showed production of three adducts from the reaction of IBAL radical with L-Trp, one of them at the nitrogen 1 and the other two at carbon 3 from the amino acid indole ring. Two adducts with m/z correspondent to the reaction between L-Trp (at carbon 3) and a hydroxypropionyl radical, and two products typically formed from singlet oxygen (formylkynurenine and an alcohol L-Trp adduct) were also observed. A Schiff base between L-Trp and IBAL was also observed. Singlet oxygen production from triplet-triplet energy transfer from excited acetone to ground state molecular oxygen was indirectly showed by EPR spin trapping with TEMP, and by MS using the anthracene derivative EAS to trap (9,10-cycloaddition) of 18O2 (1Δg). Other data reported here include the demonstration of excited species formed when DHICA, a melanin precursor, was oxidized. These results might explain the generation of DNA photochemical products (thymine dimers) in the absence of light. Altogether, we collect strong and significant evidence in this thesis that corroborate the reactivity of triplet excited species with a couple of biomolecules, providing insights over some reportedly known molecular events that are theoretically forbidden to occur in the ground state but happen in tissues non-exposed to light

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Zhang, Yuexiang. „Mass Spectrometric Study of Visible-Light Triggered Photoredox and Electrolytic Reaction Mechanisms“. Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1527760864441781.

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22

Pendlebury, Jonathon Remy. „Light Field Imaging Applied to Reacting and Microscopic Flows“. BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5754.

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Light field imaging, specifically synthetic aperture (SA) refocusing is a method used to combine images from an array of cameras to generate a single image with a narrow depth of field that can be positioned arbitrarily throughout the volume under investigation. Creating a stack of narrow depth of field images at varying locations generates a focal stack that can be used to find the location of objects in three dimensions. SA refocusing is particularly useful when reconstructing particle fields that are then used to determine the movement of the fluid they are entrained in, and it can also be used for shape reconstruction. This study applies SA refocusing to reacting flows and microscopic flows by performing shape reconstruction and 3D PIV on a flame, and 3D PIV on flow through a micro channel. The reacting flows in particular posed problems with the method. Reconstruction of the flame envelope was successful except for significant elongation in the optical axis caused by cameras viewing the flame from primarily one direction. 3D PIV on reacting flows suffered heavily from the index of refraction generated by the flame. The refocusing algorithm used assumed the particles were viewed through a constant refractive index (RI) and does not compensate for variations in the RI. This variation caused apparent motion in the particles that obscured their true locations making the 3D PIV prone to error. Microscopic PIV (µPIV) was performed on a channel containing a backward facing step. A microlens array was placed in the imaging section of the setup to capture a light field from the scene, which was then refocusing using SA refocusing. PIV on these volumes was compared to a CFD simulation on the same channel. Comparisons showed that error was most significant near the boundaries and the step of the channel. The axial velocity in particular had significant error near the step were the axial velocity was highest. Flow-wise velocity, though, appeared accurate with average flow-wise error approximately 20% throughout the channel volume.

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23

Ashby, M. K. „Reaction centre and light harvesting genes of Rhodobacter sphaeroides“. Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46944.

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Yaghoubi, Houman. „Bio-Photoelectrochemical Solar Cells Incorporating Reaction Center and Reaction Center Plus Light Harvesting Complexes“. Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5803.

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Harvesting solar energy can potentially be a promising solution to the energy crisis now and in the future. However, material and processing costs continue to be the most important limitations for the commercial devices. A key solution to these problems might lie within the development of bio-hybrid solar cells that seeks to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. The bio-photoelectrochemical cell technologies exploit biomimetic means of energy conversion by utilizing plant-derived photosystems which can be inexpensive and ultimately the most sustainable alternative. Plants and photosynthetic bacteria harvest light, through special proteins called reaction centers (RCs), with high efficiency and convert it into electrochemical energy. In theory, photosynthetic RCs can be used in a device to harvest solar energy and generate 1.1 V open circuit voltage and ~1 mA cm-2 short circuit photocurrent. Considering the nearly perfect quantum yield of photo-induced charge separation, efficiency of a protein-based solar cell might exceed 20%. In practice, the efficiency of fabricated devices has been limited mainly due to the challenges in the electron transfer between the protein complex and the device electrodes as well as limited light absorption. The overarching goal of this work is to increase the power conversion efficiency in protein-based solar cells by addressing those issues (i.e. electron transfer and light absorption). This work presents several approaches to increase the charge transfer rate between the photosynthetic RC and underlying electrode as well as increasing the light absorption to eventually enhance the external quantum efficiency (EQE) of bio-hybrid solar cells. The first approach is to decrease the electron transfer distance between one of the redox active sites in the RC and the underlying electrode by direct attachment of the of protein complex onto Au electrodes via surface exposed cysteine residues. This resulted in photocurrent densities as large as ~600 nA cm-2 while still the incident photon to generated electron quantum efficiency was as low as %3 × 10-4. 2- The second approach is to immobilize wild type RCs of Rhodobacter sphaeroides on the surface of a Au underlying electrode using self-assembled monolayers of carboxylic acid terminated oligomers and cytochrome c charge mediating layers, with a preferential orientation from the primary electron donor site. This approach resulted in EQE of up to 0.06%, which showed 200 times efficiency improvement comparing to the first approach. In the third approach, instead of isolated protein complexes, RCs plus light harvesting (LH) complexes were employed for a better photon absorption. Direct attachment of RC-LH1 complexes on Au working electrodes, resulted in 0.21% EQE which showed 3.5 times efficiency improvement over the second approach (700 times higher than the first approach). The main impact of this work is the harnessing of biological RCs for efficient energy harvesting in man-made structures. Specifically, the results in this work will advance the application of RCs in devices for energy harvesting and will enable a better understanding of bio and nanomaterial interfaces, thereby advancing the application of biological materials in electronic devices. At the end, this work offers general guidelines that can serve to improve the performance of bio-hybrid solar cells.

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Knowles, Haydn Scott. „The light activated alkylation of glycine“. Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341492.

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Widmann, John F. „Chemical reaction and thermodynamic studies of microparticles using electrodynamic balances /“. Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9873.

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Röhlecke, Cora, Ulrike Schumann, Marius Ader, Coy Brunssen, Silvia Bramke, Henning Morawietz und Richard H. W. Funk. „Stress Reaction in Outer Segments of Photoreceptors after Blue Light Irradiation“. Public Library of Science, 2013. https://tud.qucosa.de/id/qucosa%3A29060.

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The retina is prone to oxidative stress from many factors which are also involved in the pathogenesis of degenerative diseases. In this study, we used the application of blue light as a physiological stress factor. The aim of this study was to identify the major source of intracellular ROS that mediates blue light-induced detrimental effects on cells which may lead to cytotoxicity. We hypothesized that outer segments are the major source of blue light induced ROS generation. In photoreceptors, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes and the recently found respiratory chain complexes may represent a major source for reactive oxygen species (ROS), beside mitochondria and chromophores. Therefore, we investigated this hypothesis and analysed the exact localization of the ROS source in photoreceptors in an organotypic culture system for mouse retinas. Whole eyeball cultures were irradiated with visible blue light (405 nm) with an output power of 1 mW/cm2. Blue light impingement lead to an increase of ROS production (detected by H2DCFDA in live retinal explants), which was particularly strong in the photoreceptor outer segments. Nox-2 and Nox-4 proteins are sources of ROS in blue light irradiated photoreceptors; the Nox inhibitor apocynin decreased ROS stimulated by blue light. Concomitantly, enzyme SOD-1, a member of the antioxidant defense system, indicator molecules of protein oxidation (CML) and lipid oxidation (MDA and 4-HNE) were also increased in the outer segments. Interestingly, outer segments showed a mitochondrial-like membrane potential which was demonstrated using two dyes (JC-1 and TMRE) normally exclusively associated with mitochondria. As in mitochondria, these dyes indicated a decrease of the membrane potential in hypoxic states or cell stress situations. The present study demonstrates that ROS generation and oxidative stress occurs directly in the outer segments of photoreceptors after blue light irradiation.

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Röhlecke, Cora, Ulrike Schumann, Marius Ader, Coy Brunssen, Silvia Bramke, Henning Morawietz und Richard H. W. Funk. „Stress Reaction in Outer Segments of Photoreceptors after Blue Light Irradiation“. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-189180.

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The retina is prone to oxidative stress from many factors which are also involved in the pathogenesis of degenerative diseases. In this study, we used the application of blue light as a physiological stress factor. The aim of this study was to identify the major source of intracellular ROS that mediates blue light-induced detrimental effects on cells which may lead to cytotoxicity. We hypothesized that outer segments are the major source of blue light induced ROS generation. In photoreceptors, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes and the recently found respiratory chain complexes may represent a major source for reactive oxygen species (ROS), beside mitochondria and chromophores. Therefore, we investigated this hypothesis and analysed the exact localization of the ROS source in photoreceptors in an organotypic culture system for mouse retinas. Whole eyeball cultures were irradiated with visible blue light (405 nm) with an output power of 1 mW/cm2. Blue light impingement lead to an increase of ROS production (detected by H2DCFDA in live retinal explants), which was particularly strong in the photoreceptor outer segments. Nox-2 and Nox-4 proteins are sources of ROS in blue light irradiated photoreceptors; the Nox inhibitor apocynin decreased ROS stimulated by blue light. Concomitantly, enzyme SOD-1, a member of the antioxidant defense system, indicator molecules of protein oxidation (CML) and lipid oxidation (MDA and 4-HNE) were also increased in the outer segments. Interestingly, outer segments showed a mitochondrial-like membrane potential which was demonstrated using two dyes (JC-1 and TMRE) normally exclusively associated with mitochondria. As in mitochondria, these dyes indicated a decrease of the membrane potential in hypoxic states or cell stress situations. The present study demonstrates that ROS generation and oxidative stress occurs directly in the outer segments of photoreceptors after blue light irradiation.

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Vo, Hao T. H., und Hao T. H. Vo. „Transformation of Trace Organic Contaminants Involving Reactive Oxygen Species Driven By Solar Lights“. Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/626333.

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The presence of trace organic compounds (TOrCs) in wastewater effluent and surface waters has raised attention due to their health and environmental effects. Some TOrCs are naturally attenuated via biodegradation, photo-degradation and/or adsorption, but some persist in the environment as contaminants in surface and ground waters. Thus, it is crucially important to understand their transformation pathways and their mechanisms following their discharge into the environment. This work presents research in three parts: • The first part represents an investigation of photo-transformation of TOrCs (e.g., furfuryl alcohol, p-cresol, gemfibrozil) under UV254, UVA and natural sunlight, and involving reactive oxygen species including singlet oxygen, hydroxyl radicals, triplet excited states, and specific inorganic radicals that are created by effluent organic matter (EfOM). Singlet oxygen was the only ROS, generated from effluent organic matter (EfOM) that mainly contributed to the photo-transformation of these selected TOrCs. A comprehensive mechanism and complementary kinetic model were proposed to predict the trajectories of TOrC removals via reaction with singlet oxygen. Simulations built on predicted quantum efficiencies accounted for light shading and competitive effects. Agreement between measurements and simulations was excellent. • The second part of the dissertation summarizes expected removal efficiencies for fifty-five TOrCs in alternative engineered and natural treatment processes including conventional biological treatment, advanced oxidation processes (AOP), reverse osmosis (RO), granular activated carbon (GAC), and sunlight photolysis. • The last section of the dissertation follows the trajectories of a series of TOrCs and total estrogenic activity in the Santa Cruz River, following their discharge from a wastewater treatment plant in the Tucson area. The study suggests that some TOrCs tend to persist in the environment while others experience photo (or other) transformations that diminish their concentrations or activities with distance and time of travel in the river. The attenuation of estrogenic activity was dependent on sunlight and the presence of specific (unidentified) wastewater components.

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Yang, Jingchen. „Using the Transient IR Spectroscopy to Elucidate Reaction Mechanisms in Visible Light Photoredox Catalysis:“. Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:108934.

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Thesis advisor: Matthias M. Waegele
Studying the visible light-driven photoredox catalysis coupled with transition-metal complexes is of overriding importance in the development of synthetic strategy. Comparing to conventional thermal catalysis, reactions catalyzed and/ or initiated by photon energy are not only attractive for establishing a more sustainable system, but also for their unique reactivity that has previously been inaccessible. However, one issue draws our attention is that such photoredox catalytic schemes often suffer from a limited substrate scope. To develop more efficient and effective synthetic strategies applicable to broader range of substrates, it is of our interest to construct an functional and reliable instrument to identify the critical mechanistic steps that lead to low product yield. To this end, we designed a time-resolved visible-pump/ infrared-probe spectroscopic measurement technique to monitor reaction dynamics in-situ. Using our transmission infrared setup, we effectively demonstrated in-situ photoexcitation and decay process of Tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate in deuterated acetonitrile. In addition, to optimize signal resolution, an electronic filter was installed in one of the data-collecting channels to allow for concurrent AC-coupled and DC-coupled signal recording. A series of chopper wheel experiments was conducted to assure the functionality of the system and reliability of obtained data
Thesis (MS) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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Lewis, D. G. „A study of the reaction (sup(6)Li,d) on light nuclei“. Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355737.

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Sayah, Imane. „Etude de revêtements photocatalytiques à base de dioxyde de titane nanostructuré élaborés par pulvérisation cathodique magnétron en condition réactive“. Thesis, Belfort-Montbéliard, 2014. http://www.theses.fr/2014BELF0249/document.

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Le développement de photocatalyseurs en couches minces supportées constitue un intérêt majeur autorisant une séparation efficace des produits de réaction, en dépit d’une réduction de leur surface spécifique par rapport à des nanopoudres du même matériau. La synthèse de revêtements de TiO2 par pulvérisation cathodique magnétron en condition réactive fait l’objet de recherches intensives. Cette technique permet de contrôler, à travers les paramètres d’élaboration, la structure et les propriétés physicochimiques et photocatalytiques des revêtements.Afin de s’affranchir de la contamination du catalyseur par le sodium du verre lors de traitements en température ou lors de recuits de couches déposées à l’ambiante, une barrière de diffusion en SiNx est intercalée et son épaisseur est fixée pour la suite de l’étude. Différentes couches de TiO2 ont été élaborées à haute pression dans un réacteur doté d’un système de contrôle en boucle fermée basé sur la spectroscopie d’émission optique. L’effet de la cristallisation in situ à différentes températures sur les différentes propriétés des revêtements TiO2 a été étudié et les propriétés de ces derniers ont été comparées à celles des échantillons synthétisés sur des substrats froids et recuits ex situ aux mêmes températures.Enfin, des premiers travaux portant sur l’influence de l’introduction de l’argent en différentes teneurs sur l’efficacité photocatalytique sous lumière visible des couches de TiO2 cristallisées in situ et ex situ sont présentés
The development of supported photocatalysts thin films is of major interest allowing an efficient separation of the reaction products, in spite of their specific area reduction compared to nanometric scale powders. The synthesis of TiO2 coatings by reactive magnetron sputtering is the subject of intensive researches. This technique allows, trough the control of the deposition parameters, to manage the structure and the physicochemical and photocatalytic properties of the coatings. In order to hinder the sodium contamination of the catalyst from the glass substrate, either during in situ or ex situ heating of the coating, a SiNx diffusion barrier is intercalated with a fixed thickness. Different layers of TiO2 were prepared at high pressure in a reactor equipped with a closed-loop control system based on optical emission spectroscopy. The influence of the in situ crystallization at different temperatures on the properties of the TiO2 coatings was studied. These properties were compared with those of samples synthesized ex situ and at the same temperatures. Finally, first studies on the influence of silver enrichment at different contents on photocatalytic activity under visible light of TiO2 layers crystallized in situ and ex situ, are presented

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Bao, Zeqing. „Light-Dependent Biosynthesis of Silver Nanoparticles Mediated by Microalgal Cell Extract“. Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37310.

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Silver nanoparticles (AgNPs) are a promising nanomaterial with numerous applications and high level of commercialization. Biomass-mediated AgNP synthesis has emerged as a novel approach for producing AgNPs and microalgal biomasses have been found particularly advantageous. However, few studies have so far focused on microalgae-mediated biosynthesis and the mechanism of AgNP biosynthesis is still elusive. The purpose of this study was twofold: 1) to investigate effects of different parameters on the biosynthesis of AgNPs; 2) to investigate the mechanisms involved in such a bioprocess. It was found that the cell extract of Neochloris oleoabundans prepared by whole cell aqueous extraction (WCAE) in boiling water bath was able to reduce Ag+ to AgNPs. It was further discovered that sonication of algal cells before extraction could enhance the efficiency of cell extraction and enable AgNP biosynthesis using cell extract obtained by disrupted cell aqueous extraction (DCAE) at room temperature. Light was required for AgNP biosynthesis and rainbow tests showed that purple and blue lights were particularly necessary. Based on experimental results, we hypothesize the mechanism of microalgae-mediated AgNP synthesis to be a chlorophyll-mediated reaction, in which chlorophylls are excited upon absorbing photons in the purple and blue spectra and donate electrons to reduce Ag+, the lost electrons are replenished by water-splitting reaction.

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Johnson, Ethan Thoreau. „Electrostatic interactions and exciton coupling in photosynthetic light-harvesting complexes and reaction centers /“. Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/9196.

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Takakado, Akira. „Studies on Reaction Dynamics and Interdomain/Intermolecular Interactions of LOV Light-sensor Proteins“. Kyoto University, 2018. http://hdl.handle.net/2433/232272.

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Kandappa, Sunil Kumar. „Light as a Reagent for Chemical Reactions-Excited State Manipulation to Discover New Reactivity“. Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1573830383912829.

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Wahl, Sebastian. „Shed Light on Cobalt Oxides for the Oxygen Evolution Reaction – An Operando Spectroelectrochemical Study“. Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21108.

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In dieser Dissertation wird der Einfluss unterschiedlicher Sauerstoff-Koordinationsgeometrien um ein zentrales Kobaltatom evaluiert. Genauer werden Oxide, die tetraedrisch und oktaedrisch koordiniertes Kobalt enthalten, synthetisiert und charakterisiert. Zudem wird ihre Aktivität in Hinblick auf die Sauerstoffentwicklungsreaktion (OER) unter alkalischen Bedingungen untersucht. Die elektrochemischen Analysen zeigen dabei, dass Materialien, die Kobalt in tetraedrischer Sauerstoffkoordination enthalten, die besseren Katalysatorvorläufer für die OER sind. Weiterhin kann demonstriert werden, dass das Herauslösen von inaktiven Metallen aus einer Struktur die Aktivität erhöht. Darauf basierend wird das neue Material Zn0.35Co0.65O vorgeschlagen. Es kristallisiert in der Wurtzitstruktur und enthält nur tetraedrisch koordinierte Atome. In alkalischen Lösungen wandelt sich die Wurtzitstruktur über die Zwischenstufe Co(OH)2 zum gamma-Co(O)OH um, und nahezu alles Zink wird aus der Struktur herausgelöst. Dadurch wird ein Material mit einer großen elektrochemisch aktiven Oberfläche gewonnen, das unterkoordinierte CoO(6-x) Oktaeder als aktive Zentren für die OER enthält. Hierdurch wird eine herausragende katalytische Leistung erreicht. Um weitere Einblicke in die OER zu generieren, wird Diffuse Reflexions UV/Vis (DRUV) Spektroskopie verwendet. Es werden neuartige Durchflusszellendesigns vorgeschlagen, die es erlauben, DRUV Spektren während der Katalyse aufzunehmen, d.h. operando. Durch diesen spektroelektrochemischen Ansatz werden Veränderungen der Katalysatoren während der OER beobachtet. So kann die Phasenumwandlung von Zn0.35Co0.65O erfolgreich verfolgt werden. Ebenso kann gezeigt werden, dass CoAl2O4 und Co2SnO4 nur an ihrer Oberfläche katalytische Aktivität aufweisen. Durch den Vergleich mit ex situ Analysen werden eindeutige Struktur-Eigenschaftsbeziehungen vorgeschlagen und tiefere Einsichten in die katalytisch aktiven Strukturmotive erhalten.
In this PhD thesis, the influence of different coordination geometries of oxygen atoms around a central cobalt atom is evaluated. Specifically, oxides containing tetrahedral and octahedral coordinated cobalt are synthesized, characterized and their activity towards the OER under alkaline conditions is evaluated. The electrochemical analyses reveal, that materials containing cobalt in tetrahedral oxygen coordination are better precatalysts for the OER. Furthermore, it is demonstrated that leaching of inactive metals from a structure increases the activity as well. Based on the previous mentioned, the new material Zn0.35Co0.65O is proposed. It crystallizes in the wurtzite structure and contains solely tetrahedrally coordinated atoms. In alkaline solutions, it transforms from wurtzite structure via a hydroxide to gamma-Co(O)OH, and nearly all Zn is leached from the structure. By this, a material with a large electrochemically active surface area is generated, that contains under-coordinated CoO(6-x) octahedra as active centers for the OER. Thus, outstanding catalytic performance is achieved. To generate further insights into the OER, diffuse reflectance ultraviolet visible (DRUV) spectroscopy is facilitated. Novel flow-cell designs are proposed, that allow to record DRUV spectra of catalysts under working conditions, i.e. operando. By this spectroelectrochemical approach, changes the catalysts undergo during the OER are observed. The phase transitions of Zn0.35Co0.65O are successfully followed, and it can be further shown, that CoAl2O4 and Co2SnO4 are only active at their surface. By comparison to ex situ analyses, clear structure-activity correlations are proposed, and deeper insights in the catalytically active structural motifs are obtained.

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Nakasone, Yusuke. „Studies on molecular reaction dynamics and interdomain interaction of blue-light sensor protein "phototropin“. 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124442.

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Swartz, Jacobus Andreas. „A feasibility study of the (3He,8He) reaction with the K600 magnetic spectrometer“. Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4297.

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Thesis (MSc (Physics))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Highly exotic nuclei can be studied in rare reactions using stable beams, with macroscopic intensities, and thick targets. Exotic nuclei are interesting for a number of reasons e.g. for testing nuclear models under conditions of high isospins. In the case of very neutron-deficient nuclei, two-proton decay is the most recently discovered nuclear decay mode and the subject of many theoretical investigations involving cluster and shell models. This thesis presents a feasibility study of investigating light exotic nuclei near the proton drip line with the K600 magnetic spectrometer. The 27Al(3He,8He)22Al five-neutron pick-up reaction was investigated at a spectrometer angle of θlab = 8◦ with a beam energy of Elab = 220 MeV. This reaction can be used to populate highly neutron-deficient nuclei. Should the study of this reaction prove to be feasible, then a number of nuclei on the proton drip line or beyond could be investigated. A new data acquisition system, with VME electronics and MIDAS software, was used along with one new drift chamber, which consists of both an X wire plane and a U wire plane. The particles 1,2,3H and 3,4He were all identified as outgoing particles from the collision of 3He with 27Al. Cross section calculations were performed for these observed reactions. Discrete spectra for the (3He,6He) and (3He,8He) reactions could not be identified. The mass calculation of A ∼ 20 nuclei on the proton drip line depends on the determination of the Coulomb energy, which differs a lot between mirror nuclei. Mass calculations were performed for known nuclei in the mass region A ≤ 50, using the Isobaric Multiplet Mass Equation. Agreement with experimental data was found to be far better in odd nuclei than in even nuclei. Hence mass predictions were performed for odd nuclei along the proton drip line.
AFRIKAANSE OPSOMMING: Hoogs eksotiese kerne kan bestudeer word in seldsame reaksies deur middel van stabiele bundels, met makroskopiese intensiteite, en dik teikens. Eksotiese kerne is interessant om verskeie redes, onder andere om kernfisiese modelle te toets onder omstandighede van ho¨e isospin. In die geval van baie neutron-arm kerne is twee-proton verval die nuutste ontdekte tipe van kernverval. Dit is ook die onderwerp van vele teoretiese studies met betrekking tot bondel en skilmodelle. Hierdie tesis beskryf ‘n uitvoerbaarheidstudie vir die ondersoek van ligte eksotiese kerne naby die proton drup lyn met behulp van die K600 magnetiese spektrometer. Die 27Al(3He,8He)22Al vyf-neutron kaapreaksie is ondersoek by ‘n spektrometer hoek van θlab = 8◦ met ‘n bundel energie van Elab = 220 MeV. Sou die uitvoerbaarheidstudie van hierdie reaksie slaag, dan kan verskeie kerne op of anderkant die proton drup lyn ondersoek word. ‘n Nuwe data verkrygingssisteem, met VME elektronika en MIDAS sagteware, is gebruik saam met een nuwe dryfkamer, wat bestaan uit beide ‘n X draadvlak en ‘n U draadvlak. Die partikels 1,2,3H en 3,4He is almal geidentifiseer as uitgaande partikels van die botsing van 3He met 27Al. Kansvlak-berekeninge is uitgevoer vir alle waargenome reaksies. Diskrete spektra kon nie gevind word vir die (3He,6He) of (3He,8He) reaksies nie. Die massa berekening van A ∼ 20 kerne op die proton drup lyn is afhanklik van die bepaling van die Coulomb energie, wat baie verskil tussen spie¨elkerne. Massa berekeninge is uitgevoer vir bekende kerne in die massa gebied A ≤ 50, deur die gebruik van die Isobariese Multiplet Massa Vergelyking. Die ooreenstemming met eksperimentele data was baie beter in die geval van onewe kerne as met ewe kerne. Daarom was die massa voorspellings uitgevoer vir slegs onewe kerne naby die proton drup lyn.

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Choi, Suekwoo. „Studies on the reaction dynamics of structural and intermolecular interaction changes during signal transduction of the photosensor protein YtvA“. Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263494.

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Conyard, Jamie. „Ultrafast excited state reaction dynamics in light-driven unidirectional rotary molecular motors and fluorescent protein chromophores“. Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/43602/.

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Excited state dynamics on an ultrafast timescale can provide insight into primary events in photochemical and photobiological processes. In this work, excited state dynamics of two important systems are characterized: unidirectional molecular rotary motors and HBDI derivatives (synthetic chromophores of the green fluorescent protein (GFP)). In both cases, the excited state is selectively probed by ultrafast fluorescence up-conversion with a time resolution better than 50 fs. Molecular motors have biphasic (sub-picosecond and picosecond) fluorescence decays and oscillations attributed to excitation of coherently excited vibrational modes. The fluorescence data were contrasted with excited state decay and ground state recovery kinetics recorded using ultrafast transient absorption. Combining these experimental data with substituent dependence and solvent dependence studies, as well as existing calculations, we proposed a coupled two-state model for dynamics on the excited state potential energy surface. These data have implications for the design and optimisation of optically driven molecular motors. A ‘molecular propeller’ was also studied and shown to be more sensitive to medium friction than the motor. The GFP experiments focused on determining the effect of alkyl substitution upon excited state dynamics of HBDI. HBDI in solution exhibits a very low quantum yield compared to the chromophore in its protein environment. Large alkyl substituents were found to shift the spectra but to exhibit only small retardation effects upon the excited state decay time, even in highly viscous solvents. This supports an assignment of a volume conserving isomerization mechanism promoting radiationless decay. Substituents which distort the planar structure of the chromophore lead to an enhanced radiationless decay. This provides further evidence for a link between radiationless decay of the excited state and twisting of HBDI.

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Dezi, Manuela <1977&gt. „The photosynthetic bacterial reaction center in native and artificial envirnoments: effects on light-induced electron transfer“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/684/.

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In this thesis we focussed on the characterization of the reaction center (RC) protein purified from the photosynthetic bacterium Rhodobacter sphaeroides. In particular, we discussed the effects of native and artificial environment on the light-induced electron transfer processes. The native environment consist of the inner antenna LH1 complex that copurifies with the RC forming the so called core complex, and the lipid phase tightly associated with it. In parallel, we analyzed the role of saccharidic glassy matrices on the interplay between electron transfer processes and internal protein dynamics. As a different artificial matrix, we incorporated the RC protein in a layer-by-layer structure with a twofold aim: to check the behaviour of the protein in such an unusual environment and to test the response of the system to herbicides. By examining the RC in its native environment, we found that the light-induced charge separated state P+QB - is markedly stabilized (by about 40 meV) in the core complex as compared to the RC-only system over a physiological pH range. We also verified that, as compared to the average composition of the membrane, the core complex copurifies with a tightly bound lipid complement of about 90 phospholipid molecules per RC, which is strongly enriched in cardiolipin. In parallel, a large ubiquinone pool was found in association with the core complex, giving rise to a quinone concentration about ten times larger than the average one in the membrane. Moreover, this quinone pool is fully functional, i.e. it is promptly available at the QB site during multiple turnover excitation of the RC. The latter two observations suggest important heterogeneities and anisotropies in the native membranes which can in principle account for the stabilization of the charge separated state in the core complex. The thermodynamic and kinetic parameters obtained in the RC-LH1 complex are very close to those measured in intact membranes, indicating that the electron transfer properties of the RC in vivo are essentially determined by its local environment. The studies performed by incorporating the RC into saccharidic matrices evidenced the relevance of solvent-protein interactions and dynamical coupling in determining the kinetics of electron transfer processes. The usual approach when studying the interplay between internal motions and protein function consists in freezing the degrees of freedom of the protein at cryogenic temperature. We proved that the “trehalose approach” offers distinct advantages with respect to this traditional methodology. We showed, in fact, that the RC conformational dynamics, coupled to specific electron transfer processes, can be modulated by varying the hydration level of the trehalose matrix at room temperature, thus allowing to disentangle solvent from temperature effects. The comparison between different saccharidic matrices has revealed that the structural and dynamical protein-matrix coupling depends strongly upon the sugar. The analyses performed in RCs embedded in polyelectrolyte multilayers (PEM) structures have shown that the electron transfer from QA - to QB, a conformationally gated process extremely sensitive to the RC environment, can be strongly modulated by the hydration level of the matrix, confirming analogous results obtained for this electron transfer reaction in sugar matrices. We found that PEM-RCs are a very stable system, particularly suitable to study the thermodynamics and kinetics of herbicide binding to the QB site. These features make PEM-RC structures quite promising in the development of herbicide biosensors. The studies discussed in the present thesis have shown that, although the effects on electron transfer induced by the native and artificial environments tested are markedly different, they can be described on the basis of a common kinetic model which takes into account the static conformational heterogeneity of the RC and the interconversion between conformational substates. Interestingly, the same distribution of rate constants (i.e. a Gamma distribution function) can describe charge recombination processes in solutions of purified RC, in RC-LH1 complexes, in wet and dry RC-PEM structures and in glassy saccharidic matrices over a wide range of hydration levels. In conclusion, the results obtained for RCs in different physico-chemical environments emphasize the relevance of the structure/dynamics solvent/protein coupling in determining the energetics and the kinetics of electron transfer processes in a membrane protein complex.

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Adolfsson, Tobias, und Axel Dellenby. „Pre-study of optical LED units for shunting signals“. Thesis, KTH, Hälsoinformatik och logistik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296561.

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Alstom wanted to investigate the possibility of adapting its light emitting diode (LED) technology for shunting signals in train traffic. The LED technology uses 50V, but Alstom wants to adapt it for 12V. The LED technology is energy efficient but needs to be adapted for existing signal interlocking by drawing a higher current. This meant that the possibility of reactive power compensation was investigated to obtain lower thermal dissipation in dwarf signal. The essay presents a couple of possible solutions. One of the solutions is to raise the voltage by using a booster converter to use the existing 50V LED unit. Capacitors were reviewed to be used in reactive power compensation to increase current supply. One of the solutions then became a capacitor bank. Simulations indicated that a booster converter and a capacitor bank can be used to adapt the circuit. However, some modifications must be made.
Alstom ville undersöka möjligheten att anpassa sin lysdiodsteknik för dvärgsignaler i tågtrafiken. Lysdiodstekniken använder 50V men Alstom vill anpassa den för 12V. Lysdiodtekniken är strömsnål och behöver anpassas för befintliga signalställverk genom att dra en högre ström. Detta innebar att möjligheten för reaktiv kompensering undersöktes för att få en låg värmeutvecklingen i dvärgsignalen. I uppsatsen presenteras ett par möjliga lösningar. En av lösningarna för spänningen är en step-up omvandlare för att nyttja 50Vs enheten. Det gjordes också en genomgång av kondensatorer för att nyttjas i reaktivkompensering för att öka strömförbrukningen. En av lösningarna blev då ett kondensatorbatteri. Det kunde konstateras med matematisk simulering att step-up omvandlare och ett kondensatorbatteri kan användas för att anpassa kretsen dock måste vissa modifieringar utföras.

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Hughes, Robert T. „NO_x FORMATION IN LIGHT-HYDROCARBON, PREMIXED FLAMES“. UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/118.

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This study explores the reactions and related species of NOx pollutants in methane flames in order to understand their production and consumption during the combustion process. To do this, several analytical simulations were run to explore the behavior of nitrogen species in the pre-flame, post- flame, and reaction layer regions. The results were then analyzed in order to identify all "steady-state" species in the flame as well as the determine all the unnecessary reactions and species that are not required to meet a defined accuracy. The reductions were then applied and proven to be viable.

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Vorálková, Kateřina. „Zrakové vnímání řidiče v dopravním provozu“. Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-232688.

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The aim of thesis is a summary and assessment of perception of drivers in traffic from the view of psychology and its influence on various aspects and the resulting effects on driving. Furthermore, it is mainly a description of the visual system and the description of light as factor of visual perception. The thesis also presents two experiments refer to the reaction time and mental reactions of driver, depending on drank out alcohol. Results of the first test of reaction time starting at the traffic lights were just a confirmation of the mentioned values from different publications and the Internet. The results of the second test, which was focused on the emotional reaction depending on the amount of ingested alcohol would be surprising to many.

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Matthew, Burrows B. „Ab Initio Leading Order Effective Interactions for Scattering of Nucleons From Light Nuclei“. Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1600945141719748.

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Schreiner, Lisa Marie. „An Investigation of the Effectiveness of A Strobe Light As An Imminent Rear Warning Signal“. Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35887.

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Strobe lights have been used successfully in many transportation applications to increase conspicuity. It was hoped that a strobe signal could also be applied to more effectively warn distracted drivers of an unexpected rear end conflict. This "proof of concept study" used a 2 x 2 between-subjects design using thirty-three subjects (16 subjects in the strobe condition, 17 subjects in the no strobe condition) who were divided into two age groups: younger (25-35) and older (60-70). The driver unexpectedly encountered a stopped "surrogate" vehicle in the roadway (with or without a rear-facing strobe light) in a controlled on-road study at the Smart Road located at the Virginia Tech Transportation Institute (VTTI). Results suggested that younger subjects' perception times improved as a result of being exposed to the strobe signal. Faster perception of the situation allowed more time to initiate a brake response. Older subjects perception and response times remained unchanged by the strobe signal. More severe initial steering rate and subjective responses indicated that the strobe conveyed a sense of urgency irrespective of age. Visual distraction of subjects proved difficult. Hence, the impact of the strobe on attracting the attention of a visually distracted driver to the stimulus could not be as fully investigated as originally hoped. The formulation of a more difficult distraction task was suggested for future research to truly assess the ability of the strobe light at alerting visually distracted drivers.
Master of Science

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Fernández, Alvarez Víctor Miguel. „A computational approach to the mechanism of light-driven reactions in solution“. Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/402464.

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Aquesta tesi doctoral descriu l'aplicació, d'una combinació de mètodes DFT (Teoria del Funcional de la Densitat) i models cinètics, per elucidar el mecanisme de reaccions en solució iniciades per llum. Aquesta estratègia és usada per estudiar dos tipus de reaccions d'interès comercial. A la primera part, s'analitza el mecanisme de transformacions químiques activades directament per llum. En canvi, la segona part abasta reaccions en què l'activació lumínica passa a través d'un foto-catalitzador. En tots dos casos, els resultats i les propietats experimentals, com ara la selectivitat o el rendiment quàntic, van ser reeixidament reproduïts, i racionalitzats d'acord a les propietats d'estructura electrònica que defineixen els sistemes involucrats. A més, es va demostrar que els models cinètics són crucials per calcular aspectes del mecanisme de transformacions foto-induïdes, ja que la mera comparació de barreres d'energia no té en compte les grans diferències de concentracions presents.
Esta tesis doctoral describe la aplicación, de una combinación de métodos DFT (Teoría del Funcional de la Densidad) y modelos cinéticos, para elucidar el mecanismo de reacciones en solución iniciadas por luz. Esta estrategia es usada para estudiar dos tipos de reacciones de interés comercial. En la primera parte, se analiza el mecanismo de transformaciones químicas activadas directamente por luz. En cambio, la segunda parte abarca reacciones en las que la activación lumínica ocurre a través de un foto-catalizador. En ambos casos, los resultados y las propiedades experimentales, tales como la selectividad o el rendimiento cuántico, fueron exitosamente reproducidos, y racionalizados de acuerdo a las propiedades de estructura electrónica que definen a los sistemas involucrados. Además, se demostró que los modelos cinéticos son cruciales para calcular aspectos del mecanismo de transformaciones foto-inducidas, ya que la mera comparación de barreras de energía no tiene en cuenta las grandes diferencias de concentraciones presentes.
This doctoral thesis describes the application of a combination of Density Functional Theory (DFT) methods and kinetic models to elucidate the mechanism of light-driven synthesis reactions in solution. This strategy is applied to study two types of reactions of commercial interest. In the first part, the mechanism of chemical transformations directly activated by visible light is analyzed. On the other hand, the second part covers reactions in which light activation takes place via a photocatalyst. For both cases, experimental outcomes and properties such as selectivity and quantum yield were correctly reproduced and rationalized on the basis of the electronic structure properties that define the systems involved. In addition, kinetic models proved vital in the computation of mechanistic aspects of photo-induced transformations as mere comparisons of energy barriers fail to account for large differences in concentration present.

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Hong, Sampyo. „First-principles study of chemisorbed light gases on transition metal and transition metal oxide surfaces : structure, dynamics and reaction /“. Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.

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Ahmad, Ayla. „Synthesis and Evaluation of Photocatalytic Properties of BiOBr for Wastewater Treatment Applications“. Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30301.

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Visible light-driven photocatalysis has shown considerable potential in the area of clean and renewable energy, as well as in wastewater treatment. This thesis describes the synthesis, characterization and applicability of a visible-light active photocatalyst, bismuth oxybromide (BiOBr). The photocatalytic activity of BiOBr was investigated through its preparation via hydrothermal and solvothermal synthesis routes under various conditions. Hydrothermal catalyst was prepared using non template based method while for solvothermal synthesis CTAB was used as a template. Parameters of temperature and time of thermal treatment were optimized for each synthesis method and overall tests for catalyst dosage and recyclability were performed. An overall optimal route leading to high photocatalytic performance was also proposed based on the obtained results. Studies were also conducted to examine the applicability of optimally synthesized BiOBr in drinking water applications by studying catalyst-mediated disinfection of E. coli and degradation of phenol. Favourable results were obtained, confirming the prospective application of BiOBr as a viable photocatalyst for disinfection. Furthermore, the potential of enhancing BiOBr to further improve its performance is described through synthesis of a novel PdCl2/BiOBr based photocatalyst. Overall, the performance of BiOBr under various conditions in this study establishes its potential as a holistic photocatalyst and merits further development.

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Dissertationen zum Thema „Reactive light“

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