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Keenleyside, Mairi Seonaid. "Pupillometry and assessment of visual function." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258161.
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LAWSON, NICOLAS DELLETT. "LIGHT AND HUMAN RESPONSE." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1053441038.
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Vaughn, Chad Dean. "Light in response to time /." Cincinnati, Ohio : University of Cincinnati, 2008. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1212179576.
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Thesis (Master of Architecture)--University of Cincinnati, 2008.Committee/Advisors: Michael McInturf (Committee Chair), Elizabeth Riorden (Committee Co-Chair). Title from electronic theses title page (viewed Sep. 2, 2008). Includes abstract. Keywords: Light. Includes bibliographical references.
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VAUGHN, CHAD DEAN. "Light: in response to time." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212179576.
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Borevitz, Justin Oak Chidester. "Natural variation in arabidopsis light response /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3044779.
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McLachlan, Deirdre. "Benthic diatom motility in response to light." Thesis, University of Essex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435583.
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Jackson, Kristina Mary. "Mammalian cell response to long wave UV light." Thesis, Lancaster University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536057.
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Norrish, Mark Ian Keith. "The transient component of the pupillary light response." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621582.
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Jia, Wenbo. "A Numerical Study of Catalytic Light-Off Response." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461256363.
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Choudhury, Feroza Kaneez. "Rapid Metabolic Response of Plants Exposed to Light Stress." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157543/.
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Environmental stress conditions can drastically affect plant growth and productivity. In contrast to soil moisture or salinity that can gradually change over a period of days or weeks, changes in light intensity or temperature can occur very rapidly, sometimes over the course of minutes or seconds. So, in our study we have taken an metabolomics approach to identify the rapid response of plants to light stress. In the first part we have focused on the ultrafast (0-90 sec) metabolic response of local tissues to light stress and in the second part we analyzed the metabolic response associated with rapid systemic signaling (0-12 min). Analysis of the rapid response of Arabidopsis to light stress has revealed 111 metabolites that significantly alter in their level during the first 90 sec of light stress exposure. We further show that the levels of free and total glutathione accumulate rapidly during light stress in Arabidopsis and that the accumulation of total glutathione during light stress is dependent on an increase in nitric oxide (NO) levels. We further suggest that the increase in precursors for glutathione biosynthesis could be linked to alterations in photorespiration, and that phosphoenolpyruvate could represent a major energy and carbon source for rapid metabolic responses. Taken together, our analysis could be used as an initial road map for the identification of different pathways that could be used to augment the rapid response of plants to abiotic stress. In addition, it highlights the important role of glutathione in initial stage of light stress response.
Light-induced rapid systemic signaling and systemic acquired acclimation (SAA) are thought to play an important role in the response of plants to different abiotic stresses. Although molecular and metabolic responses to light stress have been extensively studied in local leaves, and to a lesser degree in systemic leaves, very little is known about the metabolic responses that occur in the different tissues that connect the local to the systemic leaves. These could be important in defining the specificity of the systemic response as well as in supporting the propagation of different systemic signals, such as the reactive oxygen species (ROS) wave. Here we report that local application of light stress to one rosette leaf resulted in a metabolic response that encompassed local, systemic and transport tissues (tissues that connect the local and systemic tissues), demonstrating a high degree of physical and metabolic continuity between different tissues throughout the plant. We further show that the response of many of the systemically altered metabolites could be associated with the function of the ROS wave, and that the level of eight different metabolites is altered in a similar way in all tissues tested (local, systemic, and transport tissues). These compounds could define a core metabolic signature for light stress that propagates from the local to the systemic leaves. Taken together, our findings suggest that metabolic changes occurring in cells that connect the local and systemic tissues could play an important role in mediating rapid systemic signaling and systemic acquired acclimation to light stress.
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Mulvihill, Shane. "Light Exposure, Refractive Error, and Red and Blue Light-Driven Pupillary Responses." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460742215.
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Schwalb, Michael. "Measuring the short term plant photosynthetic response to varying light quality using light emitting diodes (LEDs)." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121207.
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Light emitting diodes (LEDs) emit narrow bandwidth light and have the potential to increase the spectral efficiency of supplemental lighting in greenhouses by optimizing spectral output for plant growth and yields. At the moment of writing, data describing the plant response to varying light quality and quantity was limited. The objective of this research was to examine photosynthetic response of plants to varying light quality and quantity and to gather photosynthetic response data that could be used to design an optimal spectrum for a prototype LED array for plant growth experiments. The action spectrum of tomato (Solanum lycopersicum), lettuce (Lactuca sativa) and petunia (Petunia × hybrida) seedlings was measured at three irradiances (30, 60 and 120 µmol m-2 sec-1) using LED arrays with peak wavelengths from 405nm – 700nm and a bandwidth of 25nm (full width at half maximum). The action spectrums for all plant species at all three irradiances were characterized by localized blue and red action peaks within the range of 430 to 449 nm and 624 to 660 nm respectively. A peak also occurred at 595 nm for 30 µmol m-2 sec-1. The photosynthetic response of tomato, lettuce and petunia to varying red (660nm) and blue (430nm) wavelengths with and without background broadband radiation was also measured. For all three species tested, with and without background radiation, the optimum photosynthesis range occurred within the red to blue ratio (r:b) range of 5:1- 15:1 except for petunia without background radiation for which the maximum occurred at 50:1. These results suggest that the optimal red to blue ratio for photosynthetic activity for tomato, lettuce and petunia occurred between a red to blue ratio of 5:1-15:1.Les diodes électroluminescentes (DEL) émettent une lumière relativement monochromatique et pourraient accroître l'efficacité des lampes pour les serres commerciales en émettant des longueurs d'ondes optimisées pour le rendement des plantes. L'objectif de ce projet a consisté à examiner l'effet des longueurs d'ondes sur l'activité photosynthétique des plantes. L'activité photosynthétique des tomates (Solanum lycopersicum), laitues (Lactuca sativa) et pétunias (Petunia × hybrida) a été mesurée à trois puissances d'irradiation (30, 60 and 120 µmol m-2 sec-1) en utilisant des DELs avec une émission maximale entre 405 nm et 700 nm et une bande passante de 25 nm. La réponse photosynthétique maximale à chaque niveau d'irradiation se situait dans la portion bleu et rouge du spectre visible, soit respectivement entre 430 - 449 nm et 624 to 660 nm. Un maximum a aussi été observé à 595 nm à 30 µmol m-2 sec-1. L'effet de la proportion des longueurs d'onde bleue et rouge (émises par les DELs) sur l'activité photosynthétique des tomates, laitues et pétunias a aussi été mesuré avec et sans le rayonnement de fond. Pour chaque espèce, avec et sans le rayonnement de fond, la proportion optimale (en terme de rouge et bleu) pour l'activité photosynthétique se situait entre of 5:1- 15:1, sauf dans le cas du pétunia, pour lequel le maximum se situait à 50:1 sans rayonnement de fond. La proportion optimale pour l'activité photosynthétique a diminué avec le rayonnement de fond pour chaque espèce à chaque niveau d'irradiation.
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Bhatranand, Apichai. "Electrooptic light modulator with improved response linearity using optical feedback." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2750.
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The use of optical feedback for improving response linearity of electrooptic light modulators has been investigated. The modulator is configured as a straight channel waveguide flanked by electrodes in a lithium niobate (LiNbO3) substrate. Light is coupled into the waveguide in both TE and TM polarizations, and a voltage applied across electrodes causes a relative phase shift between two polarization components. An output analyzer converts the phase modulation to intensity modulation. Optical feedback of light in both polarization modes results from reflection of light at the polished edges of the substrate. Channel waveguides supporting a single guided mode for TE and TM polarizations were fabricated in x-cut LiNbO3 substrates using titanium-indiffusion technique. The waveguides and modulators were characterized at a wavelength of 1.55 ??m using a distributed feedback laser. The modulators were driven with a sinusoidal voltage waveform. To minimize harmonics of the modulating frequency in the intensity output, the magnitude of the optical feedback and the substrate temperature were adjusted. The feedback level was altered by applying refractive index-matching liquid to one or both ends of the waveguide at the edges of the crystal. It was found that a high degree of response linearity in the presence of feedback was achievable at certain substrate temperatures. The spurious-free dynamic range (SFDR) relative to the noise floor was measured at different feedback levels and substrate temperatures in an effort to maximize the modulator response linearity. An SFDR of 68.04 dB, limited by third-order nonlinearity, was achieved by applying index-matching fluid to the input end of the substrate. This compares with an SFDR of 64.84 dB limited by second-order nonlinearity when index-matching fluid was applied at both ends of the substrate. By changing the temperature of the same substrate to adjust the phase shifts experienced by TE and TM polarizations, the SFDR with index-matching fluid at the input end increased to 71.83 dB, limited by third-order nonlinearity. In tests at constant modulation depth, an improvement of as much as 9.6 dB in SFDR vs. the theoretical value for an interferometric modulator without feedback was achieved.
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Kennedy, Matthew James. "Turning off the light response in rod and cone photoreceptors /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9217.
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Park, Soohong. "Dynamic response of light-weight materials under sand blast loading." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610167.
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Hawari, Nabeha. "Sitting, standing and light activity : measurement and postprandial metabolic response." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8692/.
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A high level of sedentary behaviour has recently emerged as a distinct risk factor for a number of diseases. On the other hand, a large body of evidence has shown that physical activity (PA) can prevent several illnesses. However, there are important issues regarding the accurate measurement of SB behaviour and physical activity in observational studies which are currently unresolved. Research is particularly needed to investigate the impact of characteristics of sedentary behaviour such as type/context, sedentary bout length, breaks in sedentary time on metabolic responses and accurate quantification of PA and SB is needed to evaluate current and changing physical activity and sedentary behaviour levels on health outcomes. A number of studies have demonstrated that replacing sedentary time with light-intensity physical activity such as standing can induce a measurable metabolic benefit. However, it is unclear whether these benefits could be stimulated by simply breaking up time spent sitting down by standing up, or whether the number of transitions from sitting to standing influences metabolic changes over and above the effects of total time spent standing. The first experimental study in this thesis demonstrated, in ten overweight/obese men, that prolonged standing – where participants alternated 15 minutes of sitting with 15 minutes of standing – energy expenditure was 10.7% higher than continuous sitting (p < 0.001) over an 8-hour observation period. Intermittent standing – where participants undertook 10, 1.5-minute bouts of standing in every half-hour – led to a further increase in energy expenditure of 9.0% (p < 0.001). Participants oxidised 7.1 g more fat and 7.7 g more carbohydrate with intermittent standing compared with prolonged standing, but there was no significant effects of either prolonged or intermittent standing breaks on postprandial incremental glucose, insulin or triglyceride (TG) responses.
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Yuhas, Phillip Thomas. "Isolation of ipRGC Contribution to the Human Pupillary Light Response." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397469110.
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Romanelli, Elisa. "Growth response of Thalassiosira pseudonana under combined light and temperature changes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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The rise of atmospheric CO2 concentrations due to human activities is warming the upper levels of the ocean leading to changes in mixing and thus affecting the upward nutrient supply and the level of light available for phytoplankton. Researchers have focused on investigating how these fast-approaching changes are affecting phytoplankton; however, it is still difficult to obtain a consistent understanding of the expected response because of interactive effects to simultaneous changes in multiple stressors. This study aims to present an alternative way to determine the growth rate of phytoplankton through the measure of their optical properties (1). In addition, this study investigates the interactive effects of light and temperature changes on the growth rate (µ) of diatom Thalassiosira pseudonana CCMP 1335 (2). We monitored the growth rate of T. pseudonana at four temperatures (13.4, 18.5, 22.5 and 24.4°C) and eight light regimes (35, 50, 65, 80, 95, 110, 125 and 140µmol photons m-2s-1) by measuring the cultures chlorophyll fluorescence F0, optical density (OD680 and OD720) and cells number. Our results show an overall statistically highly significant correlation between µF0 and µOD and µ based on cell counts (n: 25 p < 0.001). We assume this relationship to be light and temperature dependent and F0 and OD to be valuable proxies for cell counts under our experimental conditions. We highlight the importance of testing the correlations for each species individually. Our multi-drivers experiments show light limitation for all our cultures at 35 and 50µmol photons m-2s-1 and temperature limitation at 13.4 and 18.5°C. Furthermore, we found the optimal growth conditions of our T. pseudonana cultures at 22.5°C and 110µmol photons m-2s-1. Interesting interactive effects between light and temperature were found at 18.5°C and 24°C and at 110µmol photons m-2s-1. These results show that simultaneous changes in temperature and light exposure lead to interactive effects.
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Li, Xiaochun. "Development and Light Response of Leaves of Metasequoia and Close Relatives." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/LiX2004.pdf.
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Scantlebury, Nadia Campos Ana Regina. "The Drosophila larval response to light: A behavioural and genetic analysis." *McMaster only, 2007.
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Nagy, Dávidné. "Visible light response semiconductor nanomaterials for heterogeneous photocatalysis in liquid phase." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33062.
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The development of sustainable and green technologies powered by renewable energy sources is highly desired to address the growing global energy need and water scarcity problems. Heterogeneous photocatalysis emerged in the past decades as promising solar-powered technology for environmental remediation applications such as wastewater treatment. The photoactivity of the materials is believed to be governed by complex mechanisms, still it was shown that it may be critically dependent on the following material properties (i) ability and effectiveness to absorb incident photons, (ii) charge separation efficiency, (iii) charge utilization efficiency, (iv) morphology including the size and shape of the nanostructure and its distribution and (v) the crystal structure, phase composition and crystallinity ... etc. Hence, most strategies aiming to improve the performance of photocatalytic materials may focus on one or more of the aforementioned aspects. Beside developing new materials or modifying existing systems, the development of sustainable, easy-to-operate systems are highly desired for developing countries such as Africa where almost half of the population are affected by water scarcity of some sort. For this motivation the immobilization of powder catalyst could be one attractive solution. In this thesis three experimental systems are presented. In the first two the effect of material properties on the photoactivity whereas in the third chapter the immobilization of powder catalyst was investigated. The first experimental project aimed to study the effect of synthesis parameters of WO3 nanostructures on its morphology, phase composition, optical properties and ultimately on the photoactivity. Understanding the role of process parameters to gain control over the material properties is still a challenge but is of great interest in photocatalysis. Here, a hydrothermal synthesis method was employed to synthesize WO3 nanostructures with various morphologies, crystal phases and optical properties. The effect of the solution pH, the polymeric surface modulator and the added EtOH was investigated on the material properties and on the photocatalytic activities. It was found that the crystal structure and the morphology of WO3 was influenced by the solution pH in the first place. It was proposed that stabilization effects between the crystal phase and the morphology could also influence the crystallization process beside supersaturation. It was revealed that despite the highest surface area of W-2.01-P20E, reduced oxidation state did not promote high photo-response. Instead the photoactivity of WO3 was seen as the compromise of the material properties including the optical, structural properties and the oxidation state. In the second experimental project the effect of Ag co-catalysis was studied on TiO2- Cu2O heterostructure formation. Coupling a wide band gap (TiO2) and a narrow band gap (Cu2O) semiconductor could benefit from extended light absorption properties and additionally from enhanced charged separation. In this study a facile wet chemical synthesis method was coupled with a UV treatment step to fabricate TiO2-Ag-CuxO ternary hybrid nano-materials. The effect of the Ag loading (1-5%) and the synthesis sequence of the Ag deposition step was evaluated on the material properties as well as on the visible photocatalytic activity. It was revealed that both the amount and the order of the Ag-deposition altered the material properties considerably. Typically TiO2/CuxO/Ag (TCA) catalysts had better visible light absorption properties but reduced affinity to adsorb methyl orange (MO) to their surface. Whereas, TiO2/Ag/CuxO (TAC) catalysts in general had better dye adsorption properties relative to TCA and had more efficient decoloration properties under visible light. TOC and HPLC-MS analysis revealed that MO and possibly its degradation products were mainly mineralized and/or adsorbed to the surface of TAC catalyst with 5% nominal Ag content in the visible process generating limited amount of byproducts in the final solution. The third experimental project focused on the immobilization of the previously prepared powder TiO2-Cu2O nanostructure. In this work a fluorine-doped tin oxide (FTO) glass sheet was used as a substrate and the doctor-blade coating technique has been employed to make TiO2-Cu2O thin films. Although this technique has a widespread use in the fabrication of solar cells to the best of our knowledge this is the first report on supported TiO2-Cu2O photocatalytic systems prepared by this method. To optimize the performance of the TiO2- Cu2O thin film under visible light irradiation, the chemical composition of the doctor-blading paste and the temperature of the final thermal treatment step was studied. It was found that both the paste composition and the heat treatment step played an important role in the material properties. When the film contained ethyl cellulose the minimum temperature to remove organic additives was 350 °C. Whereas for the films containing only alpha terpineol 300 °C was sufficient. It was revealed that the higher temperature treatment resulted in more oxidized films which were also shown in their deeper colour. The most effective film under visible light irradiation was TC-0-300 which contained no cellulose and was treated at the lowest temperature.
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Bingham, David Paul. "Response to the Sun." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/33277.
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This thesis is an attempt to address the phenomenon of the sun in architecture. Particular use is made of the notions of warmth, light, shadow and energy as form generators. Of specific concern is how one structure can work in harmony within its environment and existing constraints.
An analysis of an existing building is performed, with an eye to its strengths and weaknesses as a residence. It is an interesting challenge for an architect to take an undistinguished building - one designed for a bygone age of surplus energy - to identify those substantive elements to be retained and reused, those which are to be eliminated or substantially altered, and then harmonize them, in conjunction with a new plan, in order to create a warm, energy efficient, aesthetically appealing, and ultimately livable family residence. The possibilities concerning the highest and best changes to be made to improve the use of an existing structure are first identified.
This thesis shows how a physically and spiritually cold, unattractive, and unremarkable building, one of little or no architectural merit, can be transformed - through improved natural light and heat - to create a better environment for a family.
Master of Architecture
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Granberg, Hjalmar. "Optical Response From Paper : Angle-dependent Light Scattering Measurements, Modelling, and Analysis." Doctoral thesis, KTH, Production Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3629.
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Edelstein, Kim. "The role of the intergeniculate leaflet in the circadian response to light." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0002/NQ39623.pdf.
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Pippert, Kathy Lynn. ""In a Language Not His": Reader-Response Criticism and "Light in August"." W&M ScholarWorks, 1989. https://scholarworks.wm.edu/etd/1539625530.
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Hemphill, Brian D. "Light Emitting Diodes and a Monochrome Camera to Measure Chemical Optode Response." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1354890395.
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Hurley, Elisabeth. "Effects of early light environment on the photic response of the circadian system." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/effects-of-early-light-environment-on-the-photic-response-of-the-circadian-system(6b32d591-5394-4f1e-a422-7458eb740c2c).html.
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Early light environment has been shown to alter locomotor activity behaviour in adult rats and mice when exposed to constant light (LL), constant darkness (DD) or 12:12 hour light-dark cycles (LD). In particular, exposure to LL during lactation results in an increased ability to cope with exposure to LL as adults, implying that the ability to interpret light information is altered depending on early light environment. Therefore, the aim of this project was to explore how early light environment affects the photic response of the circadian system. The retina forms the first component of the photic response of the circadian system. We wanted to know whether being raised in DD, LD or LL would alter retinal function or structure in adult CD1 (albino) and C57BL/6J (pigmented) mice. We found that in CD1 mice, being raised in LL caused significant retinal damage and a significant reduction in retinal function. In C57BL/6J mice, we saw no such changes, implying that any changes that we see in behaviour would be due to alterations further downstream, such as the suprachiasmatic nucleus (SCN), site of the master circadian clock in the mammalian brain. We next exposed C57BL/6J mice to LL and found that mice raised in DD had significantly longer taus than mice raised in LL, implying that mice raised in DD are more sensitive to light than mice raised in LL.Previous work has shown that early light environment alters neuropeptide and astrocyte expression in the SCN of C57BL/6J mice. Furthermore, early light environment produces opposite behavioural responses in CD1 and C57BL/6J mice when exposed to LD as adults. We therefore examined how neuropeptide and astrocyte expression would be affected by early light environment in CD1 mice and whether this would reflect the differential behavioural response. We found that neuropeptide and astrocyte expression in the SCN seemed to be affected by the level of retinal damage and/or the type and intensity of the light source used. This sensitivity to lighting environment makes CD1 mice unsuitable for further studies on the photic response of the circadian system. Pigmented mice were used for the remainder of this project. The photic response of the circadian system can be quantified using a phase response curve (PRC) which measures behavioural responses to light pulses administered at different times of day. We measured the effect of a light pulse on the delay and advance portion of the PRC and found no differences due to early light environment, implying that the phasic effect of light is not altered by early light environment. Light pulses administered during the subjective night result in the upregulation of SCN intracellular photic signalling pathways. After a light pulse given during the early subjective night, we found no differences in the upregulation of different components of the photic signalling pathway due to early light environment indicating early light environment does not seem to affect the initial photic signalling pathway in the SCN.Finally, recent advances in molecular biology allow for real-time monitoring of clock gene expression in vitro. Using mPer2::luc mice, we monitored in vitro PER2::LUC expression to determine the effects of early light environment on clock gene expression. In the SCN, we found that the amplitude of PER2::LUC expression was significantly reduced in mice raised in DD compared to mice raised in LD and LL. These results suggest that early light environment affects the coupling strength between SCN neurons and this may be the mechanism mediating the changes in behaviour we have measured. In peripheral tissue, we found altered PER2::LUC expression due to early light environment in the heart, lung and spleen, implying that early light environment not only alters behaviour but may also affect heart and lung function and the immune system.
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Zazzaro, Sarah. "Plasticity in Response to Changing Light Environment for Red Spruce and Balsam Fir." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/ZazzaroS2009.pdf.
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Van, Horsten Natasha. "Photosynthetic response of Southern Ocean phytoplankton under iron and light limitations : bioassay experiments." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97861.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The Southern Ocean (SO) is of significant interest in the understanding of the global carbon cycle and therefore many studies have been conducted to determine the limiting factors controlling the biological pump within the region. During photosynthesis phytoplankton require various nutrients such as NO3, PO4, inorganic carbon and the micronutrient Fe. The SO is a High-Nutrient Low-Chlorophyll region, therefore no macronutrient limitation is experienced by resident phytoplankton but instead the micronutrient Fe is a significant limiting factor within these waters due to limited inputs. Due to deep mixed layer depths, ice cover, low sun angles and cloud cover throughout parts of the year, light is also considered a limiting factor in the SO. Fe and light limitation cause a decrease in photosynthetic efficiency and therefore a decrease in carbon fixation capabilities. During this study we conducted five bioassay shipboard incubation experiments during two cruises along the Greenwich meridian between South Africa and the ice edge, SOSCEx during March and SAFePool during January to February, in which we varied Fe concentrations and light levels to determine the effects of Fe and light limitation or co-limitation within resident phytoplankton. Spatial and temporal variations in phytoplankton response were studied to determine varying effects of limitation across water masses and different stages of bloom decline within the study area. The combined addition of Fe and light gave the largest increase in biomass, photosynthetic capacity and nutrient uptake. In support of the hypotheses tested changes in the photosynthetic apparatus led to changes in the photosynthetic efficiency and growth of the SO phytoplankton, as a result of variations in Fe and light availability. Variability was also observed in the response of phytoplankton to Fe and light amendments due to spatial and temporal variation in resident phytoplankton communities. It was therefore concluded that both Fe and light are significant controls in the resident phytoplankton photosynthetic apparatus, photosynthetic capabilities, organic carbon fixation and therefore the biogeochemical cycles within the Atlantic sector of the SO.
AFRIKAANSE OPSOMMING: Die Suidelike Oseaan (SO) is van beduidende belang in die begrip van die globale koolstofsiklus en dus is baie studies gedoen om die beperkende faktore te bepaal wat die biologiese pomp in die streek beheer. Tydens fotosintese benodig fitoplankton verskillende voedingstowwe soos NO3, PO4, anorganiese koolstof en die mikrovoedingstof Fe. Die SO is 'n High-Nutrient Lae-Chlorofil streek, dus word geen makrovoedingstof beperking ervaar deur inwoner fitoplankton maar in plaas daarvan is die mikrovoedingstof Fe 'n beduidende beperkende faktor binne hierdie waters weens beperkte insette. As gevolg van diep gemengde laag dieptes, ysbedekking, lae son hoeke en wolkbedekking deur dele van die jaar, word lig ook beskou as 'n beperkende faktor in die SO. Fe en lig beperking veroorsaak 'n afname in die fotosintetiese doeltreffendheid en dus 'n afname in koolstof binding vermoëns. Tydens hierdie studie het ons vyf biotoets inkubasie eksperimente aan boord die skeep gedoen tydens twee vaarte langs die Greenwich meridiaan tussen Suid-Afrika en die ys rand, SOSCEx gedurende Maart en SAFePool gedurende Januarie tot Februarie, waarin ons Fe konsentrasies en lig vlakke gewissel het om die gevolge van Fe en lig beperking, of medebeperking, binne inwoner fitoplankton te bepaal. Ruimtelike en temporale variasies in fitoplankton reaksie was bestudeer om wisselende gevolge van die beperking oor watermassas en verskillende stadiums van bloei afname in die studie area te bepaal. Die gekombineerde byvoeging van Fe en lig het die grootste toename in biomassa, fotosintetiese kapasiteit en voedingsopname gegee. Ter ondersteuning van die getoetste hipoteses, veranderinge in die fotosintetiese apparaat het gelei tot veranderinge in die fotosintetiese doeltreffendheid en groei van die SO fitoplankton, as 'n gevolg van variasies in Fe en lig beskikbaarheid. Veranderlikheid is ook waargeneem in die reaksie van fitoplankton om Fe en lig wysigings weens die ruimtelike en tydelike variasie in inwoner fitoplankton gemeenskappe. Dus was dit by die gevolgtrekking gekom dat beide Fe en lig beduidende kontrole in die inwoner fitoplankton fotosintetiese apparaat, fotosintetiese vermoëns, organiese koolstof binding en daarom die biogeochemiese siklusse binne die Atlantiese sektor van die SO.
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Belliveau, Janet. "Design and preparation of photo-reversible surfaces for light-controlled cardiac cell response." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121408.
Full textAbstract:
Polyelectrolyte multilayers (PEMs) are attractive surfaces for use in live-cell experiments due to their biocompatibility and ease of fabrication. PEMs of poly(allylamine hydrochloride) and poly(Disperse Red 1 acrylate-co-acrylic acid), an azo polymer, were prepared using a novel dropping method developed to conserve the materials used for film preparation. The PEMs were fabricated using a series of pH conditions as well as a different number of layers, yielding surfaces with varying properties. Embryonic chick heart cells were cultured on the PEM films; depending on film preparation conditions, we were able to selectively direct the morphology of chick heart cell growth. Although cells were expected to produce only confluent monolayers, the cells grew as aggregates of variable size or as confluent monolayers, depending on the surfaces upon which they were grown. Inclusion of the azo polymer affords surfaces with reversible photoresponsive properties; upon irradiation with visible green light at 488 nm, the azobenzene isomerizes. Optical properties of the polymer in solution and as a film were investigated. Aggregate cardiac cell beating were monitored using three different microscope setups: a macroscopic setup, a confocal microscope and a total internal reflection fluorescence (TIRF) microscope. A cellular response to 488 nm laser light on the TIRF microscope was detected in azo polymer films.Les multicouches de polyélectrolytes (MPE) sont des surfaces intéressantes pour des expériences utilisant des cellules vivantes en raison de leur biocompatibilité et de leur facilité de fabrication. Les MPE de poly(chlorhydrate d'allylamine) et poly(Disperse Red 1 acide acrylate-co-acrylique), un polymère azoïque, ont été préparées en utilisant un nouveau procédé de déposition goutte-à-goutte qui a été mis au point afin de conserver les matériaux utilisés durant la préparation du film. Les MPE ont été fabriquées en variant les conditions de pH ainsi que le nombre de couches déposées, ce qui permet d'obtenir des surfaces présentant des propriétés différentes. Des cellules cardiaques embryonnaires de poussin ont été cultivées sur les films MPE mentionnés ci-haut. Selon les conditions de préparation des films, nous avons été en mesure de diriger sélectivement la morphologie de la croissance des cellules cardiaques de poussin. Bien que nous nous attendions à ce que les cellules ne produisent que des monocouches confluentes, les cellules se sont développées sous forme d'agrégats de taille variable ou des monocouches confluentes en fonction de la surface sur laquelle elles ont été cultivées. L'inclusion du polymère azoïque offre des surfaces ayant des propriétés photosensibles réversibles. Lors d'une irradiation avec un laser qui émet dans le visible à 488 nm (vert), l'azobenzène s'isomérise. Les propriétés optiques du polymère en solution ainsi que sous forme de film ont été étudiées. Les battements des agrégats de cellules cardiaques ont été contrôlés à l'aide de trois configurations de microscopes différents: une installation macroscopique, un microscope confocal et un microscope de fluorescence par réflexion totale interne (TIRF). Une réponse cellulaire à la lumière émise par le laser à 488 nm a été détectée sur le microscope TIRF pour le film de polymère azoïque.
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Sundlöf, Sebastian. "Light and Paint:perceptual and emotional effects on space and humans." Thesis, KTH, Ljusdesign, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280082.
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In 21st century Scandinavia, the use of colored paint in the built environment has decreasedconsiderably. Instead, color changing LEDs can be found in many homes. In this thesis, an experimentwas set up to investigate how these two coloring methods differ and coincide with regards toemotional response and perception of materiality. Four cubicles, two painted and two colored bylight, were evaluated by ten participants. The painted cubicles were perceived as more material intheir appearance with regards to texture and color than their counterparts. A greater feeling ofnervousness, stress, and disorientation was felt in the light-colored cubicles as opposed to aheightened feeling of inspiration, excitement and calmness in the painted cubicles. Though it isimportant to remember the difference was not significant. In addition, preconceived connotations tothe color tone could be an influencing factor and so further studies on additional tones should beconducted. Lastly, benefits and drawbacks with the coloring methods were discussed.
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ANDREWS, ABBY S. "Persistent Variation: An Architectural Response to the Human Experience." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212077858.
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Liu, Wenfeng Ph D. Massachusetts Institute of Technology. "Assessment of high-burnup LWR fuel response to reactivity-initiated accidents." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44786.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references (p. 263-273).
The economic advantages of longer fuel cycle, improved fuel utilization and reduced spent fuel storage have been driving the nuclear industry to pursue higher discharge burnup of Light Water Reactor (LWR) fuel. A design basis accident, the Reactivity Initiated Accident (RIA), became a concern for further increase of burnup as simulated RIA tests revealed lower enthalpy threshold for fuel failure associated with fuel dispersal, which may compromise the core coolability and/or cause radiological release should this happened in LWRs. Valuable information on the behavior of high burnup fuel during RIA are provided by the simulation tests. However atypical design and operating conditions in simulated tests limited the application of experimental data directly to evaluate the failure potential of LWR fuels. To better interpret the experimental results and improve the capability of the fuel performance codes to predict high burnup fuel behavior, this thesis developed mechanistic models of high burnup fuel during an RIA and implemented models in a transient fuel performance code FRAPTRAN 1.3. Fission gas release (FGR) and swelling were systematically modeled to quantify gaseous loading effects. The grain boundary fission gas inventory is simulated prior to the transient using a diffusion model in FRAPCON 3.3 code. The restructuring of high burnup fuel in rim region is described in terms of porosity, pore size distribution, fission gas concentration, and pore overpressure. The model assumes the fragmentation of fuel upon the separation of grain boundary or when a threshold temperature is exceeded in the rim region. The fission gas in fragmented fuel is assumed to release instantaneously to the free volume when the fuel expansion and swelling creates sufficient pellet-clad gap.
(cont.) The relaxation of rim pore at rapid temperature increase and the thermal expansion of fission gas in fragmented fuel are considered as additional loads on the cladding besides the contact force due to fuel thermal expansion. An analytical approximation is made to calculate the clad radial displacement subjected to fission gas expansion accounting for the constraint of the cladding on the fission gas which would otherwise be neglected in a rigid pellet model FRACAS-I in the FRAPTRAN code. In comparison to the measured FGR from CABRI, NSRR and BIGR test facilities, this mechanistic model can reasonably predict fission gas release fraction for most of the test cases covering a burnup range of 26-64 MWd/kgU and enthalpy deposit of 37-200 cal/g. It reveals the effects of burnup and enthalpy deposit on the fission gas release: burnup is an important parameter affecting fission gas inventory and fuel micro-structure evolution during base irradiation; enthalpy deposit is directly connected to the availability of fission gas release via the grain boundary separation by the intergranular bubble over-pressurization. Analysis of the fission gas radial profile is made with the aid of the neutronic code MCODE to validate the fission gas release from the rim of UO2 fuel. The analysis indicates fission gas release is partly from the rim region and the majority of fission gas release is from grain boundaries for burnup up to 50 MWd/kgU. Fission gas induced hoop strain is predicted to be less than 0.3% in the early phase of RIA with peak fuel enthalpy less than 145 cal/g. Given the fact that the concerned failure mode is the PCMI failure at low energy deposit, the pellet thermal expansion is still considered as effective in analyzing the PCMI failure. However at high level of enthalpy deposit, when clad yield strength is decreased at escalated temperature due to film boiling, the fission gas either released into the plenum or retained in the fuel pellet might strain more the cladding.
(cont.) This is observed in the large deformation of the cladding in some test cases in NSRR and BIGR due to pressure load. A new set of heat transfer correlations were selected and implemented in the FRAPTRAN code to model the cladding-coolant heat transfer of high burnup fuel at room temperature and atmospheric pressure condition. This new set of correlations addressed the effects of subcooling and oxiation on the heat transfer characteristics at pool boiling conditions. They reflect the increase of rewetting temperature and increase of Critical Heat Flux (CHF) due to subcooling. They account for oxidation effects on the transition and film boiling regime and heat conduction through thick oxide as the oxidation is considered as a prominent feature of surface condition change of high burnup fuel. In addition to high burnup fuels tested in NSRR, several fresh fuel tests with different degree of subcooling and a few separate-effects RIA tests are also included to validate the applicabilty of this set of correlations. For fuel enthalpy up to 190 cal/g and oxidation up to 25 micron, the predicted peak cladding temperature (PCT) and duration of DNB achieves generally good agreement with the experimental data. The analysis of high burnup fuel heat transfer reveals that the surface oxidation could cause an early rewetting of high burnup fuel or suppression of DNB. Surface oxidation can delay the heat conducting to the surface while keeping the surface heat transfer in the effective nucleate boiling regime. It also raises the miniumum stable film boiling temperature by lowering the interface temperature during liquid-solid contact resulting from vapor breaking down. Also modeled was Pellet-Cladding Mechanical Interaction (PCMI) failure of irradiated and hydrided cladding. The hydride rim accumulated at outer clad is assumed to cause the crack initiation. The fracture toughness of irradiated and hydrided cladding is obtained by fitting experimental data at different temperature range.
(cont.) The model sets forth a simple criterion for failure associated with crack growth based on the J integral approach. The simplification is that for the thin clad, failure is assumed to occur at the onset of crack tip growth. In comparison to CABRI and NSRR test results and other failure models, the model shows a good capability to separate the failure cases from non-failure cases. These models have been applied to LWR conditions to determine the failure potential of high burnup fuel. It shows that, at high burnup (and therefore high hydride levels in the cladding), the failure enthalpy is smaller than at low burnup. The pulse width is an important parameter in the burnup up to 50 MWd/kg, but starts to become less important for higher burnup with highly corroded cladding.
by Wenfeng Liu.
Ph.D.
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Hikade, Stribling Emily Elizabeth. "Light, Color and Texture: How the Physical Environment Can Aid the Treatment of Cancer." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242835088.
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Varella, Alexandre Costa. "Modelling lucerne (Medicago sativa L.) crop response to light regimes in an agroforestry system." Lincoln University, 2002. http://hdl.handle.net/10182/1477.
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The general goal of this research was to understand the agronomic and physiological changes of a lucerne crop in distinct physical radiation environments and to verify the potential of lucerne to grow under shaded conditions. To achieve this, the research was conducted in four main steps: (i) firstly, experimental data collection in the field using two artificial shade materials (shade cloth and wooden slats) under inigated and non-irrigated conditions; (ii) a second experiment with data collection in a typical temperate dryland agroforestry area under non-irrigated conditions; (iii) generation of a light interception sub-model suitable for shaded crops and (iv) a linkage between the light interception sub-model and a canopy photosynthesis model for agroforestry use. In experiments 1 and 2, lucerne crop was exposed to 6 different light regimes: full sunlight (FS), shade cloth (FS+CL), wooden slats (FS+SL), trees (T), trees+cloth (T +CL) and trees+slats (T+SL). The FS+SL structure produced a physical radiation environment (radiation transmission, radiation periodicity and spectral composition) that was similar to that observed in the agroforestry site (f). The mean annual photosynthetic photon flux density (PPFD) was 41 % under the FS+CL, 44% under FS+SL and 48% under T compared with FS in clear sky conditions. Plants were exposed to an intermittent (sun/shade) regime under both FS+SL and T, whereas under FS+CL the shaded light regime was continuous. The red to far-red (RIFR) ratio measured during the shade period under the slats was 0.74 and under the trees was 0.64. However, R/FR ratio increased to 1.26 and 1.23 during the illuminated period under FS+SL and T, respectively, and these were equivalent to the ratio of 1.28 observed under the FS+CL and 1.31 in FS. The radiation use efficiency (RUE) of shoots increased under the 5 shaded treatments compared with full sunlight. The pattern of radiation interception was unchanged by radiation flux, periodicity and spectral composition and all treatments had a mean extinction coefficient of 0.82. However, the magnitude of the decrease in canopy growth was less than those in PPFD transmissivity. The mean lucerne annual dry matter (DM) yield was 17.5 t ha⁻¹ in FS and 10 t ha⁻¹ under the FS+CL, FS+SL and T regimes. This declined to 3.4 t DM ha⁻¹ under T+CL (22% PPFD transmissvity) and 4.1 t DM ha⁻¹ under T+SL (23% transmissivity). A similar pattern of response was observed for leaf net photosynthesis (Pn) rates under the shade treatments compared with full sun. In addition, spectral changes observed under the trees and slats affected plant motphology by increasing the number of long stems, stem height and internode length compared with full sunlight. Thus, there were two main explanations for the increase in RUE under shade compared with full sun: (i) preferential partition of assimilates to shoot rather than root growth and/or (ii) leaves under shade were still operating at an efficient part of the photosynthetic light curve. The changes proposed for the canopy Pn model were appropriate to simulate the radiation environment of an agroforestry system. However, the model underestimated DM yields under the continuous and intermittent shade regimes. These were considered to be mainly associated with plant factors, such as overestimation in maintenance respiration and partitioning between shoots and roots in shade and the intermittency light effect on leaf Pn rates. Further investigation in these topics must be addressed to accurately predict crop yield in agroforestry areas. Overall, the lucerne crop responded typically as a sun-adapted plant under shade. It was concluded that lucerne yield potential to grow under intermediate shade was superior to most of C3 pastures previously promoted in the literature.
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Igbalajobi, Olumuyiwa [Verfasser], and R. [Akademischer Betreuer] Fischer. "Molecular characterization of the light response in Alternaria alternata / Olumuyiwa Igbalajobi ; Betreuer: R. Fischer." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/1198309997/34.
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Cole, Victoria Anne. "Aspects of the pupil light response and colour vision using pupillometric and psychophysical tests." Thesis, University of Wolverhampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389545.
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Krishnan, Ramadasan. "Studies on genotypic variation in response to temperature and light in Theobroma cacao L." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357729.
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Vinnell, Martin Paul. "The response of the photosynthetic apparatus in Silene dioica to the changing light environment." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242334.
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Li, Tsai-Chi. "CRYPTOCHROME 1 (CRY1) Is Critical in Mediating Developmental Process in Response to Light Intensity." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244019693.
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Tseng, Yu-Yao. "Systems biology of the Neurospora circadian clock and its response to light and temperature." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/systems-biology-of-the-neurospora-circadian-clock-and-its-response-to-light-and-temperature(4680ee43-3f65-4398-bc79-bac70d463e58).html.
Full textAbstract:
Circadian clocks are internal timekeepers that aid survival by allowing organisms, from photosynthetic cyanobacteria to humans, to anticipate predictable daily changes in the environment and make appropriate adjustments to their cellular biochemistry and behaviour. Whilst many of the molecular cogs and gears of circadian clocks are known, the complex interactions of clock components in time and space that generate a reliable internal measure of external time are still under investigation. Computational modelling has aided our understanding of the molecular mechanisms of circadian clocks, nevertheless it remains a major challenge to integrate the large number of clock components and their interactions into a single, comprehensive model that is able to account for the full breadth of clock properties. An important property of circadian clocks is their ability to maintain a constant period over a range of temperatures. Temperature compensation of circadian period is the least understood characteristic of circadian clocks. To investigate possible mechanisms underlying temperature compensation, I first constructed a comprehensive dynamic model of the Neurospora crassa circadian clock that incorporates its key components and their transcriptional and post-transcriptional regulation. The model is based on a compilation of published and new experimental data and incorporates facets of previously described Neurospora clock models. Light components were also incorporated into the model to test it and to reproduce our knowledge of light response of the clock. Also, experiments were carried out to investigate the unknown mechanisms of light response, such as the molecular mechanisms supporting the correct timing of conidiation after light to dark transfer. The model accounts for a wide range of clock characteristics including: a periodicity of 21.6 hours, persistent oscillation in constant conditions, resetting by brief light pulses, and entrainment to full photoperiods. Next, I carried out robustness tests and response coefficient analysis to identify components that strongly influence the period and amplitude of the molecular oscillations. These data measure the influence of the parameters in the model and were beneficial for making and testing predictions in the model. Thermodynamic properties were then introduced into reactions that experimental observations suggested might be temperature sensitive. This analysis indicated that temperature compensation can be achieved if nuclear localisation of a key clock component, FRQ, decreases with increasing temperature. Experiments have been carried out to validate this hypothesis and simulations were made to explore other possible mechanisms. However, from my experimental data and modelling results, the restriction of FRQ nuclear localisation might not be the only mechanism required to achieve temperature compensation. In conclusion, temperature compensation is most likely a complex property and may involve a combination of multiple mechanisms regulating clock component activity over a range of temperatures.
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Saunders, Christopher S. "Sequential Transcendence: An Architectural Response to the Contemporary Multi-Site Church Typology." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427897563.
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Jansson, Emil. "Electronicharacterization of molecules with application to organic light emitting diodes." Licentiate thesis, KTH, School of Biotechnology (BIO), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4349.
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The presented thesis is devoted to the field of organic light emitting
diodes (OLEDs). Time-dependent Kohn-Sham density functional theory
(TDDFT) is applied
in order to eludicate optical properties such as fluorescence and
phosphorescence for some of the most important materials. The
accuracy of TDDFT is evaluated with respect to the calculated absorption
and emission spectra for commonly used light emitting polymers.
A continuation of this work is devoted to Polyfluorene as this polymer
has proven to be very promising. In this study the chain
length dependence of its singlet and triplet excited states is
analyzed as well as the excited state structures.
Understanding the phosphorescence mechanism of tris(2-phenylpyridine)Iridium is
of importance in order to interpret the high efficiency of OLEDs
containing these specimens. The mechanism is analyzed by calculating
the electric transition dipole moments by means of TDDFT using
quadratic response functions.
As not only the optical properties are essential for effective
devices, electron transfer properties are addressed. The electron
transfer capability of the sulfur and nitrogen analogues of Oxadiazole
is evaluated through their internal reorganization energy.
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Frederickson, Marcus A. "The light-oxygen-voltage (LOV)-histidine kinase from Brucella, a virulence factor suitable for a sustained blue-light response : unlocking the signaling state /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Evans, Jennifer Anne. "Changing the shape of circadian rhythms with light no brighter than moonlight." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3258782.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed June 8, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 169-188).
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Faithfull, Carolyn. "Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43467.
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Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios.Lake ecosystem response to environmental change
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Arshad, Naheed. "The response of a baffled plate to plane waves, with light and heavy fluid loading." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394279.
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Bissinger, Jan E. "Predicting microalgal specific growth rates in response to temperature and light : a multi-species approach." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502002.
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Temperature and light are key determinants of microalgal specific growth rates (μ) and hence also influence aquatic ecosystem dynamics. Despite this importance there is no clear consensus on the functions that should be used to model the effects of these environmental variables on within- and across-species microalgal growth rates. Therefore examining the biological basis and statistical fits of existing functions, and deriving new ones, comprise the main objective of this thesis. Using quantile regression, and information theory I have compared existing functions and derived new ones that describe microalgal maximum specific growth rates (μmax) in response to temperature, photon-flux density (PFD), daylength, and PFD, and daylength combined. The main findings are outlined in (i) to (v), below, (i) A comparison of the μmax temperature function derived here to the function of Eppley (1972), suggested that the Eppley curve intercept is too low and that models that incorporate the Eppley function may underestimate primary production by ~ 30%. (ii) My non-linear general model of microalgal growth in response to daylength will be useful in comparative studies to normalise growth rates to a standard daylength.
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Dickman, Elizabeth M. "LIGHT, NUTRIENTS, AND PLANKTIVORY EFFECTS ON PHYTOPLANKTON COMMUNITY AND STOICHIOMETRIC RESPONSE, AND FOOD CHAIN EFFICIENCY." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1186061847.
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Al-Mohanna, Mai. "Roles of p53 and p16 tumor suppressor genes in the cellular response to ultraviolet light." Thesis, University of Sussex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288775.
Full textAbstract:
The role of the tumor suppressors p53 and p16 genes in the cellular response to Ultraviolet light. SUMMARY Proliferating cells respond to DNA damage by concomitantly arresting cellular growth at checkpointsa nd activating DNA repair processesC. ell cycle arrestsa re mediated,i n part, by the inhibition of cyclin-dependent kinases (CDKs), whose function is required for cell cycle progression. p53, p21WAF' and p16`NK4aa re the products of tumor suppressor genes that play important roles during the cellular response to genotoxic stresses. p53 and p16 coding genes have been found mutated or transcriptionally silenced in different cancer types both sporadic and familial. Indeed, p16 has been found to be linked to familial melanoma, whose etiology is related to sun-light induced DNA damage. It is hence important to ascertain whether p53 and p16 are involved in the cellular response to UV damage. In this report I present evidence that p53 is not involved in UV-induced cellular growth arrest in late G1 phase. This has been demonstrated in HeLa cells synchronized at the G1/S border by aphidicolin, followed by UV exposure. Interestingly, the length of this p53-independent G1 arrest has been shown to be UV dose-dependent. Similar results were also obtained with other p53-deficient cell lines, including the human promyelocytic leukemia HL-60 and mouse p53 knock-out cells. As expected, all of these cell lines were defective in v-ray-induced cell growth arrest at late G1Using different assays I also show here that p16-compromised U20S osteosarcoma cells are deficient in the removal of UV damage, as compared to their isogenic derivatives EH1 and EH2 counterparts that express p16. This deficiency is associated with a high level of UV-induced apoptosis, which is significantly reduced in the p16-expressing EH I, EH2 and p16+/+ mouse embryonic fibroblast (MEF) cells, indicating that p16 protects cells from undergoing apoptosis in response to UV light. Importantly, this reduction in UV-mediated apoptosis was associated with down-regulation of the pro-apoptotic Bax protein, with no effect on Bcl-2 expression, suggesting that this anti-apoptotic role of p16 is mediated via the intrinsic p53-dependent mitochondrial pathway. On the other hand, p16 sensitized cells to cisplatin-mediated apoptosis through Bcl-2 decline. Furthermore, I show that p16 is involved in UV-related G1 checkpoint and controls the expression and UV-dependent activation of another CDK inhibitor, p21wAFI. Importantly, this relationship between p16 and p21 exists also in MEFs, suggesting that it is not cell type- or species-dependent. These results indicate that, in addition to its role in cell cycle control and senescence, p16 also plays an important role in the cellular response to UV damage, possibly by inhibiting apoptosis and facilitating cell cycle arrest and photolesion removal. The data presented here provide further insights into the role of p53 and p16, as tumor suppressors, in carcinogenesis and have potential implications for future therapy strategies