Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 93 for “"light levels"”.
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The effect of aberrations and light scatter on visual performance at photopic and mesopic light levels
… surgery. Increased aberrations and scattered light or abnormal processing of visual information in the retina and/or the visual pathway are the main causes of retinal image degradation. The purpose of this study was to further investigate the effect of aberrations, scatter and other parameters …
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Prescribed Fire Effects on Woodland Structure, Light Levels and Understory Plant Communities in Missouri Oak-Hickory Woodlands
… and how this structure alters transmittance of light within Drury-Mincy Conservation Area, (Taney County, Missouri). Sampling occurred in twenty 0.1 ha plots established in 2007. Plots represented: unburned degraded woodlands that were not burned since the mid twentieth century (n = 6), recently …
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Ferns as a forest farming crop: effects of light levels on growth and frond quality of selected speicies with potential in Missouri
… research is to quantify the effects of various levels of light intensity on selected fern species believed to have potential use in the floral green and landscape industries and, to determine the feasibility of commercially grown ferns in Missouri.
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Seasonal and Spatial Variation in Leaf Area Index, Litter Production, and Light Levels in Myrica Cerifera,Shrub Thickets Across a Barrier Island Chronsequence
… index (LAI), litter production and understory light levels of Myrica cergera shrub thickets were assessed on Hog Island, Virginia to quantify spatial and seasonal variations in leaf area and light attenuation among four thickets representing a successional chronosequence and compare methods of …
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A Descriptive Catalog of Dimming Cells in the Purple Shore Crab HEMIGRAPSUS NUDUS
… cells responsive to the decrease or dimming of light was identified in the Purple shore crab <em>Hemigrapsus nudus</em>. Extracellular pin electrode recordings from the optic nerve tract measured responses to decremental changes in relative light levels over the range 40 to 0.08 lux. The …
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Spatial and temporal aspects of visual performance in relation to light level and normal aging
… contrast sensitivity at photopic and mesopic light levels. The literature states that older people experience losses of retinal neurons including rods, cones and ganglion cells. Furthermore, older people tend to have particular difficulties with vision at low light levels which can be …
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Motion Processing in Direction Selective Retinal Ganglion Cells through Dynamic Environments
… dynamic environments, including contrasts and light levels. This dissertation examines how direction-selective responses are reliably generated across stimulus contrasts, and how populations of DSGCs adapt to changes in light level, spanning moonlight to daylight. In Chapter 2, I describe the …
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An investigation into morning light therapy, circadian rhythms and sleep-wake cycles in postoperative cardiac patients
… to determine the effects of the clinical lighting environment on the lengths of hospital stay of postoperative cardiac patients, and to establish whether morning light therapy improves the postoperative disruption of sleep and circadian rhythms in the patients. First, the validity of the …
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Genotypic and Environmental Effects on Soybean Canopy Photosynthesis
… taken in this study suggests that increased light penetration into the chlorophyll-deficient canopies was the cause of the observed phenomenon. In the second study, the afternoon decline in CER in crop canopies at similar light levels as compared to the morning was investigated using grain …
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Differential Canopy Leaf Flushing and Site Nitrogen Status Facilitate Invasive Species Establishment in Temperate Deciduous Forest Understories
… canopy tree species that allow higher understory light levels because of phenological differences in spring leafing as well as canopy transmission and site-nutrient availability in these understories. Six canopy types were used: <em>Populus tremuloides</em> (quaking aspen), <em>Acer saccharum …
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Canopy light environment influences apple leaf physiology and fruit quality
… on nectar production; whether instantaneous light measurements yield reliable estimates of cumulative seasonal light levels within the canopy; and the effect of the canopy light environment on spur leaf physiology and fruit quality. Defoliation of nongirdled flowering spurs had no effect on …
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Relamping hotel guestrooms to decrease operating costs
… of its operating costs used for unnecessary lighting expenses. The study was conducted at the Donaldson Brown Center in Blacksburg, Virginia with 32 hotel guests participating. Data was collected to determine light fixture usage during periods of guestroom inactivity (inactive is defined as …
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Computational 3D and reflectivity imaging with high photon efficiency
… accurate 3D and reflectivity imaging. Under low light-level conditions, in which the mean photon count is small, the inverse problem of forming 3D and reflectivity images is difficult due to the Poisson noise inherent in low-flux operation. In this thesis, we propose and study two computational …
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Performance of northern red oak (Quercus rubra) underplantings under five management regimes and across existing environmental gradients
… of physiographic province, aspect, and fencing levels. Management regimes included 1) control sites, 2) a single prescribed burn, 3) repeat prescribed burns 5) diameter-limit cuts and 4) the seedcut of a shelterwood harvest. Physiographic provinces included the Ridge and Valley and Appalachian …
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Biology of the Rare Woodland Perennial Trillium Pusillum Micheaux (Liliaceae) in Southwest Missouri
… Heckmaster, and Hoover Woods-and measured light levels, vegetation cover and diversity, soil characteristics, seed dispersal, and flower-visitation rates at each site. Populations at Baker and Heckmaster were large (approximately 6500 and 14,900 total stems, respectively) with stable stage …
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The effects of light level and temperature on freshwater microbial biomass, production, enzyme activity, and community composition
… communities, but the synergistic effects of light and temperature on this phenomenon are not well understood and have implications on carbon cycling and energy flow. We employed recirculating mesocosms held at different temperatures and light levels and filled with Typha litter and attached …
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Modeling canopy foliar traits and disturbance interactions in central Texas woodlands.
… and were shown to correlate with relative light levels in some species. Leaf nutrition is used as the basis for a leaf development model. Leaf mass and leaf area index data are utilized to calculate canopy fuels. Species presence/absence at sites is shown to result in significantly …
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Establishment and Competitive Ability of Nelumbo Lutea in Relation to Myriophyllum Spicatum
Limitations from reduced light and increasing water depth on Nelumbo lutea seedlings were determined in tank experiments. Survival was high in all tested light levels. Total biomass increased significantly with increasing light. Biomass allocation shifted significantly to root production between 3 …
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Water Quality Modeling of Freshwater Diversions in the Pontchartrain Estuary
… of occurring when the salinity, temperature and light levels are sufficient.
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CHARACTERIZATION OF LOW MOLECULAR WEIGHT C-TYPE CYTOCHROMES IN CYANOBACTERIA AND PLANTS
… regard to their ability to withstand low or high light levels. In addition, chlorophyll fluorescence studies were performed, and transcriptomic analysis was carried out for the cyanobacterial strains. Impaired growth of the ΔCyt c6C strain was seen under extremely low light or extremely high …
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