Call number: LD2668 .T4 1948 L86 / Master of Science

The light harvesting systems of photosynthetic organisms harness solar energy by efficient light capture and subsequent transport of the light’s energy to a chemical reaction center. Man-made optical devices could benefit by mimicking these naturally occurring light harvesting processes. Supramolecular organic nanostructures, composed of the amphiphilic carbocyanine dye 3,3’-bis- (2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’- dioctylbenzimida-carbocyanine (C8S3), self assemble in aqueous solution to form tubular, double-walled J-aggregates. These J-aggregates have drawn comparisons to light harvesting systems, owing to their optical and structural similarities to the cylindrical chlorosomes (antenna) from green sulfur bacteria. This research utilizes optical spectroscopy and microscopy to study the supramolecular origins of the exciton transitions and fundamental nature of exciton energy transport in C8S3 artificial light harvesting systems. Two J-aggregate morphologies are investigated: well-separated, double-walled nanotubes and bundles of agglomerated nanotubes. Linear dichroism spectroscopy of flow-aligned nanotubes is used to generate the first quantitative, polarized model for the complicated C8S3 nanotube excitonic absorption spectrum that is consistent with theoretical predictions. The C8S3 J-aggregate photophysical properties are further explored, as the Stokes shift, quantum yield, and spectral line broadening are measured as a function of temperature from 77 – 298 K. The temperature-dependent emission ratios of the C8S3 J-aggregate two-band fluorescence spectra reveal that nanotube emission is well described with Boltzmann partitioning between states, while the bundles’ is not. Finally, understanding energy transport in these materials is critical for the proposed use of artificial light harvesting systems in optoelectronic devices. The spatial extent of energy transfer in individual C8S3 J- aggregate structures is directly determined using fluorescence imaging. We find that aggregate structural hierarchy greatly influences exciton transport distances: impressive average exciton migration distances of ~ 150 nm are measured along the nanotubes, while these distances increase to over 500 nm in the bundle superstructures. / text

This creative project presents a comprehensive and detailed guide to the building of inexpensive studio lighting equipment. The projects include simple equipment such as backgrounds, snoots and scrims to more specialized equipment like the glassware table and softlight box.Each project includes figures and instructions for building the equipment. At the end of each project are examples of the effects of each piece of equipment in a photographic situation.Also included is a list of photographic data on how each of the photographs was taken.

As lighting designers, we are aware of the importance of light in constructing dynamic, interesting spaces that enhance the human experience. But light is more than simply a physical component; it also has a rich cultural meaning that affects how we perceive and comprehend the world. This study aims to compare and investigate how the lighting setting of two distinct cultural groups, Indian and Swedish, influence the way people perceive a living room in a residential space when it is used for Diwali and Christmas purposes. It also tries to ascertain whether cultural backgrounds influence the preferences & perception for light in various settings. A qualitative analysis was conducted using three methods in order to compare & learn about lighting cultures in two different cities, Stockholm and New Delhi. As well as to comprehend user perception in two lighting settings, Christmas and Diwali, and to determine whether these perception and preferences are related to the cultural background, habits, or history. The results obtained supported one another and contributed to the research and made a serious effort to understand how different lighting preferences vary among cultures. There were intriguing findings throughout the objectives aimed, illustrating how similar yet different the two lighting cultures are.

Light is seldom addressed in archaeological research, despite the fact that, at least in ancient Egypt, it would have impacted upon all aspects of life. When discussing light in Egyptology, the vast majority of scholarly attention is placed on the sun, the primary source of illumination. In comparison, artificial light receives very little attention, primarily due to a lack of archaeological evidence for lighting equipment prior to the 7th century BC. However, 19th and 20th century lychnological studies have exaggerated this point by placing an overwhelming emphasis on decorated lamps from the Greco-Roman Period. In an attempt to move beyond these antiquarian roots, recent scholarship has turned towards examining the role that light, both natural and artificial, played in aspects of ancient societies’ architecture, ideology and religion. The extensive body of archaeological, textual and iconographic evidence that remains from ancient Egypt is well suited to this type of study and forms three core data sets in this thesis. Combining a materials-based examination of artificial light with a contextualized, theoretical analysis contributes to a richer understanding of ancient Egyptian culture from the 3rd to 1st millennium BC. The first three chapters of this study establish a typology of known artificial lighting equipment, as well as a lexicon of lighting terminology. A comparison of the archaeological and textual evidence allows for a discussion on the consumption of lighting in ancient Egypt and its impact on social and economic spheres. From this material it becomes apparent that artificial light was a luxury and this corresponds to its inclusion in religious texts and iconography, as well as the presence of lighting implements in tombs of the wealthy elite. The second half of the thesis examines the ritual application of artificial light, incorporating iconographic and textual evidence, consideration of ritual space and timing, and experimental archaeology. This interdisciplinary approach allows for a discussion of the sensory experience of artificial lighting and its perceived potency in ancient Egypt. It also demonstrates the contribution that Egyptology can make to lychnological and sensory studies of the ancient Near East and Mediterranean by examining the impact of light on phenomenology and aesthetics.

Artificial light is an important and necessary part of our urban environment, but has become a threat to biodiversity. It can have substantial direct and indirect effects on populations of all kinds of organisms. While light attraction in bats and moths has been well studied other organisms such as Trichoptera have been largely neglected, despite Trichoptera being one of the most abundant insect orders in freshwater systems. The light attraction of Trichoptera was studied through seasonal data from three different locations in Sweden. The data was examined through meta- and regression analyses to compare catches in light traps and passive traps. The use of relative abundances excluded bias from the species with large populations, and the difference in individuals caught between passive traps and light traps. The results indicated that artificial light could affect Trichoptera populations. Unlike moths, female Trichoptera were more attracted to light than males and attraction to light varied between species. In both cases, size dimorphism could explain the variation. Day-, evening- and night-active species were all attracted to light, but the latter more so. Research has shown that a false flight activity can occur in day-active Trichoptera when a lamp is lit during night, which could explain the capture of day- and evening-active species in a light trap. In all, artificial light could alter Trichoptera populations, changing sex ratios and species composition. This impact should be considered when erecting light sources near waterways.

No description available.

Thesis (MScEng (Department of Electrical Engineering))--University of Cape Town, 2008. / Energy drives technological societies. Developing countries such as South Africa are caught between the desperate need for economic growth and the emerging obligations to the environment. Efficient technologies can be used to mitigate the impact of these seemingly conflicting requirements in urban and rural environments. In this thesis the commercially available white light-emitting diode (LED) with its inherent efficiency, longevity and mechanical strength, is used to show, that success in energy efficiency can be obtained. Two cases are used to illustrate the need for efficient demand-side technology: the electricity shortages of the Western Cape Province in South Africa and a white LED pilot project in Namulonge, Uganda. The Namulonge Solar-Home System (SHS) is analyzed with the intention of creating a more acceptable general lighting solution. The concept of appropriateness through self-determination is discussed within the context of location-specific information integrated into a design procedure. The major thrust and contribution of this thesis, however, is the design of an interior luminaire for Golden Arrow Bus Services (GABS). This is in part based on the hypothesis that application-specific information will lead to implementation and human-needs success, and is researched, designed, fabricated and then laboratory tested. The biggest challenge to be overcome was the spatial light distribution of the LED array. Thus non-imaging optical lens design became the main focus of this project as it held the key to utilizing available light while conserving the light-systems energy. Circular Fresnel and Linear Fresnel (an adaptation of the concentric design) lenses were designed. Electrical, mechanical and thermal aspects of design are also detailed. Far-field, horizontal plane detection over the specified area is used to best gain the uniformity of distribution. The four criteria namely luminance, illuminance, intensity and étendue (collection efficiency), against which each design and focal length iv configuration is compared to, are extensively explored and eventually lead to a final design. In the first designs, the area of the spatial distribution between 50% and 80% of its relative intensity is collimated. The Hybrid Circular Fresnel and Hybrid Linear Fresnel lenses now redirects the relative intensity in two areas, from 50% to 70% (creating parallel rays) and then from 70% to 100% (away from the central axis), renders a distinct difference is spatial uniformity and a reduction in the peak and offaxis located intensity. All four criteria are met, with a minor adjustment of configuration within the bus internal luminaire spacing, with the hybrid designs. It is proposed that GABS employ polished designs of the Hybrid Circular Fresnel, in any of the configurations, which have collection efficiencies ranging between 64.8% and 78.3%. / Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University

Disturbance from engineering works is an increasing problem in terrestrial and marine ecosystems throughout the world. Many reported declines in population size, breeding success and body condition have been diagnosed as the result of anthropogenic disturbance, however little is known about the effect of long-term disturbance from large-scale engineering works. Understanding the mechanisms by which animals respond to anthropogenic activities is fundamental to explaining interactions, and resolving potential conflicts between humans and wildlife. This thesis focuses on the factors affecting the habitat use and foraging decisions in wintering shorebirds and wildfowl. The first half of this thesis considers the direct and indirect impacts on waterbirds of a major engineering project in central Scotland; construction of the new Clackmannanshire Bridge at Kincardine-on-Forth. For individual bird species in close proximity to the bridge site, round-the-clock construction work had consequences ranging from neutral to considerably negative. Cormorant Phalacrocorax carbo declined in the area, probably as a result of the disturbance of an important low tide roost. Redshank Tringa totanus, previously abundant in the prey-rich areas adjacent to the construction site, were displaced into poorer areas for most of the construction period; where they may also have suffered from increased interference competition and elevated risk from raptorial predators. Some positive effects of industrial development were also revealed; radio-transmitters combined with tilt-switch posture sensors indicate that Redshank were able to capitalise on the improved nocturnal visibility in areas around Grangemouth docks to assist with foraging and predator detection. Evidence is presented that birds switched foraging strategy (from sight to touch feeding) depending on ambient light levels; whereby artificial light was used in a similar manner to moonlight to assist with prey detection. Redshank also avoided riverine areas at night that were used frequently by day, probably in response to an elevated threat from nocturnal predators. As the predator landscape changes from day into night, birds adopt different strategies to minimise the risk from nocturnal predators. It is clearly important, therefore, that information on nocturnal distributions is available to inform decisions on site management, especially where anthropogenic activity continues throughout the diel cycle. Behavioural decisions were shown to vary widely within a species depending on individual state, metabolic demands and previous exposure to human disturbance. Prey resources were shown to change dramatically over the course of a winter. In response to this decline, the home range of Redshank contracted over a winter season. Similarly, animals responded less and took greater risks in response to experimental disturbance events later in the winter than earlier in the winter, and on days when the temperature was lower. This effect was strongest for individuals occupying heavily disturbed areas, which were possibly already compensating for lost feeding time and a negative energy balance. The results were consistent with the hypothesis that those individuals that respond most obviously to human disturbance were those least likely to suffer fitness consequences. This is the opposite from what is commonly assumed when behaviour is used as an index of disturbance impacts, most notably in the use of flush distance in the design of wildlife buffer zones. In conclusion, this study demonstrated various negative impacts of disturbance, including local displacement, due to construction activity on overwintering waterbirds. It also revealed two key, but poorly understood, phenomena relating to mechanisms for coping with anthropogenic disturbance: routine utilisation of artificial light to extend night-time feeding opportunities amongst Redshank and an adaptive flexibility in escape responses across a range of species under varying conditions of risk.

When I was nineteen years old, I traveled to ten countries in Europe. While there, I visited many museums and monuments, but it was in the solemn churches that I first saw stained glass and my aesthetic awakening occurred. My first impression was of a "living painting". By this I mean that a stained glass window is a non-static painting, as its appearance is dependant on the quality of light that shines though its panes. The same stained glass window looks different in the morning, evening and night. It has one color scheme on a sunny day and another on a cloudy day. The same window can look like a completely different work depending on its lighting. Most of the windows I saw were figurative, but the projections they made on the wall and floors were abstract. To me these projections seemed like "color stains", that moved with the sun and the passing of time. The solemn environment of these old churches looked like a huge light installation to a young girl from a country where centuries old stained glass installations did not exist.Currently, I make my work using reflective material and light. In the case of my outdoor pieces, they capture different "colorscapes" depending on the time of day. These reflective materials patch together and create new landscapes out of their natural surroundings. In the case of my indoor pieces, when light hits the surface, a complex interplay of reflections and shadows are created. The relationship between my work and my interest in reflection is the most exciting part of my creative research. Like sound, memory, feeling and imagination, light is intangible and invisible, but its effect on our lives is profound. My interest in creating works with light is in experiencing the phenomenon of their visual qualities as well as in the creation of a relaxing and sublime space.