Opto-Thermal Characterization of Plasmon and Coupled Lattice Resonances in 2-D Metamaterial Arrays

Growing population and climate change inevitably requires longstanding dependency on sustainable sources of energy that are conducive to ecological balance, economies of scale and reduction of waste heat. Plasmonic-photonic systems are at the forefront of offering a promising path towards efficient light harvesting for enhanced optoelectronics, sensing, and chemical separations. Two-dimensional (2-D) metamaterial arrays of plasmonic nanoparticles arranged in polymer lattices developed herein support thermoplasmonic heating at off-resonances (near infrared, NIR) in addition to regular plasmonic resonances (visible), which extends their applicability compared to random dispersions. Especially, thermal responses of 2-D arrays at coupled lattice resonance (CLR) wavelengths were comparable in magnitudes to their counterparts at plasmon wavelengths. Opto-thermal characterization of 2-D arrays was conducted with a white light irradiation in the current work. Finite element analysis involving a three-dimensional (3-D) COMSOL model mimicked the heat transfer and average temperature increases in these systems at plasmon resonances with a ≤ 0.5 % discrepancy at the absorbed, extinguished power of the radiation. All-optical, mesoscopic characterization of 2-D arrays involving trichromatic particle analysis allowed detailed investigation of effects of particle populations and ordering on the optical signals of plasmon and CLR in addition to indicating a critical point of emergence for CLR. Overall, engineering these thermoplasmonic metamaterials for enhanced optothermal dissipation at visible to near-IR radiation supports their rapid implementation into emerging sustainable energy and healthcare systems

The biogeochemistry of metal cycling

The results of the Planetary Biology and Microbial Ecology's summer 1987 program are summarized. The purpose of the interdisciplinary PBME program is to integrate, via lectures and laboratory work, the contributions of university and NASA scientists and student interns. The 1987 program examined various aspects of the biogeochemistry of metal cycling, and included such areas as limnology, metal chemistry, metal geochemistry, microbial ecology, and interactions with metals. A particular area of focus was the use of remote sensing in the study of biogeochemistry. Abstracts and bibliographies of the lectures and reports of the laboratory projects are presented

The geometry of colour

This thesis explores the geometric description of animal colour vision. It examines the relationship of colour spaces to behavior and to physiology. I provide a derivation of, and explore the limits of, geometric spaces derived from the notion of risk and uncertainty aversion as well as the geometric objects that enumerate the variety of achievable colours. Using these principles I go on to explore evolutionary questions concerning colourfulness, such as aposematism, mimicry and the idea of aesthetic preference

Enumerating Trichromatic Triangles Containing the Origin in Linear Time

Consider a set P of n points in the plane each associated with one of a constant number of colours. We give an output-sensitive algorithm that runs in O(n+|T|) time to enumerate the set of triangles T, such that each triangle contains the origin, its vertices are in P and have three distinct colours

Enumerating Trichromatic Triangles Containing the Origin in Linear Time

Abstract Consider a set P of n points in the plane each associated with one of a constant number of colours. We give an output-sensitive algorithm that runs in O(n + |T |) time to enumerate the set of triangles T , such that each triangle contains the origin, its vertices are in P and have three distinct colours. Basic framework We assume, without loss of generality, that the point set lies on the unit circle. The uncoloured version of the problem has been studied previously, see With Lemma 1 in mind, we project the points that are on the upper half of the unit circle onto the lower half using the mapping x → −x. Let P 1 be the set of points originally on the lower half, and P 2 be the points originally on the upper that were projected onto the lower half of the unit circle. For a point p, we denote the angle it forms with the x-axis by α(p). Using Lemma 1, we can reduce our problem to the problem of enumerating certain subsequences s 1 , s 2 , s 3 of points in P 1 ∪ P 2 , such that: s 1 , s 2 and s 3 all have distinct colours, α(s 1 ) ≤ α(s 2 ) ≤ α(s 3 ), and either s 1 , s 3 ∈ P 1 and s 2 ∈ P 2 or s 1 , s 3 ∈ P 2 and s 2 ∈ P 1 . As a first attempt, we sketch a sorting-based algorithm to enumerate the triangles in T . We first sort the points in P 1 ∪ P 2 by the angle they form with respect to the x-axis. We then construct lists of consecutive points that have the same colour and orientation. Using this information, we can enumerate the set of triangles T in O(|T |) time. Still, this algorithm has time complexity O(n log n + |T |). If the size of the set T is o(n log n), the question of whether we can do better than O(n log n) arises. Essentially, this is equivalent to asking whether we can "avoid" sorting. To answer this question, we consider the approach for the uncoloured case followed in In the coloured version, a similar notion of a block cannot be used. Consider the case where all the points have the same colour. In such a case, the number of blocks can be large while T is empty. In order to make the running time depend on |T |, the partitioning must accordingly be "colour-sensitive". The algorithm Each point in the set P 1 ∪ P 2 has the following two attributes associated with it: its orientation (whether it belongs to P 1 or P 2 ) and its colour. We say that a point is of the type t i if it belongs to P 1 and its colour is i, and that it is of the type t i if it belongs to P 2 and its colour is i. Recall that a triangle in T is represented by a sequence of points s 1 , s 2 , s 3 . We say that a triangle has the configuration (t i , t j , t k ) if s 1 , s 2 and s 3 are points of the types t i , t j and t k respectively, and that it has the configuration (t i , t j , t k ) if s 1 , s 2 and s 3 are points of the types t i , t j and t k respectively. Since there is a constant number of such configurations, we fix a configuration (e.g. (t 0 , t 1 , t 2 )) and describe an algorithm to enumerate the triangles of this configuration. The algorithm must then be applied for all configurations. Next, we describe the key steps of the algorithm

Numerical cognition in honeybees: rule learning enables quantity discrimination, zero comprehension, simple arithmetic, and symbol use by an insect

Many non-human animals demonstrate some level of numerical ability which includes an understanding of complex numerical concepts such as arithmetic, sequential ordering of numbers, or an understanding the concept of zero. Although very little research has been done on numerical ability in invertebrates, honeybees and several other insects have been shown to possess some numerical capabilities. In my thesis, I have assessed the capacity of bees to exhibit complex numeric skills such as number categorisation, extrapolation, and simple arithmetic. I show that the use of appetitive-aversive differential conditioning improves the honeybees' ability to discriminate between quantities above the subitizing range compared to appetitive-differential conditioning. Honeybees have demonstrated an understanding of the quantitative value of nothing and placed an empty set in the correct position along a line of sequential numbers, learnt to categorise numbers as greater or lesser in context, acquired abstract colour-based rules to solve elementary incremental and decremental problems, and demonstrated an ability to match symbols with specific quantities. In some cases, honeybees have mastered numerical concepts at a level that parallels abilities demonstrated by primates, mammals, birds, and other vertebrates. I discuss these findings in relation to how number processing developed in human culture, and how subsequent work can search for number processing regions in animal brains

Structure et dynamique des cryo-écosystèmes : plates-formes de glace nordiques

Cette thèse doctorale est la première étude systématique d'une classe d’écosystèmes extrêmes nouvellement découverts dans l'environnement arctique : les communautés de tapis microbiens et leurs habitats sur les plates-formes de glace nordiques. L'objectif principal était d’examiner la structure et la dynamique de ces cryo-écosystèmes à plusieurs échelles et d'étudier l'interaction entre les aspects physiques et biologiques sur les cinq plates-formes de glace principales trouvées dans le Haut Arctique canadien. Cette étude comprend une large gamme de méthodologies, soit : l’énumération microscopique des algues ; la quantification des pigments avec la chromatographie liquide de haute performance ; les mesures automatisées de salinité, d'éclairement et de température ; des survols en hélicoptère accompagnés de prise d’échantillons ; et l’analyse d’images de télédétection. La limnologie chimique et physique des cryo-habitats à travers cet écosystème est hétérogène et une communauté diversifiée de phototrophes a été retrouvée dans les tapis microbiens. La fragmentation de l’habitat a eu peu d'effet sur la biodiversité du cryo-écosystème. Cependant, des gradients environnementaux ont été associés à la structure de la communauté des tapis microbiens. L'hypothèse stipulant que les organismes des tapis microbiens des plates-formes de glace subsistent dans des conditions sub-optimales a été évaluée en examinant des réponses métaboliques aux changements de salinité, d’éclairement et de température. Les micro-organismes hétérotrophes se sont avérés spécialisés aux conditions extrêmes répandues sur la glace, tandis que les micro-organismes photosynthétiques ont toléré une plus large gamme de conditions, suggérant ainsi qu’ils étaient des extrêmotrophes (terme défini dans cette étude comme la tolérance des microbes aux conditions locales mais possédant une croissance in situ en dehors de leurs optimums physiologiques) plutôt que des extrêmophiles (la spécialisation aux conditions locales, avec une croissance in situ près des limites physiologiques). Un assemblage de pigments accessoires et photoprotecteurs a été associé à la communauté autotrophe, ce qui peut expliquer la gamme de tolérance plus large des extrêmotrophes. Le rapport entre la couverture du tapis microbien et la perte de masse de la surface de la plate-forme de glace a été examiné. Une concentration élevée de sels nutritifs dans les tapis microbiens a indiqué que ce micro-environnement différait considérablement de l'écosystème entier. Ces résultats soulignent l'importance du couplage biotique-physique sur la plate-forme de glace autant que dans le reste de la cryosphère. Pendant la période d'étude, un événement de détachement d’une partie de la plate-forme de glace Ward Hunt ainsi que le drainage d'un lac épiplate-forme (eau douce barrée par la glace flottant sur l’océan) ont été observé. Une analyse supplémentaire a suggéré que le réchauffement du climat ait contribué à cet événement, ce qui souligne la vulnérabilité des habitats dépendants des plates-formes de glace et de leur valeur comme indicateurs des changements climatiques. Ces cryo-écosystèmes fournissent également de nouvelles connaissances reliées à la vie microbienne dans les milieux polaires extrêmes, ouvrant de nouvelles avenues sur la survie, la croissance et l'évolution pendant les périodes glaciaires du passé, y compris l'ère précambrienne.This doctoral thesis is the first systematic study of a newly discovered class of extreme ecosystems in the arctic environment: microbial mat communities and their habitats on northern ice shelves. The overarching objective was to examine the structure and dynamics of these cryo-ecosystems at several scales and to examine the interaction between physical and biological aspects on the five major ice shelves found in the Canadian High Arctic. This study made use of a broad range of methods including: microscopic enumeration of algal taxa; quantification of pigments with high performance liquid chromatography; automated over-winter measurements of salinity, irradiance and temperature; helicopter-assisted surveys and sampling; and analysis of satellite imagery. The chemical and physical limnology of the cryo-habitats across this entire ecosystem was found to be heterogeneous and a diverse community of phototrophic microorganisms was found within the microbial mats. Habitat fragmentation was shown to have little effect on the biodiversity of the cryo-ecosystem, however environmental gradients were significantly associated with microbial mat community structure. The hypothesis that ice shelf microbial mat organisms subsist in sub-optimal conditions was tested by examining metabolic responses to changes in salinity, irradiance and temperature. Heterotrophic microbiota were found to be optimized for the extreme conditions prevalent on the ice shelf, whereas photosynthetic micro-organisms tolerated a broader range, suggesting they were extremotrophic (defined by this study as tolerance by microbiota to local conditions but with in situ growth well outside their physiological optima) rather than extremophilic (a more narrow specialization to local conditions, with in situ growth close to physiological maxima). An assemblage of sunscreening and accessory pigments was associated with the autotrophic community, which may account for the extended tolerance range of the extremotrophs. The relationship between microbial mat cover and the surface ablation of the ice shelf was examined and a high concentration of nutrients within the microbial mats indicated that this microenvironment differed greatly from the properties of the bulk ecosystem. These results underscore the importance of biotic-physical coupling on the ice shelf, and in the cryosphere in general. A break-up event on the Ward Hunt Ice Shelf and the drainage of an epishelf lake (ice-dammed freshwater overlying seawater) was discovered during the study period. Further analysis suggested that climate warming contributed to this event, which highlights the vulnerability of ice shelf dependent habitats and their value as indicators of climate change. These cryo-ecosystems also provide new insights into microbial life under extreme polar conditions, with implications for survival, growth and evolution during glacial periods in the past, including the Precambrian Era