Electronic noses are targeted at determining odour character in a fashion that emulates conscious odour perception in mammals. The intention of this study was to develop an organisational framework for electronic noses and deploy a sample cheese odour discriminator within this framework. Biological olfactory systems are reviewed with the purpose of extracting the organisational principles that result in successful olfaction. Principles of gas handling, chemoreception, and neural processing are considered in the formulation of an organisational framework. An electronic nose is then developed in accordance with the biologically inspired framework. Gas sensing is implemented by an array of six commercially available (tin oxide) semiconductor sensors. These popular gas sensors are known to lack stability thus necessitating hardware and signal processing measures to limit or compensate for instability. An odorant auto-sampler was developed to deliver measured amounts of odorant to the sensors in a synthetic air medium. Each measurement event encodes a simulated sniff, and is captured across six sensor channels over a period of 256 seconds at a sampling rate of 1Hz. The simulated sniff captures sensor base references and responses to odorant introduction and removal. A technique is presented for representation and processing of sensor-array data as a two-dimensional (2D) image where one dimension encodes time, and the other encodes multi-channel sensory outputs. The near optimal, computationally efficient 2D Discrete Cosine Transform (DCT) is used to represent the 2D signal in a decorrelated frequency domain. Several coefficient selection strategies are proposed and tested. A heuristic technique is developed for the selection of transform domain coefficients as inputs to a non-linear neural network based classifier. The benefits of using the selection heuristic as compared to standard variance-based selection are evident in the results. Benefits include: significant dimensionality reduction with concomitant reduction in classifier size and training time, improved generalisation by the neural network and improved classification performance. The electronic nose produced a 99.1% classification rate across a set of seven different cheeses. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains vii, 57 p. Includes bibliographical references.

Thesis (Ph. D.)--Biology, Georgia Institute of Technology, 2005. / Hay, Mark, Committee Chair ; Dusenbery, David, Committee Member ; Kubanek, Julia, Committee Member ; Paffenhofer, Gustav-Adolf, Committee Member ; Yen, Jeannette, Committee Member. Includes bibliographical references.

Thesis (Ph. D.)--Georgia Institute of Technology, 2006. / Title from PDF t.p. (viewed on Oct. 28, 2006). Weissburg, Marc, Committee Chair ; Dusenbery, David, Committee Member ; Hay, Mark, Committee Member ; Webster, Donald, Committee Member ; Blanton, Jackson, Committee Member. Includes bibliographical references (p. 108-119).

This thesis is dedicated to developing novel photofunctional molecular materials for the applications in chemical sensing, bioimaging and electrochromic. To begin with, a brief introduction of photofunctional molecular materials and an overview of their applications in chemical sensing, bioimaging and electrochromic were presented in Chapter 1. In chapter 2, we have synthesized a series of water-soluble phosphorescent cationic iridium(III) solvato complexes (1-7) as multicolor cellular probes for imaging in living cells. All of these complexes can be dissolved in PBS. The emission of complexes can be tuned from green to red by changing the chemical structure of cyclomedtalating ligands. All complexes exhibit low cytotoxicity to living cells and exhibit cell membrane permeability and specific staining of cytoplasm. They enter the cells by the mechanism of energy-independent passive diffusion mechanisms. More importantly, complex 7 can act as a two-photon phosphorescent cellular probe, and fluorescence lifetime imaging microscopy is successfully applied for bioimaging in the presence of short-lived background fluorescence. We developed two excellent optical probes for CO2 detection in Chapter 3. The first one for the CO2 detection is a phosphorescent probe based on an iridium(III) complex with 2-phenylimidazo-[4,5-f][1,10]phenanthroline. After bubbling CO2 into the detection solution, the quenched phosphorescence by the addition of CH3COO can be recovered. Photobleaching experiment demonstrates that this phosphorescent CO2 probe shows higher photostability than some of the reported organic probes. More importantly, the time-resolved PL experiment demonstrates that this probe can be used to detect CO2 in the presence of strong background fluorescence, which improves the sensitivity and signal-to-noise ratio of the sensor in complicated media. The second one is a water-soluble fluorescent probe based on tetraphenylethene derivative. After bubbling CO2 into the detection solution, remarkable color change and fluorescence enhancement could be observed. The response of this probe to CO2 in aqueous solution is fast and the detection limit is about 2.4 × 106 M. To emphasize the practical application of this probe, a porous film was successfully fabricated by mixing the dye with sodium carboxymethyl cellulose in water, which can serve as an efficient CO2 gas sensor. More importantly, this probe exhibits low cytotoxicity towards live cells and has the ability to monitor the external CO2 concentration changes of living cells. Chapter 4 focused on the development of novel soft salt based phosphorescent probe. This type of probe consists of two oppositely charged ionic complexes with two distinguishable emission colors, which makes it a perfect candidate as a ratiometric probe. The emission color of 10 changes from blue to red with increasing pH value. 10 is cell-permeable and exhibits low cytotoxicity, and it has been successfully applied for ratiometric pH imaging with the use of confocal microscopy, demonstrating its great potential for intracellular environment monitoring. Furthermore, phosphorescence lifetime imaging experiments can detect intracellular pH variations by photoluminescence lifetime measurements, which allowed for eliminating background fluorescence and selecting long-lived phosphorescence images. Quantitative measurement of intracellular pH fluctuations caused by oxidative stress has been successfully carried out for 10 based on the pH-dependent calibration curve. A series of cationic Zn(II) complexes has been designed and synthesized in chapter 5. The photophysical properties of these Zn(II) complexes are affected by the counterions. By altering the counterions, the emission peak can be changed from 549 nm to 622 nm. Interestingly, the CIE coordinate and the emission colors can be simply tuned by adjusting the concentration of 11d in the polyether. Under an electric field of about 15 V applied onto the electrodes, the emission color of the solution of 11b-11d near the cathode changed its original emission color to sky blue. Based on this interesting electrochromic fluorescence of 11d, a quasi-solid information recording device has been successfully designed. Furthermore, data encryption has been realized by combining 1d with BODIPY, and information decoding processed has been accomplished, for the first time, by employing TPA excitation techniques, in which the large TPA cross section of 11d is differentiated from small TPA cross section of common organic dyes. Finally, Chapters 6 and 7 present the concluding remarksand the experimental details of the work described in Chapters 25

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2006. / Although the Bengal tiger, Panthera tigris tigris, appears on the IUCN Red Data List for endangered animals, very little information is available in the literature on the components of this animal's marking fluid. Scent marking is the main form of communication in all cat species. In some species, including the Bengal tiger, the liquid used for spraying is not pure urine, but is mixed with scent gland secretions. The objective of this study was to characterise the volatile components in the marking fluid of the Bengal tiger to achieve a better understanding of the semiochemical communication of this animal. The marking fluid of the tiger was characterised through the use of analytical techniques, such as gaschromatography, low resolution gas chromatography - mass spectrometry and retention time comparison. Homologous series of alkanes, alcohols, aldehydes, methyl ketones, carboxylic acids, γ- and δ-lactones, amides and lactams, as well as esters and nitrogen containing compounds, were identified. Of these identified compounds the unbranched alkanes, saturated alcohols, aldehydes, branched methyl ketones, saturated carboxylic acids and γ- and δ- lactones are commonly found in mammalian secretions. Compounds that aren't as common in their secretions are the methyl ketones, branched carboxylic acids, dimethyl esters of dicarboxylic acids and amides. The marking fluid contains a phthalic acid ester. Phthalic acid esters are used in the polymer industry and are nowadays found almost everywhere in nature. It is known that these pollutants have endocrine disrupting properties. The heat, humidity and wet conditions that are characteristic of the Bengal tiger's natural habitat makes it necessary for the tiger to make use of a fixative to prolong the life of the semiochemical message. The compounds and the concentrations in which these compounds are present in the urine and the lipid fraction of the marking fluid of the tiger was determined and compared to assess the fixative role of the lipids. This study has provided evidence that the lipid material has a greater affinity for the volatile organic constituents of the marking fluid and that it can therefore extend the lifetime of a semiochemical message left by the tiger.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / Video 1: Twin-bearing Döhne Merino ewe butting only one of her lambs in typical rejection behavior. Rejection of one twin is not a common phenomenon. (Video by Dr Marlize Viviers) / Video 2: Twin-bearing ewe # 22 accepting alien lamb # 179. The alien lamb wears a jacket her other lamb has been wearing for the preceding 24 hours. The excessive sniffing at the jacket, bleating and looking around show that the ewe is not totally satisfied with the situation. (Video by Dr Marlize Viviers) / Video 3: Ewe # 22 rejecting alien lamb # 179 after removal of the jacket it has worn in the previous video. (Video by Dr Marlize Viviers) / ENGLISH ABSTRACT: Sheep husbandry substantially contributes to South Africa’s economy. Lamb mortality is regarded as a major constraint to sustainable sheep production, and an important factor in lamb survival is the strong ewe–lamb bonding. This is a well-known phenomenon in all sheep races and strong evidence exists that the selective ewe–lamb bond formation has a pheromonal basis, in that the ewe can distinguish her lamb by its unique, familiar smell. Sheep farmers and scientists have examined various methods of making alien lambs acceptable to foster ewes. The survival rate of offspring could be substantially increased if a reliable method could be devised to prevent ewes from rejecting their own lambs or if ewes could be induced to accept alien lambs. A better understanding of the semiochemicals involved in this communication between ewe and offspring could facilitate the development of a method by which ewes can be coaxed into adopting foster lambs. This would positively contribute to efficient sheep production in South Africa. The objective of this study was to characterise the volatile constituents present in the wool and the amniotic fluid collected from the Döhne Merino lambs to achieve a better understanding of the ewe–lamb semiochemical communication. The volatile organic constituents associated with the wool and amniotic fluid were characterised and a total of 133 volatile organic compounds were identified. Several compound classes are represented in these samples and the majority of these compounds have previously been identified in the excretions and secretions of numerous mammalian species. A number of different aspects of ewe–lamb kin recognition were investigated. First, the odour profiles of twin lambs were compared to those of other twins. The results of these analyses revealed that the wool volatiles of twin lambs are qualitatively as well as quantitatively practically identical, but different from those of other lambs in the flock. Second, the change in the odour profiles of lambs was studied over a seven-day period. It was found that the odour profiles of lambs are not fixed, and for as long as a ewe makes use of olfactory recognition as the main mode of identification of her lamb she has to continue learning the odour of her lamb. Third, the amniotic fluid was investigated as a possible source of maternal labels, i.e. as chemical codes consisting of mixtures of compounds in specific quantitative ratios that are imprinted on lambs by their mothers at birth. It was found that the amniotic fluids of first- and second-born lambs are qualitatively and quantitatively different. It is possible that the duration of the lambing birth process could contribute to this change in amniotic fluid composition. Fourth, the role of residual proteins in the dissemination of the semiochemicals involved in ewe– lamb communication was investigated and six proteins were identified as amniotic fluid and wool-associated proteins. Bioassays carried out during the lambing season of 2009 confirmed the role of the odour of the lamb in ewe-lamb recognition, but bioassays carried out with synthetic pheromone formulations gave inconclusive results. / AFRIKAANSE OPSOMMING: Skaapboerdery lewer aansienlike bydrae tot die ekonomie van Suid Afrika, maar lamsterftes is een van die kwellende probleme waarmee kleinveeboere te kampe het. Die eksklusiewe band wat binne die eerste paar uur na 'n lam se geboorte tussen die ooi en haar lam ontwikkel, is die hooffaktor waarvan lammers se oorlewing afhang. Hierdie sterk binding tussen lam en ooi is 'n bekende verskynsel in alle skaap-rasse en dit is bekend dat 'n feromoon wat deur die lam vrygestel word, dit vir die ooi moontlik maak om haar lam aan sy unieke reuk uit te ken. Lamsterftes sou aansienlik verminder kon word as hierdie feromoon geïdentifiseer en gebruik kan word om ooie te verhoed om hulle eie lammers te verwerp en om die aanvaarding van vreemde lammers deur ooie moontlik te maak. Die doel van hierdie studie was die chemiese karakterisering van die vlugtige organiese verbindings aanwesig in die amniotiese vloeistof en wol van Döhne Merino lammers ten einde 'n beter begrip van die semiochemiese kommunikasie tussen ooie en lammers te verkry. In die amniotiese vloeistof is 70 vlugtige organiese verbindings geïdentifiseer. Dieselfde verbindings asook 'n verdere 63 verbindings is in lammerwol geïdentifiseer. Die meerderheid van hierdie verbindings is reeds voorheen in verskeie soogdierafskeidings gevind. Die studie het verskeie interessante aspekte van hierdie semiochemiese kommunikasie aan die lig gebring. Eerstens is daar gevind dat die samestelling van die vlugtige organiese materiaal in die wol van tweelinglammers, oftewel hul reukprofiele, feitlik identies is. Verder verskil die reukprofiele van 'n tweeling van dié van ander tweelinge en enkelinge in die trop. Tweedens is gevind dat die reukprofiel van 'n lam nie by geboorte vasgelê word en so behoue bly nie, maar dat dit geleidelik verander oor ten minste die periode van sewe dae waaroor hierdie verskynsel bestudeer is. Dit noodsaak die ooi om haar geheue met betrekking tot die lam se reuk voortdurend te verfris gedurende die tydperk wat sy hoofsaaklik van haar reuksin gebruik maak om haar lam te herken. Derdens is die amniotiese vloeistof ondersoek as moontlike bron van ‘n sogenaamde moedermerk, waardeur chemiese mengsel van verbindings wat in ‘n spesifieke kwantitatiewe samestelling by geboorte deur die ooi op haar lam agter gelaat word. Ten opsigte van kwalitatiewe en kwantitatiewe samestelling, verskil die vlugtige organiese fraksie van die amniotiese vloeistof van die tweelinglam wat eerste gebore word van die amniotiese vloeistof van die lam wat tweede gebore word. Dit is onwaarskynlik dat amniotiese vloeistowwe wat ten opsigte van hul vlugtige organiese fraksies van mekaar verskil, nagenoeg identiese moedermerke op tweeling lammers sou kon laat. Vierdens is vasgestel dat spore van ses proteïene uit die amniotiese vloeistof op die wol van lammers agtergelaat word. Daar kon ongelukkig nie vasgestel word of hierdie proteïene 'n rol in die vrystelling van semiochemiese inligting speel nie. Gedragstoetse wat tydens die lamseisoen van 2009 uitgevoer is, het bevestig dat die lam se reukprofiel deurslaggewende rol in ooi-lam herkenning speel, maar gedragstoetse wat met sintetiese feromoonmengsels uitgevoer is, het onbesliste resultate opgelewer.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The sungazer, Cordylus giganteus, is an endangered lizard species belonging to the family Cordylidae. It has been speculated that the function of semiochemical communication is performed by two types of skin glands, the femoral glands and the generation glands, which are also found in this family of lizards. Other skin glands and also the cloacal glands are further possible sources of semiochemicals. The investigation of these potential sources of chemical messages in C. giganteus, served as a starting point towards a better understanding of the chemical communication of lizard species belonging to the family Cordylidae. In continuation of this study the femoral gland secretion of the Cape girdled lizard, C. cordylus, was also investigated. Gas chromatography, low resolution GC-MS, GC-HR-MS, MO-TMS derivatisation and retention time comparison were used as analytical techniques in the chemical characterization of the femoral and generation gland secretions of C. giganteus and the femoral gland secretion of C. cordylus. Some compounds were not identified because of their low concentration in the secretions and/or mass spectra could not be obtained for pure compounds because of co-elution with other compounds. Compounds identified in the femoral gland secretion include the following: Carboxylic acids - saturated and unsaturated Alcohols Ketones Aldehydes - saturated and unsaturated Esters - saturated and unsaturated Hydrocarbons - saturated and unsaturated Nitriles Amides - saturated and unsaturated y-Lactones Squalene u-Tocopherol Steroids Quantitative analysis of the femoral and generation gland secretions of a number of sungazers indicated distinct differences between the secretions of males and females (in the case of the femoral gland secretions), but no apparent trend could be found in the differences between the femoral and generation gland secretions of individual lizards of the same gender. Qualitative seasonal differences were however observed in the femoral gland secretions of all individuals of C giganteus. / AFRIKAANSE OPSOMMING: Die ouvolk, Cordylus giganteus, is 'n bedreigde akkedisspesie van die familie Cordilidae. Daar is gespekuleer dat twee soorte velkliere wat by hierdie familie akkedisse voorkom, naamlik die femorale- en generasiekliere, betrokke is by semiochemiese kommunikasie van hierdie diere. Ander velkliere, asook die kliere in die akkedisse se kloaka, is ook potensiele bronne van semiochemiese verbindings. Die bestudering van hierdie potensiele bronne van chemiese boodskappe by C. giganteus is as 'n beginpunt gebruik om die semiochemiese kommunikasie van die akkedisse van die familie Cordilidae beter te verstaan. Ter uitbreiding van hierdie studie is die femorale klierafskeiding van die Kaapse gordelakkedis, C. cordylus, ook ondersoek. Die femorale en generasieklierafskeidings van C. giganteus en die femorale klierafskeidings van C. cordylus is chemies gekarakteriseer deur van analitiese tegnieke, naamlik gaschromatografie, lae resolusie GC-MS, GC-HR-MS, MO- TMS derivatisering en retensietydvergelyking, gebruik te maak. Talle verbindings is nie geidentifiseer nie omdat hulle in 'n baie lae konsentrasie in die afskeidings voorkom, en/of saam met ander komponente elueer, wat veroorsaak dat daar nie massaspektra vir hierdie suiwer komponente verkry kon word nie. Verbindingstipes wat in die afskeidings voorkom, sluit die volgende in: Karboksielsure - versadig en onversadig Alkohole Ketone Aldehiede - versadig en onversadig Esters - versadig en onversadig Koolwaterstowwe - versadig en onversadig Nitriele Amiede - versadig en onversadig y-Laktone Skwaleen a-Tocopherol Steroiede Kwantitatiewe analises van die femorale en generasieklierafskeidings van verskeie ouvolk akkedisse het getoon dat daar duidelike kwantitatiewe verskille tussen die afskeidings van mannetjies en wyfies is (in die geval van die femorale klierafskeidings), maar dat daar geen duidelike patroon in die verskille tussen die femorale en generasieklierafskeidings van individuele akkedisse van dieselfde geslag is rue. Daar is kwalitatiewe seisoenale verskille tussen die femorale klierafskeidings van individue van C. giganteus gevind.

Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The black wildebeest, Connochaetes gnou, is a terriorial animal and although it is not generally accepted, it is believed that it defines its territory by scent marking, using interdigital and preorbital secretions, faeces, and urine. The aim of this study was to characterize the chemical constituents of the interdigital secretion. Due to the complexity of the secretion, only one hundred and ten of the approximately 350 compounds could be determined with known techniques. Gas chromatography, low resolution GC-MS and retention-time comparison were the main analytical techniques used. Classes of compounds identified in the interdigital secretion include the following: • Hydrocarbons - Aliphatic (saturated and unsaturated) and aromatic • Alcohols - Aliphatic (saturated, unsaturated, cyclic and diols) • Phenols and Phenylalkanols • Aldehydes - Aliphatic (saturated and unsaturated) and aromatic • Ketones - Aliphatic (saturated, unsaturated, cyclic and diketones) and aromatic • Hydroxy ketones - Aliphatic and cyclic • Carboxylic acids - Aliphatic (saturated, unsaturated and cyclic) and aromatic • An anhydride • Esters - Methyl esters, ethyl and higher esters, unsaturated esters and aromatic esters • Lactams • A steroid Only small qualitative and quantitative differences were found between the male and female interdigital secretions. / AFRIKAANSE OPSOMMING: Die swartwildebees, Connochaetes gnou, is 'n territoriale dier en alhoewel dit nie algemeen aanvaar word nie, word vermoed dat hierdie bokke hul gebied afbaken met behulp van interdigitale en preorbitale afskeidings, en deur faeces en urine. Die doel van hierdie studie was om die chemiese samestelling van die interdigitale afskeiding te karakteriseer. As gevolg van die kompleksiteit van die afskeiding, kon slegs eenhonderd-en-tien van die ongeveer 350 verbindings met bekende bestaande tegnieke geïdentifiseer word. Gaschromatografie, lae resolusie GC-MS en retensietyd-vergelyking was die belangrikste analitiese tegnieke wat gebruik is. Klasse van verbindings wat bepaal is, sluit die volgende in: • Koolwaterstowwe - Alifaties (versadig en onversadig) en aromaties • Alkohole - Alifaties (versadig, onversadig, siklies en diole) • Fenole en Fenielalkanole • Aldehiede - Alifaties (versadig en onversadig) en aromaties • Ketone - Alifaties (versadig, onversadig, siklies en diketone) en aromaties • Hidroksiketone - Alifaties en siklies • Karboksielsure - Alifaties (versadig, onversadig en siklies) en aromaties • 'n Anhidried • Esters - Metiel esters, etiel en hoër esters, onversadigde esters en aromatiese esters • Laktame • 'n Steroïed Slegs klein kwalitatiewe en kwantitatiewe verskille is gevind tussen die bul en koei interdigitale afskeidings.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy