Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, M�llerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The M�llerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female�s experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles.

Abstract There are a remarkable variety of sex determination systems among different animal taxa. In most animals, sex is determined chromosomally. Although in an increasing number of animals sex determination has been found to be influenced primarily by the environment. Species with genotypic sex determination (GSD) have their sex determined at the time of fertilization, by genetic factors alone and those with environmental sex determination (ESD) have their sex determined by environmental factors that act after fertilization. Temperature-dependent Sex Determination (TSD), whereby the sex of the developing embryos depends on the temperature at which they develop is widespread in oviparous reptiles and occurs in all crocodilians, marine turtles and tuatara examined to date and is common in many freshwater turtles and lizards. SECTION ONE Temperature-dependent sex determination (TSD) was never expected to occur in viviparous reptiles, as thermoregulation by pregnant females would result in relatively stable gestation temperatures. Temperature-dependent sex determination and viviparity goes against all the basic assumptions that TSD occurs in oviparous reptiles where temperatures within a nest vary widely. However, skewed sex ratios as a result of incubation temperature indicated the possibility of TSD in the viviparous lizard Eulamprus tympanum. In my first experiments I show the first recorded case of a viviparous reptile with TSD. The developing embryos of the viviparous skink E. tympanum are subject to TSD, with gestation temperature having a highly significant effect on sex and warmer temperatures giving rise to male offspring (Chapter 1). Sex is fully determined at the time of birth and can be differentiated histologically into testes or ovaries (Chapter 2). The morphology and histological characteristics of the gonads of neonatal E. tympanum resulting from the treatment temperatures described in chapter 1 illustrate that sex in E. tympanum is easily distinguished at the time of birth and corresponds with the presence or absence of hemipenes. Males are histologically characterised by an elongated gonad consisting of seminiferous tubules with either no cortical epithelium or, if present at all, in a very thin band. If they are present, M�llerian ducts, showing signs of degeneration, are attached to the kidney by a shortened mesosalpinx. Females are histologically characterised by an irregularly shaped gonad consisting of a thick cortical epithelium that occasionally contains oocytes. The M�llerian ducts are obvious structures attached to the kidney by a fibrous mesosalpinx. The presence or absence of hemipenes is a reliable technique for determining sex in newborn E. tympanum. Sex determination is easiest to perform on neonates within the first few days of birth as hemipenes become increasingly difficult to evert as neonates age, however, with practice they are easily identified without full eversion. SECTION TWO The thermal biology of E. tympanum in the field is restricted by both the thermal properties of their habitat (Chapter 3) and behavioural modifications when faced with a predation threat (Chapter 4). The available temperatures in the field suggest that TSD is biologically relevant in the species and not just a laboratory artefact; E. tympanum can attain mean selected temperatures achieved in the laboratory but the proportion of time at the temperature is restricted. Females actively thermoregulate in the field, although they are restricted in their efficiency of thermoregulation by environmental constraints, for example, microhabitat structure, weather conditions, predator avoidance and social ranking. The highly territorial nature and high densities of E. tympanum present in Kanangra Boyd National Park potentially force less dominant individuals into less favourable habitats that are significantly cooler. An important point is that gravid females in more favourable habitats in the period encompassing the middle third of development (the assumed sex determining period) are selecting higher temperatures, with lower variance and have greater thermoregulatory efficiency than during the rest of pregnancy, therefore, thermoregulating more precisely during this thermosensitive period (Chapter 3). Chemosensory cues provide important information on the risk of predation. Hence, chemoreception is a common mechanism used by many species to detect the presence of, and subsequently respond to, a potential predator. The perceived risk of predation may force retreat to sub-optimal conditions, forcing a trade-off between the risk of predation and the ability to acquire resources. The basking regime maintained by gravid female E. tympanum, can directly alter sex ratios of offspring produced through temperature-dependent sex determination (Chapter 1). The avoidance of predator scents may restrict basking ability and in turn alter the sex of offspring produced. I measured responsiveness to chemical cues using tongue flicks as an indicator of chemical discrimination in females of different reproductive condition. I then measured activity and basking behaviour of gravid and non-gravid females in experimental enclosures in the presence of various chemical stimuli to determine if basking opportunity is compromised by the presence of a predator scent. Females respond differently depending upon reproductive condition, with gravid females responding most significantly to a predator scent. Activity, basking frequency, and time spent in the open (basking duration) are significantly reduced in gravid females in the presence of a predator stimulus. Under laboratory conditions, gravid females modify their behaviour and forego the opportunity to bask when there is a perceived predation risk (Chapter 4). SECTION THREE As female viviparous reptiles can regulate the temperature of the embryo by maternal temperature selection (Chapter 1), the occurrence of TSD in E. tympanum opens the possibility for females to select the sex of offspring. Reproducing females may benefit by facultatively adjusting their investment into sons over daughters or vice versa, in response to population wide shifts in adult sex ratios. Female E. tympanum, can manipulate the sex of their offspring in response to sex imbalances in the population using temperature-dependent sex determination (Chapter 5). When adult males are scarce, females produce male-biased litters and when adult males are common, females produce female-biased litters. The cues used by a female to assess the adult population are not known, but presumably depends upon the female�s experience throughout the breeding season and is the subject of further investigation (Chapter 6). The maternal manipulation of offspring sex ratio in E. tympanum suggests a selective advantage of temperature-dependent sex determination. Any facultative sex ratio response needs to recognise the scarcity of one sex in order to overproduce that sex in the next generation; offspring sex ratio will vary inversely with adult sex ratio. Maternal sex allocation in E. tympanum is linked with population (or adult) sex ratio (Chapter 5), and one of the mechanisms by which females recognise an imbalance may be linked to visual recognition of males (Chapter 6). Females maintained throughout pregnancy without any male stimulus produce entirely male offspring (Chapter 5). In contrast females exposed to male stimulus produce both sexes (Chapter 5). Females respond differently to varying degrees of male stimulus and visual recognition of males in a population may be more important than chemoreception. In the absence of visual cues, females produce more male offspring, even when chemosensory cues are present (Chapter 6). The study system presented here offers many advantages over oviparous species with TSD, due to E. tympanum being relatively short lived and fast maturing. Thus, the fitness consequences over multiple generations as a result of gestation can be investigated. Viviparity allows maternal control of embryonic temperature during gestation and a means of maternal sex allocation. Until now the maternal side of TSD and sex allocation has been where the mother deposits her eggs and the allocation of sex steroid hormones at oviposition, both of which have been difficult to study. The work presented and the study system itself should inspire great interest in TSD and viviparous reptiles.

The leopard gecko (Eublepharis macularius) is a reptile species in which embryonic temperature contributes both to sex determination and within- sex polymorphisms. Its life history makes the leopard gecko a model system for seeking ontogenic and proximate explanations for within-sex variation in sexually dimorphic behavior and neurophysiology, necessary attributes for reproductive success. For my dissertation I have incorporated the role of androgens that potentially modulate incubation temperature effects on behavioral and brain variation, which I approached using embryo and adult leopard geckos. First, I found that that the bias of same-sex clutch siblings is primarily incubation temperature- dependent and any maternal or genetic effects on same-sex clutch siblings are secondary. Second, I found that testosterone concentrations in the yolk-albumen were higher in eggs of late development than early development at 26 °C, a female-producing incubation temperature, but did not differ from eggs incubated at another female-biased temperature. This increase in testosterone concentrations during the temperature sensitive period in putative females is a finding opposite of reported trends in most other reptiles studied to date. Further, I found that the embryonic environment influences male sociosexual investigation in the absence of gonadal hormones. Lastly, in adult males of 32.5 °C, a male-biased incubation temperature, I found that the phosphoprotein DARPP-32 that is activated by the D1 dopamine receptor in limbic brain regions is correlated to this sociosexual investigatory behavior. Neurons immunopositive for phosphorylated DARPP-32 were not only less dense in the nucleus accumbens of males who spent more time with other males, but also more dense in the preoptic area of males who spent more time with females. The use of phosphorylated DARPP-32 as marker for sociosexual exposure is novel in a lizard species. Taken together, in support of previous studies, these results show that differences in embryonic environment stem primarily from incubation temperature, can explain behavioral differences in adulthood in the absence of hormones, and, in concert with hormonal manipulation, can influence neuronal marker sensitivity to sociosexual exposure. / text

Ectotherms (including marine turtles) being especially sensitive to climate, are at risk to the accelerated rate of human-driven climate change. This study addresses two concerns associated with marine turtles and climate change – the relationship between the timing of marine turtle nesting and sea surface temperature; and the concern over the feminization of marine turtle populations due to rising sand temperatures. Previous studies of loggerhead sea turtles (Caretta caretta) and green sea turtles (Chelonia mydas) have documented the relationship between sea surface temperatures and nesting phenology. Earlier nesting behaviors in both species have been associated with warmer sea surface temperatures. Also, sex determination for marine turtles is temperature-dependent. Due to current sand temperatures, it is estimated that loggerhead (Caretta caretta) nests along the Atlantic coast of Florida already produce over 89% female hatchlings. Using shade to reduce nest temperature and increase the proportion of male hatchlings is one option for mitigating the impacts of climate change on marine turtle sex ratios. In this study, a 21- year (1988-2008) dataset of hawksbill sea turtle (Eretmochelys imbricata) nesting at Buck Island Reef National Monument, St. Croix, U. S. Virgin Islands was analyzed in a similar manner to previous studies. It was found that warmer sea surface temperatures were associated with longer nesting seasons and later median nesting dates. Additionally, a preliminary sand shading study was conducted in the first field season (2011) with a subsequent loggerhead nest shading study in the following field season (2012). Although hatching success was not significantly impacted, temperatures were significantly reduced in the majority of shaded nests. This practice may not be immediately applicable as a means of managing sex ratios, but it could be used to reverse the temperature effects of nest relocation

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Understanding the impact of environmental factors on locomotor performance and flight energetics is of fundamental importance to understanding evolution and ecology. Increased performance that leads to increased dispersal ability can result in increased migration distance to reach optimal habitats, increased gene flow between populations and an overall contribution to the survival of individuals as well as the structuring of species‟ geographic range sizes. The temperature-dependent nature of insects, in conjunction with predicted climate change and shifting optimal climatic ranges, could have important ecological and economic consequences such as increased invasion by alien and pest species. In this study, the influence of thermal history on temperature-dependent flight performance was investigated in a notorious invasive agricultural pest, Ceratitis capitata (Diptera: Tephritidae). Flies were exposed to one of four developmental acclimation temperatures (Tacc: 15, 20, 25, 30°C) during their pupal stage and tested at random at either of those temperatures (Ttest) as adults in a full-factorial experimental design. Major factors influencing flight performance included sex, body mass, Ttest and the interaction between Ttest and Tacc. Performance increased with increasing Ttest across all acclimation groups, e.g. at 15°C only 10% of all flies had successful flight, whereas at 30°C the success rate was 76.5%. Even though Tacc alone did not affect flight performance, it did have an effect in combination with Ttest. The negative interaction term Ttest x Tacc, in combination with a multiple comparison between Tacc groups at each Ttest, indicated that flies acclimated to 15°C and 20°C performed better than those acclimated to 25°C and 30°C when tested at cold temperatures. This provides partial support for the "colder is better‟ hypothesis. To explain these results, several key, flight-related traits were examined to determine if Tacc influenced flight performance as a consequence of changes in body or wing morphology, whole-animal metabolic rate or cytochrome c oxidase (CCO) activity. Although significant effects of Tacc could be detected in several of the traits examined, with emphasis on sex-related differences, increased flight performance could not be explained solely on the basis of changes in any one of these traits. To illustrate the potential applied value of this study, the main flight performance outcomes were also coupled with a degree-day (thermal development) model to determine if knowledge of flight ability could improve predicted population dynamics. The results and insights obtained from this study are broadly applicable to a variety of insect species and demonstrate that, by recognising the impact of environmental factors on locomotor performance and flight energetics, an increased understanding of the functioning, biology and evolution of flight-capable arthropods can be obtained. / AFRIKAANSE OPSOMMING: Groter begrip van die impak van omgewingsfaktore op bewegingsprestasie en vlug-energetika is van fundamentele belang vir die verstaan van evolusie en ekologie. Verhoogde bewegingsprestasie wat lei tot verbeterde verspreidingsvermoë kan 'n toename in migrasieafstand om optimale habitat te bereik, verhoogde genevloei tussen populasies en ʼn algehele bydrae tot die oorlewing van individue sowel as die strukturering van spesies se geografiese gebiedsgroottes tot gevolg hê. Die temperatuurafhanklike aard van insekte, tesame met voorspelde klimaatsverandering en die verskuiwing van optimale klimaatsones, kan belangrike ekologiese en ekonomiese gevolge, soos verhoogde indringing deur uitheemse en pes-spesies, inhou. Die invloed van termiese geskiedenis op die temperatuurafhanklike vlugprestasie van 'n berugte indringer-landboupes, Ceratitis capitata (Diptera: Tephritidae), word in hierdie studie ondersoek. Vlieë is blootgestel aan een van vier akklimasie-temperature (Tacc: 15, 20, 25, 30°C) tydens hul papiestadium en is op ewekansige wyse in 'n vol-faktoriale eksperimentele ontwerp by een van dieselfde toetstemperature (Ttest) as volwassenes getoets. Belangrike faktore wat vlugprestasie beïnvloed het, sluit geslag, liggaamsmassa, Ttest en die interaksie tussen Ttest en Tacc in. Prestasie het verbeter met toenemende Ttest oor al die akklimasiegroepe, bv. by 15°C het net 10% van alle vlieë suksesvol gevlieg, terwyl die sukseskoers by 30°C, 76,5% was. Selfs al het Tacc alleen nie die vlugprestasie beïnvloed nie, het dit 'n effek in kombinasie met Ttest gehad. Die negatiewe interaksie term Ttest x Tacc, in samewerking met 'n meervoudige vergelyking tussen Tacc groepe by elke Ttest, het aangedui dat vlieë wat by 15°C en 20°C geakkimeer was, beter presteer het as dié wat by 25°C en 30°C geakklimeer was wanneer hulle by koue temperature getoets was. Dit bied gedeeltelike ondersteuning vir die "kouer is beter" hipotese. Om hierdie resultate te verklaar, is 'n paar sleutel vlugverwante eienskappe ondersoek om te bepaal of Tacc vlugprestasie a.g.v. veranderinge in die liggaam- of vlerkmorfologie, die hele-dier metaboliesetempo of sitochroom-c oksidase (CCO) aktiwiteit beïnvloed. Alhoewel beduidende effekte van Tacc op verskeie van hierdie eienskappe, veral wat geslagsverwante verskille betref, opgemerk is, kan verhoogde vlugprestasie nie uitsluitlik op grond van veranderinge in enige een van die eienskappe verduidelik word nie. Om die potensiële toepassingswaarde van hierdie studie te illustreer, is die hoof vlugprestasie uitkomste gekoppel aan 'n “degree-day” (termiese ontwikkeling)-model om te bepaal of kennis van vlugvermoë voorspellings van bevolkingsdinamika kan verbeter. Hierdie studie se resultate en insigte is oor die algemeen van toepassing op 'n verskeidenheid insek-spesies en toon dat erkenning van die invloed van omgewingsfaktore op bewegingsprestasie en vlug-energetika kan lei tot groter begrip van die funksionering, biologie en evolusie van geleedpotiges.

A Series of fluorophores of the general formular P(CF2)nP and P(CF2)n-1CF3 has been synthesized. Copper catalyzed coupling of 1-bromopyrene and the corresponding mono and di-iodoperfluoroalkanes were used in most cases. For the n=3 dimer, a novel 1,w-perfluoroalkylation of pyrene via bis-decarboxylation of hexafluorogultaric acid was utilized. These compounds, along with suitable hydrocarbon analogs, are being used to study the flexibility of fluorocarbon chains using emission. We have found that the excimer formation for the fluorinated pyrene monomers is highly dependent on concentration and is less efficient than for pyene. Excimer formation for the fluorinated pyrene dimers is much more efficient than for the fluorocarbon monomers and is only slightly concentraion dependent. Steady-state emission spectra indicate hydrocarbon dimers-models form excimers more efficiently than the fluorinated dimers suggesting the fluorinated chains are stiffer than the hydrocarbons. We conducted the temperature-dependent studies and quantified the conformational difference.

<p>Sex determination is a critical biological process for all sexually reproducing animals. Despite its significance, evolution has provided a vast array of mechanisms by which sexual phenotype is determined and elaborated even within amniote vertebrates. The most prevalent systems of sex determination in this clade are genetic and temperature dependent sex determination. These two systems are sometimes consistent within large groups of species, such as the mammals who nearly ubiquitously utilize XY genetic sex determination, or they can be much more mixed as in reptiles that use genetic or temperature dependent systems and even both simultaneously. The turtles are a particularly diverse group in the way they determine sex with multiple different genetic and temperature based systems having been described. We investigated the nature of the temperature based sex determination system in Trachemys scripta elegans to ascertain whether it behaved as a purely temperature based system or if some other global source of sex determining information might be apparent within thermal regions insufficient to fully induce male or female development. These experiments found that sex determination in this species is much more complex and early acting than previously thought and that each gonad within an individual has the same sexual fate established enough that it can persist even without further communication between. We established a best practice for the assembly and annotation of de novo whole transcriptomes from T. scripta RNA-seq and utilized the technique to quantify the gene regulatory events that occur across the thermal sensitive period.</p><p>Evidence is entirely lacking on the resolution of TSD when eggs are incubated at the pivitol temperature in which equal numbers or males and females are produces. We have produced a timecourse data set that allowed for the elucidation of the gene expression events that occur at both the MPT and FPT over the course of the thermal sensitive period. Our data suggests that early establishment of a male or female fate is possible when temperature is sufficiently strong enough as at MPT and FPT. We see a strong pattern of mutually antagonistic gene expression patterns emerging early and expanding over time through the end of the period of gonad plasticity. In addition, we have identified a strong pattern of differential expression in the early embryo at stages prior to the formation of the gonad. Even without the known systemic signaling attributed to sex hormones emanating from the gonad, the early embryo has a clear male and female gene expression pattern. We discuss how this early potential masculinization or feminization of the embryo may indicate that the influence of temperature may extend beyond the determination of gonadal sex or even metabolic adjustments and how this challenges the well-defined paradigm in which gonadal sex determines peripheral sexual characteristics.</p> / Dissertation

<p>Mathematical modeling of heat transfer is a common method utilized in designing thermal processes for food, modeling degradation kinetics of microorganisms and nutrients, designing food processing equipment as well as for process optimization and for ensuring scale-up feasibility of a product. It is essential to have all the necessary components for modeling including the geometry, boundary conditions, initial temperature, and the temperature-dependent thermal properties. Getting temperature-dependent thermal properties of food product is difficult due to the lack of effective and efficient devices or techniques. To show the influence of temperature-dependent thermal properties, retort processing of potato soup was simulated using both temperature-dependent (dynamic) and fixed thermal properties. Three methods, TPCell, Choi-Okos predictive model and KD2 Pro, were used to determine the thermal conductivity at 25°C and 120°C for comparison. The proximate composition of the sample was determined for prediction of thermal properties with the Choi-Okos model. The accuracy of simulation was evaluated based on the temperature at the cold spot and corresponding sterilization value. Results suggested that using temperature-dependent thermal properties in heat transfer modeling increased the accuracy of the simulation. Simulation performed with temperature-dependent properties obtained from TPCell matched very closely with experimental heat penetration data. Additionally, the sensitivity of temperature-dependent thermal properties obtained from TPCell in detecting variation in product formulation was evaluated. Four variations of potato soup were prepared to compare their respective lethality value. Thermal conductivity, specific heat capacity and density of the potato soups were measured, and simulation was performed using the measured thermal properties and a scheduled process as boundary conditions. Thermal properties of food product changed with the formulation which affected the processing time to achieve minimum lethality value. A significant difference in thermal conductivities was seen for these potato soups causing the scheduled process to be only suitable for thermal processing of some formulations while others would be undercooked that could lead to food safety risk. Since the thermal conductivity measurements were sensitive in detecting the difference in the formulation, it can be used as a tool to select a formulation that can best suit the processing conditions of the heat penetration tests. The technique described can be used for any thermal processes in the food industry including pasteurization, retort, and aseptic processing. This application will be beneficial for the industry to pre-screen the iterations and only select formulation that suits the scheduled process for successful heat penetration trials and reduce trial costs.</p>

Reptiles exhibit marked diversity in sex-determining mechanisms. Many species exhibit genotypic sex determination (GSD) with male heterogamety (XX females/XY males), others have GSD with female heterogamety (ZW females/ZZ males), and still others exhibit temperature-dependent sex determination (TSD). The distribution of these mechanisms throughout the reptile phylogeny implies evolutionary lability in sex determination, and in some lineages there has been a number of transitions between GSD and TSD. Despite this diversity, GSD and TSD have traditionally been viewed as mutually-exclusive mechanisms of sex determination in reptiles, since there is little evidence for their co-occurrence. Considerable empirical and theoretical effort has been directed towards understanding the adaptive significance of TSD in reptiles. In comparison, there has been little focus on understanding how evolutionary transitions between GSD and TSD occur at a genetic and mechanistic level. I addressed this question by applying both empirical and theoretical approaches to investigate interaction of genotypic and temperature influences in the sex determination of two endemic species of Australian lizards. The three-lined skink, Bassiana duperreyi, has XX/XY chromosomal sex determination, yet a previous investigation reported a significant male bias in the sex ratio of eggs incubated at low temperatures. To enable an explicit test for temperature induced sex reversal in this species, a 185 bp Y chromosome marker was isolated by Amplified Fragment Length Polymorphism (AFLP) analysis. The marker was subsequently converted into a duplex PCR assay that co-amplified a 185 bp (or 92 bp) Y chromosome fragment and a 356 bp fragment of the single-copy nuclear gene C-mos (from both sexes) as a positive control. The accuracy of the PCR sex assay was tested on 78 individuals for which sex reversal was not expected. PCR genotype and sex phenotype were concordant for 96% of the animals. This is one of the very few sex tests developed for a reptile, and the first report of Y chromosome sequence from a reptile. The PCR assay was subsequently applied to genotype hatchlings from both cool (16-7.5C) and warm (22-7.5C) cyclical incubation temperature treatments, and identified sex reversal in 15% of genotypically female (XX) embryos (n=26) from the cool treatment, but no sex reversal in eggs from the warmer treatment (n=35). Thus, low incubation temperatures can over-ride genotypic sex determination in B. duperreyi, indicating that GSD and TSD co-occur in this species. The Central bearded dragon, Pogona vitticeps (Agamidae), has ZZ/ZW chromosomal sex determination, and is a member of a lizard family in which GSD and TSD are both widespread, indicating evolutionary lability in sex determination. AFLP analysis was applied to isolate homologous Z and W chromosome-linked markers (71 bp and 72 bp, respectively) from this species. The AFLP sequences were subsequently extended into larger genomic fragments by a reiterated genome walking procedure, producing three non-overlapping contigs of 1.7 kb, 2.2 kb and 4.5 kb. The latter two fragments were verified as distinct, homologous Z/W chromosome fragments by PCR analyses. An amplified 3 kb fragment of the 4.5 kb contig was physically mapped to metaphase spreads, identifying the W microchromosome, and for the first time in this species, the Z microchromosome. PCR analyses indicated the presence of homologous sequences in other Australian agamid species, including both GSD and TSD species. The isolated sequences should therefore prove useful as a comparative genomic tool for investigating the genomic changes that have occurred in evolutionary transitions between sexdetermining mechanisms in agamids, by enabling the identification of chromosomes in TSD species that are homologous to the sex chromosomes of P. vitticeps. The isolated sequences were further converted into a duplex DNA sex assay that co-amplified a 224 bp W chromosome fragment and a 963 bp positive control fragment in both sexes. This PCR assay diagnosed chromosomal sex in three Pogona species, but was not effective outside the genus. Incubation treatment of P. vitticeps eggs revealed a strong and increasing female bias at high constant temperatures (34-36C), but an unbiased sex ratio between 22-32C. Hatchlings from three clutches split between 28C and 34 or 36C incubation treatments were genotyped with the W chromosome AFLP marker. At 28C, the sex ratio was 1:1 but the high temperature treatments produced 2 males and 33 females. All but one of the 30 lizards (97%) incubated at 28C had concordant sex phenotype and genotype, but only 18 of 35 animals (51%) from the high temperature treatment were concordant. All discordant animals were genotypic males (ZZ) that developed as females. Thus, temperature and genotypic influences can interact to determine sex in P. vitticeps. These empirical findings for B. duperreyi and P. vitticeps were extended into a novel theory for the evolution of sex-determining mechanisms in reptiles, working within the framework that species with temperature-induced reversal of chromosomal sex determination are a window to transitional stages of evolution between GSD and TSD. A model was derived from the observation that in both lizards, an extreme of incubation temperature causes sex reversal of the homogametic genotype. In this model, the strength of a genetic regulatory signal for sex determination must exceed a threshold for development of the homogametic sex to occur (male in Pogona, female in Bassiana). The strength of this signal is also temperature-sensitive, so diminishes at extremes of temperature. Simulation modelling demonstrated that increasing the relative magnitude of the threshold for sexual development can cause evolutionary transitions between GSD and TSD. Even more remarkably, decreasing the relative magnitude of the threshold value causes an evolutionary transition between female and male heterogametic GSD. Quantitative adjustment of a single model parameter (the threshold value) thus charts a continuous evolutionary pathway between the three principal mechanisms of sex determination in reptiles (XX/XY-ZZ/ZW-TSD), which were previously considered to be qualitatively distinct mechanisms. The experimental demonstration of temperature-induced reversal of chromosomal sex determination in both B. duperreyi and P. vitticeps presents a challenge to the traditional view that reptilian sex determination is strictly dichotomous (GSD or TSD), and suggests instead that sex determination in reptiles consists of a continuum of systems of interaction between genotypic and temperature influences. Simulation modelling provided solid theoretical support for this proposition, demonstrating that transitions along this continuum are effected simply through shifts in the mean population value for the sex-determining threshold, without requiring substantial genotypic innovation. An important implication of this theory is that transitions between XX/XY and ZZ/ZW modes of GSD may retain the same sex chromosome pair, and the same primary sexdetermining gene, in contrast to previous models for heterogametic transitions. A more immediate implication of these findings is that many reptile species believed to have strict TSD (in particular, lizards and crocodilians), may in fact have a sex-determining system of GSD-TSD interaction, where there is an equilibrium between GSD and TSD individuals within the population.

Mn-doped II-VI semiconductor nanocrystals exhibit bright dopant photoluminescence that has potential usefulness for light emitting devices, temperature sensing, and biological imaging. The bright luminescence comes from the 4T1→6A1 transition of the Mn2+ d electrons after the exciton-dopant energy transfer, which reroutes the exciton relaxation through trapping processes. The driving force of the energy transfer is the strong exchange coupling between the exciton and Mn2+ due to the confinement of exciton in the nanocrystal. The exciton-Mn spatial overlap affecting the exchange coupling strength is an important parameter that varies the energy transfer rate and the quantum yield of Mn luminescence. In this dissertation, this correlation is studied in radial doping location-controlled Mn-doped CdS/ZnS nanocrystals. Energy transfer rate was found decreasing when increasing the doping radius in the nanocrystals at the same core size and shell thickness and when increasing the size of the nanocrystals at a fixed doping radius. In addition to the exciton-Mn energy transfer discussed above, two consecutive exciton-Mn energy transfers can also occur if multiple excitons are generated before the relaxation of Mn (lifetime ~10^-4 - 10^-2 s). The consecutive exciton-Mn energy transfer can further excite the Mn2+ d electrons high in conduction band and results in the quenching of Mn luminescence. The highly excited electrons show higher photocatalytic efficiency than the electrons in undoped nanocrystals. Finally, the effect of local lattice strain on the local vibrational frequency and local thermal expansion was observed via the temperature-dependent Mn luminescence spectral linewidth and peak position in Mn-doped CdS/ZnS nanocrystals. The local lattice strain on the Mn2+ ions is varied using the large core/shell lattice mismatch (~7%) that creates a gradient of lattice strain at various radial locations. When doping the Mn2+ closer to the core/shell interface, the stronger lattice strain softens the vibrational frequency coupled to the 4T1→6A1 transition of Mn2+ (Mn luminescence) by ~50%. In addition, the lattice strain also increases the anharmonicity, resulting in larger local thermal expansion observed from the nearly an order larger thermal shift of the Mn luminescence compared to the Mn-doped ZnS nanocrystals without the core/shell lattice mismatch.