Weeks Bay, AL is a governmentally protected reserve near Mobile Bay, AL, while Old Tampa Bay, FL is an urbanized estuary, located along the western coast of Florida. Estuary health is important to local economies and the health of local marine life, with an emphasis on low levels of eutrophication. Sediment oxygen demand (SOD) is usually measured to qualify the environmental health of estuaries, but SOD is timeconsuming and expensive. Average acid volatile monosulfides (AVS) concentrations were found to accurately predict SOD variances. The Degree of Pyritization (DOP) is a measure of long-term sediment oxidation conditions, which indicates normal estuary state. Despite the urban land use practices of these two bays, the DOP of each bay is similar.

My research focuses on the development of a novel method for the fast detection of aflatoxin-producing fungi from the volatile organic compounds that they produce. Aflatoxins have received great attention because of their demonstrated potent carcinogenic effect in susceptible laboratory animals and their acute toxicological effects in humans. Traditional detection and quantification techniques are considered time-consuming, high cost, and require technical professionals. The `odor' or so called volatile metabolites released by a fungus is the key for fast detection. Several researchers have reported that diverse fungi species have unique volatile metabolite patterns. This study focuses on answering several questions: Is it possible to discriminate aflatoxins-producing fungi from other fungi based on volatile metabolites? What are the key discriminating biomarkers related to each fungus? Does the growth environment have an effect on the production of volatile metabolites? What chemicals are consistently emitted by a fungus under varied conditions? To answer these questions, one toxigenic and one nontoxigenic A. flavus isolate were studied to evaluate the microbial volatile organic compound (MVOC) profiles. The results described in chapter two of this dissertation indicate that MVOC production is time-dependent and that aflatoxigenic and non-aflatoxigenic strains have different MVOC expression patterns. Chapter three describes the effects of experimental parameters on fungal volatile metabolites. The identity and quantity of MVOCs can be affected by many factors including SPME fiber type, fungal growth media, and growth temperature. A CAR/PDMS coated fiber performed better than the other SPME fibers by collecting a larger variety and quantity of MVOCs. Fungi grown on the chemical defined liquid media produced much larger quantities of MVOCs compared to the other media. The highest MVOC production results were found at 30 degrees Celsius. The fungi discrimination study was extended in chapter four by including 3 toxigenic and 3 non-toxigenic isolates using multivariate analysis. The results indicate that volatile patterns vary even at the fungal isolate level and that discrimination of aflatoxin-producing fungi from non-toxigenic fungi is possible.

Our study focuses on the application of volatile metabolomics and chemometrics in plant pathology. Specifically, volatile metabolites or volatile organic compounds (VOCs) from the American chestnut tree (Castanea dentata) and its pathogenic fungus Cryphonectria parasitica have been investigated. The American chestnut was once a dominant tree species in the eastern forests of the United States. However, it was nearly devastated by the fungal pathogen C. parasitica. The loss of this tree species has significantly impacted the ecosystem. Therefore, preservation and restoration of American chestnut are crucial. Chapter one provides an overview of mass spectrometry based volatile metabolomics and their implementation in the investigation of plant pathology. The study of volatile metabolites profiles from virulent and hypovirulent strains of C. parasitica are presented in chapter two. The microbial volatile organic compounds (MVOCs) profiles were analyzed via nondestructive sampling method, headspace solid phase microextraction (HS-SPME), combined with gas chromatography (GC)-mass spectrometry (MS). The results indicate that the MVOCs profiles emitted from these two strains are significantly different. In general, compared with its hypovirulent strains, high emissions of sesquiterpenes were observed in the virulent strains. Furthermore, the study explored MVOCs differences associated with hypovirulence processes. The study found that both hypovirulence and aging can alter the virulent strains' MVOCs, and the process can be observed via their volatile metabolites. Chapter three describes the effects of aging, cultivation medium, and pH on fungal volatile metabolite profiles, all of which can change the strength of MVOCs emission and their composition. An acidic environment favors fungal bioactivity and therefore enhanced MVOCs emission. However, due to the inherently low MVOCs production from hypovirulent strains, the pH effect was less apparent in the hypovirulent isolates. The strength of MVOCs emission was highly correlated to the fungal expansion in virulent strains for the first 14 days. The overall emission from hypovirulent strains was relatively steady during the 28-day observation. Finally, the cultivation media are critical to the fungal MVOCs production. Among the tested media, cornmeal was least favorable for MVOCs production for both strains. Finally, Chapter Four presents a study of the total constitutive phenolic content estimation and volatile organic compounds identification from four species of chestnut tree leaf tissues. Folin Ciocalteu reagent assay with UV/Vis spectrophotometry was applied to estimate the total phenolic content in leaf tissues of American chestnut (Castanea dentata), Chinese chestnut (Castanea mollissima), and their backcross breeding generations (B3F2 and B3F3). The results from leaf tissue extraction in methanol/water (95:5 v/v), pH 2, and analyzed under the UV/Vis at 765 nm show that the variations among these tree species are significant (ANOVA, p < 0.05). The kinetics of phenolic compound solid-liquid extraction was elaborated using Peleg, second order, and power law models. Moreover, the analysis of VOCs collected from these species indicated that the distinction of American and Chinese chestnut could be archived via their VOCs, while the hybrids’ leaf VOCs are different from their parents’.

Ferroelectric non-volatile memories have gained momentous importance in the recent years. Significant research is being done on different device structures with several ferroelectric films for better data retention, lower power dissipation and higher density of integration. Metal - ferroelectric insulator – semiconductor (MIS) capacitor structures with Poly Vinylidene Fluoride(80%) - trifluoroethylene (20%) (PVDF – TrFE) copolymer are observed to demonstrate consistent dielectric properties and retainable memory action under selected operating conditions. Prior research was done on devices with MFeOS structure with an oxide buffer layer. The presence of a buffer oxide reduces the field acting on the film for memory state switching, which in effect requires the devices to be operated at higher voltages. In this work, MFeS devices with lower ferroelectric film thickness; with, and without a very thin buffer oxide have been studied. The dielectric behavior of PVDF thin film, when deposited directly on Si, is observed to exhibit reliable memory properties without significant charge injection under certain operating conditions. Electrical characteristics such as capacitance-voltage(C-V) and polarization-electric field (P-E) hysteresis with the direction of measurement and conduction properties through the junction have been comprehensively studied to establish the behavior of the MIS device for possible use in MIS FETs for high density ferroelectric memories.

In 2013, the wooden breast defect in broiler breast meat was characterized by hardened and pale areas at both the caudal and cranial regions of the breast. The objective of this study was to determine the flavor differences between severe woody and normal breast meat in both breast and patties using gas chromatography-mass spectrometry, gas chromatography-olfactometry, and sensory descriptive analysis. Forty-eight individual volatile flavor compounds were identified in both the ground and whole breast chicken samples including aldehydes, ketones, and other functional groups. Minimal differences existed in the volatile fraction of normal and severe woody breast meat. In contrast, woody breast patties had greater concentrations of many oxidation products, including aldehydes, alcohols, and hydrocarbons. The most intense aroma compounds were hexanal, 1-octen-3-ol, 2-pentylfuran, 2-ethylhexyl acetate, and 1-nonanol. The descriptive and volatile results indicated that in patties, woody breast meat was more susceptible to oxidation and off-flavors than normal breast meat.

Despite being integral to the practice of surgery, the mechanisms by which general anesthetics mediate their effects remain unknown. For this reason, it is difficult to predict adverse side-effects and to determine how treatment should be modified for specific patient populations. Recent clinical studies have reported post-operative neuropsychological and behavioral abnormalities in children and protracted periods of post-operative cognitive decline in elderly patients. Definitively linking these post-operative consequences to the agents used to induce anesthesia has been difficult, due to a lack of proper clinical controls and an abundance of confounding health factors. Animal studies, have repeatedly shown that general anesthetics can be neurotoxic and lead to lasting impairments in learning and memory acquisition in both the very young and old. However, the scope and causes of these post-exposure impairments and the reasons why age seems to measurably affect outcomes remain unclear. Here we employ multi-neuronal fluorescence imaging in the nematode Caenorhabditis elegans to measure changes in neuronal activity and connectivity across the animal’s nervous system, following exposure to the volatile anesthetic isoflurane during neurodevelopment and senescence. Employing transgenic expression of the fluorescent calcium indicator GCaMP6s, we measure neuronal activity of specific command interneurons as well as across the majority of the nervous system with single cell resolution. Isoflurane exposure during developing, results changes in the transition rate between neuronal activity states and an overall increase in excitatory connectivity. Importantly these effects are dependent on cellular stress pathways involved mTOR and daf-16 but not on apoptotic cell death (medatied by ced-3). Measuring neuronal activity across the animals lifespan, we identify substantial age-related alterations to neural activity, connectivity and functional organization of the system. These include a progressive loss of system-wide organization and a corresponding shift in individual neuron activity toward higher frequencies. We also observe a specific loss of anti-correlative (i.e. inhibitory) signaling between neurons, resulting in an overall shift in the excitatory/inhibitory balance of the system. In support of this, we find that application of the GABAA agonist muscimol diminishes certain aspects of nervous system decline in aged animals. We further identify genes that either hasten or delay the progression toward senescent neural activity patterns, including the presynaptic voltage-gated Ca2+ channel UNC-2/CaV2, and also CED-4, a key mediator of the conserved cell-death pathway. Finally, imaging post-exposure consequences of isoflurane during senescence reveals long term effects on neuronal signaling that involved a decrease in excitatory connectivity, the opposite of what is observed during development. We conclude that anesthetic exposure during development cause permanent alteration in neuronal activity and signaling which involves cellular stress pathways but that these effects are distinct from long-term effect of anesthetic exposure we observe in age animals. Our studies also begin to define the changes in neuronal dynamics with age and demonstrate the importance of excitatory/inhibitory balance in this processes. Through comprehensive multi-neuronal imaging in C. elegans, we are able to measure the progressive breakdown of neuronal activity and system dynamics with age and isoflurane exposure and begin to identify the cellular processes and changes in synaptic signaling that contribute to these declines. Moreover, we leverage this platform to gain insight into the age-dependency of isoflurane-induced insult to neural systems.

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