Browsing by Subject "volatile organic compounds"
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Item Chemical and Nutritional Ecology of Lucilia sericata (Meigen) (Diptera: Calliphoridae) as Related to Volatile Organic Compounds and Associated Essential Amino Acids(2014-08-07) Liu, WenqiThis will be the first research aiming to investigate the chemical and nutritional ecology of Lucilia sericata, (Meigen) (Diptera: Calliphoridae) focusing on 1) carrion resource associated microbial volatile organic compounds (MVOCs) emissions as insect semiochemicals in regulating the olfactory response of adult L. sericata of different biological states, 2) the impact of exposure to these VOCs on the life history related traits of L. sericata adult flies, and 3) effect of carrion associated nutritional resources on blow fly larval performance. One GFP producing Providencia was successfully constructed to be used to visualize bacteria along the alimentary canal of L. sericata larvae to implement investigation of its impact on the physiology of both L. sericata immature and adults, such as the immature developmental stages, the adult?s potential choice for food location and oviposition. Microbes play an important role in the decomposition processes of carrion associated resources producing volatile compounds (VOCs). L. sericata may use MVOCs as cues to exploit the carrion resource for food, oviposition, mate etc. Proteus and Providencia spp. are among the microbes that break down as well as synthesize the essential amino acids which are the origin of MVOC. Four bacterially produced VOCs, namely DMDS (Dimethyl disulfide), indole, PAA (Phenylacetic acid), and isobutylamine, which are associated with decomposing carrion were used to investigate the olfactory response of L. sericata of different sexes and physiological status to study the regulation of L. sericata behaviors by MVOCs in exploitation of carrion resource. Attraction and colonization of carrion resource by adult flies are followed by the subsequent development of offspring. Different responses of adult flies to volatile compounds from carrion may reflect larval preferences and performance associated with different carrion resources where they obtain nutrition and develop. In order to better understand the consequences of adult resource site selection on larval performance on the chosen carrion resource, a series of imbalanced diets deficient in essential amino acids of methionine, valine, tryptophan and phenylalanine were used to study larvae performance on carrion associated resource in term of food preferences and development. In order to investigate volatile cues sensing and physiology in L. sericata, DMDS was used to investigate whether the exposure to the volatile cues will also be involved in the regulation of physiology of L. sericata adult in terms of their life span, and defecation.Item Chemically sensitive polymer-mediated nanoporous alumina SAW sensors for the detection of vapor-phase analytes(Texas A&M University, 2005-08-29) Perez, Gregory PaulWe have investigated the chemical sensitivity of nanoporous (NP) alumina-coated surface acoustic wave (SAW) devices that have been surface-modified with polymeric mediating films. The research in this dissertation covers the refinement of the NP alumina coating, development of dendrimer and/or polymer surface modifications, design of composite ultrathin vapor-phase analyte gates, and preparation of selectively permeable, polymeric films that mediate analyte transport. Nanoporous alumina SAW devices were fabricated from planar Al SAW devices using an anodization process that yields a high-surface-area transduction platform. Refinement of the anodization process results in a homogeneously porous substrate capable of ~40 times the analyte sensitivity of conventional planar SAW devices. Attempts to directly impart selective gas-phase analyte permeation with monolayers of amine-terminated, poly(amidoamine) (PAMAM) dendrimer films were investigated with and without secondary functionalization. We also prepared and characterized pore-bridging polymeric composite ultrathin films (~12 nm) of PAMAM dendrimers and poly(maleic anhydride)-c-poly(methyl vinylether) (Gantrez). Access to the underlying pores of the NP alumina coating can be modulated through the sequential deposition of the composite film. These tailorable ultrathin films result in impermeable surface- modifications which fully gate the analyte response without filling the porous structure. Thin spin-cast films (40 nm) of polydimethylsiloxane (PDMS) were developed to simultaneously provide selective sorption and permeation characteristics towards vapor-phase analytes. The porous nature of the underlying alumina coating provides for this real-time evaluation of sorption and permeation. The results suggest that the thin films offer preferential sorption of non-polar organics and selective permeability towards water vapor.Item The development of a sensitive method to study volatile organic compounds in gaseous emissions of lung cancer cell lines(Texas A&M University, 2005-08-29) Maroly, AnupamThe ultimate objective of this research was to develop a low cost, reliable system that would lead to early detection of lung cancer. Tests involved the quantitation of gaseous metabolic emissions from immortalized lung cancer cell lines in order to correlate the chemical markers to be of cancerous origin. The specific aims of the project were the study of gas emissions in selected cancer cell lines and identification of volatile organic compounds (VOCs) in them. Disadvantages of earlier studies were that the measurements were not real time or state specific so that molecular identification was often inconclusive. Furthermore the methods of study used in the past were not quantitative, which limited their practicality for medical applications. We felt the need to prove or disprove these earlier results using a new technique. The method we proposed is different and unique when compared to previous methods because cell lines have not been studied extensively for cancer markers. We have studied cancer cell lines which are adherent, immortalized cultures originating from primary tumors obtained from patients with no prior treatment for lung cancer. We have used an alternative method for the spectrometric analysis and quantitation of the selected chemical markers. The pre-concentration method involved a Purge and Trap unit with a thermal desorber where the vapor concentration was enhanced. The concentrated head space gases were analyzed using a Gas Chromatograph ?? Mass Spectrometer setup. This setup eliminated the bulky apparatus used in earlier studies. It is simpler in design and more comprehensive so that external factors such as patient??s diet, habitat and lifestyle do not contribute to our study of recognition of cancer markers. Based on the results obtained in the above experiments, a more comprehensive, inexpensive study of lung cancer related markers could be made. The first section, after giving an introduction to lung cancer, goes on to explain the background work done by other researchers on cancer. The third section gives a detailed explanation of the experimental setup. This is followed by all the tests conducted with corresponding results. The final section deals with the conclusions drawn from all experiments.