A billion tons per year of genetically modified corn residues are soil incorporated having both direct and indirect effects on the belowground environment, soil carbon (C) sequestration, and nutrient cycling. If Bt genetic modification has non-target effects on corn stover structural/non-structural carbohydrate and nitrogen (N) concentrations, then the degradation rate of Bt-corn stover may be different than that of non-Bt isolines, possibly influencing soil C storage and N mineralization. Thus, this research focused primarily on the comparison of C and N mineralization of corn stover in soil as affected by Bt-trait, plant portion, water-availability and HFC-trait; and secondarily on the existence of Bt-related variations in the chemical structure of corn residues that might affect the degradation rate of stover in soil and consequently the soil C and N dynamics. A laboratory experiment was conducted under non-limiting N conditions with stover of Bt/non-Bt isogenic pairs of two varieties, a ?high fermentable corn? (HFC) line harvested at Snook, Texas and a non-HFC corn line harvested at the irrigated field of Snook and the non-irrigated field of College Station, Texas. The stover was partitioned into three plant portions, incorporated into a Weswood soil and incubated during 223 days. Results showed that the differences observed in the degradation in soil of Bt vs. non-Bt corn stover were dependent on environmental conditions (irrigated vs. non-irrigated settings) and hybrid variety (HFC vs. non-HFC hybrid lines). The structural composition of corn plants was affected by the Bt-trait, HFC-trait, irrigation and their interactions. Variations in the biomass fractions of the initial stover of Bt and non-Bt hybrids had minimum to non-impact on soil C and N concentrations measured at the end of the 223-day incubation period. Lignin concentration was affected by a Bt-trait*variety interaction. There were no significant differences in lignin concentration between non-Bt/Bt-corn derived stovers of the non-HFC variety irrespective of irrigation regime but Bt-hybrids of the HFC variety contained more than twice as much lignin as the non-Bt isogenic plants. The effects of higher lignin concentration on C mineralization rate appeared to be offset by an increased lignin degradability inherent in HFC-trait. Overall, results indicated that the cultivation of Bt-modified maize lines is not likely to have significant effects on soil C or N dynamics compared with the cropping of non-Bt hybrids.

Pentachlorophenol (PCP) is a chloride-containing aromatic compound which is mostly used for preserving wood and leather, but still one can easily detect this compound present in the waste water generated by various industries such as petrifaction, oil-refining, and etc. PCP, due to its chemical property of being stable and highly toxic, would cause severe and irreparable environmental pollution once exposed to open air. This study is intended to explore the feasibility of dealing the problem of PCP with biodegradation. The examination results showed that, except for absorption, the suspension of contaminated soil (aerobic incubation), nonetheless, could effectively degrade PCP during a period of 90 days without the aid of any extra carbon source. (0.62 mg/L/day). The degradation rate was further greatly improved by adding sodium acetate, molasses, and sludge cake (sodium acetate added: 4.15 mg/L/day; molasses added: 1.05 mg/L/day; sludge cake added:0.83 mg /L/day). None of four experimental groups of aerobic sludge, anaerobic sludge, contaminated soil (anaerobic incubation), and Fe3+reaction could degrade PCP after 135 days, 174 days, 250 days, and 124 days, respectively, regardless of whether any sources of carbon were added or not. A bacterium which used PCP as the sole carbon source was isolated from the contaminated soil. After 16s rDNA sequence analysis, it had 98% degree of similarity to Pseudomonas mendocina and was designated as Pseudomonas mendocina NSYSU. The PCP (40 mg/L) degradation rate of Pseudomonas mendocina NSYSU was 9.33 mg/L/day, and the degradation rate would slow down as PCP concentration increased. At a PCP concentration of 320 mg/L, PCP degradation was completely inhibited, although an active population of Pseudomonas mendocina NSYSU was still present in these cultures. The study also indicated that the addition of various carbon sources such as sodium acetate and glucose did not facilitate the degradation of PCP with the degradation rate of 8.11 mg/L/day for sodium acetate, and that of 7.55 mg/L/day for glucose. Analysis from examining several environmental factors showed that the optimal condition for PCP degradation is that of 30¢J, pH6, and in the presence of oxygen. The end products of PCP degradation were detected by GC-MS. After 6 days of incubation, PCP was gradually disappeared and the metabolic intermediate product, acetic acid was detected. The chloride ion concentration also increased by 21.8 mg/L, which is approximately equal to the original total chloride content in PCP (66% of chloride content). In conclusion, PCP could be effectively and completely degraded by Pseudomonas mendocina NSYSU.

The moisture absorption behavior of Zylon fibers was characterized in various high temperature and high humidity conditions in a controlled environment. The results of these thermal cycling tests show that PBO fibers not only absorb, but also retain moisture (approximately 0.5-3%) when exposed to elevated temperature and humidity cycles. Also, the impurities of Zylon fibers were characterized through the use of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and solid state Nuclear Magnetic Resonance (NMR). These tests demonstrated that, in addition to other impurities, PBO fibers may contain up to 0.55 weight percent phosphorus, and that this phosphorus is present in the form of phosphoric acid. It was also shown through accelerated hydrolytic degradation tests that production procedures used to neutralize the acid present in the fibers have a beneficial effect on the hydrolytic performance of the fiber. The data collected in this study was then compared and contrasted to known Kevlar studies, identifying similarities, differences, and potential trends. The results of these tests seem to indicate that there is accelerated acid catalyzed hydrolysis occurring in the fiber which is causing these fibers to degrade at an increased rate. This condition is further accelerated by heat and humidity induced permanent fiber swelling.

<p>The purpose of this thesis is to explore the concept of environmental security. A concept that have made way on to the international arena since the end of the Cold War, and have become of more importance since the 1990’s. The discussion regarding man-made environmental change and its possible impacts on the world is very topical; especially with the Nobel Peace Prize winners in 2007 the Intergovernmental panel on climate change (IPCC) and Al Gore.The concept of environmental security is examined through a conceptual investigating study. The reason for this type of study is due to the complexity of the concept and a hope to find a ‘best’ definition to it. A conceptual investigating study is said to help create order in an existing discussion of a social problem, hence the reason for it in this thesis. The outcome of this thesis is that it is near impossible to find a ‘best’ or one definition to the concept of environmental security and that another method to deal with the concept might have presented another result.</p> / <p>Syftet med denna uppsats är att undersöka konceptet environmental security. Detta koncept har gjort sin väg till ett internationellt erkännande sedan Kalla kriget, och har sedan 1990-talet blivit allt mer aktuellt. Diskussionen gällande människans inverkan på klimatförändringarna och klimathotet är ständigt aktuellt, i synnerhet med tanke på vinnarna av Nobels Freds Pris 2007, med Al Gore i spetsen.Konceptet environmental security är i denna uppsats undersökt genom en begreppsutredande studie. Anledningen till denna typ av studie är att konceptet är såpass komplext men även baserat på hoppet av att hitta en ’bästa’ möjliga definition. Begreppsutredande studier sägs kunna skapa ordning i en existerande diskussion vilket kan ses som den främsta anledningen valet av den i denna uppsats.Resultatet av studien och denna uppsats är att det är i stort sett omöjligt att etablera en bästa definition av begreppet environmental security, samt att en annan metod förmodligen hade presenterat ett annat resultat.</p>

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Pathology. Title from title-page of electronic thesis. Bibliography: leaves 105-117.

The degradation of amorphous and orientated PET is investigated by several analytical methods. In this study, samples of both amorphous and orientated PET material were exposed to wet and dry soil, various humidities and temperature as well as UV irradiation. Results of accelerated ageing studies indicate that the amorphous sheet and biaxially orientated bottles degrade mainly due to de-esterification and oxidative chain scission due to their low crystallinity. At high temperatures (70-90) breakdown, as characterisedb y viscosity and chain scission measurements,is indicative of significant polymer deterioration. Breakdown is enhanced by increasing temperature, increasing relative humidity and UV irradiation. In this regard the polyester bottles are more stable than sheet due to a greater degree of orientation and hence higher degree of crystallinity. However, the rate of degradation is also a function of the surrounding environment. During the course of degradation, an increase in crystallinity was observed for both sheet and bottles. The rate of increase in crystallinity is initially rapid and is associated with plasticization by moisture and subsequent annealing. The dry conditions and UV irradiation cause negligible increase in crystallinity . An increase in the number of end groups was observed which is due to chain scission. Whilst the carboxyl and hydroxyl end groups were increased at the same rate asthermally degraded samples, the increase of carboxyl end groups for UV degraded samples was significantly higher than hydroxyl end groups. This increase is initially sharp and then more gradual with almost the same rate as hydroxyl end groups. A higher level of carboxyl end groups is due to the release of carbon dioxide and carbon monoxide mainly on the surface of the polymer. In this work two methods were used to introduce stability to the polymer. The first was preconditioning the polymer in an inert atmosphere for 48 hours at 600C which had a better effect for bottles This stabilizing effect was observed for both thermal degradation and UV irradiation of polyester materials. The second method was stabilizing polyester against UV irradiation by the incorporation of naphthalenea nd benzophenoned erivatives to the structure of the polyester. In this case the dihydroxybenzophenone showed the greatest stabilizing effect. Hydroperoxide formation during hydrolytic degradation is found to be both temperature and humidity dependent and appears to play a secondary role in thermal oxidation.

This thesis reports the systematic approaches to overcome the key drawbacks of the pure PHBV, namely low crystallisation rate, tensile strength, ductility, melt viscosity, thermal stability and high materials cost. The physical, mechanical, thermal, and rheological properties of the pure PHBV were studied systematically first to lay a solid foundation for formulation development. The influence of blending with other biopolymers, inclusion of filler, and chain extender additives in terms of mechanical properties, rheology, thermal decomposition and crystallization kinetics were then followed. Creating lightweight structures by foaming is considered to be one of the effective ways to reduce material consumption, hence the reduction of density and morphology of PHBV-based foams using extrusion foaming technique were studied comprehensively in terms of extrusion conditions (temperature profiles, screw speed and material feeding rate) and the blowing agent content. The material cost reduction was achieved by adding low-cost filler (e.g. CaCO3) and reduction of density by foaming. The thermal instability was enhanced by incorporation of chain extender (e.g. Joncryl) and blending with a high thermal stability biopolymer (e.g. PBAT). The polymer blend also improved the ductility. Adding nucleation agent enhanced the crystallization rate to reduce stickiness of extruded sheet. The final formulation (PHBV/PBAT/CaCO3 composite) was successfully extruded into high quality sheet and thermoformed to produce prototype trays in an industrial scale trial. The effect of the extrusion conditions (temperature profiles, screw speed and material feeding rate) and the blowing agent content are correlated to the density reduction of the foams. 61 and 47 % density reduction were achieved for the commercial PHBV and the PHBV/PBAT/CaCO3 composite respectively and there exists further scope for more expansion if multiple variable optimisation of the conditions are carried out.

Genes involved in purine degradation in Sinorhizobium meliloti to date remain largely uncharacterized. Analysis of the bdhAxdhA2xdhB2 operon established a link between the degradation of purines and the carbon storage compound poly-3-hydroxybutyrate (PHB). This operon contains genes (xdhA2xdhB2) that encode xanthine oxidase / xanthine dehy- drogenase, an enzyme involved in the conversion of hypoxanthine and xanthine to uric acid. The bdhA gene located in the same operon encodes 3-hydroxybutyrate dehydrogenase, an enzyme responsible for catalyzing the second step in PHB degradation. This linkage be- tween the degradation of PHB (a carbon source) and purines (a nitrogen source) suggests a possible means by which Sinorhizobium meliloti obtains sufficient carbon and nitrogen to allow it to successfully colonize a host plant. Purine degradation genes in S. meliloti have also been studied by the phenotypic char- acterization of Tn5 mutants unable to utilize hypoxanthine. Mutations resulting in these phenotypes were found in three different genes, SMc03849 (ccmC), a cytochrome c bio- genesis mutant, SMb20684, a gene coding for a hypothetical protein possibly involved in the utilization of glyoxylate and SMb2192, a gene coding for a membrane spanning protein possibly involved in purine transport. In this study we further characterized these mutants by examining their ability to establish a symbiosis with Medicago sativa (alfalfa) and to fix atmospheric nitrogen. It was demonstrated that in the case of all the mutant strains there was a competitive deficiency in terms of gaining entry to root nodules relative to the wild-type strain. It was shown that this deficiency occurred even in strains capable of fixing atmospheric nitrogen suggesting that the inability to utilize hypoxanthine impairs the ability of S. meliloti to colonize the host plant. Of all of these genes studied thus far only one (SMb21292) is located in the region of the genome containing the greatest number of genes potentially involved in purine degra- dation. In this study we used transcriptional fusions to confirm the activation of genes in this genomic region when grown in media containing purines as carbon and nitrogen sources. These genes include xdhA1, SMb21284 and guaD1. Genes from the genome re- gion containing the mixed function operon including xdhA2 and guaD2 were also studied. In addition we were able to demonstrate the requirement of xdhC in producing a func- tional oxidase / xanthine dehydrogenase as well as the ability to grow on hypoxanthine or xanthine as a carbon and nitrogen source. This work was also able to demonstrate the critical nature of the LysR transcription regulator (SMb21291) in purine degradation in S. meliloti. Mutating this gene resulted in an inability to grow on hypoxanthine or xanthine as well as an alteration in levels of xanthine oxidase / xanthine dehydrogenase activity. By transducing the gene fusions into the LysR mutant background it was demonstrated that the protein coded for by SMb21291 acts to regulate or influence the expression of genes involved in the purine degradation cycle such as SMb21284 and xdhA1. In addition we were able to characterize strains with mutations in purine degradation genes in terms of their growth on different purines.

DAPK-1 is calcium-calmodulin regulated protein kinase involved in multiple cellular pathways including apoptosis, autophagy, cell survival and motility. The cytokine TNF-α has been reported to induce the degradation of DAPK-1. Here I identified the protease cathepsin B as a novel binding partner of DAPK-1 that protects DAPK-1 from TNF-α induced degradation. Using deletion mutants of DAPK-1, I mapped the cathepsin B binding domain on DAPK-1 to amino acids 836-947. Overexpression of this mini-protein DAPK-1(836-947) facilitated degradation of full-length DAPK-1 and apoptosis induced by TNFR-1. Moreover, siRNA mediated knock-down of DAPK-1 enhanced TNF-α induced apoptosis, confirming the role of DAPK-1 as a survival factor in the TNF-α signalling pathway. In addition, a splice variant of DAPK-1, which I have called s-DAPK-1, was discovered. s-DAPK-1 shares part of DAPK-1’s ankyrin repeats region and cytoskeletal binding domain, and possesses an unique tail region, which contains a cleavage site at its first two amino acids. Unlike DAPK-1, s-DAPK-1 does not contribute to apoptosis induced by high level of MEK/ERK signalling, but it does mimic DAPK-1’s function to induce membrane blebbing. The proteolytically processed form of s-DAPK-1 is more active in the induction of membrane blebbing, which may be due to its higher stability compared to that of full-length s-DAPK-1, suggesting that the tail region can control s-DAPK-1 stability and activity. Co-transfection of s-DAPK-1 and DAPK-1 leads to reduction in DAPK-1 expression level, suggesting a role for s-DAPK-1 to regulate DAPK-1 stability. The kinase domain of DAPK-1 is the region required for s-DAPK-1 to promote DAPK-1 degradation. Surprisingly, s-DAPK-1 does not bind directly to DAPK-1, suggesting that the interaction is indirect and mediated by as yet unidentified accessory proteins. Finally, the experiments with proteasome and lysosome inhibitors indicated that s-DAPK-1 induces DAPK-1 degradation via both lysosome and proteasome pathways.

The chlorophyll degradation pathway is central to a number of plant processes including senescence and fruit ripening. However, the regulation of the chlorophyll degradation pathway enzymes is not well understood. The aim of this thesis was to elucidate the genetic mechanisms that control changes in pigment composition leading to fruit flesh yellowing in kiwifruit. Actinidia deliciosa and A. chinensis fruit, which are green and yellow, respectively, provide an opportunity to study the regulation of chlorophyll levels. The expression of genes that code for enzymes of the chlorophyll and cytokinin metabolic pathways was measured using qRT-PCR. Candidates for chlorophyll degradation regulatory points were then characterised for functionality by transient transformation in N. benthamiana. The endogenous cytokinin levels were measured in kiwifruit and transient activation assays were carried out with the promoters of key candidate genes. Overall, expression of the chlorophyll degradation genes was elevated in yellow fruit and expression of biosynthetic genes was higher in green fruit. The chlorophyll degradation-associated protein, STAY-GREEN2 (SGR2), was more highly expressed in yellow fruit, and transient over-expression of SGR was sufficient to drive chlorophyll degradation. Expression of isopentenyl transferase (IPT), the rate-limiting step for cytokinin biosynthesis, showed an increase towards maturity in green fruit, but not in yellow fruit. However, both fruit had similar high levels of cytokinin nucleotides and free bases. A gene coding for O-glucosylation was also highly expressed in green fruit. Green fruit contained higher levels of cytokinin O-glucosides and ribosides towards maturity, suggesting differences in cytokinin signalling, which could lead to regulation of chlorophyll levels via activation of the SGR promoter by transcription factors. It is likely that the chlorophyll degradation pathway and cytokinin metabolism are linked. The differential expression of cytokinin response regulators could lead to differential regulation of cytokinin levels in the fruit of the two species, and possibly differential regulation of the chlorophyll degradation pathway. Progress towards elucidation of the control of chlorophyll levels provides knowledge of this key process in kiwifruit and potentially gene-based markers for breeding new kiwifruit cultivars.