Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 209-228). Also available via the World Wide Web.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Soil pollution is one of the problems that obstruct sustainable development in the affected regions, posing a threat to the local environment, ecosystems and human wellbeing. Phytoremediation is one of the techniques used to clean polluted soils. It relies on the ability of some plants to absorb or stabilize certain substances from soil, including organic and inorganic pollutants. Amaranth was chosen as a potential candidate for the proposed phytoremediation project in Chinandega region, Nicaragua, an area that was heavily used for cotton production in the last century, and is now characterised as having high levels of soil pollution, Cd being one of the most common one. The aspects such as opportunities and limitations for the designing of such a project, as well as its contribution to the sustainable development of the region were examined in this thesis. To further support the investigation, the laboratory experiment was performed to study the uptake rate of Cd by amaranth in a greenhouse conditions. The results of the study show that the main opportunities for the design of this project would be the possibility of combining the cleaning of soil with co-benefits such as producing food and energy, as well as additional removal of organic pollutants. The main limitations would be the lack of initial data about the pollution, and possible economic losses due to inability of using amaranth for food. The implementation of this project in real life would mean a support of sustainable development of the Chinandega region on many levels, including social, environmental and economic benefits. The results of the laboratory pot experiment are yet to be included in the study, as the experiment still continues. / <p>2017-10-30</p>

Soil pollution is one of the problems that obstruct sustainable development in the affected regions, posing a threat to the local environment, ecosystems and human wellbeing. Phytoremediation is one of the techniques used to clean polluted soils. It relies on the ability of some plants to absorb or stabilize certain substances from soil, including organic and inorganic pollutants. Amaranth was chosen as a potential candidate for the proposed phytoremediation project in Chinandega region, Nicaragua, an area that was heavily used for cotton production in the last century, and is now characterised as having high levels of soil pollution, Cd being one of the most common one. The aspects such as opportunities and limitations for the designing of such a project, as well as its contribution to the sustainable development of the region were examined in this thesis. To further support the investigation, the laboratory experiment was performed to study the uptake rate of Cd by amaranth in a greenhouse conditions. The results of the study show that the main opportunities for the design of this project would be the possibility of combining the cleaning of soil with co-benefits such as producing food and energy, as well as additional removal of organic pollutants. The main limitations would be the lack of initial data about the pollution, and possible economic losses due to inability of using amaranth for food. The implementation of this project in real life would mean a support of sustainable development of the Chinandega region on many levels, including social, environmental and economic benefits. The results of the laboratory pot experiment are yet to be included in the study, as the experiment still continues. / <p>20171030</p>

Accumulation of a given metal in plants depends on a delicate and precise balance of various biological processes. Some plants have developed strategies that allow them to tolerate heavy metals in extreme conditions without suffering toxicity. This research focuses on the characterization of two metal transporters, a member of the P1B-type (ATPase) transporter family (HMA3) and a member the Natural Resistance Associated Macrophage Protein (NRAMP) Nramp1 family. These transporters have proposed roles in ion homeostasis and mineral nutrition. The work here sought to determine if these transporters might have characteristics that suggest a role in heavy metal transport and tolerance in metal hyperaccumulating plants. These proteins are very well conserved among different taxa. Nonetheless, as little as a single amino acid change has the potential to modify their capacity to take up non essential metals such as Cd, or Pb, and/or increase affinity for other mineral nutrients. These transporters were cloned from a non-accumulator (Arabidopsis thaliana L) and two ecotypes (Prayon and Ganges) of the hyperaccumulator Noccaea caerulescens (formerly= Thlaspi caerulescens). The full cDNA of an ortholog of either Nramp1 or HMA3 was expressed in yeast in order to provide a heterologous model to elucidate how polymorphisms between the orthologs might translate into functional differences between the protein sequences. A comparison of the HMA3 sequences to each other, or the Nramp1 sequences to each other, demonstrated that major motifs and domains in each protein were highly conserved but that there were numerous single amino acid polymorphisms. Few of these polymorphisms corresponded to positions in a protein that are known to be critical for transporter function. However, metal accumulation, tolerance and cell growth assays showed that the Nramp1 and HMA3 genes from Arabidopsis encoded proteins with the expected broad selectivity for divalent ion transport. In contrast, the genes from the Thlaspi ecotypes encoded proteins that showed more selectivity for ion transport. The Thlaspi ecotypes showed high selectivity for cadmium but the accumulation of other elements differed between the Thlaspi orthologs. These results suggest that the polymorphisms present in the Thlaspi sequences have produced differences in the transport characteristics of both the HMA3 and the Nramp1 transporters.

Research on the chronic effects of toxic chemicals on individuals, populations, communities, and ecosystems is imperative to regulate pollutants and preserve threatened species and habitats. I designed a two-pronged study to investigate the effects of heavy metal contaminants on small mammal populations, communities and body condition. To compare population and community metrics, I conducted a year-long mark-and-release study from over 5,400 trap nights on a contaminated and reference site within Crab Orchard National Wildlife Refuge, a Superfund site. During the second phase, I compared contaminant residues to body condition in 29 white-footed mice (Peromyscus leucopus) and 21 southern short-tailed shrews (Blarina carolinensis) from the Refuge and from three reference sites. Body weight, age structure, trapping success or species diversity did not differ between sites. Mice from the contaminated site were more abundant with lower reproduction (as number of juveniles per adult female). Cadmium in both livers and kidneys of mice and shrews was significantly greater on the contaminated site. Elevated renal cadmium in mice (96 ± 79 mg/kg dry weight) and shrews (242 ± 166 mg/kg dry weight) from the contaminated site could likely impair physiologic functions with long-term effects. For white-footed mice, increasing renal copper, lead, and nickel were good predictors of low ash, water, and protein but did not correlate significantly with crude lipid content. In shrews, however, metals either showed no relationship or, in the case of renal cadmium and copper were positively related to body condition as increased protein content. Simply comparing animals from reference versus contaminated sites provided few insights into overall community structure or population dynamics of white-footed mice. While metals explained as much as 40% of body condition (ash) in mice, findings in both species are counter-intuitive or refute predictions. Future studies should include manipulative field experiments that pair higher-resolution, biologic responses such as histologic and biomarker assays with population and community dynamics.

No description available.

Cadmium electroplating is widely used in the aerospace industry for the corrosion protection of aircraft components like fasteners manufactured from non corrosion resisting high strength steels. However, environmental and safety concerns over the high toxicity of cadmium and its compounds have led to the investigation of suitable replacements. Alternatives to cadmium should offer effective corrosion protection and have no detrimental effects on the steel substrate. Hydrogen is known to be absorbed during processes like electroplating, thus causing hydrogen embrittlement on high strength steel fasteners. Another source of hydrogen is the water reduction occuring in parallel with the corrosion of the coating, and thus causing re–embrittlement of the steel substrate. This study has investigated the effect of the application of two aluminium–based coatings, SermeTel CR984–LT and Galvano–Aluminium Alcotec, on the hydrogen re–embrittlement of high strength steels used for aerospace applications. Slow strain rate testing has been performed to study the effect of hydrogen on the re–embrittlement of the steel substrate as a result of the corrosion of the aluminium–based coatings in a variety of environments, such as NaCl solution, salt spray and marine atmosphere. Permeation measurements have been used to measure hydrogen uptake by unplated steel membranes potentiostatically charged at the potentials of the aluminium–based coatings, so as to simulate the amount of absorbed hydrogen due to their corrosion. Corrosion tests have been utilised to evaluate the performance of SermeTel CR984–LT and Galvano–Aluminium Alcotec.

Made available in DSpace on 2014-06-11T19:23:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-08-26Bitstream added on 2014-06-13T20:10:23Z : No. of bitstreams: 1 tercariol_sg_me_botib.pdf: 134343 bytes, checksum: 2dc741989d9402537e681856cfd31580 (MD5) / Universidade Estadual Paulista (UNESP) / O objetivo do presente trabalho foi avaliar a agressividade de ratos expostos concomitantemente ao cádmio (Cd) e ao estresse por imobilização (EI). Ratos Wistar, machos, provenientes do Biotério Central da Unesp, foram divididos em 2 grupos experimentais: A- animais intrusos (sem tratamento) e B- animais residentes, os quais receberam um dos seguintes tratamentos: acetato de sódio (controle); acetato de cádmio (solução a 50 ppm de Cd na água de beber); submetidos ao estresse por imobilização (30 minutos, 3 vezes ao dia, 5 dias por semana, durante 4 semanas); expostos ao Cd e concomitantemente submetidos ao estresse por imobilização. O comportamento de agressividade dos animais residentes foi avaliado ao final da última semana do experimento, baseando-se no paradigma do animal intruso/residente, segundo os seguintes parâmetros: número total de ataques (NTA), tempo de latência para a 1º mordida (TLM), tempo total de manifestações de ataques (TTMA) e escore de agressão composta (EAC). Após a avaliação do comportamento de agressividade, o sangue e o cérebro dos animais foram coletados para dosagem de Cd por espectrometria de absorção atômica. O nível de cádmio no sangue não se alterou, mas no cérebro foi aumentado. Observou-se que exposição ao Cd ou estresse por imobilização sozinhos, não modificaram o NTA, TLM, TTMA ou EAC, porém, exposição ao Cd e EI concomitantemente aumentou significantemente o NTA, TTMA e o EAC. Esses resultados sugerem que exposição dos ratos à baixa dose de Cd associado ao estresse por imobilização pode causar interação e provocar aumento da agressividade dos animais. Um possível papel da serotonina (5-HT) e nível aumentado de cádmio no cérebro, como mecanismos responsáveis pela agressividade anormal observada, é discutido. / The aim of this study was to assess the aggressiveness in rats concomitantly exposed to cadmium (Cd) and stress by immobilization (EI). Male Wistar rats, 70 days old, from the Biotério Central – UNESP, Botucatu - SP, were allocated into 2 experimental groups: A-intruder animals (without treatment) and B-resident animals, which received one of the following treatments: sodium acetate (control); Cadmium acetate (50 ppm Cd in drinking water); stress by immobilization (30 min, three times per day, five days per week, during four weeks); Cd exposure and concomitant stress by immobilization. The aggressive behavior of resident rats was evaluated at the end of the last experimental week based on the intruder/resident animal paradigm, according to the following parameters: total number of attacks (TNA), latent time for the first bite (LTB), total time of attack manifestations (TTAM), and composed aggression score (CAS). After aggressive behavior assessement, blood and brains were collected to determine Cd through atomic absorption spectrometry. Cd level was not altered in the blood but increased in the brain. Cd exposure or EI, alone, did not modify TNA, LTB, TTAM or CAS but Cd exposure and EI, concomitantly, increased significantly TNA, TTAM and CAS. These results suggest that rat exposure to low Cd level associated with stress by immobilization may lead to interaction with consequent increased animal aggressiveness. A possible paper of serotonin (5-HT) and increased brain Cd levels as responsible mechanisms by the observed abnormal aggressiveness is discussed.