In this thesis, a synthesis concept has been developed, which uses nitrogen-rich liquid phases for sintering of Ca-α-sialon ceramics. First, keeping the Si/Al ratios constant, the effects of N/O ratio on the properties and microstructure were investigated through a liquid phase sintering process. Second, nitrogen-rich Ca-α-sialon ceramics, with nominal compositions: CaxSi12-2xAl2xN16, x < 2.0, was synthesized and characterized. Third, mechanical and thermal properties of nitrogen-rich Ca-α-sialons were investigated in terms of high temperature deformation resistance,reaction mechanism, phase stability and oxidation resistance, and further correlated to their phase assemblage and microstructure observation. It has been found that increasing the N/O and Ca/Al ratio simultaneously in the materials could result in development of a microstructure with well shaped, high-aspect-ratio Ca-α-sialon grains, and an improvement in both toughness and hardness. For the nitrogen-rich Ca-α-sialon, mono-phasic α-sialon ceramics were obtained for 0.51 ≤ x ≤ 1.32. The obtained Ca-α-sialon ceramics with elongated-grain microstructures show a combination of high hardness and high fracture toughness. Compared with the oxygen-rich Ca-α-sialons, the nitrogen-rich Ca-α-sialons exhibited approximately 150 oC higher deformation onset temperatures and decent properties even after the deformation. The α-sialon phase was first observed at 1400 oC, however the phase pure Ca-α-sialon ceramics couldn’t be obtained until 1800 oC. The nitrogen-rich Ca-α-sialons were thermal stable, no phase transformation observed in the temperatures range1400-1600 oC. In general, mixed α/β-sialon showed better oxidation resistance than pure α-sialon in the low temperature range (1250-1325 oC), while α-sialons with compositions located at α/β-sialon border-line showed significant weight gains over the entire temperature range (1250-1400 oC).

Web applications have come a long way both in terms of adoption to provide information and services and in terms of the technologies to develop them. With the emergence of richer and more advanced technologies such as Ajax, web applications have become more interactive, responsive and user friendly. These applications, often called Rich Internet Applications (RIAs) changed the traditional web applications in two primary ways: Dynamic manipulation of client side state and Asynchronous communication with the server. At the same time, such techniques also introduce new challenges. Among these challenges, an important one is the difficulty of automatically crawling these new applications. Crawling is not only important for indexing the contents but also critical to web application assessment such as testing for security vulnerabilities or accessibility. Traditional crawlers are no longer sufficient for these newer technologies and crawling in RIAs is either inexistent or far from perfect. There is a need for an efficient crawler for web applications developed using these new technologies. Further, as more and more enterprises use these new technologies to provide their services, the requirement for a better crawler becomes inevitable. This thesis studies the problems associated with crawling RIAs. Crawling RIAs is fundamentally more difficult than crawling traditional multi-page web applications. The thesis also presents an efficient RIA crawling strategy and compares it with existing methods.

Pre-eclampsia is a major cause of maternal and perinatal morbidity and mortality worldwide. A predictor of pre-eclampsia would enable intervention, close surveillance and timely delivery, and thereby reduce the negative consequences of the disorder. The overall aim of this thesis was to study potential predictors of pre-eclampsia by biochemical and epidemiological methods. Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2) are regulators of angiogenesis, which is important for placental development. In a prospective and longitudinal study of a low-risk population the Ang-1/Ang-2 ratio was evaluated. The Ang-1/Ang-2 ratio increased during pregnancy in all women but at gestational week 25 and 28 the ratios were significantly lower in women who later developed pre-eclampsia. The relevance of Histidine-rich glycoprotein (HRG), a protein with angiogenic properties, was furthermore evaluated. HRG levels decreased in all women, with significantly lower levels at gestational week 10, 25 and 28 in women who later developed pre-eclampsia. Thus both Ang-1/Ang-2 ratio and HRG may predict pre-eclampsia. To evaluate the predictive value of HRG in combination with uterine artery Doppler early in pregnancy a study was performed in a high-risk population. The results revealed that the combination was better able to predict preterm pre-eclampsia than each marker individually, with a sensitivity of 91% at a specificity of 62%.  A possible association between hyperemesis gravidarum and pre-eclampsia, as well as other placental dysfunctional disorders, was investigated. Hyperemesis gravidarum may be caused by high levels of human chorionic gonadotrophin (hCG) and increased levels of hCG in the second trimester is associated with later development of pre-eclampsia. A cohort of all pregnancies in the Swedish medical birth register between 1997 and 2009 was studied. After adjustment for confounding factors an association between hyperemesis gravidarum in the second trimester and preterm pre-eclampsia, placental abruption and infants born small for gestational age was demonstrated. In conclusion, the ratio of Ang-1/Ang-2 as well as HRG in plasma may be potential predictors of pre-eclampsia. Combination with uterine artery Doppler further increases the predictive value of HRG for preterm pre-eclampsia. Hyperemesis gravidarum in the second trimester may be considered as a clinical risk predictor of pre-eclampsia and other placental dysfunctional disorders.

Roadsides in Sweden offer suitable habitats for species that naturally occur in the old agricultural landscape, a habitat that is less common today. These species are favored by small-scale disturbance such as of mowing which is to some extent applied in roadsides for management of the road surface. The Swedish Transport Administration has worked according to the environmental directives for sustainable populations of threatened species that occur along roadsides. Roadsides with threatened species and species that represent the old agriculture landscape have been located and described. Such roadsides have been named species rich roadsides (artrik vägkant) and can be found in different environments spread across the country. The Swedish Transport Administration has developed recommendations for special management to support species of old agricultural landscape in roadsides. Previous studies have shown a negative development of the species rich roadsides, with reduced numbers of species rich roadsides.  This project has analyzed whether there is a relationship between the management of species rich roadsides and the negative development of species rich roadsides, and also make recommendations for improving management methods needed for improving the development of species rich roadsides. Data have been used from previous inventories of species rich roadsides, the study area restricted to Region Mitt.  The present management of species rich roadsides has a significant negative effect of the development of species rich roadsides. To improve the development of species rich roadsides, management must be adapted to the environment the roadside is located to.

No description available.

No description available.

Thesis (DD(Dogm.)--Universiteit van Pretoria, 2003. / Includes bibliographical references (p. 288-312).

White Island is a highly active volcano with an acidic, S-rich hydrothermal system in the Bay of Plenty, North Island, New Zealand. In this acidic environment a series of subsurface Fe-rich layers are ubiquitous in the crater sediments at shallow depth and are capable of modifying the flow and gas flux dynamics in the system. The mineralogy of the subsurface Fe-rich layer(s) and the processes leading to their formation are unknown. Here the mineralogy and formation of the subsurface Fe-rich layers in relation to the surface and subsurface environment(s) within the Main Crater at White Island are assessed. Based on geochemical analyses, subsurface Fe-rich crusts are composed of a mix of jarosite and goethite, cementing crater fill sediments into cohesive layers. Saturation index (SI) and Eh/pH assessments identify that fluids evolved at White Island are undersaturated with respect to the mineral phases present in the Fe-rich subsurface layers. Formation of the Fe-rich subsurface layers is most likely related to the transition between atmospheric gases and/or meteoric water mixing with hydrothermal fluids. This transition zone creates an environment conducive to forming jarosite and goethite forming in the same layer. Additionally, subsurface sediments including the Fe-rich layers show a consistent organic carbon isotopic signature of -23 ‰. Microscopic investigations confirm diatoms and microbes are present in the subsurface Fe-rich layers. The full extent of microbial activity in relation to the Fe-rich layers at White Island still requires further investigation. Based on chemical extractions for isotopic analyses, Fe-rich layers are shown to preserve δ¹³C signatures indicative of microbial life. Interface zones such as those identified in the hydrothermal environment at White Island can create metal-rich deposits and habitable/preservative microbial environments as well as affecting the macroscopic dynamics of volcanic and epithermal systems.

Li-ion batteries are widely used in electronics and automotives. Despite their success, improvements in cost, safety, cycle life, and energy density are necessary. One way to enhance the energy density is to find advanced cathodes such as Li-rich layered oxides, which are similar to the commonly layered oxide cathodes (e.g., LiCoO2), except there are additional Li ions in the transition-metal layer, due to their higher charge-storage capacity. Another way of advancing is to design new battery chemistries, such as those involving multivalent-ion systems (e.g., Mg2+ and Zn2+) as they could offer higher charge-storage capacities and/or cost advantages. Li-rich layered oxides have a complex first charge-discharge cycle, which affects their other electrochemical properties. Ru doping was expected to improve the performance of Li-rich layered oxides due to its electroactivity and overlap of the Ru4+/5+:4d band with the O2-:2p band, but it unexpectedly decreased the capacity due to the reduction in oxygen loss behavior. Preliminary evidence points to the formation of Ru-Ru dimers, which raises the Ru4+/5+:4d band, as the cause of this behavior. Li-rich layered oxides suffer from declining operating voltage during cycling, and it is a huge challenge to employ them in practical cells. Raising the Ni oxidation state was found to reduce the voltage decay and improve the cyclability; however, it also decreased the discharge capacity. Increasing the Ni oxidation state minimized the formation of Mn3+ ions during discharge and Mn dissolution, which led to the improvements in voltage decay and cyclability. Extraction of lithium from spinel oxides such as LiMn2O4 with acid was found to follow a Mn3+ disproportionation mechanism and depend on the Mn3+ content. Other common dopants like Cr3+, Fe3+, Co3+, or Ni2+/3+ did not disproportionate, and no ion-exchange of Li+ with H+ occurred in the tetrahedral sites of the spinel oxides. Extraction with acid of Mg and Zn from spinel oxides, such as MgMn2O4 and ZnMn2O4, were also found to follow the same mechanism as Li-spinels. The Mg-spinels, however, do experience ion exchange when Mg ions are in the octahedral sites. Chemical extraction of Mg or Zn with an oxidizing agent NO2BF4 in acetonitrile medium, however, failed due to the electrostatic repulsion felt by the migrating divalent ions. In contrast, extraction with acid was successful as Mn dissolution from the lattice opened up favorable pathways for extraction. / text

CueO is a multicopper oxidase and catalyses the four-electron reduction of dioxygen to water and functions to protect Escherichia coli against copper-induced toxicity. The mechanism of oxygen reduction in multicopper oxidases has been well studied, but the key structures of the reaction intermediates are not known. A combination of kinetic measurements, mutagenesis and X-ray crystallographic studies were conducted to entrap and structurally characterize the reaction states in CueO. CueO has a methionine-rich insert and a labile copper binding site, two features found only in multicopper oxidases involved in copper detoxification. The role of these features in CueO activity has been investigated. In a separate study, a simple mathematical model based on infectivity amongst clustered receptors was developed to explain the chemotactic sensitivity, response range and other key features of chemotaxis.This study describes the successful entrapment of three out of four functional states in CueO. The crystal structures of these reaction states are presented. Using single-turnover oxygen reduction kinetics that were measured using a stopped-flow device, the optical absorption features of three different fully oxidized forms of CueO were captured: the native intermediate, the resting oxidized state and another intermediate lying between them. Stopped-flow studies combined with electron transfer kinetic measurements revealed a role of the conserved residue, E506, in either the protonation of the native intermediate or the release of water molecules formed as a product of the reaction.Cu(I) and Ag(I) bound crystal structures of CueO were determined revealing three binding sites along the methionine-rich helix used by both metal ions. The labile, regulatory copper site in CueO was shown to be a Cu(I) susbtrate oxidation site. Ag(I) was shown to be a potent inhibitor of all CueO activities in vitro and copper detoxification by the cue system in vivo. The cus system was discovered to be necessary for removing Ag(I) inhibition of copper detoxification by the cue system. These results provide further insights into the role of CueO in copper detoxification and the effect of silver on the detoxification mechanism.