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The main focus of this thesis is the characterization of defects and microstructure in high-energy ball milled magnesium hydride powder and magnesium-based multilayered composites. Enhancement in kinetics of hydrogen cycling in magnesium can be achieved by applying severe plastic deformation. A literature survey reveals that, due to extreme instability of -MgH2 in transmission electron microscope (TEM), the physical parameters that researchers have studied are limited to particle size and grain size. By utilizing a cryogenic TEM sample holder, we extended the stability time of the hydride phase during TEM characterization. Milling for only 30 minutes resulted in a significant enhancement in desorption kinetics. A subsequent annealing cycle under pressurized hydrogen reverted the kinetics to its initial sluggish state. Cryo-TEM analysis of the milled hydride revealed that mechanical milling induces deformation twinning in the hydride microstructure. Milling did not alter the thermodynamics of desorption. Twins can enhance the kinetics by acting as preferential locations for the heterogeneous nucleation of metallic magnesium. We also looked at the phase transformation characteristics of desorption in MgH2. By using energy-filtered TEM, we investigated the morphology of the phases in a partially desorbed state. Our observations prove that desorption phase transformation in MgH2 is of nucleation and growth type, with a substantial energy barrier for nucleation. This is contrary to the generally assumed core-shell structure in most of the simulation models for this system. We also tested the hydrogen storage cycling behavior of bulk centimeter-scale Mg-Ti and Mg-SS multilayer composites synthesized by accumulative roll-bonding. Addition of either phase (Ti or SS) allows the reversible hydrogen sorption at 350C, whereas identically roll-bonded pure magnesium cannot be absorbed. In the composites the first cycle of absorption (also called activation) kinetics improve with increased number of fold and roll (FR) operations. With increasing FR operations the distribution of the Ti phase is progressively refined, and the shape of the absorption curve no longer remains sigmoidal. Up to a point, increasing the loading amount of the second phase also accelerates the kinetics. Microscopy analysis performed on 1-2 wt.% hydrogen absorbed composites demonstrates that MgH2 formed exclusively on various heterogeneous nucleation sites. During activation, MgH2 nucleation occurred at the Mg-hard phase interfaces. On the subsequent absorption cycles, heterogeneous nucleation primarily occurred in the vicinity of internal free surfaces such as cracks. / Materials Engineering

Diabetes in Indigenous Australians occurs at a younger age and at almost four times the rate of non-Indigenous Australians. While the cause for this health disparity is multi-factorial, recent studies suggest that nutrition, and particularly magnesium intake, may play a role in onset of diabetes and related pathologies. No study has ever examined whether there is any relationship between diabetes and magnesium intake in Indigenous Australians, and the present study therefore sought to establish whether any such interrelationship existed. As part of this study, dietary magnesium intake was estimated in an urban cohort of Aboriginal and Torres Strait Islander subjects and compared to the average Australian dietary intake. An ecological study then explored environmental correlates, and specifically the magnesium level in drinking water, to diabetes mortality. Finally, total and free serum magnesium concentrations were determined to identify any differences in magnesium status between diabetic and non-diabetic Indigenous and non-Indigenous Australians, and also to compare which of the two parameters was a more sensitive measure of magnesium status and diabetic risk. All Aboriginal and Torres Strait Islander people that were recruited for this study were patients of the Townsville Aboriginal and Islander Health Services, Townsville, North Queensland, who presented for health monitoring and subsequently required fasting blood tests as part of that routine care. Additional non-Indigenous people were recruited from five GP practices in the Townsville area. Inclusion criteria included persons over the age of 15 (Tanner Stage 5) who had lived in the Townsville area for at least ten days. Exclusion criteria included chronic diarrhoea, alcoholism or binge drinking in the past two weeks, use of diuretics, consumption of magnesium supplements, reduced renal function (urinary albumin to creatinine ratio exceeding > 2.5 mg/mmol in men and > 3.5 mg/mmol in women), severe mental illness, pregnancy, or breastfeeding. Our results indicated that 60% of the Indigenous people assessed in this study had a dietary intake of magnesium that was below the estimated average magnesium requirement for half the national population. Additionally, the average magnesium intake in Indigenous Australians was significantly less than the intake of non-Indigenous Australians (p<0 .001). A significant negative correlation was found between the incidence of diabetes related mortality and the concentration of magnesium in drinking water in Queensland, confirming previous reports from the USA that drinking water magnesium may be an important factor in development of diabetes. The needs assessment study confirmed that diabetes in both Indigenous and non-Indigenous Australians was associated with reduced levels of total serum magnesium, and more importantly, that total serum magnesium was lower in Indigenous Australians who did not have diabetes compared with their non-Indigenous counterparts (p=<0.001). In the absence of diabetes, the prevalence of hypomagnesaemia was 17.2% for the non-Indigenous but 36.9% for the Indigenous subjects. Finally, the ionic serum magnesium analysis confirmed the results of the total serum magnesium study, and demonstrated that ionic magnesium was strongly correlated to the total magnesium concentration (r: 0.75. p < 0.001), with the relationship being apparent irrespective of either diabetic (r: 0.66 to 0.81. p<0.001) or ethnicity (r = 0.71 to 0.81. p<0.001)." We conclude that although not causal, the evidence suggests that magnesium may be a significant contributing factor to diabetes in Australia, especially for Aboriginal and Torres Strait Islander peoples, and that further investigation of the potential relationship between magnesium and diabetes in the Australian Indigenous populations, and possible corrective interventions, is highly warranted. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1348469 / Thesis (Ph.D.) - University of Adelaide, School of Medical Sciences, 2008

Diabetes in Indigenous Australians occurs at a younger age and at almost four times the rate of non-Indigenous Australians. While the cause for this health disparity is multi-factorial, recent studies suggest that nutrition, and particularly magnesium intake, may play a role in onset of diabetes and related pathologies. No study has ever examined whether there is any relationship between diabetes and magnesium intake in Indigenous Australians, and the present study therefore sought to establish whether any such interrelationship existed. As part of this study, dietary magnesium intake was estimated in an urban cohort of Aboriginal and Torres Strait Islander subjects and compared to the average Australian dietary intake. An ecological study then explored environmental correlates, and specifically the magnesium level in drinking water, to diabetes mortality. Finally, total and free serum magnesium concentrations were determined to identify any differences in magnesium status between diabetic and non-diabetic Indigenous and non-Indigenous Australians, and also to compare which of the two parameters was a more sensitive measure of magnesium status and diabetic risk. All Aboriginal and Torres Strait Islander people that were recruited for this study were patients of the Townsville Aboriginal and Islander Health Services, Townsville, North Queensland, who presented for health monitoring and subsequently required fasting blood tests as part of that routine care. Additional non-Indigenous people were recruited from five GP practices in the Townsville area. Inclusion criteria included persons over the age of 15 (Tanner Stage 5) who had lived in the Townsville area for at least ten days. Exclusion criteria included chronic diarrhoea, alcoholism or binge drinking in the past two weeks, use of diuretics, consumption of magnesium supplements, reduced renal function (urinary albumin to creatinine ratio exceeding > 2.5 mg/mmol in men and > 3.5 mg/mmol in women), severe mental illness, pregnancy, or breastfeeding. Our results indicated that 60% of the Indigenous people assessed in this study had a dietary intake of magnesium that was below the estimated average magnesium requirement for half the national population. Additionally, the average magnesium intake in Indigenous Australians was significantly less than the intake of non-Indigenous Australians (p<0 .001). A significant negative correlation was found between the incidence of diabetes related mortality and the concentration of magnesium in drinking water in Queensland, confirming previous reports from the USA that drinking water magnesium may be an important factor in development of diabetes. The needs assessment study confirmed that diabetes in both Indigenous and non-Indigenous Australians was associated with reduced levels of total serum magnesium, and more importantly, that total serum magnesium was lower in Indigenous Australians who did not have diabetes compared with their non-Indigenous counterparts (p=<0.001). In the absence of diabetes, the prevalence of hypomagnesaemia was 17.2% for the non-Indigenous but 36.9% for the Indigenous subjects. Finally, the ionic serum magnesium analysis confirmed the results of the total serum magnesium study, and demonstrated that ionic magnesium was strongly correlated to the total magnesium concentration (r: 0.75. p < 0.001), with the relationship being apparent irrespective of either diabetic (r: 0.66 to 0.81. p<0.001) or ethnicity (r = 0.71 to 0.81. p<0.001)." We conclude that although not causal, the evidence suggests that magnesium may be a significant contributing factor to diabetes in Australia, especially for Aboriginal and Torres Strait Islander peoples, and that further investigation of the potential relationship between magnesium and diabetes in the Australian Indigenous populations, and possible corrective interventions, is highly warranted. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1348469 / Thesis (Ph.D.) - University of Adelaide, School of Medical Sciences, 2008

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.)--University of Wollongong, 2008. / Typescript. Includes bibliographical references.

Thesis (Ph.D.)--Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 200-212).

Title: Influence of Solid Solution Elements and Precipitate Formation on the Mechanical Behaviour of Magnesium Alloys Author: Mgr. Kseniya ILLKOVÁ Department / Institute: Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague Supervisor of the doctoral thesis: Doc.RNDr.František Chmelík, CSc. Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague Abstract: Mg-1 wt. % Mn alloys containing about 1 wt.% of calcium (MX10), aluminium (AM11), cerium(ME11), yttrium (MW11), neodymium (MN11) and 8 wt.% of aluminium (AM81) were indirectly extruded with two different speeds. The partially recrystallised microstructures obtained in MX10, AM11, ME11 and MW11 after slow extrusion exhibited bimodal grain size distributions. Only in the case of AM81 and MN11 a fully recrystallised microstructure was found, indicating differences in the grain nucleation rate during recrystallisation. In these alloys, the weakest texture and, correspondingly, the lowest asymmetry in mechanical properties were also observed. The acoustic emission technique was used to reveal dislocation or twin controlled deformation in differently textured fractions of the microstructure during tensile and compression testing. A direct correlation between the acoustic...