Aim of the present work was to explore the possibility of improving strength of cast Mg by alloying additions, viz., Si and Zn+Al. All the alloys were produced by squeeze casting technique using squeeze pressure of 12MPa and their microstructure, tensile and corrosion properties were studied. Mg-Si system was chosen because the intermetallic compound Mg2Si possesses many desirable properties, such as, low density, high hardness, high melting point. Hence, there is scope for improving the strength of Mg by dispersion of primary Mg2Si particles. Addition of Si to Mg resulted in the formation of �-Mg, particles of primary Mg2Si and eutectic as microstructural constituents. The morphology of primary Mg2Si changed from polyhedral shaped particles to dendrites as Si content was increased from 3.57 to 5.5 wt%. Volume fraction of primary Mg2Si increased with increase in Si content. Particle size of primary Mg2Si also increased with increase in silicon content but at the same time it was found to be dependent on melt temperature, i.e., a lower particle size was obtained at higher melt temperatures. Addition of Al and Sr was made to Mg-2Si alloy in order to further increase the strength by solid solution strengthening and refinement/modification of primary Mg2Si particles/eutectic. Addition of 1.2 wt% Al to Mg-2Si alloy resulted in irregular type of morphology of Mg2Si particles and increased particle size. Addition of 0.2 wt% SrtoMg-2Si-1.2Al alloy resulted in slight refinement of primary Mg2Si particles and modification of eutectic. Addition of 0.4 wt% Sr resulted in both refinement and restoration of morphology of Mg2Si particles from irregular to polyhedral shape. This was accompanied by destruction of eutectic, and rods containing Mg, Si, Al and Sr were observed. The addition of 1.33 wt%Si to Mg resulted in improvement in 0.2%PS by about 80 MPa,UTS by about 40MPa and these values did not change much till the addition of 3.57 wt% Si. A drop in the strength values was observed at Si content of 5.5 wt%,where transition in morphology of primary Mg2Si occurred from polyhedral to dendrite. Addition of Si resulted in reduction in % elongation by about 2%. The addition of Al and Sr did not change the tensile properties of binary Mg-2Si alloy much. It was concluded that the volume fraction and size of primary Mg2Siparticles obtained with Si addition up to 3.57 wt% did not contribute much to strength and the strengthening mainly came from the eutectic present in the matrix. As Si content was increased to 5.5 wt% in order to increase the volume fraction of primary Mg2Si particles, the morphology of Mg2Si changed to dendritic type resulting in reduction in strength. Thus, the maximum increase in strength is achieved at near eutectic composition,i.e.,intheMg-1.33Sialloy,andfurtherincreaseinstrengthdoesnotseem to be feasible with this alloy system. The ductility of all the Mg-Si based alloys was also low, i.e, 0.5% elongation to fracture or less. Regarding the corrosion behaviour, the addition of Si to Mg deteriorated the corrosion resistance and the addition of Al and Sr further worsened it. Since further improvement in tensile properties did not seem feasible with Mg-Si alloy system, the focus was shifted to Mg-Zn-Al alloy system. There is scope for improvement in strength in Mg-Zn-Al alloy system by solid solution strengthening, grain refinement and precipitation hardening. It was observed that the addition of Zn and Al resulted in microstructure containing α-Mg grains and secondary phase at the grain boundary. XRD analysis showed the secondary phase to be Al5Mg11Zn4 but EDS analysis did not match with this composition. Therefore, the nature of this phase remains uncertain. Addition of 6 wt% Zn and 1 wt% Al resulted in improvement in strength as well as ductility: 0.2%PS improved by about 70 MPa, UTS by about 100 MPa and % elongation by about 7%. Addition of small amounts of Caresultedinrefinementofmicrostructurecausingimprovementinstrengthwithout much decrease in % elongation. Increase in Al content from 1 to 4 wt% resulted in increase in 0.2%PS but UTS slightly decreased, as % elongation reduced. Alloys subjected to T6 heat treatment showed improvement in strength but slight reduction in % elongation. ZA64 alloy in T6 condition gave 130 MPa 0.2%PS, 225 MPa UTS and 4.9% elongation, which are much higher tensile properties as compared Mg-Si alloys. All the three mechanisms mentioned above contribute to the strengthening. There is scope for further improvement in strength by employing a more suitable heat treatment. Regarding corrosion behaviour, addition of 6 wt% Zn and 1 wt% of Al to Mg did not deteriorate its corrosion resistance much. Addition of small amounts of Ca was found to be beneficial for corrosion resistance, whereas an increase in Al content lowered the corrosion resistance. Heat treatment also reduced the corrosion resistance.

Orientadora: Profa. Dra. Giselle Cerchiaro / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Biossistemas, Santo André, 2018. / Em doencas neurodegenerativas amiloidais o estresse oxidativo tem um papel importante juntamente com a proteina ¿À-amiloide (A¿À), associada a formacao de placas senis na Doenca de Alzheimer. Tais condicoes demonstraram desbalanco de metais, como cobre e zinco, tanto na concentracao celular e quanto nos processos antioxidantes. A Cu,Zn-Superoxido Dismutase (SOD1), em condicoes neurodegenerativas, pode demonstrar alteracoes estruturais e funcionais, tendo menor afinidade pelo cobre e pelo zinco. Diante destas condicoes, o objetivo principal desta tese foi em condicoes oxidativa (H2O2) e neurodegenerativa (A¿À1-42) avaliar os danos a biomoleculas, concentracao metais e a influencia da enzima SOD1 em linhagens de celulas neuronais (NSC-34 e mHippoE2). Diferentes respostas quanto a sensibilidade das linhagens neuronais foi observada durante as condicoes oxidativas e neurodegenerativa. Quanto os danos ao DNA a linhagem NSC-34 demonstrou maior sensibilidade a condicao oxidativa, com aumento de danos ao DNA, lesoes oxidativas em bases nitrogenadas que indicaram a presenca de lesoes tipo 8-oxo-G, corroborando com anormalidades nucleares e inibicao do processo de divisao celular. Nesta mesma linhagem quantidades aumentadas de Cu foram observadas, juntamente com a presenca da enzima SOD1 a nivel citoplasmatico e nuclear na condicao oxidativa (H2O2), alem de resultados significantes para danos permanentes ao DNA (anormalidades nucleares e quebras cromossomicas). A linhagem mHippoE2 apresentou aumentos significativos mediante a condicao oxidativa e neurodegenerativa, como oxidacao de proteinas e lipidios, demonstrando tambem alteracoes morfologicas citoplasmaticas. O tratamento com A¿À1-42 demonstrou aumento de danos ao DNA, lesoes oxidativas 8-oxo-G e tambem em bases purinicas. Podemos observar nesta mesma linhagem a forte influencia do Zn na condicao neurodegenerativa, atividade da SOD1 em ambas condicoes e tambem danos permanentes ao DNA mediante condicao neurodegenerativa. Dentre os resultados obtidos salientamos a relevancia dos achados na condicao neurodegenerativa ocasionada pelo peptideo A¿À1-42 nos ensaios para avaliacao genotoxica e mutagenica. Tal condicao demonstrou a presenca de danos importantes a bases nitrogenadas, tanto purinicas quando pirimidinicas, apontando tambem para possiveis efeitos mutagenicos detectados pelos eventos de quebras cromossomicas associados as anormalidades nucleares, bem como a presenca da enzima SOD1 no nucleo das celulas. / In neurodegenerative diseases, oxidative stress plays an important role associated with â-amyloid protein (Aâ), associated with the formation of amyloid plaques in Alzheimer's Disease (AD). In AD condition it has been demonstrated an imbalance of essential metals, such as copper and zinc, their cellular concentration and antioxidant processes alterations. The antioxidant enzyme Cu, Zn-Superoxide Dismutase (SOD1), under neurodegenerative conditions has structural and functional changes, such as lower affinity for copper and zinc. According to these conditions, the main objective of this thesis was to investigate how the oxidative (H2O2) and neurodegenerative (Aâ1-42) conditions cause biomolecules damage, metal alteration and SOD1 location in neuronal cell lines (NSC-34 and mHippoE2). Different responses in neuronal cell lines were observed during the conditions evaluated. For DNA damage, the NSC-34 cells demonstrated greater sensitivity to the oxidative condition, with increased DNA damage, oxidative lesions on nitrogenized bases indicating the presence of 8-oxo-G type lesions. In this same cell line we observed an increase of Cu amount, together with the presence of the SOD1 enzyme at the cytoplasmic and nuclear level in the oxidative condition (H2O2). The mHippoE2 cell line presented increased protein oxidation through the oxidative and neurodegenerative condition. Treatment with Aâ1-42 demonstrated increased DNA damage in this cell, 8-oxo-G oxidative lesions and also purine bases. We observed, in this same cell line, the strong influence of Zn on the neurodegenerative condition, SOD1 activity in both conditions and it was observed permanent damages to DNA in the neurodegenerative condition. Among the results, we highlight the relevance of the findings in the neurodegenerative condition caused by the Aâ1-42 peptide in the genotoxic and mutagenic evaluation trials. This condition demonstrated the presence of important damages to nitrogenated bases, both purine and pyrimidine, also pointing to possible mutagenic effects detected by the events of chromosomal breaks associated with nuclear abnormalities, as well as the translocation of the SOD1 enzyme to nuclei.

Subject of this diploma thesis is analysis of selected heavy metals in soils which are exposed to long-time cause of contaminants from metallurgical industry in localities Třinec and Ostrava. For assessment of the contamination, indexes for evaluation of soils were chosen. Those indexes are focusing mainly on rate of enrichment of the soils by selected heavy metals and resulting ecological and possibly health risk for human organism. Within every location, 26 samples were extracted, while every sample extract location, were selected to map the level of pollution around metallurgical plants in the most complex way. The analysis of the samples was done by techniques F-AAS and AMA 254 and established metals were mercury, lead, copper, chrome, nickel, manganese and zinc.

Die vorliegende Arbeit beschäftigt sich im ersten Teil mit einer Methodenentwicklung zur korrosionsfreien Ermittlung der elektromotorischen Kraft von zinkbasierten intermetallischen Verbindungen bei Raumtemperatur. Die durchgeführten Messungen bezüglich der elektrochemischen Potentiale von Verbindungen der binären intermetallischen Phasen Cu5Zn8, ZnPd und ZnPt mit jeweils verschiedenen elementaren Zusammensetzungen dienen als Basis zur Ermittlung der jeweiligen intrinsischen Aktivitäten der Einzelkomponente Zink. Messungen an der Referenzphase Cu5Zn8 wurden dabei zur Verifizierung der entwickelten Messmethodik durchgeführt. Die Untersuchungen an ZnPd- und ZnPt-Verbindungen liefern erstmalig thermodynamische Daten dieser Phasen bei Raumtemperatur. Der zweite Teil dieser Arbeit beschäftigt sich mit der katalytischen Untersuchung von intermetallischen äquimolaren ZnPd-Elektroden hinsichtlich der elektrolytischen Wasserstoffentwicklung. Die durchgeführten Experimente legen den Schluss nahe, dass die katalytische Aktivität der intermetallischen Elektroden durch eine gezielte anodische Vorbehandlung signifikant gesteigert werden kann. Ex situ Charakterisierungen geben Grund zu der Annahme, dass die gesteigerte katalytische Aktivität durch die simultane Präsenz von oxidischer und metallischer beziehungsweise intermetallischer Spezies hervorgerufen wird.

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<p> G93A SODI mice (G93A mice) are a transgenic model over-expressing a mutant human Cu/Zn-SOD gene, and are a model for amyotrophic lateral sclerosis (ALS), a predominantly motor neurodegenerative disease. Hippocampal neurogenesis in the subgranular zone (SGZ) of dentate gyms (DG) occurs throughout the life. It is regulated by many pathological and physiological processes. There is controversy with respect to the basal level of hippocampal neurogenesis and its response to exercise in neurodegenerative diseases and their mouse models. Little information regarding hippocampal neurogenesis is available in G93A mice. The present study was designed to study the impact of treadmill exercise and sex differences on hippocampal neurogenesis in this model. In addition, potential molecular mechanisms regulating hippocampal neurogenesis including growth factors (BDNF and IGFl) and oxidative stress (SOD2, catalase, 8-0Hdg, and 3-NT) were also addressed in the study. Bromodeoxyuridine (BrdU) was used to label newly generated cells. G93A and wild type (WT) mice were subjected to treadmill exercise (EX) or a sedentary (SEO) lifestyle. Immunohistochemistry was used to detect BrdU labeled newly proliferating cells, surviving cells, and their phenotype, as well as for determination of oxidative stress. BDNF and IGFl mRNA expression was assessed by in situ hybridization. Results showed that (1) G93A mice had an elevated basal level of hippocampal neurogenesis for both cell survival and neuronal differentiation, a growth factor (BDNF mRNA), and an oxidative stress marker (NT), as compared to wild type sedentary mice. (2) Treadmill running did not show any further effect on hippocampal neurogenesis, growth factors, oxidative stress, and antioxidant enzymes in G93A mice, while treadmill running promoted hippocampal neurogenes1s and expression of the growth factor (BDNF mRNA), and lowered oxidative stress (8-0Hdg) in WT mice. (3) There also were sex differences in hippocampal neurogenesis in G93A mice, whereby male G93A mice had a significant higher level of cell proliferation but a lower level of survival than female G93A mice. (4) The DG BDNF mRNA was associated with cell survival and neuronal differentiation in sedentary G93A mice, suggesting that BDNF is associated with a higher basal level of hippocampal neurogenesis in G93A mice. We conclude that G93A mice are more permissive in the context of hippocampal neurogenesis, which is associated with elevated DG BDNF mRNA expression. Running did not have impact on hippocampal neurogenesis and BDNF mRNA expression in G93A mice, probably due to a 'ceiling effect' of the already heightened basal levels of hippocampal neurogenesis and BDNF mRNA in this model. In addition, sex differences also affect hippocampal neurogenes1s, but the further study is needed to clarify the underlying molecular mechanisms. </p> / Thesis / Doctor of Philosophy (PhD)

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