Tesi sul tema "Manganese"
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1
EMANE, MBA SEVERIN. "Evolution morphogenique et pedogenetique du plateau manganesifere okouma (haut-ogooue, gabon). Consequences sur l'environnement". Université Louis Pasteur (Strasbourg) (1971-2008), 1997. http://www.theses.fr/1997STR1GE03.
Testo completoAbstract (sommario):
Le plateau okouma est situe dans la province du haut-ogooue au gabon, entre 13'10' et 13'15' de longitude est et 1'25' et 1'30' de latitudes sud. Il appartient a une ancienne surface d'aplanissement et renferme des teneurs economiques en manganese. Son etude permet de s'interroger sur les environnements paleoclimatiques depuis l'eocene; de dissocier dans l'evolution morphogenique un faconnement ancien et un plus recent ; de proposer une dynamique de l'evolution actuelle de la morphologie du plateau; de definir les mecanismes mis en jeu au cours de la morphogenese et de la pedogenese et enfin de preciser les consequences sur l'environnement de la morphogenese et de la pedogenese. Les methodes utilisees sont : la granulometrie, la morphoscopie, les limites d'atterberg, les bilans geochimiques. L'evolution du plateau apparait fortement liee aux changements climatiques, a l'erosion des cours d'eau, aux caracteristiques physiques des formations superficielles et a la pedogenese. Ces differents facteurs s'inscrivent dans 5 etapes distincts de l'eocene aux temps presents. Elles sont caracterisees par les alternances de climats a saisons contrastees et de saisons chaudes et humides. Les climats determinent les orientations de la morphogenese fluviatile, de la pedogenese et de l'erosion mecanique. La morphogenese fluviatile est differentielle. Elle depend de la nature geologique des roches, de leur degre de durete et de la consistance des formations superficielle. Les phenomenes pedogenetiques actuelles sont la ferrallitisation (les mineraux neoformes sont la metahalloysite, la kaolinite, la gibbsite, la goethite et l'anatase) et l'appauvrissement en argile. L'erosion mecanique est limitee en surface. Elle affecte plus facilement les formations tendres que les formations dures ou indurees. Les materiaux soustraits sur le plateau okouma, riches en manganese, ont un impact au niveau du sol car il devient acide et riche en mn2+ toxique. Le paysage resultant de la morphogenese et de la pedogenese est constitue par des collines en demi-orangesThe okouma plateau is situated in the haut-ogooue province in gabon, beetween 13'10' and 13'15' of east longitude and 1'25' and 1'30' of south latitude. It is owned at an old planation surface and has economic contents in manganese. Its studie permits to wonder about paleoclimatic environments since the eocene, to separate in the morphogenic evolution an old shaping and another more recent, to porpose a dynamic of the present evolution of the okouma morphology, to define the mechanisms occuring in morphogenesis and pedogenesis and finally to specify environmental consequences of morphogenesis and pedogenesis. The methods used are : granulometry, morphoscopy, atterberg limits and evaluations. The plateau evolution appears strongly linked to climatic changes, river erosion, physics characteristics of superficial deposits and pedogenesis. Those different factors enrol in 5 distinct stages since eocene to present times. They are characterised by contrasted seasons climats alternation and hot and humid seasons. The climats determine the orientations of fluviatile morphogenesis, pedogenesis and mechanical weathering. Fluviatile morphogenesis is differential. It depends on the geological nature of rocks, of their degree of hardness and of superficial deposits consistency. The recent pedogenetical events are ferralitization (neo-formed minerals are metahalloysite, kaolinite, gibbsite, goethite and anatase) and clay impoverishment. Mechanical weathering is limited on the area. It affects more easily soft formations than hard or hardened formations. Deposits substracted from the okouma plateau, rich in manganese, have an impact on the soil because it becomes acid and rich in toxic mn2+. The landscapes resultint of morphogenesis and pedogenesis is constitued by half-orange hills
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Annie, Lundberg. "Environmental transformations of Manganese and Manganese oxide nanoparticles". Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289637.
Testo completoAbstract (sommario):
Engineered nanoparticles (NPs) are produced in increased quantities. Due to this increase, itis vital to understand the full lifecycle and fate of these NPs to prevent any possible environmental stress. As a result of their size, NPs may interact differently with their environment compared to bulk materials with the same composition, this both gives NPs their usage as well as risks. The risks often include unwanted interaction with biological systems which may lead to generation of toxicity. This study focused on environmental transformations of manganese and manganese oxide (Mn3O4) NPs. Applications these nanoparticles are often in battery technology and catalysis. A solution intended to mimic the composition of freshwater was used as the environmental media to study these transformations. Exposure of NPs was performed both with and without added natural organic matter (NOM). Several experiments were preformed such as Atomic absorption spectroscopy (AAS) for dissolution of the NPs, Nanoparticle Tracking Analysis (NTA) for particle size, and Attenuated total reflection Fourier transform infrared spectroscopy (ATR- FTIR) for adsorption studies. The production of reactive oxygen species (ROS) was also investigated, and simulations of metal speciation using Visual MINTEQ were also performed. The results from NTA and AAS (for Mn3O4) were not very reliable due to inconsistencies in the results which were probably caused by problems with preparation. However, for both, the results point towards that the dissolution rates of the particles are slightly slowed down when NOM is added. From ATR-FTIR and the simulations it was confirmed that NOM, carbonate, and sulfur will adsorb onto both particles, possibly in multiple layers. As for increased ROS development, no evidence of such an increase was found. However, the method used does not test for increased hydrogen peroxide development so this would in interesting test as well. Other studies which also would contribute to a more nuanced picture of this system is studies regarding zeta potential and studies which furtherinvestigates the type of adsorption mechanism which occurs at the particles surface.Industriella nanopartiklar används i allt större utsträckning. Därför är det av stor vikt attundersöka hela livscykeln som dessa produkter går igenom for att säkerhetsställa att de inte utgör någon fara för miljön och ekosystemen som de kan komma att hamna i. Som ett resultat av deras storlek interagerar nanopartiklar annorlunda med sin omgivning om man jämför med bulkmaterial av samma sammansättning, detta nanopartiklar både sina unika fördelar och risker. Riskerna innefattar ofta oönskade interaktioner med biologiska kretslopp som kan resultera i toxicitet. I den här rapporten läggs fokus på just denna typ av kemiska omvandlingar som nanopartiklar av mangan och manganoxid kan tänkas genomgå i det naturliga kretsloppet. Applikationer man ofta ser dessa partiklar i är batteriteknologi och katalys. De medium som används för att studera omvandlingarna är en lösning som efterliknar ytvatten från en klar sjö. Exponeringar gjordes både med denna lösning så som den är och med tillsatt naturligt organiskt material, NOM.En rad olika experiment gjordes så som analyser med AAS för att undersöka partiklarnas upplösning, NTA för partikelstorlekar och ATR-FTIR som undersökte adsorption på partiklarna. Även en studie med en DCFH metod där ökat ROS aktivitet undersöktes och en rad med SHM simuleringar gjorda i Visual MINTEQ utfördes. Resultaten från NTA och AAS analysen visade sig inte vara särskilt tillförlitliga på grund av tvetydliga resultat som troligen orsakats av problem med provpreparationen. Men resultaten från båda dessa pekar mot att upplösningshastigheten blir något hämmad då man tillsätter naturligt organiskt material, för båda partiklarna. Från ART-FTIR och simuleringarna kunde de säkerhetsställas att adsorption av NOM, karbonat och svavel sker på båda partiklarna, möjligen i fler än ett lager. När det kommer till ROS studien kunde inga bevis på ökad ROS aktivitet hittas med den använda metoden. Dock så kunde inte ökat väteperoxid aktivitet mätas med den metod som användes så detta hade varit av intresse att testa i framtiden. Andra studier som också skulle vara hjälpsamma för att ge en mer nyanserad bild av detta system är en studie om partiklarnas zeta potential och merundersökningar om vilken typ av adsorptions mekanism som sker vid partiklarnas yta.
3
Novokhatska, A. O., G. Ya Akimov, A. V. Zhebel, O. I. Linnik, V. T. Dovgiy e V. V. Burkhovetskiy. "Forming of Nanoscale Structure in Manganite Ceramics with Superstoichiometric Manganese". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35335.
Testo completoAbstract (sommario):
The new method for obtaining of the nanoscale structure by means of superstoichiometric manganese
in lanthanum manganite (La0.65Sr0.35)1 – xMn1 + xO3 +_ Δ (x = 0, 0.1, 0.2) ceramics sintered at 1500 °C is developed.
The increasing of x content from 0.1 to 0.2 leads to forming internal nanosize multilayer structure of
ceramic grains with layer size of 190 and 280 nm, respectively. The correlation between such nanostructure
and magnetoresistive properties is revealed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35335
4
Sayyari, Zahan Mohammad Hassan. "Manganese efficiency and manganese uptake kinetics of different crop species". Göttingen Cuvillier, 2008. http://d-nb.info/991005724/04.
Testo completo
5
Santos, Bruno Adriano Schaustz dos [UNESP]. "Otimização de procedimentos para a determinação de maganês em amplo intervalo de concentração por espectrometria de absorção atômica em chama". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/97831.
Testo completoAbstract (sommario):
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Este trabalho descreve estratégias instrumentais para a determinação de Mn em amplo intervalo de concentração por espectrometria absorção atômica em chama com fonte contínua e de alta resolução (HR-CS FAAS), por meio do uso de diferentes linhas atômicas (principal, secundária, alternativa ou o ajuste do arranjo instrumental) desde que seus intervalos de concentração se completem, sem a necessidade de amplas diluições da amostra. O método proposto foi aplicado as amostras de água de abastecimento, fertilizante foliar, poli vitamínico e material certificado de ligas metálicas. A exaltidão e precisão foram avaliadas por testes de significância (t de student e t - pareado), adição e recuperação, e materiais de referência do Instituto de Pesquisa Tecnológica do Estado de São Paulo, e os resultados foram concordantes ao nível de 95% de confiança em sua grande maioria. Obteve-se curvas analíticas nos intervalos 0,1-2 mg L-1 (279,482 nm), 2-25 mg L-1 (403,075 nm), 25-500 mg L-1 (209,250 nm ou 403,075 nm com queimador a 90 graus), com coeficiente de correlação linear melhor do que 0,9936 em ambas as técnicas (utilizou a espectrometria de absorção atômica em chama com fonte de linhas - LS FAAS - como técnica comparativa). Os limites de detecção para a HR-CS FAAS foram 1,1x10-3 mg L-1 (279,482 nm), 9,8 x 10-3 mg L-1 (403,075 nm), 1,7 mg L-1 (209,250 nm), 7,3x10-2 mg L-1 (403,075 nm com queimador a 90 graus), e para a LS FAAS foram 1,0x10-2 mg L-1, 0,10 mg L-1, 24,8 mg L-1, 7,0 mg L-1, respectivamente. Em HR-CS FAAS, o RSD% variou 0,9 a 1,3, enquanto para a LS FAAS variou 1,1 a 11,8%. As concentrações encontradas pela HR-CS FAAS foram: < 1,1x10-3 mg L-1 (água de abastecimento)...
This paper describes instrumental strategies for the determination of Mn in a wide range concentration by high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) by means of different atomic lines (primary, secondary, alternative or adjusting the instrumental arrangement) provided that their concentration intervals complete one another, without need for large sample dilutions. The proposed method was applied to water, foliar fertilizer, poly vitamin and metal alloys certified materials. Accuracy and precision were evaluated by tests of significance (Student's t test and paired - t test), addition and recovery, and reference materials from the Institute of Technological Research of São Paulo. Analytical curves in the intervals 0.1-2 mg L-1 (279.482 nm), 2-25 mg L-1 (403.075 nm), 25-500 mg L-1 (209.250 nm or 403.075 nm burner 90 degrees) were obtained with linear correlation coefficient better than 0.9936. Line source flame atomic absorption spectrometry (LS FAAS) were used as a comparative technique. The detection limits HR-CS FAAS were 1.1x10-3 mg L-1 (279.482 nm), 9.8 x 10-3 mg L-1 (403.075 nm), 1.7 mg L-1 (209.250 nm), 7.3x10-2 mg L-1 (403.075 nm burner 90 degrees). And by LS FAAS were 1.0x10-2 mg L-1, 0.10 mg L-1, 24.8 mg L-1, 7.0 mg L-1 respectively. In HR-CS FAAS, the RSD ranged from 0.9 to 1.3%, while for LS FAAS from 1.1 to 11.8%. The Mn concentrations found by HR-CS FAAS were < 1.1x10-3 mg L-1 (water supply), 4728 ± 62 mg L-1 (foliar fertilizer), 3.65 ± 2 mg g-1 (poly vitamin), 0.709 ± 0.116 mg L-1 (Alloy 14A), 0.998 ± 0.042 mg L-1 (alloy 25). For LS FAAS, the concentrations wer... (Complete abstract click electronic access below)
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Santos, Bruno Adriano Schaustz dos. "Otimização de procedimentos para a determinação de maganês em amplo intervalo de concentração por espectrometria de absorção atômica em chama /". Araraquara, 2012. http://hdl.handle.net/11449/97831.
Testo completoAbstract (sommario):
Orientador: José Anchieta Gomes NetoCoorientador: Adriana Paiva de Oliveira
Banca: Márcia Andreia Mesquita Silva da Veiga
Banca: Gian Paulo Giovanni Freschi
Resumo: Este trabalho descreve estratégias instrumentais para a determinação de Mn em amplo intervalo de concentração por espectrometria absorção atômica em chama com fonte contínua e de alta resolução (HR-CS FAAS), por meio do uso de diferentes linhas atômicas (principal, secundária, alternativa ou o ajuste do arranjo instrumental) desde que seus intervalos de concentração se completem, sem a necessidade de amplas diluições da amostra. O método proposto foi aplicado as amostras de água de abastecimento, fertilizante foliar, poli vitamínico e material certificado de ligas metálicas. A exaltidão e precisão foram avaliadas por testes de significância (t de student e t - pareado), adição e recuperação, e materiais de referência do Instituto de Pesquisa Tecnológica do Estado de São Paulo, e os resultados foram concordantes ao nível de 95% de confiança em sua grande maioria. Obteve-se curvas analíticas nos intervalos 0,1-2 mg L-1 (279,482 nm), 2-25 mg L-1 (403,075 nm), 25-500 mg L-1 (209,250 nm ou 403,075 nm com queimador a 90 graus), com coeficiente de correlação linear melhor do que 0,9936 em ambas as técnicas (utilizou a espectrometria de absorção atômica em chama com fonte de linhas - LS FAAS - como técnica comparativa). Os limites de detecção para a HR-CS FAAS foram 1,1x10-3 mg L-1 (279,482 nm), 9,8 x 10-3 mg L-1 (403,075 nm), 1,7 mg L-1 (209,250 nm), 7,3x10-2 mg L-1 (403,075 nm com queimador a 90 graus), e para a LS FAAS foram 1,0x10-2 mg L-1, 0,10 mg L-1, 24,8 mg L-1, 7,0 mg L-1, respectivamente. Em HR-CS FAAS, o RSD% variou 0,9 a 1,3, enquanto para a LS FAAS variou 1,1 a 11,8%. As concentrações encontradas pela HR-CS FAAS foram: < 1,1x10-3 mg L-1 (água de abastecimento)... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This paper describes instrumental strategies for the determination of Mn in a wide range concentration by high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) by means of different atomic lines (primary, secondary, alternative or adjusting the instrumental arrangement) provided that their concentration intervals complete one another, without need for large sample dilutions. The proposed method was applied to water, foliar fertilizer, poly vitamin and metal alloys certified materials. Accuracy and precision were evaluated by tests of significance (Student's t test and paired - t test), addition and recovery, and reference materials from the Institute of Technological Research of São Paulo. Analytical curves in the intervals 0.1-2 mg L-1 (279.482 nm), 2-25 mg L-1 (403.075 nm), 25-500 mg L-1 (209.250 nm or 403.075 nm burner 90 degrees) were obtained with linear correlation coefficient better than 0.9936. Line source flame atomic absorption spectrometry (LS FAAS) were used as a comparative technique. The detection limits HR-CS FAAS were 1.1x10-3 mg L-1 (279.482 nm), 9.8 x 10-3 mg L-1 (403.075 nm), 1.7 mg L-1 (209.250 nm), 7.3x10-2 mg L-1 (403.075 nm burner 90 degrees). And by LS FAAS were 1.0x10-2 mg L-1, 0.10 mg L-1, 24.8 mg L-1, 7.0 mg L-1 respectively. In HR-CS FAAS, the RSD ranged from 0.9 to 1.3%, while for LS FAAS from 1.1 to 11.8%. The Mn concentrations found by HR-CS FAAS were < 1.1x10-3 mg L-1 (water supply), 4728 ± 62 mg L-1 (foliar fertilizer), 3.65 ± 2 mg g-1 (poly vitamin), 0.709 ± 0.116 mg L-1 (Alloy 14A), 0.998 ± 0.042 mg L-1 (alloy 25). For LS FAAS, the concentrations wer... (Complete abstract click electronic access below)
Mestre
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AL, ALI NAJLA HUSSEIN. "Relation Between Dietary Manganese Intake and Biological Markers of Manganese Exposure". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1211985289.
Testo completo
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Wei, Duo. "Iron, manganese and rhenium-catalyzed (de)hydrogenation and hydroelementation reactions". Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S105.
Testo completoAbstract (sommario):
L’objectif de ce travail doctoral a été de développer de nouvelles méthodes éco-compatibles pour réaliser efficacement des réactions de (dé)hydrogénation et d’hydroélémentation catalysées par des catalyseurs bien définis de fer, de manganèse et également de rhénium. La première partie de ce travail porte sur le développement des premiers exemples de réaction de borylation de dérivés styrènes et acétyléniques terminaux avec le pinacolborane via une réaction d’activation de liaison C-H catalysée par des systèmes à base de Fe(PMe3)4 ou de Fe(OTf)2/ DABCO. Dans une seconde partie, des complexes de fer à base de ligands carbènes N-hétérocycliques (NHC) tels que Fe(CO)4(IMes) et [CpFe(CO)2(IMes)][I] ont été efficacement utilisés pour la synthèse d’une grande variété d’amines cycliques (pyrrolidines, pipéridines et azépanes) via une réaction d’amination réductrice catalytique en présence d’hydrosilanes. De façon très intéressante, les catalyseurs commerciaux Mn2(CO)10 et Re2(CO)10 en présence de triéthylsilane, ont permis de réduire sélectivement les esters, acides carboxyliques et amides en acétals, alcools et amines correspondants. En complément de l’hydrosilylation, l’hydrogénation d’aldéhydes, cétones et aldimines a pu être efficacement menée grâce à l’utilisation de nouveaux précatalyseurs bien définis de manganèse à base de ligands bidentes facilement accessibles tels que la pyridinyl-phosphine et la 2-picolylamine. Dans la continuité de notre intérêt pour le développement de nouveaux catalyseurs à base de métaux du groupe 7, une série de complexes de rhénium coordinés à des ligands amino-bisphosphino a montré une excellente aptitude à promouvoir l’hydrogénation de composés carbonylés (aldéhydes, cétones), la mono-méthylation sélective d’amines avec le méthanol comme agent de méthylant durable et la synthèse quinolines substituées. La dernière partie de se travail décrit le développement d’oxydations aérobies d’amines pour préparer des aldimines, des composés N-hétéroaromatiques et des dérivés de type benzoimidazole via une catalyse au manganèse en l’absence de ligands ou d’additifsThis research work is aimed at developing advanced eco-friendly methodologies in the area of iron, manganese and rhenium-catalyzed (de)hydrogenation and hydroelementation reactions. Initially, we reported the first examples of highly selective catalytic direct C-H borylation of styrene derivatives and terminal alkynes with pinacolborane using Fe(PMe3)4 and Fe(OTf)2/DABCO as catalyst systems, respectively. Afterwards, N-heterocyclic carbene (NHC) based iron complexes Fe(CO)4(IMes) and [CpFe(CO)2(IMes)][I] were efficiently employed in the catalytic reductive amination reactions with hydrosilanes to access a large variety of cyclic amines (pyrrolidines, piperidines and azepanes). Interestingly, with the commercially available Mn2(CO)10 or Re2(CO)10 as catalyst and Et3SiH as an inexpensive hydrosilane source, carboxylic esters, acids and amides can be chemospecifically reduced to the corresponding acetals, alcohols and amines. Besides hydrosilylation, we also explored the application of a series of well-defined manganese pre-catalysts featuring readily available bidendate pyridinyl-phosphine and 2-picolylamine ligands in hydrogenation reactions of aldehydes, ketones and aldimines. In line with our interest in developing group 7 metals based catalysts, we have also demonstrated that a series of amino-bisphosphino ligands coordinated rhenium catalysts can efficiently promote the hydrogenation of carbonyl derivatives, the mono N-methylation of anilines with methanol and the dehydrogenative synthesis of substituted quinolines. Lastly we also developed the Mn-catalysed ligand- and additive-free aerobic oxidation of amines to prepare aldimines, N-heteroaromatics and benzoimidazole derivatives
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Reginato, Nada McGlinchey Michael J. "Polycyclic compounds of manganese /". *McMaster only, 2003.
Cerca il testo completo
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Turkeli, Altan. "Microsegregation in manganese steels". Thesis, University of Sheffield, 1990. http://etheses.whiterose.ac.uk/15023/.
Testo completoAbstract (sommario):
Dendritic morphology and microsegregation in the ternary Fe- 1.6% Mn - 0.1 to 0.8 % C alloys have been investigated by quenching the unidirectionally solidified specimens. The microprobe analysis of these specimens showed that the manganese segregation was significantly controlled by the back diffusion. This back diffusion was extremely high in the case of ferritic solidification whereas only a small rise in Cmin was obtained for the austenitic phase. It was found that the manganese microsegregation between the primary arms was always higher than between the secondary arms. The measured segregation ratios indicated a rise with increasing carbon content for both morphologies. No clear effect of cooling rate on segregation was seen for secondary arms and only a sliqht increase was recorded with increasing the cooling rate for primary arms. Secondary dendrite arms solidified to produce asymmecric distribution profiles (saw-tooth or TGZM effect). Measurements of the secondary dendrite arms during qrowth showed that the rate of the coarsening in these manganese steels was higher than other steels resulting in high homogenization between the arms . No tertiary arms have been observed. The primary arms grew mainly in the so-called 'close packed' arrangement and their spacinq did not chanqe with time. By increasing the qrowth rate and the temperature qradient in the liquid a decrease in primary arm spacings was seen. The results agree well with available experimental data in the literature. The microsegregation calculations obtained from the secondary dendrite arm coarseninq model is in a very good agreement with the experimental measurements. The same model without arm coarsening was applied to different primary arm morphologies and the predictions of these models are also in reasonable agreement with observations.
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Drahoš, Bohuslav. "Potential contrast agents for MRI based on manganese (II) complexes". Thesis, Orléans, 2011. http://www.theses.fr/2011ORLE2039/document.
Testo completoAbstract (sommario):
La thèse se concentre sur la synthèse et la caractérisation de nouveaux complexes de manganèse comme alternative possible aux complexes de gadolinium, actuellement les agents de contraste de choix pour l’Imagerie par Résonance Magnétique (IRM). Dans cette perspective, nous nous sommes intéressés à trois groupes de ligands pentadentés pour la complexation de Mn2+. Des nombres de coordination de 6 ou 7 ont été déterminés par cristallographie pour ces complexes, permettant la coordination d’une ou deux molécules d’eau en première sphère de coordination de Mn2+. La stabilité thermodynamique de ces complexes est plus faible que celle de complexes polyaminocarboxylates et leur dissociation est très rapide comparée à [Mn(nota)] et [Mn(dota)]2-. Seuls les complexes de Mn2+ avec des ligands macrocycliques à 12 atomes sont oxydés en Mn3+ à l’air. Les relaxivités des complexes bishydratés sont deux fois plus élevées que celles des complexes monohydratés et elles sont comparables à celles des agents de contraste commerciaux. Les données de RMN d’17O mesurées à différentes températures ont montré que l’échange d’eau peut être lent, intermédiaire, ou rapide selon le ligand. Les mesures à hautes pressions ont confirmé que le mécanisme d’échange est de type dissociatif pour les complexes avec un nombre de coordination de 7 et de type associatif pour les complexes avec un nombre de coordination de 6. Les petits anions bidentés endogènes peuvent remplacer une molécule d’eau dans les complexes bishydratés de macrocycles pentaazotés à 15 atomes, alors que pour les autres soit le complexe se décompose, soit il n’y a pas d’influenceThe thesis is focused on the synthesis and characterization of novel manganese complexes as alternative to Gd3+ chelates which are wide-spread contrast agents in Magnetic Resonance Imaging (MRI). In this perspective, three structurally different groups of pentadentate ligands for Mn2+ complexation have been investigated. Coordination numbers of 6 or 7 were determined in the crystal structure of the Mn2+ complexes enabling one or two water molecules in the first sphere. The thermodynamic stability of the chelates is lower than that of polyaminocarboxylate complexes and their dissociation is very fast in comparison to [Mn(nota)] and [Mn(dota)]2–. Only Mn2+ complexes with 12- membered ligands undergo oxidation in air to Mn3+ species. The proton relaxivities of the bishydrated complexes are two times higher than those for monohydrated complexes and are comparable to those of commercial contrast agents. Variable-temperature 17O NMR data revealed that the water exchange varies from slow to intermediate or to extremely fast, depending on the ligand. High-pressure 17O NMR measurements confirmed dissociative water exchange mechanism on complexes with CN = 7 and associative mechanism on complexes with CN = 6. Small endogenous bidentate anions are capable of replacing only one water molecule in the bishydrated complex with the 15-membered pentaaza ligand (L2), while in other cases the complex is decomposed or no influence is observed
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Ingersoll, Russell Taylor 1966. "Central nervous system toxicity of manganese: Mechanism of manganese concentration in the ventral mesencephalon". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282218.
Testo completoAbstract (sommario):
In the lateral choroid plexus, Mn was sequestered from the blood against a concentration gradient. Intrathecal administration of Mn²⁺ showed that the choroid plexus does not remove Mn from the cerebrospinal fluid and that intrathecal Mn²⁺ rapidly caused neurological abnormalities. Either 1 or 2 mg Mn²⁺/kg intrathecally resulted one day after dosage in a 91% and 95% decrease in the spontaneous motor activity of rats, respectively. Control activity was unchanged by intrathecal NaCl. Five days after administration, dopamine was decreased 70%; and Mn in the ventral mesencephalon was increased 14-fold as compared to controls. Mn in the central nervous system reached a maximum and dopamine reached a minimum 6 hours after 250 μg Mn²⁺/rat, intrathecally. The ventral mesencephalon contained more Mn than any other brain region (p < 0.001). Neurotransmitter reuptake carriers were inhibited in an effort to reduce the Mn concentration in the CNS. To inhibit neurotransmitter reuptake, rats were given cocaine i.p. and later Mn intrathecally. Mn²⁺ caused the ventral mesencephalon Mn concentration to increase from 0.57 μg/g to 31.8 μg/g. Cocaine prior to Mn decreased the concentration from 31.8 μg/g to 3.3 μg/g. To decrease neurotransmitter concentration, rats were given reserpine i.p. and later Mn intrathecally. Mn2+ caused the ventral mesencephalon Mn concentration increased from 0.77 μg/g to 29.9 μg/g. Reserpine prior to Mn decreased the concentration from 29.9 μg/g to 3.7 μg/g. Cocaine or reserpine decreased the Mn concentration in the occipital pole, frontal lobe and caudate putamen but not in the cerebellum. Manganese, cocaine or reserpine decreased the dopamine concentration in the caudate putamen from 10.5 to 6.3, 4.1 or 0.8 μg/g, respectively. The results suggest that intrathecal Mn²⁺ can rapidly cause dopaminergic specific neurotoxicity resulting in: (1) decreased spontaneous motor activity, (2) increased Mn concentration in the ventral mesencephalon and (3) decreased dopamine concentration in the caudate putamen. Mn concentration in the CNS is related to neurotransmitter uptake carriers since inhibiting reuptake or reducing concentrations of neurotransmitters resulted in decreased Mn concentrations in many brain regions.
13
Pinto, Anderson Santos [UNESP]. "Adubação com manganês em soja: efeitos no solo e na planta". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/88251.
Testo completoAbstract (sommario):
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pinto_as_me_jabo.pdf: 267820 bytes, checksum: a262f69f5ba14a4bf28ea1eccaf4cd5d (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Foram instalados dois experimentos em condições de campo, num solo Argissolo Vermelho-Amarelo distrófico, com alto valor de pH na camada superficial e com problemas de deficiência de Mn. O primeiro experimento procurou estudar o efeito da adição de doses (0, 2, 5, 8, 11 e 14 kg ha-1 de Mn) e fontes de Mn (sulfato de Mn e Mn-“fritas”), aplicadas via solo, na produção de matéria seca da parte aérea e de grãos de soja, nas concentrações de Mn nas folhas e na parte aérea, assim como, na distribuição do micronutriente em frações (reservatórios) do solo (trocável, matéria orgânica, óxidos de Fe e Al cristalino e pouco cristalino e residual) e na disponibilidade para a leguminosa, avaliada através das soluções extratoras DTPA, Mehlich-1, Mehlich-3 e HCl. Procurou-se determinar o nível crítico de Mn no solo e nas folhas, identificando a fração do solo (reservatório) com que o Mn predominantemente se associa após a sua aplicação e, relacionar o micronutriente nas diversas frações com o Mn extraível pelas soluções de DTPA, HCl, Mehlich-3 e Mehlich-1, assim como, com a quantidade do micronutriente absorvida e acumulada na parte aérea das plantas. Devido o Mn aplicado em solo com alto pH poder tornar-se indisponível às plantas, foi realizado um segundo experimento, onde procurou-se estudar em três cultivares de soja, o efeito de fontes de Mn aplicadas via foliar (sulfato de Mn, Mn-EDTA e cloreto de Mn) e de doses (0, 200, 400 e 600 g ha-1 de Mn) aplicadas nos estádio V4, V6 e V9, respectivamente. Foi avaliada a produtividade de grãos de soja e as concentrações de Mn na folha diagnóstica. Houve aumento significativo na produção de soja (grãos e M.S.) com o incremento das diferentes fontes e doses de Mn, sendo a melhor dose via solo foi a...
Two experiments were carried out under field conditions, a soil loam Ultisol, with high pH in the surface layer and Mn deficiency problems. The first experiment aimed to study the effect of adding doses (0, 2, 5, 8, 11 and 14 kg ha-1 Mn) and sources of Mn (Mn sulfate and Mn-chips) applied to soil, in dry matter production of shoots and soybean, the concentrations of Mn in leaves and shoots, as well as the distribution of micronutrient in fractions (reservoirs) soil (exchangeable, organic matter, Fe and Al oxides crystalline and poorly crystalline and residual) and the availability for legume, evaluated through the DTPA, Mehlich-1, Mehlich-3 and HCl. We sought to determine the critical level of Mn in soil and leaves, identifying the fraction of the soil (reservoir) with the Mn predominantly associates after their application, and relate the micronutrient in the various fractions with Mn extractable with DTPA HCl, Mehlich-3 and Mehlich-1, as well as with the amount of micronutrient absorbed and accumulated in the shoots. Because the applied Mn in soil with high pH can become unavailable to the plants, we performed a second experiment where we tried to study in three soybean cultivars, the effect of sources of foliar applied Mn (Mn sulfate, Mn- EDTA chloride and Mn) and doses (0, 200, 400 and 600 g ha-1 Mn) applied in stage V4, V6 and V9, respectively. We evaluated the productivity of soybeans and the concentrations of Mn in the diagnostic leaf. A significant increase in soybean production (grain and MS) with increasing doses of different sources and Mn, the best dose... (Complete abstract click electronic access below)
14
Pinto, Anderson Santos. "Adubação com manganês em soja : efeitos no solo e na planta /". Jaboticabal, 2012. http://hdl.handle.net/11449/88251.
Testo completoAbstract (sommario):
Orientador: Edson Luiz Mendes CoutinhoBanca: José Eduardo Corá
Banca: Anice Garcia
Resumo: Foram instalados dois experimentos em condições de campo, num solo Argissolo Vermelho-Amarelo distrófico, com alto valor de pH na camada superficial e com problemas de deficiência de Mn. O primeiro experimento procurou estudar o efeito da adição de doses (0, 2, 5, 8, 11 e 14 kg ha-1 de Mn) e fontes de Mn (sulfato de Mn e Mn-"fritas"), aplicadas via solo, na produção de matéria seca da parte aérea e de grãos de soja, nas concentrações de Mn nas folhas e na parte aérea, assim como, na distribuição do micronutriente em frações (reservatórios) do solo (trocável, matéria orgânica, óxidos de Fe e Al cristalino e pouco cristalino e residual) e na disponibilidade para a leguminosa, avaliada através das soluções extratoras DTPA, Mehlich-1, Mehlich-3 e HCl. Procurou-se determinar o nível crítico de Mn no solo e nas folhas, identificando a fração do solo (reservatório) com que o Mn predominantemente se associa após a sua aplicação e, relacionar o micronutriente nas diversas frações com o Mn extraível pelas soluções de DTPA, HCl, Mehlich-3 e Mehlich-1, assim como, com a quantidade do micronutriente absorvida e acumulada na parte aérea das plantas. Devido o Mn aplicado em solo com alto pH poder tornar-se indisponível às plantas, foi realizado um segundo experimento, onde procurou-se estudar em três cultivares de soja, o efeito de fontes de Mn aplicadas via foliar (sulfato de Mn, Mn-EDTA e cloreto de Mn) e de doses (0, 200, 400 e 600 g ha-1 de Mn) aplicadas nos estádio V4, V6 e V9, respectivamente. Foi avaliada a produtividade de grãos de soja e as concentrações de Mn na folha diagnóstica. Houve aumento significativo na produção de soja (grãos e M.S.) com o incremento das diferentes fontes e doses de Mn, sendo a melhor dose via solo foi a... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Two experiments were carried out under field conditions, a soil loam Ultisol, with high pH in the surface layer and Mn deficiency problems. The first experiment aimed to study the effect of adding doses (0, 2, 5, 8, 11 and 14 kg ha-1 Mn) and sources of Mn (Mn sulfate and Mn-"chips") applied to soil, in dry matter production of shoots and soybean, the concentrations of Mn in leaves and shoots, as well as the distribution of micronutrient in fractions (reservoirs) soil (exchangeable, organic matter, Fe and Al oxides crystalline and poorly crystalline and residual) and the availability for legume, evaluated through the DTPA, Mehlich-1, Mehlich-3 and HCl. We sought to determine the critical level of Mn in soil and leaves, identifying the fraction of the soil (reservoir) with the Mn predominantly associates after their application, and relate the micronutrient in the various fractions with Mn extractable with DTPA HCl, Mehlich-3 and Mehlich-1, as well as with the amount of micronutrient absorbed and accumulated in the shoots. Because the applied Mn in soil with high pH can become unavailable to the plants, we performed a second experiment where we tried to study in three soybean cultivars, the effect of sources of foliar applied Mn (Mn sulfate, Mn- EDTA chloride and Mn) and doses (0, 200, 400 and 600 g ha-1 Mn) applied in stage V4, V6 and V9, respectively. We evaluated the productivity of soybeans and the concentrations of Mn in the diagnostic leaf. A significant increase in soybean production (grain and MS) with increasing doses of different sources and Mn, the best dose... (Complete abstract click electronic access below)
Mestre
15
Cortez, Juliana 1984. "Construção e avaliação de um instrumento para espectroscopia de emissão em plasma induzido por laser (LIBS) : aplicação em ligas metalicas". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249949.
Testo completoAbstract (sommario):
Orientador: Celio PasquiniDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Neste trabalho um instrumento LIBS com resolução temporal (TRELIBS) foi construído e seu desempenho foi avaliado para análise qualitativa e quantitativa. Além disso, este trabalho apresenta estudos exploratórios acerca da influência de parâmetros que afetam as análises em LIBS. O instrumento foi montado empregando-se óptica e sistema de detecção de última geração: um detector ICCD, um policromador echelle e um laser Q-switched de Nd:YAG. Três configurações do sistema LIBS foram avaliadas. No último arranjo do sistema, o pulso de laser era refletido por um espelho dicróico à 45º para uma lente de distância focal de 25 cm que focava o pulso de laser na superfície da amostra. A radiação foi coletada por uma lente de curta distância focal e depois enviada para o echelle, por uma fibra óptica, e posteriormente para o ICCD. Na análise qualitativa foram avaliados os espectros de uma placa de cobre e zinco, obtendo-se espectros condizentes com a literatura, de acordo com a resolução do echelle. Na avaliação quantitativa, determinou-se manganês em aços acalmados. O sistema apresentou resposta às diferentes concentrações de manganês em 293,30 nm e curvas analíticas foram obtidas. A energia do pulso de laser mostrou ser um fator determinante no desempenho da análise quantitativa. Outros parâmetros como tempo de integração do sinal, tempo de atraso, ganho do MCP, co-adição de pulsos e distância foco-amostra também mostraram ter influência na análise quantitativa. Imagens de MEV e mapeamentos de EDS das crateras formadas pelo laser foram ferramentas importantes para o entendimento do processo de interação laser-amostra-atmosfera
Abstract: In this work a time resolved LIBS instrument (TRELIBS) was built and its performance evaluated in qualitative and quantitative analysis. Additionally, exploratory studies are presented on the influence of parameters that affect the LIBS analysis. The instrument was built employing optical systems and devices of modern technology: an ICCD device, an echelle polychromator and an Q-switched Nd:YAG laser. Three configurations of LIBS system were evaluated. In the last configuration, the laser pulse was reflected by a dicroic mirror at 45º to a lens of 25 cm focal distance that focused the laser pulse on the sample surface. The plasma emission was collected by a lens of short focal distance and sent to the echelle, through of an optical fiber, and later to the ICCD. In qualitative analysis, spectra of copper and zinc foils were evaluated and the spectral lines were found in agreement with literature, considering the echelle resolution. In quantitative analysis, manganese was determined in killed steel. The system presented signals at 293,30 nm whose intensities changes in function of manganese concentration and analytical curves were obtained. The laser pulse energy showed to be an important factor for the success of quantitative analysis. Others parameters such as width, delay time, MCP gain, accumulated laser pulses and distance sample-focusing lens also showed have influence in quantitative analysis. MEV images and surface scanner by EDS of the craters formed by laser were important tools to understanding laser-sample-atmosphere interaction processes
Mestrado
Quimica Analitica
Mestre em Química
16
Oliveira, Kamilla Silva. "Pulverização foliar de manganês com adição de silício é viável para plantas de milho e de sorgo /". Jaboticabal, 2019. http://hdl.handle.net/11449/181638.
Testo completoAbstract (sommario):
Orientador: Renato de Mello PradoBanca: Anelisa de Aquino Vidal Lacerda Soares
Banca: Jairo Osvaldo Cazetta
Resumo: A pulverização foliar de manganês (Mn) é amplamente utilizada em cultivos anuais dada a deficiência do micronutriente no solo. A adição de silício (Si) na calda com o Mn poderia favorecer aspectos fisiológicos e nutricionais e a produção de plantas de milho e sorgo. Objetivou-se avaliar os efeitos do Mn e Si fornecidos via pulverização foliar na nutrição foliar de plantas de milho e de sorgo sob deficiência de Mn. Foram desenvolvidos dois experimentos, um com a cultura do milho (experimento milho) em casa de vegetação e outro com a cultura do sorgo granífero (experimento sorgo) em sala climatizada. O experimento milho foi composto de arranjo fatorial 4x2, sendo concentrações de Mn 0,0; 0,29; 0,58 e 0,87 g L-1na ausência e presença de Si (0,476 g L-1de Si) aplicados via foliar no estágio V4 e V6.O experimento sorgo foi realizado em arranjo fatorial 4x2 com concentrações de Mn 0,0; 0,17; 0,34 e 0,51 g L-1 na ausência e presença de Si (0,476 g L-1de Si) aplicados via foliar no estágio V4 e V6. Em ambos os experimentos avaliaram-se variáveis fisiológicas e de produção de massa seca para verificar efeito do Si e Mn na nutrição das plantas. A pulverização foliar de Mn com adição de Si na calda incrementou o acúmulo do micronutriente, o índice relativo de clorofila, a eficiência quântica do FSII, a eficiência do uso da água e refletiu na produção de massa seca das plantas de milho e sorgo. A pulverização foliar de Mn com adição de Si na calda é viável para as plantas de milho e de ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Foliar spraying of manganese (Mn) is widely used in annual crops due to micronutrient deficiency in the soil. The addition of silicon (Si) in the application liquid with Mn could favor physiological and nutritional aspects and the production of maize and sorghum plants. The objective of this study was to evaluate the effects of Mn and Si supplied by foliar spraying on leaf nutrition of maize and sorghum plants under Mn deficiency. Two experiments were carried out, one with maize (corn experiment) in greenhouse and the other with sorghum (sorghum experiment) in climatized room. The corn experiment was composed of factorial arrangement 4x2, with concentrations of Mn 0,0; 0.29; 0.58 and 0.87 g L-1 in the absence and presence of Si (0.476 g L-1 of Si) applied via leaf in stage V4 and V6. The sorghum experiment was performed in a 4x2 factorial arrangement with concentrations of Mn 0,0; 0.17; 0.34 and 0.51 g L-1 in the absence and presence of Si (0.476 g L-1 of Si) applied via foliar in stage V4 and V6. In both experiments were evaluated the physiological and dry mass production variables to verify the effect of Si and Mn on plant nutrition. Foliar spraying of Mn with addition of Si in application liquid increased micronutrient accumulation, relative chlorophyll index, FSII quantum efficiency, water use efficiency, and reflected in the dry mass production of corn and sorghum plants. Foliar spraying of Mn with addition of Si in application liquid is viable for maize and sorghum ... (Complete abstract click electronic access below)
Mestre
17
Kern, Cynthia H. "Neurotoxicity of neonatal manganese exposure /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
Testo completo
18
Zini, Simone. "Synthesis of manganese organometallic complexes". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22235/.
Testo completoAbstract (sommario):
Il presente lavoro di tesi si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione per lo sviluppo di catalizzatori da impiegare in reazioni di catalisi omogenea. In particolare il mio progetto si è concentrato sulla sintesi di complessi organometallici di manganese con leganti carbenici N-eterociclici (NHC). La scelta dei leganti è stata effettuata in modo tale da poter avere leganti chelanti NHC di tipo MIC (mesoionic carbene) sintetizzati tramite cicloaddizione tra un alchino ed un azide catalizzata da rame (CuAAC) e N-alchilazione. Lo studio di questi complessi a base di manganese è ancora tutt’oggi agli albori, leganti NHC vengono molto utilizzati grazie alla possibilità di variarne le proprietà steriche ed elettroniche e alla possibilità di formare legami forti con quasi tutti i metalli. Il manganese è stato scelto poiché un elemento abbondante, poco tossico e poco costoso.
The present thesis work is part of a research project aimed at the synthesis of new transition metal complexes to be used in homogeneous catalysis reactions. In particular my project focused on the synthesis of manganese organometallic complexes with N-heterocyclic carbene ligands (NHC). The choice of ligands was carried out to have NHC chelating ligands of the class of MIC (mesoionic carbene). These ligands are synthesized by cycloaddition between alkyl and azide with a copper-catalyzed reaction (CuAAC) and N-alkylation in order to obtain MIC after deprotonation. The study of these manganese-based complexes is still in its infancy today, NHC ligands are widely used thanks to the possibility of varying their steric and electronic properties and the possibility of forming strong bonds with almost all metals. The choice of manganese was made because is an abundant, low-toxic and inexpensive element.
19
Lee, Bo Yeon. "Action of manganese on puberty". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/5871.
Testo completoAbstract (sommario):
Manganese (Mn) is considered important for normal growth and reproduction. Because Mn can cross the blood brain barrier and accumulate in the hypothalamus, and because it has been suggested that infants and children are potentially more sensitive to Mn than adults, we wanted to determine the effects of Mn exposure on puberty-related hormones and the onset of puberty, and discern the site and mechanism of Mn action. We demonstrated that the central administration of manganese chloride (MnCl2) stimulated luteinizing hormone (LH) release in prepubertal rats. Incubation of medial basal hypothalamus (MBH) in vitro showed this effect was due to a Mn-induced stimulation of luteinizing hormone releasing hormone (LHRH). Further demonstration that this is a hypothalamic site of action was shown by in vivo blockade of LHRH receptors and the lack of a direct pituitary action of Mn to stimulate LH release in vitro. Chronic supplementation of low dose of MnCl2 caused elevated serum levels of LH, follicle stimulating hormone (FSH) and estradiol or testosterone. Importantly, Mn supplementation advanced the timing of puberty in both sexes. We investigated the mechanism by which Mn induces LHRH/LH release from the hypothalamus. Blocking the NMDA receptor, IGF1 receptor, or inhibiting nitric oxide synthase in vivo was ineffective in altering Mn-induced LH release. Dose-response, pharmacological blockade and nitrite assessments indicated that the lowest doses of Mn used stimulated LHRH release, but did not induce nitric oxide (NO) production, while only the highest dose of Mn stimulated NO. Conversely, a dose-dependent inhibition of Mn-induced LHRH release was observed in the presence of ODQ, a specific blocker of soluble guanylyl cyclase. Furthermore, Mn stimulated the release of cyclic GMP (cGMP) and LHRH from the same MBH, and a protein kinase G (PKG) inhibitor, KT5823, blocked Mn-induced LHRH release. Collectively, these data demonstrate that Mn can stimulate specific puberty-related hormones both acutely and chronically, and furthermore, suggest that low levels of Mn facilitate the normal onset of puberty. The principal action of Mn within the hypothalamus is to facilitate the activation of guanylyl cyclase, which subsequently stimulates the cGMP/PKG pathway resulting in the stimulation of prepubertal LHRH secretion.
20
Cao, Xiangzhi. "Electrorefining of high purity manganese". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59447.
Testo completoAbstract (sommario):
Manganese is an important industrial metal used as an additive for production of various steels, non-ferrous alloys, electronic components and special chemicals. The traditional electrowinning process is not suitable for the production of high-purity manganese. Therefore, a novel ion exchange - electrorefining process for production of high-purity manganese is proposed to solve the problems. The ammonium chloride – manganese chloride electrolyte was selected as the most promising for refining. The physical properties of the electrolyte were first studied. The density increases when increasing concentrations of the ammonium chloride and manganese chloride. The maximum electrical conductivity is obtained with high concentrations of ammonium chloride and high temperature. Viscosity is minimized by high temperature and by low concentrations of manganese chloride. The electrorefining process introduces impurities into the anolyte from the dissolving anode. The purification of the electrolyte by cementation and ion exchange were investigated. This thesis reports the uptake of copper, nickel, cobalt, cadmium, zinc and manganese from manganese chloride solution onto the chelating resin Lewatit® MDS TP220 and Purolite S930Plus in batch and column experiments. The results demonstrate the ability for Lewatit® MDS TP220 to remove contaminants to an extent satisfying the quality criteria required for electrorefining. However, cementation of impurities by manganese powder and ion exchange with Purolite S930Plus are not suitable for purification to satisfy the quality criteria. In the electrorefining process, the individual and synergistic effects of selected impurities on manganese deposit quality were first investigated. The purity of manganese deposit did not change significantly in the presence of impurities. An addition of 0.15–5.0 mg/l Zn²⁺ to the catholyte increases the cathodic current efficiency. The parameters of current density, deposition time, and cathode usage frequency were investigated. Current density, deposition time and cathode usage frequency could affect current efficiency, specific energy consumption and surface morphology. With increasing the current density, the cathodic current efficiency first increased, reached a maximum value and then decreased. With increasing deposition time from 24 hours to 48 hours, the manganese current efficiency decreased and the deposit became more dendritic. The more times the cathode was used, the lower the current efficiency.Applied Science, Faculty of
Graduate
21
Inglis, Ross. "Oxime based manganese molecular magnets". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4755.
Testo completoAbstract (sommario):
The synthesis and characterisation of a large family of hexametallic [MnIII 6] Single-Molecule Magnets with general formula [MnIII 6O2(R-sao)6(X)2(L)4-6] (where sao2- = dianion of salicylaldoxime; R = H, Me, Et, Ph; X = O2CR' (R' = H, Me, Ph etc), Hal , O2PHPh or O2P(Ph)2; L = solvent) are presented. Deliberate structural distortions of the [Mn3O] trinuclear moieties within the complexes are used to tune the observed magnetic properties. These findings highlight a qualitative magnetostructural correlation whereby the type (anti- or ferromagentic) of each Mn2 pairwise magnetic exchange is dominated by the magnitude of each individual Mn-N-O-Mn torsion angle. To shed further light on this intriguing family of nanomagnets, a large family of the analogous “half” molecules has been synthesised and fully characterised. These trimetallic [MnIII 3] complexes can be divided into three categories with general formulae (type 1) [MnIII 3O(R-sao)3(X)(sol)3-4] (where R = H, Me, tBu; X = O2CR (R = H, Me, Ph etc); sol = py and / or H2O), (type 2) [MnIII 3O(R-sao)3(X)(sol)3-5] (where R = Me, Et, Ph, tBu; X = O2CR (R = H, Me, Ph etc); sol = MeOH, EtOH and / or H2O), and (type 3) [MnIII 3O(R-sao)3(sol)3](XO4) (where R = H, Et, Ph, Naphth; sol = py, MeOH, -pic, Et-py, tBu-py; X = Cl, Re). In the crystals the ferromagnetic triangles are involved in extensive inter-molecular H-bonding which is clearly manifested in the magnetic behaviour, producing exchange-biased SMMs. These interactions can be removed by ligand replacement to give “simpler” SMMs. The [MnIII 6] and [MnIII 3] molecular nanomagnets are then exploited as building blocks to construct supramolecular architectures by means of host-guest interactions and coordination driven self-assembly. A number of discrete and infinite architectures based on the molecular triangle [Mn3] and various pyridyl-type ligands were obtained and structurally and magnetically characterised.
22
Horn, Clare Jane. "Spin fluctuations in manganese intermetallics". Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484869.
Testo completoAbstract (sommario):
Magnetic ground states and dynamics in manganese systems have been investigated for two different types of structure, the binary ~-Mnl.xMx and ternary RMn4AIs intermetallics where M represents cobalt or ruthenium and Ris a rare earth elemenVyttriumlscandium. For ~-Mn alloys containing cobalt impurities, astatic ground state of spin glass-like character has been stabilised for concentrations above 5% Co; there is an absence however of long range order in these systems, up to the highest measured concentration of 25at.% Co. The ~-Mnl.xRux alloys enter aspin glass-type state for all measured concentrations (above x=0.03), in conjunction with a higher-temperature transition to along range antiferromagnetically ordered state for x= 0.12, coexistent with the spin glass phase. These findings are evidenced by peaks in the muon spin relaxation rate, with acharacteristic stretched exponential relaxation function observed below the spin glass transition temperature. Further support is provided by susceptibility and polarized neutron measurements. Clear magnetic Bragg peaks in neutron powder diffraction data, in addition to specific heat anomalies, confirm the presence of the long-range ordered state in the ruthenium alloys. Neutron Iineshapes in anumber of samples of both series may also imply Non-Fermi liqUid scaling. These results are of particular significance in view of the fact that cobalt and ruthenium solutes are shown to substitute onto Site I of the ~-Mn crystal structure, as opposed to the more strongly magnetic Site II as for previously reported spin glass alloy systems, in which the impurity lifts magnetic frustration by removal of configurational degeneracy. Expansion appears to playa key role in ~-Mnl.xRux, with the introduction of ruthenium appearing to drive the system to an intermediate state between the weak itinerant and localized moment regimes. In the RMn4Als compounds, a range of interesting behaviour has been observed: this includes the first evidence of a magnetic phase transition in LaMn4Als, in the form of a peak in the low temperature J.lSR data together with weak Bragg peaks in polarized neutron measurements; PrMn4AIs has shown an oscillatory muon response, indicative of long range order in the Mn sublattice since inelastic neutron data shows Pr3+ to be in a singlet ground state. For systems with heavy rare earths (R = Er, Tb, Dy, Gd and Ho), interaction between the Rand Mn sublattices has been implied by J.lSR measurements, in which separate relaxation contributions have been ascribed to each species. For the RMn4Als with R= Y, Ce and Sc, aspin gap reported previously has been directly observed with inelastic neutron scattering. This is reflected in atwo-featured response in LaMn4Als, and may have its origins in aquasi-one dimensional Mn sublattice.
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Hallside, Michal S. "Manganese(III)-mediated radical cyclisations". Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540245.
Testo completo
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Ferguson, Karen Elizabeth. "The electrodeposition of zinc-manganese". Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/14124/.
Testo completoAbstract (sommario):
Electroplated zinc alloys can provide increased corrosion protection for automotive body panels compared with zinc coatings of similar thickness. As a result, their use is becoming widespread. In particular, outstanding results have been reported in the literature for the corrosion resistance of zinc-manganese, and the alloys are said to offer good paintability, weldability and formability. However, the production of zinc-manganese coatings is restricted by the instability of the sulphate-citrate bath from which the alloy is usually deposited. The solution deteriorates rapidly and precipitates appear in the bath. The aim of this research was to investigate both the process of alloy deposition from the sulphate-citrate bath and the solution instability. The electrodeposition of zinc-manganese was assessed in terms of the polarisation behaviour of the system, in order to determine the role of the bath components and the operating parameters in the deposition process. The coatings were analysed using scanning electron microscopy, and the efficiency of metal deposition was established. The sodium citrate complexant was not found to significantly move the deposition potentials of zinc and manganese together. Instead, its action as a buffer can be used to explain metal deposition and the polarisation behaviour of the system. The sodium citrate suppresses the hydrogen evolution reaction, such that manganese can be deposited from the electrolyte. The bath deterioration with time and the resulting precipitate were examined using a variety of chemical techniques including spectroscopic methods, namely ultraviolet and visible, atomic absorption and infrared. Bath discolouration and precipitation were found to be two separate phenomena. The precipitate was determined to be a citrate of known composition with a ratio of Mn2+ ions to Zn2+ ions of 2:1. The formation took several days, and it was precipitated once the solubility limit in the bath was exceeded. Solution discolouration resulted from reactions occurring after the oxidation of Mn2+ ions and could be delayed by the use of antioxidants.
25
Menton, Kevin. "Intracellular mechanisms of manganese neurotoxicity". Thesis, University of Sunderland, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311078.
Testo completo
26
Brown, Simon Brown. "Itinerant magnetism in manganese silicide". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335694.
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27
Yoo, Jae. "Polynuclear manganese single-molecule magnets /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9988317.
Testo completo
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Ng, Nga Chun. "Synthesis and studies of n-base appended manganese corroles /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202003%20NG.
Testo completo
29
Swain, Lindsay Ellen. "The Effects of Manganese-Reducing Bacteria on Desorption of Manganese from MnOx(s) Coated Media". Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71643.
Testo completoAbstract (sommario):
In the past, water treatment plants have stopped the application of pre-filter oxidants to create a bioactive filtration process to remove soluble Mn. After the cessation of pre-filter oxidants, a Mn desorption phenomenon was seen where effluent Mn exceeds influent Mn concentrations. The reason for the sudden increase in effluent Mn was not known, but it was hypothesized that Mn-reducing bacteria on the filter media play a substantial role in this phenomenon. The primary goal of this research was to assess the role of Mn-reducing microorganisms in the desorption of MnOx(s) from coated filters once pre-filtration chlorine ceased. A secondary objective included the development of a molecular detection method for Mn-reducing microorganisms in laboratory and environmental samples. Bench-scale filter column studies were completed to investigate the impacts of Mn-reducing microbial populations on desorption of Mn from MnOx(s) coatings. Secondarily, the effects of influent carbon loading and MnOx(s) age on Mn desorption were investigated. In situ vial assays were created to gain insight into the impacts of MnOx(s) age on Mn reducing microorganism bioavailability. Lastly, a qPCR detection method was developed that targeted the mtrB gene. Results determined that microbially mediated Mn desorption was possible when sufficient numbers of Mn-reducing microorganisms were present on the MnOx(s) surface and that those organisms contributed to the Mn desorption phenomenon. qPCR detection methods were able to show a greater number of Mn-reducing microorganisms in studies where Mn desorption was observed. Lastly, MnOx(s) age was shown to play an important, but unexplained, role in bioavailability.Master of Science
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Cunha, Fernando de Jesus. "Caraterização de Pó de Despoeiramento da Fabricação de Ligas de Manganês e Avaliação de seu Potencial Agronômico". Universidade Federal de Viçosa, 2007. http://locus.ufv.br/handle/123456789/5537.
Testo completoAbstract (sommario):
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The dusty from the siderurgical industry (PD) it is an industrial solid residue originating from the processes of the metallurgy of the ore of manganese (Mn). This material contains significant concentration of Mn. The responsible industrial unit for the production of approximately 2000 ton/month of PD's is Rio Doce Manganês (RDM), company of the group of the Company is Worth of Rio Doce (CVRD), nowadays, Company is Worth. PD's were characterized chemically (stage 1) and soon afterwards, appraised as source of Mn for soy plants (Glicine max L.), of the variety it Conquers and eucalyptus plants (Eucalyptus globulus), of the hybrid Urograndis, vegetation home (stage 2). Para the stage 1 of the research, they were chosen ten materials of PD's collected in the industrial units of Barbacena/MG, Ouro Preto/MG, Salvador/Ba and Corumbá/MS, respectively. The samples of PD's were analyzed according to the lixiviação procedures and solubilization of solid residues (ABNT NBR 10005 and 10006, 2004). The tenors of metals of PD ́s were quantified through espectrofotometry in optic emission with plasma coupled induced (ICP-OES) and espectrofotometry for atomic absorption (AAS). Soon afterwards, the experiment was accomplished vegetation home (stage 2), being used samples of two Latossolos (LVa), a loamy one (TG) and other sandy (TM), of the cities Viçosa/MG and Three Marias/MG, respectively. As sources of Mn, were appraised samples of PD's in natura originating from five industrial units of RDM/CVRD and two prepared fertilizers starting from PD's: the sulfate of manganese (SM-PD) and the oxide of manganese (OM-PD). it was included as treatment controls another fertilizer sulfate of commercial manganese (SM- with). The materials were applied in equivalent amount to the doses 0,0; 2,5; 5,0; 7,5 and 30,0 mg kg-1 of Mn, except for applied OM-PD just in the doses 2,5 and 30,0 mg kg-1 of Mn. The plants were collected and droughts in greenhouses with ventilation forced of hot air. Soon afterwards, they were determined the tenors of P, Mn, Zn, Ass, Faith, Cr, Ni, You and If, with xiextraction of nítric acid and percloric (3:1), for espectrofotometry of optical emission with plasma coupled induced (ICP-OES). The data were submitted to the analysis of multiple lineal regression, being evaluated the production of the mass of dry matter, concentration and accumulation of the chemical elements in the aerial part and roots of the soy plants and eucalyptus. The results obtained with the extracts solubilizados (stage 1), they presented tenors of The, Pb, If, Hg, Mn, Faith and Al in values above the maximum limits established by ABNT (I Enclose G, ABNT NBR 10004, 2004). on the other hand, the tenors of metals found in the leached extracts didn't result in high values, second referred her norm. There was not significant answer with the sources of applied Mn in the treatments, in what he/she concerns the production of the mass of dry matter of the soy plants and eucalyptus (stage 2). there also was not, accumulation of heavy metals in the fabrics of the same ones in levels that represented any risk to his/her development. PD's in natura made available Mn to the cultivated plants, in amounts comparable to liberated them to SM-PD, OM-PD and the SM-COM. It is ended that, so much PD's in natura, as for the materials produced starting from PD's (SM-PD and OM-PD) they were efficient as sources of Mn to the soy plants and eucalyptus cultivated vegetation home. The obtained results indicate that the use of PD can be viable, as source of Mn for the industry of fertilizers.
O Pó de Despoeiramento (PD) é um resíduo sólido industrial proveniente dos processos da metalurgia do minério de manganês (Mn). Este material contém concentração significativa de Mn. A unidade industrial responsável pela produção de aproximadamente 2000 toneladas/mês de PD s é a Rio Doce Manganês (RDM), empresa do grupo da Companhia Vale do Rio Doce (CVRD), atualmente, Companhia VALE. Os PD s foram caracterizados quimicamente (etapa 1) e em seguida, avaliados como fonte de Mn para plantas de soja (Glicine max L.), da variedade Conquista e plantas de eucalipto (Eucalyptus globulus), do híbrido Urograndis, em casa de vegetação (etapa 2). Para a etapa 1 da pesquisa, foram escolhidos dez materiais de PD s coletados nas unidades industriais de Barbacena/MG, Ouro Preto/MG, Salvador/Ba e Corumbá/MS, respectivamente. As amostras de PD s foram analisadas segundo os procedimentos de lixiviação e solubilização de resíduos sólidos (ABNT NBR 10005 e 10006, 2004). Os teores de metais dos PD ́s foram quantificados por meio de espectrometria em emissão ótica com plasma acoplado induzido (ICP-OES) e espectrometria por absorção atômica (AAS). Em seguida, foi realizado o experimento em casa de vegetação (etapa 2), utilizando-se amostras de dois Latossolos (LVa), um argiloso (TG) e outro arenoso (TM), das cidades Viçosa/MG e Três Marias/MG, respectivamente. Como fontes de Mn, foram avaliadas amostras dos PD s in natura proveniente de cinco unidades industriais da RDM/CVRD e dois fertilizantes preparados a partir dos PD s: o sulfato de manganês (SM-PD) e o óxido de manganês (OM- PD). Foi incluído como tratamento controle um outro fertilizante sulfato de manganês comercial (SM-Com). Os materiais foram aplicados em quantidade equivalente às doses 0,0; 2,5; 5,0; 7,5 e 30,0 mg kg -1 de Mn, com exceção do OM-PD aplicado apenas nas doses 2,5 e 30,0 mg kg -1 de Mn. As plantas foram coletadas e secas em estufas com ventilação forçada de ar quente. Em seguida, determinaram-se os teores de P, Mn, Zn, Cu, Fe, Cr, Ni, Ti e Se, com ixextração de ácido nítrico e perclórico (3:1), por espectrometria de emissão óptica com plasma acoplado induzido (ICP-OES). Os dados foram submetidos à análise de regressão linear múltipla, avaliando-se a produção da massa de matéria seca, concentração e acúmulo dos elementos químicos na parte aérea e raízes das plantas de soja e eucalipto. Os resultados obtidos com os extratos solubilizados (etapa 1), apresentaram teores de As, Pb, Se, Hg, Mn, Fe e Al em valores acima dos limites máximos estabelecidos pela ABNT (Anexo G, ABNT NBR 10004, 2004). Por outro lado, os teores de metais encontrados nos extratos lixiviados não resultaram em valores elevados, segundo a referida norma. Não houve resposta significativa com as fontes de Mn aplicadas nos tratamentos, no que diz respeito à produção da massa de matéria seca das plantas de soja e eucalipto (etapa 2). Não houve também, acúmulo de metais pesados nos tecidos das mesmas em níveis que representassem qualquer risco ao seu desenvolvimento. Os PD s in natura disponibilizaram Mn às plantas cultivadas, em quantidades comparáveis às liberadas ao SM-PD, OM- PD e o SM-Com. Conclui-se que, tanto os PD s in natura, quanto aos materiais produzidos a partir dos PD s (SM-PD e OM-PD) foram eficientes como fontes de Mn às plantas de soja e eucalipto cultivadas em casa de vegetação. Os resultados obtidos indicam que o uso do PD pode ser viável, como fonte de Mn para a indústria de fertilizantes.
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Clarasó, Petit Carlota. "Rational design of bioinspired iron and manganese catalysts for the effective and selective epoxidation of alkenes and oxidation of alkanes". Doctoral thesis, Universitat de Girona, 2019. http://hdl.handle.net/10803/666958.
Testo completoAbstract (sommario):
Metalloenzymes are a fundamental source of inspiration for synthetic chemists. Oxidation metalloenzymes catalyze oxidation reactions with high efficiency under very mild experimental conditions exhibiting exquisite regio- and stereoselectivity. The present dissertation aims at designing efficient and selective bioinspired oxidation catalysts. Looking at the literature there’s a very limited number of aliphatic diamines incorporated as ligand backbones in tetradentate aminopyridine based complexes, which have been revealed as one of the most successful catalysts for these transformations with peroxide type of oxidants. Thus, this thesis is focused on the synthesis of chiral iron and manganese complexes based on novel diamine backbones and employ them as catalysts in the stereoselective epoxidation of olefins and oxidation of C-H bonds by using hydrogen peroxide as oxidantEls metal·loenzims són una font fonamental d'inspiració per als químics sintètics. Els metal·loenzims oxidants catalitzen reaccions d'oxidació amb gran eficiència sota condicions experimentals molt suaus que presenten regio- i estereoselectivitats exquisides. L'objectiu d’aquesta tesi es basa en el disseny de catalitzadors d'oxidació bioinspirats eficients i selectius. Analitzant la literatura, es denota que hi ha una limitació important en el nombre i la naturalesa de la diamina incorporada als lligands en complexos basats en lligands tetradentats amb aminopiridines, que s'han demostrat com uns dels catalitzadors més exitosos per a aquestes transformacions amb oxidants de tipus peròxid. Així doncs, aquesta tesi se centra en la síntesi de complexos quirals de ferro i manganès basats en lligands tetradentats que incorporen noves diamines i el seu ús com a catalitzadors en l'epoxidació estereoselectiva d’olefines i l'oxidació dels enllaços C-H utilitzant el peròxid d'hidrogen com a oxidant
32
Elangovan, Saravanakumar. "Well-defined iron and manganese catalysts for reduction and dehydrogenation reactions". Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S008/document.
Testo completoAbstract (sommario):
La substitution des métaux nobles par des métaux de transition abondants et bon marché est un challenge majeur de ce siècle en chimie de synthèse. Récemment, les métaux abondants tels que le fer et le manganèse (1er et 3ème en abondance dans l'écorce terrestre) ont connu un essor remarquable en catalyse homogène, notamment en réduction. Les travaux de thèse ont portés sur le développement de nouveaux catalyseurs bien-définis efficaces du fer et du manganèse pour effectuer des réactions d'hydrogénation de dérivés carboxyliques, de réduction par prêt d'hydrogène et de déshydratation d'amidesThe substitution of noble metals by abundant and cheap transition metals is a major challenge of this century in synthetic chemistry. Recently, abundant metals such as iron and manganese (1st and 3rd in abundance in the Earth's crust) have seen remarkable growth in homogeneous catalysis, especially in reduction. The thesis work focused on the development of new well-defined efficient catalysts of iron and manganese to carry out reactions of hydrogenation of carboxylic derivatives, reduction by hydrogen and dehydration of amides
33
Hoyland, Victoria Wheaton. "Evaluating the use of manganese-oxidizing bacteria in surface water treatment plants". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19226.
Testo completoAbstract (sommario):
Soluble manganese (Mn) presents a significant treatment challenge to many water utilities, causing aesthetic and operational concerns. Surface water treatment plants using ozonation followed by biofiltration are unable to apply free chlorine across the filter, a method used by many utilities for soluble Mn control. These facilities are vulnerable to periodic problems of elevated Mn in the finished water. Manganese-oxidizing bacteria (MOB) readily oxidize Mn in groundwater treatment applications, which normally involve pH values above 7.0. However, the ability of MOB to facilitate Mn oxidation under lower pH conditions (6.2--6.3) often employed to optimize organics removal has not been demonstrated. Laboratory-scale biofilters were operated to evaluate the ability of MOB to accomplish soluble Mn control at a range of pH (6.3--7.3). The biofilters were able to oxidize Mn at a pH as low as 6.3 at greater than 98% removal. Ozonation by-product removal was also greater than 90% in all filter columns. Stress studies indicated that well-acclimated MOB can withstand variations in Mn concentration, hydraulic loading rate, and temperature typically found at surface water treatment plants, at least for relatively short (1-2 days) periods of time. Pilot studies demonstrated that there are unknown factors that affect MOB acclimation, and MOB may be present in full-scale biofilters already. MOB are difficult to identify with current biological analysis techniques and comprise small percentages of the total microbial population. MOB have demonstrated potential for use in surface water treatment plants, but further research is needed before this application is fully feasible.Master of Science
34
Du, Jing-Long. "Syntheses and magnetic studies of manganese(II) monophenylphosphinates and some cadmium(II) doped compounds". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26250.
Testo completoAbstract (sommario):
Anhydrous monophenylphosphinates of manganese(II), Mn[H(C₆H₅)PO₂]₂ (Form I, Form II and Form 1(B)) and cadmium(II), Cd[H(C₆H₅)PO₂]₂ (Form I and Form II) were synthesized and characterized by solubility tests, Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, X-ray Powder Diffractometry, Electron Spin Resonance (ESR) spectroscopy, magnetic susceptibility measurements and Electron Spectroscopy for Chemical Analysis (ESCA). These materials are considered to be polymeric with metal ions connected in chains by double bridging phosphinate groups with cross-linkage forming sheets and octahedral metal centers.
Magnetic susceptibility studies showed that Mn[H(C₆H₅)PO₂]₂ (Form I) exhibits relatively strong antiferromagnetic exchange interactions (J is about -4.50 cm⁻¹) and the effects on this magnetic exchange of doping diamagnetic cadmium ions into the material have been investigated. A series of mixed metal phosphinates of the form Mn₁₋x Cdx [H(C₆H₅)PO₂]₂ (Form I) where x=0 to 1.00 were prepared and investigated. The effect of doping with cadmium is to break the infinite manganese(II) monophenylphosphinate chain into finite segments and to generate monomer impurities in odd numbered segments. As the extent of doping is increased the average chain length decreases and the fraction of monomer increases. In addition, the exchange coupling constant, J, was found to decrease (from -4.50 to -2.70 cm⁻¹) as the average chain length decreases. Mn[H(C₆H₅)PO₂]₂ (Form 1(B)), which is precipitated from concentrated solutions, contains much shorter chain fragments than the pure Form I material. Mn[H(C₆H₅)PO₂]₂ (Form II) has a distinct infrared spectrum and X-ray powder diffraction pattern and shows much weaker antiferromagnetic behavior (J is about -2.40 cm⁻¹) than the Form I compound. Magnetic studies suggest that in this compound the average chain length is significantly smaller than in Mn[H(C₆H₅)PO₂]₂ (Form I).
The hydrated monophenylphosphinates of manganese(II), Mn[H(C₆H₅)PO₂]₂•H₂0 and Mn[H(C₆H₅)PO₂]₂•2H₂0, were synthesized and characterized in this work. The structures of these compounds are considered to be similar to those of the anhydrous materials except in the hydrated compounds one or two of the metal coordination sites are occupied by water molecules. The dihydrate shows only very weak antiferromagnetic properties (J is about -0.50 cm⁻¹). The diphenylphosphinates of manganese(II) and cadmium(II) were also prepared and characterized. The infrared spectra and X-ray powder diffraction patterns for these materials are distinct from each other,which indicates the compounds are not isomorphous. Only rather weak magnetic exchange was observed in the manganese compound. Zn[H(C₆H₅)PO₂]₂ has also been synthesized and partially characterized in this work. The infrared spectrum and X-ray powder diffraction pattern obtained for this compound are unique among all the metal phosphinates studied in this work.Science, Faculty of
Chemistry, Department of
Graduate
35
Haakonsen, Fredrik. "Optimizing of Strømhard austenitic manganese steel". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5605.
Testo completoAbstract (sommario):
In the present doctoral thesis the focus has been on two different ways to achieve improvement of the mechanical properties of an austenitic manganese steel. One of them was to introduce substrate particles and see if this could nucleate grains during solidification, giving grain refinement. The other one was to add a strong carbide forming element to the alloy, and affect the mechanical properties by precipitating carbides in the microstructure. The base for the experiments was the steel Strømhard. Strømhard is a former patented steel produced by Scana Steel Stavanger AS. It is a modification of the Hadfield steels, and is used as a wear steel for typically handling and crushing rock and stone. As one of the main products of this company and with the expiration of the patent, an upgrade of this alloy was desired, to continue to be leading in this marked. Cerium was chosen as the most likely grain refinement addition. As a highly reactive compound, cerium reacts with oxygen and sulfur already in the melt, forming cerium oxides and -sulfides which acts as substrate particles for melted steel to solidify on. Different amounts of additions, some times in combination with aluminum, were performed. Grain refinement was obtained in a casting added cerium in combination with aluminum, in which CeO2 was the supposed substrate particle. To form carbides, vanadium was added in different amounts to form various alloys. Several heat treatments were carried out, to create a microstructure with increased resistance to abrasive wear, by precipitating carbides within the grains. Increased hardness with aging after austenitizing was detected, but most of these microstructures did not improve the wear resistance. Two heat treatment procedures seemed to give promising microstructures. One of these was the standard form of heat treatment for austenitic manganese steels, which left a portion of the vanadium carbides remaining in the microstructure, the other being the standard heat treatment followed by aging at 950 °C for 200 hours, giving evenly distributed carbides within the grains. However, neither of these treatments improved the wear properties.
36
Parker, Michael William. "Structural studies on manganese superoxide dismutase". Thesis, University of Oxford, 1985. https://ora.ox.ac.uk/objects/uuid:b8fff51f-1e2f-41b1-baff-4e95b499f0de.
Testo completoAbstract (sommario):
Superoxide dismutases are widely distributed enzymes which catalyse the dismutation of superoxide radicals to dioxygen and hydrogen peroxide and are considered to be an important agent of an organism's defence against oxygen toxicity. The crystallization and low resolution structure determination of manganese superoxide dismutase (E.G. 1.15.1.1) from Bacillus stearothermophiluB is described. The enzyme crystallized in space group P21212 with two monomers per asymmetric unit and cell dimensions of ̲a=72.2Ã
, ̲b=111.1Ã
and ̲c=51.1Ã
. The crystals diffracted to beyond 2Ã
resolution but were fragile and prone to cell dimension changes. The cell dimension variability was overcome to some extent by crossllnking with glutaraldehyde. An electron density map was calculated to 6Ã
resolution initially by the method of multiple isomorphous replacement using data obtained from six heavy atom derivatives. The final map was calculated from single isomorphous replacement data using a map modification procedure. The fitting of an alpha carbon model of iron superoxide dismutase into the map suggested the iron and manganese enzymes are structurally related. The position of the metal atoms in the model solved difference Patterson maps calculated from data collected from a manganese-free crystal and from anomalous dispersion data. The latter data were collected using synchrotron radiation tuned close to the manganese absorption edge. The low resolution map and the availability of 2.4Ã
resolution native data paves the way for higher resolution X-ray studies of the crystals. A detailed analysis of amino acid sequences has been carried out on the various metal-containing superoxide dismutases. The results indicate that the enzymes can be classified according to their metal cofactor. The distribution and homology of the enzyme classes supports the endosymbiotic theory of the origin of cell organelles. The presence of the copper/zinc enzyme in Photobacterium leiognathi is shown to support the case for a eukaryote to prokaryote gene transfer.
37
Elghoul, Zoelfikar. "Manganese phosphate coating mini-line lab". Thesis, Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-23122.
Testo completoAbstract (sommario):
The following report is conducted in collaboration with the University of Halmstad. As the development of today's vehicles demands environmentalregulations require reduced emissions of CO2, performance, economy and safety, Lighter and efficient vehicles in transmission, this intensive development coupledwith re-optimization of the conflicting demands driveability, durability,efficiency and noise comfort. During the past 10 year the design margins hasbeen reduced. This means that the former research experience must be renewedfor development continues. As a part of the research conducted at HalmstadUniversity is an interest in being able to prepare these surfaces in different ways,in a lab environment. In this thesis, two processes in question, manganesephosphate and coating treatment. The purpose of this project is to construct a mini lab which will achieve theprocess of the surface treatment of machine element components in a laboratoryenvironment. The purpose of this project is to design and control the process which willconfigure all the details and specification required to achieve stagesof phosphate process as well the properties of every details in the chain ofimmersion and safety environment during the process stages, the task alsoincluding Risk analysis. The method that used was the same that was used by us during earlier courses inconstruction method written by Fredy Olsson, method principle /primary andmanufacturing. The development of the design has been done using brainstorming. The basic idea is a common idea where this since developed into aprototype.
38
Guo, Xiaoming. "Manganese-Bismuth prepared by rapid solidification". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39567.
Testo completoAbstract (sommario):
The low temperature phase (LTP) of MnBi, an interesting material with large magnetic anisotropy, has been obtained for the first time in bulk quantities in almost single-phase form ($>$95$ sp{wt}$%) by melt-spinning, followed by annealing.X-ray, electron microscope and differential scanning calorimetry (DSC) studies indicate that the melt-spun MnBi is amorphous, and may be phase separated. A mechanism is suggested for the glass formation in MnBi. Upon heating, amorphous MnBi first crystallizes around 440 K, then forms LTP around 540 K. DSC and thermomagnetometry studies show that the LTP transforms to high temperature phase around 630 K through two separate processes: a composition transition and a magneto-structural transition.
The anisotropy field, $H sb{a}$ of LTP, is measured from 147 to 586 K by a pulsed magnet combined with the singular point detection technique (SPD). $H sb{a}$ increases with temperature, and reaches a maximum value of 9 T at 530 K. The critical field for spin reversal of a ferrimagnetic phase of MnBi is also detected by SPD from 80 to 200 K, reaching a maximum value of 8 T at 120 K. The coercivity of LTP is successfully described by a model of domain wall pinning which predicts, at 300 K, a domain wall energy of 15.7 $erg/cm sp2$ and a wall thickness of 70 A.
39
Bramhall, M. D. "The toughness of iron manganese alloys". Thesis, Sheffield Hallam University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234820.
Testo completo
40
Ali, Sarfraz. "The deposition of manganese phosphate coatings". Thesis, Brunel University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363476.
Testo completo
41
Hughes, Timothy John. "Luminescent collisions of energetic manganese atoms". Thesis, Northumbria University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262819.
Testo completo
42
James, Leanne. "Manganese complexes with biomimetic antioxidant activity". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7073.
Testo completoAbstract (sommario):
Several seven-coordinate manganese complexes have been synthesised, characterised and tested for both superoxide dismutase and catalase activity. Macrocyclic ring contractions have led to a series of new seven coordinate mononuclear manganese(II) macrocycles that have potential for their use as working superoxide dismutase mimics. Numerous polynuclear seven coordinate manganese(II) macrocycles have been synthesised via Schiff base condensation. Subsequent reduction of the imine bonds has led to a variety of reduced amine analogues with varying axial ligands. The geometry has been compared about the manganese centres where possible. From the results of each complex tested for superoxide dismutase activity, the µ-chloro bridged tetranuclear complex [Mn2(C24H29N6O2)(Cl)2]2(ClO4)2 has proved to be the most efficient mimic with a calculated KMcCF value of 7.7 x 106 [M-1 s-1]. A method for measuring catalase activity has been developed, and the most efficient catalase active compound was found to be [Mn5(C24H29N6O2)2(OAc)2(ClO4)2](ClO4)2 with one molecule of complex breaking down approximately 59000 molecules of hydrogen peroxide after one minute. Catalase testing showed that a reduction of the imine bonds produced an increase in activity overall for the complexes of H2L1 (C24H29N6O2), but a decrease was observed for the reduced tripodal complexes. An increase in the number of manganese centres resulted in a rise in catalase activity. Many of the complexes tested for catalase activity showed an induction period prior to the activity being observed. This may suggest that the complexes undergo a change in structure, or that there is a rearrangement occurring before catalase activity may be observed. The results that are presented indicate that the axial ligands have an effect on the rate of catalase activity and the observed induction period. Of the molecules that were tested for both superoxide dismutase and catalase activity, the pentanuclear complex [Mn5(C24H29N6O2)2(OAc)2(ClO4)2](ClO4)2 showed high activity for both analyses. This may be due to the extra manganese centre within the complex and the axial ligands that are present when compared with other tetranuclear complexes. The complex [Mn5(HL1)(OAc)2(ClO4)2](ClO4)2 may prove to be a good candidate for a working superoxide dismutase mimic. Ring contracted complexes show high rates of superoxide dismutase activity but possess limited catalase activity. Attempts have been made to produce a direct method of measuring superoxide dismutase activity using a stop-flow technique to complement the results using the indirect NBT (Nitro blue Tetrazoleum) method. This was carried out by analysing low concentration solutions of both complex and superoxide on a millisecond timescale. Progress has been made for this method with preliminary results being obtained.
43
Parsons, Thomas. "The anion chemistry of manganese perovskites". Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497068.
Testo completo
44
Franklin, Paul Anthony. "Zinc and manganese homeostasis in brain". Thesis, University of Sunderland, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283763.
Testo completo
45
Lewis, Elizabeth A. "Functional models of manganese superoxide dismutases". Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247034.
Testo completo
46
Wilfred, Cecilia Devi. "Tandem oxidation processes using manganese dioxide". Thesis, University of York, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416232.
Testo completo
47
Brown, Nathan Charles. "Redox-active carbonyl complexes of manganese". Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294929.
Testo completo
48
Westerhaus, Felix Alexander. "Manganese-catalyzed carbonylation of alkyl iodides". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55103.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.Vita. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-125).
The palladium-catalyzed cross-coupling of aryl bromides with zirconocene-benzyne complexes has been investigated by S.L. Buchwald and coworkers. This method allows the formation of substituted biphenyls and terphenyls, however only two ortho-substituents are tolerated in this transformation. The studies reportd herein aimed at the synthesis of tri- and tetra substituted biaryls, since they are important precursors to biaryl phosphine ligands. The project did not succeed due to stability problems of the formed substituted zirconium biaryl. A general method for the manganese-catalyzed carbonylation of alkyl iodides while using a variety of nucleophiles was developed. The method concerns the alkoxy and amino carbonylation as well as the use of more unconventional nucleophiles such as thiols, azide and hydride. The method employs alkyl iodides although bromides are also feasible substrates through in situ Finkelstein reaction with catalytic to substoichiometric amounts of sodium iodide. The functional group tolerance is high and the conditions for the transformation are mild using only 40 psi of carbon monoxide pressure and temperatures between r.t. and 90°C for more difficult cases.
by Felix Alexander Westerhaus.
S.M.
49
Huang, Haitao. "Manganese spinels for rechargeable lithium batteries". Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/13603.
Testo completoAbstract (sommario):
The synthesis, characterisation and performance of lithium manganese oxide spinels have been studied in terms of their application as cathode materials in rechargeable lithium batteries. A new air stable synthesis based on a solution route has been proposed. Powder X-ray diffraction demonstrates that formation of single phase spinel is possible at temperatures as low as 200 °C. Chemical analysis indicates that the compositions of the spinels prepared by the new solution route depend on the firing temperature. A temperature of 200 °C gives a composition of LiMn2O4.1 and the oxygen content decreases with increasing firing temperature, reaching LiMn2O4 .02 at 600 °C and LiMn2O4 at 800 °C. TEM indicates that the solution based spinels possess small particle sizes, less than 1 ?m. All these characteristics differ markedly from the highly stoichiometric and crystalline spinel prepared by traditional solid state reaction over 800 °C. Electrochemical cells based on the new spinel cathodes were constructed and subjected to galvanostatical cycling at a high discharge rate of C/2 for 300 cycles (charging at C/4). The material fired at 200 °C exhibits excellent performance at 3 V cells. An initial capacity of around 140 mAhg-1 is obtained, very close to the theoretical capacity (148 mAhg-1 ) expected for LiMn2O4 . An enhancement of capacity retention by nearly 50 % after 300 cycles is obtained if < 1 wt % of carbon is added to the solution during synthesis. After 300 cycles, 64 % of the initial capacity remains. The spinel prepared by the solution route and fired at 600 °C gives excellent performance in 4 V cells. An initial capacity of 120 mAhg-1 is obtained and around 75 % of capacity remains after 300 cycles. Ex-situ X-ray diffraction and electrochemical studies such as ac impedance and cyclic voltammetry including the use of microelectrodes were carried out to understand self-discharge and capacity loss on cycling. Spinel dissolution in the electrolyte as well as layer formed on the electrode surface may play an important part in the cycle life of the 4 V spinel cathode. The capacity loss in the 3 V cells arises from incomplete reversibility of the phase transition between cubic and tetragonal spinel which accompanies each cycle.
50
Truong, Dao Y. Nhi. "Thermoelectric properties of higher manganese silicides". Caen, 2015. http://www.theses.fr/2015CAEN2020.
Testo completoAbstract (sommario):
CE TRAVAIL VISE À COUVRIR UNE VARIÉTÉ D’ASPECTS RELATIFS AU SILICIURE DE MANGANESE (HMS), PAR EXEMPLE, LES COMPOSITES, LES SUBSTITUTIONS, LES MÉTHODES DE SYNTHÈSE, ET LES ÉVOLUTIONS STRUCTURALES. LES COMPOSITES FAITS DE COMPOSÉS À BASE DE HMS ET DE NANO-INCLUSIONS ONT ÉTÉ PRÉPARÉS PAR DEUX PROCÉDURES DIFFÉRENTES, I. E. (I) LA RÉACTION À L’ÉTAT SOLIDE, LE MÉLANGE MANUEL, ET LE PRESSAGE À CHAUD, OU (II) LE BROYAGE À BILLES DANS DES CONDITIONS DOUCES ET LE FRITTAGE RÉACTIF. LA DERNIÈRE APPROCHE A PROUVÉ SON EFFICACITÉ DANS LA PRÉPARATION DES COMPOSITES NANOTUBE DE CARBONE MULTIFEUILLET (MWCNT)/MATÉRIAU À BASE DE HMS, QUI CONTIENNENT PRINCIPALEMENT DES PHASES HMS AVEC UNE RÉPARTITION HOMOGÈNE DE MWCNTS. IL A ÉTÉ DÉMONTRÉ QU’ UNE RÉPARTITION FINE DES NANO-INCLUSIONS A JOUÉ UN RÔLE CRUCIAL DANS LA RÉDUCTION DE LA CONDUCTIVITÉ THERMIQUE À TRAVERS L’AMÉLIORATION DE LA DISSIPATION DES PHONONS DANS LES MATÉRIAUX À BASE DE HMS, RÉSULTANT EN UNE AUGMENTATION D’ENVIRON 20% DE L’EFFICACITÉ MAXIMALE POUR LA COMPOSITE MWCNT/MATÉRIAU À BASE DE HMS AVEC 1,0% EN MASSE DE MWCNT. LA SUBSTITUTION DU MOLYBDÈNE, DU TUNGSTÈNE, OU D’ARGENT SUR LES SITES DE Mn, ET DE GERMANIUM OU D’ALUMINIUM SUR LES SITES DE Si, A ÉTÉ ÉTUDIÉE POUR LES MATÉRIAUX À BASE DE HMS. LA MEILLEURE EFFICACITÉ THERMOÉLECTRIQUE ENTRE DIFFÉRENTS TENEURS DE Ge A ÉTÉ OBTENUE DANS LE MÉLANGE DE PHASE DE LA COMPOSITION NON STOECHIOMÉTRIQUE MnSi1. 75Ge0. 02, QUI A ENSUITE ÉTÉ CHOISI COMME LE MATÉRIAU DE BASE POUR LES AUTRES SUBSTITUTIONS. AUCUNE MODIFICATION ESSENTIELLE DES PROPRIÉTÉS ÉLECTRIQUES N’A ÉTÉ OBSERVÉE, MAIS UNE DIMINUTION IMPORTANTE DE LA CONDUCTIVITÉ THERMIQUE DE RÉSEAU A ÉTÉ OBTENUE EN RAISON D’UNE MEILLEUR DISSIPATION DES PHONONS, AVEC LA PLUS GRANDE RÉDUCTION JUSQU’ À 25% POUR LA SUBSTITUTION DU MOLYBDÈNE. LE FACTEUR DE MÉRITE MAXIMALE, ZT, ÉTAIT D’ENVIRON 0,40 POUR LE MATÉRIAU AVEC 2% DE MOLYBDÈNE SUR LES SITES DE Mn. LES VALEURS ZT MAXIMALES VARIANT DE 0,31 À 0,42 ONT ÉTÉ ATTEINTES POUR DIVERSES COMPOSITIONS PRÉPARÉES PAR L’ALLIAGE MÉCANIQUE, LE BROYAGE MÉCANIQUE, ET LE TRAITEMENT THERMIQUE DANS UN FOUR CONVENTIONNEL, AINSI QUE PAR LA RÉACTION À L’ÉTAT SOLIDE, QUI POURRAIENT ÊTRE AMÉLIORÉES PAR ÉLIMINER COMPLÈTEMENT LES PRODUITS SECONDAIRES. PAR LA SUITE, UN PROCESSUS SIMPLE ET EFFICACE A ÉTÉ UTILISÉ POUR LA SYNTHÈSE DE HMS NON DOPÉ, IMPLIQUANT LE BROYAGE À BILLES AVEC N-HEXANE DANS DES CONDITIONS DOUCES POUR OBTENIR DES MÉLANGE HOMOGÈNES D’ÉLÉMENTS CONSTITUTIFS, ET LE FRITTAGE FLASH SUBSÉQUENTE POUR LA RÉACTION DIRECTE À L’ÉTAT SOLIDE. LES PARTICULES FINES OBTENUES APRÈS LE BROYAGE AVEC N-HEXANE ONT PERMIS D’AMÉLIORER LE TAUX DE RÉACTION PLUS TARD, RÉSULTANT DES MATÉRIAUX PURS DE HMS. EN CONSÉQUENCE, LE FACTEUR DE MÉRITE MAXIMAL ÉTAIT DE 0,55 À 850 K, UNE VALEUR ÉLEVÉE POUR UN HMS NON DOPÉ. DE PLUS, LES MONOCRISTAUX DE HMS ONT ÉTÉ PRÉPARÉS EN UTILISANT LE TRANSPORT CHIMIQUE EN PHASE VAPEUR À TRÈS FAIBLE RENDEMENT, MAIS LEURS MAUVAISES QUALITÉS ENTRAÎNÉ EN BASSE RÉSOLUTION DE DIFFRACTION DES RAYONS X SUR MONOCRISTAUX. LES MATÉRIAUX À BASE DE HMS, Y COMPRIS CEUX AVEC DES RATIOS ATOMIQUES Si/Mn DIFFÉRENTS ET DIVERS DOPANTS, PAR EXEMPLE, Ge, Al, Cr ET Mo, ONT ÉTÉ PRÉPARÉS POUR ETUDIER L’ÉVOLUTION STRUCTURALE ENGENDREE PAR UNE AUGMENTATION DE LA TEMPÉRATURE. LA FORMULE STRUCTURALE MOYENNE À LA TEMPÉRATURE AMBIANTE ET SA DÉPENDANCE DE LA TEMPÉRATURE ONT ÉTÉ FORTEMENT INFLUENCÉE PAR LA COMPOSITION DES MATÉRIAUX DE DÉPART AINSI QUE PAR LA NATURE DES DOPANTS. LES MESURES DES PROPRIÉTÉS PHYSIQUES SUR LE COMPOSÉ MnSi1. 75 ONT RÉVÉLÉ QU’UNE CORRÉLATION ENTRE LES PROPRIÉTÉS THERMOÉLECTRIQUES ET LA FORMULE STRUCTURALE MOYENNE DES MATÉRIAUX À BASE DE HMS POURRAIT ÊTRE ATTENDUTHIS WORK AIMS TO COVER A VARIETY OF ASPECTS RELATED TO THE HIGHER MANGANESE SILICIDE (HMS) SYSTEM, E. G. COMPOSITES, SUBSTITUTIONS, SYNTHESIS METHODS, AND STRUCTURAL EVOLUTIONS. THE COMPOSITES MADE OF HMS-BASED COMPOUNDS AND NANO-INCLUSIONS HAVE BEEN PREPARED VIA TWO DIFFERENT PROCEDURES, I. E. (I) SOLID STATE REACTION, MANUALLY MIXING, AND HOT PRESSING, OR (II) SOFT BALL MILLING AND REACTIVE SPARK PLASMA SINTERING. THE LATER APPROACH HAS PROVED ITS EFFECTIVENESS IN PREPARING THE MULTI-WALLED CARBON NANOTUBE (MWCNT)/HMS-BASED MATERIAL COMPOSITES MAINLY CONTAINING THE HMS PHASES WITH A HOMOGENEOUS DISTRIBUTION OF MWCNTS. IT WAS DEMONSTRATED THAT A FINE DISTRIBUTION OF THE NANO-INCLUSIONS PLAYED A CRUCIAL ROLE IN REDUCING THERMAL CONDUCTIVITY THROUGH ENHANCING PHONON SCATTERING IN HMS-BASED MATERIALS, RESULTING IN AN IMPROVEMENT BY ABOUT 20% FOR THE MAXIMUM EFFICIENCY FOR THE MWCNT/HMS-BASED MATERIAL COMPOSITE WITH 1. 0 WT. -% MWCNTs. THE SUBSTITUTION OF MOLYBDENUM, TUNGSTEN, OR SILVER AT THE Mn SITES, AND OF GERMANIUM OR ALUMINIUM AT THE Si SITES HAS BEEN STUDIED FOR THE HMS-BASED MATERIALS. THE BEST THERMOELECTRIC EFFICIENCY AMONG DIFFERENT Ge CONTENTS WAS ACHIEVED FOR THE PHASE MIXTURE OF THE NON-STOICHIOMETRIC COMPOSITION MnSi1. 75Ge0. 02, WHICH WAS THEN CHOSEN TO BE THE BASE MATERIAL FOR FURTHER SUBSTITUTIONS. NO CRUCIAL MODIFICATION OF THE ELECTRICAL PROPERTIES OF THE BASE MATERIAL WAS OBSERVED, BUT LARGE DECREASES OF LATTICE THERMAL CONDUCTIVITY WERE ACHIEVED BECAUSE OF ENHANCED PHONON SCATTERING, WITH THE HIGHEST REDUCTION UP TO 25% FOR MOLYBDENUM SUBSTITUTION. THE MAXIMUM FIGURE OF MERIT, ZT, VALUE WAS APPROXIMATELY 0. 40 FOR THE MATERIAL WITH 2 AT. -% MOLYBDENUM SUBSTITUTION AT THE Mn SITES. THE MAXIMUM ZT VALUES RANGING FROM 0. 31 TO 0. 42 HAVE BEEN ACHIEVED FOR VARIOUS COMPOSITIONS PREPARED BY MECHANICAL ALLOYING, MECHANICAL MILLING AND HEAT TREATING IN CONVENTIONAL FURNACE, AS WELL AS BY SOLID STATE REACTION, WHICH COULD POSSIBLY BE IMPROVED BY COMPLETELY ELIMINATING THE SIDE PRODUCTS. SYBSEQUENTLY, A SIMPLE AND EFFECTIVE PROCESS WAS USED TO SYNTHESIZE UNDOPED. HMS, INVOLVING BALL MILLING IN N-HEXANE UNDER SOFT CONDITIONS TO OBTAIN HOMOGENEOUS MIXTURES OF CONSTITUTING ELEMENTS, AND SUBSEQUENT SPARK PLASMA SINTERING FOR A DIRECT SOLID STATE REACTION. THE OBTAINED FINE PARTICLES AFTR THE MILLING PROCESS IN N-HEXANE HELPED TO IMPROVE THE REACTION RATE LATER ON, RESULTING IN PURE HMS MATERIALS. AS A CONSEQUENCE, THE MAXIMUM THERMOELECTRIC FIGURE OF MERIT OBTAINED WAS 0. 55 AT 850 K, A HIGH VALUE FOR UNDOPED HMS. MOREOVER, SINGLE CRYSTALS OF HMS HAVE BEEN PREPARED USING CHEMICAL VAPOR TRANSPORT WITH VERY LOW YIELD, BUT THEIR POOR QUALITITES RESULTED IN LOW RESOLUTION IN SINGLE CRYSTAL X-RAY DIFFRACTION. HMS-BASED MATERIALS INCLUDING THE ONES WITH DIFFERENT Si/Mn ATOMIC RATIOS AND VARIOUS DOPANTS, E. G. Ge, Al, Cr, AND Mo, HAVE BEEN PREPARED FOR THE INVESTIGATION OF STRUCTURAL EVOLUTION UPON HEATING UP FROM ROOM TEMPERATURE TO HIGH TEMPERATURE. THE AVERAGE STRUCTURAL FORMULA AT ROOM TEMPERATURRE AND ITS TEMPERATURE DEPENDENCE WERE STRONGLY IMPACTED BY THE PHASE COMPOSITIONS OF THE STARTING MATERIALS AS WELL AS THE NATURE OF DOPANTS. PHYSICAL PROPERTY MEASUREMENTS ON THE MnSi1. 75 COMPOUND REVEALED THAT A CORRELATION BETWEEN THE THERMOELECTRIC PROPERTIES AND THE AVERAGE STRUCTURAL FORMULA OF BULK HMS-BASED MATERIALS COULD BE EXPECTED