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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Sinteza, karakterizacija i primena sorbenata na bazi gvožđa i mangana za uklanjanje arsena iz vode / Synthesis, characterisation and application iron and manganeous based sorbents for arsenic removal from water

Nikić Jasmina 12 July 2019 (has links)
<p>Prisusutvo&nbsp; arsena&nbsp; u&nbsp; podzemnim&nbsp; vodama,&nbsp; koje&nbsp; se&nbsp; primenjuju&nbsp; za vodosnabdevanje stanovni&scaron;tva je globalan problem. Različiti&nbsp; konvencionalni<br />procesi&nbsp; se primenjuju&nbsp; za&nbsp; uklanjanje&nbsp; arsena iz vode, uključujući koagulaciju i<br />flokulaciju,&nbsp; sorpciju,&nbsp; membransku&nbsp; filtraciju&nbsp; i&nbsp; jonsku&nbsp; izmenu.&nbsp; Uzimajući&nbsp; u<br />obzir relativnu nisku cenu, jednostavnu kontrolu procesa i održavanje, visok<br />stepen uklanjanja arsena, sorpcija se smatra jednom od najpodobnijih tehnika<br />za uklanjanje arsena u tretmanu vode za piće. Premda su na trži&scaron;tu dostupni<br />različiti&nbsp; sorbenti&nbsp; za&nbsp; uklanjanje&nbsp; arsena,&nbsp; postoji&nbsp; potreba&nbsp; za&nbsp; iznalaženjem&nbsp; i<br />razvojem&nbsp; novih&nbsp;<em> low-cost&nbsp;</em> sorbenata,&nbsp; a&nbsp; kojima&nbsp; bi&nbsp; se&nbsp; pak&nbsp; mogao&nbsp; obezbediti<br />visok stepen uklanjanja oba oksidaciona oblika&nbsp; arsena,&nbsp; i&nbsp; As(III) i As(V). Cilj<br />ovog rada bio je usmeren na sintezu i karakterizaciju novih sorbenata na bazi<br />gvožđa&nbsp; i&nbsp; mangana&nbsp; odnosno&nbsp; Fe-Mn&nbsp; binarnog&nbsp; oksida,&nbsp; ispitivanje&nbsp; njihovog<br />potencijala&nbsp; za&nbsp; uklanjanje&nbsp; arsena&nbsp; iz&nbsp; vode&nbsp; i&nbsp; utvrđivanje&nbsp; da&nbsp; li&nbsp; novosintetisani<br />sorbenti po pitanju efikasnosti, mogu konkurisati postojećim komercijalnim i<br />&scaron;iroko kori&scaron;ćenim sorbentima u tretmanima voda.<br />Metodom&nbsp; precipitacije,&nbsp; sintetisani&nbsp; su&nbsp; Fe-Mn&nbsp; binarni&nbsp; oksidi&nbsp; sa&nbsp; različitim Fe:Mn&nbsp; molskim&nbsp; odnosima&nbsp; 1:1,&nbsp; 3:1,&nbsp; 6:1&nbsp; i&nbsp; 9:1,&nbsp; dok&nbsp; su&nbsp; kombinacijom heterogene&nbsp; nukleacione&nbsp; tehnike&nbsp; i&nbsp; precipitacije,&nbsp; sintetisana&nbsp; i&nbsp; četiri&nbsp; sorbenta magnetnih&nbsp; svojstava&nbsp; (Mag,&nbsp; Mag-Fe,&nbsp; Mag-Mn,&nbsp; Mag-FeMn).&nbsp; Modifikacijom biopolimera&nbsp; Chitosana&nbsp; i&nbsp; GAC,&nbsp; sa&nbsp; Fe-Mn&nbsp; binarnim&nbsp; oksidom,&nbsp; razvijena&nbsp; su preostala&nbsp; dva&nbsp; materijala&nbsp; Chit-FeMn,&nbsp; odnosno&nbsp; GAC-FeMn.&nbsp; Sintetisani sorbenti su karakterisani različitim tehnikama i metodama (SEM/EDS, XRD,FTIR, BET).Fizičko-hemijskom karakterizacijom sintetisanih sorbenata ustanovljeno je da se Fe-Mn binarni oksidi i magnetni materijali, karakteri&scaron;u relativno velikim specifičnim&nbsp; povr&scaron;inama&nbsp; (109-300&nbsp; m<sup> 2 </sup>/g)&nbsp; i&nbsp; zapreminama&nbsp; mezopora (0,144-0,403&nbsp; cm <sup>3</sup> /g).&nbsp; Velika&nbsp; specifična&nbsp; povr&scaron;ina&nbsp; i&nbsp; razvijena&nbsp; mikroporozna struktura uočena je kod GAC-FeMn (996 m<br /><sup>2</sup> /g; 0,394 cm<sup> 3 /</sup>g). U poređenju sa ostalim&nbsp; sintetisanim&nbsp; sorbentima,&nbsp; Chit-FeMn&nbsp; je&nbsp; karakterisala&nbsp; najmanja specifična&nbsp; povr&scaron;ina&nbsp; i&nbsp; zapremina&nbsp; mezopora&nbsp; (1,99&nbsp; m<br /><sup>2 </sup>/g;&nbsp; 0,014&nbsp; cm <sup>3</sup> /g).&nbsp; XRD analiza&nbsp; Fe-Mn&nbsp; binarnih&nbsp; oksida&nbsp; ukazala&nbsp; je&nbsp; da&nbsp; je&nbsp; fazna&nbsp; struktura&nbsp; sintetisanih Fe-Mn&nbsp; binarnih&nbsp; oksida&nbsp; slična&nbsp; ferihidratu&nbsp; dok&nbsp; je&nbsp; fazna&nbsp; struktura&nbsp; magnetnih materijala ukazala na prisustvo magemita.<br />Ispitivanja kinetike sorpcionog procesa ukazala su da je mehanizam sorpcije<br />As(III)&nbsp; i&nbsp; As(V)&nbsp; na&nbsp; sintetisanim&nbsp; sorbentima&nbsp; sloţena&nbsp; kombinacija&nbsp; povr&scaron;inske<br />hemisorpcije,&nbsp; koja&nbsp; se&nbsp; odvija&nbsp; kroz&nbsp; granični&nbsp; sloj&nbsp; čestica&nbsp; sorbenata&nbsp; i unutarčestične difuzije. Tome u prilog i&scaron;li su i rezultati FTIR analize kojima<br />je potvrđeno da se sorpcija arsena na sintetisanim sorbentima ostvaruje kroz<br />interakcije hidroksilnih grupa gvožđa prisutnih na povr&scaron;ini sorbenata i arsena.<br />Dodatno, pokazano je da se za razliku od sorpcije As(V), sorpcija As(III) na sorbentima&nbsp; koji&nbsp; pored&nbsp; oksida&nbsp; gvožđa&nbsp; sadrže&nbsp; i&nbsp; okside&nbsp; mangana&nbsp; (Fe-Mn binarni oksidi, Mag-FeMn, Mag-Mn,Chit-FeMn i GAC-FeMn) odvija u dva koraka. U prvom koraku As(III) se oksiduje do As(V), dok u drugom koraku, oksidovani&nbsp; As(V)&nbsp; mehanizmom&nbsp; ligandne&nbsp; izmene&nbsp; formira&nbsp; komplekse&nbsp; na povr&scaron;ini ovih sorbenata.<br />Afiniteti sorpcije Fe-Mn binarnih oksida (na osnovu K<sub>d</sub> vrednosti)&nbsp; za As(III) opadali su u nizu Fe-Mn 3:1 &gt; Fe-Mn 1:1 &gt; Fe-Mn 6:1 &gt; Fe-Mn 9:1 odnosno kod&nbsp; As(V):&nbsp; Fe-Mn&nbsp; 6:1&nbsp; &gt;&nbsp; Fe-Mn&nbsp; 3:1&nbsp; &gt;&nbsp; Fe-Mn&nbsp; 9:1&nbsp; &gt;&nbsp; Fe-Mn&nbsp; 1:1.&nbsp; Kod magnetnih kompozita,&nbsp; najveća K<sub>d</sub> vrednost za As(III) i As(V) ustanovljena je kod&nbsp; Mag-FeMn.&nbsp; Uop&scaron;teno,&nbsp; Kd<br />vrednosti&nbsp; za&nbsp; As(III),&nbsp; kod&nbsp; magnetnih kompozita,&nbsp; opadale&nbsp; su&nbsp; u&nbsp; nizu:&nbsp; Mag-FeMn&nbsp; &gt;&nbsp; Mag-Mn&nbsp; &gt;&nbsp; Mag&nbsp; &gt;&nbsp; Mag-Fe, Slično, afinitet sorbenata za As(V), opadao je na sledeći način: Mag-FeMn &gt; Mag&nbsp; &gt;&nbsp; Mag-Fe&nbsp; &gt;&nbsp; Mag-Mn.&nbsp; U&nbsp; poređenju&nbsp; sa&nbsp; neimpregniranim,&nbsp; K<sub>d</sub> vrednosti bile su daleko veće kod obloţenih materijala, Chit-FeMn i GAC-FeMn, &scaron;to je ukazalo&nbsp; na&nbsp; značajan&nbsp; doprinos&nbsp; Fe-Mn&nbsp; binarnog&nbsp; oksida&nbsp; adsorpcionom kapacitetu neimpregniranih medija za As(III) i As(V). U&nbsp; odnosu&nbsp; na&nbsp; ostale&nbsp; ispitivane&nbsp; anjone,&nbsp; najveći&nbsp; uticaj&nbsp; na&nbsp; sorpciju&nbsp; oba&nbsp; oblika arsena&nbsp; na&nbsp; svim&nbsp; sintetisanim&nbsp; sorbentima&nbsp; uočen&nbsp; je&nbsp; kod&nbsp; fosfata,&nbsp; dok&nbsp; je&nbsp; uticaj nitrata i hlorida, u svim slučajevima bio bez značaja. Uticaj ispitivanih anjona na&nbsp; sorpciju&nbsp; As(III)&nbsp; i&nbsp; As(V)&nbsp; na&nbsp; Fe-Mn&nbsp; binarnim&nbsp; oksidima,&nbsp; magnetnim materijalima, Chit-FeMn kao i na sorpciju As(V) na GAC-FeMn, opadao je u nizu: fosfati &gt; silikati &gt; karbonati &gt; sulfati &gt; nitrati &gt; hloridi. Slično, uticaj ispitivanih&nbsp; anjona&nbsp; na&nbsp; sorpciju&nbsp; As(III)&nbsp; na&nbsp; GAC-FeMn&nbsp; je&nbsp; opadao&nbsp; na&nbsp; sledeći način: fosfati &gt; silikati &gt; sulfati &gt; karbonati &gt; nitrati &gt; hloridi.Primenom&nbsp; sme&scaron;e&nbsp; NaCl-NaOH-NaOCl&nbsp; odnosno&nbsp; primenom&nbsp; 0,1&nbsp; M&nbsp; i&nbsp; 0,5&nbsp; M&nbsp; rastvora NaOH, ustanovljeno je da se sintetisani sorbenti mogu jednostavno i&nbsp; efikasno&nbsp; regenerisati&nbsp; i&nbsp; vi&scaron;estruko&nbsp; primeniti,&nbsp; &scaron;to&nbsp; je&nbsp; od&nbsp; izuzetnog&nbsp; značaja&nbsp; sa ekolo&scaron;kog i ekonomskog aspekta.&nbsp; Najmanje smanjenje sorpcionog kapaciteta&nbsp; i za As(III) i za As(V), nakon pet ciklusa sorpcije -desorpcije, ustanovljeno je kod binarnog oksida sa Fe:Mn molskim odnosom 3:1 i Mag-FeMn.&nbsp; Na osnovu rezultata prikazanih u ovom radu, može se zaključiti da sintetisani sorbenti,&nbsp; Fe-Mn&nbsp; binarni&nbsp; oksidi&nbsp; i&nbsp; magnetni&nbsp; kompoziti,&nbsp; posebno&nbsp; Mag-FeMn, mogu&nbsp; biti&nbsp; efikasna&nbsp; i&nbsp; ekonomična&nbsp; alternativa&nbsp; skupim&nbsp; komercijalnim sorbentima&nbsp; i&nbsp; drugim&nbsp; sofisticiranim&nbsp; tehnologijama.&nbsp; Visok&nbsp; oksidacioni&nbsp; i sorpcioni kapacitet ovih&nbsp; materijala, koji obezbeđuje istovremeno uklanjanje&nbsp; oba oksidaciona oblika arsena daje veliku prednost ovim sorbentima i čini ih veoma&nbsp; atraktivnim&nbsp; i&nbsp; obećavajućim&nbsp; u&nbsp; tretmanu&nbsp; voda.&nbsp; Dodatni&nbsp; benefit<br />magnetnih&nbsp; sorbenata,&nbsp; pre&nbsp; svega&nbsp; Mag-FeMn,&nbsp; ogleda&nbsp; se&nbsp; u&nbsp; njegovoj jednostavnoj separaciji iz vodenog medijuma i recirkulaciji u sistemu. Glavne prednosti&nbsp; sintetisanih&nbsp; Chit-FeMn&nbsp; i&nbsp; GAC-FeMn,&nbsp; ogledaju&nbsp; se&nbsp; u&nbsp; mogućnosti&nbsp; njihove primene kao efikasne filtracione ispune.</p> / <p>The&nbsp; presence&nbsp; of&nbsp; inorganic&nbsp; arsenic&nbsp; in&nbsp; groundwater&nbsp; used&nbsp; for&nbsp; drinking&nbsp; water supply&nbsp; is&nbsp; a&nbsp; global&nbsp; problem.&nbsp; Different&nbsp; techniques&nbsp; such&nbsp; as&nbsp; oxidation, coagulation,&nbsp; adsorption,&nbsp; ion&nbsp; exchange,&nbsp; and&nbsp; membrane&nbsp; filtration&nbsp; have&nbsp; been developed&nbsp; and&nbsp; applied&nbsp; for&nbsp; arsenic&nbsp; removal&nbsp; from&nbsp; aqueous&nbsp; media.&nbsp; Among these&nbsp; technologies,&nbsp;&nbsp; adsorption&nbsp; is&nbsp; regarded&nbsp; as&nbsp; one&nbsp; of&nbsp; the&nbsp; most&nbsp; promising approaches to remove arsenic from water because of its high efficiency, low cost, simplicity of operation. Although many sorbents for arsenic removal are available on the market, there is still a need to identify and develop new&nbsp; lowcost&nbsp; sorbents which are highly effective in removing both oxidation states of arsenic, As(III) and As(V). This dissertation therefore presents the synthesis and&nbsp; characterization&nbsp; of&nbsp; ten&nbsp; new&nbsp; iron&nbsp; and&nbsp; manganese&nbsp; based&nbsp; sorbents specifically developed for effective As removal. The Fe- Mn binary oxides were prepared with Fe:Mn molar ratios of 1:1, 3:1,6:1 and 9:1, while four heterogeneous magnetic composites (Mag, Mag-Fe,Mag-Mn,&nbsp; Mag-FeMn)&nbsp; were&nbsp; synthesized&nbsp; by&nbsp; combining&nbsp; the&nbsp; heterogeneous nucleation&nbsp; technique&nbsp; with&nbsp; precipitation.&nbsp; The&nbsp; remaining&nbsp; two&nbsp; materials, Chit-FeMn&nbsp; and&nbsp; GAC-FeMn,&nbsp; were&nbsp; created&nbsp; by&nbsp; modifying&nbsp; the&nbsp; Chitosan&nbsp; and GAC&nbsp; biopolymers&nbsp; with&nbsp; Fe-Mn&nbsp; binary&nbsp;&nbsp; oxide&nbsp; (Chit-FeMn&nbsp; and&nbsp; GAC-FeMn).Multiple&nbsp; techniques&nbsp; were&nbsp; applied&nbsp; to&nbsp; determine&nbsp; the&nbsp; physical&nbsp; and&nbsp; chemical characteristics&nbsp; of&nbsp; the&nbsp; resulting&nbsp; sorbents&nbsp; (including&nbsp; SEM/EDS,&nbsp; XRD,&nbsp; FTIR and BET analyses). In order to establish which sorbents show&nbsp; the greatest promise for application during&nbsp; drinking&nbsp; water&nbsp; treatment,&nbsp; the&nbsp; sorption&nbsp; capacity&nbsp; of&nbsp; the&nbsp; sorbents,&nbsp; theAs(III)&nbsp; and&nbsp; As(V)&nbsp; sorption&nbsp; mechanisms,&nbsp; and&nbsp; the&nbsp; impact&nbsp; of&nbsp; various&nbsp; factors relevant to arsenic sorption, including the regeneration potential and the reuse potential of the sorbents, were all investigated in&nbsp; batch experiments. During the physical characterisation, the Fe-Mn binary oxides and magnetic materials&nbsp; were&nbsp; found&nbsp; to&nbsp; have&nbsp; relatively&nbsp; large&nbsp; specific&nbsp; surface&nbsp; areas (109-300 m 2 /g) and mesopore volumes (0.144-0.403 cm 3 /g).&nbsp; A large specific surface&nbsp; area&nbsp; and&nbsp; microporous&nbsp; structure&nbsp; was&nbsp; observed&nbsp; for&nbsp; GAC-FeMn&nbsp; (996 m 2 /g;&nbsp; 0.394&nbsp; cm 3 /g).&nbsp; In&nbsp; comparison&nbsp; with&nbsp; the&nbsp; other&nbsp; synthesized&nbsp; sorbents,&nbsp; Chit-FeMn has the smallest specific surface area and pore volume (1.99 m 2 /g; 0.014&nbsp; cm 3 /g).&nbsp; XRD&nbsp; analyses&nbsp; of&nbsp; the&nbsp; Fe-Mn&nbsp; binary&nbsp; oxides&nbsp; indicated&nbsp; that&nbsp; the phase&nbsp; structure&nbsp; of&nbsp; the&nbsp; synthesized&nbsp; Fe-Mn&nbsp; binary&nbsp; oxides&nbsp; was&nbsp; similar&nbsp; to ferrihydrate,&nbsp; while&nbsp; the&nbsp; phase&nbsp; structure&nbsp; of&nbsp; the&nbsp; magnetic&nbsp; materials&nbsp; showed&nbsp; a good agreement with the XRD diffractogram of maghemite. Investigations into As sorption process kinetics have shown that the sorption mechanism&nbsp; for&nbsp; both&nbsp; As(III)&nbsp; and&nbsp; As(V)&nbsp; on&nbsp; the&nbsp; synthesized&nbsp; sorbents&nbsp; is&nbsp; a combination&nbsp; of&nbsp; surface&nbsp; hemisorption,&nbsp; which&nbsp; takes&nbsp; place&nbsp; through&nbsp; the boundary&nbsp; layer&nbsp; of&nbsp; sorbent&nbsp; particles,&nbsp; and&nbsp; intracellular&nbsp; diffusion.&nbsp; The&nbsp; FTIR analyses&nbsp; confirmed&nbsp; that&nbsp; arsenic&nbsp; sorption&nbsp; was&nbsp; accomplished&nbsp; through&nbsp; the interactions&nbsp; of&nbsp; the&nbsp; hydroxyl&nbsp; groups&nbsp; of&nbsp; iron&nbsp; present&nbsp; on&nbsp; the&nbsp; surface&nbsp; of&nbsp; the sorbents and arsenic. In contrast to the sorption of As(V), it was also shown that&nbsp; As(III)&nbsp; sorption&nbsp; onto&nbsp; sorbents&nbsp; containing&nbsp; manganese&nbsp; oxides&nbsp; (Fe-Mn binary&nbsp; oxides,&nbsp; Mag-FeMn,&nbsp; Mag-Mn,&nbsp; Chit-FeMn&nbsp; and&nbsp; GAC&nbsp; -FeMn)&nbsp; takes place in two steps. In the first step As(III) is oxidized to As(V), while in the second&nbsp; step,&nbsp; the&nbsp; oxidized&nbsp; As(V)&nbsp; forms&nbsp; complexes&nbsp; on&nbsp; the&nbsp; surface&nbsp; of&nbsp; the sorbents via ligand exchange. The&nbsp; Fe-Mn&nbsp; binary&nbsp; oxide&nbsp; sorption&nbsp; capacities&nbsp; (expressed&nbsp; as&nbsp; Kd values)&nbsp; for As(III)&nbsp;&nbsp; followed the trend Fe-Mn 3:1 &gt; Fe-Mn 1:1 &gt; Fe-Mn 6:1 &gt; Fe-Mn 9:1, whereas the&nbsp; As(V) trend was Fe-Mn 6:1 &gt; Fe-Mn 3:1 &gt; Fe-Mn 9:1 &gt; Fe-Mn 1:1. In the magnetic&nbsp; composites, the largest&nbsp; Kd value for As(III) and As(V) was&nbsp; obtained&nbsp; for&nbsp; Mag-FeMn.&nbsp; Generally,&nbsp; the&nbsp; Kd values&nbsp; for&nbsp; As(III)&nbsp; in&nbsp; the magnetic composites decreased in the series: Mag-FeMn &gt; Mag-Mn &gt; Mag &gt; Mag-Fe.&nbsp; Similarly,&nbsp; the&nbsp; affinity&nbsp; of&nbsp; the&nbsp; sorbents&nbsp; for&nbsp; As(V)&nbsp; was&nbsp; as&nbsp; follows: Mag-FeMn&nbsp; &gt;&nbsp; Mag&nbsp; &gt;&nbsp; Mag-Fe&nbsp; &gt;&nbsp; Mag- Mn.&nbsp; In&nbsp; comparison&nbsp; to&nbsp; the&nbsp; nonimpregnated&nbsp; materials,&nbsp; the&nbsp; Kd values&nbsp; were&nbsp; much&nbsp; higher&nbsp; for&nbsp; the&nbsp;&nbsp; boated materials,&nbsp; Chit-FeMn&nbsp; and&nbsp; GAC-FeMn,&nbsp; demonstrating&nbsp; the&nbsp; significant advantage&nbsp; Fe-Mn&nbsp; binary&nbsp; oxides&nbsp; provide&nbsp; in&nbsp; increasing&nbsp; As(III)&nbsp; and&nbsp; As(V)&nbsp; adsorption capacities. One&nbsp; of&nbsp; the&nbsp; most&nbsp; problematic&nbsp; limiting&nbsp; factors&nbsp; in&nbsp; applying&nbsp; adsorption technologies during drinking water treatment is the presence of other water constituents which interfere with the adsorption process.&nbsp; Investigations into the inhibitory effect of competive anions on the adsorption of both forms of arsenic&nbsp; revealed&nbsp; that&nbsp; phosphates&nbsp; were&nbsp; the&nbsp; worst&nbsp; offenders&nbsp; in&nbsp; terms&nbsp; ofreducing&nbsp; the&nbsp; arsenic&nbsp; removal&nbsp; efficacy&nbsp; of&nbsp; sorbents&nbsp; investigated.&nbsp; From&nbsp; the largest&nbsp; to&nbsp; the&nbsp; smallest&nbsp; negative&nbsp; influence&nbsp; of&nbsp; the&nbsp; anions&nbsp; investigated,&nbsp; for As(III)&nbsp; and&nbsp; As(V)&nbsp; adsorption&nbsp; on&nbsp; Fe-Mn&nbsp; binary&nbsp; oxides,&nbsp; magnetic&nbsp; materials and Chit-FeMn, as well as As(V) adsorption on GAC-FeMn, the order was: phosphates &gt; silicates &gt; carbonates &gt; sulfates &gt; nitrates &gt; chlorides, with the presence&nbsp; of&nbsp; the&nbsp; latter&nbsp; two&nbsp; anions&nbsp; proving&nbsp; almost&nbsp; irrelevant&nbsp; to&nbsp; the&nbsp; As adsorption&nbsp; process.&nbsp; Similarly,&nbsp; the&nbsp; negative&nbsp; influence&nbsp; of&nbsp; anions&nbsp; on&nbsp; As(III) sorption on GAC-FeMn was: phosphates &gt; silicates &gt; sulphates &gt; carbonates &gt; nitrates &gt; chlorides. Another&nbsp; issue&nbsp; with&nbsp; applying&nbsp; adsorption&nbsp; in&nbsp; real&nbsp; treatment&nbsp; conditions&nbsp; is&nbsp; the need to regularly&nbsp; regenerate and/or replace the spent sorbent. In this work, a simple&nbsp; and&nbsp; efficient&nbsp; process&nbsp; for&nbsp; sorbent&nbsp;&nbsp; rfegeneration&nbsp; is&nbsp; demonstrated.&nbsp; This regeneration&nbsp; process&nbsp; can&nbsp; be&nbsp; applied&nbsp; to&nbsp; the&nbsp; sorbents&nbsp; investigated&nbsp; multiple times, and uses an NaCl-NaOH-NaOCl mixture, or 0.1 M and 0.5 M NaOH solutions.&nbsp; This&nbsp; finding&nbsp; is&nbsp; of&nbsp; great&nbsp; importance&nbsp; from&nbsp; an&nbsp; ecological&nbsp; and economic point of view. The minimum reduction in the sorption capacity for both As(III) and As(V), after five sorption-regeneration cycles, was found in&nbsp; the&nbsp; binary&nbsp; oxide&nbsp; with&nbsp; a&nbsp; 3:1&nbsp; Fe:Mn&nbsp; molar&nbsp; ratio&nbsp; and&nbsp; Mag-FeMn.&nbsp; Arsenic sorption&nbsp; behaviour&nbsp; was&nbsp; also&nbsp; investigated&nbsp; using&nbsp; real&nbsp; groundwater&nbsp; samples, with the results demonstrating the great potential of 3:1 Fe-Mn binary oxide and Mag- FeMn. However, Chit-FeMn and GAC-FeMn were less effective at adsorbing As from the groundwater samples.Based on the results presented in this dissertation, it can&nbsp; be concluded that the synthesized&nbsp; sorbents,&nbsp; especially&nbsp; the&nbsp; Fe-Mn&nbsp; binary&nbsp; oxides&nbsp; and&nbsp; magnetic composites,&nbsp; and&nbsp; Mag-FeMn&nbsp; in&nbsp; particular,&nbsp; can&nbsp; be&nbsp; efficient&nbsp; and&nbsp; economical alternatives&nbsp; to&nbsp; expensive&nbsp; commercial&nbsp; sorbents&nbsp; and&nbsp; other&nbsp; sophisticated&nbsp; As removal&nbsp; technologies.&nbsp; The&nbsp; high&nbsp; oxidation&nbsp; and&nbsp; sorption&nbsp; capacity &nbsp; of&nbsp; these materials,&nbsp; which&nbsp; ensure&nbsp; the&nbsp; simultaneous&nbsp; removal&nbsp; of&nbsp; arsenic&nbsp; with&nbsp; both oxidation states, is a large advantage for these sorbents and makes them very attractive&nbsp; and&nbsp; promising&nbsp; for&nbsp; application&nbsp; in&nbsp; drinking&nbsp; water&nbsp; treatment.&nbsp; An additional&nbsp; benefit of the magnetic sorbents, primarily Mag-FeMn, is the ease with&nbsp; which&nbsp; they&nbsp; may&nbsp; be&nbsp; separated&nbsp; from&nbsp; the&nbsp; aqueous&nbsp; medium,&nbsp; allowing&nbsp; for simple&nbsp; recirculation within a system. Similarly,&nbsp; the main advantages of&nbsp; the synthesized Chit- FeMn and GAC-FeMn are reflected in their application as effective filtration media.</p>
62

Contribution à l'étude de la dépollution de l'air chargé en composés organiques volatils par un procédé associant un plasma de décharge à barrière diélectrique impulsionnelle et des catalyseurs / Removal of volatile organic compounds using pulsed dielectric barrier discharge plasma combined to catalysts

Pham, Huu Thien 29 September 2014 (has links)
Cette thèse s’inscrit dans le cadre général de la dépollution d’effluents gazeux faiblement chargés en Composés Organiques Volatils (COV). L’étude concerne l'oxydation de trois COV cibles (méthane, propène, et toluène) dans l'air à la pression atmosphérique dans d'une part un réacteur plasma de décharge à barrière diélectrique (DBD) pulsée et un réacteur catalytique utilisés séparément et d'autre part, dans un réacteur hybride associant le réacteur plasma aux catalyseurs dans deux configurations: le catalyseur au coeur de la décharge et le catalyseur en post-décharge. Les catalyseurs sont à base de Pd, Mn, Cu, et Co supportés sur des billes de Al2O3. Ils ont été caractérisés par ICP-OES, TEM/EDX, XRD, XPS, et DRIFTS. L’efficacité de conversion des COV, la sélectivité en CO/CO2, ainsi que la nature et les concentrations des produits formés pour les trois molécules avec les trois systèmes ont été étudiées en fonction de la température du gaz, de l'énergie injectée, de la concentration des COV, de la taille du support, du type de métal et sa teneur, et de la vitesse volumique horaire. Dans tous les cas, l’activation des catalyseurs à basse température a été démontrée quand ces derniers sont couplés au plasma et les principaux produits de réaction identifiés et quantifiés par spectroscopie infrarouge à transformée de Fourier. Le couplage plasma-catalyseur améliore de façon significative l’efficacité de conversion du méthane, du propène, et du toluène dans l’air ainsi que la sélectivité en sous-produits. L'effet de synergie entre le plasma et les catalyseurs pour la conversion des COV a été démontré dès lors que le plasma est généré directement au sein du réacteur catalytique. / The focus of this thesis is the application of non-thermal plasma and catalysis in chemical processing, in particular for the removal of Volatile Organic Compounds (VOC) diluted in air. In a first part, the oxidation of three pollutants (methane, propene, and toluene) is studied experimentally in a pulsed dielectric barrier discharge (DBD) reactor and in a catalyst reactor working independently. In a second part, a hybrid plasma-catalyst reactor either in a single-stage or in a two-stages configuration, in which the catalyst is located inside or downstream from the plasma reactor, respectively. Catalyst materials based on Pd, Mn, Cu, and Co supported on alumina beads were tested and characterized by ICP-OES, TEM/EDX, XRD, XPS, and DRIFTS. Products were analyzed and quantified by infrared spectroscopy. Achieved VOCs removal efficiencies and CO/CO2 selectivity, as well as nature and concentrations of the formed products, were evaluated as function of many factors, particularly the specific input energy, the gas temperature, the initial VOCs concentration, the nature of catalyst (size support, metal loading), and the hourly space velocity. It has been successfully demonstrated that the combination of plasma and catalyst in the both configurations has many benefits compared to traditional thermal-catalysis and plasma alone treatment including a lowering of the catalyst operating temperature, an improvement of the conversion of VOCs at similar temperatures, and a better end-products selectivity and energy efficiency. The mutual interaction lead to a synergistic effect in plasma-catalysis especially when the discharge is in direct contact with the catalyst whatever the VOCs studied.
63

Vers une alternative aux aimants à base de terres rares : hexaferrites nanostructurés et alliages Mn-Al / Towards an alternative to rare-earth magnets : nanostructuration of hexaferrites and Mn-Al alloys

Tyrman, Muriel 29 June 2017 (has links)
Dans le cadre d'un projet de transport automobile propre pour la mise en place de véhicules électriques décarbonés grand public, les aimants représentent un enjeu important au niveau des moteurs électriques. Il est alors nécessaire de se passer des aimants à base de terres rares, peu écologiques et dont un seul pays détient le monopole. Deux voies sont explorées ici : la nanostructuration des hexaferrites de type M par frittage flash de type SPS (Spark Plasma Sintering), et la synthèse d'alliages Mn-Al-C par la méthode de la trempe rapide sur roue. Concernant le premier matériau, l'optimisation du protocole de synthèse a permis d'augmenter le champ coercitif d'un facteur 2. Deux outils de caractérisation des aimants ont été mis en place : le premier évalue la texture du matériau (modèle de Stoner et Wohlfarth), le second étudie les processus d'aimantation (Preisach). Pour les alliages Mn-Al-C, nous avons pu démontrer la présence d'un couplage antiferromagnétique entre les atomes de Mn des sites 1a et 1d. La diffraction de neutrons à également pu montrer que le moment magnétique du Mn du site 1d est par ailleurs très supérieur à celui du site 1a. Un broyage cryogénique suivi d'un frittage SPS à haute pression (400 MPa) a permis d'augmenter la valeur du champ coercitif de 40 %. Les résultats obtenus sont très prometteurs quant à la faisabilité d'alternatives aux aimants à base de terres rares. / In the context of green car development for mass market, development of low cost rare-earth-free magnets is clearly a milestone, because the rare-earth are expensive and their production is not ecological and a monopoly of one country. Two routes are explored herein : nanostructuration of M-type hexaferrites by flash sintering (Spark Plasma Sintering), and the synthesis of Mn-Al-C alloys by melt spinning. Concerning the first material, the optimization of the synthesis protocol allowed to increase the coercive field by a factor of 2. Two characterization tools of the magnets were set-up : the first evaluates the texture of the material (Stoner and Wohlfarth model), the second, based on Preisach model, is used to infer the magnetization processes. For Mn-Al-C alloys, we have evidenced from Weiss plots the antiferromagnetic coupling between 1a and 1d-sites Mn atoms. Neutron diffraction confirmed this result and shown that the magnetic moment of the 1d-site Mn is also much larger than that of 1a-site. Cryogenic ball milling followed by high-pressure SPS (400 MPa) increased the coercive field by 40 %. The results obtained are very promising as to the feasibility of alternatives to rare-earth magnets.
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Studium indiem dopované slitiny s tvarovou pamětí Ni2MnGa / Study of indium doped shape-memory alloy Ni2MnGa

Cejpek, Petr January 2021 (has links)
Title: Study of indium doped shape-memory alloy Ni2MnGa Author: Petr Cejpek Department: Department of Condensed Matter Physics Supervisor: RNDr. Milan Dopita, PhD., Department of Condensed Matter Physics Abstract: The alloys related to Ni-Mn-Ga system exhibit effects connected to the magnetic shape-memory and martensitic transformation and therefore attract attention of researchers for their application potential. Properties and especially transformation temperatures are strongly dependent on composition, doping and also on external conditions as a magnetic field or pressure. The main aim of the work was to prepare own single crystals of Ni2MnGa1−xInx and to study their properties with respect to the temperature and applied fields in dependence on a various indium doping. The transformation temperatures obtained from the measurement of electrical resistivity and magnetisation re- vealed the systematic decrease of martensitic transformation temperature TM , pre-martensitic transformation temperature TP and Curie temperature TC. The martensitic transformation should vanish at indium concentration of x ≈ 0.10. The decrease with indium content is much faster than in the study published previously on the polycrystalline samples (vanishing at x ≈ 0.20). This dis- crepancy is probably caused by the residual stress...
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The Effect of Temperature Gradients During Intercritical Annealing of Advanced High Strength Steels : Method Development for Experimental Streamlining

Ek Jendrny, Helena January 2023 (has links)
The third-generation advanced high strength steels, AHSS, represent an opportunity for today’s steel development, where lighter materials with maintained strength and toughness are in demand. The unique properties of these materials often stem from a tailored microstructure. In the continued development of these steels, without relying on expensive alloying methods, process design in the form of precise heat treatments plays an increasingly important role. This work focuses on Medium Mn AHSS with the aim of investigating one of these heat treatments, intercritical annealing, which is essential for achieving the desired material properties. Experimental testing of annealing effects is acknowledged to be a challenging process, and this study aims to present a novel approach for these types of tests. During experimental testing of intercritical annealing, the thermomechanical testing system Gleeble 3800 is a recognized tool. The mounting technique employed in the Gleeble results in an inhomogeneous heat distribution in the samples, generating a thermal gradient. This report aims to utilize this gradient as an opportunity to test the effect of several intercritical annealing temperatures on one sample, thereby increasing the efficiency of experimental work. The method is based on data retrieved from thermocouples attached to the specimen during Gleeble trials with the intent to identify the thermal gradient. This data is combined with x-ray diffraction measurements where the retained austenite fraction is measured. Thermodynamic calculations of expected retained austenite fraction following intercritical annealing are performed parallel to experimental work. The results of this work show that it is possible to utilize the thermal gradient to retrieve extensive data regarding the effect of intercritical annealing using only one sample. The results show a distinct thermal gradient and a corresponding gradient of retained austenite fraction along the specimen. The results for retained austenite fraction at room temperature can be rationalized on the basis of computational predictions. These variations potentially arise due to the material not reaching equilibrium within the annealing timeframe. This conclusion is supported by other computational results concerning austenite composition. In summary, the present work illustrates a new approach streamlining experimental work that, with some refinements, has the potential to benefit the broader scienitific community, in addition to providing a powerful new tool for rapid technological advancement in the steel industry / Tredje generationens avancerade höghållfasta stål representerar en möjlighet för dagens stålutveckling där lättare material med bibehållen styrka och seghet efterfrågas. De unika egenskaperna hos dessa material härrör ofta frän en skräddarsydd mikrostruktur. Vid fortsatt utveckling av dessa stål är det önskvärt att minimera användningen av legeringsämnen, vilket betyder att processdesign i form av korrekta värmebehandlingar blir  av  stor  betydelse.  Detta  arbete  fokuserar  på  Medium  Mn  avancerade höghållfasta stål med syftet att undersöka en av dessa värmebehandlingar, interkritisk glödgning,  vilken  har  en  avgörande  betydelse  för  att  uppnå önskad  prestanda. Experimentell  testning  av  glödgningseffekter  anses  vara  en  utmanande  process och avsikten med denna studie är att presentera ett nytt tillvägagångssätt för denna typ av test. Under experimentell utvärdering av glödgningseffekter används ofta det termomekaniska testsystemet  Gleeble  3800.  Provmonteringen  i  Gleeblen  resulterar i en  inhomogen värmefördelning i proverna vilket medför en temperaturgradient. Denna rapport syftar till att använda gradienten som en möjlighet att testa effekten av flera  glödgningstemperaturer  på  ett  enda  prov  och  därigenom  öka  effektiviteten i det  experimentella  arbetet.  Metoden  grundas  på  data  från  termoelement  fästa  på provet under Gleebleförsök, med avsikt att identifiera den termiska gradienten. Denna data kombineras sedan med XRD-mätningar där austenitfraktion efter värmebehandling utvärderas.  Termodynamiska  beräkningar  av  förväntad  austenitfraktion  efter interkritisk glödgning genomförs parallellt med experimentellt arbete. Resultaten  från  detta  arbete  påvisar  att  den  presenterade  metoden  är  genomförbar då omfattande data gällande interkritisk glödgningseffekt grundat på endast ett prov erhålls. Resultaten visar en tydlig termisk gradient och en motsvarande gradient av austenitfraktion längs provet, vilka är i överensstämmelse med tidigare experimentella resultat för samma material. Resultaten för austenitfraktion vid rumstemperatur uppvisar  betydande  likheter  med  de  termodymiska  beräkningarna, med  några  undantag. Orsaken till dessa variationer ¨ar troligen en otillräcklig glödgningstid, vilket gör att  materialet  inte  når  jämvikt.  Denna  hypotes  stöds  av andra  beräkningsresultat gällande austenitens sammansättning. Sammanfattningsvis presenterar denna rapport ett nytt tillvägagångssätt för att effektivisera experimentellt arbete, som med vissa förbättringar har potential att gynna det bredare forskarsamhället.
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Characterization and Process Development of CVD/ALD-based Cu(Mn)/Co(W) Interconnect System

Shima, Kohei, Tu, Yuan, Han, Bin, Takamizawa, Hisashi, Shimizu, Hideharu, Shimizu, Yasuo, Momose, Takeshi, Inoue, Koji, Nagai, Yasuyoshi, Shimogaki, Yukihiro 22 July 2016 (has links) (PDF)
A new materials system of a single layered Co(W) barrier/liner coupled with a Cu(Mn) alloy seed was investigated. Atom probe tomography visualized the sub-nanoscale structure of Cu(Mn)/Co(W) system, and thereby revealed Cu diffusion behavior of Co(W). Grain boundaries of Co were found to be the diffusion path, and successfully stuffed by W. Mn in Cu(Mn) also segregated to stuff the grain boundaries of Co. Combination of these two additives enabled high barrier property against Cu diffusion of Cu(Mn)/Co(W). Foreseeing tiny and high-aspect-ratio Cu interconnect features, Cu(Mn)/Co(W) was fabricated by ALD/CVD processes. To maximize the performance, minor impurities of the film incorporated from the ligand of the precursors were controlled by precursor selection. Thin, conformal, and smooth films were finally demonstrated onto a trench substrate.
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Magnetic and Structural Investigation of Manganese Doped SnO_2 and In_2 O_3 Nanocrystals

Sabergharesou, Tahereh January 2013 (has links)
Diluted magnetic semiconductor oxides (DMSOs) have received great attention recently due to their outstanding applications in optoelectronic and spintronic devices. Ever since the initial observation of ferromagnetism at room temperature in cobalt-doped titania, extensive effort is concentrated on preparation of transition metal doped wide band gap semiconductors, especially Mn- doped ZnO. Compared to Mn-doped ZnO, magnetic interactions in SnO! and In!O! semiconductors have been underexplored. SnO! and In!O! semiconductors have many applications, owing to their high charge carrier density and mobility as well as high optical transparency. Investigation on electronic structure changes induced by dopants during the synthesis procedure can effectively influence magnetic interactions between charge carriers. In this work, a combination of structural and spectroscopic methods was used to probe as-synthesized SnO! and In!O! nanocrystals doped with Mn!! and Mn!! as precursors. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy are powerful techniques to explore formal oxidation state of manganese dopant, electronic environment, number of nearest neighbors around the absorbent, and bond lengths to the neighboring atoms. Analysis reveals the presence of multiple oxidation states in the doped nanocrystals, and establishes a relation between !"!! ratio and expansion or contraction of lattice parameters. !"!! Although doping semiconductors are crucial for manipulating the functional properties, the influence of dopants on nanocrystals structure is not well understood. Nanocrystalline films prepared from colloidal Mn-doped SnO! and In!O! nanocrystals through spin coating process exhibit ferromagnetic behavior in temperatures ranging from 5 K to 300 K. Magnetic transformation from paramagnetic in free-standing Mn-doped nanocrystals to strong ferromagnetic ordering in nanocrystalline films is attributed to the formation of extended structural defects, e.g., oxygen vacancies at the nanocrystals interface. Magnetic circular dichroism (MCD) studies clearly show that Mn!! occupies different symmetry sites in indium oxide, when bixbyite and rhombohedral In!O! nanocrystals (NCs) are compared.
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Elastic constants and sound velocities of Fe0.87Mn0.13 random alloy from first principles

Norell, Jesper January 2012 (has links)
In this study the elastic properties of a fcc Fe0.87Mn0.13 random alloy are studied by ab initio calculations. Ground state lattice parameters and elastic properties are calculated with Density Functional Theory using the Exact Muffin-Tin Orbital method and the Coherent Potential Approximation. Several magnetic models, approximations and distortion techniques are evaluated for optimized results, which are obtained by a Disordered Local Moment model with the Frozen Core and Generalized Gradient approximations using volume-conserving distortions.  Conclusively the longitudinal sound velocities are calculated from second order elastic stiffness constants and visualized by two different codes. The importance of magnetism for elastic properties is confirmed, as is the usefulness of the optimized computational scheme; all quantities obtained via the scheme is in accord with earlier theoretical and experimental results. Volume-conserving distortions are found to be more precise than volume-altering for calculation of elastic constants but also to be highly dependent on the precision of bulk modulus determination. The two sound-velocity codes are in complete agreement.
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Etude du mécanisme de régulation du gène et de l'importance biologique de la superoxyde dismutase à manganèse dans la croissance tumorale mammaire / Study of the regulation mechanism of manganese superoxide dismutase gene and its biological importance in the mammary tumoral growth

Minig, Vanessa 27 March 2009 (has links)
La superoxyde dismutase à Manganèse (SOD Mn ou SOD2) est une enzyme importante dans la défense antioxydante, qui semble jouer un rôle mal défini dans le développement des tumeurs selon l’expression constitutive de son gène. Cependant, les mécanismes de régulation de cette expression constitutive sont mal connus, en particulier dans les cellules tumorales mammaires. Ce travail a reposé sur la mise en évidence préalable d’une protéine, appelée la Damaged DNA Binding 2 (DDB2) protein, se fixant spécifiquement sur la région promotrice du gène SOD2. La DDB2 est connue pour sa participation dans la réparation de l’ADN par excision de nucléotides. Dans un 1er temps, nous avons caractérisé la séquence d’ADN spécifiquement reconnue dans la région proximale du promoteur du gène SOD2, sur laquelle la DDB2 s’y fixe sous la forme d’un monomère, pour réguler négativement la transcription constitutive de la SOD Mn dans les cellules tumorales mammaires non métastatiques de type MCF-7. Par ailleurs, la DDB2 n’est pas impliquée dans le mécanisme d’induction du gène SOD2, lorsque les cellules MCF-7 sont exposées à des substances inductrices. En revanche, nous avons montré que l’absence de la protéine DDB2, associée à celle du facteur de transcription AP-2?, déjà connu comme répresseur du gène SOD2, entraîne une expression constitutive élevée de la SOD Mn dans les cellules tumorales mammaires métastatiques n’exprimant pas le récepteur aux œstrogènes (ER-). De plus, cette expression constitutive élevée est principalement dépendante du facteur de transcription Sp1. Dans un 2ème temps, nous avons évalué la signification biologique de la régulation de l’expression constitutive de la SOD Mn par la DDB2 dans les cellules tumorales mammaires. Nos résultats montrent que la DDB2 active la prolifération des cellules tumorales mammaires ER+, en exerçant sa régulation négative sur l’expression de la SOD Mn. Dans un 3ème temps, nous avons cherché à montrer les conséquences sur la croissance des cellules tumorales mammaires ER-, qui surexpriment naturellement la SOD Mn. Nos résultats révèlent que l’enzyme antioxydante joue un rôle important dans les mécanismes moléculaires impliqués dans le pouvoir invasif des cellules tumorales mammaires ER-. La surexpression de la SOD Mn, associée à un taux faible des enzymes éliminant l’H2O2, entraînent une augmentation du pouvoir invasif déjà élevé des cellules tumorales mammaires ER-, associée une augmentation de l’activité de la métalloprotéinase 9. L’élimination, en présence d’antioxydants, de l’H2O2 libéré par l’activité de la SOD Mn surexprimée, entraîne une inhibition à la fois de la croissance et des capacités invasives des cellules tumorales mammaires ER-. L’ensemble de ce travail contribue à mieux comprendre l’importance de la SOD Mn et du mécanisme de régulation de son gène dans la croissance et l’invasion tumorales. Ainsi ce travail révèle également la SOD Mn et la DDB2 comme de potentiels facteurs prédictifs de la progression tumorale mammaire. Enfin, la découverte de la nouvelle activité biologique de la DDB2 ouvre un vaste champ de perspectives intéressantes en cancérologie mammaire. / Manganese superoxide dismutase (Mn SOD or SOD2) is an important enzyme in the antioxidizing defence, which seems to play an unclear role in the cancer development, according to the constitutive expression of its gene. However, the regulation of this constitutive expression is not totally known, particularly in the breast cancer cells. This work is based on a preliminary revealing that a protein, called Damaged DNA Binding 2 (DDB2), specifically binds the SOD2 gene promoter. The DDB2 is known for its involvement in the nucleotide excision repair. At first step, we characterized the specific DNA sequence recognized in the proximal area of the SOD2 gene promoter, on which a DDB2 monomer binds, in order to regulate negatively the Mn SOD transcription in the MCF-7 non metastatic breast cancer cells. Besides, DDB2 is not involved in the mechanism of SOD2 gene induction, when MCF-7 cells are exposed to induced substances. However, we showed that the lack of the DDB2 protein, associated with the lack of the AP-2a transcription factor, already known as a repressor of the SOD2 gene, lead to a high Mn SOD constitutive expression in the metastatic breast cancer cells. Furthermore, this high constitutive expression is mainly dependent of the Sp1 transcription factor. Secondly, we estimated the biological meaning of the regulation of the Mn SOD constitutive expression by the DDB2 in the breast cancer cells. Our results show that the DDB2 activates the positive ER breast cancer cell proliferation, by exercising its negative regulation on the Mn SOD expression. Thirdly, we tried to show the consequences on the negative ER breast cancer cell growth, which naturally and highly express the Mn SOD. Our results reveal that the antioxidizing enzyme plays an important role in the molecular mechanisms involved in the invasive capacities of the negative ER breast cancer cells. The high Mn SOD expression, associated in a decrease of the H2O2 detoxifying enzymes expression, enhance the negative ER breast cancer cell invasion and an increase of the matrix metallopeptidase-9 activity. The H2O2 elimination, with specific antioxidants, decreases both negative ER breast cancer cell growth and invasive capacities. This whole work contributes to better understand the Mn SOD importance and the mechanism of its gene regulation, in the tumoral growth and invasion. This work also reveals the Mn SOD and DDB2 as potential predictive factors of the breast cancer progress. Finally, the discovery of this new DDB2 biological activity opens a huge field of interesting perspectives in breast cancer research.
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Immunopathologie des podocytopathies acquises : rôle de c-mip dans les perturbations immunitaires et podocytaires / Immunopathology of acquired podocytopathy : role of c-mip in alterations of immune system and podocytes

N'Gome Sendeyo, Kelhia 17 December 2013 (has links)
Le Syndrome Néphrotique à Lésions Glomérulaires Minimes (SNLGM) et la glomérulonéphrite extra membraneuse (GEM) sont deux podocytopathies primitives d'origine immunitaire associant des altérations immunes et des atteintes podocytaires à l'origine d'un syndrome néphrotique. Cependant, bien que l'origine dysimmunitaire soit confortée par de nombreux arguments cliniques, les mécanismes impliqués restent obscurs. Initialement identifié dans les lymphocytes T (LT) de patients en phase de poussée de SNLGM, le gène c-mip est également exprimé dans les podocytes de patients atteints de SNLGM et de GEM, alors qu'il est physiologiquement réprimé. Ainsi, les objectifs de ce travail étaient : 1) appréhender le rôle de c-mip dans le LT d'une part à travers l'étude d'un modèle murin transgénique (Tg), et 2) comprendre la fonction de c-mip au niveau du podocyte grâce au modèle expérimental de GEM humaine induit chez le rat.Le modèle murin Tg Lck-cmip surexprime spécifiquement c-mip dans les LT matures périphériques. Cette surexpression est à l'origine d'un phénotype lymphocytaire altéré marqué par une accumulation de LT naïf, et une inhibition de la synthèse de cytokines de type TH1 et TH2, après une activation T spécifique ex vivo. Cette régulation négative est associée à une accumulation des formes inactives des kinases de la famille des Src et un blocage du recrutement des lipids rafts nécessaire à la formation de la synapse immunologique. Ces résultats suggèrent donc que c-mip est un régulateur négatif de l'activation T impliqué dans la signalisation proximale lymphocytaire et pourrait être impliqué dans l'hyporéactivité lymphocytaire observée chez les patients atteints de SNLGM actif.L'étude de la néphrite de Heymann passive, un modèle expérimental de GEM humaine, montre que l'induction podocytaire de c-mip coïncide avec l'apparition de la protéinurie. Cette surexpression est associée d'une part, à une diminution des taux de synaptopodine qui engendre une diminution de l'activité RhoA, à l'origine d'une désorganisation du cytosquelette podocytaire, et d'autre part à une induction de DAPK (death-associated protein kinase) et ILK (Integrin Linked Kinase) impliquées dans des phénomènes pro-apoptotiques. La cyclosporine A en inhibant l'expression de c-mip restaure les taux de DAPK et ILK ainsi que l'activité RhoA. Ainsi dans le podocyte, c-mip semble impliquer dans les troubles de la signalisation podocytaire aboutissant à une protéinurie néphrotique.C-mip semble donc jouer un rôle crucial dans les perturbations podocytaires et lymphocytaires observées chez les patients atteints de podocytopathies primitives et représente à ce titre une cible thérapeutique.Mots clefs :C-mip, Syndrome Néphrotique à Lésions Glomérulaires Minimes, Glomerulonéphrite Extra Membraneuse, signalisation proximale, lymphocyte T, podocyte, cytosquelette / Minimal Change Nephrotic Syndrome (MCNS) and Membranous Nephropathy (MN) are two primitive immune podocytopathies associating immune alterations and podocyte damage ultimately leading to proteinuria. Although the immune origin of the disease is corroborated by numerous clinical data, the mechanisms involved are still unknown. In previous works by the team, the c-mip protein was found expressed in T lymphocytes (TL) from patients with MCNS relapse, and in podocytes from MCNS and MN patients, while it is physiologically repressed. The aims of the present work were: firstly, to investigate the rôle of c-mip in TL by the study of Lck-cmip transgenic mice (Tg); secondly, to understand c-mip function in podocyte using a rat experimental model of human MN (Heymann nephritis).Transgenic mice overexpressed specifically c-mip in peripheral mature TL. This expression led to an altered TL phenotype characterized by accumulation of naïve LT associated with inhibition of TH1's and TH2's cytokines, after T-specific activation ex vivo. This negative regulation was correlated with an increase in the inactive forms of Src kinases and a blockage of the lipid raft clustering required for immunological synapse formation. These results suggest that (i) c-mip is a negative regulator of the proximal signaling events associated with TL activation involved in proximal signaling and (ii) it could be involved in the TL hyporeactivity described in SNLGM patients.In the study based on passive Heymann Nephritis, the experimental model of MN, the results highlight a correlation between podocyte expression of c-mip and proteinuria. This expression is associated, on the one hand, with a decrease in synaptopodin levels, which generate a decrease of RhoA activity resulting in podocyte cytoskeleton disorganization, and on the other hand with DAPK (Death Associated Protein Kinase) and ILK (Integrin Linked Kinase) induction, known to be involved in pro-apoptotic mechanisms. Cyclosporin A inhibited c-mip expression and restored the basal levels of DAPK, ILK and Rhoa activity. These results suggest that in podocyte, c-mip could be involved in proximal signaling alterations leading to nephrotic proteinuria.In conclusion, c-mip could play a crucial rôle in both the lymphocyte and podocyte alterations observed in patients suffering from primitive podocytopathies, strongly suggesting its potential as a therapeutic target in these disorders.Key words :C-mip, MCNS, MN, proximal signaling, Src kinase, T lymphocyte, podocyte, cytoskeleton

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