Hepatocellular carcinoma (HCC) is one of the most common and devastating malignant tumors in Taiwan. Due to an imbalanced between reactive oxygen species (ROS) production and detoxification, oxidative stress, has been implicated in liver carcinogenesis. Superoxide dismutases (SODS) play a key role in the detoxification of superoxide radicals and thus protect cells from damage induced by free radicals. Manganese superoxide dismutase (MnSOD or SOD2) is a member of the superoxide dismutase family located in mitochondria. SOD2 transforms toxic superoxide, a byproduct of the mitochondrial electron transport chain, into hydrogen peroxide and diatomic oxygen. Though reduced SOD2 protein level and activities have been reported in hepatoma tissues, it remains unclear how SOD2 expression affected the tumorigenic processes of hepatoma cells. Expression analysis of an array of human HCC cell lines revealed that SOD2 were down-regulated in poorly differentiated SK-Hep-1 hepatoma cells. Moreover, SOD2 is downregulated in 68.8% of resected HCC samples (97 out of 141 cases). Adenovirus-mediated SOD2 gene delivery increased the cellular SOD2 protein level and H2O2 production, but reduced the superoxide anion level in SK-Hep-1 cells. Furthermore, SOD2 restoration significantly reduced the proliferation, motility, and colony formation of SK-Hep-1 cells. In vivo animal model, the finding of SOD2 overexpression inhibited the proliferation of Sk-Hep-1 hepatoma cells while reduced the tumor growth in mice. Flow cytometry analysis showed that SOD2 gene transfer inhibited the growth of hepatoma cells through induction of cell cycle arrest at G2/M phase. This was associated with declined cdc2/cdk1 and cyclin B1 expression and upregulation p21Cip1 by SOD2 gene delivery. However, SOD2 overexpression had no effect on the secretion of matrix metalloproteinase-2 (MMP-2) and MMP-9.In conclusion, SOD2 overexpression suppresses the tumorigenicity of hepatoma cells and may hold promise for HCC treatment.

The electronic structures of Mn £_-doped epitaxial GaN films grown on sapphire substrates are studied by scanning tunneling microscopy in this work. Local structural information and the corresponding electronic properties of Mn £_-doped GaN films are probed by the combination of scanning tunneling microscopy and atomic-scale scanning tunneling spectroscopy measurements. According to the electronic local density of states analysis indicates that Mn ions develop an acceptor level in GaN, revealing a gap state located at ~ 1.4 eV above the valence band edge of GaN. Furthermore, the energy position of the charge transfer levels of substitutional MnGa within GaN energy gap is also elucidated and discussed in the work.

In this study, the shape memory response of Ni2MnGa and NiMnCoIn magnetic shape memory alloys was observed under compressive stresses. Ni2MnGa is a magnetic shape memory alloy (MSMA) that has been shown to exhibit fully reversible, stressassisted magnetic field induced phase transformation (MFIPT) in the I X-phase transformation because of a large magnetostress of 7 MPa and small stress hysteresis. The X-phase is a recently discovered phase that is mechanically induced, however, the crystal structure is unknown. To better understand the transformation behavior of Ni2MnGa single crystal with [100] orientation, thermal cycling and pseudoelasticity tests were conducted with the goal of determining the Clausius-Clapeyron relationships for the various phase transformations. This information was then used to construct a stresstemperature phase diagram that illustrates the stress and temperature ranges where MFIPT is possible, as well as where the X-phase may be found. NiMnCoIn is a recently discovered meta-magnetic shape memory alloy (MMSMA) that exhibits unique magnetic properties. The ferromagnetic parent phase and the paramagnetic martensite phase allow the exploitation of the Zeeman energy. To gain a better understanding of the transformation behavior of NiMnCoIn, thermal cycling and pseudoelasticity tests were conducted on single crystals from two different batches with crystallographic orientations along the [100](011), [087], and [25 7 15] directions. A stress-temperature phase diagram was created that illustrates the Clausius- Clapeyron relationships for each orientation and batch. SQUID tests revealed the magnetic response of the alloy as well as the suppression of the martensite start temperature with increasing magnetic field. Pseudoelasticity experiments with and without magnetic field were conducted to experimentally quantify the magnetostress as a function of magnetic field. For the first time, it has been shown that NiMnCoIn is capable of exhibiting magnetostress levels of 18-36 MPa depending upon orientation, as well as nearly 6.5% transformation strain in the [100] direction. The results of this study reveal increased actuation stress levels in NiMnCoIn, which is the main limitation in most MSMAs. With this increased blocking stress, NiMnCoIn is a strong candidate for MFIPT.

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ABSTRACT STEREOSELECTIVE SYNTHESIS OF OPTICALLY ACTIVE CYCLITOL PRECURSORS VIA CHEMOENZYMATIC METHOD AND SYNTHESIS OF A NUCLEOSIDE PRECURSOR Oguzkaya, Funda M.S., Department of Chemistry Supervisor: Prof. Dr. Cihangir Tanyeli June 2006, 99 pages &amp / #945 / &#039 / -acetoxylation of &amp / #945 / ,&szlig / -unsaturated cyclic ketones was adjusted via Mn(OAc)3 in regioselective manner. Then, PLE hydrolysis was carried out so as to afford enantiomerically enriched &amp / #945 / &#039 / -acetoxylated and &amp / #945 / &#039 / -hydroxylated cyclic compounds. From our knowledge about the literature and previous works dealing with &amp / #945 / &#039 / -hydroxylated products which are easily racemized, protection was directly adjusted via acetylation so as to prevent this possibility. Resulting enantiomerically enriched products were subjected to Upjohn Dihydroxylation to obtain cyclitol precursors and following Luche Reduction of ketone was adjusted so as to obtain corresponding cyclitols. In addition with such synthetic design, firstly dimethyl cyclopent-3-ene-1,1-dicarboxylate was obtained so as to reach in former manner 3-cyclopentene-1,1-dicarboxylic acid, and in latter manner cyclopent-3-enecarboxylic acid. Resulting compound was converted to 6-iodo-2-oxa-bicyclo[2.2.1]heptan-3-one and followingly to the target nucleoside precursor which is 2-oxa-bicyclo[2.2.1]hept-5-en-3-one.

Chiral polyfunctionalized 1,5-dicarbonyl compounds are important synthetic intermediates and starting materials for many biologically active compounds so their synthesis has a great importance in the literature. In the first step, 1,3-cyclohexandione and other b-diketone derivatives are protected under acid catalyzation and their corresponding b-keto enol ether derivatives are obtained. These b-keto enol ethers are then converted to a-acetoxy enones in racemic form by Mn(OAc)3 mediated oxidation. Enzymatic kinetic resolution is applied to the racemic acetoxy enones by using different lipases and enantiomerically pure a-acetoxy and hydroxy enones are obtained. Then, dicarbonyl derivatives are obtained by hydrolizing racemic a-acetoxy enones. Oxidative cleavage of racemic a-acetoxy diketones in the presence of oxone gives corresponding racemic 1,5-dimethyl ester derivatives. By using this reaction as a reference, same reactions are applied to the chiral a-acetoxy and hydroxy diketones in order to synthesize chiral a-acetoxy and hydroxy 1,5-diester derivatives.

Die vorliegende Arbeit untersucht Struktur und Mn-Wertigkeit von La0,7Sr0,3MnO3 (LSMO)/SrTiO3 (STO)-Dünnschichten, die mit außeraxialer gepulster Laserdeposition auf STO(0 0 1)-Substrat abgeschieden wurden. Aufgrund der hohen Spinpolarisation der Ladungsträger und der hohen Curie-Temperatur von LSMO sowie der geringen Gitterfehlpassung zwischen LSMO und STO erscheinen solche Dünnschichtsysteme interessant für magnetoresistive elektronische Bauelemente wie LSMO/STO/LSMO-Tunnelkontakte. Da das mit steigender Temperatur rasch abnehmende Magnetwiderstandsverhältnis derartiger Tunnelkontakte vor allem auf die atomistische Struktur der LSMO/STO-Grenz?fläche und den damit gekoppelten Ladungszustand der Mn-Ionen zurückgeht, stellt diese Arbeit eine hoch ortsaufgelöste Charakterisierung von Kristallstruktur und Mn-Wertigkeit mit im TEM aufgezeichneten Abbildungen und Elektronen-Energieverlust-Ionisationskanten vor. Der hinsichtlich des Einfl?usses auf die Qualität der Messdaten durchgeführte Vergleich verschiedener TEM-Präparationsverfahren zeigt, dass die konventionell ionengedünnten Querschnitte geringere Verbiegungen aufweisen als die mit fokussiertem Ionenstrahl präparierten und daher besser für die hochau?flösende TEM geeignet sind. Zur Quantifizierung der Mn-Wertigkeit werden die O-K- und Mn-L2,3-Nahkantenfeinstrukturen herangezogen, die sich in charakteristischer Weise mit dem Sr-Gehalt x und damit der Mn-Valenz in La1-xSrxMnO3 ändern. Hierbei reagieren die Kantenenergieabstandsmaße am empfindlichsten auf die Mn-Wertigkeit und ermöglichen eine Valenzbestimmung mit einer Genauigkeit von bis zu ?0,08. Die für das Innere der untersuchten LSMO-Schichten ermittelte Mn-Wertigkeit stimmt mit dem nominalen Wert von 3,3 überein, wohingegen an manchen LSMO/STO-Grenz?flächen zwischen Substrat und Schicht sowie zwischen den Schichten von Multilagen eine Reduktion um 0,1...0,2 zu beobachten ist. Dies kann auf eine La0,7Sr0,3O/TiO2-terminierte Grenz?fläche zurückgeführt werden und deutet darauf hin, dass sich die abschließenden Atomlagen messbar auf die grenzfl?ächennahe Mn-Wertigkeit auswirken. Weiterhin äußert sich der Ein?fluss der Grenz?fläche in dem Auftreten einer Schulter an der Flanke geringeren Energieverlusts der Mn-L3-Kante. Hierfür werden mögliche Ursachen wie Gitterdeformationen und Sauerstoffleerstellen diskutiert. Die geometrische Phasenanalyse von HRTEM-Aufnahmen und TEM-Hellfeldaufnahmen belegen eine tetragonale Verzerrung des LSMO-Schichtkristalls, der aus nadelförmigen Zwillingsdomänen besteht. Aus hochaufgelösten Raster-TEM-Abbildungen mit den unter großem Winkel gestreuten Elektronen geht hervor, dass die LSMO/STO-Grenz?flächen eine kohärente, gelegentlich mit Elementarzellenstufen versehene Gitterstruktur aufweisen. Insbesondere vermitteln die Stufen (Einfach- und Mehrfachstufen) die wellige Struktur der LSMO/STO-Multilagen. Schließlich wird gezeigt, dass die mit konvergenter Beugung bestimmte Fehlorientierung zwischen LSMO-Schicht und STO-Substrat bei geringer durchstrahlter Dicke der TEM-Lamelle die erwartete Netzebenenneigung der Zwillinge übersteigt. Dafür wird eine nachträgliche Relaxation der LSMO-Schicht während der Ionendünnung verantwortlich gemacht.

<p>Processing of nanostructured WC-Co and W-Co powders,modelling of Fe-Mn-Si alloy, swelling of Fe-Cu alloy, andmechanical properties and sintering of Fe-Mn-Si steels havebeen studied in the present thesis.</p><p>W-Co precursors made by chemical synthesis were used toproduce nanostructured WCCo and W-Co powders by calcination,reduction and carburization. The phase constituents in thecalcined powders depend on temperature and atmospheres. Cobaltcan accelerate the reduction rate of the W-Co precursors as acatalyst, and cobalt influences the formation of intermediatephases during the reduction of the precursors.</p><p>The ratio of carbon monoxide to carbon dioxide controlscarburization process, gives different intermediate phases andcarburization rates. There exist several intermediate phases: W₆Co₆C, W₃Co₃C, W₂C due to varying carbon monoxide content in thecarburization gases. Nanostructured WC-Co powders with aparticle size of 20-50 nm have been obtained.</p><p>The effect of silicon content on the particle sizedistribution of milled Fe-Mn-Si master alloy powders is muchmore significant than that of manganese content. A finer finalparticle size can be obtained in the alloy powders with highersilicon compositions. Long time milling results in theagglomeration of small particles. The grinding process can bedescribed using classic batch grinding equation based on thepopulation balance model. A swelling model for Fe-Cu alloyssintered at the temperatures above the melting point of copperhas been established based on the penetration mechanism. In themodel, the particle coordination number and heating rate wereused to express the porosity and the thickness of the diffusionlayers between iron and copper particles respectively.</p><p>The effects of sintering temperature and time on theproperties of sintered steels have been studied. Fe-Mn-Simaster alloys made by cast-milling, atomizing, and acombination of atomization and milling have been covered. Themilled, and atomizationmilled alloy steels showed goodmechanical properties with small dimensional change. Transientliquid phase of the Fe-Mn-Si alloys accelerates densification,and offer fast diffusion of alloying elements. The addition ofa small amount of Fe-Mn-Si master alloy to Astaloy 85Mo powdercan lead to high strength with zero dimensional change.</p><p><b>Key words:</b>Processing; Modelling; Nanostructured powder;WC-Co; W-Co; Calcination; Reduction; Carburization; Particlesize; Sintered steel; Fe-Cu alloy; Swelling; Fe-Mn-Si masteralloy; Mechanical properties; Sintering parameters.</p>

A new technique based on the study of the transmitted neutron beam has been developed to study the low-temperature decomposition of austenite in a 0.4 wt.% C–3 wt.% Mn–2 wt.% Si steel. Experiments were conducted in which the neutron beam continuously passed through a specially designed layered sample, the temperature of which could be controlled to allow for a high-temperature austenization treatment followed by accelerated cooling to an isothermal transformation temperature in the range of 275–450 °C. It was possible to measure the volume fraction of the face-centred cubic (fcc) and body-centred cubic (bcc) phases and the carbon concentration of the fcc phase by characterizing the neutron Bragg edges in the transmitted beam. This provides a technique for in situ continuous measurements on the decomposition of austentite. The technique has been validated by comparing the data with other experimental techniques such as dilatometry, quantitative optical metallography and room temperature X-ray diffraction.

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.