Made available in DSpace on 2014-12-17T14:07:11Z (GMT). No. of bitstreams: 1 TarcisioEA.pdf: 3014778 bytes, checksum: 38f5a976aab626176f2743ebff3ec735 (MD5) Previous issue date: 2006-02-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Sisal is a renewable agricultural resource adapted to the hostile climatic and soil conditions particularly encountered in the semi-arid areas of the state of Rio Grande do Norte. Consequently, sisal has played a strategic role in the economy of the region, as one of few options of income available in the semi-arid. Find new options and adding value to products manufactured from sisal are goals that contribute not only to the scientific and technological development of the Northeastern region, but also to the increase of the family income for people that live in the semi-arid areas where sisal is grown. Lignocellulosic fibers are extracted from sisal and commonly used to produce both handcrafted and industrial goods including ropes, mats and carpets. Alternatively, addedvalue products can be made using sisal to produce alumina fibers (Al2O3) by biotemplating, which consists in the reproduction of the natural fiber-like structure of the starting material. The objective of this study was to evaluate the conditions necessary to convert sisal into alumina fibers by biotemplating. Alumina fibers were obtaining after pretreating sisal fibers and infiltrating them with a Al2Cl6 saturated solution, alumina sol from aluminum isopropoxide or aluminum gas. Heat-treating temperatures varied from 1200 ?C to 1650 ?C. The resulting fibers were then characterized by X-ray diffraction and scanning electronic microscopy. Fibers obtained by liquid infiltration revealed conversion only of the surface of the fiber into α-Al2O3, which yielded limited resistance to handling. Gas infiltration resulted in stronger fibers with better reproduction of the inner structure of the original fiber. All converted fibers consisted of 100% α-Al2O3 suggesting a wide range of technological applications especially those that require thermal isolation / O sisal ? um recurso estrat?gico para a regi?o Nordeste e, particularmente, para o estado do Rio Grande do Norte, por ser uma cultura renov?vel e adaptada ?s condi??es do semi-?rido. Em virtude das condi??es adversas de clima e solo, o sisal ?, em algumas regi?es, o ?nico produto agr?cola rent?vel pass?vel de plantio. Agregar valor aos produtos manufaturados a partir do sisal contribui n?o s? para o desenvolvimento cient?fico e tecnol?gico da regi?o, como tamb?m para a gera??o de renda das popula??es dos munic?pios potiguares produtores de sisal. Da planta, obtem-se fibras ligninocelul?sicas utilizadas na produ??o artesanal de cordas e industrial de mantas e tapetes. Uma alternativa ? o aproveitamento da estrutura da fibra para a produ??o de fibras de alumina (Al2O3) pelo processo de biomodelagem, que consiste na reprodu??o da estrutura natural do material de partida e convers?o qu?mica de sua composi??o. Os objetivos deste projeto foram avaliar o potencial de convers?o do sisal em alumina por biomodelagem. Os m?todos utilizados foram infiltra??es com solu??o de cloreto de alum?nio, solu??o sol-gel de alumina utilizando como precursor isoprop?xido de alum?nio e infiltra??o de alum?nio gasoso, para obten??o final das fibras de alumina. As temperaturas de sinteriza??es variaram de 1200 ?C a 1650 ?C. As caracteriza??es das fibras de alumina foram realizadas atrav?s de difra??o de raios X e microscopia eletr?nica de varredura. Para as fibras obtidas por infiltra??o liquida, os resultados mostraram a convers?o completa apenas da superf?cie da fibra de sisal em α-Al2O3, resultando em baixa resist?ncia ao manuseio. O m?todo de infiltra??o de alum?nio gasoso resultou em fibras com melhor reprodu??o da estrutura interna do sisal. O potencial tecnol?gico de aplica??o das fibras e mantas estende-se a aplica??es que requerem propriedades t?rmicas, especificamente isolamento t?rmico, j? que a composi??o qu?mica final das fibras foi 100% α-Al2O3

Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-02-24Bitstream added on 2014-06-13T18:29:01Z : No. of bitstreams: 1 britto_pf_me_ilha.pdf: 560643 bytes, checksum: 54cea600ab279deb0d7e2d6533cdb694 (MD5) / A combinação de diferentes tipos de materiais para obtenção de novas propriedades tem despertado grande interesse em vários campos da ciência de materiais. Em processos de separação, é de considerável interesse o uso de materiais com propriedades básicas extremamente diferentes. Entre os suportes mais usados está a sílica gel, um material com tamanho de partículas e porosidade bem definidas, elevada área superficial, e estabilidades mecânica, química e térmica elevadas. Neste contexto, a sílica gel modificada com grupos organofuncionais pode ser utilizada para a adsorção de íons metálicos em soluções aquosas e não aquosas, pré-concentração e separação de íons metálicos. Neste trabalho, a sílica gel 60 (Merck), com tamanho de partículas entre 0,2 e 0,05 mm e área superficial específica de 486 m2.g-1, foi quimicamente modificada em duas etapas. Primeiro, a sílica gel foi quimicamente modificada com 3-cloropropiltrimetoxisilano, resultando o 3-cloropropil sílica gel (CPSG). Na segunda etapa, o produto resultante, CPSG, reagiu com 2-mercaptopirimidina e 4-amino-2-mercaptopirimidina, resultando os materiais sólidos 2-mercaptopirimidina-propil sílica gel (MPSG) e 4-amino-2-mercaptopirimidinapropil sílica gel (AMSG). As quantidades de grupos funcionais conectados na superfície da sílica gel, N0, foram 7,007 x 10-4 mols e 7,416 x 10-4 mols de moléculas por grama de sílica, para MPSG e AMSG, respectivamente. Conhecendo a área superficial específica e assumindo que as moléculas cobrem uniformemente a superfície, a densidade média, d, das moléculas ancoradas e a distância intermolecular média, l, podem ser calculadas aplicando as equações d = N0 N/SBET e l = (l/d) 1/2 , onde N é o número de Avogadro. Os valores calculados são d = 1,42 moléculas.nm2 e l = 0,979 nm, e d = 1,166 moléculas.nm2 e l = 0,926 nm, para MPSG e... . / The combination of different type of materials for achieving novel properties has always been of high interest in many fields of the materials sciences. The use of materials with extremely different basic properties, like organic and inorganic compounds, is of considerable interest in separation processes. Among the supports the most used is silica gel, a material of well-established particle sizes and well-define porosity, high surface area, and high mechanical, chemical, and thermal stability. In this context, silica gel modified with organofunctional groups has been used for adsorption of metal ions from aqueous and non-aqueous solutions, pre-concentration and separation of metallic ions. In this work, silica gel 60 (Merck) having secondary particles sized between 0,2 and 0,05 mm and specific surface area of 486 m2.g-1 was modified using a two step approach. First, the silica gel was chemically modified with 3- chloropropyltrimetoxysilane, resulting the 3-chloropropyl-silica gel (CPSG). Second, the resultant product, CPSG, reacted with 2-mercaptopyrimidine and 4-amino-2- mercaptopyrimidine, resulting the solid materials 2-mercaptopyrimidine-propyl-silica gel (MPSG) and 4-amino-2-mercaptopyrimidine-propyl-silica gel (AMSG). The quantities of functional groups attached on the silica gel surface, No, were 7,007 x 10-4 mols e 7,416 x 10-4 mols .g-1 of molecules per gram of silica, for MPSG and AMSG, respectively. It being known the specific surface area and assuming that the molecules uniformly cover the surface, the average density, d, of the attached molecules and the average intermolecular distance, l, can be calculated by applying the equations: d = N0 N /SBET and l = (l/d)1/2, where N is Avogadro's number. The calculated values were d = 1,042 molecules.nm-2 and l = 0,979 nm and d = 1,166 molecules.nm-2 and... (Complete abstract click electronic address below).

Orientador: Pedro Luiz Onófrio Volpe / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T19:42:54Z (GMT). No. of bitstreams: 1 Fozia_D.pdf: 5148812 bytes, checksum: 468649b9d5c06383a0fcd0b39c0fc098 (MD5) Previous issue date: 2014 / Resumo: Híbridos polisilsesquioxanos arranjados em pontos, foram sintetizados e caracterizados por análise elementar, espectroscopia de absorção na região do infravermelho, ressonância magnética nuclear no estado sólido, difração de raios X, microscopia eletrônica de varredura e transmissão eletrônica. Os dados de sorção/dessorção de nitrogênio para sílica pura, SBA-15 e os híbridos funcionalizados resultaram na isoterma do tipo IV com histerese do tipo H1. A estrutura da sílica mesoporosa ficou preservada após a pós-funcionalização com cadeias orgânicas. Pos-funcionalização da superfície com amina e outros grupos orgânicos contendo estrutura hidrofóbica, resultou numa diminuição da área da superfície 802,4-63,0 m2g-1 e volume de poros de 0,09 nm e aumento capacidade de carga de ibuprofeno a partir de 18,0 até 29% e um muito lento taxa de liberação ao longo do período de 72,5 h. Para investigar a taxa de liberação e o mecanismo a partir desses materiais híbridos sintetizados, zero-ordem, primeira ordem, Higuchi, Hixson-Crowell, Peppas e Korsmeyer-Peppas modelos cinéticos foram aplicados. Os materiais foram utilizados para a liberação controlada do fármaco ibuprofeno. Estes também foram avaliados quanto à capacidade de remover o corante aniônico azul reativo-15 e o corante catiônico verde brilhante de soluções aquosas. As sílicas modificadas apresentaram alta capacidade de carregamento do fármaco ibuprofeno e de sorção seletiva para o corante azul reativo 15. A sílica não modificada, SBA-15, apresentou alta capacidade de remover o corante verde brilhante. As isotermas de equilíbrio obtidas foram ajustadas aos modelos de Langmuir, Freundlich e Sips e os dados cinéticos foram ajustados aos modelos de pseudo-primeira-ordem e pseudo-segunda-ordem. Os resultados sugerem que os compostos organofuncionalizados de sílica podem ser um método simples, eficiente, barato e conveniente para a liberação controlada de fármacos e também para a remoção eficaz e seletiva de poluentes orgânicos tais como, corantes em soluções aquosas / Abstract: Bridged polysilsesquioxane silica hybrids, synthesized by the combination of SBA-15 type silica with new synthesized silylating agents containing bridged chains, were characterized by elemental analysis, absorption spectroscopy in the infrared region, nuclear magnetic resonance in the solid state, X-ray diffraction, scanning/transmission electron microscopy and thermogravimetry. The sorption/desorption of nitrogen to pure silica, SBA-15 and functionalized hybrids resulted in the isotherms of type IV with type H1 hysteresis. The structure of the precursor mesoporous silica was preserved after post-functionalization with bridged organic bridged chains. The precursor and its derivative silicas were ibuprofen-loaded for controlled delivery in simulated biological fluids. Surface functionalization with amine and other organic groups containing bridged hydrophobic structure resulted in significantly decreased surface area from 802.4 to 63.0 m2g-1 and pore volume to 0.09 nm, which ultimately increased the drug-loading capacity from 18.0 up to 29 % and a very slow release rate of ibuprofen over the period of 72.5 h. To investigate the release rate and mechanism from these synthesized hybrid materials, Zero-order, first-order, Higuchi, Hixson-Crowell and Peppas and Korsmeyer-Peppas kinetic models were applied. The synthesized materials were also evaluated for their ability to remove the anionic dye reactive blue-15 and cationic dye brilliant green from aqueous solutions. The hybrid silica showed selective sorption capacity for the anionic dye, reactive blue 15. The unmodified silica, SBA -15 showed high ability to remove the cationic dye, brilliant green from the aqueous medium. The obtained equilibrium isotherms were fitted to Langmuir, Freundlich and Sips models and the kinetic data were used to fit pseudo-first-order and pseudo-second-order. The results suggest that the organo-functionalized hybrid silicates could be a simple, efficient, inexpensive and convenient for the controlled release of drugs and for effective and selective removal of organic pollutants such as dyes from the aqueous solutions / Doutorado / Quimica Inorganica / Doutora em Ciências

The thesis entitled “Evolution of New Lipids and Molecular Gelators: Syntheses, Aggregation Properties and Applications” elucidates the design, synthesis, aggregation properties and application of new lipids based on α-tocopheryl backbone and also with triazacyclononane (TACN) moiety. This thesis also elucidates the synthesis and aggregation properties of molecular gelators based on pyrene-pentapeptide and naphthalene diimide (NDI) moiety. The work has been divided into five chapters. Chapter 1: Introduction: Self-assembled Molecular Aggregates and their Potential Applications This chapter describes the importance of different self-assemble mainly lipids and molecular gelator. Lipids mediated gene delivery, drug delivery and metal ion induced interaction are discussed. For liposomal gene delivery here we mainly describe example of cationic gemini lipids. This chapter also gives a comprehensive account of the research towards the development of novel liposomal drug delivery containing tocopheryl backbone. It also includes the utilization of liposome which could coordinate with metal ions and their interaction with different biological analyte. Here we also discuss a wide range of molecular gelator mainly based on NDI and amino acid or peptide. Chapter 2A: Physicochemical Characterization of Bilayer Membranes Derived from (±) α-Tocopherol Based Gemini Lipids and their Interaction with plasmid-DNA and Phosphatidylcholine Bilayers In this sub-chapter we discuss the membrane formation and aggregation properties of a series of (±) α-tocopherol based cationic gemini lipids (Figure 1) varying polymethylene spacer length (TnS; n = 3, 4, 5, 6, 8 and 12) are studied extensively while comparing with corresponding properties of monomeric counterpart (TM). Liposomal suspensions of all cationic lipids are characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements and small angle x-ray diffraction studies. Aggregation properties of the gemini lipids are highly dependent on the spacer length and were significantly distinct from that of monomeric lipid (TM). Figure 1. Molecular structures of (±) α-tocopherol based cationic monomeric and six gemini lipids that differ in polymethylene spacer length. Stable monolayer formation at air water interface formation of each amphiphile is studied by Langmuir film balance technique. Interaction of liposome with plasmid DNA is studied by ethidium bromide (EB) intercalation assay. Micellar sodium dodecyl sulphate (SDS) mediated release of the plasmid DNA from various pre-formed lipoplex is also studied. Structural transformation of pDNA upon complexation with liposome is characterized by circular dichroism (CD) spectroscopy. Interaction of all tocopheryl lipids with a model phospholipid, L-α-dipalmitoyl phosphatidylcholine (DPPC) derived vesicles is thoroughly examined by differential scanning calorimetry (DSC) and DPH fluorescence anisotropy measurements. Succinctly, we perform a detailed physicochemical characterization on cationic monomeric and gemini lipids bearing tocopherol as their hydrophobic backbone. Chapter 2B: Physicochemical Characterization of Bilayer Membranes Derived from (±) α-Tocopherol Based Gemini Lipids Containing Hydroxyethyl Functionality in the Headgroups and their Interaction with plasmid-DNA and Phosphatidylcholine Bilayers This sub-chapter describes the synthesis and aggregation properties of series of tocopheryl-based monomeric and gemini cationic lipids with hydroxyethyl functionality (Figure 2) in the headgroup region. Gemini lipids of this given series differ in their polymethylene spacer -(CH2)n- chain lengths between cationic headgroups. All monomeric and gemini lipids are found to generate stable suspensions in aqueous media. Average hydrodynamic diameter and surface charge of liposome are characterized by DLS and zeta potential measurements. Atomic force microscopy and transmission electron microscopic studies show that all lipids form vesicular Figure 2. Molecular structures of (±) α-tocopherol based cationic monomeric and five new lipids with hydroxyethyl functionality in the headgroups that differ in polymethylene spacer length aggregates in aqueous media. XRD studies with the cast films of lipids reveal interdigitated bilayer arrangement of liposome. pDNA binding and release studies show that the interactions between gemini lipids and DNA depend upon the nature of head group as well as the length of the spacer between cationic head groups. Circular Dichroism (CD) spectra of lipoplex are measured to characterize structural transformation of pDNA upon complexation with liposome. DPH anisotropy and DSC studies of the DPPC-cationic lipid co-aggregates show that ~20 mol-% of of the tocopheryl gemini lipids is enough to abolish phase transition of DPPC membranes whereas more than 20 mol-% is required in case of their monomeric counterparts. Furthermore thermotropic properties of co-aggregates depend upon the length of the spacer of gemini lipid included in the mixture. Chapter 2C: Transfection Efficacies of α-Tocopherol Based Cationic Gemini Lipids with Hydroxyethyl Containing Headgroups. In this sub-chapter, we demonstrate transfection efficiency of five α-tocopheryl gemini lipid with hydroxyethyl containing headgroups (Figure 3). Co-liposomal formulations with helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) form highly stable formulations in water. Co-liposomal formulations with high molar ratio of DOPE (1.5:1 and 2:1) show higher transfection efficiency than liposome with low DOPE content liposome. Co-liposome of gemini lipids with longer spacer (n = 8 and 12) have higher level of luciferase expression in HepG2 cell line. In A549 and MCF-7 cell lines also co-liposomes of TH8S (2:1) are proved to be better than other co-liposome. N/P ratios of highest transfection are 1-1.5. These formulations are more potent than L2K in all three cancer cell line. The comparison with gemini lipid (T8T) without Figure 3. Molecular structures of (±) α-tocopherol based cationic gemini lipids that differ in polymethylene spacer length and helper lipid DOPE. hydroxylethyl group also proves the importance of hydroxyethyl functionalities. High serum stability of DOPE-gemini lipid formulation is attributed to tocopherol backbone and also hydroxyethyl functionalities. Circular dichroism data also show that lipoplex of DOPE-TH8S (2:1) have different conformation than the other. Relatively moderate binding efficiency and easy release of pDNA is also observed with DOPE-TH8S (2:1) in the EB-displacement assay which could be plausible reason for high transfection efficiency. Chapter 2D: Reduction Responsive Nanoliposomes of α-Tocopheryl-Lipoic Acid Conjugate for Efficacious Drug Delivery to Sensitive and Resistant Cancer Cells In this sub-chapter, we present lipid conjugates derived from biologically relevant molecules, i.e., tocopherol and lipoic acid (Figure 4). These conjugates (TL1 and TL2) are able to form stable nanoliposomes (~100 nm) that respond to the reducing environment of cells as shown by the treatments of 1,4-Dithiothreitol (DTT) and Glutathione (GSH). Figure 4. Molecular structures of tocopheryl-lipoic acid conjugates, TL1 and TL2 Nanoliposomes could efficiently load the drug (DOX) molecules and release them in response to the stimulus. Nanoliposomes are stable enough in the presence of serum and could deliver DOX inside drug sensitive and drug resistant cells in an efficient manner that is even better than the drug alone treatments as shown by means of flow cytometry and confocal microscopy analysis. DOX loaded nanoliposomal formulations show relatively less cell viability counts than those drug alone treatments. Chapter 3A: Interaction of Nickel (II) and mida ole it Triazacyclononane Modified Chelator Amphiphiles: A Potential Substrate for Immobilization of His-tag Protein on Hydrophilic Surface This sub-chapter describes two chelator amphiphiles based on 1, 4, 7-traiazaclonone (TACN) (Figure 5). These compounds could bind efficiently Ni2+ ion. Self-assemble of these amphiphiles form vesicular aggregates. Their packing properties of these amphiphiles are influence by Ni2+ and imidazole. Also influence of Ni2+ and imidazole in Langmuir monolayer isotherm of these amphiphiles at air-water interface are also studied. Figure 5. Molecular structures of TACNA chelator amphiphiles. These studies show the newly synthesized amphiphiles could immobilize histidine tagged protein on both bilayer and monolayer surface. One of these compounds with Ni2+ (C16TACNA-Ni2+) is used to transfer a His-tagged protein nucleolin on hydrophilicobic glass surface by Langmuir-Blodgett transfer technique. So, these compounds with Ni2+ could be very useful to attach different His-tagged protein or polypeptide of interest on the bilayer (liposome) or monolayer surface. Chapter 3B: Supramolecular Hosts for Enhancing the Selectivity of TACN Based Probes towards Copper (II): Differential Output Signals for Cysteine and Histidine In this sub-chapter, we have developed a new amphipathic probe compound 1 having TACN as the binding site and dansyl as signaling moiety (Figure 6). As TACN is known for its’ unspecific interaction with multiple ions, the probe shows response with most of the transition metal ions. However, incorporation into different supramolecular hosts (like micelle and vesicles) drastically improves the selectivity of compound 1 towards Cu2+ (diminution of bright green fluorescence) in water. Then we Figure 6. Molecular structures of dansylated TACN chelator amphiphiles. have also employed the Cu2+ complex of compound 1 for selective estimation of amino acids. Addition of cysteine regains the green emission of compound while histidine exhibits blue intense emission upon formation of ternary conjugate. Chapter 4: Transforming a β-Sheet Pyrenylated-VPGKG Sequence into pH Tolerent, Thixotropic Hydrogel by Arene-Perfluoroarene Interactions and Visualized Sensing of Calcium (II) Ion In this chapter we discuss self-assembly studies of a novel thermoresponsive, lipidated, pyrene-appended peptide, PyP (Figure 7). Size of the vesicular aggregates of the β-sheet forming peptide, PyP, strongly depends on the temperature of the solution in water. Further pyrene-octafluoronaphthalene (OFN) pair has been used as supramolecular synthon to induce hydrogelation of PyP in presence of equimolar amount of OFN via complementary quadrupole-quadrupole interactions. The gel shows excellent pH tolerant as well as thixotropic behavior. Detailed studies suggested the lamellar packing of the gelator in a right-handed helical fashion yielded vesicular aggregates. The sticky vesicles form gel via inter- Figure 7. Molecular structure of the Pyrenylated-VPGKG peptide (PyP) and octafluoronapthalene (OFN). Ca2+ ion reinforces the mechanical strength and also reduces the critical gelator concentration of the native gel through coordination with the free -COO- group of the gelator. Therefore, this present system could be used as a visualized sensor of Ca2+ ion. Chapter 5: First Report of Naphthalenediimide Based Metallo(organo)gel In this chapter, we have demonstrated synthesis of a novel asymmetric bolaamphiphilic (Figure 8). NDI derivative is capable of self assemble into stable gel in EtOH. Detailed studies reveal the gelator molecule of 1 adopt a parallel alignment in the lamellae during self-aggregation as nanoscopic spherical assemblies. In addition, dried gel of 1 shows nematic liquid crystalline phase. Further, we synthesize a novel metal-ligand discrete complex 2 in a nearly quantitative yield by reacting equimolar amount of 1 and PdCl2(PhCN)2. Figure 8. NDI derivative, 1, and its discrete metal complex 2. Complex 2 has been found to yield stable gel in dichloromethane (DCM) or chloroform (CHCl3) through the formation of high aspect ratio fibers. ROESY NMR experiment of Complex 2 has been found to yield stable gel in dichloromethane (DCM) or chloroform (CHCl3) through the formation of high aspect ratio fibers. ROESY NMR experiment of

Mechanism underlying nanotoxicity has remained elusive. Hence, efforts to understand whether nanoparticle properties might explain its toxicity are ongoing. Considering three different types of organo-coated silver nanoparticles (AgNPs): citrate-coated AgNP, polyvinylpyrrolidone-coated AgNP, and branched polyethyleneimine-coated AgNP, with different surface charge scenarios and core particle sizes, herein we systematically evaluate the potential role of particle size and surface charge on the toxicity of the three types of AgNPs against two model organisms, Escherichia coli and Daphnia magna. We find particle size, surface charge, and concentration dependent toxicity of all the three types of AgNPs against both the test organisms. Notably, Ag+ (as added AgNO3) toxicity is greater than each type of AgNPs tested and the toxicity follows the trend: AgNO3>BPEI-AgNP>Citrate-AgNP>PVP-AgNP. Modeling particle properties using the general linear model (GLM), a significant interaction effect of primary particle size and surface charge emerges that can explain empirically-derived acute toxicity with great precision. The model explains 99.9% variation of toxicity in E. coli and 99.8% variation of toxicity in D. magna, revealing satisfactory predictability of the regression models developed to predict the toxicity of the three organo-coated AgNPs. We anticipate that the use of GLM to satisfactorily predict the toxicity based on nanoparticle physico-chemical characteristics could contribute to our understanding of nanotoxicology and underscores the need to consider potential interactions among nanoparticle properties to explaining nanotoxicity.

Šiuo metu vyraujanti pasaulinė ekonominė krizė, taip pat ankstesni bendrovių bankrotų pavyzdžiai (tokių kaip Enron, Parmalat) signalizuoja apie būtinybę tinkamai sureguliuoti bendrovių valdymo teisinę bazę, o ypač aspektus susijusius su bendrovės akcininkų ir valdymo organo santykiais. Todėl šiame magistro darbe yra analizuojamos teisinės priemonės, kurios padeda sumažinti interesų konfliktus kylančius tarp bendrovių, kurių vertybiniais popieriais yra prekiaujama reguliuojamoje rinkoje, akcininkų ir valdymo organo. Šiam tikslui pasiekti yra išskiriamos penkios teisinio reguliavimo sritys: bendrovių kontrolės rinkos ir bendrovių perėmimo, informacijos atskleidimo, valdymo organo narių finansinio skatinimo, valdymo organo struktūros bei bendrovės akcininkų teisių teisinis reguliavimas. Kiekviena reguliavimo sritis yra aptariama dviem aspektais, pirmiausia, analizuojant Europos Sąjungos lygiu egzistuojantį teisinį reguliavimą, po to vertinant tokio reguliavimo įgyvendinimą Lietuvos Respublikoje bei pateikiant pastabas ir pasiūlymus. Darbe padaroma išvada, kad norint sumažinti neigiamas pasekmes atsirandančias dėl nuosavybės teisės ir valdymo atskyrimo bendrovėse, reikia, kad visos aukščiau išvardintos priemonės papildytų viena kitą ir būtų taikomos sistemiškai. / The ongoing economic crisis around the world and the recent events in corporate bankruptcy sector (including Enron and Parmalat cases) have shown a clear signal to regulate more efficiently the corporate governance laws and especially the relations between shareholders and the governance body of the company. This thesis paper addresses the regulatory framework issues, which mitigate the conflict of interests between the shareholders and the governance body of publicly traded companies. Five legal instruments are analyzed in order to achieve this objective: market for corporate control and takeovers, information disclosure, director remuneration, structure of governance body and shareholder empowerment. Each legal instrument is analyzed from two legal perspectives, first, the European Union legal framework is described and then analysis concentrates on the implementation of European law in the Republic of Lithuania. Comments and proposals are given to existing implementation problems. The conclusion emphasizes that a systematic use of all the above mentioned legal instruments is required in order to mitigate the costs of separation of ownership and control in publicly traded companies.

Foram estudadas onze amostras de fosfatos de três grandes depósitos brasileiros para produção de fertilizantes organo-fosfatados: uma amostra associada ao complexo alcalino-carbonatítico de Jacupiranga/SP, sete amostras associadas ao complexo alcalino-carbonatítico de Catalão/GO e três amostras associadas ao depósito sedimentar de Patos de Minas/MG. Com exceção de uma amostra de Catalão, alimentação da usina de concentração na data da amostragem, as demais são minérios marginais, rejeitos da lavra, rejeitos da usina e minérios complexos ao beneficiamento. As amostras, com exceção daquela de Jacupiranga, foram submetidas à caracterização tecnológica, com realização de análises granulométricas, separações minerais (em líquido denso e magnética) , análises químicas e difratométricas. A caracterização buscou levantar as principais características destes fosfatos para a produção de um novo fertilizante organo-fosfatado. Verificou-se a grande dificuldade na obtenção de concentrados ricos em P2O5 com boas recuperações. Os rejeitos dos minérios oxidados de Catalão apresentam baixa liberação da apatita frente à ganga silicática e férrica, além de apresentarem um recobrimento da apatita por óxidos/hidróxidos de ferro, prejudicial à flotação. As amostras sílico-carbonatadas apresentam altos teores de carbonatos, problemáticos na separação por flotação, principalmente a dolomita. Os minérios de Patos de Minas apresentam uma íntima associação da apatita com o quartzo e outros silicatos, de difícil ou quase impossível liberação. O novo processo de produção de fertilizante organo-fosfatado baseia-se no ataque do fosfato pelo ácido nítrico e na utilização de amônia como fonte primária do reagente ácido. A combustão do amoníaco ao ar, em temperaturas entre 650°C e 800°C se auto mantém, produzindo óxidos nítricos que, em contato com a umidade da mistura fosfato+matéria orgânica, transformam-se em ácido nítrico nascente na própria superfície das partículas. As diferentes amostras de fosfatos misturadas à turfa da região do baixo Ribeira de Iguape e a uma turfa comercial francesa foram processadas em equipamento micropiloto e os resultados agronômicos mostraram boa liberação de fósforo no primeiro mês de cultivo, assim como a continuidade de liberação, em menor escala, nos cinqüenta dias seguintes. Obtiveram-se fertilizantes com teores de 12% até 73% de fósforo solúvel em ácido cítrico a 2%, que nos ensaios agronômicos permitiram a assimilação de 23% a 81% de fósforo pela planta. / Onze échantillons de phosphates de trois importants gisements brésiliens ont été étudiés pour la production des engrais organo-phosphatés : un échantillon associé au complexe alcaline-carbonatitique de Jacupiranga/SP, sept échantillons associés au complexe alcaline-carbonatitique de Catalão/GO et trois échantillons associés au gisement sédimentaire de Patos de Minas/MG. Sauf un échantillon de Catalão, qui alimentait l\'usine de concentration pendant l\'échantillonnage, les outres sont minerais marginaux, rejets de la mine, rejets de l\'usine et minerais complexes au traitement. Les échantillons sauf celui de Jacupiranga, ont été caractérisés technologiquement, avec réalisation des analyses granulométriques, séparations minéraux (au liquide dense et magnétique), analyses chimiques e difratométriques. La caractérisation a défini les principaux caractéristiques des phosphates pour la production d\'un nouveau engrais organo-phosphaté. On a constaté la grande difficulté en l\'obtention de concentrés riche en P2O5 avec des bonnes récupérations. Les rejets des minerais oxydés de Catalão présentent baisse libération de l\'apatite de la gangue siliceuse et ferreuse, et, en plus, ils présentent aussi un recouvrement de l\'apatite par les oxydes/hydroxydes de fer, qui sont préjudiciables à la flottation. Les échantillons silico-carbonatés présentent hautes teneurs des carbonates, qui sont difficiles à séparer par flottation, principalement la dolomite. Les minerais de Patos de Minas présentent une intime association de l\'apatite avec le quartz et les autres silicates, de difficile ou presque impossible libération. Le nouveau procédé de production des engrais organo-phosphatés est basée sur la dissolution du phosphate par l\'acide nitrique et sur l\'utilisation de gaz ammoniac comme source primaire du réactif acide. La combustion du ammoniac à l\'air, en températures entre 650°C et 800°C se auto-conserve produisant oxydes d\'azote qui, en contact avec la humidité de la mélange phosphate + matière organique, se transforme en l\'acide nitrique naissant à la surface des particules. Les différentes échantillons de phosphates mélangés à la tourbe de la région du \'Baixo Ribeira de Iguape/SP\' et à une tourbe commerciale française ont été traités en équipement micro-pilote et les résultats agronomiques présentent une bonne libération du phosphore pendant le première mois de culture, et la continuité de la libération, en mineur quantité, dans les cinquante jours suivants. Les engrais produits ont obtenu 12% jusqu\'à 73% de phosphore soluble dans l\'acide citrique à 2%, lesquels, pendant les essais agronomiques, ont permis l\'assimilation entre 23% et 81% de phosphore par la plante.

Ce manuscrit présente des développements récents dans le domaine des réactions d'arylation ou d'hydroarylation d'oléfines catalysées par des complexes de métaux de transition (rhodium et ruthénium). L'utilisation des trifluoro(organo)borates de potassium a permis d'effectuer une réaction de Heck catalysée par un complexe de rhodium en l'absence de base et d'oxydant. Ces conditions sont plus douces que celles qui sont généralement décrites dans la littérature et elles pourraient être utilisées pour la synthèse de molécules sensibles aux conditions basiques ou oxydantes. Un nouveau système catalytique à base de ruthénium actif dans des procédés d'hydroarylation d'alcènes, via l'activation de liaisons C-H ortho-dirigée, a également été mis au point. Il présente l'avantage d'être généré in situ à partir de précurseurs stables de ruthénium, de formiate de sodium et de triphénylphosphine, mais surtout, il est possible de modifier ses propriétés électroniques et stériques en jouant sur les ligands du ruthénium. Cette adaptabilité a été mise à profit pour l'activation et la fonctionnalisation de nombreux substrats. En particulier, un procédé d'hydroarylation anti-Markovnikov des styrènes a été mis au point avec ce système catalytique. Enfin, l'utilisation d'un solvant protique a permis de diminuer grandement la température de la réaction, permettant d'obtenir une bonne activité catalytique dans des conditions plus douces.

Made available in DSpace on 2014-12-17T14:07:07Z (GMT). No. of bitstreams: 1 JulianaCS.pdf: 1007525 bytes, checksum: 74d4bf5035436a1b506b801dce77838f (MD5) Previous issue date: 2006-03-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The metalceramic crowns are usually used in dentistry because they provide a resistant structure due to its metallic base and its aesthetics from the porcelain that recovers this structure. To manufacture these crowns, a series of stages should be accomplished in the prosthetic laboratories, and many variables can influence its success. Changes in these variables cause alterations in the metallic alloy and in the porcelain, so, as consequence, in the adhesion between them. The composition of the metal alloy can be modified by recasting alloys, a common practice in some prosthetic laboratories. The aim of this paper is to make a systematic study investigating metalceramic crowns as well as analyzing the effect of recasting Ni-Cr alloys. Another variable which can influence the mechanism of metalceramic union is the temperature used in firing porcelain procedure. Each porcelain has to be fired in a fixed temperature which is determined by the manufacturer and its change can cause serious damages. This research simulate situations that may occur on laboratory procedures and observe their consequences in the quality of the metalceramic union. A scanning eletron microscopy and an optic microscopy were accomplish to analyse the metal-ceramic interface. No differences have been found when remelting alloys were used. The microhardness were similar in Ni-Cr alloys casted once, twice and three times. A wettability test was accomplished using a software developed at the Laborat?rio de Processamento de Materiais por Plasma, on the Universidade Federal do Rio Grande do Norte. No differences were found in the contact angle between the solid surface (metallic substratum) and the tangencial plane to the liquid surface (opaque). To analyse if the temperature of porcelain firing procedure could influence the contact area between metal and porcelain, a variation in its final temperature was achieve from 980? to 955?C. Once more, no differences have been found / Durante o processo de confec??o de coroas metalocer?micas, ? necess?rio que todas as informa??es passadas pelo fabricante sejam seguidas de forma criteriosa. Caso isto n?o ocorra, podem acontecer altera??es tanto na liga met?lica como na porcelana e como conseq??ncia, na ades?o entre elas. Um fator que deve ser levado em considera??o, consiste em analisar o efeito das refus?es, uma vez que nos laborat?rios prot?ticos torna-se comum a pr?tica do reaproveitamento da ligas. Outro fator importante ao se preparar coroas metalocer?micas ? a temperatura de sinteriza??o da porcelana. Sabe-se que a temperatura de sinteriza??o pode influenciar na microestrutura, afetando diretamente suas propriedades f?sicas e mec?nicas. Nesse trabalho, um estudo sistem?tico ? realizado com o intuito de investigar a ades?o metal-cer?mica em ligas Ni-Cr fundidas sob diferentes graus de reaproveitamento, assim como analisar o efeito de diferentes temperaturas de sinteriza??o da porcelana. Procura-se aqui simular situa??es poss?veis de ocorrer durante procedimentos laboratoriais prot?ticos e observar suas conseq??ncias na qualidade da ades?o metal-cer?mica. Deste modo, coroas de ligas de n?quel-cromo refundidas em 1 e 2 vezes, foram comparadas com aquelas apenas fundidas. Uma an?lise por microscopia ?ptica e eletr?nica foi realizada para se avaliar o contato entre o metal e o opaco da porcelana. Al?m do mais, testes de microdureza sobre a liga met?lica foram executados. Neste estudo, procurou-se tamb?m avaliar a molhabilidade da porcelana sobre ligas met?licas com diferentes estados de fus?o, al?m de realizar uma sinteriza??o da porcelana em diferentes temperaturas (980?C e 955?C). Como resultado encontrou-se que n?o houve diferen?a na interface entre as liga em diferentes est?gios de fus?o e a porcelana. Com rela??o ? microdureza, os resultados indicaram que, na medida em que se aumenta o n?mero de refus?es, os valores de microdureza n?o se alteram e com rela??o ? molhabilidade n?o houve diferen?a estatisticamente significativa entre as amostras. Tamb?m n?o se encontrou diferen?a entre as ?reas de contato formadas entre a porcelana e a liga fundida quando a porcelana foi sinterizada em diferentes temperaturas, mostrando que uma diminui??o de 25?C na temperatura final de sinteriza??o n?o interfere na uni?o metal-cer?mica

Orientador: Marlene Cristina Alves / Resumo: A compactação do solo em sistemas plantio direto (SPD) tem comprometido a sua sustentabilidade. Para contornar esse problema, a escarificação mecânica e a manutenção da cobertura vegetal são sugeridas como práticas de manejo a fim de restabelecer as condições ideais de cultivo. Assim, o objetivo deste trabalho foi avaliar o efeito a curto prazo da escarificação e do uso de diferentes plantas de cobertura na manutenção do SPD envolvendo as culturas do arroz de “terras altas” e feijão de “inverno”). O trabalho foi desenvolvido em Selvíria, MS em 2014/15 e 2015/16, em um Latossolo Vermelho Distrófico de textura argilosa. Utilizou-se o delineamento em blocos casualizados disposto em parcelas subdivididas, tendo nas parcelas as condições da superfície do solo em SPD (com e sem escarificação mecânica) e nas subparcelas as plantas de cobertura (pousio, Cajanus cajan, Crotalaria juncea, Urochloa ruziziensis (Syn. Brachiaria ruziziensis) e Pennisetum glaucum), com quatro repetições, cultivadas com arroz e feijão. Foram avaliadas as características fitotécnicas das culturas e atributos físicos e químicos do solo em quatro camadas (0 a 0,05; 0,05 a 0,10; 0,10 a 0,20 e 0,20 a 0,40 m). Realizou-se a análise de variância e teste de Tukey a 5%de probabilidade para comparação de médias. Além disso, na camada de 0 a 0,05 m do solo também foram analisadas as características das nanopartículas e nanoestruturas do solo. Para essas análises incluiu-se o solo de Cerrado remanescente para comparaçã... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Soil compaction in no-tillage systems (NTS) affects the sustainability of this management. To overcome the problem, mechanical chiseling and maintenance of the cover crop were suggested as management practices reestablishing ideal cultivation conditions. Thus, the objective of this study was to evaluate the short-term effect of mechanical chiseling and the use of different cover crops in the maintenance of NTS involving as crops "dryland” rice and "winter" common bean. The experiment was conducted in Selvíria, state of Mato Grosso do Sul, Brazil, during the 2014/15 and 2015/16 growing season, on a typical clayey dystrophic Red Latosol, with experiment was evaluated in a randomized block design in split plots, with the main plots as SPD soil surface conditions (with and without mechanical chiseling) and in the subplots as cover crop (fallow, Cajanus cajan, Crotalaria juncea, Urochloa ruziziensis and Pennisetum glaucum), with four replications, cultivated with “dryland” rice and "winter" common bean. The agronomic characteristics of the crops and soil physical and chemical attributes in four layers (0 a 0.05; 0.05 a 0.10; 0.10 a 0.20 e 0.20 a 0.40 m). The analysis of variance and Tukey's test were performed at a 5% probability for comparison of average. In addition, treatments of the 0 to 0.05 m layer of the soil were also compared to the natural closed area, through the conventional chemical and physical properties and characteristics of its nanoparticles and nanostructures. F... (Complete abstract click electronic access below) / Doutor