961 resultados para polyacetylene and derivatives


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L'analyse statistique des données a été effectuée avec le logiciel R.

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Suite à la crise financière globale de 2008, ainsi qu’aux différents facteurs qui y ont mené, il est étonnant qu’une alternative éthique et juste pour une finance lucrative et stable n’existe toujours pas (ou du moins, demeure oubliée). Ayant décidé de contribuer au domaine pluri-centenaire du Droit Commercial de la Chari’a, nous avons été surpris par la découverte d’une problématique à l’origine de cette thèse. En France, nous avons suivi des débats doctrinaux intéressants dont les conclusions se rapprochent de la perception générale Occidentale quand à la nature de la finance Islamique, que ce soit au niveau de la finance basée sur le Droit de la Chari’a ou encore les exigences de sa pleine introduction dans le système juridique français de l’époque. Cet intérêt initial dans la finance islamique a ensuite mené à un intérêt dans la question des avantages d’éthique et de justice du Droit Commercial de la Chari’a dans son ensemble, qui est au coeur de cette thèse. Dans le monde moderne du commerce et de la finance d’aujourd’hui, les transactions sont marquées par une prise de risque excessive et un esprit de spéculation qui s’apparente aux jeux de hasard, et menant à des pertes colossales. Pire encore, ces pertes sont ensuite transférées à la collectivité. Par conséquent, y at-il des préceptes, des principes ou des règles éthiques et juridiques qui peuvent fournir une certaine forme de sécurité et de protection dans les marchés financiers d'aujourd'hui? Est-ce réalisable? Cette thèse soutient que la richesse de la jurisprudence islamique ainsi que ses règles dont les avantages n’ont pas encore été pleinement saisis et régénérés en réponse aux nouveaux défis d’aujourd'hui, peuvent encore fournir continuellement des solutions, et réformer des produits financiers de façon à refléter des principes de justice et d'équité. Dans ce processus, un éclairage nouveau sera apporté à certains sujets déjà connus dans le cadre de la contribution prévue de cette thèse, mais ne sera pas le principal objectif de la thèse.

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La crisis financiera hipotecaria de 2008 en la que se declaró en quiebra el banco de inversión Lehman Brothers, se desarrolló en un ambiente que contemplaba apalancamientos financieros excesivos y el uso de derivados financieros de crédito innovadores. Razón por la cual, a partir del estudio de caso de quiebra de este banco de inversión y el análisis de las causas y consecuencias del ambiente desregulatorio que surgió en Estados Unidos desde la década de los 30 hasta el 2000, se orienta la investigación a indagar sobre lo que sucede en términos regulatorios y empresariales en el mercado de valores colombiano y así lograr definir objetivos que permitan el crecimiento del mercado de derivados exóticos en Colombia bajo un marco de responsabilidad financiera y ética empresarial.

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La crisis financiera del 2008 provocó la pérdida de riqueza y el derrumbe de los mercados bursátiles y de la economía real, traducida en desempleo, reducción de la productividad, recesión profunda, e incertidumbre en los mercados financieros. En el marco de la crisis de deuda soberana europea, es cuestionable también el grado de certeza de los CDS (Credit Default Swap) como garantía para los inversionistas, considerando las negociaciones existentes entre emisores y bancos europeos para evitar el default de estos instrumentos y por tanto, evitar la indemnización a los inversionistas en su calidad de acreedores. Remontándonos, la crisis financiera internacional del año 2008 tuvo como uno de sus orígenes a las hipotecas denominadas como “subprime”. Estas hipotecas fueron “empaquetadas” junto a otras de alta calificación, en grupos de hipotecas para ser titularizadas y colocadas en el mercado bursátil, mediante instrumentos denominados CDO (Collateralized Debt Obligations), y a aseguradas en algunos casos, través de los CDS (Credit Default Swap), siendo principalmente estos últimos instrumentos financieros, blanco de las críticas y señalados como uno de los culpables de la crisis financiera internacional. Bajo estas consideraciones, se pretende en esta investigación, analizar específicamente los CDS (Credit Default Swap), para determinar su naturaleza jurídica como verdaderos seguros contra cesación de pagos, o como permutas de incumplimiento crediticio. Comprender su estructuración legal como instrumento de garantía para los inversionistas institucionales o particulares, considerando el acontecimiento de la quita de los bonos griegos, la crisis de deuda soberana europea y el default de la deuda argentina, así como las consideraciones del ISDA (International Swaps and Derivatives Association) en estos puntos; su marco legal, su contribución en la reducción del riesgo, su papel especulativo y su incidencia real en la crisis financiera del año 2008.

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The CH(2)Cl(2) and MeOH extracts from leaves of Piper caldense were subjected to chromatographic separation procedures to afford the new prenylated benzoic acid, caldensinic acid (3-[(2`E,6`E,10`E)-11`-carboxy-3`,7`,15`-trimethylhexadeca-2`,6`,10`,14`-tetraenyl]-4,5-dihydroxybenzoic acid) whose structure was determined by spectral analysis, mainly NMR ((1)H, (13)C, HSQC, HMBC) and ESI-MS. The natural compound and derivatives displayed antifungal activity against the phytopathogenic fungi Cladosporium cladosporioides and C. sphaerospermum by direct bioautography. (C) 2009 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.

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The nonadiabatic photochemistry of the guanine molecule (2-amino-6-oxopurine) and some of its tautomers has been studied by means of the high-level theoretical ab initio quantum chemistry methods CASSCF and CASPT2. Accurate computations, based by the first time on minimum energy reaction paths, states minima, transition states, reaction barriers, and conical intersections on the potential energy hypersurfaces of the molecules lead to interpret the photochemistry of guanine and derivatives within a three-state model. As in the other purine DNA nucleobase, adenine, the ultrafast subpicosecond fluorescence decay measured in guanine is attributed to the barrierless character of the path leading from the initially populated (1)(pi pi* L-a) spectroscopic state of the molecule toward the low-lying methanamine-like conical intersection (gs/pi pi* L-a)(CI). On the contrary, other tautomers are shown to have a reaction energy barrier along the main relaxation profile. A second, slower decay is attributed to a path involving switches toward two other states, (1)(pi pi* L-b) and, in particular, (1)(n(o)pi*), ultimately leading to conical intersections with the ground state. A common framework for the ultrafast relaxation of the natural nucleobases is obtained in which the predominant role of a pi pi*-type state is confirmed.

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This paper critically reviews analytical applications of the chemiluminescence from tris(2,2-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2-bipyridyl)ruthenium(II).

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31P, 19F and 13C solid state NMR analysis has been used to investigate the intercalation/de-intercalation of both anions and cations in electrochemically synthesized polypyrrole films. Use of a phosphonium-based ionic liquid, tri(hexyl)(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide, allows the separate detection of the cation and anion by analysis of the phosphorous and fluorine resonances, respectively. Initial results indicate the incorporation of both cations and anions during film growth in the ionic liquid. There is a notable change in the 31P chemical shift of the cation on incorporation into the film, consistent with a significant change in environment compared to the pure ionic liquid. Despite its large size, the phosphonium cation can be completely expelled from the film by oxidation.

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Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully synthesised using ionic liquids as both the growth medium and the electrolyte. Both imidazolium and pyrrolidinium-based TFSA ionic liquids were used to assess the influence of the nature of the medium on the morphology and electrochemical activity of the resulting materials.

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Esta pesquisa tem por objeto a análise sistemática da jurisprudência brasileira sobre os contratos de distribuição entre os anos de 1.980 e 2.000, procurando identificar qual a posição dos nossos Tribunais face a esses contratos. Nessa linha, constatou-se que os casos (acórdãos) abrem-se em cinco grandes blocos, quais sejam: (1) atribuição/divisão territorial; (2) questões possessórias; (3) renovatória de locação; (4) rescisão dos contratos de distribuição. Este grupo divide-se (i) naqueles contratos sujeitos à Lei Ferrari, (ii) naqueles referentes ao setor de combustíveis e derivados e (iii) naqueles não subsumíveis a tal diploma; (5) questões processuais relevantes, dividido em (i) litisconsórcio necessário e (ii) título executivo extrajudicial. Além disso, por se tratar de uma avenca atípica na maioria dos casos, a pesquisa procurou extrair de cada um dos casos qual o conceito de contrato de distribuição adotado.

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A modelagem da estrutura a termo da taxa juros tem grande relevância para o mercado financeiro, isso se deve ao fato de ser utilizada na precificação de títulos de crédito e derivativos, ser componente fundamental nas políticas econômicas e auxiliar a criação de estratégias trading. A classe de modelos criada por Nelson-Siegel (1987), foi estendida por diversos autores e atualmente é largamente utilizada por diversos bancos centrais ao redor do mundo. Nesse trabalho utilizaremos a extensão proposta por Diebold e Li (2006) aplicada para o mercado brasileiro, os parâmetros serão calibrados através do Filtro de Kalman e do Filtro de Kalman Estendido, sendo que o último método permitirá estimar com dinamismo os quatros parâmetros do modelo. Como mencionado por Durbin e Koopman (2012), as fórmulas envolvidas no filtro de Kalman e em sua versão estendida não impõe condições de dimensão constante do vetor de observações. Partindo desse conceito, a implementação dos filtros foi feita de forma a possibilitar sua aplicação independentemente do número de observações da curva de juros em cada instante de tempo, dispensando a necessidade de interpolar os dados antes da calibração. Isso ajuda a refletir mais fielmente a realidade do mercado e relaxar as hipóteses assumidas ao interpolar previamente para obter vértices fixos. Também será testada uma nova proposta de adaptação do modelo de Nelson-Siegel, nela o parâmetro de nível será condicionado aos títulos terem vencimento antes ou depois da próxima reunião do Copom. O objetivo é comparar qualidade da predição entre os métodos, pontuando quais são as vantagens e desvantagens encontradas em cada um deles.

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Em economias com regimes de metas de inflação é comum que Bancos Centrais intervenham para reduzir os níveis de volatilidade do dólar, sendo estas intervenções mais comuns em países não desenvolvidos. No caso do Brasil, estas intervenções acontecem diretamente no mercado à vista, via mercado de derivativos (através de swaps cambiais) ou ainda com operações a termo, linhas de liquidez e via empréstimos. Neste trabalho mantemos o foco nas intervenções no mercado à vista e de derivativos pois estas representam o maior volume financeiro relacionado à este tipo de atuação oficial. Existem diversos trabalhos que avaliam o impacto das intervenções e seus graus de sucesso ou fracasso mas relativamente poucos que abordam o que levaria o Banco Central do Brasil (BCB) a intervir no mercado. Tentamos preencher esta lacuna avaliando as variáveis que podem se relacionar às intervenções do BCB no mercado de câmbio e adicionalmente verificando se essas variáveis se relacionam diferentemente com as intervenções de venda e compra de dólares. Para tal, além de utilizarmos regressões logísticas, como na maioria dos trabalhos sobre o tema, empregamos também a técnica de redes neurais, até onde sabemos inédita para o assunto. O período de estudo vai de 2005 a 2012, onde o BCB interveio no mercado de câmbio sob demanda e não de forma continuada por longos períodos de tempo, como nos anos mais recentes. Os resultados indicam que algumas variáveis são mais relevantes para o processo de intervenção vendendo ou comprando dólares, com destaque para a volatilidade implícita do câmbio nas intervenções que envolvem venda de dólares, resultado este alinhado com outros trabalhos sobre o tema.

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With the new discoveries of oil and gas, the exploration of fields in various geological basins, imports of other oils and the development of alternative fuels, more and more research labs have evaluated and characterized new types of petroleum and derivatives. Therefore the investment in new techniques and equipment in the samples analysis to determine their physical and chemical properties, their composition, possible contaminants, especification of products, among others, have multiplied in last years, so development of techniques for rapid and efficient characterization is extremely important for a better economic recovery of oil. Based on this context, this work has two main objectives. The first one is to characterize the oil by thermogravimetry coupled with mass spectrometry (TG-MS), and correlate these results with from other types of characterizations data previously informed. The second is to use the technique to develop a methodology to obtain the curve of evaluation of hydrogen sulfide gas in oil. Thus, four samples were analyzed by TG-MS, and X-ray fluorescence spectrometry (XRF). TG results can be used to indicate the nature of oil, its tendency in coke formation, temperatures of distillation and cracking, and other features. It was observed in MS evaluations the behavior of oil main compounds with temperature, the points where the volatilized certain fractions and the evaluation gas analysis of sulfide hydrogen that is compared with the evaluation curve obtained by Petrobras with another methodology

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Kalanchoe brasiliensis Cambess (Crassulaceae), commonly known as saião , coirama branca , folha grossa , is originally from Brazil and commonly found in São Paulo to Bahia, mainly in the coastal zone. Regarding of biological activities, most preclinical studies were found in the literature, mainly about the anti-inflammatory activity of extracts obtained from leaves and / or aerial parts of K. brasiliensis. As regards the chemical constitution, it has been reported mainly the presence of flavonoids in the leaves of the species, but until this moment did not knows which are the active compounds. Although it is a species widely used in traditional medicine in Brazil, there is no monograph about the quality parameters of the plant drug. In this context, this study aims to characterize and quantify the chemical markers of hydroethanolic extract (HE) from the leaves of K. brasiliensis, which can be used in quality control of plant drug and derivatives obtained from this species. The methodology was divided into two parts: i. Phytochemical study: to fractionate, isolate and characterizate of the chemical (s) marker (s) of the HE from the leaves of K. brasiliensis; ii. To Developed validate of analytical method by High Performance Liquid Chromatography (HPLC)-diode array detector (DAD) to quantify the chemical (s) marker (s) of the EH. i. The EH 50% was prepared by turbo extraction method. It was then submitted to liquid-liquid partition, obtaining dichloromethane, n-butanol and ethyl acetate (AcOEt) fractions. The AcOEt fraction was selected to continue the fractionation process, because it has a chemical profile rich in flavonoids. The acOEt fraction was submitted to column chromatography using different systems for obtaining the compound Kb1. To identify this compound, it was submitted to UV analysis ii. For quantitative analysis, the EH was analyzed by HPLC, using different methods. After selecting the most appropriate method, which showed satisfactory resolution and symmetrical peaks, it was validated according to parameters in the RE 899/2003. As result, it was obtained from the AcOEt fraction the compound Kb1 (2.7 mg). Until this moment, the basic nucleus was characterized by UV analysis using shift reagents. The partial chemical structure of the compound Kb1 was identified as a flavonol, containing hydroxyls in 3 , 4 position (ring A), 5 and 7 free (ring B) and a replacement of the C3 hydroxyl by a sugar. As the analysis were performed in the HPLC coupled to a DAD, we observed that the UV spectrum of the major peaks of EH from K. brasiliensis shown similar UV spectrum. According to the literature, it has been reported the presence of patuletin glycosydes derivatives in the leaves of this species. Therefore, it is suggested that the compound Kb1 is glycosylated patuletin derivative. Probably the sugar (s) unit(s) are linked in the C3 in the C ring. . Regarding the development of HPLC analytical method, the system used consists of phase A: water: formic acid (99,7:0,3, v / v) and phase B: methanol: formic acid (99,7:0,3, v / v), elution gradient of 40% B - 58% B in 50 minutes, ccolumn (Hichrom ®) C18 (250x4, 0 mm, 5 μm), flow rate 0.8 mL / min, UV detection at 370 nm, temperature 25 ° C. In the analysis performed with the co-injection of thecompound Kb1 + HE of K. brasiliensis was observed that it is one of the major compounds with a retention time of 12.47 minutes and had a content of 15.3% in EH of leaves from K. brasiliensis. The method proved to be linear, precise, accurate and reproducible. According to these results, it was observed that compound Kb1 can be used as a chemical marker of EH from leaves of K. brasiliensis, to assist in quality control of drug plant and its derivatives

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The Oil industry in Brazil has gone through several stages during the economical, political and social historical process. However, the significative changes have happened in the last fifteen years, due to market opening arising from the relaxation of the state monopoly over the Oil deposits and its derivatives. The edition of the Constitutional Amendment #9, changing the first paragraph of the 177th item of the Federal Constitution, marked the end of a stiffness about the monopoly that the Brazilian state kept in relation to the exploration and research of Oil and Gas. The economical order was fundamental to actualize the idea contained in the #9 Amendment, since its contents has the power to set up measures to be adopted by public power in order to organize the economical relations from a social viewpoint. The new brazilian Oil scenery, called pre-salt, presents itself in a way to amaze the economical markets, in addition to creating a new perspective to the social sector. This work will identify, in this new scenario, the need for change in the legal system. Nevertheless, this subject must not be treated in a thoughtless way: being an exhaustible good, we shall not forget that the future generations also must benefit from the exploration of natural resources recently discovered. The settlement of a new regulatory mark, including the change in the concession contract model to production and sharing is one of the suggested solutions as a bill in the National Congress, in an attempt to ensure the sovereignty of the nation. The constitutionality of a new regulatory mark is questioned, starting from an analysis of the state monopoly, grounding the comprehnsions in the brazilian constitutions, the relevance of the creation of Petrobras for self-assertion of the state about the monopoly of Oil and derivatives, and its posture after the Constitutional Amendment nº 9 (1995), when a company stops having control of the state monopoly, beginning to compete in a fairly way with other companies. The market opening and private initiative are emphasized from the viewpoint of the Constitutional Principles of the Economical and Social Order. The relaxation of the monopoly regarding the exploratory activity in the Federal Constitution doesn't deprive from the Union the ownerships of underground goods, enabling to this federal entity to contract, directly or by concession of exploration of goods, to state-owned or private companies. The existing oil in the pre-salt layer transforms the scenario from very high risk to low risk, which gives the Union the possibility of defining another way of exploring this resources in the best interests of the Public Administration