From Rational Design of Drug Crystals to Understanding of Nucleic Acid Structures: Lamivudine Duplex

A DNA-like duplex of nucleosides is probable to exist even without the 5`-phosphate groups needed to assemble the chain backbone. However, double-stranded helical structures of nucleosides are unknown. Here, we report a duplex of nucleoside analogs that is spontaneously assembled due to stacking of the neutral and protonated molecules of lamivudine, a nucleoside reverse transcriptase inhibitor (NTRI) widely used in anti-HIV drug combinatory medication. The left-handed lamivudine duplex has features similar to those of i-motif DNA, as the face-to-face base stacking and the helix rise per base pair. Furthermore, the protonation pattern on alternate bases expected for it DNA-like duplex stabilized by pairing of neutral and protonated cytosine fragments was observed for the first time in the lamivudine double-stranded helix. This structure demonstrates that hydrogen bonds can substitute for covalent phosphodiester linkage in the stabilization of the duplex backbone. This interesting example of spontaneous molecular self-organization indicates that the 5`-phosphate group could not be a requirement for duplex assembly.

Glass-to-Vitroceramic Transition in the Yttrium Aluminoborate System: Structural Studies by Solid-State NMR

The crystallization of laser glasses in the system (B(2)O(3))(0.6){(Al(2)O(3))(0.4-y)(Y(2)O(3))(y)} (0.1 <= y <= 0.25) doped with different levels of ytterbium oxide has been investigated by X-ray powder diffraction, differential thermal analysis, and various solid-state NMR techniques. The homogeneous glasses undergo major phase segregation processes resulting in crystalline YBO(3), crystalline YAI(3)(BO(3))(4), and residual glassy B(2)O(3) as the major products. This process can be analyzed in a quantitative fashion by solid-state (11)B, (27)Al, and (89)Y NMR spectroscopies as well as (11)B{(27)Al} rotational echo double resonance (REDOR) experiments. The Yb dopants end up in both of the crystalline components, producing increased line widths of the corresponding (11)B, (27)Al, and (89)Y NMR resonances that depend linearly on the Yb/Y substitution ratio. A preliminary analysis of the composition dependence suggests that the Yb(3+) dopant is not perfectly equipartitioned between both crystalline phases, suggesting a moderate preference of Yb to substitute in the crystalline YBO(3) component.

Spectral flow and iteration of closed semi-Riemannian geodesics

We introduce the notion of spectral flow along a periodic semi-Riemannian geodesic, as a suitable substitute of the Morse index in the Riemannian case. We study the growth of the spectral flow along a closed geodesic under iteration, determining its asymptotic behavior.

New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium. MEM, at 37 degrees C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and ""in vitro"" cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM It remains passivated until the transpassivation potential, above which generalized corrosion occurs F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558. ISO 5832-9 and F138 do not present cytotoxic character Therefore, these results suggest that P558 SS can be applied in orthopedic implants (C) 2010 Elsevier BV All rights reserved

Fenchyl substituted 1,2-dioxetanes as an alternative to adamantyl derivatives for bioanalytical applications

The synthesis and study of the chemiluminescence parameters and thermal stability of 1,2-dioxetanes containing a spirofenchyl substituent are reported. Three fenchyl-substituted 1,2-dioxetanes were synthesized by photooxygenation of the corresponding alkenes, obtained by Barton-Kellogg olefination of the readily available (-)-fenchone. The fenchyl-substituted 1,2-dioxetanes showed thermal stabilities similar to those of the corresponding spiroadamantyl-substituted derivatives, although being slightly more labile with respect to unimolecular decomposition than the latter derivatives, which are widely utilized as labels in a great variety of chemiluminescent immunoassays. Fluoride induced decomposition of one triggerable fenchyl 1,2-dioxetane derivative showed kinetic parameters similar to those of the corresponding adamantyl-substituted derivative. The chemiluminescence quantum yields in the one percent range are also similar to that of other widely utilized chemiluminescence systems as the luminol reaction. These results indicate that fenchyl-substituted 1,2-dioxetanes can potentially be utilized as a cheaper alternative to substitute the corresponding spiroadamantyl derivatives in bioanalytical applications. (C) 2010 Elsevier B.V. All rights reserved.

Biobased composites from tannin-phenolic polymers reinforced with coir fibers

Tannin-phenolic polymers prepared using tannin, a macromolecule obtained from natural sources, were used in the preparation of composites reinforced with coir fibers. The composites based on tannin-phenolic polymers (50% (w/w) of tannin as substitute of the phenol) were prepared using the coir fibers as reinforcement (30-70% (w/w), 3.0-6.0 cm, randomly distributed). The Izod impact strength of the composites showed an improvement in this property due to the incorporation of coir fibers in the tannin-phenolic matrices. The SEM images showed excellent adhesion at the fiber/matrix interface. The coir fiber had bundles regularly spaced, which enhanced the diffusion of the resin into the fiber. In addition, the high lignin content of this fiber results in a high concentration of aromatic rings, which increased the compatibility with the matrix. The values of the diffusion coefficient of water, determined using Fick`s laws, show that there was no correlation between the fiber percentage and the water diffusion. The DMTA curves showed that the storage moduli of the composites reinforced with coir fibers were considerably higher than that of the thermoset, and the increase in the proportion of fibers led to a proportional increase in the storage moduli of these materials. The biobased composites obtained have potential for non-structural applications, such as in the internal parts of automotives vehicles. To our knowledge, this is the first study on this kind of biobased composites. (C) 2010 Elsevier B.V. All rights reserved.

What factors affect the destination choice of Jordanian tourists?A panel data analysis

This paper investigates what factors affect the destination choice for Jordanian to 8 countries (Oman, Saudi Arabia, Syria, Tunisia, Yemen, Egypt, Lebanon and Bahrain) using panel data analysis. Number of outbound tourists is represented as dependent variable, which is regressed over five explanatory variables using fixed effect model. The finding of this paper is that tourists from Jordan have weak demand for outbound tourism; Jordanian decision of traveling abroad is determined by the cost of traveling to different places and choosing the cheapest alternative.

Ah, Libraries: How I Love the Smell of... Electronic Access?!

In the olden days, we Baby-Boomers would walk into our university or college libraries and pause just long enough to take in that wonderful smells of high grade cowhide leather and aging papyrus before rushing off to study. There was something about opening any leather bound edition of anything and being transported by the smell to some distant land, not unlike Charles Swann in Marcel Proust’s famous French novel, A La Recherché du Temps Perdu, Remembrance of Things Past.

Vertigo, and a Void

Why the Internet is no substitute for a library.

Filmes finos dielétricos para dispositivos microeletrônicos avançados

Apresentamos mecanismos de formação e de degradação térmica de filmes fi- nos (espessura da ordem de 10 nm) de diferentes dielétricos sobre substrato de silício monocristalino. Tendo em vista a aplicação dessas estruturas em MOSFETs (transistores de efeito de campo metal-óxido-semicondutor), estudamos o consagrado óxido de silício (SiO2), os atuais substitutos oxinitretos de silício (SiOxNy) e o possível substituto futuro óxido de alumínio (Al2O3). Nossos resultados experimentais baseiam-se em técnicas preparativas de substituição isotópica e de caracterização física com feixes de íons (análise com reações nucleares) ou raios- X (espectroscopia de fotoelétrons). Observamos que: (a) átomos de silício não apresentam difusão de longo alcance (além de ~ 2 nm) durante o crescimento de SiO2 por oxidação térmica do silício em O2; (b) nitretação hipertérmica é capaz de produzir filmes finos de oxinitreto de silício com até dez vezes mais nitrogênio que o resultante do processamento térmico usual, sendo que esse nitrogênio tende a se acumular na interface SiOxNy/Si; e (c) átomos de oxigênio, alumínio e silício migram e promovem reações químicas durante o recozimento térmico de estruturas Al2O3/SiO2/Si em presença de O2. Desenvolvemos um modelo de difusão-reação que poderá vir a permitir o estabelecimento de condições ótimas de processamento térmico para filmes finos de Al2O3 sobre silício a serem empregados na fabricação de MOSFETs.

Aprendizagem, racionalidade limitada e comportamento econômico

O objetivo desta pesquisa é discutir a idéia de aprendizagem em Economia. A idéia básica a ser considerada é que a hipótese das expectativas Racionais não é consistente com tal idéia e que a fim de incluí-la em nossa disciplina será necessário substituí-la por uma espécie do raciocínio indutivo. Será considerado também como tal raciocínio e pode ser aplicado com alguns modelos técnico e de política econômico.

On common agency with informed principals

This thesis consists of three chapters that have as unifying subject the frame-work of common agency with informed principals. The first two chapters analyze the economic effects of privately informed lobbying applied to tariff protection (Chapter 1) and to customs unions agreements (Chapter 2). The third chapter investigates the choice of retailing strutures when principals (the producers) are privately informed about their production costs. Chapter 1 analyzes how lobbying affects economic policy when the interest groups have private information. I assume that the competitiveness of producers are lobbies private information in a Grossman and Helpman (1994) lobby game. This allows us to analyze the e¤ects of information transmission within their model. I show that the information transmission generates two informational asymmetry problems in the political game. One refers to the cost of signaling the lobby's competitiveness to the policy maker and the other to the cost of screening the rival lobby's competitiveness from the policy maker. As an important consequence information transmission may improve welfare through the reduction of harmful lobbying activity. Chapter 2 uses the framework of chapter 1 to study a customs union agreement when governments are subject to the pressure of special interest groups that have better information about the competitiveness of the industries they represent. I focus on the agreement's effect on the structure of political influence. When join a customs union, the structure of political pressure changes and with privately informed lobbies, a new effect emerges: the governments can use the information they learn from the lobby of one country to extract rents from the lobbies of the other country. I call this the "information transmission effect". This effect enhances the governments'bargaining power in a customs union and makes lobbies demand less protection. Thus, I find that information transmission increases the welfare of the agreement and decreases tari¤s towards non-members. I also investigate the incentives for the creation of a customs union and find that information transmission makes such agreement more likely to be politically sustainable. Chapter 3 investigates the choice of retailing structure when the manufacturers are privately informed about their production costs. Two retailing structures are analyzed, one where each manufacturer chooses her own retailer (exclusive dealing) and another where the manufacturers choose the same retailer (common agency). It is shown that common agency mitigates downstream competition but gives the retailer bargaining power to extract informational rents from the manufacturers, while in exclusive dealing there is no downstream coordination but also there are no incentives problem in the contract between manufacture and retailer. A pre- liminary characterization of the choice of the retailing structure for the case of substitute goods shows that when the uncertainty about the cost increases relatively to the size of the market, exclusive dealing tends to be the chosen retailing structure. On the other hand, when the market is big relatively to the costs, common agency emerges as the retailing structure. This thesis has greatly benefited from the contribution of Professors Humberto Moreira and Thierry Verdier. It also benefited from the stimulating environment of the Toulouse School of Economics, where part of this work was developed during the year of 2007.

A substituição de trabalhadores como instrumento para redução de gastos com salários: evidências para a indústria paulista

Labor churning is an important component of labor turnover in Brazil, which includes job reallocation between firms. The labor churning evolution in the nineties, at least for the industry sector in Sao Paulo, folows a very similar path for di erent groups of firms (divided by size or by subsectors), suggesting that changes in the macroeconomic environment a ect labor churning in a very similar way for different firms. This paper proposes a model to explain the path of formal labor churning in Brazil. The model admits that employers, when facing exogenous shocks that rise real wage, may substitute employees to reduce wage costs, particularly in low inflation periods, when real wages are more rigid. An econometric analysis is conducted using disaggregated data by firms for the industry sector in the Metropolitan Region of Sao Paulo. The results confirm the models main hipotesis. The results also suggest that, after the monetary estabilization, controlling for inflation and with valid instruments, labor churning is relatively higher

Correlação entre achados colposcópicos e diagnóstico histológico segundo a Classificação Colposcópica da Federação Internacional de Patologia Cervical e Colposcopia de 2002

Objetivo: Avaliar a acurácia da colposcopia utilizando a Classificação Colposcópica Internacional de 2002. Métodos: 3040 pacientes de população geral foram rastreadas para patologia cervical através de exame citopatológico, captura híbrida para HPV de alto risco e inspeção cervical. As colposcopias que resultaram em biópsia (n=468) executadas no rastreamento e acompanhamento destas pacientes foram gravadas, revistas por dois colposcopistas cegados e incluídas para análise. Resultados: Os observadores apresentaram excelente concordância (Kappa=0.843) no relato dos achados pela nova nomenclatura. A colposcopia apresentou sensibilidade de 86% e especificidade de 30.3% em diferenciar colo normal de colo anormal (LSIL, HSIL ou carcinoma); quando a colposcopia objetivava diferenciar colo normal ou LSIL de HSIL ou carcinoma, apresentou sensibilidade de 61.1% e especificidade de 94.4%. Os achados colposcópicos classificados como “maiores” pela nova classificação apresentaram valores preditivos positivos elevados para HSIL. Presença do achado colposcópico na zona de transformação e tamanho da lesão estavam associados a HSIL. Bordas externas definidas, associação de múltiplos achados distintos e presença de zona iodo negativa não estavam relacionados à gravidade das lesões. Conclusão: A colposcopia utilizando a Classificação Internacional de 2002 mostra-se um bom método de rastreamento, mas como método diagnóstico apresenta falhas, não podendo substituir a avaliação histológica. A categorização em achados colposcópicos “maiores” e “menores” apresentada pela nova classificação é adequada. Na realização da colposcopia, é importante também que a lesão seja situada em relação à zona de transformação e que seu tamanho seja indicado, já que estes foram fatores associados a lesões de alto grau.

The role of bond covenants and short-term debt: evidence from Brazil

Esta dissertação tem como objetivo analisar a relação entre covenants e alavancagem financeira no curto e longo prazo com oportunidades de crescimento. A partir de uma amostra de 159 debêntures, encontramos evidência de que: 1) Covenants e dívida de curto-prazo podem ser considerados substitutos na atenuação do conflito de agência, uma vez que apresentaram relação negativa e significante e; 2) A relação negativa existente entre dívida de curto prazo e oportunidades de crescimento pode ser reduzida através da utilização de covenants.