Dissertação de Mestrado em Finanças Empresariais; Este trabalho tem como objetivo verificar os determinantes da estrutura de capital das empresas exportadoras portuguesas, comparando, sempre que possível, os resultados obtidos com outros trabalhos já desenvolvidos sobre o tema. Aplicando o Modelo dos Efeitos Fixos (MEF) a uma amostra de 7.001 empresas no período 2007-2013, concluiu-se que os determinantes com maior significância no nível de endividamento empresarial são: a rendibilidade, a dimensão, o crescimento e ainda os outros benefícos fiscais. Em relação às exportações, verificou-se através da variável dummy “exportar”, que o facto de as empresas terem exportações superiores a 10% das vendas totais, têm uma relação positiva com o endividamento de médio e longo prazo mas negativa com o endividamento de curto prazo. Perante estes resultados admitimos que as empresas exportadoras ao diversificarem (na fase inicial) o seu portfólio de clientes conseguem maiores níveis de cash-flows, o que as dispensa de algum endividamento de curto prazo, mas no médio e longo prazo as necessidades de investimento para fazer face a mercados muito competitivos está associada a um maior nível de endividamento. Relativamente à importância explicativa das variáveis “peso das vendas para o mercado comunitário” e “peso das vendas para o mercado extra comunitário”...

Las enfermedades del aparato circulatorio son la principal causa de muertes en el mundo occidental. La pseudo-coartación arterial es una anormalidad que se consideraba benigna, pero se sabe ahora que puede conducir a aneurismas y otras complicaciones. Para estudiar esta condición se formuló un problema de pandeo longitudinal en un tubo cilíndrico de material hiper-elástico fibrorreforzado. En primer lugar se propuso un esquema de solución mediante el método del elemento finito (MEF). Alternativamente, se realizó la implementación de soluciones de carácter semi-analítico de versiones simplificadas del mismo problema. La complejidad de la implementación del MEF impidió la obtención de resultados que se pudieran comparar con los de las aproximaciones semi-analíticas; sin embargo el diagrama de flujo correspondiente, los detalles necesarios y una versión de la implementación en lenguaje MATLAB, que no estaban disponibles en la literatura, quedaron en un estado listo para intentar la producción de resultados o bien para tener un entendimiento suficientemente claro de lo que implica usar ecuaciones constitutivas especiales en software comercial de elementos finitos. Por su parte, las soluciones semi-analíticas mostraron que la tendencia al pandeo incrementa con la presión luminar y la tensión circunferencial...

Orientadora : Profª Drª Cynara de L.N. Cunha; Tese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Métodos Numéricos em Engenharia. Defesa: Curitiba, 27/03/2015; Inclui referências : f. 64-66; Resumo: Modelos matemáticos são utilizados para representar sistemas físicos, de maneira que se possam quantificar as informações obtidas com esse modelo, entendendo melhor o que acontece nesse sistema. A equação de difusão-advecção pode ser utilizada para descrever o transporte de poluentes, auxiliando na solução de problemas ambientais, como por exemplo, o estudo da distribuição espacial de contaminantes em reservatórios ou rios. O modelo matemático de transporte difusivo-advectivo bi-dimensional, que descreve o transporte de certa substância em um meio fluido, será resolvido aqui utilizando o Método dos Elementos de Contorno (MEC). Os princípios fundamentais para a formulação básica do MEC serão apresentados para o problema proposto. Também serão incluídos alguns exemplos numéricos para verificação e validação do método. Duas formulações são desenvolvidas, em uma delas é possível considerar uma forma generalizada para campos de velocidades variável no espaço. Com a presença de integrais de domínio...

Feeding state and food availability can dramatically alter an animals' sensory response to chemicals in its environment. Dynamic changes in the expression of chemoreceptor genes may underlie some of these food and state-dependent changes in chemosensory behavior, but the mechanisms underlying these expression changes are unknown. Here, we identified a KIN-29 (SIK)-dependent chemoreceptor, srh-234, in C. elegans whose expression in the ADL sensory neuron type is regulated by integration of sensory and internal feeding state signals. We show that in addition to KIN-29, signaling is mediated by the DAF-2 insulin-like receptor, OCR-2 TRPV channel, and NPR-1 neuropeptide receptor. Cell-specific rescue experiments suggest that DAF-2 and OCR-2 act in ADL, while NPR-1 acts in the RMG interneurons. NPR-1-mediated regulation of srh-234 is dependent on gap-junctions, implying that circuit inputs regulate the expression of chemoreceptor genes in sensory neurons. Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression. While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons...

Cis-elements (-933 to -641) upstream of the human M creatine kinase gene cap site contain an enhancer that confers developmental and tissue-specific expression to the chloramphenicol acetyltransferase gene in C2C12 myogenic cells transfected in culture. Division of the enhancer at -770 into a 5' fragment that includes the MyoD binding sites (-933 to -770) and a 3' fragment that includes the MEF-2 binding site (-770 to -641) resulted in two subfragments that showed minimal activity but in combination interacted in a position- and orientation-independent fashion to enhance activity of the SV40 promoter in transient transfection experiments. A 5' enhancer construct (-877 to -832) including only one (the low affinity) MyoD binding site was active when present in multiple copies. In contrast, a 3' enhancer construct (-749 to -732) including the MEF-2 binding site was inactive even when present in multiple copies. However, if the 5' construct was extended to include the high-affinity MyoD binding site (-877 to -803) the 5' and 3' constructs interacted in a position- and orientation-independent fashion to activate the SV40 promoter. Thus, the human M creatine kinase enhancer comprises multiple functional interacting domains.

To counteract the deleterious effects of DNA damage, cells are equipped with specialized polymerases to bypass DNA lesions. Previous biochemical studies revealed that DinB family DNA polymerases, including Escherichia coli DNA polymerase IV and human DNA polymerase κ, efficiently incorporate the correct nucleotide opposite some N2-modified 2′-deoxyguanosine derivatives. Herein, we used shuttle vector technology and demonstrated that deficiency in Polk or Poli in mouse embryonic fibroblast (MEF) cells resulted in elevated frequencies of G→T and G→A mutations at N2-(1-carboxyethyl)-2′-deoxyguanosine (N2-CEdG) and N2-carboxymethyl-2′-deoxyguanosine (N2-CMdG) sites. Steady-state kinetic measurements revealed that human DNA polymerase ι preferentially inserts the correct nucleotide, dCMP, opposite N2-CEdG lesions. In contrast, no mutation was found after the N2-CEdG- and N2-CMdG-bearing plasmids were replicated in POLH-deficient human cells or Rev3-deficient MEF cells. Together, our results revealed that, in mammalian cells, both polymerases κ and ι are necessary for the error-free bypass of N2-CEdG and N2-CMdG. However, in the absence of polymerase κ or ι, other translesion synthesis polymerase(s) could incorporate nucleotide(s) opposite these lesions but would do so inaccurately.

Despite progress in developing defined conditions for human embryonic stem cell (hESC) cultures, little is known about the cell-surface receptors that are activated under conditions supportive of hESC self-renewal. A simultaneous interrogation of 42 receptor tyrosine kinases (RTKs) in hESCs following stimulation with mouse embryonic fibroblast (MEF) conditioned medium (CM) revealed rapid and prominent tyrosine phosphorylation of insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R); less prominent tyrosine phosphorylation of epidermal growth factor receptor (EGFR) family members, including ERBB2 and ERBB3; and trace phosphorylation of fibroblast growth factor receptors. Intense IGF1R and IR phosphorylation occurred in the absence of MEF conditioning (NCM) and was attributable to high concentrations of insulin in the proprietary KnockOut Serum Replacer (KSR). Inhibition of IGF1R using a blocking antibody or lentivirus-delivered shRNA reduced hESC self-renewal and promoted differentiation, while disruption of ERBB2 signaling with the selective inhibitor AG825 severely inhibited hESC proliferation and promoted apoptosis. A simple defined medium containing an IGF1 analog, heregulin-1β (a ligand for ERBB2/ERBB3), fibroblast growth factor-2 (FGF2)...

Macrolide resistance in Streptococcus pneumoniae emerged in the U.S. and globally during the early 1990's. The RNA methylase encoded by erm(B) and the macrolide efflux genes mef(E) and mel were identified as the resistance determining factors. These genes are disseminated in the pneumococcus on mobile, often chimeric elements consisting of multiple smaller elements. To better understand the variety of elements encoding macrolide resistance and how they have evolved in the pre- and post-conjugate vaccine eras, the genomes of 121 invasive and ten carriage isolates from Atlanta from 1994 to 2011 were analyzed for mobile elements involved in the dissemination of macrolide resistance. The isolates were selected to provide broad coverage of the genetic variability of antibiotic resistant pneumococci and included 100 invasive isolates resistant to macrolides. Tn916-like elements carrying mef(E) and mel on the Macrolide Genetic Assembly (Mega) and erm(B) on the erm(B) element and Tn917 were integrated into the pneumococcal chromosome backbone and into larger Tn5253-like composite elements. The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements. The data indicate that integration of elements by conjugation was infrequent compared to recombination. Thus...

Yme1L is an AAA protease that is embedded in the mitochondrial inner membrane with its catalytic domain facing the mitochondrial inner-membrane space. However, how Yme1L regulates mammalian mitochondrial function is still obscure. We find that endogenous Yme1L locates at punctate structures of mitochondria, and that loss of Yme1L in mouse embryonic fibroblast (MEF) cells results in mitochondrial fragmentation and leads to significant increased ‘kiss-and-run' type of mitochondrial fusion; however, Yme1L knockdown (shYme1L (short hairpin-mediated RNA interference of Yme1L)) cells still remain normal mitochondrial fusion although shYme1L mitochondria have a little bit less fusion and fission rates, and the shYme1L-induced fragmentation is due to a little bit more mitochondrial fission than fusion in cells. Furthermore, shYme1L-induced mitochondrial fragmentation is independent on optic atrophy 1 (OPA1) S1 or S2 processing, and shYme1L results in the stabilization of OPA1 long form (L-OPA1); in addition, the exogenous expression of OPA1 or L-OPA1 facilitates the shYme1L-induced mitochondrial fragmentation, thus this fragmentation induced by shYme1L appears to be associated with L-OPA1's stability. ShYme1L also causes a slight increase of mitochondrial dynamics proteins of 49 kDa and mitochondrial fission factor (Mff)...

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2010.; Esta tese, através de estudos numéricos e experimentais, apresenta o desenvolvimento de um conector de cisalhamento proposto para uso em vigas mistas de aço-concreto. O conector proposto é de fácil confecção e pode servir como alternativa ao uso do conector stud. Foi idealizada uma geometria para o conector que propiciasse confinamento do concreto da laje, maior área de contato com o concreto além de maior rigidez. Um conector em forma de ‘V’, feito de cantoneira metálica, foi concebido e de início exaustivamente estudado pelo método dos elementos finitos (MEF) via programa Ansys. O estudo numérico investigou até o colapso a distribuição de tensão, a formação de fissuras e o deslizamento do perfil em relação à laje. Os resultados destas análises foram comparados com iguais análises tanto do conector stud como também do conector em forma de ‘U’. A comparação dos resultados numéricos mostrou as vantagens do conector ‘V’ sugerido. A partir destes resultados numéricos estabeleceu-se um programa experimental que envolveu 16 ensaios de push-out a fim de confirmar as boas expectativas obtidas nas análises numéricas pelo MEF. Nos experimentos foram investigados aspectos de ductilidade...

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2015.; Este trabalho propõe uma abordagem que acopla o método dos elementos finitos generalizados global-local (MEFGgl) e o MEFG-CK para a modelagem de problemas bidimensionais que contemplem concentração de tensões. O primeiro método combina o MEF global-local clássico com a estrutura da partição da unidade, construindo funções de enriquecimento numericamente. Estas funções são geradas a partir da solução de problemas de valor de contorno locais na vizinhança de características locais, sendo usadas para enriquecer o problema global. O segundo método é bastante similar ao MEFG clássico (MEFG-C0), exceto pela partição da unidade (PU) que é arbitrariamente suave, gerando campos de tensões arbitrariamente diferenciáveis, o que não é possível com o MEFG-C0 devido à descontinuidade das derivadas normais ao longo das arestas dos elementos. O método proposto é chamado MEFGgl-Ck e sua formulação utiliza funções PU Ck no problema local, construídas através da PU de Shepard, e funções PU C0 nos problemas globais inicial e enriquecido. Assim, o método proposto não depende de soluções analíticas e somente a solução local é usada no problema global como enriquecimento. Neste contexto...

The photoluminescence (PL) quantum yield of single-walled carbon nanotubes (SWNTs) is relatively low, with various quenching effects by metallic species reported in the literature. Here, we report the first case of metal enhanced fluorescence (MEF) of surfactant-coated carbon nanotubes on nanostructured gold substrates. The photoluminescence quantum yield of SWNTs is observed to be enhanced more than 10-fold. The dependence of fluorescence enhancement on metal-nanotube distance and on surface plasmon resonance (SPR) of the gold substrate for various SWNT chiralities is measured to reveal the mechanism of enhancement. Surfactant-coated SWNTs in direct contact with metal exhibit strong MEF without quenching, suggesting a small quenching distance for SWNTs on the order of the van der Waals distance, beyond which the intrinsically fast non-radiative decay rate in nanotubes is little enhanced by metal. The metal enhanced fluorescence of SWNTs is attributed to radiative lifetime shortening through resonance coupling of SWNT emission to the re-radiating dipolar plasmonic modes in the metal.; Comment: JACS, in press

The dynamical spin susceptibility as relevant for underdoped cuprates is analysed within the memory-function (MeF) approach. A phenomenological damping function combined with a $T$-independent sum rule is used to describe the anomalous normal state and the resonant peak in the superconducting state, in particular its position and its relative intensity to the normal state. The relation with the random-phase approximation is discussed. The MeF method is generalized to the bilayer system in order to compare with inelastic neutron scattering experiments on YBa$_2$Cu$_3$O$_{6+x}$ which alows also for a quantitative comparison. In this context the problem of missing integrated spectral intensity within the experimentally accessible energy window is also discussed.; Comment: 6 pages (RevTex), 4 Postscript figures(*.eps), 2 Tables included in the text. Original paper (v1) expanded into an article with (sub)sections; first part of content unchanged. Added Fig.4, Table II, section on comparison with experiments and two references. Corrected typo in Table I (2nd row, last entry)

The fluorescence of organic fluorophore molecules is enhanced when they are placed in contact with certain metals (Al, Ag, Cu, Au, etc.) whose surface plasmon waves couple into the radiative modes of the molecules and increase the radiative efficiency. Here, we report a hitherto unknown size dependence of this metal enhanced fluorescence (MEF) effect in the nanoscale. When the molecules are deposited in nanoporous anodic alumina films with exposed aluminum at the bottom of the pores, they form organic nanowires standing on aluminum nanoparticles whose plasmon waves have much larger amplitudes. This increases the MEF strongly, resulting in several orders of magnitude increase in the fluorescence intensity of the organic fluorophores. The increase in intensity shows an inverse super-linear dependence on nanowire diameter because the nanowires also act as plasmonic 'waveguides' that concentrate the plasmons and increase the coupling of the plasmons with the radiative modes of the molecules. Furthermore, if the nanoporous template housing the nanowires has built-in electric fields due to space charges, a strong molecule-specific red- or blue-shift is induced in the fluorescence peak owing to a renormalization of the dipole moment of the molecule. This can be exploited to detect minute amounts of target molecules in a mixture using their optical signature (fluorescence) despite the presence of confounding background signals. It can result in a unique new technology for bio- and chemical-sensing.

We study the production characteristics of 557 pairs of charmed hadrons produced in $\pi^{-}-Cu$\ interactions at 230~GeV/c using a momentum estimator for charmed hadrons with missing decay products. We find, the mean value of the transverse momentum squared of the charmed pairs is $<$\pts$>=(1.98\pm 0.11\pm 0.09)\;$ GeV$^2$/c$^2$, the mean rapidity difference is $<|$\yd$|>=0.54\pm 0.02\pm 0.24$, and the mean effective mass is $<$\mef$>=(4.45\pm 0.03\pm 0.13)\;$ GeV/c$^2$. Comparing these results with the next-to-leading order QCD predictions we find an agreement for the \yd\ and \mef, whilst the measured mean value of \pts\ is significantly larger than the predicted value.; Comment: 10 pages, LaTeX, 4 (pages) postscript figures

17 páginas, 9 figuras.; Retinoic Acid (RA) treatment of SH-SY5Y neuroblastoma cells results in activation of phosphatidyl-inositol-3-kinase (PI3K) signaling pathway, and this activation is required for RA-induced differentiation. Here we show that RA activates PI3K and ERK1/2 MAP Kinase signaling pathways through a rapid, non-genomic mechanism that does not require new gene transcription or newly synthesized proteins. Activation of PI3K by RA appears to involve the classical nuclear receptor RAR, on the basis of the pharmacological profile of the activation, loss and gain of function experiments with MEF-RAR(αβγ)L-/L- null cells, and the physical association between liganded RAR and PI3K kinase activity. The association of RAR with the two subunits of PI3K was differentially regulated by the ligand. Immunoprecipitation experiments performed in SH-SY5Y cells showed stable association between RARα and p85, the regulatory subunit of PI3K, independently of the presence of RA. In contrast, ligand administration increased the association of p110, the catalytic subunit of PI3K, to this complex. The intracellular localization of RAR resulted to be relevant for PI3K activation. A chimerical RAR receptor fusing c-Src myristylation domain to the N-terminal of RARα (Myr-RARα) was targeted to plasma membrane. Transfection of Myr-RARα to MEF-RAR(αβγ)L-/Lnull cells and COS-7 cells results in strong activation of PI3K signaling pathway...

Consultable des del TDX; Títol obtingut de la portada digitalitzada; Streptococcus pyogenes és un patogen humà responsable d'un ampli ventall d'infeccions que varien des d'infeccions superficials com faringitis i impetigen a formes sistèmiques greus com fascitis necrosant (FN) i síndrome del xoc tòxic estreptocòccic (SSTS). El ressorgiment i persistència de formes invasives greus descrit des de mitjans dels anys 1980 ha motivat una intensa recerca sobre els aspectes epidemiològics, microbiològics i clínics d'aquestes infeccions. S'ha realitzat un estudi retrospectiu de base hospitalària que inclou 126 soques de S. pyogenes (27 procedents d'infeccions invasives i 99 d'infeccions no invasives) aïllades entre gener de 1999 i juny de 2003. Les soques de S. pyogenes es van caracteritzar en base a la distribució de tipus i subtipus emm i els perfils genètics de superantígens (SAgs) (speA-C, speF-J, speL, speM, ssa i smeZ). Tanmateix, es va determinar la prevalença i els mecanismes de resistència a macròlids, tetraciclina i levofloxacino. Les formes clíniques més freqüents d'infecció invasiva van ser les infeccions de la pell i teixits tous (40,7%). La SSTS es va registrar en quatre (14,8%) dels casos invasius i es va associar a FN en la meitat dels casos. La majoria dels pacients afectats de quadres invasius eren adults...

Descripció del recurs: 16 oct. 2013; En aquesta tesi s'ha desenvolupat una recerca teòrica i empírica de l'efecte rebot directe i indirecte causat per les millores d'eficiència energètica, centrada –pel que fa la vessant empírica de la recerca– en les millores d'eficiència en el conjunt de serveis energètics que utilitzen electricitat a les llars a Catalunya. L'efecte rebot directe d'un servei energètic es produeix quan una millora en la seva eficiència energètica no es tradueix en tot l'estalvi energètic que potencialment s'hauria de produir en aquell àmbit. Això és degut a què la millora produeix un abaratiment del cost del servei energètic, que s'acaba traduint en una major demanda d'aquest, compensant total o parcialment l'estalvi derivat de la major eficiència. L'efecte rebot indirecte es produeix quan la millora d'eficiència modifica els patrons de consum, produint l'increment en el consum d'altres béns i serveis que també necessiten energia per a ser produïts. Malgrat hi ha consens entre la comunitat científica sobre el fet que l'efecte rebot existeix, hi ha discrepàncies a l'hora de determinar la seva magnitud. Mentre alguns sostenen que una millora de l'eficiència produeix cert estalvi d'energia...

Este trabalho aborda o estudo de modelos constitutivos a fim de analisar o comportamento mecânico de um biopolímero derivado de óleo de mamona (Ricinus communis). A importância deste trabalho se dá ao fato de: servir como roteiro de ensaio de materiais poliméricos; completar caracterização do material estudado além do regime viscoelástico, bem como aplicação da análise do comportamento do material além do regime viscoelástico linear. A aplicação dos modelos avaliados via Método dos Elementos Finitos (MEF) exigiu o levantamento das propriedades e do comportamento mecânico do biopolímero, bem como a preparação dos ensaios, com as devidas especificações sugeridas pela ASTM (American Society for Testing and Materials) para cada tipo de ensaio. Assim, foram obtidos os corposde- prova (CDP) para a realização dos ensaios mecânicos quase-estáticos de tração, compressão e flexão (monotônicos e cíclicos), bem como, ensaio para análise dinâmicomecânica (Dynamic Mechanical Analysis - DMA) para a obtenção de propriedades associada às parcelas viscosas do material. Com estes foram obtidos parâmetros inerentes a cada tipo de ensaio, permeados com uma cuidadosa revisão bibliográfica sobre as implicações para a realização de cada ensaio. Uma outra etapa foi a verificação de modelos de plastificação baseados na teoria de von Mises...

Se confeccionó un modelo numérico que resuelve las ecuaciones 2D del flujo y del transporte de contaminante en un medio poroso teniendo en cuenta la dispersión hidrodinámica. Se trabaja en el plano vertical y con densidad del fluido constante o variable. Se aplica el Método de los Elementos Finitos (MEF) para la discretización en el espacio y el Método de las Diferencias Finitas (MDF) para la discretización en el tiempo. En el modelo se utiliza el triángulo lineal. El modelo se formula en términos de la carga hidráulica y de la concentración de la sustancia contaminante como funciones incógnitas. Toda la implementación computacional se realiza con el asistente matemático MATLAB. Se verificó y se comprobó el algoritmo numérico comparándose con soluciones de otros modelos reportados en trabajos de la literatura. ABSTRACT A numerical model was made that solves the 2D flow and transport of polluting agent equations in porous media considering hydrodynamic dispersion. The model works in the vertical plane and with constant or variable fluid density. The method of Finite Elements (MEF) for the spatial discretization and the method of Finite Differences (MDF) for the time discretization are applied. In the model the linear triangle is used. The model is formulated in terms of the hydraulic head and the concentration of the polluting substance like unknow functions. All the computacional implementation is made with mathematical assistant MATLAB. It was verified and the numerical algorithm was verified comparing itself with solutions of other models reported in another works of Literature.