161,419 research outputs found
The agential fork : the hidden consequences of agency for plenitude in David Lewis' thesis of genuine modal realism
No full textIn this dissertation, I argue that David Lewis' abductive argument for Genuine Modal Realism (GMR) has the unwelcome, and hidden, implication of being unable to
accommodate agent causation theories of free will. This is because of his formulation of plenitude, which basically says that every way that a world or a part of a world could be is the way that some world, or part of some world is. This formulation tacitly assumes
that chance and nomological principles are sufficient to account for everything that happens at worlds. However, agent causation theories argue that free will is neither reducible to chance nor determined by physics. My argument recasts a fork argument made by Andrew Beedle. I proceed by arguing that chance-based principles evince an ontologically distinct kind of modality than agent causation principles. However,
plenitude only accounts for the physics/chance-based kind of modality. There is no similar principle of plenitude that can be given for agential modality that does not
collapse into the chance-based principle. But even if such a principle could be found, it would violate the doctrine in GMR that claims worlds are causally isolated. If no agential plenitude principle can be found and there is agential modality, then plenitude fails. If there is no agency at our world, and Lewis’ original formulation of plenitude is correct, then GMR implies no agency at any
world. This is the fork: If there is agency and GMR holds, then either plenitude fails, or isolation fails. But if there is no agency, and GMR holds, then there is no agency at any possible world. The latter prong is too strong a claim for an abductive argument like GMR. The
former proves that GMR cannot accommodate agent-causation theories. GMR loses its neutrality either way, to its detriment
O realismo modal de David K. Lewis e suas implicações epistêmicas
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-Graduação em Filosofia.Uma das dificuldades encontradas na lógica modal diz respeito à semântica. Geralmente, não é possível calcular o valor de 9" a partir do valor de ", ou seja, se " é falsa parece claro que 9" também o é, uma vez que 9" significa que " é necessariamente verdadeira. Se pelo contrario, " é verdadeira, como saber se é contingente ou necessária? O mesmo se dá com "". Se " é verdadeira, "" é verdadeira. Mas qual será o valor de "" se " é falsa? Mesmo falsa, " poderia ser possível. Posta esta dificuldade, foi criada por Saul Kripke a semântica dos mundos possíveis. Enquanto na lógica proposicional clássica uma interpretação consiste na atribuição de valores {V,F} às letras sentenciais e, por extensão, uma atribuição de valores a todas as fórmulas, em lógica modal uma interpretação consiste em um conjunto de mundos possíveis com uma atribuição de valores às fórmulas em cada um deles. Chamamos esta interpretação de modelo de mundos possíveis ou modelo de Kripke. A posição realista de David K. Lewis quanto à semântica de Mundos Possíveis para lógicas modais acarreta muitas objeções entre as quais uma epistemológica. Podemos afirmar nosso conhecimento sobre questões modais, uma vez que tal teoria afirma que não há relações espaço-temporais e causais entre os mundos? É possível conhecer algo que não está acessível à inspeção direta? Lewis faz sua defesa utilizando-se de argumentos a favor do realismo matemático. Alguns dos opositores de Lewis fazem objeção a essa estratégia e contra-argumentam de muitas formas. O objetivo geral do trabalho, além de expor da maneira mais clara possível a discussão em torno do tema, é mostrar que, mesmo que uma defesa cabal do realismo modal seja muito complicada, pelo menos no caso das objeções epistemológicas formuladas por Tom Richards, Willian Lycan e Brian Skyrms, Lewis se sai bem na defesa de sua teoria. Por outro lado, o objetivo específico e principal desta dissertação é fazer uma defesa à objeção epistemológica de Charles Chihara, uma vez que a defesa apresentada por Lewis a seus críticos não o satisfez e a resposta à objeção de Chihara deixou de ser dada por Lewis
<i>No se sabe</i>: entrevista a Lucas Gagliardi
No full textEntrevista al Licenciado y Profesor en Letras (UNLP) Lucas Gagliardi. Se especializa en literatura en lengua inglesa y en crítica genética. Se desempeña como profesor en la Universidad Pedagógica (UNIPE), en institutos de formación docente y escuelas secundarias. Ha participado en proyectos de investigación sobre archivos de escritores, publicaciones impresas. Participa en el programa de voluntariado universitario de la Facultad de Trabajo Social (UNLP) en articulación con la Biblioteca Ambulante del Hospital de Niños dictando talleres de lectura y escritura.Al hacer clic en el enlace que figura en "Documentos relacionados", pueden accederse a todos los trabajos de Lucas Gagliardi presentes en el repositorio.Radio Universidad Nacional de La Plat
Mechanistic insights into Lewis and Brønsted acid catalyzed conversion of sugars to platform furan derivatives in aqueous media
No full textBiomass, the only renewable source of organic carbon, can play a key role in mitigating the rising concerns over greenhouse gas emissions and diminishing petroleum reserves. A promising approach in this regard entails biomass conversion to furanic compounds that have potential to substitute petroleum precursors in producing chemicals, polymers, and fuels. This thesis is focused on gaining thermodynamic, catalytic, and mechanistic insights into the production of versatile platform furan derivatives 5-(hydroxymethyl)furfural (HMF) and furfural from biomass derived simple sugars, glucose and xylose, respectively, in aqueous media. ☐ The role of solvent in the thermochemistry of sugar dehydration reactions has been investigated. The reaction free energies were calculated using ab initio (G4) calculations combined with the COSMO-SAC solvation model. It is shown that aldose (glucose, xylose)-to-ketose (fructose, xylulose) isomerization is an equilibrium-limited reaction, whereas the ketose dehydration to the respective furan derivative is practically an irreversible reaction. Further, the choice of solvent can affect product distribution in biomass conversion; as an example, a small fraction of water in organic media suppresses anhydroglucose formation from glucose and can improve HMF selectivity. ☐ In kinetic experiments, we found that the Brønsted acid catalyzed sugar dehydration strongly depends on its molecular structure. The ketose dehydration to the respective furan derivative is much faster than the aldose dehydration. High yields of furfural (~75%) and HMF (~60%) from xylose and glucose, respectively, were obtained by combining the aldose-ketose isomerization with the ketose dehydration in a cascade of reactions in aqueous media at much lower temperature (413 K) than reported earlier. This is achieved using a Lewis acid (CrCl3 or Sn-beta) as the isomerization catalyst with a Brønsted acid (HCl or Amberlyst-15) as the dehydration catalyst in a single reactor. ☐ In order to gain mechanistic insights, the role of various metal ions in the aldose-ketose isomerization using a metal salt such as CrCl3 and AlCl3, has been investigated. Speciation of the metal salts in aqueous media was modeled, and used in conjunction with kinetics experiments; we revealed for the first time that the partially hydrolyzed ions, [Cr(H2O)5OH]2+ or [Al(H2O)5OH]2+, respectively, are the most active species for the aldose-ketose isomerization. Additionally, complex interactions between the Lewis and Brønsted acid catalysts have been explained in the sugar conversion: Brønsted acid decelerates the aldose-ketose isomerization by suppressing the equilibrium concentration of the partially hydrolyzed ions, whereas the Lewis acid promotes side reactions during fructose dehydration and HMF rehydration reactions. Thus, the catalyst loading and reactions conditions in sugar conversion need to be optimized. ☐ A strong interaction between the Cr cation and the glucose molecule in the first coordination sphere of the metal ion is indicated using extended X-ray absorption fine structure spectroscopy analysis and Car-Parrinello molecular dynamics simulation. More interestingly, mechanistic similarities are revealed among the homogeneous (CrCl3, AlCl3) and heterogeneous (Sn-beta) catalysts for the aldose-ketose isomerization using isotopic-labeling experiments. An intra-hydride transfer (C2 to C1) is the dominant reaction channel for the isomerization and a Lewis acid-Brønsted base bifunctional site is the most active site for all three catalysts. A reaction mechanism has been proposed for the Lewis acid-catalyzed isomerization and the energetics of the reaction pathway was calculated using ab initio for the Sn-beta catalyzed isomerization. Mechanistic insights are qualitatively consistent with the experimental data. ☐ The reaction mechanism of the Brønsted acid catalyzed fructose dehydration to HMF was investigated using isotopic-labeling experiments with nuclear magnetic resonance spectroscopy (NMR). The hydrogen transfer from C1 is the rate limiting step in the dehydration mechanism in both water and dimethyl sulfoxide (DMSO). Additionally, resonances corresponding to alkene and carbonyl groups were observed that compare well with an intermediate identified in the fructose dehydration reaction in DMSO. These observations suggest that the fructose dehydration in water and DMSO follows a similar reaction mechanism.University of Delaware, Department of Chemical EngineeringPh.
Lewis Carroll et les mythologies de l'enfance
No full textL’enfance est au cœur de l’œuvre carrollienne – mais comment cerner cette problématique ? Le thème des « mythologies de l’enfance » a pour but de l’approcher, en évoquant non seulement l’enfance comme mythe, mais également la question de l’enfance comme fonctionnement mythique dans l’œuvre de Carroll. Rassemblées à l’issue d’un colloque international, les études de ce recueil se donnent pour objectif d’interroger le statut ambigu de l’enfance dans l’œuvre de Lewis Carroll, fasciné par cette saison de la vie dont il n’eut de cesse de célébrer l’exceptionnelle sensibilité, dans ses textes comme dans ses photographies. La mythologie de l’enfance dans cette œuvre multiforme ne peut se comprendre qu’en mettant d’abord en perspective les différentes étapes par lesquelles le mythe s’est constitué, afin de saisir comment l’œuvre carrollienne élucide et élude par le même mouvement la problématique de l’enfance, puis comment la réception de l’œuvre s’est appuyée sur le thème de l’enfance, quitte parfois à le subvertir ou à en abuser. La question de la légitimité du mythe se pose ensuite : faut-il (et peut-on) démythifier le mythe ? Comment questionner sa portée pour comprendre ce qui se joue dans l’œuvre ? C’est dans le prolongement de cette interrogation que se pose enfin la question de la représentation de l’enfance dans l’œuvre carrollienne et dans les œuvres d’autres créateurs inspirés par l’imaginaire et l’univers carrolliens
Chalcogen bonding in solution: Interactions of benzotelluradiazoles with anionic and uncharged lewis bases
No full textChalcogen bonding is the noncovalent interaction between an electron-deficient, covalently bonded chalcogen (Te, Se, S) and a Lewis base. Although substantial evidence supports the existence of chalcogen bonding in the solid state, quantitative data regarding the strengths of the interactions in the solution phase are lacking. Herein, determinations of the association constants of benzotelluradiazoles with a variety of Lewis bases (Cl–, Br–, I–, NO3– and quinuclidine, in organic solvent) are described. The participation of the benzotelluradiazoles in chalcogen bonding interactions was probed by UV–vis, 1H and 19F NMR spectroscopy as well as nano-ESI mass spectrometry. Trends in the free energy of chalcogen bonds upon variation of the donor, acceptor and solvent are evident from these data, including a linear free energy relationship between chalcogen bond donor ability and calculated electrostatic potential at the tellurium center. Calculations using the dispersion-corrected B97-D3 functional were found to give good agreement with the experimental free energies of chalcogen bonding.Peer reviewedFinal article publishe
<i>No se sabe</i>: entrevista a Laura Sombra del Río
No full textEntrevista a la profesora de Matemática Laura Sombra del Río, integrante del Instituto de Metodología Alternativa para la Enseñanza de la Ciencia (IMApEC). Se especializa en tecnología informática aplicada a la educación, especialmente de las ciencias duras como la matemática.Al hacer clic en el enlace que figura en "Documentos relacionados", pueden accederse a todos los trabajos de Laura Sombra del Río presentes en el repositorio.Facultad de Ingenierí
Lewis Base Activation of Lewis Acids: Development of a Lewis Base Catalyzed Selenolactonization
No full textThe concept of Lewis base activation of Lewis acids has been applied to the selenolactonization reaction. Through the use of substoichiometric
amounts of Lewis bases with “soft” donor atoms (S, Se, P) significant rate enhancements over the background reaction are seen. Preliminary
mechanistic investigations have revealed the resting state of the catalyst as well as the significance of a weak Brønsted acid promoter
Recueil de décrets, ordonnances, traités de paix, manifestes, proclamations, discours, &c. &c. de Napoléon Bonaparte et des membres du gouvernement français, depuis le 18 Brumaire, an 8, (novembre, 1799) jusqu' à l'année 1812, inclusivement / [6] Supplément au recueil des décrets, manifestes, discours, etc. de Napoléon Bonaparte et des membres de son gouvernement : contenant tout ce qui s'est passé en France pendant sa dernière usurpation en 1815
No full textNapoléon Bonaparte ; extraits du Moniteur, par Lewis Goldsmit
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