Search

La presente investigación tuvo por objetivo analizar las representaciones sociales de estudiantes chilenos respecto al significado que tiene para ellos la Educación Física, disciplina que estudian. Se utilizó un diseño no experimental, de corte transversal y carácter mixto; la muestra estuvo compuesta por 200 estudiantes de la carrera de Pedagogía en Educación Física de 12 universidades del país, seleccionados bajo un criterio no probabilístico intencionado. Los resultados muestran como palabras definidoras con mayor peso semántico: salud, deporte, motricidad y movimiento. Se concluye que las representaciones sociales de esta especialidad están vinculadas a la salud y bienestar, asociadas al movimiento y estudio de la motricidad humana, otorgando un valor pedagógico a través de elementos como la actividad física, la recreación y el deporte.

Both associative and dissociative H(2)O adsorption on SnO(2)(110), TiO(2)(110), and Ti-enriched Sn(1-x)Ti(x)O(2)(110) surfaces have been investigated at low ((1)/(12) monolayer (ML)) and high coverage (1 ML) by density functional theory calculations using the Gaussian and plane waves formalism. The use of a large supercell allowed the simulation at low symmetry levels. On SnO(2)(110), dissociative adsorption was favored at all coverages and was accompanied by stable associative H(2)O configurations. Increasing the coverage from (1)/(12) to 1 ML stabilized the (associatively or dissociatively) adsorbed H(2)O on SnO(2)(110) because of the formation of intermolecular H bonds. In contrast, on TiO(2)(110), the adsorption of isolated H(2)O groups ((1)/(12) ML) was more stable than at high coverage, and the favored adsorption changed from dissociative to associative with increasing coverage. For dissociative H(2)O adsorption on Ti-enriched Sn(1-x)Ti(x)O(2)(110) surfaces with Ti atoms preferably located on 6-fold-coordinated surface sites, the analysis of the Wannier centers showed a polarization of electrons surrounding bridging O atoms that were bound simultaneously to 6-fold-coordinated Sn and Ti surface atoms. This polarization suggested the formation of an additional bond between the 6-fold-coordinated Ti(6c) and bridging O atoms that had to be broken upon H(2)O adsorption. As a result, the H(2)O adsorption energy initially decreased, with increasing surface Ti content reaching a minimum at 25% Ti for (1)/(12) ML. This behavior was even more accentuated at high H(2)O coverage (1 ML) with the adsorption energy decreasing rapidly from 145.2 to 101.6 kJ/mol with the surface Ti content increasing from 0 to 33%. A global minimum of binding energies at both low and high coverage was found between 25 and 33% surface Ti content, which may explain the minimal cross-sensitivity to humidity previously reported for Sn(1-x)Ti(x)O(2) gas sensors. Above 12.5% surface Ti content, the binding energy decreased with increasing coverage, suggesting that the partial desorption of H(2)O is facilitated at a high fractional coverage.

The composition and thermodynamic stability of the (110) surface of Sn 1 - x Ti x O 2 rutile solid solutions was investigated as a function of Ti-distribution and content up to the formation of a full TiO 2 surface monolayer. The bulk and (110) surface properties of Sn 1 - x Ti x O 2 were compared to that of the pure SnO 2 and TiO 2 crystal. A large supercell of 720 atoms and a localized basis set based on the Gaussian and plane wave scheme allowed the investigation of very low Ti-content and symmetry. For the bulk, optimization of the crystal structure confirmed that up to a Ti-content of 3.3 at.%, the lattice parameters ( a , c ) of SnO 2 do not change. Increasing further the Ti-content decreased both lattice parameters down to those of TiO 2 . The surface energy of these solid solutions did not change for Ti-substitution in the bulk of up to 20 at.%. In contrast, substitution in the surface layer rapidly decreased the surface energy from 0.99 to 0.74 J/m 2 with increasing Ti-content from 0 to 20 at.%. As a result, systems with Ti atoms distributed in the surface (surface enrichment) had always lower energies and thus were thermodynamically more favorable than those with Ti homogeneously distributed in the bulk. This was attributed to the lower energy necessary to break the Ti O bonds than Sn O bonds in the surface layer. In fact, distributing the Ti atoms homogeneously or segregated in the (110) surface led to the same surface energy indicating that restructuring of the surface bond lengths has minimal impact on thermodynamic stability of these rutile systems. As a result, a first theoretical prediction of the composition of Sn 1 - x Ti x O 2 solid solutions is proposed.

By means of ab initio molecular dynamics, we have investigated the molecular adsorption of acetaldehyde on Pt 13 nanoparticles in the presence of coadsorbed hydrogen on the surface of the metal par...

The presence of a tertiary amine plays a role in accelerating the catalysis of ketones hydrogenation on a platinum surface covered by hydrogen. Ab initio molecular dynamics has been applied to achieve an atomistic understanding of this base effect. The interaction of trimethylamine with hydrogen adsorbed on a platinum nanoparticle has been simulated for 22 ps revealing that hydrogen increases its oscillatory modes upon interaction with the base therefore its activation. Nonetheless in the case of trimethylamine, competing interactions appear in the form of skeletal hydrogen (from the methyl group) interacting with the metal particle. Such interactions distract the action of the base and predominate at the end of the simulation. The interaction of the trimethylamine molecule with hydrogen adsorbed on platinum is compared to the corresponding interaction of the quinuclidine moiety of cinchonidine, which is the most widely applied chiral modifier for the platinum catalyzed enantioselective hydrogenations. Th...

Characterization of organic functional groups grafted to magnetic nanoparticles often causes considerable difficulty because of lack of information concerning their accessibility and chemical reactivity. Classical solid-state techniques only allow gaining qualitative information and the determination of upper bounds of the total loading of organic moieties. To overcome this limitation we applied attenuated total reflection (ATR) infrared spectroscopy in a specially designed mechanically stirred in situ batch reactor-cell. Using the example of iron oxide magnetic nanoparticles embedded in a silica matrix that have been functionalized by grafting aminopropyl groups, we elucidated the accessibility and reactivity of amino groups. Reactivity tests using the transformation of the amine to benzaldimine revealed that less than 40% of the introduced amino groups reacted to the corresponding benzaldimine indicating that the theoretical loading provides only an upper bound of active functional groups. The reactivit...

A series of peptides, all containing the natural amino acid tryptophan (Trp), have been used as chiral surface modifiers for asymmetric hydrogenation reactions on alumina supported platinum catalysts. The surface chiral sites have been investigated using density functional theory calculations in order to elucidate the structure of the asymmetric environment produced by the adsorption of the peptides on the metal surface. As a test reaction, ketopantolactone (KPL) has been asymmetrically hydrogenated using the modified catalyst. Catalytic results were tested against a computational model to shed light on the phenomenon of chiral induction. The choice of Trp as the first member of the peptidic chain is due to its structural resemblance to cinchona alkaloids, already successfully used as modifiers for asymmetric hydrogenation reactions. The amino acidic moiety of Trp was elongated by addition of other natural amino acids via a peptidic bond, and the resulting peptides were tested as chiral modifiers. The ind...

A magnetic Pt/SiO2/Fe3O4 catalyst consisting of chirally modified platinum supported on silica coated magnetite nanoparticles was prepared using an easy synthetic route and successfully applied for the enantioselective hydrogenation of various activated ketones. The magnetic catalyst modified with cinchonidine showed a catalytic performance (activity, enantioselectivity) in the asymmetric hydrogenation of various activated ketones in toluene comparable to the best known Pt/alumina catalyst used for these reactions. The novel catalyst can be easily separated from the reaction solution by applying an external magnetic field and recycled several times with almost complete retention of activity and enantioselectivity.

The adsorption of naphthalene and quinoline on Pt(111), Pd(111) and Rh(111) surfaces is studied using density functional theory. The metal surfaces are simulated by means of large confined clusters and for Pt by means of a slab with periodic boundary conditions (PBC). Calculation parameters such as basis set convergence, basis set superposition error and effects of cluster relaxation and size are analyzed in order to assess the aptness of the cluster model. For all the metals, the preferred sites of adsorption are analyzed, thus revealing their different behaviors concerning structure and stability of adsorption modes. On Pt, the molecules have the richest theoretical configurational variety. Naphthalene and quinoline are found to adsorb preferentially on di-bridge[7] sites on the three metals, and Rh exhibits higher adsorption energies than Pt and Pd. Structural features of the adsorbed molecules are correlated to the calculated adsorption energies. The di-bridge[7] adsorption modes are studied in deeper detail decomposing the adsorption energies in two terms arising from molecular distortion and binding interaction to the metal. Molecular distortion is correlated to the HOMO-LUMO energy gap. The larger adsorption energies found for interactions with Rh result from the lower contribution of the distortion term. Binding interactions are described by analyzing the wave functions of naphthalene and quinoline adsorbed on a subunit of the large clusters in order to reduce the complexity of the analysis. Molecular orbitals are studied using concepts of Frontier Molecular Orbitals theory. This approach reveals that in the adsorption of naphthalene and quinoline on Pt and Pd, an antibonding state lies below the Fermi energy, while on Rh all antibonding states are empty, in agreement with the larger interaction energies. In addition, further insight is gained by projecting the density of states on the d band of the clean surfaces and of the adsorbed systems. This results in the rationalization of the structural features in terms of the concepts of electronic structure theory. The distributions of electronic density are described by means of Hirshfeld charges and isosurfaces of differential electron density. The net electron transfer from the metals to the molecules for most of the sites correlates with the trends of the adsorption energies.

The adsorption behavior of cinchona-type chiral modifiers (β-isocinchonine, cinchonidine, and cinchonine) on model rhodium and platinum catalysts has been studied using attenuated total reflection infrared (ATR-IR) spectroscopy and density functional theory (DFT). The ATR-IR studies performed under conditions closely resembling those encountered during enantioselective hydrogenation as well as in the absence of hydrogen revealed significant differences in the adsorption mode of the modifiers, depending on the rotational flexibility of the modifier, the platinum group metal, and the presence of hydrogen. The more rigid β-isocinchonine showed preferential tilted adsorption on both metals, independent of the presence or absence of hydrogen. Cinchonidine and cinchonine were adsorbed on Pt predominantly with the quinoline ring nearly parallel to the surface, irrespective of the presence or absence of hydrogen, whereas on Rh in the presence of hydrogen only tilted species were observed. The latter behavior is a...

The adsorption behavior of O-methyl and O-trimethylsilyl derivatives of cinchonidine (CD), employed as chiral modifiers for heterogeneous enantioselective hydrogenations on supported Pt catalysts, has been investigated by using attenuated total reflection infrared spectroscopy (ATR-IR) and density functional theory (DFT) electronic structure calculations. The ATR-IR spectroscopic investigation provided detailed insight of the adsorbed modifiers under conditions close to those employed during catalytic processes, and electronic structure calculations were used as a complement to the experiments to uncover the implications of conformational changes in generating the topology of the surface chiral site. The structural investigation of the adsorbed modifiers revealed a relationship between the spatial positions of the ether substituents and the enantiodifferentiation induced by the modified catalyst observed in the hydrogenation of alpha-activated ketones. Experiments and calculations corroborate a model, according to which the addition of a bulky ether group to CD reshapes the chiral sites, thus generating catalytic chiral surfaces with different and, in some cases (e.g. hydrogenation of ketopantolactone), even opposite enantioselective properties to those obtained with CD without altering the absolute configuration of the modifier. The study also confirms that active surface conformations of cinchona modifiers are markedly different from those existing in vacuum and in solution, thus underlying the necessity of investigating the surface-modifier interaction in order to understand enantioselectivity.

Systematic structural variations of cinchona-type modifiers used in the platinum-catalyzed hydrogenation of ketones give insight into the adsorption mode of the modifier and its interaction with the substrate on the platinum surface under truly in situ conditions. The performance of a new modifier, O-(2-pyridyl)-cinchonidine, is compared to that of O-phenyl-cinchonidine and cinchonidine (CD). In the hydrogenation of ethyl pyruvate, ketopantolactone, and 2-methoxyacetophenone, CD gives the (R)-alcohol in excess. Introduction of the bulky O-phenyl group favors the (S)-enantiomer, whereas upon replacement of the phenyl by a 2-pyridyl group the (R)-alcohol is again the major product. This finding is particularly striking, because the two ether groups have virtually identical van der Waals volumes. A catalytic study including the nonlinear behavior of modifier mixtures, and attenuated total reflection infrared spectroscopy of the solid-liquid interface in the presence of hydrogen, revealed the adsorption mode and strength of the modifiers on Pt. Theoretical calculations of the modifier-substrate interactions offered a feasible explanation for the different role of the bulky ether groups: repulsion by the phenoxy and attraction by the 2-pyridoxy groups. Simulation of the interaction of o-pyridoxy-CD with ketopantolactone on a model Pt surface suggests that formation of two N-H-O-type H-bonds--involving the quinuclidine and pyridine N atoms, and the two keto-carbonyls in the substrate--controls the adsorption of the substrate during hydrogen uptake. This mechanistic study demonstrates the potential of insertion of suitable substituents into CD and their influence on adsorption and stereocontrol on the platinum surface.

Chirally modified platinum surfaces as used in enantioselective hydrogenation have been generated by adsorption of O-phenyl derivatives of cinchonidine on Pt/Al2O3 films. The adsorption behavior as well as the structure of the resulting chiral solid−liquid interfaces has been investigated using attenuated total reflection infrared (ATR-IR) spectroscopy. In particular O-phenyl-cinchonidine, O-(3,5-dimethylphenyl)-cinchonidine, and O-[(3,5-bis(trifluoromethyl)phenyl]-cinchonidine have been analyzed, and their behavior has been compared to that of the parent alkaloid. The ATR-IR spectroscopic investigation provided insight into submolecular structural details of the conformation of the adsorbates under conditions close to those existing during the catalytic enantioselective hydrogenation. As a complement to the spectroscopic observations, electronic structure calculations were performed using density functional theory (DFT). The result of the conformational study of each adsorbed modifier revealed a correlat...

Understanding the sub-molecular structure of conformationally complex adsorbed molecules is still a difficult task for experimentalists interested in the structure of modified surfaces, therefore first principles calculations can be a fundamental tool for the investigation of structural details otherwise impossible to identify. Density functional theory (DFT) calculations of the adsorption of cinchonidine (CD) and O-phenyl-cinchonidine (OPhCD) have been performed, using large metal clusters to simulate the metal surface and a zero order regular approximation (ZORA) Hamiltonian to account for relativistic effects due to the heavy nuclei involved. The local geometry of chiral surface sites formed by CD was investigated in detail and discussed in relation to the reaction of enantioselective hydrogenation of activated ketones on cinchona modified platinum. Also, the relevant conformations of OPhCD were investigated and the resulting structure of the chiral sites is discussed and compared to those obtained for...

The directing effect of the CF 3 group on Pt/alumina modified by cinchonidine in the enantioselective hydrogenation of activated ketones was studied experimentally and theoretically using aliphatic α , α , α -trifluoromethyl ketones as model compounds. α , α , α -Trifluoromethyl ketones with varying steric hindrances of the groups on the two sides of the keto group (methyl-trifluoromethyl ketone 1a , adamantyl-trifluoromethyl ketone 2a , and tert -butyl-trifluoromethyl ketone 3a ) were examined. The catalytic results show that in weakly polar solvents, in which the interaction of the solvent with the substrate, modifier, and Pt is less important, the three alcohols 1b , 2b , and 3b have the same absolute configuration ( R ). This indicates that enantioselectivity is guided by the trifluoromethyl substitution rather than by the relative bulkiness of the substituents at the two sides of the carbonyl group. The fluorinated substrate has a preferential interaction on the side of the α , α , α -trifluoromethyl group, as corroborated by the calculation of hydrogen–bonding interactions. When this interaction mode is calculated for the system alkaloid–trifluoroacetone, an energy difference between the Pro( R ) and the Pro( S ) configurations is found. Our findings suggest that electronic effects give a bias toward the formation of the ( R )-enantiomer.

The conformations of cinchonidine (CD) adsorbed on a Pt(111) surface were studied using first-principles methods. Eight conformationally different adsorption states due to different degrees of rotation around the τ 1 and τ 2 degrees of freedom were identified and their possible role in the formation of chiral surface sites relevant to enantioselective hydrogenation investigated in light of the currently existing experimental evidence. Comparison of the conformational behavior of CD in solution and on platinum has revealed the effect of the metal surface on the internal mobility of the alkaloid. Although the study corroborates the outstanding role of the adsorbed Open(3) conformer suggested previously, the rich conformational flexibility observed on the platinum surface points to the possibility that other conformers of CD also may be involved in enantiodifferentiation. Closed conformations of CD are found to play an important role in the conformational equilibria on the surface due to their stability and are identified as precursors of the less stable, but presumably more active, open conformers. Although the open and closed conformers are closely related to the correspondent ones found in solution, surface species that are also adsorbed via quinuclidine moiety are characteristic of the metal–modifier interaction and should serve as precursors to catalytically active conformations.

In the Pt-catalyzed hydrogenation of 1,1,1-trifluoro-2,4-diketones, addition of trace amounts of cinchonidine, O-methyl-cinchonidine, or (R,R)-pantoyl-naphthylethylamine induces up to 93% ee and enhances the chemoselectivity up to 100% in the hydrogenation of the activated carbonyl group to an OH function. A combined catalytic, NMR and FTIR spectroscopic, and theoretical study revealed that the two phenomena are coupled, offering the unique possibility for understanding the substrate-modifier-metal interactions. The high chemo- and enantioselectivities are attributed to the formation of an ion pair involving the protonated amine function of the chiral modifier and the enolate form of the substrate. DFT calculations including the simulation of the interaction of a protonated amine with the enolate adsorbed on a Pt 31 cluster revealed that only the C-O bond next to the CF3 group of the substrate is in direct contact with Pt and can be hydrogenated. The present study illustrates the fundamental role played by the metal surface and indicates that also the enol form can be the reactive species in the hydrogenation of the activated ketone on chirally modified Pt.

The adsorption mode of cinchonidine on platinum is discussed in the light of new computational studies in which the alkaloid is adsorbed on a large metal cluster. Previous computations focused on the role of 1(S)-(4-quinolinyl)ethanol as anchoring group, but in the present study the role of the quinuclidine ring is analyzed, leading to a consistent view of the roles of both moieties of the alkaloid in the adsorption process. The tertiary nitrogen of the quinuclidine moiety can participate in the anchoring of the alkaloid and can be protonated by surface hydrogen. The conformational flexibility of the quinuclidine moiety was investigated by attenuated total reflection infrared experiments under nearly in situ conditions, by comparing the adsorption behavior of cinchonidine and O -phenyl-cinchonidine on platinum. Close agreement was found between experimental observations and theoretical calculations. A mechanism is proposed whereby the tertiary nitrogen can promote charge polarization of hydrogen and its transfer to the substrate.

O-Phenylcinchonidine (PhOCD) is known to efficiently induce inversion of enantioselectivity with respect to cinchonidine (CD) in the enantioselective hydrogenation of various activated ketones on Pt/Al(2)O(3). To understand the origin of the switch of enantioselective properties of the catalyst, the adsorption of PhOCD has been studied by in situ ATR-IR spectroscopy, in the presence of organic solvent and dissolved hydrogen, i.e., under conditions used for catalytic hydrogenation. The adsorption structures and energies of the anchoring group of CD and PhOCD were calculated on a Pt 38 cluster, using relativistically corrected density functional theory (DFT). Both approaches indicate that both modifiers are adsorbed via the quinoline ring and that the spatial arrangement of the quinuclidine skeleton is critical for the chiral recognition. New molecular level information on the conformation of CD relative to PhOCD adsorbed on a surface is extracted from the ATR spectra and supported by DFT calculations. The result is a clearer picture of the role played by the phenyl group in defining the chiral space created by the modifiers on Pt. Moreover, when CD was added to a pre-equilibrated adsorbed layer of PhOCD, a chiral adsorbed layer was formed with CD as the dominant modifier, indicating that CD adsorbs more strongly than PhOCD. Conversely, when PhOCD was added to preadsorbed CD, no significant substitution occurred. The process leading to nonlinear effects in heterogeneous asymmetric catalysis has been characterized by in situ spectroscopy, and new insight into a heterogeneous catalytic R-S switch system is provided.

O catabolismo do colageno no aparelho locomotor implica em liberacao de um nivel de Hidroxiprolina (HP) aumentado na excrecao urinaria, o qual, por sua vez, constitui um marcador bioquimico indicador de danos nos tecidos conjuntivos. O objetivo do presente estudo foi verificar em qual dos meios, liquido ou terrestre, de realizacao do flexionamento dinâmico se observa o menor grau de catabolismo do colageno do aparelho locomotor atraves do nivel de HP excretado na urina de 10 homens adultos nao atletas, com faixa etaria entre 24 e 45 anos. Foram selecionados quatro movimentos limitados pela elasticidade muscular e pela mobilidade articular para a realizacao do flexionamento dinâmico,e para os procedimentos metodologicos foram utilizadas tres coleta de urina para analise laboratorial. As coletas foram realizadas durante um periodo de duas horas (2h) apos hidratacao, sendo entregues ao laboratorio num periodo de ate 3 horas. O metodo utilizado foi o HPLC (System Liquid Chromatographic Determination of total Hydroxyproline in Urine), com valor de referencia de 15-43mg/d (CHERNECKY et al., 1993). A primeira coleta foi realizada 24 horas antes do flexionamento dinâmico para verificacao basal do nivel de HP como referencial do grupo de voluntarios. A segunda e a terceira coletas ocorreram 24h apos o flexionamento realizado em ambos os meios. Os resultados encontrados nos niveis de HP (para p = 0,05) foram: para os niveis basais, de 39,07 ± 15,27; para os niveis 24h pos-treino terra, os niveis foram de 71,28 ± 12,15; e para os niveis 24h pos treino agua, de 66,74 ± 10,31. Conclui-se que existe diferenca nas concentracoes de HP entre os instantes basal e 24 h pos-treinos, indicando, portanto, a ocorrencia de lesao do tecido conjuntivo. A analise direta entre os ambientes nao apresentou diferenca significativa (para p

The adsorption of several ketones interesting for the enantioselective hydrogenation on cinchona-modified platinum has been modeled using relativistically corrected density functional theory. Two metal clusters, containing 19 and 31 Pt atoms, respectively, have been used to model a Pt(111) surface. The two adsorption modes η1 and η2 have been described, and their importance for the mechanism of hydrogenation has been pointed out. The effect of an ester group in α position and of α-fluorination of a ketone on its adsorption has been studied, and an explanation for the reactivity enhancement due to the ketone substitution has been proposed.

The relation between the electronic structure of α-substituted ketones and their reactivity in the racemic and enantioselective platinum-catalyzed hydrogenation has been investigated using a combined theoretical and experimental approach. A correlation between the keto carbonyl orbital energy and the hydrogenation rate has been found, which rationalizes the effect of the substituent on the rate of hydrogenation. The uncovered relationship between the keto carbonyl orbital energy and the hydrogenation rate provides a rational explanation for the often observed rate acceleration that occurs when cinchona-modified platinum is used as a enantioselective hydrogenation catalyst. The previously suggested model for enantiodiscrimination based on the different stability of the diastereomeric complexes formed between the reactant and the cinchona modifier is discussed in the light of the new kinetic findings.

The origin of the rate acceleration in enantioselective hydrogenation of α-functionalised ketones over cinchona alkaloid modified platinum has been studied using a combined experimental and theoretical approach, and the rate acceleration is traced to a lowering of the energy of the carbonyl Π orbitals in the diastereomeric complex formed between reactant and modifier.

Vibrational circular dichroism (VCD) spectra of the chiral modifiers cinchonidine, an alkaloid, and (R)-2-(pyrrolidin-1-yl)-1-(1-naphthyl)ethanol (PNE) were measured and simulated. For cinchonidine independent information from NMR investigations on the distribution of conformers was used to simulate VCD spectra from calculated spectra of the individual conformers. Agreement with experiment is reasonably good. For the structurally similar synthetic modifier PNE VCD spectra show that an open conformer predominates in solution. The difference between the most stable conformers of cinchonidine and PNE in solution is the intramolecular hydrogen bond found in the latter, which forms due to the enhanced flexibility of the pyrrolidinyl moiety in PNE as compared to the quinuclidine moiety in cinchonidine. The similar enantiodifferentiating power of cinchonidine and PNE as chiral modifiers in the heterogeneous enantioselective hydrogenation of ethyl pyruvate indicates that the rigidity of this part of the molecule is not a prerequisite for enantioselection. It is furthermore shown that binding of a non-chiral carboxylic acid to the alkaloid induces VCD in vibrations associated with the acid. Observation of this induced VCD allows probing of the chiral binding site.

Durante el proceso de desarrollo humano, la relación de interacción entre el hombre y el deporte se convirtió indiscutible. El deporte, además de compañero atendió diversos anhelos humanos, actuando como una estrategia para entrenamiento de las habilidades sociales, especialmente en el universo de los proyectos deportivos sociales. El objetivo del presente estudio fue por medio de la investigación documental investigar el proceso de desarrollo de los proyectos deportivos sociales en la ciudad de Rio de Janeiro, sobre todo con el apoyo del gobierno local. Los resultados favorecen la compresión de que este tipo de acción, que tiene como objetivo la difusión de preceptos positivos a través del desenvolvimiento deportivo, presentó crecimiento y fomentación indudable, sobre todo después de la participación gubernamental, pero su surgimiento no presentó el apoyo del gobierno. Los objetivos deseados en los proyecto administrados por la Secretaria Municipal de Deporte y Ocio de la ciudad del Rio de Janeiro, favorecen la comprensión de que muchos objetivos son deseados. Siendo así, fue posible concluir que iniciativas análogas, deben ser estimuladas en todos los sectores de la sociedad, especialmente con el fin de ofrecer todos los beneficios envueltos en el deporte y así contribuir para la formación de ciudadanos, During the process of human development, the relationship of interaction between man and sport became indisputable. The sport, in addition to companion, attended to various human aspirations, acting as a strategy for training social skills, especially in the universe of social sports projects. The objective of this study was through documentary research to investigate the development process of social sports projects in the city of Rio de Janeiro, especially with the support of the local government. The results favor the understanding that this type of action, which aims to disseminate positive precepts through sports development, presented undoubted growth and development, especially after government participation, but its emergence did not present the support of the government. The desired objectives in the projects administered by the Municipal Secretary of Sport and Leisure of the city of Rio de Janeiro, favor the understanding that many objectives are desired. This being so, it was possible to conclude that similar initiatives should be stimulated in all sectors of society, especially in order to offer all the benefits involved in sports and thus contribute to the training of citizens.

The previously proposed model for reactant–modifier interaction in the enantioselective hydrogenation of activated carbonyl compounds over platinum chirally modified by cinchona alkaloids has been extended to platinum modified by synthetic pyrrolidinyl–naphthyl–ethanol modifiers. As in the case of cinchonidine, the most used modifier, the model predicts enantiomeric excess in nearly quantitative agreement with experiment. Excellent agreement is achieved despite the fact that structural assumptions had to be made and the platinum surface was not explicitly taken into account. The one-to-one interaction between modifier and reactant was calculated at the ab initio level. A comparison of the results for different modifiers leads to the conclusion that steric repulsion caused by the anchoring group plays an important role in the enantiodifferentiating interaction. The favoured formation of the (R)-product is traced to the fact that the pro-(S) complex leading to the (S)-product upon hydrogenation is more destabilised due to repulsive interaction than the pro-(R) complex. The model calculations are a useful tool for designing effective modifiers and for gaining insight into the mechanism of enantiodifferentiation.

La relación entre el Hombre y la práctica de actividad física ha obtenido fama reconocida en los últimos años. Sin embargo, la actuación del Profesional de Educación Física en la gestión de esta relación, a pesar de efectiva, tenía una carencia de conocimiento técnico y científico, un hecho que dificultó la consolidación del trabajo en la sociedad contemporánea. En esto universo emergió la Ciencia de la Motricidad Humana, un área del conocimiento científico que ha surgido con la función de proporcionar apoyo científico y técnico para los Profesionales de Educación Física, fundamentalmente al mostrar que le deporte trasciende el universo deportivo y una nueva comprensión de Hombre es posible. Vale la pena señalar que estos preceptos han logrado un éxito considerable, principalmente en la República Federativa del Brasil, que se caracterizó por la relación indiscutible entre el Hombre y la práctica de actividad física, junto con el fomento través de mecanismos legales para el crecimiento del deporte y asegurar en reconocimiento de los Profesionales de Educación Física.

O estudo se baseou na Teoria dos Sistemas Ecológicos (Micro-Meso-Exo- Macrossistema) e discutiu o lazer como direito social ao analisar o impacto das políticas públicas no desenvolvimento do cidadão. Trata-se de um estudo descritivo- analítico com análise de conteúdo das entrevistas semiestruturadas. Amostra (n=42) usuários de atividades de lazer (Micro); (n=6) gerentes da SMEL (Exo). Na entrevista com o Micro se identificaram 202 relatos (F.a), igual a 100% (F.r.), categorizados em elementos impactantes. Concluiu-se que houve impacto dos ambientes ecológicos sobre o Micro, prevalecendo interferências do Macro no Micro e menor interdependência entre os sistemas, embora o Micro tenha recebido interferência de todos os níveis. O Exo é importante nessa teia ao provocar interconexões ambientais que refletem no desenvolvimento do homem, que busca o lazer como direito de preservação da vida e exercício de cidadania.

El estudio tiene como objetivo presentar la relacion entre el hombre y el deporte a la mientras de la historia. Se observo que el deporte ha acompanado al hombre desde la prehistoria en el que surgio la naturaleza para la supervivencia, trascendiendo hasta la Antigua Grecia, termino que se refiere al periodo de la historia de Grecia. En este periodo de la Historia Griega, los deportes recibieron el estatus de asociado con la belleza y la sabiduria. En la Antigua Roma el deporte tenia sustancial importancia politica y una funcion principal que fue la coaptacion de los espectadores, a diferencia de la Epoca Medieval, donde se limitaba a los Clerigos con las practicas deportivas de juego, quedando a la “gente comun” a la observacion. Al final de la Segunda Guerra Mundial, la politica deportiva recibio el desarrollo sustancial debido la disputa entre los paises del bloque capitalista y el bloque comunista, con objeto de demostrar su fuerza y superioridad a traves del escenario de las competiciones deportivas. En el siglo XIX lo deporte moderno, se basa en los conceptos de Rousseau, que influyen directamente en los ideales de Pierre de Coubertin, que utiliza el deporte con el objetivo de la pacificacion y unificacion del pueblo, a traves de el establecimiento de la Tregua o Paz Olimpica durante los Juegos. Sin embargo, la magnitud del deporte trasciende los cambios momentaneos, como se ha senalado en el deporte para fines sociales, donde el deporte asume la funcion de entrenador de habilidades sociales, proporcionando una alternativa a la poblacion pobre. Como se ha senalo el deporte a la mientras de la historia humana asistio a un universo de posibilidades y necesidades. Sin embargo, los caminos para lograr su crecimiento, depende de la formacion de los profesionales implicados, una de las maneras de alcanzar su empoderamiento, es la necesidad de los profesionales implicados, lo que necesitan conocer y buscar la manera de sacar provecho de todo el universo de posibilidades inherentes a este fenomeno social llamado el deporte.

RESUMO: Tratar o lazer como elemento essencial para o desenvolvimento social e algo que vem sendo defendido como uma ideia que expressa a garantia de direitos. Historicamente, o lazer compos a rotina social dos individuos, tanto que os registros de tais fatos remontam a Idade Antiga. Porem, ressalta-se que ao longo da historia, o lazer foi analogamente tratado como ocio. Com o advento da Revolucao Industrial tornou-se mais evidente a relacao com a produtividade na sociedade capitalista e a necessidade de descanso e tempo livre. A partir dai, a relevância do lazer como agente minimizador de acidentes de trabalho e desgastes de natureza profissional consolidou-se nos setores de producao publicos e privados. Nesse sentido, este artigo enfatiza o marco historico do lazer no setor de producao industrial desde o seculo XIX ate o presente. No Brasil o fortalecimento da construcao de uma politica para o lazer se da atraves do SESC e do SESI. THE HISTORICAL CONTEXT OF PUBLIC POLICY FOR LEISURE IN BRAZIL ABSTRACT: Treating leisure as an essential element for social development is something that has been seen as an idea which expresses the guarantee of human rights. Historically, leisure composed the social routine of individuals, given that records of such events remote to ancient Rome and Greece. However, it is clear that leisure was historically understood in its essence as a characterization of idleness. With the Industrial Revolution, the relationship between productivity in a capitalist society and the need for rest and leisure time became more evident. Since then, leisure was established as a relevant agent for minimizing working accidents and other professional drawbacks in public and private sectors of production. Thus, this article emphasizes the historic milestone in leisure in the segment of industrial production since the 19th century to the present. In Brazil, the strengthening of building a policy for leisure is brought up by the SESC and SESI.

Este estudio tiene como objetivo relacionar el ser y el deporte mediante la adopción de un programa intervencionista deejercicios aeróbicos como base de la competencia deportiva. Con la participación de 20 niños de bajo nivel socioeconómico,con edades de siete a diez años, y entre el primero y cuarto grados de la enseñanza primaria, y con ciertas habilidadesnecesarias para aeróbica, se han investigado los posibles cambios comportamentales proporcionados a estos jóvenes poruna vida deportiva, que, además de los beneficios físicos y socioeducativos, les ayuda a definir una nueva forma de pensar yactuar. Se ha aplicado un cuestionario sobre el grado de satisfacción en la realización de estas prácticas, y sobre lamotivación para la continuación de la formación y la relación entre alumno y profesor. Se han constatado mejoras en lacalidad de la estructura corporal de estos niños y niñas, además de los manifiestos progresos intelectuales. Este ensayoplantea para el educador un formato de integración social producida a través del deporte.

The description of the conformational space generated by metal nanoparticles is a fundamental issue for the study of their physicochemical properties. In this investigation, an exhaustive exploration and a unified view of the conformational space of a gold nanocluster is provided using a Au 12 cluster as an example. Such system is characterized by coexisting planar/quasiplanar and tridimensional conformations separated by high-energy barriers. The conformational space of Au 12 has been explored by means of Born-Oppenheimer ab initio metadynamics, i.e., a molecular dynamics simulation coupled with a history dependent potential to accelerate events that might occur on a long time scale compared to the time step used in the simulations (rare events). The sampled conformations have complex, in general not intuitive topologies that we have classified as planar/quasiplanar or tridimensional, belonging to different regions of the free energy surface. Three conformational free energy basins were identified, one for the planar/quasiplanar and two for the tridimensional structures. At thermodynamic equilibrium, the planar/quasi-planar and tridimensional conformations were found to coexist, to be fluxional and to be separated by high-free-energy barriers. The comparison between the free energy and the potential energy revealed the relevance of the entropic contribution in the equilibrium distribution of the conformations of the cluster.

The structure and electronic properties of gold nanoparticles (Au 12, Au 13, Au 14, Au 15, Au 20, Au 34, and Au 55) have been investigated using Born-Oppenheimer ab initio molecular dynamic simulations of 50 to 80 ps in order to have an insight in the recently proposed fluxional character of nanosized gold. The dynamic changes in shape, symmetry, and atomic coordination of atoms within clusters, occurring in the time scale of picoseconds, which are characteristic of fluxionality, have been investigated for all the above systems at 300 K. Except for Au 20, all systems have been found to have fluxional properties. The extent and the type of fluxional behavior changed according to the number of atoms constituting the particle. At 300 K Au 12 and Au 13 rapidly generate several different topologies which cyclically interconvert. Au 14 shows a rotation of 8 external gold atoms around a core of six atoms. Au 15 is more rigid, but interestingly shows the interconversion between enantiomeric structures within the time scale of the simulation. Au 20 shows a high stability of the pyramidal topology and is the only one of the investigated systems not to show fluxionality within the assigned temperature and time scale. Au 34 and Au 55 show fluxionality of the outer shell and within the sampled time scale are able to change coordination of the outer shell atoms and thus open and close surface holes. For all the particles in study the structures forming the local minima were isolated and separately optimized, and the electronic properties of the thus obtained structures were analyzed.

The structure sensitivity of enantioselective hydrogenations on chirally modified metals was investigated using Pt nanoparticles of different shapes. All three samples had an average particle size of 10 nm, but the fraction of dominantly cubic, cubooctahedral, and octahedral particles varied with decreasing {100} and increasing {111} faces in the same order. In the absence of chiral modifier the hydrogenation of ethyl pyruvate was independent of the shape of the Pt nanoparticles; variation of the specific reaction rates did not exceed the experimental error on all self-prepared catalysts and on a commercial Pt/Al(2)O(3) used as reference. Addition of cinchonidine or quinine induced a significant rate enhancement by a factor of 4-15, and the rate was always higher with quinine. Also, 72-92% ees were achieved, and the reaction was shape selective: both the rate and the ee increased with increasing Pt{111}/Pt{100} ratio. A similar correlation in the hydrogenation of ketopantolactone confirmed that decarbonylation or aldol-type side reactions of ethyl pyruvate were not the reason for structure sensitivity. A combined catalytic and theoretical study revealed that the probable origin of the particle shape dependency of enantioselective hydrogenation is the adsorption behavior of the cinchona alkaloid. DFT studies of cinchonidine interacting with Pt(100) and Pt(111) terraces indicated a remarkably stronger interaction on the former crystallographic face by ca. 155 kJ/mol. The higher adsorption strength on Pt(100) was corroborated experimentally by the faster hydrogenation of the homoaromatic ring of the alkaloid, which fragment interacts the strongest with Pt during its adsorption. Thus, an ideal catalyst for the hydrogenation of activated ketones contains dominantly Pt{111} terraces, which crystallographic face is more active and affords higher enantioselectivity, combined with the higher stability of the modifier.

We present a study on structural and electronic properties of bulk platinum and the two surfaces (111) and (100) comparing the Gaussian and plane wave method to standard plane wave schemes, normally employed for density functional theory calculations on metallic systems. The aim of this investigation is the assessment of methods based on the expansion of the Kohn-Sham orbitals into localized basis sets and on the supercell approach, in the description of the metallicity of Pt. Electronic structure calculations performed at Gamma-point only on supercells of different sizes, from 108 up to 864 atoms, are compared to the results obtained for the unit cell of four Pt atoms where the k-point expansion of the wave function over Monkhorst-Pack grids up to (10x10x10) has been employed. The evaluation of the two approaches with respect to bulk properties is done through the calculation of the equilibrium lattice constant, the bulk modulus, and the total and the d-projected density of states. For the Pt(111) and Pt(100) surfaces, we consider the relaxation of the first layers, the surface energies, the work function, the total density of states, as well as the center and filling of the d bands. Our results confirm that the accuracy of two approaches in the description of electronic and structural properties of Pt is equivalent, providing that consistent supercells and k-point meshes are used. Moreover, we estimate the supercell size that can be safely adopted in the Gaussian and plane wave method in order to obtain the same reliability of previous theoretical studies based on well converged plane wave calculations available in literature. The latter studies, in turn, set the level of agreement with experimental data. In particular, we obtain excellent agreement in the evaluation of the density of states for either bulk and surface systems, and our data are also in good agreement with previous works on Pt reported in literature. We conclude that Gaussian and plane wave calculations, with simulation cells of 400-800 atoms, can be safely used in the study of chemistry related problems involving transition metal surfaces.

Docking of molecules to surface chiral sites generated by adsorbed chiral organic modifiers is a fundamental step in heterogeneous metal-catalyzed asymmetric hydrogenation. The understanding of such docking events is nonetheless limited by the technical difficulties in obtaining experimental submolecular information for complex adsorbed structures. In addition an accurate theoretical analysis is computationally very demanding due to the need of including the metal surface. The present investigation explores by means of density functional theory the supramolecular docking structures of ketopantolactone within the chiral sites formed by cinchonidine adsorbed on a platinum surface, a crucial step in the enantioselective hydrogenation of ketopantolactone over cinchonidine-modified platinum. The study is performed using periodic slabs exposing Pt(111) surfaces of (6 × 6) and (8 × 8) atoms with a depth of four layers and including complete relaxation of the first three. Twenty six docking sites are investigated...

Adsorption of cinchonidine on monometallic Au and bimetallic Pt-Au and Pd-Au thin model films prepared by physical vapor deposition has been investigated with attenuated total reflection infrared (ATR-IR) spectroscopy. On Au the alkaloid forms an adsorbed layer that shows higher stability against desorption than the corresponding adsorption on Pt. In this adsorption layer the intermolecular interactions dominate over metal-adsorbate interactions as indicated by the absence of the spectroscopic features attributed to strongly flat adsorbed species. This behavior is further supported by Density Functional Theory (DFT) calculations indicating that flat and tilted orientations of the quinoline ring have comparable adsorption energy on Au but lower (7-10 kcal/mol) compared to adsorption on Pt (ca. 40 kcal/mol). As a consequence, the creation of a metal surface with isolated chiral sites is prevented by formation of an adsorbed structure formed by intermolecularly bound cinchonidine molecules on Au. While the binding to Pt is due to the formation of sigma-bonds to surface atoms, such aggregates are bound to Au mainly by van der Waals forces. Given this different nature of bonding of cinchonidine to Au and Pt, addition of Au to Pt and Pd films could be used to probe the changes of fractional coverage of the different adsorbed species of cinchonidine on the platinum metals. It is demonstrated that the lowering of the domain size of the platinum group metal by Au can simulate the effect of particle size on the distribution of the surface conformations of the alkaloid on a metal surface.

The adsorption of anisole, 3,5-dimethylanisole, and 3,5-bis-(trifluoromethyl)-anisole on Pt(111) was studied theoretically and compared to the adsorption of benzene using relativistically corrected density functional theory. A cluster of 31 platinum atoms was used to simulate the surface. The three anisoles were found to be less strongly adsorbed than the parent molecule benzene, 3,5-bis-(trifluoromethyl)-anisole showing weakest adsorption, with an adsorption energy of only one-third that of benzene. The theoretical study was complemented by in situ ATR-IR spectroscopy of the adsorption of the anisole derivatives on a polycrystalline Pt film. The spectroscopic study indicated that the adsorption strength of the anisoles follows the same order as predicted by the calculations. In addition, catalytic hydrogenation tests showed that the propensity to aromatic ring hydrogenation can also be correlated to the mode and strength of adsorption of the anisoles. The degree of saturation followed the same order as the adsorption strength found by the calculations and indicated by spectroscopy. Although 3,5-dimethyl substitution on anisole resulted in only a partial loss of adsorption energy and reactivity toward ring hydrogenation as compared to anisole, the substitution by CF(3) groups led to a large loss of adsorption energy and complete loss of reactivity toward aromatic ring saturation. Along with the study of the substituent effect on the adsorption of aromatic molecules, the correlation between adsorption and propensity to saturation of aromatic substrates could be corroborated.

The enantioselective hydrogenation of ring-substituted acetophenones that possess no functional group in the α-position to the keto group represents the latest extension of the application range of the Pt–cinchona system. The influence of the type of solvent, pressure, temperature, and modifier/substrate/Pt molar ratios was investigated in the hydrogenation of 3,5-di(trifluoromethyl)acetophenone. Modification of a 5 wt% Pt/Al2O3 catalyst by cinchonidine (CD) afforded the corresponding (S)-1-phenylethanol (69.5% ee). Working in strongly polar solvents, addition of trifluoroacetic acid in a weakly polar solvent, and replacing CD by its ether derivatives resulted in the inversion of enantioselectivity. Addition of CD or any of its derivatives always led to a lower reaction rate, contrary to the generally observed rate acceleration in the hydrogenation of α-functionalized activated ketones over the same catalyst system. Another fundamental difference to the hydrogenation of α-functionalized activated ketones is that both the quinuclidine N and the OH functions of CD influence the stereochemical outcome of the reaction, as clarified by using O- and N-substituted derivatives of CD. Ab initio calculations confirmed these remarkable mechanistic differences. Inversion of enantioselectivity in the presence of strongly polar and acidic solvents is attributed to special interactions with the OH function of CD, and to the formation of a CD–acid ion pair, respectively. A possible explanation for the moderate ee\'s in the hydrogenation of ring-substituted acetophenones is that a reaction pathway without involvement of the OH function of CD is also feasible. This competing pathway is even faster and provides low ee to the opposite enantiomer.

The adsorption of cinchonidine on platinum has been calculated with relativistically corrected density-functional theory, by first studying the interaction of the 1(S)-(4-quinolinyl)ethanol with a platinum cluster of 31 metal atoms, and by successive addition and separate optimization of the quinuclidine moiety. The conformations of the alkaloid on the surface were analyzed and their possible interactions with a surface chemisorbed methylpyruvate and acetophenone are discussed. A chiral space that is able to selectively accommodate surface enantiomers and to promote their rapid hydrogenation in a ligand-accelerated fashion has been determined. The role of the O-alkylation of the alkaloid in the modulation of enantioselectivity has been rationalized within the new interaction model.

Density Functional Theory (DFT) has been applied to characterize the early stages of the reaction of dioxygenation of [(triphos)M(catecholate)]+ complexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)3], which have been considered to be models of ring-opening dioxygenases. The structural features of the starting complexes and of the intermediate complexes formed by addition of O2 to the coordinated catecholato ion are well reproduced. The calculations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site.