Transformações químicas, caracterizações e estudo de modelagem molecular do clerodano bioativo trans-desidrocrotonina

In this work it were developed synthetic and theoretical studies for clerodane-type diterpenes obtained from Croton cajucara Benth which represents one of the most important medicinal plant of the Brazil amazon region. Specifically, the majoritary biocompound 19-nor-clerodane trans-dehydrocrotonin (t-DCTN) isolated from the bark of this Croton, was used as target molecule. Semi-synthetic derivatives were obtained from t-DCTN by using the followed synthetic procedures: 1) catalytic reduction with H2, 2) reduction using NaBH4 and 3) reduction using NaBH4/CeCl3. The semi-synthetic 19-nor-furan-clerodane alcohol-type derivatives were denominated such as t-CTN, tCTN-OL, t-CTN-OL, t-DCTN-OL, t-DCTN-OL, being all of them characterized by NMR. The furan-clerodane alcohol derivatives t-CTN-OL and tCTN-OL were obtained form the semi-synthetic t-CTN, which can be isolated from the bark of C. cajucara. A theoretical protocol (DFT/B3LYP) involving the prevision of geometric and magnetic properties such as bond length and angles, as well as chemical shifts and coupling constants, were developed for the target t-DCTN in which was correlated NMR theoretical data with structural data, with satisfactory correlation with NMR experimental data (coefficients ranging from 0.97 and 0.99) and X-ray diffraction data. This theoretical methodology was also validated for all semi-synthetic derivatives described in this work. In addition, topological data from the Quantum Theory of Atoms in Molecules (QTAIM) showed the presence of H-H and (C)O--H(C) intramolecular stabilized interactions types for t-DCTN e t-CTN, contributing to the understanding of the different reactivity of this clerodanes in the presence of NaBH4.

Influência da desordem estrutural nas propriedades magnéticas de filmes finos de Co2FeAl

Thin films of Co2FeAl (CFA) and trilayers with CFA/M/CFA, where M is Au or Ag, produced by magnetron sputtering onto glass and oriented (MgO (100)) substrates were investigated. The structural, magnetic static and magnetic dynamics properties were analyzed by distinct experimental techniques. Through X-ray diffraction was observed an A2 phase for the samples (completely disordered), where the atoms are randomly located in the lattice. The static magnetic behavior, in some samples, reveal a plateau behavior generated by a biphasic system. The magnetoimpedance measurements were performed by varying the angle between the external magnetic field and current with respect of anisotropy direction. For this reason, the MI results show a asymmetric magnetoimpedance (AMI) behavior. For the single and trilayers samples with 500 nm-thick, the AMI effect is more evident in comparison with samples with 1000 nm-thick. Therefore, in this work was stablished a route to produce Heusler alloy samples with A2 phase in thin film geometry onto amorphous and oriented substrates, and due to structural disorder was possible to study the hysteretic and MI asymmetric effects.

Novos protocolos teóricos utilizados nos estudos das ligações hidrogênio-hidrogênio, na estabilidade do tetraedrano, seus derivados e das reações de diels-alder e na quantificação da afinidade de fármacos

This thesis was performed in four chapters, at the theoretical level, focused mainly on electronic density. In the first chapter, we have applied an undergraduate minicourse of Diels-Alder reaction in Federal University of Rio Grande do Norte. By using computational chemistry tools students could build the knowledge by themselves and they could associate important aspects of physical-chemistry with Organic Chemistry. In the second chapter, we studied a new type of chemical bond between a pair of identical or similar hydrogen atoms that are close to electrical neutrality, known as hydrogen-hydrogen (H-H) bond. In this study performed with complexed alkanes, provides new and important information about their stability involving this type of interaction. We show that the H-H bond playing a secondary role in the stability of branched alkanes in comparison with linear or less branched isomers. In the third chapter, we study the electronic structure and the stability of tetrahedrane, substituted tetrahedranes and silicon and germanium parents, it was evaluated the substituent effect on the carbon cage in the tetrahedrane derivatives and the results indicate that stronger electron withdrawing groups (EWG) makes the tetrahedrane cage slightly unstable while slight EWG causes a greater instability in the tetrahedrane cage. We showed that the sigma aromaticity EWG and electron donating groups (EDG) results in decrease and increase, respectively, of NICS and D3BIA aromaticity indices. In addition, another factor can be utilized to explain the stability of tetra-tert-butyltetrahedrane as well as HH bond. GVB and ADMP were also used to explain the stability effect of the substituents bonded to the carbon of the tetrahedrane cage. In the fourth chapter, we performed a theoretical investigation of the inhibitory effect of the drug abiraterone (ABE), used in the prostate cancer treatment as CYP17 inhibitor, comparing the interaction energies and electron density of the ABE with the natural substrate, pregnenolone (PREG). Molecular dynamics and docking were used to obtain the CYP1ABE and CYP17-PREG complexes. From molecular dynamics was obtained that the ABE has higher diffusion trend water CYP17 binding site compared to the PREG. With the ONIOM (B3LYP:AMBER) method, we find that the interaction electronic energy of ABE is 21.38 kcal mol-1 more stable than PREG. The results obtained by QTAIM indicate that such stability is due a higher electronic density of interactions between ABE and CYP17

Estudo da evolução das tensões residuais através da difratometria de raios x em aço rolamento submetido a esforços cíclicos

The micro-deformations caused by cyclic loading origins the variation of the distances between atoms of the crystal lattice producing the irreversible component. In order to study and understand the microstructural behavior of the material this paper investigated the influence suffered by residual stresses in thrust rolling bearing races fabricated in AISI 52100 steel, after tests by cyclic rolling contact in a tribometer at 1m/s under two contact pressures (500 MPa and 1400 MPa) in dry and boundary lubrication conditions. Procedures of tests thermo-acustically isolated were developed for monitoring the contact temperature and sound pressure level signals to establish a comparison between the residual stress measurements, micro-hardness Vickers and micrographic registers searching an indication of wear evolution. The sin²ψ method by X-ray diffraction technique was used to quantify the residual stresses. Three raceway zones were selected for the evaluation of wear and surface morphology after predetermined cycling, comparing with their new condition ("as received"). Micro-hardness and residual stress measurements showed significant changes after the tests and it was possible to observe the relationship between the increase of sound pressure level and the residual stress for dry and lubricated conditions.

Estudo da evolução das tensões residuais através da difratometria de raios x em aço rolamento submetido a esforços cíclicos

The micro-deformations caused by cyclic loading origins the variation of the distances between atoms of the crystal lattice producing the irreversible component. In order to study and understand the microstructural behavior of the material this paper investigated the influence suffered by residual stresses in thrust rolling bearing races fabricated in AISI 52100 steel, after tests by cyclic rolling contact in a tribometer at 1m/s under two contact pressures (500 MPa and 1400 MPa) in dry and boundary lubrication conditions. Procedures of tests thermo-acustically isolated were developed for monitoring the contact temperature and sound pressure level signals to establish a comparison between the residual stress measurements, micro-hardness Vickers and micrographic registers searching an indication of wear evolution. The sin²ψ method by X-ray diffraction technique was used to quantify the residual stresses. Three raceway zones were selected for the evaluation of wear and surface morphology after predetermined cycling, comparing with their new condition ("as received"). Micro-hardness and residual stress measurements showed significant changes after the tests and it was possible to observe the relationship between the increase of sound pressure level and the residual stress for dry and lubricated conditions.

Estudo teórico das propriedades eletrônicas e termodinâmicas de nanofitas quasiperiódicas BCN

Nanoscale materials composed of boron, nitrogen, and carbon have unique properties and may be useful in new technologies. In this thesis, we investigate some properties of BCN nanoribbons constructed according to the Fibonacci quasiperiodic sequence. We analyze properties such as structural stability, electronic density of states, electronic specific heat, band structure, and energy band gap. We have performed first-principles calculations based on density functional theory implemented in the SIESTA code. The results showed that nanoribbons present a fixed value of the formation energy. The electronic density of states was used to calculate the specific heat. We found an oscillatory behavior of the electronic specific heat, in the low temperature regime. We analyze the electronic band structure to determine the energy band gap. The energy band gap oscillates as a function of the Fibonacci generation index n. Our work suggest that appropriate choice of the building block materials of the quasiperiodic sequence, may lead to a tuneable band gap of the quasiperiodic nanoribbons.

O Ensino de ligações químicas por meio do conceito de energia: uma proposta didática para o ensino médio

This work presents discussions on the teaching of Chemical Bonds in high school and some implications of this approach in learning chemistry by students. In general, understanding how the chemicals combine to form substances and compounds, it is a key point for understanding the properties of substances and their structure. In this sense, the chemical bonds represent an extremely important issue, and their knowledge is essential for a better understanding of the changes occurring in our world. Despite these findings, it is observed that the way in which this concept is discussed in chemistry class has contributed, paradoxically, to the emergence of several alternative designs, making the understanding of the subject by students. It is believed that one of the explanations for these observations is the exclusive use of the "octet rule" as an explanatory model for the Chemical Bonds. The use of such a model over time eventually replace chemical principles that gave rise to it, transforming knowledge into a series of uninteresting rituals and even confusing for students. Based on these findings, it is deemed necessary a reformulation in the way to approach this content in the classroom, taking into account especially the fact that the explanations of the formation of substances should be based on the energy concept, which is fundamental to understanding how atoms combine. Thus, the main question of the survey and described here of the following question: Can the development of an explanatory model for the Chemical Bonds in high school based on the concept of energy and without the need to use the "octet rule"? Based on the concepts and methodologies of modeling activity, we sought the development of a teaching model was made through Teaching Units designed to give subsidies to high school teachers to address the chemical bonds through the concept of energy. Through this work it is intended to make the process of teaching and learning of Chemical Bonds content becomes more meaningful to students, developing models that contribute to the learning of this and hence other basic fundamentals of chemistry.

O Ensino de ligações químicas por meio do conceito de energia: uma proposta didática para o ensino médio

This work presents discussions on the teaching of Chemical Bonds in high school and some implications of this approach in learning chemistry by students. In general, understanding how the chemicals combine to form substances and compounds, it is a key point for understanding the properties of substances and their structure. In this sense, the chemical bonds represent an extremely important issue, and their knowledge is essential for a better understanding of the changes occurring in our world. Despite these findings, it is observed that the way in which this concept is discussed in chemistry class has contributed, paradoxically, to the emergence of several alternative designs, making the understanding of the subject by students. It is believed that one of the explanations for these observations is the exclusive use of the "octet rule" as an explanatory model for the Chemical Bonds. The use of such a model over time eventually replace chemical principles that gave rise to it, transforming knowledge into a series of uninteresting rituals and even confusing for students. Based on these findings, it is deemed necessary a reformulation in the way to approach this content in the classroom, taking into account especially the fact that the explanations of the formation of substances should be based on the energy concept, which is fundamental to understanding how atoms combine. Thus, the main question of the survey and described here of the following question: Can the development of an explanatory model for the Chemical Bonds in high school based on the concept of energy and without the need to use the "octet rule"? Based on the concepts and methodologies of modeling activity, we sought the development of a teaching model was made through Teaching Units designed to give subsidies to high school teachers to address the chemical bonds through the concept of energy. Through this work it is intended to make the process of teaching and learning of Chemical Bonds content becomes more meaningful to students, developing models that contribute to the learning of this and hence other basic fundamentals of chemistry.

La poesía social de Juan L. Ortiz (1936-1946)

En 1943, y de manera concluyente, Alvaro Yunque incluyó a Juan L. Ortiz en el selecto y reducido grupo de "Poetas Comunistas" que coronan los dos tomos de la antología Poetas sociales de la Argentina. Dicha ubicación representa un hito en la trayectoria de la figura y de la obra de Ortiz dentro de la sociabilidad comunista, y supone un contraste no solo con la imagen que se tiene hoy de él (un poeta aislado en su comarca, en las riberas entrerrianas) sino con los signos propios de su escritura evanescente y simbolista. El primer capítulo de esta tesis, «Juan L. Ortiz y el comunismo criollo», incluye una exhaustiva revisión de publicaciones y testimonios tendientes a conformar un cuerpo documental que acredite dicho vínculo. Representa, a su vez, un ajuste no sólo en relación a su imagen de poeta, sino también a la circulación de sus poemas en el período. El capítulo que le sigue, «La poesía social de Juan L. Ortiz», da cuenta de los nuevos horizontes que abre esta perspectiva y coloca su obra -específicamente la escrita entre los años 1936 y 1946- en relación con la tradición de la poesía social en argentina, y, de manera puntual, con la tradición de los escritores e intelectuales vinculados al Partido Comunista Argentino, especialmente con los poetas José Portogalo, José Pedroni, Luis Gudiño Kramer, Emma Barrandeguy, Amaro Villanueva y Raúl González Tuñón, y con la producción crítica de Alvaro Yunque y Héctor Pablo Agosti

La poesía social de Juan L. Ortiz (1936-1946)

En 1943, y de manera concluyente, Alvaro Yunque incluyó a Juan L. Ortiz en el selecto y reducido grupo de "Poetas Comunistas" que coronan los dos tomos de la antología Poetas sociales de la Argentina. Dicha ubicación representa un hito en la trayectoria de la figura y de la obra de Ortiz dentro de la sociabilidad comunista, y supone un contraste no solo con la imagen que se tiene hoy de él (un poeta aislado en su comarca, en las riberas entrerrianas) sino con los signos propios de su escritura evanescente y simbolista. El primer capítulo de esta tesis, «Juan L. Ortiz y el comunismo criollo», incluye una exhaustiva revisión de publicaciones y testimonios tendientes a conformar un cuerpo documental que acredite dicho vínculo. Representa, a su vez, un ajuste no sólo en relación a su imagen de poeta, sino también a la circulación de sus poemas en el período. El capítulo que le sigue, «La poesía social de Juan L. Ortiz», da cuenta de los nuevos horizontes que abre esta perspectiva y coloca su obra -específicamente la escrita entre los años 1936 y 1946- en relación con la tradición de la poesía social en argentina, y, de manera puntual, con la tradición de los escritores e intelectuales vinculados al Partido Comunista Argentino, especialmente con los poetas José Portogalo, José Pedroni, Luis Gudiño Kramer, Emma Barrandeguy, Amaro Villanueva y Raúl González Tuñón, y con la producción crítica de Alvaro Yunque y Héctor Pablo Agosti

La poesía social de Juan L. Ortiz (1936-1946)

En 1943, y de manera concluyente, Alvaro Yunque incluyó a Juan L. Ortiz en el selecto y reducido grupo de "Poetas Comunistas" que coronan los dos tomos de la antología Poetas sociales de la Argentina. Dicha ubicación representa un hito en la trayectoria de la figura y de la obra de Ortiz dentro de la sociabilidad comunista, y supone un contraste no solo con la imagen que se tiene hoy de él (un poeta aislado en su comarca, en las riberas entrerrianas) sino con los signos propios de su escritura evanescente y simbolista. El primer capítulo de esta tesis, «Juan L. Ortiz y el comunismo criollo», incluye una exhaustiva revisión de publicaciones y testimonios tendientes a conformar un cuerpo documental que acredite dicho vínculo. Representa, a su vez, un ajuste no sólo en relación a su imagen de poeta, sino también a la circulación de sus poemas en el período. El capítulo que le sigue, «La poesía social de Juan L. Ortiz», da cuenta de los nuevos horizontes que abre esta perspectiva y coloca su obra -específicamente la escrita entre los años 1936 y 1946- en relación con la tradición de la poesía social en argentina, y, de manera puntual, con la tradición de los escritores e intelectuales vinculados al Partido Comunista Argentino, especialmente con los poetas José Portogalo, José Pedroni, Luis Gudiño Kramer, Emma Barrandeguy, Amaro Villanueva y Raúl González Tuñón, y con la producción crítica de Alvaro Yunque y Héctor Pablo Agosti

Time beyond clock: time use-surveys revisited

Time use surveys -despite having represented a turning point in the study of inequalities between women and men- continue hiding care times and subtracting relevance to the qualitative dimensions of time. This due both, to the ideological conception that lies behind this type of studies that consider more relevant market process as to surveys methodology. This article analyzes the theoretical model that lies behind time use surveys and, consequently, the study of the conceptual aspects, the methodology and the potential of these surveys as an analytical instrument. The aim is to unraveling the limitations presented by the surveys to take in account the subjective dimensions of time related to the wellbeing of  people.

Facultad por Facultad. Origen familiar y empleo de los licenciados en CCSS y Humanidades de la UCM en el año 2003

Muchos estudios encuentran un efecto del origen social sobre la ocupación y el salario incluso tras controlar la educación. Este efecto, que suele ser pequeño, puede ser un artificio resultante del deficiente control de la educación. Este trabajo examina la importancia de controlar en detalle la educación desagregando las carreras universitarias. Estudiamos el clasismo del mercado de trabajo para una promoción de titulados en Ciencias Sociales y Humanidades de la Universidad Complutense de Madrid (UCM) en los seis años entre su graduación en 1997 y 2003. Esta es la fecha de la encuesta gracias a la cual podemos medir la influencia del status social de los padres sobre las oportunidades de empleo de los hijos no con título universitario en general, sino con el mismo título universitario. Encontramos que la influencia del origen social sobre la clase profesional y los ingresos disminuye mucho cuando se controlan las titulaciones, y que no se observa en la mayor parte de ellas, pero sí en algunas, en concreto Políticas y Sociología y Económicas. Esta concreción allana el camino para investigar las vías por las que esta influencia se produce.

Enigmas monetarios en el derecho local. Los mencales y maravedís en los fueros castellanos

La historia de la moneda en la Castilla medieval ha estado siempre mediatizada por la convivencia no siempre armónica entre dos sistemas monetarios muy diferentes. Uno basado en la plata, de origen europeo, otro centrado en el oro, de raíces árabes. La necesidad de conectar y de establecer unas equivalencias entre ellos se convirtió pronto en una necesidad, máxime cuando las monedas de oro incrementaron sus variantes. En esta compleja situación aparecen mencales y maravedís citados conjuntamente en muchos fueros: Zorita, Uclés, Cuenca,... sin que su naturaleza quede del todo clara. Este artículo compara estas referencias y analiza las equivalencias que los unen. Como colofón al trabajo podemos afirmar que los maravedís citados en cada texto corresponden a monedas áureas de distinto peso y valor mientras el mencal es identificado con un ponderal de oro que los relaciona.

The beginning of tourism in La Palma Island: Sixty years of the XX century

The sixties was a time of great interest for tourism development on the La Palma island. Various actions of public and private, as the policy of building a new airport, various tourist resorts, the tourism plan of 1968 or insular government also creating public entity "La Palma, Tourism SA” in 1969, will be the basis for future development of tourism on the island and will result push for private investment in this economic sector. Indeed, in the sixties, private investors had opened two hotels, while at least three others over a hundred beds each, weren´t finished.