Redes neurais e suas aplicações em calibração multivariada

Neural Networks are a set of mathematical methods and computer programs designed to simulate the information process and the knowledge acquisition of the human brain. In last years its application in chemistry is increasing significantly, due the special characteristics for model complex systems. The basic principles of two types of neural networks, the multi-layer perceptrons and radial basis functions, are introduced, as well as, a pruning approach to architecture optimization. Two analytical applications based on near infrared spectroscopy are presented, the first one for determination of nitrogen content in wheat leaves using multi-layer perceptrons networks and second one for determination of BRIX in sugar cane juices using radial basis functions networks.

Estudo do estado fundamental de aglomerados de silício via redes neurais

We introduce a global optimization method based on the cooperation between an Artificial Neural Net (ANN) and Genetic Algorithm (GA). We have used ANN to select the initial population for the GA. We have tested the new method to predict the ground-state geometry of silicon clusters. We have described the clusters as a piling of plane structures. We have trained three ANN architectures and compared their results with those of pure GA. ANN strongly reduces the total computational time. For Si10, it gained a factor of 5 in search speed. This method can be easily extended to other optimization problems.

Anestésicos locais: interação com membranas de eritrócitos de sangue humano, estudada por ressonância magnética nuclear de ¹H e 31P

The literature carries many theories about the mechanism of action of local anesthetics (LA). We can highlight those focusing the direct effect of LA on the sodium channel protein and the ones that consider the interaction of anesthetic molecules with the lipid membrane phase. The interaction between local anesthetics and human erythrocyte membranes has been studied by ¹H and 31P nuclear magnetic resonance spectroscopy. It was found that lidocaine (LDC) and benzocaine (BZC) bind to the membranes, increase the mobility of the protons of the phospholipid's acyl chains, and decrease the mobility and/or change the structure of the polar head groups. The results indicate that lidocaine molecules are inserted across the polar and liquid interface of the membrane, establishing both electrostatic (charged form) and hydrophobic (neutral form) interactions. Benzocaine locates itself a little deeper in the bilayer, between the interfacial glycerol region and the hydrophobic core. These changes in mobility or conformation of membrane lipids could affect the Na+-channel protein insertion in the bilayer, stabilizing it in the inactivated state, thus causing anesthesia.

Parentesco, redes familiares y sociabilidad en el mundo hispanoamericano en los siglos XVII y XIX

Hasta hace algunos años, el interés por la historia de la familia, aunque no era escaso, estaba orientado a enfoques de tipo macrohistórico, ya que el énfasis estaba puesto en las estructuras de la sociedad. La dominación de los planteamientos cuantitativistas impuestos por los Annales, así como la fuerte influencia del marxismo, coadyuvaron en la consideración de la familia, no como objeto de investigación en sí misma, sino como expresión o ilustración de un funcionamiento económico social global. Los numerosos y excelentes trabajos sobre la élite colonial americana ejemplifican esta clase de acercamiento, fundamentado a partir de una reflexión acerca de los grupos sociales definidos en base a criterios socio-económicos. De la misma marreta, si la familia servia de base a los estudios de demografía histórica,lo que se pretendía a través de ella era la deconstrucción de modelos de comportamiento demográfico para un espacio definido. Fuera de estos planteos con sesgos estructuralistas y funcionalistas, la historia de la familia fue el refugio de la historiografia más tradicional y a veces rancia, fundada muchas veces en la aplicación de la reconstrucción genealógica como único método de estudio de los sectotes sociales más poderosos a nivel económico o político.

Desempenho físico-químico de metais e estruturas de concreto de redes de distribuição de energia: estudo de caso na região de Manaus

The influence of natural aging furthered by atmospheric corrosion of parts of electric transformers and materials, as well as of concrete poles and cross arms containing corrosion inhibitors was evaluated in Manaus. Results for painted materials, it could showed that loss of specular gloss was more intensive in aliphatic polyurethane points than in acrylic polyurethane ones. No corrosion was observed for metal and concrete samples until 400 days of natural aging. Corrosion in steel reinforcement was noticed in some poles, arising from manufacturing faults, such as low cement content, water/cement ratio, thin concrete cover thickness, etc. The performance of corrosion inhibitors was assessed by many techniques after natural and accelerated aging in a 3.5% saline aqueous solution. The results show the need for better chemical component selection and its concentration in the concrete mixture.

Convergencia de Servicios en redes de próxima generación

Descripción de la realidad que acompaña a la industria de las telecomunicaciones

Redes de acción : el caso de Birmania

El objetivo del presente ensayo es analizar el papel de las nuevas tecnologías en la formación de redes de acción. Para ello, comenzaré analizando brevemente ciertos puntos y características de las redes de acción y sus tipos, para a continuación, centrar el análisis en un caso real y de ardiente actualidad, como es el caso de Birmania.Una red de acción es un sistema que interconecta nodos. Estos nodos son autónomos y autoorganizados, de manera que cada uno de ellos aporta información y la red se encarga de intercambiar dicha información proveniente de los distintos nodos, así como proyectarla hacia espacios mayores de interacción. Por lo tanto, una red es un sistema exógeno, en la medida que trabaja en la búsqueda constante de interacciones e intercambios mas allá de sus propias fronteras. Las redes responden a la necesidad de conversar con otros para producir acuerdos, arreglos y consensos. Por lo que la red precisa de la polivalencia y la capacidad de adquirir nuevas competencias, por parte de los sujetos que la forman.

Preparação e caracterização físico-química de complexos de inclusão entre anestésicos locais e hidroxipropil-beta-ciclodextrina

S(-) Bupivacaine (S(-)BVC) and Lidocaine (LDC) are widely used local anesthetics (LA). Hydroxypropyl beta-cyclodextrin (HP-beta-CD) is used as a drug-carrier system. The aim of this work was to characterize inclusion complexes between LA and HP-beta-CD. The affinity constants determined at different pHs show favourable complexation. The release kinetics experiments showed that S(-)BVC and LDC changed the released profiles in the presence of HP-beta-CD. Nuclear magnetic resonance experiments gave information about the interaction between LA and the cyclodextrin cavity. This study focused on the physicochemical characterization of drug-delivery formulations that come out as potentially new therapeutic options for pain treatment.

Parentesco, redes familiares y sociabilidad en el mundo hispanoamericano en los siglos XVIII y XIX

Hasta hace algunos años, el interés por la historia de la familia, aunque no era escaso, estaba orientado a enfoques de tipo macrohistórico, ya que el énfasis estaba puesto en las estructuras de la sociedad. La dominación de los planteamientos cuantitativistas impuestos por los Annales, así como la fuerte influencia del marxismo, coadyuvaron en la consideración de la familia, fio como objeto de investigación en sí misma, sino como expresión o ilustración de un funcionamiento económico social global.

Utilização de solos locais para tratamento de efluentes do refino de petróleo contendo metais

The employment of local soils for extraction of metallic elements was evaluated through batch tests to treat wastewaters generated in a petroleum refinery plant in southern Brazil. Clay and organic carbon content and clay mineralogy provide these soils, in principle, with moderate metal retention capacity. The following retention order was established: Cr3+ > Pb2+ > Cu2+ > Hg2+ > Cd2+, with total amount of metals retained varying from 36 to 65 meq kg-1. The results show the high efficiency of local soils for extracting metals from liquid effluents through sorption and precipitation processes under acid pH conditions.

Principais carbonilas no ar de locais públicos no Rio de Janeiro

An air quality evaluation of indoor environments with focus on lower carbonyls was carried out in 50 public places using TO-11A methodology. Formaldehyde levels (ranging from 12.5 to 1034 mg m-3) were above the threshold limit in 49 of 50 analyzed samples while acetaldehyde (ranging from 5.2 to 840 mg m-3) and acetone (ranging from 5.5 to 4839 mg m-3) were respectively bellow the limits of OSHA and NIOSH in all samples. However all samples were bellow the threshold limits suggested by the Brazilian legislation - NR-15. A correlation study between the carbonyls and temperature and humidity was also done.

Las redes de innovación docente de la Universitat de Girona : la perspectiva de los coordinadores

In 2009 the University of Girona (Spain) created four interest groups on teaching innovation. The objective of the project is that lecturers with an interest in teaching innovation can exchange their points of view and learn from one another, so University teaching is improved as a result. There are four such groups: “Problem based learning (ABP)”, “Cooperative learning”, “Evaluation”, and “Information and Communication Technologies (ICTs) and Teaching”. The coordinators of the groups or networks, as they are also called, are chosen on a free basis by its members. This paper presents their point of view as regards the current activity of encouragement of interest in higher education and they elaborate on the main difficulties involved. The implications of the interdisciplinary work are explored, as well as the challenges of an initiative of this kind. The evolution of the ongoing work is reviewed, taking into account the context of a changing University, the lack of previous experience regarding projects of this kind, the asynchronous communication among the participants, and the necessity of a flexible approach in organizational matters

A tabela periódica dos elementos químicos prevista por redes neurais artificiais de Kohonen

Although several chemical elements were not known by end of the 18th century, Mendeleyev came up with an astonishing achievement: the periodic table of elements. He was not only able to predict the existence of (then) new elements but also to provide accurate estimates of their chemical and physical properties. This is certainly a relevant example of the human intelligence. Here, we intend to shed some light on the following question: Can an artificial intelligence system yield a classification of the elements that resembles, in some sense, the periodic table? To achieve our goal, we have fed a self-organized map (SOM) with information available at Mendeleyev's time. Our results show that similar elements tend to form individual clusters. Thus, SOM generates clusters of halogens, alkaline metals and transition metals that show a similarity with the periodic table of elements.