Análisis de interacciones en foro y chat : consolidación de grupo y liderazgo comunicativo en un curso de lógica matemática.

Monográfico con el título: 'Web 2.0 : dispositivos móviles y abiertos para el aprendizaje'. Resumen basado en el de la publicación

Breaking down the barriers to firm growth in Europe: The fourth EFIGE policy report. Bruegel Blueprint 18, 28 August 2012

Large firms contribute disproportionately to the economic performance of countries: they are more productive, pay higher wages, enjoy higher profits and are more successful in international markets. The differences between European countries in terms of the size of their firms are stark. Firms in Italy and Spain, for example, are on average 40 percent smaller than firms in Germany. The low average firm size translates into a chronic lack of large firms. In Italy and Spain, a mere 5 percent of manufacturing firms have more than 250 employees, compared to a much higher 11 percent in Germany. Understanding the roots of these differences is key to improving the economic performance of Europe’s lagging economies. So why is there so much variation in firm size in different European countries? What are the barriers that keep firms in some countries from growing? And which policies are likely to be most effective in breaking down those barriers? This policy report aims to answer these questions by developing a quantitative model of the seven European countries covered by the EFIGE survey (Austria, France, Germany, Hungary, Italy, Spain and the UK). The EFIGE survey asked 14,444 firms in those countries about their performance, their modes of internationalisation, their staffing decisions, their financing structure, and their competitive environment, among other topics.

Temporal behaviour of toroidal rotation velocity in the TCABR tokamak

A new method for determining the temporal evolution of plasma rotation is reported in this work. The method is based upon the detection of two different portions of the spectral profile of a plasma impurity line, using a monochromator with two photomultipliers installed at the exit slits. The plasma rotation velocity is determined by the ratio of the two detected signals. The measured toroidal rotation velocities of C III (4647.4 angstrom) and C VI (5290.6 angstrom), at different radial positions in TCABR discharges, show good agreement, within experimental uncertainty, with previous results (Severo et al 2003 Nucl. Fusion 43 1047). In particular, they confirm that the plasma core rotates in the direction opposite to the plasma current, while near the plasma edge (r/a > 0.9) the rotation is in the same direction. This technique was also used to investigate the dependence of toroidal rotation on the poloidal position of gas puffing. The results show that there is no dependence for the plasma core, while for plasma edge (r/a > 0.9) some dependence is observed.

Structural Characterization of Photopolymerizable Binary Liposomes Containing Diacetylenic and Saturated Phospholipids

The use of liposomes to encapsulate materials has received widespread attention for drug delivery, transfection, diagnostic reagent, and as immunoadjuvants. Phospholipid polymers form a new class of biomaterials with many potential applications in medicine and research. Of interest are polymeric phospholipids containing a diacetylene moiety along their acyl chain since these kinds of lipids can be polymerized by Ultra-Violet (UV) irradiation to form chains of covalently linked lipids in the bilayer. In particular the diacetylenic phosphatidylcholine 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine (DC8,9PC) can form intermolecular cross-linking through the diacetylenic group to produce a conjugated polymer within the hydrocarbon region of the bilayer. As knowledge of liposome structures is certainly fundamental for system design improvement for new and better applications, this work focuses on the structural properties of polymerized DC8,9PC:1,2-dimyristoyl-sn-glycero-3-phusphocholine (DMPC) liposomes. Liposomes containing mixtures of DC8,9PC and DMPC, at different molar ratios, and exposed to different polymerization cycles, were studied through the analysis of the electron spin resonance (ESR) spectra of a spin label incorporated into the bilayer, and the calorimetric data obtained from differential scanning calorimetry (DSC) studies. Upon irradiation, if all lipids had been polymerized, no gel-fluid transition would be expected. However, even samples that went through 20 cycles of UV irradiation presented a DSC band, showing that around 80% of the DC8,9PC molecules were not polymerized. Both DSC and ESR indicated that the two different lipids scarcely mix at low temperatures, however few molecules of DMPC are present in DC8,9PC rich domains and vice versa. UV irradiation was found to affect the gel fluid transition of both DMPC and DC8,9PC rich regions, indicating the presence of polymeric units of DC8,9PC in both areas, A model explaining lipids rearrangement is proposed for this partially polymerized system.

Electrochemical method for studying localized corrosion beneath disbonded coatings under cathodic protection

This paper presents a new method for measuring localized corrosion under disbonded coatings by means of an electrochemical sensor, denoted differential aeration sensor (DAS). It measures the distribution of electrochemical currents over an electrode array surface partially covered by a crevice that simulates a disbonded coating. The DAS has been evaluated using immersion tests at open circuit and under cathodic protection (CP) conditions. Under both conditions, anodic as well as cathodic current densities were detected within the crevice. A fundamental understanding for the detection of anodic currents under CP has been explained in terms of basic electrochemistry. Based on the current distribution data provided by the sensor, two different analysis methods have been used to estimate corrosion and its distribution. These methods consisted of a direct application of Faraday's Law to the anodic currents detected by the array, and on a sensor-specific method denoted corrected currents' method. It has been demonstrated that under diffusion controlled conditions this latter method produces a better corrosion estimation than the direct application of Faraday's Law. The corrected currents' method allowed the estimation of corrosion patterns outside the crevice under CP. Good correlation between electrochemical calculations and surface profilometry results has been obtained.

Electrochemically monitoring localized corrosion patterns and CP effectiveness under disbonded coatings

© 2015 by Nace International. This paper presents new experimental evidences on the capability of a novel electrochemical corrosion monitoring sensor, which was recently conceived, for measuring localized corrosion under disbonded pipeline coatings. The sensor's design includes an artificial crevice for simulating the conditions developed under disbonded coatings and an electrode array for measuring current density distribution over its surface. The sensor capabilities were further evaluated by studying the dependency of corrosion patterns and current density distribution on the Cathodic Protection (CP) potential applied upon immersion in an aqueous environment. At the less negative CP potential, a good correlation was found between the inhomogeneous corrosion distribution under the disbonded coating as measured by the sensor and actual metal loss and corrosion attack observed on its surface at the end of the test. At more negative CP potentials no corrosion was detected or observed on the sensor's surface. In addition, characteristic changes in the cathodic current distribution at different CP potentials illustrated the possibility of employing the sensor to obtain valuable feedback on the performance of a given CP setup, without requiring its interruption or compensation of IR-drops. Furthermore, the sensor's capability to detect some of the effects of overprotection were shown at the most negative CP potential applied.

Traduzindo a alteridade : a questão da identidade nacional em Eduardo Acevedo Díaz e Euclides da Cunha

A presente tese intitulada Traduzindo a Alteridade: a questão da identidade nacional em Eduardo Acevedo Díaz e Euclides da Cunha tem como objetivo analisar a construção dos arquétipos nos textos Ismael e Os Sertões e de como tais tipos colaboraram para a construção do conceito de nação nas obras em questão, bem como analisar a utilização da imagem do outro nessa mesma construção. Com base na Literatura Comparada, nos Estudos de Tradução, na Teoria da Literatura e em outras áreas do conhecimento, foi possível constatar que os autores uruguaio e brasileiro se valeram da obra Facundo: civilização e barbárie no pampa argentino, de Domingo Faustino Sarmiento, para comporem suas obras, ainda que distantes temporalmente e com visões diferentes. Esse movimento mostra que as produções literárias latino-americanas possuem uma ligação porque igualmente registraram os tipos presentes no lugar e o próprio lugar em que habitavam, colaborando, assim, para a construção do sistema literário latino-americano, visto que, em alguns casos, esses arquétipos eram comuns entre os diferentes países. A convergência desses arquétipos, como o gaúcho/gaucho do pampa do Rio Grande do Sul do Brasil, do Uruguai e da Argentina, demonstra que a cultura ultrapassa fronteiras políticas, e corrobora a idéia de Ángel Rama acerca da existência da comarca cultural. No caso do arquétipo do sertanejo, fundamentado por Euclides da Cunha, não há um correspondente nas demais produções em questão, principalmente porque sua identidade está impregnada de cor local, cujas particularidades não são compartilhadas pelos demais países. A convergência ou divergência das características de cada tipo local interfere na produção das traduções, uma vez que, quando dessemelhantes, a visibilidade do tradutor é necessária e sua interferência acontece no sentido de aproximar o diferente da cultura alvo. Também os Estudos de Tradução e as análises tradutórias colaboraram igualmente para que as investigações acerca das obras evoluíssem no sentido de estudarmos como se deu, na escrita dos autores e dos tradutores, a consciência do outro no processo de construção do eu nacional.

Abordando as relações ctsa no ensino da química a partir das crenças e atitudes de licenciandos: uma experiência ormativa no Sertão Nordestino

Este estudio investigó las actitudes y creencias de los estudiantes universitarios en Ciencias Químicas por la Universidad de Río Grande do Norte (UERN) como un paso hacia la elaboración de una propuesta de material didáctico para el estudio de las relaciones CTSA en la licenciatura en química. Para el conocimiento de las actitudes y creencias fue utilizado dos instrumentos (Escala Likert y un cuestionario), que proporcionó un análisis dentro del nuevo paradigma de investigación (cuantitativa y cualitativa) en la Enseñanza de la Ciencia y Matemáticas. Los resultados mostraron que los estudiantes de licenciatura en química tienen creencias positivistas y que suelen son considerados por algunos como ingenuas, como la creencia en el modelo de decisión tecnocrática, la linealidad del desarrollo científico y tecnológico que lleva a el bienestar social y neutralidad de los conocimientos científicotecnológico. Basándose en estos datos y la literatura sobre el tema se elaboraron tres módulos de aprendizaje: a) Cuestionando la hegemonía del conocimiento técnico y científico, b) Las relaciones entre ciencia, tecnología, sociedad y medio ambiente - las relaciones CTSA c) Propuesta de temática para la enseñanza de la química en una perspectiva de CTSA: El Río Mossoró. Por último, el material producido se utilizó en dos cursos ocurridos en el Campus Central en el Centro de Educación Superior en São Miguel, ambos de UERN. Los participantes expresaron su aprobación al enfoque trajo de el experimento propuesto y de el caso de simulación contenidos en la propuesta de

Análise das provas objetivas de química dos vestibulares da UFRN de 1997 a 2010: uma caracterização a partir das mudanças

Las pruebas de vestibular, en los últimos años en el Brasil, han sido objeto de diversas investigaciones, considerando que ese proceso selectivo es una de las vias para ingresar en las universidades públicas y termina por influenciar la enseñanza en las escuelas. De esa forma, algunos vestibulares han pasado por cambios, de un simple proceso selectivo clasificatorio a un proceso fundamentado en reflexiones sociológica, pedagógica y crítica, lo que ha promovido cuestionamientos respecto del aprendizaje y de su papel en la escuela. Delante de esa realidad, la Universidad Federal de Rio Grande del Norte (UFRN) ha implementado cambios en sus vestibulares procurando una aproximación a las Orientaciones Curriculares Nacionales, como los PCNEM, los PCN+ y las OCEM. Siendo así, el objetivo de este estudio fue caracterizar el avance cualitativo en las pruebas de preguntas objetivas a partir de los cambios ocurridos en el vestibular de la UFRN en el periodo de 1997 a 2010, definiéndose las siguientes cuestiones de estudio: ¿Cuáles son los tipos de preguntas que caracterizan las pruebas objetivas de Química del vestibular? ¿Cuáles cuestiones presentan las mayores dificultades para los candidatos? ¿Cuáles son los contenidos conceptuales privilegiados? ¿En qué tipo de preguntas los candidatos presentan mayores índices de éxitos? ¿Qué diferencias pueden ser establecidas entre las preguntas antes y después del periodo que establece los cambios en el vestibular de la UFRN? Las discusiones teóricas del estudio están fundamentadas en las siguientes referencias: PCNEM (BRASIL, 1999), PCN+ (BRASIL, 2001), OCEM (BRASIL, 2006), Zabala (1999), Jiménez Aleixandre et al. (2003), Pozo (1999), Álvarez de Zayas (1992), Núñez (2009), Relatorios Comperve/UFRN (1997 a 2010), e en relación a las evaluaciones: Pasquali et al. (2003), Silva y Núñez (2008), Marín y Benarrouch (2009). Para el estudio fueran construidas las siguientes categorías que permitieran el análisis de las cuestiones: contextualización de la cuestión, temas conceptuales, problema, representación semiótica, cálculo matemático, pertinencia de la cuestión e índice de acierto. Los resultados muestran un avance cualitativo de las preguntas de Química, en los cuales se observa un modelo de prueba que prioriza el uso de verdaderos problemas, de situaciones contextualizadas, de pocos cálculos, dándose prioridad al razonamiento que implica la comprensión, la aplicación y la interpretación de los conocimientos conceptuales, todo lo que puede estimular una enseñanza más adecuada en relación a las exigencias actuales de la Educación en Química

Natural Polysaccharides as Active Biomaterials in Nanostructured Films for Sensing

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nanocompósitos eletroativos de poli-o-metoxianilina e polissacarídeos naturais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de um novo complexo macrocíclico do sistema cobalto cyclam

In this work were synthesized and studied the spectroscopic and electrochemical characteristics of the coordination compounds trans-[Co (cyclam)Cl2]Cl, trans- Na[Co(cyclam)(tios)2], trans-[Co(en)2Cl2]Cl and trans-Na[Co(en)2(tios)2], where tios = thiosulfate and en = ethylenediamine. The compounds were characterized by: Elemental Analysis (CHN), Absorption Spectroscopy in the Infrared (IR), Uv-Visible Absorption Spectroscopy, Luminescence Spectroscopy and Electrochemistry (cyclic voltammetry). Elemental Analysis (CHN) suggests the following structures for the complex: trans- [Co(cyclam)Cl2]Cl.6H2O and trans-Na[Co(cyclam)(tios)2].7H2O. The electrochemical analysis, when compared the cathodic potential (Ec) processes of the complexes trans- [Co(cyclam)Cl2]Cl and trans-[Co(en)2Cl2]Cl, indicated a more negative value (-655 mV) for the second complex, suggesting a greater electron donation to the metal center in this complex which can be attributed to a greater proximity of the nitrogen atoms of ethylenediamine in relation to metal-nitrogen cyclam. Due to the effect of setting macrocyclic ring to the metal center, the metal-nitrogen bound in the cyclam are not as close as the ethylenediamine, this fact became these two ligands different. Similar behavior is also observed for complexes in which the chlorides are replaced by thiosulfate ligand, trans-Na[Co(en)2(tios)2] (-640 mV) and trans-Na[Co(cyclam)(tios)2] (-376 mV). In absorption spectroscopy in the UV-visible, there is the band of charge transfer LMCT (ligand p d* the metal) in the trans-Na[Co(cyclam)(tios)2] (350 nm, p tios  d* Co3+) and in the trans-Na[Co(en)2(tios)2] (333 nm, p tios d* Co3+), that present higher wavelength compared to complex precursor trans- [Co(cyclam)Cl2]Cl (318 nm, pCl  d* Co3+), indicating a facility of electron density transfer for the metal in the complex with the thiosulfate ligand. The infrared analysis showed the coordination of the thiosulfate ligand to the metal by bands in the region (620-635 cm-1), features that prove the monodentate coordination via the sulfur atom. The νN-H bands of the complexes with ethylenediamine are (3283 and 3267 cm-1) and the complex with cyclam bands are (3213 and 3133 cm-1). The luminescence spectrum of the trans-Na[Co(cyclam)(tios)2] present charge transfer band at 397 nm and bands dd at 438, 450, 467, 481 and 492 nm.

Uso do pó da palha de carnaúba em compósitos de quitosana

In this work a biodegradable composite using the carnauba straw s powder as reinforcement on chitosan matrix polymeric were manufactured. Firstly, were carried out the chemistry characterization of the carnauba straw s powder before and after treatments with NaOH and hexane. Goering and Van Soest method (1970), flotation test, moisture absorption, FTIR, TG/DTG, DSC and SEM have also being carried out. Composites were developed with variations in granulometry and in powder concentrations. They were characterized by TG/DTG, SEM and mechanicals properties. The results of chemical composition showed that the carnauba straw s powder is composed of 41% of cellulose; 28,9% of hemicellulose and 14% of lignin.The flotation test have indicated that the chemical treatment with NaOH decreased the powder s hidrophilicity.The thermal analysis showed increased of thermal stability of material after treatments. The results of FTIR and SEM revealed the removal of soluble materials from the powder (hemicelluloses and lignin), the material became rougher and clean. The composites obtained showed that the mechanicals properties of the composites were decreased in respect at chitosan films, and the composites with the powder at 150 Mesh showed less variation in the modulus values. The speed test of 10 mm/min showed the better reproducibility of the results and is in agreement to the standard ASTM D638. The SEM analysis of fracture showed the low adhesion between the fiber/matrix. The increase of volume of powder in the composite caused a decrease in values of stress and strain for the samples with untreated powder and treated with hexane. The composite with 50% of the powder s treated in NaOH didn t have significant variation in the values of stress and strain as compared with the composites with 10% of the powder, showing that the increase in the volume of fiber didn t affect the stress and strain of the composite. Thereby, it is concluded that the manufacture of polymeric composites of chitosan using carnauba straw s powder can be done, without need for pre-treatment of reinforcement, become the couple of carnauba straw s powder-chitosan a good alternative for biodegradable composites

Estudo do equilíbrio e cinética de adsorção de um corante aniônico em quitosana

The phenomenon of adsorption is of fundamental importance for the treatment of textile effluents and removal of dyes. Chitosan is characterized as an excellent adsorbent material, not only for its adsorption capacity but also the low cost production. Equilibrium and kinetic studies were developed in this study to describe the mechanism of adsorption of the anionic azo dye Orange G in chitosan, with the isotherms obtained from the variation of the concentration of dye in the continuous phase. The kinetics of the process was analyzed based on models involving the adsorption of molecules of the dye in nonpolar and polar sites. Adsorption experiments were carried out in water and in saline media with different NaCl concentrations, both for the determination of the equilibrium time as isotherms for making kinetic curves in which the amount of dye adsorbed measured indirectly varied with time. The experiments revealed the opening of the biopolymer structure with increasing concentration of Orange G, accompanied by high pH values and change on the type of interaction between the dye and the adsorbent surface, suggesting behavior advocated by the Langmuir equation in a certain range of concentration of the adsorbate and following the Henry's Law at higher concentrations, from the increased number of sites available for adsorption. The studies conducted showed that the saline medium reduces the chitosan s adsorption capacity according to a certain concentration, the occurrence of the cooperative adsorption process steps kinetic mechanism suggested as a new alternative for the interpretation of the phenomenon

Problemas de aprendizagem sobre ligações químicas para estudantes de graduação

This research aims at identifying the learning problems in newly undergraduate students at university, interpreting the nature and causes of these problems, offering subsidies to overcome these difficulties and enabling a meaningful learning through which students give meaning to their learning. As an object for this work was chosen the theme Chemical Bonds - where were studied the forces between atoms to form molecules, compound ions and ionic crystalline structures - and is characterized as one of the most important subjects of Chemistry. In research, it was used a questionnaire with five open questions, answered by 147 students from the early periods of degrees in Chemistry at Universidade Federal do f Rio Grande do Norte. The answers revealed uncertainty on the part of students, both conceptual and representation, with superficial justifications, always using the octet rule to describe models of chemical bonds. Results suggest that these students had inadequate training in high school and that the examinations for entrance into the ranks were made according to flexible criteria less demanding in terms of knowledge. These observations have led to the conclusion that for future changes, it is necessary for high schools and in the early periods in universities favoring the adoption of pedagogical approaches in context and applying strategies to overcome the teaching of superficial memorization on Chemical Bonds, which probably have applied to the teaching of other subjects of chemistry