The revolution will be tweeted : how the internet can stimulate the public exercise of freedoms

This article discusses how new technologies of communication, especially the Internet and, more specifically, social network services, can interfere in social interactions and in political relations. The main objective is to problematize the concept of public liberty and verify how the new technologies can promote the reoccupation of public spaces and the recovery of public life, in opposition to the tendency to valorize the private sphere, observed in the second half of the twentieth century. The theoretical benchmark adopted for the investigation is Hannah Arendt's theory about the exercise of fundamental political capacities in order to establish a public space of freedom, as presented in “On Revolution”. The “Praia da Estação” (“Station Beach”) case is chosen to test the hypothesis. In 2010 in the Brazilian city of Belo Horizonte, different individuals articulated a movement through blogs, Twitter and facebook, in order to protest against the Mayor’s act that banned the assembling of cultural events in one of the main public places of the city, the “Praça da Estação” (Station Square). By applying Arendt's concepts to the selected case, it is possible to demonstrate that the Internet can assume an important role against governmental arbitrariness and abuse of power, as it can stimulate the public exercise of fundamental freedoms, such as freedom of assembly and manifestation

Sistema de instrumentação mecanizada Hyflex EDM

A Endodontia é uma área em constante evolução. Consideráveis desenvolvimentos nos materiais e técnicas têm sido essenciais para o melhoramento dos resultados nos tratamentos realizados. É exemplo disso mesmo a constituição dos instrumentos Endodônticos primordiais, construídos em cordas de piano, com evolução para aço de carbono, material este que sofria corrosão provocado pelo cloro presente no hipoclorito de sódio. O aço de carbono evoluiu para aço inoxidável e deste as limas endodônticas passaram a ser feitas em níquel-titânio, conferindo-lhes melhor flexibilidade e efeito de memória de forma. Mesmo com todas estas melhorias significativas, fraturas de instrumentos e erros durante a instrumentação continuam a acontecer e com eles veio a necessidade da pesquisa de possíveis melhorias da constituição das limas em NiTi. Como resultado surgiram ligas como o M-wire, fase-R e CM-wire, criadas a partir de tratamentos térmicos, que trouxeram às limas Endodônticas maior flexibilidade e resistência à fratura que os instrumentos feitos em NiTi convencional. A mais recente evolução das limas Ni-Ti, desenvolvida pela Coltene Whaldent (Allstätten, Suiça), são as limas Hyflex EDM, limas para canais radiculares de 5ª geração. O seu processo de fabrico por eletroerosão cria uma superfície única fazendo com que estas limas sejam mais duras e resistam mais à quebra, aliado à sua alta flexibilidade. É possível assim reduzir o número de limas para a limpeza e modelagem dos canais durante os tratamentos endodônticos sem comprometer a preservação da anatomia dos canais. As limas Hyflex EDM possuem, tal como as limas Hyflex CM, o efeito de controle de memória (CM), o que confere propriedades muito similares entre os dois sistemas.Considerable research has been taken into Endodontics in order to improve materials and techniques which have been crucial to achieve better results in the performed treatments. Example of that is the constitution of ancient Endodontic instruments, made of piano strings, which evolved to carbon steel, but as corrosion occurred due to chloride present in sodium hypochlorite, there was a new evolution from carbon steel to stainless steel and thus Endodontic files began to be made of titanium nickel offering them greater flexibility and shape memory effects. Even with all these significant improvements, Endodontic instruments fracture and mistakes during instrumentation still occur, so there was the need to research for possible constitution improvements in Ni-Ti files. As a result, alloys such as M-Wire, R- Phase and CM-Wire, created from thermal treatments, appeared and brought more flexibility and fracture resistance to Endodontic files than the instruments made in conventional Ni-Ti. Hyflex EDM files, the first Endodontic instruments manufactured with EDM, for root canal 5th generation are the most recent Ni-Ti files evolution developed by Coltene Whaledent (Allstätten, Switzerland). Its manufacturing process by electro erosion creates a single surface enabling these files to be tougher and more resistant to fracture, allied to its greater flexibility. Thus, it´s possible to reduce the number of files for cleaning and shaping of canals during endodontic treatments without compromising the preservation of their autonomy. Hyflex EDM files have, such as Hyflex CM files, memory control (CM) effect, which provides very similar properties between the two systems

Hydration and interactions between C3S and C3A polymorphs in the presence of different calcium sulfates

Calcium sulfate is an important constituent in Portland cement nowadays. It is used to control the setting time of Portland cement. However, many questions about the role of calcium sulfate on the cement phases (C3A and C3S) hydration and its mechanisms persist. A critical overview of the effect of sulfates on Portland cement hydration and properties is presented here in a review manuscript form. In this sense, several knowledge gaps, such as the influence of C3S and C3A polymorphs and the calcium sulfate composition on the sulfate balance in Portland cement, were identified. To address some of the questions identified in the review three different experimental studies were executed. The first one was focused to understand how gypsum accelerates the C3S hydration and whether aluminum incorporated in its structure plays an essential role or not. The effects of gypsum on the hydration of C3S and aluminum-doped C3S (Al-C3S) hydration were assessed. Calorimetry, XRD, TGA, and 27Al and 29Si MAS-NMR were performed to analyze gypsum’s influence on the hydration of C3S and Al-C3S. The results showed that the inclusion of gypsum retarded the initial hydration (first 3 h) for both C3S and Al-C3S, due to the interaction between the sulfate ions and C3S. In contrast, gypsum enhanced the hydration of both C3S and Al-C3S afterward. This acceleration effect occurred earlier for the Al-C3S due to the removal of aluminum from the solution. However, this is not the main mechanism behind the acceleration of C3S by gypsum, which mainly results from changes in C-S-H morphology and increases in the ionic strength. Secondly, the mechanism responsible for the higher reactivity of orthorhombic C3A (ort-C3A) in sulfate-containing solutions, compared with cubic C3A (cb-C3A), which was previously related to either the difference in crystal structure or the sodium in ort-C3A pore solution were investigated. The hydration of cbC3A (in water and NaOH solution) and Na-doped ort-C3A in the presence of gypsum and hemihydrate were analyzed using isothermal calorimetry, in-situ XRD, TGA, SEM, and rheological tests. The results showed that NaOH accelerated the hydration of cb-C3A, but ortC3A still presented a higher hydration rate. Ort-C3A pastes revealed more and larger ettringite crystals at 30-120 minutes, resulting in higher viscosities and yield stresses than cb-C3A pastes. The replacement of gypsum with hemihydrate accelerated ort-C3A hydration but retarded cbC3A hydration. Overall, the higher reactivity of ort-C3A is related to differences in crystal structure rather than the sodium in pore solution. Finally, the hydration of three-phase systems (C3S-C3A-calcium sulfate) was analyzed. Two C3S (T1 pure C3S and M1 aluminum-doped C3S), two C3A polymorphs (cubic and orthorhombic), and two calcium sulfates (gypsum and hemihydrate) were evaluated. For each system, the hydration of four different SO3 contents was evaluated by calorimetry. From the calorimetry results, a 1.5 wt.% SO3 content was fixed, and the mixtures were evaluated by in-situ XRD and TGA. The C3S type was the factor that most affected the sulfate balance of the systems. The mixes with Al-C3S presented higher ettringite formation in the first hours, resulting in much earlier sulfate depletions when compared to the mixes with C3S. The mixes with ort-C3A also presented faster sulfate depletions, due to its higher reactivity compared with cb-C3A. Finally, the replacement of gypsum by hemihydrate, also resulted in faster sulfate depletions, which is the consequence of the higher solubility of hemihydrate

Semilinear fractional differential equations: global solutions, critical nonlinearities and comparison results

In this work we study several questions concerning to abstract fractional Cauchy problems of order α ∈ (0, 1). Concretely, we analyze the existence of local mild solutions for the problem, and its possible continuation to a maximal interval of existence. The case of critical nonlinearities and corresponding regular mild solutions is also studied. Finally, by establishing some general comparison results, we apply them to conclude the global well-posedness of a fractional partial differential equation coming from heat conduction theory.Conselho Nacional de Desenvolvimento Científico e TecnológicoCoordenação de aperfeiçoamento de pessoal de nivel superiorFundação de Amparo à Pesquisa do Estado de São PauloMinisterio de EducaciónMinisterio de Ciencia e InnovaciónJunta de Andalucí