Direito como efetividade e luta pela terra no Brasil

Tese (doutorado)—Universidade de Brasília, Faculdade de Direito, Programa de Pós-Graduação em Direito, 2016.

Síntesis, caracterización, propiedades eléctricas y electroquímicas de Na₃V₂-xAlx(PO₄)2F₃ (x=0,0.02, 0.05, 0.1) como cátodos para su aplicación en baterías de ion-litio

Propósito y Método del Estudio: La demanda de baterías recargables ha aumentado de manera significativa cada año durante la última década impulsada por las necesidades vinculadas con el desarrollo tecnológico (portabilidad, alto desempeño de dispositivos electrónicos, vehículos eléctricos). La batería ión-litio es el dispositivo de mayor consumo, está diseñado para el almacenamiento y conversión de energía eléctrica basado en electrodos de intercalación. En la actualidad los esfuerzos están dirigidos a la mejora y/o remplazo de los componentes actuales de las baterías: ánodo, cátodo (LiCoO2) y electrolito, por materiales que tengan más altos rendimientos en términos de energía, potencia, costo, confiabilidad, tiempo de vida y seguridad. En este trabajo de investigación se prepararon y caracterizaron cuatro compuestos Na3V2-xAlx(PO4)2F3 (x= 0, 0.02, 0.05, 0.1) como materiales catódicos para baterías ión-litio. Estos materiales se obtuvieron mediante el método Pechini. La caracterización morfológica y microestructural se llevó a cabo por Microscopia Electrónica de Barrido de Emisión de Campo (FESEM), el análisis textural por Fisisorción de N2 por la técnica BET; la composición química y cristalográfica se determinó por Espectroscopia de Emisión de Plasma de Acoplamiento Inductivo (ICP-OES), Espectroscopia de Energía Dispersiva de Rayos X (EDXS) y Difracción de Rayos X (XRD), mientras que por Espectroscopia de Impedancia Electroquímica (EIS) se realizó la caracterización eléctrica; por último la aplicación de los materiales como cátodos en baterías ión-litio se evaluó mediante pruebas Galvanostáticas de carga/descarga. Contribuciones y Conclusiones: Se establecieron las condiciones de síntesis para los materiales Na3V2-xAlx(PO4)2F3 x= 0, 0.02, 0.05 y 0.1 vía método Pechini. El dopaje de la fase Na3V2-xAlx(PO4)2F3 se llevó a cabo con éxito hasta x=0.1 moles de aluminio, dado que se conservó la estructura cristalina tetragonal del Na3V2(PO4)2F3 (JCPDS 01-089-8485). Los materiales obtenidos tienen una microestructura formada por partículas de forma granular de tamaño nanométrico (40-100nm), esto se atribuye al efecto del carbono residual en la muestra (en promedio 8% en peso) ya que inhibe el crecimiento de partícula, además que permite mejorar el contacto entre las partículas lo que beneficia a la conductividad electrónica del material. Los materiales obtenidos tienen en promedio un tamaño de poro de 20 nm, con un área superficial del orden 30 m2/g. La fase con 0.05 moles de aluminio presentó el mejor resultado bajo las condiciones de estudio. Conjuga dos de las características básicas de una batería, presenta una alta capacidad de carga/descarga (123/101 mAh/g a un voltaje de celda de 4.4 V vs Li) y una buena capacidad de retención (82%), en comparación al material sin dopar (128/63 mAh/g y 49% de retención). Por lo anterior, el dopaje de la fase Na3V2(PO4)2F3 con Al, logró la estabilización de la estructura frente a los procesos de ciclado. Por lo cual es un material prometedor para su aplicación como cátodos en baterías ión-litio o ión-sodio.

Graphene nanodots encaged 3-D gold substrate as enzyme loading platform for the fabrication of high performance biosensors

Herein, a uniform three-dimensional (3-D) graphene nanodots-encaged porous gold electrode was prepared via ion beam sputtering deposition (IBSD) and mild corrosion chemistry for efficient enzyme electrode fabrication. Enzymes, like glucose oxidase and catalase, were modified with pyrene functionalities and then loaded into the graphene nanodots encaged porous gold electrode via non-covalent π-π stacking interaction between pyrene and graphene. The fabricated enzyme electrodes showed profound reusability and repeatability, high sensitivity, inherent selectivity and enhanced detection range. As for glucose analysis a broad linear range from 0.05 to 100 mM was obtained and the linear range for hydrogen peroxide was 0.005 to 4 mM. Detection limits of 30 μM for glucose and 1 μM for hydrogen peroxide were achieved (S/N = 3), respectively. These electrodes can be applied to analyze the clinical samples with reliable results. The formation mechanism and 3-D structure of the porous electrode were investigated using high resolution transmission electron microscope (HRTEM), atomic force microscopy (AFM), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). Most importantly, various other ideal biosensors can be fabricated using the same porous electrode and the same enzyme modification methodology.

In situ measurement of pipeline coating integrity and corrosion resistance losses under simulated mechanical strains and cathodic protection

A novel experimental assembly consisting of a specially designed tensile testing rig and a standard electrochemical flat cell has been designed for simulating buried high pressure pipeline environmental conditions in which a coating gets damaged and degrades under mechanical strain, and for studying the influence of mechanically induced damages such as the cracking of a coating on its anti-corrosion property. The experimental assembly is also capable of applying a cathodic protection (CP) potential simultaneously with the mechanical strain and environmental exposure. The influence of applied mechanical strain as well as extended exposure to the corrosive environment, coupled with the application of CP, has been investigated based on changes in electrochemical impedance spectroscopy (EIS). Preliminary results show that the amplitude of the coating impedance decreases with an increase in the applied strain level and the length of environmental exposure. The EIS characteristics and changes are found to correlate well with variations in coating cracking and degradation features observed on post-test samples using both optical microscopy and scanning electron microscopy. These results demonstrate that this new experimental method can be used to simulate and examine coating behaviour under the effects of complex high pressure pipeline mechanical, electrochemical and environmental conditions.

Tin Oxide Based Composites Derived Using Electrostatic Spray Deposition Technique as Anodes for Li-Ion Batteries

Recent advances in the electric & hybrid electric vehicles and rapid developments in the electronic devices have increased the demand for high power and high energy density lithium ion batteries. Graphite (theoretical specific capacity: 372 mAh/g) used in commercial anodes cannot meet these demands. Amorphous SnO2 anodes (theoretical specific capacity: 781 mAh/g) have been proposed as alternative anode materials. But these materials have poor conductivity, undergo a large volume change during charging and discharging, large irreversible capacity loss leading to poor cycle performances. To solve the issues related to SnO2 anodes, we propose to synthesize porous SnO2 composites using electrostatic spray deposition technique. First, porous SnO2/CNT composites were fabricated and the effects of the deposition temperature (200,250, 300 oC) & CNT content (10, 20, 30, 40 wt %) on the electrochemical performance of the anodes were studied. Compared to pure SnO2 and pure CNT, the composite materials as anodes showed better discharge capacity and cyclability. 30 wt% CNT content and 250 oC deposition temperature were found to be the optimal conditions with regard to energy capacity whereas the sample with 20% CNT deposited at 250 oC exhibited good capacity retention. This can be ascribed to the porous nature of the anodes and the improvement in the conductivity by the addition of CNT. Electrochemical impedance spectroscopy studies were carried out to study in detail the change in the surface film resistance with cycling. By fitting EIS data to an equivalent circuit model, the values of the circuit components, which represent surface film resistance, were obtained. The higher the CNT content in the composite, lower the change in surface film resistance at certain voltage upon cycling. The surface resistance increased with the depth of discharge and decreased slightly at fully lithiated state. Graphene was also added to improve the performance of pure SnO2 anodes. The composites heated at 280 oC showed better energy capacity and energy density. The specific capacities of as deposited and post heat-treated samples were 534 and 737 mAh/g after 70 cycles. At the 70th cycle, the energy density of the composites at 195 °C and 280 °C were 1240 and 1760 Wh/kg, respectively, which are much higher than the commercially used graphite electrodes (37.2-74.4 Wh/kg). Both SnO2/CNTand SnO2/grapheme based composites with improved energy densities and capacities than pure SnO2 can make a significant impact on the development of new batteries for electric vehicles and portable electronics applications.

Electrochemical Immunosensing of Cortisol in an Automated Microfluidic System Towards Point-of-Care Applications

This dissertation describes the development of a label-free, electrochemical immunosensing platform integrated into a low-cost microfluidic system for the sensitive, selective and accurate detection of cortisol, a steroid hormone co-related with many physiological disorders. Abnormal levels of cortisol is indicative of conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiencies and more recently post-traumatic stress disorder (PTSD). Electrochemical detection of immuno-complex formation is utilized for the sensitive detection of Cortisol using Anti-Cortisol antibodies immobilized on sensing electrodes. Electrochemical detection techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been utilized for the characterization and sensing of the label-free detection of Cortisol. The utilization of nanomaterial’s as the immobilizing matrix for Anti-cortisol antibodies that leads to improved sensor response has been explored. A hybrid nano-composite of Polyanaline-Ag/AgO film has been fabricated onto Au substrate using electrophoretic deposition for the preparation of electrochemical immunosening of cortisol. Using a conventional 3-electrode electrochemical cell, a linear sensing range of 1pM to 1µM at a sensitivity of 66µA/M and detection limit of 0.64pg/mL has been demonstrated for detection of cortisol. Alternately, a self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) has been fabricated for the modification of sensing electrode to immobilize with Anti-Cortisol antibodies. To increase the sensitivity at lower detection limit and to develop a point-of-care sensing platform, the DTSP-SAM has been fabricated on micromachined interdigitated microelectrodes (µIDE). Detection of cortisol is demonstrated at a sensitivity of 20.7µA/M and detection limit of 10pg/mL for a linear sensing range of 10pM to 200nM using the µIDE’s. A simple, low-cost microfluidic system is designed using low-temperature co-fired ceramics (LTCC) technology for the integration of the electrochemical cortisol immunosensor and automation of the immunoassay. For the first time, the non-specific adsorption of analyte on LTCC has been characterized for microfluidic applications. The design, fabrication technique and fluidic characterization of the immunoassay are presented. The DTSP-SAM based electrochemical immunosensor on µIDE is integrated into the LTCC microfluidic system and cortisol detection is achieved in the microfluidic system in a fully automated assay. The fully automated microfluidic immunosensor hold great promise for accurate, sensitive detection of cortisol in point-of-care applications.

Real-time Biosensor for the Assessment of Nanotoxicity and Cancer Electrotherapy

Knowledge of cell electronics has led to their integration to medicine either by physically interfacing electronic devices with biological systems or by using electronics for both detection and characterization of biological materials. In this dissertation, an electrical impedance sensor (EIS) was used to measure the electrode surface impedance changes from cell samples of human and environmental toxicity of nanoscale materials in 2D and 3D cell culture models. The impedimetric response of human lung fibroblasts and rainbow trout gill epithelial cells when exposed to various nanomaterials was tested to determine their kinetic effects towards the cells and to demonstrate the biosensor’s ability to monitor nanotoxicity in real-time. Further, the EIS allowed rapid, real-time and multi-sample analysis creating a versatile, noninvasive tool that is able to provide quantitative information with respect to alteration in cellular function. We then extended the application of the unique capabilities of the EIS to do real-time analysis of cancer cell response to externally applied alternating electric fields at different intermediate frequencies and low-intensity. Decreases in the growth profiles of the ovarian and breast cancer cells were observed with the application of 200 and 100 kHz, respectively, indicating specific inhibitory effects on dividing cells in culture in contrast to the non-cancerous HUVECs and mammary epithelial cells. We then sought to enhance the effects of the electric field by altering the cancer cell’s electronegative membrane properties with HER2 antibody functionalized nanoparticles. An Annexin V/EthD-III assay and zeta potential were performed to determine the cell death mechanism indicating apoptosis and a decrease in zeta potential with the incorporation of the nanoparticles. With more negatively charged HER2-AuNPs attached to the cancer cell membrane, the decrease in membrane potential would thus leave the cells more vulnerable to the detrimental effects of the applied electric field due to the decrease in surface charge. Therefore, by altering the cell membrane potential, one could possibly control the fate of the cell. This whole cell-based biosensor will enhance our understanding of the responsiveness of cancer cells to electric field therapy and demonstrate potential therapeutic opportunities for electric field therapy in the treatment of cancer.

Online impedance spectroscopy estimation of a battery

Electrochemical impedance spectroscopy (EIS) is a helpful tool to understand how a battery is behaving and how it degrades. One of the disadvantages is that it is typically an 'off-line' process. This paper investigates an alternative method of looking at impedance spectroscopy of a battery system while it is on-line and operational by manipulating the switching pattern of the dc-dc converter to generate low frequency harmonics in conjunction with the normal high frequency switching pattern to determine impedance in real time. However, this adds extra ripple on the inductor which needs to be included in the design calculations. The paper describes the methodology and presents some experimental results in conjunction with EIS results to illustrate the concept.

A ambivalência da opinião pública em Georg WF Hegel

A concepção hegeliana da Opinião Pública é um dos mais interessantes entendimentos estando reservado ao conceito um papel determinante dentro das mediações lógico-políticas. Hegel concedelhe inclusivamente uma força transformadora enquanto agente histórico e social. Nesta reflexão, apresentamos o modo como Georg WF Hegel descreve a Opinião Pública no quadro da sua Filosofia Política. Concentrando-nos nos Princípios da Filosofia do Direito, discutiremos a centralidade do princípio de publicidade e da comunicação nas relações políticas. No pensamento de Hegel, a publicidade não é tanto condição moral e política quanto um princípio inabalável da consciência do sujeito livre. É indissociável da liberdade formal e da liberdade subjectiva de opinar. O sujeito livre da modernidade resulta do processo do Espírito onde a contradição comanda o movimento de consciência. Na génese do espírito público, encontramos a oposição entre a consciência privada e a consciência pública. A Opinião Pública vive, pois, por entre esta dualidade de responder a exigências éticas e simultaneamente emanar de interesses particulares privados. A ambivalência da Opinião Pública decorre, então, do seu carácter eminentemente contraditório. Eis uma Opinião Pública em movimento perpétuo atravessada pelo particular e pelo universal. Verdade e erro compõemna. Esta é a inerente contradição que resume o estatuto ambivalente que Hegel concede à Opinião Pública. E esta é, talvez, a maior contribuição de Hegel para reflectirmos sobre o conceito na contemporaneidade.

A ambivalência da opinião pública em Georg WF Hegel

A concepção hegeliana da Opinião Pública é um dos mais interessantes entendimentos estando reservado ao conceito um papel determinante dentro das mediações lógico-políticas. Hegel concedelhe inclusivamente uma força transformadora enquanto agente histórico e social. Nesta reflexão, apresentamos o modo como Georg WF Hegel descreve a Opinião Pública no quadro da sua Filosofia Política. Concentrando-nos nos Princípios da Filosofia do Direito, discutiremos a centralidade do princípio de publicidade e da comunicação nas relações políticas. No pensamento de Hegel, a publicidade não é tanto condição moral e política quanto um princípio inabalável da consciência do sujeito livre. É indissociável da liberdade formal e da liberdade subjectiva de opinar. O sujeito livre da modernidade resulta do processo do Espírito onde a contradição comanda o movimento de consciência. Na génese do espírito público, encontramos a oposição entre a consciência privada e a consciência pública. A Opinião Pública vive, pois, por entre esta dualidade de responder a exigências éticas e simultaneamente emanar de interesses particulares privados. A ambivalência da Opinião Pública decorre, então, do seu carácter eminentemente contraditório. Eis uma Opinião Pública em movimento perpétuo atravessada pelo particular e pelo universal. Verdade e erro compõemna. Esta é a inerente contradição que resume o estatuto ambivalente que Hegel concede à Opinião Pública. E esta é, talvez, a maior contribuição de Hegel para reflectirmos sobre o conceito na contemporaneidade.

Development and optimisation of protocols for surface cleaning of cultural heritage metals

The conservation and valorisation of cultural heritage is of fundamental importance for our society, since it is witness to the legacies of human societies. In the case of metallic artefacts, because corrosion is a never-ending problem, the correct strategies for their cleaning and preservation must be chosen. Thus, the aim of this project was the development of protocols for cleaning archaeological copper artefacts by laser and plasma cleaning, since they allow the treatment of artefacts in a controlled and selective manner. Additionally, electrochemical characterisation of the artificial patinas was performed in order to obtain information on the protective properties of the corrosion layers. Reference copper samples with different artificial corrosion layers were used to evaluate the tested parameters. Laser cleaning tests resulted in partial removal of the corrosion products, but the lasermaterial interactions resulted in melting of the desired corrosion layers. The main obstacle for this process is that the materials that must be preserved show lower ablation thresholds than the undesired layers, which makes the proper elimination of dangerous corrosion products very difficult without damaging the artefacts. Different protocols should be developed for different patinas, and real artefacts should be characterised previous to any treatment to determine the best course of action. Low pressure hydrogen plasma cleaning treatments were performed on two kinds of patinas. In both cases the corrosion layers were partially removed. The total removal of the undesired corrosion products can probably be achieved by increasing the treatment time or applied power, or increasing the hydrogen pressure. Since the process is non-invasive and does not modify the bulk material, modifying the cleaning parameters is easy. EIS measurements show that, for the artificial patinas, the impedance increases while the patina is growing on the surface and then drops, probably due to diffusion reactions and a slow dissolution of copper. It appears from these results that the dissolution of copper is heavily influenced by diffusion phenomena and the corrosion product film porosity. Both techniques show good results for cleaning, as long as the proper parameters are used. These depend on the nature of the artefact and the corrosion layers that are found on its surface.

Estudos sobre carotenóides com atividade de provitamina "A" em cultivares de mandioca (Manihot esculenta CRANTZ) em ecossistema de terra firme DE Manaus, Amazonas, Brasil.

Foram conduzidos experimentos de competição entre cultivares de mandioca (Manihot esculenta Crantz) em ecossistema de terra firme (Manaus - Amazonas), com objetivo de obter melhores cultivares de mandioca com relação a produtividade e teor de caroteno pró-vitamínico A. Raízes de sete cultivares de mandioca amarela foram selecionadas para identificação e quantificação de carotenos com atividade de vitamina A, mediante o método descrito por Rodriguez. Observou-se, também, as perdas de pró-vitamina A pelo processamento e armazenamento de farinha. Constatou-se a presença de três isômeros do beta - caroteno (o 13 - eis -beta - caroteno, o beta - caroteno todo trans e o 9 - eis -beta - caroteno U). Quanto aos teores de vitamina A, expressos em equivalente de retinol, nas raízes variaram de 4,4 a 18,8. Com relação a perda de atividade da vitamina A pelo processamento variou de 25,0 a 40,0 %, enquanto que o armazenamento por 6 meses em sacos plásticos transparentes, à temperatura ambiente e à exposição de luz, resultou em degradação total de seus carotenóides. Os resultados permitem concluir que três cultivares (IM 232; IM 104 e BGM 021) apresentaram os maiores teores de pró-vitamina A.