Modelos analíticos para rádio fontes extragalácticas

The great majority of analytical models for extragalactic radio sources suppose self-similarity and can be classified into three types: I, II and III. We have developed a model that represents a generalization of most models found in the literature and showed that these three types are particular cases. The model assumes that the area of the head of the jet varies with the jet size according to a power law and the jet luminosity is a function of time. As it is usually done, the basic hypothesis is that there is an equilibrium between the pressure exerted both by the head of the jet and the cocoon walls and the ram pressure of the ambient medium. The equilibrium equations and energy conservation equation allow us to express the size and width of the source and the pressure in the cocoon as a power law and find the respective exponents. All these assumptions can be used to calculate the evolution of the source size, width and radio luminosity. This can then be compared with the observed width-size relation for radio lobes and the power-size (P-D) diagram of both compact (GPS and CSS) and extended sources from the 3CR catalogue. In this work we introduce two important improvement as compared with a previous work: (1)We have put together a larger sample of both compact and extended radio sources

Implementação da técnica de difração de elétrons de baixa energia

The purpose of this study is to describe the implementation of the Low Energy Electron Diffaction (LEED) technique in the Laboratory of Magnetic Nanostructures and Semiconductors of the Department of Theoretical and Experimental Physics of the Universidade Federal do Rio Grande do Norte (UFRN), Natal, Brazil. During this work experimental apparatus were implemented for a complete LEED set-up. A new vacuum system was also set up. This was composed of a mechanical pump, turbomolecular pump and ionic pump for ultra-high vacuum and their respective pressure measurement sensors (Pirani gauge for low vacuum measures and the wide range gauge -WRG); ion cannon maintenance, which is basically mini-sputtering, whose function is sample cleaning; and set-up, maintenance and handling of the quadrupole mass spectrometer, whose main purpose is to investigate gas contamination inside the ultra-high vacuum chamber. It should be pointed out that the main contribution of this Master's thesis was the set-up of the sample heating system; that is, a new sample holder. In addition to the function of sample holder and heater, it was necessary to implement the function of sustaining the ultra-high vacuum environment. This set of actions is essential for the complete functioning of the LEED technique

Condições de energia de hawking e ellis e a equação de raychaudhuri

In the Einstein s theory of General Relativity the field equations relate the geometry of space-time with the content of matter and energy, sources of the gravitational field. This content is described by a second order tensor, known as energy-momentum tensor. On the other hand, the energy-momentum tensors that have physical meaning are not specified by this theory. In the 700s, Hawking and Ellis set a couple of conditions, considered feasible from a physical point of view, in order to limit the arbitrariness of these tensors. These conditions, which became known as Hawking-Ellis energy conditions, play important roles in the gravitation scenario. They are widely used as powerful tools for analysis; from the demonstration of important theorems concerning to the behavior of gravitational fields and geometries associated, the gravity quantum behavior, to the analysis of cosmological models. In this dissertation we present a rigorous deduction of the several energy conditions currently in vogue in the scientific literature, such as: the Null Energy Condition (NEC), Weak Energy Condition (WEC), the Strong Energy Condition (SEC), the Dominant Energy Condition (DEC) and Null Dominant Energy Condition (NDEC). Bearing in mind the most trivial applications in Cosmology and Gravitation, the deductions were initially made for an energy-momentum tensor of a generalized perfect fluid and then extended to scalar fields with minimal and non-minimal coupling to the gravitational field. We also present a study about the possible violations of some of these energy conditions. Aiming the study of the single nature of some exact solutions of Einstein s General Relativity, in 1955 the Indian physicist Raychaudhuri derived an equation that is today considered fundamental to the study of the gravitational attraction of matter, which became known as the Raychaudhuri equation. This famous equation is fundamental for to understanding of gravitational attraction in Astrophysics and Cosmology and for the comprehension of the singularity theorems, such as, the Hawking and Penrose theorem about the singularity of the gravitational collapse. In this dissertation we derive the Raychaudhuri equation, the Frobenius theorem and the Focusing theorem for congruences time-like and null congruences of a pseudo-riemannian manifold. We discuss the geometric and physical meaning of this equation, its connections with the energy conditions, and some of its several aplications.

Criação da matéria em cosmologias com velocidade da luz variável e eletrônico não-linear

In this work we obtain the cosmological solutions and investigate the thermodynamics of matter creation in two diferent contexts. In the first we propose a cosmological model with a time varying speed of light c. We consider two diferent time dependence of c for a at Friedmann-Robertson- Walker (FRW) universe. We write the energy conservation law arising from Einstein equations and study how particles are created as c decreases with cosmic epoch. The variation of c is coupled to a cosmological Λ term and both singular and non-singular solutions are possible. We calculate the "adiabatic" particle creation rate and the total number of particles as a function of time and find the constrains imposed by the second law of thermodynamics upon the models. In the second scenario, we study the nonlinearity of the electrodynamics as a source of matter creation in the cosmological models with at FRW geometry. We write the energy conservation law arising from Einstein field equations with cosmological term Λ, solve the field equations and study how particles are created as the magnetic field B changes with cosmic epoch. We obtain solutions for the adiabatic particle creation rate, the total number of particles and the scale factor as a function of time in three cases: Λ = 0, Λ = constant and Λ α H2 (cosmological term proportional to the Hubble parameter). In all cases, the second law of thermodynamics demands that the universe is not contracting (H ≥ 0). The first two solutions are non-singular and exhibit in ationary periods. The third case studied allows an always in ationary universe for a suficiently large cosmological term

Estudos in silico da proteína AlkB e prospecção de bactérias alcanotróficas em solos da bacia petrolífera potiguar

Some microorganisms from virgin ecosystems are able to use petroleum it as source of carbon and energy. The knowledge of microbial biodiversity can help to reveal new metabolic systems for utilization alkanes with biotechnological importance. The aim of this study is: i) Accomplish an in silico study of the AlkB protein aimed to understand the probable mechanism involved on selectivity of alkanes in Gram positive and Gram negative bactéria. ii) prospect and analyze the response of the microbial alkanotrophics communities in soil and mangrove sediments of BPP RN and soil of Atlantic forest in the Horto Dois Irmãos Reserve area/PE using the molecular biomarker, gene alkB; with the PCR and PCR-DGGE approach

Tomate salada: uma alternativa como fonte de antioxidante para uso tópico

Tomato Salad: An Alternative as Antioxidant Source for Topic Use. Tomato is the principal source of lycopene, a carotenoid with high antioxidant activity which can be used topically as a phytocosmetic to combat skin aging. The aim of this study was to get a lycopene-rich extract from salad tomato pulp. The extract was analyzed using UV/vis spectroscopy, thin layer chromatography and high performance liquid chromatography. Oxidant activity was analyzed using the free radical DPPH method. The presence of lycopene in the salad tomato was confirmed. It was present in the apolar fraction rich in carotenoids, which was 96.70% lycopene. In the evaluation of the antioxidant activity, using the radical DPPH, the extract showed activity (IC(50) = 0,311 mg/mL). We conclude that the salad tomato can be used as a source of antioxidants for topic use.

Algumas considerações sobre o ensino e a aprendizagem do conceito de energia

Neste artigo procuramos abordar alguns aspectos relevantes sobre o ensino e a aprendizagem do conceito de energia, tais como as concepções de energia do senso comum e as relações entre transformações de energia e meio ambiente, bem como destacar a viabilidade da utilização de textos com abordagens históricas e, finalmente, analisamos um texto interdisciplinar que relaciona energia e meio ambiente. Com relação ao referido texto, discutimos a possibilidade de o mesmo levar o estudante a um entendimento das noções fundamentais de energia, mediante a contextualização histórica, social, política, econômica e ambiental dessas noções.

Modelo de programação matemática para controle do crescimento da vegetação sob redes de distribuição de energia elétrica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação do comportamento termoanalítico e oxidativo do biodiesel de mamona

In this work biodiesel was gotten through the transesterification reaction using the oil of castor as source of triglycerides and using the methylic route for obtaining of esters. For the characterization of biodiesel and its mixtures with mineral diesel oil, physical chemical parameters and several analytical techniques had been used, as well as: gas chromatography (GC), nuclear magnetic resonance of proton (1H NMR), infrared spectroscopy (IR) and thermal analysis. The chromatography confirmed the complete reaction of esters in biodiesel presenting a 97,08% conversion. The 1H - NMR presented singlet in 3,6 ppm corresponding to the hydrogen of the group ester RCOO CH3. The infrared presented a strong band in 1741 cm-1 referring to stretching C=O of ester and an average band in 1175 cm-1 referring C O deformation. With the data of thermal analysis it was possible to observe the thermal and oxidative stability of the samples changing the atmospheres of synthetic air and nitrogen, where stages of the thermal decomposition had been verified and had been attributed to the volatilization and/or decomposition of the triacylglycerides. The thermal degradation of the samples was carried through 150 and 210°C during 1, 12, 24 and 48 hours and was observed change in the thermogravimetric profile, therefore an increase in the number of stages of the thermal decomposition also occurred indicating characteristic intermediate composites of polymerization, being this confirmed through the rheological study that presented brusque increase of viscosity. The kinetic study showed that the activation energy has the following order: biodiesel > mineral diesel oil > mixtures biodiesel/diesel

Síntese, caracterização e aplicação do MCM-41 e A1-MCM-41 na pirólise do resíduo atmosférico de petróleo

In present work, mesoporous materials of the M41S family were synthesized, which were discovered in the early 90s by researchers from Mobil Oil Corporation, thus allowing new perspectives in the field of catalysis. One of the most important members of this family is the MCM-41, which has a hexagonal array of mesopores with pore diameters ranging from 2 to 10 nm and a high surface area, enabling it to become very promising for the use as a catalyst in the refining of oil in the catalytic cracking process, since the mesopores facilitate the access of large hydrocarbon molecules, thereby increasing the production of light products, that are in high demand in the market. The addition of aluminum in the structure of MCM-41 increases the acidity of the material, making it more beneficial for application in the petrochemical industry. The mesoporous materials MCM-41 and Al-MCM-41 (ratio Si / Al = 50) were synthesized through the hydrothermal method, starting with silica gel, NaOH and distilled water. CTMABr was used as template, for structural guiding. In Al-MCM-41 the same reactants were used, with the adding of pseudoboehmite (as a source of aluminum) in the synthesis gel. The syntheses were carried out over a period of four days with a daily adjustment of pH. The optimum conditions of calcination for the removal of the organic template (CTMABr) were discovered through TG / DTG and also through analysis by XRD, FTIR and Nitrogen Adsorption. It was found that both the method of hydrothermal synthesis and calcination conditions of the studies based on TG were promising for the production of mesoporous materials with a high degree of hexagonal array. The acidic properties of the materials were determined by desorption of n-butylamine via thermogravimetry. One proved that the addition of aluminum in the structure of MCM-41 promoted an increase in the acidity of the catalyst. To check the catalytic activity of these materials, a sample of Atmospheric Residue (RAT) that is derived from atmospheric distillation of oil from the Pole of Guamaré- RN was used. This sample was previously characterized by various techniques such as Thermogravimetry, FTIR and XRF, where through thermal analysis of a comparative study between the thermal degradation of the RAT, the RAT pyrolysis + MCM-41 and RAT + Al- MCM-41. It was found that the Al-MCM-41 was most satisfactory in the promotion of a catalytic effect on the pyrolysis of the RAT, as the cracking of heavy products in the waste occurred at temperatures lower than those observed for the pyrolysis with MCM-41, and thereby also decreasing the energy of activation for the process and increasing the rates of conversion of residue into lighter products

A energia e suas implicações no ensino-aprendizagem da química

The area of Education in Chemistry in Brazil has appeared over 30 years and its growth has been accelerated by the need of comprehension of the processes of teaching and learning in chemistry. Many researches, in this area, has among its investigation objects the teaching tools like teaching materials and the learning processes of students in high school and basic education, but when dealing with higher levels of education, they are seldom portrayed. This study aimed to investigate the General Chemistry textbooks with respect to approach the concept of energy; know the main ideas of graduate students in Chemistry on the relation of the concept of energy and chemical transformations; finally, developing a cicle of studies with the proposition of an approach wich inter-relate the concept of energy and its implications in the teaching-learning process of a chemical transformation. To do so, we used as instruments a questionnaire, press conference, conceptual map and experimental activities. All activities of the study cicle were videotaped and recorded, transcribed and the results organized in tables. For the activities of the study cicle texts that have been developed and inter-relating concepts of chemistry and energy, which in turn gave theoretical support to the activities in the cycle. In the analysis it was used as a theoretical content the analysis of Laurence Bardin. The results revealed that the analysis of the book might be perceived that not always the concept of energy is used in order to generate the abstract thought of chemical transformations, but that the main macroscopic thermodynamic variables are present in the explanation of these transformations. During the study cicle, were studied two chemical reactions: the first one, made possible to approach the macroscopic dimension to quantify the concept of energy and the second one, made possible to demonstrate the macro and microscopic dimension of the concept of energy during a chemical transformation. In all reactions proposed, students used, in most of the times, as explanations, only macroscopic observations of the reactions under study and failed to realize that the concept of energy can be used to explain macro and microscopic chemical transformation. As a final action of the study cicle, students requested further discussion, to clarify the link between the concept of energy and the meanings constructed in the process of studying the reactions. This is done through an oral explanation, during the cycle, and registered in this thesis and attempts to show the interrelationship existing conceptual

Síntese, caracterizaçao e propriedades catalicas da peneira molecular nanoestruturada modificada com lantanio

The nanostructured molecular sieve SBA-15 was synthesized by the hydrothermal method, and modified with lanthanum with Si/La molar ratios of 25, 50, 75 and 100. The materials were evaluated as catalysts for the cracking of n-hexane model reaction. Type SBA- 15 and LaSBA-15 mesoporous materials were synthesized using tetraetilortosilicato as a source of silica, hydrochloric acid, heptahydrate lanthanum chloride and distilled water. Pluronic P123 triblock. polymer was used as structure template. The syntheses were carried out by 72 hours. The obtained SBA-15 samples were previously analyzed by thermogravimetry, in order to check the conditions of calcination for removal of organic template. Then, the calcined materials were characterized by X-ray diffraction, infrared spectroscopy, adsorption and desorption of nitrogen, scanning electron microscopy and X-ray microanalysis by dispersive energy. The acidity of the samples was determined using adsorption of n-bulinamina and desorption followed by thermogravimetry. It was found that the hydrothermal synthesis method was suitable for the synthesis of the SBA-15 mesoporous materials, with an excellent degree of hexagonal ordering. The reactions of catalytic cracking of n-hexane were carried out using a fixed bed continuous flow microreactor, coupled on-line to a gas chromatograph. From the catalytic evaluation, it was observed that the mesoporous materials containing lanthanum showed different results for the reaction of cracking of nhexane compared to the unmodified mesoporous material SBA-15. As a result of cracking was obtained as main products hydrocarbons in the range of C1 to C5. The catalyst that showed better properties in relation to the acidity and catalytic activity was LaSBA-15 with the ratio Si/La = 50

O impacto dos custos não-gerenciáveis na determinação das tarifas de energia elétrica: um estudo nas companhias distribuidoras do nordeste que tiveram revisão tarifária nos exercícios de 2003 e 2004

This work presents results derived from a study related to impact on non-controllable costs in the determination of energy taxes. This is done analyzing tax review practiced by concessionaries responsible for the distribution of electrical energy located in the Northeastern Region of Brazil, between 2003 and 2004. This Region was chosen as a study area due to the researcher s expectation in congregating companies that deliver services to markets that have similar social-economical profiles. A brief explanation related to the restructuring of the electrical sector in Brazil is presented, pointing out that there was privatization of the great majority of these companies. The study also points out the definition of regulating rules in service delivery process. The components of taxes that are practiced by these companies aimed at final consumers, as well as the market as a whole and the revision process that is executed by Agência Nacional de Energia Elétrica ANEEL for the definition of these taxes are demonstrated in the research. A brief historical of the concessionaires that were focus of the research is presented, totaling five companies. Some data used by ANEEL in the tax review process was analyzed as well as data on components of approved taxes. It is concluded that as a media 47, 49% of the components of taxes in the researched companies correspond to the non-controllable costs. These is done considering previous classification by ANEEL in the tax review process. Although, if it is considered that these companies since 2006, by the means of participation in energy auctions are able to negotiate energy prices for their own needs, it is concluded that these concession contracts guarantee the delivery of the service to the costumer in the total tribute. The percentage of non-controllable costs is 16, 27% average of the tax. This means, amongst other information, that the government has a great deal of responsibility in the formation of price practiced by these companies and its target markets

Impacto do racionamento nos resultados das empresas concessionárias do serviço público de distribuição de energia elétrica: um estudo nas empresas privadas da Região Nordeste

This work verifies the impact caused by the Emergencial Program of Reduction of Consumption of Electric Energy (energy-rationing program) in the results of the concessionary private companies of the public service of electric energy distribution localized in the Northeast Area. As the rationing invigorated from June 2001 to February 2002, its effects are diluted in the results presented by these companies in the second semester of 2001 and first quarter of 2002, with prominence for the last quarter of 2001, when the revenue of extraordinary tariff restore was instituted by the National Agency of Electric Energy (ANEEL), consequence of the so-called General Agreement of the Electric Sector made between the federal government and the companies of the electric sector. The structure of a generic electric sector and a historical review of the Brazilian electric sector from the time it was controlled by the private enterprises, including the State control period, about 1960, and returning to the control of the private enterprises in 1990, under a new regulation structure are presented. An explanation of the models of economic regulation that Brazil used for the electric sector is made, with prominence for the price cap that is the actual effective model. The process of tariff revision foreseen in the concession contracts signed by the federal government and the concessionary companies is presented, highlighting its two stages: the tariff rebalancing that defines the new price cap and the calculation of the factor X that establishes the efficiency goals for the companies. There is made a presentation of the Emergencial Program of Reduction of Consumption of Electric Energy and of the consequent General Agreement of the Electric Sector, which created the revenue of extraordinary tariff restore. A conceptual revision on reviews is presented, regarding to concepts, accomplishment and recognition. A brief review of the six companies that made part of the worked sample is also presented. Analyzing the quarters historical review and of amount of sold energy, it was possible to conclude that the energy-rationing altered the results of the studied companies significantly and that alteration was masked by the accounting process of the revenue of extraordinary tariff restore

Teorias f(R) de gravidade na formulação de Palatini

In this dissertation, after a brief review on the Einstein s General Relativity Theory and its application to the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological models, we present and discuss the alternative theories of gravity dubbed f(R) gravity. These theories come about when one substitute in the Einstein-Hilbert action the Ricci curvature R by some well behaved nonlinear function f(R). They provide an alternative way to explain the current cosmic acceleration with no need of invoking neither a dark energy component, nor the existence of extra spatial dimensions. In dealing with f(R) gravity, two different variational approaches may be followed, namely the metric and the Palatini formalisms, which lead to very different equations of motion. We briefly describe the metric formalism and then concentrate on the Palatini variational approach to the gravity action. We make a systematic and detailed derivation of the field equations for Palatini f(R) gravity, which generalize the Einsteins equations of General Relativity, and obtain also the generalized Friedmann equations, which can be used for cosmological tests. As an example, using recent compilations of type Ia Supernovae observations, we show how the f(R) = R − fi/Rn class of gravity theories explain the recent observed acceleration of the universe by placing reasonable constraints on the free parameters fi and n. We also examine the question as to whether Palatini f(R) gravity theories permit space-times in which causality, a fundamental issue in any physical theory [22], is violated. As is well known, in General Relativity there are solutions to the viii field equations that have causal anomalies in the form of closed time-like curves, the renowned Gödel model being the best known example of such a solution. Here we show that every perfect-fluid Gödel-type solution of Palatini f(R) gravity with density and pressure p that satisfy the weak energy condition + p 0 is necessarily isometric to the Gödel geometry, demonstrating, therefore, that these theories present causal anomalies in the form of closed time-like curves. This result extends a theorem on Gödel-type models to the framework of Palatini f(R) gravity theory. We derive an expression for a critical radius rc (beyond which causality is violated) for an arbitrary Palatini f(R) theory. The expression makes apparent that the violation of causality depends on the form of f(R) and on the matter content components. We concretely examine the Gödel-type perfect-fluid solutions in the f(R) = R−fi/Rn class of Palatini gravity theories, and show that for positive matter density and for fi and n in the range permitted by the observations, these theories do not admit the Gödel geometry as a perfect-fluid solution of its field equations. In this sense, f(R) gravity theory remedies the causal pathology in the form of closed timelike curves which is allowed in General Relativity. We also examine the violation of causality of Gödel-type by considering a single scalar field as the matter content. For this source, we show that Palatini f(R) gravity gives rise to a unique Gödeltype solution with no violation of causality. Finally, we show that by combining a perfect fluid plus a scalar field as sources of Gödel-type geometries, we obtain both solutions in the form of closed time-like curves, as well as solutions with no violation of causality