Introduction All experimental studies involving charged particle induced nuclear reactions require a precise knowledge of monitor reactions. A number of well described proton induced monitor reactions exist in the lower energy range [1], which is covered by most medical cyclotrons. Concerning proton energies above 20 MeV, however, the accuracy of the monitor reactions declines as cross section data becomes scarcer. Furthermore, the growing interest in precise determination of projectile energies by comparing of ratios of monitor reaction cross sections demands new measurements and evaluations of known data for high threshold monitor radionuclides. In this work cross section measurements on the formation of 61Cu were done and energy de-pendent radionuclide ratios were calculated. Material and Methods For investigation of the natCu(p,x)61Cu reaction copper foils of natural isotopic composition (Goodfellow Ltd.) were irradiated. The targets were of 10 and 20 μm thickness, having a diameter of 15 mm. Proton bombardments up to 45 MeV incident energy were done in the stacked-foil arrangement at the accelerator JULIC of the Nuclear Physics Institute (IKP) of the Forschungszentrum Jülich. In addition to an internal irradiation possibility the cyclotron is equipped with an external target station which was used for most experiments. It can adapt standard and slanting solid target holders and is equipped with a water cooled four sector collimator and additional helium cooling of the entry foil. Several irradiations were executed. In each stack, besides copper samples, aluminium absorbers and additional nickel monitor foils were also placed, the latter for the determination of the respective beam current. The produced radioactivity of 61Cu was analysed non-destructively using HPGe γ-ray detectors (EG&G Ortec). Results and Conclusion Reaction cross sections of the natCu(p,x)61Cu process up to 45 MeV were measured and com-pared with existing data from the literature (FIG. 2). Except for the data of Williams et al. our results are in good agreement, showing a maxi-mum of about 165 mbarn at 37.5 MeV proton energy. The overall uncertainty of the new cross section data is between 8 and 10 %. In FIG. 3, the excitation functions of the relevant monitor reactions on Cu are shown. In combination with the excitation function of the natCu(p,xn)62Zn reaction, isotope ratios were calculated which can be used for determination of the proton energy within a target stack in the energy range of 22–40 MeV as described by Piel et al. [3]. FIGURE 4 shows the cross section ratio in dependence of the proton energy. Above this energy, 65Zn could be used to generate isotope ratios for energy determination, although the long half-life (T½ = 244.3 d) of that radionuclide may be a problem. Additional cross section measurements are planned in order to further strengthen the data base of this potential monitor reaction. The results of this work shall be evaluated in the framework of an ongoing Coordinated Research Project of the IAEA.

Introduction The worldwide use of PET has proven beyond dispute the importance for both routine diagnosis and physiological, oncological and pharmacological research. In many ways the present success of PET relies on the mature technology of PET compact medical cyclotrons. As long time developers of new targets, isotopes and com-pounds, we have been inclined to look for new block-buster applications, high power targets and sustainable ways of embracing the GMP and regional distribution, but recent pioneering development [1] around very small cyclotrons and “embedded synthesis and qc” has pointed out an old, but important nuclear physics lesson now halfway forgotten: that many PET isotopes can be made in high yields with proton energies far below 10 MeV [2]. This has opened a new interest in small cyclotrons and their targets. We have been testing the first GE Healthcare Prototype for a 7.8 MeV negative ion, internal ion source cyclotron with 3 production targets mounted on a short beamline. Here we present the first experimental yields of some of the important PET radionuclides. Materials and methods The prototype cyclotron (FIG. 1) has been in-stalled and tested without self-shield in designated experimental area in order to establish the neutron field around accelerator and targets in order to qualify design calculations for a future integrated shield. The cyclotron energy is fixed by the radial position of the extraction foil, while the azimuth determines which of the 3 targets are being irradiated. The beam energy at front of target foil was determined on several occasions: 7.8 ± 0.1 MeV by a 2 copper-foil sandwich method (adopted from [3]). The available beam inside the cyclotron at extractor position is > 50 μA, and 35 μA are easily and long term reliably extracted (> 90 %) on to any of the 3 target positions. The prototype is capable of delivering more than 40 μA to target, but target current was limited to 35 μA under present unshielded conditions. Results 18F We have tested the prototype gridded (> 80 % transmission) niobium body target with 10μm Havar foil using 95 % 18O water and 35 μA on target + grid with yields given in TABLE 1. The observed yields corrected for stopping in foil, grid loss and water enrichment are 75 % of theoretical. One Fastlab FDG run using 2 h irradiation yielded 16 GBq FDG EOS, confirming the “usual” 18F activity. Results 11C Using gridded target and a 10μm foil with 99% N2 + 1 % O2 at 10 bar followed by trapping into ascarite gave EOB activity as shown in TABLE 2. Results 13N We know that the 16O(p,alpha)13N cross section is a very steep function of energy around 7.8 MeV. In the hope of using the simple water target route to 13N NH3 we have measured the 13N yields (corrected for 18F contribution). It is still unclear if these yields can be improved to make useful single doses of ammonia. Results for other isotopes We have used solid targets to make 45Ti, 64Cu, 68Ga and 89Zr. The development of these solid targets is still in progress, but especially the 68Ga yield looks promising (3 GBq EOB after 1 h on natural Zn will give > 15 GBq on enriched 68Zn).

Introduction A method based on neutron activation is being developed to assist in resolving discrepancies between the expected yield and actual yield of radionuclides produced with the vertical-beam target station (VBTS) at iThemba LABS. The VBTS is routinely employed for multi-Ci batch productions of the radionuclide pairs 22Na/68Ga and 82Sr/68Ga using standardized natMg/natGa and natRb/natGa tandem targets, respectively [1]. The metal-clad target discs are bombarded with a primary beam of 66 MeV protons at an intensity of nominally 250 µA. The encapsulation materials are either Nb (for Mg and Ga) or stainless steel (for Rb) which serve to contain the molten target materials during bombardment and act as a barrier to the high-velocity cooling water which surrounds the targets in a 4π geometry. The natRb/natGa targets are typically bombarded according to a two-week cycle while natMg/natGa targets are bombarded on an ad-hoc basis, depending on a somewhat unpredictable 22Na demand. A too-large deviation between expected yield and actual yield has at times plagued this programme. These deviations can manifest both as an apparent loss or an apparent gain (relative to the expected yield) by up to about 15% in either direction. The resulting uncertainty of up to 30% (in the worst case) from one production batch to another can be costly and is unacceptable in a large-scale production regimen. This phenomenon is believed to be brought about by two types of problems: (1) Production losses, e.g. during the radio-chemical separation process or incomplete recovery of activated target material during the decapsulation step. (2) Incorrect values obtained for the accumulated proton charge. A problem of type (1) will always result in a loss of yield. A problem of type (2) can manifest as an apparent loss or gain. In an effort to get a handle on this second type of problem, neutron activation of suitable material samples, embedded in a target holder, is being investigated as an independent indicator of the total yield. For this purpose, samples of Co, Mn, Ni and Zn were activated during production runs and Co was found to be the most appropriate. Preliminary results will be presented after first discussing why the determination of the accumulated pro-ton charge is a problem with the VBTS. Materials and Methods The VBTS consists of a central region in which a target holder is located during bombardment as well as two half-cylindrical radiation shields which completely surround the target. The shields can be moved away from the central region on dedicated rails, e.g. when repairs or maintenance is required. FIGURE 1 shows the VBTS with the shields moved to the “open” position. As some components of the station are located below the vault floor, with the target position near floor level, it proved difficult to electrically isolate the VBTS as was done for the two horizontal-beam target stations at iThemba LABS [1]. The VBTS does not act as a Faraday cup like the other target stations. Instead, the beam current and accumulated charge is measured by means of a calibrated capacitive probe [1,2]. There appears to be a variation in the response of the capacitive probe, sensitive to the beam microstructure, in particular a dependence on the beam packet length. This problem is not yet fully resolved. FIGURE 2 (a) shows the beamstop of a VBTS target holder with several Co samples mounted on the outside as well as one each of Ni, Mn and Zn. The samples are small “tablets” with a 10 mm diameter and 1 mm thickness. The reactions of interest are 59Co(n,γ)60Co, 59Co(n,3n)57Co, nat-Ni(n,X)60Co, natNi(n,X)57Co, natZn(n,X)65Zn and 55Mn(n,2n)54Mn. The relevant half-lives are 60Co(5.271 a), 57Co(271.8 d), 65Zn(244.3 d) and 54Mn(312.2 d). The half-life should be long compared to the two-week cycle in order to reduce the dependence on the exact beam history, which is very fragmented over any production period. In this respect, 60Co is considered to be particularly attractive as its long half-life of more than 5 years leads to a negligible effect by the beam history. Note that the tandem targets, shown in FIGURE 2 (b), are mounted just upstream of the beamstop – in fact, the targets and beamstop form a single unit before being fitted into the target holder. At the end of bombardment, all samples were assayed for their characteristic γ-emissions using standard off-line γ-ray spectrometry with an HPGe detector connected to a Genie 2000 MCA. Calculations of the neutron fluence density in the central sample volume on the beamstop were also performed using the Monte Carlo radiation transport code MCNPX. For these calculations, the entire VBTS, a Rb/Ga target and the vault walls were included in the model. Results and Conclusion All samples activated significantly – copious amounts of 60Co were detected in the Co discs after a two-week run. The neutron fluence density for the case of a 250 µA, 66 MeV proton beam on a natRb/natGa tandem target is shown in FIGURE 3. The dominance of low-energy neutrons is evident, which is in part due to the large amount of paraffin-wax shielding material in close proximity to the target. While reactions such as the (n,2n) and (n,3n) would be sensitive to the more energetic part of the neutron spectrum, the (n,γ) capture reaction benefits from the large low-energy component. This explains the copious amounts of 60Co formed. It was therefore decided to only retain the central Co sample for subsequent bombardments, as shown in FIGURE 4. The first results are shown in TABLE 1. The accumulated charge as obtained from the capacitive probe (Q), the specific 60Co activity (A) at the end of bombardment (EOB), and their ratio (A/Q) are presented in the table, together with the deviation of individual ratios relative to their average for the case of the Mg/Ga tandem tar-gets only. Note that all samples were counted until the statistical uncertainties were negligible. Any systematic uncertainties are ignored at this stage as they are considered to remain the same from one batch production to another. For the sake of argument, the average value of the ratio is taken as the expected value. A positive deviation of the A/Q value is then indicative of a too-small value of the accumulated charge obtained from the capacitive probe, leading to a corresponding overproduction. Likewise, a negative value is indicative of a too-large value of the accumulated charge, leading to a corresponding underproduction. It is certainly true that the data in TABLE 1 are currently very limited. It is envisaged, however, that with time the growing database of values will assist in reducing the uncertainty in determining the accumulated charge and reduce the discrepancies between predicted and actual yields significantly. TABLE 1 illuminates the underlying problem satisfactorily. The four Mg/Ga tandem target bombardments, on identical targetry, were performed successively. The neutron activation correlates well the with actual yields, pointing directly to the current integration as the main source of error. The method already proves to be useful. An indication of an over or underprediction can be obtained prior to the target processing by recovering and measuring the Co disc. This in-formation can be used to make a decision concerning the present batch production and/or the subsequent one. One can either add beam to the present production target and/or in-crease/reduce the total beam on the subsequent production target to compensate for an expected overproduction or shortfall. In conclusion, we would like to stress that the capacitive probes show great promise and that better understanding and/or possibly some development of their signal processing algorithm may improve their ability to measure the accumulated charge to the desired accuracy. Segmented capacitive probes used at iThemba LABS and elsewhere for beam position measurement [1,3] are not affected by beam microstructure as only the ratios of the signal strengths on the different sectors are important. In this case, changes in response affect all sec-tors equally and the ratios are unaffected.

[pt] Neste trabalho foi estudada a formação de camadas de produtos de corrosão em dois aços, o API 5L X80 usado para transporte de óleo e gás e o API 5CT utilizado em poço de petróleo case tubing. Foram utilizadas as técnicas de perda de massa e técnicas eletroquímicas tais como resistência a polarização linear RPL, curvas tafel e espectroscopia de impedância eletroquímica EIS foram empregadas para determinar as taxas de corrosão. Os ensaios foram realizados em condições estáticas numa solução de salmoura 3 porcento wt de NaCl sob 55 bar de pressão parcial de CO2 e total de 75bar, tempos de exposição de 7, 15, 21 e 30 dias e temperaturas de 25 Graus Celsius, 50 Graus Celsius e 75 Graus Celsius. Microscopia eletrônica de varredura MEV foi usada para a análise da morfologia. DRX e EDS foram utilizadas para determinar a composição química. As camadas formadas foram avaliadas em função da espessura, morfologia e composição química. Encontrou-se que a 25 Graus Celsius só houve formação de camada de carbonato de ferro após 30 dias de imersão para ambos os aços e que para 50 Graus Celsius e 75 Graus Celsius houve formação de duas camadas para todos os tempos de imersão cuja composição química mostrou o carbonato de ferro FeCO3 como principal produto de corrosão para os dois aços. A condição de teste que apresentou menor taxa de corrosão e maior proteção da camada de carbonato de ferro FeCO3 foi para 75 Graus Celsius e 30 dias de tempo de imersão. Os resultados de RPL e EIS são semelhantes aos obtidos por perda de massa mantendo a mesma tendência de redução com o tempo e a temperatura. / [en] This study evaluated the CO2 corrosion layer formation on the surface of two different steels, the API 5L X80 used for oil and gas transportation and the API 5CT used in oil production (case tubing). Techniques such as weight loss and electrochemical techniques as linear polarization resistance (LPR), Tafel curves, electrochemical impedance spectroscopy (EIS) were employed to determine the corrosion rate. Tests were conducted under static conditions in a brine 3 percent wt solution of of NaCl under CO2 partial pressure of 55 bar and total of 75 bar, immersion times of 7, 15, 21 and 30 days and temperatures of 25 Celcius, 50 Celcius and 75 Celcius. Analysis of the scale morphology was carried out by Scanning Electron Microscopy (SEM), and X-ray Diffraction. (XRD) and Energy Dispersive Spectroscopy (EDS) were used to determine the chemical composition. The layers formed were evaluated as a function of its thickness, morphology and chemical composition. It was found out that at 25 Celcius only after 30 days of immersion there was iron carbonate layer formation for both steels and at 50 Celcius and 75 Celcius there was the growth of two layers for all immersion times, being the chemical composition of these layers identifyed as iron carbonate FeCO3 as the main corrosion product for the two steels. The lowest corrosion rate and most protective layer of iron carbonate FeCO3 was for the condition at 75 Celcius and 30 days of immersion. The results obtained of LPR and EIS were similar to those obtained by mass loss showing the same tendency, reducing with time and temperature.

[pt] A integração do grafeno nos dispositivos nanoeletrônicos depende da disponibilidade de processos de deposição de forma direta sobre o substrato. A deposição direta pode fornecer grafeno uniforme, com alta qualidade e em grande área sobre substratos semicondutores como sílicio ou germânio. Nesta tese, foi sintetizado grafeno diretamente sobre germânio dopado tipo p e com uma orientação cristalina (100) empregando a deposição química na fase vapor. Foi estudada a influência da relação de fluxo entre os gases CH4 e H2 no crescimento de grafeno. As técnicas empregadas para verificar a qualidade das amostras e o tipo de crescimento obtido foram a espectroscopia Raman, microscopia de varredura eletrônica, de tunelamento e de força atômica, e a espectroscopia de tunelamento. Determinamos que para as condições empregadas, o crescimento de grafeno sobre germânio é autolimitado, com a deposição de apenas uma única camada, com poucos defeitos na sua rede cristalina e com o nível de Fermi característico de um material com dopagem tipo n. / [en] The integration of graphene into nanoelectronic devices is dependent on the availability of direct deposition processes, which can provide uniform, large-area and high-quality graphene on semiconductor substrates such as Ge or Si. In this dissertation, we synthesized graphene directly on ptype Ge(100) substrates by chemical vapor deposition. The influence of the CH4:H2 flow ratio on the graphene growth was investigated. Raman Spectroscopy, Raman mapping, Scanning Electron Microscopy, Atomic Force Microscopy and Scanning Tunnelling Microscopy/Scanning Tunnelling Spectroscopy were the techniques employed to verify the quality of the samples and the type of growth. We determined that for the conditions employed, the growth of graphene is self-limited, with only a single layer deposition, with few defects in its crystalline lattice and with Fermi level characteristic of a material with doping type n.

Made available in DSpace on 2014-10-09T12:54:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:02Z (GMT). No. of bitstreams: 1 12444.pdf: 2861377 bytes, checksum: f197a83330e61c5fa6654676c3363a7f (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

Made available in DSpace on 2014-10-09T12:54:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:02Z (GMT). No. of bitstreams: 1 12444.pdf: 2861377 bytes, checksum: f197a83330e61c5fa6654676c3363a7f (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Fisica, Universidade de Sao Paulo - IF/USP

[pt] Corpos relativamente pequenos do sistema solar não possuem atmosfera (ou muito rarefeita, chamada exosfera) e nem campo magnético: encontram-se praticamente desprotegidos da influência do ambiente espacial no qual estão inseridos. Tais corpos (como a maioria dos asteroides, luas e cometas distantes do Sol), estão sujeitos aos efeitos do chamado intemperismo espacial. Com o objetivo de simular e estudar este fenômeno em laboratório, três amostras de meteoritos do tipo condrito ordinário foram irradiadas por feixes de H(positivo) com energia de 1,0 MeV. Uma das amostras foi, também, irradiada por feixe de N(positivo) de 2,0 MeV. Os efeitos da irradiação foram monitorados por espectroscopias Raman e UV-VIS-NIR. Os resultados Raman mostram variações sistemáticas do número de onda, da intensidade e da largura das bandas vibracionais estudadas, evidências de modificações estruturais. As seções de choque de destruição das ligações Si-O presentes nas estruturas cristalinas foram determinadas. A espectroscopia UV-VIS-NIR por refletância de esfera integrada foi usada para monitorar as modificações nas características espectrais. Os espectros obtidos mostram escurecimento e avermelhamento progressivos das amostras irradiadas; a amplitude destas modificações depende do conteúdo inicial de ferro na estrutura. É proposto que o avermelhamento observado com o aumento da fluência (ou dose) da irradiação deve-se ao aumento do coeficiente de absorção na faixa azul que, por sua vez, decorre da diminuição do gap óptico do material. Estes resultados são relevantes para a modelagem da evolução físico-química de asteroides expostos ao vento solar. / [en] Relatively small bodies in the solar system have no atmosphere (or very thin, called the exosphere) and no magnetic field: they are virtually unprotected from the influence of the space environment in which they are inserted. Such bodies (like most asteroids, moons, and comets far from the sun), are subject to the effects of so-called space weathering. To simulate and study this phenomenon in the laboratory, three samples of ordinary chondrite meteorites were irradiated by H(positive) beams with 1.0 MeV energy. One of the samples was also irradiated by a 2.0 MeV N(positive) beam. The effects of irradiation were monitored by Raman and UV-VIS-NIR spectroscopies. The Raman results show systematic variations in the wavenumber, intensity, and width of the studied vibrational bands, evidence of structural modifications. The shock sections of the destruction of Si-O bonds present in the crystalline structures were determined. Integrated sphere reflectance UV-VIS-NIR spectroscopy was used to monitor changes in spectral characteristics. The obtained spectra show progressive darkening and reddening of the irradiated samples; The extent of these modifications depends on the initial iron content in the structure. It is proposed that the redness observed with the increase of irradiation creep (or dose) is due to the increase in the absorption coefficient in the blue band, which, in turn, results from the decrease of the optical gap of the material. These results are relevant for modeling the physicochemical evolution of asteroids exposed to the solar Wind.

INTRODUÇÃO: A qualidade da interface osso-implante pode ser influenciada diretamente pela rugosidade da superfície e determina a forma como as células interagem, aderem-se e fixam-se a ela, podendo potencializar e encurtar o tempo de osseointegração. Este estudo propôs-se analisar qualitativamente a topografia e arquitetura de diferentes superfícies de implantes dentários, compará-las, descrevê-las e correlacioná-las com os possíveis eventos moleculares e celulares iniciais da osseointegração. MATERIAIS E MÉTODOS: cinco implantes com diferentes tratamentos de superfície foram analisados em três diferentes áreas: apical, região de roscas (topos, flancos e vales) e região cervical por microscopia eletrônica de varredura (MEV) e topo do ápice em microscopia de força atômica (MFA). RESULTADOS: as superfícies dos implantes NanoTite®, SLA® e Xive® TG plus, no MEV, são semelhantes pelo seu aspecto de lacunas, diferindo no plano superficial; a superfície do implantes TiUnite® apresenta características coraliformes/vulcanoides, enquanto a do implante Exopro® apresenta estrias em formas de pequenos sulcos. A rugosidade média (Ra) à MFA, apresentou-se maior no implante TiUnite®, seguido pelos implantes Xive®TG plus, NanoTite®, Exopro® e SLA®. A área analisada se restringe a pequenos pontos (nanométricos), que não possibilita uma visão panorâmica de todas as estruturas (micrométricas), e consequentemente não permite uma real comparação da rugosidade. CONCLUSÕES: a metodologia ideal para análise das superfícies com o objetivo de compreender como as células às colonizam e se aderem deve ser em escala micrométrica, destacando-se à MEV em detrimento da MFA. As duas metodologias, MEV e MFA, são fundamentais na análise de superfície de implantes dentários, porém devem ser conjuntamente e/ou simultaneamente empregadas. A MFA parece ser a mais adequada para estudos que visem a interação da superfície dos implantes com estrutura de nível molecular e à MEV, no nível celular. Cada tratamento de superfície promove um tipo específico de topografia, cujos benefícios moleculares, teciduais e clínicos devem ser estudados caso a caso. / Introduction: Bone-implant interface quality may be influenced by surface roughness and determines how cells interact, cling to and fix to, therefore can enhance and shorten the time for osseointegration. This study aims to analyze qualitatively the topography and architecture of different dental implants surfaces, to compare and describe them. MATERIALS AND METHODS: five implants with different surface treatments were evaluated in three different areas: apical, region of threads (tops, sides and valleys) and cervical region by scanning electron microscopy (SEM) and atomic force microscopy (AFM), correlating the possible molecular and cellular initials events of osseointegration. RESULTS: the surfaces of the implants NanoTite®, SLA® and ® Xive® TG plus, in the SEM, are similar by their appearance of gaps, although they differ in surface plane; the surface of TiUnite® implants have features such as corals and/or volcanos, while the implant Exopro ® has stretch marks in form of small grooves. The average roughness (Ra) to the AFM, appeared higher in TiUnite ® implant, followed by Xive® TG plus NanoTite®, Exopro® and SLA® implants. The area analyzed in the AFM, is restricted to small points (nanometrics), and do not allow denote a panoramic view of all structures (micrometrics), not allowing a real comparison of surface roughness. CONCLUSIONS: the optimal methodology for surfaces analysis with the objective of understanding how the cells colonize and fix to dental implants should be in the micrometer scale, highlighting the SEM over AFM. The AFM seems to be most suitable for studies aiming the interaction of the implant surface with molecular-level and SEM at the cellular level. Each treatment promotes a specific surface topography whose benefits molecular, tissue, and clinical should be studied separately.

Submitted by Ana Paula Lisboa Monteiro (monteiro@univates.br) on 2009-01-14T13:36:45Z No. of bitstreams: 1 Marjorie Kauffmann.pdf: 4282594 bytes, checksum: f34139bb222a8be8fc60f7c50443d474 (MD5) / Made available in DSpace on 2009-01-14T13:36:45Z (GMT). No. of bitstreams: 1 Marjorie Kauffmann.pdf: 4282594 bytes, checksum: f34139bb222a8be8fc60f7c50443d474 (MD5) / A avaliação dos processos de formação, evolução, manutenção e estabilidade dos ecossistemas tem se tornado cada vez mais significativa nos estudos atuais em ecologia. Na tentativa de esclarecer a evolução dos biomas durante o tempo, um dos elementos que vem sendo utilizado é o acompanhamento das variações florísticas ocorridas nos mesmos, tendo em vista que as plantas são excelentes marcadores ambientais. Uma das formas de registro relacionado à vegetação é o charcoal, o qual é prova direta da ocorrência de incêndios vegetacionais e seu estudo se torna um procedimento fundamental para o entendimento da evolução dos ambientes, permitindo, assim, a interpretação do passado e o estabelecimento de parâmetros de variação ambiental, atuais e futuros. Com base na importância deste tipo de registro, avaliou-se aqui a presença ou não de charcoal em amostras de turfeira coletadas no município de Cambará do Sul, situado na região nordeste do estado do Rio Grande do Sul. Utilizando parâmetros específicos, foram identificados em laboratório fragmentos com características de charcoal, os quais foram separados e avaliados sob Microscópio Eletrônico de Varredura (MEV). A partir das análises em MEV foi possível identificar a ocorrência de charcoal em todos os intervalos de profundidade, variando, todavia, quanto à quantidade. A idade dos charcoal foi definida entre 0 e 31.764,71 anos, sendo possível concluir que em cada uma das amostras avaliadas, os quais, em termos de tempo correspondem aproximadamente a 1.000 anos, existiu pelo menos um grande evento de incêndio. Assim, foi possível confirmar que a ocorrência de incêndios vegetacionais de origem ainda indefinida, é um evento relativamente comum e recorrente na área de estudo. Conseqüentemente, quando houver novas discussões em relação aos fatores importantes na manutenção dos Campos de Cima da Serra como sistema consolidado, é fundamental que se leve em consideração que o fogo é elemento natural integrante do mesmo.