Part I. The syntheses of a series of stable ferrocenylsilane compounds and their corresponding polyradical cations are reported. Electron spin properties of these molecules were investigated by cyclic voltammetry, ESR, and magnetic susceptibility measurements. All the compounds presented, showed significant electronic communication (>100 mV) between the redox centers by CV. Part II. Baeyer-Villiger oxidation of (1,9-dimethyl-PCU-8,11-dione) was performed using m-chloroperoxybenzoic acid in 1:2 molar ratios. The product obtained was the corresponding dilactone 113. The structure of the reaction products was established unequivocally via single crystal X-ray diffraction methods. The reaction of the 1,9-dimethyl-PCU-8,11-dione with 1:1 molar ratio of m-chloroperoxybenzoic acid produced again the dilactone 113, and not the expected monolactone 114. Ceric ammonium nitrate (CAN) promoted oxidation reaction of 1,9-dimethyl-PCU-8,11-dione afforded a mixture of dimethylated lactones, which indicated unique reaction mechanism pathways. These individual isomers, 115 and 116, have been isolated from these mixtures via column chromatography by using silica gel as adsorbent followed by fractional recrystallization of individual chromatography fractions. Structures of these pure products have been established unequivocally by application of single crystal X-ray crystallographic methods.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016 / The theoretical and experimental investigation of electron spin-resonance relaxation to deposit thermal energy into liquid gadolinium-based contrast agents for cancer hyperthermia treatment is presented. Previous works suggest that using protons in water are inadequate, with a thermal deposition rate of approximately 1 ◦C per two years. A novel component of this research relies on the use of gadolinium-chelated molecules, which are currently used as contrast agents in clinical MRI scans. The chelating agents, or ligands, investigated are Gadobenate (MultiHance R ), Gadopentetate (Magnevist R ), Gadoterate (DotaremR ) and Gadoteridol (ProHance R ). The gadolinium atom has seven unpaired electrons in its inner f shell orbital and as a result has a 660 times stronger paramagnetic response when placed in an external magnetic field. The research tests the hypothesis that by using an appropriate external homogeneous DC magnetic field, together with a radiofrequency excited resonator, that a measurable amount of thermal energy is deposited into a liquid gadolinium-based contrast agent. The aim of this research is to ultimately discover a new cancer hyperthermia treatment. The research theory suggests that a temperature rate of 13.4 ◦C · s−1 can be achieved using the gadolinium-based contrast agents under certain experimental conditions, and a maximum of 29.4 ◦C · s−1 under more optimal conditions. The temperature rates are calculated using parameter values commonly found in literature and practice. The simulation and design of the DC magnetic field coil system is discussed, together with the simulation results and design parameters of the radiofrequency loop-gap resonator. The experimental results and analysis indicate that the selected contrast agents have varied responses based on their chemical nature and that only two out of the four contrast agents, Dotarem and ProHance, show a measurable effect albeit sufficiently small that statistical techniques were necessary to distinguish the effect from background. A model fit to the data is performed in order to determine the spin-lattice relaxation time of the contrast agents under the specified experimental conditions. The model estimate is significantly smaller than the values found in literature under similar conditions, with a spin-lattice relaxation time τ1e of approximately 0.2 ps compared to the literature value of 0.1 ns. Although the observed electron spin resonance heating rate is in the milli-Watt range it is still notably larger (167 000 times) compared to the heating rate obtained using protons. The low temperature rates suggest that a more suitable agent or molecule with a larger spin-relaxation time be used, in order to achieve clinical useful temperature rates in the range of 14 ◦C · s−1. / MT2017

A survey of the optical and electron paramagnetic resonance (E.F.R.) absorption in a large number of diamonds from all major sources of production has revealed that perfect diamond is virtually non-existent. One or more of eleven different types of defect centres is found in each specimen. The presence or absence of nitrogen has long been known to give rise to the distinctive properties of Type I and Type II diamond.The present survey has shown that the form in which the nitrogen is present is significant. In most specimens the nitrogen is present in substitutional, non-paramagnetic platelet form, and these specimens were classified as Type Ia diamonds. A small group of transparent natural diamonds was found to contain dispersed paramagnetic nitrogen. The optical properties of these diamonds are unlike those of other diamond types and have hitherto not been reported. It is proposed that these diamonds be classified as Type lb.Three new systems of E.P.R. lines were found in Type Ib diamond. They are shown to be due to: (i) 13C atoms situated in different positions relative to the substitutional nitrogen, (ii) interaction of the small quadrupole moment of the nitrogen with the electric field gradient, and (iii) the presence of the l5N isotope. Synthetic diamonds are found to be exclusively of the Type Ib variety, whereas natural Type Ib diamond are rare exceptions. This is attributed to the growth history of the specimens. In order to investigate the defect centres associated with nitrogen in diamond, Type Ia and Ib diamond were irradiated with 0.78 MeV electrons. The effects observed were complicated and therefore led to a general investigation of irradiation damage, and the annealing of irradiation damage in diamond. In addition to the G.R.l and U.V. bands induced in all diamond by irradiation damage, another optical absorption feature, the N.D.l band, is found in all Type Ia diamond after irradiation and limited heating. It is suggested that the N.D.l centre arises from the combination of a carbon interstitial, and nitrogen in platelet form, and that the other primary product of irradiation damage, a vacancy, is responsible for both the G.R.l and U.V. bands. The N.D.l centre acts as an acceptor, the G.R.l centre as a donor. In the ionized state G.R.l is inactive in optical absorption; N.D.l is active. Electron transfer by thermal excitation results in the bleaching of G.R.l and the enhancement of N.J.l. Illumination with light in the N.D.l band causes electron transfer in the reverse direction, restoring band strengths to their former condition. A model is proposed which defines the energies within the forbidden gap of the ground and excited states of G.R.l and N.D.l. On heat treatment at temperatures of 500°C and above, the G.R.l band in all diamonds anneals out. The rate of annealing, however, is founa to be dependent on the nitrogen concentration. Thus in Type IIa diamond (which contains no nitrogen) G.R.l anneals very slowly, resulting in the formation of an absorption tail. In Type Ia diamond G.R.l anneals much faster (the actual rate depending on the nitrogen concentration), and two optical absorption bands, 5032A and H2, are formed. It is proposed that the vacancy in diamond becomes mobile at about 500° C, and that the G.R.l band in Type IIa diamond anneals because of the agglomeration of vacancies, which results in the formation of defects responsible for the absorption tail. In Type Ia diamond the nitrogen platelets are ideal sinks for vacancies, because the lattice on either side of a platelet is in compression. G.R.l therefore anneals more rapidly and 5032A centres are formed due to the combination of a vacancy and a nitrogen platelet. The nature of the H2 centre is much more obscure, but a possible explanation is that H2 centres are formed in addition, because the N.D.l centres (nitrogen platelets with embedded interstitials) also succeed in trapping vacancies. Vacancy/interstitial recombinations are prevented since these defects are pinned to different locations in the platelet region. In type Ib diamonds N. D.l centres were found to form at a lower temperature than in Type Ia diamond. It is suggested that the carbon interstitial in diamond is mobile, and combines with Substitutional nitrogen in isolated positions at temperatures below 250°C. In Type Ia specimens, where the nitrogen is segregated in platelets, this process only occurs at about 250°C, when the interstitial has enough kinetic energy to overcome the energy barrier preventing it from combining with nitrogen inside the platelet region where it will relieve strain. Because of the different substitutional nitrogen configuration, the energy levels of N.D.l centres in Type Ib diamond are such that electron transfer by thermal excitation from G.R.l to N.D.l occurs at room temperature. Most of the G.R.l centres are therefore permanently ionized and optically inactive. After heat treatment, a new band called the 6400A band is formed in irradiated Type Ib diamond. It is suggested that 6400A centres are formed by the combination of mobile vacancies with substitutional nitrogen in isolated positions. The 6400A band is therefore analogous to the 5032A band produced in Type Ia diamond. As expected no analogue of the H2 is formed in Type Ib diamond, as both an interstitial and a vacancy cannot co-exist in combination with a single isolated substitutional nitrogen atom.

Neste trabalho são apresentados o desenvolvimento e construção de um sistema de microondas para espectroscopia paramagnética eletrônica em baixa freqüência (bandas L e S). Basicamente o sistema é composto de um oscilador que opera na faixa de 1,0 a 2,0 GHZ, uma cavidade do tipo Bridged Loop-Gap, acopladores direcionais, circuladores, atenuadores, detetor, sistemas de controle automático de freqüência CAF e pré-amplificador. Todo o arranjo compõe uma ponte de microondas que é acoplada à unidade de processamento e registro do espectrômetro VARIAN (E-109) do Laboratório do grupo de biofísica do IFQSC. No sistema apresentado os estágios de amplificação de baixo ruído, circuito de CAF, pré-amplificador e sistema ressonante foram desenvolvidos e implantados localmente. A conveniência em se utilizar um espectrômetro de RPE em baixa freqüência é permitir o estudo de amostras que apresentam características espectrais vindas das interações hiperfinas e superhiperfinas parcialmente resolvidas em freqüências mais altas. Também é possível obter-se parâmetros de energia de campo zero de sistemas de spin com S &#62 1 se o sistema puder ser tratado por métodos aproximativos em banda X. Um exemplo utilizando o íon Cr3+ no garnet CGGG é mostrado neste trabalho / In this work a microwave bridge for electron paramagnetic resonance spectroscopy hás been developed. The system is suitable for operation at low frequency, basically L and S-band. It is composed of an oscilator with a 1.0 to 2.0 GHz bandwith, a Bridged loop-gap resonator, directional couplers, circulators, attenuators, reverse diode detector, AFC sub-system and a pré-amplifier. All these modules are assembled to a constitute a microwave bridge, which is coupled to the processing and register unit of the VARIAN E-109 EPR spectometer of the Biophysics Laboratory at IFQSC. The low-noise amplifier, AFC sub-system, pre-amplifier and the Bridged Loop-Gap resonator have been entirely developed in this work. The advantage in the use of the low frequency EPR spectometer is that it allows the study of samples which present paramagnetics structures that are obscured by g-strain at high frequency (X, Q band). These structures come out from hiperfine and superhiperfine poorly resolved in the high frequency range that could be conventienly resolved at low frequency. It is also possible, to obtain the zero field splitting parameters in spin systems with S &#62 1, if a perturbative approximation is useful, comparing the spectre in X and L band. One example of this new approad using Cr3+ as impurity in the CGGG garnet is presented.

As ferroporfirinas sintéticas são sistemas complexos que vêm sendo amplamente estudadas. A dificuldade em obter informações estruturais, reações químicas e ligantes do íon central vêm estimulando o estudo pormenorizado desses sistemas. Nestes trabalho é apresentada a caracterização da série de FeP fluorosubstituídas, que compreende as mono-, di-, tri e tetra- fluorofenilporfirina, denominadas FeTF5PP, FeTF10PP, FeTF15PP e FeTF20PP, respectivamente. Essas FeP são estudadas em função dos solventes diclorometano (DCM), metanol (MeOH) e das várias misturas em volume desses dois. As técnicas espectroscópicas de Absorção Eletrônica na região do Ultravioleta ao Visível (UV-Vis) e Ressonância Paramagnética Eletrônica (EPR) são as duas ferramentas de estudos escolhidas para caracterizar esses sistemas. Partindo-se de uma solução de FeP dissolvida em DCM, foram adicionadas alíquotas de Me0H até completar-se 50% em volume desses dois solventes. Através dessa titulação, observamos a formação de diferentes espécies como conseqüência da coordenação do Me0H à FeP. Notamos também, as modificações estruturais reveladas principalmente pelo EPR, ocasionadas pelos diferentes números de substituintes fluorofenis. Essa técnica espectroscópica revelou ainda a existência de interações que não foram anteriormente observadas. Para a FeTFloPP foi verificada a interação super hiperfina entre o Fe e o ligante CF além da interação super hiperfina entre o Fe e os nitrogênios do anel porfirínico. Para a FeTF20PP foi verificada apenas a interação super hipeOna entre o Fe e o ligante Cl-. As demais FeP não apresentaram essas interações / Synthetic iron porphyrins are complex systems that have been largely studied. Difficulties to obtain structural information, chemical reactions and ligands of the central ions have been a subject to investigate details of these systems. In this work, a systematic characterization of one series of fluorophenyl iron porphyrins is presented. Mono-, di-, tri- and tetrafluorophenyl substituents called FeTF5PP, FeTF10PP, FeTF15PP, and FeTF20PP, respectively, are included in this series. Iron porphyrins were studied as a function of dichloromethane, methanol solvents and several of their mixture in volume. These systems were characterized by Ultraviolet- Visible and Electron Paramagnetic Resonance Spectroscopes. From iron porphyrin solutions, dissolved in dichloromethane, aliquots of methanol were added up to 50% in volume of these two solvents. With this titration, we found different species because of the methanol coordination to the iron porphyrins. We also observed the structures modification revealed by the EPR spectroscopy, as a function of different numbers of fluorophenyl substituents. The EPR spectroscopy also revealed the existence of the super hyperfine interactions not observed before. It was found for FeTFloPP between the central ion and the axial ligand chlorine Cl - ion, besides the hyperfine interaction between iron and the nitrogen of the pyrrole ring. For FeTF20PP only the super hyperfine interaction, Fe-C1 was found. These interactions were not observed for the other iron porphyrins

Estudos dosimétricos em hidroxiapatita (HAp) podem ser utilizados para a determinação da dose absorvida em tecidos duros em diversas situações, tais como acidentes radiológicos, controle de processos de esterilização e datação arqueológica. Essa tese apresenta estudos da resposta à dose de radiação tanto do sinal de Ressonância Paramagnética Eletrônica (RPE) quanto de termoluminescência (TL) para HAp. A fauna de mamíferos fósseis encontrada na Planície Costeira do Rio Grande do Sul é conhecida desde o final do século XIX, porém ainda pouco se sabe sobre seu contexto bio e cronoestratigráfico. Neste trabalho foram datadas, por RPE, onze amostras de dentes de mamíferos extintos, coletados no Arroio Chuí e ao longo da praia, proveniente do sul da costa do Rio Grande do Sul. As idades obtidas para essas amostras contribuem para um melhor entendimento da origem dos depósitos fossilíferos. Em um segundo momento do trabalho, é proposto um novo procedimento de decomposição de espectros complexos de RPE, voltados para a dosimetria e datação. O método consiste na utilização de funções do pacote de funções do software \"Easyspin\", que é gratuito, associadas a métodos de minimização de funções. Após a validação, o método foi aplicado na decomposição de espectro de duas amostras de dentes de Stego-mastodon waringi, provenientes do nordeste do Brasil. A decomposição visa verificar o efeito que tem as componentes sobrepostas ao sinal dosimétrico sobre o cálculo da dose acumulada e mostrou-se útil para melhorar a precisão na determinação da dose. Por fim, hidroxiapatita sintética carbonatada do tipo-A e hidroxiapatita natural extraída de dentes fósseis foram caracterizadas por TL. Os resultados obtidos por essa técnica mostrou que esses dois tipos de amostra são capazes de responder a radiação ionizante. Contudo, esses mesmos resultados também revelaram a impossibilidade de se fazer dosimetria por termoluminescência com fins à datação, para esse tipo de amostra. / Dosimetric studies on hydroxyapatite (HAp) can be used to determine the absorbed dose in hard tissues in several situation, such as radiologic accidents, control of sterilization process and archaeological dating. This PhD thesis presents studies about radiation dose response assessed by electron paramagnetic resonance (EPR) as well as thermoluminescence in HAp. The fossil mammalian fauna from the Coastal Plain of Rio Grande do Sul State has been known since the late XIX century; however, its biostratigraphic and chronostratigraphic context is still poorly known. The present works describes the results of electron spin resonance (ESR) dating on teeth of extinct mammals collected along the Chuí Creek and coastline. The ages obtained for these samples contribute to a better knowledge about the origin of these fossil. In a second stage of this work, we propose a new EPR spectrum deconvolution (or decomposition) procedure aimed to dosimetry and dating. The method uses the EasySpin (a freeware software) set of functions associated with minimization procedures. After validation, the method was applied in spectrum deconvolution of two Stegomastodon waringi enamel samples, originated from northeast of Brazil. The spectrum econvolution is aimed to verify the superposed components effects on the dosimetric signal over the accumulated dose calculation. The results have shown to be helpful in improving the dose calculation accuracy. In the last stage of this work, synthetic carbonated A-typ hydroxyapatite and natural one were investigated by Thermoluminescence. The obtained results shown that the two samples respond linearly to the ionizing radiation dose. However, the short thermoluminescent glow-peak lifetime suggest that it\'s inadequate for dating purpose.

Lapis Lazuli é um mineral de silicato, que foi objeto do presente estudo. Trata-se de uma solução sólida complexa de outros quatro minerais de silicato, a saber: sodalita, noselita, huainita, e lazurita. Essa composição da solução sólida não permite estimar a porcentagem de cada mineral componente, no analise de fluorescência de raios X, onde se obteve que os principiais óxidos componentes do lapis lazuli são, (em % mol) SiO_2 (33,2), CaO (16,3), MgO (12,1) e Al_2 O_3 (10,1) e, em menor concentração , Na_2 O (6,10), SiO_3 (5,90), Fe_2 O_3 (2,05), K_2 O (1,90) e outros óxidos em concentrações menores. Para a caracterização da amostra de lapis lazuli, foram utilizados termoluminescência (TL), ressonância paramagnética eletrônica (EPR) e técnicas de espectroscopia de reflectância. Em TL, é claro, as curvas de emissão da amostra natural, irradiada ou com tratamento térmico têm sido utilizadas. Uma curva de emissão da amostra natural apresentou picos em 296°C e a 372°C , mas as amostras irradiadas mostraram picos em 140°C, 250°C e 350°C. Logo mostrou - se que o pico em 140°C, é na verdade, uma sobreposição dos picos em 116°C e 160°C. O segundo pico cresce linearmente com a dose até cerca de 7000-8000 Gy. O lápis-lazúli apresenta um decaimento anômalo. O primeiro pico decaiu a partir de 3400 (u.a) para 1700 (u.a), em 45 horas, o segundo pico decaiu a partir de 8500(u.a) para 3000 (u.a), nas mesmas 45 horas. Para a Avaliação da parâmetros E e s, o método de forma de pico e Tm- Tstop. O terceiro método com base em diversas taxas de aquecimento para a leitura TL, com a utilização direta do método resultou em valores de E e s irrealistas. Não se encontrou a explicação por que, mas ao fazer deconvolução das curvas de emissão para cada taxa de aquecimento encontramos resultados mais realistas. A deconvolução mostrou quatro picos em 110°C, 146°C, 191°C 245°C, com valores E, respectivamente iguais a 1,229 eV ; 1,23eV; 1,24eV e 1,25eV . O espectro de EPR da amostra experimental apresentou seis sinais de Mn^(2+) e um sinal grande de Fe^(3+) com g= 2,0. A irradiação da ordem de dezenas de kGy produzido um sinal em torno de g=2,003 devido ao centro em F induzido pela radiação. O espectro de refletância mostra um vale em torno de 600 a 800 nm, que corresponde a uma banda de absorção do mesmo comprimento de onda e é responsável pela coloração azul. / Lapis Lazuli is a natural silicate mineral investigated in the present work. It is a complex solid solution of four other silicate minerals, sodalite, Nosean, Hanyne and Lazurite. This compositon of solid solution does not allow the estimate of the percentage of each mineral component from the result of X ray fluorescence analysis, which has revealed as main oxide components of lapis lazuli as (in mol % ) SiO_2 (33,2), CaO (16,3), MgO (12,1) and Al_2 O_3 (10,1) and in smaller concentrations Na_2 O (6,10), SiO_3 (5,90), Fe_2 O_3 (2,05), K_2 O (1,90) plus others in even smaller concentration. For the characterization of the lapis lazuli sample, we used thermoluminescence (TL), electronic paramagnetic resonance (EPR) and reflectance spectroscopy techniques. In TL, of course, glow curves of natural or irradiated or annealed samples have been used.\\\\ A typical glow curve presented peaks at 296.5°C and at 372°C, but irradiated sample has shown peaks at 140°C, 250°C and 350°C. Later it was shown that 140 °C peak is actually a superposition of 116°C and 160°C peaks. The second peak is the prominent one and its height grows linearly with the dose up to about 7000 to 8000 Gy. Lapis lazuli presents an anomalous fading. The first peak decays from 3400 (a.u.) to 1700 (a.u.) in 45 hours, the second peak decays from 8500 (a.u.) to 3000 (a.u.) in the same 45 hours. For the evalution of parameters E and s, peak shape method and Tm-Tstop methods have been used. The third method based on various heating rates for TL reading, with the direct use of method yielded unrealistic E and s values. We did not find explanation why, but doing the deconvolution of glow curves for each heating rate we found more realistic results. The deconvolution has shown four peaks at 110°C, 146°C, 191°C ands 245°C with E-values, respectively equal to 1.229eV, 1,23eV, 1.24eV and 1,25 eV. The EPR spectrum of natural sample consisted of six signals of Mn^(2+) and strong Fe^(3+) signal at g=2,0. The irradiation of the order of tens of kGy produced a signal around g=2,003 due to radiation induced F-center. The reflectance spectrum shows a dip around 600- 800nm which corresponds to an absorption band of the same wavelength and is responsible for blue colour.

este trabalho estudamos a interação do hormônio peptídico bradicinina (BK, \'Arg POT.1\'-\'Pro POT.2\'-\'Pro POT.3\'-\'Gly POT.4\'-\'Phe POT.5\'-\'Ser POT.6\'-\'Pro POT.7\'-\'Phe POT.8\'-\'Arg POT.9\')e seus fragmentos (des-\'Arg POT.1\'-BK, des-\'Arg POT.9\'-BK e \'BK POT.1-5\'-) com membranas lipídicas, utilizando as técnicas de Fluorescência e Ressonância Pararnagnética Eletrônica (EPR. Por fluorescência, monitoramos as alterações espectrais da sonda fluorescente extrínseca ácido orto-aminobenzóico (Abz), incorporada à bradicinina (Abz-BK) e a seus fragmentos. Observamos um deslocamento espectral em direção ao azul, de aproximadamente 6 nm e um aumento dos valores de anisotropia e tempo de vida da fluorescência na presença de vesículas de dimiristoil fosfatidilglicerol (DMPG), indicativo da interação peptídeo-membrana. Os resultados das medidas de anisotropia com resolução temporal confirmaram esses dados, sendo que para os peptídeos em solução, encontramos um tempo de correlação rotacional da ordem de ps, e na presença de uma concentração saturante de DMPG houve um aumento desses tempos. A sonda extrínseca Abz foi inicialmente testada, para nos assegurarmos da sua validade, ou seja, de que não estaria interferindo nos processos de interação. Pela técnica de EPR, monitoramos as alterações causadas pelos peptídeos na estrutura das membranas lipídicas de DMPG, através de diferentes marcadores de spin inseridos em diferentes posições da cadeia hidrocarbônica. Para temperaturas acima da transição de fase líquido-cristalina do DMPG ( 20°C), todos os marcadores usados indicaram que I O % em moles dos peptídeos, em relação ao sistema lipídico, interagem com as vesículas de DMPG, tornando a membrana menos fluida, sugerindo urna penetração parcial dos peptídeos na membrana. Na fase gel, a bradicinina causou uma forte diminuição na fluidez da membrana, sendo que a l5°C o sistema BK-DMPG apresentou o efeito de histerese, evidenciada pelo diferente alargamento dos espectros quando a amostra era resfriada (45 a 0°C) e aquecida novamente (O a 45°C). Esses resultados são específicos do sistema BK-DMPG, não sendo encontrados com os fragmentos da bradicinina, nem com os cátions testados: o íon monovalente (Na+) e divalente (Zn++ ), nem com o peptídeo pentalisina. / In this work we studied the interaction of the peptide hormone bradykinin (BK, \'Arg POT.1\'-\'Pro POT.2\'-\'Pro POT.3\'-\'Gly POT.4\'-\'Phe POT.5\'-\'Ser POT.6\'-\'Pro POT.7\'-\'Phe POT.8\'-\'Arg POT.9\') and fragments (des-Arg 1-BK, des-Arg9-BK e BK1-5) with model lipid membranes, using two different techniques: Fluorescence and Electron Paramagnetic Resonance (EPR). We monitored the spectral alterations of the extrinsic fluorescent probe ortho­ aminobenzoic acid (Abz), bound to the peptide bradykinin (Abz-BK) and its fragments. A blue shift of 6 nm in the emission spectra and an increase in fluorescence anisotropy and lifetime in the presence of dimyristoyl phosphatidylglycerol (DMPG) were observed, indicating the peptide­ membrane interaction. Time resolved anisotropy measurements are in accord with these results. For the peptides in solution, we found a rotational correlation time on the ps range, and in the presence of a saturating concentration of DMPG this time was increased. The fluorescence properties of the extrinsic probe were tested to ensure its validity, i. e., the minimum interference of the probe in the peptide-lipid interaction process. By EPR we monitored the alterations caused by the peptide on the structure of DMPG bilayers, using spin labels incorporated in the membrane at two different positions of the hydrocarbon chain (5 and 12). For temperatures above the lipid gel-liquid crystal thermal transition 2(0°C) all the spin labels used indicated that at 10 mol % peptide, interact with DMPG turning the membrane less fluid, suggesting a partial penetration of these peptides in the membrane. In the lipid gel phase, BK was found to cause a decrease of membrane fluidity. At l5°C, the BK-DMPG system presents a hysteresis effect, evidenced by the different spectra yielded upon cooling (45 to 0°C) and heating (O to 45°C) the sample. These results were found to be different from those elicited by the BK fragments, and other cations tested: the monovalent (Na+,the divalent (Zn++), and the peptide peptide pentalysine

No presente trabalho foram estudadas algumas propriedades de Termoluminescência (TL), Ressonância Paramagnética Eletrônica (RPE) e Refletância de uma amostra natural e de amostras artificiais de diopsídio. A curva de emissão TL das amostras tratadas termicamente a 600 `GRAUS´ C/1hr e irradiadas com dose gama mostraram um pico em aproximadamente em 160 `GRAUS´ C, que depois ficou demonstrado ser uma superposição de três picos em 160 `GRAUS´ C, 197 `GRAUS´ C e 230 `GRAUS´ C, além dos picos TL em 300 `GRAUS´ C, 350 `GRAUS´ C e 450 /C, mas de intensidade bem menor que os dos outros. Foram produzidas amostras artificiais de diopsídio, pelo método de devitrificação, uma pura e outras dopadas, separadamente, com Al, Fe e Mn. A amostra artificial pura apresentou todos os picos entre 160 e 350 `GRAUS´ C, encontrados no diopsídio natural, indicando que todos esses picos são devido a defeitos intrínsecos. A presença de Al e Mn afeta esses picos TL. O Fe, conhecido como \"killer\" abafa praticamente todos os picos, exceto o de 450 `GRAUS´ C que não depende de irradiação como os outros. O espectro de emissão TL da amostra natural apresentou uma banda em 435 nm indicando que só há um centro de recombinação, que é devido à presença de Al. A sensibilidade TL aumenta com o tratamento térmico antes da irradiação. Os picos TL crescem linearmente com a dose gama de irradiação, exceto na amostra artificial dopada com Al onde o pico em 410 `GRAUS´ C cresce sublinearmente. A irradiação UV produz decaimento na intensidade TL (fotoesvaziamento). Por outro lado induz picos TL em 90 `GRAUS´ C e 170 `GRAUS´ C nas amostras naturais pré-recozidas a 600 `GRAUS´ C por uma hora, picos não observados com banda em 1050 nm também foi observada no diopsídio artificial dopado com Fe; as bandas em 1390 nm (OH), 1910 nm H2O, 2310 nm e 2385 nm decrescem de intensidade com o aquecimento, sendo que algumas até desaparecem. No espectro de RPE foram detectados três centros. Um devido ao `Mn POT.2+´, cujo espectro RPE da amostra em pó apresenta as seis linhas hiperfinas típicas na região de 3000 a 4500 G, sendo que esses sinais não são afetados pela radiação gama e nem pelo recozimento térmico. Na amostra monocristalina orientada na direção z foram observadas todas as linhas do `Mn POT.2+´. O segundo centro é devido ao `Fe POT.3+´ em g=4,3, o recozimento na região de 500 até 900 `GRAUS´ C mostrou que o íon `Fe POT.2+´ oxida-se para `Fe POT.3+´, esse mesmo comportamento foi observado nas medidas de refletância. O terceiro centro identificado por RPE localizado em g=2,007, é o `E\' IND.1´. Os três centros observados por RPE na amostra natural, foram confirmados nas amostras artificiais de diopsídio. A emissão de luz TL envolve centros de Ti, de Al e centros `E\' IND.1´. O seguinte mecanismo de emissão TL e formação dos picos TL entre 160 e 230 `GRAUS´ C, em torno de 300 `GRAUS´ C e em torno de 350 `GRAUS´ C, é proposto: A irradiação cria os centros de Ti, de Al e o centro `VO POT.2-´. `VO POT.2-´ corresponde à vacância de oxigênio que capturou dois elétrons. Durante o aquecimento: Entre 150 e 250 `GRAUS´ C, o centro `VO POT.2-´ libera um elétron, que se recombina com os centros de Ti e de Al dando lugar ao centro `E\' IND.1´ e emissão de luz TL de 435 nm. O pico TL em torno de 160 `GRAUS´ C, composto de 3 picos é formado. O centro de Ti é eliminado, mas parte do centro de Al ainda permanece. Entre 250 e 300 `GRAUS´ C, os centros `VO POT.2-´ continua emitindo elétrons, cada um dos quais se recombina com uma parte do centro de Al remanescente emitindo a luz TL de 435 nm e formando mais centros `E\' IND.1´. Como, experimentalmente, se sabe que a concentração de centros `E\' IND.1´ atinge o máximo em 300 `GRAUS´ C, é natural admitir que, todos os centros `VO IND.2-´ se converteram em centros `E\' IND.1´. Entre 300 e 400 `GRAUS´ C, os elétrons dos centros `E\' IND.1´, formados acima, são liberados, cada um dos quais se recombina com os centros de Al que restam, observando-se a emissão de luz TL em 435 nm. Nessa temperatura, tanto os centros `E\' IND.1´ dão lugar às vacâncias de oxigênio VO, como os centros de alumínio [`AlO IND.4´/h] dão lugar aos centros `[`AlO IND.4´] POT.-´ que, para neutralidade de carga atraem íons alcalinos `M POT.+´ para formarem os centros `[`AlO IND.4´/`M POT.+´] POT. 0´. O pico em 350 `GRAUS´ C é originado nesse processo. A partir de diopsídio natural foi obtido vidro. O vidro apresentou sinais RPE de `Fe POT.3+´ em torno de 1700 G e as seis linhas típicas do `Mn POT.2+´ em torno de 3470 G. Uma banda de refletância devido a `Fe POT.2+´ com um máximo ao redor de 1000 nm é observada. / Diopside of chemical formula, CaMgSi2O6, a natural silicate mineral has been investigated concerning its Thermoluminescence (TL), Electron Paramagnetic Resonance (EPR) and Reflectance properties. Synthetic, pure or doped diopside, produced in the laboratory, has been investigated. Samples annealed at 600 `GRAUS´ C for one hour, to eliminate previously induced TL, and irradiated at several gamma-doses, presented glow curves with TL peaks around 160, 300, 350 and 450 `GRAUS´ C. Later on, the broad peak around 160 `GRAUS´ C was proved to be a superposition of peaks at 160, 197 and 230 `GRAUS´ C. The pure synthetic diopside presented TL peaks at 160 to 350 `GRAUS´ C, indicating that these peaks are due to intrinsic defects. Synthetic samples containing Al or Mn have indicated that these dopants interfere with TL peaks found in the natural diopside. Fe, on the other hand, known as \"killer\", precludes the appearance of all the peaks, except at 450 `GRAUS´ C, peak that is not affected by radiation and heat. The TL emission spectrum has presented only one band around 435 nm. This fact indicates that there is only one kind of recombination center. An annealing at temperatures above 800 `GRAUS´ C up to 1000 `GRAUS´ C yields an enhancement in the TL sensitivity up to a factor of 2. Beyond 1000 `GRAUS´ C heating, an opposite effect takes place. Except for 410 `GRAUS´ C peak found in the Al-doped artificial diopside, all the other peaks grow linearly with radiation dose, but saturate beyond `DA ORDEM DE´ kGy. In a previously gamma-irradiated sample, all the peaks are bleached rapidly under ultraviolet radiation shining. The UV light, on the other hand is able to induce TL, however only TL peaks around 90 and 170 `GRAUS´ C are observed. No explanation has been found as yet, why gamma-rays and UV light induce TL with different results.The spectrum of reflectance has shown several bands at 1050, 1390, 1910, 2310 and 2385 nm. The 1050 nm band is due to Fe2+ which is substitutional to a Mg2+ ion. This band was also observed in Fe- doped synthetic diopside. 1390 nm band is due to OH and 1910 nm to H2O; they, together with 2310 and 2385 nm bands decrease with temperature. In the EPR measurements, hyperfine signals due to Mn2+ in the region of 3000 to 4000 Gauss, g=4.3 Fe3+ signal and g=2.007 lines due to `E\' IND.1-´ center have been detected. Two first ones do not depend on irradiation. On the other hand, an annealing between 500 and 900 `GRAUS´ C decreases 1050 nm Fe2+ band followed by increase in g=4.3 Fe3+ lines, because of the oxidation of Fe2+ converts this ion into Fe3+ ion. The EPR signal of `E\' IND.1´ center increases with temperature, reaching a maximum value at 300 `GRAUS´ C, but decreasing for higher temperatures, with its extinction at 400 `GRAUS´ C. The TL light emission involves `i- , Al- and `E\'IND.1-´ centers. The following mechanism is here proposed. The irradiation creates Ti- , Al- and `VO POT.2-´ - centers. where the is an oxygen vacancy has captured two electrons. Ti- and Al- centers are of the form [`TiO IND.4´/h] and [`AlO IND.4´/h], respectively, where h denotes a hole. During heating for TL read out: Between 150 and 250 `GRAUS´ C , the `VO POT.2-´ center releases an electron that recombines with the Ti and Al centers giving the `E\' IND.1´ center and emission of light at 435 nm. The TL peak around 160 `GRAUS´ C composed of three individual peaks is formed. The Ti center is eliminated while the Al center still stays. Between 250 and 300 `GRAUS´ C, the `VO POT.2-´ centers continue to liberate electrons and their recombinations with holes in Al centers, result in the emission of TL light at 435 nm. Additional `E\' IND.1´ center is created. Experimentally it is known that the concentration of `E\' IND.1´ centers reaches its maximum at 300 `GRAUS´ C, for this, we can say that all the `VO POT.2-´ centers were converted into `E\' IND.1´ centers. Between 300 and 400 `GRAUS´ C, the `E\' IND.1´ centers liberate their electrons and each one recombines with a hole in remaining Al centers. Then, the TL light at 435 nm is emitted again. At this temperature, the `E\' IND.1´ centers give place to oxygen vacancies VO and the [`AlO IND.4´/h] centers convert to `[`AlO IND.4´] POT.-´ centers. To neutralize the charge this centers attract `M POT.+´ alcali ions to form the `[`AlO IND.4´/`M POT.+´] POT.0´ centers. The TL peak at 350 `GRAUS´ C is due to this process. From the natural diopside samples was obtained glass of diopside. The glass shows EPR component of `Fe POT.3+´ around 1700 G and six typical lines of `Mn POT.2+´ around 3470 G. A reflectance band due to `Fe POT.2+´ at approximately 1000 nm was observed

Neste trabalho a difusão de V, Cr, Mn e Fe por troca iônica, eletrodifusão e implante iônico foi efetuada na amostra natural de berilo incolor (goshenita). As medidas de termoluminescência (TL), ressonância spin paramagnética (EPR) e absorção ótica (AO) foram feitas na amostra natural com a finalidade de comparar as amostras apos a difusão em alguns casos a observação da variação das propriedades medidas. A amostra natural após a irradiação - delta com 10 Gy apresentou 3 picos TL a aproximadamente 150, 250 e 320ºC. Para altas doses o primeiro pico aumentou muito sua intensidade, sobrepondo-se sobre os outros dois picos de temperaturas altas. A amostra natural apresentou sinais EPR referentes aos íons Mn POT.2+ localizados na posição de Al POT.3+ e Fe POT.3+ no canal do cristal. As amostras irradiadas com altas doses de até 10 POT.6 Gy, além dos sinais mencionados, apresentaram novos sinais referentes ao CH IND.3, CO POT.-IND.3, H POT.GRAUS e Fe POT.3+. Este último íon, localizado em um ambiente tetraédrico, tem sinais na região de campos magnéticos baixos. As medidas de obsorção ótica na amostra natural apresentaram bandas muito intensas das moléculas de H IND.2O, situadas no canal, o que indica que os canais dessas amostras estão entupidos destas. A banda típica na região de 820 nm devido ao Fe POT.2+ no canal foi, também observada. As amostras, irradiadas com as mesmas doses que nas medidas de EPR, apresentaram bandas referentes ao Fe POT.+ na posição do Al POT.3+ na região entre 350 e 500 nm, bandas devido ao CO POT.-IND.3 na região entre 570 e 720 nm, o que geralmente é encontrado em berilos de tipo \"maxixe\" e, por último, uma banda na região entre 280 e 350 nm referentes ao Fe POT.3+ na posição do Be POT.2+. Para o processo de difusão, as amostras orientadas com a superfície ao longo do eixo-C PAE e perpendicular a este PEE foram usadas, com as dimensões de ) 8*6*1 mm3. No processo de difusão simples, 3 técnicas foram empregadas e denominadas difusão simples A, B e encapsulado. Para a difusão simples A e encapsulado uma camada fina de sal foi colocado numa das faces da amostra. Nestes dois processos os tempos de difusão foram de 1, 2 e 3 semanas à temperatura de 750ºC. Para a difusão simples B a amostra foi submersa dentro do sal num cadinho e a difusão foi feita à temperatura de 600ºC durante um mês. Para o processo de eletrodifusão uma camada de sal numa das faces da amostra PEE foi colocada (seta sobreE// C). Voltagens de 2500 V/cm e 5000 V/cm foram aplicadas entre os eletrodos. As amostras foram aquecidas até 500ºC. A eletrodifusão ao ar foi feita durante 24 horas e sob vácuo durante 5 dias. Além das experiências de difusão e eletrodifusão também foram feitos implantes de V, Cr, Mn e Fe nas amostras PAE e PEE. A energia usada no processo de implante foi de 400 keV e, as doses recebidas foram de 2.10 POT.16 átomos/cm POT.2 para Fe, Cr e Mn e de 9.10 POT.15 átomos/cm POT.2 para o V. As medidas de EPR, AO e TL das amostras após a difusão, eletrodifusão e implante iônico foram feitas. Devido à baixa concentração de íons difundidos no cristal as medidas de EPR das amostras, em todos os processo de difusão empregados, não mostraram sinais significativos dos íons difundidos com exceção do Fe difundido pelo processo simples A e encapsulado. O mesmo tem acontecido com as medidas de AO. Foram encontradas somente bandas devido aos íons de Fe e Cr na difusão simples A e B. Segundo estes resultados tudo indica que os íons estão se difundindo pelo mecanismo de vacância em maior proporção e em menor por interstícios. As medidas de TL mostraram um aumento considerável nos picos TL de altas temperaturas 250 e 320ºC talvez devido à criação de defeitos de estrutura devido à temperatura de difusão. Segundo os resultados obtidos ) para o coeficiente de difusão e energia de ativação tem se observado que os íons se difundem mais facilmente nas amostras PEE que nas PAE e, dos quatro íons empregados, V, Cr, Mn e Fe), o íon de Fe tem-se mostrado mais fácil de se difundir no cristal. Foi também observado que o campo cristalino exerce influência no processo de difusão. / In the present work diffusion of the ions V, Cr, Mn and Fe was carried out using ionic exchanges, electro diffusion and implant techniques in the natural uncolored beryl (goshenite). For comparison measurements of hermoluminescence (TL), electron paramagnetic resonance (EPR) and optical absorption (OA) were carried out on natural and ion diffused goshenite samples. The TL measurements of natural samples irradiates to 10 Gy additional delta-rays revealed three peaks around 150, 250 and 320GRAUSC. for higher delta doses the first peak intensity increases so rapidly to cover two other TL peaks. The typical Mn POT.2+ and Fe POT.3+ signals are found in the natural samples after EPR measurements. Mn POT.2+ is subtitutional to Al POT.2+ and Fe POT.3+ are located in the channel. Irradiation to 10 POT.6 Gy EPR signals due to CH IND.3, CO POT.-IND.3, H POT.GRAUS and Fe POT.3+ in tetrahedric position are added. The optical absorption spectrum of natural samples is characterized by 820 nm Fe POT.2+ band and very intense H IND.2O molecules band indicating the channels full of water molecules. After 10 POT.6 Gy irradiation absorption bands due to Fe POT.3+ subtitutional to Al POT.3+ between 35C and 500nm, band due to CO POT.-IND.3 between 570 and 720 nm (maxixe type) and a band between 280 and 350 nm due to Fe POT.3+ substituting Be POT.2+ are found. For diffusion thin plates of goshenite 1mm thick were prepared. Those with the surface perpendicular to C-axis was dominated PAE and those parallel to C-axis PEE. In the process of diffusion 3 techniques were used and denominated as: simple diffusion A, B and encapsulated diffusion. For the simple diffusion A and encapsulated a fine layer of salt was put in the faces of the sample. In these two process the diffusion times were of 1,2 and 3 weeks and in a furnace at 750°C. For the simple diffusion B the sample was kept immersed inside of the salt to be diffused during one month at 600°C. the electro diffusion process was also used for PEE plates under a field of 2500V/cm in one case and 5000 V/cm in another. The temperature varied from room temperature up to 500°C for 24 hours. The eletrodiffusion in air atmosphere was made during 24 hours and eletrodiffusion in vacuum for 5 days. Implant of V, C, Mn and Fe ions was also made. The energy used in the implant process was of 400 KeV and, the received doses were of 2.10 POT.16 atoms/cm² for Fe, Cr and Mn and 9.10 POT.15 atoms/cm² for the V. Due to relatively small concentration of ions diffused into the crystal only in the case of Fe introduced by technique A and encapsulated one a significant change in the EPR spectrum was observed. Again only for technique A and B produced variation in the optical absorption spectra. These results indicate the vacancy mechanism for diffusion. The measures of TL showed a considerable increase for the TL peaks of high temperatures 250 and 320°C. according to the results obtained for the diffusion coefficient and activation energy it seems that the ions are diffused more easily in the samples PEE that in PAE and among four ions (V, Cr, Mn and Fe) the ion of Fe has shown to diffuse easily in the crystal. It was also observed that the crystalline field influences the diffusion process.