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Search Results: 1 - 10 of 2835 matches for " Geraldo Friedermann "
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Metil coenzima M redutase (MCR) e o fator 430 (F430)
Nakagaki, Shirley;Friedermann, Geraldo Roberto;Caiut, José Maurício Almeida;
Química Nova , 2006, DOI: 10.1590/S0100-40422006000500022
Abstract: this review presents studies on methyl coenzyme m reductase, the biological system factor 430 (f430) and the use of nickel(ii) complexes as structural and functional models. the ability of f430 and nickel(ii) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the ch3-s bond cleavage of methyl com (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system f430 was reviewed. the importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed.
Magneto-V1: um programa para o cálculo de corre？？es diamagnéticas e de momentos magnéticos efetivos
Friedermann, Geraldo Roberto;Nunes, Giovana Gioppo;Soares, Jaísa Fernandes;
Química Nova , 2005, DOI: 10.1590/S0100-40422005000200029
Abstract: a new computer program has been developed to help the users of force methods for magnetic moment determination. it provides a user-friendly interface for the calculation of corrected magnetic susceptibilities of paramagnetic materials and enables the user to simulate a number of chemical formulations for the sample under study. the program is written in the perl scripting language and runs on a unix platform.
Metil coenzima M redutase (MCR) e o fator 430 (F430)
Nakagaki Shirley,Friedermann Geraldo Roberto,Caiut José Maurício Almeida
Química Nova , 2006,
Abstract: This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed.
2-Mercaptobenzoxazole pentacyanoferrate(II/III) complexes: UV-Visible, M ssbauer, electron paramagnetic resonance, electrochemistry and molecular modeling
Luiz Juciane B,Andrade Fabiano M. de,Sá Eduardo L. de,Friedermann Geraldo R
Journal of the Brazilian Chemical Society , 2004,
Abstract: 2-Mercaptobenzoxazole pentacyanoferrate(II/III) complexes, [FeII/III(CN)5(bzoxs)]3-/2- , were prepared in MeOH/H2O 75:25% solutions and characterized by spectroscopic UV-Vis, M ssbauer, electron paramagnetic resonance (epr) and electrochemical-cyclic voltammetry- techniques. UV-Vis and epr spectra along with the electrochemical behavior suggested the coordination of the multi-functional N,S,O- donor ligand, bzoxs, to iron(III) through the sulfur atom. The crystal field parameters, DqL and Dt, calculated for the iron(II) complex, in addition to the reversible redox process FeIII-bzoxs + e- -> FeII-bzoxs also pointed to coordination via the sulfur atom. The results were compared with the chemical properties of pentacyanoferrate complexes containing other monodentate N-, S- and O-donor ligands. Ab initio calculations revealed the composition of the frontier orbitals of bzoxs and are in agreement with the mode of coordination proposed from the experimental data.
Synthesis, characterization, EPR spectroelectrochemistry studies and theoretical calculations of manganese(II) complexes with the ligands H3bpeten and H3bnbpeten
Romanowski, Stela Maris de M.;Machado, Sérgio P.;Friedermann, Geraldo R.;Mangrich, Antonio S.;Hermann, Monique de F.;Lima, Hugo Orofino;Nakagaki, Shirley;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000500011
Abstract: the synthesis and characterization of the manganese(ii) complexes [mnii(hbpeten)] and [mnii(hbnbpeten)], where h3bpeten and h3bnbpeten are respectively [n,n'-bis-(2-hydroxybenzyl)-n-(2-pyridylmethyl)-n'-(2-hydroxyethyl)ethane-1,2-diamine] and [n,n'-bis-(5-nitro-2-hydroxybenzyl)-n'-(2-hydroxyethyl)ethane-1,2-diamine], are reported. the characterization was carried out by elemental analyses, cyclic voltammetry, spectroscopic methods (uv-vis, ftir, 1h nmr), electronic paramagnetic resonance spectroelectrochemistry (epr) and theoretical dft calculations. the electrochemistry and epr espectroelectrochemistry data were consistent with the reduction of one of the nitro groups in free h3bnbpeten and in the respective manganese(ii) complex. these results were supported by dft calculations, which showed that only one nitro group contributes to the lumo. the theoretical data appear to be suitable to describe the electronic properties of the compounds.
New phenoxyl radical complexes of manganese, gallium, indium and iron based on an H2bbpen ligand derivative
Anjos, Ademir dos;Bortoluzzi, Adailton J.;Caro, Miguel S. B.;Peralta, Rosely A.;Friedermann, Geraldo R.;Mangrich, Antonio S.;Neves, Ademir;
Journal of the Brazilian Chemical Society , 2006, DOI: 10.1590/S0103-50532006000800009
Abstract: reported herein are the synthesis and characterization of the hexadentate h2l pro-ligand (n,n',n,n'-bis[(2-hydroxy-3,5-di-tert -butylbenzyl)(2-pyridylmethyl)]ethylenediamine), as a further derivative of the well known pro-ligand h2bbpen which contains two phenolate and two pyridyl pendant arms. the phenolate groups in h2l are suitably protected by bulky substituents (tert-butyl) in the ortho- and para- positions, from which stable phenoxyl radical complexes can be formed. thus, we have synthesized four new mononuclear complexes with mniii, gaiii, iniii and feiii which through electrochemical oxidation generate one- and two-electron oxidized phenoxyl species in solution. these radical species were characterized by uv-vis, electronic paramagnetic resonance and electrochemical studies. as expected, in the case of the gaiii, iniii and feiii complexes no metal-centered oxidation was observed. however, the manganese complex undergoes metal- and ligand-centered oxidation processes and therefore a phenoxyl radical-mniv complex can be generated in solution. the crystal structures of the [mniii(l)]+ and [gaiii(l)]+ complexes were determined by x-ray crystallographic analyses revealing monocationic complexes with distorted octahedral geometries.
2-Mercaptobenzoxazole pentacyanoferrate(II/III) complexes: UV-Visible, M？ssbauer, electron paramagnetic resonance, electrochemistry and molecular modeling
Luiz, Juciane B;Andrade, Fabiano M. de;Sá, Eduardo L. de;Friedermann, Geraldo R;Mangrich, Antonio S;Barclay, J. Elaine;Evans, David J;Hasegawa, Tai;Nunes, Fábio S;
Journal of the Brazilian Chemical Society , 2004, DOI: 10.1590/S0103-50532004000100003
Abstract: 2-mercaptobenzoxazole pentacyanoferrate(ii/iii) complexes, [feii/iii(cn)5(bzoxs)]3-/2- , were prepared in meoh/h2o 75:25% solutions and characterized by spectroscopic uv-vis, m？ssbauer, electron paramagnetic resonance (epr) and electrochemical-cyclic voltammetry- techniques. uv-vis and epr spectra along with the electrochemical behavior suggested the coordination of the multi-functional n,s,o- donor ligand, bzoxs, to iron(iii) through the sulfur atom. the crystal field parameters, dql and dt, calculated for the iron(ii) complex, in addition to the reversible redox process feiii-bzoxs + e- ？ feii-bzoxs also pointed to coordination via the sulfur atom. the results were compared with the chemical properties of pentacyanoferrate complexes containing other monodentate n-, s- and o-donor ligands. ab initio calculations revealed the composition of the frontier orbitals of bzoxs and are in agreement with the mode of coordination proposed from the experimental data.
Mortality of varroa destructor in broodless africanized and carnica honey bee (apis mellifera l.) colonies
Moretto,Geraldo;
Interciencia , 2002,
Abstract: summary varroa destructor infestation varies with climate conditions and race of apis mellifera bees. africanized bees show greater tolerance to varroa compared to bees of european races. reproductive ability of female mites, hygienic behavior and grooming behavior are important factors in population dynamics of this parasite. the present study shows the mortality rate of the v. destructor mite in africanized and carnica bee colonies in southern brazil. the daily proportion of dead and live mite fallen on the bottom of the hive was determined when the total mite population was of adult bees. in africanized bee colonies the daily proportion of dead mite was 6.30%, while in carnica bee colonies was 2.11%. the daily proportion of live mite on the bottom of the hive was 2.45% and 0.82% in africanized and carnica bee colonies, respectively.
A？？o comunicativa e rela？？es internacionais
Miniuci, Geraldo;
Novos Estudos - CEBRAP , 2005, DOI: 10.1590/S0101-33002005000300006
Abstract: this article discusses the ideas of the german political scientist harald müller concerning the use of habermas？ theory of communicative action to analyze international political relations. it raises the main problems of this proposal and discusses the possibilities of examining these relations against the framework of the communicative process without borrowing concepts from the habermasian theory.
Estudantes em situa？？o de risco e preven？？o
Caliman, Geraldo;
Ensaio: Avalia？？o e Políticas Públicas em Educa？？o , 2006, DOI: 10.1590/S0104-40362006000300007
Abstract: elementary education, in brazil and in other countries, is continually being reformed. the historic passage from a school for the elite to a school for the masses coincides with a period in which the child comes to be seen as a citizen endowed with rights. the article shows how the student body in our time consists of children and adolescents of different social origins. each has a life history which, for some, is "normal," but for others is characterized by a great variety of situations of social risk, marked by failure, disadvantages, malaise and suffering. at it is impossible to keep the social context from invading the classroom, there is a need to ponder the requirements and rights of a range of students in situations of disadvantage and social risk, difficulties in school achievement, difficulties related to expressions of hostility, difficulties in adaptation to the role of student and difficulties relative to social interaction. the article also shows how, in recent history, interpretation of the relationship between conditions of social disadvantage and instruction has been based on different hypotheses. each of these hypotheses (socio-cultural disadvantage as diversity of talents, as a natural handicap or as a disadvantage of the structural type; disadvantages due to qualitative-organizational characteristics of the school, the school's incapacity to provide adequate teaching or a damaged teacher-student relationship) has, in the post-war period, adopted different models for facing the situation.
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