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Química Nova, Volume: 33, Número: 8, Publicado: 2010
  • Ciência, tecnologia e inovação devem ser políticas de estado Editorial

    Torresi, Susana I. Córdoba de; Pardini, Vera L.; Ferreira, Vitor F.
  • Poluição por mercúrio em aterros urbanos do período colonial no extremo sul do Brasil Artigo

    Fragomeni, Luiz Paulo de Moura; Roisenberg, Ari; Mirlean, Nicolai

    Resumo em Inglês:

    Land reclamation fills in the city of Rio Grande (RS) are polluted by mercury with concentrations ranging from 0.3 to 18.7 mg kg-1. The level of Hg pollution decreases from the oldest landfills of 18th century to recent ones. Mercury distribution along vertical profiles resembles the same for copper, lead, and zinc, what allow supposing that mercury distribution has an autochthonous character. It is suggested that the principal source of mercury pollution was the activities related to animal skin and fair hair treatment, using ancient technology known as "carroting". Similar scenario of environmental risk could be met in other Brazilian cities with similar colonization history.
  • TiO2 photocatalytic inactivation under simulated solar light of bacterial consortia in domestic wastewaters previously treated by UASB, duckweed and facultative ponds

    Rengifo-Herrera, Julián Andrés; Pulgarin, Cesar; Machuca, Fiderman; Sanabria, Janeth

    Resumo em Inglês:

    In this work, TiO2 photocatalysis was used to disinfect domestic wastewaters previously treated by different biological treatment systems: Upward-flow Anaerobic Sludge Blanket (UASB), facultative pond, and duckweed pond. The microorganisms monitored were E. coli, total coliforms, Shigella species, and Salmonella species. Photocatalytic experiments were carried out using two light sources: a solar simulator (UV intensity: 68-70 W m-2) and black-light lamps (BLL UV intensity: 17-20 W m-2). Samples were taken after each treatment stage. Results indicate that bacterial photocatalytic inactivation is affected by characteristics of the effluent, including turbidity, concentration of organic matter, and bacterial concentration, which depend of the type of biological pretreatment previously used.
  • Degradação de corantes reativos por processo foto-fenton envolvendo o uso de peneira molecular 4A modificada com Fe3+ Artigo

    Ignachewski, Franciély; Fujiwara, Sérgio Toshio; Cótica, Luiz Fernando; Carneiro, Livia Melo; Tauchert, Elias; Peralta-Zamora, Patricio

    Resumo em Inglês:

    In this work the preparation and characterization of a supported catalyst intended for degradation of reactive dyes by Fenton-like processes is described. The photocatalyst was prepared by immobilization of Fe3+ into the molecular sieve (4A type) surface and characterized by x-ray diffractometry and infrared, Mössbauer and EPR spectroscopy. The solid containing 0.94% (w/w) of ferric ions was used in degradation studies of aqueous reactive-dyes samples with really promissory results. Generally, Vis-assisted photochemical processes leads to almost total decolorization of all tested dyes at reaction times lower than 30 min. It was also observed that the iron-molecular sieve matrix can be reused.
  • Desidratação de etanol sobre material nanoestruturado do tipo LaSBA-15 Artigo

    Luz Jr, Geraldo E.; Melo, Ana C. R.; Lima, Stevie H.; Araujo, Antônio S.; Fernandes Jr., Valter J.

    Resumo em Inglês:

    La-incorporated SBA-15 mesopourous molecular sieves (LaSBA-15) were directly synthesized with aim to convert ethanol to ethylene. The samples were characterized by XRD, XRF, nitrogen sorption and acidity, by thermodesorption of n-buthylamine. The results have indicated that all the samples have showed high ordered mesostructure with a large average pore size, and that the lanthanum incorporation has caused an increase in the acidity of the SBA-15. The LaSBA-15 samples have improved, with low deactivation rate, the conversion of the ethanol to water, ether, acetaldehyde and ethylene. In addition, they have increased the ethylene selectivity.
  • Estudo químico e atividade antibacteriana do caule de Aristolochia esperanzae kuntze (Aristolochiaceae) Artigo

    Pacheco, Alison G.; Silva, Thiago M.; Manfrini, Rozângela M.; Sallum, William S. T.; Duarte, Lucienir Pains; Piló-Veloso, Dorila; Alcântara, Antônio F. de C.; Knupp, Vagner F.

    Resumo em Inglês:

    From the ethanolic extract of the stem of A. esperanzae ethyl and methyl fatty acid esters, fatty acids, aristolochic I and II acids, and β-cubebin were isolated. In addiction asarinin, populifolic and 2-oxo-populifolic acids, aristolactams AIa and AII, and sitosterol 3-O-β-D-glucopyranoside were also isolated and firstly described in the species. Asarinin and β-cubebin showed antibacterial activity against Bacillus cereus and aristolochic acid I against Staphylococcus aureus and Listeria monocitogenes.
  • Análise térmica aplicada à caracterização da sinvastatina em formulações farmacêuticas Artigo

    Oliveira, Marcelo Antonio de; Yoshida, Maria Irene; Gomes, Elionai Cassiana de Lima; Mussel, Wagner da Nova; Vianna-Soares, Cristina Duarte; Pianetti, Gérson Antônio

    Resumo em Inglês:

    Thermogravimetry (TG) and differential scanning calorimetry (DSC) are used in pharmaceutical studies for drugs characterization, purity, formulations compatibility, polymorphism identification, stability evaluation, and thermal decomposition of drugs and pharmaceutical formulations. Simvastatin showed fusion at 138.5 ºC and thermal stability up to 248 ºC. Simvastatin was incompatible with preservative excipient butylhydroxyanisole (BHA) performing a process of crystal amorphization. The drug showed morphological polymorphism, where it has the same unit cell but with different crystal habits according to the recrystallization solvent.
  • Estabilidade da sílica biogênica extraída de capim Jaraguá (Hyparrhenia rufa) em solução de NaOH Artigo

    Costa, Liovando M.; Moreau, Ana Maria S. S.; Moreau, Mauricio S.

    Resumo em Inglês:

    Biogenic silica is used to describe compounds of hydrated silica (SiO2.nH2O), with specific shapes and sizes, deposited in plants. The chemical composition of biogenic silica and its stability in Jaraguá grass was studied in increasing concentration of NaOH. The analytical results demonstrated high concentration of Si, Al, Fe, Mg, P and low of Cu, Cd and Zn in the phytoliths composition. The silica bodies stability in NaOH solution with increasing concentration was different among the shapes and sizes. Silicified stomata and silicified plant tissues were dissolved along with the dumbbells because they are the less stable forms of biogenic silica.
  • Effect of the structure of commercial poly(ethylene oxide-b-propylene oxide) demulsifier bases on the demulsification of water-in-crude oil emulsions: elucidation of the demulsification mechanism

    Ramalho, João Batista V. S.; Lechuga, Fernanda C.; Lucas, Elizabete F.

    Resumo em Inglês:

    Water-in-crude oil emulsions are formed during petroleum production and asphaltenes play an important role in their stabilization. Demulsifiers are added to destabilize such emulsions,however the demulsification mechanism is not completely known. In this paper, the performances of commercial poly(ethylene oxide-b-propylene oxide) demulsifiers were studied using synthetic water-in-oil emulsions and model-systems (asphaltenes in organic solvent). No change in the asphaltene aggregate size induced by the demulsifier was observed. The demulsification performance decreased as the asphaltene aggregate size increased, so it can be suggested that the demulsification mechanism is correlated to the voids between the aggregates adsorbed on the water droplets surface.
  • Biodiesel metílico de Dipteryx lacunifera: preparação, caracterização e efeito de antioxidantes na estabilidade à oxidação Artigo

    Araújo, Francisca Diana da Silva; Moura, Carla Verônica Rodarte de; Chaves, Mariana H.

    Resumo em Inglês:

    The objective of this work was to study the potentialities of Dipteryx lacunifera Ducke seeds oil for biodiesel production. The yield in oil was of 46.11 ± 0.37%. Methyl biodiesel was prepared by base catalyzed transesterification yielding 88.13% and percentage conversion of triglycerides to corresponding methyl ester of 89.1%. The addition of the tertiary butylhydroquinone (TBHQ, 50 ppm), butylated hydroxytoluene (BHT, 50 ppm) and cashew nut shell liquid (CNSL, 2000 ppm) antioxidants in the biodiesel contributed to the increase of the induction period of 2.97 h for 8.08; 6.06 and 6.02 h, respectively.
  • Rejeito de mineração de carvão como adsorvente para remoção da acidez, Fe (III), Al (III) e Mn (II) em drenagem ácida Artigo

    Geremias, Reginaldo; Laus, Rogério; Fávere, Valfredo Tadeu de; Pedrosa, Rozangela Curi

    Resumo em Inglês:

    This study aimed the use of coal mining waste as a new adsorbent for H3O+ and removal of Al (III), Fe (III) and Mn (II) from acid mine drainage. Data from kinetic and equilibrium of the adsorption of H3O+ followed the pseudo second-order and Langmuir isotherm models. The maximum adsorption capacity of H3O+ was 316 mmol kg-1. The adsorbent removed 100% of Al (III), 100% of Fe (III) and 89% of Mn (II), suggesting its use as an alternative for the treatment of acid mine drainage.
  • Validação de método para a determinação de 5-hidroximetilfurfural em mel por cromatografia líquida e sua influência na qualidade do produto Artigo

    Lemos, Gisele da Silveira; Santos, José Soares dos; Santos, Maria Lúcia Pires dos

    Resumo em Inglês:

    In honey 5-hydroxymethyl-2-furaldehyde (HMF) is one of the most typical products of degradation: it is usually absent in fresh honey, but its concentration tends to rise as a result of heating processes or long-term storage. The validation protocol was performed in terms of detection and quantification limits, precision (by repeatability and intermediate precision), linearity and accuracy (by recovery tests). The method has been tested on 15 honey samples of different ages and geographical origin. HMF correlated highly with the age of the samples has been considered a very important parameter to put these honeys on the market or not and/or to estimate their shelf life.
  • Biodegradação de alcoóis, ftalatos e adipatos em um solo tropical contaminado Artigo

    Ferreira, Ieda Domingues; Morita, Dione Mari

    Resumo em Inglês:

    The adipic and phthalic acid esters are plasticizers, have low water solubility, high partition octanol/water coefficients (Kow) and accumulate in soil and sediments. These compounds are considered teratogenic, carcinogenic and endocrine disruptors chemicals. This study evaluated the bioremediation of tropical soil contaminated with plasticizers process wastes, in aerobic conditions, with and without introduction of acclimated bacteria. It was selected 200 kg of contaminated tropical soil for the biodegradation study. The plasticizers concentrations in soil ranged between 153 mgDOA/kg up to 15552 mgDIDP/kg and after 90 days of biodegradation, the lower removal efficiencies were 72% with a 1-2 log simultaneous bacterial growth.
  • Avaliação da liberação de NH4NO3 ocluido em zeólita 4A a partir de soluções salinas Artigo

    Andrade, Jardel Cavalcante Rolim de Almeida; Loiola, Adonay Rodrigues; Silva, Lindomar Roberto Damasceno da; Romero, Ricardo Espíndola

    Resumo em Inglês:

    The zeolite 4A was used to evaluate the thermo kinetics parameters of NH4+ and NO3- ions occluded in its structure. The Osawa method for activation energy calculation was used to evaluate its thermal stability, and the results shown that the ion species interact differently depending on the zeolite pores, which determines the controlled release by its structure.
  • Utilização de diferentes tipos de policloretos de alumínio para purificação de hidrolisado de bagaço de cana através da técnica de coagulação e floculação Artigo

    Noronha, Leonardo de Lima; Fonseca, Christiane Reis; Silva, Cássia Cavalcanti da; Silva, Messias Borges; Faria, Luís Fernando Figueiredo

    Resumo em Inglês:

    In order to investigate the action of the flocculating agents Panfloc and Panclar a full factorial design 2³ and a Central Composite design 2² were carried out. The control variables were the flocculant concentration, pH and temperature. The response variables were phenolic compounds reduction and spectral area reduction. The best conditions of treatment was hydrolyzate at pH 9 for both coagulants, but the use of Panfloc was more effective in the phenolic compounds reduction (73.9%) and spectral area reduction (65.8%).
  • Efecto del catión, del anión y del co-ión sobre la agregación de líquidos iónicos en solución acuosa

    Guzmán, Nólides Marina; Fernández, José Francisco; Parada, Mónica; Orbegozo, Carlos; Rodríguez, María Alejandra; Padrón, Alida; Thöming, Jorg

    Resumo em Inglês:

    The aggregation behavior of thirteen 1-alkyl-3-methylimidazolium based ionic liquids in aqueous solution is presented, considering variations of the alkyl side chain length as well as the anionic moiety. Cation and anion molecular volumes are selected as appropriate molecular descriptors. Additionally, the existing relationship between critical micelle concentration (CMC) and electrolyte concentration in solution is established, aiming to clarify ion effects. CMC values were obtained by measuring electrical conductivity and surface tension. It was confirmed that aggregation of ionic liquids in aqueous solution and in presence of inorganic salts is affected by the factors developed in this study.
  • Viscoelásticos oftálmicos: comparação entre os comerciais e formulações de galactomanana de Dimorphandra gardneriana Artigo

    Pires, Natália R.; Cunha, Pablyana L. R. da; Paula, Regina C. M. de; Feitosa, Judith P. A.; Jamacaru, Francisco V. F.; Moraes Filho, Manoel O.

    Resumo em Inglês:

    Ophthalmic viscosurgical devices (OVD) are materials injected in intraocular space during cataract removal to reduce trauma in the patient's eye. Three Brazilian commercially available OVDs (Medilon®, Metilcelulose® and Ofthyal®) were evaluated as well as formulations based on Dimorphandra gardneriana galactomannan. Viscosity and viscoelastic parameters, such as viscosity at zero shear, pseudoplasticity index, elastic and viscous moduli, relaxation time, were determined and compared. Characteristics of an effective OVD were proposed. None of the Brazilian devices studied fulfill the rheological requirements. Only the galactomannan at 3% concentration showed potential to be used as effective OVD.
  • Caracterização físico-química do fármaco antichagásico benznidazol Artigo

    Maximiano, Flávia Pires; Costa, Guilherme Hideki Yoshizane; Souza, Jacqueline de; Cunha-Filho, Marcílio Sérgio Soares da

    Resumo em Inglês:

    Currently, benznidazole (BNZ) is a unique therapeutic alternative available in Brazil to treat Chagas disease. Despite its traditional medical use, little is known about the chemical nature of this drug. A detailed study of the physicochemical properties of BNZ was performed using multiple assays. Thermal, diffractometric, morphological and reological drug profiles were obtained. The partition coefficient and solubility results allowed this drug to be classified as a class IV drug according to the biopharmaceutical classification system. This information will be useful for the development of more effective BNZ formulations and for establishing the quality profile of BNZ.
  • Estabilidade de compostos bioativos em polpa congelada de amora-preta (Rubus fruticosus) cv. Tupy Artigo

    Jacques, Andresa Carolina; Pertuzatti, Paula Becker; Barcia, Milene Teixeira; Zambiazi, Rui Carlos; Chim, Josiane Freitas

    Resumo em Inglês:

    Rubus fruticosus (Rosaceae), popularly known as Blackberry, is a highly nutritious fruit, rich in bioactive compounds. Their stability during processing has been the focus of several studies. This work describes the evaluation of the stability of the main phytochemicals of pulp from blackberry cv. Tupy, stored under different temperature conditions for six months. The storage at -10 °C was not sufficient to cause significant changes in total phenolics content, anthocyanins content and antioxidant capacity during two months of storage. Likewise, at -18 °C, total phenolics content and antioxidant capacity were kept for four months, but total anthocyanins and β-carotene content were kept for two and six months of storage, respectively.
  • Aplicação do delineamento simplex-centroide no estudo da cinética da oxidação de biodiesel B100 em mistura com antioxidantes sintéticos Artigo

    Borsato, Dionísio; Dall'Antonia, Luiz Henrique; Guedes, Carmen Luísa B.; Maia, Elaine Cristina R.; Freitas, Heverson Renan de; Moreira, Ivanira; Spacino, Kelly Roberta

    Resumo em Inglês:

    Antioxidants are an alternative to prevent or slow the degradation of the biofuel. In this study, it was evaluated the oxidative stability of B100 biodiesel from soybean oil in the presence of three commercial synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), pure or blended, from the experimental design of simplex-centroid mixture. The reaction order and rate constant were also calculated for all tests. The treatment containing pure TBHQ proved to be the most effective, proven by design, the optimum mix obtained and the rate constant. Binary and ternary mixtures containing TBHQ also showed appreciable antioxidant effect.
  • Metodologia para o estudo da porosidade de dolomita em ensaio de sulfatação interrompida Artigo

    Ávila, Ivonete; Crnkovic, Paula M.; Milioli, Fernando E.

    Resumo em Inglês:

    The aim of this work is to propose a methodology to evaluate the evolution of the pore blockage of limestone during the sulfation reaction. The experiments were performed for a national limestone (dolomite) with average particle size of 545 μm in interrupted sulfation tests were conducted at seven different times and at three different temperatures of the process. The empirical data were obtained from porosimetry tests to establish BET surface area, volume and average size of pore and distribution of pore sizes of the sulfated samples. Thermogravimetric tests were performed to evaluate the preparation methodology of the samples used in the porosimetry tests.
  • Eudesmane and rearranged eudesmane sesquiterpenes from Nectandra cissiflora

    Garcez, Fernanda R.; Garcez, Walmir S.; Hamerski, Lidilhone; Miranda, Ana Carolina de M.

    Resumo em Inglês:

    Four eudesmane-type sesquiterpenes, costic acid (1), 12-carboxyeudesman-3,11(13)-diene (2), viscic acid (3), 3-oxo-γ-costic acid (4) and two rearranged eudesmane derivatives, 3α-hydroxyisoiphion-11(13)-en-12-oic acid (5) and 5β-hydroxy-4-oxo-11(13)-dehydroiphionan-12-oic acid (6), in addition to (-)-epicatechin, have been isolated from the trunk bark of Nectandra cissiflora. This is the first reported occurrence in the Lauraceae of 3-6. The structures of the isolated compounds have been established on the basis of 1D and 2D NMR spectroscopic techniques. The 13C NMR assignments of 3, 5 and 6 are given here for the first time, as well as some corrections to the previously reported chemical shift assignments of 4.
  • HIV: mecanismo de replicação, alvos farmacológicos e inibição por produtos derivados de plantas Revisão

    Ferreira, Roberta Costa Santos; Riffel, Alessandro; Sant'Ana, Antônio Euzébio Goulart

    Resumo em Inglês:

    The AIDS epidemy has spread out and led to the diversification on the research for new antiviral drugs. Natural products, especially those derived from plants, are well-recognized as excellent sources of new drugs. Several of them have inhibitory activity against HIV replication, and some have been already clinically tested, with favorable results. This review presents the biochemical basis of the viral cycle and the research up to date on the identification, determination of the mechanism of biological action together with the therapeutical potential of plants-derived natural products, in the inhibition of HIV.
  • Compostos magnéticos moleculares: o desenvolvimento de novos materiais magnéticos nanoestruturados Revisão

    Guedes, Guilherme P.; Allão, Rafael A.; Mercante, Luiza A.; Vaz, Maria G. F.; Novak, Miguel A.

    Resumo em Inglês:

    The development of new magnetic materials has attracted attention of researchers of different areas. In the last decades, a distinguished class of materials emerged in magnetism, in which the magnetic moment is delocalized over molecules. By varying the synthetic conditions it is possible to obtain a large variety of structures and properties using the same starting molecules. These materials have a great scientific appeal due to the possibility of presenting not only magnetic, but also optical or electrical transport properties. In this review we will present an overview of some molecular magnetic compounds, in particular molecular nanomagnets.
  • Voltametria de micropartículas imobilizadas: fundamentos e aplicações analíticas Revisão

    Carvalho, Leandro M. de; Hilgemann, Maurício; Spengler, Cristiane; Nascimento, Paulo C. do; Bohrer, Denise

    Resumo em Inglês:

    The theoretical aspects of Voltammetry of Immobilized Microparticles (VIM) were discussed. The immobilization of microparticles on electrode surface, the electrode cleaning processes and the electrode materials were analyzed. The three-phase electrode model and the possible reactions between the immobilized particle and the electrolytic solution were discussed. In addition, this work discusses some selected applications of VIM published in the last years.
  • Pilhas de combustíveis microbianas utilizadas na produção de eletricidade a partir de rejeitos orgânicos: uma perspectiva de futuro Revisão

    Rachinski, Silvio; Carubelli, Ademir; Mangoni, Ana Paula; Mangrich, Antonio S.

    Resumo em Inglês:

    In this review is presented an innovative technology for use of animal and vegetable waste with high pollution levels in microbial fuel cell (MFC) as an alternative to waste remediation and simultaneously producing electricity and fertilizer for agriculture. A brief history of MFC, the studies about the electron transfer mechanisms, discussion of the biological nanowires in bacteria and the use of chemical mediators or carriers of electrons are explained. The factors influencing the performance of MFCs, the application in waste and sewage treatment and power generation are also discussed.
  • Reator de UV-Ozônio com lâmpada a vapor de mercúrio a alta pressão modificada para tratamento superficial de óxidos transparentes condutivos utilizados em dispositivos poliméricos eletroluminescentes Nota Técnica

    Santos, Emerson Roberto; Correia, Fábio Conte; Wang, Shu Hui; Hidalgo, Pilar; Fonseca, Fernando Josepetti; Burini Júnior, Elvo Calixto; Andrade, Adnei Melges de

    Resumo em Inglês:

    An UV-Ozone reactor was developed with an ignition tube extracted into HID mercury lamp used to irradiation on zinc oxide (ZnO) and fluorinated tin oxide (FTO) films for PLEDs devices. Different exposures times were used. In contact angle measurements revealed better results for ZnO and FTO by 15 and 5 min, respectively. In Diffuse Reflectance Infra-red Fourier Transformed (DRIFT) spectroscopy allowed the observation of water, hydrocarbon and carbon dioxide adsorbed on the untreated TCO surfaces. After the UV-Ozone treatment the contaminants were significantly reduced or eliminated and the PLEDs devices decreased threshold voltages in comparison with respectively untreated TCOs.
  • Comparação interlaboratorial para análise de dureza total e cloreto em água Nota Técnica

    Andrade, Débora França de; Clemente, Armando Augusto; Harcar, Vera; Melo, Jefferson Lee Lima de; Pereira, Sônia Elisa Carvalho; Santos, Lucia Helena Menezes; Ferreira-Leitão, Viridiana Santana

    Resumo em Inglês:

    Interlaboratorial comparison of the determination of hardness and chloride in water had been performed by 38 and 37 laboratories, respectively. In all cases the participating laboratories used its routine methods. Homogeneity and stability testing were performed on the samples sent to the laboratories. The codified results are graphically reported and compared to assigned value, determined by the consensus of the laboratories. Satisfactory results were obtained for 71 and 73% of the laboratories, considering hardness and chloride determination, respectively.
  • Terbinafine: optimization of a LC method for quantitative analysis in pharmaceutical formulations and its application for a tablet dissolution test

    Tagliari, Monika P.; Kuminek, Gislaine; Borgmann, Sílvia H. M.; Bertol, Charise D.; Cardoso, Simone G.; Stulzer, Hellen K.

    Resumo em Inglês:

    A simple liquid chromatographic method was optimized for the quantitative determination of terbinafine in pharmaceutical hydroalcoholic solutions and tablets, and was also employed for a tablet dissolution test. The analysis was carried out using a RP-C18 (250 mm × 4.6 mm, 5 μm) Vertical® column, UV-Vis detection at 254 nm, and a methanol-water (95:5, v/v) mobile phase at a flow-rate of 1.2 mL min-1. Method validation investigated parameters such as linearity, precision, accuracy, robustness and specificity, which gave results within the acceptable range. The tablets dissolution was quite fast: 80% of the drug was dissolved within 15 min.
  • Validación de un método analítico empleando cromatografía líquida de alta eficiencia para la determinación de ibuprofeno en medios biorrelevantes

    Gómez, Sandra M.; Martínez, Jorge A.; Martínez, Fleming

    Resumo em Inglês:

    An analytical method by liquid chromatography has been proposed and validated to study the apparent solubility of ibuprofen in biorelevant dissolution media. The main properties of the studied media were pH values of 5.0 and 6.5 and the presence or absence of some natural surfactant agents. The parameters evaluated were specificity, linearity, precision, accuracy, and detection and quantification limits, as well as the drug stability under the analysis conditions. The developed method was useful to determine the apparent solubility of this drug as a function of temperature and surfactants concentration to demonstrate the validity of the Biopharmaceutics Classification System.
  • O experimento de Clement-Desormes no século XXI Educação

    Bottecchia, Otávio Luiz

    Resumo em Inglês:

    The Clement-Desormes experiment is reviewed. By reason of a finite difference between the pressure within the system and its surroundings, Bertrand and McDonald have criticized the usual consideration of the adiabatic expansion as reversible. Garland, Nibler and Shoemaker oppose, defining regions through virtual boundaries where the surroundings do not operate. For Holden, the use of virtual boundaries is expendable. Experiments cannot support a hypothesis testing due to experiment's intrinsic uncertainty. The role of polytropy in uncertainty is discussed. Both thermodynamic definitions and kinetic model depict the real processes as irreversible phenomena and the reversible ones as a limiting hypothetical case.
  • Síntese de fotoprotetores e sua imobilização em poli(metacrilato de metilo): um projeto integrado de química orgânica, química de polímeros e fotoquímica Educação

    Murtinho, Dina Maria B.; Serra, Maria Elisa S.; Pineiro, Marta

    Resumo em Inglês:

    Dibenzalacetone and other aldol condensation products are known sunscreens commonly used in cosmetics. This type of compounds can easily be prepared in an Organic Chemistry Lab by reaction of aldehydes with ketones in basic medium. These compounds can be incorporated in poly(methyl methacrylate) and used as UV light absorbers, for example in sunglasses. This project has the advantage of using inexpensive reagents which are readily available in Chemistry Laboratories. This experiment can also be a base starting point for discussions of organic, polymer and photochemistry topics.
  • A formação inicial em química baseada em conceitos representados por meio de modelos mentais Educação

    Gibin, Gustavo Bizarria; Ferreira, Luiz Henrique

    Resumo em Inglês:

    The current legislation determines that the chemist must have a solid comprehension about chemical concepts. Literature presents the concept of mental model, which is determinant to the learning of phenomena and concepts. This paper presents some mental models that students of the Chemistry course at UFSCar have about chemical concepts. A lot of incoherence was observed in student's mental models, which is an evidence that there are problems in the learning of chemistry education.
  • Acetatos homo e heterotrinucleares de ferro: um experimento para o laboratório de química de coordenação Educação

    Santos, Reginaldo da Silva; Jannuzzi, Sergio Augusto Venturinelli; Formiga, André Luiz B.

    Resumo em Inglês:

    Homo and heterotrinuclear acetates are unique compounds having μ3-oxo bridge and many interesting properties of such compounds are derived from this structure. Some undergraduate inorganic textbooks discuss several aspects of these compounds and we present here an undergraduate experiment for the high-yield synthesis of [Fe2MO(CH3CO2)6(H 2O)3], with M = Fe3+, Co2+ and Ni2+, as well as their characterization using infrared spectroscopy and cyclic voltametry. The proposed experiment gives the opportunity to discuss several concepts of coordination chemistry that follow the characterization techniques, such as: types of acetate coordination, reversibility of electrochemical processes, quelate and trans effects and lability.
  • Controvérsias sobre a proteção patentária de segundo uso médico de compostos químicos conhecidos Assuntos Gerais

    Silva, Maria Lucia Abranches da; Britto, Adriana Campos Moreira; Antunes, Adelaide Maria de Souza

    Resumo em Inglês:

    The present work provides an overview of patent protection for second medical use of known chemical compounds, in Brazil and other countries, through the approach of the main controversies related to this theme. That issues encompass aspects related to the legality of the protection granted by the patent, the general requirements of patenteability, the ethic and social concepts and the politic and economic factors involved. This work also introduces the diverging views of the two Brazilian government agencies involved in the procedure for granting patent in the pharmaceutical area, INPI and ANVISA.
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