Formic acid oxidation on platinum electrodes: A detailed mechanism supported by experiments and calculations on well-defined surfaces

[EN] In spite of the fact that the formic acid oxidation reaction on electrode surfaces has been extensively investigated, a detailed mechanism explaining all the available experimental evidence on platinum has not been yet described. Herein, using a combined experimental and computational approach, the key elements in the mechanism of the formic acid oxidation reaction on platinum have been completely elucidated, not only for the direct path, through an active intermediate, but also for the CO formation route. The experimental results suggest that the direct oxidation path on platinum takes place in the presence of bidentate adsorbed formate. However, the results reported here provide evidence that this species is not the active intermediate. Monodentate adsorbed formate, whose evolution to the much more favorable bidentate form would be hindered by the presence of neighboring adsorbates, has been found to be the true active intermediate. Moreover, it is found that adsorbed formic acid would have a higher acid constant than in solution, which suggests that adsorbed formate can be originated not only from solution formate but also from formic acid. The CO formation path on platinum can proceed, also from monodentate adsorbed formate, through a dehydrogenation process toward the surface, during which the adsorbate transitions from a Pt-O adsorption mode to a Pt-C one, to form carboxylate. From this last configuration, the C-OH bond is cleaved, on the surface, yielding adsorbed CO and OH. The results and mechanisms reported here provide the best explanation for the whole of the experimental evidence available to date about this reaction, including pH, surface structure and electrode potential effects.This work has been financially supported by the MCINN-FEDER (Spain) and Generalitat Valenciana (Feder) through projects CTQ2016-76221-P and PROMETEOII/2014/013, respectively.Ferre Vilaplana, A.; Perales, JV.; Buso-Rogero, C.; Feliu, J.; Herrero, E. (2017). Formic acid oxidation on platinum electrodes: A detailed mechanism supported by experiments and calculations on well-defined surfaces. Journal of Materials Chemistry A. 5(41):21773-21784. https://doi.org/10.1039/c7ta07116gS2177321784541Bagotzky, V. S., Vassiliev, Y. B., & Khazova, O. A. (1977). Generalized scheme of chemisorption, electrooxidation and electroreduction of simple organic compounds on platinum group metals. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 81(2), 229-238. doi:10.1016/s0022-0728(77)80019-3Beden, B., Bewick, A., & Lamy, C. (1983). A comparative study of formic acid adsorption on a platinum electrode by both electrochemical and emirs techniques. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 150(1-2), 505-511. doi:10.1016/s0022-0728(83)80230-7Capon, A., & Parsons, R. (1973). The oxidation of formic acid at noble metal electrodes Part III. Intermediates and mechanism on platinum electrodes. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 45(2), 205-231. doi:10.1016/s0022-0728(73)80158-5Capon, A., & Parson, R. (1973). The oxidation of formic acid at noble metal electrodes. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 44(1), 1-7. doi:10.1016/s0022-0728(73)80508-xWolter, O., Willsau, J., & Heitbaum, J. (1985). Reaction Pathways of the Anodic Oxidation of Formic Acid on Pt Evidenced by 18O Labeling—A DEMS Study. Journal of The Electrochemical Society, 132(7), 1635-1638. doi:10.1149/1.2114179Willsau, J., & Heitbaum, J. (1986). Analysis of adsorbed intermediates and determination of surface potential shifts by dems. Electrochimica Acta, 31(8), 943-948. doi:10.1016/0013-4686(86)80008-1Chen, Y. X., Miki, A., Ye, S., Sakai, H., & Osawa, M. (2003). Formate, an Active Intermediate for Direct Oxidation of Methanol on Pt Electrode. Journal of the American Chemical Society, 125(13), 3680-3681. doi:10.1021/ja029044tSamjeské, G., & Osawa, M. (2005). Current Oscillations during Formic Acid Oxidation on a Pt Electrode: Insight into the Mechanism by Time-Resolved IR Spectroscopy. Angewandte Chemie International Edition, 44(35), 5694-5698. doi:10.1002/anie.200501009Cuesta, A., Cabello, G., Gutiérrez, C., & Osawa, M. (2011). Adsorbed formate: the key intermediate in the oxidation of formic acid on platinum electrodes. Physical Chemistry Chemical Physics, 13(45), 20091. doi:10.1039/c1cp22498kCuesta, A., Cabello, G., Osawa, M., & Gutiérrez, C. (2012). Mechanism of the Electrocatalytic Oxidation of Formic Acid on Metals. ACS Catalysis, 2(5), 728-738. doi:10.1021/cs200661zChen, Y.-X., Heinen, M., Jusys, Z., & Behm, R. J. (2006). Bridge-Bonded Formate:  Active Intermediate or Spectator Species in Formic Acid Oxidation on a Pt Film Electrode?†. Langmuir, 22(25), 10399-10408. doi:10.1021/la060928qChen, Y. X., Heinen, M., Jusys, Z., & Behm, R. J. (2006). Kinetics and Mechanism of the Electrooxidation of Formic Acid—Spectroelectrochemical Studies in a Flow Cell. Angewandte Chemie International Edition, 45(6), 981-985. doi:10.1002/anie.200502172Chen, Y.-X., Heinen, M., Jusys, Z., & Behm, R. J. (2007). Kinetic Isotope Effects in Complex Reaction Networks: Formic Acid Electro-Oxidation. ChemPhysChem, 8(3), 380-385. doi:10.1002/cphc.200600520Joo, J., Uchida, T., Cuesta, A., Koper, M. T. M., & Osawa, M. (2013). Importance of Acid–Base Equilibrium in Electrocatalytic Oxidation of Formic Acid on Platinum. Journal of the American Chemical Society, 135(27), 9991-9994. doi:10.1021/ja403578sJoo, J., Uchida, T., Cuesta, A., Koper, M. T. M., & Osawa, M. (2014). The effect of pH on the electrocatalytic oxidation of formic acid/formate on platinum: A mechanistic study by surface-enhanced infrared spectroscopy coupled with cyclic voltammetry. Electrochimica Acta, 129, 127-136. doi:10.1016/j.electacta.2014.02.040Brimaud, S., Solla-Gullón, J., Weber, I., Feliu, J. M., & Behm, R. J. (2014). Formic Acid Electrooxidation on Noble-Metal Electrodes: Role and Mechanistic Implications of pH, Surface Structure, and Anion Adsorption. ChemElectroChem, 1(6), 1075-1083. doi:10.1002/celc.201400011Perales-Rondón, J. V., Brimaud, S., Solla-Gullón, J., Herrero, E., Jürgen Behm, R., & Feliu, J. M. (2015). Further Insights into the Formic Acid Oxidation Mechanism on Platinum: pH and Anion Adsorption Effects. Electrochimica Acta, 180, 479-485. doi:10.1016/j.electacta.2015.08.155Clavilier, J., Parsons, R., Durand, R., Lamy, C., & Leger, J. M. (1981). Formic acid oxidation on single crystal platinum electrodes. Comparison with polycrystalline platinum. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 124(1-2), 321-326. doi:10.1016/s0022-0728(81)80311-7Adžić, R. R., Tripković, A. V., & O’Grady, W. E. (1982). Structural effects in electrocatalysis. Nature, 296(5853), 137-138. doi:10.1038/296137a0Ferre-Vilaplana, A., Perales-Rondón, J. V., Feliu, J. M., & Herrero, E. (2014). Understanding the Effect of the Adatoms in the Formic Acid Oxidation Mechanism on Pt(111) Electrodes. ACS Catalysis, 5(2), 645-654. doi:10.1021/cs501729jPerales-Rondón, J. V., Herrero, E., & Feliu, J. M. (2015). On the activation energy of the formic acid oxidation reaction on platinum electrodes. Journal of Electroanalytical Chemistry, 742, 90-96. doi:10.1016/j.jelechem.2015.02.003Clavilier, J., Armand, D., Sun, S. G., & Petit, M. (1986). Electrochemical adsorption behaviour of platinum stepped surfaces in sulphuric acid solutions. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 205(1-2), 267-277. doi:10.1016/0022-0728(86)90237-8C. Korzeniewski , V.Climent and J. M.Feliu, in Electroanalytical Chemistry: A Series of Advances, ed. A. J. Bard and C. Zoski, CRC Press, Boca Raton, 2012, vol. 24, pp. 75–169N. Garcia-Araez , V.Climent and J.Feliu, in Mod Asp Electrochem, ed. C. G. Vayenas, Springer, New York, 2011, vol. 51, ch. 1, pp. 1–105Grozovski, V., Climent, V., Herrero, E., & Feliu, J. M. (2009). Intrinsic Activity and Poisoning Rate for HCOOH Oxidation at Pt(100) and Vicinal Surfaces Containing Monoatomic (111) Steps. ChemPhysChem, 10(11), 1922-1926. doi:10.1002/cphc.200900261Delley, B. (1990). An all‐electron numerical method for solving the local density functional for polyatomic molecules. The Journal of Chemical Physics, 92(1), 508-517. doi:10.1063/1.458452Delley, B. (2002). Hardness conserving semilocal pseudopotentials. Physical Review B, 66(15). doi:10.1103/physrevb.66.155125Hammer, B., Hansen, L. B., & Nørskov, J. K. (1999). Improved adsorption energetics within density-functional theory using revised Perdew-Burke-Ernzerhof functionals. Physical Review B, 59(11), 7413-7421. doi:10.1103/physrevb.59.7413Delley, B. (2000). From molecules to solids with the DMol3 approach. The Journal of Chemical Physics, 113(18), 7756-7764. doi:10.1063/1.1316015Delley, B. (2006). The conductor-like screening model for polymers and surfaces. Molecular Simulation, 32(2), 117-123. doi:10.1080/08927020600589684Neugebauer, J., & Scheffler, M. (1992). Adsorbate-substrate and adsorbate-adsorbate interactions of Na and K adlayers on Al(111). Physical Review B, 46(24), 16067-16080. doi:10.1103/physrevb.46.16067Henkelman, G., & Jónsson, H. (2000). Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points. The Journal of Chemical Physics, 113(22), 9978-9985. doi:10.1063/1.1323224Keith, J. A., & Jacob, T. (2010). Theoretical Studies of Potential-Dependent and Competing Mechanisms of the Electrocatalytic Oxygen Reduction Reaction on Pt(111). Angewandte Chemie International Edition, 49(49), 9521-9525. doi:10.1002/anie.201004794Monkhorst, H. J., & Pack, J. D. (1976). Special points for Brillouin-zone integrations. Physical Review B, 13(12), 5188-5192. doi:10.1103/physrevb.13.5188Grozovski, V., Vidal-Iglesias, F. J., Herrero, E., & Feliu, J. M. (2011). Adsorption of Formate and Its Role as Intermediate in Formic Acid Oxidation on Platinum Electrodes. ChemPhysChem, 12(9), 1641-1644. doi:10.1002/cphc.201100257Rodes, A., Pastor, E., & Iwasita, T. (1994). An FTIR study on the adsorption of acetate at the basal planes of platinum single-crystal electrodes. Journal of Electroanalytical Chemistry, 376(1-2), 109-118. doi:10.1016/0022-0728(94)03585-7Xu, J., Yuan, D., Yang, F., Mei, D., Zhang, Z., & Chen, Y.-X. (2013). On the mechanism of the direct pathway for formic acid oxidation at a Pt(111) electrode. Physical Chemistry Chemical Physics, 15(12), 4367. doi:10.1039/c3cp44074ePerales-Rondón, J. V., Herrero, E., & Feliu, J. M. (2014). Effects of the anion adsorption and pH on the formic acid oxidation reaction on Pt(111) electrodes. Electrochimica Acta, 140, 511-517. doi:10.1016/j.electacta.2014.06.057Herrero, E., Franaszczuk, K., & Wieckowski, A. (1994). Electrochemistry of Methanol at Low Index Crystal Planes of Platinum: An Integrated Voltammetric and Chronoamperometric Study. The Journal of Physical Chemistry, 98(19), 5074-5083. doi:10.1021/j100070a022Wang, H.-F., & Liu, Z.-P. (2009). Formic Acid Oxidation at Pt/H2O Interface from Periodic DFT Calculations Integrated with a Continuum Solvation Model. The Journal of Physical Chemistry C, 113(40), 17502-17508. doi:10.1021/jp9059888Schwarz, K. A., Sundararaman, R., Moffat, T. P., & Allison, T. C. (2015). Formic acid oxidation on platinum: a simple mechanistic study. Physical Chemistry Chemical Physics, 17(32), 20805-20813. doi:10.1039/c5cp03045ePerales-Rondón, J. V., Ferre-Vilaplana, A., Feliu, J. M., & Herrero, E. (2014). Oxidation Mechanism of Formic Acid on the Bismuth Adatom-Modified Pt(111) Surface. Journal of the American Chemical Society, 136(38), 13110-13113. doi:10.1021/ja505943hClavilier, J. (1987). Pulsed linear sweep voltammetry with pulses of constant level in a potential scale, a polarization demanding condition in the study of platinum single crystal electrodes. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 236(1-2), 87-94. doi:10.1016/0022-0728(87)88020-8Fernandez-Vega, A., Feliu, J. M., Aldaz, A., & Clavilier, J. (1991). Heterogeneous electrocatalysis on well-defined platinum surfaces modified by controlled amounts of irreversibly adsorbed adatoms. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 305(2), 229-240. doi:10.1016/0022-0728(91)85521-pGrozovski, V., Climent, V., Herrero, E., & Feliu, J. M. (2010). Intrinsic activity and poisoning rate for HCOOH oxidation on platinum stepped surfaces. Physical Chemistry Chemical Physics, 12(31), 8822. doi:10.1039/b925472bGrozovski, V., Solla-Gullón, J., Climent, V., Herrero, E., & Feliu, J. M. (2010). Formic Acid Oxidation on Shape-Controlled Pt Nanoparticles Studied by Pulsed Voltammetry. The Journal of Physical Chemistry C, 114(32), 13802-13812. doi:10.1021/jp104755bKoper, M. T. M. (2013). Theory of multiple proton–electron transfer reactions and its implications for electrocatalysis. Chemical Science, 4(7), 2710. doi:10.1039/c3sc50205hKoper, M. T. M. (2015). Volcano Activity Relationships for Proton-Coupled Electron Transfer Reactions in Electrocatalysis. Topics in Catalysis, 58(18-20), 1153-1158. doi:10.1007/s11244-015-0489-3Neurock, M., Janik, M., & Wieckowski, A. (2009). A first principles comparison of the mechanism and site requirements for the electrocatalytic oxidation of methanol and formic acid over Pt. Faraday Discuss., 140, 363-378. doi:10.1039/b804591gGao, W., Keith, J. A., Anton, J., & Jacob, T. (2010). Theoretical Elucidation of the Competitive Electro-oxidation Mechanisms of Formic Acid on Pt(111). Journal of the American Chemical Society, 132(51), 18377-18385. doi:10.1021/ja1083317Gamboa-Aldeco, M. E., Herrero, E., Zelenay, P. S., & Wieckowski, A. (1993). Adsorption of bisulfate anion on a Pt(100) electrode: A comparison with Pt(111) and Pt(poly). Journal of Electroanalytical Chemistry, 348(1-2), 451-457. doi:10.1016/0022-0728(93)80151-7Clavilier, J., & Sun, S. G. (1986). Electrochemical study of the chemisorbed species formed from formic acid dissociation at platinum single crystal electrodes. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 199(2), 471-480. doi:10.1016/0022-0728(86)80021-3Sun, S. G., Clavilier, J., & Bewick, A. (1988). The mechanism of electrocatalytic oxidation of formic acid on Pt (100) and Pt (111) in sulphuric acid solution: an emirs study. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 240(1-2), 147-159. doi:10.1016/0022-0728(88)80319-xHerrero, E., Fernández-Vega, A., Feliu, J. M., & Aldaz, A. (1993). Poison formation reaction from formic acid and methanol on Pt(111) electrodes modified by irreversibly adsorbed Bi and As. Journal of Electroanalytical Chemistry, 350(1-2), 73-88. doi:10.1016/0022-0728(93)80197-pHerrero, E., Feliu, J. M., & Aldaz, A. (1994). Poison formation reaction from formic acid on Pt(100) electrodes modified by irreversibly adsorbed bismuth and antimony. Journal of Electroanalytical Chemistry, 368(1-2), 101-108. doi:10.1016/0022-0728(93)03032-kIwasita, T., Xia, X., Herrero, E., & Liess, H.-D. (1996). Early Stages during the Oxidation of HCOOH on Single-Crystal Pt Electrodes As Characterized by Infrared Spectroscopy. Langmuir, 12(17), 4260-4265. doi:10.1021/la960264sCorrigan, D. S., & Weaver, M. J. (1988). Mechanisms of formic acid, methanol, and carbon monoxide electrooxidation at platinum as examined by single potential alteration infrared spectroscopy. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 241(1-2), 143-162. doi:10.1016/0022-0728(88)85123-4Chang, S. C., Leung, L. W. H., & Weaver, M. J. (1990). Metal crystallinity effects in electrocatalysis as probed by real-time FTIR spectroscopy: electrooxidation of formic acid, methanol, and ethanol on ordered low-index platinum surfaces. The Journal of Physical Chemistry, 94(15), 6013-6021. doi:10.1021/j100378a072Clavilier, J., Fernandez-Vega, A., Feliu, J. M., & Aldaz, A. (1989). Heterogeneous electrocatalysis on well defined platinum surfaces modified by controlled amounts of irreversibly adsorbed adatoms. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 258(1), 89-100. doi:10.1016/0022-0728(89)85164-2Herrero, E., Climent, V., & Feliu, J. M. (2000). On the different adsorption behavior of bismuth, sulfur, selenium and tellurium on a Pt(775) stepped surface. Electrochemistry Communications, 2(9), 636-640. doi:10.1016/s1388-2481(00)00093-xMaciá, M. (1999). Formic acid self-poisoning on bismuth-modified Pt(755) and Pt(775) electrodes. Electrochemistry Communications, 1(2), 87-89. doi:10.1016/s1388-2481(99)00009-0Maciá, M. D., Herrero, E., Feliu, J. M., & Aldaz, A. (2001). Formic acid self-poisoning on bismuth-modified stepped electrodes. Journal of Electroanalytical Chemistry, 500(1-2), 498-509. doi:10.1016/s0022-0728(00)00389-2Maciá, M. ., Herrero, E., & Feliu, J. . (2002). Formic acid self-poisoning on adatom-modified stepped electrodes. Electrochimica Acta, 47(22-23), 3653-3661. doi:10.1016/s0013-4686(02)00335-3Garcia-Araez, N., Climent, V., Herrero, E., Feliu, J. M., & Lipkowski, J. (2005). Determination of the Gibbs excess of H adsorbed at a Pt(111) electrode surface in the presence of co-adsorbed chloride. Journal of Electroanalytical Chemistry, 582(1-2), 76-84. doi:10.1016/j.jelechem.2005.01.03

Cultura de ápices caulinares e termoterapia na recuperação de plantas livres de vírus de alho

A cultura de ápices caulinares de alho, associada à termoterapia a seco (exposição dos bulbilhos a temperatura de 37°C, por um período de 35 dias) foi essencial para recuperação de plantas livres de vírus das cultivar de alho Amarante. Nestas condições, 70% dos explantes inoculados se desenvolveram in vitro e produziram plantas, das quais 77% não apresentaram partículas virais quando indexadas por ISEM. Isto resulta em um índice de aproveitamento de 54% dos bulbilhos submetidos à termoterapia. O aumento da temperatura na termoterapia para 40°C reduziu a regeneração in vitro para 20%, e 90% dessas plantas estavam livres de vírus, com um índice final de aproveitamento de 18%.Garlic shoot tip culture associated with dry heat thermotherapy (cloves exposed to 37°C for 35 days) were essential for recovering virus free plants of the cv Amarante. In this condition 70% of the explants developed in vitro and produced plants. A total of 77% of those plants was virus free when indexed by ISEM, which resulted in a final index of 54% of virus free plants from treated cloves. The percentage of regeneration decreased to 20% as the temperature increased up to 40°C. However 90% of those plants were virus free, leading to a final index of 18% virus free plants out of treated cloves

Cleavage of the C-C bond in the ethanol oxidation reaction on platinum. Insight from experiments and calculations

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b03117, see http://pubs.acs.org/page/policy/articlesonrequest/index.html".[EN] Using a combination of experimental and computational methods, mainly FTIR and DFT calculations, new insights are provided here in order to better understand the cleavage of the C–C bond taking place during the complete oxidation of ethanol on platinum stepped surfaces. First, new experimental results pointing out that platinum stepped surfaces having (111) terraces promote the C–C bond breaking are presented. Second, it is computationally shown that the special adsorption properties of the atoms in the step are able to promote the C–C scission, provided that no other adsorbed species are present on the step, which is in agreement with the experimental results. In comparison with the (111) terrace, the cleavage of the C–C bond on the step has a significantly lower activation energy, which would provide an explanation for the observed experimental results. Finally, reactivity differences under acidic and alkaline conditions are discussed using the new experimental and theoretical evidence.This work has been financially supported by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013).Ferre Vilaplana, A.; Buso-Rogero, C.; Feliu, JM.; Herrero, E. (2016). Cleavage of the C-C bond in the ethanol oxidation reaction on platinum. Insight from experiments and calculations. Journal of Physical Chemistry C. 120(21):11590-11597. https://doi.org/10.1021/acs.jpcc.6b03117S11590115971202

Holocene Vegetation and Climate inferences from Phytoliths and Pollen from Lagoa do Macuco, North Coast of Espírito Santo State (Brazil)

An interproxy approach focused on phytoliths and pollen, including radiocarbon dating and sediment particle-size analyses, has been carried out at Lagoa do Macuco, Linhares municipality, Espírito Santo State, Brazil. Three pollen zones were identified: the first one (MAC-C I) indicates the presence of mangrove vegetation between 7700 cal yr BP and 4396 cal yr BP; the second one a displacement of the vegetation from the lower areas to the more elevated margins of the valley (MAC-C II, from between 4396 to 1287 cal. yr BP) and third one (MAC-C III), representing the period of the current lake evolution, between 1287 cal. yr BP and the present day. The displacement of the mangrove seems to be connected to the landward migration of the palaeo-estuary and the flooding of the lower parts of the valley, reflecting the relative sea-level highstand, which occurred after 7000 cal yr BP. The phytolith analysis indicated four main zone. The phytolith zone I (7700-7100 cal yr BP) did not show the presence of phytoliths. The phytoliths zone II (7100-3400 cal yr BP) indicates the presence of an open vegetation predominantly of grasses while phytolith zone III (3400-400 cal yr BP) shows a phase with more forested vegetation. Finally, the phytolith zone IV (400 cal yr BP to modern) has a decrease in tree cover and the setting of vegetation with a strong grasses component. Phytoliths indices indicate trends of humidity and temperature at a more local scale, allowing understanding the environmental conditions during the formation of the current lake

Anheteromeyenia vitrea (Porifera: Demospongiae) nova espécie de esponja continental no Brasil

The siliceous spicules of continental sponges have proved to be valuable tools in paleoenvironmental reconstructions, whenever they are perceived in columns of recovered quaternary sediments. The spicules of such sponge collected at grassland subjected to short flooding periods in the Vale Nature Reserve, a preserved coastal area of Atlantic Rain Forest at Espirito Santo State (Brazil), were detected in soil samples recovered in the same region. Study under SEM of materials of the collected specimens indicated the need for description of Anheteromeyenia vitrea n. sp. and redefinition of genus Anheteromeyenia, with Nearctic/Neotropical distribution.Key words: Neotropical freshwater sponges, genus Anheteromeyenia redefined, Spodosol, preserved coastal area.As espículas silicosas das esponjas continentais vêm se mostrando instrumentos valiosos em reconstruções paleoambientais sempre que são detectadas em colunas de sedimentos quaternários recuperados. As espículas de uma dessas esponjas, coletada em ambiente de campos nativos na Reserva Natural da Vale, área preservada de Mata Atlântica no Estado do Espírito Santo (Brasil), foram identificadas em amostras de solo coletadas na mesma região. Estudos ao MEV de materiais dos espécimes coletados indicaram a necessidade da descrição de Anheteromeyenia vitrea sp. n. e redefinição do gênero Anheteromeyenia, com distribuição Neartica/Neotropical.Palavras-chave: Esponjas de água doce neotropicais, gênero Anheteromeyenia redefinido, Espodossolo, área costeira preservad

An 11,000-year record of depositional environmental change based upon particulate organic matter and stable isotopes (C and N) in a lake sediment in southeastern Brazil

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O objetivo do presente estudo é investigar e analisar como os métodos e técnicas de metodologias ativas de ensino-aprendizagem podem ser eficazes na compreensão e no enfrentamento do fenômeno da violência escolar. Este trabalho configura-se como um estudo teórico, pesquisa do tipo bibliográfica e exploratória em quatro bases de dados pesquisadas online sobre as metodologias ativas de ensino e aprendizagem, em articulação com o enfrentamento do fenômeno da violência nas escolas. As referidas bases de dados pesquisadas foram: PERIÓDICOS CAPES; GOOGLE ACADÊMICO; ERIC; SCIELO.  Os resultados da pesquisa denotam que as metodologias ativas de ensino e aprendizagem podem ser úteis no enfrentamento dos diversos tipos de violências que ocorrem nos espaços educativos. Atividades inovadoras e dinâmicas realizadas em grupos operativos ou reflexivos com alunos e professores podem gerar respostas evolutivas e significativas para a melhoria das relações interpessoais e sociais, promovendo saúde e qualidade de vida entre os pares. O fenômeno da violência nas escolas é complexo e são necessárias alternativas diferenciadas no processo de enfrentamento dessa problemática tão danosa à saúde humana. 

Saúde é política… Há uma grande desordem sob o céu: a experiência “comunal” do 15ºº Congresso Paulista de Saúde Pública

Este texto tem por finalidade apresentar um breve relato das atividades preparatórias do 15º Congresso Paulista de Saúde Pública, realizado no segundo semestre de 2017. No material utilizado, estavam inclusas notas tomadas durante as reuniões preparatórias, trechos de mensagens trocadas e, fundamentalmente, o registro vivo contido na memória dos autores, enquanto participantes do processo de organização. Apresentamos, então, os contornos da necessária politização da saúde e as principais tendências observadas nas atividades desenvolvidas em todos os núcleos regionais da Associação Paulista de Saúde Pública. É realçada, ademais, a particularidade do congresso, que mostrou forte inovação na proposta de programa; foi um congresso desconstruído, em movimento, que contou com a realização de nove eventos nas regiões que sediam núcleos da associação. O décimo evento, realizado como atividade de finalização, ocorreu em São Paulo na forma de celebração teórico-política. Ao final, destacamos o fortalecimento dos laços associativos e a consolidação da organização em núcleos.This text aims to present a brief account of the preparatory activities of the 15th Congresso Paulista de Saúde Pública, held in the second half of 2017. Within the material that was used, there are notes taken during the preparatory meetings, excerpts from the exchanged messages and, fundamentally, the living record contained in the memory of the authors, as participants in the organization process. We present then the contours of the necessary health politicization and the trends that were mainly observed in the activities carried out in all the regional centers of the Associação Paulista de Saúde Pública. It was also highlighted the particularity of the congress, which presented a very innovative program proposal; it was a forward-looking propulsive congress, composed by nine events hosted in the regions in which are located the association centers. The 10th event (a closing activity) took place in São Paulo as a theoretical-political celebration. At last, we highlight the strengthening of associative ties and the consolidation of the organization into nuclei

Genesis and variation spatial of Podzol in depressions of the Barreiras formation, northeastern Espírito Santo State, Brazil, and its implications for Quaternary climate change

Variations in relief associated with pedogenetic processes promote different intensities in weathering of sediments of the Barreiras Formation and may thus lead to the formation of different soil types, like Podzols, Acrisols and Ferralsols. The Podzols of tropical regions contain important information on climate and vegetation changes that occurred mainly in late Pleistocene and Holocene; however few studied, regarding their spatial variation, that can be investigated through ground penetrating radar (GPR). The aim was to study morphological, physical, chemical, stable C isotopic properties and spatial distribution of soils within depressions of the Barreiras Formation and characterize the 14C chronology of two Podzols and their B spodic horizons, along a transect grassland to forest in northeastern Espírito Santo State, Brazil. The profiles encompass a sequence of A-E-Bhm horizons, except for P3 and P6 with histic H and A-Bt, respectively. The GPR images showed patterns corresponding to these soil horizons, and the GPR data reveal the presence of diagnostic subsurface horizons characteristic of spodic horizons with cemented layers. The influence of relief factors and original materials was observed, associated with ferrolysis and podzolisation as main actors in the genesis of soils studied. The monomorphic organic matter filling the voids evidences the processes of imobilization, illuviation and precipitation, with the genesis of the spodic horizon. The Podzols profiles of Pleistocene organic matter ages accumulated compounds of C3 plants from the vegetation cover in the B spodic horizons of the profiles P4 and P1, since at least 14,251 and 38,890 cal BP, respectively, suggesting the dominance of a humid climate at least during the studied period in the region