Electrochemical studies based on local interfacial ph changes of gold nanoparticles immobilized on polystyrene brushes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A cubic silsesquioxane modified with purpald (r) : preparation, characterization and a voltammetric application for determination of sulfite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A novel hybrid composite formed by reaction of 4,5-diphenyl-2-imidazolethiol with hexacyanoferrate (iii) and subsequent reaction with copper (ii): preparation, characterization and a voltammetric application for determination of l-glutatione

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the Parameters Affecting the Photoelectrocatalytic Reduction of CO2 to CH3OH at Cu/Cu2O Electrode

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Silver Nanoparticles in a Hydroxyapatite Coating applied by Atmospheric Plasma Spray

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fabrication and characterization of ferrocenece containing hydrogel for glucose biosensor application

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sugars Electrooxidation at Glassy Carbon Electrode Decorate with Multi-Walled Carbon Nanotubes with Nickel Oxy-Hydroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parcelamento e doses de nitrogênio em cobertura na produção, acúmulo de nutrientes e qualidade de cenoura

Pós-graduação em Agronomia (Horticultura) - FCA

Probing the Enamel Topography After Acid Erosion by Scanning Electrochemical Microscopy

In this work, we present an investigation on the thickness of the eroded enamel layer in tooth samples after exposure to citric and hydrochloric acid by using Scanning Electrochemical Microscopy (SECM). Approaching curves with typical negative feedback behavior were obtained in enamel samples for evaluation of topographic changes. In a control experiment, SECM images showed no significant difference in the current monitored during the scan, implying that enamel demineralization did not occur in mineral water medium. Topographic SECM images obtained after contact with citric and hydrochloric acid for different periods of time showed a significant increase in the current relative to a previously protected surface, indicating the structural loss of enamel. The thickness of the enamel layer eroded after contact with hydrochloric acid was significantly higher when compared to the one obtained with citric acid. Hence, our results showed that the enamel acid erosion is a relatively fast process, which is strongly dependent on parameters such as pH, time, acid strength and acid concentration.

Investigation of a Pt3Sn/C Electro-Catalyst in a Direct Ethanol Fuel Cell Operating at Low Temperatures for Portable Applications

A 20% Pt3Sn/C catalyst was prepared by reduction with formic acid and used in a direct ethanol fuel cell at low temperatures. The electro-catalytic activity of this bimetallic catalyst was compared to that of a commercial 20% Pt/C catalyst. The PtSn catalyst showed better results in the investigated temperature range (30 degrees-70 degrees C). Generally, Sn promotes ethanol oxidation by adsorption of OH species at considerably lower potentials compared to Pt, allowing the occurrence of a bifunctional mechanism. The bimetallic catalyst was physico-chemically characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The presence of SnO2 in the bulk and surface of the catalyst was observed. It appears that SnO2 can enhance the ethanol electro-oxidation activity at low potentials due to the supply of oxygen-containing species for the oxidative removal of CO and CH3CO species adsorbed on adjacent Pt active sites.

Reducing Water and Chloride Penetration Through Silicate Treatments for Concrete as a Mean to Control Corrosion Kinetics

There are currently many types of protective materials for reinforced concrete structures and the influence of these materials in the chloride diffusion coefficient and water penetration still needs more research. The aim of this work is to analyze the contributions regarding the typical three surface concrete protection systems (coatings, linings and pore blockers) and discusses the results of three pore blockers (sodium silicate) tested in this work. To this end, certain tests were used: one involving permeability mechanism (low pressure-immersion absorption), one involving capillary water absorption, and the last, a migration test used to estimate the effective chloride diffusion coefficient in saturated condition. Results indicated reduction in chloride diffusion coefficients and capillary water absorption, therefore, restrictions to water penetration from external environmental. As a consequence, a reduction of the corrosion kinetics and a control of the chloride ingress are expected.

Electrochemical Reduction as a Powerful Tool to Highlight the Possible Formation of By-Products More Toxic Than Sudan III Dye

The present work describes the electrochemical reduction of the azo dye Sudan III in methanol/0.01 mol l(-1) Bu4NBF4 at applied potential of -1.2V, which promotes 98% discoloration of the commercial sample. The reduction products were analyzed by high performance liquid chromatography, after optimized conditions for 20 aromatic amines with carcinogenic potentiality. The harmful compounds such as: aniline, benzidine, o-toluidine, 2,6-dimethylaniline, 4,4'-oxydianiline, 4,4'-metileno-bis-2-methylaniline and 4-aminobiphenyl are formed after azo bond cleavage. The electrochemical reduction is compared with chemical reduction by using sodium thiosulfate. Our findings illustrates that commercial Sudan III under reductive condition can forms a number of products, which some are known active genotoxins. The technique could be used to mimic important redox reactions in human metabolism or environment, highlighting the possible formation of by-products more toxic than the original dyes.

New Approaches for the Ethanol Oxidation Reaction of Pt/C on Carbon Cloth Using ATR-FTIR

This work describes the study of the ethanol oxidation reaction of a Pt/C Etek electrocatalyst that was supported on different substrates, such as gold, glassy carbon and carbon cloth treated with PTFE. In the ethanol oxidation reaction, the activity varies with the substrate, as well as the pathways for ethanol oxidation, as studied by an ATR-FTIR in situ setup using the carbon cloth as the electrocatalyst support. The electrocatalyst Pt/C supported on gold starts acetaldehyde production from ethanol oxidation at an onset potential of 0.1 V less than that observed for the same process on Teflon-treated carbon cloth. The Pt/C supported on the carbon cloth starts its CO2 production for the same oxidation process at 0.2 V less than on the Pt/C supported on gold substrate. The differences in catalytic activity for the ethanol oxidation reaction depend not only on the electrocatalyst but also on various electrode factors, such as the substrate, the roughness of the electrode and the charge transfer resistance.

A Sociological Study of the Political Subsystem in Yugoslavia

In this critical analysis of sociological studies of the political subsystem in Yugoslavia since the fall of communism Mr. Ilic examined the work of the majority of leading researchers of politics in the country between 1990 and 1996. Where the question of continuity was important, he also looked at previous research by the writers in question. His aim was to demonstrate the overall extent of existing research and at the same time to identify its limits and the social conditions which defined it. Particular areas examined included the problems of defining basic concepts and selecting the theoretically most relevant indicators; the sources of data including the types of authentic materials exploited; problems of research work (contacts, field control, etc.); problems of analysisl and finally the problems arising from different relations with the people who commission the research. In the first stage of the research, looking at methods of defining key terms, special attention was paid to the analysis of the most frequently used terms such as democracy, totalitarianism, the political left and right, and populism. Numerous weaknesses were noted in the analytic application of these terms. In studies of the possibilities of creating a democratic political system in Serbia and its possible forms (democracy of the majority or consensual democracy), the profound social division of Serbian society was neglected. The left-right distinction tends to be identified with the government-opposition relation, in the way of practical politics. The idea of populism was used to pass responsibility for the policy of war from the manipulator to the manipulated, while the concept of totalitarianism is used in a rather old-fashioned way, with echoes of the cold war. In general, the terminology used in the majority of recent research on the political subsystem in Yugoslavia is characterised by a special ideological style and by practical political material, rather than by developed theoretical effort. The second section of analysis considered the wider theoretical background of the research and focused on studies of the processes of transformation and transition in Yugoslav society, particularly the work of Mladen Lazic and Silvano Bolcic, who he sees as representing the most important and influential contemporary Yugoslav sociologists. Here Mr. Ilic showed that the meaning of empirical data is closely connected with the stratification schemes towards which they are oriented, so that the same data can have different meanings in shown through different schemes. He went on to show the observed theoretical frames in the context of wider ideological understanding of the authors' ideas and research. Here the emphasis was on the formalistic character of such notions as command economy and command work which were used in analysing the functioning and the collapse of communist society, although Mr. Ilic passed favourable judgement on the Lazic's critique of political over-determination in its various attempts to explain the disintegration of the communist political (sub)system. The next stage of the analysis was devoted to the problem of empirical identification of the observed phenomena. Here again the notions of the political left and right were of key importance. He sees two specific problems in using these notion in talking about Yugoslavia, the first being that the process of transition in the FR Yugoslavia has hardly begun. The communist government has in effect remained in power continuously since 1945, despite the introduction of a multi-party system in 1990. The process of privatisation of public property was interrupted at a very early stage and the results of this are evident on the structural level in the continuous weakening of the social status of the middle class and on the political level because the social structure and dominant form of property direct the majority of votes towards to communists in power. This has been combined with strong chauvinist confusion associated with the wars in Croatia and Bosnia, and these ideas were incorporated by all the relevant Yugoslav political parties, making it more difficult to differentiate between them empirically. In this context he quotes the situation of the stream of political scientists who emerged in the Faculty of Political Science in Belgrade. During the time of the one-party regime, this faculty functioned as ideological support for official communist policy and its teachers were unable to develop views which differed from the official line, but rather treated all contrasting ideas in the same way, neglecting their differences. Following the introduction of a multi-party system, these authors changed their idea of a public enemy, but still retained an undifferentiated and theoretically undeveloped approach to the issue of the identification of political ideas. The fourth section of the work looked at problems of explanation in studying the political subsystem and the attempts at an adequate causal explanation of the triumph of Slobodan Milosevic's communists at four subsequent elections was identified as the key methodological problem. The main problem Mr. Ilic isolated here was the neglect of structural factors in explaining the voters' choice. He then went on to look at the way empirical evidence is collected and studied, pointing out many mistakes in planning and determining the samples used in surveys as well as in the scientifically incorrect use of results. He found these weaknesses particularly noticeable in the works of representatives of the so-called nationalistic orientation in Yugoslav sociology of politics, and he pointed out the practical political abuses which these methodological weaknesses made possible. He also identified similar types of mistakes in research by Serbian political parties made on the basis of party documentation and using methods of content analysis. He found various none-sided applications of survey data and looked at attempts to apply other sources of data (statistics, official party documents, various research results). Mr. Ilic concluded that there are two main sets of characteristics in modern Yugoslav sociological studies of political subsystems. There are a considerable number of surveys with ambitious aspirations to explain political phenomena, but at the same time there is a clear lack of a developed sociological theory of political (sub)systems. He feels that, in the absence of such theory, most researcher are over-ready to accept the theoretical solutions found for interpretation of political phenomena in other countries. He sees a need for a stronger methodological bases for future research, either 1) in complementary usage of different sources and ways of collecting data, or 2) in including more of a historical dimension in different attempts to explain the political subsystem in Yugoslavia.

Panel 3: Encounters of Perpetrators and Victims of Genocides

Panel 3: Encounters of Perpetrators and Victims of Genocides Lina Nikou, University of Hamburg, Germany: “Coming Back Home? Berlin Presents Itself to Refugees of the Nazi Regime Living Abroad” Download paper (login required) Michelle Bellino, Harvard University: “Whose Past, Whose Present? Historical Memory among the ‘Postwar’ Generation in Guatemala” Download paper (login required) Srdjan Radovic, Belgrade University/Institute of Ethnography SASA, Serbia: “Memory Culture, Politics of Place, and Social Actors in the Remembrance of Belgrade's World War II Camp” Download paper (login required) Chair: Michael Nolte and Michael Geheran, Clark University Comment: Omer Bartov, Brown University