Influence of the acaricide emulsion pH on the effectiveness of spray products to control the cattle tick: laboratory and field investigations.

The current work evaluated the efficacy of 10 commercial acaricides in different pHs (4.5, 5.5, and 6.5) in laboratory (adult immersion tests (AIT), pH evaluation over time) and field assays (tick counts and efficacy). In the AIT (n=70), higher efficacies were obtained when the acaricide emulsion had a more acidic pH (4.5), mainly for two combinations of pyrethroids + organophosphate (acaricide 3 and acaricide 9). For amidine, a higher pH (6.5) showed a higher efficacy. Over time, there was a trend in the pH of these emulsions increasing. When the efficacy of chlorpyrifos + cypermethrin + piperonyl butoxide (acaricide 3) at different pHs was evaluated over time (0, 6, 12, and 24h) by AIT, the less acidic pH (6.5) showed a strongly variation in the acaricide efficacy range. The mean pH of the water samples from different regions of Brazil was 6.5. In the field, the association of pyrethroid + organophosphates (acaricide 9) with pH of 4.5 and 5.5 were more effective in tick control than the emulsion prepared with this same spray formulation at pH 6.5. The pH of the acaricide emulsions is an important point of attention and is recommended that the veterinary industry start to develop/share information regarding how the pH can affect the acaricide efficacy.

Biochemical hydrogen potential assay for predicting the patterns of the kinetics of semi-continuous dark fermentation.

The performance and kinetics response of thermophilic semi-continuous dark fermentation (DF) of simulated complex carbohydrate-rich waste was investigated at various hydraulic retention times (HRT) (2, 2.5, and 3 d) and compared with data obtained from biochemical hydrogen potential assay (BHP). A culture of Thermoanaerobacterium thermosaccharolyticum was used as the inoculum and dominated both in BHP and semi-continuous reactor. Both the modified Gompertz and first-order models described the DF kinetics well (R2 = 0.97-1.00). HRT of 2.5 d was found to be optimal in terms of maximum hydrogen production rate and hydrogen potential, which were 3.97 and 1.26 times higher, respectively, than in BHP. The hydrolysis constant was highest at HRT of 3 d and was closest to the value obtained in the BHP. Overall, BHP has been shown to be a useful tool for predicting H2 potential and the hydrolysis constant, while the maximum H2 production rate is greatly underestimated.

A eletrorredução de benzodiazepinas e a sua avaliação matemática / Benzodiazepines' electrochemical reduction and its mathematical evaluation

O processo da eletrorredução de benzodiazepinas, uma ferramenta, capaz de usar-se em pesquisa eletroanalítica, foi analisado dos pontos de vista mecanístico e matemático. O modelo correspondente veio sendo investigado por meio da teoria de estabilidade linear e análise de bifurcações e, por meio da sua análise, pôde-se obter o requisito da melhor eficiência do processo, investigar a pH-dependência do seu desempenho, bem como as condições das instabilidades oscilatória e monotónica. Faz-se uma tentativa de uma análise mecanística sistemática do desempenho de sensores eletroquímicos de benzodiazepinas.

The benzodiazepines' electrochemical reduction process, a tool, capable to be used in electroanalytic investigation, was anaylzed by mechanistic and mathematical means. The correspondent model was analyzed by means of linear stability theory and bifurcation analysis, and by its mean it was possible to get the requisite for the best process efficiency, the pH-dependence of its function, like also of oscillatory and monotonic instability. An effort is made fot the systematic mechanistic analysis of the work of benzodiazepine electrochemical sensors.

Bio-hydrogen and bio-methane potentials of skim latex serum in batch thermophilic two-stage anaerobic digestion.

Anaerobic digestion by two-stage process, containing hydrogen-producing (acidogenic) first stage and methanogenic second stage, has been proposed to degrade substrates which are difficult to be treated by single stage anaerobic digestion process. This research was aimed to evaluate the bio-hydrogen and the bio-methane potentials (BHP and BMP) of skim latex serum (SLS) by using sequential batch hydrogen and methane cultivations at thermophilic conditions (55°C) and with initial SLS concentrations of 37.5-75.0% (v/v). The maximal 1.57 L H2/L SLS for BHP and 12.2L CH4/L SLS for BMP were both achieved with 60% (v/v) SLS. The dominant hydrogen-producing bacteria in the H2 batch reactor were Thermoanaerobacterium sp. and Clostrdium sp. Meanwhile, the CH4 batch reactor was dominated by the methanogens Methanosarcina mazei and Methanothermobacter defluvii. The results demonstrate that SLS can be degraded by conversion to form hydrogen and methane, waste treatment and bioenergy production are thus combined.

A descrição matemática do desempenho de sensores e biossensores eletroquímicos de pH, baseados em polímeros condutores, nos processos de medição do pH dos líquidos de cavidade bucal no modo de voltagem constante / Mathematical description of the performance of pH-electrochemical sensors and biosensors, based on conducting polymers, on the pH-measurement of the liquid oral cavity operating at constant voltage

O desempenho de sensores e biossensores de pH, baseados nos polímeros condutores, usados no modo de voltagem constante para medir o pH da cavidade bucal, foi descrito matematicamente. Por meio da análise do respetivo modelo, foram inferidas as condições da melhor precisão do indicador, da multiplicidade de estado estacionário e do comportamento oscilatório em parâmetro eletroquímico.

The work of pH-sensors and biosensors, based on conducting polymers, used in constant-voltage mode for mouth cavity pH-measurement, was mathematically described. By the analysis of the respective model, the best accuracy of the indicator, the steady-states´ multiplicity and oscillatory behavior conditions were derived.

Modelagem matemática do desempenho de elétrodos, modificados por camada de ferroceno, nos processos da eletrooxidação de compostos orgânicos em meios neutro e ácido / Modelación matemática del comportamiento de electrodos, modificado por los procesos de la capa de ferroceno en la electro-oxidación de los compuestos orgánicos en medios neutros y ácidos

O comportamento de elétrodos modificados por camada de ferroceno nos processos da eletrooxidação de certos compostos orgânicos em meios neutro e ácido foi descrito matematicamente, sendo os modelos correspondentes analisados por meio da teoria de estabilidade linear e da análise de bifurcações. Através da comparação dos modelos foi avaliada a influência do pH ao comportamento dos elétrodos, modificados por ferroceno.

The behavior of the electrodes modified by ferrocene layer in the electrooxidation of certain organic compounds in neutral and acid media was mathematically described and the mathematical models were analyzed by linear stability theory and bifurcation analysis. Comparing the models, the influence of pH on the electrodes´ behavior was evaluated.

El estudio de estabilidad en el proceso del desempeño de los sensores y biosensores, basados en los polímeros conductores en medio fuertemente ácido / Stability study in the performance of sensors and biosensors based on conductor polymers in strong acidic media

Por medio del desarrollo del modelo matemático y su análisis (aplicándose la teoría de estabilidad lineal y el análisis de bifurcaciones) se investigó el comportamiento electroquímico, observado en el caso del desempeño de los sensores y biosensores electroquímicos basados en los polímeros conductores en una solución altamente ácida. Fueron derivadas las condiciones de estabilidad del estado estacionario; de las inestabilidades oscilatorias y monotónicas para el desempeño del biosensor en modo de potencia estática. Los resultados del análisis para el caso del medio fuertemente ácido se compararon con los anteriormente obtenidos para el de la solución neutral y básica; por lo cual, así pudo ser inferida la conclusión sobre la influencia del pH al funcionamiento de los sensores y biosensores electroquímicos.

Developing and constructing the mathematical model (applying the linear stability theory and bifurcation analysis), the electrochemical behavior, observed during the work of the CP-based electrochemical sensors and biosensors in strongly acid solution, was investigated. The conditions for the steady-state stability and oscillatory and monotonic instabilities were derived for the work of the biosensor in potentiostatic mode. The results of the analysis for the case of strongly acid solution were compared to the previously obtained for the case of neutral and basic solution and in such way it´s possible to make conclusions about the influence of pH on the functioning of sensors and biosensors.