Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Influência da natureza do meio nas propriedades semicondutoras do filme passivo formado em aço inoxidável AISI304 e sua relação com a corrosão localizada

Orientador: Prof. Dr. Kleber Franke PortellaCoorientador: Prof. Dr. Juliano de AndradeDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE. Defesa : Curitiba, 26/02/2018Inclui referências: p. 81-86Resumo: Os aços inoxidáveis são materiais que apresentam alta resistência à corrosão generalizada, porém, em determinadas condições ambientais são bastante suscetíveis à corrosão localizada. O "pitting" ocorre como resultado da ruptura local do filme passivo protetor, produzindo perfurações estreitas e profundas no material. O filme passivo formado nos aços inoxidáveis possui propriedades semicondutoras e conhecer sua estrutura eletrônica pode fornecer informações valiosas referentes à resistência à corrosão desses materiais. A partir da aplicação de técnicas eletroquímicas como voltametria cíclica, espectroscopia de impedância eletroquímica e obtenção dos gráficos de Mott-Schottky, o comportamento do aço inoxidável AISI304 foi avaliado em meios eletrolíticos que simulam a água natural de circulação de um sistema de refrigeração. As soluções aquosas foram preparadas em um tampão de pH 8 e continham diferentes concentrações de sulfato de sódio, cloreto de sódio e hidróxido de amônio. As voltametrias cíclicas indicaram o efeito inibidor dos íons sulfatos na corrosão por pites do aço inoxidável. O efeito mais pronunciado ocorreu na solução onde a proporção entre a concentração molar do íon inibidor sulfato e do íon agressivo cloreto foi de 1:1. Nas medidas de espectrosocopia de impedância eletroquímica, os valores obtidos para a resistência á transferência de carga corroboraram os resultados das voltametrias cíclicas variando entre 0,4 e 0,7 M Ômega cm2. O filme passivo formado no aço inoxidável AISI 304 apresentou comportamento semicondutor, em todos os meios estudados concordando com o modelo de presença do óxido de cromo (Cr2O3) na camada mais interna e do óxido de ferro (Gama-Fe2O3), na região mais externa do filme. Os filmes passivos formados apresentaram-se altamente dopados, com valores de densidade de dopantes na ordem de 1020-21 cm-1 e foi possível correlacionar o aumento nos valores com o aumento da concentração de íons em solução. A maior diferença entre o potencial de corrosão e o potencial de banda plana foi encontrado nas soluções onde o material apresentou menor suscetibilidade à corrosão.Abstract: Stainless steels have high general corrosion resistance. However, at some conditions, they are susceptible to localized corrosion. Pitting occurs as a result of local rupture of the protective passive film, which produces narrow and deep holes on the material. The passive films formed on stainless steels presents semiconducting properties and to know their electronic structure can provide valuable information about their corrosion resistance. The application of electrochemical techniques, as cyclic voltammetry, electrochemical impedance spectroscopy and Mott-Schottky plots provided the evaluation of AISI304 stainless steel behavior in simulated media of circulating water from cooling system. The aqueous solutions were prepared in a pH 8 buffer with distinct compositions of sodium chloride, sodium sulphate and ammonium hydroxide from maximum and minimum values of each salt. The cyclic voltammetry results indicated the inhibitory effect of sulfate ions on pitting corrosion of stainless steel. The most pronounced effect occurred in the solution with 1:1 ratio between the molar concentration of the sulfate inhibitor ion and the aggressive chloride ion. The results obtained from electrochemical impedance spectroscopy measures corroborated the corrosion behavior founded in the voltammetries. The values of the charge transfer resistance ranged from 0,4 to 0,7 M Ômega cm2. The passive film formed on stainless steel presented semiconducting behavior in all the medias studied. It had also confirmed the model that present an inner chromium oxide (Cr2O3) layer and an outer iron oxide (Gama-Fe2O3). The passive films are high doped, with dopant density in the range of 1020-21 cm-1. The increase of solution concentration was proportional to the increase of the dopant's density. The biggest difference between the corrosion potential and flatband potential were obtained in the solutions where the material showed less susceptibility to corrosion

Interfacial Characterization of Polypyrrole/AuNP Composites towards Electrocatalysis of Ascorbic Acid Oxidation

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs’ deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior

PEDOT: PSS/AuNPs-Based Composite as Voltammetric Sensor for the Detection of Pirimicarb

An electrochemical sensor for the pesticide Pirimicarb (PMC) has been developed. A screen-printed electrode (SPCE) was used and modified with the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) and gold nanoparticles (AuNPs) to enhance electrochemical proprieties. Electrode characterizations were performed using scattering electron microscopy (SEM) and cyclic voltammetry (CV). With the SPCE/PEDOT:PSS/AuNPs modified electrode, a new peak at 1.0 V appeared in the presence of PMC related to the PMC oxidation. To elucidate the mechanism of PMC oxidation, Gas Chromatography-Mass Spectrometry (GC-MS), where two major peaks were identified, evidencing that the device can both detect and degrade PMC by an electro-oxidation process. Exploring this peak signal, it was possible the sensor development, performing detection from 93.81–750 µmol L−1, limits of quantification (LOQ) and detection (LOD) of 93.91 µmol L−1 and 28.34 µmol L−1, respectively. Thus, it was possible to study and optimization of PMC degradation, moreover, to perform detection at low concentrations and with good selectivity against different interferents using a low-cost printed electrode based on graphite modified with conductive polymer and AuNPs

Global urban environmental change drives adaptation in white clover.

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale