The mutualistic fungus Piriformospora indica protects barley roots from a loss of antioxidant capacity caused by the necrotrophic pathogen Fusarium culmorum

Fusarium culmorum causes root rot in barley (Hordeum vulgare), resulting in severely reduced plant growth and yield. Pretreatment of roots with chlamydospores of the mutualistic root-colonizing basidiomycete Piriformospora indica (Agaricomycotina) prevented necrotization of root tissues and plant growth retardation commonly associated with Fusarium root rot. Quantification of Fusarium infections with a real-time PCR assay revealed a correlation between root rot symptoms and the relative amount of fungal DNA. Fusarium-infected roots showed reduced levels of ascorbate and glutathione (GSH), along with reduced activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). Consistent with this, Fusarium-infected roots showed elevated levels of lipid hydroperoxides and decreased ratios of reduced to oxidized forms of ascorbate and glutathione. In clear contrast, roots treated with P. indica prior to inoculation with F. culmorum showed levels of ascorbate and GSH that were similar to controls. Likewise, lipid peroxidation and the overall reduction in antioxidant enzyme activities were largely attenuated by P. indica in roots challenged by F. culmorum. These results suggest that P. indica protects roots from necrotrophic pathogens at least partly, through activating the plant’s antioxidant capacity

Inverse modeling of thin layer flow cells for detection of solubility, transport and reaction coefficients from experimental data

Thin layer flow cells are used in electrochemical research as experimental devices which allow to perform investigations of electrocatalytic surface reactions under controlled conditions using reasonably small electrolyte volumes. The paper introduces a general approach to simulate the complete cell using accurate numerical simulation of the coupled flow, transport and reaction processes in a flow cell. The approach is based on a mass conservative coupling of a divergence-free finite element method for fluid flow and a stable finite volume method for mass transport. It allows to perform stable and efficient forward simulations that comply with the physical bounds namely mass conservation and maximum principles for the involved species. In this context, several recent approaches to obtain divergence-free velocities from finite element simulations are discussed. In order to perform parameter identification, the forward simulation method is coupled to standard optimization tools. After an assessment of the inverse modeling approach using known realistic data, first results of the identification of solubility and transport data for O2 dissolved in organic electrolytes are presented. A plausibility study for a more complex situation with surface reactions concludes the paper and shows possible extensions of the scope of the presented numerical tools

Inverse modeling of thin layer flow cells for detection of solubility, transport and reaction coefficients from experimental data

Thin layer flow cells are used in electrochemical research as experimental devices which allow to perform investigations of electrocatalytic surface reactions under controlled conditions using reasonably small electrolyte volumes. The paper introduces a general approach to simulate the complete cell using accurate numerical simulation of the coupled flow, transport and reaction processes in a flow cell. The approach is based on a mass conservative coupling of a divergence-free finite element method for fluid flow and a stable finite volume method for mass transport. It allows to perform stable and efficient forward simulations that comply with the physical bounds namely mass conservation and maximum principles for the involved species. In this context, several recent approaches to obtain divergence-free velocities from finite element simulations are discussed. In order to perform parameter identification, the forward simulation method is coupled to standard optimization tools. After an assessment of the inverse modeling approach using known real-istic data, first results of the identification of solubility and transport data for O2 dissolved in organic electrolytes are presented. A plausibility study for a more complex situation with surface reactions concludes the paper and shows possible extensions of the scope of the presented numerical tools

On the Differential Capacitance and Potential of Zero Charge of Au(111) in Some Aprotic Solvents

Voltammetric and Gouy-Chapman capacitance minimum measurements were conducted on Au(111) and roughened Au(111) electrodes in aprotic electrolytes in the absence and presence of specifically adsorbed ions for concentrations ranging from 0.001 to 0.5 M. Negative of the point of zero charge (pzc), the capacitance maximum increases in the order Ca2+<Li+<K+, but the pzc value is independent of cation nature. The capacitance values have a slight dependence on cation type at a more negative potential. The pzc depends on the solvent and is influenced by the dielectric constant, metal-solvent interactions and donor number; it is shifted to more positive values with increasing water content. Specific anion adsorption shifts the pzc to more negative values. The pzc value is more negative for the roughened electrode compared to the single crystal electrode. Propylene carbonate (PC) adsorption in the presence of perchlorate and iodide was examined on gold film by surface-enhanced infrared absorption spectroscopy (SEIRAS). The potential dependent intensity is explained by a stronger electric field and thus a better alignment of the PC molecules when the absolute potential difference to the pzc is large. The capacitance curves were theoretically modelled. From the capacitance maxima on both sides of the pzc the ionic volume and thus the solvation numbers were estimated. The width of the capacitance minimum is believed to be related to the layer of adsorbed solvent molecules. © 2021 The Authors. ChemElectroChem published by Wiley-VCH Gmb

The electro-oxidation of water and alcohols at BDD in hexafluoroisopropanol

Boron doped (BDD) diamond electrodes have a wide potential window and thus allow the formation of radicals and the investigation of their reactions. Hexafluoroisopropanol is able to extend greatly the lifetime of radical cations. Here, we investigated the oxidation of a series of the hydroxyl containing species at a BDD electrode in that solvent: water and the simplest primary, secondary, and tertiary alcohols, i.e. methanol, i-propanol, and t-butanol. The ease of their oxidation does not follow the hydrogen basicity but rather the bond dissociation energy. The radicals formed from water, methanol, and i-propanol are very short-lived and we can detect electrochemically only the second reaction product, i.e. the hydrogen ions. In contrast, t-butanol is oxidised to an intermediate, which is transformed much more slowly within some seconds to another species. This species can be further oxidised more easily than the first intermediate or the initial reactant. There is some evidence, that the reactant molecules play a dual role: on the one hand they undergo oxidative hydrogen abstraction. On the other hand, they stabilise the produced hydrogen ions. (C) 2013 Elsevier B.V. All rights reserved

A Highly Efficient Bifunctional Catalyst for Alkaline Air-Electrodes Based on a Ag and Co3O4 Hybrid: RRDE and Online DEMS Insights

Enhanced catalytic activity towards oxygen reduction (ORR) and evolution (OER) reactions has been achieved by combination of spinel Co3O4 nanoparticles with Ag particles. Quasi-stationary polarization curves showed that the mixed catalyst, Ag + Co3O4 (10 wt%), outperformed its components. Rotating ringdisc electrode (RRDE) measurements revealed a negligible peroxide species formation and a 4-electron pathway for ORR. A tafel slope of ca. 75 mV dec�1 has been observed. The overpotential for ORR at 10% Co3O4 catalyst is ca. 70 mV lower than that of Ag and only ca. 80 mV higher than that of the commercial Pt catalyst. DEMS technique provided a direct evidence for oxygen evolution at these bimetallic catalysts. This hybrid is therefore one of the (or even the) most active, carbon-free, durable, non-precious ORR and OER electrocatalysts reported to date