Electrolyte Imbalance Determination of a Vanadium Redox Flow Battery by Potential‐Step Analysis of the Initial Charging

Vanadium redox flow batteries (VRFB) suffer from capacity fades owing to side reactions and crossover effects through the membrane. These processes lead to a deviation of the optimal initial average oxidation state (AOS=+3.5) of vanadium species in both half‐cell electrolytes. To rebalance the electrolyte solutions, it is first necessary to determine the current AOS. In this study, a new method was developed that enables an accurate determination of the AOS. A potential‐step analysis was performed with mixed electrolyte solutions of both half‐cells during the initial charging. The potential was recorded with a simple open‐circuit voltage (OCV) cell, and the potential‐steps were analyzed. A correlation between the duration of the potential plateaus in the OCV and the amount of vanadium ions of a certain oxidation state in the half‐cell electrolytes was found and used to precisely determine the AOS with a maximum error of 3.6 %

Seasonal Ammonia Emissions from a Free-Stall Dairy in Central Texas

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Electrolyte Imbalance Determination of a Vanadium Redox Flow Battery by Potential-Step Analysis

Development of a new method to determine the average oxidation state of mixed electrolytes by using a standard open circuit voltage cell

Aerobic Degradation of Mercaptosuccinate by the Gram-Negative Bacterium Variovorax paradoxus Strain B4 ▿ †

The Gram-negative bacterium Variovorax paradoxus strain B4 was isolated from soil under mesophilic and aerobic conditions to elucidate the so far unknown catabolism of mercaptosuccinate (MS). During growth with MS this strain released significant amounts of sulfate into the medium. Tn5::mob-induced mutagenesis was successfully employed and yielded nine independent mutants incapable of using MS as a carbon source. In six of these mutants, Tn5::mob insertions were mapped in a putative gene encoding a molybdenum (Mo) cofactor biosynthesis protein (moeA). In two further mutants the Tn5::mob insertion was mapped in the gene coding for a putative molybdopterin (MPT) oxidoreductase. In contrast to the wild type, these eight mutants also showed no growth on taurine. In another mutant a gene putatively encoding a 3-hydroxyacyl-coenzyme A dehydrogenase (paaH2) was disrupted by transposon insertion. Upon subcellular fractionation of wild-type cells cultivated with MS as sole carbon and sulfur source, MPT oxidoreductase activity was detected in only the cytoplasmic fraction. Cells grown with succinate, taurine, or gluconate as a sole carbon source exhibited no activity or much lower activity. MPT oxidoreductase activity in the cytoplasmic fraction of the Tn5::mob-induced mutant Icr6 was 3-fold lower in comparison to the wild type. Therefore, a new pathway for MS catabolism in V. paradoxus strain B4 is proposed: (i) MPT oxidoreductase catalyzes the conversion of MS first into sulfinosuccinate (a putative organo-sulfur compound composed of succinate and a sulfino group) and then into sulfosuccinate by successive transfer of oxygen atoms, (ii) sulfosuccinate is cleaved into oxaloacetate and sulfite, and (iii) sulfite is oxidized to sulfate

Clinical Use of Colistin Induces Cross-Resistance to Host Antimicrobials in \u3ci\u3eAcinetobacter baumannii\u3c/i\u3e

The alarming rise in antibiotic resistance has led to an increase in patient mortality and health care costs. This problem is compounded by the absence of new antibiotics close to regulatory approval. Acinetobacter baumannii is a human pathogen that causes infections primarily in patients in intensive care units (ICUs) and is highly antibiotic resistant. Colistin is one of the last-line antibiotics for treating A. baumannii infections; however, colistin-resistant strains are becoming increasingly common. This cationic antibiotic attacks negatively charged bacterial membranes in a manner similar to that seen with cationic antimicrobials of the innate immune system. We therefore set out to determine if the increasing use of colistin, and emergence of colistin-resistant strains, is concomitant with the generation of cross-resistance to host cationic antimicrobials. We found that there is indeed a positive correlation between resistance to colistin and resistance to the host antimicrobials LL-37 and lysozyme among clinical isolates. Importantly, isolates obtained before and after treatment of individual patients demonstrated that colistin use correlated with increased resistance to cationic host antimicrobials. These data reveal the overlooked risk of inducing cross-resistance to host antimicrobials when treating patients with colistin as a last-line antibiotic

Supplying electricity and heat to low-energy residential buildings by experimentally integrating a fuel cell electric vehicle with a docking station prototype

The integration of renewable energy sources like wind and solar leads to new challenges for a reliable power supply since they are fluctuating and can cause power shortages in times of low solar irradiation and wind. In the present work, the suitability and efficiency of fuel cell electric vehicles (FCEVs) as mobile coupled power and heat sources for residential buildings were investigated to bypass times of low PV and wind generation. For this, a scenario analysis was performed using the open energy modelling framework (OEMOF) for FCEVs providing both, electricity and heat, to a neighbourhood compiled of well-insulated all-electric buildings. Scenarios with and without storages (for heat and electricity) and the influence of an increasing number of battery electric vehicles to be charged were analysed. Preliminary and for the parameterisation of the FCEVs in the simulations, experiments with a modified passenger FCEV and a prototype docking station for the transfer of electricity and heat out of the FCEV were carried out. The results show that the additional heat transferred from the FCEVs to the buildings can cover up to 43% of the heat demand of the neighbourhood. Net efficiencies of over 90% from hydrogen conversion to direct current (DC) and heat were achieved with the test setup. Although hydrogen supply via the internal tanks is possible, a larger number of FCEVs would be needed to cover the necessary power capacities. A stationary supply or the use of larger FCEVs such as trucks would be beneficial for different technical aspects. The focus is on low energy neighbourhoods, therefore, the results are only valid for modern highly energy efficient buildings