Browsing by Subject "Degradation"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Publication
    Binder‐free N‐functionalized carbon electrodes for oxygen evolution reaction
    (2023) Song, Feihong; Straten, Jan W.; Lin, Yang‐Ming; Ding, Yuxiao; Schlögl, Robert; Heumann, Saskia; Mechler, Anna K.
    The oxygen evolution reaction (OER) is one of the bottlenecks of electrochemical water splitting. Metal‐free carbons from biomass are highly abundant and can be easily synthesized. Their low price, high conductivity and functionalization makes them promising materials. Herein, we report about free‐standing carbon electrodes as electrocatalysts for the OER. In contrast to powder‐based catalysts, free‐standing electrodes not only avoid additives, but also facilitate post analysis and better reflect industrial conditions. Here, the performance of pure carbon electrodes is compared to those of N‐functionalized ones. Utilizing several analytical techniques, the difference in performance can be rationalized by physical properties. Especially, the analysis of the gaseous products is shown to be of crucial importance. It reveals that N‐doped carbons generate more oxygen and are more robust against carbon corrosion. This illustrates the importance of measuring selectivity especially for carbon electrocatalysts, as higher currents do not necessarily result in higher catalytic activity.
  • Thumbnail Image
    Publication
    Nature's contributions to human well‐being under climate change: Evidence from Central and Eastern Madagascar
    (2024) Petzold, Jan; Kosanic, Aleksandra; Rakoto Joseph, Felana; Rajaonarivelo Andrianina, Princy; Ranaivosoa‐Toandro, Sitraka Mireille; Andriamihaja, Onintsoa Ravaka; Voahanginirina, Leonnie Marcelline; Thien, Lara; Razanajatovo, Mialy
    Anthropogenic climate change has an unprecedented impact on ecosystems and their services, with severe consequences for human well‐being, particularly for the marginalised and vulnerable members of society in the Global South. The well‐being of communities relies not only on material and regulating services ecosystems provide but also on non‐material services. In this paper, we unravel the diverse ways that climate change impacts affect Nature's Contributions to People (NCP) and the well‐being of rural populations in four sites in Madagascar—a biodiversity hotspot but one of the economically poorest countries in the world. We conducted participatory community workshops, mapping and semi‐structured interviews with local residents across social subgroups to understand the mechanisms of climate‐related degradation and the resulting impacts on different dimensions of human well‐being through an NCP lens. We found that non‐material services are generally more often associated with well‐being effects. Climate change degrades material and non‐material services through sea level rise, biodiversity loss, drought, precipitation and temperature variability, with consequences for materials, companionship and labour, food and feed, and physical and psychological experiences. Loss of land and forests is expressed through ecological grief. The outcome of our research provides evidence‐based information to local policymakers, conservation practitioners, and climate change agencies. This information can help improve government efforts toward holistic conservation and climate change adaptation by addressing the impacts on the physical and mental well‐being of the most vulnerable communities. Read the free Plain Language Summary for this article on the Journal blog.
  • Thumbnail Image
    Publication
    Studies on the extent of ruminal degradation of phytate from different feedstuffs
    (2017) Haese, Eva; Rodehutscord, Markus
    The predominant storage form of phosphorus (P) in plant seeds and grains is phytate (InsP6). To cleave the phosphate group and, thus, make the bound P available for absorption by the animal, the enzyme phytase is required. Rumen microorganisms show substantial phytase activity, however, recent studies have suggested that the extent of InsP6 hydrolysis in ruminants is variable leading to an incomplete hydrolysis of InsP6 in specific conditions followed by the excretion of P from undegraded InsP6. As P is an essential element for the metabolism in animals it is important to ensure that the animals’ requirements are met. Diets for ruminants are often supplemented with mineral P (Pi). However, the global phosphate resources are finite and the excretion of surplus P contributes to eutrophication of surface water when applied to the farmland with manure in excessive amounts. Thus, dietary P supply is of environmental concern. Better knowledge about ruminal InsP6 hydrolysis could help to optimise the utilisation of InsP6 and, thus, reduce the use of Pi as well as unnecessary excretion of P. Hence, the objectives of the present thesis were to examine the InsP6 hydrolysis from different feedstuffs in ruminants and to identify factors that might affect the extent of InsP6 hydrolysis. In the first study, the total digestive tract disappearance of InsP6 from diets differing in amount and source of P was determined in lactating dairy cows. The results confirmed the high potential of rumen microorganisms to hydrolyse InsP6, but the composition of the diet influenced the extent of hydrolysis in vivo. In the second study, two in vitro experiments were conducted in order to determine the InsP6 hydrolysis from maize grain and RSM. In experiment 1, two diets differing in P- and InsP6-P concentration were fed to the donor animals of rumen fluid. In experiment 2, a diet similar to the high P diet of experiment 1 was fed to the donor animals of rumen fluid and the rumen fluid was mixed with artificial saliva containing Pi (PI: 120 mg Pi/l) or no Pi. Maize and RSM were incubated for 3, 6, 12, and 24 h in both experiments and the InsP6 concentration was analysed in fermenter fluids and bag residues. InsP6 disappearance from maize proceeded faster than from RSM. The disappearance of InsP6 was higher when the diet with high P concentration was fed (experiment 1) and lower when the rumen fluid was mixed with Pi containing buffer (experiment 2). In the third study, the in situ disappearance of InsP6 from five different concentrates was examined. Maize, wheat, RSM, heat treated RSM (hRSM), and soybean meal were incubated in the rumen of fistulated dairy cows fed with three diets differing in P- and InsP6-P concentration. Concentrations of InsP6 and isomers of InsP5, InsP4, and InsP3 were determined in the bag residues after 2, 4, 8, 16, and 24 h of incubation. The disappearance of InsP6 from cereals proceeded faster than from oilseed meals, however, averaged over the diets, after 24 h of incubation 95% had disappeared from all concentrates except for hRSM (57%). Feeding the diet with high InsP6 concentrations increased InsP6 disappearance from oilseed meals but not from cereals, while feeding the high Pi diet did not influence ruminal InsP6 hydrolysis from any concentrate. The results derived from analysis of lower InsPs suggested that intrinsic plant phytase activity plays only a minor role in the rumen and that active phytases in the rumen react differently to changes in the ruminal environment. The results of the present thesis suggest that the composition of the diet fed to ruminants affects the extent of ruminal InsP6 hydrolysis. While high InsP6 concentrations have the potential to increase InsP6 hydrolysis, a decrease of InsP6 hydrolysis can occur after addition of Pi to the diet. Differences in the pace of InsP6 hydrolysis between concentrates occurred which could be of importance at high ruminal passage rates when the time available for ruminal hydrolysis decreases.