Dependence of the preparation method on the phase composition and particle size of the binary NiO–ZrO2 system oxides

Was studied how preparation method influences phase composition, oxide particle size and catalytic activity of the binary NiO–ZrO2 systems. The processes taking place under the thermal influence while NiO–ZrO2 catalysts are formed from precursors, obtained using a variety of methods, were determinated using the methods of simultaneous TGA-DTG/DSC analysis and XFA. Was studied the influence of the precursor preparation method upon the catalysts' phase composition, sizes of the nickel oxide and zirconium dioxide particles. The research revealed that preparation of precursor using coprecipitation method makes it possible to obtain a binary system, where nickel oxide has minimal size, determined by CSR, and monoclinic phase prevails in ZrO2, after heating it to 800 °C. The research unearthed that the catalyst exhibiting maximal catalytic activity by deep oxidation of methane is nickel oxide-zirconium dioxide, containing equal amounts of monoclinic and tetragonal phases of ZrO2

Synergistic effect in Ag/Fe-MnO2 catalysts for ethanol oxidation

Here we report the synergistic effect of OMS-2 catalysts tested in ethanol oxidation, and the effects produced by both the addition of an Fe modifier in the catalyst preparation stage, and the introduction of Ag on its surface by the impregnation method. To analyze the action of each component, the Fe-modified, Ag-containing OMS-2 catalysts with different Mn/Fe ratios were prepared. Combined XPS and XRF elemental analysis confirms the states and distribution of the Ag- and Fe-containing species between the surface and bulk of the OMS-2 catalysts, which form highly dispersed Ag species on the surface of 0.05Fe–OMS-2, and are also incorporated into the OMS-2 crystalline lattice. The cooperative action of Ag and Fe modifiers improves both reoxidation ability (TPO results) and the amount of adsorbed oxygen species on the catalyst surface. The introduction of Ag to the OMS-2 and 0.05 Fe–OMS-2 surface allows a high level of activity (T80 = 150–155 °C) and selectivity (SAc80 = 93%) towards the acetaldehyde formation

Measured and modelled source water δ18O based on tree-ring cellulose of larch and pine trees from the permafrost zone

To identify source water for trees growing on permafrost in Siberia, we applied mechanistic models that quantify physical and biochemical fractionation processes, leading to oxygen isotope variation (δ18O) in plant organic matter. These models allowed us to investigate the influence of a variety of climatic factors on tree-ring cellulose from two dominant species: Larix cajanderi Mayr. from northeastern Yakutia (69° 22′ N, 148° 25′ E, ~ 250 m a.s.l.) and Pinus sylvestris L. from Central Yakutia (62°14′ N, 129°37′ E, ~ 220 m a.s.l.). The climate of the region is highly continental with short growing seasons, low amount of precipitation and these forest ecosystems are growing on permafrost, which in turn impact the water cycle and climate variation in the δ18O of source water. We compared outputs of the Land surface Processes and eXchanges (LPX-Bern v. 1.3), and Roden-Lin-Ehleringer (RLE) models for the common period from 1945 to 2004. Based on our findings, trees from northeastern and central Yakutia may have access to additional thawed permafrost water during dry summer periods. Owing to differences in the soil structure, active thaw soil depth and root systems of trees at two Siberian sites, Larix cajanderi Mayr. trees can access water not more than from 50 cm depth, in contrast to Pinus sylvestris L. in Central Yakutia which can acquire water from up to 80 cm soil depth. The results enhance our understanding of the growth and survival of the trees in this extreme environment

Increasing relevance of spring temperatures for Norway spruce trees in Davos, Switzerland, after the 1950s

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Manganese catalysts to obtain olefins from C1-C4 alkanes

Oxidative transformations of C1-C4 alkanes into olefins on oxide manganese catalysts were under study. We also studied oxidative coupling of methane (OCM) into ethylene on deposited and applied on the silicon dioxide catalysts. We studied the influence of chemical composition of catalyst and promotors on the OCM. Adding a little amount of ethane and propane hydrocarbons to methane allows increasing the concentration of ethylene in gases and significantly increasing productivity in ethylene. The study also shows the impact of the amount of manganese and promotors applied on SiO2 on the yield of olefins during the conversion of C3-C4 alkanes

Updating the Dual C and O Isotope—Gas-exchange Model: A Concept to Understand Plant Responses to the Environment and Its Implications for Tree Rings

The combined study of carbon (C) and oxygen (O) isotopes in plant organic matter has emerged as a powerful tool for understanding plant functional responses to environmental change. The approach relies on established relationships between leaf gas exchange and isotopic fractionation to derive a series of model scenarios that can be used to infer changes in photosynthetic assimilation and stomatal conductance driven by changes in environmental parameters (CO2, water availability, air humidity, temperature, nutrients). We review the mechanistic basis for a conceptual model, in light of recently published research, and discuss where isotopic observations do not match our current understanding of plant physiological response to the environment. We demonstrate that (1) the model was applied successfully in many, but not all studies; (2) although originally conceived for leaf isotopes, the model has been applied extensively to tree-ring isotopes in the context of tree physiology and dendrochronology. Where isotopic observations deviate from physiologically plausible conclusions, this mismatch between gas exchange and isotope response provides valuable insights into underlying physiological processes. Overall, we found that isotope responses can be grouped into situations of increasing resource limitation versus higher resource availability. The dual-isotope model helps to interpret plant responses to a multitude of environmental factors

The influence of decision-making in tree ring-based climate reconstructions.

Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794-2016 CE at 0.79 (p < 0.001), reveals summer cooling in the years following large volcanic eruptions, and exhibits strong warming since the 1980s. Differing in their mean, variance, amplitude, sensitivity, and persistence, the ensemble members demonstrate the influence of subjectivity in the reconstruction process. We therefore recommend the routine use of ensemble reconstruction approaches to provide a more consensual picture of past climate variability