Chromium(iii) oxidation by biogenic manganese oxides with varying structural ripening

2014 ◽  
Vol 16 (9) ◽  
pp. 2127-2136 ◽  
Author(s):  
Yuanzhi Tang ◽  
Samuel M. Webb ◽  
Emily R. Estes ◽  
Colleen M. Hansel
Keyword(s):  
Environmental Conditions ◽  
Manganese Oxides ◽  
Natural Systems ◽  
Mn Oxides

Manganese (Mn) oxides, which are generally considered biogenic in origin within natural systems, are the only oxidants of Cr(iii) under typical environmental conditions.

scholarly journals The effects of population synchrony, life history, and access constraints on benefits from fishing portfolios

2020 ◽  
Author(s):  
Kiva L. Oken ◽  
André E Punt ◽  
Daniel S. Holland
Keyword(s):  
Environmental Conditions ◽  
Life Histories ◽  
Oncorhynchus Tshawytscha ◽  
Environmental Drivers ◽  
Management Options ◽  
Population Synchrony ◽  
Natural Systems ◽  
Advantages And Disadvantages ◽  
Interannual Fluctuations ◽  
Short Time

Natural resources often exhibit large interannual fluctuations in productivity driven by shifting environmental conditions, and this translates to high variability in the revenue resource users can earn. However, users can dampen this variability by harvesting a portfolio of resources. In the context of fisheries, this means targeting multiple populations, though the ability to actually build diverse fishing portfolios is often constrained by the costs and availability of fishing permits. These constraints are generally intended to prevent overcapitalization of the fleet and ensure populations are fished sustainably. As linked human-natural systems, both ecological and fishing dynamics influence the specific advantages and disadvantages of increasing the diversity of fishing portfolios. Specifically, a portfolio of synchronous populations with similar responses to environmental drivers should reduce revenue variability less than a portfolio of asynchronous populations with opposite responses. We built a bioeconomic model characterized by the Dungeness crab (Metacarcinus magister), Chinook salmon (Oncorhynchus tshawytscha), and groundfish fisheries in the California Current, and used it to explore the influence of population synchrony and permit access on revenue patterns. As expected, synchronous populations reduced revenue variability less than asynchronous populations, but only for portfolios including crab and salmon. Synchrony with longer-lived groundfish populations was not important because environmentally-driven changes in groundfish early life survival were mediated by growth and natural mortality over the full population age structure, and overall biomass was relatively stable across years. Thus, building a portfolio of diverse life histories can buffer against the impacts of extremely poor environmental conditions over short time scales, though not for long-term declines. Increasing access to all permits generally led to increased revenue stability and decreased inequality of the fleet, but also resulted in less revenue earned by an individual from a given portfolio because more vessels shared the available biomass. This means managers are faced with a tradeoff between the average revenue individuals earn and the risk those individuals accept. These results illustrate the importance of considering connections between social and ecological dynamics when evaluating management options that constrain or facilitate fishers’ ability to diversify their fishing.

Metazoan endoparasites diversity of Pseudoplatystoma corruscans (Siluriformes: Pimelodidae) as an indicator of environmental alterations on a tropical aquatic system

2014 ◽  
Vol 59 (3) ◽  
Author(s):  
Thamy Ribeiro ◽  
Maria Lizama ◽  
Ricardo Takemoto
Keyword(s):  
Environmental Conditions ◽  
Parasite Species ◽  
Parasite Fauna ◽  
Local Extinction ◽  
Aquatic System ◽  
Dominance Index ◽  
Host Switch ◽  
River Floodplain ◽  
Natural Systems ◽  
Paraná River Floodplain

AbstractThe aim of the present study was to detect the alterations of Pseudoplatystoma corruscans parasite infracommunity structure, after the construction of the Porto Primavera dam on the high Paraná River floodplain. The execution of this research was based on 119 host specimens collected between March 2011 and September 2012, and the results were compared to studies performed on periods before the reservoir’s construction, when 110 fishes were collected between March 1992 and February 1993. Five parasite species still remain on the environment, despite the environmental modifications: Choanoscolex abscissus, Spasskyelina spinulifera, Nomimoscolex pertierrae, Harriscolex kaparari and Contracaecum sp 2. The Berger-Parker dominance index, calculated to the parasite fauna of 1992, did not show the dominance of any species, while, on the present days, this same index accused the dominance of Nomimoscolex pertierrae (49%) and Choanoscolex abscissus (50%). The present study reports the disappearance of Megathylacus travassosi, Contracaecum sp. 1, Contracaecum sp. 3, Procamallanus (Spirocamallanus) sp. and Cucullanus pseudoplatystomae, suggesting the possibility of a local extinction or a host switch of these species. It has also been registered an Acanthocephala specimen, a genus not observed on this host yet. The results here presented show that the antropic influences on natural systems alter the environmental conditions, what is reflected on the richness and diversity parasite levels.

Li/Fe substitution in Li-rich Ni, Co, Mn oxides for enhanced electrochemical performance as cathode materials

2019 ◽  
Vol 7 (25) ◽  
pp. 15215-15224 ◽  
Author(s):  
Juliette Billaud ◽  
Denis Sheptyakov ◽  
Sébastien Sallard ◽  
Daniela Leanza ◽  
Michael Talianker ◽  
...  
Keyword(s):  
Electrochemical Performance ◽  
Manganese Oxides ◽  
Rate Capability ◽  
Potential Drop ◽  
Specific Charge ◽  
Nickel Cobalt ◽  
Charge Potential ◽  
Enhanced Electrochemical Performance ◽  
Fe Substitution ◽  
Mn Oxides

The addition of Fe in Li-rich nickel cobalt manganese oxides allows for higher specific charge, potential drop mitigation and enhanced rate capability.

scholarly journals Insights into the structure–property–activity relationship in molybdenum-doped octahedral molecular sieve manganese oxides for catalytic oxidation

2018 ◽  
Vol 8 (24) ◽  
pp. 6493-6502 ◽  
Author(s):  
Homer C. Genuino ◽  
Diego Valencia ◽  
Steven L. Suib
Keyword(s):  
Co Oxidation ◽  
Catalytic Oxidation ◽  
Molecular Sieve ◽  
Manganese Oxides ◽  
Activity Relationship ◽  
Computational Studies ◽  
Structure Property ◽  
Catalytic Activities ◽  
Mn Oxides

Experimental and computational studies on the properties of Mo-substituted octahedral molecular sieve Mn oxides provide insights into their excellent catalytic activities and stability for CO oxidation.

Influence of Inhibition Layer on Adhesion of a Galvanized High Al Dual Phase Steel

2011 ◽  
Vol 295-297 ◽  
pp. 1669-1674
Author(s):  
Zhao Jun Deng ◽  
Jing Liu ◽  
Zhi Hong Lu ◽  
Hui Wang ◽  
Cheng Jiang Lin
Keyword(s):  
Electron Microscopy ◽  
Manganese Oxides ◽  
Dual Phase Steel ◽  
Steel Substrate ◽  
Dual Phase ◽  
Inhibition Layer ◽  
Good Adhesion ◽  
Transmission Electron ◽  
Mn Oxides ◽  
Scanning Electron

The morphology of inhibition layer and adhesion of Zn coating about a 600MPa grade high Al dual phase steel were studied by grow discharge spectrometry (GDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the inhibition layer is mainly composed of Fe2Al5-xZnx particles with a size of 0.5~1μm, and the adhesion is directly related to the density of the inhibition layer, the denser the inhibition layer, the better the adhesion. It is found: for the samples with good adhesion that besides the Fe2Al5-xZnx particles, there are also some small spherical Al-Mn oxides particles in sizes from 30 to 100nm uniformly distributed in the inhibition layer; for the samples with bad adhesion, the steel substrate is not fully covered by Fe2Al5-xZnx particles and large amount manganese oxides are detected at the non-covered positions.

scholarly journals The influence of environmental conditions on kinetics of arsenite oxidation by manganese-oxides

2015 ◽  
Vol 16 (1) ◽  
Author(s):  
Matthew H. H. Fischel ◽  
Jason S. Fischel ◽  
Brandon J. Lafferty ◽  
Donald L. Sparks
Keyword(s):  
Environmental Conditions ◽  
Manganese Oxides ◽  
Arsenite Oxidation ◽  
Kinetics Of

scholarly journals Electrochemical characterization of manganese oxides as a water oxidation catalyst in proton exchange membrane electrolysers

2019 ◽  
Vol 6 (5) ◽  
pp. 190122 ◽  
Author(s):  
Toru Hayashi ◽  
Nadège Bonnet-Mercier ◽  
Akira Yamaguchi ◽  
Kazumasa Suetsugu ◽  
Ryuhei Nakamura
Keyword(s):  
Water Oxidation ◽  
Manganese Oxides ◽  
Proton Exchange Membrane ◽  
Water Electrolysis ◽  
Electrode System ◽  
Proton Exchange ◽  
Oxidation Catalyst ◽  
Carbon Supports ◽  
Exchange Membrane ◽  
Mn Oxides

The performance of four polymorphs of manganese (Mn) dioxides as the catalyst for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolysers was examined. The comparison of the activity between Mn oxides/carbon (Mn/C), iridium oxide/carbon (Ir/C) and platinum/carbon (Pt/C) under the same condition in PEM electrolysers showed that the γ-MnO 2 /C exhibited a voltage efficiency for water electrolysis comparable to the case with Pt/C, while lower than the case with the benchmark Ir/C OER catalyst. The rapid decrease in the voltage efficiency was observed for a PEM electrolyser with the Mn/C, as indicated by the voltage shift from 1.7 to 1.9 V under the galvanostatic condition. The rapid deactivation was also observed when Pt/C was used, indicating that the instability of PEM electrolysis with Mn/C is probably due to the oxidative decomposition of carbon supports. The OER activity of the four types of Mn oxides was also evaluated at acidic pH in a three-electrode system. It was found that the OER activity trends of the Mn oxides evaluated in an acidic aqueous electrolyte were distinct from those in PEM electrolysers, demonstrating the importance of the evaluation of OER catalysts in a real device condition for future development of noble-metal-free PEM electrolysers.

scholarly journals Exceptional Tl-bearing manganese oxides from Zalas, Krakow area, southern Poland

Mineralogia ◽  
2015 ◽  
Vol 46 (1-2) ◽  
pp. 3-17 ◽  
Author(s):  
Bożena Gołębiowska ◽  
Grzegorz Rzepa ◽  
Adam Pieczka
Keyword(s):  
Manganese Oxides ◽  
Early Paleozoic ◽  
Groundwater System ◽  
Southern Poland ◽  
Small Fault ◽  
Sandy Limestone ◽  
Polymetallic Mineralization ◽  
Native Bismuth ◽  
Mn Oxides ◽  
Fault Breccia

AbstractIn the Permian rhyodacite quarry at Zalas near Krakow, southern Poland, thallium-bearing Mn oxides occur in a small fault zone cutting Middle Jurassic sandy limestone poorly encrusted by an oxidized polymetallic mineralization. The encrustation comprises sulphides (pyrite, chalcopyrite, chalcocite, covellite, galena, marcasite), native bismuth, hematite, goethite, cuprite, mottramite, iodargyrite, unrecognized Cu sulphates and Bi oxychlorides as supergene minerals, barite and rare tiny grains of gold. It is most likely connected with rejuvenation of Early-Paleozoic faults during the Alpine orogeny on the Oligocene–Miocene boundary. Rare Tlbearing Mn oxides occur in an outside zone of the encrustations, filling small fractures and voids in limestone forming the fault breccia. Tl contents, reaching 20.82wt% as Tl2O, exceed by more than two orders of magnitude those reported in similar minerals before, making the oxides unique on a world scale. The Tl-bearing Mn oxides from Zalas reflect intensive weathering of an older Tl-bearing sulphide mineralization in an arid climate, involving saline fluids delivered to the groundwater system as the nappe structure of the Carpathians was developing during the Sava tectonic phase Oligocene/Miocene boundary.

scholarly journals Ecosystem functioning from a geomicrobiological perspective – a conceptual framework for biogeochemical iron cycling

2010 ◽  
Vol 7 (5) ◽  
pp. 399 ◽  
Author(s):  
Caroline Schmidt ◽  
Sebastian Behrens ◽  
Andreas Kappler
Keyword(s):  
Conceptual Framework ◽  
Environmental Conditions ◽  
Spatial Location ◽  
Iron Cycling ◽  
Dynamic Interactions ◽  
Natural Systems ◽  
Microbial Ecosystems ◽  
Key Variables ◽  
Flow Directions ◽  
Iron Redox

Environmental context.Microbial ecosystems are characterised by the interplay of various microorganisms with their biotic and abiotic environment. Biogeochemical niches host adapted microbial communities that are in constant competition for substrates and nutrients. Their natural distribution, interactions and responses to fluctuating environmental conditions are often impossible to simulate in laboratory studies. Using biogeochemical iron redox cycling as an example, we suggest the application of a conceptual framework to improve our understanding of the principal functioning of (geo)microbial ecosystems. Abstract.Our knowledge on how microbial ecosystems function profits from the support of biogeochemical concepts which describe the cycling of elements through various geochemical gradients. Using the example of the iron cycle in freshwater sediments, we propose a theoretical framework that describes the dynamic interactions between chemical and microbial FeII oxidation and FeIII reduction, their spatial location and how they are affected by changing environmental conditions. This contribution emphasises the complexity ecological research faces when dealing with heterogeneous and dynamic natural systems. Our concept aims to provide further insights into how flows of energy and matter are controlled during microbial and chemical Fe redox transformations and how various key variables, such as substrate availability and competition as well as thermodynamic and kinetic parameters, affect flow directions.

Introduction: The dynamics of coupled human and natural systems

2006 ◽  
Vol 11 (1) ◽  
pp. 9-13 ◽  
Author(s):  
JOHN G. McPEAK ◽  
DAVID R. LEE ◽  
CHRISTOPHER B. BARRETT
Keyword(s):  
Environmental Conditions ◽  
Special Section ◽  
Well Being ◽  
Natural Systems

This essay introduces a special section of this issue containing a set of papers on the dynamics of coupled human and natural systems. We frame this introduction by setting out some of the major issues confronting researchers who wish to incorporate both economic and biophysical dynamics in their analysis. We contrast the three papers contained in this section in terms of how they respond to these different issues. We conclude that these papers provide important new insights on both how to model and analyze dynamic coupled human and natural systems and how to define policies that will lead to improved human well being and environmental conditions.

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