scholarly journals Worm tubes as conduits for the electrogenic microbial grid in marine sediments

2019 ◽  
Vol 5 (7) ◽  
pp. eaaw3651 ◽  
Author(s):  
Robert C. Aller ◽  
Josephine Y. Aller ◽  
Qingzhi Zhu ◽  
Christina Heilbrun ◽  
Isaac Klingensmith ◽  
...  
Keyword(s):  
Marine Sediments ◽  
Redox Reaction ◽  
Three Dimensional ◽  
Morphological Adaptation ◽  
Fe Oxide ◽  
Chaetopterus Variopedatus ◽  
Reaction Zones

Electrogenic cable bacteria can couple spatially separated redox reaction zones in marine sediments using multicellular filaments as electron conductors. Reported as generally absent from disturbed sediments, we have found subsurface cable aggregations associated with tubes of the parchment worm Chaetopterus variopedatus in otherwise intensely bioturbated deposits. Cable bacteria tap into tubes, which act as oxygenated conduits, creating a three-dimensional conducting network extending decimeters into sulfidic deposits. By elevating pH, promoting Mn, Fe-oxide precipitation in tube linings, and depleting S around tubes, they enhance tube preservation and favorable biogeochemical conditions within the tube. The presence of disseminated filaments a few cells in length away from oxygenated interfaces and the reported ability of cable bacteria to use a range of redox reaction couples suggest that these microbes are ubiquitous facultative opportunists and that long filaments are an end-member morphological adaptation to relatively stable redox domains.

Fast pseudocapacitive reactions of three-dimensional manganese dioxide structures synthesized via self-limited redox deposition on microwave-expanded graphite oxide

RSC Advances ◽  
2016 ◽  
Vol 6 (10) ◽  
pp. 8330-8335 ◽  
Author(s):  
Wencong Zeng ◽  
Yuan Zhao ◽  
Kun Ni ◽  
Yanwu Zhu
Keyword(s):  
Manganese Dioxide ◽  
Graphite Oxide ◽  
Redox Reaction ◽  
Three Dimensional ◽  
Expanded Graphite ◽  
3D Structures

Self-limited redox reaction between KMnO4 and microwave-expanded graphite oxide was utilized to deposit birnessite-type MnO2 3D structures on the surface of MEGO.

scholarly journals Application of Binary Diagnostic Ratios of Polycyclic Aromatic Hydrocarbons for Identification of Tsunami 2004 Backwash Sediments in Khao Lak, Thailand

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Siwatt Pongpiachan
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Marine Sediments ◽  
Aromatic Hydrocarbons ◽  
Organic Molecules ◽  
Three Dimensional ◽  
Diagnostic Ratios ◽  
Tsunami Deposit ◽  
Tsunami Deposits ◽  
Sedimentary Characteristics ◽  
Polycyclic Aromatic

Identification of Tsunami deposits has long been a controversial issue among geologists. Although there are many identification criteria based on the sedimentary characteristics of unequivocal Tsunami deposits, the concept still remains ambiguous. Apart from relying on some conventional geological, sedimentological, and geoscientific records, geologists need some alternative “proxies” to identify the existence of Tsunami backwash in core sediments. Polycyclic aromatic hydrocarbons (PAHs) are a class of very stable organic molecules, which can usually be presented as complex mixtures of several hundred congeners; one can assume that the “Tsunami backwash deposits” possess different fingerprints of PAHs apart from those of “typical marine sediments.” In this study, three-dimensional plots of PAH binary ratios successfully identify the Tsunami backwash deposits in comparison with those of global marine sediments. The applications of binary ratios of PAHs coupled with HCA are the basis for developing site-specific Tsunami deposit identification criteria that can be applied in paleotsunami deposits investigations.

scholarly journals Investigation of Fluid-driven Carbonation of a Hydrated, Forearc Mantle Wedge using Serpentinite Cores in High-pressure Experiments

2020 ◽  
Vol 61 (3) ◽  
Author(s):  
Melanie J Sieber ◽  
Gregory M Yaxley ◽  
Jörg Hermann
Keyword(s):  
High Pressure ◽  
Inductively Coupled Plasma ◽  
Three Dimensional ◽  
High Resolution Computed Tomography ◽  
Inductively Coupled ◽  
Piston Cylinder ◽  
Replacement Process ◽  
Plasma Mass Spectrometry ◽  
Reaction Zones ◽  
Forearc Mantle

Abstract High-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1·5–2·5 GPa and 375–700 °C. This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2–H2O–CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within ∼96 h at 2 GPa and 600 °C. With decreasing CO2,aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.

Ionic cocrystals of dithiobispyridines: the role of I...I halogen bonds in the building of iodine frameworks and the stabilization of crystal structures

2021 ◽  
Vol 77 (8) ◽  
Author(s):  
Kinga Wzgarda-Raj ◽  
Martyna Nawrot ◽  
Agnieszka J. Rybarczyk-Pirek ◽  
Marcin Palusiak
Keyword(s):  
Solid State ◽  
Redox Reaction ◽  
Quantum Chemical ◽  
Three Dimensional ◽  
Halogen Bonds ◽  
High Nitrogen ◽  
Spontaneous Condensation ◽  
Proton Sponges ◽  
Quantum Chemical Computations

It has been confirmed that mercaptopyridines undergo spontaneous condensation in redox reaction with iodine-forming dithiopyridines. In the solid state, these compounds are protonated at the N atoms and cocrystallize with iodine forming salt structures, namely, 2-[(pyridin-2-yl)disulfanyl]pyridinium triiodide sesquiiodine, C10H9N2S2 +·I3 −·1.5I2, and 4,4′-(disulfanediyl)dipyridinium pentaiodide triiodide, C10H10N2S2 2+·I5 −·I3 −. Dithiopyridine cations are packed among three-dimensional frameworks built from iodide anions and neutral iodine molecules, and are linked by hydrogen, halogen and chalcogen interactions. Quantum chemical computations indicated that dithiopyridines exhibit anomalously high nitrogen basicity which qualify them as potential proton sponges.

The orbit of Pluto over a long interval of time

1966 ◽  
Vol 25 ◽  
pp. 227-229 ◽  
Author(s):  
D. Brouwer
Keyword(s):  
Periodic Orbit ◽  
Numerical Integration ◽  
Restricted Problem ◽  
Three Dimensional ◽  
The Third ◽  
Circular Restricted Problem ◽  
Resonance Relation

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.

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