Nitrogen Content in the Earth's Outer Core Bajgain, Suraj K.; Mookherjee, Mainak; Dasgupta, Rajdeep ...
Geophysical research letters,
16 January 2019, Letnik:
46, Številka:
1
Journal Article
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Using first principles molecular dynamic simulations, we explore the effects of nitrogen (N) on the density and sound velocity of liquid iron and evaluate its potential as a light element in the ...Earth's outer core. Our results suggest that Fe‐N melt cannot simultaneously explain the density and seismic velocity of the Earth's outer core. Although ~2.0 wt.% N can explain the bulk sound velocity of the outer core, such N content only lowers the density of liquid Fe by ~3%. Matching both the velocity and density by the other light elements limits the N in the core to ≪2.0 wt.%. Our finding suggests that nitrogen is a minor to trace element in the Earth's core and is consistent with the geochemical mass balance with terrestrial abundance of N and alloy‐silicate partitioning data, which suggest that there cannot be significant N in the core.
Plain Language Summary
Physical properties of liquid iron cannot explain the seismological observations of density and sound wave velocities in the liquid outer core. In this study we explore the effect of light element nitrogen on the physical properties of liquid iron and provide an upper bound of the amount of nitrogen in the outer core if nitrogen were the sole light element.
Key Points
Nitrogen decreases density and enhances bulk sound velocity of liquid iron
We provide an upper bound of nitrogen in the liquid outer core
The amount of the light elements required to explain density and velocity correlates with the atomic number of the light elements
Deeply subducted carbonates likely cause low-degree melting of the upper mantle and thus play an important role in the deep carbon cycle. However, direct seismic detection of carbonate-induced ...partial melts in the Earth’s interior is hindered by our poor knowledge on the elastic properties of carbonate melts. Here we report the first experimentally determined sound velocity and density data on dolomite melt up to 5.9 GPa and 2046 K by in-situ ultrasonic and sink-float techniques, respectively, as well as first-principles molecular dynamics simulations of dolomite melt up to 16 GPa and 3000 K. Using our new elasticity data, the calculated VP/VS ratio of the deep upper mantle (∼180–330 km) with a small amount of carbonate-rich melt provides a natural explanation for the elevated VP/VS ratio of the upper mantle from global seismic observations, supporting the pervasive presence of a low-degree carbonate-rich partial melt (∼0.05%) that is consistent with the volatile-induced or redox-regulated initial melting in the upper mantle as argued by petrologic studies. This carbonate-rich partial melt region implies a global average carbon (C) concentration of 80–140 ppm. by weight in the deep upper mantle source region, consistent with the mantle carbon content determined from geochemical studies.
Knowledge about the incorporation and role of carbon in silicate magmas is crucial for our understanding of the deep mantle processes. CO
bearing silicate melting and its relevance in the upper ...mantle regime have been extensively explored. Here we report first-principles molecular dynamics simulations of MgSiO
melt containing carbon in three distinct oxidation states - CO
, CO, and C at conditions relevant for the whole mantle. Our results show that at low pressures up to 15 GPa, the carbon dioxide speciation is dominated by molecular form and carbonate ions. At higher pressures, the dominant species are silicon-polyhedral bound carbonates, tetrahedral coordination, and polymerized di-carbonates. Our results also indicate that CO
component remains soluble in the melt at high pressures and the solution is nearly ideal. However, the elemental carbon and CO components show clustering of carbon atoms in the melt at high pressures, hinting towards possible exsolution of carbon from silicate melt at reduced oxygen contents. Although carbon lowers the melt density, the effect is modest at high pressures. Hence, it is likely that silicate melt above and below the mantle transition zone, and atop the core-mantle boundary could efficiently sequester significant amounts of carbon without being gravitationally unstable.
Key Clinical Message
The presentation of a Morel‐Lavallée lesion in the lumbosacral region following a road traffic accident is an uncommon clinical entity. Knowledge of this rare site of occurrence ...can help in early diagnosis and proper management.
Deep subcutaneous fluid collection in the lumbosacral region suggesting Morel‐Lavallée lesion, a rarely encountered location for this uncommon entity.
Electrocardiogram (ECG) signal analysis has received special attention of the researchers in the recent past because of its ability to divulge crucial information about the electrophysiology of the ...heart and the autonomic nervous system activity in a noninvasive manner. Analysis of the ECG signals has been explored using both linear and nonlinear methods. However, the nonlinear methods of ECG signal analysis are gaining popularity because of their robustness in feature extraction and classification. The current study presents a review of the nonlinear signal analysis methods, namely, reconstructed phase space analysis, Lyapunov exponents, correlation dimension, detrended fluctuation analysis (DFA), recurrence plot, Poincaré plot, approximate entropy, and sample entropy along with their recent applications in the ECG signal analysis.
Considering the biodiesel composition, blend percentage, and temperature as input variables in the models to predict biodiesel-diesel blends’ properties is imperative. However, there are no models ...available in the literature to predict the properties of biodiesel-diesel blends that consider all these variables. The accuracy of spray and combustion models for diesel engines depends on the accuracy at which the fuel properties are estimated. Thus, straightforward approaches to accurately predict the properties of biodiesel-diesel blends are required. A novel reference property-based approach is proposed in the present work to predict the biodiesel-diesel blends’ properties to address this research gap. Models available in the literature correlating the properties of interest to fuel temperature were modified by including a reference property measured at 293 K. The effect of biodiesel composition and blend percentage are captured by including a reference property as an input variable. For model calibration, an extensive experimental database is created with 119 samples, including the density, dynamic viscosity, and kinematic viscosity of diesel, biodiesel produced from different feedstocks, and biodiesel-diesel blends at temperatures ranging from 293 K to 373 K. The proposed models predicted the dynamic viscosity, kinematic viscosity, and density of 24 external validation samples with a mean absolute percentage error (MAPE) of 2.15%, 4.73%, and 0.13%, respectively. Overall, the models developed in the present study are reliable and straightforward that can predict the properties of diesel, biodiesels, and biodiesel-diesel blends by considering the effects of biodiesel composition, biodiesel blend proportion in diesel, and temperature simultaneously, unlike the available literature models.
New Semi-empirical mass formulas were developed for the (n, p), (n, α), and (n, 2n) reaction cross-sections at 14.5 MeV neutron energy by using the literature data available on EXFOR library. The new ...formulas were derived on the basis of the statistical model considering Q − value dependence. The results obtained from the present exercise were compared with other systematic formulas developed in past years as well as with the experimental literature data reported on EXFOR library. The comparison has been done on the basis of statistical model as well as on the asymmetry parameter dependence. The present work offers an alternative to reproduce nuclear data at 14.5 MeV incident neutron energies.
•New Semi empirical formulas have been developed using semi empirical approach.•Statistical model and asymmetry dependence were taking into account.•New formulas successfully reproduce (n,p), (n, a), and (n,2n) cross sections.•Experimental and literature data were also compared with the present systematics.
In the present paper, facile synthesis of Ag@ZnO core-shell nanocomposites is reported where zinc oxide is coated on biogenic silver nanoparticles synthesized using Andrographis paniculata and Aloe ...vera leaf extract. Structural features of as synthesized nanocomposites are characterized by UV-visible spectroscopy, XRD, and FTIR. Morphology of the above core-shell nanocomposites is investigated by electron microscopy. As synthesized nanocomposite material has shown antimicrobial activity against Candida krusei, which is an opportunistic pathogen known to cause candidemia. The possible mode of activity of the above material has been studied by in-vitro molecular techniques. Our investigations have shown that surface coating of biogenic silver nanoparticles by zinc oxide has increased its antimicrobial efficiency against Candida krusei, while decreasing its toxicity towards A431 human epidermoid carcinoma cell lines.
Selective and controlled oxidation of olefins to aldehydes is a commonly used important transformation in chemistry. However, chemists still use the dangerous and inconvenient ozonolysis method or ...the less selective, low-yielding Lemieux–Johnson protocol. In a program of developing effective catalysts for this important reaction, we disclose here that an ancillary ligand can play a dramatic role in the above catalytic phenomenon, depending on the design of the ligand precursor chosen. Proof-of-principle is demonstrated with the help of two newly designed LnRuII-NHC precatalysts (NHC = an imidazolydene-based NHC, Im-NHC, or a triazolydene-based NHC, Trz-NHC; Ln = para-cymene) for catalytic selective oxidation of olefins/alkynes to carbonyl compounds. With the electron-deficient Trz-NHC ligand, (para-cymene)RuII(Im-Trz)+ precatalyst was found to be an order of magnitude more efficient than the (para-cymene)RuII(Im-NHC)+ precatalyst.
Herein described are the first efficient nitrogen-atom transfer reactions mediated by iron N,N′-dimethyl-N,N′-bis(2-pyridinylmethyl)cyclohexane-1,2-diamine- (MCP-) and ...2-({1-(pyridin-2-ylmethyl)pyrrolidin-2-ylpyrrolidin-1-yl}methyl)pyridine-type (PDP-type) complexes. These catalysts affect styrene aziridination under mild conditions based on a limiting quantity of olefin substrate.
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