scholarly journals Fast anisotropic Mg and H diffusion in wet forsterite

2021 ◽  
Author(s):  
Joshua Muir ◽  
Feiwu Zhang ◽  
Andrew Walker
Keyword(s):  
Density Functional ◽  
Diffusion Rate ◽  
Water Concentration ◽  
Experimental Conditions ◽  
Functional Theory ◽  
Strong Function ◽  
Effect Of Water ◽  
Large Numbers ◽  
Relationship Of ◽  
The Relationship

Mg diffusion, which is important for properties of forsterite such as conductivity and deformation, is a strong function of water content. The mechanism behind this effect, however, has not been fully elucidated. In this study we use Density Functional Theory to predict the diffusivity of 〖(2H)〗_Mg^X and we find that they are around 1000 times slower than H-free Mg vacancies V_Mg^''. In most wet conditions the concentration of 〖(2H)〗_Mg^X is much higher than that of V_Mg^'' and thus the primary effect of water on increasing the Mg-diffusion rate in forsterite is by producing large numbers of H-bearing Mg vacancies. A water induced increase in diffusion rate is predicted to be accompanied by a large increase in diffusional anisotropy primarily in the [001] direction. Using a previously developed model of H distribution in forsterite we predict that the effect of water on Mg diffusion is strongly dependent upon environmental conditions such as pressure or temperature. An exponent (r) describing the relationship of water concentration to Mg diffusion is found to vary between 0.5-1.6 across common experimental conditions with pressure decreasing this exponent and temperature increasing it. With 100 wt. ppm water Mg diffusion rates are predicted to increase by over 2 orders of magnitude at high temperature and low pressure (2000 K, 0 GPa) and by over 3.5 orders of magnitude at low temperature and high pressure (1000 K, 10 GPa) while the anisotropy of diffusion is predicted to increase by ~2/over 5.5 orders of magnitude respectively. A conversion from “dry” to “wet” rheological laws is predicted to occur at <~1 ppm. These results suggest that Mg diffusion in wet forsterite could vary considerably throughout mantle conditions in ways that cannot be captured with a simple one component equation. Finally we considered the effects of the diffusion of H-bearing Mg vacancies on conductivity in forsterite and olivine. We combined our diffusivity results with experimentally determined results for phonon conductivity but this predicted significaly lower conductivities than have been observed experimentally in olivine, particularly at low temperatures (~1000 K). This suggests that the effect of water on olivine conductivity is not primarily due to bulk 〖(2H)〗_Mg^X diffusion and operates via a different unknown mechanism.

ADSORPTION REACTION OF POLAR ORGANIC MOLECULES ON ${\rm Si}^+_n$ CLUSTER IONS

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2502-2507
Author(s):  
WAKANA NAKAGAWARA ◽  
HIRONORI TSUNOYAMA ◽  
ARI FURUYA ◽  
FUMINORI MISAIZU ◽  
KOICHI OHNO
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Organic Molecules ◽  
Theoretical Calculations ◽  
Cluster Ions ◽  
Silicon Cluster ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Relationship Of ◽  
The Relationship

We have examined chemical reactions of small silicon cluster ions [Formula: see text] for n = 7 - 16 with polar organic molecules M ( M = CH 3 CN , CD 3 OD , C 2 H 5 CN , and C 2 H 5 OH ). The intensities of the adsorption products [Formula: see text] for m = 1 and 2 were investigated as a function of n. We found for all polar molecules that the relative intensity of Si n M + to the unreacted [Formula: see text] is smaller for n = 11, 13, and 14, that is, the adsorption reactivity is smaller for these n than others. It was also commonly observed that the [Formula: see text] ion are more intense than neighboring n. We discussed the relationship of the reactivity with the geometrical structures and the stabilities of the bare [Formula: see text] ions and adsorbed [Formula: see text] ions, from theoretical calculations based on density functional theory.

scholarly journals An Investigation of the Relationship between Cyniclomyces guttulatus and Rabbit Diarrhoea

Pathogens ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 880
Author(s):  
Tuanyuan Shi ◽  
Xinlei Yan ◽  
Hongchao Sun ◽  
Yuan Fu ◽  
Lili Hao ◽  
...  
Keyword(s):  
New Zealand ◽  
Body Weight Gain ◽  
Animal Experiments ◽  
Zealand White Rabbit ◽  
Opportunistic Pathogen ◽  
Large Numbers ◽  
New Zealand White Rabbits ◽  
Positive Rate ◽  
Relationship Of ◽  
The Relationship

Cyniclomyces guttulatus is usually recognised as an inhabitant of the gastrointestinal (GI) tract in rabbits. However, large numbers of C. guttulatus are often detected in the faeces of diarrhoeic rabbits. The relationship of C. guttulatus with rabbit diarrhoea needs to be clearly identified. In this study, a C. guttulatus Zhejiang strain was isolated from a New Zealand White rabbit with severe diarrhoea and then inoculated into SPF New Zealand white rabbits alone or co-inoculated with Eimeriaintestinalis, another kind of pathogen in rabbits. Our results showed that the optimal culture medium pH and temperature for this yeast were pH 4.5 and 40–42 °C, respectively. The sequence lengths of the 18S and 26S ribosomal DNA fragments were 1559 bp and 632 bp, respectively, and showed 99.8% homology with the 18S ribosomal sequence of the NRRL Y-17561 isolate from dogs and 100% homology with the 26S ribosomal sequence of DPA-CGR1 and CGDPA-GP1 isolates from rabbits and guinea pigs, respectively. In animal experiments, the C. guttulatus Zhejiang strain was not pathogenic to healthy rabbits, even when 1 × 108 vegetative cells were used per rabbit. Surprisingly, rabbits inoculated with yeast showed a slightly better body weight gain and higher food intake. However, SPF rabbits co-inoculated with C. guttulatus and E. intestinalis developed more severe coccidiosis than rabbits inoculated with C. guttulatus or E. intestinalis alone. In addition, we surveyed the prevalence of C. guttulatus in rabbits and found that the positive rate was 83% in Zhejiang Province. In summary, the results indicated that C. guttulatus alone is not pathogenic to healthy rabbits, although might be an opportunistic pathogen when the digestive tract is damaged by other pathogens, such as coccidia.

Relation of blood flow to VO2, PO2, and PCO2 in dog gastrocnemius muscle

1988 ◽  
Vol 255 (5) ◽  
pp. H1004-H1010 ◽  
Author(s):  
D. E. Mohrman ◽  
R. R. Regal
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Gastrocnemius Muscle ◽  
Muscle Blood Flow ◽  
Carbon Dioxide Tension ◽  
Experimental Conditions ◽  
Muscle Oxygen ◽  
Muscle Oxygen Consumption ◽  
Relationship Of ◽  
The Relationship

We pump-perfused gastrocnemius-plantaris muscle preparations at constant pressure to study the relationship of muscle blood flow (Q) to muscle oxygen consumption (VO2), venous oxygen tension (PVO2), and venous carbon dioxide tension (PVCO2) during steady-state exercise at different rates. Tests were performed under four experimental conditions produced by altering the perfusate blood-gas status with a membrane lung. The consistency of the relationship of Q to other variables was evaluated by statistical analysis of fitted curves. Not one of the above listed variables had the same relationship with Q in all four of the experimental conditions we tested. However, we did find that a consistent relationship existed among Q, PVO2, and PVCO2 in our data. That relationship is well described by the equation (Q-23).[PVO2 - (0.5.PVCO2) - 3] = 105 (when Q is expressed in ml.100 g-1.min-1 and PVO2 and PVCO2 in mmHg). One interpretation of this result is that both PO2 and PCO2 are important variables in the control of blood flow in skeletal muscle the combined influence of which could account for nearly all of the hyperemia response to steady-state muscle exercise.

Pressure effect on the structural, phonon, elastic and thermodynamic properties of L12phase RH3TA: First-principles calculations

2018 ◽  
Vol 32 (14) ◽  
pp. 1850169
Author(s):  
Leini Wang ◽  
Zhang Jian ◽  
Wei Ning
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Approximation Model ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Relationship Of ◽  
G Ratio ◽  
Wide Pressure

The phonon, elastic and thermodynamic properties of L12phase Rh3Ta have been investigated by the density functional theory (DFT) approach combined with the quasi-harmonic approximation model. The results of the phonon band structure show that L12phase Rh3Ta possesses dynamical stability in the pressure range from 0–80 GPa due to the absence of imaginary frequencies. The pressure dependences with the elastic constants C[Formula: see text], shear modulus G, bulk modulus B, Young’s modulus Y, Poisson’s ratio and B/G ratio have been analyzed. The results of the elastic properties studies show that L12phase Rh3Ta compound is mechanically stable and possesses a higher hardness, improved ductility and plasticity under higher pressures. The pressure and temperature relationship of the thermodynamic properties, such as the Debye temperature [Formula: see text], heat capacity C[Formula: see text], thermal expansion coefficient [Formula: see text] and the Grüneisen parameter [Formula: see text] are predicted by the quasi-harmonic Debye model in a wide pressure (0–80 GPa) and temperature (0–750 K) ranges.

scholarly journals First-Principles Mechanistic Insights into the Hydrogen Evolution Reaction on Ni2P Electrocatalyst in Alkaline Medium

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 307
Author(s):  
Russell W. Cross ◽  
Nelson Y. Dzade
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Density Functional Theory Calculations ◽  
Transition Metal Doping ◽  
Experimental Conditions ◽  
Functional Theory ◽  
Alkaline Conditions ◽  
Modification Of The Surface

Nickel phosphide (Ni2P) is a promising material for the electrocatalytic generation of hydrogen from water. Here, we present a chemical picture of the fundamental mechanism of Volmer–Tafel steps in hydrogen evolution reaction (HER) activity under alkaline conditions at the (0001) and (10 1 ¯ 0) surfaces of Ni2P using dispersion-corrected density functional theory calculations. Two terminations of each surface (Ni3P2- and Ni3P-terminated (0001); and Ni2P- and NiP-terminated (10 1 ¯ 0)), which have been shown to coexist in Ni2P samples depending on the experimental conditions, were studied. Water adsorption on the different terminations of the Ni2P (0001) and (10 1 ¯ 0) surfaces is shown to be exothermic (binding energy in the range of 0.33−0.68 eV) and characterized by negligible charge transfer to/from the catalyst surface (0.01−0.04 e−). High activation energy barriers (0.86−1.53 eV) were predicted for the dissociation of water on each termination of the Ni2P (0001) and (10 1 ¯ 0) surfaces, indicating sluggish kinetics for the initial Volmer step in the hydrogen evolution reaction over a Ni2P catalyst. Based on the predicted Gibbs free energy of hydrogen adsorption (ΔGH*) at different surface sites, we found that the presence of Ni3-hollow sites on the (0001) surface and bridge Ni-Ni sites on the (10 1 ¯ 0) surface bind the H atom too strongly. To achieve facile kinetics for both the Volmer and Heyrovsky–Tafel steps, modification of the surface structure and tuning of the electronic properties through transition metal doping is recommended as an important strategy.

scholarly journals Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 100 ◽  
Author(s):  
Weiwei Wang ◽  
Dahuai Zheng ◽  
Mengyuan Hu ◽  
Shahzad Saeed ◽  
Hongde Liu ◽  
...  
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Density Functional ◽  
Lattice Distortion ◽  
Stable Structure ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Specific Configuration ◽  
The Relationship

Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.

scholarly journals Theoretical Investigation on Structure-Property Relationship of Asymmetric Clusters (CH3FBN3)n (n = 1– 6)

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Deng-Xue Ma ◽  
Yao-Yao Wei ◽  
Yun-Zhi Li ◽  
Guo-Kui Liu ◽  
Qi-Ying Xia
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Dft Method ◽  
Energy Difference ◽  
Structure Property ◽  
Functional Theory ◽  
Size Dependent ◽  
Stable Clusters ◽  
Chemical Inertness ◽  
Relationship Of

The structural, relative stability, electronic, IR vibrational, and thermodynamic properties of asymmetric clusters (CH3FBN3)n (n = 1–6) are systematically investigated using density functional theory (DFT) method. Results show that clusters (CH3FBN3)n (n = 2–6) form a cyclic structure with a B atom and a Nα atom binding together. Five main characteristic regions are observed and assigned for the calculated IR spectra. The size-dependent second-order energy difference shows that clusters (CH3FBN3)3 and (CH3FBN3)5 have relatively higher stability and enhanced chemical inertness compared with the neighboring clusters. These two clusters may serve as the cluster-assembled materials. The variations of thermodynamic properties with temperature T or cluster size n are analyzed, respectively. Based on enthalpies in the range of 200–800 K, the formations of the most stable clusters (CH3FBN3)n (n = 2–6) from monomer are thermodynamically favorable. These data are helpful to design and synthesize other asymmetric boron azides.

scholarly journals Complex phosphorylation activity in neurosecretosomal membranes isolated from ox neurohypophyses

1980 ◽  
Vol 188 (3) ◽  
pp. 657-666 ◽  
Author(s):  
M Treiman ◽  
S Worm-Petersen ◽  
N A Thorn
Keyword(s):  
Cyclic Amp ◽  
Gel Electrophoresis ◽  
Major Part ◽  
Sodium Dodecyl ◽  
Experimental Conditions ◽  
Pituitary Glands ◽  
Relationship Of ◽  
The Relationship ◽  
The Brain ◽  
Soluble Components

Homogenates of neural lobes of bovine pituitary glands were fractionated on Ficoll gradients to yield neurosecretosomes (nerve endings). The neurosecretosomes were lysed in a hypo-osmotic buffer and the membranes were separated from the soluble components by centrifugation. On incubation with [gamma-32P]ATP this membrane preparation showed an endogenous phosphorylation activity, which was studied by means of gel electrophoresis in the presence of sodium dodecyl sulphate, and subsequent autoradiography. The major part of the [32P]Pi detected on the gel was shown to be incorporated into three protein bands, termed A, B and C, with minimal mol.wts. of 83 000, 59 000 and 47 000 respectively. The phosphorylation of these three proteins was studied under a variety of experimental conditions. The patterns obtained were partly similar. However, important individual differences were noted, particularly with respect to the effects of cyclic AMP, Mg2+ and Ca2+. On the basis of these differences, it is suggested that in this system the phosphorylation activity is heterogenous, bands A, B and C each reflecting the presence of a different site of phosphate turnover. The relationship of bands A, B and C to several of the previously described phosphoproteins in the brain is discussed.

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