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Background Cholangiocarcinoma (CCA) is one of the deadliest cancers of the digestive tract. The prognosis of CCA is poor and the 5-year survival rate is low. Bioinformatic analysis showed that early mitotic inhibitor 2 (EMI2) was overexpressed in CCA but the underlying mechanism is not known. Methods The data on bile duct carcinoma from TCGA and GEO databases were used to detect the expression of EMI2. The transcription factors of EMI2 were predicted using JASPAR and PROMO databases. Among the predicted transcription factors, YY1 has been rarely reported in cholangiocarcinoma, and was verified using the luciferase reporter gene assay. RT-PCR was performed to predict the downstream pathway of EMI2, and PI3K/Akt was suspected to be associated with it. Subsequently, in vivo and in vitro experiments were conducted to verify the effects of silencing and overexpressing EMI2 and YY1 on the proliferation, invasion, and metastasis of the bile duct cancer cells. Results EMI2 was highly expressed in CCA. Silencing EMI2 inhibited the proliferation, invasion, and migration of CCA cells, arrested cell cycle in the G1 phase, and promoted of apoptosis. The luciferase reporter gene assay showed that YY1 bound to the promoter region of EMI2, and after silencing YY1, the expression of EMI2 decreased and the progression of CCA was inhibited. Moreover, key proteins in the PI3K/Akt signaling pathway decreased after silencing EMI2. Conclusion EMI2 may be one of the direct targets of YY1 and promotes the progression of CCA through the PI3K/Akt signaling pathway.

The origin and involvement of fluid in the generation of Cenozoic basalts in Northeast China are still under debate. Here we apply the machine learning methods of random forest and deep neural network to train models using data sets of global island arc and ocean island basalts. The trained models predict that most Cenozoic basalts in Northeast China are influenced by fluid and that the fluid activity decreases from east to west. The boundary defined by fluid activity coincides with the westernmost edge of the present-day stagnant Pacific slab determined by seismic tomography and with the geochemical boundary defined by magnesium isotopes. These observations support the view that the fluid involved in the generation of the basalts is controlled by the stagnant Pacific slab instead of driven by the plume induced by the sinking Izanagi Plate. Plain Language Summary Many volcanoes are erupted in Northeast China, and it is of great interest to study the origin of these volcanoes. Previously, the chemical compositions of these volcanoes and typically elemental ratios such as Ba/Th are used to find the answer. In the present study, modern machine learning methods called random forest and deep neural network are used to do the work. The advantage of the new methods is that they can obtain a whole picture of the chemical compositional data instead of a particular one from an elemental ratio. The new methods find that the generation of these basalts is closely related to the Pacific slab, subducting downward at Japan, reaching similar to 600-km depth at the border of eastern China, and extending horizontally to the Mongolia border. Materials released from the slab, such as fluid and melt and the elements dissolved in them, move upward and trigger the volcanoes we see on the surface. The boundary between volcanoes affected dominantly by the slab-derived fluid and those that are not coincides with the westernmost edge of the deeply buried Pacific slab. These findings deepen our understanding of the generation of these volcanoes.

Objective: To investigate the effect of recombinant human brain natriuretic peptide (BNP) on inflammatory factors, neuroendocrine hormones and cardiac function indexes in patients with acute myocardial infarction complicated with heart failure. Methods: A total of 91 cases of acute myocardial infarction with heart failure patients were divided into the control group (n=44) and observation group (n=47) according to the random data table, two groups of patients were given conventional treatment, based on this, the control group was given intravenous infusion of Nitroglycerin Injection treatment, the observation group received intravenous injection of recombinant human brain natriuretic peptide treatment, compared serum inflammatory factors, neuroendocrine hormone and cardiac function and other indexes of two groups before and after treatment. Results: there was no significant difference between the two groups before treatment. After treatment, the levels of TNF-α, hs-CRP, IL-6, MCP-1, LVESD and LVEDD in the two groups were significantly lower than those within the group before treatment, and the observation group was significantly lower than the control group; The two groups after treatment LVEF levels were significantly higher than those in the group before treatment, and the observation group was significantly higher than that of control group; the observation group after treatment PRA, Ang II and ALD and NE levels were significantly lower than those before treatment, and was significantly lower than the control group after treatment, the difference was significant, PRA, Ang, ALD and NE levels of control group before and after the treatment was no significant difference. Conclusion: recombinant human brain natriuretic peptide in the treatment of acute myocardial infarction with heart failure can effectively reduce the serum inflammatory factors and neuroendocrine hormone levels, improve heart function, and have a certain clinical value.

Objective: To investigate the effect of folic acid combined with vitamin B12 supplementation with conventional drugs on the levels of serum inflammatory factors, Hcy and NT-proBNP in elderly patients with chronic heart failure. Methods: 89 elderly patients with chronic heart failure were randomly divided into control group (n=47) and observation group (n=42) based on the random data table. The control group was given diuretics, ACEI and β receptor inhibitor group of three categories of drugs combined treatment, on this basis, the observation group supplemented by folic acid tablets and vitamin B12 treatment, both groups were treated for 8 weeks. The levels of TNF-α, hs-CRP and visfatin, Hcy and NT-proBNP were measured before and after treatment in both groups. Results: There was no significant difference in TNF-α, hs-CRP, visfatin, Hcy and NT-proBNP between the control group and the observation group before treatment. After treatment, the levels of TNF-α, hs-CRP, visfatin, Hcy and NTproBNP in the two groups decreased significantly ,the difference was significant, the level of the above indexes of the observation group after treatment was significantly lower than that of the control group ,the difference was statistically significant. Conclusion: Folic acid combined with vitamin B12 can reduce the levels of serum inflammatory factors, Hcy and NT-proBNP in elderly patients with coronary heart disease and heart failure, which has certain clinical value.

The high conductivity of the Earth's core discovered through first-principles and experimental studies requires that the core must start very hot and cool down slowly to generate the Earth's magnetic field by thermal buoyancy. The requirement is difficult to satisfy due to the fast cooling of the overlying magma ocean and consequently of the underlying core. This is in direct conflict with the early appearance of the Earth's paleomagnetic field. Recently, it was proposed that significant amount of magnesium (Mg) can be partitioned into the core through the high temperature created by the Moon-forming Giant Impact. Due to its intrinsic low solubility, subsequent cooling would cause Mg precipitation to generate compositional buoyancy to power the geodynamo in the early history of the Earth. Here we show using first-principles molecular dynamics simulations that the equilibrium constant of magnesium dissolution in molten iron depends on temperature, entirely consistent with recent experimental data. We further show that Mg partitioned into the core during giant impacts and reaching a concentration of about 2 wt% can precipitate out at around 3.5 Ga, much earlier than the onset of inner core nucleation. During the subsequent evolution of the Earth, silicon (Si) concentration of the Earth's core will remain constant while Mg and oxygen (O) concentrations decrease significantly. Consequently, the current Si concentration in the core reflects the accretion processes of the Earth while O and Mg concentrations in the core is the combined result of both accretion and the subsequent evolution of the Earth core. Forward modeling shows that for MgO precipitation to provide enough power to generate the magnetic field in the early history of the Earth, initially high silicon content of the core is preferred, which is accommodated readily in the Grand Tack accretion scenario. The geodynamo driven by MgO precipitation explains the secular decline of palaeomagnetic field intensity in the early history of the Earth.

The two-phase thermodynamic (2PT) model [S.-T. Lin et al., J. Chem. Phys. 119, 11792–11805 (2003)] provides a promising paradigm to efficiently determine the ionic entropies of liquids from molecular dynamics. In this model, the vibrational density of states (VDoS) of a liquid is decomposed into a diffusive gas-like component and a vibrational solid-like component. By treating the diffusive component as hard sphere (HS) gas and the vibrational component as harmonic oscillators, the ionic entropy of the liquid is determined. Here we examine three issues crucial for practical implementations of the 2PT model: (i) the mismatch between the VDoS of the liquid system and that of the HS gas; (ii) the excess entropy of the HS gas; (iii) the partition of the gas-like and solid-like components. Some of these issues have not been addressed before, yet they profoundly change the entropy predicted from the model. Based on these findings, a revised 2PT formalism is proposed and successfully tested in systems with Lennard-Jones potentials as well as many-atom potentials of liquid metals. Aside from being capable of performing quick entropy estimations for a wide range of systems, the formalism also supports fine-tuning to accurately determine entropies at specific thermal states.

In this paper, a software–hardware mixed design of synchronization and triggering system for multi-functional LXI instruments is proposed. A solution based on open-source software PTPd and DP83640 is introduced and the synchronous deviation can be limited to ±20 ns. And the trigger state machine is implemented in a FPGA while trigger service requests and trigger resources are processed or managed by Linux application programs. Equipped with IVI-COM programming interface and Lua scripting platform, the design can be used to build an efficient and interchangeable test system. In addition, an event log mechanism is also provided to assist fault analysis. Test results indicate that the design strictly conforms to the IviLxiSync Specification, and the precision of synchronization and triggering system satisfies the recommendations of LXI Device Specification.

The adsorption interaction between a water cage and a methane molecule, shown by the cage–methane PMF (potential of mean force), is key to understanding hydrate formation mechanisms. We investigate how the cage type and adsorption face affect the PMF. The PMF is found to depend on the face size rather than the cage type, and the adsorption interaction becomes stronger as the face size increases. However, once the face becomes 7-membered, it no longer adsorbs methane but allows methane crossing it to enter the cage. The results suggest that a preferential direction may exist during hydrate nucleation and growth.

In the field of coming war, integrated logistics support for military equipment is a asked high-reliability system engineering. Based on the theory of Man-Machine-Environment reliability, the paper set forth the significance and conception of the question discussed in the paper. A discussion was given to get over the present challenge of reliability engineering and To ensure the reliability and the trend of the research, the basic direction of improving reliability are introduced in detail are introduced.

Carbon (C) is one of the candidate light elements proposed to account for the density deficit of the Earth’s core. In addition, C significantly affects siderophile and chalcophile element partitioning between metal and silicate and thus the distribution of these elements in the Earth’s core and mantle. Derivation of the accretion and core–mantle segregation history of the Earth requires, therefore, an accurate knowledge of the C abundance in the Earth’s core. Previous estimates of the C content of the core differ by a factor of ∼20 due to differences in assumptions and methods, and because the metal–silicate partition coefficient of C was previously unknown. Here we use two-phase first-principles molecular dynamics to derive this partition coefficient of C between liquid iron and silicate melt. We calculate a value of 9 ± 3 at 3,200 K and 40 GPa. Using this partition coefficient and the most recent estimates of bulk Earth or mantle C contents, we infer that the Earth’s core contains 0.1–0.7 wt% of C. Carbon thus plays a moderate role in the density deficit of the core and in the distribution of siderophile and chalcophile elements during core–mantle segregation processes. The partition coefficients of nitrogen (N), hydrogen, helium, phosphorus, magnesium, oxygen, and silicon are also inferred and found to be in close agreement with experiments and other geochemical constraints. Contents of these elements in the core derived from applying these partition coefficients match those derived by using the cosmochemical volatility curve and geochemical mass balance arguments. N is an exception, indicating its retention in a mantle phase instead of in the core.

In order to ravel out the problem of serious corrosion and difficult repeated construction on the sea, the fluorocarbon coatings for external surface of ocean platform has been researched. The UV light stability, salt fog resistance, acid and alkali corrosion resistance of fluorocarbon coatings are investigated. The comparison data between fluorocarbon coating and chlorinated rubber coatings, acrylic polyurethane coatings and silicone coatings are given.

The aim of the present study was to determine the effects of the short-term application of pantoprazole on the co-treatment of acute ST-segment elevation myocardial infarction (STEMI) with aspirin and clopidogrel. A total of 207 acute patients showing primary symptoms of STEMI, who received successful emergent percutaneous coronary intervention treatment during hospitalization were randomly divided into two groups. In the test group proton pump inhibitors (PPIs), the patients were treated with a combination of aspirin and clopidogrel and pantoprazole, while those in the control group were treated only with aspirin and clopidogrel. Gastrointestinal bleeding events and major adverse cardiac events (MACEs) were observed in the two groups. Gastrointestinal bleeding events of the two groups mostly occurred within the first week of hospitalization, although the incidence in the PPIs group was significantly higher than that in the control group (p0.05). In conclusion, the results of the present study have shown that the short-term application of pantoprazole combined with aspirin and clopidogrel does not increase the incidence of MACEs in patients with acute STEMI, reduces the risk of gastrointestinal bleeding, and is thus worth promoting clinically, particularly for high-risk groups.

With the continuous development of national economy and the construction technology, a lot of large-span spatial structures with unique form and complex construction are emerging. The health monitoring system that mainly used in bridge structure is applied in large-span spatial structures gradually. Parameter identification and damage alarming are the core technology of health monitoring. In this paper some structural modal parameter identification methods based on ambient excitation are introduced. Finally, for large span structures with characteristics of low-intensive modes, the response data based on large span structures for modal parameter identification method was summed up, and the critical issues for further research in this field are also presented.

The discrete finite element (FE) model often cannot reflect structure characteristics accurately due to imply more idealistic assumptions and simplifications. Therefore, it is necessary to update FE model for structural damage identification, response calculation, safety evaluation, optimization design, and so on. This article will illustrate respectively three key steps of updating parameters selection, target function selection and optimization method in process of dynamic FE model updating of footbridge structures based on ambient excitation, and put forward a feasible updating method: combine empirical method with sensitivity analysis method to select updating parameters; joint natural frequencies, MAC and modal flexibility as target function; adopt optimization algorithm based on the optimization theory.

The phase relation and structural evolution of Holl-I and Holl-II in the composition KAlSi3O8 at 0 K have been investigated by the first-principles method up to 130 GPa. Holl-I and Holl-II are polymorphs of KAlSi3O8 stable at low pressures and high pressures, respectively. The transition pressure is determined at ∼23(5) GPa, in agreement with recent experimental observations. All experimentally observed major changes associated with this phase transition such as the deviation of the γ-angle from 90°, splitting of the a- and b-axes, as well as its P-V evolution, are successfully simulated. By evaluating the effect of different Al/Si substitution mechanisms on the computing cell of Holl-I, we have found: (1) different Al/Si substitution mechanisms do not result in apparent difference in the minimized cohesive energies, suggesting a possible random distribution of Al and Si; (2) different Al/ Si substitution mechanisms lead to different powder X-ray diffraction features, which, compared to the experimentally observed powder X-ray diffraction data, implies that local non-random distribution of Al and Si exists to some extent in the Holl-I structure; and (3) the phase transition from Holl-I to Holl-II might be associated with a change in the distribution pattern of Al and Si in the structure. From the simulated compression data, we have derived K0 = 174 GPa and V0 = 244.82 A 3 for Holl-I, and K0

Construction control is the key technique for cable dome. During the actual engineering, however, it is difficult to ensure no difference between the real prestress distribution and the designed value due to existed construction errors. The practical problem for cable dome construction is to determine how much is allowable errors limit. To solve the problem, sensitivity analysis of manufacture errors of bearing and cable length are carried out in this paper. The random errors are simulated by Monte Carlo method. In a numerical model of cable dome with the diameter of 62m, the sensitivity of effect of bearing and cable length manufacture errors on structural performance is analyzed. Numerical results show that the manufacture errors of radial bearing, hoop cable 2, ridge cable 3, diagonal cable 3 and hoop cable 1 should be strictly controlled. Besides, the maximum allowable errors are proposed referring to the domestic existing specifications.

The static stability capacity is the main index to measure the whole mechanical performance of single-layer latticed shells. Three single-layer cylindrical latticed shells with different height to span ratio were modeled, and their seismic damage were assessed by the degradation of static stability capacity incurred by earthquakes. Two different static load patterns were considered: dead load and the combination of dead load and half span live load. The results show that the damage assessment method is applicable to single-layer cylindrical latticed shells, and the static load patterns have no big influence on the damage assessment of the single-layer cylindrical latticed shells.

In order to study the friction contact effect between cable and membrane in cable-membrane structures, a tensioned cable-membrane FE model which has a stable cable (valley cable) is created with FEA software ANSYS. The friction contact between the valley cable and membrane surface is simulated by contact elements in ANSYS, and the effect of friction contact surface is considered by the introduction of friction coefficients. Three different design valley cable forces (15kN, 20kN and 25kN) are considered in form-finding and static analysis, and valley cable force losses are analyzed. Results show that valley cable force loss due to friction contact should be considered obviously when design valley cable force is relatively small.

To analysis progressive collapse behavior of single-layer reticulated shell under severe earthquake, based on spatial fiber beam element failure criteria, a simulation method on progressive collapse of shell is presented, which account of mechanical properties of components after buckling and damage accumulation effect of combine hardening material. And a computation program is developed correspondingly. At last the method and program proves to be applicable by an example.

First principles studies based on density functional theory (DFT) calculations within the generalized gradient approximations (GGA) and GGA + U approach using the full-potential, augmented plane wave + local orbitals (APW + lo) method, as implemented in the WIEN2k code, have been used to investigate the structural, electronic and magnetic properties of spinel-structure LiV2O4, in particular regarding the heavy fermion (HF) behaviour. The calculations were performed for ferromagnetic, anti-ferromagnetic, and ferrimagnetic configurations using two kinds of magnetic structures (tetragonal and rhombohedral). The GGA results showed that the Fermi energy lies in the V 3d (t2g) bands with 1.5 electrons per V atom occupying this band, and the V 3d bands are separated by a ∼1.9 eV energy gap from the O 2p bands and further split into t2g and eg bands with a ∼1.0 eV energy gap, which are in good agreement with the photoelectron spectra. The GGA + U method indicates that the ground state of LiV2O4 is the tetragonal ...

By performing 400 molecular dynamics simulations, we observe that the rigid dodecahedral water cluster (DWC) encaging a methane molecule has an affinity for other methane molecules diffusing freely in liquid water and can adsorb them by chance. Utilizing the affinity, we successfully prepare seven series (200 runs in each series) of DWCs adsorbing 0−12 methane molecules, and study how the adsorbed methane molecules affect the DWC lifetime. The results show that the adsorbed methane molecules can prolong the lifetime of DWC. The structures and dynamics of the DWC and its surroundings are also analyzed. We find that the adsorbed methane molecules slow down the water molecules in both the DWC and its surroundings, reduce the number of H-bonds that tend to break the DWC, and change the H-bond networks of the DWC surroundings from the liquid water structure toward the cagelike structure. On the basis of these observations, a methane aggregation mechanism caused by the DWC adsorbing dissolved methane molecules ...

The molar volumes and bulk moduli of CaSiO3 perovskite are calculated in the temperature range from 300 to 2,800 K and the pressure range from 0 to 143 GPa using molecular dynamics simulations that employ the breathing shell model for oxygen and the quantum correction in addition to the conventional pairwise interatomic potential models. The performance of five equations of state, i.e., the Keane, the generalized-Rydberg, the Holzapfel, the Stacey–Rydberg, and the third-order Birch–Murnaghan equations of state are examined using these data. The third-order Birch–Murnaghan equation of state is found to have a clear tendency to overestimate the bulk modulus at very high pressures. The Stacey–Rydberg equation of state degrades slightly at very high pressures along the low-temperature isotherms. In comparison, the Keane and the Holzapfel equations of state remain accurate in the whole temperature and pressure range considered in the present study. K 0′ derived from the Holzapfel equation of state also agrees best with that calculated independently from molecular dynamics simulations. The adiabatic bulk moduli of CaSiO3 perovskite along lower mantle geotherms are further calculated using the Keane and the Mie-Gruneisen–Debye equations of state. They are found to be constantly higher than those of the PREM by ~5%, and also very similar to those of the MgSiO3 perovskite. Our results support the view that CaSiO3 perovskite remains invisible in the Earth’s lower mantle.

We perform molecular dynamics simulations to study whether the H-bond topology affects the lifetimes of cagelike water clusters immersed in liquid water. Six clusters with H-bond topologies of different energy levels are considered. The lifetimes of each cluster are measured 200 times independently. Statistical analyses show that the H-bond topology has no effect on the lifetimes and the lifetime data obey the lognormal distribution. The implications of these results for the studies on gas hydrate nucleation mechanisms are discussed.

Elastic constants of akimotoite at high-temperatures and pressures are calculated by using molecular dynamics simulations to study the anisotropic properties of akimotoite. We find that akimotoite becomes more anisotropic with increasing temperature but less with increasing pressure. On the (0 0 1) face, S-wave splitting and azimuthal anisotropy will occur simultaneously while the P-wave velocity remains almost constant. Polarization directions of the two S-waves are neither strictly perpendicular nor parallel to the crystallographic face. The polarization direction of the fast S-wave is more parallel with the plane than that of the slow S-wave for all wave propagation directions. On the (1 0 0) face, no S-wave splitting will occur for waves passing along the crystallographic c-axis, and the P-wave velocity along the axis is smaller than that in other directions. Polarization anisotropy changes its sign with the variation of wave propagation directions, giving rise to the dependence of the relative magnitude of VSH and VSV on the seismic wave propagation directions. We further calculate the anisotropic properties of a mineral assemblage containing ringwoodite, akimotoite, and Ca perovskite to infer the effect that akimotoite may have on the anisotropy of the lower portion of the mantle transition zone. We find that the mineral assemblage is much less anisotropic than akimotoite, but possesses many anisotropy features of akimotoite. Comparison of the anisotropy features with seismological observations indicates that a vertical flow direction is required in areas close to the subduction zones, which may be caused by the downward penetration of slabs to the lower mantle as well as upwelling of fluids and light materials in the mantle wedge associated with deep dehydration reactions of the slabs.

Molecular dynamics simulations are performed at 6543 and 3310 K to investigate how the viscosity and self-diffusion coefficient scale with system size in the liquid BKS silica system. We find that at high temperature the finite-size effect on shear viscosity is negligible. However, the size effect on the diffusion coefficient still exists and scales linearly with 1/N1/3, where N is the total number of particles in the system. At low temperature, the size effect on the viscosity becomes stronger than that on diffusion, and the logarithm of the viscosity and the diffusion coefficient scale linearly with 1/N. These results are consistent with previous theoretical developments, and demonstrate that the finite-size effect should be considered in both high- and low-temperature molecular dynamics simulations of liquid silica.

Following Guo, G.-J., and Zhang, Y.-G., 2001, Molec. Phys., 99, 283, which calculates the bulk and shear viscosities of SPC/E water at 30°C and 0.999 g cm−3, further molecular dynamics simulations have been performed at state points of 0°C, −20°C, −40°C, and −60°C along an approximate isobar with the previous state point. SACF and BACF (stress autocorrelation functions related to shear and bulk viscosities, respectively) of high precision have been obtained and compared for their similarities and differences. Shear and bulk viscosities calculated from them showed an increased deviation from real water with decreasing temperature. These correlation functions were then fitted using a uniform two-step relaxation function including a fast oscillatory Kohlrausch law and a slow straightforward Kohlrausch law. The fitting parameters of SACF and BACF have been analysed in detail, and several interesting dynamic phenomena were observed. (1) The oscillation frequency of SACF (44 ~ 48ps−1) for short time intervals a...

Twenty independent equilibrium molecular dynamics simulations were performed in NVE ensemble to calculate the bulk viscosity of water at a temperature of 303 K and a density of 0.999 gcm−3. The energy of each simulation with a production time of 200ps was conserved within 1 part in 104. By stopping the velocity-scaling procedure at a proper step, the energies of independent simulations were specified precisely. This caused the simulations of different start configurations to sample the same NVE ensemble. The shear viscosity of SPC/E water obtained in the present study was 6.5±0.4 × 10−4 Pas, which is in close agreement with a previous calculation in the NVT ensemble (Balasubramanian, S., Mundy, C. J., and Klein, M. L., 1996, J. clzern. Phys., 105, 11 190). The bulk viscosity was 15.5 ± 1.6 × 10−4 Pas, which is 27% smaller than the experimental value. Thus, like its behaviour in predicting the shear viscosity, the SPC/E model also underestimates the bulk viscosity of real water.

Bulk viscosity is closely related to bulk dissipation of seismic waves. To understand the potential bulk dissipation in the Earth’s outer core, molecular dynamics simulations were conducted in the present study to calculate the bulk viscosity of liquid iron–nickel (Fe–Ni) alloy at the temperatures and pressures of the Earth’s outer core. Results from these simulations showed that bulk viscosities of liquid Fe–Ni alloy are in the order of 10 −3 Pa s. These values are in the same order of magnitude as those of pure liquid iron [Phys. Chem. Minerals 27 (2000) 164], indicating that nickel has a negligible effect on the bulk viscosity of liquid iron. Consequently, the large bulk viscosity of the outer core inferred from seismological studies should be accounted for through concentration fluctuations or other mechanisms with light elements such as sulfur or oxygen involved in [Nature 285 (1980) 204; Science 277 (1997) 219], or using the particle suspension model [J. geophys. Res. 88 (1983) 2445]. In addition, using the activation energy and volume calculated from these bulk viscosity data, it was found that the seismically induced phase change model for a partial melt system [J. Geophys. Res. 73 (1968) 7675] might not be capable to account for the bulk attenuation of the outer core.

The compositions of aqueous fluids in equilibrium with enstatite + forsterite were investigated at temperatures from 900 to 1200 °C and pressures from 1.0 to 2.0 GPa. Experiments, performed in a piston-cylinder apparatus, involved the location of phase boundaries between the stability fields of enstatite and enstatite + forsterite, and enstatite + forsterite and forsterite. The intersection of these two phase-boundaries near the H2O apex was used to define the fluid composition. The results indicated a systematic increase in the concentration of silica in the fluid phase with increasing temperature. The experiments indicated that the concentration of dissolved MgO was below 0.3 mol% and not resolvable using our techniques. This finding was corroborated by microprobe analyses of quench precipitates from the fluid phase, which gave on average 0.2 mol% MgO. Because of the low MgO concentrations, the mean values of the intercepts with SiO2-H2O binary of the fitted lines representing, respectively, the phase boundaries between the enstatite and enstatite + forsterite and between the enstatite + forsterite and forsterite stability fields were taken to represent the concentrations of dissolved silica at the various temperatures and pressures of the present study. The concentrations increased from 0.6 mol% at 900 °C to 3.9 mol% at 1200 °C at 1.0 GPa. The pressure effect from 1.0 to 2.0 GPa at 1000 °C appeared to be minor and not resolvable using our techniques. At 1.0 GPa, the base 10 logarithm of the molal concentration of dissolved silica in equilibrium with enstatite + forsterite was obtained combining data from the present study with those from Nakamura and Kushiro (1978) and Manning and Boettcher (1994): ![Formula][1] Comparison with studies of the solubility of quartz (Manning 1994) indicated that thermodynamic properties of aqueous silica derived from silica-saturated systems may not be applicable to calculations in silica-deficient systems at high pressure. [1]: /embed/tex-math-1.gif

Molecular dynamics simulations employing a many-body embedding potential model have been conducted to calculate both bulk and shear viscosity of pure liquid iron at the Earth's outer core conditions. Liquid iron shear viscosity thus obtained is in the order of 10−2 Pa · s and is in close agreement with previous estimates. In contrast, liquid iron bulk viscosity is in the order of 10−3 to 10−4 Pa · s and is much smaller than previous estimates. Consequently, the ratio of bulk to shear viscosity is close to 0.1. This value disagrees with both the common speculation that bulk and shear viscosities are equal at ambient pressure, and the previous inference that bulk viscosity of liquid iron is much larger than shear viscosity at outer core conditions. Potential implications of present data are also briefly given for the dynamic state of the outer core.

The properties of fluids in the CO 2 CH 4 H 2 O system including CO 2 H 2 O and CH 4 H 2 O binary and CO 2 CH 4 H 2 O ternary mixtures with total gas compositions varying from 5.5 to 16.5 mole% were studied at temperatures between 400° and 600°C and pressures between 1000 and 3000 bar. Gas-loading techniques described in Part 1 combined with synthetic fluid inclusion methods were utilized to produce fluid inclusions of known composition. Densities, isochores, liquid-vapor curves and clathrate melting relations were determined for the binary and ternary compositions using measurements of the melting temperature of solid carbon dioxide, the homogenization temperature of carbon dioxide, the clathrate melting temperature and the homogenization temperature of the bubble. The liquid-vapor curves for the CH 4 H 2 O binary were found to be in excellent agreement with previously published results of H. Welsch while significant differences exist for the CO 2 H 2 O binary when compared to those of S. Takenouchi and G.C. Kennedy. Isochores resulting from this study vary significantly from theoretical calculations particularly in the case of low CO 2 concentrations in the CO 2 H 2 O binary.

By performing constrained molecular dynamics simulations in the methane-water system, we successfully calculated the potential of mean force (PMF) between a dodecahedral water cage (DWC) and dissolved methane for the first time. As a function of the distance between DWC and methane, this is characterized by a deep well at approximately 6.2 A and a shallow well at approximately 10.2 A, separated by a potential barrier at approximately 8.8 A. We investigated how the guest molecule, cage rigidity and the cage orientation affected the PMF. The most important finding is that the DWC itself strongly adsorbs methane and the adsorption interaction is independent of the guests. Moreover, the activation energy of the DWC adsorbing methane is comparable to that of hydrogen bonds, despite differing by a factor of approximately 10% when considering different water-methane interaction potentials. We explain that the cage-methane adsorption interaction is a special case of the hydrophobic interaction between methane molecules. The strong net attraction in the DWC shell with radii between 6.2 and 8.8 A may act as the inherent driving force that controls hydrate formation. A cage adsorption hypothesis for hydrate nucleation is thus proposed and discussed.

[1] The magma ocean process in the early history of the Earth has a great influence on the light element identities and contents of the core which subsequently affect the energy of the geodynamo provided by the compositional convection and the inner core growth through their effect on the phase diagram of iron alloy. In the present work, a twophase ab-initio molecular dynamics method is established to study the solubility of silicon and oxygen in liquid iron in equilibrium with silicate melt. The ab-initio results are found to be in close agreement with experimental data. At the base of a deep magma ocean (39 GPa and 3116 K), liquid iron contains 2.7 wt% silicon and 0.5 wt% oxygen at the current bulk Earth composition. The oxygen content is low compared with its current estimate in the core, indicating a deeper magma ocean may need to be invoked. Citation: Zhang, Y., and G. Guo (2009), Partitioning of Si and O between liquid iron and silicate melt: A two-phase ab-initio molecular dynamics study, Geophys. Res. Lett., 36, L18305

By performing a large scale of molecular dynamics simulations, we analyze 60 x 10(6) hydration shells of methane to examine whether the dodecahedral water cluster (DWC) can naturally form in methane aqueous solutions--a fundamental question relevant to the nucleation mechanisms of methane hydrate. The analyzing method is based on identifying the incomplete cages (ICs) from the hydration shells and quantifying their cagelike degrees (zetaC=0-1). Here, the zetaC is calculated according to the H-bond topological network of IC and reflects how the IC resembles the complete polyhedral cage. In this study, we obtain the zetaC distributions of ICs in methane solutions and find the occurrence probabilities of ICs reduce with zetaC very rapidly. The ICs with zetaC>or=0.65 are studied, which can be regarded as the acceptable cagelike structures in appearance. Both increasing the methane concentration and lowering the temperature can increase their occurrence probabilities through slowing down the water molecules. Their shapes, cage-maker numbers, and average radii are also discussed. About 13-14 of these ICs are face saturated, meaning that every edges are shared by two faces. The face-saturated ICs have the potential to act as precursors of hydrate nucleus because they can prevent the encaged methane from directly contacting other dissolved methane when an event of methane aggregation occurs. The complete cages, i.e., the ICs with zetaC=1, form only in the solutions with high methane concentration, and their occurrence probabilities are about 10(-6). Most of their shapes are different from the known hydrate cages, but we indeed observe a standard 5(12)6(2) hydrate cage. We do not find the expected DWC, and its occurrence probability is estimated to be far less than 10(-7). Additionally, the IC analysis proposed in this work is also very useful in other studies not only on the formation, dissociation, and structural transition of hydrates but also on the hydrophobic hydration of apolar solutes.

[1] The first pressure derivative of isothermal bulk modulus at zero pressure (K′0T) is a key equation of state (EOS) parameter. Its variation with temperature is poorly constrained and may influence the inference of composition and temperature of the deep Earth. In the present study, molecular dynamics simulations are performed to derive the K′0T of MgO from 300 to 3000 K using directly the definition of K′0T and without relying on any EOS. The most important finding of the present study is that K′0T depends strongly on temperature. The cross derivative ∂2K0T/∂P∂T is found to be 5.1 ± 1.6 × 10−4 K−1 at 300 K, passing to 9.9 ± 2.7 × 10−4 K−1 at 1600 K, and reaches 15.1 ± 3.8 × 10−4 K−1at 3000 K. The value at 300 K agrees with 3.9 ± 1.0 × 10−4 K−1 of Isaak (1993) within the uncertainty. The experimental adiabatic cross derivative of Chen et al. (1998), which is 2.7 ± 1.1 × 10−3 K−1 and often considered too high, is not far from our value of 1.1 ± 0.3 × 10−3 K−1 at 1600 K when the experimental and calculation uncertainties are considered. The obtained K′0T are further compared with those from EOS fittings to infer the valid temperature domains of several commonly used EOSs. With this knowledge, the consistency of zero-pressure isothermal bulk modulus (K0T) from different experimental techniques (direct resonance measurements and fitting isothermal P-V data by an EOS) is demonstrated.

In a recent paper, Hess and Evans [Phys. Rev. E 64, 011207 (2001)] propose a method different from the conventional Green-Kubo and Einstein methods to calculate viscosity in equilibrium molecular dynamics simulations. For a comparison, we calculate the shear viscosity of SPC/E water at 303 K using these three different methods. We find that the Hess-Evans method is not as good as the other two in practical application, especially for the fluids with high viscosity and complicated relaxation.

Recent advances in the molecular dynamics simulations of spontaneous nucleation and growth of methane hydrate show that an amorphous phase of the hydrate is first reached. However, the amorphous hydrate has not been well described, due to the insufficient identification of cage structures. Here, we develop a method, called ‘‘face-saturated incomplete cage analysis’’, which can identify all face-saturated cages in a given system. As a result, it is found that thousands of cage types and abundant occupancy states are present in the amorphous hydrate. Moreover, the crystallinity of amorphous hydrate is evaluated according to the quantitative calculation of cage linking structures, and the critical nucleus of hydrate is also estimated on the basis of clustering analysis for all face-saturated cages.

The compositions of fluid inclusions in natural minerals provide a valuable source of information from which the conditions of formation of rock systems can be interpreted. The concentrations of trace elements and ionic complexes in the fluids within individual inclusions are especially important. Analysis by X-ray fluorescence using an X-ray microprobe combined with synchroton radiation has proved to be a useful tool for this purpose. Using multilayer mirrors in conjunction with the Kirkpatrick-Baez mirror geometry, a 10-keV synchrotron X-ray beam can be focussed to a spot 5–10 μm in diameter within an individual inclusion. The resulting fluorescence can then be used to determine the numbers of moles and concentrations of the elements contained in the fluid. Due to absorption, the intensity of the fluorescent radiation varies with the element analyzed, the composition of the host mineral, and the depth of the inclusion. To test the method, quartz crystals containing synthetic inclusions with known fluid compositions were analyzed. X-ray scans were made across inclusions containing calcium chloride, manganese chloride and zinc chloride. Accurate determination of the number of picograms contained within an inclusion can be made using thin glass films of known composition as standards. Concentrations, however, are dependent on knowing the volume of the inclusions and are thus less accurate.

One of the principal difficulties in investigating mixed-volatile reactions under hydrothermal conditions has been in loading the experimental charges with gas mixtures of known composition. A new technique has been developed based on the fact that solid compounds with pore structures adsorb gases at low temperatures. A gas pipetting apparatus was constructed whereby a known quantity of a gas or gas mixture can be drawn into the experimental capsule by placing it in a low-temperature bath. A solid, such as a zeolite or a gel, is included in the experimental charge. Due to the adsorption of gas by these materials, the resulting vapor pressures are normally

Using the synthetic fluid-inclusion method, the temperature, pressure, and compositional limits of fluid immiscibility in the binary system CaCl 2 H 2 O have been determined at 600° and 700°C at pressures between 1 and 2 kbar. The limits of the immiscible regions were determined by observation of two different inclusion types in the samples and by measurements of the depression of ice melting temperatures. The region of immiscibility in this system extends to much higher pressures than that of the NaClH 2 O system with similar compositional ranges. A similar study was done on the CaCl 2 H 2 OCO 2 system at 500°, 600° and 700°C at pressures of 1, 1.5, 2 and 3 kbar. In the ternary system, the presence of two different inclusion types and the measurement of clathrate melting temperatures were used to delineate the compositional regions of immiscibility. The presence of CO 2 extends the regions of immiscibility shown in the binary system study to much higher pressures. Tie-lines in the two-phase regions were determined by measuring the homogenization temperatures of CO 2 vapor and liquid phases and the volume ratios of inclusion bubble to total inclusion in vapor-rich type inclusions. The locations of these tie-lines indicate that the CaCl 2 is heavily partitioned towards the more liquid-rich phase. The experimental results show that with even relatively small amounts of a divalent salt such as CaCl 2 , immiscibility can exist to very high temperatures and pressures. From these results immiscibility should be a very common phenomenon in geologic processes ranging from sedimentary to quite high-grade metamorphic environments, and that it should have a very important effect on reactions between hydrothermal fluids and rocks and the resulting mineral assemblages.