ALBERT

Description: Magnetic holes (MHs), with a scale much greater than ρ i (proton gyroradius), have been widely reported in various regions of space plasmas. On the other hand, kinetic-size magnetic holes (KSMHs), previously called small size magnetic holes (SSMHs), with a scale of the order of magnitude of or less than ρ i have only been reported in the Earth's magnetospheric plasma sheet. In this study, we report such KSMHs in the magnetosheath whereby we use measurements from the Magnetospheric Multiscale (MMS) mission, which provides three-dimensional (3D) particle distribution measurements with a resolution much higher than previous missions. The MHs have been observed in a scale of 10 ~ 20 ρ e (electron gyroradii) and lasted 0.1 ~ 0.3 s. Distinctive electron dynamics features are observed, while no substantial deviations in ion data are seen. It is found that at the 90° pitch angle, the flux of electrons with energy 34 ~ 66 eV decreased while for electrons of energy 109 ~ 1024 eV increased inside the MHs. We also find the electron flow vortex perpendicular to the magnetic field, a feature self-consistent with the magnetic depression. Moreover, the calculated current density is mainly contributed by the electron diamagnetic drift, and the electron vortex flow is the diamagnetic drift flow. The electron magnetohydrodynamics (EMHD) soliton is considered as a possible generation mechanism for the KSMHs with the scale size of 10 ~ 20 ρ e .

Description: Dipolarization fronts (DFs) are believed to play important roles in transferring plasmas, magnetic fluxes and energies in the magnetotail. Using the Cluster observations in 2003, electromagnetic energy conversion at the DFs is investigated by case and statistical studies. The case study indicates strongest energy conversion at the DF. The statistical study shows the similar features that the energy of the fields can be significantly transferred to the plasmas (load, J·E 〉0) at the DFs. These results are consistent with some recent simulations. Examining the electromagnetic fluctuations at the DFs, we suggest that the wave activities around the lower hybrid frequency may play an important role in the energy dissipation.

Description: Abstract Whistler mode waves are important for precipitating energetic electrons into Earth's upper atmosphere, while the quantitative effect of each type of whistler mode wave on electron precipitation is not well understood. In this letter, we evaluate energetic electron precipitation driven by three types of whistler mode waves: plume whistler mode waves, plasmaspheric hiss, and exohiss observed outside the plasmapause. By quantitatively analyzing three conjunction events between Van Allen Probes and POES/MetOp satellites, together with quasi‐linear calculation, we found that plume whistler mode waves are most effective in pitch angle scattering loss, particularly for the electrons from 10s to 100s keV. Our new finding provides the first direct evidence of effective pitch angle scattering driven by plume whistler mode waves and is critical for understanding energetic electron loss process in the inner magnetosphere. We suggest the effect of plume whistler mode waves be accurately incorporated into future radiation belt modeling.

Description: The impact of sandwich foehn on air pollution in Urumqi, a gap town located on the northern leeside of the Tianshan Mountains of China, is analyzed. The results show that during days with high pollution, the boundary layer over the city and the down-valley area can be divided into a three-layer structure, with the southeasterly foehn sandwiched between the northwesterly winds on top and the cold-air surface pool beneath. The southeasterly foehn at heights between 480 and 2,100 m results in a very stable boundary layer structure. In combination with the decoupling between the foehn flow and cold air pool, such boundary layer structure prevents vertical mixing of atmospheric pollutants. In the up-valley area from the northern leeside flank to the southern urban area, the ground-based foehn confronts the thermally driven valley breeze and forms a “mini-front,” which moves northwards in the morning and retreats southwards in the afternoon. Although the mini-front disappears in the early evening, the wind shear of the mountain breeze between the southern suburb and downtown areas is still remarkable, which is favorable for a convergence line to persist around the city all day long. In this case, air pollutants emitted from the up-valley and down-valley areas are transported toward the urban area. Therefore, the air pollutants accumulate daily, leading to the frequent occurrence of heavy pollution events in Urumqi. This indicates that the sandwich foehn plays a critical role in the formation of heavy air pollution events in Urumqi.

Description: The iron stable isotope compositions ( δ 56 Fe) and iron valence states of ultrahigh-pressure (UHP) eclogites from Bixiling in the Dabie orogen belt, China, were measured to trace changes of geochemical conditions during vertical transportation of earth materials, for example, oxygen fugacity. The bulk Fe 3+ /ΣFe ratios of retrograde eclogites, determined by Mössbauer spectroscopy, are consistently higher than those of fresh eclogites, suggesting oxidation during retrograde metamorphism and fluid infiltration. The studied eclogites (five samples) display limited MORB-like (~0.10 ‰) δ 56 Fe values, which are indistinguishable from their protoliths, i.e., gabbro cumulates formed through differentiation of mantle-derived basaltic magma. This suggests that Fe isotope fractionation during continental subduction is limited. Garnet separates display limited δ 56 Fe variation ranging from -0.08 ± 0.07 ‰ to 0.02 ± 0.07‰, whereas coexisting omphacite displays a large variation of δ 56 Fe values from 0.15 ± 0.07 ‰ to 0.47 ± 0.07 ‰. Omphacite also has highly variable Fe 3+ /ΣFe ratios from 0.367 ± 0.025 to 0.598 ± 0.024, indicating modification after peak metamorphism. Omphacite from retrograde eclogites has elevated Fe 3+ /ΣFe ratios (0.54 - 0.60) compared to that from fresh eclogites (~0.37), whereas garnet displays a narrow range of ferric iron content with Fe 3+ /ΣFe ratios from 0.039 ± 0.013 to 0.065 ± 0.022. The homogenous δ 56 Fe values and Fe 3+ /ΣFe ratios of garnet suggest that it survived the retrograde metamorphism and preserved its Fe isotopic features and ferric contents of peak metamorphism. Because of similar diffusion rates of Fe & Mg in garnet and omphacite, and constant Δ 26 Mg omphacite-garnet values (1.14 ± 0.04‰), equilibrium iron isotope fractionation between garnet and omphacite was probably achieved during peak metamorphism. Elevated Fe 3+ /ΣFe ratios of omphacite from retrograde eclogites and variant Δ 56 Fe omphacite-garnet values of the studied eclogites (0.13 ± 0.10 ‰ to 0.48 ± 0.10 ‰) indicate that oxidized geofuild infiltration resulted in elevation of δ 56 Fe values of omphacite during retrograde metamorphism. This article is protected by copyright. All rights reserved.

Description: Magnetic holes (MHs), characteristic structures where the magnetic field magnitude decreases significantly, have been frequently observed in space plasmas. Particularly, small size magnetic holes (SSMHs) which the scale is less than or close to the proton gyroradius are recently detected in the magnetospheric plasma sheet. In this study of Cluster observations, by the timing method, the minimum directional difference (MDD) method, and the spatio-temporal difference (STD) method, we obtain the propagation velocity of SSMHs in the plasma flow frame. Furthermore, based on electron magnetohydrodynamics (EMHD) theory we calculate the velocity, width and depth of the electron solitary wave and compare it to SSMH observations. The result shows a good accord between the theory and the observation.

Description: The electrical conductivity of brine-saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone, oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water-wet. The simulations included the formation of a water film in the pipes invaded by the non-wetting fluid. During simulated drainage/imbibition we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of “universality”, i.e., insensitivity to the type of lattice used (SC, BCC or FCC). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log-log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental datasets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al . [2011] could be extended to the partial brine saturation case when water films were not present.

Description: Due to its low water solubility and slow dissolution rate, genipin was micronized by an antisolvent precipitation process using ethanol as solvent and n -hexane as antisolvent. The effects of various experimental parameters on the mean particle size (MPS) of micronized genipin were investigated. By analysis of variance, only the concentration of the genipin solution has a significant effect on the MPS in genipin micronization. Under the optimum conditions, micronized genipin with an MPS of 1.8 μm was obtained. The micronized genipin was characterized by various methods, e.g., scanning electron microscopy and thermogravimetry. The analysis results indicated that the chemical structure of micronized genipin was not changed, but the crystallinity was reduced. The dissolution rate and solubility of the micronized genipin were 2.08 and 1.64 times that of the raw drug. In addition, the residual amounts of n -hexane and ethanol were less than the International Conference on Harmonization limit for solvents. Micronized genipin with a mean particle size of 1.8 μm was prepared by the antisolvent precipitation process. The chemical structure of micronized genipin remained unchanged, but the crystallinity was reduced. The dissolution rate and solubility of the micronized genipin were 2.08 and 1.64 times that of the raw drug, and the amounts of residual n -hexane and ethanol were lower than the International Conference on Harmonization limit for solvents.

Description: A novel chemical soft-sensor approach for the prediction of the melt index (MI) in the propylene polymerization industry is presented. The MI is considered as one of the important variables of quality that determine the product specifications. Thus, a reliable estimation of the MI is crucial in quality control. An accurate optimal predictive model of MI values with the relevance vector machine (RVM) is proposed, where the RVM is employed to build the MI prediction model; a modified particle swarm optimization (MPSO) algorithm is then introduced to optimize the parameter of the RVM, and the MPSO-RVM model is thereby developed. An online correcting strategy (OCS) is further carried out to update the modeling data and to revise the model's parameter self-adaptively whenever model mismatch happens. Based on the data from a real polypropylene production plant, a detailed comparison is carried out among the least squares support vector machine (LS-SVM), RVM, MPSO-RVM, and OCS-MPSO-RVM models. The research results reveal the prediction accuracy and validity of the proposed approach. A chemical soft-sensor approach for the prediction of the melt index (MI) in the propylene polymeriza-tion industry is presented. The relevance vector machine (RVM) is employed to build the MI prediction model. A modified particle swarm optimization algorithm is then introduced to optimize the parameter of the RVM and an online correcting strategy is carried out to update the modeling data.