ALBERT

Description: [1]  A recent global study has revealed that seismicity near the hypocenter prior to large earthquakes, which could be a proxy for preseismic moment rate, accelerates before inter-plate earthquakes, while it rarely does before intra-plate earthquakes. Understanding the amplitude of preseismic deformation is important in assessing the possibility of its detection. For a class of rate-state friction laws without a characteristic speed-related parameter (e.g., aging law and slip law), a dimensional analysis has shown that if the moment rate increases more mildly than 1/ t f where t f is the time-to-failure, then the amplitude of preseismic moment rate is smaller for a smaller quasistatic slip rate. Three-dimensional numerical simulations have revealed that the aging law yields 1/ t f acceleration, while the slip law causes milder acceleration. If the latter is the case, faults with very low long-term slip rates (e.g., intra-plate faults) may have very small preseismic moment rates.

Description: Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent dramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase.

Description: Fast azimuthal auroral expansion and poleward expansion are characteristic features of the expansion phase of substorms. In the first study of its kind, we have investigated the azimuthal auroral expansion and its magnetospheric counterpart using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers and multiple spacecraft. During the tail season in 2008–2009, we found 16 events of azimuthally expanding aurora that passed near the magnetic footprints of the multiple spacecraft operating in the near-Earth plasma sheet. In the magnetosphere, these events commonly showed fast azimuthal and earthward flows associated with intense electric fields and magnetic dipolarization. The speed of the propagating structure, which was estimated from the time difference of the depolarization observed by the multiple spacecraft, was close to the measured azimuthal plasma flow velocity. We also found that this azimuthal plasma transport was dominated by the E × B drift speed associated with the enhanced electric field. In a statistical analysis, the averaged speeds of the leading edge of the westward and eastward auroral expansion were 8.8 and 5.3 km/s, respectively. When mapped onto the equatorial magnetosphere, these speeds (267 and 162 km/s) were comparable to the averaged azimuthal plasma (E × B) flow speeds observed by the spacecraft, which were 193 (239) km/s in the westward direction and 112 (139) km/s in the eastward direction. Our events showed that E × B flows and auroral expansion predominantly propagated westward, indicating an effect of westward background convection in the Harang flow shear. From these results, we concluded that the azimuthal auroral expansion was closely related to magnetic dipolarization which expanded azimuthally at the E × B drift speed. On the basis of the abrupt formation of the fast E × B flows and their propagation away from the onset location, we suggest that the effects of the intense large-scale electric fields, which are possibly generated through substorm onset turbulence, propagate to the ionosphere along the magnetic field lines and lead to azimuthal expansion of an auroral arc.

Description: Toward the understanding of the effect of the magnetosphere originated disturbances on the global ionospheric electric field and current system, we developed a two-dimensional ionospheric potential solver based on the so-called “thin shell model.” The important extension from the previous studies is that our model covers the pole-to-pole ionosphere without placing any boundary at the equator. By using this solver, we investigate how the ionospheric electric field changes from undershielding condition to overshielding condition as the field aligned current (FAC) distribution changes. Calculations are performed by changing IR2/IR1 (the ratio of current intensities of region 2 (R2) and region 1 (R1) FACs) and by moving R2-FAC relative to the fixed R1-FAC. The results are summarized as follows: (1) The turning point, at which the ionosphere turns from undershielding to overshielding is IR2/IR1 = 0.7 ∼ 0.8. (2) With increasing the local time deference between the R1 and R2-FAC peaks, the efficiency of the shielding by R2-FAC increases but the associated potential skews to the nightside. (3) At the same time the shielding effect is weakened around noon, where the R1-potential intrudes to the low latitude region instead, but the R2-potential remains dominant at other local times. The result suggests that the overshielding or undershielding should be identified by observations not only in a limited local time sector but also in the overall ionosphere as much as possible. In order to accurately describe the ionospheric condition, we suggest new classification terms, “complete-overshielding” and “incomplete-overshielding.”

Description: The passage of an interplanetary (IP) shock was detected by Wind, ACE, Geotail, and THEMIS-B in the solar wind on 24 November 2008. From the propagation time of the IP shock at the spacecraft, it is expected that the IP shock front is aligned with the Parker spiral and strikes the postnoon dayside magnetopause first. Using multipoint observations of the sudden commencement (SC) at THEMIS probes, GOES 11, and ETS in the dayside magnetosphere, we confirmed that the magnetospheric response to the IP shock starts earlier in the postnoon sector than in the prenoon sector. We found that the estimated normal direction of the SC front is nearly aligned with the estimated IP shock normal. We also found that the SC front normal speed is much slower than the fast mode speed and is about 22–56% of the IP shock speed traveling in the solar wind. Thus, we suggest that the major field changes of the SC in the dayside magnetosphere are not due to the magnetic flux carried by hydromagnetic waves but to the increased solar wind dynamic pressure behind the shock front sweeping the magnetopause. The SC event appears as a step-like increase in the H component at the low-latitude Bohyun station and a negative-then-positive variation in the H component at the high-latitude Chokurdakh (CHD) station in the morning sector. During the negative perturbation at CHD, the SuperDARN Hokkaido radar detected a downward motion in the ionosphere, implying westward electric field enhancement. Using the THEMIS electric field data, it is confirmed that the westward electric field corresponds to the inward plasma motion in the dayside magnetosphere due to the magnetospheric compression.

Description: Synthesis yields of organic reactions are one of the most important factors in ranking synthesis routes created by synthesis route design systems such as Transform-Oriented Synthesis Planning and Knowledge base-Oriented Synthesis Planning. If it is possible to predict the yields of synthesis reactions before starting experiments, one can easily determine an order of synthesis routes for experimental works. In the present study, the reaction profiles of the Curtius rearrangement with different substituents were calculated to generate an equation predicting experimental yields of this reaction. Reactions followed by the formation of isocyanates were also analyzed to consider the relationship between reaction times and experimental yields. A partial least squares (PLS) regression was used to correlate the experimental yields with the calculated activation energies, E a ( calc ), together with experimental conditions such as dielectric constants of solvents, reaction times, and reaction temperatures as explanatory variables. Although the PLS regression using all the data gave very poor results, we succeeded in making a model equation with R 2  = 0.887 using a modified data set. However, there is a conflict between the predictability and the interpretability on the reaction time. This discrepancy mainly comes from unnecessarily long reaction times in the experiments for azides with calculated E a values of less than 33 kcal mol –1 . To construct a good model equation for the experimental yields of the Curtius reaction, we have to use data sets obtained from within 90 min of the reaction for the PLS regression. Copyright © 2011 John Wiley & Sons, Ltd. We tried to predict the yields observed for the Curtius rearrangement using the Ea ( calc ) values from DFT calculations, together with the reaction conditions. In order to construct a good model equation for the experimental yields of the Curtius reaction, we have to use those obtained from the reaction within 90 min for the PLS regression.

Description: Characteristics of photoelectron flows and presence of a field-aligned potential drop on the open magnetic field lines in the polar cap are systematically investigated using the data obtained by the FAST satellite during geomagnetically quiet periods in July 2002. We found high occurrence frequencies of the potential drop larger than ∼10 V, reaching ∼90% (small field-aligned current (FAC) case) and ∼83% (all data). A typical magnitude of the potential drop above ∼3800 km altitude is ∼20 V. This value is significantly larger than the potential drop below ∼3800 km altitude (probably ∼1–3 V), although the typical potential drop is smaller by a factor of ∼2–3 in comparison to the modeling results that suggested presence of a field-aligned potential jump at several earth radii. The net escaping electron number flux negatively correlates with the upward electron number flux and with the magnitude of the potential drop. This relation is contrary to expectation from photoelectron-driven polar wind models that an increase in the photoelectrons drives the larger polar wind flux, since the net escaping electron number flux balances the flux of polar wind ions under zero net FAC conditions. An increase in the upward backscatter of reflected electrons with an increasing potential drop may explain the negative correlations. A potential drop at high altitudes would provide a polar wind system regulated by a negative feedback, and the most appropriate balance for polar wind ions would be achieved near the median of the reflection potential.

Description: It is well known that the aryl hydrocarbon receptor (AhR) is involved in the toxicity of halogenated aromatic hydrocarbons (HAH) and polycyclic aromatic hydrocarbons (PAH). Recent experiments have shown the induction of impaired tooth and hard-tissue formation by AhR pathway activation, however, the effect on periodontal ligament (PDL) tissue remains unclear. Here, we investigated the effects of benzo(a)pyrene (BaP), a member of PAH, on the extracellular matrix (ECM) remodeling-related molecules, collagen type I (COL-I), matrix metalloproteinase-1 (MMP-1), alpha-smooth muscle actin (α-SMA) expression and apoptosis in two different human periodontal ligament cells (HPDLCs). The transduction of AhR from the cytoplasm to the nucleus and the increase of AhR-responsive genes; i.e., cytochrome P450 1A1 ( CYP1A1 ), cytochrome P450 1B1 ( CYP1B1 ), and aryl-hydrocarbon receptor repressor ( AhRR ), expression was induced by BaP exposure in both HPDLCs. BaP treatment significantly enhanced MMP-1 mRNA expression and MMP-1 protein production, while markedly suppressing COL-I and a-SMA mRNA expression in both HPDLCs. Furthermore, these BaP-treated HPDLCs fell into apoptotic cell death as evidenced by induction in annexin V and caspase-3/7 staining and reduction of total cell number and Bcl-2 mRNA expression. Thus, BaP exposure altered the expression of ECM-related molecules and induced apoptosis in HPDLCs through activation of the AhR pathway. Overactivity of the AhR pathway may induce an inappropriate turnover of PDL tissue via disordered ECM remodeling and apoptosis in PDL cells. J. Cell. Biochem. © 2012 Wiley Periodicals, Inc.

Description: In this study, the tautomeric equilibrium between the keto and enol forms has been studied for five typical ketones and aldehydes: i-butanal, acetaldehyde, acetone, acetylacetone, and dimedone. The level of theory used in the gas-phase calculation was Becke, three-parameter, Lee–Yang–Parr/6-311G(d,p)//Becke, three-parameter, Lee–Yang–Parr/6-31G(d). The free energies of solvation were included in the calculation by using the free-energy perturbation method based on Monte Carlo simulation, that is, the quantum mechanical/Monte Carlo/free-energy perturbation method. Three different models, incorporating no-water, one-water, and two-waters, were adopted. The results showed that in the gas phase the addition of water molecules to the reaction mechanism caused the activation barriers (Δ G ‡ gas ) to decrease by half relative to the water-free mechanism, but there was no effect on the relative difference in free energy, Δ G gas . The solvation effects (Δ G sol ), based on quantum mechanical/Monte Carlo/free-energy perturbation calculations, were added to those of the gas-phase results of the one-water and two-waters models. The two-waters model produced values that were very consistent with the experimental data for all of the tautomers. The differences in the relative Gibbs free energy (Δ G rxn ) were less than 1.0 kcal mol –1 . In summary, the inclusion of solvent molecules in gas-phase calculations plays a very important role in producing results consistent with experimental data. Copyright © 2012 John Wiley & Sons, Ltd. The tautomeric equilibrium between the keto and enol forms has been studied for five typical ketones and aldehydes. The free energies of solvation were included in the calculation by using quantum mechanical/Monte Carlo/free-energy perturbation method. The two-water model using quantum mechanical/Monte Carlo/free-energy perturbation method produced values that were very consistent with the experimental data for all of the tautomers.

Description: We have elucidated depth variations in the stress field associated with the 2007 Noto Hanto, Japan, earthquake by stress tensor inversion using high-quality aftershock data obtained by a dense seismic network. Aftershocks that occurred above 4 km in depth indicated a strike-slip stress regime. By contrast, aftershocks in deeper parts indicated a thrust faulting stress regime. This depth variation in the stress regime correlates well with that in the slip direction derived from a finite source model using geodetic data. Furthermore, the maximum principal stress (σ1) axis was stably oriented approximately W20°N down to the depth of the mainshock hypocenter, largely in agreement with the regional stress field, but, below that depth, the σ1 axis had no definite orientation, indicating horizontally isotropic stress. One likely cause of these drastic changes in the stress regime with depth is the buoyant force of a fluid reservoir localized beneath the seismogenic zone.