The effect of iron spin transition on electrical conductivity of (Mg,Fe)O magnesiowüstite

We measured the electrical conductivity of Mg_0.81Fe_0.19O magnesiowüstite, one of the important minerals comprising Earth’s lower mantle, at high pressures up to 135 GPa and 300 K in a diamond-anvil cell (DAC). The results demonstrate that the electrical conductivity increases with increasing pressure to about 60 GPa and exhibits anomalous behavior at higher pressures; it conversely decreases to around 80 GPa and again increases very mildly with pressure. These observed changes may be explained by the high-spin to low-spin transition of iron in magnesiowüstite that was previously reported to occur in a similar pressure range. A very small pressure effect on the electrical conductivity above 80 GPa suggests that a dominant conduction mechanism changes by this electronic spin transition. The electrical conductivity below 2000-km depth in the mantle may be much smaller than previously thought, since the spin transition takes place also in (Mg,Fe)SiO₃ perovskite.     

Microscopically controlled oxidation of H/Si(1 0 0) by lateral surface electric field studied by emission electron microscopies

The ultrathin oxidation of a H/Si(1 0 0) surface with microfabricated pn-junctions was studied by photoemission electron microscopy (PEEM), mirror electron microscopy (MEM) and microscopic X-ray photoelectron spectroscopy (μ-XPS). The ultrathin oxidation inverts the contrast of the junctions in PEEM images. It is found by analyzing the intensity profiles of images that the potential distribution across the pn-junctions is also inverted by the oxidation. The charging of the oxide by ultraviolet irradiation from a light source of PEEM is attributed as the cause of the inversion of the contrast shown by μ-XPS and MEM.     

Non-decoupling effects in supersymmetric Higgs sectors

A wide class of Higgs sectors is investigated in supersymmetric standard models. When the lightest Higgs boson (h  ) looks the standard model one, the mass (mh$m_h$) and the triple Higgs boson coupling (the hhh   coupling) are evaluated at the one-loop level in each model. While mh$m_h$ is at most 120–130 GeV in the minimal supersymmetric standard model (MSSM), that in models with an additional neutral singlet or triplet fields can be much larger. The hhh coupling can also be sensitive to the models: while in the MSSM the deviation from the standard model prediction is not significant, that can be 30–60% in some models such as the MSSM with the additional singlet or with extra doublets and charged singlets. These models are motivated by specific physics problems like the μ-problem, the neutrino mass, the scalar dark matter and so on. Therefore, when h   is found at the CERN Large Hadron Collider, we can classify supersymmetric models by measuring mh$m_h$ and the hhh coupling accurately at future collider experiments.     

Electric conductance of metal nanowires at mechanically controllable break junctions under electrochemical potential control

We have developed the mechanically controllable break junction setup with an electrochemical cell (EC-MCBJ) to measure the electric conductance of metal nanowires under electrochemical potential control. The electric conductance of Au nanowires was investigated in 0.1 M Na₂SO₄ solution using EC-MCBJ. The conductance of the Au nanowires was quantized in units of G₀ (=2e²/h), showing clear features in the conductance histogram. The atomic contact with a specific conductance value was kept for >5 s, indicating the relatively high stability of the present EC-MCBJ system.     

Hardness and slip systems of orthorhombic hen egg-white lysozyme crystals

Hardness and slip systems by an indentation method were investigated on different habit planes of orthorhombic hen egg-white lysozyme (O-HEWL) crystals containing water. A dependence of the hardness on the water-evaporation time exhibits three stages as incubation, transition and saturated ones, as tetragonal (T)-HEWL crystals reported previously. The hardness values of (1 1 0), (0 1 0) and (0 1 1) habit planes of O-HEWL in the incubation stage or wet condition exhibits 6, 8 and 10 MPa, respectively. The hardness depends on indented planes but it is independent of the air-humidity and crystal volumes. These values correspond to the intrinsic hardness for O-HEWL crystals containing water. In the incubation stage, the slip traces are clearly observed around the indentation mark and the corresponding six kinds of slip systems are identified to be {0 1 1}<1 0 0>, {1 1 0}<1 1 0>, {0 1 1}<0 1 1>, {1 1 0}<0 0 1>, {1 0 0}<0 0 1> and {0 1 0}<0 0 1>.     

A new fluorescent probe for zinc(II): an 8-hydroxy-5-N,N-dimethylaminosulfonylquinoline-pendant 1,4,7,10-tetraazacyclododecane

A new fluorescent probe for Zn2+, namely, 8-hydroxy-5-N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L8), was designed and synthesized (cyclen=1,4,7,10-tetraazacyclododecane). By potentiometric pH, 1H NMR, and UV spectroscopic titrations, the deprotonation constants pKa1-pKa6 of L(8)4 HCl were determined to be <2, <2, <2 (for amino groups of the cyclen and quinoline moieties), 7.19+/-0.05 (for 8-OH of the quinoline moiety), 10.10+/-0.05, and 11.49+/-0.05, respectively, at 25 degrees C with I=0.1 (NaNO3). The results of 1H NMR, potentiometric pH, and UV titrations, as well as single-crystal X-ray diffraction analysis, showed that L8 and Zn2+ form a 1:1 complex [Zn(H-1L8)], in which the 8-OH group of the quinoline ring of L8 is deprotonated and coordinates to Zn2+, in aqueous solution at neutral pH. On addition of one equivalent of Zn2+ and Cd2+, the fluorescence emission of L8 (5 microM) at 512 nm in aqueous solution at pH 7.4 [10 mM HEPES with I=0.1 (NaNO3)] and 25 degrees C increased by factors of 17 and 43, respectively. We found that the cyclen moiety has the unique property of quenching the fluorescence emission of the quinolinol moiety when not complexed with metal cations, but enhancing emission when complexed with Zn2+ or Cd2+. In addition, the Zn2+-L8 complex [Zn(H-1L8)] is much more thermodynamically and kinetically stable (Kd{Zn(H-1L8)}=[Zn2+]free[L8]free/[Zn(H-1L8)]=8 fM at pH 7.4) than the Zn2+ complexes of our previous Zn2+ fluorophores ([Zn(H-1L2)] and [Zn(L3)]). Furthermore, formation of [Zn(H-1L8)] is much faster than those of [Zn(H-1L2)] and [Zn(L3)]. The staining of early-stage apoptotic cells with L8 is also described.     

Visualization of Heterogeneous Oxygen Storage Behavior in Platinum‐Supported Cerium‐Zirconium Oxide Three‐Way Catalyst Particles by Hard X‐ray Spectro‐Ptychography

The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce₂Zr₂O_x (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce₂Zr₂O_x particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts.     

Chemical trend of Ln-M exchange couplings in heterometallic complexes with Ln = Gd, Tb, Dy, Ho, Er and M = Cu, V

The 4f-3d exchange couplings were definitively and precisely determined in the dinuclear complexes (Ln-M) involving double μ-oxo-bridges, by means of combined high-frequency electron paramagnetic resonance and pulsed-field magnetization techniques, revealing a monotonic decrease of ferromagnetic J(Ln-Cu) in the order of the atomic number, (64)Gd to (68)Er.