Complete Fermi surface in BaFe2As2 observed via Shubnikov-de Haas oscillation measurements on detwinned single crystals

We show that the Fermi surface (FS) in the antiferromagnetic phase of BaFe(2)As(2) is composed of one hole and two electron pockets, all of which are three dimensional and closed, in sharp contrast to the FS observed by angle-resolved photoemission spectroscopy. Considerations on the carrier compensation and Sommerfeld coefficient rule out existence of unobserved FS pockets of significant sizes. A standard band structure calculation reasonably accounts for the observed FS, despite the overestimated ordered moment. The mass enhancement, the ratio of the effective mass to the band mass, is 2-3.     

Real-time direct observations of polarization reversal in a piezoelectric crystal: Pb(Mg1/3Nb2/3)O3-PbTiO3 studied via in situ electrical biasing transmission electron microscopy

The ultrahigh piezoelectricity of lead magnesium niobate-lead titanate (PMN-PT) single crystals is utilized for medical imaging and ultrasonic devices. It has been revealed that the domain structure is miniaturized down to the nanometer scale, indicating that the domain structure and its response to electric fields could play more roles. In this Letter, we report real-time direct observations of polarization reversals in PMN-PT with the use of in situ electrical biasing transmission electron microscopy. We find that a dominant behavior is a reversible response composed of the reorientation of nanoscale non-180° domain walls (DWs) and movement and/or elimination of microscale DWs. These results basically agree with some predictions made by adaptive phase theory (Jin et al. [J. Appl. Phys. 94, 3629 (2003)]) which gives explanations of extrinsic contributions to the high piezoelectricity of this material.     

Tolerance of start-up control of rotation in parametric pendulum by delayed feedback

In this Letter, we propose a control method for establishing periodic rotation inherent in parametric pendulum based on a delayed feedback control. The experiments elucidate the existing range of periodic rotation in the domain of delay. The range of existence possibly represents the tolerance of proposed control with mistuned delay. It is confirmed that forced synchronization governs the existence and the width. The result assures that the frequency synchronization characteristics overcome the mistuned difference of delay in the control through entrainment.     

Tour time in a two-route traffic system controlled by signals

We study the dynamic behavior of vehicular traffic in a two-route system with a series of signals (traffic lights) at low density where the number of signals on route A is different from that on route B. We investigate the dependence of the tour time on the route for some strategies of signal control. The nonlinear dynamic model of a two-route traffic system controlled by signals is presented by nonlinear maps. The vehicular traffic exhibits a very complex behavior, depending on the cycle time, the phase difference, and the irregularity. The dependence of the tour time on the route choice is clarified for the signal strategies.     

Schedule and complex motion of shuttle bus induced by periodic inflow of passengers

We have studied the dynamic behavior of a bus in the shuttle bus transportation with a periodic inflow. A bus schedule is closely related to the dynamics. We present the modified circle map model for the dynamics of the shuttle bus. The motion of the shuttle bus depends on the loading parameter and the inflow period. The shuttle bus displays the periodic, quasi-periodic, and chaotic motions with varying both loading parameter and inflow rate.     

Crystal structure of stable protein CutA1 from psychrotrophic bacterium Shewanella sp. SIB1

CutA1 is widely found in bacteria, plants and animals, including humans. The functions of CutA1, however, have not been well clarified. It is known that CutA1s from Pyrococcus horikoshii, Thermus thermophilus and Oryza sativa unfold at temperatures remarkably higher than the growth temperatures of the host organisms. In this work the crystal structure of CutA1 from the psychrotrophic bacterium Shewanella sp. SIB1 (SIB1-CutA1) in a trimeric form was determined at 2.7?? resolution. This is the first crystal structure of a psychrotrophic CutA1. The overall structure of SIB1-CutA1 is similar to those of CutA1 from Homo sapiens, Escherichia coli, Pyrococcus horikoshii, Thermus thermophilus, Termotoga maritima, Oryza sativa and Rattus norvergicus. A peculiarity is observed in the β2 strand. The β2 strand is divided into two short β strands, β2a and β2b, in SIB1-CutA1. A thermal denaturation experiment revealed that SIB1-CutA1 does not unfold completely at 363?K at pH 7.0, although Shewanella sp. SIB1 cannot grow at temperatures exceeding 303?K. These results indicate that the trimeric structural motif of CutA1 is the critical factor in its unusually high stability and suggest that CutA1 needs to maintain its high stability in order to function, even in psychrotrophs.     

Structure-reactivity relationship of piperidine nitroxide: electrochemical, ESR and computational studies

We have synthesized several nitroxides with different substituents which vary the steric and electronic environment around the N-O moiety and have systematically investigated the role of substituents on the stability of the radicals. Our results demonstrated the reactivity toward ascorbate correlates with the redox potential of the derivatives. Furthermore, ab initio calculations also indicated a correlation between the reduction rate and the computed singly occupied molecular orbital-lowest unoccupied molecular orbital energy gap, but not with solvent accessible surface area of the N-O moiety, supporting the experimental results and suggesting that the electronic factors largely determine the radicals' stability. Hence, it is possible to perform virtual screening of nitroxides to optimize their stability, which can help to rationally design novel nitroxides for their potential use in vivo.     

Inhibition of restriction enzymes EcoRI, BamHI and HindIII by phenethylphenylphthalimides derived from thalidomide

We discovered inhibitors of the restriction enzymes EcoRI, BamHI and HindIII by screening our library of compounds with a phenethylphenylphthalimide skeleton, based on α-glucosidase inhibitors and liver X receptor antagonists derived from thalidomide. Structural development afforded the potent restriction enzyme inhibitors 25 and 26.     

Mechanistic study on the facilitation of enzymatic hydrolysis by α-glucosidase in the presence of betaine-type metabolite analogs

Recently we reported that betaine-type metabolite analogs structure-dependently facilitate enzymatic hydrolysis reaction for α-glucosidases, β-glucosidases, and alkaliphosphatases. To understand the facilitation mechanism for enzymes, in this study we expanded the analog library and measured the properties of analog solutions. The structural investigation on α-glucosidase-mediated hydrolysis reaction indicated that suitable structures to facilitate the enzyme reaction efficiently should have the ammonium cation in the betaine structure possess triplicate aliphatic chains from C1 to C7 without any polar functional groups. Analyses of the solution properties revealed that such analogs possess a large hydration layer with low water density. Such a specific hydration environment is generated by the characteristic structure of the betaine-type metabolite analogs. The characteristic hydration indirectly regulates enzyme activity and stability. These findings not only increase our understanding enzyme activation by betaine-type metabolite analogs, but also will contribute to the molecular design of enzyme regulators.     

Parametrization of \text{ PSL }(2,\mathbb C )-representations of surface groups

For an oriented surface of genus $g$ with $b$ boundary components, we construct a rational map from a subset of $\mathbb{C }^{6g-6+3b}$ onto an open algebraic subset of the $\text{ PSL }(2,\mathbb C )$ -character variety as an analogue of the Fenchel-Nielsen coordinates. After taking the quotient by an action of a finite group, we obtain a parametrization of a subset of the $\text{ PSL }(2,\mathbb C )$ -character variety, and similarly for the $\text{ SL }(2,\mathbb C )$ -character variety. We can systematically calculate a set of matrix generators by rational functions of the parameters. We give transformation formulae under elementary moves of pants decompositions.