Model Construction and a Possibility of Cupratelike Pairing in a New d

Effective models are constructed for a newly discovered superconductor (Nd,Sr)NiO_{2}, which has been considered as a possible nickelate analog of the cuprates. Estimation of the effective interaction, which turns out to require a multiorbital model that takes account of all the orbitals involved on the Fermi surface, shows that the effective interactions are significantly larger than in the cuprates. A fluctuation exchange study suggests occurrence of d_{x^{2}-y^{2}}-wave superconductivity, where the transition temperature should be lowered from the cuprates due to the larger interaction.

Higgs Mode in the d-Wave Superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+x} Driven by an Intense Terahertz Pulse.

We investigate the terahertz (THz)-pulse-driven nonlinear response in the d-wave cuprate superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+x} (Bi2212) using a THz pump near-infrared probe scheme in the time domain. We observe an oscillatory behavior of the optical reflectivity that follows the THz electric field squared and is markedly enhanced below T_{c}. The corresponding third-order nonlinear effect exhibits both A_{1g} and B_{1g} symmetry components, which are decomposed from polarization-resolved measurements. A comparison with a BCS calculation of the nonlinear susceptibility indicates that the A_{1g} component is associated with the Higgs mode of the d-wave order parameter.

Three-dimensional porous graphene networks expand graphene-based electronic device applications.

In recent years, there has been increasing demand for 3D porous graphene structures with excellent 2D characteristics and great potential. As one avenue, several approaches for fabricating 3D porous graphene network structures have been proposed to realize multi-functional graphene materials with 2D graphene structures. Herein, we overview characteristics of 3D porous graphene for applications in future electronic devices along with physical insights into "2D to 3D graphene", in which the characters of 2D graphene such as massless Dirac fermions are well preserved. The present review thus summarizes recent 3D porous graphene studies with a perspective for providing new and board applications of graphene in electronic devices.

Improvement in Oral Health-related Quality of Life by Periodontal Treatment: A Case Report on Elderly Patient with Chronic Periodontitis.

We report a case of an elderly patient with chronic periodontitis requiring periodontal surgery. An 86-year-old man presented to Tokyo Dental College Suidobashi Hospital with the chief complaint of tooth fracture in the anterior region and occlusal pain in the posterior region. Clinical examination revealed 47% of sites with a probing depth (PD) of ≥4 mm and 47% of sites with bleeding on probing. Radiographic examination revealed generalized moderate horizontal bone loss with localized vertical defects. A clinical diagnosis of moderate chronic periodontitis was made. The patient's oral health-related quality of life (QoL) was also assessed at the time of each periodontal assessment. Initial periodontal therapy was provided followed by periodontal surgery. Open flap debridement was performed at sites with a PD of ≥5 mm (teeth #15-17). Surgical crown lengthening with an apically positioned flap was performed on #11 and 13 to gain an adequate biological width for the subsequent crown restoration. After confirming the stability of the periodontal tissue, provisional restorations were replaced with final restorations. No further deterioration was observed in the periodontal condition during the subsequent 1-year period of supportive periodontal therapy. Oral health-related QoL was markedly improved by the periodontal therapy. This suggests that periodontal therapy plays an important role in improving and maintaining oral health-related QoL in elderly people.

Interaction-Driven Topological Insulator in Fermionic Cold Atoms on an Optical Lattice: A Design with a Density Functional Formalism.

We design an interaction-driven topological insulator for fermionic cold atoms in an optical lattice; that is, we pose the question of whether we can realize in a continuous space a spontaneous symmetry breaking induced by the interatom interaction into a topological Chern insulator. Such a state, sometimes called a "topological Mott insulator," has yet to be realized in solid-state systems, since this requires, in the tight-binding model, large off-site interactions on top of a small on-site interaction. Here, we overcome the difficulty by introducing a spin-dependent potential, where a spin-selective occupation of fermions in A and B sublattices makes the on-site interaction Pauli forbidden, while a sizeable intersite interaction is achieved by a shallow optical potential with a large overlap between neighboring Wannier orbitals. This puts the system away from the tight-binding model, so that we adopt density functional theory for cold atoms, here extended to accommodate noncollinear spin structures emerging in the topological regime, to quantitatively demonstrate the phase transition to the topological Mott insulator.

Supersolid phase accompanied by a quantum critical point in the intermediate coupling regime of the Holstein model.

We reveal that electron-phonon systems described by the Holstein model on a bipartite lattice exhibit, away from half filling, a supersolid (SS) phase characterized by coexisting charge order (CO) and superconductivity (SC), and an accompanying quantum critical point (QCP). The SS phase, demonstrated by the dynamical mean-field theory with a quantum Monte Carlo impurity solver, emerges in the intermediate-coupling regime, where the peak of the Tc dome is located and the metal-insulator crossover occurs. On the other hand, in the weak- and strong-coupling regimes the CO-SC boundary is of first order with no intervening SS phases. The QCP is associated with the continuous transition from SS to SC and characterized by a reentrant behavior of the SS around it. We further show that the SS-SC transition is hallmarked by diverging charge fluctuations and a kink (peak) in the superfluid density.

Synthesis and evaluation of curcumin derivatives toward an inhibitor of beta-site amyloid precursor protein cleaving enzyme 1.

To research a new non-peptidyl inhibitor of beta-site amyloid precursor protein cleaving enzyme 1, we focused on the curcumin framework, two phenolic groups combined with an sp2 carbon spacer for low-molecular and high lipophilicity. The structure-activity relationship study of curcumin derivatives is described. Our results indicate that phenolic hydroxy groups and an alkenyl spacer are important structural factors for the inhibition of beta-site amyloid precursor protein cleaving enzyme 1 and, furthermore, non-competitive inhibition of enzyme activity is anticipated from an inhibitory kinetics experiment and docking simulation.

Nematicity-enhanced superconductivity in systems with a non-Fermi liquid behavior.

We explore the interplay between nematicity (spontaneous breaking of the sixfold rotational symmetry), superconductivity, and non-Fermi liquid behavior in partially flat-band (PFB) models on the triangular lattice. A key result is that the nematicity (Pomeranchuk instability), which is driven by many-body effect and stronger in flat-band systems, enhances superconducting transition temperature in a systematic manner on theTcdome. There, a plausiblesx2+y2-dx2-y2-dxy-wave symmetry, in place of the conventionaldx2-y2-wave, governs the nematicity-enhanced pairing with a sharp rise in theTcdome on the filling axis. When the sixfold symmetry is spontaneously broken, the pairing interaction is shown to become stronger with more compact pairs in real space than when the symmetry is enforced. These are accompanied by a non-Fermi character of electrons in the PFBs with many-body interactions.

Accessing surface Brillouin zone and band structure of picene single crystals.

We have experimentally revealed the band structure and the surface Brillouin zone of insulating picene single crystals (SCs), the mother organic system for a recently discovered aromatic superconductor, with ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction with a laser for photoconduction. A hole effective mass of 2.24m(0) and the hole mobility µ(h)≥9.0 cm(2)/V s (298 K) were deduced in the Γ-Y direction. We have further shown that some picene SCs did not show charging during UPS even without the laser, which indicates that pristine UPS works for high-quality organic SCs.

Dynamical band flipping in fermionic lattice systems: an ac-field-driven change of the interaction from repulsive to attractive.

We show theoretically that the sudden application of an appropriate ac field to correlated lattice fermions flips the band structure and effectively switches the interaction from repulsive to attractive. The nonadiabatically driven system is characterized by a negative temperature with a population inversion. We numerically demonstrate the converted interaction in an ac-driven Hubbard model with the nonequilibrium dynamical mean-field theory solved by the continuous-time quantum Monte Carlo method. Based on this, we propose an efficient ramp-up protocol for ac fields that can suppress heating, which leads to an effectively attractive Hubbard model with a temperature below the superconducting transition temperature of the equilibrium system.

Metal-intercalated aromatic hydrocarbons: a new class of carbon-based superconductors.

New carbon-based superconductors are synthesized by intercalating metal atoms into the solid-phase hydrocarbons picene and coronene. The highest reported superconducting transition temperature, T(c), of a hydrocarbon superconductor is 18 K for K(3)picene. The physics and chemistry of the hydrocarbon superconductors are extensively described for A(x)picene (A: alkali and alkali earth-metal atoms) for x = 0-5. The theoretical picture of their electronic structure is also reviewed. Future prospects for hydrocarbon superconductors are discussed from the viewpoint of combining electronics with condensed-matter physics: modification of the physical properties of hydrocarbon solids is explored by building them into a field-effect transistor. The features of other carbon-based superconductors are compared to clarify the nature of hydrocarbon superconductors.

Comparison of expression patterns of shell matrix protein genes in the mantle tissues between high- and low-quality pearl-producing recipients of the pearl oyster, Pinctada fucata.

The production of a cultured pearl is the result of a complex interplay between the donor and recipient oysters. However, there is a paucity of information on the relationship between donor and recipient oyster gene expression patterns and pearl quality. Shell matrix proteins affect not only the formation of the shell, but also that of the pearls. We compared the gene expression patterns of five shell matrix proteins (msi60, nacrein, msi31, prismalin-14, and aspein) in the mantle edge (ME), which forms the prismatic layer, and the mantle center (MC), which forms the nacreous layer, between high- (HP) and low quality pearl- (LP) producing recipient oysters. After culturing for about two months, ME and MC tissues were collected from nine recipient oysters: four with HP, five with LP. In the ME, the average threshold cycle (ΔC(T)) for aspein was higher in HP than in LP (t-test, p = 0.03). Additionally, in the MC, the average ΔC(T) for msi60 was lower in HP than in LP (p = 0.06). This means the relative expression level of msi60 in the mantle of HP was higher than that of LP, and expression level of aspein in the mantle of HP was lower than that of LP. Pearl quality was closely related to the expression patterns of shell matrix protein genes of recipient oysters.

Two-orbital model explains the higher transition temperature of the single-layer Hg-cuprate superconductor compared to that of the La-cuprate superconductor.

In order to explore the reason why the single-layered cuprates, La(2-x)(Sr/Ba)(x)CuO4 (T(c)≃40 K) and HgBa2CuO(4+δ) (T(c)≃90 K) have such a significant difference in T(c), we study a two-orbital model that incorporates the d(z2) orbital on top of the d(x2-y2) orbital. It is found, with the fluctuation exchange approximation, that the d(z2) orbital contribution to the Fermi surface, which is stronger in the La system, works against d-wave superconductivity, thereby dominating over the effect of the Fermi surface shape. The result resolves the long-standing contradiction between the theoretical results on Hubbard-type models and the experimental material dependence of T(c) in the cuprates.

Divergent northern and southern populations and demographic history of the pearl oyster in the western Pacific revealed with genomic SNPs.

In the open ocean without terrain boundaries, marine invertebrates with pelagic larvae can migrate long distances using ocean currents, suggesting reduced genetic diversification. Contrary to this assumption, however, genetic differentiation is often observed in marine invertebrates. In the present study, we sought to explain how population structure is established in the western Pacific Ocean, where the strong Kuroshio Current maintains high levels of gene flow from south to north, presumably promoting genetic homogeneity. We determined the population structure of the pearl oyster, Pinctada fucata, in the Indo-Pacific Ocean using genome-wide genotyping data from multiple sampling localities. Cluster analysis showed that the western Pacific population is distinct from that of the Indian Ocean, and that it is divided into northern (Japanese mainland) and southern (Nansei Islands, China, and Cambodia) populations. Genetic differentiation of P. fucata can be explained by geographic barriers in the Indian Ocean and a local lagoon, and by environmental gradients of sea surface temperature (SST) and oxygen concentration in the western Pacific. A genome scan showed evidence of adaptive evolution in genomic loci, possibly associated with changes in environmental factors, including SST and oxygen concentration. Furthermore, Bayesian simulation demonstrated that the past population expansion and division are congruent with ocean warming after the last glacial period. It is highly likely that the environmental gradient forms a genetic barrier that diversifies P. fucata populations in the western Pacific. This hypothesis helps to explain genetic differentiation and possible speciation of marine invertebrates.

Quantum Hall plateau transition in graphene with spatially correlated random hopping.

We investigate how the criticality of the quantum Hall plateau transition in disordered graphene differs from those in the ordinary quantum Hall systems, based on the honeycomb lattice with ripples modeled as random hoppings. The criticality of the graphene-specific n = 0 Landau level is found to change dramatically to an anomalous, almost exact fixed point as soon as we make the random hopping spatially correlated over a few bond lengths. We attribute this to the preserved chiral symmetry and suppressed scattering between K and K' points in the Brillouin zone. The results suggest that a fixed point for random Dirac fermions with chiral symmetry can be realized in freestanding, clean graphene with ripples.

Risk of accidental invasion and expansion of allochthonous mice in Tokyo metropolitan coastal areas in Japan.

House mouse (Mus musculus) is one of the perilous animal vectors for imported zoonosis such as a lymphocytic choriomeningitis (LCMV) infectious disease, and probably unknown emerging and/or re-emerging infectious diseases as well. It is necessary to prevent such diseases by regular surveys for behavioral trends of these allochthonous mice. However, such a trial has never been attempted in Japan. From 1998 to 2002, we analyzed partial sequences of the D-loop region in mtDNA, which provides powerful diagnostic SNPs for subspecies identification in the Mus musculus species, from 301 individuals of mice collected in 23 international bays or airports in Japan. We found that invasion of many allochthonous mice, which were identified as European subspecies, Mus musculus domesticus, occurred in Tokyo metropolitan coastal area. Based on the evidence, we warn that extensive invasion of allochthonous mice has occurred recently and, therefore, the risk of emerging and/or re-emerging infectious diseases invasion might be high in Tokyo metropolitan area.

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis.

Mass mortality that is acompanied by reddish browning of the soft tissues has been occurring in cultured pearl oyster, Pinctada fucata martensii. The disease is called Akoya oyster disease (AOD). Although spreading pattern of the disease and transmission experiments suggest that the disease is infectious, the causative agent has not yet been identified. We used shotgun and 16S rRNA-based metagenomic analysis to identify genes that are present specifically in affected oysters. The genes found only in diseased oysters were mostly bacterial origin, suggesting that the causative agent was a bacterial pathogen. This hypothesis was supported by the inhibition of AOD development in naïve oysters injected with the hemolymph of diseased animals followed immediately with penicillin bath-administration. Further analyses of the hemolymph and mantle specifically and universally detected genes of bacteria that belong to phylum Spirochaetes in diseased pearl oysters but not in healthy oysters. By in situ hybridization or immunostaining, a Brachyspira-like bacterium was observed in the smears of hemolymph from affected oysters, but not from healthy oysters. Phylogenetic analysis using 16S rRNA sequences showed that the presumptive causative bacterium was outside of but most closely related to family Brachyspiraceae. We propose 'Candidatus Maribrachyspira akoyae' gen. nov, sp nov., for this bacterium.

Electric Properties of Dirac Fermions Captured into 3D Nanoporous Graphene Networks.

Nanoporous graphene- based electric-double-layer transistors (EDLTs) are successfully fabricated. Transport measurements of the EDLTs demonstrate that the ambipolar electronic states of massless Dirac fermions with a high carrier mobility are well preserved in 3D nanoporous graphene along with anomalous nonlinear Hall resistance and exceptional transistor on/off ratio. This study may open a new avenue for device applications of graphene.

Light-induced collective pseudospin precession resonating with Higgs mode in a superconductor.

Superconductors host collective modes that can be manipulated with light. We show that a strong terahertz light field can induce oscillations of the superconducting order parameter in NbN with twice the frequency of the terahertz field. The result can be captured as a collective precession of Anderson's pseudospins in ac driving fields. A resonance between the field and the Higgs amplitude mode of the superconductor then results in large terahertz third-harmonic generation. The method we present here paves a way toward nonlinear quantum optics in superconductors with driving the pseudospins collectively and can be potentially extended to exotic superconductors for shedding light on the character of order parameters and their coupling to other degrees of freedom.

Pearl microstructure and expression of shell matrix protein genes MSI31 and MSI60 in the pearl sac epithelium of Pinctada fucata by in situ hybridization.

Expression patterns of the shell matrix protein genes MSI31 and MSI60 in the pearl sac epithelium were examined by in situ hybridization 38 days after implantation, and related to pearl quality. A pearl sac that produced a nacreous pearl showed very weak expression of MSI31 and strong expression of MSI60. A pearl sac, which yielded a prismatic pearl, strongly expressed MSI31 and very weakly expressed MSI60. In a complex pearl, whose surface consisted of a mosaic of both nacreous and prismatic layers, the expression pattern of MSI31 and MSI60 similarly corresponded to the underlying surface structures of the pearl. A nacreous pearl whose pearl sac showed strong MSI31 expression had an entirely nacreous surface composed of a laminar structure with unusual tablet growth at the corresponding site. MSI31 and MSI60 are the major components of the shell matrix proteins of the nacreous and prismatic layers. Clearly, high expression of MSI31 does not always result in prismatic secretion. These observations cannot be explained solely on the basis of the expression patterns of MSI31 and MSI60. We propose that, in addition to the MSI genes that form the prismatic and nacreous layers, upstream from these genes there are regulatory master genes that determine whether a nacreous layer (aragonite) or a prismatic layer (calcite) is formed.