Correlated Electronic Structures and the Phase Diagram of Hydrocarbon-based Superconductors

We have investigated correlated electronic structures and the phase diagram of electron-doped hydrocarbon molecular solids, based on the dynamical mean-field theory. We have found that the ground state of hydrocarbon-based superconductors such as electron-doped picene and coronene is a multi-band Fermi liquid, while that of non-superconducting electron-doped pentacene is a single-band Fermi liquid in the proximity of the metal-insulator transition. The size of the molecular orbital energy level splitting plays a key role in producing the superconductivity of electron-doped hydrocarbon solids. The multi-band nature of hydrocarbon solids would boost the superconductivity through the enhanced density of states at the Fermi level.X11910sciescopu

Weakening of the stratospheric polar vortex by Arctic sea-ice loss

Successive cold winters of severely low temperatures in recent years have had critical social and economic impacts on the mid-latitude continents in the Northern Hemisphere. Although these cold winters are thought to be partly driven by dramatic losses of Arctic sea-ice, the mechanism that links sea-ice loss to cold winters remains a subject of debate. Here, by conducting observational analyses and model experiments, we show how Arctic sea-ice loss and cold winters in extra-polar regions are dynamically connected through the polar stratosphere. We find that decreased sea-ice cover during early winter months (November-December), especially over the Barents-Kara seas, enhances the upward propagation of planetary-scale waves with wavenumbers of 1 and 2, subsequently weakening the stratospheric polar vortex in mid-winter (January-February). The weakened polar vortex preferentially induces a negative phase of Arctic Oscillation at the surface, resulting in low temperatures in mid-latitudes.open11167174Ysciescopu

Observation of a kink during the formation of the Kondo resonance band in a heavy-fermion system

We have shown that the kink behavior in the spectral function of a heavy fermion can appear during the formation of the Kondo resonance (KR) band and the hybridization gap. We have investigated the heavy fermion compound CeCoGe2, using a combined approach of the density functional theory and the dynamical mean field theory. Low temperature T spectral functions show dispersive KR states, similarly to the recent experimental observation. During the evolution from the non-f conduction band state at high T to the dispersive KR band state at low T, which have topologically different band shapes, we have found the existence of kinks in the non-f spectral function near the Fermi level E-F. The observation of kink is clearly in correspondence with the multiple temperature scales of the formation of the KR band.X1186sciescopu

Twinning-mediated formability in Mg alloys

Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability.112514Ysciescopu

Optimized ZT of Bi2Te3-GeTe compounds from first principles guided by homogeneous data

We predict the thermoelectric properties of layered [GeTe](m)[Bi2Te3](n) (GBT) compounds ( 1 <= m <= 8, 1 <= n <= 3), using first-principles-Boltzmann transport calculations of the homogeneous (Bi2Te3 and GeTe) data. The lattice strain and the quantum-confinement effects of compounds evolve the band-gap structures, resulting in asymmetric and large Seebeck coefficient, at high GeTe content. Using semiempirical calculations of electron scattering rate 1/tau(e), dominated by electron-acoustic phonon scattering, we reproduce reported TE properties of GBT compounds. We predict that, due to small Seebeck coefficient, the GBT compounds with high n- and p-type doping (similar to 10(20) cm(-3)), do not have high ZT near room temperature. However, we predict that the moderately doped (similar to 10(19) cm(-3)), p-type GBT compounds have enhanced ZT approximate to 1.4 near room temperature.1132Ysciescopu

Printing three-dimensional tissue analogues with decellularized extracellular matrix bioink

The ability to print and pattern all the components that make up a tissue (cells and matrix materials) in three dimensions to generate structures similar to tissues is an exciting prospect of bioprinting. However, the majority of the matrix materials used so far for bioprinting cannot represent the complexity of natural extracellular matrix (ECM) and thus are unable to reconstitute the intrinsic cellular morphologies and functions. Here, we develop a method for the bioprinting of cell-laden constructs with novel decellularized extracellular matrix (dECM) bioink capable of providing an optimized microenvironment conducive to the growth of three-dimensional structured tissue. We show the versatility and flexibility of the developed bioprinting process using tissue-specific dECM bioinks, including adipose, cartilage and heart tissues, capable of providing crucial cues for cells engraftment, survival and long-term function. We achieve high cell viability and functionality of the printed dECM structures using our bioprinting method.open11349353sciescopu

Electronic structures and magnetic properties of RB4 (R=Yb,Pr,Gd,Tb,Dy)

Most rare-earth tetraborides RB4 have antiferromagnetic ground states except for YbB4 and PrB4. We have investigated the electronic structures and magnetic properties of RB4 (R=Yb, Pr, Gd, Tb, Dy) employing the first-principles total energy band method. It is found that YbB4 has the paramagnetic ground state, while the other tetraborides are in the magnetic ground state, which is in agreement with experiments. We have obtained the spin and orbital magnetic moments and discussed the importance of the spin-orbit interaction and the on-site Coulomb repulsion (U) in these systems. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3058707]ope

3D-Printed Drug/Cell Carrier Enabling Effective Release of Cyclosporin A for Xenogeneic Cell-Based Therapy

Systemic administration of the immunosuppressive drug cyclosporin A (CsA) is frequently associated with a number of side effects; therefore, sometimes it cannot be applied in sufficient dosage after allogeneic or xenogeneic cell transplantation. Local delivery is a possible solution to this problem. We used 3D printing to develop a CsA-loaded 3D drug carrier for the purpose of local and sustained delivery of CsA. The carrier is a hybrid of CsA-poly(lactic-co-glycolic acid) (PLGA) microsphere-loaded hydrogel and a polymeric framework so that external force can be endured under physiological conditions. The expression of cytokines, which are secreted by spleen cells activated by Con A, and which are related to immune rejection, was significantly decreased in vitro by the released CsA from the drug carrier. Drug carriers seeded with xenogeneic cells (human lung fibroblast) were subcutaneously implanted into the BALB/c mouse. As a result, T-cell-mediated rejection was also significantly suppressed for 4 weeks. These results show that the developed 3D drug carrier can be used as an effective xenogeneic cell delivery system with controllable immunosuppressive drugs for cell-based therapy.1176Ysciescopu

Quantitative analysis on electric dipole energy in Rashba band splitting

We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime.1131Ysciescopu

Low phonon conductivity of layered BiCuOS, BiCuOSe, and BiCuOTe from first principles

Combining the effect of layer mixing, mass mismatch, and intrinsic defects, we have investigated the origin of very low phonon conductivity k(p) in thermoelectric (TE) BiCuOQ (Q: S, Se, Te) compounds. Based on the first-principles anharmonic, lattice dynamics calculations, we use the single-mode relaxation time approximation of the linearized phonon Boltzmann equation, which shows good agreement with experiments. Here, we found that the most important parameter for low k(p) is the interlayer interaction between the BiO and CuQ layers. By analyzing the phonon linewidth distribution, which indicates the phonon scattering rate, we propose that the interlayer interactions play a critical role on suppressing k(p), i.e., the heterolayered crystal controls these interlayer interactions, achieving low k(p) and optimal TE properties.1133Ysciescopu