Simultaneously optimizing the interdependent thermoelectric parameters in Ce(Ni1−x_{1-x}Cux_x)2_2Al3_3

Substitution of Cu for Ni in the Kondo lattice system CeNi$_2$Al$_3$ results in a simultaneous optimization of the three interdependent thermoelectric parameters: thermoelectric power, electrical and thermal conductivities, where the electronic change in conduction band induced by the extra electron of Cu is shown to be crucial. The obtained thermoelectric figure of merit $zT$ amounts to 0.125 at around 100 K, comparable to the best values known for Kondo compounds. The realization of ideal thermoelectric optimization in Ce(Ni$_{1-x}$Cu$_x$)$_2$Al$_3$ indicates that proper electronic tuning of Kondo compounds is a promising approach to efficient thermoelectric materials for cryogenic application.Comment: 4 pages, 4 figures. Accepted for publication in Physical Review

Role of f0(980)f_0(980) and a0(980)a_0(980) in the B−→π−K+K−B^- \to \pi ^- K^+ K^- and B−→π−K0Kˉ0B^- \to \pi ^- K^0 \bar K^0 reactions

In this work we study the role of the $f_0(980)$ and $a_0(980)$ resonances in the low $K ^{+} K^{-}$ and $K^0 \bar K^0$ invariant-mass region of the $B^- \to \pi ^- K^+ K^-$ and $B^- \to \pi ^- K^0 \bar K^0$ reactions. The amplitudes are calculated by using the chiral unitary $\rm SU(3)$ formalism, in which these two resonances are dynamically generated from the unitary pseudocalar-pseudoscalar coupled-channel approach. The amplitudes are then used as input in the evaluation of the mass distributions with respect to the $K^{+}K^{-}$ and $K^{0}\bar K^{0}$ invariant-masses, where the contributions coming from the $I=0$ and $I=1$ components are explicitly assessed. Furthermore, the contribution of the $K^{\ast }(892)^0 K^-$ production and its influence on the $\pi^{-} K^+$ and $K^{+} K^-$ systems are also evaluated, showing that there is no significant strength for small $K^{+} K^-$ invariant mass. Lastly, the final distributions of $M_{\rm inv}^2( K^{\pm}K^{\mp} )$ for the $B^{\mp} \to \pi ^{\mp} K^{\pm}K^{\mp}$ reactions are estimated and compared with the LHCb data. Our results indicate that the $I=0$ component tied to the $f_0(980)$ excitation generates the dominant contribution in the range of low $K ^{+} K^{-}$ invariant-mass.Comment: 11 pages, 10 figure

Manipulating transgenes using a chromosome vector

Recent technological advances have enabled us to visualize the organization and dynamics of local chromatin structures; however, the comprehensive mechanisms by which chromatin organization modulates gene regulation are poorly understood. We designed a human artificial chromosome vector that allowed manipulation of transgenes using a method for delivering chromatin architectures into different cell lines from human to fish. This methodology enabled analysis of de novo construction, epigenetic maintenance and changes in the chromatin architecture of specific genes. Expressive and repressive architectures of human STAT3 were established from naked DNA in mouse embryonic stem cells and CHO cells, respectively. Delivery of STAT3 within repressive architecture to embryonic stem cells resulted in STAT3 activation, accompanied by changes in DNA methylation. This technology for manipulating a single gene with a specific chromatin architecture could be utilized in applied biology, including stem cell science and regeneration medicine

Multiplet ligand-field theory using Wannier orbitals

We demonstrate how ab initio cluster calculations including the full Coulomb vertex can be done in the basis of the localized, generalized Wannier orbitals which describe the low-energy density functional (LDA) band structure of the infinite crystal, e.g. the transition metal 3d and oxygen 2p orbitals. The spatial extend of our 3d Wannier orbitals (orthonormalized Nth order muffin-tin orbitals) is close to that found for atomic Hartree-Fock orbitals. We define Ligand orbitals as those linear combinations of the O 2p Wannier orbitals which couple to the 3d orbitals for the chosen cluster. The use of ligand orbitals allows for a minimal Hilbert space in multiplet ligand-field theory calculations, thus reducing the computational costs substantially. The result is a fast and simple ab initio theory, which can provide useful information about local properties of correlated insulators. We compare results for NiO, MnO and SrTiO3 with x-ray absorption, inelastic x-ray scattering, and photoemission experiments. The multiplet ligand field theory parameters found by our ab initio method agree within ~10% to known experimental values