Zero-temperature Phase Diagram of Two Dimensional Hubbard Model

We investigate the two-dimensional Hubbard model on the triangular lattice with anisotropic hopping integrals at half filling. By means of a self-energy functional approach, we discuss how stable the non-magnetic state is against magnetically ordered states in the system. We present the zero-temperature phase diagram, where the normal metallic state competes with magnetically ordered states with $(\pi, \pi)$ and $(2\pi/3, 2\pi/3)$ structures. It is shown that a non-magnetic Mott insulating state is not realized as the ground state, in the present framework, but as a meta-stable state near the magnetically ordered phase with $(2\pi/3, 2\pi/3)$ structure.Comment: 4 pages, 4 figure

Mott transitions in two-orbital Hubbard systems

We investigate the Mott transitions in two-orbital Hubbard systems. Applying the dynamical mean field theory and the self-energy functional approach, we discuss the stability of itinerant quasi-particle states in each band. It is shown that separate Mott transitions occur at different Coulomb interaction strengths in general. On the other hand, if some special conditions are satisfied for the interactions, spin and orbital fluctuations are equally enhanced at low temperatures, resulting in a single Mott transition. The phase diagrams are obtained at zero and finite temperatures. We also address the effect of the hybridization between two orbitals, which induces the Kondo-like heavy fermion states in the intermediate orbital-selective Mott phase.Comment: 21 Pages, 17 Figures, to appear in Progress of Theoretical Physics (YKIS2004 Proceedings

Finite-temperature Mott transitions in multi-orbital Hubbard model

We investigate the Mott transitions in the multi-orbital Hubbard model at half-filling by means of the self-energy functional approach. The phase diagrams are obtained at finite temperatures for the Hubbard model with up to four-fold degenerate bands. We discuss how the first-order Mott transition points $U_{c1}$ and $U_{c2}$ as well as the critical temperature $T_c$ depend on the orbital degeneracy. It is elucidated that enhanced orbital fluctuations play a key role to control the Mott transitions in the multi-orbital Hubbard model.Comment: 8 pages, 7 figure

Proteoglycan form of macrophage colony-stimulating factor binds low density lipoprotein

We recently isolated a proteoglycan form of macrophage colony-stimulating factor (PG-M-CSF) that carries a chondroitin sulfate glycosaminoglycan chain. Here, we examined the interaction of PG-M-CSF with low density lipoprotein (LDL). When LDL preincubated with PG-M-CSF was fractionated by molecular size sieving chromatography, it was eluted earlier than untreated LDL. When LDL was preincubated with chondroitin sulfate-free 85-kD M-CSF instead of PG-M-CSF, the elution profile of LDL remained unchanged, indicating specific interaction between PG-M-CSF and LDL. The level of PG-M-CSF binding in the wells of a plastic microtitration plate precoated with LDL was significant, this binding being completely abolished by pretreatment of PG-M-CSF with chondroitinase AC, which degrades chondroitin sulfate. The addition of exogenous chondroitin sulfate or apolipoprotein B inhibited the binding of PG-M-CSF to LDL in a dose-dependent manner, indicating that the interaction between PG-M-CSF and LDL was mediated by the binding of the chondroitin sulfate chain of PG-M-CSF to LDL apolipoprotein B. PG-M-CSF was also demonstrated in the arterial wall, and there were increased amounts of PG-M-CSF in atherosclerotic lesions. The in vitro interaction between PG-M-CSF and LDL thus appears to have physiological significance

Possible Ordered States in the 2D Extended Hubbard Model

Possible ordered states in the 2D extended Hubbard model with on-site (U>0) and nearest-neighbor (V) interaction are examined near half filling, with emphasis on the effect of finite V. First, the phase diagram at absolute zero is determined in the mean field approximation. For $V<0$, a state where d_{x^{2}-y^{2}}-wave superconductivity (dSC), commensurate spin-density-wave (SDW) and $\pi$-triplet pair coexist is seen to be stabilized. Here, the importance of $\pi$-triplet pair on the coexistence of dSC and SDW is indicated. This coexistent state is hampered by the phase separation (PS), which is generally expected to occur in the presence of finite-range attractive interaction, but survives. For V>0, a state where commensurate charge-density-wave (CDW), SDW and ferromagnetism (FM) coexist is seen to be stabilized. Here, the importance of FM on the coexistence of CDW and SDW is indicated. Next, in order to examine the effects of fluctuation on each mean field ordered state, the renormalization group method for the special case that the Fermi level lies just on the saddle points, ($\pi$,0) and (0,$\pi$), is applied. The crucial difference from the mean field result is that superconductivity can arise even for U>0 and $V\geq0$, where the superconducting gap symmetry is d_{x^{2}-y^{2}}-wave for U>4V and s-wave for U<4V. Finally, the possibilities that the mean field coexistent states survive in the presence of fluctuation are discussed.Comment: 12 pages, 19 figures included, revised versio

A study of the etapipi channel produced in central pp interactions at 450 GeV/c

The reaction pp -> pf (eta pi pi) ps has been studied at 450 GeV/c. There is clear evidence for an a2(1320)pi decay mode of the eta2(1645) and eta2(1870). In addition, there is evidence for an a0(980)pi$ decay mode of both resonances and an f2(1270)eta decay mode of the eta2(1870). No evidence is found for a JPC = 2++ a2(1320)pi wave.Comment: 15 pages, Latex, 4 Figures Branching ratio a2pi /f2 eta correcte

Acid secretion by the boring organ of the burrowing giant clam, Tridacna crocea

The giant clam Tridacna crocea, native to Indo-Pacific coral reefs, is noted for its unique ability to bore fully into coral rock and is a major agent of reef bioerosion. However, T. crocea\u27s mechanism of boring has remained a mystery despite decades of research. By exploiting a new, two-dimensional pH-sensing technology and manipulating clams to press their presumptive boring tissue (the pedal mantle) against pH-sensing foils, we show that this tissue lowers the pH of surfaces it contacts by greater than or equal to 2 pH units below seawater pH day and night. Acid secretion is likely mediated by vacuolar-type H+-ATPase, which we demonstrate (by immunofluorescence) is abundant in the pedal mantle outer epithelium. Our discovery of acid secretion solves this decades-old mystery and reveals that, during bioerosion, T. crocea can liberate reef constituents directly to the soluble phase, rather than producing sediment alone as earlier assumed