Charge ordering and phase separation in the infinite dimensional extended Hubbard model

We study the extended Hubbard model with both on-site (U) and nearest neighbor (V) Coulomb repulsion using the exact diagonalization method within the dynamical mean field theory. For a fixed U (U=2.0), the T-n phase-diagrams are obtained for V=1.4 and V=1.2, at which the ground states of n=1/2 system is charge-ordered and charge-disordered, respectively. In both cases, robust charge order is found at finite temperature and in an extended filling regime around n=1/2. The order parameter changes non-monotonously with temperature. For V=1.4, phase separation between charge-ordered and charge-disordered phases is observed in the low temperature and n < 0.5 regime. It is described by an "S"-shaped structure of the n-/mu curve. For V=1.2, the ground state is charge-disordered, and a reentrant charge-ordering transition is observed for 0.42 < n < 0.68. Relevance of our results to experiments for doped manganites is discussed.Comment: 9 pages, 7 figures, submitted to Phys. Rev.

Mott-Hubbard transition in infinite dimensions

We analyze the unanalytical structure of metal-insulator transition (MIT) in infinite dimensions. By introducing a simple transformation into the dynamical mean-field equation of Hubbard model, a multiple-valued structure in Green's function and other thermodynamical quantities with respect to the interaction strength $U$ are found at low temperatures. A unified description of stable, metastable and unstable phases is obtained in the regime $U_{c1}(T)<U<U_{c2}(T)$, and the Maxwell construction is performed to evaluate the MIT line $U^{\ast}(T)$. We show how the first-order MIT at $U^{\ast}(T)$ for $T>0$ evolves into second-order one at $U_{c2}(0)$ for $T=0$. The phase diagram near MIT is presented.Comment: 5 pages with 3 figures, text and figures revise

Faddeev fixed-center approximation to the ηK∗Kˉ∗\eta K^*\bar{K}^*, πK∗Kˉ∗\pi K^*\bar{K}^* and KK∗Kˉ∗KK^*\bar{K}^* systems

The three-body $\eta K^*\bar{K}^*$, $\pi K^*\bar{K}^*$ and $KK^*\bar{K}^*$ systems are investigated within the framework of fixed-center approximation to the Faddeev equations, where $K^*\bar{K}^*$ is treated as the scalar meson $f_0(1710)$. The interactions between $\pi$, $\eta$, $K$ and $K^*$ are taking from the chiral unitary approach. By scattering the $\eta$ meson on the clusterized $(K^*\bar{K}^*)_{f_0(1710)}$ system, we find a peak in the modulus squared of the three-body scattering amplitude and it can be associated as a bound state with quantum numbers $I^G(J^{PC})=0^+(0^{-+})$. Its mass and width are around 2054 MeV and 60 MeV, respectively. This state could be associated to the $\eta(2100)$ meson. For the $\pi (K^*\bar{K}^*)_{f_0(1710)}$ scattering, we find a bump structure around 1900-2000 MeV with quantum numbers $1^-({0^{-+}})$. While for the $K K^* \bar{K}^*)_{f_0(1710)}$ system, there are three structures. One of them is much stable and its mass is about 2130 MeV. It is expected that these theoretical predictions here could be tested by future experimental measurements, such as by the BESIII, BelleII and LHCb collaborations.Comment: 10 pages, 15 figure

Theoretical study on Λc+→ΛK+Kˉ0\Lambda_c^+ \to \Lambda K^+\bar{K}^0 decay and Ξ∗(1690)\Xi^*(1690) resonance

We present a theoretical study of $\Xi^*(1690)$ resonance in the $\Lambda_c^+ \to \Lambda K^+ \bar{K}^0$ decay, where the weak interaction part proceeds through the Cabibbo-favored process $c \to s + u\bar{d}$. Next, the intermediate two mesons and one baryon state can be constructed with a pair of $q\bar{q}$ with the vacuum quantum numbers. Finally, the $\Xi^*(1690)$ is mainly produced from the final state interactions of $\bar{K}\Lambda$ in coupled channels, and it is shown in the $\bar{K}\Lambda$ invariant mass distribution. Besides, the scalar meson $a_0(980)$ and nucleon excited state $N^*(1535)$ are also taken into account in the decaying channels $K^+\bar{K}^0$ and $K^+\Lambda$, respectively. Within model parameters, the $K^+ \bar{K}^0$, $\bar{K}^0 \Lambda$ and $K^+ \Lambda$ invariant mass distributions are calculated, and it is found that our theoretical results can reproduce well the experimental measurements, especially for the clear peak around $1690$ MeV in the $\bar{K}\Lambda$ spectrum. The proposed weak decay process $\Lambda_c^+ \to \Lambda K^+ \bar{K}^0$ and the interaction mechanism can provide valuable information on the nature of the $\Xi^*(1690)$ resonance.Comment: 9 pages, 5 figure

Transforming growth factor-&#946; in graft vessels: histology and immunohistochemistry

OBJECTIVES: The biological functions of transforming growth factor-&#946; signaling that involves Smad proteins have not been previously investigated with respect to coronary artery bypass grafts. The aim of the present study was to observe the immunostaining of proteins that are related to this signaling pathway. METHODS: Fifteen remnants of coronary artery bypass grafts, including nine saphenous veins, three radial arteries and three mammary arteries, were collected from 12 patients who were undergoing coronary artery bypass. Hematoxylin and eosin, Masson's trichrome, and immunohistochemical staining of transforming growth factor-&#946;1, type I receptor of transforming growth factor-&#946;, Smad2/3, Smad4, and Smad7 were performed. RESULTS: The saphenous veins showed more severe intimal degeneration, more severe smooth muscle cell proliferation and more collagen deposition than the arterial grafts, as evidenced by hematoxylin and eosin and Masson's trichrome stainings. Immunohistochemical assays demonstrated that the majority of the transforming growth factor-&#946;1 signaling cytokines were primarily localized in the cytoplasm in the medial layers of all three types of grafts, whereas ectopic transforming growth factor-&#946;1, type I receptor of transforming growth factor-&#946;, and Smad7 overexpressions in the interstices were observed particularly in the saphenous vein and radial arterial grafts. CONCLUSION: Enhanced transforming growth factor-&#946;1 signal transduction with medial smooth muscle cell proliferation and ectopic transforming growth factor-&#946;1, the presence of the type I receptor of transforming growth factor-&#946;, and Smad7 overexpressions in the extracellular matrix may provide primary evidence for early or late graft failure

Transforming growth factor-β in graft vessels: histology and immunohistochemistry

OBJECTIVES: The biological functions of transforming growth factor-&#946; signaling that involves Smad proteins have not been previously investigated with respect to coronary artery bypass grafts. The aim of the present study was to observe the immunostaining of proteins that are related to this signaling pathway. METHODS: Fifteen remnants of coronary artery bypass grafts, including nine saphenous veins, three radial arteries and three mammary arteries, were collected from 12 patients who were undergoing coronary artery bypass. Hematoxylin and eosin, Masson's trichrome, and immunohistochemical staining of transforming growth factor-&#946;1, type I receptor of transforming growth factor-&#946;, Smad2/3, Smad4, and Smad7 were performed. RESULTS: The saphenous veins showed more severe intimal degeneration, more severe smooth muscle cell proliferation and more collagen deposition than the arterial grafts, as evidenced by hematoxylin and eosin and Masson's trichrome stainings. Immunohistochemical assays demonstrated that the majority of the transforming growth factor-&#946;1 signaling cytokines were primarily localized in the cytoplasm in the medial layers of all three types of grafts, whereas ectopic transforming growth factor-&#946;1, type I receptor of transforming growth factor-&#946;, and Smad7 overexpressions in the interstices were observed particularly in the saphenous vein and radial arterial grafts. CONCLUSION: Enhanced transforming growth factor-&#946;1 signal transduction with medial smooth muscle cell proliferation and ectopic transforming growth factor-&#946;1, the presence of the type I receptor of transforming growth factor-&#946;, and Smad7 overexpressions in the extracellular matrix may provide primary evidence for early or late graft failure

Design and implementation of wire tension measurement system for MWPCs used in the STAR iTPC upgrade

The STAR experiment at RHIC is planning to upgrade the Time Projection Chamber which lies at the heart of the detector. We have designed an instrument to measure the tension of the wires in the multi-wire proportional chambers (MWPCs) which will be used in the TPC upgrade. The wire tension measurement system causes the wires to vibrate and then it measures the fundamental frequency of the oscillation via a laser based optical platform. The platform can scan the entire wire plane, automatically, in a single run and obtain the wire tension on each wire with high precision. In this paper, the details about the measurement method and the system setup will be described. In addition, the test results for a prototype MWPC to be used in the STAR-iTPC upgrade will be presented.Comment: 6 pages, 10 figues, to appear in NIM

Synthesis of A Spacer-Armed Disulfated Tetrasaccharide of SB1a, A Carbohydrate Hapten Associated with Human Hepatocellular Carcinoma

A disulfated tetrasaccharide fragment with a spacer arm of human hepatocellular carcinoma carbohydrate antigen SB1a, namely, 2-aminoethyl 3-O-sulfo-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-β-d-galactopyranosyl-(1→4)-3-O-sulfo-β-d-galactopyranosyl-(1→4)-β-d-glucopyranoside was synthesized via a [2+1+1] block building mode. In the last coupling step toward the trisaccharide acceptor 8, benzoyl protected galactosyl bromide donor 14 was found to be much more reactive than the acetyl-protected donors. A disulfated tetrasaccharide fragment with a spacer arm of human hepatocellular carcinoma carbohydrate antigen SB1a was synthesized via a [2+1+1] block building mode