554 research outputs found
Revising consensus in portal hypertension
Portal hypertension is associated with the most severe complications of cirrhosis, including ascites, hepatic encephalopathy, and bleeding from gastro-esophageal varices. Despite the progress achieved over the last decades, the 6-week mortality associated with variceal bleeding is still in the order of 10–20%. Awareness of the difficulty inherent to the evaluation of diagnostic tools and the design and conduct of good clinical trials for the treatment of portalhypertensionhas led to theorganization, since1986,of a series of consensus meetings. The first one was organized by Andrew Burroughs in Groningen, The Netherlands [1]. After Groningen, other meetings followed, in Baveno in 1990 (Baveno I) [2] and in 1995 (Baveno II) [3,4], in Milan in 1992 [5], in Reston, USA, in 1996 [6], in Stresa in 2000 (Baveno III) [7,8], again in Baveno in 2005 (Baveno IV) [9,10], and in Atlanta in 2007 [11]. The aims of these meetings were to develop definitions of key events in portal hypertension and variceal bleeding, to review the existing evidence on the natural history, the diagnosis and the therapeutic modalities of portal hypertension, and to issue evidence-based recommendations for the conduct of clinical trials and the management of patients. All these meetings were successful and produced consensus statements on some important points, although some issues remained unsettled. To continue the work of the previous meetings, a Baveno V workshop was held on May 21–22, 2010. The workshop was attended by many of the experts responsible for most of the major achievements of the last years in this field. Many of them had attended the previous meetings as well. The main fields of discussion of the Baveno V workshop were the same as in Baveno I–IV, i.e. the definitions of key events concerning the bleeding episode and the therapeutic options in patients with portal hypertension. For each of these topics, a series of consensus statements were discussed and agreed upon. As in Baveno IV, whenever applicable, the level of existing evidence was evaluated and the recommendations were ranked according to the Oxford System [12] (i.e.: level of evidence from 1 = highes
Quasi-Particle Spectra, Charge-Density-Wave, Superconductivity and Electron-Phonon Coupling in 2H-NbSe2
High-resolution photoemission has been used to study the electronic structure
of the charge density wave (CDW) and superconducting (SC) dichalcogenide, 2H-
NbSe2. From the extracted self-energies, important components of the
quasiparticle (QP) interactions have been identified. In contrast to previously
studied TaSe2, the CDW transition does not affect the electronic properties
significantly. The electron-phonon coupling is identified as a dominant
contribution to the QP self-energy and is shown to be very anisotropic
(k-dependent) and much stronger than in TaSe2.Comment: 4 pages, 3 figures, minor changes, to appear in PR
Quasiparticle Interference on the Surface of Topological Crystalline Insulator Pb(1-x)Sn(x)Se
Topological crystalline insulators represent a novel topological phase of
matter in which the surface states are protected by discrete point
group-symmetries of the underlying lattice. Rock-salt lead-tin-selenide alloy
is one possible realization of this phase which undergoes a topological phase
transition upon changing the lead content. We used scanning tunneling
microscopy (STM) and angle resolved photoemission spectroscopy (ARPES) to probe
the surface states on (001) PbSnSe in the topologically
non-trivial (x=0.23) and topologically trivial (x=0) phases. We observed
quasiparticle interference with STM on the surface of the topological
crystalline insulator and demonstrated that the measured interference can be
understood from ARPES studies and a simple band structure model. Furthermore,
our findings support the fact that PbSnSe and PbSe have
different topological nature.Comment: 5 pages, 4 figure
Hole-Like Fermi Surface in the Overdoped Non-Superconducting BiPbSrCuO
In high-temperature cuprate superconductors, the anti-ferromagnetic spin
fluctuations are thought to have a very important role in naturally producing
an attractive interaction between the electrons in the -wave channel. The
connection between superconductivity and spin fluctuations is expected to be
especially consequential at the overdoped end point of the superconducting
dome. In some materials, that point seems to coincide with a Lifshitz
transition, where the Fermi surface changes from the hole-like centered at
() to the electron-like, centered at the point causing a
loss of large momentum anti-ferromagnetic fluctuations. Here, we study the
doping dependence of the electronic structure of
BiPbSrCuO in angle-resolved photoemission and
find that the superconductivity vanishes at lower doping than at which the
Lifshitz transition occurs. This requires a more detailed re-examination of a
spin-fluctuation scenario.Comment: 6 pages, 3 Figures, 1 Tabl
Renormalization of spectral lineshape and dispersion below Tc in Bi2Sr2CaCu2O8+d
Angle-resolved photoemission (ARPES) data in the superconducting state of
Bi2Sr2CaCu2O8+d show a kink in the dispersion along the zone diagonal, which is
related via a Kramers-Kronig analysis to a drop in the low-energy scattering
rate. As one moves towards (pi,0), this kink evolves into a spectral dip. The
occurrence of these anomalies in the dispersion and lineshape throughout the
zone indicate the presence of a new energy scale in the superconducting state.Comment: New Figure 3 with expanded discussio
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