Double Exchange model for nanoscopic clusters

We solve the double exchange model on nanoscopic clusters exactly, and specifically consider a six-site benzene-like nanocluster. This simple model is an ideal testbed for studying magnetism in nanoclusters and for validating approximations such as the dynamical mean field theory (DMFT). Non-local correlations arise between neighboring localized spins due to the Hund's rule coupling, favoring a short-range magnetic order of ferro- or antiferromagnetic type. For a geometry with more neighboring sites or a sufficiently strong hybridization between leads and the nanocluster, these non-local correlations are less relevant, and DMFT can be applied reliably.Comment: 9 pages, 9 figures, 1 tabl

Estimation of the methane emission factor for the Italian Mediterranean buffalo

In order to contribute to the improvement of the national greenhouse gas emission inventory, this work aimed at estimating a country-specific enteric methane (CH4) emission factor for the Italian Mediterranean buffalo. For this purpose, national agriculture statistics, and information on animal production and farming conditions were analysed, and the emission factor was estimated using the Tier 2 model of the Intergovernmental Panel on Climate Change. Country-specific CH4 emission factors for buffalo cows (630 kg body weight, BW) and other buffalo (313 kg BW) categories were estimated for the period 1990–2004. In 2004, the estimated enteric CH4 emission factor for the buffalo cows was 73 kg/head per year, whereas that for other buffalo categories it was 56 kg/head per year. Research in order to determine specific CH4 conversion rates at the predominant production system is suggested

Physical interaction between MYCN oncogene and polycomb repressive complex 2 (PRC2) in neuroblastoma: Functional and therapeutic implications

This article is made available through the Brunel Open Access Publishing Fund. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.CLU (clusterin) is a tumor suppressor gene that we have previously shown to be negatively modulated by the MYCN proto-oncogene, but the mechanism of repression was unclear. Here, we show that MYCN inhibits the expression of CLU by direct interaction with the non-canonical E box sequence CACGCG in the 5′-flanking region. Binding of MYCN to the CLU gene induces bivalent epigenetic marks and recruitment of repressive proteins such as histone deacetylases and Polycomb members. MYCN physically binds in vitro and in vivo to EZH2, a component of the Polycomb repressive complex 2, required to repress CLU. Notably, EZH2 interacts with the Myc box domain 3, a segment of MYC known to be essential for its transforming effects. The expression of CLU can be restored in MYCN-amplified cells by epigenetic drugs with therapeutic results. Importantly, the anticancer effects of the drugs are ablated if CLU expression is blunted by RNA interference. Our study implies that MYC tumorigenesis can be effectively antagonized by epigenetic drugs that interfere with the recruitment of chromatin modifiers at repressive E boxes of tumor suppressor genes such as CLU.SPARKS, The Neuroblastoma Society, a Wellcome Trust grant (to A. S.), and the Italian Association for Cancer Research

Shear viscosity of neutron matter from realistic nucleon-nucleon interactions

The calculation of transport properties of Fermi liquids, based on the formalism developed by Abrikosov and Khalatnikov, requires the knowledge of the probability of collisions between quasiparticles in the vicinity of the Fermi surface. We have carried out a numerical study of the shear viscosity of pure neutron matter, whose value plays a pivotal role in determining the stability of rotating neutron stars, in which these processes are described using a state-of-the-art nucleon-nucleon potential model. Within our approach medium modifications of the scattering cross section are consistently taken into account, through an effective interaction obtained from the matrix elements of the bare interaction between correlated states. Inclusion of medium effects lead to a large increase of the viscosity at densities larger than $\sim 0.1$ fm^{-3}.Comment: 4 pages, 4 figures. Corrected typo

Local Electronic Correlation at the Two-Particle Level

Electronic correlated systems are often well described by dynamical mean field theory (DMFT). While DMFT studies have mainly focused hitherto on one-particle properties, valuable information is also enclosed into local two-particle Green's functions and vertices. They represent the main ingredient to compute momentum-dependent response functions at the DMFT level and to treat non-local spatial correlations at all length scales by means of diagrammatic extensions of DMFT. The aim of this paper is to present a DMFT analysis of the local reducible and irreducible two-particle vertex functions for the Hubbard model in the context of an unified diagrammatic formalism. An interpretation of the observed frequency structures is also given in terms of perturbation theory, of the comparison with the atomic limit, and of the mapping onto the attractive Hubbard model.Comment: 29 pages, 26 Figures. Accepted for publication in Phys. Rev.

Chern-Simons Solitons, Chiral Model, and (affine) Toda Model on Noncommutative Space

We consider the Dunne-Jackiw-Pi-Trugenberger model of a U(N) Chern-Simons gauge theory coupled to a nonrelativistic complex adjoint matter on noncommutative space. Soliton configurations of this model are related the solutions of the chiral model on noncommutative plane. A generalized Uhlenbeck's uniton method for the chiral model on noncommutative space provides explicit Chern-Simons solitons. Fundamental solitons in the U(1) gauge theory are shaped as rings of charge `n' and spin `n' where the Chern-Simons level `n' should be an integer upon quantization. Toda and Liouville models are generalized to noncommutative plane and the solutions are provided by the uniton method. We also define affine Toda and sine-Gordon models on noncommutative plane. Finally the first order moduli space dynamics of Chern-Simons solitons is shown to be trivial.Comment: latex, JHEP style, 23 pages, no figur

Exercise intolerance at high altitude (5050 m): critical power and W'

The relationship between work rate (WR) and its tolerable duration (t(LIM)) has not been investigated at high altitude (HA). At HA (5050 m) and at sea level (SL), six subjects therefore performed symptom-limited cycle-ergometry: an incremental test (IET) and three constant-WR tests (% of IET WR(max), HA and SL respectively: WR(1) 70±8%, 74±7%; WR(2) 86±14%, 88±10%; WR(3) 105±13%, 104±9%). The power asymptote (CP) and curvature constant (W') of the hyperbolic WR-t(LIM) relationship were reduced at HA compared to SL (CP: 81±21 vs. 123±38 W; W': 7.2±2.9 vs. 13.1±4.3 kJ). HA breathing reserve (estimated maximum voluntary ventilation minus end-exercise ventilation) was also compromised (WR(1): 25±25 vs. 50±18 l min(-1); WR(2): 4±23 vs. 38±23 l min(-1); WR(3): -3±18 vs. 32±24 l min(-1)) with near-maximal dyspnea levels (Borg) (WR(1): 7.2±1.2 vs. 4.8±1.3; WR(2): 8.8±0.8 vs. 5.3±1.2; WR(3): 9.3±1.0 vs. 5.3±1.5). The CP reduction is consistent with a reduced O(2) availability; that of W' with reduced muscle-venous O(2) storage, exacerbated by ventilatory limitation and dyspnea. Copyright © 2011 Elsevier B.V. All rights reserved

Exercise respiratory cycle time components in patients with emphysema

Background: We have recently demonstrated that in patients with COPD the severity of emphysema (E) measured by high resolution computed tomography (HRCT) correlated with: ratio VTpeak/FEV1; VE/VCO2 slope and PETCO2 values at peak exercise. The aim of this study was to further investigate if exercise respiratory cycle time components correlated with % of E measured by HRCT. Method: Twelve patients (age = 65±8 yrs; FEV1 = 55±17%pred) with moderate to severe E (quantified by lung HRCT as % voxels < −910 HU) were evaluated with incremental cardiopulmonary exercise testing (CPET). Mean inspiratory time (TiM), mean total respiratory cycle time (TtotM), mean expiratory time during exercise (TeM) and mean expiratory time during the last third of exercise (TeM-end), has been calculated. Results: Both TeM and TeM-end had a good linear correlation with % of E (r = 0,61; p = 0,004 and r = 0,63; p = 0,003). Moreover, by dividing the patients in two groups based on the % of E (>50% and <50%), we observed that patients with higher % of E had longer TeM (TeM: 1,72±0,26sec vs 1,34±0,27sec, p = 0,005) and TeM-end. A good linear correlation has been observed also between TeM and PETCO2 and VE/VCO2 (r = 0,64; p = 0,002 and r = 0,7; p = 0,0005). TeM did not correlated with resting lung function values or inspiratory capacity (IC). Conclusion: The data confirm that distinct physiologic response pattern can be detected at CPET in these patients