Relaxation time spectrum of low-energy excitations in one- and two-dimensional materials with charge or spin density waves

The long-time thermal relaxation of (TMTTF)$_2$Br, Sr$_{14}$Cu$_{24}$O$_{41}$ and Sr$_2$Ca$_{12}$Cu$_{24}$O$_{41}$ single crystals at temperatures below 1 K and magnetic field up to 10 T is investigated. The data allow us to determine the relaxation time spectrum of the low energy excitations caused by the charge-density wave (CDW) or spin-density wave (SDW). The relaxation time is mainly determined by a thermal activated process for all investigated materials. The maximum relaxation time increases with increasing magnetic field. The distribution of barrier heights corresponds to one or two Gaussian functions. The doping of Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$ with Ca leads to a drastic shift of the relaxation time spectrum to longer time. The maximum relaxation time changes from 50 s (x = 0) to 3000 s (x = 12) at 0.1 K and 10 T. The observed thermal relaxation at x=12 clearly indicates the formation of the SDW ground state at low temperatures

Bifidobacteria and lactobacilli in the gut microbiome of children with non-alcoholic fatty liver disease: which strains act as health players?

Introduction: Non-alcoholic fatty liver disease (NAFLD), considered the leading cause of chronic liver disease in children, can often progress from non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH). It is clear that obesity is one of the main risk factors involved in NAFLD pathogenesis, even if specific mechanisms have yet to be elucidated. We investigated the distribution of intestinal bifidobacteria and lactobacilli in the stools of four groups of children: obese, obese with NAFL, obese with NASH, and healthy, age-matched controls (CTRLs). Material and methods: Sixty-one obese, NAFL and NASH children and 54 CTRLs were enrolled in the study. Anthropometric and metabolic parameters were measured for all subjects. All children with suspected NASH underwent liver biopsy. Bifidobacteria and lactobacilli were analysed in children’s faecal samples, during a broader, 16S rRNA-based pyrosequencing analysis of the gut microbiome. Results: Three Bifidobacterium spp. (Bifidobacterium longum, Bifidobacterium bifidum, and Bifidobacterium adolescentis) and five Lactobacillus spp. (L. zeae, L. vaginalis, L. brevis, L. ruminis, and L. mucosae) frequently recurred in metagenomic analyses. Lactobacillus spp. increased in NAFL, NASH, or obese children compared to CTRLs. Particularly, L. mucosae was significantly higher in obese (p = 0.02426), NAFLD (p = 0.01313) and NASH (p = 0.01079) than in CTRLs. In contrast, Bifidobacterium spp. were more abundant in CTRLs, suggesting a protective and beneficial role of these microorganisms against the aforementioned diseases. Conclusions: Bifidobacteria seem to have a protective role against the development of NAFLD and obesity, highlighting their possible use in developing novel, targeted and effective probiotics

An Electron Spin Resonance Selection Rule for Spin-Gapped Systems

The direct electron spin resonance (ESR) absorption between a singlet ground state and the triplet excited states of spin gap systems is investigated. Such an absorption, which is forbidden by the conservation of the total spin quantum number in isotropic Hamiltonians, is allowed by the Dzyaloshinskii-Moriya interaction. We show a selection rule in the presence of this interaction, using the exact numerical diagonalization of the finite cluster of the quasi-one-dimensional bond-alternating spin system. The selection rule is also modified into a suitable form in order to interpret recent experimental results on CuGeO$_3$ and NaV$_2$O$_5$.Comment: 5 pages, Revtex, with 6 eps figures, to appear in J. Phys. Soc. Jpn. Vol. 69 No. 11 (2000

Study of the phase transition in the 3d Ising spin glass from out of equilibrium numerical simulations

Using the decay of the out equilibrium spin-spin correlation function we compute the equilibrium Edward-Anderson order parameter in the three dimensional binary Ising spin glass in the spin glass phase. We have checked that the Edward-Anderson order parameter computed from out of equilibrium numerical simulations follows with good precision the critical law as determined in experiments and in numerical studies at equilibrium. We have also studied the dependence of the order parameter with the lattice size. Finally we present a large time study of the scaling of the off-equilibrium fluctuation-dissipation relations.Comment: 14 pages, 7 Postscript figure

Closed trajectories of a particle model on null curves in anti-de Sitter 3-space

We study the existence of closed trajectories of a particle model on null curves in anti-de Sitter 3-space defined by a functional which is linear in the curvature of the particle path. Explicit expressions for the trajectories are found and the existence of infinitely many closed trajectories is proved.Comment: 12 pages, 1 figur

Effects of the environment on galaxies in the Catalogue of Isolated Galaxies: physical satellites and large scale structure

We aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in the Catalogue of Isolated Galaxies (CIG), as well as the effects of the Large Scale Structure (LSS) using the SDSS-DR9. To recover the physically bound galaxies we focus on the satellites which are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbours. The tidal strengths affecting the primary galaxy are estimated to quantify the effects of the local and LSS environments. We also define the projected number density parameter at the 5$^{\rm th}$ nearest neighbour to characterise the LSS around the CIG galaxies. Out of the 386 CIG galaxies considered in this study, at least 340 (88\% of the sample) have no physically linked satellite. Out of the 386 CIG galaxies, 327 (85\% of the sample) have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with likely younger stellar populations and rather high star formation with respect to older, redder CIG galaxies with companions. Reciprocally, the satellites are redder and with an older stellar populations around massive early-type CIG galaxies, while they have a younger stellar content around massive late-type CIG galaxies. This suggests that the CIG is composed of a heterogeneous population of galaxies, sampling from old to more recent, dynamical systems of galaxies.Comment: 19 pages, 10 figures, 1 table, accepted for publication in Astronomy & Astrophysic

The merging/AGN connection: A case for 3D spectroscopy

We discuss an ongoing study of the connection between galaxy merging/interaction and AGN activity, based on integral field spectroscopy. We focus on the search for AGN ionization in the central regions of mergers, previously not classified as AGNs. We present here the science case, the current status of the project, and plans for future observations.Comment: 4 pages, 3 figure, Euro3D Science Workshop, Cambridge, May 2003, AN, accepte

Evaluation of graft success of grapevine after incubation room by means of thermographic, electrical and mechanical techniques

Grafting is an important technique for getting good yields in plant multiplication. Understanding the success of the graft after the incubation stage is important to the evaluation of the suitable grafting for the open field (nursery). Successful grafting in vines requires the development of a functional vascular system between the scion and the rootstock. The graft compatibility and its augmentation depend upon various natural factors like environment, soil conditions and protective measures. The present study examines the capability of thermographic, mechanical and electrical techniques to assess the graft quality and success after the incubation stage. The trial was carried out at Vivai Mannone, (Petrosino, Western Sicily, 37\uc2\ub042'26.28''N - 12\uc2\ub029'09.57''E). After the different tests, various grafting combinations were planted in the nursery and followed for the vegetative season. Before the evaluation procedure was performed graft unions have been subjected to a moderate heating from ambient temperature, then the thermal transient toward ambient temperature was monitored by means of a thermal imaging camera. As far as the electrical testing procedure was concerned, a sinusoidal voltage was applied through the grafts-cuttings, and the voltage attenuation at different points at increasing distances from the source was measured by an oscilloscope. The mechanical strength of the graft undergoing a controlled rate flexural loading was monitored by a PC remote controlled digital dynamometer. Experimental results show that we were able to distinguish the successful grafting only with the thermographic test. Moreover, this technique was the only non-destructive test from which it was possible to derive quantitative parameters, useful to provide successful nursery forecast. Engraftment results detected at the nursery showed a 15% error in forecast based on the proposed thermal image method, which is a satisfactory value for a feasibility study