Electron-phonon interaction and antiferromagnetic correlations

We study effects of the Coulomb repulsion on the electron-phonon interaction (EPI) in a model of cuprates at zero and finite doping. We find that antiferromagnetic correlations strongly enhance EPI effects on the electron Green's function with respect to the paramagnetic correlated system, but the net effect of the Coulomb interaction is a moderate suppression of the EPI. Doping leads to additional suppression, due to reduced antiferromagnetic correlations. In contrast, the Coulomb interaction strongly suppresses EPI effects on phonons, but the suppression weakens with doping.Comment: 4 pages and 5 figure

Special Issue: Anti-Inflammatory Activity of Plant Polyphenols

Inflammation is considered the first physiological response of the human body to infection or injury, playing a critical role in both innate and adaptive immunity [...]

Local magnetic moments in iron and nickel at ambient and Earth's core conditions

Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d- or f-orbitals, which leads to the formation of local magnetic moments. The combination of these two effects is usually considered of little relevance to strongly correlated materials. Here we show that it represents, instead, the underlying physical mechanism in two of the most important ferromagnets: nickel and iron. In nickel, the van Hove singularity has an unexpected impact on the magnetism. As a result, the electron-electron scattering rate is linear in temperature, in violation of the conventional Landau theory of metals. This is true even at Earth's core pressures, at which iron is instead a good Fermi liquid. The importance of nickel in models of geomagnetism may have therefore to be reconsidered.Comment: Supplementary Information available at https://www.nature.com/articles/ncomms16062#supplementary-informatio

TANNINS FROM RUBUS AND FRAGARIA BERRIES FOR THE CONTROL OF GASTRIC INFLAMMATION: IN VITRO AND IN VIVO STUDIES

Gastritis and ulcers are very common inflammatory-based diseases which can be caused by Helicobacter pylori (H. pylori) infection, chemical factors or immunological disorders[3]. H. pylori is the leading cause of gastritis[1], it colonizes the gastric mucosa of over 80% of human population in developing countries[3] and at least 50% of the world\u2019s human population[36]. Gastric epithelial cells, during H. pylori infection, show increased levels of cytokines/chemokines including IL-1\u3b2, IL-6, TNF\u3b1 and IL-8[66]. Epithelial cells stimulated with TNF\u3b1, IL-1\u3b2 or bacterial infection, release a variety of cytokines (TNF\u3b1, IL-1\u3b2, IL-8) and increase expression of cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS). The activation of nuclear factor \u3baB (NF-\u3baB) is deeply involved in the control of transcription of inflammatory mediators in the stomach[95]. Ellagitannins (ET) have shown anti-inflammatory and anti-H.pylori properties; however, their anti-inflammatory activity at gastric level was not previously investigated. Rubus berries (raspberries and blackberries) and Fragaria berries (strawberries) are considered a rich source of phenolic compounds, including anthocyanins, tannins, ET and ellagic acid (EA) derivatives conjugated[308]. The aim of the present research was to evaluate the effects of tannins, in particular ET, from Rubus and Fragaria berries, the most common sources of ET in the European diet, on gastric inflammation. Tannin enriched extracts (TEs) were prepared from Rubus fruticosus L. (blackberry), Rubus idaeus L. (raspberry), Fragaria X ananassa Duch. (strawberry) and Fragaria vesca L. (wild strawberry). The anti-inflammatory activity was tested in vitro on gastric cell line AGS stimulated by TNF\u3b1 and IL-1\u3b2. TEs inhibited TNF\u3b1-induced NF-\u3baB driven transcription and reduced NF-kB nuclear translocation. TEs inhibited also IL-8 secretion induced by TNF\u3b1 and IL-1\u3b2 at low concentrations (IC50 range: 0.5\u20138.8 \ub5g/mL). The effect of an in vitro gastric digestion on TEs activity was also evaluated. Sanguiin H-6, lambertianin C, (the major ET present in Rubus berries) and agrimoniin (ET from Fragaria berries), were found to be responsible, at least in part, for the effect of the mixtures. In vivo the protective effect of TEs was evaluated in a rat model of ethanol-induced gastric lesions. Rats were treated orally for ten days with 20 mg/kg/day of TEs, and ethanol was given one hour before the sacrifice. Gastric mucosa was isolated and used for the determination of IL-8 release, NF-\u3baB nuclear translocation, Trolox equivalents, superoxide dismutase and catalase activities. TEs of blackberry and raspberry decreased Ulcer Index by 88% and 75% respectively and protected from the ethanol-induced oxidative stress in rats. CINC-1 (the rat homologue of IL-8) secretion in the gastric mucosa was reduced in the animals receiving blackberry and raspberry TEs. The effect of TEs on CINC-1 was associated to a decrease of NF-\u3baB nuclear translocation in TEs treated animals. The anti-inflammatory activity exerted by TEs occurs at extremely low concentrations, even below the concentration of 1 \u3bcg/mL, values that are considered easy to reach by the ingestion of a portion of berries (approximately 5 mg/mL). These results show that tannins interfere with the metabolic cascade deriving from the activation and translocation of NF-\u3baB that in turn activates the transcription of target genes involved in inflammation, including IL-8. ET do not require any absorption to reach the stomach and their concentrations are not reduced by metabolic processes in this district. In this study was demonstrated for the first time that ET from blackberries and raspberries are able to protect the stomach against the gastric lesions caused by ethanol. The outcome of this research suggests the use of ET as integration in dietary regimens designed for treat or prevent inflammatory gastric diseases

Fluctuation diagnostics of the electron self-energy: Origin of the pseudogap physics

We demonstrate how to identify which physical processes dominate the low-energy spectral functions of correlated electron systems. We obtain an unambiguous classification through an analysis of the equation of motion for the electron self-energy in its charge, spin and particle-particle representations. Our procedure is then employed to clarify the controversial physics responsible for the appearance of the pseudogap in correlated systems. We illustrate our method by examining the attractive and repulsive Hubbard model in two-dimensions. In the latter, spin fluctuations are identified as the origin of the pseudogap, and we also explain why $d-$wave pairing fluctuations play a marginal role in suppressing the low-energy spectral weight, independent of their actual strength.Comment: 6 pages, 2 figures + 4 pages supplementar

Evidence for a Bulk Complex Order-Parameter in Y0.9Ca0.1Ba2Cu3O7-delta Thin Films

We have measured the penetration depth of overdoped Y0.9Ca0.1Ba2Cu3O7-delta (Ca-YBCO) thin films using two different methods. The change of the penetration depth as a function of temperature has been measured using the parallel plate resonator (PPR), while its absolute value was obtained from a quasi-optical transmission measurements. Both sets of measurements are compatible with an order parameter of the form: Delta*dx2-y2+i*delta*dxy, with Delta=14.5 +- 1.5 meV and delta=1.8 meV, indicating a finite gap at low temperature. Below 15 K the drop of the scattering rate of uncondensed carriers becomes steeper in contrast to a flattening observed for optimally doped YBCO films. This decrease supports our results on the penetration depth temperature dependence. The findings are in agreement with tunneling measurements on similar Ca-YBCO thin films.Comment: 11 pages, 4 figure

A Review on the Anti-Inflammatory Activity of Pomegranate in the Gastrointestinal Tract

Several biological activities of pomegranate have been widely described in the literature, but the anti-inflammatory effect in the gastrointestinal tract has not been reviewed till now. The aim of the present paper is to summarize the evidence for or against the efficacy of pomegranate for coping with inflammatory conditions of the gastro-intestinal tract. The paper has been organized in three parts: (1) the first one is devoted to the modifications of pomegranate active compounds in the gastro-intestinal tract; (2) the second one considering the literature regarding the anti-inflammatory effect of pomegranate at gastric level; (3) the third part considers the anti-inflammatory effect of pomegranate in the gut. In vivo studies performed on the whole fruit or juice, peel, and flowers demonstrate antiulcer effect in a variety of animal models. Ellagic acid was the main responsible for this effect, although other individual ellagitannins could contribute to the biological activity of the mixture. Different preparations of pomegranate, including extracts from peels, flowers, seeds, and juice, show a significant anti-inflammatory activity in the gut. No clinical studies have been found, thus suggesting that future clinical studies are necessary to clarify the beneficial effects of pomegranate in the gastrointestinal tract

Structure and cytotoxic activity of sesquiterpene glycoside esters from Calendula officinalis L.: studies on the conformation of viridiflorol

Topic applications of Calendula officinalis L. lipophilic extracts are used in phytotherapy to relieve skin inflammatory conditions whereas infusions are used as a remedy for gastric complaints. Such a different usage might be explained by some cytotoxicity of lipophilic extracts at gastric level but little is known about this. Therefore, we screened the CH2Cl2 extract from the flowers of C. officinalis by MTT and LDH assays in human epithelial gastric cells AGS. This bioassay-oriented approach led to the isolation of several sesquiterpene glycosides which were structurally characterized by spectroscopic measurements, chemical reactions and MM calculations. The conformational preferences of viridiflorol fucoside were established and a previously assigned stereochemistry was revised. The compounds 1a, 2a and 3f showed comparably high cytotoxicity in the MTT assays, whereas the effect on LDH release was lower. Our study provides new insights on the composition of C. officinalis extracts of medium polarity and identifies the main compounds that could be responsible for cytotoxic effects at gastric level