Effect of spatial inhomogeneity on the mapping between strongly interacting fermions and weakly interacting spins

A combined analytical and numerical study is performed of the mapping between strongly interacting fermions and weakly interacting spins, in the framework of the Hubbard, t-J and Heisenberg models. While for spatially homogeneous models in the thermodynamic limit the mapping is thoroughly understood, we here focus on aspects that become relevant in spatially inhomogeneous situations, such as the effect of boundaries, impurities, superlattices and interfaces. We consider parameter regimes that are relevant for traditional applications of these models, such as electrons in cuprates and manganites, and for more recent applications to atoms in optical lattices. The rate of the mapping as a function of the interaction strength is determined from the Bethe-Ansatz for infinite systems and from numerical diagonalization for finite systems. We show analytically that if translational symmetry is broken through the presence of impurities, the mapping persists and is, in a certain sense, as local as possible, provided the spin-spin interaction between two sites of the Heisenberg model is calculated from the harmonic mean of the onsite Coulomb interaction on adjacent sites of the Hubbard model. Numerical calculations corroborate these findings also in interfaces and superlattices, where analytical calculations are more complicated.Comment: 7 pages, 6 figure

Investigation of on-site inter-orbital single electron hoppings in general multi-orbital systems

A general multi-orbital Hubbard model, which includes on-site inter-orbital electron hoppings, is introduced and studied. It is shown that the on-site inter-orbital single electron hopping is one of the most basic interactions. Two electron spin-flip and pair-hoppings are shown to be correlation effects of higher order than the on-site inter-orbital single hopping. It is shown how the double and higher hopping interactions can be well-defined for arbitrary systems. The two-orbital Hubbard model is studied numerically to demonstrate the influence of the single electron hopping effect, leading to a change of the shape of the bands and a shrinking of the difference between the two bands. Inclusion of the on-site inter-orbital hopping suppresses the so-called orbital-selective Mott transition.Comment: 5 pages, 3 figure

Muscle transcriptomic profiles in pigs with divergent phenotypes for fatness traits

Background: Selection for increasing intramuscular fat content would definitively improve the palatability and juiciness of pig meat as well as the sensorial and organoleptic properties of cured products. However, evidences obtained in human and model organisms suggest that high levels of intramuscular fat might alter muscle lipid and carbohydrate metabolism. We have analysed this issue by determining the transcriptomic profiles of Duroc pigs with divergent phenotypes for 13 fatness traits. The strong aptitude of Duroc pigs to have high levels of intramuscular fat makes them a valuable model to analyse the mechanisms that regulate muscle lipid metabolism, an issue with evident implications in the elucidation of the genetic basis of human metabolic diseases such as obesity and insulin resistance. Results: Muscle gene expression profiles of 68 Duroc pigs belonging to two groups (HIGH and LOW) with extreme phenotypes for lipid deposition and composition traits have been analysed. Microarray and quantitative PCR analysis showed that genes related to fatty acid uptake, lipogenesis and triacylglycerol synthesis were upregulated in the muscle tissue of HIGH pigs, which are fatter and have higher amounts of intramuscular fat than their LOW counterparts. Paradoxically, lipolytic genes also showed increased mRNA levels in the HIGH group suggesting the existence of a cycle where triacylglycerols are continuously synthesized and degraded. Several genes related to the insulin-signalling pathway, that is usually impaired in obese humans, were also upregulated. Finally, genes related to antigen-processing and presentation were downregulated in the HIGH group. Conclusion: Our data suggest that selection for increasing intramuscular fat content in pigs would lead to a shift but not a disruption of the metabolic homeostasis of muscle cells. Future studies on the post-translational changes affecting protein activity or expression as well as information about protein location within the cell would be needed to to elucidate the effects of lipid deposition on muscle metabolism in pigs

Broken time-reversal symmetry probed by muon spin relaxation in the caged type superconductor Lu5Rh6Sn18

The superconducting state of the caged type compound Lu5Rh6Sn18 has been investigated by using magnetization, heat capacity, and muon spin relaxation or rotation (?SR) measurements, and the results interpreted on the basis of the group theoretical classifications of the possible pairing symmetries and a simple model of the resulting quasiparticle spectra. Our zero-field ?SR measurements clearly reveal the spontaneous appearance of an internal magnetic field below the transition temperature, which indicates that the superconducting state in this material is characterized by broken time-reversal symmetry. Further, the analysis of the temperature dependence of the magnetic penetration depth measured using the transverse-field ?SR measurements suggests an isotropic s?wave character for the superconducting gap. This is in agreement with the heat capacity behavior, and we show that it can be interpreted in terms of a nonunitary triplet state with point nodes and an open Fermi surface

Fermi Liquid instabilities in two-dimensional lattice models

We develop a procedure for detecting Fermi liquid instabilities by extending the analysis of Pomeranchuk to two-dimensional lattice systems. The method is very general and straightforward to apply, thus providing a powerful tool for the search of exotic phases. We test it by applying it to a lattice electron model with interactions leading to $s$ and d-wave instabilities.Comment: 8 pages, 3 figure

Pull-off force of coated fine powders under small consolidation

In this paper, a three-dimensional model taking into account the contact deformation and surface area coverage (SAC) of nanoadditives is proposed to predict the force required to separate two contacting particles (the pull-off force) under consolidation stress up to 10 KPa, for cornstarch, a Geldart group C powder, sparsely and densely dry-coated with nanosilica. The experimental pull-off force measurement is conducted in a Seville powder tester. Comparison of the predicted results with the experimental results indicates (1) that the pull-off force of sparsely coated cornstarch is larger than that of densely coated cornstarch due to the greater hardness and small particle radius of fumed silica; (2) there is not a continuous variation in the pull-off force with the coverage of silica; on the contrary, values of the pull-off force of sparsely coated samples are grouped in similar range, while the values of the pull-off force of densely coated samples are grouped in another range of lower values.(3) Within a range, the SAC does not have a big effect on the pull-off force for sparsely coated samples and only a slight effect for densely coated samples (4) the pull-off force increases with increasing consolidation force due to larger deformation in the contact area; (5) under consolidation stresses up to 10 KPa, the deformation of the cornstarch particles is not large enough to fully embed the nanosized silica

Manejo De Residuos Sólidos Hospitalarios En La Unidad Oncológica Solca-Chimborazo

It was determined that the handling of the solid waste generated by the SOLCA – Chimborazo cancer hospital was not appropriate, both internally and externally. Because of that, the classification, transport, storage, deactivation, and intermediate disposition are inconvenient. Thus, it was realized that it is important to have the requirements and documents to follow and comply the objectives that are specified within the management, focusing on feedback and continuous improvement. To learn about the nature of the generated residuals, they were characterized in the hospital. Common, infectious, radioactive, organic and sharp residuals were found during the months of September, November and December. The common waste is comprised of cardboard, paper and plastic. The per-capita production of residuals was 0.76 kg/patient/day. The environmental impact caused by the generation of hospital solid waste was 56% severe impacts and 44% moderate impacts, which could elicit health problems in the population surrounding the hospital. For this reason, the appropriate management of solid waste allowed to obtain large environmental benefits and reduce the pollution generated by the hospital solid waste. It is recommended to SOLCA-Chimborazo and other health institutions the implementation of an adequate solid waste management, which will allow them to comply with all the requirements enforced by the environmental regulations

Second litter syndrome in Iberian pig breed: factors influencing the performance

Second litter syndrome (SLS) consists of a loss of prolificacy in the second parity (P2), when a sow presents the same or lower results for litter size than in the first parity (P1). This syndrome has been reported for modern prolific breeds but has not been studied for rustic breeds. The objectives of this study are to determine how and to what degree Iberian sows (a low productivity breed recently raised on intensive farms) are affected by SLS; to establish a target and reference levels; and to assess the factors influencing the performance. Analysed data correspond to 66 Spanish farms with a total of 126 140 Iberian sows. The average Iberian sow prolificacy in P1 was 8.91 total born (TB) and 8.47 born alive (BA) piglets, whereas in P2, it decreased by −0.05 TB and −0.01 BA piglets, suggesting some general incidence of SLS. At the sow level, 56.63% did not improve prolificacy in terms of BA piglets in P2, and 16.98% had a clear decrease in prolificacy, losing ≥3 BA piglets in P2. Within herds, a mean of 57.75% of sows showed SLS, with an evident decrease in the number of BA piglets in P2. The plausible target for the Iberian farm’s prolificacy comes from the quartile of farms with the lowest percentage of SLS sows within the farms with the highest prolificacy between P1 and P2 (mean of 8.77 BA). So, in this subset of farms (N = 17), 47.3% of sows improved their prolificacy in P2 (i.e. did not show SLS). Hence, half the sows could be expected to show SLS even on farms with a good performance. Finally, this study brings out the main factors reducing P2 prolificacy through SLS in the Iberian breed: later age at first farrowing, long first lactation length, medium weaning to conception interval and large litter size in P1. In conclusion, improving the reproductive performance of Iberian farms requires reducing the percentage of sows with SLS, paying special attention to those risk factors. The knowledge derived from this study can provide references for comparing and establishing objectives of performance on Iberian sow farms which can be used for other robust breeds.info:eu-repo/semantics/publishedVersio