10,515 research outputs found

    Phase structure of a generalized Nambu Jona-Lasinio model with Wilson fermions in the mean field or large NN-expansion

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    We analyze the vacuum structure of a generalized lattice Nambu--Jona-Lasinio model with two flavors of Wilson fermions, such that its continuum action is the most general four-fermion action with 'trivial' color interactions, and having a SU(2)VxSU(2)ASU(2)_V x SU(2)_A symmetry in the chiral limit. The phase structure of this model in the space of the two four-fermion couplings shows, in addition to the standard Aoki phases, new phases with !=0 != 0, in close analogy to similar results recently suggested by some of us for lattice QCD with two degenerate Wilson fermions. This result shows how the phase structure of an effective model for low energy QCD cannot be entirely understood from Wilson Chiral Perturbation Theory, based on the standard QCD chiral effective Lagrangian approach.Comment: 24 pages, 3 figures, sent to Nuclear Physics

    Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm

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    In this article we study the classical nearest-neighbour spin-ice model (nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm. The nnSI describes several of the salient features of the spin-ice materials. Despite its simplicity it exhibits a remarkably rich behaviour. The model has been studied using a variety of techniques, thus it serves as an ideal benchmark to test the capabilities of the Wang Landau algorithm in magnetically frustrated systems. We study in detail the residual entropy of the nnSI and, by introducing an applied magnetic field in two different crystallographic directions ([111] and [100],) we explore the physics of the kagome-ice phase, the transition to full polarisation, and the three dimensional Kasteleyn transition. In the latter case, we discuss how additional constraints can be added to the Hamiltonian, by taking into account a selective choice of states in the partition function and, then, show how this choice leads to the realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure

    A Housing Design Audit for England

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    With the drive to deliver more homes across the country has come a loud call for those developments to be of a high standard of design in order to deliver high quality, liveable and sustainable environments for residents. Research has consistently shown that high quality design makes new residential developments more acceptable to local communities and delivers huge value to all. Housing design audits represent systematic approaches to assess the design quality of the external residential environment. This new audit evaluates the design of 142 large-scale housing-led development projects across England against seventeen design considerations. It provides enough data for comparisons to be made regionally and against the results of previous housing design audits conducted over a decade ago. It establishes a new baseline from which to measure progress on housing design quality in the future. Whilst some limited progress has been made in some regions, overwhelmingly the message is that the design of new housing environments in England are ‘mediocre’ or ‘poor’. Collectively, we need to significantly raise our game if we are to create the sorts of places that future generations will feel proud to call home

    Quantum fluctuations in thin superconducting wires of finite length

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    In one dimensional wires, fluctuations destroy superconducting long-range order and stiffness at finite temperatures; in an infinite wire, quasi-long range order and stiffness survive at zero temperature if the wire's dimensionless admittance μ\mu is large, μ>2\mu > 2. We analyze the disappearance of this superconductor-insulator quantum phase transition in a finite wire and its resurrection due to the wire's coupling to its environment characterized through the dimensionless conductance KK. Integrating over phase slips, we determine the flow of couplings and establish the μ\mu--KK phase diagram.Comment: 4 pages, 2 figure

    Distribution and genetic variability of Staphylinidae across a gradient of anthropogenically influenced insular landscapes

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    This paper describes the distribution and genetic variability of rove beetles (Coleoptera Staphylinidae) in anthropogenically influenced insular landscapes. The study was conducted in the Azores archipelago, characterized by high anthropogenic influence and landscape fragmentation. Collections were made in five islands, from eight habitats, along a gradient of anthropogenic influence. The species of Staphylinidae from the Azores collected for this study were widely distributed and showed low habitat fidelity. Rove beetle richness was associated with anthropogenic influence and habitat type, increasing from less to more anthropogenic impacted habitats. However, genetic diversity of profiled species (i.e. with three or more specimens per species/habitat) does not seem affected by anthropogenic influence in the different habitat types, isolation or landscape fragmentation. COI haplotypes were, as a rule, not exclusive to a given island or habitat. High level of genetic divergence and nucleotide saturation was found in closely related morphological designated species, demonstrating possible disparities between currently defined taxonomic units based on morphology and molecular phylogenies of Staphylinidae. This study found evidence of cryptic speciation in the Atheta fungi (Gravenhorst) species complex which had thus far remained undetected. Similar trends were found for Oligota parva Kraatz, Oxytelus sculptus Gravenhorst, Oligota pumilio Kiesenwetter. Previous studies with lower taxonomical resolution may have underestimated the biotic diversity reported in the Azores in comparison to other Macaronesian archipelagos.info:eu-repo/semantics/publishedVersio

    Infinitesimals without Logic

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    We introduce the ring of Fermat reals, an extension of the real field containing nilpotent infinitesimals. The construction takes inspiration from Smooth Infinitesimal Analysis (SIA), but provides a powerful theory of actual infinitesimals without any need of a background in mathematical logic. In particular, on the contrary with respect to SIA, which admits models only in intuitionistic logic, the theory of Fermat reals is consistent with classical logic. We face the problem to decide if the product of powers of nilpotent infinitesimals is zero or not, the identity principle for polynomials, the definition and properties of the total order relation. The construction is highly constructive, and every Fermat real admits a clear and order preserving geometrical representation. Using nilpotent infinitesimals, every smooth functions becomes a polynomial because in Taylor's formulas the rest is now zero. Finally, we present several applications to informal classical calculations used in Physics: now all these calculations become rigorous and, at the same time, formally equal to the informal ones. In particular, an interesting rigorous deduction of the wave equation is given, that clarifies how to formalize the approximations tied with Hook's law using this language of nilpotent infinitesimals.Comment: The first part of the preprint is taken directly form arXiv:0907.1872 The second part is new and contains a list of example

    The visceral adiposity index is associated with insulin sensitivity and IGF-I levels in adults with growth hormone deficiency

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    The visceral adiposity index, based on anthropometric and metabolic parameters, has been shown to be related to adipose tissue function and insulin sensitivity. We aimed to evaluate the performance of the visceral adiposity index in adult patients with growth hormone deficiency. We enrolled 52 patients(mean age 51\u2009\ub1\u200913 years) with newly diagnosed growth hormone deficiency and 50 matched healthy subjects as controls at baseline. At baseline and after 12 and 24 months of treatment we evaluated anthropometric measures, lipid profile, glucose and insulin during an oral glucose tolerance test, hemoglobin A1c, homeostasis model assessment estimate of insulin resistance, quantitative insulin sensitivity check index, insulin sensitivity index Matsuda, insulin-like growth factor-I and visceral adiposity index. At baseline growth hormone deficiency patients showed higher waist circumference (p\u2009<\u20090.001), low-density lipoprotein cholesterol (p\u2009<\u20090.001) and visceral adiposity index (p\u2009=\u20090.003) with lower insulin sensitivity index (p\u2009=\u20090.007) and high-density lipoprotein cholesterol (p\u2009=\u20090.001) than controls. During growth hormone treatment we observed a significant increase in insulin-like growth factor-I (p\u2009<\u20090.001), high-density lipoprotein (p\u2009<\u20090.001) with a trend toward increase in insulin sensitivity index (p\u2009=\u20090.055) and a significant decrease in total cholesterol (p\u2009<\u20090.001) and visceral adiposity index (p\u2009<\u20090.001), while no significant changes were observed in other clinical and metabolic parameters. The visceral adiposity index was the only parameter that significantly correlated with growth hormone peak at diagnosis (p\u2009<\u20090.001) and with insulin-like growth factor-I and insulin sensitivity index both at diagnosis (p\u2009=\u20090.009 and p\u2009<\u20090.001) and after 12 (p\u2009=\u20090.026 and p\u2009=\u20090.001) and 24 months (p\u2009<\u20090.001 and p\u2009=\u20090.001) of treatment. The visceral adiposity index, which has shown to be associated with both insulin-like growth factor-I and insulin sensitivity, proved to be the most reliable index of metabolic perturbation, among the most common indexes of adiposity assessment and a marker of benefit during treatment in adult growth hormone deficiency patients

    Correlation between Severity of Growth Hormone Deficiency and Thyroid Metabolism and Effects of Long-Term Growth Hormone Treatment on Thyroid Function in Children with Idiopathic Growth Hormone Deficiency.

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    BACKGROUND/AIM: The significance of changes in thyroid function in children during growth hormone (GH) treatment remains uncertain. We aimed to evaluate the impact of GH replacement on thyroid status in children with idiopathic GH deficiency (GHD). METHODS: Data of 105 GHD children (82 M, 23 F; aged 11.13 years) during a 36-month follow-up were analyzed. At diagnosis the areas under the curve of GH (AUCGH) were calculated during a GH-releasing hormone + arginine (GHRH-Arg) and insulin tolerance test. RESULTS: A significant \u394fT3 (p < 0.001) was documented at 12 months, without any further change at 24 and 36 months and without fT4 and TSH modifications. Grouping patients according to \u394fT3 at 12 months into those with lower (n = 80, 76%) or greater values than the 75th percentile (n = 25, 24%), the latter showed lower AUCGH and GH peak during a GHRH-Arg (p = 0.018 and 0.014, respectively) and insulin tolerance test (p = 0.023 and 0.020, respectively) at diagnosis. In addition, children with lower GH at diagnosis showed a greater \u394fT3 at 12 months (p = 0.030). CONCLUSIONS: In GHD children, GH treatment is associated with a significant increase in fT3 in the first 12 months, more pronounced in patients with more severe GHD, highlighting the strong correlation between severity of GHD and thyroid metabolism

    Dark Matter searches using gravitational wave bar detectors: quark nuggets and newtorites

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    Many experiments have searched for supersymmetric WIMP dark matter, with null results. This may suggest to look for more exotic possibilities, for example compact ultra-dense quark nuggets, widely discussed in literature with several different names. Nuclearites are an example of candidate compact objects with atomic size cross section. After a short discussion on nuclearites, the result of a nuclearite search with the gravitational wave bar detectors Nautilus and Explorer is reported. The geometrical acceptance of the bar detectors is 19.5 m2\rm m^2 sr, that is smaller than that of other detectors used for similar searches. However, the detection mechanism is completely different and is more straightforward than in other detectors. The experimental limits we obtain are of interest because, for nuclearites of mass less than 10−510^{-5} g, we find a flux smaller than that one predicted considering nuclearites as dark matter candidates. Particles with gravitational only interactions (newtorites) are another example. In this case the sensitivity is quite poor and a short discussion is reported on possible improvements.Comment: published on Astroparticle Physics Sept 25th 2016 replaced fig 1
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