267 research outputs found

    QCD with light Wilson quarks on fine lattices (I): first experiences and physics results

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    Recent conceptual, algorithmic and technical advances allow numerical simulations of lattice QCD with Wilson quarks to be performed at significantly smaller quark masses than was possible before. Here we report on simulations of two-flavour QCD at sea-quark masses from slightly above to approximately 1/4 of the strange-quark mass, on lattices with up to 64x32^3 points and spacings from 0.05 to 0.08 fm. Physical sea-quark effects are clearly seen on these lattices, while the lattice effects appear to be quite small, even without O(a) improvement. A striking result is that the dependence of the pion mass on the sea-quark mass is accurately described by leading-order chiral perturbation theory up to meson masses of about 500 MeV.Comment: TeX source, 17 pages, figures include

    Chirality transfer from Graphene Quantum Dots

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    Chiral graphene quantum dots were prepared by acidic exfoliation and oxidation of graphite, dialysis, and esterification with enantiomerically pure (R) or (S)‐2‐phenyl‐1‐propanol. Circular dichroism studies support the formation of supramolecular aggregates with pyrene molecules, where a transfer of chirality occurs from the chiral graphene quantum dots to the pyrene

    QCD with light Wilson quarks on fine lattices (II): DD-HMC simulations and data analysis

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    In this second report on our recent numerical simulations of two-flavour QCD, we provide further technical details on the simulations and describe the methods we used to extract the meson masses and decay constants from the generated ensembles of gauge fields. Among the topics covered are the choice of the DD-HMC parameters, the issue of stability, autocorrelations and the statistical error analysis. Extensive data tables are included as well as a short discussion of the quark-mass dependence in partially quenched QCD, supplementing the physics analysis that was presented in the first paper in this series.Comment: TeX source, 35 pages, figures include

    Nonlinear effects in tunnelling escape in N-body quantum systems

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    We consider the problem of tunneling escape of particles from a multiparticle system confined within a potential trap. The process is nonlinear due to the interparticle interaction. Using the hydrodynamic representation for the quantum equations of the multiparticle system we find the tunneling rate and time evolutions of the number of trapped particles for different nonlinearity values.Comment: 10 pages, 3 figure

    Borrelia Lyme Group

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    Borreliaceae is a family of the phylum Spirochaetales and includes two genera, Borrelia and Cristispira genus. Borrelia genus is divided into three groups, namely Lyme group (LG), Echidna‐Reptile group (REPG) and Relapsing Fever group (RFG). All Borrelia species have an obligate parasitic lifestyle, as they depend on their hosts for most of their nutritional needs. Borreliæ are transmitted among vertebrate hosts by arthropod vectors (ticks and lice). Transtadial transmission within their carriers occurs for the Borreliæ RF Group, while this does not (or rarely occurs) for the Borreliæ Lyme Group. Phylogenetic data demonstrated that these two groups are genetically similar but distinct, forming independent clades sharing a common ancestor. In nature, the vectors of LB belong to the genus Ixodes spp. frequently found in the Northern Hemisphere, while the vectors of RF are usually the soft-ticks (Ornithodoros spp.). Borreliae share a unique genomic structure consisting of a single highly conserved linear chromosome and several linear and circular extrachromosomal plasmids which can vary widely between strains. In addition to Lyme and RF borreliosis, an intermediate group, called Echidna-Reptile borreliosis, has recently been identified. Lyme disease (LD) is caused by the spirochæte Borrelia burgdorferi sensu lato (s.l.) and transmitted to humans by the bite of a hard tick of the genus Ixodes, and LD reservoir are usually small rodents. LD is present in America, Eurasia, Africa, while its presence in Australia is not yet well documented. Not all Borreliæ Lyme Groups cause this disease in humans. Of the 23 Borreliæ burgdorferi s.l. currently known only 9 have been identified in human infection, namely Borrelia burgdorferi sensu stricto, B. afzelii, B. bavarensis, B. bissettii, B. garinii, B. lusitaniae, B. spielmani, B. valaisiana, and B. mayonii. LD is an organotropic infection, but there is also a spirochætemic form, caused by Borrelia mayonii, which gives fever similarly to the Borreliosis RF Group. A third variant of LD is Baggio-Yoshinari Syndrome (BYS), which is transmitted by another hard tick, Amblyomma cajennense. This Borrelia has not been isolated in culture, therefore its membership in the Lyme Group is not yet proven. All three of these Sub-Groups can manifest early with erythema migrans. Clinical features of LD are wide and variable, with clinical manifestations linked to distinct tissue tropisms of specific Borrelia burgdorferi s.l. genospecies. The early infection is localized and, in the absence of treatment, the spirochete can spread. The organs most frequently involved are skin, joints, muscles, nervous system, heart and eyes. B. burgdorferi s.s. is more often associated with Lyme arthritis, Borrelia garinii with neuroborreliosis and B. afzelii with acrodermatitis chronica atrophicans

    An archaeology of borders: qualitative political theory as a tool in addressing moral distance

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    Interviews, field observations and other qualitative methods increasingly are being used to inform the construction of arguments in normative political theory. This article works to demonstrate the strong salience of some kinds of qualitative material for cosmopolitan arguments to extend distributive boundaries. The incorporation of interviews and related qualitative material can make the moral claims of excluded others more vivid and possibly more difficult to dismiss by advocates of strong priority to compatriots in distributions. Further, it may help to promote the kind of perspective taking that has been associated with actually motivating a willingness to aid by individuals. Illustrative findings are presented from field work conducted for a normative project on global citizenship, including interviews with unauthorized immigrants and the analysis of artifacts left behind on heavily used migrant trails

    Avances en el diagnóstico de la discapacidad auditiva: técnica de la audiometría por Microfónicos Cocleares

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    Los problemas de audición que hacen necesario el uso de audífonos afectan a todo tipo de personas, pero especialmente a aquellas que presentan dificultades para realizar la audiometría tonal subjetiva por su falta de colaboración en la prueba. La inexistencia de pruebas de audiometría objetivas equivalente a la tonal da lugar a un impreciso diagnóstico y a un dudoso tratamiento. Los microfónicos cocleares son señales eléctricas producidas por las células ciliadas internas y externas al estímulo de la presión sonora vibrátil del sonido. La determinación de la audición hasta la cóclea inclusive permite separar los problemas de audición según su origen: los debidos a patologías existentes hasta la cóclea, parte de ésta incluida, y los debidos a patologías que afectan desde este tejido hasta el córtex. En este trabajo se exponen los avances obtenidos en el Laboratorio de Bioinstrumentación y Nanomedicina del Centro de Tecnología Biomédica de la UPM. Se ha demostrado que la señal eléctrica es una función de la presión sonora, a mayor presión mayor amplitud de la señal registrada. Comprobación del Recruitment con el equipo experimental de laboratorio, que la técnica de los MC es en realidad una medida objetiva de la pérdida auditiva y que es posible diseñar un nuevo prototipo más sensible capaz de registrar los microfónicos cocleares en humanos

    Stability of lattice QCD simulations and the thermodynamic limit

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    We study the spectral gap of the Wilson--Dirac operator in two-flavour lattice QCD as a function of the lattice spacing aa, the space-time volume VV and the current-quark mass mm. It turns out that the median of the probability distribution of the gap scales proportionally to mm and that its width is practically equal to a/Va/\sqrt{V}. In particular, numerical simulations are safe from accidental zero modes in the large-volume regime of QCD

    A de novo transcriptional atlas in Danaus plexippus reveals variability in dosage compensation across tissues

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    A detailed knowledge of gene function in the monarch butterfly is still lacking. Here we generate a genome assembly from a Mexican nonmigratory population and used RNA-seq data from 14 biological samples for gene annotation and to construct an atlas portraying the breadth of gene expression during most of the monarch life cycle. Two thirds of the genes show expression changes, with long noncoding RNAs being particularly finely regulated during adulthood, and male-biased expression being four times more common than female-biased. The two portions of the monarch heterochromosome Z, one ancestral to the Lepidoptera and the other resulting from a chromosomal fusion, display distinct association with sex-biased expression, reflecting sample-dependent incompleteness or absence of dosage compensation in the ancestral but not the novel portion of the Z. This study presents extended genomic and transcriptomic resources that will facilitate a better understanding of the monarch's adaptation to a changing environment
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