4,751 research outputs found
Heavy Quark Fluorescence
Heavy hadrons containing heavy quarks (for example, Upsilon-mesons) feature a
scale separation between the heavy quark mass (about 4.5 GeV for the b-quark)
and the QCD scale (about 0.3 GeV}) that controls effective masses of lighter
constituents. Therefore, as in ordinary molecules, the de-excitation of the
lighter, faster degrees of freedom leaves the velocity distribution of the
heavy quarks unchanged, populating the available decay channels in
qualitatively predictable ways. Automatically an application of the
Franck-Condon principle of molecular physics explains several puzzling results
of Upsilon(5S) decays as measured by the Belle collaboration, such as the high
rate of Bs*-anti Bs* versus Bs*-anti Bs production, the strength of three-body
B-anti B + pion decays, or the dip in B momentum shown in these decays. We
argue that the data is showing the first Sturm-Liouville zero of the
Upsilon(5S) quantum mechanical squared wavefunction, and providing evidence for
a largely b-anti b composition of this meson.Comment: 4 pages, 4 figures, Figure 2 updated and some typos corrected. To be
published in Physical Review Letter
Minimum of and the phase transition of the Linear Sigma Model in the large-N limit
We reexamine the possibility of employing the viscosity over entropy density
ratio as a diagnostic tool to identify a phase transition in hadron physics to
the strongly coupled quark-gluon plasma and other circumstances where direct
measurement of the order parameter or the free energy may be difficult.
It has been conjectured that the minimum of eta/s does indeed occur at the
phase transition. We now make a careful assessment in a controled theoretical
framework, the Linear Sigma Model at large-N, and indeed find that the minimum
of eta/s occurs near the second order phase transition of the model due to the
rapid variation of the order parameter (here the sigma vacuum expectation
value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added,
typos corrected and certain arguments clarified, revised for PR
Descripcion y cultivo de un nuevo mixomicete, Licea succulenticola
A new succulenticolous myxomycete of the genus Licea is described based on material from Spain (the Canary Islands), Mexico and the USA.Se describe una nueva especie de Myxomycetes, perteneciente al genero Licea, que se desarrolla en plantas suculentas. Los materiales proceden de España (Islas Canarias), México y Estados Unidos. Se parece a L biforis pero difiere en sus pequenos esporóforos y en sus esporas mayores, amarillo-naranjas, con una gruesa pared que gradualmente hacia un lado se adelgaza y se vuelve mas pálida. La estabilidad de estos caracteres ha quedado demostrada por el cultivo de espora a espora en laboratorio.This research has been supported by the Cooperation Program between the Consejo Superior de Investigaciones Científicas (CSIC) and the Consejo Nacional de Ciencia y Tecnología of Mexico (CONACyT) (grant 2001MX0014), and the Ministerio de Ciencia y Teconología of Spain (grant REN2002-00445).Peer reviewe
Three body systems with strangeness and exotic systems
We report on four 's and three 's, in the 1500 - 1800 MeV
region, as two meson - one baryon S-wave resonances found by solving
the Faddeev equations in the coupled channel approach, which can be associated
to the existing = -1, low lying baryon resonances. On the
other hand we also report on a new, hidden strangeness state, mostly made
of , with mass around 1920 MeV, which we think could be
responsible for the peak seen in the around this
energy. Finally we address a very novel topic in which we show how few body
systems of several mesons can be produced, with their spins aligned up
to J=6, and how these states found theoretically can be associated to several
known mesons with spins J=2,3,4,5,6.Comment: Talk at the 21st European Conference on Few Body Problems in Physics,
Salamanca, Sep. 201
Laccase gene silencing negatively effects growth and development in Pleurotus ostreatus
42-51In this study we describe the effects of Pleurotus ostreatus transformants that have been silenced for laccase genes. Using the RNAi strategy, transformants with different levels of phenotypic alteration were obtained with respect to their oxidation capacity of 2,6-dimethoxyphenol (DMP). The analysis of laccase activity on DMP allowed us to select transformants with severe, medium and light phenotypic alteration in comparison to the PoB strain. The measurements of the average growth rate of the transformants with severe phenotypic alteration suggested that laccase expression could play a role in the vegetative growth of P. ostreatus. It was observed that both in solid and liquid cultures, PoB and the transformants express mRNA for lacc10, although the transformants with medium and severe phenotypic alteration present a decrease in intensity, especially in solid culture. This suggests that the product of this gene is responsible for the development of the mycelium and probably participates in the production of biomass in solid culture and also could be related to the decrease in the intensity of the constant isoenzyme observed in both culture systems
A new perspective on the Faddeev equations and the system from chiral dynamics and unitarity in coupled channels
We review recent work concerning the interaction and Faddeev
equations with chiral dynamics which allow us to look at the from a
different perspective and pay attention to problems that have been posed in
previous studies on the subject. We show results which provide extra
experimental evidence on the existence of two states. We then
show the findings of a recent approach to Faddeev equations using chiral
unitary dynamics, where an explicit cancellation of the two body off shell
amplitude with three body forces stemming from the same chiral Lagrangians
takes place. This removal of the unphysical off shell part of the amplitudes is
most welcome and renders the approach unambiguous, showing that only on shell
two body amplitudes need to be used. With this information in mind we use an
approximation to the Faddeev equations within the fixed center approximation to
study the system, providing answers within this approximation to
questions that have been brought before and evaluating binding energies and
widths of this three body system. As a novelty with respect to recent work on
the topic we find a bound state of the system with spin S=1, like a bound state
of -deuteron, less bound that the one of S=0, where all recent efforts
have been devoted. The width is relatively large in this case, suggesting
problems in a possible experimental observation.Comment: 18 pages, 7 figures, one misprint corrected, Nuclear Physics A in
pres
Localization of Leaks in Water Distribution Networks using Flow Readings
This paper presents a novel approach to localize single and sequential leaks based on the lumped model of a water distribution network (WDN). The principal features of such a model are: a new friction term expressed as a power-law and a suitable representation expressed only in terms of the flow rate. From the response of this model and flow rate measurements at junctions of the pipelines composing the WDN, a set of residuals1 is proposed for each pipeline. The residuals closest to zero will indicate the leak positions in the faulty pipelines. We present some simulation tests based on data from PipelineStudio® from Energy Solutions to illustrate the suitability of our method
Biodiversidad de Myxomycetes en el Desierto de Monte (Argentina)
A biodiversity survey for myxomycetes was carried out in the Monte Desert (Argentina) and surrounding areas in November 2006 and late February and March 2007. Specimens were collected in seven different provinces (Catamarca, Jujuy, La Rioja, Salta, San Juan, San Luis and Tucumán), between 23º and 33º S latitude, and a total of 105 localities were sampled. Cacti and succulent plants were the most common type of substrate investigated, but shrubs and herbs characteristic of this biome were also included in the survey. Almost six hundred specimens of myxomycetes from 72 different species in 22 genera were collected either in the field, or from moist chamber cultures prepared with samples of plant material obtained from the same collecting sites. The results include 1 species new to science, Macbrideola andina three more species recently described based on material from this survey, 5 species cited for the first time for the Neotropics, 11 new records for South America and 38 new records for Argentina. Taxonomic comments on rare or unusual species are included and illustrated with photographs by LM and SEM. Data are presented on the development of some species and microenvironmental factors are discussed. An analysis of the biodiversity of myxomycetes in this area, and a comparison with other desert areas, are included.Con el objetivo de estudiar la biodiversidad de Myxomycetes en el Desierto de Monte (Argentina) y áreas circundantes, se realizó un muestreo en los meses de noviembre de 2006 y febrero y marzo de 2007. Se recolectaron especímenes en un total de 105 localidades pertenecientes a siete provincias (Catamarca, Jujuy, La Rioja, Salta, San Juan, San Luis y Tucumán), situadas entre los paralelos 23º y 33º de latitud sur. Los cactus y plantas suculentas fueron los tipos de sustratos más estudiados, pero también se analizaron arbustos y plantas herbáceas características de este bioma. Casi 600 especímenes de mixomicetes pertenecientes a 72 especies y 22 géneros fueron recolectados en el campo o se obtuvieron en el laboratorio, por cultivo en cámara húmeda, a partir de plantas procedentes de las mismas localidades. Los resultados incluyen una nueva especie, Macbrideola andina, otras tres recientemente descritas y basadas en material de este estudio, 5 especies que se citan por primera vez para el Neotrópico, 11 nuevos registros para América del Sur y 38 nuevos registros para Argentina. Se añaden comentarios taxonómicos e ilustraciones fotográficas, tanto con microscopía óptica como electró ni ca, de aquellas especies raras o poco comunes. Se discuten nuevos datos sobre el desarrollo de algunas especies y cómo influyen determinados factores microambientales. También se incluye un análisis de la biodiversidad de mixomicetes en esta zona árida y se compara con la obtenida en otros desiertos de América
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