6,643 research outputs found
An example of resonance saturation at one loop
We argue that the large-Nc expansion of QCD can be used to treat a Lagrangian
of resonances in a perturbative way. As an illustration of this we compute the
L_10 coupling of the Chiral Lagrangian by integrating out resonance fields at
one loop. Given a Lagrangian and a renormalization scheme, this is how in
principle one can answer in a concrete and unambiguous manner questions such as
at what scale resonance saturation takes place.Comment: 9 pages, 5 figures. Enlarged discussion, results unchanged. To be
published in Phys. Rev.
Reunion overseas: introduced wild boars and cultivated orange trees interact in the Brazilian Atlantic forest
Little is known concerning novel interactions between species that typically
interact in their native range but, as a consequence of human activity, are also interacting out of their original
distribution under new ecological conditions. Objective: We investigate the interaction between the orange tree
and wild boar, both of which share Asian origins and have been introduced to the Americas (i.e. the overseas).
Methods: Specifically, we assessed whether i) wild boars consume orange (Citrus sinensis) fruits and seeds
in orchards adjacent to a remnant of the Atlantic Forest of Brazil, ii) the orange seeds are viable after passing
through boar’s digestive tract and iii) whether the orange tree may naturalise in the forest remnant assisted by
wild boars. Results: Our camera surveys indicated that wild boar was by far the most frequent consumer of
orange fruits (40.5 % of camera trap-days). A considerable proportion of sown orange seeds extracted from fresh
boar feces emerged seedlings (27.8 %, N = 386) under controlled greenhouse conditions. Further, 37.6 % of sown
seeds (N = 500) in the forest remnant emerged seedlings in July 2015; however, after ~4 years (March 2019)
only 9 seedlings survived (i.e. 4.8 %, N = 188). Finally, 52 sweet orange seedlings were found during surveys
within the forest remnant which is intensively used by wild boars. This study indicates a high potential of boars
to act as effective seed dispersers of the sweet orange. However, harsh competition with native vegetation and
the incidence of lethal diseases, which quickly kill sweet orange trees under non-agricultural conditions, could
seriously limit orange tree establishment in the forest. Conclusions: Our results have important implications not
only because the wild boar could be a vector of potential invasive species, but also because they disperse seeds
of some native species (e.g. the queen palm, Syagrus romanzofiana) in defaunated forests, where large native
seed dispersers are missing; thus, wild boars could exert critical ecological functions lost due to human activityinfo:eu-repo/semantics/publishedVersio
Decay of pseudoscalars into lepton pairs and large-Nc QCD
The counterterm combination that describes the decay of pseudoscalar mesons
into charged lepton pairs at lowest order in chiral perturbation theory is
considered within the framework of QCD in the limit of a large number of
colours Nc. When further restricted to the lowest meson dominance approximation
to large-Nc QCD, our results agree well with the available experimental data.Comment: 5 pages, 2 figure
Electroweak Hadronic Contributions to the muon g-2
We reanalyze the two-loop electroweak hadronic contributions to the muon g-2
that may be enhanced by large logarithms. The present evaluation is improved
over those already existing in the literature by the implementation of the
current algebra Ward identities and the inclusion of the correct short-distance
QCD behaviour of the relevant hadronic Green's function.Comment: 29 pages, 6 figures, LaTeX. Typos fixe
Long-distance dimension-eight operators in B_K
Besides their appearance at short distances \gtrsim 1/M_W, local
dimension-eight operators also contribute to kaon matrix elements at long
distances of order \gtrsim 1/mu_ope, where mu_ope is the scale controlling the
Operator Product Expansion in pure QCD, without weak interactions. This comes
about in the matching condition between the effective quark Lagrangian and the
Chiral Lagrangian of mesons. Working in dimensional regularization and in a
framework where these effects can be systematically studied, we calculate the
correction from these long-distance dimension-eight operators to the
renormalization group invariant B_K factor of K^0-K^0bar mixing, to
next-to-leading order in the 1/Nc expansion and in the chiral limit. The
correction is controlled by the matrix element <0|\bar s_L \tilde{G}_{mu
nu}gamma^mu d_L|K^0>, is small, and lowers B_K.Comment: 14 pages, LaTeX. Explanatory comments added to match version in
journa
Effects of adenotonsillectomy on plasma inflammatory biomarkers in obese children with obstructive sleep apnea: A community-based study.
BackgroundObesity and obstructive sleep apnea syndrome (OSA) are highly prevalent and frequently overlapping conditions in children that lead to systemic inflammation, the latter being implicated in the various end-organ morbidities associated with these conditions.AimTo examine the effects of adenotonsillectomy (T&A) on plasma levels of inflammatory markers in obese children with polysomnographically diagnosed OSA who were prospectively recruited from the community.MethodsObese children prospectively diagnosed with OSA, underwent T&A and a second overnight polysomnogram (PSG) after surgery. Plasma fasting morning samples obtained after each of the two PSGs were assayed for multiple inflammatory and metabolic markers including interleukin (IL)-6, IL-18, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), adiponectin, apelin C, leptin and osteocrin.ResultsOut of 122 potential candidates, 100 obese children with OSA completed the study with only one-third exhibiting normalization of their PSG after T&A (that is, apnea-hypopnea index (AHI) ≤1/hour total sleep time). However, overall significant decreases in MCP-1, PAI-1, MMP-9, IL-18 and IL-6, and increases in adropin and osteocrin plasma concentrations occurred after T&A. Several of the T&A-responsive biomarkers exhibited excellent sensitivity and moderate specificity to predict residual OSA (that is, AHI⩾5/hTST).ConclusionsA defined subset of systemic inflammatory and metabolic biomarkers is reversibly altered in the context of OSA among community-based obese children, further reinforcing the concept on the interactive pro-inflammatory effects of sleep disorders such as OSA and obesity contributing to downstream end-organ morbidities
A relativistic chiral quark model for pseudoscalar emission from heavy mesons
The amplitudes for one-pion mediated transitions between heavy meson excited
states are obtained in the framework of the relativistic chiral quark model.
The effective coupling constants to pions and the decay widths of excited heavy
mesons with l<=2 for non-radially excited, and the l=0 radially excited mesons
are presented for both charmed and beauty mesons. We also discuss the allowed
decays of strange excited heavy mesons by emission of a K-meson.Comment: 20 pages, revte
Rotura bilateral de tendón cuadricipital asociado a tratamiento con atorvastatina.
La rotura del tendón del cuádriceps es una lesión relativamente poco frecuente. Puede asociarse a
enfermedades sistémicas, trasplante renal, tratamientos crónicos u ocurrir de forma espontánea. Presentamos un
caso de rotura bilateral de cuádriceps asociada a tratamiento crónico con atorvastatina.Quadriceps tendon rupture is a relatively rare lesion. It has been associated with chronic systemic
diseases, renal transplantation or it may occur spontaneously. We present a case of bilateral quadriceps tendon
rupture associated with chronic atorvastatin treatment
Nonfactorizable QCD and Electroweak Corrections to the Hadronic Z Boson Decay Rate
We present an analysis of two-loop mixed QCD and electroweak corrections to
the decay of the Z boson into light quarks. We find that the naive
factorization of QCD and electroweak corrections does not describe correctly
the two-loop effects. The nonfactorizable corrections shift the width of the Z
boson by approximately -0.55(3) MeV and increase the central value of the
strong coupling constant determined at LEP by 0.001.Comment: 9 pages, Revte
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