130 research outputs found
Low-lying spectrum of the Y-string three-quark potential using hyper-spherical coordinates
We calculate the energies of three-quark states with definite permutation
symmetry (i.e. of SU(6) multiplets) in the N=0,1,2 shells, confined by the
Y-string three-quark potential. The exact Y-string potential consists of one,
so-called three-string term, and three angle-dependent two-string terms. Due to
this technical complication we treat the problem at three increasingly accurate
levels of approximation: 1) the (approximate) three-string potential expanded
to first order in trigonometric functions of hyper-spherical angles; 2) the
(approximate) three-string potential to all orders in the power expansion in
hyper-spherical harmonics, but without taking into account the transition(s) to
two-string potentials; 3) the exact minimal-length string potential to all
orders in power expansion in hyper-spherical harmonics, and taking into account
the transition(s) to two-string potentials. We show the general trend of
improvement %convergence of these approximations: The exact non-perturbative
corrections to the total energy are of the order of one per cent, as compared
with approximation 2), yet the exact energy differences between the
-plets are shifted to 2:2:0.9,
from the Bowler and Tynemouth separation rule 2:2:1, which is obeyed by
approximation 2) at the one per cent level. The precise value of the energy
separation of the first radial excitation ("Roper") -plet
from the -plet depends on the approximation, but does not become
negative, i.e. the "Roper" remains heavier than the odd-parity
-plet in all of our approximations.Comment: 19 pages, 6 figure
Critique of a Pion Exchange Model for Interquark Forces
I describe four serious defects of a widely discussed pion exchange model for
interquark forces: it doesn't solve the "spin-orbit problem" as advertised, it
fails to describe the internal structure of baryon resonances, it leads to
disastrous conclusions when extended to mesons, and it is not reasonably
connected to the physics of heavy-light systems.Comment: 20 pages, 6 figures; some clarifications and references adde
Negative Parity 70-plet Baryon Masses in the 1/Nc Expansion
The masses of the negative parity SU(6) 70-plet baryons are analyzed in the
1/Nc expansion to order 1/Nc and to first order in SU(3) breaking. At this
level of precision there are twenty predictions. Among them there are the well
known Gell-Mann Okubo and equal spacing relations, and four new relations
involving SU(3) breaking splittings in different SU(3) multiplets. Although the
breaking of SU(6) symmetry occurs at zeroth order in 1/Nc, it turns out to be
small. The dominant source of the breaking is the hyperfine interaction which
is of order 1/Nc. The spin-orbit interaction, of zeroth order in 1/Nc, is
entirely fixed by the splitting between the singlet states Lambda(1405) and
Lambda(1520), and the spin-orbit puzzle is solved by the presence of other
zeroth order operators involving flavor exchange.Comment: 31 pages, 3 figure
Evaluation of light-emitting diodes as attractant for sandflies (Diptera: Psychodidae: Phlebotominae) in northeastern Brazil
Phlebotomine sand fly survey in the focus of leishmaniasis in Madrid, Spain (2012-2014): seasonal dynamics, Leishmania infantum infection rates and blood meal preferences
BACKGROUND: An unusual increase of human leishmaniasis cases due to Leishmania infantum is occurring in an urban area of southwestern Madrid, Spain, since 2010. Entomological surveys have shown that Phlebotomus perniciosus is the only potential vector. Direct xenodiagnosis in hares (Lepus granatensis) and rabbits (Oryctolagus cuniculus) collected in the focus area proved that they can transmit parasites to colonized P. perniciosus. Isolates were characterized as L. infantum. The aim of the present work was to conduct a comprehensive study of sand flies in the outbreak area, with special emphasis on P. perniciosus. METHODS: Entomological surveys were done from June to October 2012-2014 in 4 stations located close to the affected area. Twenty sticky traps (ST) and two CDC light traps (LT) were monthly placed during two consecutive days in every station. LT were replaced every morning. Sand fly infection rates were determined by dissecting females collected with LT. Molecular procedures applied to study blood meal preferences and to detect L. infantum were performed for a better understanding of the epidemiology of the outbreak. RESULTS: A total of 45,127 specimens belonging to 4 sand fly species were collected: P. perniciosus (75.34%), Sergentomyia minuta (24.65%), Phlebotomus sergenti (0.005%) and Phlebotomus papatasi (0.005%). No Phlebotomus ariasi were captured. From 3203 P. perniciosus female dissected, 117 were infected with flagellates (3.7%). Furthermore, 13.31% and 7.78% of blood-fed and unfed female sand flies, respectively, were found infected with L. infantum by PCR. The highest rates of infected P. perniciosus were detected at the end of the transmission periods. Regarding to blood meal preferences, hares and rabbits were preferred, although human, cat and dog blood were also found. CONCLUSIONS: This entomological study highlights the exceptional nature of the Leishmania outbreak occurring in southwestern Madrid, Spain. It is confirmed that P. perniciosus is the only vector in the affected area, with high densities and infection rates. Rabbits and hares were the main blood meal sources of this species. These results reinforce the need for an extensive and permanent surveillance in this region, and others of similar characteristics, in order to control the vector and regulate the populations of wild reservoirs.This study was partially sponsored and funded by: Dirección General de Salud Pública, Consejería de Sanidad, Comunidad de Madrid; Colegio de Veterinarios de Madrid; Colegio de Biólogos de Madrid and EU grant
FP7-261504 EDENext (http://www.edenext.eu).S
Phlebotomine sand fly survey in the focus of leishmaniasis in Madrid, Spain (2012–2014): seasonal dynamics, Leishmania infantum infection rates and blood meal preferences
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