We investigate the topological structure of the vacuum in SU͑3͒ lattice gauge theory. We use under-relaxed cooling to remove the high-frequency fluctuations and a variety of ''filters'' to identify the topological charges in the resulting smoothened field configurations. We find a densely packed vacuum with an average instanton size, in the continuum limit, of ϳ0.5 fm. The density at large decreases rapidly as 1/ ϳ11 . At small sizes we see some signs of a trend towards the asymptotic perturbative behavior of D()ϰ 6 . We find that an interesting polarization phenomenon occurs: the large topological charges tend to have, on the average, the same sign and are over-screened by the smaller charges which tend to have, again on the average, the opposite sign to the larger instantons. We also calculate the topological susceptibility, t , for which we obtain a continuum value of t 1/4 ϳ187 MeV. We perform the calculations for various volumes, lattice spacings and numbers of cooling sweeps, so as to obtain some control over the associated systematic errors. The coupling range is 6.0рр6.4 and the lattice volumes range from 16 3 ϫ48 to 32 3 ϫ64. ͓S0556-2821͑98͒01813-X͔
The effects of levamisole, isoprinosine and Corynebacterium parvum on Trypanosoma cruzi (Y strain) experimental infection of mice were studied. In prophylactic treatment these drugs reduced the peak of parasitaemia, and had no apparent effect on mortality rate or on histopathological and electrocardiographic findings. Levamisole and isoprinosine had no effect when used after infection. Electrocardiograms were obtained from all chronic chagasic mice. The most frequent changes were left atrial overload and first degree atrio-ventricular block. These findings became more frequent the longer the animals survived. The net effect of the non-specific immunopotentiators seems to depend on several factors: host immune state, severity of infection, dose and timing of drug administration. This probably explains the variable published results and the paradoxical findings of different laboratories.
A cross-sectional community study was conducted in the village of Kivaa in Machakos District, Kenya, to determine the prevalence and disease spectrum of visceral leishmaniasis. The disease was first diagnosed in 1978. Demographic data was collected from 50 households comprising 374 individuals. Clinical examination, laboratory investigations and leishmanin skin tests were performed. The results showed that in spite of the presence of a susceptible population, visceral leishmaniasis occurred with a low prevalence in Kivaa as evidenced by the small number of individuals with active disease (0.30%), a low leishmanin positivity rate (7.2%) and the presence of leishmanial antibodies in only 3.7% of the population. The infection affected individuals in homesteads with or without nearby termite hills. Leishmanial antibodies and leishmanin positivity were found among asymptomatic household contacts of patients as well as in isolated individuals in non-infected homesteads. These findings suggest the existence of a spectrum of disease ranging from asymptomatic to self-healing to severe clinical illness. Furthermore, there was significant clustering of leishmanin reactors in the households of patients. The aetiology of this striking focality of visceral leishmaniasis remains obscure. Possible explanations are discussed.
An exploratory study of the low-lying eigenvalues of the Wilson-Dirac operator and their corresponding eigenvectors is presented. Results for the eigenvalues from quenched and unquenched simulations are discussed. The eigenvectors are studied with respect to their localization properties in the quenched approximation for the cases of SU(2) and SU(3).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.