Monte Carlo Simulations of Star Clusters - IV. Calibration of the Monte Carlo Code and Comparison with Observations for the Open Cluster M67

We outline the steps needed in order to incorporate the evolution of single and binary stars into a particular Monte Carlo code for the dynamical evolution of a star cluster. We calibrate the results against N-body simulations, and present models for the evolution of the old open cluster M67 (which has been studied thoroughly in the literature with N-body techniques). The calibration is done by choosing appropriate free code parameters. We describe in particular the evolution of the binary, white dwarf and blue straggler populations, though not all channels for blue straggler formation are represented yet in our simulations. Calibrated Monte Carlo runs show good agreement with results of N-body simulations not only for global cluster parameters, but also for e.g. binary fraction, luminosity function and surface brightness. Comparison of Monte Carlo simulations with observational data for M67 shows that is possible to get reasonably good agreement between them. Unfortunately, because of the large statistical fluctuations of the numerical data and uncertainties in the observational data the inferred conclusions about the cluster initial conditions are not firm.Comment: 15 pages, 24 figure

Hepatozoon canis infecting dogs in the State of Espírito Santo, southeastern Brazil

From May 2007 to March 2008, blood samples were collected from 92 healthy dogs living in 21 households (17 farms in rural area, and 4 homes in urban area) in 6 counties of the State of Espírito Santo, southeastern Brazil. In addition, ticks were collected from these dogs. A mean of 4.4 ± 3.0 dogs (range: 1 12) were sampled per household; 78 and 14 dogs were from rural and urban areas, respectively. Polymerase chain reaction (PCR) designed to amplify fragments of the 18S rDNA gene of Babesia spp or Hepatozoon spp revealed amplicons of the expected size in 20 (21.7%) dogs for Babesia, and 54 (58.7%) dogs for Hepatozoon. All Babesia-positive dogs were also Hepatozoon-positive. Among the 21 households, 15 (71.4%) from 3 counties had at least one PCR-positive dog, including 13 farms (rural area) and 2 homes (urban area). A total of 40 PCR products from the Hepatozoon-PCR, and 19 products from the Babesia-PCR were submitted to DNA sequencing. All generated sequences from Hepatozoon-PCR were identical to each other, and to corresponding 18S rDNA sequences of H. canis in GenBank. Surprisingly, all generated sequences from the Babesia PCR were also identical to corresponding 18S rDNA sequences of H. canis in GenBank. Dogs from 10 rural and 2 urban households were found infested by Rhipicephalus sanguineus ticks. Immature of Amblyomma cajennense ticks were found in dogs from only 4 rural households (also infested by R. sanguineus). All but one household with R. sanguineus-infested dogs had at least one Hepatozoon-infected dog. Statistical analysis showed that the presence of ticks (i.e. R. sanguineus) infesting dogs in the households was significantly (P < 0.05) associated with at least one PCR-positive dog. There was no significant association (P > 0.05) between PCR-positive dogs and urban or rural households. Canine hepatozoonosis caused by H. canis is a high frequent infection in Espírito Santo, Brazil, where it is possibly vectored by R. sanguineus. Since all infected dogs were found apparently healthy, the pathogenicity of H. canis for dogs in Espírito Santo is yet to be elucidate