Auctions without auctioneers: Distributed auction protocols

Abstract. It is quite natural for electronic institutions to follow the structure of their physical counterparts. However, this is not always appropriate or desirable in a virtual setting. We report on the prototyping of an alternative architecture for electronic auctions based around the concept of an interagent and building on the considerable body of work in the distributed algorithms literature to plot a path toward resilient trading frameworks. In particular, we have adapted the classical Leader Election algorithm for resolving bids in a generic auction scheme as well as identifying the factors which differentiate the physical auction protocols in such a way that new auction protocols can be plugged into the scheme by the specification of the relevant (sub-)processes. We have used the process algebra called the-calculus to specify both the generic scheme and the specific protocols of first-price, second-price, Dutch and English. The bid resolution process has been prototyped in Pict and is now going to be integrated into the FishMarket electronic auction house

Prevalence of antibodies to the BK and JC papovaviruses in isolated populations Prevalência de anticorpos contra os papovavirus BK e JC em populações isoladas

A total of 173 sera from isolated Brazilian Indian populations, 39 from the Diauarun area, and 68 from the Alto Xingú area, respectively in the North and the South of the Xingú National Park and 66 Kren-Akorore Indians, were examined for hemagglutination - inhibiting (HI) antibodies against BK and JC viruses. The global percentages of positive sera (<FONT FACE=Symbol>></FONT> 1:40) were 5.2% for BK virus and 1.7% for JC virus. The distribution of positive sera according to the population groups showed one individual to be positive for BK virus in the Diauarun Indians and none of the sera contained HI antibody to JC virus; in the Alto Xingú Indians, 4 were positive for BK virus and 3 others were positive for JC virus; as regards Kren-Akorore Indians none of the sera contained antibody to JC virus, and only 4 were BK positive. Due to the limited number of observations it was neither possible to determine the time of occurrence of seroconversion nor correlate the positivity rates for both viruses in the different tribes with the respective "contact" with the white population.<br>Foram estudados 173 soros de índios brasileiros, sendo 39 da área Diauarum, 68 do Alto Xingú e 66 índios Kren-Akorore. A pesquisa de anticorpos inibidores da hemaglutinação para os papovavirus BK e JC mostrou uma percentagem global de positividade (<FONT FACE=Symbol>></FONT> 40) para os virus BK de 5,2% e para o virus JC de 1,7%. A distribuição dos soros positivos segundo sua origem foi a seguinte: dos 39 índios Diauarum somente um apresentou titulo significante para o virus BK e nenhum deles foi positivo para o virus JC; dos 68 índios do Alto Xingú, 4 apresentaram título significante para o virus BK e 3 para o virus JC, sendo estes últimos diferentes dos indivíduos positivos para o virus BK; dos 66 índios Kren-Akorore, 4 mostraram possuir título significante para o virus BK, sem positividade para o virus JC. O número reduzido de soros não permitiu estabelecer o momento da ser o conservação, em termos de idade, como não permitiu relacionar as taxas de positividade com o maior ou menor "contato" com a população branca