We have previously reported that tick-borne encephalitis (TBE) is endemic in a specific area of Hokkaido, Japan. In Oshima, the southern part of Hokkaido, TBE virus was isolated from sentinel dogs, ticks and rodents in 1995 and 1996. To identify when these TBE viruses emerged in Hokkaido, the times of divergence of TBE virus strains isolated in Oshima and far-eastern Russia were estimated. TBE virus was isolated in Khabarovsk in 1998 and the nucleotide sequences of viral envelope protein genes of isolates from Oshima and Khabarovsk were compared. From the synonymous substitution rate of these virus strains, the lineage divergence time of these TBE virus strains was predicted phylogenetically to be about 260-430 years ago. Furthermore, the virulence of TBE virus isolates from Oshima and Khabarovsk were compared in a mouse model. The results showed that the isolates possessed very similar virulence in mice. This report provides evidence that the Oshima strains of TBE virus in Hokkaido emerged from far-eastern Russia a few hundred years ago and this explains why these strains possess virulence similar to the TBE viruses isolated in Russia.

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Rf electron guns require an external magnetic field focussing to produce a low emittance electron beam. A dc magnetic field focuses electrons in the beam already inside the cavity as they leave the photocathode. In superconducting rf guns (srf) the possibility of external magnetic focussing is quite limited. In this paper we investigate an effect of rf focussing in the first half cell of a 3+1/2 cell srf gun cavity without a dc magnetic focussing. The shape of the first half cell is optimized. The calculations were done to fulfil the beam requirements of the injector for the ELBE project [1]. Besides normalized transversal emittances of the order of 1 π mm·mrad for bunch charges up to 1 nC were obtained. In the paper a graphic explanation of the rf focusing effect is represented.

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