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Data on walrus (Odobenus rosmarus) sightings during four scheduled cruises of the research expedition vessel Mikhail Somov in the Barents, Kara, and Laptev seas (August–November, 2010; September–October, 2011; November–December 2011; and July–October, 2012) and during an expedition on the Polyaris motor ship in August–September, 2012, are presented. The data collected support and expand the existing knowledge on the distribution and abundance of the Atlantic and Laptev walrus subspecies. [ABSTRACT FROM AUTHOR]

Based on a novel combination of approaches and instruments, this article presents campaign-based results from atmospheric boundary layer (ABL) height and aerosol optical depth (AOD) measurements carried out at two different experimental sites in Sofia, as well as from three-point measurements of aerosol number concentrations. Several instruments (lidar (developed by the IE), ceilometer, aerosol particle counter, sun photometer and meteorological sensors) were used in this study. Based on joint interpretation of the instruments' data we assess the influence of the atmospheric aerosol in the planetary boundary layer and the significant influence of aerosol layers and high clouds on AOD values. Measurements of AOD in the city basin gave values in the range 0.22–0.41 for cloud-free skies, and up to around 0.8 under partly cloudy conditions. The information obtained during the two campaigns indicates that aerosol particle concentrations were lower in park areas than along heavy-traffic thoroughfares in the city, but higher than in the mountain area. In conclusion, our study demonstrates the potential of employing a broad array of instruments for the study of boundary layer and aerosol over large, valley-situated and heavily urbanized city areas. [ABSTRACT FROM AUTHOR]

The paper presents the results of a long-term comparative study of the infection of Ixodes tick imagoes with the pathogen of tularemia by using the biological assay and antibody neutralization test. The infection rates determined by both methods were found to be identical or close. If there was a difference in the rates in some years, it was not statistically significant. A statistically significant difference could not be found in the infection rates for ticks and in the dependence on their species composition though the level of infection in representatives of one species greatly differed from that in others. The serological study of Ixodes tick imagoes, aimed at determining their infection with a tularemia pathogen, yielded the results which are comparable with those of the biological assay and may be used in epizootological studies without using the biological test or by significantly limiting its use.

The organism of arthropods and warm-blooded vertebrates as a habitat of a virus determines the population genetic structure of tick-borne encephalitis (TBE) virus strains. The pattern of hybridization by variable zones of TBE genomes gradually changes in the course of intracerebral passages of the virus in newborn white mice. During intracelomal passages in Ixodidae hybridization alters as early as during the first passage, both for variable and (in individual cases) conservative zones. Ixodid ticks should be regarded as a mechanism maintaining the heterogeneity of virus communities (strains and populations). Vertebrates and communities of dugout arthropods appear to be the mechanism reducing the effect of ecologic isolation of TBE strains.