This paper deals with an effect of a chemical processing and an exposure time to the diffraction efficiency and the signal/noise ratio of diffraction gratings made on silver-halide emulsions Agfa Gevaert. The results of measurements on gratings treated by 14 different chemical processes are presented. and Práce se zabývá vlivem chemického zpracování a osvitu na difrakční účinnost a poměr šumu k signálu u difrakčních mřížek zhotovených do halogeno-stříbrných emulzí Agfa Gevaert. Jsou zde zpracovány výsledky měření na mřížkách zpracovaných 14 různými chemickými procesy.
The European hedgehog, Erinaceus europaeus Linnaeus, 1758, is a common host of Ixodes ricinus L. and I. hexago-nus Leach, vectors of the Lyme disease spirochaete, Borrelia burgdorferi sensu iato. To investigate whether hedgehogs are reservoirs for li- burgdorferi, hedgehogs were captured in a suburban area suitable for both tick species and in an urban area where /. ricinus is absent. The infection status of the hedgehogs was determined by xenodiagnosis using I. ricinus and I. hexagonus larvae. /. hexagonus and/or I. ricinus were found on all hedgehogs (n = 8) from the suburban area. In contrast, only I. hexagonus was infesting animals (n = 5) from the urban area. A total of 12/13 hedgehogs harboured B. burgdorferi infected ticks. Xeno-diagnostic I. ricinus and I. hexagonus larvae that fed on hedgehogs became infected. The results clearly show that European hedgehogs are reservoir hosts of the Lyme disease spirochetes. DNA of B. burgdorferi sensu stricto, В. garinii and В. afzelii was detected in culture from ear biopsy and needle aspiration material and characterized by using a genospecies-specific PCR assay. One hedgehog presented a mixed infection of the skin with fi. burgdorferi sensu stricto and fi. garinii. This study also identifies an enzootic transmission cycle in an urban area involving E europaeus and /. hexagonus. The close association of /. hexagonus with the burrows of its hosts mean that the risks of contact between /. hexagonus and humans may be low.
In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intra-tegumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.
Five types of presumed ciliate sensory receptors were detected in the forebody papillae of the adult fish trematode, Crepidostomum metoecus (Braun, 1900). The cilia are short and submerged in a tegumental pit. The apical bulb part of all types of receptors observed is supported by a dense collar and connected to the tegument basal plasma membrane by a circular septate junction. In sensory receptors types I and III no rootlet is present; the bulbs of sensory receptors types III and IV contain an electron-dense formation.
Extrasporogonic stages of Sphaerospora sp. from the kidneys of Atlantic salmon (Salmo salar L.) were successfully transmitted via intra-peritoneal injection to naive Atlantic salmon and brown trout (Salmo trutta L.). Rainbow trout (Oncorhynchus mykiss Walbaum) could not be infected in this way. Transmitted extrasporogonic stages continued their development to form sporogonie stages and mature spores in the kidney tubules. Extrasporogonic stages, sporogonie stages and mature spores of the parasite in both experimentally infected hosts were morphologically identical to the equivalent stage in naturally infected Atlantic salmon, although minor differences were seen in spore dimensions. A farm-based exposure experiment confirmed the susceptibility of brown trout to the salmon Sphaerospora, These results are consistent with the view that the salmon Sphaerospora is Sphaerospora truttae Fischer-Scherl, El-Matbouli et Hoffmann, 1986. The parasite is redescribed according to the guidelines of Lom and Arthur (1989) since details of extrasporogonie stages, the ultrastructure of extrasporogonic and sporogonie stage development, and of the parasite’s epidemiology are known from Atlantic salmon but not from other reports.
The present study is focusing on the transmission of the monogenean ectoparasite Gyrodactylus salaris Malmberg, 1957, a major pathogen on natural populations of Norwegian Atlantic salmon, Salmo salar L. In laboratory experiments the transmission rate of G. salaris after direct host to host contact was positively correlated with water temperature (1.2, 4,7 and 12.2°C). The transmission of detached G. salaris in the planktonie drift was studied in field experiments where salmon parr were individually isolated for 24 hours in small wire mesh cages suspended in the water column. Ten out of 157 salmon parr (prevalence 6.4%, mean intensity 1.0) contracted G. salaris infections after this exposure. Furthermore, 200 uninfected marked salmon parr were released into the same area of the river. After 24 and 48 hours, respectively 18 and 19 marked parr were caught by electro-fishing. The prevalence of G. salaris was 44.4% (mean intensity 1.9) after 24 hours, rising to 57.9% (mean intensity 2.3) after 48 hours. Gyrodactylids have no specific transmission stage or swimming ability, but detached G. salaris drifting in the water column were found to infect salmon parr. However, the transmission rate was markedly higher to free-living fish, suggesting that transmission routes such as indirect transmission from the substrate or direct contact transmission from infected live and/or dead fish, are relatively more important than transmission by drifting detached parasites.
Transnationalism and diaspora are concepts that are often intertwined but nonetheless differ. This article examines the link between transnationalism and integration processes among return migrants from the Armenian diaspora and examines the role social networks play in integration in Armenia. Returnees to Armenia can be divided into those who have returned from the Armenian diaspora (second and subsequent generations of migrants) and those who emigrated from Armenia and decided to return. This is reflected in the literature as a distinction between the 'old' and the 'new' Armenian diaspora, the latter having emerged in the 1990s. Before returning, both groups maintained ties with people in Armenia and may differ only by the extent and frequency of use of these ties. These ties can then accompany them when they return to Armenia and help them to (re-)integrate. The integration of returnees has its own specifics, compared to the integration of migrants, and may not be as simple as it might seem. This article focuses on the transnational ties of 23 migrants of Armenian descent who returned to Armenia after a long time abroad and draws on original research on return migration in Armenia conducted in 2016 and 2018. Semi-structured interviews with returnees revealed that their participation in the labour market is instrumental to their integration into mainstream society, and their work may involve transnational activities. The article shows the different opportunities that weak and strong ties provide returnees and that may facilitate their integration. Weak ties on a local level are crucial for returnees to be able to reintegrate and fully participate in life in Armenia. The article aims to understand the return strategy as one of the migration options that may or may not be permanent. A return may be followed by re-migration, under certain conditions and if obstacles to sustainable reintegration, and the article also explores the motivations for re-migration.
This article deals with Ukrainian student migration and the convergence of integration and transnationalism. Its main focus is the self-identification of young Ukrainians studying in the Czech Republic. The authors explore and describe international students' different integration and transnational dispositions and also discuss whether these dispositions could be seen as part of antagonistic or synergetic processes. The interconnection between transnationalism and integration is widely discussed in both sociological and anthropological literature, and most scholars identify them as synergetic processes. In the case of Ukrainian students in the Czech Republic, however, the authors argue that these processes can be understood as both synergetic and antagonistic because what matters is the students' self-identification. Most of the analysis presented in this article is based on in-depth interviews with Ukrainian students conducted between 2012 and 2019. The results of qualitative research are also compared to and discussed in relation to the findings from an on-line survey conducted among 258 Ukrainian students in 2018. The article suggests that Ukrainian students themselves could incline in both directions, towards an antagonistic and a synergetic understanding of integration and transnationalism, because it depends on their self-expressed dispositions. However, most participants most of the participants in the research express the synergy.