Population regulation of vendace (Coregonus albula) in Lake Pyhäjärvi, southwest Finland

Previous time series analysis on vendace population dynamics in Lake Pyhäjärvi, 1971–1990, revealed a 2-year cycle in year-class strength, implying powerful density-dependent regulation. Here we have extended this analysis by using multiple regression models to test whether the recruitment series is influenced by density-independent factors. We chose population size with a lag of 1 year as the density-dependent factor; the density-independent factors were the summer water temperature with a lag of 2 years (temperature sum for June, July and August, indicating the year-class strength of predators) and the temperature-derived length of the larval period of vendace. For the years 1972–1990 the coefficient of determination ( r ²) of this regression model was 0·77. We suggest that the basic mechanism producing a persistent 2-year cycle of vendace in Lake Pyhäjärvi is the asymmetrical food competition between age groups. The abundance of predators in the lake and the warming of the water after the hatching of larvae in spring together determine the final year-class strength of vendace.     

Witchcraft and the limits of mass mediation in Malawi

This article explores what the study of witchcraft in an African setting can contribute to current efforts to theorize mass mediation and the imagination it fosters. Recent ethnographies of witchcraft discourses in Africa have continued to associate them with the formation of small-scale groups, but evidence from Malawi shows how they enable subjects to imagine sociality on an indeterminate scale. The article deploys the concept of mediation to theorize how in this imagination witches mediate sociality as the unrecognized third parties who give rise to recognized social relationships of varying scale. The ethnography of witchcraft discourses in radio broadcasting and an impoverished peri-urban area demonstrates not only their relevance to apparently disparate contexts but also their potential to exceed the impact of the mass media. The case of a violent conflict involving Pentecostal Christians, South Asian entrepreneurs, Muslims, and members of a secret society provides an example of how arguments about witchcraft had a greater impact on the popular imagination than a mass-mediated report of the same conflict. The article concludes by arguing that witchcraft discourses should be accorded weight equal to the mass media in theorizing the imagination.     

Grazing of bacteria and phytoplankton by heterotrophic nanoflagellates in a Baltic Sea sample

Grazing by heterotrophic nanoflagellates on bacteria and phytoplankton was studied in a laboratory experiment, using a natural pelagic community originating from the Tvärminne sea area off the southern coast of Finland. Water was prescreened to remove larger grazers. Four experimental treatments were used: light and dark, with and without added nutrients. The growth of the large heterotrophic flagellates was stimulated by increased production of < 3 m phytoplankton. Clearance rates for heterotrophic nanoflagellates were estimated and were found to be within the range of previously reported values.     

Monitoring and analysis of dynamic growth of human embryonic stem cells: comparison of automated instrumentation and conventional culturing methods

Background  

Human embryonic stem cells (hESCs) are a potential source of cells for use in regenerative medicine. Automation of culturing, monitoring and analysis is crucial for fast and reliable optimization of hESC culturing methods. Continuous monitoring of living cell cultures can reveal more information and is faster than using laborious traditional methods such as microscopic evaluation, immunohistochemistry and flow cytometry.     

Winter diets of wolfCanis lupus and lynxLynx lynx in Estonia and Latvia

Winter diets of wolfCanis lupus Linnaeus, 1758 and lynxLynx lynx Linnaeus, 1758 in Latvia and Estonia were investigated in 1997–2000 based on stomach contents of hunted animals and scats. Ungulates appeared to be the staple food for both predators. Lynx diet to a high extent consisted of cervids (Estonia 52% frequency of prey, Latvia 88%), roe deer dominating. Mountain hareLepus timidus made up from 9% (Latvia) to 31% (Estonia) of the lynx diet, and red foxVulpes vulpes 7% in Estonian sample. Wolf diet was more diverse; besides cervids (44% in Latvia, 63% in Estonia) it included wild boar Sus scrofa (32% in Latvia, 17% in Estonia), carrion, small rodents, and other food items. Proportion of empty stomachs was high both in wolves (37%) and lynxes (35%) in Latvia. Range of stomach content weights varied from zero to more than 4 kg in wolves and almost 1.5 kg in lynx. Pianka’s indices of food niche overlapped significantly between species and countries (0.85–0.99).     

Ethyl[2-Deoxy-5-O-(4,4′-dimethoxytrityl)-α- and β-D-erythro-Pentofuranosyl] Acetates as Versatile Intermediates in Nucleic Acid Chemistry

Abstract

The title compounds (1a,b) were synthesized in three steps from 2-deoxy-D-ribose, and used in the preparation of oligonucleotide conjugates, branched oligonucleotides as well as homo-N-nucleosides.     

HPLC as a Tool to Study the Kinetics of Parallel and Consecutive Reactions: Competitive Interconversion,Dephosphorylation, Deamination and Depyrimidination of Cytidine 2′- and 3′-Monophosphates in Aqueous Acid

Abstract

The applicability of HPLC as a method to study the kinetics of complicated reaction systems of nucleosides and nucleotides has been demonstrated by using the hydrolytic reactions of cytidine 2′- and 3′-monophosphates as an example.