Methane fluxes, microbial activities and community structures in a wet tundra of the Lena Delta

Wet tundra environments of the Arctic are natural sources of the climate relevant trace gas methane. The underlying biogeochemical processes are not yet well understood. The field investigations were carried out on the island Samoylov (N 72°, E 126°) located in the Lena Delta, Siberia. The study site represented an area of typical polygonal patterned grounds with ice-wedges, which were considered for analyses of methane fluxes, organic matter quality and microbial communities.The mean flux rate of the depression was 53.2 ± 8.7 mg CH4 m-2 d-1, whereas the mean flux rate of the dryer rim part of the polygon was 4.7 ± 2.5 CH4 m-2 d-1. The quantity of dissolved organic matter (DOM), which represents an important C pool for microbial communities, correlated significant with the total concentrations of phospholipid fatty acids and ether lipids (PLFA and PLEL) a measure for microbial biomass. Although permafrost soils represent a large carbon pool, it was shown, that the reduced quality of organic matter leads to a substrate limitation of the microbial metabolism. This is an important finding for modelling and calculating trace gas fluxes from permafrost environments, because the known models are consider only the total carbon amount.It can be concluded by the presented results firstly that microbial communities in permafrost environments are composed by members of all three domains of life at numbers comparable to temperate soil ecosystems and secondly that the permafrost microorganisms are well adapted to the extreme temperature gradient of their environment

Dialects and Borders: Face-to-Face and Back-to-Back in Latin American Spanish

This essay explores a relatively underrepresented facet of Latin American Spanish, namely dialect contact along national borders. It is well known that Spanish American dialect zones rarely coincide with national boundaries, but also that prevailing dialectal traits often evoke nationalistic sentiments. The extent to which these tendencies interact is explored through a series of vignettes involving speech communities along the borders between nations whose principal (e.g. capital city) dialect traits differ substantially. Among the proposed factors that influence linguistic behavior in border communities are physical and political ease of border crossing, inter-nation economic imbalances, proximity of major urban areas, trans-border indigenous communities, relative proportion of locally-born residents, and historical rivalries and conflicts. In each of the scenarios, variations in the relative importance of these factors yields a different sociolinguistic configuration

Cultivation of a novel cold-adapted nitrite oxidizing betaproteobacterium from the Siberian Arctic

Permafrost-affected soils of the Siberian Arctic were investigated with regard to identification of nitrite oxidizing bacteria active at low temperature. Analysis of the fatty acid profiles of enrichment cultures grown at 4°C, 10°C and 17°C revealed a pattern that was different from that of known nitrite oxidizers but was similar to fatty acid profiles of Betaproteobacteria. Electron microscopy of two enrichment cultures grown at 10°C showed prevalent cells with a conspicuous ultrastructure. Sequence analysis of the 16S rRNA genes allocated the organisms to a so far uncultivated cluster of the Betaproteobacteria, with Gallionella ferruginea as next related taxonomically described organism. The results demonstrate that a novel genus of chemolithoautotrophic nitrite oxidizing bacteria is present in polygonal tundra soils and can be enriched at low temperatures up to 17°C. Cloned sequences with high sequence similarities were previously reported from mesophilic habitats like activated sludge and therefore an involvement of this taxon in nitrite oxidation in nonarctic habitats is suggested. The presented culture will provide an opportunity to correlate nitrification with nonidentified environmental clones in moderate habitats and give insights into mechanisms of cold adaptation. We propose provisional classification of the novel nitrite oxidizing bacterium as 'Candidatus Nitrotoga arctica'

Friction and Wear of Radiation Resistant Composites, Coatings and Ceramics in Vacuum and Low Temperature Environment

ABSTRACT Superconducting magnets used in accelerators such as the Superconducting Super Collider @SC) are exposed to fast neutron and gamma irradiation. Some of the components used in the SSC cryostat are fabricated from organic materials with low radiation resistance. The slide bearing material presently supporting the magnet assembly contains Teflon and must be replaced with a material of improved radiation resistance. A group of sliding materials, most of which have suitable radiation resistance, were tested under conditions of pressure, temperature, velocity, and vacuum typically encountered in normal cryostat operation. As this was a preliminary screening test, the samples were only cooled to liquid nitrogen temperature. The group of materials tested consists of composites, coated base metals, and ceramics. The criteria was to maintain a low coefficient of friction throughout the experiment in spite of changes in temperature and vacuum. Subsequent tests will expose finalist materials to fast neutron irradiation at liquid helium temperatures. This paper describes the experimental setup and presents data of the friction coefficient measurements taken for the various samples

Family Involvement in Charter Elementary Schools: A Case Study Using the Family Involvement Questionnaire-Elementary Version (FIQ-E)

Family involvement has been shown to have positive effects on the academic and socio-emotional and behavioral outcomes of school-aged children across all age ranges, but most especially among elementary-aged students. The Family Involvement Questionnaire-Elementary (FIQ-E) has been validated for use with students in grades 1-6 across public and parochial elementary schools in the US, which has been extended to primary schools in New Zealand and Belize. The FIQ-E was used in the current study in a charter elementary school in the Midwest. The participants included 40 family responses and one administrator. The results indicated there was a statistically significant difference in family involvement among students receiving ELL services. On average, participants whose students did not receive ELL services reported higher levels of total family involvement compared to those whose students did receive ELL services. Although this study sample was limited to one charter elementary school, the results were unique in that the sample occurred during a global pandemic. The results of this study support the effects of the pandemic on family involvement in schools, such that Home-Based Learning was higher than both Home-School Involvement and School-Based Learning, respectively. Implications for future research are discussed

¿EXISTE UN DIALECTO “ECUATOGUINEANO” DEL ESPAÑOL?

Guinea Ecuatorial como pregunta abierta: hacia el diálogo entre nuestras otredade

Armin Schwegler y Graciela Maglia, eds. Palenque (Colombia): oralidad, identidad y resistencia. Bogotá: Editorial Pontificia Universidad Javeriana e Instituto Caro y Cuervo, 2012.

Otros caribes: de las Antillas al continente (sudamérica, centroamérica y norteamérica