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

Comparison of the Structure of Equation Systems and the GPU Multifrontal Solver for Finite Difference, Collocation and Finite Element Method

AbstractThe article is an in-depth comparison of numerical solvers and corresponding solution pro- cesses of the systems of algebraic equations resulting from finite difference, collocation, and finite element approximations. The paper considers recently developed isogeometric versions of the collocation and finite element methods, employing B-splines for the computations and ensuring Cp−1 continuity on the borders of elements for the B-splines of the order p. For solving the systems, we use our GPU implementation of the state-of-the-art parallel multifrontal solver, which leverages modern GPU architectures and allows to reduce the complexity. We analyze the structures of linear equation systems resulting from each of the methods and how different matrix structures lead to different multifrontal solver elimination trees. The paper also considers the flows of multifrontal solver depending on the originally employed method

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

¿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

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