In-Space Propulsion: Connectivity to In-Space Fabrication and Repair

The connectivity between new in-space propulsion technologies and the ultimate development of an in-space fabrication and repair infrastructure are described in this Technical Memorandum. A number of advanced in-space propulsion technologies are being developed by NASA, many of which are directly relevant to the establishment of such an in-space infrastructure. These include aerocapture, advanced solar-electric propulsion, solar-thermal propulsion, advanced chemical propulsion, tethers, and solar photon sails. Other, further-term technologies have also been studied to assess their utility to the development of such an infrastructure

Young Children Learning Languages in a Multilingual Context

Luxembourg is a trilingual country where residents communicate in Luxembourgish, French and German concurrently. Children therefore study these languages at primary school. In this paper I explore how six eight-year-old Luxembourgish children use and learn German, French and English in formal and informal settings over a period of one year. Their eagerness to learn and use German and English contrasted with their cautious and formal approach to the learning of French. My findings demonstrate that second language learning in a multilingual country is not an 'automatic' or 'natural' process but, rather, children's language behaviour depends on their personal goals, interests, competence, confidence and understanding of what counts as appropriate language use. These factors are influenced by the formal approach to language learning at school

Active absorption of Cl^- and Na⁺ in posterior gills of Chinese crab <i>Eriocheir sinensis</i>: Modulation by dopamine and cAMP

Isolated posterior gills from the Chinese crab Eriocheir sinensis acclimated to freshwater (FW) were used for perfusion. Dopamine and dibutyryl cAMP (db-cAMP) induced a significant increase of 36Cl- influx. When amiloride, a specific sodium selective channels blocker, was added to the incubation saline, it induced a dramatic decrease of 22Na+ influx, and such ail effect could be reversed by dopamine or db-cAMP. In the same experimental condition, we observed that ouabain added to the scrosal side induced a marked decrease of the stimulating effect of db-cAMP on 22Na+ uptake across the epithelium to the hemolymph, suggesting that dopamine stimulates Na+ and Cl- influxes via cAMP and Na+/K+-ATPase pathways