Operational and Strategic Decisions in Hospitality. Lessons from an Action Research Process

Systemic Practice and Action Research - The aim of this article is to find measures that reduce personnel costs in a catering company through the optimization of routes and tasks for staff to...     

Effect of enkephalins in the presence of the antibiotic bacitracin in the longitudinal muscle strip preparation from guinea-pig ileum

Summary The antibiotic bacitracin (5×10^–5–4×10^–4 M) increases the inhibition of the contractile response caused by both enkephalin release and direct application of Met-enkephalin 5×10^–7 M in the longitudinal muscle strip preparation from guinea-pig ileum. This effect is attributed to an inhibition of enkephalin degrading peptidases by bacitracin.     

Superconductivity in the non-magnetic state of iron under pressure.

Ferromagnetism and superconductivity are thought to compete in conventional superconductors, although in principle it is possible for any metal to become a superconductor in its non-magnetic state at a sufficiently low temperature. At pressures above 10 GPa, iron is known to transform to a non-magnetic structure and the possibility of superconductivity in this state has been predicted. Here we report that iron does indeed become superconducting at temperatures below 2 K at pressures between 15 and 30 GPa. The transition to the superconducting state is confirmed by both a drop in resistivity and observation of the Meissner effect.     

Superconductivity in compressed lithium at 20 K

Superconductivity at high temperatures is expected in elements with low atomic numbers, based in part on conventional BCS (Bardeen-Cooper-Schrieffer) theory. For example, it has been predicted that when hydrogen is compressed to its dense metallic phase (at pressures exceeding 400 GPa), it will become superconducting with a transition temperature above room temperature. Such pressures are difficult to produce in a laboratory setting, so the predictions are not easily confirmed. Under normal conditions lithium is the lightest metal of all the elements, and may become superconducting at lower pressures; a tentative observation of a superconducting transition in Li has been previously reported. Here we show that Li becomes superconducting at pressures greater than 30 GPa, with a pressure-dependent transition temperature (T(c)) of 20 K at 48 GPa. This is the highest observed T(c) of any element; it confirms the expectation that elements with low atomic numbers will have high transition temperatures, and suggests that metallic hydrogen will have a very high T(c). Our results confirm that the earlier tentative claim of superconductivity in Li was correct.