Determination of radiative lifetimes of excited states in neutral gold using time-resolved vacuum-ultraviolet laser spectroscopy

Natural radiative lifetimes of the states in the highly perturbed 5d10np 2P sequence in neutral gold, Au i, for n=69, as well as of four of the perturbing 5d96s6p 2P states, have been measured. This was done by direct excitation from the ground state with short-pulse vacuum-ultraviolet laser light and time-resolved detection of the laser-induced fluorescence. We found the lifetimes to be (6p 2P1/2)=6.2(2) ns, (6p 2P3/2)=4.7(2) ns, (7p 2P1/2)=6.4(7) ns, (7p 2P3/2)=5.3(7) ns, (8p 2P1/2)=63(3) ns, (8p 2P3/2)=24(2) ns, (9p 2P1/2)=28(2) ns, and (9p 2P3/2)=75(4) ns. For the perturbing states (two states of each term have been observed) we found (2P1/2, 60 983.05 cm-1)=17.5(10) ns, (2P1/2, 62 540.65 cm-1)=6.7(7) ns, (2P3/2, 58 826.30 cm-1)=2.1(15) ns, and (2P3/2, 63 005.62 cm-1)=2.7(15) ns. Furthermore, we have investigated the hyperfine structure of the 6p 2P3/2 state. © 1994 The American Physical Society

Boundary Variations: An introduction

This introduction to a themed section of Society and Space explores some of the implications that boundaries are enacted rather than given

Situating technoscience: an inquiry into spatialities

This paper explores the spatial characteristics of science and technology. Originally seen as universal, and therefore outside space and place, studies in science, technology, and society (STS) located it first in specific locations -- laboratories -- and then in narrow networks linking laboratories. This double location implied that science is caught up in and enacts two topological forms -- region and network -- since objects in networks hold their shape by freezing relations rather than fixing Euclidean coordinates. More recent STS work suggests that science and technology also exist in and help to enact additional spatial forms. Thus some technoscience objects are fluid, holding their form by shifting their relations. And yet others achieve constancy by enacting simultaneous absence and presence, a topological possibility which we call here fire . The paper concludes by arguing that the 'global' includes and is enacted in all four of these topological systems

Glucose tolerance and plasma insulin response to intravenous glucose infusion and test meal in rats with microencapsulated islet allografts

Albino Oxford rats made diabetic with 75 mg/kg streptozotocin were intraperitoneally transplanted with 2500-2900 alginate-polylysine microencapsulated Lewis islets (n = 9, total islet tissue volume 8.0-11.0 µl), or a similar volume of non-encapsulated Lewis islets (n = 5). All rats with microencapsulated islets became normoglycaemic, and remained normoglycaemic for 5-16 weeks. In rats with non-encapsulated islet grafts, only a temporary decrease in blood glucose was observed, and all were again severely hyperglycaemic at 1 week after implantation. At 5-6 weeks after transplantation, glucose tolerance in rats with microencapsulated islets was tested by intravenous glucose infusion (10 mg/min over 20 min) and test meal administration (n = 4). During glucose infusion, maximum glucose levels were 13.0 ± 0.4 mmol/l in rats with microcapsules and 8.9 ± 0.4 mmol/l in healthy control rats (p < 0.01). Concomitant maximum plasma insulin levels were 215 ± 17 pmol/l in rats with microcapsules and 715 ± 85 pmol/l in controls (p < 0.001). After the test meal, maximum blood glucose was 10.6 ± 0.9 mmol/l in rats with microcapsules and 6.2 ± 0.1 mmol/l in controls (p < 0.001), with concomitant maximum plasma insulin levels of 247 ± 11 pmol/l and 586 ± 59 pmol/l, respectively (p < 0.001). In conclusion, although the glucose tolerance is impaired and plasma insulin responses to intravenous glucose-load and test-meal are reduced, the alginate-polylysine membrane does provide adequate immunoisolation for the prolongation of allograft survival, resulting in prolonged normoglycaemia in streptozotocin diabetic rats.