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- Lacy, R. A, et al.
(författare)
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Photoionization-pumped gain at 185 nm in a laser-ablated indium plasma
- 1989
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 6:6, s. 1209-1216
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Tidskriftsartikel (refereegranskat)abstract
- We reportwhat is to our knowledge the first production of gain by inner-shell photoionization of ions. Photoionization of 4d electrons from In$+$ ions created a population inversion on a 185-nm In2$+$ transition. This scheme is an isoelectronic scaling of the 442-nm Cd$+$ laser. A single-pass gain constant of 0.9 {\textpm} 0.3 cm{\textminus}1 over a 0.4-cm path was pumped by soft x rays generated by less than 50 mJ of 1.06-$\mu$m light focused onto a tantalum target. Laser ablation of a liquid-indium target provided a high density (1016 cm{\textminus}3) of ground-state In$+$ ions for this scheme. An indium amplified spontaneous emission laser and a synchronously pumped indium laser oscillator are proposed.
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- Levin, J.C., et al.
(författare)
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Production of very cold, highly charged ions by synchrotron radiation: Comparisons of the “scalpel” and “hammer” methods
- 1987
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 262:1, s. 106-109
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of kinetic energies of highy charged argon ions produced by inner-shell photoionization and by ion-beam impact have been made using time-of-flight techniques. High-charge-state recoil ions produced by beams of ∼ 0.5-1 MeV/u Cl5+ are found to have energies one to two orders of magnitude higher than ions of the same charge produced by vacancy cascades following inner-shell photoionization by synchrotron radiation. The results may have application to the development of a very cold ion source useful for angle-resolved atomic collision studies.
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- Nilsson, O G, et al.
(författare)
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Spatial learning and memory following fimbria-fornix transection and grafting of fetal septal neurons to the hippocampus
- 1987
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Ingår i: Experimental Brain Research. - 0014-4819. ; 67:1, s. 195-215
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Tidskriftsartikel (refereegranskat)abstract
- The ability of intrahippocampal grafts of fetal septal-diagonal band tissue, rich in developing cholinergic neurons, to ameliorate cognitive impairments induced by bilateral fimbria-fornix transections in rats was examined in three experiments using the Morris water-maze to test different aspects of spatial memory. Experiment 1. Rats with fimbriafornix lesions received either septal cell suspension grafts or solid septal grafts; normal rats and rats with lesions alone were used as controls. Sixteen weeks after surgery, the rats' spatial learning and memory were tested in the water-maze using a place test, designed to investigate place navigation performance, in which rats learned to escape from the water by swimming to a platform hidden beneath the water's surface. After 5 days of training, the rats were given a spatial probe test in which the platform was removed from the tank to test spatial reference memory. Experiment 2. The same rats used in Exp. 1 were tested in a delayed-match-to-sample, working memory version of the water-maze task. The platform was located in one of two possible locations during each trial, which was composed of 2 swims. If the rat remembered the location of the platform on the 2nd swim of a trial, it should find the platform more quickly on that swim, and thereby demonstrate working memory. Experiment 3. Prior to receiving fimbria-fornix lesions, normal rats were trained in a modification of the water-maze task using alternating cue navigation and place navigation trials (i.e., with visible or non-visible escape platforms). The retention and reacquisition of the place task and the spatial probe test were examined in repeated tests up to 6 months after the lesion and intrahippocampal grafting of septal cell suspensions. The effects of central muscarinic cholinergic receptor blockade with atropine were also tested. Normal rats performed well in both the place and spatial probe tests. In contrast, rats with fimbria-fornix lesions only were unable to acquire or retain spatial information in any test. Instead, these rats adopted a random, non-spatial search strategy, whereby their latencies to find the platform decreased in the place navigation tasks. Sixty to 80% of the rats with septal suspension or solid grafts had recovered place navigation, i.e., the ability to locate the platform site in the tank, in Exp. 1 and 3, and they showed a significantly improved performance in the working memory test in Exp. 2. Atropine abolished the recovered place navigation in the grafted rats, whereas normal rats were impaired to a lesser extent.(ABSTRACT TRUNCATED AT 400 WORDS)
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- Short, R. T., et al.
(författare)
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Production of very-low-energy highly charged ions by synchrotron radiation
- 1986
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Ingår i: Physical Review Letters. - 1079-7114. ; 56:24, s. 2614-2617
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Tidskriftsartikel (refereegranskat)abstract
- Very-low-energy highly charged ions have been produced by use of white and monochromatic x rays from a wiggler line at the Stanford Synchrotron Radiation Laboratory to generate vacancy cascades following inner-shell photoionization. Recoil-ion energies have been determined and are shown to correspond essentially to room temperatures, even for high charge states. Promising applications to study of the interaction of stellar radiation with cold matter, to high-brightness ionsource development, to precision spectroscopy, and to angle-resolved chemical-physics reactive-scattering studies are discussed.
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