We have used the beam-foil technique to study the spectrum of oxygen between 270 and 490 Å. We have measured the mean lives of the 3d2F, 3d4P, 3d4D, 3d′ 2D, 3d′ 2F, 4d4P, and 4d4D terms of O II, the 3s1P0, 3s3P0, 3S5P, 3s′ 3D, 3d3P, 3d3D, 3d3F, and 3d5P terms of O III, and the 3S2S, 3P2P0, and 3s4P0 terms of O IV. All cascade components are adequately explained. Good agreement is found with previous measurements in most cases, but significant discrepancies are found with some earlier results obtained using branches above 2000 Å. Generally satisfactory agreement is also found with theoretical predictions, although disagreement is found for several members of the 2p3–2p23d array in O II f-Values are computed for 18 individual lines, and compared with other experimental and theoretical results. Finally, we discuss briefly the f-value trends along the 2p23P–2p3s3P0 (O III), 2p21D–2p3s1P0 (O III), 2s2p24P–2s2p(3P0)3s4P0 (O IV), and 2p2P0–3s2S (O IV) isoelectronic sequences.

Some practical methods are suggested for applying the Arbitrarily Normalized Decay Curve (ANDC) method for cascade-correction in beam-foil lifetime measurements. These methods are used to analyze decay curves recorded for the ns2S-np2P0 resonance doublet in Ar VIII, Kr VIII and Xe VIII by including the np2P0-nd2D cascade transitions in the analysis. The f-values derived from the np lifetimes for the ns-sp multiplet are in good agreement with recent theoretical estimates for Ar VIII and Kr VIII and agree with theory for Xe VIII within the combined experimental and theoretical uncertainties.

A population‐based case‐control study was conducted in Ontario, Canada, to assess the relation between the risk of childhood leukemia and residential exposure to magnetic fields. Participating subjects consisted of 201 cases, diagnosed at 0 to 14 years of age during 1985–1993, ascertained from the records at the Hospital for Sick Children (Toronto), and 406 individually matched controls. Where possible, point‐in‐time measurements of magnetic fields were made in all residences occupied by subjects during the period of inquiry in the defined catchment area. Three different classification schemes of wire code were assigned to each residence. Detailed information was collected by interviewer‐administered questionnaires, which enabled risk estimates to be adjusted for socio‐economic characteristics, medical history of parent(s) and child and environmental exposures. Inconsistent elevations in risk were associated with time‐weighted averages of magnetic fields both inside and outside the home for subjects having residential point‐in‐time measurements that represented at least 70% of their etiological period. These risks increased in magnitude when analysis was restricted to children under 6 years of age at diagnosis or to those with acute lymphoblastic leukemia. For children younger than 6 years at diagnosis, outside perimeter measurements of the residence, ≥0.15 μT, were associated with increased leukemia risk (OR = 3.45, 95% CI = 1.14–10.45). Evaluation of different exposure times for point‐in‐time magnetic field measurements and wire configuration suggested that exposures earliest in the etiological period were associated with greater risks for children diagnosed at a younger age (OR = 2.50, 95% CI = 1.14–5.49). Our findings did not support an association between leukemia and proximity to power lines with high current configuration. Int. J. Cancer 82:161–170, 1999. © 1999 Wiley‐Liss, Inc.

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We have used the beam-foil technique to study spectra of aluminium in the wavelength range 300 Å to 2000 Å, and measured radiative mean lives for 22 levels in Al II-Al VII. Where possible, our results are compared with theory and other experimental work.