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- Ivchenko, Nickolay, et al.
(författare)
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Quasiperiodic oscillations observed at the edge of an auroral arc by Auroral Turbulence 2
- 1999
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 26:22, s. 3365-3368
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Tidskriftsartikel (refereegranskat)abstract
- The Auroral Turbulence II (AT2) sounding rocket carried three payloads into the auroral ionosphere where they crossed several are structures. At the border of an auroral are a quasiperiodic structure was observed by the magnetic and electric field instruments as well as by the particle detectors. The variations were temporal oscillations, but existed only in a narrow (approximate to 7 km) region transverse to the are, with a correlation length along the are of at least several km. The relation between the electric and magnetic field amplitude indicates the Alfvenic nature of the variations. Field aligned electron precipitation is correlated to the field variations. The narrow band nature of the oscillations and frequency around 0.6 Hz is consistent with waves confined in the ionospheric Alfven resonator.
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- Jernström, Helena, et al.
(författare)
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Pregnancy and risk of early breast cancer in carriers of BRCA1 and BRCA2
- 1999
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Ingår i: The Lancet. - 1474-547X. ; 354:9193, s. 1846-1850
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Early age at first full-term pregnancy and increasing parity are associated with a reduced risk of breast cancer. However, whether pregnancy decreases the risk of early-onset hereditary breast cancer is unknown. There is concern that pregnancy may increase breast-cancer risk in carriers of BRCA1 and BRCA2 germline mutations. We aimed to establish whether pregnancy is a risk factor for hereditary breast cancer. METHODS: We did a matched case-control study of breast cancer in women who carry deleterious BRCA1 or BRCA2 mutations. Cases were carriers who developed breast cancer by age 40 years, and controls were carriers of the same age without breast cancer, or who were diagnosed with breast cancer after age 40 years. Women who had undergone preventive mastectomy, hysterectomy, or oophorectomy, or who were diagnosed with ovarian cancer before the age at which breast cancer was diagnosed in the matched case were excluded. Information about pregnancies and pregnancy outcome was derived from a questionnaire completed by women in the course of genetic counselling. FINDINGS: A higher proportion of cases than controls had had a full term pregnancy (173/236 vs 146/236; odds ratio 1.71 [95% CI 1.13-2.62], p=0.01). The mean number of births was also greater for cases than for controls (1.62 vs 1.38, p=0.04). The risk increased with the number of births and did not diminish with time since last pregnancy. There were no significant differences in age at first birth or age at last birth between cases and controls. INTERPRETATION: Carriers of the BRCA1 and BRCA2 mutations who have children are significantly more likely to develop breast cancer by age 40 than carriers who are nulliparous. Each pregnancy is associated with an increased cancer risk. An early first pregnancy does not confer protection for carriers of BRCA1 or BRCA2 mutations.
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- Lynch, A., et al.
(författare)
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Multiple-point electron measurements in a nightside auroral arc : Auroral Turbulence II particle observations
- 1999
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 26:22, s. 3361-3364
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Tidskriftsartikel (refereegranskat)abstract
- We report here three-point measurements of bursty, velocity-dispersed, field-aligned electron precipitation at the poleward edge of a northward-moving, post-breakup, nightside auroral arc. The three-point measurement allows detection of the proper motion of the inverted-V arc, which is shown to be 550 m/sec northward. The velocity dispersion patterns are fitted to find the source altitude of the precipitation bursts as a function of distance from the poleward edge of the are. These source points are interpreted to trace out the low-altitude boundary of the inverted-V potential drop, which is seen to rise both in time, and in the northward direction. The precipitation bursts under the inverted-V are seen to have an are-aligned velocity which varies with time, and which is consistent with the measured E x B local drift speed.
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