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- Escoubet, C P, et al.
(author)
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Density in the magnetosphere inferred from ISEE 1 spacecraft potential
- 1997
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In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - ROYAL INST TECHNOL,ALFVEN LAB,DIV PLASMA PHYS,S-10044 STOCKHOLM,SWEDEN.. ; 102:A8, s. 17595-17609
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Journal article (peer-reviewed)abstract
- The potential of ISEE 1 spacecraft has been used to derive the plasma density in the magnetosphere and its environment. First, we show that using the equilibrium of currents flowing in and out of a spacecraft, we could numerically derive a relation between the spacecraft potential and the density of the surrounding plasma, After verifying: that this relation was in good agreement with the measurement of the density made by other instruments during selected periods of time, we apply this relation to the spacecraft potential measured continuously from 1977 to 1984 on ISEE 1, An image of the plasma density in the magnetosphere and its environment is obtained as a result, All principal magnetospheric regions are clearly identified: the solar wind with a density around 5 cm(-3) : the magnetosheath with a density around 50 cm(-3), the magnetosphere with a density around 1 cm(-3) the plasma sheet with a density around 0.5 cm(-3), and finally, the more tenuous tail lobes with a density below 0.1 cm(-3), The plasma density was observed slightly higher on the dawnside than on the duskside of the magnetosphere, In addition, the magnetosheath was closer to the Earth on the dawnside than on the duskside, When the magnetic activity increased (recorded by the AE index), the dayside magnetosphere was compressed/eroded by about 1 to 2 R-E, while the plasmasphere/inner magnetosphere became quite irregular and expanded in the dawn-midnight and in the dusk-noon sectors, In addition, during high magnetic activity, the plasma sheet at Y-GSM = 0 was thicker and slightly denser than at low-activity, On the other hand, the flanks of the plasma sheet were thinner and slightly less dense during high-activity than during low-activity.
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- Escoubet, C. P., et al.
(author)
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Imaging the magnetosphere using ISEE-1 spacecraft potential
- 1996
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :392, s. 179-187
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Journal article (peer-reviewed)abstract
- The potential of ISEE 1 spacecraft has been used to derived the plasma density in the magnetosphere and its environment. First we show that using the equilibrium of currents flowing in and out of a spacecraft, we could derive numerically a relation between the spacecraft potential and the density of the surrounding plasma. After verifying that this relation was in good agreement with the measurement of the density made by other instruments during selected periods of time, we apply this relation to the spacecraft potential measured continuously from 1977 to 1984 on ISEE-1. An image of the plasma density in the magnetosphere and its environment is obtained as a result. All principal magnetospheric regions are clearly identified, from the solar wind with a density around 5 cm-3 , the magnetosheath around 50 cm-3, the magnetosphere around 1 cm-3, the plasma sheet around 0.5 cm-3 and finally the more tenuous tail lobes below 0.1 cm-3. The plasma density was observed slightly higher on the dawnside than on the dusk side of the magnetosphere. In addition the magnetosheath was closer to the Earth on the dawnside than on the duskside. When the magnetic activity increased (recorded by the AE index), the dayside magnetosphere was compressed/eroded by about 1 to 2 RE while the plasmasphere/inner magnetosphere became quite irregular and expanded in the dawn-midnight and in the dusk-noon sectors. In addition, during high magnetic activity, the plasmasheet at Ygsm = 0 was thicker and denser than at low activity. On the other hand the flanks of the plasmasheet were thinner and less dense during high activity than during low activity.
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- Gustafsson, G, et al.
(author)
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The electric field and wave experiment for the Cluster mission
- 1997
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In: Space Science Reviews. - 0038-6308 .- 1572-9672. ; 79, s. 137-156
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Journal article (peer-reviewed)abstract
- The electric-field and wave experiment (EFW) on Cluster is designed to measure the electric-field and density fluctuations with sampling rates up to 36 000 samples s(-1). Langmuir probe sweeps can also be made to determine the electron density and temperature. The instrument has several important capabilities. These include (1) measurements of quasi-static electric fields of amplitudes lip to 700 mV m(-1) with high amplitude and time resolution, (2) measurements over short periods of time of up to five simualtaneous waveforms (two electric signals and three magnetic signals from the seach coil magnetometer sensors) of a bandwidth of 4 kHz with high time resolution, (3) measurements of density fluctuations in four points with high time resolution. Among the more interesting scientific objectives of the experiment are studies of nonlinear wave phenomena that result in acceleration of plasma as well as large- and small-scale interferometric measurements. By using four spacecraft for large-scale differential measurements and several Langmuir probes on one spacecraft for small-scale interferometry, it will be possible to study motion and shape of plasma structures on a wide range of spatial and temporal scales. This paper describes the primary scientific objectives of the EFW experiment and the technical capabilities of the instrument.
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- Harvey, P, et al.
(author)
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The electric field instrument on the Polar satellite
- 1995
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In: Space Science Reviews. - 0038-6308 .- 1572-9672. ; 71, s. 583-596
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Journal article (peer-reviewed)abstract
- The Polar satellite carries a system of four wire booms in the spacecraft spin plane and two rigid booms along the spin axis. Each of the booms has a spherical sensor at its tip along with nearby guard and stub surfaces whose potentials relative to that of their sphere are controlled by associated electronics. The potential differences between opposite sphere pairs are measured to yield the three components of the DC to >1 MHz electric field. Spheres can also be operated in a mode in which their collected current is measured to give information on the plasma density and its fluctuations. The scientific studies to be performed by this experiment as well as the mechanical and electrical properties of the detector system are described.
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- Jorgensen, F S, et al.
(author)
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MULTISCAN--a Scandinavian multicenter second trimester obstetric ultrasound and serum screening study
- 1999
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In: Acta Obstetricia et Gynecologica Scandinavica. - 1600-0412. ; 78:6, s. 501-510
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Journal article (peer-reviewed)abstract
- AIM: To study the detection rates of second trimester ultrasound screening for neural tube defects (NTD), abdominal wall defects (AWD) and Down's syndrome (DS) in low risk populations at tertiary centers, and to compare the ultrasound screening detection rates with those that were obtainable by biochemical serum screening (double test: alpha-fetoprotein/human chorion gonadotrophin/age test). STUDY DESIGN: Prospective multicenter study with a three year inclusion period: 1/1/1989-31/12/1991. SUBJECTS: 27,844 low-risk women at 18-34 years of age who had a second trimester ultrasound screening examination. Of these, 10,264 also had a serum test. METHODS: An ultrasound malformation scan and a serum test were carried out at 17-19 weeks of gestation. Risk calculations regarding DS were based on alpha-fetoprotein, human chorion gonadotrophin and maternal age; performed retrospectively for the first two years. RESULTS: In total 73 cases were identified in the study population: NTD (n=34), AWD (n=7) and DS (n=32). The detection rates, (%, with 95% confidence interval) for ultrasound screening were: NTD: 79.4 (62.1-91.3); AWD: 85.7 (42.1-99.6); DS: 6.3 (0.8-20.8). In the subgroup of women who had both tests, the detection rates for ultrasound screening vs double test were: NTD: 62.5 (24.5-91.5) vs 75.0 (34.9-96.8); AWD: 66.7 (9.4-99.2) vs 100 (29.2-100.0); DS: 7.7 (0.2-36.0) vs 46.2 (19.2-74.9). The false positive rates (%) for ultrasound screening vs double test were: NTD: 0.01/3.3; AWD: 0.01/3.3; DS: 0.1/4.0. CONCLUSION: Second trimester ultrasound screening in a low risk population gave a low detection rate for fetal DS (6.3%) and an acceptable detection rate for NTD (79.4%) and AWD (85.7%). In the subgroup of women who had both tests, serum screening performed better than ultrasound as applied in the present study, especially regarding DS.
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| 21. |
- Svardh, C, et al.
(author)
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Self-rated health among cardiovascular drug users in a study of Swedish twins
- 1998
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In: Scandinavian journal of social medicine. - : SAGE Publications. - 0300-8037. ; 26:3, s. 223-231
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Journal article (peer-reviewed)abstract
- The aim of this study was to analyse the relationship between self-perceived health and cardiovascular disease with and without drug treatment. Mental health and genetic effects were controlled for in the analyses. The data for these analyses were collected in 1984 as part of the Swedish Adoption/Twin Study of Aging (SATSA). In the first set of analyses, 1147 persons (mean age 60 years, 72% older than 50 years) were included. In the second part of the study, twin pairs discordant with respect to having a cardiovascular disease and/or drug use were included in the analyses. Cardiovascular disease was related to poor, self-rated health among both men and women. The proportion with bad health was largest among those with a drug-treated disease. In multivariate analyses, a strong relationship between cardiovascular disease, drug therapy and low self-rated health remained after controlling for mental health. The co-twin control analyses indicate that cardiovascular drugs have at most a marginal negative effect on health beyond the effects of the disease and genetic liability to self-perceived poor health.
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