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| 2. |
- Ungstrup, E., et al.
(author)
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Rocket-borne particle, field, and plasma observations in the cleft region
- 1975
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 2:7, s. 345-348
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Journal article (peer-reviewed)abstract
- First results of comprehensive observations of magnetic and electric fields, and ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region are reported. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Our observations of electron temperatures, electric fields and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer, which is associated with the appearance of the ‘slant E condition’ identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.
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| 3. |
- Gotfredsen, Klaus, et al.
(author)
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Implants and/or teeth: consensus statements and recommendations.
- 2008
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In: Journal of oral rehabilitation. - : Wiley. - 1365-2842 .- 0305-182X. ; 35:Suppl 1, s. 2-8
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Research review (peer-reviewed)abstract
- In August 23-25, 2007, the Scandinavian Society for Prosthetic Dentistry in collaboration with the Danish Society of Oral Implantology arranged a consensus conference on the topic 'Implants and/or teeth'. It was preceded by a workshop in which eight focused questions were raised and answered in eight review articles using a systematic approach. Twenty-eight academicians and clinicians discussed the eight review papers with the purpose to reach consensus on questions relevant for the topic. At the conference the consensus statements were presented as well as lectures based on the review articles. In this article the methods used at the consensus workshop are briefly described followed by the statements with comments.
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| 4. |
- Gustafsson, Georg, et al.
(author)
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First results of electric field and density observations by Cluster EFW based on initial months of operation
- 2001
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In: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:12-okt, s. 1219-1240
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Journal article (peer-reviewed)abstract
- Highlights are presented from studies of the electric field data from various regions along the CLUSTER orbit. They all point towards a very high coherence for phenomena recorded on four spacecraft that are separated by a few hundred kilometers for structures over the whole range of apparent frequencies from I mHz to 9 kHz. This presents completely new opportunities to study spatial-temporal plasma phenomena from the magnetosphere out to the solar wind. A new probe environment was constructed for the CLUSTER electric field experiment that now produces data of unprecedented quality. Determination of plasma flow in the solar wind is an example of the capability of the instrument.
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| 5. |
- 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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| 7. |
- Marklund, Göran, et al.
(author)
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Observations of the electric field fine structure associated with the westward traveling surge and large-scale auroral spirals
- 1998
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 103:A3, s. 4125-4144
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Journal article (peer-reviewed)abstract
- The characteristics of the fine scale electric field associated with the westward traveling surge and large-scale auroral spirals and surges are investigated using high-resolution electric field, magnetic field, particle and UV imager observations from four eveningside auroral oval crossings by the Freja satellite. Three of the crossings were associated with signatures of auroral substorms and one crossing went directly through the head of a surge close in time and space to substorm onset. Three passes were adjacent to auroral spiral formations, one poleward of and one equatorward of such forms and one through the multiple arc region near the front of an extended region of auroral activity. The ambient electric field was found to intensify in the direction toward the spiral head (or the center of the auroral activity region) over a region comparable to the size of the visible auroral forms. These results confirm previous findings that the spiral or surge head is associated with negative space charge and an intense upward field-aligned current. The fourth pass, directly through the surge head reveals a very complicated structure of the surge region. Narrowly structured, intense (up to 700 mV/m) and mostly converging electric fields associated with intense electron precipitation (of both high and medium energies) and balanced field-aligned currents (up to 30 μA/m2) are seen near the edge of the surge head and adjacent to auroral structures in the wake. These narrow regions are embedded within more extended regions of intense high-energy electron precipitation but very weak electric fields and field-aligned currents. According to some existing models of the surge, a pronounced westward electric field component and a southward polarisation electric field is expected within the entire high-conductivity region but evidence in support of this was not found in the data. Rather, these suggest that a significant part of the upward surge current is closed by distributed downward field-aligned currents from the near surroundings. The Freja electric field is typically seen to intensify at the edges of or in-between bright auroral structures and to decrease within the arcs similar to what is observed in the ionosphere. The surge electric field is, however, much more intense than previously observed or anticipated at these altitudes with characteristics rather similar to those observed in the auroral acceleration region. Since the particle data indicate that most of the acceleration takes place above Freja altitudes, it seems as if Freja traversed the lower part of the auroral acceleration region associated with the surge.
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| 12. |
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| 13. |
- Brenning, Nils, et al.
(author)
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Critical ionization velocity interaction in the CRIT I rocket experiment
- 1990
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In: Advances in Space Research. - : Elsevier BV. - 0273-1177. ; 10, s. 63-66
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Journal article (peer-reviewed)abstract
- In the rocket experiment CRIT I, launched from Wallops Island on 13 May 1986, two identical Barium shaped charges were fired from distances of 1.3 km and 3.6 km towards the main experiment payload, which was separated from a sub-payload by a couple of km along the magnetic field. The relevance of earlier proposed mechanisms for electron heating in ionospheric critical velocity experiments is investigated in the light of the CRIT I results. It is concluded that both the "homogeneous" and the "ionizing front" models can be applied, in different parts of the stream. It is also possible that a third, entirely different, mechanism may contribute to the electron heating. This mechanism involves direct energization of electrons in the magnetic-field-aligned component of the DC electric field. © 1989.
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| 14. |
- Brenning, Nils, et al.
(author)
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Electrodynamic interaction between the CRIT I ionized barium streams and the ambient ionosphere
- 1990
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In: Advances in Space Research. - : Elsevier BV. - 0273-1177. ; 10, s. 67-70
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Journal article (peer-reviewed)abstract
- In the CRIT I Critical Velocity experiment, launched from Wallops Island on 13 May, 1986, two fast barium streams were ejected by means of shaped charges. Their electrodynamic interaction with the ambient ionosphere is discussed. An outstanding feature of the DC electric field observed within the streams was a large magnetic-field-aligned component, persisting on the time scale of the passage of the streams. One interpretation of the DC electric field data is that the internal electric fields of the streams is not greatly modified by Birkeland currents, i.e. a state is established, where the transverse currents are to a first approximation divergence-free. It is argued that this interpretation can explain why a reversal of the strong explosion-directed electric field was observed in the first explosion but not in the second (more distant one). © 1989.
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| 15. |
- Brenning, Nils, et al.
(author)
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Interpretation of the Electric Fields Measured in an Ionospheric Critical Ionization Velocity Experiment
- 1991
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In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 96, s. 9719-9733
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Journal article (peer-reviewed)abstract
- This paper deals with the quasi-dc electric fields measured in the CRIT I ionospheric release experiment, which was launched from Wallops Island on May 13, 1986. The purpose of the experiment was to study the critical ionization velocity (CIV) mechanism in the ionosphere. Two identical barium shaped charges were fired from distances of 1.99 km and 4.34 km towards a main payload, which made full three-dimensional measurements of the electric field inside the streams. There was also a subpayload separated from the main payload by a couple of kilometers along the magnetic field. The relevance of earlier proposed mechanisms for electron heating in CIV is investigated in the light of the CRIT I results. It is concluded that both the “homogeneous” and the “ionizing front” models probably apply, but in different parts of the stream. It is also possible that electrons are directly accelerated by a magnetic-field-aligned component of the electric field; the quasi-dc electric field observed within the streams had a large magnetic-field-aligned component, persisting on the time scale of the passage of the streams. The coupling between the ambient ionosphere and the ionized barium stream in CRIT I was more complicated than is usually assumed in CIV theories, with strong magnetic-field-aligned electric fields and probably current limitation as important processes. One interpretation of the quasi-dc electric field data is that the internal electric fields of the streams were not greatly modified by magnetic-field-aligned currents, i.e., a state was established where the transverse currents were to a first approximation divergence-free. It is argued that this interpretation can explain both a reversal of the strong explosion-directed electric field in burst 1 and the absence of such a reversal in burst 2.
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| 20. |
- Fälthammar, Carl-Gunne, et al.
(author)
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Hannes Alfven : 30 May 1908 - 2 April 1995
- 2006
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In: Proceedings of the American Philosophical Society. - 0003-049X .- 2326-9243. ; 150:4, s. 649-662
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Journal article (peer-reviewed)
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| 21. |
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| 22. |
- 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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| 23. |
- Lindh, T, et al.
(author)
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A meta-analysis of implants in partial edentulism.
- 1998
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In: Clinical Oral Implants Research. - 0905-7161 .- 1600-0501. ; 9:2, s. 80-90
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Journal article (peer-reviewed)abstract
- A meta-analytic technique was used to estimate the survival of implants supporting bridges or single crowns in partially edentulous patients. A survey of the literature revealed 66 studies, published between 1986 and 1996. Nine studies on single implants and 10 studies on fixed partial dentures met the inclusion criteria for the meta-analysis. Data from a total of 2686 implants, 570 single crowns (SC) and 2116 in fixed partial dentures (FPD), were analyzed. In order to calculate annual survival rates for individual studies a life-table analysis was conducted. Maximum follow-up time ranged between 1 and 8 years. After 1 year the success rate was calculated to be at least 85.7% for FPD and 97.2% for SC. When the results from the FPD studies were pooled the survival rate was 93.6% after 6-7 years. The corresponding value for SC was 97.5%.
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| 24. |
- Lindh, T, et al.
(author)
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Tooth-implant supported fixed prostheses : A retrospective multicenter study
- 2001
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In: International Journal of Prosthodontics. - 0893-2174 .- 1139-9791. ; 14:4, s. 321-328
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Journal article (peer-reviewed)abstract
- Purpose: The purpose of this retrospective multicenter study on implants combined with natural teeth was to investigate the implant survival rate and loss of marginal bone, as well as indications and complications pertinent to this form of implant therapy. Materials and Methods: The study comprised 185 implants in 111 patients from six different clinics in Sweden. Gathering of data, which were taken from patient records, followed a strict protocol. The registrations included indications for treatment, failure of implants, radiographs from baseline and follow-up, and information on complications. Results: The cumulative implant survival was found to be 95.4% (standard error 4.5%) up to 3 years of follow-up. The marginal bone level at baseline was lower in the maxilla compared with the mandible (P = .015), but any further loss did not differ between the jaws. The most severe complication other than loss of osseointegration (6/185) or periimplant infections (4/183) was intrusion of the abutment teeth, which occurred in 5% of the cases. In all instances, the intrusion was seen in constructions with nonrigid forms of connection between the implants and teeth. Conclusion: The tooth-implant supported prosthesis using the Branemark system is in the short term an equally predictable treatment as the completely implant-supported prosthesis concerning implant survival and loss of marginal bone. When combining implants and teeth, a rigid form of connection should be used to prevent tooth intrusion.
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Wu, D.J., et al.
(author)
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An analytical solution of finite‐amplitude solitary kinetic Alfvén waves
- 1995
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 2, s. 4476-4481
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Journal article (peer-reviewed)abstract
- An analytical solution of finite-amplitude solitary kinetic Alfven waves (SKAWs) in a low-beta (beta much less than m(e)/m(i) much less than 1) plasma is presented. This solution has been compared with the solution of the Korteweg-de Vries (KdV) equation in the small-amplitude limit. It is found that the KdV soliton solution is valid only for the maximum relative density perturbation N-m<0.1. For the larger N-m, the exact analytical solution shows that the SKAWs have a much wider structure and much stronger perturbed fields than the KdV solitons with the same N-m. Moreover, the relations between the width and the amplitude of SKAWs are also considerably different from that of the KdV solitons. In addition the possibility for applying these results to some events observed from the Freja scientific satellite is discussed. (The Freja is a Swedish-German scientific project for the investigation of ionospheric and magnetospheric plasmas, and the Freja satellite was launched on a Long-March II rocket of China on October 6, 1992.) (C) 1995 American Institute of Physics.
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| 29. |
- Wu, D J, et al.
(author)
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Coupling Alfvenic and ion-acoustic solitons
- 1996
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In: Chinese Physics Letters. - 0256-307X .- 1741-3540. ; 13, s. 594-597
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Journal article (peer-reviewed)abstract
- An exact nonlinear equation governing the coupling Alfvenic aad ion-acoustic solitons and criterion for their existence are presented. For the case of low-beta plasmas. the two modes decouple. In the small amplitude limit, the analytical results lead to KdV solitons.
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| 30. |
- Wu, D J, et al.
(author)
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Solitary kinetic Alfven waves in the two-fluid model
- 1996
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 3, s. 2879-2884
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Journal article (peer-reviewed)abstract
- Employing the two-fluid model, a generalized Sagdeev equation governing solitary kinetic Alfven waves (SKAWs) and the criterion for the existence of SKAWs, which are valid for different ranges of plasma pressure parameter beta, are presented. In the limit cases of beta much greater than m(e)/m(i) and beta much less than m(e)/m(i), the present results correspond, respectively, with conclusions obtained by Hasegawa ct al. [Phys. Rev. Lett. 37, 690 (1976)] and by Shukla et al. [J. Plasma Phys. 28, 125 (1982)], that is, SKAWs accompanied by, respectively, hump and dip density solitons for beta much greater than m(e)/m(i) and beta much less than m(e)/m(i). However, for the case of beta similar to m(e)/m(i), the present results show that SKAWs accompanied by both hump and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying these results to electromagnetic spikes observed by the Freja scientific satellite is discussed [detailed information about the Freja satellite experiments can be found in serial papers presented in Space Sci. Rev. 70, Nos. 3/4 (1994)]. (C) 1996 American Institute of Physics.
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