PubMed Health⌕ Search

Biomedical subjects

A J Coates

Publications and source records attributed to A J Coates.

8 recordsLinked to original sources
PubMed2006

The interaction of the atmosphere of Enceladus with Saturn's plasma.

During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 x 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 x 10(27) H(2)O molecules per second) is inferred.

Atmosphere↗
PubMed2006

Plasma acceleration above martian magnetic anomalies.

Auroras are caused by accelerated charged particles precipitating along magnetic field lines into a planetary atmosphere, the auroral brightness being roughly proportional to the precipitating particle energy flux. The Analyzer of Space Plasma and Energetic Atoms experiment on the Mars Express spacecraft has made a detailed study of acceleration processes on the nightside of Mars. We observed accelerated electrons and ions in the deep nightside high-altitude region of Mars that map geographically to interface/cleft regions associated with martian crustal magnetization regions. By integrating electron and ion acceleration energy down to the upper atmosphere, we saw energy fluxes in the range of 1 to 50 milliwatts per square meter per second. These conditions are similar to those producing bright discrete auroras above Earth. Discrete auroras at Mars are therefore expected to be associated with plasma acceleration in diverging magnetic flux tubes above crustal magnetization regions, the auroras being distributed geographically in a complex pattern by the many multipole magnetic field lines extending into space.

Journal Article↗
PubMed2005

Composition and dynamics of plasma in Saturn's magnetosphere.

During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.

Atmosphere↗
PubMed2005

Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae.

The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.

Journal Article↗
PubMed2000

Usage of denture adhesives.

OBJECTIVES: There have been few reports in the dental literature on the number of denture wearers who regularly use denture adhesive. The objectives of this study were to see what the incidence of usage of denture adhesive was by a surveyed edentulous population, to determine the degree of success of its usage and the reasons for its current use or nonuse. METHODS: In this study, 146 patients attending the Adelaide Dental Hospital for denture treatment were surveyed regarding their usage of denture adhesive, using a prepared questionnaire. The surveyed group was divided into three categories--those who had never tried denture adhesive, those who had tried denture adhesive but no longer used it, and those who currently used denture adhesive. RESULTS: In the survey, there were 52 males (35.6%) and 94 females (64.4%) and 96 (65.7%) were over 60 years of age. Of these 78 patients (54.9%) had worn their dentures for 10 years or more, and 26 (17.8%) for 20 years or more. A total of 98 patients (67.1%) had never tried denture adhesive: 48 patients (32.9%) had tried denture adhesive but only 10 (6.9%) currently used it. Various reasons for trying denture adhesive and for its continued use or nonuse were given. CONCLUSIONS: In this study, 52% of patients surveyed saw no need for the use of denture adhesive as they managed their dentures well; 20.5% of patients did not know that denture adhesives existed; and 32.9% had tried denture adhesive but only 6.9% continued to use it on a regular basis.

Adhesives↗
PubMed1996

Removable prosthodontics: a survey of practices and attitudes among South Australian dentists.

All dentists registered in South Australia were surveyed in July 1993 in relation to removable prosthodontics. The replies indicated that removable prosthodontics constituted a significant part of most dental practices. Most dentists felt that removable prosthodontics should be an essential part of the undergraduate curriculum. They felt that more expertise is now required to manage the treatment of the ageing population with either their first or replacement removable prostheses. The majority of dentists felt that their own undergraduate training had equipped them well to manage removable prosthodontic treatment for their patients; however, many helpful suggestions were made on areas that they thought required more emphasis.

Adult↗
PubMed1995

Denture adhesives: a review.

This review article explores the current status of denture adhesives. Their many uses are discussed with the philosophy of their use and their disadvantages and contra-indications. With an increase in the number of elderly edentulous patients, there is likely to be a greater demand for denture adhesives. Dentists will need to be more aware of the need to prescribe denture adhesives and manufacturers are encouraged to improve commercially available products.

Adhesives↗