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M A Slade

Publications and source records attributed to M A Slade.

3 recordsLinked to original sources

Binary asteroids in the near-Earth object population.

Radar images of near-Earth asteroid 2000 DP107 show that it is composed of an approximately 800-meter-diameter primary and an approximately 300-meter-diameter secondary revolving around their common center of mass. The orbital period of 1.755 +/- 0.007 days and semimajor axis of 2620 +/- 160 meters constrain the total mass of the system to 4.6 +/- 0.5 x 10(11) kilograms and the bulk density of the primary to 1.7 +/- 1.1 grams per cubic centimeter. This system and other binary near-Earth asteroids have spheroidal primaries spinning near the breakup point for strengthless bodies, suggesting that the binaries formed by spin-up and fission, probably as a result of tidal disruption during close planetary encounters. About 16% of near-Earth asteroids larger than 200 meters in diameter may be binary systems.

Journal Article↗

Topography of the lunar poles from radar interferometry: a survey of cold trap locations.

Detailed topographic maps of the lunar poles have been obtained by Earth-based radar interferometry with the 3.5-centimeter wavelength Goldstone Solar System Radar. The interferometer provided maps 300 kilometers by 1000 kilometers of both polar regions at 150-meter spatial resolution and 50-meter height resolution. Using ray tracing, these digital elevation models were used to locate regions that are in permanent shadow from solar illumination and may harbor ice deposits. Estimates of the total extent of shadowed areas poleward of 87.5 degrees latitude are 1030 and 2550 square kilometers for the north and south poles, respectively.

Ice↗

Response to hepatitis B vaccination in a primary care setting: influence of HIV infection, CD4+ lymphocyte count and vaccination schedule.

Factors affecting the response to hepatitis B vaccination in a primary care setting were examined by means of a review of case notes of patients attending 22 sexually transmissible disease services. Where not available from the notes, presence of antibody to hepatitis B surface antigen (anti-HBs) was determined by testing available stored serum. One hundred and ninety-five patients completed a course of 3 injections and had an anti-HBs assay performed. The highest response rate (anti-HBs > or = 10 IU/L) was found in human immunodeficiency virus (HIV)-negative heterosexual women (16 of 17, 94.1%) followed by HIV-negative heterosexual men (11 of 12, 91.7%); HIV-negative homosexual men (105 of 120, 87.5%); and HIV-positive homosexual men (6 of 14, 42.9%). (For HIV-positive vs HIV-negative homosexual men, P = 0.0003). Eleven of 14 (78.6%) homosexual men of unknown HIV status responded to vaccination. There was a trend to lower CD4+ lymphocyte counts among HIV-infected patients who responded to hepatitis B vaccination (mean 482 cells/cm2) when compared to those that did not respond (632 cells) but this difference was not statistically significant (P = 0.330). Neither the type of vaccine (recombinant, plasma-derived or mixed) nor the length of vaccination course (mean 6.2 months; range 2 to 18) affected response. This study confirmed that vaccination against hepatitis B is much less effective in HIV-infected homosexual men and marginally less effective for HIV-negative homosexual men, though the mechanism for this reduced response is uncertain. Reassuringly vaccine response was not affected by common variables in primary care settings such as vaccine type or delays in the vaccine schedule.

Adult↗