A 0.6 Mpc H I structure associated with Stephan's Quintet.

Stephan's Quintet (SQ, co-moving radial distance = 85 ± 6 Mpc, taken from the NASA/IPAC Extragalactic Database (NED)1) is unique among compact groups of galaxies2-12. Observations have previously shown that interactions between multiple members, including a high-speed intruder galaxy currently colliding into the intragroup medium, have probably generated tidal debris in the form of multiple gaseous and stellar filaments6,8,13, the formation of tidal dwarfs7,14,15 and intragroup-medium starbursts16, as well as widespread intergalactic shocked gas5,10,11,17. The details and timing of the interactions and collisions remain poorly understood because of their multiple nature18,19. Here we report atomic hydrogen (H I) observations in the vicinity of SQ with a smoothed sensitivity of 1σ = 4.2 × 1016 cm-2 per channel (velocity bin-width Δv = 20 km s-1; angular resolution = 4'), which are about two orders of magnitude deeper than previous observations8,13,20,21. The data show a large H I structure (with linear scale of around 0.6 Mpc) encompassing an extended source of size approximately 0.4 Mpc associated with the debris field and a curved diffuse feature of length around 0.5 Mpc attached to the south edge of the extended source. The diffuse feature was probably produced by tidal interactions in early stages of the formation of SQ (>1 Gyr ago), although it is not clear how the low-density H I gas (NH i ≲ 1018 cm-2) can survive the ionization by the intergalactic ultraviolet background on such a long time scale. Our observations require a rethinking of properties of gas in outer parts of galaxy groups and demand complex modelling of different phases of the intragroup medium in simulations of group formation.

Enzyme amplified immunoassay: a novel technique applied to direct detection of Chlamydia trachomatis in clinical specimens.

Endocervical swabs from 212 women and urethral swabs from 100 men were tested by the routine methods for McCoy cell culture and simultaneously by a novel enzyme amplified immunoassay test to detect chlamydia antigen. Overall correlation of the amplified test with culture was 96.5%. The test proved to be a suitable screening procedure for genital chlamydial infection, particularly for large numbers of specimens or in cases in which culture was not available.

Legionnaires' disease in Nottingham, England.

Legionnaires' disease bacterium was identified as the cause of severe pneumonia in some Nottingham, England, patients in 1977. Laboratory studies were not restricted to Nottingham but included several other areas in England. The 41 cases identified were evenly divided between areas; they also accounted for about one half of all cases for the entire country. No source of infection has been identified in these sporadic cases. There was no contact between patients, and only a few had travelled abroad before their illnesses. Serologic sampling of populations in Nottingham did not reveal a large background of infection. Only 31 of 2023 sera tested had low titer antibody to the Pontiac antigen used. Guinea-pig antisera to two positive lung extracts showed an antigenic relation to the Pontiac but not to the Togus strain,suggesting strain variation.

Comparison of radial haemolysis with haemagglutination inhibition in estimating rubella antibody.

Radial haemolysis (RH) for assaying rubella antibody was studied in parallel tests with haemagglutination-inhibition (HAI) on 1102 sera from adult women. Simple to perform and economical in reagents, the RH test is as sensitive as the HAI test and is a useful method of screening antenatal and other sera for rubella immunity. It detects IgG but not IgM antibody.