Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays

Average charged multiplicities have been measured separately in $b$, $c$ and light quark ($u,d,s$) events from $Z^0$ decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of $b$ and light quark events, and reconstructed charmed mesons were used to select $c$ quark events. We measured the charged multiplicities: $\bar{n}_{uds} = 20.21 \pm 0.10 (\rm{stat.})\pm 0.22(\rm{syst.})$, $\bar{n}_{c} = 21.28 \pm 0.46(\rm{stat.}) ^{+0.41}_{-0.36}(\rm{syst.})$ $\bar{n}_{b} = 23.14 \pm 0.10(\rm{stat.}) ^{+0.38}_{-0.37}(\rm{syst.})$, from which we derived the differences between the total average charged multiplicities of $c$ or $b$ quark events and light quark events: $\Delta \bar{n}_c = 1.07 \pm 0.47(\rm{stat.})^{+0.36}_{-0.30}(\rm{syst.})$ and $\Delta \bar{n}_b = 2.93 \pm 0.14(\rm{stat.})^{+0.30}_{-0.29}(\rm{syst.})$. We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters

Pattern in the simple moss-turf communities of the sub-Antarctic and maritime Antarctic

(1) Grids of 1500 (300 × 5) 2 × 2 cm quadrats have been recorded on three moss-turf sites: South Georgia in the Sub-Antarctic (three dominant species), and in the maritime Antarctic on Signy Island (two dominant species) and on Galindez Island (a virtual monoculture of Polytrichum alpestre). (2) Two methods of pattern analysis, the stepped blocked quadrats variance method and the two-term local quadrat variance method, have been used on all data. It is stressed that there is as yet no satisfactory technique for exploring pattern in belt transects. (3) It is suggested that the pattern in the simplest of these communities, Galindez Island, is due to the alternation of mossy areas, or hummocks, and bare ground. (4) At Signy Island there is a well developed pattern, with two scales of heterogeneity at about 20 cm and at 1.2-2.0 m. The latter is considered to be due to the history of vegetation development, which is determined by the distribution of rocks now beneath the surface of the moss carpet. (5) The South Georgia community has two scales of pattern similar to those on Signy Island, but the factors determining them are unknown. In this three-species community both positive and negative associations are indicated. (6) On all sites, virtually all analyses indicated a small scale of pattern at about 20 cm. It is considered that this scale is important when sampling both the vegetation and the animal communities living within the moss-turf communities

Analytical Population Dynamics

xii,371 hal,;ill,;23 c

Arthropod communities in a maritime Antarctic moss-turf habitat: multiple scales of pattern in the mites and collembola

(1) A sampling programme has been designed to detect whether multiple scales of pattern (or aggregation) occur in arthropod distributions. A secondary aim was to relate arthropod pattern with environmental pattern. (2) Two transects, each of thirty-six contiguous cores, were cut from a moss-turf habitat on Signy Island in the maritime Antarctic. The analyses concentrate on six taxa of arthropods, two species of moss, and two environmental variables. (3) The Collembolan Cryptopygus showed two scales of pattern, at about 10 and 60 cm, in the surface layer of the moss-turf. Another Collembolan, Friesea, which occurs deeper in the moss-turf, only showed a single scale of pattern, at 5 cm. There was no small scale pattern in the predatory mite Gamasellus. The three prostigmatid mite taxa, Ereynetes, Eupodes and Nanorchestes, all had distinct patterns, usually with a scale less than 30-40 cm. (4) Small scale pattern in Polytrichum moss occurred at 10-20 cm, though the scales were slightly larger (up to 30 cm) in Chorisodontium moss and the lichens. Analysis of water content and dry weight data indicated trends along the transects as well as a variety of smaller scale patterns. (5) An analysis for different spatial scales indicated that the correlation between numbers of arthropods and environmental variables was important at large scales (40-50 cm and over), whereas correlation at smaller scales (5-20 cm) was generally associated with the relationships between the species themselves. (6) It is concluded that multiple scales of pattern occur in the distribution of most arthropod species of this Antarctic site. However, randomness of distribution tends to be the norm for the predator, Gamasellus

Laboratory studies of predation by the Antarctic mite Gamasellus racovitzai (Acarina: Mesostigmata)

Laboratory investigations of predation by Gamasellus racovitzai (Acarina: Mesostigmata) on Cryptopygus antarcticus (Insecta: Collembola) are described. The predator appeared to search at random, but, when contact with prey had been made, a rapid attack involved looping the forelegs over the prey to hold it whilst the chelicerae moved forward horizontally to puncture the side of the prey. The mean predation rate by deutonymphs, approximately one prey per predator per 12 days, was independent of prey density, but with adults this rate increased to about one prey per predator per 3 days. A study of leg geometry predicted a maximum prey size that could be captured: some experimental evidence suggested that mites selected prey near to this predicted size. The contribution of the laboratory results towards understanding the dynamics of field populations is discussed

The Antarctic predatory mite Gamasellus racovitzai (Trouessart) (Mesostigmata) - A morphometric study of two subspecies

57 morphological characters were scored on a sample of 46 male and 55 characters on a sample of 40 female Gamasellus racovitzai, which had been collected from 10 localities in the maritime Antarctic. A lectotype of G. racovitzai, selected from the collection studied by TROUESSART, is designated. The same morphological characters have been scored for the lectotype and for the holotype of G. r. neo-orcadensis. Principal co-ordinates analysis indicates that there is a morphological separation between specimens of G. racovitzai from the South Orkney Islands and from elsewhere in the maritime Antarctic. Since LISTER (1984a) also found esterase differences, it is concluded that two subspecies of G. racovitzai should be recognised. The nominate subspecies is distributed along the Antarctic Peninsula, its offshore islands, and the South Shetland Islands, whilst subspecies neo-orcadensis is restricted to the South Orkney Island. G. r. neoorcadensis is redefine