The analysis of the NSW wheat variety database. I. Modelling trial error variance

The retrospective analysis of a large database on wheat variety testing in New South Wales (NSW) is considered. This analysis involved three key steps. Initially error variance heterogeneity is modelled, indicating significant differences in error variance due to trial location, year of trialling, sowing date and trial mean yield. The implication of this modelling for the estimaion of variance components is discussed.     

The Probability Distribution of the Amount of an Individual''s Genome Surviving to the following Generation

The probability that at least p% of an individual's genome is passed on collectively to his children is calculated. With data availability the consideration of the chromosome as a whole rather than discrete loci becomes of increasing practical importance. Assuming the genomic continuum model, which allows for recombination, the crossover process in a chromosome pedigree is viewed as a continuous-time Markov random walk on the vertices of a hypercube with time parameter map distance along the chromosome. The desired probability corresponds to the probability of sojourn times of the process in a small set of vertices, which are well approximated via the Poisson clumping heuristic. Results are given for the human genome. It is very likely that an individual with at least four children passes on at least 90% of his genome. There exists no ``equivalent' number of independently segregating loci for this distribution.     

Fluoranthene as a model toxicant in sediment studies with Chironomus riparius

The bioavailability of fluoranthene (as a model toxicant) in freshwater sediment tests with Chironomus riparius was investigated in relation to the partitioning of the chemical between water and sediment. Effects on survival and successful development of newly hatched larvae through to adult emergence were measured over a range of sediment concentrations. Radiolabelled fluoranthene was employed to enable sediment, aqueous and tissue concentrations to be determined. A significant effect on emergence was obtained at a measured sediment concentration of 80 mg kg^-1 (dry weight). The measured concentration in the overlying water was 88 g l^-1. Although effects at 170 mg kg^-1 (dry weight) were more severe, the measured concentration in the overlying water was similar (89 g l^-1), probably reflecting the approach towards the solubility limit. Bioaccumulation of fluoranthene, determined by analysis of emerging adults, was approximately proportional to the sediment concentration. Although the aqueous phase concentration appeared to be the principal factor controlling bioavailability, the increasing toxicity, when water concentrations had reached a plateau, suggested that other mechanisms may also be involved. Different sediment spiking procedures resulted in broadly similar partitioning of the chemical between the sediment and the overlying water. There were only minor differences in toxicity between the procedures, two of which allowed the carrier solvent used for spiking to be eliminated before addition of the test organisms. It was concluded that, for most purposes, all four procedures were equally acceptable, and by retaining a flexible approach, even for standardised regulatory tests, spiking procedures may be tailored to the physico-chemical properties of the test material.     

The effects of tail autotomy on survivorship and body growth of Uta stansburiana under conditions of high mortality

We examined the effects of tail autotomy on survivorship and body growth of both adult and juvenile Uta stansburiana by directly manipulating tail condition. Tail loss decreased neither survivorship nor rate of body growth for individuals in two natural populations. Lack of an influence of tail loss on survivorship in these two populations may be the result of high mortality. Under high mortality any differential effects of tail loss will be lower than in populations facing lower mortality. Growth experiments in the laboratory demonstrated that, under conditions of minimal environmental variation and social interactions, there is no tradeoff between body growth and tail regeneration as has been suggested for other species of lizards. One possible reason for this difference is that U. stansburiana does not use the tail as a storage organ for lipids. The original and regenerated tails are composed mainly of protein. In general, any differential body growth between tailed and tailless individuals may be due to social interactions and not a diversion of limited energy into tail regeneration.     

Roles of novobiocin-sensitive topoisomerases in chloroplast DNA replication in Chlamydomonas reinhardtii.

We have examined DNA replication in Chlamydomonas reinhardtii chloroplasts in vivo when chloroplast type II topoisomerases are inactivated with sublethal doses of novobiocin. DNA replication is at first inhibited under these conditions. However, after a delay of several hours, chloroplast chromosomes initiate a novobiocin-insensitive mode of DNA replication. This replication starts preferentially near a hotspot of recombination in the large inverted repeats, instead of from the normal chloroplast origins, oriA and oriB. It replicates one, but not the other single-copy region of the chloroplast chromosome. We speculate that novobiocin-insensitive DNA replication in chloroplasts requires recombination in this preferred initiation region.     

Medical direction and control of emergency medical services in Canada.

OBJECTIVE: To determine the level of physician involvement in prehospital emergency medical services (EMS) in Canada, as compared with published principles of medical control and direction. DESIGN: Mail and telephone survey by means of a questionnaire from March to November 1991. SETTING: All Canadian provinces and territories. PARTICIPANTS: Fifty-six key prehospital EMS physicians, senior government administrators and senior representatives of the agencies responsible for licensing physicians in each province or territory. MAIN OUTCOME MEASURES: Responses to questions regarding the legislation, organization, administration, practice and regulation of medical direction and control by physicians in each province or territory. RESULTS: EMS legislation describing medical direction and control was completely lacking in five provinces and both territories and was incomplete in the remainder. Provincial guidelines written by physicians for prehospital patient care were present in only four provinces. Formal organization of medical directors varied from none to partially remunerated networks. Regional medical-director systems were present in three provinces, and local medical directors were required for all communities in three. Most rural ambulance services were found to engage physicians only when there was local interest. CONCLUSIONS: The level of physician involvement in the medical direction and control of EMS appears to be inconsistent across Canada and insufficient in most jurisdictions, as compared with accepted principles.