Window of opportunity: an episode of recruitment in a Banksia hybrid zone demonstrates continuing hybridization and phenotypic plasticity.

BACKGROUND AND AIMS: In perennial plants (especially post-fire resprouters), extant populations may reflect recruitment events in the distant past. This is true of hybrid zones formed by two Banksia species of swamps and woodlands in south-eastern Australia, Banksia robur and B. oblongifolia. Both resprout after fire but recruitment is dependent on periodic fires. Although plants of intermediate morphology have also been identified as hybrids using allozyme markers, the extent of ongoing hybridization is unknown. This study investigates whether both microsatellite markers and morphological measurements can be used to distinguish between the two species and their hybrids. A recent recruitment event and microsatellite markers allow the frequency of ongoing hybridization to be estimated, and also the effects of environmental variation on the morphology of plants and seedlings to be tested. METHODS: Variation at seven microsatellite loci was scored and seven leaf characteristics within putatively pure stands and mixed stands of both species were measured, revealing that the two species were genetically and morphologically distinct and that mixed stands also contained genetically and sometimes morphologically distinct hybrids. An opportunity created by wildfires was used to analyse the genetics and morphometrics of adults and seedlings from two hybrid zones. KEY RESULTS: Approximately 9 % of adults and 21 % of seedlings were identified as genetic hybrids in both hybrid zones. Within these sites, the genotype of mature plants correlated well with morphology, except for some hybrid plants that had parental morphology. However, seedling morphology was highly variable and insufficient to describe the composition of the hybrid zone in this cohort. Greater phenotypic plasticity was evident among seedlings growing within the hybrid zones than seedlings growing in pots. CONCLUSIONS: The hybrid zones are complex and the range of genotypes detected in seedlings reveals both continuing hybridization and introgression.

Magnetometry of low-dimensional electron and hole systems.

The high-magnetic-field, low-temperature magnetic properties of low-dimensional electron and hole systems reveal a wealth of fundamental information. Quantum oscillations of the thermodynamic equilibrium magnetization yield the total density of states, a central quantity in understanding the quantum Hall effect in 2D systems. The magnetization arising from non-equilibrium circulating currents reveals details, not accessible with traditional measurements, of the vanishingly small longitudinal resistance in the quantum Hall regime. We review how the technique of magnetometry has been applied to these systems, the most important discoveries that have been made, and their theoretical significance.

Thoracic epidural catheters via the caudal and lumbar approaches using styletted multiple port catheters in pediatric patients: a report of three cases.

Advancing catheters from the lumbar and caudal epidural spaces to the thoracic level has been reported to be an alternative to the direct thoracic approach. However, as children grow, the threading of catheters in the epidural space becomes increasingly difficult. This report describes three cases of thoracic epidural placement using a multiport catheter threaded from the caudal and lumbar spaces using electrical stimulation guidance. In the first case, a multiport catheter was threaded 22 cm from the lumbar space to T8 following a failed attempt with a single-port catheter in a 9-year-old boy scheduled to undergo a right nephrectomy. In the second case, a multiport catheter was threaded 26 cm from the caudal space to T9 in a 3-year-old girl undergoing fundoplication. In the last case, a multiport catheter was inserted at the completion of a fundoplication in a 2-year-old girl after it had been confirmed that the single-port catheter inserted prior to surgery had not advanced to the desired thoracic level. The multiport catheter was threaded 17 cm without resistance from the caudal space to T9. In all cases, electrical stimulation was used to confirm the location of the catheter tip at the time of insertion. The position of the catheters was later confirmed by X-ray. The multiport catheter incorporates a stylet, which extends to a closed distal tip, within a catheter body that ejects fluid from three lateral holes in a direction perpendicular to the advancing catheter. These properties may facilitate the reliable advancement of catheters in the epidural space.

An integrated approach to team assessment in head injury.

The development of multidisciplinary teams for the assessment and treatment of traumatic brain injury has not seen a parallel development in methods of coordinating and collating the information gathered by different professions. The team at the Head Injury Rehabilitation Centre (HIRC), Sheffield uses a process of assessment that encourages the coordination of such information, particularly across the areas that do not fall neatly into the remit of specific disciplines. The framework of the assessment is presented, together with discussion of methods of gathering information and of sharing that information. The advantages of this approach are discussed in terms of benefits for the client, for the professionals involved in the assessment and for other services that might be involved with the client.

After the forest. AIDs as ecological collapse in Thailand.

PIP: Numerous parallels can be drawn between the systematic destruction of Thailand's forests and the emergence, in the same time period, of acquired immunodeficiency syndrome (AIDS) as an irreversible societal crisis. Both the disintegration of the body's defense system implicit in AIDS and the erosion of Thailand's ecosystem provoked by deforestation policies are examples of assaults by capitalist economic policies on previously self-regulating systems. Centralization and industrial development have driven a substantial proportion of young Thai villagers to the cities, where they sell their labor as sex workers (there may be as many as 2 million prostitutes in Thailand) or become heroin users. Conservative estimates project 1.6 million AIDS-infected Thais by the end of 1995. Just as generally benign conditions such as the common cold can annihilate a body ravaged by the AIDS virus, Thailand's ecosystem, degraded by unregulated logging and state-subsidized, for-profit rubber planting, is no longer able to absorb natural occurrences such as heavy rainfall. The loss of forestland--the traditional source of food, shelter, tools, and medicine and the repository of cultural icons--has forced villagers to obtain cash to meet their needs, and Thailand's sex industry offers one of the highest rates of remuneration. Legislation enacted in response to AIDS and deforestation shares an emphasis on the victims (e.g., the prostitutes and not their clients or the owners of sex establishments, and impoverished forest squatters rather than plantation companies and land speculators). A powerful, combative environmental movement is successfully resisting government attempts to destroy living communities. Needed as well is resistance on the part of women growing up in the age of AIDS to societal definitions that polarize females (virgins and prostitutes) and uphold one-sided monogamy.^ieng