Journal and Proceedings of
The Royal Society of New South Wales
Volume 133 Parts 3 and 4
Funeral Arrangements for Plants: An Essay in Organic Geochemistry
The 32nd Liversidge Research Lecture
Wilson, M.A., Kannangara, G.S. Kamali & Smeulders, D.E.
Abstract: Organic geochemistry literally is the dead end of science since it is concerned with the transformation of decaying plant material into humic substances, coal, petroleum and natural gas. The transformation process is primarily controlled by the possible degree of oxidation. Under reducing conditions coal and gas are formed and under oxidising conditions humic material is formed. Not surprisingly, the nature of the input vegetation also has an effect on the type of decomposed organic matter produced. One new finding for oxidising environments, reported here, is the concept of a host-guest structures where smaller molecules reside within a framework of a macromolecular host primarily derived from lignin. The guests within the host cannot be removed by physical separation. The structure of the host can be determined by pyrolysis gas chromatography mass spectrometry and nuclear magnetic resonance techniques. Differential thermal analysis, methylation and gas chromatography mass spectrometry and nuclear magnetic resonance data can be used to identify the guests. Some of the guests are probably held by hydrogen bonding but others are true prisoners in that they are alkanes and hence have no binding sites.
Keywords: Humic substances, Host-guest theory, COSY NMR, Differential thermal analysis
Minerals of the Queen Sally Mine, North-west Queensland
Munro-Smith, V., Ramsden, A.R., Sharpe, J.L. & Williams, P.A.
Abstract
The Queen Sally deposit is located near Kajabbi, north-west Queensland. Primary
cobalt mineralization comprises cobaltite and glaucodot, an assemblage that is
consistent with a hydrothermal origin, possibly associated with the emplacement
of the nearby Naraku granite. Oxidized cobalt mineralization consists of
cobaltian calcite, erythrite and heterogenite-2H, which is unusual in that it
carries up to 2.2% by weight of vanadium. Oxidation of V3+ in the
lattice to V4+ may explain an early report of "blue"
erythrite in the
oxidized zone of the deposit.
ABSTRACTS OF THESES
Physical Activity, the IGF-I Axis, and Body Composition in 55 to 75 Year-old Women
Ross D. Hansen
Abstract of a Thesis Submitted for the Degree of Doctor of Philosophy, University of Sydney, New South Wales, Australia.
Similar effects of human growth hormone (GH) deficiency and ageing on body composition suggest that age-related losses of bone and muscle mass and fat accumulation may be caused by reduced GH secretion.
The anabolic effects of GH are partly mediated by insulin-like growth factor-I (IGF-I), released by the liver and other tissues in response to pituitary GH secretion. As both GH and IGF-I increase acutely with exercise, stimulation of the GH/IGF-I axis represents a means whereby regular physical activity can attenuate or reverse the effects of age on bone, muscle and fat. Studies investigating this have, however, produced conflicting findings, and information on postmenopausal women is scarce.
This cross-sectional study investigated the relationships between habitual physical activity, IGF-I bioavailability and body composition in 53 healthy postmenopausal women aged 55 to 75 years. A subgroup of 28 women receiving oestrogen replacement therapy were included, to describe interactions between oestrogen and IGF-I. Subjects underwent a multi-compartment body composition assessment to define water, protein, bone mineral, fat and muscle masses (Hansen et al, 1999). Habitual physical activity pattern was determined by a semi-structured interview. Fasting serum hormone levels (IGF-I, IGF binding protein-3, acid-labile sub-unit, and oestradiol) were determined by radio-immunoassay.
The subjects were representative of Caucasian women of the same age in regard to body composition, IGF-I status, and prevalence of habitual activity. Based on regular involvement in moderate to vigorous activity, the sample was stratified into high (n = 27) and low (n = 26) activity groups. The most common activities pursued were aerobic in nature, including walking, dancing, floor exercises and swimming. Significant (p<0.05) age-related declines were evident in bone, muscle, physical activity, and IGF-I axis parameters. There was some accumulation of central fat with advancing age. Protein, mineral and skeletal muscle fractions of fat-free mass showed an accelerated decline after 65 years of age. Although high activity subjects had relatively more bone and muscle, but less central adipose tissue, throughout the age range, they experienced similar overall rates of change with age to low activity subjects.
Multiple linear regression showed that advancing age, increased adiposity, and a high oestradiol level impacted negatively on IGF-I levels. Physical activity level was not a determinant of the IGF-I axis. As expected, oestradiol status and physical activity were both positive, independent predictors of bone mass. Adiposity was also a positive determinant of bone mass. Neither age nor IGF-I were predictors of bone parameters. Both age and physical activity were independent predictors of skeletal muscle mass, such that a highly active 70 year-old had on average the same skeletal muscle mass as a less active 56 year-old woman. However, IGF-I status was not related to muscle mass.
These data do not show a hypothesised positive relationship between habitual physical activity and serum IGF-I parameters, or between the IGF-I axis and body composition, in postmenopausal women. The most plausible explanation for this is that localised factors, such as target tissue production or modulation of IGF-I, are involved in mediating the effects of physical activity on bone and muscle.
The interaction between oestradiol and IGF-I supports previous claims of a biphasic influence of oestrogen on IGF-I, whereby moderate serum oestradiol levels can increase, but high oestradiol levels can depress, IGF-I axis activity. This phenomenon should be further investigated in a longitudinal study.
The study provides strong evidence that moderate intensity, aerobic type activities can contribute significantly to the maintenance of bone and muscle in postmenopausal women. Such activities are generally acceptable to older women, and the age range studied is known to be characterised by progressive declines in bone and muscle status, with accompanying frailty and loss of independence. These activities should therefore confer significant benefits in terms of what has been coined ``successful'' ageing (Hansen et al, 2000) - that is, maintaining a high degree of functionality and independence in the latter part of one's life.
References
Hansen R.D., Raja C., Aslani A., Smith R.C. and Allen B.J., 1999. Determination of skeletal muscle and fat-free mass by nuclear and dual-energy x-ray absorptiometry methods in men and women aged 51 to 84 years. American Journal of Clinical Nutrition, 70, 228--233.
Hansen R.D., Raja C.\ and Allen B.J., 2000. Total body protein in chronic diseases and in aging. Annals of the New York Academy of Sciences 904, 345--352.
Dr R.D. Hansen,
Gastrointestinal Investigation Unit (11E),
Royal North Shore Hospital,
Pacific Highway, St Leonards,
NSW, 2065
Australia
email: hansen@med.usyd.edu.au
(Manuscript received 9-11-2000)
Mathematical and Computer Modelling of the Human Brain with Reference to Cortical Magnification and Dipole Source Localisation in the Visual Cortex
Monica K. Hurdal
Abstract of Thesis Submitted for the Degree of Doctor of Philosophy, Queensland University of Technology, Brisbane, Queensland, Australia.
Mathematical and computer models are important tools that are available to investigate natural phenomena. They can be used to model many systems. In this thesis, mathematical models are developed, implemented and applied to research involving the human brain and in particular, the human visual cortex. The visual cortex constitutes a relatively large part of the cerebral cortex. It is often used in investigations of the human brain because conclusions regarding the visual cortex can be extended to other regions of the brain. Virtually all information from the visual system is recognised as first being processed by the primary visual cortex and is then passed to other regions of the brain involved in more complex processing.
The primary visual cortex has a retinoptic mapping in that one spot in the retinal visual field maps directly to a spot on the primary visual cortex. However, there is disagreement as to the amount of cortex that is allocated to the representation of central vision or other portions of the visual field. A mathematical formulation of this mapping is presented and mapping functions which transform the surface representing the retina to the surface representing the visual cortex are developed.
If the head is modelled as three concentric spherical shells and neural sources of brain activity are modelled as dipoles, then a mathematical model which incorporates biophysical properties can be used to estimate the location of sources which generate a set of electrical potentials measured on the surface of the scalp. This model is known as dipole source localisation. The forward problem, which is the predication of a potential distribution due to a given electrical source is implemented, and the inverse problem, which is to determine a dipole source that is the best generator of a given potential distribution is solved in the least squares sense. Monte Carlo simulations and mathematical analysis show that the optimum reference electrode to use in dipole analysis is a weighted version of the common average electrode. Monte Carlo simulations are also used to investigate the accuracy of confidence regions surrounding the estimated dipole parameters.
Subsequently, a methodology for modelling a region of cortex from magnetic resonance images is developed. This methodology is applied to the calcarine fissure and surrounding grey matter to produce a three dimensional surface reconstruction of the visual cortex. This model is used to provide anatomical constraints in the dipole source localisation model. These models are then applied to visual evoked potential data obtained from an experiment which uses a chromatic grating stimulus. Results reveal that these mathematical and computer models, combined with imaging and experimental approaches, elicit new information and improved results in investigations of the human brain.
Dr. Monica Hurdal,
Florida State University, Department of Mathematics,
Tallahassee FL, USA 32306-4510
email: mhurdal@math.fsu.edu
(Manuscript received 11.01.2000)
Tectonic Evolution of the Marlborough Region, South Island, New Zealand
Kao Ming-Hung
Abstract of Thesis Submitted for the degree of Doctor of Philosophy University of Waikato, New Zealand.
The tectonic evolution of the Marlborough region has been studied by application of fission track thermo-chronology and finite element (FE) methods. The region lying within the Australian-Pacific plate boundary zone is considered to have a transcurrent fault system, known as the Marlborough Faults System (MFS). The MFS is viewed as comprising secondary transforms connecting the Hikurangi subduction margin with the main Alpine Fault oblique-slip boundary. This fault system appears to have developed sequentially towards the southeast during the past 5 million years.
Based on the principles of rock mechanics and FE method, the numerical modelling results reveal that the accommodation percentage of total displacements in Marlborough is about 85% of the total plate motion. The contour of instantaneous displacements estimated by the FE modelling can be compared to the topography of Marlborough. According to the results of the FE modelling cases, the main conclusions drawn are:
- A curved fault (the Alpine Fault) resulted from a change in the plate motion vector.
- The development of the MFS reflects the continuation of tectonic rotations.
- Three secondary faults may have developed within a short period of one another.
- Uplift movements still continue.
- A pre-existing fault offset of the Alpine Fault is not a unique result in the FE modelling.
The extremely young fission track ages (<~10 Ma) in the vicinity of the Alpine Fault bend and Seaward Kaikoura Range coincide with the recent raid uplift/erosion in these areas. All the apatite ages indicate that the host rocks in Marlborough have experienced exposure to elevated temperatures in the zone of partial annealing for apatite, some of them having been reset. Except for the samples in the Marlborough Sounds region, zircon fission track ages are older than 119 Ma, reflecting that the host rocks of the samples have not experienced temperatures in the zircon partial annealing zone since the mid Cretaceous. Apatite fission track ages and mean lengths indicate that there are two major cooling events: one occurring from the early Miocene (~20 Ma) and the other in the mid Cretaceous (~100 Ma).
The largest amount of rock uplift (~11.5 km) occurs in the area of the Alpine Fault bend. The amounts of rock uplift and denudation derived from the fission track parameters are in the range 0.7-11.5 km and 0.6-11.0 km, respectively. In the Seaward Kaikoura Range, high elevation coincides with large amounts of denudation. Compared with the region of continent-continent convergence to the south in Canterbury, the amounts of rock uplift and denudation in Marlborough are relatively small, revealing the differences between a fully developed continent-continent collision zone and the continental transform setting in Marlborough.
The horizontal movements determined by the FE modelling can be converted into vertical movements. Both the FE modelling and fission track results show that the pattern of vertical deformation is consistent with the topography in Marlborough. The FE modelling and fission track results reveal the character of the tectonic evolution of Marlborough and are a step towards its quantification.
Ming-Hung Kao
182 Tramway Road
Hamilton
New Zealand
(Manuscript received 06.01.2000)