Cattle, crops and clearing: Regional drivers of landscape change in the Brigalow Belt, Queensland, Australia, 1840–2004

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the current knowledge of the underlying drivers of landscape change, a conceptual framework of regional landscape change was developed which integrated population, economic and cultural values, policy and science/technology. Using the Southern Brigalow Belt biogeographic region of Queensland as a case study, the role of natural and human drivers in landscape change was investigated in four phases of settlement since 1840. The Brigalow Belt has experienced comparable rates of vegetation clearance over the past 50 years to areas of tropical deforestation. Economic factors were important during all phases of development, but the five regional drivers often acted in synergy. Environmental constraints played a significant role in slowing rates of change. Temporal trends of deforestation followed a sigmoidal curve, with initial slow change accelerating though the middle phases then slowing in recent times. Future landscape management needs to take account of the influence of all the components of the conceptual framework, at a range of organisational levels, if more ecologically sustainable outcomes are to be achieved.     

Molecular basis of the constitutive activity and STI571 resistance of Asp816Val mutant KIT receptor tyrosine kinase

The receptor tyrosine kinase, KIT, displays activating mutations in the kinase domain, which are associated with various cancers. We have used homology modelling based on the crystal structures of the insulin receptor kinase in active and inactive conformations to predict the corresponding structures of the KIT kinase domain. We have prepared four KIT models, one each for the active and inactive conformations of the wild-type and of the Asp816Val mutant proteins. We have also placed ATP into the active conformations and the inhibitor, STI571, into the inactive conformations. All models have been fully energy minimised. The molecular modelling studies described here explain (i) why Asp816Val KIT is constitutively active, (ii) why the nature of the substituting amino acid at residue 816 is relatively unimportant, and (iii) why the Asp816Val substitution confers resistance to the KIT-inhibitory drug STI571. The models will be valuable for predicting other kinase inhibitory drugs that may be active on wild-type and mutant forms of KIT. During the course of this work, a crystal structure of the active conformation of the KIT kinase domain has been published. Our model of the active conformation of the Asp816Val mutant is strikingly similar to this crystal structure, whereas our model of the active conformation of the wild-type kinase domain of KIT differs from the crystal structure in some respects. The reasons for this apparent discrepancy are discussed.     

A fast, digitally controlled flow proportional gas injection system for studies in lung function

The aim of this paper is to describe a device for flow proportional injection of tracer gas in the lungs of mechanically ventilated patients. This device may then be used for the study of the multiple breath indicator gas washout technique to determine the end-expiratory lung volume. Such a tracer gas injection device may also be used in the study of other techniques that rely on uptake and elimination of tracer gas by the lungs. In this paper, an injector is described which enables injection of indicator gas at a predetermined concentration in a breathing circuit independent of the type of breathing. The presented setup uses a control computer to produce steering signals to a multivalve array in proportion to the input breathing signals. The multivalve array consists of ten circular valves, each with a different diameter, which can be opened or closed individually according to the input signal of the array. By opening of a certain combination of valves an amount of sulphur hexafluoride gas proportional to the inspiratory breathing signal is released. The rate of transmission between the components of the injection system was 80 Hz. The injector has a full flow range between 0-10 L/min. The delay time between the breathing signal and the flow response was 70 ms. The aimed washin gas concentration of 1% SF6 was achieved after 0.5 s. The study describes the results of tests to determine valve-flow ratios, step response and dynamic response of the injector. The flow output response of the injector system was shown to increase in input frequencies above 3 Hz. The valve flow ratios showed the largest relative deviation in the two smallest valves of the 10 valve array, respectively 0.005 L/min (25%) and 0.002 L/min (20%). We conclude that the injector can achieve a stable concentration of indicator gas in a breathing system with an accuracy of 0.005 L/min to execute the multiple breath indicator washout test in human subjects. The results of the study indicate that the injector may be of use in other application fields in respiratory physiology in which breathing circuit injection of indicator gas is required.     

High density hydrophilic and hydrophobic brush coatings using a polymeric primer layer

Polymer brush coatings, consisting of polymer chains covalently attached to a surface and being less than a hundred nanometer thick, allow the creation of functional surfaces without altering the inherent bulk properties or appearance of a product. Surface properties depend on the type and length of the polymer used, as well as on the grafting density of the polymer brush. By making use of a polymeric primer layer that is covalently linked to the substrate and creates a uniform and highly functionalized surface, polymer brush coatings with high grafting densities can be created. In this paper we report the preparation of hydrophilic as well as hydrophobic brush coatings on different substrates through the use of a poly(acrylic acid) primer layer. In addition, hydrophilic poly(ethylene glycol) brush coatings thus produced were shown to decrease adhesion of marine bacteria.     

Design of a magnetic spectrograph for surface, interface and thin-layer analysis

The design of a magnetic spectrograph of the QDQ type, to be coupled to a 6 MV Van de Graaff accelerator for the analysis with Rutherford backscattering and recoil spectroscopy of surfaces and thin layers, will be shown. Due to the high energy resolution of. the instrument (ΔE/E ≈ 2 × 10⁻⁴) the depth resolution is determined mainly by energy straggling and the combined effect of angular and lateral straggling, and is close to l monolayer near the surface. The mass discrimination of the spectrograph in combination with the energy dispersion of the detector in the focal plane makes possible the background-free detection of light (¹H−¹⁹F) atoms recoiling from a heavier substrate. The design of the total setup is such that channeling and channeling plus blocking experiments can be carried out, so that the position of light (or heavy) atoms on or in monocrystalline samples can be measured. The detector in the focal plane is position-sensitive in two dimensions so that with one setting of the spectrograph an energy range of 2% and an angular distribution of 5° (with a resolution of 0.1°) can be measured simultaneously. The opening angle in the energy-dispersive direction is 0.1°. The whole spectrograph, including the scattering chamber, can be rotated over 120° with respect to the beam line. For this purpose a bellows construction is made between the beam line and the scattering chamber, permitting the rotation while maintaining a vacuum of ≈ 10⁻¹⁰ Torr in the chamber.     

Immunological Properties of Inulin-Type Fructans

Beneficial effects of inulin-type fructans are discussed in view of studies that applied the oligosaccharides in colon cancer, chronic inflammatory diseases, vaccination efficacy, and prevention of infection and allergy. In the present paper, we discuss their immunomodulating effects. It is suggested that immunomodulation is elicited through indirect and direct mechanisms. Indirect mechanisms encompass stimulation of growth and activity of lactic acid bacteria, but can also be caused by fermentation products of these bacteria, i.e., short chain fatty acids. Evidence for direct effects on the immune system generally remains to be confirmed. It is suggested that inulin-type fructans can be detected by gut dendritic cells (DCs), through receptor ligation of pathogen recognition receptors (PRRs) such as Toll-like receptors, nucleotide oligomerization domain containing proteins (NODs), C-type lectin receptors, and galectins, eventually inducing pro- and anti-inflammatory cytokines. DCs may also exert antigen presenting capacity toward effector cells, such as B cells, T cells, and natural killer cells locally, or in the spleen. Inulin-type fructans may also ligate PRRs expressed on gut epithelium, which could influence its barrier function. Inulin-type fructans are potent immunomodulating food components that hold many promises for prevention of disease. However, more studies into the mechanisms, dose-effect relations, and structure-function studies are required.     

How do gait frequency and serum-replacement interval affect polyethylene wear in knee-wear simulator tests?

Polyethylene wear (PE) is known to be a limiting factor in total joint replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed: (a) Bovine serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does serum-replacement interval affect the wear rate of total knee replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one replacement interval. The ISO standard should be revised to address the marked effects of lubricant replacement interval on wear rate.