A method of analysing stream channel response to environmental change: gauge data for the Tully River

Gauging data are available from numerous streams throughout Australia, and these data provide a basis for historical analysis of geomorphic change in stream channels in response to both natural phenomena and human activities. We present a simple method for analysis of these data, and a briefcase study of an application to channel change in the Tully River, in the humid tropics of north Queensland. The analysis suggests that this channel has narrowed and deepened, rather than aggraded: channel aggradation was expected, given the intensification of land use in the catchment, upstream of the gauging station. Limitations of the method relate to the time periods over which stream gauging occurred; the spatial patterns of stream gauging sites; the quality and consistency of data collection; and the availability of concurrent land-use histories on which to base the interpretation of the channel changes.

Implication of the visual system in the regulation of activity cycles in the absence of solar light: 2-[I-125]iodomelatonin binding sites and melatonin receptor gene expression in the brains of demersal deep-sea gadiform fish

Relative eye size, gross brain morphology and central localization of 2-[I-125]iodomelatonin binding sites and melatonin receptor gene expression were compared in six gadiform fish living at different depths in the north-east Atlantic Ocean: Phycis blennoides (capture depth range 265-1260 m), Nezumia aequalis (445-1512 m), Coryphaenoides rupestris (706-1932 m), Trachyrincus murrayi (1010-1884 m), Coryphaenoides guentheri (1030 m) and Coryphaenoides (Nematonurus) armatus (2172-4787 m). Amongst these, the eye size range was 0.15-0.35 of head length with a value of 0.19 for C.(N.) armatus, the deepest species. Brain morphology reflected behavioural differences with well-developed olfactory regions in P.blennoides, T.murrayi and C. (N.) armatus and evidence of olfactory deficit in N. aequalis, C. rupestris and C. guentheri. All species had a clearly defined optic tectum with 2-[I-125] iodomelatonin binding and melatonin receptor gene expression localized to specific brain regions in a similar pattern to that found in shallow-water fish. Melatonin receptors were found throughout the visual structures of the brains of all species. Despite living beyond the depth of penetration of solar light these fish have retained central features associated with the coupling of cycles of growth, behaviour and reproduction to the diel light-dark cycle. How this functions in the deep sea remains enigmatic.

Asymmetric MRI magnet design using a hybrid numerical method

This paper describes a hybrid numerical method for the design of asymmetric magnetic resonance imaging magnet systems. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. A new type of asymmetric magnet is proposed in this work. The asymmetric MRI magnet allows the diameter spherical imaging volume to be positioned close to one end of the magnet. The main advantages of making the magnet asymmetric include the potential to reduce the perception of claustrophobia for the patient, better access to the patient by attending physicians, and the potential for reduced peripheral nerve stimulation due to the gradient coil configuration. The results highlight that the method can be used to obtain an asymmetric MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1.2 m in length. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries. (C) 1999 Academic Press.

Encapsulation of lemon oil by paste method using beta-cyclodextrin: Encapsulation efficiency and profile of oil volatiles

Microencapsulation of lemon oil was undertaken by kneading with beta-cyclodextrin, at a beta-cyclodextrin to lemon oil ratio of 88:12 (w/w). The resulting paste samples of the complex were vacuum- or spray-dried. Ten selected lemon oil flavor volatiles (alpha-pinene, sabinene, beta-pinene, beta-myrcene, limonene, gamma-terpinene, terpinolene, linalool, neral, and geranial) in the complex were analyzed periodically after 1, 2, 5, 10, 15, 20, and 30 min of kneading time. The results indicated that the levels of these volatiles were not significantly different (P > 0.05) irrespective of mixing time or type of the drying (vacuum- or spray-drying) used. An optimum mixing time was found to be 15 min, at which time the maximum encapsulation of lemon oil (97.7 mg/g of beta-cyclodextrin) was obtained in the complex powder.

Visual function: How spiders find the right rock to crawl under

Animals that go on hunting expeditions face the problem of finding the way home at the end of the day. A group of hunting spiders has now been added to the list of animals that use the celestial pattern of polarized light as a compass for navigation. (C) 1999 Elsevier Science Ltd. All rights reserved.

Comparison of trends in method-specific suicide rates in Australia and England & Wales, 1968-97

Objective: To compare secular trends in method-specific suicide rates among young people in Australia and England & Wales between 1968 and 1997. Methods: Australian data were obtained from the Australian Bureau of Statistics, and for England & Wales from the Office for National Statistics. Overall and method-specific suicide rates for 15-34 year old males and females were calculated using ICD codes E950-9 and E980-9 except E988.8. Results: In both settings, suicide rates have almost doubled in young males over the past 30 years (from 16.8 to 32.9 per 100,000 in Australia and from 10.1 to 19.0 in England & Wales). Overall rates have changed little in young females. In both sexes and in both settings there have been substantial increases in suicide by hanging (5-7 fold increase in Australia and four-fold increase in England & Wales). There have also been smaller increases in gassing in the 1980s and '90s. In females, the impact of these increases on overall rates has been offset by a decline in drug overdose, the most common method in females. Conclusions: Rates of male suicide have increased substantially in both settings in recent years, and hanging has become an increasingly common method of suicide. The similarity in observed trends in both settings supports the view that such changes may have common causes. Research should focus on understanding why hanging has increased in popularity and what measures may be taken to diminish it.

Computation of bifurcation boundaries for power systems: A new Delta-plane method

This paper is devoted to the problems of finding the load flow feasibility, saddle node, and Hopf bifurcation boundaries in the space of power system parameters. The first part contains a review of the existing relevant approaches including not-so-well-known contributions from Russia. The second part presents a new robust method for finding the power system load flow feasibility boundary on the plane defined by any three vectors of dependent variables (nodal voltages), called the Delta plane. The method exploits some quadratic and linear properties of the load now equations and state matrices written in rectangular coordinates. An advantage of the method is that it does not require an iterative solution of nonlinear equations (except the eigenvalue problem). In addition to benefits for visualization, the method is a useful tool for topological studies of power system multiple solution structures and stability domains. Although the power system application is developed, the method can be equally efficient for any quadratic algebraic problem.

Novel silica gel supported TiO2 photocatalyst synthesized by CVD method

TiO2 in anatase crystal phase is a very effective catalyst in the photocatalytic oxidation of organic compounds in water. To improve the recovery rate of TiO2 photocatalysts, which in most cases are in fine powder form, the chemical vapor deposition (CVD) method was used to load TiO2 onto a bigger particle support, silica gel. The amount of titania coating was found to depend strongly on the synthesis parameters of carrier gas flow rate and coating time. XPS and nitrogen ads/desorption results showed that most of the TiO2 particles generated from CVD were distributed on the external surface of the support and the coating was stable. The photocatalytic activities of TiO2/silica gel with different amounts of titania were evaluated for the oxidation of phenol aqueous solution and compared with that of Degussa P25. The optimum titania loading rate was found around 6 wt % of the TiO2 bulk concentration. Although the activity of the best TiO2/silica gel sample was still lower than that of P25, the synthesized TiO2/silica gel catalyst can be easily separated from the treated water and was found to maintain its TiO2 content and catalytic activity.

A simplified, sequential, phosphorus fractionation method

Hedley er al. (1982) developed what has become the most widely used land modified), phosphorus (P) fractionation technique. It consists of sequential extraction of increasingly less phytoavailable P pools. Extracts are centrifuged at up to 25000 g (RCF) and filtered to 0.45 mu m to ensure that soil is not lost between extractions. In attempting to transfer this method to laboratories with limited facilities, it was considered that access to high-speed centrifuges, and the cost of frequent filtration may prevent adoption of this P fractionation technique. The modified method presented here was developed to simplify methodology, reduce cost, and therefore increase accessibility of P fractionation technology. It provides quantitative recovery of soil between extractions, using low speed centrifugation without filtration. This is achieved by increasing the ionic strength of dilute extracts, through the addition of NaCl, to flocculate clay particles. Addition of NaCl does not change the amount of P extracted. Flocculation with low speed centrifugation produced extracts comparable with those having undergone filtration (0.025 mu m). A malachite green colorimetric method was adopted for inorganic P determination, as this simple manual method provides high sensitivity with negligible interference from other anions. This approach can also be used for total P following digestion, alternatively non-discriminatory methods, such as inductively coupled plasma atomic emission spectroscopy, may be employed.

Spectral tuning and the visual ecology of mantis shrimps

The compound eyes of mantis shrimps (stomatopod crustaceans) include an unparalleled diversity of visual pigments and spectral receptor classes in retinas of each species. We compared the visual pigment and spectral receptor classes of 12 species of gonodactyloid stomatopods from a variety of photo environments, from intertidal to deep water ( > 50 m), to learn how spectral tuning in the different photoreceptor types is modified within different photic environments. Results show that receptors of the peripheral photoreceptors, those outside the midband which are responsible for standard visual tasks such as spatial vision and motion detection, reveal the well-known pattern of decreasing lambda(max) with increasing depth. Receptors of midband rows 5 and 6, which are specialized for polarization vision, are similar in all species, having visual lambda(max)-values near 500 nm, independent of depth. Finally the spectral receptors of midband rows 1 to 4 are tuned for maximum coverage of the spectrum of irradiance available in the habitat of each species. The quality of the visual worlds experienced by each species we studied must vary considerably, but all appear to exploit the full capabilities offered by their complex visual systems.

A method for setting the size of plant conservation target areas

Realistic time frames in which management decisions are made often preclude the completion of the detailed analyses necessary for conservation planning. Under these circumstances, efficient alternatives may assist in approximating the results of more thorough studies that require extensive resources and time. We outline a set of concepts and formulas that may be used in lieu of detailed population viability analyses and habitat modeling exercises to estimate the protected areas required to provide desirable conservation outcomes for a suite of threatened plant species. We used expert judgment of parameters and assessment of a population size that results in a specified quasiextinction risk based on simple dynamic models The area required to support a population of this size is adjusted to take into account deterministic and stochastic human influences, including small-scale disturbance deterministic trends such as habitat loss, and changes in population density through processes such as predation and competition. We set targets for different disturbance regimes and geographic regions. We applied our methods to Banksia cuneata, Boronia keysii, and Parsonsia dorrigoensis, resulting in target areas for conservation of 1102, 733, and 1084 ha, respectively. These results provide guidance on target areas and priorities for conservation strategies.

Determining complicated winding patterns for shim coils using stream functions and the target-field method

In a magnetic resonance imaging equipment, gradient and shim coils are needed to produce a spatially varying magnetic field throughout the sample being imaged. Such coils consist of turns of wire wound on the surface of a cylindrical tube. Shim coils in particular, must sometimes be designed to produce complicated magnetic fields to correct for impurities. Streamline patterns for shim coils are much more complicated than those for gradient coils, In this work we present a detailed analysis of streamline methods and their application to shim coil design, A method is presented for determining the winding patterns to generate these complicated fields. (C) 2002 John Wiley & Sons, Inc.

A method for the design of MRI radiofrequency coils based on triangular and pulse basis functions

This paper presents a numerical technique for the design of an RF coil for asymmetric magnetic resonance imaging (MRI) systems. The formulation is based on an inverse approach where the cylindrical surface currents are expressed in terms of a combination of sub-domain basis functions: triangular and pulse functions. With the homogeneous transverse magnetic field specified in a spherical region, a functional method is applied to obtain the unknown current coefficients. The current distribution is then transformed to a conductor pattern by use of a stream function technique. Preliminary MR images acquired using a prototype RF coil are presented and validate the design method. (C) 2002 Elsevier Science B.V. All rights reserved.

NMR shim coil design utilising a rapid spherical harmonic calculation method

A rapid spherical harmonic calculation method is used for the design of Nuclear Magnetic Resonance shim coils. The aim is to design each shim such that it generates a field described purely by a single spherical harmonic. By applying simulated annealing techniques, coil arrangements are produced through the optimal positioning of current-carrying circular arc conductors of rectangular cross-section. This involves minimizing the undesirable harmonies in relation to a target harmonic. The design method is flexible enough to be applied for the production of coil arrangements that generate fields consisting significantly of either zonal or tesseral harmonics. Results are presented for several coil designs which generate tesseral harmonics of degree one.