The impact of superphosphate and surface-applied lime on the profitability and sustainability of wool production on the tablelands of NSW

Soil acidification is one of the major forms of soil degradation in higher rainfall areas of the tablelands of NSW. A grazing experiment was conducted near Sutton, NSW, to assess the effect of various rates of superphosphate, lime, sewage ash and stocking rates on wool production and sustainability between 1999 and 2008. The results from the discounted cash flow analysis show that the net present value of the treatment without lime, the lower rate of superphosphate and the lowest stocking rate returned the highest net present value of $266.30/ha. Raising the application of superphosphate from 125kg/ha every two to three years to 250kg/ha every year on un-limed and limed soil reduced the net present value by$278.70/ha and $249.30/ha, respectively. The addition of lime at the rate of 4t/ha on un-limed soil at the low superphosphate level reduced the net present value by about$234.60/ha. The net present value fell by $205.24/ha when the level of superphosphate rate increased to 250kg/ha every year. The net present value decreased as the level of stocking rate increased. We conclude that wool producers will be unlikely to use lime to ameliorate acid soil, even though production will not be sustainable, unless there are more favourable input and commodity prices in the market and government intervention.economic, acid soil, lime, superphosphate, sewage ash, stocking rate, policy,

Estimation of instantaneous venous blood saturation using the Photoplethysmograph (PPG) waveform

Non-invasive estimation of regional venous saturation (SxvO2) using a conventional pulse oximeter could provide a means of obtaining clinically relevant information. This study was carried out in order to investigate the hypothesis that SxvO2 could be estimated by utilising the modulations created by positive pressure ventilation in the photoplethysmograph (PPG) signals. The modulations caused by the mechanical ventilator were extracted from oesophageal PPG signals obtained from 12 patients undergoing cardiothoracic surgery. The signals analysed in this work were acquired in a previous study. For the purpose of this analysis the raw PPG signal was considered to have three major components, ac PPG signal (cardiac related component), a static component or dc PPG signal (created mostly by the absorption of light by surrounding tissue) and the ventilator modulation component. These components were then used to estimate instantaneous arterial blood oxygen saturation (SpO2) and SxvO2 by utilising time-frequency analysis technique of smoothed-pseudo Wigner–Ville distribution (SPWVD). The results showed that there was no significant difference in the traditionally-derived (time-domain) arterial saturation and the instantaneous arterial saturation. However, the instantaneous venous saturation was found to be significantly lower than the estimated time-domain and instantaneous arterial saturation (P=<0.001, n=12)

Grassland Management–The PROGRAZE™ Approach

Three courses PROGRAZE™, PROGRAZE™ Plus and STOCKPLAN® have been developed to provide a complete package to assist farmers manage their variable grassland grazing systems. As each package is separate the farmer can use the relevant tool to help them work through major issues they are dealing with at any point in time. All courses are based on the same principle, they do not give answers but rather provide training in skills development, provide key background knowledge and a framework to assist farmers plan and if needed to work through their problems to reach a solution they are comfortable with

Preliminary evaluation of a new fibre-optic cerebral oximetry system

A new system for measuring the oxygen saturation of blood within tissue has been developed, for a variety of patient monitoring applications. A particular unmet need is in the central nervous system, and this project aims to devise a means for measuring blood oxygen saturation in the brain tissue of patients recovering from neurosurgery or head injury. Coupling light sources and a photodetector to optical fibres results in a probe small enough to pass through a cranial bolt of the type already in use for intra-cranial pressure monitoring. The development and evaluation of a two-wavelength fibre-optic reflectance photoplethysmography (PPG) system are described. It was found that good quality red and near-infrared PPG signals could be obtained from the finger using a fibre-optic probe. Experiments were conducted to find the inter-fibre spacings that yield signals most suitable for calculating oxygen saturation. Reliable signals could be obtained for inter-fibre spacings between 2 mm and 5 mm, the latter being the size of the maximum aperture in the cranial bolt. A preliminary measurement from human brain tissue is also presented

Optical fibre catheter photoplethysmograph

A fibre optic system for monitoring arterial oxygen saturation of internal tissue sites utilising the principle of reflectance pulse oximetry is being developed. It was shown that it is possible to obtain a stable photoplethysmograph (PPG) signal from the fingertip using a twin optical fibre catheter. The results of experiments to optimise the detection of PPG signals using optical fibres are presented. Possible applications of this method include measuring SpO2 in the oesophagus, trachea, large intestine, brain tissue and spinal cord

Investigation of the characteristics of photoplethysmographic signals in the human oesophagus in anaesthetised patients undergoing routine surgery

The continuous monitoring of arterial blood oxygen saturation in patients with compromised peripheral perfusion is often difficult or impossible, since conventional non-invasive techniques such as pulse oximetry (SpO2) fail. Measurements of oxygen saturation are unreliable when patients are peripherally cool with low cardiac output or poor peripheral circulation. These clinical situations commonly occur after major surgery including cardiopulmonary bypass. It is suggested that the above difficulties might be overcome if the sensor were to monitor a better perfused central part of the body such as the oesophagus. A reflection probe has been constructed utilising miniaturised opto-electronic devices designed to fit into a transparent oesophageal stomach tube. A system to detect and preprocess the photoplethysmograph (PPG) signals has been developed. The PPG output is sampled and recorded by a data acquisition system and a laptop personal computer. The characteristics of the pulsatile signal in the oesophagus of anaesthetised adult patients undergoing routine elective surgery has been investigated. Preliminary results show that good quality photoplethysmograpic (PPG) signals can be measured in the human oesophagus. The oesophageal signal amplitudes were found to be approximately a factor of two greater than the amplitudes of conventional finger PPGs. The characteristics of the PPG signals obtained at various depths in the oesophagus have been studied and the results will be presented. This investigation indicates the suitability of the oesophagus as an alternative site for the reliable monitoring of oxygen saturation (SpO2) in patients with poor peripheral perfusion

Electro-optical techniques for the investigation of oesophageal photoplethysmographic signals and blood oxygen saturation in burns

Pulse oximetry is widely used in anaesthesia and intensive care monitoring. It is a valuable, non-invasive optical monitoring technique used for continuous measurement of arterial blood oxygen saturation (SpO2). Sites for pulse oximeter sensors are frequently difficult to find in patients with major thermal injury. Therefore blood oxygen saturation readings are often unobtainable at just the time when they would be most valuable. An oesophageal SpO2 probe has been designed to record reliable photoplethysmographic (PPG) signals and SpO2 values from the oesophagus of burned patients. Seven adult patients were studied. Good quality oesophageal PPG signals with large amplitudes were measured from various depths within the oesophagus. The optimal monitoring oesophageal depth ranged from 13 cm to 20 cm, measured from the upper lip. It was found that the oesophageal pulse oximeter saturation results were in good agreement with those from the CO-oximeter. This study suggests that the oesophagus can be used as an alternative site for monitoring arterial blood oxygen saturation by pulse oximetry in burned patients

Investigation of Photoplethysmographic Changes using a Static Compression Model of Spinal Cord Injury

Little is known about cell death in spinal cord tissue following compression injury, despite compression being a key component of spinal injuries. Currently models are used to mimic compression injury in animals and the effects of the compression evaluated by observing the extent and duration of recovery of normal motor function in the days and weeks following the injury. A fiber-optic photoplethysmography system was used to investigate whether pulsation of the small arteries in the spinal cord occurred before, during and after compressive loads were applied to the tissue. It was found that the signal amplitudes were reduced and this reduction persisted for at least five minutes after the compression ceased. It is hoped that results from this preliminary study may improve knowledge of the mechanism of spinal cord injury

Investigation of photoplethysmographic signals in the human oesophagus

The continuous monitoring of blood oxygen saturation in patients with compromised peripheral perfusion is often difficult or impossible, since conventional non-invasive techniques such as pulse oximetry fail. Measurements of oxygen saturation are unreliable when patients are peripherally cool with low cardiac output and poor peripheral circulation. These clinical situations commonly occur after major surgery including cardiopulmonary bypass. We suggest that the above difficulties might be overcome if the sensor were to monitor a more central part of the body. It is proposed to use the oesophagus as measurement site and reflection techniques on the hypothesis that this site should be better perfused. A new probe was constructed utilising miniaturised opto-electronic devices designed to fit into a transparent oesophageal stomach tube. One infrared wavelength was used in this study at 880 nm and a circuit to analyse the photoplethysmograph (PPG) signal was developed. The output PPG signals were sampled and recorded by a data acquisition system and a laptop personal computer. Initial measurements were carried out to investigate the amplitude of the pulsatile signal in the oesophagus and preliminary results are presented