Intragastric Infusion and Its Use in the Investigation of Nitrogen and Glucose Metabolism in Ruminants

1. Current techniques used for measurements of the composition of feeds given to ruminants and of the subsequent utilization of nutrients by these animals were reviewed. Intragastric infusion, an alternative technique for the precise control of nutrient supply under experimental conditions, was introduced and its use for the investigation of nutrient utilization was discussed. 2. Experiments were undertaken to develop the intragastric infusion technique for use at the HRI for investigations into the effects of propionate supply on N utilization in ruminants. 3. In the first experiment propionate was isoenergetically withdrawn from 'control' infusions given to a cow which were designed to provide an above-maintenance supply of energy together with adequate protein to sustain zero N retention (420mg N/kgW 0.75 per d). The quantity of N excreted by the cow was increased from 47 to 54g/d (15%) in response to propionate withdrawal. The animal maintained its homeostasis, as judged by its plasma glucose concentration, and was able to derive 2.37g glucose/kgW 0.75 per d from the protein that was catabolised. In view of the types of glucose-precursor supplied to the animal, this quantity of glucose was equivalent to the animal's minimum requirement. 4. A more extensive study of the effects of propionate supply on N utilization was conducted with a larger group of animals and this was most conveniently achieved using sheep. Propionate was isoenergetically withdrawn from 'control' infusions and N excretion was increased by 2.64g/d (27%). From this a minimum glucose requirement of 2.44g/kgW 0.75 per d was calculated and proportions of this requirement were used to supplement isoenergetic propionate-free infusions in subsequent treatments. When glucose was reintroduced in quantities equivalent to the minimum requirement, a positive retention of N of 0.06g/kgW 0.75 per d was measured, despite there being no change in the 480mg casein N/kgW 0.75 per d provided by the infusions. When glucose was again isoenergetically withdrawn from the infusions the quantity of N excreted by the animals was 13% lower than in the identical treatment initially imposed. It appeared that restriction of glucose-precursor supply was associated with increased efficiency of utilization of N and/or a reduction in glucose utilization. The effects of the treatments on the plasma concentrations of certain metabolites and amino acids suggested glucose sparing could have occurred and that non-essential amino acids were major contributors to gluconeogenesis. This despite the provision of ME in quantities calculated to allow positive energy retention. 5. In a third experiment, after an initial 'control' period (P1), propionate was withdrawn from the infusions (P2) and then reintroduced at 50% of the quantities given in (P1) for a prolonged period (P3, 32d). Finally propionate was fully reintroduced (P4). Blood analyses were made to provide information on the time scale and nature of the metabolic response. In P2 there was an increase in N excretion from 0.41 to 0.59g/kgW 0.75 per d (43%) despite a constant supply of 413mg Casein N/kgW 0.75 per d throughout the experiment. In P3 and P4, 0.38 and 0.36g N/kgW 0.75 per d were excreted respectively. P3 was intended to perpetuate the adaptive response initiated in P2 but, judging by the quantities of N excreted and the changes in the blood plasma constituents that were measured, the adaptive response had not been perpetuated and there was little difference in the effects of restricting propionate by 50% (P3) or not restricting propionate supply at all (P1 and P4). 6. A more severe perturbation of glucose-precursor supply was imposed on the animals. Following an initial 'control' period (P1), propionate was isoenergetically withdrawn from the infusions (P2) for as long as was practicable for the animals to avoid clinical hypoglycaemia. Propionate was then reintroduced to the infusions (P3) in the same quantities as given in P1. The N excreted by the animals during the 3 treatments was 0.47, 0.64 and 0.46g/kgW 0.75 per d respectively despite the provision of 473mg casein N/kgW 0.75 per d throughout the experiment. Analysis of the N data from P2 showed there to be a tendency for N excretion to fall after the first 5 days of the treatment. This change in N excretion was not, however, associated with any changes in the constitutents of blood plasma that were measured. (Abstract shortened by ProQuest.)

Nitrate pollution from horticultural production systems : tools for policy and advice from field to catchment scales

The implementation of the Nitrates Directive has imposed a requirement to restrict N fertiliser and manuring practices on farms across the EU in order to reduce nitrate losses to water. These requirements have since been extended by the more demanding Water Framework Directive, which broadens the focus from the control of farm practices to a consideration of the impacts of pollutants from all sources on water quality at a catchment or larger scale. Together, these Directives set limits for water quality, and identify general strategies for how these might be achieved. However, it is the responsibility of policy makers in each Nation State to design the details of the management practices and environmental protection measures required to meet the objectives of the legislation, to ensure they are appropriate for their specific types of land use and climate. This paper describes various modelling tools for comparing different cropping and land use strategies, and illustrates with examples how they can inform policy makers about the environmental benefits of changing management practices and how to prioritise them. The results can help to provide the specific advice on N fertiliser and land use management required by farmers and growers at a field scale, and by environmental managers at a catchment or larger scale. A further example of how results from multiple catchments can be up-scaled and compared using Geographic Information Systems is also outlined

Analysis and determinants of sustainability policy choice of local councils in Australia : a test of stakeholder theory

Since the early 1990’s, issues of sustainability involving community, government and industry have gained momentum, and the environment has become the focus of numerous studies, such as those undertaken by Young and Hayes (2002); Yuan (2001); Staley (2006); Mellahi and Wood (2004); Hezri and Hasan (2006); Dowse 2006; Wilmhurst and Frost (2000); and Qian, Burritt and Monroe (2010). Cotter and Hannan (1999, p.11) also discussed the impetus of a United Nations summit in 1992, known as the Earth Summit, which resulted in Local Agenda 21, a blueprint for action to achieve sustainable development. Global sustainability is currently a major focus for policies in both the public and private sectors. Local government in Australia is currently undergoing historic changes as a result of a major thrust to restructure through amalgamation, in order to improve efficiencies and effectiveness in local government. Amalgamations are considered necessary for the financial survival of local government, as there is growing evidence to suggest that too many small councils will not be financially viable in the future. Moreover, local government worldwide is now more accountable than ever before for sustainable policy choices and the impact of those policy choices on their communities. Sustainable policy choices of local councils worldwide will have an enormous economic and environmental impact on the planet. Previous studies into the effects of sustainability issues and their relationship to local councils have been carried out by Kloot and Martin (2001); O’Brien (2002); Reid (1999); Bulkeley (2000); and Tebbatt (2006). This empirical quantitative study examines the sustainability policy choices of local government Australia-wide, and looks specifically at the determinants of such choices in local government. It also investigates the influence of stakeholders on the sustainability policy choices of each local government, the results of which have the potential to affect society’s quality of life. Identifying stakeholders who influence sustainability policy choices is therefore of great importance for the future. All five hundred and fifty eight local Australian government entities listed by the Australian Local Government Association (ALGA) were invited to participate in this study. Data were gathered through the use of a structured questionnaire, and an analysis was undertaken to identify those stakeholders who influence the sustainability policies of Australian local government. This is the first research to examine all Australian local government entities to find out why they make the sustainability choices they do. To date, most studies relating to local government have been in areas of disclosure, such as those carried out by Royston (2001); Priest, Ng and Dolley (1999); and Piaseka (2006). The findings of this study support the assertion of Mitchell, Agle and Wood (1997), that stakeholder salience is positively related to the cumulative number of the three variable attributes of power, legitimacy and urgency. In addition, this study ranked stakeholders from one to eight according to the perceptions of local government CEOs. It is interesting to note that, of the listed stakeholders, government did not rank as number one. The results indicated that stakeholder influence on local government sustainability policy choices varied depending on local government size, location, and whether they were urban or rural according to their government classification. The researcher was surprised to learn that many councils did not know their own government classification. The study also revealed that local government took sustainability seriously in all its forms and applications. As in previous research, the CEO of each council was selected as the respondent for the questionnaire. It was discovered that many of the larger councils had specialist positions dealing with these issues. This study is significant because it contributes original research in the area of stakeholder influence on sustainability policy choices of local government in Australia. It is important for future sustainability studies to have an understanding of which stakeholders influence local government in making their sustainability policy choices. This study also clarifies the perceived salience of local government stakeholders from the perspective of Australian local government CEOs. Moreover, the study proves quite clearly that local government is not homogenous, and the potential exists for future studies to investigate the importance and consequence of heterogeneous local government in Australia and around the world

Some determinants of success and failure in first-year university business units at private colleges

This study investigates some of the determinates of academic success and failure (and dropout) from first year university level Business units at two private business colleges in Perth, Western Australia. Private business colleges are convenient vehicles for international and Western Australian students who do not possess adequate academic assessments for direct entry into university, and for students who might benefit from an enhanced pastoral support system, in the transition from secondary education to tertiary education. The study is important to private providers and to universities who are trying to help students succeed at university. The study utilises a model of two dependent variables (achievement at first attempt and achievement at second attempt); five independent variables (motivation to achieve, outside work commitments, performance to expectations, family problems, and attendance); and three situation variables (age, gender and whether English is the first language of the student). The variables in the model were identified from various studies in the literature, as likely to be most strongly related to academic success or failure. The model suggests a number of bivariate relationships between the dependent variables andthe independent variables and between the dependent variables and the situation variables. The model also suggests a number of joint relationships between the dependent, independent and situation variables. The dependent variables were measured for eight first year units of study which are generic to Bachelor Degree programmes at most universities for Business or Commerce; Accounting, Economics, Finance, Information Systems, Legal Framework, Management, Marketing and Statistics. The sample consists of 195 students from private provider A and 92 students from private provider B in Perth, Western Australia (a total of 287 students). Data were collected by means of a questionnaire which was distributed to students in both private colleges in mid-semester 1996, and which students completed on a voluntary basis. Each of the independent variables were measured from student self-report data and the private colleges provided the individual student results in each of the eight Business subjects to use as measures of the dependent variables. Analysis took the form of cross-tabulations, zero-order correlations and multiple regression to test the relationships between the dependent and independent variables, as suggested by the model. The computer package SPSS (Statistical Package for the Social Sciences) was used for the analysis. The conclusions relating to the zero-order correlations are presented in two parts: those relating Achievement at the first attempt and Achievement at the second attempt (as dependent variables) with the five independent variables and those relating the dependent variables with the three situation variables. (i) The five independent variables have small or no correlations with the two dependent variables. (ii) The three situation variables have small or no correlations with the two dependent variables. In each case, the amount of explained variance in the dependent variable was 7% or less and hence the relationships are of no practical significance for any of the eight Business subjects, for students or private providers. The conclusions relating to the multiple regression analysis are presented in three parts: those relating the dependent variables with the independent variables, those relating the dependent variables with the situation variables, and those relating the dependent variables with the independent and situation variables together. (iii) The five independent variables together account for less than 9% variance in the dependent variables. (iv) The three situation variables together account for less than 10% of variance in the dependent variables. (v) The five independent variables and the three situation variables together account for less than 15% of variance in the dependent variables. These relationships are so small that they are of no practical significance for any of the eight Business subjects, for students or private providers. While there do not appear to be any direct implications for private providers or students, flowing from this study, there are direct implications for further research. In particular, a better model needs to be developed that uses variables that can explain more of the variance in achievement at the first and second attempts. This may mean that different and better measures of the independent variables need to be made and that new independent variables need to be uncovered, perhaps, by interviewing students at private providers

Two-Particle Dark State in the Transport through a Triple Quantum Dot

We study transport through a triple quantum dot in a triangular geometry with applied bias such that both singly- and doubly- charged states participate. We describe the formation of electronic dark states -- coherent superpositions that block current flow -- in the system, and focus on the formation of a two-electron dark state. We discuss the conditions under which such a state forms and describe the signatures that it leaves in transport properties such as the differential conductance and shotnoise.Comment: (9 pages, 7 figures), we now consider two different sets of charging energie

Elastomeric microfluidic diode and rectifier work with Newtonian fluids

We report on two microfluidic elastomeric autoregulatory devices—a diode and a rectifier. They exhibit physically interesting and complex nonlinear behaviors (saturation, bias-dependent resistance, and rectification) with a Newtonian fluid. Due to their autoregulatory properties, they operate without active external control. As a result, they enable increased microfluidic device density and overall system miniaturization. The demonstrated diode and rectifier would also be useful components in future microfluidic logic circuitry

Electrical microfluidic pressure gauge for elastomer microelectromechanical systems

We report on an electrical microfluidic pressure gauge. A polydimethylsiloxane microvalve closes at a characteristic applied pressure determined by the material's properties and the valve's dimensions. Hence, when the same pressure is applied to all valves of a heterogeneous valve array, some valves close while others remain open. The state of the array is combined with knowledge of the respective characteristic closing pressures of the individual valves to yield an estimate of the applied pressure. The state of each valve is obtained by electrical measurements, since the electrical resistance of the respective underlying fluid-filled channel increases by at least two orders of magnitude as the valve closes and its insulating elastomer material interrupts the electrical circuit. The overall system functions as a pressure gauge with electrical readout. This device would be a critical component in active pressure-regulation loops in future integrated microfluidic systems

Leggett-Garg inequalities for the statistics of electron transport

We derive a set of Leggett-Garg inequalities (temporal Bell's inequalities) for the moment generating function of charge transferred through a conductor. Violation of these inequalities demonstrates the absence of a macroscopic-real description of the transport process. We show how these inequalities can be violated by quantum-mechanical systems and consider transport through normal and superconducting single-electron transistors as examples.Comment: 5 pages; 3 figure

Experimentally validated quantitative linear model for the device physics of elastomeric microfluidic valves

A systematic experimental study and theoretical modeling of the device physics of polydimethylsiloxane “pushdown” microfluidic valves are presented. The phase space is charted by 1587 dimension combinations and encompasses 45–295 µm lateral dimensions, 16–39 µm membrane thickness, and 1–28 psi closing pressure. Three linear models are developed and tested against the empirical data, and then combined into a fourth-power-polynomial superposition. The experimentally validated final model offers a useful quantitative prediction for a valve's properties as a function of its dimensions. Typical valves (80–150 µm width) are shown to behave like thin springs