Oxidative Instability of Fuels: Nickel Catalyzed Reactions

The reactions that lead to long-term storage instability of fuels are not fully understood. Various reports in the literature link particular fuels with specific reactions, usually oxidation or free radical processes. Trace quantities of metals are present in all processed fuels. The metal source can be naturally occurring or present from fuel handling. The usual case is to look at the reaction of the metal or metal ion with molecular oxygen or other active oxygen species such as hydroperoxides. This article reports on the reaction of a nitrogen heterocycle, indole. We propose a mechanism that shows that catalytic amounts of nickel can produce compounds of higher molecular weight and increased polarity.     

Pumping test data interpretation and drift inflow assessment by finite-difference radial modelling

A digital radial (r-z-t) finite-difference model for the simulation of constant-discharge pumping-tests in multilayered ground is described. The model is particularly useful for the interpretation of multiport piezometer data since the drawdown at each port can be independently simulated on the r-z-t grid. Unlike conventional methods of pumping-test interpretation, where flow and ground properties are usually averaged over one or two layers, the radial (r-z-t) model allows a detailed approximation of the vertical variation in ground hydraulic properties. A case study is described in which the radial (r-z-t) model is applied to the interpretation of multiport piezometer data from two pumping-tests carried out in a site investigation for a proposed new surface drift. The resulting permeability distribution is then used as input data to model inflows to the proposed drift under construction. Three-dimensional inflows to a short length of unlined drift open section are approximated using steady-state radial (r-z) flow models. Use of the numerical modelling techniques result in a better understanding of the groundwater system than that obtained from conventional analytical techniques.     

Modelling of electrostatic gate operations in the Kane solid state quantum computer

The nuclear spin quantum computer proposed by Kane [Nature 393 (1998) 133] exploits as a qubit array ³¹P dopants embedded within a silicon matrix. Single-qubit operations are controlled by the application of electrostatic potentials via a set of metallic ‘A’ gates, situated above the donors, on the silicon surface, that tune the resonance frequency of individual nuclear spins, and a globally applied RF magnetic field that flips spins at resonance. Coupling between qubits is controlled by the application of potentials via a set of ‘J’ gates, between the donors, that induce an electron-mediated coupling between nuclear spins. We report the results of the study of the electric field and potential profiles arising within the Kane device from typical gate operations. The extent to which a single nuclear spin can be tuned independently of its neighbours, by operation of an associated A-gate, is examined and key design parameters in the Kane architecture are addressed. Implications for current fabrication strategies involving the implantation of ³¹P atoms are discussed. Solution of the Poisson equation has been carried out by simulation using a TCAD modelling package (Integrated Systems Engineering AG).     

Stephen L. Gans Visiting Guest Lecture: central venous catheters for parenteral nutrition: a double-edged sword

The objective of this study was to critically evaluate the usefulness of atrial natriuretic factor (ANF), the N-terminal fragment of the ANF pro-hormone (pro-ANF) and B-type (brain) natriuretic peptide (BNP) determination as screening tests for identifying patients with mild left ventricular (LV) impairment. The sample consisted of a consecutive series of 254 patients undergoing diagnostic left-sided cardiac catheterization. Logistic regression analysis showed that plasma BNP was the best predictor of increased LV end-diastolic pressure, decreased LV ejection fraction and LV dysfunction (LV ejection fraction < or = 45% and LV end-diastolic pressure > or = 15 mm Hg). For the detection of LV dysfunction the areas under the receiver-operating characteristic function, an index of overall diagnostic accuracy, were 0.789 for BNP, 0.665 for ANF and 0.610 for pro-ANF. In conclusion, plasma BNP appears to be a better indicator of LV function than plasma ANF or pro-ANF. However, the overall diagnostic value of circulating ANF, pro-ANF, and BNP as indicators of mild LV dysfunction is relatively modest.     

Nicotinic and muscarinic cholinergic receptor binding in the human hippocampal formation during development and aging

High-affinity nicotine, alpha-bungarotoxin (alpha BT) and muscarinic receptor binding was measured in the human hippocampal formation in a series of 57 cases aged between 24 weeks gestation and 100 years. Changes in nicotine receptor binding during development and aging were more striking than differences in alpha BT and muscarinic binding. Nicotine binding was higher at the late foetal stage than at any other subsequent time in all areas investigated. In the hippocampus a fall in binding then occurred within the first six months of life, with little or no subsequent fall during aging, whereas in the entorhinal cortex and the presubiculum the major loss of nicotine binding occurred after the fourth decade. alpha BT binding was significantly elevated in the CA 1 region, but in no other region of the hippocampus, in the late foetus, and there was also a fall in alpha BT binding in the entorhinal cortex during aging from the second decade. The modest changes in total muscarinic binding, which appeared to reflect those in M1 and M3 + 4 rather than M2 binding, were a rise in the entorhinal cortex between the foetal stage and childhood and a tendency for receptors to fall with age in the hippocampus and subicular complex. These findings implicate mechanisms controlling the expression of nicotinic receptors to a greater extent than muscarinic receptors in postnatal development and aging in the human hippocampus.     

THE SEPARATION OF m-DIISOPROPYLBENZENE FROM p-DIISOPROPYLBENZENE BY AZEOTROPIC DISTILLATION

m-Diisopropylbenzene can be separated from p-diisopropyl-benzene by azeotropic distillation when the azeotrope forming agent is selected from certain ketones, e.g. acetophenone; alcohols, e.g. o-isopropyl-phenol; esters, e.g. methyl benzoate; ethers, e.g. dipropylene glycol dimethyl ether or nitrogeneous compounds, e.g. 2-nitrotoluene.     

Did a local distribution company procure prudently during the California electricity crisis?

To manage cost risk, prudent procurement of electric power requires that some portion of a buyer's energy demand be met through long-term contracting. Under cost-of-service regulation or performance-based regulation, a local distribution company (LDC) should be allowed to fully recover all prudently incurred power procurement costs. However, the regulatory test of prudence is an ex post review with the threat of disallowance. This paper presents an economic analysis of procurement prudence involving a small LDC, Bear Valley Electric Service (BVES), which serves a resort area in Southern California. The key findings are: (a) high and volatile prices and rolling blackouts characterized the market environment faced by the owner of BVES, Southern California Water Company (SCWC), at its signing of a 5-year fixed price contract; (b) SCWC was a price-taker with no incentive to act imprudently; (c) the contract was obtained via a competitive bidding process; (d) the contract price was comparable to the benchmark price of contemporaneous contracts; (e) the fixed price contract was economic when compared to available alternatives; and (f) despite (a)–(e), a negotiated settlement with the state regulator and a large user resulted in substantial disallowance. The policy implication is that a regulator should approve a prudent procurement plan proposed by an LDC to remove the unreasonable risk of an ex post review. If the LDC strictly adheres to the plan, the resulting electricity purchases are per se prudent and should entitle the LDC to full cost recovery.