Solving applied general equilibrium models represented as a mixture of linearized and levels equations

General equilibrium moels are usually represented as a system of levels equations (e.g., in North America) or a system of linearized equations (e.g., in Australia). Either representation can be used to obtain accurate solutions. General-purpose software is available in both cases-GAMS or MPS/GE is typically used by levels modellers and GEMPACK by linearizers. Some equations (notably accounting identities) are naturally expressed in the levels while others (especially behavioural equations) are naturally expressed in a linearized form. This paper describes the new GEMPACK facility for solving models represented as a mixture of levels and linearized equations and discusses the advantages to modellers of using such a representation.     

An automated, parallel processing approach to biomolecular sample preparation

Sample preparation for DNA and RNA assays is a prime candidate for laboratory automation. A novel, parallel processing device that performs the three separate liquid-handling functions necessary for such sample preparation-dispensing, pipetting, and pressurizing-is presented. The device comprises an array of fine nozzles connected by fluidic channels to automatically and precisely distribute flow between one source and an array of points. The design principles, as well as the experimental and computational methods used to develop the device, are described. Test results, including accuracy, uniformity, volume range, and timing, are presented. The functionality of the device is demonstrated by performing a solid-phase extraction of DNA with two types of microcolumns.     

Analysis of solvent extracts of bituminous coal macerals by chromatography, 1H n.m.r. and field-desorption mass spectrometry

Analysis of the carbon disulphide extracts of nine samples of UK coal-maceral concentrates by ¹H highresolution n.m.r. spectroscopy, gas-liquid chromatography and field-desorption mass spectrometry indicates the presence of components with a wide molecular weight range extending up to 1200 amu; these are attributed to n-alkanes up to ≈C₅₀ and highly condensed polynuclear aromatic compounds.     

Characteristics of heavy-oil-in-water emulsions containing produced sand

Heavy-oil-in-water (o/w) emulsions containing produced sand were prepared using commercially available emulsifiers. The emulsions were tested in beakers for emulsion type, quality, and sand-retention characteristics. The apparent viscosities of the o/w emulsions were measured. The effects of polymer addition on the apparent viscosity and sand-carrying capability of the emulsions were also studied. The results of the breaker tests indicate that most emulsifier solutions water-wet the beaker wall and temporarily improve heavy-oil flow characteristics. However, most of the chemicals also water-wet the sand particles and cause sand dropout. The Flothin F2 chemical alone showed stable oil dispersion and, in combination with the Flocon 4800C polymer, showed very good sand-retention, viscosity-reduction, and stable oil-dispersion characteristics.     

Allelochemical resistance of bald cypress,Taxodium distichum,heartwood to the subterranean termite,Coptotermes formosanus

The heartwood of bald cypress,Taxodium distichum (L.) Rich., resisted feeding attack by the Formosan subterranean termite,Coptotermes formosanus Shiraki. Hexane-extracted heartwood, however, was consumed at > 12 times the amount of sound heartwood eaten. A bioassay usingT. distichum sapwood as a feeding substrate was employed to assess the antitermitic activity of successive hexane, acetone, and methanol extracts of heartwood shavings and isolates derived from the active hexane extract. Two fractions, eluted from the crude hexane extract by liquid chromatography, significantly reduced termite feeding compared to the parent extract, while a third fraction was less active than the original hexane extract. Each fraction contained one major component. All three components were structurally related diterpenes. The two most active heartwood constituents were identified by GC-MS and NMR as ferruginol and manool, while the third and least active, but most prevalent, compound in heartwood was identified as nezukol. Results of bioassays suggest that these allelochemicals act principally as feeding deterrents with accompanying termite mortality due to starvation.     

Analytic center cutting plane method for multiple kernel learning

Multiple Kernel Learning (MKL) is a popular generalization of kernel methods which allows the practitioner to optimize over convex combinations of kernels. We observe that many recent MKL solutions can be cast in the framework of oracle based optimization, and show that they vary in terms of query point generation. The popularity of such methods is because the oracle can fortuitously be implemented as a support vector machine. Motivated by the success of centering approaches in interior point methods, we propose a new approach to optimize the MKL objective based on the analytic center cutting plane method (accpm). Our experimental results show that accpm outperforms state of the art in terms of rate of convergence and robustness. Further analysis sheds some light as to why MKL may not always improve classification accuracy over naive solutions.     

Dual Verbal Elicitation: The Complementary Use of Concurrent and Retrospective Reporting Within a Usability Test

Verbal protocols are the primary tool for understanding users' task-solving behaviors during usability testing. A qualitative study that examined the utility of combining a concurrent and retrospective think-aloud within the same usability test is described. The results indicate that although there was significant overlap between the types of utterances produced during each think-aloud, the retrospective phase produced more verbalizations that were relevant to usability analysis, for example, helpful self-assessments of performance, yielding insights into the impact of encountered difficulties. However, a small number of less desirable utterance types emerged: hypothesising, rationalizing, and forgetting. When used together, both methods contributed to an understanding of usability issues; the concurrent phase yielded more usability issues overall, and the retrospective data improved the understanding of these by (a) reinforcement: users highlighted the impact of an issue on their experience, (b) elaboration: users would provide causal explanations of encountered difficulties, and (c) context: users provided information about the product's context of use.