FORECASTING MINERAL SUPPLY FROM MINERAL RENT DATA

An optimal control model of exhaustible resources is used to clarify the long run relationship between mineral rent and depletion cost at the industry level. A standard first order condition of the time rate of change of rents is reformulated to reveal that rent data may be used to help forecast the rise in extraction costs resulting from resource depletion. This application of the theory of exhaustible resources is illustrated using historical mineral industry rent and extraction cost data. A forecast of U.S. coal extraction costs, following the method proposed in this paper, suggests that future rates of extraction cost increases will be similar to rates experienced in the past.     

R-Matrices for Leibniz Algebras

Leibniz agebras are a generalization of Lie algebras, where no symmetry properties of the bracket are required. In this Letter we introduce a notion of R-matrices for this structure and the related Yang–Baxter equations, and discuss some of their basic properties.     

Monitoring hydration state conversion by TG-DTA

Characterization of the solid-state form (hydrate or polymorph) of a pharmaceutical active is a key scientific and regulatory requirement during development of and prior to seeking approval for marketing of the drug product. A variety of analytical methods are available to perform this task. By nature of the fundamental information it provides, TG-DTA offers advantages over other methods in regards to monitoring and quantitation of hydration state changes. In a single experiment with only a few milligrams of sample, TG-DTA perceives minor changes in phase, quantitates total water content and percent conversion, and illustrates hydrate type. All of this is accomplished without the necessity of generating time-consuming standard curves representing the differing ratios of hydrated to anhydrous forms. This study describes the use of TG-DTA to monitor and quantitate humidity induced solid–solid phase conversion of nitrofurantoin and risedronate. Percent conversion was qualitatively observed by both TG and DTA signals and quantitated by the TG.     

Thermal activation of molecularly-wired gold nanoparticles on a substrate as catalyst

The ability to prepare nanostructured metal catalysts requires the ability to control size and interparticle spatial and surface access properties. In this work, we report novel findings of an atomic force microscopic investigation of a controlled thermal activation strategy of gold catalysts nanostructured via molecular wiring or linking on a substrate surface. Gold nanocrystals of approximately 2 nm diameter capped by decanethiolate and wired by 1,9-nonanedithiolate on mica substrates were studied as a model system. By manipulating the activation temperature (200-250 degrees C), the capping/wiring molecules can be removed to produce controllable particle size and interparticle spatial morphology. The electrocatalytic activity of the activated nanostructures toward methanol oxidation, which is of fundamental importance to fuel cell catalysis, has been demonstrated. The novelty of the findings is the viability of a thermal activation strategy of core-shell nanostructured catalysts based on molecularly predefined interparticle spatial properties on a substrate, which upon further investigation may form the basis for spatially controllable nanostructured catalysts.     

Purification of neutral protease by dye affinity chromatography

Twenty triazinic dyes were assayed as ligands for the chromatographic affinity purification of a neutral protease from Flavourzyme^™, a commercial preparation. Screening at pH 4.0 allowed the selection of eight dyes on the basis of their high protease adsorption. When the pH was set to 5.0 in order to increase selectivity, only Yellow HE-4R, Red HE-3B, and Cibacron Blue F3G-A maintained protease adsorption at high values. Neither maximum capacities nor dissociation constants calculated from isotherms measured at 8 and 25°C showed great differences. By contrast, a strong temperature effect was evidenced in the elution step: elution at 8°C allowed 70, 81, and 98% recovery of adsorbed protease with Yellow HE-4R, Red HE-3B, and Cibacron Blue F3G-A, respectively, whereas only 20% recovery was attained at 25°C. Based on the results obtained, a purification process for the neutral protease contained in Flavourzyme with Cibacron Blue F3G-A as the affinity ligand was developed, yielding 96% of electrophoretically pure enzyme in a single step, the specific activity rising from 850 to 3650 U/mg.     

The free solution mobility of DNA in Tris-acetate-EDTA buffers of different concentrations,with and without added NaCl

The free solution mobility of a high-molecular-weight DNA, linear pUC19, and a 20-bp oligomer called dsA5 have been studied as a function of Tris-acetate-EDTA (TAE) buffer concentration, with and without added NaCl. The two DNAs migrate as separate peaks during capillary electrophoresis, because the mobility of linear pUC19 is higher than that of the 20-bp oligomer. In TAE buffers ranging from 10-400 mM in concentration, the migration times and peak areas of the two DNAs are independent of whether they are electrophoresed separately or in mixtures, indicating that DNA-DNA and DNA-buffer interactions are absent in these solutions. The migration times of the two DNAs vary and the peak areas are not additive when the TAE buffer concentration is reduced to 5 mM or below, indicating that DNA-DNA and DNA-buffer interactions are occurring at very low TAE buffer concentrations. The mobilities of linear pUC19 and dsA5 decrease slowly with increasing conductivity or ionic strength when the conductivity is increased by increasing the TAE buffer concentration. When the Tris buffer concentration is held constant and the conductivity is increased by adding various concentrations of NaCl to the solution, the mobilities of linear pUC19 and dsA5 first increase slightly, then become independent of solution conductivity (or ionic strength), and finally decrease when the NaCl concentration is increased above approximately 50 mM. The mobility variations observed in the various TAE and TAE-NaCl solutions are described qualitatively by Manning's theory, although quantitative agreement is not achieved. The free solution mobilities of single-stranded pUC19 and two 20-base oligonucleotides have also been measured. The free solution mobility of single-stranded pUC19 is approximately 15% lower than that of native pUC19, in agreement with other results in the literature. Somewhat surprisingly, the mobilities of the single- and double-stranded 20-mers are equal to each other in TAE buffers with and without added NaCl.