One-Dimensional Poisson Growth Models With Random and Asymmetric Growth

Suppose there is a Poisson process of points X _i on the line. Starting at time zero, a grain begins to grow from each point X _i , growing at rate A _i to the left and rate B _i to the right, with the pairs (A _i , B _i ) being i.i.d. A grain stops growing as soon as it touches another grain. When all growth stops, the line consists of covered intervals (made up of contiguous grains) separated by gaps. We show (i) a fraction 1/e of the line remains uncovered, (ii) the fraction of covered intervals which contain exactly k grains is (k–1)/k!, (iii) the length of a covered interval containing k grains has a gamma(k–1) distribution, (iv) the distribution of the grain sizes depends only on the distribution of the total growth rate A _i +B _i , and other results. Similar theorems are obtained for growth processes on a circle; in this case we need only assume the pairs (A _i , B _i ) are exchangeable. These results extend those of Daley, et al. (2000) who studied the case where A _i =B _i =1. Simulation results are given to illustrate the various theorems.     

Identification by high-performance liquid chromatography of tyrosine ammonia-lyase activity in purified fractions of Phaseolus vulgaris phenylalanine ammonia-lyase.

Activities of phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) were assessed at each stage of a three-step purification of PAL. Assays were performed by high-performance liquid chromatographic (HPLC) separation and ultraviolet detection of reaction products. Use of HPLC permitted assay of low activities of PAL and TAL for periods up to approximately four and two days, respectively. HPLC also facilitated the accurate quantitation of the product of the TAL reaction, trans-p-coumaric acid, which was observed to isomerize readily under experimental conditions. PAL and TAL were associated throughout the purification procedure, with TAL activity at 0.6-1.3% of PAL activity. It was concluded that, contrary to previous reports, TAL and PAL activities are mediated by the same enzyme, or else by chromatographically very similar enzymes.     

Protonated ethanol and its neutral counterparts

Collisionally activated dissociation and neutralization-reionization experiments reveal that protonation of ethanol leads to two distinct isomers, the classical ion CH₃CH₂OH⁺₂ and the proton-bound complex C₂H₄…H⁺…OH₂. The neutral counterpart of the latter is unstable, whereas that of the former can be produced in a bound state if the CH₃CH₂OH⁺₂ precursor ion is formed under low ion source pressure conditions and, thus, with higher internal energies. This suggests that there are substantial differences in the geometries of CH₃CH₂OH⁺₂ and the hypervalent CH₃CH₂OH₂ ·. This provides only a partial explanation for unusual isotope effects; C₂H₅OD₂ ·, CH₃CD₂OD₂ ·, and CD₃CH₂OD₂ · are substantially more stable than C₂D₅OD₂ · and C₂H₅OH₂ ·.     

Silber

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Harze und Harzs?uren

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Zur Bestimmung von Schwefel und Halogenen

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Korrosion und Schutzanstriche

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Colorimetrische, spektrographische und photometrische Me?methoden

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Zur Trennung des Nickels von Eisen

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