Markov Chain Analysis for One-Dimensional Asynchronous Cellular Automata

We consider the finite homogeneous Markov chain induced by a class of one-dimensional asynchronous cellular automata—automata that are allowed to change only one cell per iteration. Furthermore, we confine to totalistic automata, where transitions depend only on the number of 1s in the neighborhood of the current cell. We consider three different cases: (i) size of neighborhood equals length of the automaton; (ii) size of neighborhood two, length of automaton arbitrary; and (iii) size of neighborhood three, length of automaton arbitrary. For each case, the associated Markov chain proves to be ergodic. We derive simple-form stationary distributions, in case (i) by lumping states with respect to the number of 1s in the automaton, and in cases (ii) and (iii) by considering the number of 0–1 borders within the automaton configuration. For the three-neighborhood automaton, we analyze also the Markov chain at the boundary of the parameter domain, and the symmetry of the entropy. Finally, we show that if the local transition rule is exponential, the stationary probability is the Boltzmann distribution of the Ising model.     

High-precision quadruple isotope dilution method for simultaneous determination of nitrite and nitrate in seawater by GCMS after derivatization with triethyloxonium tetrafluoroborate

Quadruple isotope dilution mass spectrometry (ID⁴MS) has been applied for simultaneous determination of nitrite and nitrate in seawater. ID⁴MS allows high-precision measurements and entails the use of isotopic internal standards (¹⁸O-nitrite and ¹⁵N-nitrate). We include a tutorial on ID⁴MS outlining optimal experimental design which generates results with low uncertainties and obviates the need for direct (separate) evaluation of the procedural blank. Nitrite and nitrate detection was achieved using a headspace GCMS procedure based on single-step aqueous derivatization with triethyloxonium tetrafluoroborate at room temperature. In this paper the sample preparation was revised and fundamental aspects of this chemistry are presented. The proposed method has detection limits in the low parts-per-billion for both analytes, is reliable, precise, and has been validated using a seawater certified reference material (MOOS-2). Simplicity of the experimental design, low detection limits, and the use of quadruple isotope dilution makes the present method superior to the state-of-the-art for determination of nitrite and nitrate, and an ideal candidate for reference measurements of these analytes in seawater.     

Iodine-catalyzed one-pot synthesis of unsymmetrical meso-substituted porphyrins

The wide range use of 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin is well established, but its synthesis requires two steps and is not very practical. This article describes an iodine-catalyzed one-pot synthesis of this unsymmetrical porphyrin that uses commercial reagents and reactants as such, without prior distillation. Unsymmetrical mono functionalized porphyrins with various functional groups have also been obtained to validate this method. The influence of electronic effects of functional groups (donor or acceptor) has also been studied.     

Instantaneous and simultaneous planar velocity field measurements of two phases for turbulent mixing of high pressure sprays

This paper describes the tests of accuracy and the first application of a combined planar visualization technique. Its goal is two-phase flow discrimination, i.e. simultaneous measurements of velocity of droplets and ambient gas in the case of two-phase flow mixing, at the same location and with possible conditioning by “apparent diameter” (AD) of the droplets. It combines the mature techniques of particle image velocimetry (PIV), planar Mie scattering diffusion (PMSD), planar laser-induced fluorescence (PLIF), and it necessitates two synchronized cross-correlation systems, digital image treatment and analysis. This technique was developed with the objective of better describing the mixing between liquid and gaseous phases as in the case of high-pressure spray atomization in quiescent ambient gas. The basic principle of separation is to seed the ambient gas with micrometer particles and to tag the liquid with fluorescent dye. We use digital image treatment and analysis to discriminate between the phases. We use two cross-correlation PIV systems in order to obtain the velocity field of the droplets and gas simultaneously and separately at the same location. The digital image processing for separating the phases involves geometric measurement of droplet shapes. This leads to measurement of droplet parameters close to their real diameter, which could be used for analysis of actual mixing. A synchronized system composed of two CCD cameras is used for image recording, and two Nd:YAG lasers are used for generating pulsed light sheets at times t and t + δt. Tests were performed to check for different sources of errors. The combined technique was applied to measurements in high-pressure spray flow atomizing in a quiescent ambient gas, and first results are presented.     

Electronic structure of thallous centres and Tl+ - Vk recombination in KCl crystal

Parameters of impurity Tl ion required for the calculation of different thallous centres in alkali halides are obtained for the semiempirical method of the intermediate neglect of differential overlap (INDO). The electronic structure of Tl⁺, Tl²⁺ centres in KCl is calculated. The potential energy curves for the recombination of nearest Tl⁺, V_$\text{k}$ centres against the breathing vibrational mode of the V_$\text{k}$ centre are calculated. This recombination (hole trapping) is found to be nonradiative tunneling with small activation energy rather than radiative one. A number of experimental data is also discussed in the light of the present calculations.     

Umwandlungen glasförmiger BSCCO-Vorstoffe in den kristallinen Zustand

The glassy precursors were fabricated by quenching the melted materials with copper plates. In the case of heating the properties of the quenched samples were changed, because as a result of solid-state reactions formation of cuprate occurs. The amorphous samples were annealed in air and transformed to the crystalline state. This process can be seen by DTA and electric resistivity behaviours. The microscopic observation of the polished surfaces show the growth of the superconducting phase Bi₂Sr₂CaCu₂O_8+x (for composition Bi-2212) and Bi₂Sr₂CaCu₂O_8+x with Bi₂Sr₂Ca₂Cu₃O_10+x (for composition Bi-2223 and Bi-2234), respectively.