Scanning LLL x-ray interferometry

A new formalism is presented for the theory of scanning LLL x-ray interferometry, which takes account also of the amount of x-ray absorption and of crystal yawing. It is based on the Takagi approach to the dynamical theory of x-ray diffraction and uses, to a great extent, the formalism of quantum mechanics, in order to reduce the algebraic complexity of the Ewald-von Laue approach. The formalism presented here is an easy-to-handle tool for the study of x-ray propagation in multicrystal systems and for the investigation into deviations of the travelling-fringe period from the spacing of diffracting planes, as it explains how interference features change when moving in paramater space.     

Multivariate Gini Indices

Two extensions of the univariate Gini index are considered:R_D, based on expected distance between two independent vectors from the same distribution with finite meanμ ^d; andR_V, related to the expected volume of the simplex formed fromd+1 independent such vectors. A new characterization ofR_Das proportional to a univariate Gini index for a particular linear combination of attributes relates it to the Lorenz zonoid. TheLorenz zonoidwas suggested as a multivariate generalization of the Lorenz curve.R_Vis, up to scaling, the volume of the Lorenz zonoid plus a unit cube of full dimension. Whend=1, bothR_DandR_Vequal twice the area between the usual Lorenz curve and the line of zero disparity. Whend>1, they are different, but inherit properties of the univariate Gini index and are related via the Lorenz zonoid:R_Dis proportional to the average of the areas of some two-dimensioned projections of the lift zonoid, whileR_Vis the average of the volumes of projections of the Lorenz zonoid over all coordinate subspaces.     

A model of the kinetics of macrocyclic BPA carbonate formation

Cyclic oligocarbonates are synthesized by two-phase interfacial reactions of aryl bischloroformates in the presence of an amine phase transfer catalyst and an alkali: nClOCOArOCOCl + 4nNaOH → (OArOCO)_n + 2nNaCl + nNa₂CO₃ + 2nH₂O. The organocarbonate product may be a macrocyclic oligomer or a linear chain polymer. A qualitative mechanism for this behavior has been proposed by Brunelle, Boden, and co-workers. Four steps are identifiable: activation of the aryl bischloroformate by the amine catalyst, hydrolysis of a portion of this intermediate at the aqueous/organic phase interface, oligomerization between activated and hydrolyzed moieties also at the interface, and chain terminating carbamate formation that leads to polymer. An important modification is made within the framework of the Brunelle and Boden mechanism. While the intramolecular cyclization reaction is formally second-order overall, it behaves as a first-order process. The kinetic constants for both this pseudo-first-order cyclization step and the corresponding second-order linearization step are simply related. It is speculated that the above relationship can be generalized for a whole class of pseudo-first- and second-order rate constants for similar macrocyclic reactions.     

Synthesis and properties of Hg-based high-T c superconductors

Il Nuovo Cimento D - The formation of Hg-based HTSC materials was investigated through the development of non-conventional techniques. The former was based on a singlestep synthesis at temperatures...     

Analysis of atmospheric particular matter and water using atomic emission spectrometry with inductively-coupled plasma and two-jet plasmatron

Summary A method for the atomic emission spectrometric analysis of air and water with inductively coupled and two-jet direct current plasmas has been developed. The method has been applied to the determination of impurity contents with good accuracy and sensitivity.     

Velocity spectrum for non-Markovian Brownian motion in a periodic potential

Non-Markovian Brownian motion in a periodic potential is studied by means of an electronic analogue simulator. Velocity spectra, the Fourier transforms of velocity autocorrelation functions, are obtained for three types of random force, that is, a white noise, an Ornstein—Uhlenbeck process, and a quasimonochromatic noise. The analogue results are in good agreement both with theoretical ones calculated with the use of a matrix-continued-fraction method, and with the results of digital simulations. An unexpected extra peak in the velocity spectrum is observed for Ornstein-Uhlenbeck noise with large correlation time. The peak is attributed to a slow oscillatory motion of the Brownian particle as it moves back and forth over several lattice spaces. Its relationship to an approximate Langevin equation is discussed.     

New olefinic functionalized disilanes. Synthesis and NMR spectroscopical investigations

The new olefinic substituted aminodisilanes, which are obtained from the reaction of organometallic reagents with aminochlorodisilanes, are converted into the chlorodisilanes by equilibration reactions or treatment with HCI. The resulting olefinic functionalized disilanes are identified by means of ²⁹Si, ¹³C, ¹H NMR and GC MS measurements.     

Monitoring of electromagnetic fields in the environment. II. Fluctuations in the parameters of atmospheric electricity

The problems of determining and investigating the informative parameters of atmospheric electricity are discussed. It is shown that short-period variations in atmospheric electricity are ecologically significant. An automated system for monitoring atmospheric electricity and a method of processing the results of measurements are described. V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 88–98, May, 1998.