Structure of Glasses of the TeO2 – MoO3 System

Structural models for glasses of the TeO₂–MoO₃ system are suggested. On the basis of X-ray and infrared spectral investigations, by comparing with known crystalline structures of TeO₂, MoO₃ and Te₂MoO₇(T₂M), it is shown that the glasses from TeO₂ to Te₂MoO₇ possess [TeO₄] and [MoO₅] groups as basic structural units. The latter are connected to form [Mo₂O₈] complexes. The glasses in the MoO₃-rich compositional range are built up of [TeO₃] and [MoO₆] polyhedra. The glass-formation tendency is discussed in relation to the role of the free electron pair and the disruption of secondary and weak primary bonds in the crystals.     

Exploration of the electrophoretic behaviour of borane cluster anions and of the capability of capillary electrophoresis to separate them chirally

Mobilities of investigated boron cluster compounds in 3-(N-morpholino)propanesulfonic and phosphate buffers adjusted to pH 7 either with sodium hydroxide or with tris(hydroxymethyl)aminomethane depend on both buffer ions. The zone width and zone asymmetry, which are usually markedly higher than those of organic or common inorganic ions of comparable size, depend on the type of the borane cluster anion. Unusual shapes of zones of two investigated compounds have been found in tris phosphate buffer. Acetonitrile was superior to methanol as an organic additive to separation systems from the viewpoint of the zone symmetry and separation speed. Narrow trigonal zones, typical of organic ions non-interacting with the capillary wall, have been observed for some bridged sandwich cobalt complexes in run buffers with the addition of acetonitrile. The interaction of borane cluster anions with beta-cyclodextrin cavity is excessively strong in purely aqueous solutions. Methanol and acetonitrile, which generally weaken the interaction, sometimes affect the separation enantioselectivity of various compounds in different ways in addition to the weakening effect. Chiral discrimination was reached for all ten investigated anions, which belong to four different structural types of cluster boranes. Stability constants estimated for some analyte-beta-cyclodextrin complexes range between 100 and 1800 l/mol in acceptable separations. The relative difference of the constants was from 3 to 20%.     

Kinetics of homogeneous acetoxylation of cyclododecene and 1,5,9-cyclododecatriene catalyzed by Pd(OAc)2

The kinetics of acetoxylation of cyclododecene and (E,E,E)-1,5,9-cyclododecatriene catalyzed by Pd(OAc)₂ has been studied in glacial acetic acid solutions at 323–343 K and atmospheric pressure. The experimental data were described by kinetic equations of the Michaelis-Menten type.     

Determination of arsenate and organic arsenic via potentiometric titration of its heteropoly anions

Determination of arsenate based on its conversion to molybdoarsenate heteropoly anions followed by potentiometric titration is described. The titration is realized on the ion-pairing principle using cetylpyridinium chloride (or an analogous titrant containing a lipophilic cation), and is monitored by a carbon paste electrode, although other liquid-polymeric membrane-based electrodes can also be used. Calibration plots of the titrant end-point consumption versus concentration of arsenic were constructed and used to evaluate the content of arsenic in aqueous samples. The method could be applied in the analyses of samples with quite low arsenic content (amounts approximately 10 mug As in 50 cm(3) could be titrated). Organic arsenic was determined analogously after the Sch?niger combustion of the sample and conversion of its arsenic to arsenate.     

“Relationship” specification in Z-notation

Initially, relational model of data has been specified by E. F. Codd with the naming conventions to the attributes called “relationship”. It is something between relations and tables, i.e., between implementation and user view on data. In this paper, ideas for “relationship” are formally specified in Z-notation. The last one is an ISO standard now. The purpose of this paper is to reinvestigate ideas behind the “relationships” in a more formal way. This approach is useful for further research in extending relation model of data to capture multimedia data and data streams, which are, usually, generated by different kinds of sensors.     

Statistical Estimation of the Shannon Entropy

The behavior of the Kozachenko–Leonenko estimates for the(differential) Shannon entropy is studied when the number of i.i.d. vector-valued observations tends to infinity. The asymptotic unbiasedness and L~2-consistency of the estimates are established. The conditions employed involve the analogues of the Hardy–Littlewood maximal function. It is shown that the results are valid in particular for the entropy estimation of any nondegenerate Gaussian vector.     

Intermolecular Dipole–Dipole Relaxation of Xe Dissolved in Water

Intermolecular ¹²⁹Xe–¹H nuclear Overhauser effects and ¹²⁹Xe longitudinal relaxation time measurements were used to demonstrate that the dipole–dipole coupling is the dominant relaxation mechanism for ¹²⁹Xe in water, at room temperature. ¹²⁹Xe–¹H cross-relaxation rates were derived to be ς_XeH 3.2 ± 0.3 × 10⁻³ s⁻¹, independent of xenon pressure (in the range of 1–10 bar) and of the presence of oxygen. Corresponding xenon–proton internuclear distances were calculated to be 2.69 ± 0.12 Å. Using the magnitude of the dipole–dipole coupling and the spin density ratio between dissolved xenon and bulk water, it is estimated that ¹²⁹Xe–¹H spin polarization-induced nuclear Overhauser effects would yield little net proton signal enhancement in water.     

Statistical Model for Assessing the Optical Density of Laser-Produced Microplasma

The space and time change of the optical density of laser-produced microplasma is studied. A statistical model is proposed which allows its utilization for assessing plasma optical density at a constant, as well as at a changing laser radiation intensity.