Determination of tributyltin oxide in coastal marine sediments and mussels by electrothermal atomic absorption spectrometry

We have devised a new method for bis(tributyltin)oxide (TBTO) determination in marine sediments and mussels. This technique involves an n-hexane/methylene chloride mixture extraction and extract purification with a sodium hydroxide wash in order to eliminate interfering compounds. TBTO is then extracted again by nitric acid and converted into an inorganic tin species; the analysis has been effected using Zeeman graphite furnace-atomic absorption spectrophotometry. The method detection limit for the matrices examined is 0.004 μg TBTO g^?1 (wet weight) and is sufficient for the analysis in real samples. The percentage recovery of TBTO from sediments and mussels samples is higher than 85% and 95% respectively. This method has been applied to TBTO level determination in sediments and mussels (Mytilus galloprovincialis) sampled in the harbour area in Taranto, where mussel culture activities are much developed; the TBTO levels obtained in sediments and mussels were in the range 15-47 ng g^?1 (wet weight) and 11-30 ng g^?1 (wet weight) respectively. Such values are comparable with those found in other harbour areas in the Mediterranean Sea.     

A symmetry-adapted force-constant lattice-dynamical model for single-walled carbon nanotubes

We develop a lattice-dynamical model based on the screw symmetry of single-walled carbon nanotubes that allows for reducing the size of the dynamical matrix to six, for all tube chiralities. The model uses force constants derived from fitting to the phonon dispersion of 2D graphite. We present the calculation procedure in a clear and transparent way, making the model easier to follow. We calculate the phonon dispersions of a number of nanotubes of different chiralities. The splitting of two highest Raman active modes and the radial breathing mode frequency are studied by changing the tube diameter and chirality.     

Applications of fast atom bombardment mass spectrometry (FAB MS) to organometallic and coordination chemistry

This article describes the technique of fast atom bombardment mass spectrometry (FAB MS) and its applications to the analysis of organometallic and coordination complexes. Sections on ion generation and matrices are followed by a Periodic Group-based review of FAB MS results obtained from Transition Metal and Main Group compounds, organometallic cluster carbonyls and their derivatives, and salts of poly-oxo-anions. The literature has been surveyed from 1981 to approximately mid-1986.     

Effect of errors on the efficiency of local active sound absorbers

Effect of errors of different origin on the efficiency of sound absorption by a local active absorber is investigated. Degradation of the efficiency of absorption because of the errors is shown to be minimal in the case when the controller does not detect the field of the secondary radiator. Estimates of admissible errors are presented. Several active absorber configurations in which the radiator does not affect the receiver are considered.     

Statistical characteristics of quasi-elastically scattered light in analysis of size of aggregated biological particles

The spectra of the intensity fluctuations of light scattered by large (erythrocytes of whole blood) and small (vesicles of surgical bile) particles in natural conditions were studied. It is shown that photon correlation spectroscopy can be used in analysis of variations in the size of biological particles in normal and pathological conditions and as an express method of noninvasive diagnostics of diseases.     

Riemannian Hilbert submanifolds of nonpositive extrinsic curvature

We consider strongly parabolic, Hilbert submanifolds in Riemannian Hilbert manifolds. We prove that their properties are analogous to the known properties in the finite-dimensional case. The main geometric result consists of Theorem 3: a complete, Riemannian, Hilbert submanifold of nonpositive extrinsic curvature and finite codimension in a Hilbert sphere is a great sphere.Translated from Ukrainskii Geometricheskii Sbornik, No. 33, pp. 91–100, 1990.The author expresses his thanks to Professor A. A. Borisenko for posing the problem and guiding the work.     

The large-particle method in arbitrary nets and its application to the solution of problems in the aeroelasticity of a parachute

Modifications are introduced into the large-particle method to make it possible to use the method in arbitrary nonrectangular computing nets in the study of the flow of an ideal compressible gas over mobile thin permeable membranes. A problem in the aeroelasticity of a parachute is stated. An example is given of the solution of a problem in the stationary formulation for an axially symmetric parachute in the wake of a cylindrical leading body for supersonic flow.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 16–22