Selective determination of oxygenates in complex samples with the O-FID analyzer

A gas-chromatographic analyzer allowing the selective detection of individual oxygenates in complex organic mixtures, such as gasolines, is described. The analyzer is based on the oxygen-specific response flame ionization detection (O-FID) method. The system operates with capillary columns and includes a cracking reactor to convert any oxygenate to carbon monoxide and a special FID equipped with a microreactor for the catalytic hydro-genation of CO and detection as methane. Hydrocarbons give no signal. The selectivity of the method is better than 1:10⁷ and the linear range approaches 10⁵. The analysis of modern fuels containing oxygenated additives, to improve octane ratings, may greatly benefit from the proposed analytical method.     

Quantum-chemical approach to the elementary steps of plasma etching

We derive for the first time a mechanism of reactive plasma etching in the system Si/F by the quantum-chemical approach. SiF₂-like species at the surface play an important role. SiF₃ surface complexes also occur. The final etching product SiF₄ is formed with high probability in the gas phase.     

After-effects of Auger ionization following electron capture in organic 125iodine compounds

The emission Mössbauer spectra of ¹²⁵I labeled iodobenzene, methyl iodide, and of their dilute solutions in benzene and hexane, were computer analyzed. Two species were observed, in one of which tellurium is presumably attached to two organic moieties, while in the other, tellurium is attached to a single organic moiety.     

Schwefel(IV)-Verbindungen als Liganden. II. Die Kristall- und Molekülstruktur von Pentacarbonyl-(schwefeldioxid)chrom

Sulfur(IV) Compounds as Ligands. II. The Crystal and Molecular Structure of Pentacarbonyl--(sulfur dioxide)chromium The structure of pentacarbonyl(sulfurdioxide)chromium ( 1 ) has been determined from single crystal X-ray data. The compound crystallizes with eight formula units in the rhombic unit cell (space group Pbn2₁) of the dimensions a = 657.8(2) pm, b = 1245.2(4) pm, c = 2177.4(5) pm (at 180 K). The sulfur dioxide is η¹-coplanar coordinated, the Cr? S distance is 219 pm, the shortest bond reported so far between chromium(0) and sulfur. The Cr? C(ax) bond (189 pm) was found only marginally shorter than the Cr? C(eq) bonds (190 pm) providing proof of the high π-acceptor capacity of SO₂.     

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Self-Rotation of Dust Particles in Induction-Type RF Discharge

Technical Physics - Self-rotation (rotation about the center of mass) of dust particles in a magnetic field has been investigated. The angular velocity of self-rotation in a dust trap produced by...     

A New Approach to the 3D Faddeev Equation for Three-body Scattering

A novel approach to solve the Faddeev equation for three-body scattering at arbitrary energies is proposed. This approach disentangles the complicated singularity structure of the free three-nucleon propagator leading to the moving and logarithmic singularities in standard treatments. The Faddeev equation is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. In its simplest form the Faddeev equation for identical bosons, which we are using, is an integral equation in five variables, magnitudes of relative momenta and angles. The singularities of the free propagator and the deuteron propagator are now both simple poles in two different momentum variables, and thus can both be integrated with standard techniques.     

Electronic structure and structural stability of LaAl2 and LaAl3—A comparative study

The large structural stability regime of LaAl₂ and LaAl₃ as a function of pressure is investigated by the band structure calculations using the FP-LAPW method. An earlier experimental study has revealed that there is no structural phase transition at ∼35 and ∼30 GPa for LaAl₂ and LaAl₃, respectively. Our calculations indicate that in the density of states curve of LaAl₂, the Fermi level (E_F) lies in a slope between bonding maxima and antibonding minima. At high pressures the E_F moves slightly towards the valley, but this shifting does not affect its structural stability. In LaAl₃, the E_F falls in a flat region in the density of states and does not move even up to 33 GPa. The band dispersion curves for both the compounds show movement of bands under the influence of pressure. Some of them cross the Fermi level leading to so called Lifshitz transitions. However, it is seen that these electronic changes do not manifest into any volume anomaly in LaAl₃ under pressure. Our study clearly shows that the density of states behavior for LaAl₂ and LaAl₃ satisfies the Yamashita-Asano criterion for structural stability. The theoretical equations of state, bulk modulus and its pressure derivative values are compared with the experimental values.     

Enhancement of L-Asparaginase Production by Isolated <Emphasis Type="Italic">Bacillus circulans</Emphasis> (MTCC 8574) Using Response Surface Methodology

L-asparaginase production was optimized using isolated Bacillus circulans (MTCC 8574) under solid-state fermentation (SSF) using locally available agricultural waste materials. Among different agricultural materials (red gram husk, bengal gram husk, coconut, and groundnut cake), red gram husk gave the maximum enzyme production. A wide range of SSF parameters were optimized for maximize the production of L-asparaginase. Preliminary studies revealed that incubation temperature, moisture content, inoculum level, glucose, and L-asparagine play a vital role in enzyme yield. The interactive behavior of each of these parameters along with their significance on enzyme yield was analyzed using fractional factorial central composite design (FFCCD). The observed correlation coefficient (R ²) was 0.9714. Only L-asparagine and incubation temperature, were significant in linear and quadratic terms. L-asparaginase yield improved from 780 to 2,322 U/gds which is more than 300% using FFCCD as a means of optimizing conditions.