Hybrid method for the determination of the relative orientation between displaced images

A hybrid method for solving the problem of the determination of the relative orientation between two displaced images is described. The method is based on obtaining the angular distribution of the power spectrum by means of a rotating slit placed on the Fourier plane, and concentrating the passing light intensity into a detector. The signal is introduced into the computer where the correlation function with the following signal of another image is calculated.     

Quality assurance in pesticide residue analysis

Summary During the last few years, the Working Group Pesticide Residues of the Food Chemistry and Forensic Chemistry Division of the Gesellschaft Deutscher Chemiker (German Chemical Society) has organised six laboratory performance tests on the analysis of pesticide residues in which numerous laboratories were involved. In these tests the choice of the analytical methods for the examination of fats or vegetable substrates was free. Organochlorine pesticides in concentrations of over 0.01 mg/kg were mostly readily identified, whereas in the analysis of organophosphorus residues often only the classic compounds (parathion, diazinon, etc.) were reported. Many a false positive result could have been avoided by using more adequate methods for confirmatory analysis. The quantitative results, however, were generally quite reliable and were mostly within the official acceptable dispersion range. It can be concluded that the performance of a residue laboratory is by no means constant, and that it is necessary to assess regularly the quality of the analytical results by participating in such interlaboratory tests.

---

Qualitätssicherung bei Rückstandsanalysen von PflanzenschutzmittelnErfahrungen aus Ringversuchen

     

Electronic structure and chemical bonding in actinide oxides: Monoxides and dioxides of Np,Pu, Am,Cm and Bk

First-principles molecular cluster calculations of the electronic structure of actinide monoxides and dioxides have been carried out in the local density formalism. AcO₆^10? clusters representative of monoxides and AcO₈^12? clusters for dioxides (Ac = Np, Pu, Am, Cm and Bk) have been studied in spin-restricted and spinpolarized models, using the discrete variational method with numerical atomic basis functions. One-electron energy level diagrams, atomic configurations, charge and spin densities were obtained. It is found that significant covalent mixing of O 2ρ and Ac 5f atomic orbitais occurs for heavy actinide compounds, contrary to the assumption of free-ion models. X-ray photoelectron line shape calculations agree rather well with experimental data on the dioxides. Analogies between systematics of the energy levels of actinide and rare-earth compounds are discussed.     

Whole cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and in situ structure analysis of streptocidins, a family of tyrocidine-like cyclic peptides

Streptocidins, a family of tyrocidine-like cyclic decapeptides, are an ideal demonstration object for the detection and in situ structure analysis of natural compounds directly in microbial cells using whole cell matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry (MALDI-TOFMS), an emerging technique that can be used for rapid sensitive metabolic profiling of microorganisms. Five main members of the streptocidin family (A-E) were detected in Brevibacillus cells picked from agar plates and identified by in situ structure analysis with post-source decay MALDI-TOFMS. This efficient modern method allows the precise detection of metabolites within minutes without the need to isolate and purify the target compounds. The generated mass spectra are of similar quality to those obtained for the purified peptides. In addition, surface extracts were prepared by treating Brevibacillus cells with 70% acetonitrile in the presence of 0.1% trifluoroacetic acid and fractionated by high-resolution reversed-phase high-performance liquid chromatography (HPLC). In this way ten minor streptocidins were detected demonstrating the full biosynthetic variety of streptocidin production on the cellular level. The streptocidins differ from the well-known tyrocidines essentially in position 3 of the decapeptide chain by replacement of the aromatic amino acid (F/W) found in tyrocidines by L-leucine or L-valine.     

Ionic equilibria in neutral amphiprotic solvents; resolution of acid strength in tert-butyl alcohol

The dissociation constants of several families of acids and their tetrabutylammonium salts, as well as the ternary-ion formation constants, in tert-butyl alcohol medium, were determined by potentiometric and conductometric methods. The comparison of the calculated pK values of the acids with those obtained in other amphiprotic media shows the better resolution of acid strength in tert-butyl alcohol. The different behaviour of acids of the same family, for two main series studied, phenols and mercaptopyrimidines, has been explained in terms of structure.     

Isolation and total synthesis of (E)-6, 10-dimethyl-9-methylidene-undec-5-en-2-one,a constituent of Costus root oil

(E)-6, 10-Dimethyl-9-methylidene-undec-5-en-2-one ( 1 ) has been isolated from Costus root oil. A total synthesis of this compound is reported.