Frequency dependent conductivity of the interrupted strand model

We present rigorous results on the frequency dependence of the Kubo-Greenwood conductivity of the interrupted-strand — or bond-percolation model, for which exists strong evidence to be relevant for a class of quasi one-dimensional organic conductors and for some mixed valent complex compounds like K₂Pt(CN)₄ Br_0.30 3H₂O. The model describes a linear sequence of one-dimensional metallic boxes or segments separated from each other by perfectly insulating lattice defects. We used both Lotentzian and rectangular averages to obtain the frequency-averaged conductivity as a well-defined physical quantity and found a sharply peaked structure of the conductivity spectrum resulting from the non-zero energy level spacing of one metallic box. Since one has to look very carefully on different frequency average procedures and on the consequences of the energy spectrum of an entire strand one has to precise arguments and results on the low frequency behaviour of the conductivity obtained from numerical considerations recently proposed by P.S. Riseborough.     

Precise atomic masses of147Eu,147Gd,and151Tb derived from their decay properties

Theβ-decay energies of¹⁴⁷Eu,¹⁴⁷Gd, and¹⁵¹Tb were determined by usingγ-spectroscopical methods. The comparison of experimental with calculatedK-capture probabilities yielded theQ _EC values 1.690( _?16 ⁺²¹ )MeV and 2.203( _?13 ⁺¹⁹ )MeV for¹⁴⁷Eu and¹⁴⁷Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in¹⁴⁷Eu decay, the decay energiesQ _EC=1.702(13) MeV andQ _EC=1.709(18)MeV were derived. Also fromEC/β ⁺ ratios the valuesQ _EC=2.225(75) MeV for¹⁴⁷Gd, andQ _EC=2.566(12)MeV for¹⁵¹Tb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studiesγ-decay properties of¹⁴⁷Eu and¹⁴⁷Gd were reinvestigated.     

Polarographisches Verhalten von Pesticiden mit Organohalogenbindungen

Summary The dp-polarographic behaviour of different pesticides with carbon-halogen bonds was investigated in dimethylsulfoxide and methanol/water as solvents; the peak-potentials are demonstrated graphically. From peak-height the pesticides are detectable up to 100 ng · ml^–1. The investigations are of interest for the development of multistage-combined procedures by h.p.l.c. with amperometric detection.

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Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet     

Study on multimers and their structures in molecular association mixture

Self-association system of(R)-1,3-butanediol in dilute carbon tetrachloride(CCl4)solution is studied as a model of molecular association mixture.Analysis methods including FSMWEFA(fixed-size moving window evolving factor analysis)combined with PCA(principal component analysis),SIMPLISMA (simple-to-use interactive self-modeling mixture analysis),and ITTFA(iterative target transformation factor analysis)are adopted to resolve infrared spectra of(R)-1,3-butanediol solution.Association number and equilibrium constant are computed.(R)-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system.Theoretical investigation of trimer structures is carried out with DFT(density functional theory),and structural factors are analyzed.     

<Emphasis Type="Italic">Brønsted</Emphasis> Acids in Ionic Liquids: Fundamentals,Organic Reactions,and Comparisons

Summary. A background for studying acids in various solvents is developed, emphasizing the importance of knowing to what extent a solvent conducts electricity and is therefore ionized, the dissociation equilibria of common molecular solvents and the acidic and basic species generated by solvent leveling. Acidity measurements in the atypical solvent water are discussed and the common method of expressing acidity in other systems – by Hammett values – is introduced. Representative examples of reactions involving Br?nsted acids in ionic liquids are presented and attention paid to the questions of speciation and acidity values. It is found that the gas phase proton affinity of a base is often a better guide to the acidity of its conjugate acid in an ionic liquid than is the dissociation constant of the said acid in water.     

Use of γ-γ Coincidence Spectrometry in the Geochemical Study of Diamictites from South Africa

We used - coincidence spectrometry to investigate the possible presence of a meteoritical component in 27 samples of South African diamictites. Recently, several studies have suggested that some tillites/diamictites may represent impact breccias, but a petrographical study by our group found no evidence for the presence of impact-characteristic shocked minerals. The siderophile elements, such as Cr, Co, Ni, and, especially, the platinum group elements, have high abundances in meteorites, but low abundances in terrestrial crustal rocks. The Ir content of the diamictites was measured with the new iridium coincidence spectrometer (ICS) at the University of Vienna, with detection limits of around 0.02 ppb. No enrichments in the contents of Ir and other siderophile elements compared to average crustal concentrations were found; thus, no unequivocal evidence for an impact origin of these diamictites of the South African Dwyka Group can be documented.     

Über Verbindungen der Siliciumtetrahalogenide mit aromatischen N-Heterocyclen: Bestätigung und Berichtigung

Zusammenfassung Von den früher⁶ beschriebenen Additionsverbindungen zwischen Siliciumtetrahalogeniden und Pyridin bzw. seinen Homologen konnten J₄Sipy ₄ ⁷ und HSiCl₃ py ₂ eindeutig bestätigt und in ihren Eigenschaften wie einigen chemischen Reaktionen näher festgelegt werden. Nicht dagegen existieren Verbindungen zwischen SiJ₄ und Chinolin, -Picolin, Acridin oder Collidin. SiF₄ bildet bei direktem Einleiten in Chinolin eine bereits kurz oberhalb Raumtemperatur zersetzliche Additionsverbindung F₄Si(chin)₂.

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From addition compounds of silicon tetrahalogenides and pyridine, published⁶ in 1954, the somewhat doubtful J₄Sipy ₄ ⁷ and HSiCl₃ py ₂ could be confirmed and fixed in their properties as well as in some chemical reactions. On the contrary compounds between SiJ₄ and quinoline, -picoline, acridine and collidine do not exist. On passing SiF₄ directly into quinoline, an addition compound F₄Si(chin)₂ is formed which decomposes already at temperatures somewhat higher than room temperature.

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64. Mitt.:H. Bürger, M. Schulze undU. Wannagat, Inorg. Nucl. Chem. Letters3, 43 (1967).

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Zugleich 4. Mitt. über Verbindungen von Nichtmetallhalogeniden mit Pyridin und seinen Homologen; 3. Mitt.:U. Wannagat undG. Schindler, Angew. Chem.69, 784 (1957).

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Mit Auszügen aus der DissertationK. Hensen, Techn. Hochschule Aachen 1962.

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Mit Auszügen aus der DiplomarbeitP. Petesch, T. H. Aachen 1958.     

Alkylamino- und Dialkylamino-phenoxy-methylsilane

Zusammenfassung Alkyl-und Dialkylamino-phenoxy-methylsilane ließen sich sowohl durch Umsetzung von Phenoxy-methyl-chlorsilanen mit primären und sekundären Aminen unter Cl/NRR-Austausch als auch durch Reaktion von Phenoxymethylsilanen mit substituierten Alkaliamiden unter C₆H₅O/NRR-Austausch gemäß den Gl. (1) bis (6) darstellen. Ihre Eigenschaften sind aus Tab. 1 zu ersehen.

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We succeeded in preparing alkyl- and dialkylamino-phenoxymethylsilanes by reaction of phenoxy-methyl-chlorosilanes with primary and secondary amines (Cl/NRR-exchange) as well as by reaction of phenoxymethylsilanes with substituted alkaliamides (C₆H₅O/NRR-exchange)according equations (1) to (6). Their properties are to be seen in table 1.

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53. Mitt.:U. Wannagat undG. Schreiner, Mh. Chem.96, 1902 (1965).

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Mit Auszügen aus der DissertationG. Schreiner und der DiplomarbeitJ. Pohl, Techn. Hochsch. Graz, 1964.     

Phenanthroline complexes bearing diamide-anion recognition sites

The synthesis and anion binding properties of new ruthenium(II) and cobalt(II) phenanthroline complexes, containing two amide subunits are described. Evidence for anion binding in dimethyl sulfoxide (DMSO) solution was obtained from u.v.–vis titration experiments. Results indicated that these receptors showed strong affinity for F⁻ and AcO⁻, and showed weak affinity for OH⁻ and H₂PO ₄ ⁻ , and showed no affinity for Cl⁻, Br⁻, I⁻. These receptors interacted with various anions examined through hydrogen-bond formation.     

Development of a non-invasive method for the determination of the macroscopic neutron cross sections of a sample matrix in large-sample prompt-gamma neutron activation analysis

In order to correct for neutron self-shielding in large-sample prompt gamma NAA, a method has been developed to determine the macroscopic scattering and absorption cross sections, i.e., Σ _a and Σ _s, using four Cu flux monitors placed around the sample. With Monte Carlo computations, the neutron densities throughout the sample and the resulting and the corresponding self-shielding factor as calculated from the Σ _a and Σ _s as obtained through the Cu monitors were compared to the true values. The derived Σ _a and Σ _s were found to be sufficiently accurate as long as Σ _t = Σ _a + Σ _s was less than 0.6 cm⁻¹ and Σ _s/Σ _t was greater than 0.1.