Singular covers in free lattices

A covering a>b in a lattice is called a singular cover if a is join irreducible and b is meet irreducible. A classification of the singular covers which occur in free lattices is given.     

Isomerization and disproportionation of 1-methylnaphthalene on zeolites

The catalytic conversions of 1-methylnaphthalene in the presence of HY, HM, HZSM-5 and SAPO-5 have been studied under varying experimental conditions. While the main reaction is the isomerization, disproportionation also takes place. A correlation between the pore size and acidity of the catalysts and their activity, selectivity and stability is observed.     

Kinetik und Mechanismus der Oxydation von 1,2,4,5-Tetramethylbenzol in essigsaurem Medium

The liquid phase oxidation of 1.2.4.5-tetramethylbenzene catalysed by cobaltous acetate and promoted by KBr in acetic acid was kinetically studied. In view of deriving the kinetic equation for the absorption of oxygen, a number of experiments were carried out. The values of the activation energy and of the preexponentA=10¹⁴ were determined as well. The resulting kinetic equation: $$ - \frac{{d\left[ {O_2 } \right]}}{{d\tau }} = 10^{14} \cdot \exp \left( { - \frac{{84,460 \times 10^3 }}{{RT}}} \right) \cdot C_{C_6 H_2 (CH_3 )_4 }^{0,5} \cdot C_{Co(OAc)_2 }^{0,5} \cdot C_{KBr}^{0,5} $$ is in accordance with the theoretically derived expression of this type.     

Application of Mössbauer spectroscopy in pyritic and copper calcines studies

In the present study, Mössbauer spectroscopy is applied to the qualitative and quantitative investigation of pyritic and copper calcines prepared by the roasting of untreated concentrates and those which have received a preliminary treatment in a magnetic field. It was established that there are no significant differences in phase content between those calcines which have received a preliminary treatment and those which have not.

New phases were found in copper calcines depending on the intensifying factor applied.     

Darstellung und Eigenschaften von Trinorbornylbor-Verbindungen

Synthesis and Properties of Trinorbornyl Boron Compounds Tris(1-norbornyl), Tris(2-norbornyl), and Tris(7-norbornyl) boron were synthesized from boron trifluoride diethylether and 1-norbornyl lithium or 2- and 7-norbornyl magnesium halides respectively. The compounds were characterized by the IR-, ¹³C-, ¹¹B-NMR, and mass spectra. Furthermore 1-norbornyl lithium was isolated in the crystalline state and investigated in detail.     

POPs: a QSAR system for developing categories for persistent, bioaccumulative and toxic chemicals and their metabolites

This paper presents the framework of a QSAR-based decision support system which provides a rapid screening of potential hazards, classification of chemicals with respect to risk management thresholds, and estimation of missing data for the early stages of risk assessment. At the simplest level, the framework is designed to rank hundreds of chemicals according to their profile of persistence, bioaccumulation potential and toxicity often called the persistent organic pollutant (POP) profile or the PBT (persistent bioaccumulative toxicant) profile. The only input data are the chemical structure. The POPs framework enables decision makers to introduce the risk management thresholds used in the classification of chemicals under various authorities. Finally, the POPs framework advances hazard identification by integrating a metabolic simulator that generates metabolic map for each parent chemical. Both the parent chemicals and plausible metabolites are systematically evaluated for metabolic activation and POPs profile.     

Darstellung und Eigenschaften von Norbornylquecksilberverbindungen

Preparation and Properties of Norbornyl Mercury Compounds Bis(1-norbornyl) and bis(2-norbornyl)mercury, 1- und 2-norbornylmercury chloride and 1-norbornylmercury i-butyl were synthesized and characterized by ¹³C-N.M.R. investigations and in case of bis(1-norbornyl) mercury also by the I.R. and mass spectrum. The ¹J(¹⁹⁹Hg? ¹³C) coupling constants of the 1-norbornyl compounds demonstrate the trans-influence of the norbornyl anion.     

Electrochemical oxidation of some tetrahydropteridine derivatives at the platinum electrode

6 and 7-substituted 2-amino-4-hydroxy-5,6,7,8-tetrahydropteridines are oxidized at a platinum electrode in several waves in the potential range between hydrogen and oxygen evolution potentials. The electrode process in the first (main) anodic wave was investigated in more detail using a stationary and rotating disc platinum electrode. The process in this wave is “semireversible” with an exchange of two electrons. The standard rate constants of this reaction were determined. The oxidation product is deactivated by an irreversible chemical reaction. Some of the products block the surface of the electrode.