Damage of Industrial Reinforced Concrete Chimneys Caused by High Temperatures

The paper deals with the resistance of reinforced concrete against fire and the degradation of reinforced concrete due to high temperatures. In the first part the processes of degradation of concrete are solved due to the evaporation of water and its change of state with respect to the different thermal expansion of aggregates and concrete reinforcement members. The main part is focused on the construction of monolithic and prefabricated structures of industrial chimneys. The most common types of protection of the chimney's internal parts from the exhaust gases are discussed here. Also the possibilities of designing individual expansion joints are described. In the experiment, the problem of chimney damage, with the subsequent description of the chimney diagnostics in the premises of Unipetrol in Litvínov, was solved due to an extraordinary event - explosion of the ethylene unit.

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere have a great advantage. There are several types of dynamic helicity controls, including the responsive helicity inversion. In this review article, dynamic helical structures based on oligo(salamo) metal complexes are described as one of the possible designs. The introduction of chiral carboxylate ions into Zn3La tetranuclear structures as an additive is effective to control the P/M ratio of the helix. The dynamic helicity inversion can be achieved by chemical modification, such as protonation/deprotonation or desilylation with fluoride ion. When (S)-2-hydroxypropyl groups are introduced into the oligo(salamo) ligand, the helicity of the resultant complexes is sensitively influenced by the metal ions. The replacement of the metal ions based on the affinity trend resulted in a sequential multistep helicity inversion. Chiral salen derivatives are also effective to bias the helicity; by incorporating the gauche/anti transformation of a 1,2-disubstituted ethylene unit, a fully predictable helicity inversion system was achieved, in which the helicity can be controlled by the molecular lengths of the diammonium guests.

Surface-assisted dehydrogenative homocoupling and cyclodehydrogenation of mesityl groups on a copper surface

A route via surface-assisted dehydrogenative homocoupling and cyclodehydrogenation of mesityl groups to form an ethylene unit and aromatic six-membered rings has been achieved.