Tris(pentafluorophenyl)borane-catalyzed Hydride Transfer Reactions in Polysiloxane Chemistry-Piers-Rubinsztajn Reaction and Related Processes.

Tris(pentafluorophenyl)borane (TPFPB) is a unique Lewis acid that catalyzes the condensation between hydrosilanes (Si-H) and alkoxysilanes (Si-OR), leading to the formation of siloxane bonds (Si-OSi) with the release of hydrocarbon (R-H) as a byproduct-the so-called Piers-Rubinsztajn reaction. The analogous reactions of hydrosilanes with silanols (Si-OH), alcohols (R-OH), ethers (R-OR') or water in the presence of TPFPB leads to the formation of a siloxane bond, alkoxysilane (Si-OR or Si-OR') or silanol (Si-OH), respectively. The above processes, often referred to as Piers-Rubinsztajn reactions, provide new synthetic tools for the controlled synthesis of siloxane materials under mild conditions with high yields.

Self-Restructuring of Polyhydromethylsiloxanes by the Hydride Transfer Process: A New Approach to the Cross-Linking of Polysiloxanes and to the Fabrication of Thin Polysiloxane Coatings.

The branching and cross-linking of siloxane polymers are important processes in silicone technology. A new type of such a process has been developed, which is a self-restructuring of linear polyhydromethylsiloxane (PHMS). This process involves the reorganization of the PHMS to form a highly branched siloxane polymer or finally a cross-linked siloxane network.

Copper Modulates the Catalytic Activity of Protein Kinase CK2.

Casein kinase 2 (CK2) is an evolutionarily conserved serine/threonine kinase implicated in a wide range of cellular functions and known to be dysregulated in various diseases such as cancer. Compared to most other kinases, CK2 exhibits several unusual properties, including dual co-substrate specificity and a high degree of promiscuity with hundreds of substrates described to date. Most paradoxical, however, is its apparent constitutive activity: no definitive mode of catalytic regulation has thus far been identified.

Porous SiC and SiC/C Ceramic Microspheres Derived from Polyhydromethylsiloxane by Carbothermal Reduction.

A simple and inexpensive method for the preparation of porous SiC microspheres is presented. Polysiloxane microspheres derived from polyhydromethylsiloxane (PHMS) cross-linked with divinylbenzene (DVB) were ceramized under conditions leading to the removal of oxygen from the material. The content of free carbon (C) in highly crystalline silicon carbide (SiC) particles can be controlled by using various proportions of DVB in the synthesis of the pre-ceramic material.

A novel method to determine linac mechanical isocenter position and size and examples of specific QA applications.

The most important geometric characteristic of stereotactic treatment is the accuracy of positioning the target at the treatment isocenter and the accuracy of directing the radiation beam at the treatment isocenter. Commonly, the radiation isocenter is used as the reference for the treatment isocenter, but its method of localization is not strictly defined, and it depends on the linac-specific beam steering parameters. A novel method is presented for determining the linac mechanical isocenter position and size based on the localization of the collimator axis of rotation at arbitrary gantry angle.