Evaluation of the efficiency of using a tubular turbulent apparatus in the step of titanium catalyst preparation in isoprene rubber production

Changes in the process parameters and quality of the synthesized SKI-3 isoprene rubber, caused by using a small tubular turbulent apparatus of diffuser–confuser design in the step of titanium catalyst preparation, are analyzed. The use of this apparatus in the industrial process leads to a decrease in the catalyst consumption and to an increase in the polymer yield without significant changes in the polymer characteristics.     

Enhancement of the activity of a neodymium catalyst for the synthesis of stereoregular polyisoprene

A new ligand based on two pyrazole cycles linked with each other was synthesized. Its interaction with Cu(II), Ni(II), Co(II), Mn(II), Cr(III), Zn(II), and Cd(II) cations in ethanol was studied by the spectrophotometric method.     

Determination of the polynomial uniformizing a given compact Riemann surface

Mathematical Notes - An approximate method for finding the polynomial uniformizing a given Riemann surface is proposed. The method is based on joining this surface with another surface by a smooth...     

LIGA technology for the synthesis of diffractive refractive intraocular lenses

The manufacturing of test diffractive refractive intraocular lenses is illustrated by means of LIGA (deep X-ray LIthography and GAlvanoplastics and polymer forming). Dynamic X-ray lithography used while rotating the substrate versus an X-ray mask fixed in a beam of synchrotron radiation (SR) yields smooth optical 3D surfaces with roughnesses of 10–30 nm rms in polymethylmethacrylate (PMMA) layers. The axisymmetric diffractive refractive profile of a lens is predetermined by the radial angular function of the X-ray mask topology. The quality of the optical surface is reproduced for the nickel master form, which is electroplated onto a gold layer atop the PMMA relief. The optical quality also remains high for replicated lenses synthesized in this manner during silicon polymerization.     

Multiphonon mechanism of the ionization of traps in Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Experiment and numerical simulation

Charge transfer in Al₂O₃ has been investigated experimentally and theoretically. The experimental results are in qualitative agreement with the theory of the multiphonon ionization of deep centers. The thermal (W _T = 1.5 eV) and optical (W _opt = 3.0 eV) energies of the deep centers have been determined. It has been found that the experimental data are unsatisfactorily described by the Pool-Frenkel mechanism, which provides a non-physically small frequency factor and anomalously large effective tunneling mass.