Lubricant formulations with improved bioresistance

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 8, pp. 29–30, August, 1992.     

Immobilization of papain on crosslinked polymer supports: Role of the macromolecular matrix on enzymic activity

Papain was immobilized on polymer supports with spacer arms of varying nature and length. As the length of the spacer arm increased, there was a marked increase in the extent of enzyme immobilization and activity of immobilized enzymes. When a long, flexible and hydrophilic polyethylene glycol spacer was introduced between the polystyrene backbone and the functional group used for immobilization, the extent of coupling and enzyme activity increased. Dependence of enzyme activity on the nature and extent of crosslinking and on the nature of the polymeric backbone was investigated. Hydrophilic polyacrylamide-based supports were found to be more efficient supports for immobilization compared to hydrophobic polystyrene-based supports.     

Many-body effects and electron tunneling in metal-insulator-p-type semiconductor structures

Investigation of the tunneling conductivity σ _d(V) of structures made on a highly doped, narrow-gap p-type semiconductor HgCdTe reveals an abrupt increase in this quantity at voltages corresponding to the start of tunneling into the conduction band. It is shown that the observed functions σ _d(V) cannot be described in the framework of a model based on single-particle tunneling. It is proposed that the abrupt increase in σ _d(V) is attributable to tunneling into exciton states. Fiz. Tekh. Poluprovodn. 32, 1069–1072 (September 1998)     

Nonconvex Problems of Global Optimization: Linear-Quadratic Control Problems with Quadratic Constraints

In this paper, we study a class of optimization problems,which are of certain interest for control theory. These problemsare of global constrained optimization and may be nonconvex ingeneral. A simple approach to their solution is presented. Aspecial attention is paid to the case when the objective andconstraints functions are quadratic functionals on a Hilbertspace. As an example of an application of the general approach,a methodology is presented by which an optimal controller canbe synthesized for a finite-horizon linear-quadratic controlproblem with quadratic constraints. Both inequality and equalityconstraints are considered. The objective and constraints functionalsmay be nonconvex and may contain both integral and terminal summands.It is shown that, under certain assumptions, the optimal controlexists, is unique, and has feedback structure. Furthermore, theoptimal controller can be computed by the methods of classiclinear-quadratic control theory coupled with those of finitedimensional convex programming.