Abstract: The use of a mixture of at least one alkanolamide of general formula (I), RC(O)NH(A).sub.n H, wherein R is a hydrocarbon group having 7-23 carbon atoms, preferably 11-23 carbon atoms, A is an alkyleneoxy group having 2-4 carbon atoms and n is 2-12, preferably 2-8, and at least one ionic surfactant selected from the group consisting of anionic, cationic, amphoteric and zwitterionic, in a proportion between the alkoxylated alkanolamide and the ionic surfactant from 100:1 to 1:2, preferably in the range from 50:1 to 1:1 for producing a water-base liquid system with reduced flow resistance between the flowing, water-base liquid system and a solid surface.

Abstract: A solid surface having anionic groups capable of reacting with a polyethylene imine substituted at least in part by at least 50% by weight of a hydrophilic nonionic polymer having a molecular weight within the range from about 400 to about 200,000 is provided with a hydrophilic biopolymer-repellent outer surface layer thereof by reacting such a polyethylene imine substituted by nonionic hydrophilic polymer with anionic groups on the solid surface, in an amount sufficient to produce biopolymer-repellent solid surface, and accordingly having low spontaneous adsorption of proteins and other biopolymers through electrostatic attraction and/or hydrophobic interaction.