Supermacroporous poly(N-isopropylacrylamide) (PNIPAAm) cryogels containing urease were prepared via UV irradiation technique and hydrogen peroxide as initiator. Specifically, due to the cryostructuration phenomenon urease molecules were embedded into the dense cryogel walls. Thus, although the enzyme is physically entrapped, the system exhibited remarkable resistance against leaking due to the dense polymer network formed in the cryogel walls. The immobilized urease can catalyze the hydrolysis of urea in a broad temperature range in both batch and flow regime. The interconnected macropores assist for unhindered diffusion of the substrate and reaction products through the gel, thus, paving the way for consecutive reuse at a constant activity, in contrast to the conventional PNIPAAm hydrogel. Due to the spongy-like morphology PNIPAAm cryogels containing urease can be exploited as highly permeable membrane for direct removal of traces of urea from continuously flowing feed solutions.

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We present experimental results for an investigation of both parametric and Raman scattering processes simultaneously occurring in optical fibers. The generation of Stokes as well as of anti-Stokes components under the influence of the parametric effects, is considered. The generated new optical frequencies can yield more favorable conditions concerning the material dispersion and the losses in fibers. Substantially nonlinear regime of interaction with a mutual exchange between the excited radiation and the generated signal frequencies is analyzed by solving the full system of equations with account of the real and imaginary parts of the nonlinear optical susceptibility.