Multilayer films for naked collation packaging of single packs comprising at least a core layer, an inner layer and an outer layer, wherein the inner and outer layer, equal to or different from each other, consist of one or more olefin polymers wherein:outer layer: polymers having a melting point in the range 65\xb0 C. The present invention has been carried out in order to solve the above problems. The dialysis device has a composition sensor containing a potassium-sensitive electrode for measuring a potassium ion concentration in one or more of the patient’s blood and the dialysate fluid and an infusate pump operated to adjust a potassium ion concentration in the dialysate fluid based at least in part on data from the composition sensor. The actual chemical compounds in one mode of this mixture are the methyl esters of about 59% glutaric acid, about 20% succinic acid, and about 21% adipic acid. These andor other example characteristics may be captured in a database at the message server and may be evaluated to determine whether a persistent save operation is required or can be omitted. In minimizing the variations in refractive index within the lateral light path, while providing active cooling directly below the tissue contact surface, the invention prevents internal reflections and beam distortion and greatly improves the efficiency and durability of the laterally directing probe.