Abstract: A thermal change computation apparatus is used with a machine tool that includes a machining mechanism for machining a workpiece and a driving mechanism for changing a relative position between the machining mechanism and the workpiece. The apparatus comprises a driving state detecting unit for detecting a driving state of a machine tool to be used; a holding time computing unit for computing a holding time where a thermal change substantially remains; a change amount computing unit for computing a thermal change amount of the machine tool based on the driving state detected at every designated operation; and a change amount adding unit for computing a present thermal change amount of the machine tool by adding an influence of a thermal change amount computed previously to a thermal change amount computed newly when the previously computed thermal change amount is available and the holding time inherent in the machine tool does not elapse since the change amount computing unit computes.

Abstract: In a machine tool having a main shaft, a thermal change amount between two sampling times is computed on the basis of the movement distance of the main shaft during a period from time 0 to time 1a. After thermal change amounts are computed, a total thermal change amount which results from adding these thermal change amounts is computed. Since the thermal change amount is based on the movement distances (driving states) that are detected at the respective time points and the influence of the thermal change amounts that has been computed previously are added to the computed thermal change amount, it is possible to compute the total thermal change amount corresponding to the driving states at the respective time points.

Abstract: Derivatives of a nonimmunogenic plasminogen activator which comprises at least one polyalkylene glycol group chemically bonded with at least one coupling agent to amino acid side chains of said plasminogen activator, wherein said polyalkylene glycol has a molecular weight of about 200-20,000 and is unsubstituted or is substituted with one or more alkyl, alkoxy or alkanoyl groups or a mixture thereof.The plasminogen activator derivatives have an extended circulating life in the mammalian bloodstream and also inhibit the formation of thrombus in the same.

Abstract: A derivative of a human-originated non-immunogenic plasminogen activator is disclosed which comprises at least one polyalkylene glycol attached with at least one coupling agent to amino acid side chains of said plasminogen activator, said polyalkylene glycol having a molecular weight of 200-20,000 and optionally containing one or more alkyl and/or alkanoyl groups as substituents. Also disclosed are a process for producing such derivative and a thrombolytic agent containing such derivative.