Abstract: A deformable cap for scalp cooling is provided. The cap contains a cap member obtained by discharging air inside a hollow ball made of flexible material and a plurality of small pieces of high water content hydrogel contained in the cap member. The hydrogel is prepared by casting an aqueous solution of polyvinyl alcohol into a mold, cooling the cast aqueous solution to -10.degree. C. or lower to obtain a cooled frozen mass followed either by thawing the cooled frozen mass and one to seven additional cooling and thawing operations or by partially dehydrating the cooled frozen mass in vacuum.

Abstract: A method of making a phantom for NMR diagnosis contains the steps of placing at least one small container having at least a portion of its wall made of a thin film of a plastic material in a large container made of a plastic material, charging a first aqueous solution of polyvinyl alcohol into the small container, charging a second aqueous solution of polyvinyl alcohol into a space defined by the outer wall of the small container and the inner wall of the large container, freezing the first and second aqueous solutions of polyvinyl alcohol to obtain frozen masses, and then thawing the frozen masses. A composition of the first aqueous solution of polyvinyl alcohol is different from a composition of the second aqueous solution of polyvinyl alcohol.

Abstract: A phantom for diagnosis by nuclear magnetic resonance imaging comprises a container made of a synthetic resin and a hydrogel sealingly contained in the container. The container has at least one opening into which a sample material is inserted. The hydrogel is prepared by charging an aqueous solution of a polyvinyl alcohol into the container, cooling the aqueous solution to minus 10.degree.C. or lower to obtain a cooled frozen mass and thawing the cooled frozen mass. Also disclosed is a method for determining resolution power or discrimination capacity of an NMR imaging apparatus.

Abstract: This invention relates to a method for sterilization, by irradiation with .gamma.-ray, of a hydrogel obtained by freezing an aqueous polyvinyl alcohol solution and then thawing it or by partially dehydrating (3% or more in weight reduction rate of the frozen body) the aqueous polyvinyl alcohol solution as it is frozen under vacuum and by selecting dosage of the .gamma.-ray of 3-10 Mrad, stable sterilization effect can be obtained with less soluble decomposition products. Especially, this method is effective and most suitable as a method for sterilization of polyvinyl alcohol hydrogel molded article for medical use.

Abstract: A method for applying electromagnetic wave and ultrasonic wave therapies is provided. According to the method, a material simulating a living tissue is applied and pressed onto a surface of a human body so that the material is intimately contacted with the body surface with substantially no spaces present therebetween. Electromagnetic or ultrasonic wave is generated and irradiated to the body through the material. The material comprises a hydrogel having a high water content. The hydrogel is prepared by the steps of casting an aqueous polyvinyl alcohol solution into a mold, cooling the cast aqueous solution to obtain a cooled frozen mass and thawing the cooled frozen mass. The cooling and thawing steps may be repeated up to eight cycles. The hydrogel is also prepared by subjecting the cooled frozen mass to a partial dehydration step in vacuum.

Abstract: A process for the preparation of a gel for use as a cooling medium is provided which comprises the steps of casting an aqueous solution or suspension containing a polyvinyl alcohol having a degree of hydrolysis of not less than 95 mol % and a viscosity average polymerization degree of not less than 1500 into a mold having desired shape and dimensions, cooling the cast aqueous solution to a temperature of not higher than - (minus) 6.degree. C., and then dehydrating without thawing the cooled mass of the cast aqueous solution in vacuum until the percentage dehydration rate reaches not less than 5 wt %.

Abstract: A skin marker is provided for diagnosis by X-ray tomography and nuclear magnetic resonance imaging. The skin marker is composed of a vessel in which a non-magnetic and X-ray radioopaque material is dispersed, and a hydrogel of high water content filled in the vessel. The hydrogel is prepared by a process comprising a casting step of casting into the vessel an aqueous solution containing more than 8 wt % and not more than 20 wt % of a polyvinyl alcohol having a degree of hydrolysis of not less than 98 mol % and an average polymerization degree of not less than 1,000, a freezing step of cooling the case aqueous solution to a temperature of not higher than - (minus)n 10.degree. C. to obtain a frozen mass, a thawing step of thawing the frozen mass, and one to seven additional cyclic processing steps each including the freezing and thawing steps.

Abstract: A denture base contains an elastic support for supporting at least one artificial tooth and fittings fixed to the elastic support for removably positioning the denture base. The elastic support is made of a hydrogel prepared by a process comprising a casting step of casting into a mold an aqueous solution containing more than 5 wt % and not more than 40 wt % of a polyvinyl alcohol having a degree of hydrolysis of not less than 95 mol % and an average polymerization degree of not less than 700, a freezing step of cooling the cast aqueous solution to a temperature of not higher than - (minus) 10.degree. C. to obtain a frozen mass, a thawing step of thawing the frozen mass, and one to seven additional cyclic processing steps each including the freezing and thawing steps.

Abstract: A process for preparing an artificial biological membrane in which an aqueous solution containing 6 wt % or more of polyvinyl alcohol having a degree of hydrolysis of not less than 95 mol % and an average polymerization degree of not less than 700 and containing a biological substance or a substance which does not hinder the gelation of the polyvinyl alcohol is subjected to a freezing step followed by a thawing step. Then, the mass thus obtained is further subjected to at least one additional cyclic processing step including the freezing and thawing steps. The product hydrogel is hard or not too soft and not swollen in water.

Abstract: A material for diagnosis by nuclear magnetic resonance imaging is provided. The material comprises a hydrogel having a high water content. The hydrogel is prepared by the steps of casting an aqueous polyvinyl alcohol solution into a mold, cooling the case aqueous solution to obtain a cooled frozen mass and thawing the cooled frozen mass. The cooling and thawing steps may be repeated up to eight cycles. The hydrogel is also prepared by subjecting the cooled frozen mass to a partial dehydration step in vacuum.

Abstract: A process for preparing a fluid for traction drive from a fraction containing compounds having at least four aromatic rings is disclosed. The fraction is a by-product produced at the time of the preparation of alpha-methyl-benzylalkylbenzenes by alkylation of at least one compound selected from C.sub.7 -C.sub.10 alkylbenzenes with styrene in the presence of an acid catalyst. The process comprises the steps of decomposing the fraction in an atmosphere of hydrogen at a predetermined temperature and pressure, collecting a decomposition product having a boiling range not higher than 450.degree. C. and then subjecting the decomposition product to nuclear hydrogenation at aromatic rings thereof in the presence of a catalyst capable of nuclear hydrogenation.

Abstract: This invention is directed to an electrode for use in electroretinography. The electrode contains a thin membrane made of a hydrogel of high water content and a conductor connected to the thin membrane. The thin membrane is prepared by casting an aqueous polyvinyl alcohol solution into a mold, freezing the cast aqueous solution to obtain a frozen mass, thawing the frozen mass and subjecting the thawed mass to one to seven additional cyclic freezing and thawing treatments. The thin membrane can also be prepared by subjecting the frozen mass to partial dehydration in a vacuum until the percentage dehydration rate reaches not less than 3 wt %.

Abstract: Provided is a medical material comprising a molded hydrogel obtained by pouring an aqueous solution containing not less than 6 wt. % of a polyvinyl alcohol which has a degree of hydrolysis not less than 97 mole % and average polymerization degree not less than 1,100, into a desired shape of a vessel or mold, freeze-molding the aqueous solution at a temperature lower than -5.degree. C., then partially dehydrating the resulting molded product without thawing it up to a percentage dehydration not less 5 wt. %, and if required, immersing the partially dehydrated, molded product in water to attain a water content thereof in the range of 45 to 95 wt. %.

Abstract: A hydrogel which has a water content of 20 to 92 weight % and which is stable and superior in mechanical properties is obtained by preparing a 3 to 25 weight % aqueous solution of a polyvinyl alcohol having a degree of hydrolysis not less than 95 mol % and a viscosity-average polymerization degree of not less than 1,500, then pouring the aqueous polyvinyl alcohol solution into a desired shape of a vessel or a mold, then freeze-molding the aqueous polyvinyl alcohol solution at a temperature lower than -6.degree. C., thereafter dehydrating the molded article without thawing it until the dehydration percentage reaches 5 weight % or more and, if required, immersing the dehydrated product in water.

Abstract: This invention relates to a process for producing immobilized L-asparaginase preparations. Its principal object is to produce immobilized L-asparaginase preparations which are excellent in antithrombogenicity and mechanical strength.The present invention is concerned with production of immobilized L-asparaginase preparations by pouring an aqueous solution containing 6% or more of a polyvinyl alcohol with a degree of hydrolysis of 97 mol. % or higher and a viscosity-average degree of polymerization of 1,800 or more an antileukemic asparaginase into a vessel or a mold of an appropriate shape, subjecting the solution to cooling, solidification and molding at a temperature of -15.degree. C. or lower and partially dehydrating the molded mass without thawing to a dehydration ratio of 5% by weight or more and, if desired, immersing the product in water.According to the invention, L-asparaginase can be embedded in a highly hydrous gel excellent in antithrombogenicity and mechanical strength by simple procedures.

Abstract: According to the invention, a deformable bag for use as a cooling medium is provided. The bag comprises small pieces of gel packed in a flexible envelope. The gel is prepared by casting into a mold an aqueous solution or suspension containing a polyvinyl alcohol and a water-soluble organic compound, and cooling the cast aqueous solution or suspension to -10.degree. C. or lower and then partially, dehydrating, without thawing, the thus obtained cooled mass in vacuum. The bag of the invention can be applied on different objects or portions having various configurations.

Abstract: Provided is a wound covering material produced by applying an aqueous solution containing a polyvinyl alcohol with a degree of hydrolysis not less than 95 mol. % and a viscosity-average degree of polymerization not less than 1,500, a water-soluble C.sub.2-20 polyhydric alcohol having 2-8 hydroxyl groups in the molecule and a high-viscosity water-soluble macromolecular substance being different from polyvinyl alcohol with a viscosity of the 2% aqueous solution of 25.degree. C. not less than 300 cP, concentrations of said polyvinyl alcohol, said water-soluble polyhydric alcohol and said water-soluble macromolecular substance being adjusted respectively to 1.5-8% by weight, 10-85% by weight and 0.2-15% by weight, onto a flat or curved plate having 30,000-200,000 projections per m.sup.2, the total area occupied by the projections being 10-70% to a thickness from 0.5 to 5 mm, cooling the applied plate to a temperature not higher than -6.degree. C.

Abstract: A process for the preparation of a hydrogel is provided. The process comprises the steps of solidifying an aqueous solution containing 2.5 to 25 wt % of a polyvinyl alcohol of an average polymerization degree of not less than 800 and 1 to 80 wt % of a water-soluble polyhydric alcohol by cooling the aqueous solution to not higher than -3.degree. C. and then dehydrating in vacuum the solidified mass into a percent dehydration degree of 5 to 95 wt %. The hydrogel is suitable for use as a cooling medium.

Abstract: Traction fluids for traction drive transmissions, prepared by hydrogenating an alkylation product obtained by the reaction of xylene and/or toluene, together with or without ethylbenzene, with styrene.

Abstract: In a method for oxidizing sulfur dioxide by contacting a sulfur dioxide-containing gas and an oxygen-containing gas with an aqueous solution containing pentavalent vanadium and divalent manganese as a catalyst, the method for regenerating and recycling the oxidation catalyst which comprises adding at least one calcium compound selected from the group consisting of calcium oxide, calcium hydroxide and calcium carbonate and an oxygen-containing gas as an oxidizing agent to at least a part of the aqueous solution catalyst used in the oxidation reaction, separating the resulting gypsum, and recycling the recovered aqueous solution catalyst for use in the oxidation of sulfur dioxide.