Estimation methods for the longest Rouse relaxation time ( R ) of an entangled polymer in a semidilute solution were examined. We evaluated R by fitting the dynamic modulus (GЈ) with the Rouse model theory in the power law range, where GЈ was proportional to the square root of the angular frequency (). The R values thus obtained for polystyrene (PS) solutions in tricresyl phosphate (TCP) were employed to derive an empirical formula for the evaluation of R from the viscosity (. M is the molecular weight, and c is the mass of polymer per unit volume; M e ϭ cRT/G N is the entanglement molecular weight, where G N is the GЈ value at the inflection point of the graph of log GЈ versus log . The subscript indicates that R is derived from data. The proposed equation was also applicable to bulk PS and bulk polyisoprene. Discrepancies among reported R values in semidilute solutions seem to be mostly due to discrepancies in M e values. For PS solutions in dioctyl phthalate, a ⌰ solvent, the R value derived from was much larger than that from the GЈ curve. Apart from the evaluation method of R , we observed for PS that M e was independent of temperature for good solvent systems and melts, that M e for solutions in TCP agreed with that for solutions in another good solvent, and that M e for a ⌰-solvent system was equal to that for good solvent systems with the same M and c values.
Diffuse cavernous hemangioma of the rectum (DCHR) is a relatively rare disease. A 40-year-old man presented with long-standing lower abdominal discomfort and hematuria. At the time of hospitalization, his vital signs and hemoglobin level were normal. Colonoscopy showed markedly dilated blood vessels in the sigmoid mucosa, which was confirmed on magnetic resonance imaging and computed tomography as cavernous hemangioma. Without surgery, there have been no signs of progression of DCHR during a 3-year follow-up period.
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