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The diffusion coefficient (D) of peptide and protein drugs needs to be determined to examine the permeability through biological barriers and to optimize delivery systems. In this study, the D values of fluorescein isothiocyanate (FITC)-labelled dextrans (FDs) and peptides were determined and the permeability through a porous membrane was discussed. The observed D values of FDs and peptides, except in the case of insulin, were similar to those calculated based on a relationship previously reported between the molecular weight and D of lower-molecular-weight compounds, although the molecular weight range was completely different. The observed D value of insulin was between the calculated values for the insulin monomer and hexamer. The permeability of poly-lysine and insulin through the membrane was determined and the observed values were compared with predicted values by using the relationship between molecular weight and D and an equation based on the Renkin function. The observed permeability of insulin through the membrane was between that of the predicted permeability for the insulin monomer and hexamer. For the permeation of insulin, the determination of D was useful for estimating the permeability because of the irregular relationship between molecular weight and D. The methodology used in this study will be useful for a more quantitative evaluation of the absorption of peptide and protein drugs applied to mucous membranes.

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To evaluate fire suppression efficiency of halon replacements, flammability limits and peak concentrations of hydrocarbon-air mixtures with the suppressants have been measured by tubular flame burner system. The system gives reproducible peak concentrations and wider flammable regions than those obtained by the explosion vessel methods. Adiabatic flame temperatures of the mixtures with the suppressants at the flammability limits have been calculated to know fire suppression mechanisms. The adiabatic flame temperatures are independent of inert gases in the case where the mixtures have the equal equivalence ratio. The fact indicates the inert gases act as physical heat sinks in the flame extinguishing process. Regarding the fire suppression efficiency of the halon replacements, the adiabatic flame temperature at the limit mixture reveals that their behavior is the same as inert gases in rich mixtures. On the other hand, they play the roles as both combustible and chemical inhibitor in lean mixtures.Since January 1994, production of bromofluorocarbon fire extinguishing agents, halons, is stopped to prevent depletion of the stratospheric ozone layer. Several potential candidates of halon replacements have been reported as fruits of many efforts of development, but the candidates have never been superior in fire suppression efficiency to halons. For the appropriate use of halon replacements, it is desirable to evaluate the fire suppression efficiency of the agents with as good reliability as possible. Evaluation of Fire Suppression Efficiency of Halon ReplacementsToday, two types of test method are used to evaluate the fire suppression efficiency. One is inerting tests and the other is flame extinguishing tests using diffusion flames. In the inerting tests, a "peak concentration" is taken as a measure of the fire suppression efficiency. Here, the peak concentration means the minimum concentration of agent in a combustible mixture that will inhibit flame propagation for any concentration of fuel. Thus, the peak concentration is one of particular points on the flammability limit curve of a fuel-air-suppressant mixture. In the case of flame 0097-6156/95/0611-0243$12.00/0

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