m.a. ranjbar

Among the available coolingmethods in the combustion chamber of liquid propellant engine, regenerative cooling is widely used due to its good performance used. In this paper, a combustion chamber of liquid propellant engine is simulated numerically and effect of increasing cooling channel surface roughness on cooling performance is studied. The results showed that maximum temperature of combustion chamber wall is in the throat and by increasing surface roughness in cooling channel, the temperature in throat decrease and the heat transfer from the combustion gases to the cooling fluid increases. The temperature drop in the throat is  and  when water and liquid hydrogen is used as cooling fluid respectively. Also in the roughness height between  and  by increasing the surface roughness, temperature drop in throat increase.

Statement of Problem:

 Candidal colonization on soft liners is important in the development of pathogenesis, such as denture stomatitis. It has heen reported that combining anti-fungal agents into soft liners might be used in treatment and prevention of denture stomatitis.

The aim of this in-vitro study was to determine whether incorporating clotrimazole (C) into the silicone soft liner (S), would inhibit the growth of C. albicans when the specimens are stored in distilled water and washed daily with wet cotton.Methods and Materials: Experimental specimen disks incorporated with clotrimazole (Sc1, Sc30, Sc60) and without clotrimazole (S1, S30, S60) into the soft liner (no=8) were fabricated aseptically against the polyester film to produce a smooth surface. The treated and control disks were stored in distilled water for 1, 30 and 60 days and washed daily with wet cotton. For fungal growth assessment, they were inoculated with C.albicans suspension. The disks were rinsed and sonicated in sterile water to remove surface organisms. The attached yeast was measured by inoculation of the yeast suspension on Sabouraud's agar. The data were compared using two-way ANOVA.

The mean colony forming units (CFU) per mm2 for the specimens without clotrimazole after water storage and washing with wet cotton for 1, 30 and 60 days was 6.5Î106, 5.8Î106 and 6.1Î106, respectively. CFU for specimens with clotrimazole decreased significantly to 2.6Î106 and 3.9Î106 and 4.6Î106 after 1, 30, and 60 days, respectively. In comparison to those of the control disks, clotrimazole in treated disks was effective in inhibiting C.albicans growth significantly following storage in water for 2 months (P<0.05).

The addition of clotrimazole significantly reduced C.albicans growth to the surface of the silicone soft liner. The samples continued to inhibit the fungal growth when they were washed daily with wet cotton for 2 months.