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Petrosia sp. is one of the sponges from the demospongia class that has biological activity as anti-inflammatory, antimalarial, cytotoxic agent, and can be used in nanoemulgel formulation. Nanoemulsion system is thermodynamically stable and produces globule size that can increase the permeability and diffusibility of Petrosia sp. The presence of gelling agent in the nanoemulgel gives the viscosity and spreadability of Petrosia sp nanoemulsion optimally to increase the effectiveness of the active substances on the skin. This study aims to determine the formulation, characterization, and physical stability of nanoemulgel ethanol extract of sponge Petrosia sp. with carbopol 940 as the gel base. Nanoemulsion characterization included transmittance value, particle size, polydispersity index, and type of emulsion formed. The physical stability test of nanoemulgel included centrifugation and freeze thaw tests with organoleptic, pH, viscosity, and dispersibility evaluation. Nanoemulsion of Petrosia sp ethanolic extract with a composition of 1% VCO, 7% Tween-80, and 2% PEG-400 produced an oil-in-water (O/W) nanoemulsion, transmittance value of 94.84%, droplet size of 23.9 nm and particle size distribution of 0.176. The optimum formula for nanoemulgel is F1 with a nanoemulsion concentration of 75 mL and 25 g of gel base produced a clear and transparent nanoemulgel, semi-solid, soft texture, distinctive aroma, pH value of 5, viscosity of 28,000, dispersibility of 5.7 cm and the shape/color did not change after freeze thaw stability test. Based on the data above, it can be concluded that the F1 nanoemulgel formula with carbopol 940 as the base gel produced an optimal nanoemulgel.

The objective of this research was to examine and to quantify the stability of mixed grain sediment beds previously exposed to different time length of uniform antecedent flow hydrograph. The assessment of bed stability was carried out based on the observation of temporal pattern of eroded sediment during two identical stability tests with time varying flow and higher peak discharge. This was linked to the movement of individual sediment fractions to obtain fractional critical shear stress in a bimodal sediment mixture. The stability tests suggest a considerable increased in the stability of individual grain. Longer exposure time by antecedent flow clearly had an influence in the increasing stability of the bed. The increased rate of fractional critical shear stress during stability tests varied between 16 % and 35 % in the coarse mode whilst in the fine mode the rate of increase varied between 27 % and 39 %.