Judul: Kajian Aktivitas Antibakteri Ekstrak Tempe Komak terhadap Bakteri Staphylococcus aureus dan Escherichia coli
Abstrak: Tempe is a modified product fermented by Rhizopus sp. which contains active substances, such as antibacterial substances. The objectives of the study are to compare the yield of hyacinth tempe and bench-scale soybean tempe and to determine the antibacterial activity from hyacinth tempe against bacteria: Staphylococcus aureus and Escherichia coli. The yield is determined by comparing the tempe’s mass and bean’s mass. The antibacterial activities of the extracts are analyzed using well diffusion method. The study shows that the yield of hyacinth tempe (154 %) is higher than the yield of bench-scale soybean (151 %). The study also shows that hyacinth tempe extract has no antibacterial activity against S. aureus 0.0 mm, while commercial-scale and bench-scale soybean tempe extract have antibacterial activity against S. aureus, respectively, 8.9 mm and 7.0 mm. However, all of the tempe extract have no antibacterial activity against E. coli. The raw material of tempe gives contribution to produce antibacterial substance against S. aureus during fermentation by R. oligosporus.
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Judul: Pengujian Aktivitas Antibakteri Ekstrak Tempe Koro Pedang (Canavalia ensiformis L.) terhadap Escherichia coli dan Staphylococcus aureus
Abstrak: Tempeh is a fermented food product usually made from soybean fermented by Rhizopus sp. The objectives of this study were to compare jack bean tempeh characteristics against soybean tempeh and to determine antibacterial activity of jack bean tempeh against Escherichia coli dan Staphylococcus aureus using well diffusion method. The tempeh extraction was conducted by methanol extraction following freezing to separate fatty compound. Characteristic of jack bean tempeh and soybean tempeh were different in moisture content, colour (L and a), and tenderness. The differences in moisture content and tenderness were caused by the difference of soaking time. The colour of jack bean tempeh and soybean tempeh were different because of the beans’s colour. The result showed that jack bean tempeh extracts did not have antibacterial activity against E. coli and S. aureus. Meanwhile, methanol extracts of soybean tempeh from laboratory and market were showed antibacterial activity against S. aureus (7.0 mm and 8.9 mm); but did not have antibacterial activity against E. coli.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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