Judul: Aktivitas Antimikroba Ekstrak Daun Bambu Tali (Gigantochloa apus) dalam Menghambat Pertumbuhan Bakteri Escherichia coli dan Salmonella typhimurium.
Abstrak: Tujuan dari penelitian ini adalah untuk mengamati aktivitas antibakteri pada daun bambu tali (Gigantochloa apus) dengan jenis pelarut berbeda terhadap bakteri E. coli dan S. Typhimurium. Daun bambu tali diekstrak dengan metode maserasi menggunakan etanol 70% dan metanol. Uji aktivitas antibakteri dilakukan dengan menggunakan metode Kirby dan Bauer difusi agar. Konsentrasi dari ekstrak daun bambu yang digunakan adalah 0.00%, 0.02%, 0.04%, 0.06%, 0.08% dan 0.02% cotrimoxazole sebagai kontrol positif. Nilai MIC dan MBC dihitung berdasarkan aktivitas antibakteri tertinggi. Hasil pada penelitian ini menunjukkan bahwa ekstrak etanol daun bambu tali pada level 0.04%, 0.06% dan 0.08% memiliki aktivitas antibakteri yang rendah (<5 mm), sedangkan ekstrak metanol hingga level 0.08% tidak memiliki aktivitas antibakteri terhadap pertumbuhan E. Coli dan S. Typhimurium. Nilai MIC ekstrak etanol daun bambu terhadap bakteri Escherichia coli dan Salmonella typhimurium adalah 0.2% dan 0.3%. Berdasarkan hasil pada penelitian ini, dapat disimpulkan bahwa daun bambu yang di ekstrak dengan etanol memiliki aktivitas antibakteri lebih baik dibandingkan metanol dengan MIC 0.2% dan 0.3%.
Keyword: Aktivitas antibakteri, Diare, E. coli, G. apus, S. typhimurium

Judul: Kajian Aktivitas Antibakteri Daun Gatel (Laportea decumana (Roxb.) Wedd.) dan Daun Benalu Cengkeh
Abstrak: Many researches showed that several plants have a good antibacterial activity. The leaves of gatel and clove mistletoe are empirically used to cure several diseases. The aims of this research were: (1) to study the potential of antibacterial activity of gatel and clove mistletoe hexane, ethyl acetate and methanol extracts against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Pseudomonas aeruginosa by the well diffusion method; (2) to calculate the minimum inhibitory concentration (MIC) value of the potential extracts; and (3) to study the effect of various pH to antibacterial activity of the extracts. The results showed ethyl acetate and methanol extracts of the studied plants have low antibacterial activity against B. cereus and E. coli. Based on the MIC values, the ethyl acetate extract of gatel leaves showed over 99% percent inhibition against E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0%. The same result was obtained by modifying the pH (4, 5 and 6) at the extracts concentration of 5% and 10%. The methanol extract of gatel leaves showed below 60% inhibition of B. cereus at a concentration of extract 4.0%, 4.5%, 5.0%, 5.5% and 6.0%, and more than 90% inhibition at the pH. The ethyl acetate extract of clove mistletoe showed more than 98% inhibition againts E. coli at a concentration of 3.5%, 4.0%, 4.5% and 5.0% and at pH 4, 5 and 6. Percent of inhibition less than 50% occured in the methanol extract of clove mistletoe at 4.0%, 4.5%, 5.0%, 5.5% and 6.0% concentration against B. cereus. For the methanol extract of clove mistletoe, the effect of pH variation (4, 5, 6 and 7) resulted in 92%-97% inhibition. The result may increase the utilization of research plant not only for health purposes but also as a natural food preservative and open new possibilities for the development of natural functional foods.
Keyword: 

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.
Keyword: