Judul: Aktivitas Antibakteri Fraksi Kaya-Naringenindari Daun Gude(Cajanuscajan (L.) Millsp.) Terhadap Bakteri Salmonella Thypi
Abstrak: Gude (Cajanus cajan (L.) Millsp.) dikenal sebagai salah satu tanaman obat dan memiliki kandungan senyawa metabolit sekunder, serta berdasarkan kepercayaan masyarakat Kabupaten Bone, Sulawesi Selatan daunnya mampu mengobati penyakit tifus. Sampai saat ini belum ada upaya untuk mengidentifikasi senyawa aktif yang berpotensi menghambat bakteri Salmonella thyphi yang merupakan penyebab penyakit tifus. Oleh karena itu, penelitian ini bertujuan mengidentifikasi senyawa aktif dari daun gude tersebut dan menentukan kemampuan penghambatannya terhadap bakteri S.thypi. Serbuk daun gude diekstraksi dengan metode maserasi menggunakan pelarut metanol (20.30%). Selanjutnya ekstrak metanol diekstraksi cair-cair dan diperoleh fraksi n-heksana, etil asetat dan metanol. Fraksi etil asetat yang positif dalam menghambat bakteri S. thypi selanjutnya dielusi dengan kromatografi kolom gravitasi menggunakan eluen n-heksana dan etil asetat yang kepolarannya ditingkatkan secara bergradien dan diperoleh 70 subfraksi. Subfraksi 1 membentuk kristal kekuningan dan diperoleh 2 noda pada profil kromatografi lapis tipisKLT 1-dimensi dan 2-dimensi yang mengindikasikan kemurnian dari subfraksi tersebut. Identifikasi dengan kromatografi cair spektroskopi massa menunjukkan bahwa subfraksi 1 memiliki m/z 272 dengan fragmentasi stabil pada m/z 271. Senyawa yang memiliki m/z 272 sesuai dengan senyawa naringenin yang merupakan golongan flavanon dengan pola fragmentasi lanjut m/z 271, 177, 151, 119, 107, 93, dan 83. Fraksi kaya-naringenin diuji kemampuan penghambatannya terhadap bakteri S.thypi menggunakan metode Kirby-Bauer dan diperoleh diameter penghambatan 11 mm. Kontrol positif yang digunakan ialah kloramfenikol. Dapat disimpulkan bahwa fraksi kaya-naringenin memiliki kemampuan aktivitas antibakteri dan dapat digunakan untuk mengobati tifus.
Keyword: aktivitas antibakteri, Cajanus cajan, flavanon, Salmonella thypi, tifus

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.
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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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