Judul: Aktivitas Antibakteri Ekstrak Kulit Rambutan (Nephelium lappaceum) Terhadap Staphylococcus aureus & Escherichia coli
Abstrak: Tanaman rambutan adalah salah satu jenis tanaman buah yang banyak ditanam oleh masyarakat Indonesia. Namun masyarakat hanya menggunakan daging buahnya saja, sedangkan kulit buah rambutan terbuang menjadi limbah. Penelitian ini bertujuan mengetahui konsentrasi minimum ekstrak kulit rambutan yang mampu menghambat dan membunuh pertumbuhan bakteri Gram positif ( Staphylococcus aureus) dan bakteri Gram negatif (Escherichia coli). Kulit rambutan diekstraksi menggunakan dua pelarut yaitu pelarut etanol 70% dan pelarut air. Nilai rendemen ekstrak dari pelarut etanol 70% dan air yaitu masingmasing sebesar 21.10% dan 33.54%. Hasil analisis fitokimia diketahui bahwa ekstrak etanol 70% dan ekstrak air kulit rambutan mengandung senyawa tanin, saponin, flavonoid, alkaloid, dan triterpenoid. Uji aktivitas antibakteri menunjukkan adanya daya hambat pada bakteri Gram positif (Staphylococcus aureus) tetapi tidak menghambat bakteri Gram negatif (Escherichia coli). KHTM pada bakteri S. aureus terlihat pada konsentrasi 20 mg/mL dengan diameter zona hambat yang dihasilkan oleh ekstrak etanol 70% dan ekstrak air masing-masing sebesar 7.11 mm dan 7 mm. Sedangkan KBM ekstrak etanol 70% dan ekstrak air terhadap S. aureus pada konsentrasi 60 mg/mL yang ditandai dengan tidak adanya koloni bakteri yang tumbuh pada media agar setelah kontak selama 10 menit dengan ekstrak.
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Judul: Aktivitas antibakteri zat ekstraktif kulit kayu rambai (Baccaurea motleyana Muell. Arg.)
Abstrak: Rambai (Baccaurea motleyana Muell.Arg.) belongs to the family Euphorbiaceae have potency for developed as antibacterial. The aims of this research were to determine the antibacterial activity and to screen phytochemically constituents of bark extract of B. motleyana. Bark of B. motleyana used in traditional medicine for the treatment of eye diseases was extracted by maceration in ethanol and aqueous. In vitro antibacterial activity was determined using agar well diffusion method on Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa. The results showed that that 50 mg/ml of the aqueous extract was most active and it inhibited the growth of all the bacterial with zones of inhibitation ranging from 4.10 to 8.67 mm. Fractionation to aqueous extract can decreases minimum inhibitory concentration (MIC) values and increases sensitivity of bacteria to that fraction. MIC of the aqueous extract for three bacterial strains ranging from 5.40 mg/ml to 6.82mg/ml, the methanol-insoluble fraction 4.09 mg/ml to 6.72 mg/ml, n-hexaneinsoluble fraction 3.77mg/ml to 4.56 mg/ml and the subfraction (F ) 0.39 to 0.61 mg/ml. Results of phytochemical screening showed the presence of saponin and flavonoid in the aqueous extract. Identified with FTIR, LCMS and NMR's Proton showed that active compound that potentially as antibacterial is aglikon of saponin's compound.
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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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