Judul: Pemanfaatan Bakteri Streptococcus mutans sebagai Perapuh Gigi Seri pada Tikus Putih
Abstrak: Rat incisor keeps growing along with rat’s life. Rat incisor can be controlled by gnawing, however it may bring disadvantages to human such as plant cultivation damage and household tool. The strenght of rat’s teeth is high, so they can consume something hard. Usage of Streptococcus mutans as rat incisor fragility agent is one of the ways to solve this matter. S. mutans can be examined 4 treatment, i.e. control, 3x104, 3x106, and 3x108 cfu/ml and different period of time, i.e. 4 and 8 days. The variable which observed are hardness of the rat incisor and preference of consumption to paddy and pellets. In this experiment, the bacteria decreases the hardness of rat incisor and consumption to paddy in all consentration. Consumption to pellets increased after the application but it’s not appropriate during application. Interaction of those factors is the longer S. mutans given to the rat, the more fragility will happen to rat incisor and will impact to the paddy consumption, except control and 3x108cfu/ml. Decreasing of paddy consumption could be taken place between 46.8% to 59.4%.
Keyword: consumpsion., bactery teeth fragility, incisor hardness

Judul: Penapisan Streptomyces spp. Penghasil Senyawa Penghambat  Pertumbuhan Streptococcus mutans yang Diisolasi dari Plak Gigi
Abstrak: Pembentukan dan perkembangan plak gigi yang disebabkan oleh bakteri mulut seperti S. mutans, perlu dikurangi untuk mencegah kerusakan gigi dengan menggunakan senyawa antibakteri. Dalam penelitian ini, dilakukan penapisan 6 Streptomyces spp. isolat lokal yaitu IVNF1-1, PS1-4, PS4-16, PD2-9, SLW8-1, dan B56-2 penghasil senyawa antibakteri yang memberikan daya hambat terhadap S. mutans yang diisolasi dari plak gigi manusia. Daya hambat tersebut dibandingkan dengan daya hambat yang dihasilkan oleh minyak atsiri daun sirih dan natrium fluorida (NaF). Tiga dari lima isolat Streptococcus spp. mempunyai karakteristik S. mutans. Satu dari tiga isolat tersebut, yaitu S. mutans 4 digunakan sebagai bakteri target dalam uji antagonis. Dari 6 isolat Streptomyces spp. yang diuji, isolat IVNF1-1 mampu menghambat pertumbuhan S. mutans 4. Zona hambat filtrat kultur IVNF1-1 pada konsentrasi 0.50% (b/v) yaitu 2.12±0.18 mm. Zona hambat tersebut lebih besar dari zona hambat minyak atsiri daun sirih dan NaF pada konsentrasi yang sama, secara berurutan yaitu 1.75±0.35 mm dan 1.00±0.71 mm. Pada konsentrasi 1.00% (b/v), filtrat kultur isolat IVNF1-1, minyak atsiri daun sirih, dan NaF menghasilkan zona hambat secara berturut-turut yaitu 3.50±0.71 mm, 3.88±0.18 mm, dan 3.00±0.35 mm. Hasil penelitian ini menunjukkan bahwa senyawa bioaktif yang dihasilkan oleh Streptomyces sp. IVNF1-1 berpotensi sebagai agen kontrol pertumbuhan S. mutans 4
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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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