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: Potensi Antibakteri Campuran Propolis Trigona spp dan Garam  Kelapa Terhadap Streptococcus mutans
Abstrak: Karies gigi merupakan masalah kesehatan yang umum terjadi di kalangan masyarakat Indonesia. Faktor yang paling banyak menyebabkan karies gigi adalah plak gigi. Bakteri yang dominan dalam plak gigi adalah Streptococcus mutans. Salah satu bahan antibakteri kariogenik yang biasa dipakai dalam pasta gigi saat ini adalah fluor. Penggunaan pasta gigi berfluor dapat menimbulkan fluorosis yaitu pelemahan email gigi bila dipakai dalam konsentrasi yang berlebihan. Propolis dan garam kelapa merupakan bahan alami yang berpotensi sebagai antibakteri pengganti fluor. Penelitian bertujuan untuk menguji aktivitas antibakteri dari campuran propolis dan garam kelapa dan membandingkan keefektifannya dengan antibakteri NaF yang terdapat dalam pasta gigi komersial. Uji aktivitas antibakteri S. mutans dilakukan dengan metode hitungan cawan yaitu penghitungan jumlah bakteri yang tumbuh di media sampel dalam cawan petri. Propolis kasar diekstrak dengan alkohol 70% dan didapatkan rendemen sebesar 8.52%. Hasil penelitian menunjukkan bahwa campuran propolis 6.25% dan garam kelapa 1 M mempunyai kemampuan paling besar sebagai antibakteri dan dapat menghambat S. mutans lebih baik daripada NaF 0.3%. Keefektifan campuran tersebut terhadap NaF 0.3% sebesar 203.88%.
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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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