Judul: Analisis probit untuk pembandingan tingkat toksisitas ekstrak kasar akar tuba dan buah pinang
Abstrak: Golden snail pests become a very important issue in any lowland rice farming. Generally farmers control this pests mechanically by taking existing golden snail. In addition, farmers also use synthetic pesticides to kill golden snail. However, both ways are not effective enough. One way to overcome this problem is to use a plant pesticide tuba root and areca-nut fruit coarse extract. It is known that both of these pesticides can cause death of golden snail. But the effective dose and relative toxicity of the two plant pesticides is not yet known, but it is important to know especially in dealing with critical issues. Determination of effective dose can be done through the determination of the lethal concentration (LC), for example, LC50 and LC90. This research use probit analysis to modeling a connection between golden snail death response (binary data) and both of plant pesticides concentration. Analysis result show that areca-nut coarse extract are more effective than tuba root extract since toxicity level of areca-nut (LC50 = 0.381 g/l and LC90 = 1.098 g/l) higher than tuba root (LC50 = 0.675 g/l and LC90 = 1.182 g/l). Supported by the terms of practically to obtain and how to manufacture, areca-nut coarse extract is recommended for use in eradication of golden snail pests.
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Judul: Efektivitas Ekstrak Daun Nangka dan Daun Sukun sebagai Moluskisida Nabati terhadap Daya Hidup Keong Mas (Pomacea canaliculata Lamarck)
Abstrak: Golden apple snails (Pomacea canaliculata Lamarck) are pests that attack water plants, especiallypaddy field until 30 days old. One effort to eradicate the snails without leaving chemicals residue in plants is by the provision of natural pesticides such as molluscicides. Jackfruit and breadfruit leaves maybe used as natural molluscicides for snail because they contain saponins. This study aims to test the jackfruit leaf and breadfruit leaf extracts to the survival of snails and determine the effectiveness of the leaf extract based on the LC50. The experiment was conducted separately for small (operculum diameter 5-10 mm) and large golden snails (operculum diameter of 11-20 cm). During the experiment the snails were put in a jars filled with water without leaf extract as the control, and jars with leaf extract at a concentration of 5 g/L, 10 g/L, and 25 g/L as treatments. Observations were carried out by counting the number of snails survives after 24, 48, and 72 hours. The results were analyzed to obtain LC50 values. Jackfruit and breadfruit leaves extracts have potential as molluscicides, since they caused all the snails died on the third day of treatment (72 hours). Decreasing rate of their survival is faster at higher concentrations. The presence of mucus in the body of the dead snails showing symptoms of the effect of saponins. Inconsistent results seem appear on LC50 (24 and 48 hours) of breadfruit extract. LC50 of 24 hours (large snails) and 48 hours (small snails) since they are not detected at the treatment using jackfruit leaves. This suggests the need to redesign the method and the concentration used for better research results.
Keyword: snails., Bogor Agricultural University (IPB), breadfruit, Pomacea canaliculata, Pomacea canaliculata, molluscicides, jackfruit

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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