Judul: Komunitas Staphylinidae (Coleoptera) di Kebun Ubi Jalar
Abstrak: Staphylinidae is a member of order Coleoptera (beetle). This family characterized by elongated slender body, large abdominal section and tapered end of the abdomen, and very short elitra. Most of staphylinids role as predators, saprofag, polifag, and as bioindicators of soil fertility. This research aimed to study the community of staphylinids in the sweet potato fields at Bogor. Observations and collections of beetle were done by using road sampling method. Samples collected were preserved in the ethanol 70% for identification purposes. Environmental factors, i.e. air temperature, humidity, and light intensity were measured during observations of beetles. Result showed that the community of staphylinids found in the sweet potato fields were Paederus fuscipes (subfamili Paederinae), Medon sp. (subfamili Paederinae), and Stenus sp. (subfamili Steninae). The dominant staphylinid species in the sweet potato was P. fuscipes
Keyword: Community, Coleoptera, staphylinid, sweet potato fields.

Judul: Komunitas Staphylinidae (Coleoptera) di Persawahan Sekitar Bogor dan Struktur Histologi Paederus fuscipes Curt.
Abstrak: The insect is an important component in the rice field ecosystem. One of the groups of insects in rice field ecosystems is family Staphylinidae. Staphylinids are charactarized by short elytra, so it does not cover the all abdominal segments. This research aimed to study community of staphylinids in some rice field in Bogor. Histological structures of Paederus fuscipes were studied. Collections of the beetles were done by road sampling method. The weathers, i.e temperature, humidity, and light intensity were measured during collections of staphylinids. Histological structure of P. fuscipes were observed based on paraffin method. Staphylinids collected in the three locations of rice field were Paederus fuscipes, Cryptobium abdominale, and Stenus sp. Staphylinids dominant in rice fields was P. fuscipes. An histological structure of P. fuscipes identified were the stomach, Malpighian tubule, rectum and anus.
Keyword: Staphylinid, diversity, Paederus fuscipes, histological structure

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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