Judul: Jenis dan Karakteristik Koloni Kutudaun (Hemiptera: ...Aphididae) pada Gulma di Bogor
Abstrak: Information on the aphids that associated with weeds is relatively limited. The research aimed to study the diversity of aphids and their colony characteristics in weeds at Bogor. The experiments were conducted by doing aphid sampling in 20 locations at Bogor area. Size of colonies, winged aphids (alatae), wingless aphids (aptera), symptomp caused by aphids, and aphids-ants association were observed. Slide preparation of aphids were used to identify the species. The studies have shown that there were nine aphid species found in weeds in Bogor area:, Aphis craccivora Koch, Aphis euginae van der Goot, Aphis gossypii Glover, Aphis spiraecola Patch, Hysteroneura setariae (Thomas), Jaksonia papillata Theobald, Melanaphis sorghi (Theobald), Schizapis graminum (Rondani), and Sitobion miscanthi (Takahashi). H. setariae was found numerously on the weeds. Wingless aphids was found in a big number of population. Weeds belong to the Family Asteraceae were the most attacked by aphids. Fifteen species of ants associated with aphids, they were Acanthomyrmex sp., Acropyga sp., Cardiocondyla sp., Camponotus sp., Cerapachys sp., Crematogaster sp., Dolichoderus sp., Loweriella sp., Monomorium sp., Myrmecina sp., Paratrecina sp., Philidris sp., Polyrhachis sp., Pseudolasius sp., and Tetramorium sp. The pictorial and dichotomy identification keys of aphids were constucted based on the morfological characters.
Keyword: Bogor Agricultural University (IPB), weeds., identification key, colony, aphids, ants

Judul: Identifikasi Kutudaun (Hemiptera: Aphididae) pada Tanaman Buah di Bogor
Abstrak: Aphids (Hemiptera: Aphididae) is a group of insect pests that have a very wide host range. Almost all plants are the host of aphids. Aphids can reduce the quality and quantity of fruit. This research aimed to know the species diversity of aphids on fruit crops in Bogor. The method used in this research is by collecting aphids and ants on 13 districts in Bogor. Sample of aphids were put in plastic bag then labelled by the location and the name of host plants. Samples then were taken to the laboratory and the number of individuals and the number of winged and wingless aphids in the colony were counted. Aphid specimens in the microscope slides were used for identification to species level using published keys based on morphological characters. Identification of aphids were using these keys: Aphids on the World’s Trees, Aphids of the World Crop, and Aphids on the World’s Herbaceous Plants and Shrubs. There were seven aphid species identified, they were Aphis gossypii Glover, Aphis spiraecola Patch, Brachycaudus helichrysi (Kaltenbach), Pentalonia nigronervosa Coquerel, Toxoptera aurantii (Boyer de Fonscolombe), Toxoptera citricidus (Kirkaldy), and Toxoptera odinae (van der Goot). T. aurantii was the most abundant aphid species found in the area. The plant family of Myrtaceae was the most host frequently attacked by aphids. The ants found in the aphid colonies were Dolichoderus sp. and Technomyrmex sp. Based on the morphological character, a pictorial and dichotomous keys of aphids associated with fruit crops were constructed
Keyword: Bogor Agricultural University (IPB), identification., hemiptera, fruit, Aphididae, Aphids

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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