Judul: Leaf Beetle Phyllotreta striolata Fabr. (Coleoptera: Chrysomelidae): Biology and Infestation on Chinese Flowering Cabbage Brassica rapa Var. Parachinensis L. in Bogor Regency, West Java
Abstrak: Tanaman caisim (Brassica rapa var. parachinensis L.) merupakan komoditas sayuran yang sangat diusahakan dan diminati karena nilai ekonominya yang tinggi dan kandungan nutrisinya yang penting. Kabupaten Bogor, salah satu wilayah utama dalam produksi sayuran di Indonesia, mengalami masalah serius akibat serangan kumbang daun Phyllotreta striolata pada tanaman caisim. Kumbang ini menyebabkan kerusakan pada daun, bunga, dan akar tanaman, dengan potensi kerugian mencapai 62,5%. Meskipun begitu, penelitian terkait karakteristik dan peran hama ini di Indonesia masih terbatas. Oleh karena itu, penelitian yang memperdalam pemahaman tentang siklus hidup dan perilaku Phyllotreta striolata pada caisim diperlukan untuk mengembangkan strategi pengendalian yang lebih efektif dan perlindungan bagi tanaman caisim dari serangan merugikan ini. Pengamatan aspek biologi P. striolata melibatkan pengumpulan dan identifikasi imago P. striolata dari pertanaman caisim serta observasi biologisnya, fokus pada morfologi kumbang dan fase perkembangannya. Populasi imago dikumpulkan dari tanaman caisim berumur 2, 4, dan 6 Minggu Setelah Tanam. Evaluasi intensitas serangan dilakukan di empat Kecamatan di Kabupaten Bogor pada tanaman caisim berumur 4 MST dengan teknik sampling pada lahan 8 x 10 m dan plot contoh 1 m², memeriksa 25 tanaman dan 5 daun di setiap plot. Pada tahap perkembangan, telur P. striolata berwarna kuning, larva berbentuk silindris putih, dan pupa berwarna putih bertipe kampodeiform dalam media tanam caisim. Siklus hidupnya rata-rata 27,15 hari. Imago memiliki perbedaan morfologi jantan dan betina, terutama pada bagian antena. Studi menunjukkan stadia imago berlangsung rata-rata 119,10 hari, dengan masa praoviposisi rata-rata 3,08 hari. Hasil pengamatan populasi imago P. striolata menunjukkan bahwa populasi P. striolata cenderung menurun seiring bertambahnya usia tanaman caisim. Hal ini diduga disebabkan oleh perbedaan dalam faktor lingkungan dan ketersediaan sumber makanan selama berbagai tahap pertumbuhan tanaman. Serangan P. striolata pada tanaman caisim dapat mengakibatkan kerusakan berupa lubang-lubang kecil pada daun, nekrosis, dan bintik-bintik kuning. Kerugian ini dapat mengurangi hasil panen dan kualitas daun caisim. Intensitas serangan bervariasi di berbagai lokasi pengamatan. Intensitas serangan P. striolata pada tanaman caisim bervariasi di beberapa lokasi pengamatan. Leuwimalang menunjukkan intensitas serangan paling rendah (23,56%) dengan kerusakan ringan, sementara Laladon memiliki intensitas tertinggi (48,76%) dengan kerusakan sedang. Hal ini menandakan bahwa karakteristik lingkungan di Leuwimalang mungkin membantu tanaman caisim menjadi lebih tahan terhadap serangan hama daun.
Keyword: Brassicaceae, infestation intensity, insect rearing, population

Judul: Keragaman serangga yang berasosiasi dengan tanaman caisim (Brassica rapa var. chinensis L.: Cruciferae) pada area pertanian tepi hutan
Abstrak: The aim of the research was to study insect diversity associated with chinese cabbage (Srassica rcpipa var. chi~remis}i n forest edge agicr;!t;re. &ese cabbzge were p!mied h 9.x Iocations with different distance, they were 0 m and 400 m frm the forest margin. Insect ebs=r:&ccs -xeze &nt eveiy two hoaxs, ficm 08 am =ti! 02 pm. Qbm11n-n~w ere s81?ed hfii 2 until 45 day after planted PAP). Sample of insects were caught by sweep net fbr identification. Idc~tXedin sect were classified based on their role as phytophagous, pollinator, and predator. Environment condition, include: temperature, humidity, and Iight intensity were measured Data were analysed by Shetnnon's diversity index @'j and evennes Q and s&J sidW~in-d ex (Cj). Total number of phytophagous, polhator, and predator insect were tested by t-fmt. Insect diversity associated with chinese cabbage were phytophagous (67%), pollinator (14%), and predator (19%). Insect diversity in 0 m was higher @'=2.498, E= 0.304) than 400 m &om the forest edge (IT-Z.344, E4298). Abundance of phytophagous and pollinator insect in 400 m was lower than in 0 m fiom the edge, whiIe predatory insect was higher in 400 m. Based on the observation time, the number of individual and species of insect were highest at 08 am, lower at 10 am d l12 pm and lowest at 02 pm. Based on plant age, the number of individual aad insect species were fluctuation Simillarity of insect associated with chinese cabbage in two bcations was higher (Cj=0.9).
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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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