Judul: Nematoda Pucuk Putih Padi Aphelenchoides besseyi Christie di Sumatera Barat.
Abstrak: Aphelenchoides besseyi is an important pest that could reduce rice production. West Sumatera. This study aims to explore the presence of A. besseyi, to detect and identify seed-borne A. besseyi nematode in West Sumatera utilizing morphology and morphometric characters. Samples of rice seeds used are local varieties of rice and hybrid varieties from Agam District, Lima Puluh Kota District, and Solok District. Methods include nematode extraction from seeds, population counting, morphological and morphometric identification, and preparation of slide preparate. The results of this study showed that A. besseyi have infected Junjuang, Sokan, Kuriak, Pulau Sarundang, Sarundang Baru, Batang Pasaman, Pulau Bendang, Pulau Mundam, Bendang Baru, 42 C, Pulut Merah, CK, Mundam Pasaman, Damasraya, Koritiang, Ale-Ale, Hitam Putih, Sijunjung, Junjuang, Sokan, Marujang Bujang, Batang Piaman, Anak Daro, Cisokan, PB 42, and 42 C with number of nematode populations from 1.56-125.44 / 10 g of seed. The morphological characters of A. besseyi found were a vermiform body, slender, smooth body annulation, set off lips, a spear-like stylet with an enlarged knob at the base, a large and oval-shaped median bulb, clear esophageal ring, overlapping esophagus, vulva located at 60 -75% of the body, the posterior part of the body of the male nematode is curved up to 90 °, the spicules are rose thorns, and 2-3 star shaped mucros. Morphometric characteristics with total body length (L) 362.54-672.70 μm, stilet length (S) 9.80-14.01 μm, body diameter (D) 10.41-16.86 μm, tail length (T) 23.81-39.66 μm, vulva distance from anterior divided by total body length (V) 54.48-75.97%, L / D (A) 33.86-63.58 μm, L / distance of the esophageal base from the anterior (B) 5.18-9.97 μm, L / T (C) 9.84-26.04 μm.
Keyword: Aphelenchoides besseyi, morphology, morphometric, rice seed

Judul: Morfologi dan Morfometri Aphelenchoides besseyi Christie, Nematoda Terbawa Benih Padi.
Abstrak: Aphelenchoides besseyi adalah nematoda penyebab penyakit pucuk putih pada padi. Gejala yang paling mudah diamati pada tanaman padi ialah klorosis pada ujung daun. Penelitian ini bertujuan untuk mengidentifikasi nematoda A. besseyi berdasarkan karakter morfologi dan morfometri. Nematoda didapat dari 5 varietas benih padi: Inpari 19, Pertiwi, Ciherang, Sintanur, dan IPB 3S. Benih padi didapat dari toko pertanian di Dramaga, Bogor. Ekstraksi nematoda dari benih padi menggunakan metode corong Baermann yang dimodifikasi. Pengamatan morfologi mengacu pada buku Pictorial Key to Genera of Plant Parasitic Nematodes. Karakter morfologi yang diamati adalah bentuk dan ukuran stilet, tipe anulasi, bentuk esofagus, bentuk ekor, ada atau tidaknya tumpang tindih antara esofagus dan saluran pencernaan. Pengukuran morfometri mengacu pada formula J.G. de Man pada 20 nematoda betina dan 10 nematoda jantan. Nematoda yang ditemukan pada 5 varietas benih padi adalah A. besseyi karena karakter morfologi dan morfometri yang diamati sesuai dengan kunci identifikasi dan data pembanding. Tidak ada perbedaan morfologi nematoda antar varietas. Terdapat beberapa ukuran nematoda yang berbeda dari data pembanding yang mungkin dipengaruhi faktor lingkungan dan inang.
Keyword: formula de Man, metode corong Baermann, penyakit pucuk putih

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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