Judul: Keragaman Rice ragged stunt virus dan Rice grassy stunt virus berdasarkan analisis sikuen nukleotida
Abstrak: nfeksi virus merupakan kendala penting dalam produksi padi di Indonesia. Tiga penyakit utama yang disebabkan oleh virus pada padi adalah tungro, kerdil rumput, dan kerdil hampa, masing-masing penyakit disebabkan oleh virus tungro, Rice grassy stunt virus (RGSV), dan Rice ragged stunt virus (RRSV). Kejadian penyakit kerdil rumput dan kerdil hampa masih jarang ditemukan, sedangkan penyakit tungro telah diketahui menyebabkan epidemi di beberapa daerah. Penelitian ini bertujuan untuk mempelajari keragaman RGSV dan RRSV berdasarkan sikuen nukleotida. Fragmen spesifik virus diamplifikasi dengan metode polymerase chain reaction menggunakan primer spesifik untuk RGSV (RGSV-S3-F/RGSV-S3-R), dan RRSV (RRSV-S9-F/RRSV-S9-R). Fragmen DNA spesifik RGSV dan RRSV berhasil diamplifikasi dari sampel Subang, Jawa Barat dan Klaten, Jawa Tengah. Sikuen nukleotida yang diperoleh dari produk PCR dan analisis sikuen menunjukkan homologi yang tinggi (> 99%) antara isolat Subang dan Klaten, baik untuk RGSV maupun RRSV. Analisis lebih lanjut yang melibatkan sikuen di Genbank menunjukkan bahwa homologi antara isolat RRSV dan RGSV dari Asia Tenggara sangat tinggi, yaitu masing-masing mencapai 91-99% dan 95-99%.
Keyword: polymerase chain reaction, sequence homology, specific primers

Judul: Keragaman Gen Protein Selubung Isolat Rice tungro bacilliform tungrovirus (RTBV) dan Rice grassy stunt tenuivirus (RGSV) dari beberapa Kabupaten di Pulau Jawa, Keragaman Gen Protein Selubung Isolat Rice tungro bacilliform tungrovirus (RTBV) dan Rice grassy stunt tenuivirus (RGSV) dari beberapa Kabupaten di Pulau Jawa
Abstrak: Indonesia is the largest consumer of rice in the world. International Rice Research Institute (IRRI) estimated that Indonesia may require an increase in rice production for the next 25 years. Among many constrains in rice production increement is plant diseases including tungro and grassy stunt diseases. Tungro disease is caused by infection of two viruses, Rice tungro bacilliform tungrovirus (RTBV) and Rice tungro spherical waikavirus (RTSV). These viruses are transmitted by the rice leaf hopper vectors which mainly is green leafhoppers (Nephotettix virescens). RTBV is a determinant of the disease symptoms eventhough it could not infect rice without the presence of RTSV. Infected plants showed typical tungro symptoms involving stunting, yellow or orange-yellow discoloration of the leaves, reduced number of tillers and rust-colored spots on the leaves. In 2006 a new symptoms was found in paddy crop in Indonesia, i.e. yellow-orange discoloration of the leaves, reduced number of tillers without any reduction in plant height. It was reported that the disease is caused by infection of Rice grassy stunt tenuivirus (RGSV) the cause of grassy stunt disease. Symptoms similarity of tungro and RGSV infection may cause difficulty in disease diagnosis and cause confusion in determining diseases control strategies. Therefore research on symptoms and genetic diversity of RTBV and RGSV is necessary to determine the appropriate control strategy. The genetic diversity of RTBV isolates from South Asia and Southeast Asia as well as from some tungro endemic area in Indonesia based on the symptoms variation and diversity of coat protein gene have been reported. The genetic diversity of the isolates RGSV from two areas in Taiwan and Philippines based on symptoms variation have also been reported. Genetic and symptoms diversity of RTBV and RGSV could be analysed through the diversity of coat protein gene. Coat protein gene is known as a determinant factor of infection, virulence, and symptoms induction. The research is conducted to study the diversity of symptoms and coat protein gene of RTBV and RGSV from several districts in Java. The areas in Bogor, Subang, Pandeglang, Klaten, Batang, Sleman, Jember and Banyuwangi were selected as disease survey location because these regions were reported as endemic areas for tungro disease and brown leafhopper. The study includes three main activities, i.e. observation of symptoms in the field and sampling of infected plants, detection of RTBV and RGSV, and analysis of diversity of coat protein gene of RTBV and RGSV. Most infected plants in the fields showed tungro-like symptoms. Two variations of symptoms can be classified by the number of tillers and plant height. These symptoms variations can be caused by RTBV or RGSV infection or mix infection of RTBV and RGSV as indicated by detection results using PCR. Identification of total 64 samples showed infection of RTBV in 13 samples, RGSV in 36 samples and mix of RTBV and RGSV in 2 samples. The results showed that tungro-like symptoms were positive from infection of RGSV. Therefore identification of diseases based only on symptoms are not sufficient. The whole coat protein gene of RTBV was amplified using DA-F and DA-R primers with the amplicon
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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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