Judul: Viabilitas dan Daya Simpan Benih Lobak (Raphanus sativus L.) Lokal dan Impor Setelah Disimpan pada Ruang Simpan Berbeda
Abstrak: The objective of this research was to study the viability local and imported radish seed after storage period and different room storage condition. This research was conducted at IPB Seed Science and Technology Laboratory for five months. This research used completely randomized design with two factors. The first factor is storage period consisting of 0, 2, 4, 6, 8, 10 and 12 weeks, and the second factor is the room storage condition, such as the room (27-30.7 oC) and the AC (18.7-27.9 oC) with four replicates, used local and imported radish seed. The results showed that local and imported radish seed still have a high viability after 12 weeks storage period, and the both of seeds could be stored in room or AC condition depend on the available of own room to maintain the viability still high during storage period. First and final count of the germination test should be performed on days 3 and 5.
Keyword: storage period, seed viability test, local seed, imported seeds

Judul: Determination of Short Term Storage to Maintain Quality of Water Spinach Seeds (Ipomoea reptans Poir.)
Abstrak: Benih yang dipanen saat masak fisiologis akan memiliki mutu yang maksimal. Benih perlu disimpan pada kondisi yang optimum untuk mempertahankan mutunya. Penelitan ini bertujuan menetapkan kondisi simpan jangka pendek benih kangkung sehingga mutunya dapat dipertahankan. Rancangan yang digunakan adalah rancangan acak lengkap faktorial dua faktor dengan 4 ulangan. Faktor pertama adalah warna benih kangkung yaitu hitam, cokelat gelap, dan cokelat terang. Faktor kedua adalah ruang simpan yaitu ruang ber-AC (suhu 16 - 21 °C, RH 55 – 63%) dan ruang kamar (suhu 27,4 – 30,3 °C, RH 64 - 87%). Setiap ulangan terdiri atas 25 benih. Hasil penelitian menunjukkan bahwa benih kangkung darat berwarna hitam dan cokelat gelap telah mencapai masak fisiologis, sehingga viabilitas dan vigor lebih tinggi dibandingkan warna cokelat terang. Benih berwarna cokelat terang belum mencapai masak fisiologis, dan memiliki viabilitas yang rendah. Ruang ber-AC (suhu 16 - 21 °C, RH 55 – 63%) dan ruang kamar (suhu 27,4 – 30,3 °C, RH 64 - 87%) dapat digunakan untuk mempertahankan mutu benih kangkung darat yang dikemas dalam aluminium foil dengan kadar air awal 9% untuk penyimpanan jangka pendek (14 minggu)., The seed quality is highest when it reaches physiological maturity. In order to maintain the quality, the seed needs to be stored in an optimum condition. The study was aimed to determine the proper short term storage conditions for kangkong seeds for maintaining the quality. This study was arranged in a completely randomized design with two factors and repeated 4 times. The first factor was seed coat color i.e. black, dark brown, and light brown and the second factor was the storage condition i.e. air-conditioned room (temperature 16-21 °C, RH 55-63%) and ambient room (temperature 27,4 – 30,3 °C, RH 64 - 87%). Each replicates consisted of 25 seeds. The results showed that the black and dark brown colors of kangkong seeds has reached physiological maturity therefore had higher viability and vigor than that of the light brown seeds. The light brown seed is physiologically immature, and have low viability. For short term storage (14 weeks) air-conditioned room (temperature 16-21 °C, RH 55-63%) and ambient room (temperature 27,4 – 30,3 °C, RH 64 - 87%) were sufficient to maintain the quality of kangkong seeds packed in aluminium foil with 9% initial moisture content.
Keyword: seed coat color, storage condition, viability, vigo

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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