Judul: Perlakuan Benih dan Bibit Cabai (Capsicum annuum L.) dengan Rizobakteri Meningkatkan Pertumbuhan Tanaman dan Menurunkan Kejadian Penyakit Busuk Phytophthora
Abstrak: Penggunaan rizobakteri dalam mengendalikan penyakit busuk phytophthora merupakan salah satu pilihan ramah lingkungan daripada menggunakan fungisida. Penelitian ini bertujuan untuk mengetahui pengaruh perlakuan benih dan bibit menggunakan agen hayati yang dapat meningkatkan pertumbuhan tanaman dan menurunkan kejadian penyakit busuk phytophthora. Penelitian ini terdiri atas tiga percobaan dengan menggunakan rancangan acak lengkap. Percobaan pertama (in vitro) terdiri atas sepuluh taraf perlakuan yaitu tujuh macam konsentrasi metalaksil, dua metode aplikasi rizobakteri, dan kontrol. Percobaan kedua (persemaian) menggunakan tiga taraf perlakuan terhadap benih yaitu merendam benih dalam larutan metalaksil 800 ppm, suspensi rizobakteri ST116B, atau larutan ekstrak kentang (PDA) sebagai kontrol. Percobaan ketiga (rumah kaca) menggunakan rancangan acak lengkap dua faktor dengan faktor pertama (pemberian metalaksil atau rizobakteri) tersarang pada faktor kedua (kondisi tanah yaitu tanah diinokulasi atau tidak diinokulasi P. capsici). Metalaksil 800 ppm dan isolat rizobakteri ST116B secara in vitro dapat menghambat pertumbuhan P. capsici. Perlakuan benih dengan isolat rizobakteri ST116B dapat menurunkan tingkat kejadian penyakit busuk phytophthora dari 61,9% menjadi 9,5%. Perlakuan benih dengan rizobakteri ST116B dengan atau tanpa perlakuan bibit meningkatkan tinggi tanaman dan jumlah daun dibandingkan kontrol negatif pada kondisi tanah tanpa inokulasi P. capsici. Artinya, rizobakteri ST116B dapat berperan sebagai antagonis P. capsici sekaligus PGPR.
Keyword: metalaksil, PGPR, Phytophthora capsici, vigor benih

Judul: Perlakuan Benih Cabai (Capsicum annuum L.) dengan Rizobakteri secara Tunggal ataupun Kombinasi untuk Mengendalikan Phytophthora capsici dan Meningkatkan Pertumbuhan Tanaman.
Abstrak: Seed treatment of hot pepper using rhizobacteria is an alternative to fungicide in controlling phytophthora blight disease that caused by Phytophthora capsici fungus pathogen. The objectives of this research were to evaluate: (1) the effectiveness of rhizobacteria isolates in inhibiting P. capsici growth, and (2) the effect of seed treatment using rhizobacteria on seed vigor and plant growth, and incidence of phytophthora blight disease. This research consisted of three experiments, all experiments were arranged in completely randomized design using one factor. The first experiment (in vitro) consisted of nine levels i.e. seven combination isolates of rhizobacteria, metalaxyl and untreated control. The second experiment (on the seedbed) consisted of five levels of seed treatments i.e. ST116B rhizobacteria, CM8 rhizobacteria, ST116B + CM8 rhizobacteria, metalaxyl and control. The third experiment (in the green house) consisted of six levels of seed treatments i.e. ST116B rhizobacteria, CM8 rhizobacteria, ST116B + CM8 rhizobacteria, metalaxyl, positive and negative control. Results of in vitro experiment showed that all rhizobacteria, single or combinations, were able to inhibit P. capsici growth. The highest inhibitions were shown by CM8, ST116B, and ST116B + CM8 consequtively. Seed treatments of hot pepper using ST116B, CM8 and ST116B + CM8 rhizobacteria did not increase seed vigor but increased the number of leaves 6 weeks after transplanting, and reduced the incidence of phytophthora blight disease. There were no significant differences whether the rhizobacteria was applied singly or in combination of the two isolates. Rhizobacteria ST116B is suggested to be used in hot pepper seed treatment before planting.
Keyword: biological agents, metalaxyl, phytophthora blight disease, rhizobacteria isolates

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.
Keyword: