Judul: Effectiveness of P14 and J8 Bacteria as Biocontrol Agents Against Downy Mildew on  Cucumber in Tegal
Abstrak: Mentimun merupakan salah satu jenis sayuran yang populer ditanam di Indonesia. Salah satu faktor yang menurunkan produktivitas mentimun adalah penyakit tanaman. Penyakit penting yang menyerang daun yaitu penyakit downy mildew yang disebabkan oleh Pseudoperonospora cubensis. Pemanfaatan bakteri sebagai agens hayati merupakan salah satu alternatif pengendalian yang tidak berdampak negatif bagi lingkungan. Tujuan penelitian ini adalah mengetahui keefektifan dari bakteri agens hayati tunggal dan kombinasi P14 dan J8 terhadap penyakit downy mildew dan pengaruhnya terhadap pertumbuhan tanaman serta hasil mentimun di Kabupaten Tegal. Percobaan dilakukan dengan menggunakan dua bakteri galur P14 dan J8, yang terdiri dari empat taraf perlakuan. Perlakuan terdiri dari kontrol, perendaman benih dengan bakteri P14, bakteri J8, dan dengan kombinasi P14 dan J8. Penelitian disusun dalam rancangan acak kelompok (RAK) dengan enam ulangan. Isolat bakteri P14 dan J8 diproduksi massal kemudian diaplikasikan pada benih. Pengamatan dilakukan pada pertumbuhan tanaman mentimun, kemunculan pertama penyakit, nilai AUDPC, insidensi, keparahan penyakit, dan produksi mentimun. Hasil penelitian menunjukkan bahwa aplikasi tunggal atau kombinasi bakteri P14 dan J8 tidak mempengaruhi pertumbuhan tanaman kecuali perlakuan kombinasi bakteri P14 dan J8 mempengaruhi daya kecambah benih serta produksi mentimun meningkat. Aplikasi kombinasi P14 dan J8 mampu menekan penyakit downy mildew mentimun secara nyata dan meningkatkan hasil mentimun di Tegal., Cucumber is a type of vegetable crop popularly grown in Indonesia. One factor that decreases the yield of cucumber productivity is plant disease. An important disease that attacks leaves is downy mildew caused by Pseudoperonospora cubensis. The utilization of bacteria as biological agents is an alternative control with no negative impact to the environment. The purpose of this research was to determine the effectiveness of single biological agent bacteria and a combination of P14 and J8 against downy mildew disease and their effect on plant growth and cucumber yield. Experiment was conducted using two bacterial strains P14 and J8, consisting of four treatment levels. The treatments consisted of control, soaking the seeds with P14 bacteria, J8 bacteria, and with combination of P14 and J8. The research was arranged in randomized block design (RCBD) with six replication. Bacterial isolates P14 and J8 were mass produced and then applied by seed treatment. The observations were made on cucumber plant growth, the first symptoms that appear on plants, AUDPC value, incidence, disease severity, and cucumber production. The result showed that the single application or combination of P14 and J8 bacteria didn’t affect plant growth except the combination treatment of P14 and J8 bacteria affects seed germination. The application of the combination of P14 and J8 can significantly suppress the incidence and severity downy mildew of cucumber and increase cucumber yield in Tegal.
Keyword: biological control, cucurbitaceae, PGPR

Judul: Effectiveness of Mixture Two Biocontrol Agents (J8 & P14) against Downy Mildew of Melon (Cucumis melo L.).
Abstrak: Produksi melon terus mengalami peningkatan lima tahun terakhir sehingga pengembangan melon kedepan harus mulai memasuki pasar ekspor. Saat ini ekspor melon Indonesia masih relatif rendah karena terkendala regulasi batas maksimum residu (BMR). Tingginya serangan organisme pengganggu tanaman (OPT) membuat petani menggunakan pestisida secara masif hingga melebihi batas. Salah satu OPT melon adalah penyakit embun bulu yang disebabkan Pseudoperenopora cubensis. Oleh karena itu, perlu dicarikan solusi pengendalian penyakit embun bulu yang lebih sehat. Penelitian ini bertujuan mengetahui keefektifan pengendalian campuran dua agen pengendali hayati (J8 & P14) terhadap penyakit embun bulu pada melon (Cucumis melo L.) dengan berbagai cara aplikasi. Metode yang digunakan adalah rancangan acak kelompok (RAK) non faktorial dengan analisis data one way annova dan uji lanjut beda nyata jujur (BNJ) dihitung secara manual. Penggunaan campuran dua bakteri J8 dan P14 dapat meningkatkan daya berkecambah melon. Perlakuan C dapat meningkatkan pertumbuhan yang meliputi tinggi tanaman dan jumlah daun terutama pada umur muda. Seluruh cara aplikasi APH kecuali A, efektif menekan insidensi dan keparahan penyakit. Cara aplikasi APH yang efektif dan tanpa penggunaan fungisida adalah perlakuan C. Keefektifan cara aplikasi C dalam menekan insidensi dan keparahan penyakit embun bulu pada melon sebesar 41,74%., Melon production has continued to increase in the last five years so the development of melons in the future must begin to the export market. Currently, Indonesia's melon exports are still relatively low due to constraints on the regulation of the maximum residue limit (MRLs). The high number of pest attacks makes farmers use pesticides massively to exceed the limit. One of the diseases of melons is downy mildew by Pseudoperonospora cubensis. Therefore, it is necessary to develop alternative control the disease of downy mildew. This research aims to determine the effectiveness of mixture two biocontrol agents (J8 & P14) against downy mildew of melon (Cucumis melo L.). The method used randomize complete block design with one way annova data analysis and further testing of tukey 0,05%. The results of the reasearch using two bacteria J8 and P14 can increase the germination of melons by 11%. Biocontrol agenst (J8 & P14) can improve plant growth (height and number of leaves). Most effective way of applying biocontrol agenst with minimal fungicide is the C treatment (seed treatment, one week old seedling application, and weekly applications). The effectiveness was able to suppress the severity of the disease at control rate of 41.74%.
Keyword: batas maksimum residu (BMR), insidensi, Pseudoperenopora cubensis, effective, Pseudoperonospora cubensis, way of applying

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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