Judul: Eksplorasi dan Uji Potensi Nematoda Entomopatogen Heterorhabditis sp. terhadap Tenebrio molitor (Coleoptera: Tenebrionidae) secara In Vivo
Abstrak: Penggunaan insektisida sintetik mempunyai dampak negatif seperti pencemaran lingkungan, tertinggalnya residu pestisida, dan matinya beberapa musuh alami. Pentingnya pengendalian hayati akan terus bertambah pada saat sekarang ini. Terutama dalam pertanian berkelanjutan dan pengendalian hama yang ramah lingkungan. Upaya tersebut dapat dilakukan dengan menggali potensi organismeorganisme yang berasal dari lingkungan sekitar, antara lain nematoda entomopatogen (NEP) yang selanjutnya dimanfaatkan sebagai bioinsektisida. Penelitian ini bertujuan mengeksplorasi spesies-spesies nematoda entomopatogen yang efektif untuk pengendalian hama dengan menggunakan serangga uji Tenebrio molitor. Metode yang digunakan adalah: eksplorasi, identifikasi, dan uji efikasi. Eksplorasi dilakukan dengan menguji sampel tanah yang berasal dari wilayah Bogor dan Sukabumi. Setelah itu, uji efikasi dilakukan dengan menggunakan lima tingkat konsentrasi JI (Juvenil Infektif) 200, 400, 800, 1600, 3200 JI/ml. Persentase mortalitas dihitung pada jam ke-24, 30, 36, 42, 48, 54, dan 60 setelah infestasi JI. Nematoda entomopatogen yang di peroleh dari hasil eksplorasi teridentifikasi sebagai genus Heterorhabditis sp. dengan kemampuan mematikan serangga Tenebrio molitor pada kisaran kerapatan dan waktu uji, yaitu sebesar 42.85 % mortalitas tergolong sangat efektif dengan berkisar antara 96.67-100.00%, 5.71% mortalitas tergolong efektif dengan berkisar antara 76.67-80.00%, 11.42% mortalitas tergolong cukup efektif dengan berkisar antara 60.00- 70.00%, 5.71% mortalitas tergolong agak efektif dengan berkisar antara 40.00-43.33%, 8.57% mortalitas tergolong kurang efektif dengan berkisar antara 30.00-36.67%, dan 28.57% mortalitas tergolong tidak efektif dengan berkisar antara 0.00-23.33%. Berdasarkan nilai lethal concentration (LC) dan lethal time (LT) pada tingkat 50.00 dan 95.00%, tingkat kerapatan 1600 dan 3200 JI/ml adalah paling efektif.
Keyword: efikasi, eksplorasi, nematoda entomopatogen, ramah lingkungan, Tenebrio molitor

Judul: Efikasi Nematoda Entomopatogen Heterorhabditis sp. dan Steinernema sp. Isolat Bogor Sebagai Bioinsektisida Terhadap Rayap Tanah Coptothermes curvignathus Holmgren (Isoptera : Rhinotermitidae)
Abstrak: The subterranean termite, Coptotermes curvignathus Holmgren (Isoptera: Rhinotermitidae) is the most important wood destroying termites in many regions in Indonesia. Their infestation on buildings, agricultural crops, and forest trees has caused significant economic loses. Meanwhile termite control technology still depend on termiticide application, which cause negative effect to environment. On the other hand, entomopathogenic nematodes is one of agents potential bio-control in controlling subterranean termites without negative effect to environment. A research was conducted to evaluate the effectiveness of the entomopathogenic nematodes Heterorhabditis sp and Steinernema sp as a biological control agents against subterranean termites Coptotermes curvignathus Holmgren in field test. Procedures of the research included the rearing of the entomopathogenic nematodes, both in-vivo and in-vitro, the evaluation of the nematodes toxicity against subterranean termites (LC50 and LT50) and field evaluation of entomopahogenic nematodes against subterranean termite at field. The mortality of termites was analysis with Completed Randomized Design and Tukey's Test. The effective deusity 600 IJ/ml of entomopathogenic nematodes Heterorhabditis sp and Steinernema sp caused 100% mortality of subterranean termites C. curvignathus. The LC50 value for the population of subterranean termites C. curvignathus for Steinernema sp was 322 IJ/ml and Heterorhabditis sp was 355 IJ/ml. The LT50 value for the population of subterranean termites C. curvignathus was 33,94 hours for Steinernema sp and was 34,90 hours Heterorhabditis sp. For the efficacy test, the mortality value of subterranean termites C. curvignathus caused by Steinernema sp and Heterorhabditis sp were 90,23 % and 85,65 % respectively. In field testing the mortality value of subterranean termites C. curvignathus caused by Steinernema sp and Heterorhabditis sp were 79,51 % and 94,40 % respectively. It is conclued that Steinernema sp and Heterorhabditis sp can be used as biological control against C. curvignathus.
Keyword: 

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: