Judul: Deteksi dan Identifikasi Nematoda pada Tanaman Krisan di PT Natalia Nursery, Kecamatan Tenjolaya, Kabupaten Bogor
Abstrak: Produksi tanaman krisan di Indonesia fluktuatif, namun cenderung meningkat selama periode 2012-2016. Kendala peningkatan produksi krisan salah satunya adalah penyakit yang disebabkan nematoda tanaman. Namun, penelitian tentang nematoda pada tanaman krisan masih sedikit. Penelitian ini bertujuan mendeteksi dan mengidentifikasi nematoda pada tanaman krisan. Pengambilan sampel tanaman krisan dilakukan dengan metode diagnostik berdasarkan gejala penyakit antara lain kerdil, daun menguning, dan distribusi tanaman sakit mengelompok. Ekstraksi nematoda dari sampel tanaman krisan dilakukan dengan metode penggabutan. Nematoda dibuat preparat semi-permanen dan diidentifikasi secara morfologi. Nematoda parasit tanaman pada tanaman krisan yaitu Rotylenchus, Pratylenchus dan Meloidogyne. Nematoda non-parasit pada tanaman krisan adalah Acrobeles, Prodorylaimus dan Dorylaimus.
Keyword: krisan, morfologi, nematoda, non-parasit, parasit

Judul: Inventory of Parasitic Nematodes of Chrysanthemum  Plants in the Kebun Mandiri Florist, Cidahu District, Bogor Regency, West Java
Abstrak: Krisan (Chrysanthemum spp.) merupakan komoditas florikultura dengan produksi dan volume ekspor tertinggi dari tanaman hias lainnya di Indonesia. Hama dan penyakit tanaman menjadi faktor penghambat utama dalam budidaya krisan, salah satunya adalah nematoda parasit (fitonematoda). Penelitian bertujuan menginventarisasi dan mengidentifikasi fitonematoda yang berasosiasi dengan tanaman krisan di Kebun Mandiri Florist. Pengambilan sampel tanah dan akar dilakukan pada umur 13, 15, dan 16 MST (minggu setelah tanam). Nematoda diekstraksi dari sampel tanah dengan metode flotasi-sentrifugasi dan sampel akar dengan metode pengabutan (mist chamber). Identifikasi morfologi nematoda berdasarkan pada karakteristik anterior (bentuk mulut dan stilet), posterior (bentuk ekor dan organ reproduksi), serta anulasi tubuh nematoda. Pengukuran karakter morfometrik dilakukan mengacu pada formula J G De Man. Data morfometrik nematoda ditabulasikan dengan Microsoft Excel 2019. Empat genus yang diidentifikasi, yaitu Pratylenchus, Rotylenchulus, Tylenchus, dan Coslenchus. Fitonematoda yang dominan pada krisan adalah Pratylenchus dengan populasi absolut mencapai 9737,78/4 g akar dan frekuensi absolut 100% pada semua umur dan derajat kesehatan tanaman., Chrysanthemum (Chrysanthemum spp.) is the flower with the highest production and export volume compared to other types of flowers in Indonesia. Pests and diseases are the causes of sub-optimal flower production, one of which is plant parasitic nematodes. The research aimed to make an inventory and identify plant-parasitic nematodes associated with chrysanthemum plants in Kebun Mandiri Florist. Soil and root samples were collected at 13, 15, and 16 WAP (weeks after planting). Nematodes were extracted from soil samples using the flotation centrifugation method, and from root samples using the mist chamber method. The morphological identification of nematodes was based on anterior characteristics (mouth and stylet shape), posterior characteristics (tail shape and reproductive organs), and body annulation. Measurements of morphometric characters were carried out in reference to the J G De Man formula. Nematode morphometric data was tabulated with Microsoft Excel 2019. Four genera were identified: that are Pratylenchus, Rotylenchulus, Tylenchus, and Coslenchus. The dominant phytomatode in chrysanthemums was Pratylenchus with an absolute population reaching 9737,78/4 g of roots and an abolute frequency of 100% at all ages and degrees of plant health.
Keyword: frekuensi absolut, morfologi, morfometri, absolute frequency, morphology, morphometry

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: