Judul: Potato Cyst Nematodes at Several Altitudes in The Dieng Potato Production Center of Central Java
Abstrak: Nematoda Sista Kentang (NSK) merupakan salah satu nematoda parasit utama pada tanaman kentang di dunia, termasuk Indonesia. Penelitian identifikasi spesies NSK dilakukan di beberapa ketinggian di Dataran Tinggi Dieng, Jawa Tengah. Sampel tanah diambil secara purposif pada tujuh lokasi dengan enam ketinggian berbeda, antara lain 1450 m, 1650 m, 1750 m, 1850 m, 1950 m, dan 2050 m di atas permukaan laut (dpl). Identifikasi spesies NSK secara morfologi dengan mengamati ciri-ciri juvenil 2 (J2) dan pola perineum betina. Hasil penelitian menunjukkan NSK yang diperoleh dari tujuh lokasi pada enam ketinggian dengan kepadatan 17-121 kista/100 ml tanah. Spesies NSK diidentifikasi sebagai Globodera rostochiensis., Potato Cyst Nematode (PCN) is a significant parasitic nematode affecting potato plants globally, including in Indonesia. A study was conducted to identify PCN species at various elevations in the Dieng Plateau, Central Java. Soil samples were intentionally collected from seven locations at six different elevations: 1450 m, 1650 m, 1750 m, 1850 m, 1950 m, and 2050 m above sea level (asl). The PCN species were identified morphologically by examining the characteristics of juvenile 2 (J2) and the perineal patterns of females. The research found PCN at all seven locations across the six elevations, with densities ranging from 17 to 121 cysts per 100 ml of soil. The identified PCN species was Globodera rostochiensis.
Keyword: cyst density, morphological charateristic, perineal pattern

Judul: Hubungan antara kerapatan populasi Globodera spp. dengan tingkat keparahan penyakit dan hasil umbi pada tanaman kentang
Abstrak: This study was carried out to estimate the population of Globodera spp. associated with disease severity and potato yield. This research was conducted from September 2011 until January 2012 in one of the central potato plantation in Dieng Plateau, Central Java. Identification of Potato Cyst Nematoda (PCN) species using morphological character was performed by the perennial pattern method. Research was conducted using 2-stages sampling method with the first stage as altitude and second stage as disease severity. Soil and plant sampling was taken from two levels of elevation, i.e 1250-1500 m and 1750-2000 m above sea level (asl). Three locations were selected for each elevation and 3 focus for each location. Five plant with different level of disease severity were taken. Disease severity was assessed based on the plant height, degree of chlorosis, fresh weight and tuber weight per plant. PCN population were counted based on the number of cyst per 100 ml soil and the average number of eggs and juvenile’s per cyst. The increasing of NSK density has a positive correlation with the increasing of disease severities which shown by a decrease in plant height as well as fresh plant weight, and an increase in percentage of plant chlorosis. In contrary, there was a negative correlation in number of tuber produced by plant which shown by the decrease of tuber yield when there was an increase of NSK population. Population of G. pallida dominated population of G. rostochiensis at both altitudes. The prevalence levels of G. pallida to G. rostochiensis were 63% at 1250-1500 m and 70% at 1750-2000 m asl.
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: