Judul: Penyakit Busuk Buah Pada Terong Di Kecamatan Rancabungur dan Kemang Kabupaten Bogor
Abstrak: Eggplant is one of the most wanted vegetables in Indonesia, even the world. It contains antioxidants which can be used to prevent periodontic disease. It also contains vitamin A and B, and it is good to be consumed by diabetics. Among many diseases in eggplant, fruit rot is one of the major factors as a limited factor in production of this crop. The objective of this study was to observe fruit rot disease condition in subdistricts Rancabungur and Kemang, the district of Bogor. The fruit rot pathogens identified as Phomopsis vexans and Colletotrichum melongenae were covered in all observation plots. Besides of fruit, these pathogens also caused the symptom on stems and/or branches. In one symptomized plant part, these two pathogens were able to appear singly or mixed with the other. In the dry season the symptom was only detected on fruit, while in the wet season can also occurred on stems and/or branches. The disease incidence on fruit during dry season was less than 5% and in the early wet season it increased up to 8%. In wet season observation, disease severity of each plant was varied and mostly higher in the mature plants. Single observation of 20 samples on diseased branches and stems, C. melongenae dominated (80%) as the causal agent.
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Judul: Survei Penyakit Keriting (Cladosporium cladosporioides) pada Tanaman Pepaya di Bogor
Abstrak: Papaya is one fruit crops which are widely grown and consumed in Indonesia. Some pests and diseases in papaya are known to be limiting factor on the papaya production. Among o the diseases existing, the new disease namely leaf curl disease caused by Cladosporium cladosporioides has been reported since 2011 in Bogor. The objectives of this survey was to determine the status of this disease in the fields and same agricultural practices that may affect its development. The survey was conducted in two subdistricts Rancabungur and Sukaraja where papaya mostly cultivated. The results showed that leaf curl disease is widely spread in those two districts as indicated by the disease incidence, the disease incidence in Rancabungur and Sukaraja was 86.7% and 95.7% respectively. However, the disease severity is still moderate with average ranging from 24.2 to 27.6%. Generally the disease incidence in moderate type (Caliporan) and monoculture cropping system was lower than the large type (Bangkok) and multiple cropping system. Meanwhile, the disease severity did not show much differences due to the fruit type and cropping system. Other cultivated practices did not show much differences effect, both to the disease incidence and severity.
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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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