Judul: Peningkatan Keragaan Coleus (Coleus sp.) melalui Induksi Mutasi Fisik dengan Iradiasi Sinar Gamma
Abstrak: The objectivse of this study were to see the effect in applicating several doses of gamma-ray irradiation (15, 30, 45, and 60 gray (Gy)), to obtain Lethal Dose 50 (LD50) values, and to gain new coleus performances in relatively short time. The study was conducted inside green house located at cikabayan experimental field, Bogor Agricultural University, Darmaga, Bogor on May to June 2013. The results showed that application of several doses of gamma irradiation on coleus were significantly different in character of height, number of leaves, and number of stem segment. Increasing the dose level of gamma irradiation given tend to inhibit the growth of the plants. Based on the result of the study, LD50 for yellow/green, green/brown, variegated green/brown of Coleus blumei, and Coleus amboinicus Lour were 48.66, 65.2, 52.81, and 37.62 Gy respectively. Coleus amboinicus Lour irridiated at a dose level of 45 Gy produced different leaf shapes compared to control.
Keyword: torbangun, ornamental plant, LD50 values, gamma-ray irradiation, coleus

Judul: Pengaruh iradiasi sinar gamma terhadap pertumbuhan plb anggrek Dendrobium lasianthera (JJ. Smith) secara in vitro
Abstrak: This research aimed to learn the effect of gamma ray-irradiation on protocorm like bodies (plb) Dendrobium lasianthera and determined Lethal dosage (LD) 30 and 50. The irradiation has done at the Center of Technology Application of Isotops and Radiation, Nuclear Energy Agency (PATIR-BATAN), the research started from February 2014 to July 2014. The research implemented the completely randomized design (CRD) with a single factor that gamma rayirradiation dosage were 0 Gy, 20 Gy, 40 Gy, 60 Gy, 80 Gy, and 100 Gy. Each dose of gamma ray-irradiation treatment was repeated 5 times, of which there were 30 units of the experiment and each experimental unit consisted of five culture bottles were individually planted 4 plb Dendrobium lasianthera. The results of this research showed that the effect of gamma ray-irradiation dose significantly decreased the percentage of live plb, percentage of plb germination, number of leaves, number of roots, the percentage of rooted plant. Plantlets changes observed among other wide leaves, and the spiral leaves. Lethal dose 30% (LD30) was at 19.7697 Gy irradiation dose and LD50 was at 67.3504 Gy irradiation dose.
Keyword: Bogor Agricultural University (IPB), mutation, Lethal Dosage (LD), in vitro, gamma ray-irradiation, Dendrobium lasianthera

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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