Judul: Analisis Fitokimia Dan Aktivitas Antioksidan Ekstrak Daun Sengon (Paraserianthes falcataria (L) Nielsen) Menggunakan Metode DPPH
Abstrak: Kedawung (Mimosaceae family) has been shown to have high antioxidant content. Therefore, sengon leaf that belong to the Mimosaceae family is alleged to have potential as a source of natural antioxidants. Utilization of sengon leaf as food supplements with antioxidant activity has not been done. Therefore, this study aims to examine and to analyze the antioxidant activity of bioactive components. The antioxidant activity was determined by DPPH method and measured with a spectrophotometer at a wavelength of 517 nm. The results showed that the antioxidant activity is highest in the 96% ethanol extract of leaves sengon expressed as IC50, specifically 2.76 ppm. The antioxidant activity was caused by the content of secondary metabolites in the sengon leaf, such as alkaloids, saponins, flavonoids, tannins and phenolics, steroids and triterpenoids. The analysis showed that the antioxidant activity, total phenolic content (275.74 GAE mg/g) and total flavonoid (83.60 CE mg/g) sengon leaf are quite good and can be used as benchmark for natural antioxidant source.
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Judul: Total Fenolik dan Flavonoid serta Aktivitas Antioksidan Ekstrak Kulit Kayu Sengon (Paraserianthes falctaria (L.))
Abstrak: (Paraserianthes falcataria (L)) is widely used in wood industry and resulted many wastes. The leaf was found to have antioxidant activity, but the bark is still reused. The researches about (Paraserianthes falcataria (L)) bark that have been conducted was not studied to show potency of natural antioxidant. This research was performed to determine the antioxidant activity of (Paraserianthes falcataria (L)) bark extract. Phytochemical scavenging showed that aqueous, ethanol 70%, and 96% bark extracts were positively reacted to saponin, flavonoid, tanin, steroid, and triterpenoid test, while the only negative result was happened to alkaloid test. The highest ammount of total phenolic and flavonoid was found in ethanol 70% extract, those were 161.57 ± 3.93 GAE (mg/g) and 64.46 ± 2.94 CE (mg/g) respectively. The highest IC50 value was found in ethanol 96% extract with value of 40.17 ± 0.65 mg/L.
Keyword: antioxidant, flavonoid, phenolic, Paraserianthes falcataria (L) bark

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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