Judul: Antioxidant Activity of Extract and Active Fraction of Temukunci (Boesenbergia pandurata).
Abstrak: Temukunci (Boesenbergia pandurata Roxb.) is one of the herbal plants in tropical Asian countries used for cooking and as medicine plant. The aim of this research is to determine antioxidant activity of extract and its active fractions. Antioxidant activity of temukunci was determined using the spectrophotometric 2,2’-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method. Active fraction was identified by spraying DPPH 0.04% in metanol using thin layer chromatography. IC50 of its extract was 100 ppm and its active fraction was 99 ppm. These values were higher than BHT (butylated hidroxytoluene) as positive control that was 6.46 ppm.
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Judul: Hubungan kada pigmen dan kadar senyawa fitokimia daun temu kunci (Boesenbergia pandurata) dengan aktivitas antioksidan
Abstrak: Hubungan kadar pigmen dan kadar senyawa fitokimia terhadap antioksidan daun temu kunci (Boesenbergia pandurata) telah ditentukanSpektroskopi ultraviolet-tampak digunakan dalam penentuan kadar klorofil, karotenoid, antosianin, total fenol, total flavonoid, dan total tanin. Aktivitas antioksidan ditentukan menggunakan metode 1,1- difenil-2-pikril hidrazil (DPPH), ferric reducing antioxidant capacity (FRAP), dan cupric ion reducing antioxidant capacity (CUPRAC). Kadar klorofil, karotenoid, dan antosianin berkorelasi negatif dengan ketiga aktivitas antioksidan, sedangkan total fenol, dan total tanin berkorelasi positif terhadap aktivitas antioksidan. Korelasi antioksidan metode DPPH dengan klorofil adalah R2=0.573, dengan karotenoid R2 =0.579, dan dengan antosianin R2 =0.020. Korelasi metode FRAP dengan klorofil adalah R2 =0.455, dengan karotenoid R2 =0.496, dan antosianin R2 =0.021. Korelasi metode CUPRAC dengan klorofil adalah R2 =0.180, dengan karotenoid R2 =0.139, dan dengan antosianin R2 =0.098. Dengan demikian, kandungan metabolit sekunder lebih berkorelasi dengan antioksidan dibandingkan pigmen pada daun temu kunci.
Keyword: antioxidant, CUPRAC, DPPH, FRAP, temu kunci

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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