Judul: Elektrode Pasta Karbon Termodifikasi Nanopartikel Emas untuk Mendeteksi Zat Aktif pada Ekstrak Temu Lawak
Abstrak: The quality of temu lawak is determined by its active substance that contained therein. Determination of the active substance needs quick and low cost method, as well as, accurate measurement. Voltammetry technique is chosen because it meets these criteria. A gold nanoparticle-modified carbon paste electrode was used as a working electrode and its performances needs to be tested. Performance test was done for several parameters such as potential effects and deposition time, pH, and concentration. The optimum potential and deposition time were 0.5 V and 800 seconds, respectively, while the optimum pH obtained was 6.0. The electrode showed linear response toward concentration of the extract in the range of 0.5˗ 3.5% (w/v) with determination coefficient of 0.9630
Keyword: Bogor Agricultural University (IPB), temu lawak, gold nanoparticle, carbon paste electrode

Judul: Elektrode pasta karbon termodifikasi nanopartikel perak untuk deteksi zat aktif pada ekstrak rimpang temu lawak
Abstrak: Temu lawak (Curcuma xanthorriza) adalah tanaman obat yang memiliki banyak khasiat. Tanaman ini mengandung komponen aktif utama berupa kurkuminoid dan minyak atsiri. Pada penelitian ini, dilakukan deteksi komponen aktif dari ekstrak rimpang temu lawak menggunakan elektrode pasta karbon termodifikasi nanopartikel perak. Deteksi tersebut dilakukan dengan cara mengamati pengaruh potensial dan waktu deposisi, pH bufer, serta konsentrasi ekstrak yang dianalisis. Modifikasi nanopartikel perak pada permukaan elektrode dilakukan dengan teknik elektrodeposisi. Voltammogram siklik ekstrak rimpang temu lawak menunjukkan puncak oksidasi pada selang potensial –0.5–1.0 V dengan potensial deposisi optimum –0.4 V selama 800 detik pada pH 6.0. Arus oksidasi yang diamati menunjukkan peningkatan seiring dengan bertambahnya konsentrasi ekstrak.
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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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