Judul: Variation of Antioxidant Activity and Total Flavonoid Content of The Rhizome  of Curcuma xanthorrhiza Roxb. with Three Different Cultivation Locations
Abstrak: Temulawak (Curcuma xanthorrhiza Roxb.) dapat menghasilkan metabolit sekunder dan memiliki peran sebagai sumber antioksidan. Temulawak dapat menghasilkan variasi akumulasi metabolit sekunder jika ditanam pada lokasi dengan kondisi lingkungan yang berbeda-beda. Penelitian ini bertujuan memperoleh pola interaksi genotipe temulawak dengan lingkungan penanaman multilokasi (Bogor, Cianjur, dan Sukabumi) serta memperoleh hasil evaluasi stabilitas dari setiap genotipe. Kadar total flavonoid temulawak tertinggi diperoleh dari penanaman di Sukabumi dengan nilai 21,3791 mg QE/g bobot kering. Genotipe dengan kadar total flavonoid tertinggi adalah G6 dengan nilai 23,2428 mg QE/g bobot kering. Aktivitas antioksidan tertinggi berdasarkan lokasi diperoleh dari penanaman di Sukabumi dengan nilai 9,6371 μmol TE/g bobot kering dan berdasarkan genotipe yakni G3 dengan nilai 9,1943 μmol TE/g bobot kering. Keragaman ulangan berpengaruh nyata pada parameter kadar total flavonoid dan tidak ditemukan interaksi genotipe dan lingkungan pada kedua parameter. Genotipe yang stabil pada ketiga lokasi (Bogor, Cianjur, Sukabumi) adalah G5 untuk kadar total flavonoid dan G3 dan G4 untuk aktivitas antioksidan. Genotipe G5 memiliki potensi stabil pada lokasi penanaman di Bogor dengan parameter aktivitas antioksidan.
Keyword: antioxidant, flavonoids, multilocation, temulawak

Judul: Interaction of Genotype and Environment on The Phenolic Levels and Antioxidant Activity of Temulawak (Curcuma xanthorrhiza Roxb.)
Abstrak: Rimpang temulawak (Curcuma xanthorrhiza Roxb.) memiliki potensi sebagai sumber antioksidan karena terdapat senyawa bioaktif metabolit sekunder seperti senyawa fenolik. Perbedaan kondisi abiotik lingkungan, seperti air dan suhu, menyebabkan cekaman pada tanaman dan akan terbentuk variasi akumulasi metabolit sekunder tanaman. Penelitian ini bertujuan mengevaluasi produktivitas kadar fenolik dan aktivitas antioksidan serta mendapatkan informasi mengenai stabilitas genotipe rimpang temulawak pada kadar fenolik dan aktivitas antioksidan terhadap penanaman di tiga lokasi (Bogor, Cianjur, Sukabumi). Tahapan penelitian meliputi pengujian kadar fenolik dan aktivitas antioksidan metode DPPH serta daya adaptasi genotipe temulawak pada penanaman multilokasi dengan metode AMMI. Produktivitas kadar fenolik tertinggi diperoleh dari lokasi Sukabumi (7,8744 mg GAE/g), dan genotipe G5 (7,5394 mg GAE/g), sedangkan aktivitas antioksidan tertinggi diperoleh dari lokasi Cianjur (20,1519 μmol TE/g), dan genotipe G6 (21,1797 μmol TE/g). Keragaman lokasi berpengaruh nyata pada kadar fenolik, serta tidak terdapat interaksi genotipe dan lingkungan pada kedua parameter. Genotipe yang stabil pada ketiga lokasi adalah G2 untuk kadar fenolik, G3 dan G4 untuk aktivitas antioksidan, G1 dan G6 untuk kedua parameter, sementara G4 berpotensi stabil di Bogor untuk kadar fenolik., Temulawak rhizomes (Curcuma xanthorrhiza Roxb.) have the potentials as antioxidant sources because they contain bioactive secondary metabolites such as phenolics. Differences in environmental abiotic factors, such as water and temperature, cause stress on plants and will create variations in the secondary metabolites’ accumulations. This research aims to evaluate the phenolic levels productivity and antioxidant activity and to obtain information about the stability of temulawak rhizome genotypes on phenolic content and antioxidant activity on planting in three locations (Bogor, Cianjur, Sukabumi). The research stages included the phenolic content and antioxidant activity (DPPH method) test, as well as the adaptability of the temulawak genotype in multilocation planting using the AMMI method. The highest phenolic content productivity was obtained from Sukabumi (7.8744 mg GAE/g), and G5 (7.5394 mg GAE/g), while the highest antioxidant activity was obtained from Cianjur (20.1519 μmol TE/g), and G6 (21.1797 μmol TE/g). Location diversity has a significant effect on phenolic levels, and there is no interaction of genotype and environment on both parameters. The stable genotypes at all three locations were G2 for phenolic content, G3 and G4 for antioxidant activity, G1 and G6 for both parameters, while G4 was potentially stable only in Bogor for phenolic content.
Keyword: antioxidant, Curcuma xanthorrhiza, genotype, phenolics, stability

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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