Judul: Total Phenolic Content and Antioxidant Activity of Gandarusa Leaf (Justicia gendarussa Burm.f.) Extract with Difference of Concentraction of Solvent and Duration of Extraction
Abstrak: Konsentrasi pelarut yang digunakan dalam ekstraksi dan durasi ekstraksi akan memengaruhi kadar total fenolik dan aktivitas antioksidan daun gandarusa. Penelitian ini bertujuan untuk mengukur dan membandingkan pengaruh antara konsentrasi pelarut dan durasi ekstraksi daun gandarusa terhadap kadar total fenolik dan aktivitas antioksidan. Daun gandarusa diekstraksi dengan menggunakan pelarut metanol pada konsentrasi dan durasi yang berbeda. Kadar total fenolik diukur dengan menggunakan Uji Folin-Ciocalteu dan aktivitas antioksidan diukur dengan menggunakan uji DPPH dan CUPRAC. Kadar total fenolik tertinggi terdapat pada perlakuan konsentrasi metanol sebesar 30% dengan durasi 180 menit (0,1024 mg GAE/g bobot kering). Aktivitas antioksidan tertinggi pada uji DPPH (0,1853 μmol TE/g bobot kering) dan CUPRAC (5,2444 μmol TE/g bobot kering) terdapat pada perlakuan konsentrasi metanol 30% dengan durasi 180 menit., Concentration of solvent and duration of extraction will affect the total phenolic content and antioxidant activity of gandarusa leaf. This research was aimed to measure and compare the effect of concentration of solvent and duration of extraction on Total Phenolic Content (TPC) and antioxidant activity. Gandarusa leaf was extracted using the methanol solvent with different concentration and duration. Total phenolic content was measured with FolinCiocalteu and antioxidant activity was measured with DPPH and CUPRAC. The highest TPC is gandarusa leaf’s extract with 30% of methanol for 180 minutes (0,1024 mg GAE/mg dry weight). The highest antioxidant activity with DPPH (0,1853 µmol TE/gr dry weight) and CUPRAC (5,2444 µmol TE/gr dry weight) is gandarusa leaf’s extract with 30% of methanol for 180 minutes
Keyword: Antioxidant Activity, Concentration of Solvent, Duration of Extraction, Gandarusa Leaf, Phenolic

Judul: Optimization of Extraction of Phenolic Content and  Antioxidant Activity of Gandarusa (Justicia gendarussa Burm f.) Leaf with  Response Surface Methodology (RSM)
Abstrak: Ektraksi daun gandarusa (Justicia gendarussa Burm f.) dapat dipengaruhi oleh pelarut, suhu, dan waktu ekstraksi. Penelitian ini bertujuan menentukan suhu, waktu, dan konsentrasi pelarut optimum kadar total fenolik dan aktivitas antioksidan ekstrak etanol daun gandarusa dengan metode Respon Surface Methodology (RSM). Parameter uji yang dilakukan terhadap ekstrak daun gandarusa antara lain penentuan kadar total fenolik dengan metode Folin-Ciocalteu serta aktivitas antioksidan DPPH dan FRAP. Variabel bebas yang digunakan dalam desain eksperimen adalah konsentrasi etanol (10%, 50%, dan 90%), suhu (30℃, 45℃, dan 60℃) dan waktu ekstraksi (60, 120, dan 180 menit). Kadar total fenolik menunjukan korelasi yang positif dan signifikan terhadap aktivitas antioksidan FRAP daun gandarusa. Kondisi optimal untuk kadar total fenolik dan aktivitas antioksidan DPPH dan FRAP ekstrak daun gandarusa yaitu pelarut etanol 16,8%; suhu 30℃; dan waktu 180 menit. Nilai prediksi dan nilai verifikasi kadar total fenolik dan aktivitas antioksidan DPPH tidak berbeda secara signifikan., Extraction of gandarusa leaves (Justicia gendarussa Burm f. ) can be affected by solvent, temperature, and extraction time. This study aimed to determine the optimum temperature, time, and concentration of solvents, the total phenolic contents and antioxidant activity of gandarusa leaf ethanol extract by the Response Surface Methodology (RSM). Parameters of the test carried out on the extract of gandarusa leaf include determination of total phenolic contents using the Folin-Ciocalteu method as well as the antioxidant activity of DPPH and FRAP. The independent variables used in the experimental design were ethanol concentration (10%, 50%, and 90%), temperature (30℃, 45℃, and 60℃) and extraction time (60, 120, and 180 minutes). Total phenolic content showed a positive and significant correlation to the antioxidant activity of FRAP gandarusa leaves. Optimal conditions for total phenolic content and antioxidant activity of DPPH and FRAP of gandarusa leaf extract are 16,8% ethanol solvent; temperature 30℃; and time 180 minutes. The predictive value and verification value of the total phenolic content and antioxidant activity of DPPH did not different significantly.
Keyword: Antioxidant activity, gendarussa, independent variables, phenolic, RSM

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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