Judul: Aktivitas antibakteri ekstrak Daun Jawer Kotok (Coleus scutellaroides [L.] Benth.)
Abstrak: Penelitian ini mempelajari aktivitas antibakteri dan Konsentrasi Hambat Tumbuh Minimum (KHTM) dari ekstrak daun jawer kotok terhadap bakteri Gram positif (Staphylococcus aureus & Bacillus subtilis) dan bakteri Gram negatif (Escherchia coli & Pseudomonas aeruginosa), serta penentuan senyawa metabolit pada jawer kotok. Filtrat daun muda dan tua diuji aktivitas antibakterinya. Daun jawer kotok tua secara umum memiliki aktivitas antibakteri yang lebih besar. Daun jawer kotok tua diekstraksi menggunakan tiga pelarut, yaitu heksana, air, dan aseton. Ekstrak daun jawer kotok diuji aktivitas antibakterinya. Ekstrak aseton memiliki zona hambat paling besar terhadap bakteri uji. Ampisilin 0.4 mg/mL digunakan sebagai kontrol positif. Uji kualitatif fitokimia ekstrak aseton menunjukkan hasil positif untuk uji senyawa alkaloid dan steroid. Zona hambat yang dihasilkan memiliki korelasi positif dengan konsentrasi ekstrak daun jawer kotok. Konsentrasi Hambat Tumbuh Minimum ekstrak daun jawer kotok terhadap bakteri B. Subtilis, S. aureus, E. coli, dan P. aeruginosa adalah 0,1 mg/mL dengan zona hambat berturut-turut adalah 6.6438, 6.5, 6.8062, dan 6.6188 mm. Zona hambat ampisilin 0.4 mg/mL terhadap B. subtilis, S. aureus, E. coli, dan P. aeruginosa masing-masing sebesar 26.2, 25.6042, 24.7708, dan 25.5292 mm.
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Judul: Aktivitas Antimikroba Ekstrak Etanol Daun Jawer Kotok (Coleus atropurpureus) Terhadap Bakteri Kulit Wajah Berjerawat.
Abstrak: The misused of antibiotics will resist the bacteria. The increasing of resistance in antibiotic needs exploration other alternative resources which could kill or obstruct bacteria to grow. One of resources is jawer kotok (Coleus atropurpureus) leave. The objectives of this research are to assay jawer kotok leave’s etanol extract as antibacterial for pimpled skin. Those bacteria are Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus sp., and Micrococcus sp.. The bacterias were challenged with gradual extract consentration, starting from 20%, 40%, 60%, 80% and campared with 1% clindamycin antibiotic. The result of the research showed that jawer kotok leave’s etanol extract had potency as good antibacterial. The diameter of antibacterial inhibition zone range from 13.80 ± 1.09 mm until 17,00 ± 0,70 mm. Secondary metabolites in jawer kotok leave consist of flavonoids, polyphenols, tannins and terpenoids which had potency as antibacterial.
Keyword: Coleus atropurpureus, antimicrobial activity, jawer kotok extract, flavonoids, tannin, polyphenols, terpenoids

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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