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: Uji Daya Hambat Ekstrak Etanol Kulit Batang Kayu Manis (Cinnamomum burmannii) Sebagai Antimikroba Terhadap Bakteri Pada Wajah.
Abstrak: Resistance of microorganisms to antimicrobial agent such as antibiotic makes treatment with antibiotic become ineffective, so it is necessary to develop alternative antimicrobial from plants. One of the herbs that have antimicrobial activity is cinnamon. The aim of this research was to compare the effectivity of cinnamon bark (Cinnamomum burmannii) ethanol extract at various concentrations with clindamycin in inhibiting the growth of Gram-positive cocci bacteria isolated from facial skin. The method used for in vitro antimicrobial inhibition test was agar well diffusion method. The test results showed that cinnamon bark extract has antimicrobial effectivity in inhibiting the growth of Gram-positive cocci bacteria but not as good as clindamycin. However, extract with concentration 20% and 40% in Micrococcus sp. showed better antimicrobial activity than clindamycin.
Keyword: antimicrobial, bacteria, face, cinnamon, Cinnamomum burmannii

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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