Judul: Antibacterial Activity of Neem (Azadirachta indica) Leaf Extract Using Agar Disc Diffusion Method
Abstrak: SETIYANINGSIH and USAMAH AFIFF Neem (Azadirachta indica) has traditionally been considered one of the most versatile medicinal plants that possesses a wide spectrum of biological properties including anti–inflammatory, anti–arthritic, anti–pyretic, anti–gastric ulcer, antibacterial, antifungal, antiviral, antioxidant, antimalarial, antidiabetic and antitumor activities. In this study, the agar disc diffusion method was used to determine the antibacterial activity of ethanolic neem leaf extract against three Staphylococcus aureus isolates from different sources which are human skin, snake mouth and cow milk, Staphylococcus epidermidis, Micrococcus sp., Bacillus sp., and Serratia sp. Neem leaf extract at concentrations of 40%, 60% and 80% were used with negative controls of water and ethanol as well as a positive control of Penicillin-G antibiotics. Inhibition zones were observed after 24-hour incubation, of the neem leaf extract at all concentrations to all Gram–positive bacteria which are S. aureus, S. epidermidis, Micrococcus sp. and Bacillus sp. Bacillus sp. was shown to have the highest sensitivity to the neem leaf extract. The largest zones of inhibition were observed at the 80% concentration of neem leaf extract in all bacteria excluding Serratia sp. Gram–negative bacteria Serratia sp. was resistant to the antibacterial effects of the neem leaf extract.
Keyword: Agar disc diffusion, antibacterial, Azadirachta indica, Bacillus sp., Micrococcus sp, Neem, Serratia sp., Staphylococcus aureus, Staphylococcus epidermidis

Judul: Antibacterial Activity of Neem (Azadirachta indica) Leaf Extract Using Agar Disc Diffusion Method
Abstrak: Neem (Azadirachta indica) has traditionally been considered one of the most versatile medicinal plants that possesses a wide spectrum of biological properties including anti–inflammatory, anti–arthritic, anti–pyretic, anti–gastric ulcer, antibacterial, antifungal, antiviral, antioxidant, antimalarial, antidiabetic and antitumor activities. In this study, the agar disc diffusion method was used to determine the antibacterial activity of ethanolic neem leaf extract against three Staphylococcus aureus isolates from different sources which are human skin, snake mouth and cow milk, Staphylococcus epidermidis, Micrococcus sp., Bacillus sp., and Serratia sp. Neem leaf extract at concentrations of 40%, 60% and 80% were used with negative controls of water and ethanol as well as a positive control of Penicillin-G antibiotics. Inhibition zones were observed after 24-hour incubation, of the neem leaf extract at all concentrations to all Gram–positive bacteria which are S. aureus, S. epidermidis, Micrococcus sp. and Bacillus sp. Bacillus sp. was shown to have the highest sensitivity to the neem leaf extract. The largest zones of inhibition were observed at the 80% concentration of neem leaf extract in all bacteria excluding Serratia sp. Gram–negative bacteria Serratia sp. was resistant to the antibacterial effects of the neem leaf extract.
Keyword: Agar disc diffusion, antibacterial, Azadirachta indica, Bacillus sp., Micrococcus sp., Neem, Serratia sp., Staphylococcus aureus, Staphylococcus epidermidis

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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