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: Aktivitas Antibakteri Ekstrak Daun Sengon (Falcataria moluccana (L) Nielsen) terhadap Bakteri Staphylococcus aureus dan Escherichia coli
Abstrak: Disease by infection is most suffered by people and developed from time to time in medicines. The last research showed that Falcataria moluccana leafs had fitochemical compounds and potential as antibactery. The research aimed to study the antibacterial compounds activity of Falcataria moluccana leafs extract at S. aureus and E. coli with gel diffusion (well method). The leafs used in this research were leaf extract from extraction of aquades, ethanol 70%, ethanol 96%, and ethyl acetate. The concentrations were 50, 100, 150, 200, 250, and 300 mg/mL for each solvents. The result showed that aquades extract could not inhibit the growth of bacteria, while ethyl acetate and ethanol extracts showed antibacterial activity. The largest antibacterial activity showed by ethyl acetate extract at concentration 300 mg/mL with inhibiton areas 6.90 and 4.97 mm for S. aureus and E. coli. This values included in medium category. The result of Analysis of Variance with SPSS 16. program for windows showed that variance of solvents and concentration were significantly difference for inhibition areas.
Keyword: Falcataria moluccana (L) Nielsen, S. aureus, E. coli, antibactery

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
Keyword: