Judul: Ekstrak Sarang Semut (Hydnophytum formicarum) dan Potensinya sebagai Antihiperglikemik
Abstrak: Sarang semut (Hydnophytum formicarum) as an epiphyte of mangrove plant from Papua is increasingly popular to be used as antidiabetic medicine. Inhibition of α-glucosidase is one of mechanism of actions of an oral antidiabetic for diabetes mellitus treatment. The purpose of this research was to determine the antihyperglycemic activity of the sarang semut extract as α-glucosidase inhibitor. The research was performed in several steps: extraction of tuber of sarang semut, phytochemical test, α-glucosidase inhibition test, toxicity test using BSLT method. The phytochemical test indicated that methanol extract contained phenol and flavonoid, and water extract contained phenol, flavonoid, and tannin. Flavonoid concentration of methanol and water extracts were 0.559% (b/b) and 0.585% (b/b). Methanol extract inhibited α-glucosidase activity up to 98.55%, while water extract up to 9.37%. LC50 value of methanol extract was 735.02 ppm (categorized as a low toxic material), and water extract was 258166.58 ppm (as non toxic material).
Keyword: 

Judul: Pengaruh Media Pertumbuhan terhadap Potensi Antibakteri dan Antihiperglikemik Kapang Endofit Tumbuhan Pesisir Sarang Semut Hydnophytum formicarum
Abstrak: Sarang semut plant is traditionally used for medical purposes. The aim of this research was to observe the antibacterial and α-glucosidase enzyme inhibitor activities of the fungal extracts isolated from sarang semut plant which was cultivated in different culture media. The fungus cultivated using PDB medium grew faster in comparison with one in Hagem medium. During 21 days of cultivation, pH value was 4-5. The best results of antibacterial activity against Escherichia coli and Staphylococcus aureus were extract of culture medium with PDB treatment in 18 days cultivation, with inhibitor zone was 17.6 mm and 16.5 mm, respectively. IC50 value for α-glucosidase inhibitor was 9345.777 ppm showed by extract of culture in Hagem medium.
Keyword: Bogor Agricultural University (IPB), Hydnophytum formicarum., endophytic fungi, biomass, antihyperglycemic, antibacterial

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: