Judul: Analisis Kestabilan Mangsa-Pemangsa Lotka-Volterra dengan Allee Effects
Abstrak: Allee effects adalah hubungan positif antara kepadatan populasi dan laju pertumbuhan. Tujuan dari penulisan karya ilmiah ini ialah mempelajari pengaruh allee effects terhadap kestabilan sistem dan menganalisis perubahan kestabilan titik tetap dari model tersebut. Model yang dibahas terdiri dari dua model, yaitu model tanpa allee effects dan dengan allee effects. Perbedaan dari kedua model tersebut adalah terdapat besaran allee effects pada model dengan allee effects. Simulasi dilakukan dengan mengambil parameter yang berbeda untuk masing- masing kasus. Hasil simulasi menunjukkan bahwa ada pengaruh allee effects terhadap kestabilan, yaitu diperlukan waktu yang lebih lama untuk mencapai kestabilan. Meningkatnya allee effects akan menurunkan kepadatan populasi. Allee effects juga mengubah sifat kestabilan dari simpul stabil menjadi spiral stabil.
Keyword: Allee effects, Stability, Population density, Growth rate, Steady state, Kepadatan populasi, Laju pertumbuhan, Titik tetap, Penentuan titik tetap

Judul: Analisis kestabilan model dinamik mutualistik
Abstrak: Suatu komUllitas terdiri dari beberapa populasi yang saling berinteraksi, Salall satUllya adalall interaksi mutualistik. Interaksi ini mengasumsikan bal,wa kehadiran populasi spesies tertentu dapat meningkalkan laju pertumbnhan populasi dan spesies yang lain. Salah satu model matematika yang banyak digunakan nntuk menggambarkan interaksi dwispesies mutnalistik ini adalah model Lotka-Volterra [May, R. M., 197Gb]. Berdasarkan aSUlllsinya, maka laju pertUlllbuhan kedua populasi spesies dapat meningkat tanpa batas melebihi daya dukung lingkUllgannya [May, R. M., 197Gb]. Melihat kondisi tersebut, Heithaus, et. al. (1982) membuat snatu model untuk interaksi tiga spesies yaitu dengan menamballkan predator sebagai spesies ketiga pada sistem dwispesies mutualistik dan menganggap per/Ullya suatu jaminan dari kriteria kestabilan matematika agar sistem tersebut stabil, sehingga populasi spesies dapat hidup bersama (koeksis).
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Judul: Pemurnian dan karakterisasi protein inhibitor RNA helikase virus hepatitis C
Abstrak: Hepatitis C virus (HCV) infection is the second most common chronic viral infection in the world with global prevalence. This infection is contribution to chronic hepatitis and liver cirrhosis, often leading to hepatocellular carcinoma. There is no effective drug and vaccine available against HCV. The current standard treatment, a combination of pegylated interferon-α with ribavirin, is limited by its suboptimal response rate in a significant patient population, side effects, and affordability. Therefore, development of effective drug is needed. One approach to find out the candidate of antiviral drug is to discover the inhibitor of enzyme that essential for virus replication, such as RNA helicase. Streptomyces chartreusis 5-095 produce the inhibitor of HCV RNA helicase. The aim of this study was to purify the protein inhibitor which has inhibition activity against ATPase activity of RNA helicase HCV from S. chartreusis 5-095. The supernatant of culture S. chartreusis 5-095 exhibited high inhibiton activity against ATPase activity of RNA helicase HCV (approximately 72%) at 10 days of incubation. The extracellular protein inhibitor was partially purified by procedures of precipitation with ammonium sulfate to 65% saturation and gel filtration (Sephadex G50) using methanol water solution (4:6) as an eluen. The purity of protein inhibitor was monitored by SDS PAGE. The protein inhibitor showed a relative molecular mass were estimated to be 14 kDa and increased the purity 23,08 fold than those of the crude protein. The specific activity and IC50 after purification were 13,1338 U/mg and 0,0767 mg/mL, respectively. The activity of purified protein inhibitor showed its stability over pH range from 5-8 and optimum at pH 7,4. The inhibition activity showed its stability up to 70% at temperature 100 oC. The purified protein inhibitor relatively stable its activity at storage in the range of -20 oC to room temperature for 35 days.
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