Judul: Karakterisasi gen nifD bakteri metanotrof asal sawah
Abstrak: Methanotrophic bacteria are methane oxidizing bacteria. Some methanotrophs able of fix nitrogen using nitrogenase enzyme. Nitrogenase is composed of two multisubunit metallo protein. Component I contains the active site to nitrogen reduction, encoded by the nifD and nifK genes. Methanotrophic isolates of BGM 3 and BGM 9 had high ammonium accumulation cultured in Nitrate Mineral Salts (NMS) free nitrogen medium. nifD gene fragmens from BGM 3 and BGM 9 were amplified and sequenced. Sequences analyzed using bioinformatics tools such as Blast-N, Blast-X, Expasy Translate Tools, Conserved Domain (CDD) and Scan PROSITE. Phylogenetic construction made using MEGA 4 software. Sequence analysis showed that the nifD sequences of BGM 3 and BGM 9 most closely related to nifD fragmen of Xanthobacter autotropicus PY2. The Identity values of nifD sequences was 92% and 91% respectively. nifD genes from these isolates encode FeMo protein, which was 4Fe4S and 2Fe2S clusters. The nifD gene of BGM 3 and BGM 9 suspected to have same ancestor with the nifD gene of Xanthobacter autotropicus PY2 and Bradyhizobium japonicum USDA 110.
Keyword: 

Judul: Seleksi dan Uji Aktivitas Fiksasi Nitrogen (N2) Bakteri Metanotrof Asal Sawah pada Konsentrasi Oksigen (O2) Berbeda.
Abstrak: Methanotrophic bacteria is methane oxydizing bacteria. This bacteria has a specific enzyme known as methane monooksigenase (MMO) catalizing reaction of CH4 and O2 to methanol. Methanotrophic bacteria also have ability to fix nitrogen. Methanotrophic bacteria type II and type X could fix nitrogen using nitrogenase enzyme. This enzyme is very sensitive to oxygen. As many as 19 isolates of methanotrophic bacteria was recultured and determined their nitrogen fixation activity at different oxygen concentration. Nitrogen fixation activity was determined by measuring ammonium accumulation in NMS free nitrogen medium. High ammonium accumulation was found at cultures of BGM 1, BGM 3, BGM 5, dan BGM 9 isolates. The highest ammonium accumulation (88,816 <M) was showed by BGM 9 isolate on 30% oxygen concentration and the highest cell density was showed by BGM 5 isolate (OD 0,103) on 80% oxygen concentration.
Keyword: 

Judul: Pricing of Lookback Options with Floating Strike Price Using The Monte Carlo Method
Abstrak: Opsi lookback adalah opsi yang payoff-nya bergantung pada harga saham terbesar atau harga saham terkecil yang dicapai selama masa berlaku opsi. Opsi lookback dikatakan dengan floating strike price jika nilai dari strike price sebesar harga saham pada saat jatuh tempo. Nilai hampiran opsi lookback ditentukan dengan metode Monte Carlo, sedangkan nilai eksak didapat dari nilai simulasi terbesar yang mampu dihitung oleh komputer. Berdasarkan hasil penghitungan, nilai galat relatif yang dihasilkan semakin kecil dengan semakin bertambah banyaknya simulasi yang dilakukan, sehingga metode Monte Carlo untuk menghitung harga opsi lookback dengan floating strike price konvergen ke nilai eksaknya., Lookback option is an option whose payoff depends on the maximum or minimum of the asset price reached during the option period. The lookback option is said to be a floating strike price if the value of the strike price is equal to the stock price at maturity. The value of the lookback option is determined by the Monte Carlo method, while the exact value is obtained from the largest simulation value that the computer can compute. Based on the calculation results, the resulting relative error value get smaller with the increasing number of simulations performed. Therefore, the Monte Carlo method to calculate the price of the lookback option with the floating strike price converges to the exact value.
Keyword: lookback option, floating strike price, Monte Carlo method, convergent