Judul: Karakterisasi Molekular dan Uji Aktivitas Bakteri Pereduksi Nitrat dari Muara Cimandiri Pelabuhan Ratu Sukabumi Jawa Barat
Abstrak: The activity of nitrate reducing bacteria in aquatic environment can produce nitrous oxide (N2O) via either denitrification and dissimilative nitrate reduction to ammonium processes. This research isolated and characterized nitrate reducing bacteria from Cimandiri Estuary. Twenty-two isolates of nitrate reducing bacteria isolated from enrichment medium with 100 μM and 2000 μM nitrate, 15 isolates were denitrifier bacteria and 7 isolates were dissimilative nitrate ammonifier bacteria. NFR1, NFR2, NFR3, NFR4, FR1 and FR2 isolates had the higher nitrate reducing activity. The activity of nitrate reduction was started in the first hour incubation and the highest nitrate reducing activity was occured during the exponential phase after 12 hours incubation. The Vmax value of NFR1, NFR2, NFR3, NFR4, FR1 and FR2 isolates were 0.65 mM.h-1, 0.49 mM.h-1, 0.25 mM.h-1, 0.27 mM.h-1, 0.38 mM.h-1 and 0.56 mM.h-1, respectively. While Km value were 2.93 mM, 3.16 mM, 1.40 mM, 1.15 mM, 1.78 mM and 2.93 mM, repectively. While umax value were 0.34 cell.h-1, 0.22 cell.h-1, 0.14 cell.h-1, 0.19 cell.h-1, 0.21 cell.h-1 and 0.33 cell.h-1, respectively. Based on 16S-rRNA sequence similarity, NFR1 isolate was closely related to Microbacterium sp; NFR2 and NFR4 isolates were closely related to Shewanella algae; FR2 isolate was closely related to Shigella flexneri.
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Judul: Aktivitas reduksi nitrat dan kinetika bakteri denitrifikasi dari Muara Sungai pada sumber karbon berbeda
Abstrak: fermentatif, yang dapat mendegradasi senyawa organik dalam kondisi lingkungan anaerob dan aerob. Penggunaan nitrat sebagai akseptor elektron oleh kelompok bakteri ini, dapat mengurangi kadar nitrat di perairan, akan tetapi bakteri tersebut menghasilkan gas N2O (nitrous oxida) sebagai produk samping, senyawa tersebut berpotensi meningkatkan pemanasan global. Bakteri denitrifikasi pada umumnya mereduksi nitrat menjadi gas-gas nitrogen seperti nitrit oxida, nitrous oxida atau dinitrogen, akan tetapi terdapat beberapa bakteri pereduksi nitrat yang menghasilkan amonium. Aktivitas reduksi nitrat bakteri denitrifikasi yang berasal dari daerah tropik belum banyak diketahui, diantaranya dalam percobaan terhadap berbagai sumber karbon. Oleh karena itu perlu dilakukan penelitian pengaruh sumber karbon terhadap aktifitas reduksi nitrat bakteri denitrifikasi. Empat isolat kelompok bakteri denitrifikasi terseleksi dari muara sungai daerah tropikal, telah diuji pertumbuhan dan aktivitas reduksi nitratnya pada sumber karbon asetat, glukosa, gliserol, dan suksinat. Keempat isolat tersebut adalah isolat NFR1, NFR4 ( berasal dari muara Cimandiri) dan isolat LNF, HNF5 (berasal dari muara sungai Cisadane).
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Judul: Pemodelan Harga Saham Menggunakan Model Lévy dan Model Black-Scholes
Abstrak: Stock may produce high profits. However, it has a high risk as well, because the stock prices fluctuate over time. Therefore, a model is required to estimate the future stock prices accurately. In this paper, Lévy model is compared to Black-Scholes model in estimating the stock price at Bank of America Corporation. As a result, it is concluded that the Black-Scholes model is more accurate than Lévy model.
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