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.
Keyword: 

Judul: Aktivitas reduksi nitrat bakteri denitrifikasi dari muara sungai pada konsentrasi oksigen yang berbeda
Abstrak: Denitrifikasi dan reduksi nitrat menjadi amonium disimilatif adalah proses utama untuk menghilangkan senyawa nitrat di perairan termasuk muara sungai. Aktivitas reduksi nitrat oleh bakteri di lingkungan perairan dapat menghasilkan nitrous oksida (N2O). Penelitian ini bertujuan untuk mengetahui aktivitas reduksi nitrat bakteri denitrifikasi dari muara sungai dan hubungannya dengan konsentrasi oksigen. Hubungan konsentrasi oksigen dengan produk akhir bakteri denitrifikasi di ekosistem muara sungai, diharapkan menjadi pelengkap pengetahuan fisiologi bakteri pereduksi nitrat dari muara sungai di daerah tropis. Pengetahuan tersebut diharapkan dapat dimanfaatkan dalam pengelolaan lingkungan terutama pengurangan emisi N2O dan pencemaran nitrat di perairan. Sebanyak empat isolat bakteri denitrifikasi dari muara sungai yang merupakan koleksi laboratorium Mikrobiologi FMIPA IPB dikonfirmasi kemurniannya dan dilakukan uji reaksi Gram dan uji fermentatif. Isolat murni diremajakan dalam media cair. Isolat yang telah diremajakan diuji pertumbuhan dan kemampuan reduksi nitratnya pada konsentrasi oksigen berbeda. Konsentrasi oksigen berbeda dibuat dengan cara mengatur saturasi udara pada head space. Isolat yang pertumbuhannya bagus, tinggi kemampuan reduksi nitrat dan responsif terhadap perbedaan konsentrasi oksigen dipilih untuk perlakuan selanjutnya.
Keyword: 

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.
Keyword: