Judul: Isolation and Selection Nitrogen Fixing Methanotrophic Bacteria from Ricefields in Sragen, Jawa Tengah.
Abstrak: Metan adalah salah satu gas yang menyebabkan pemanasan global. Penurunan emisi metan 20-60 kali lebih efektif dalam penurunan potensi pemanasan global dibandingkan dengan penurunan emisi karbon dioksida. Penelitian ini bertujuan untuk mengisolasi bakteri metanotrof dari lahan sawah di daerah Sragen, Jawa Tengah, dan menyeleksinya berdasarkan pada aktivitas oksidasi metan dan efektifitas fiksasi nitrogen (N2). Aplikasi bakteri metanotrof dapat mengurangi emisi metan dari sawah. Ekplorasi bakteri metanotrof dari contoh sedimen asal sawah di Sragen yang ditumbuhkan pada media Nitrat Mineral Salts (NMS) menghasilkan 52 isolat bakteri metanotrof. Sebanyak 31 isolat bakteri metanotrof diperoleh dari hasil isolasi menggunakan media NMS lengkap, dan 21 isolat bakteri metanotrof diperoleh dari hasil isolasi menggunakan media NMS bebas nitrogen. Aktivitas oksidasi metan diukur dengan menggunakan kromatografi gas, sedangkan aktivitas fiksasi nitrogen diukur berdasarkan kadar akumulasi amonium dalam kultur. Lima isolat bakteri metanotrof dengan aktivitas oksidasi metan tertinggi di media NMS lengkap adalah isolat 1AN1, 2DN1, 2AN1, 3DN1, dan 3CN1. Lima isolat bakteri metanotrof dengan oksidasi metan tertinggi di media NMS bebas nitrogen adalah isolat 2C1, 4C2, 3D1, 3C2, dan 3A1. Lima isolat bakteri metanotrof dengan fiksasi nitrogen tertinggi adalah isolat bakteri metanotrof 2C2, 1C2, 4C1, 1B1, dan 4D1.
Keyword: 

Judul: Efektivitas fiksasi N2 dan oksidasi metan kultur campuran bakteri metanotrof asal sawah
Abstrak: CH4 emissions in a rice field and wetlands is mostly produced by methanogenic bacteria and 80% of the CH4 is oxidized by methanotrophs. Besides of their ability to oxidize methane, methanotrophs also have ability to fix nitrogen. Four selected isolates of methanotrophs which had high nitrogen fixation activity i.e.(BGM 1, BGM 3, BGM 5, and BGM 9 isolates were combined with SKM 14 isolate which had high methane oxidation activity to obtain ideal formulations of the methanotrophs that have high activity of nitrogen fixation and methane oxidation activities. Nitrogen fixation activity was determined by measuring accumulated ammonium in medium and acetylene reduction assay (ARA). The highest concentraion of ammonium on single culture of methanotrophic bacterium was performed BGM 1 isolate (1,86 μM ammonium), and mixed culture of BGM3 and BGM9 isolates had the highest ammonium accumulation (4,905 μM ammonium). The highest nitrogenase activity was performed by mixed culture of BGM1 and SKM14 isolates, it was 11,27 μmol/ml cultures/hour. Whereas the higest methane oxidation was performed by mixed culture of BGM5 and BGM9 isolates, it was 18,20 ppm /ml cultures /day.
Keyword: 

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
Keyword: