Judul: Biosintesis dan karakterisasi nanopartikel silika (SiO2) dari sekam oleh Fusarium oxysporum
Abstrak: Silica nanoparticles have many advantages such as large surface, heat resistance, mechanical strength, and inert. Therefore has been used as a precursor catalyst, an adsorben, and a composit filter. Biosynthesis is a method to find the nanoparticles through enzymatical mechanism from microbe. This research aims to produce the silica nanoparticles by F.oxysporum with a phase growth and an amount of rice husk as substrate optimization. F.oxysporum is grown in a media pH 4-6, incubation temperature 27ºC, and 200 rpm aeration system. The presence of extracellular enzymes F.oxysporum views based on their ability in reducing the silica which is contained in the rice husk. The number of optimum substrate is determined by the two treatments, 2.5 gram and 5 gram of rice husks. The F.oxysporum biomass has been harvested in 72th hour, when the cells entered the stationary phase based on the growth curve. SEM analysis results for both types of treatments shows the number of particles agregate each other and have undifferent particle size with variations in size between 200-1000 nm. The three highest peaks are found in the FTIR absorption spectrum which is located at peaks 3408.18 cm-1 for the group H2O, peaks 1639.04 cm-1 for the group CO32-, and peaks 1078.71 cm-1 for the group Si-O-Si. The husk with F.oxysporum treatment indicated to be changed from the structure basic forms (amorphous) to the crystalline silica nanoparticles (crystoballite) based on XRD analysis.
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Judul: Optimization Nanoparticle Silica Biosynthesis with Rice Husks Substrate by Fusarium oxysporum.
Abstrak: Sekam padi merupakan hasil samping dari produksi padi yang mengandung silika cukup tinggi. Silika tersebut dapat digunakan sebagai nanopartikel silika yang berperan dalam biosensor, pelabelan sel, penghantaran obat. Metode biosintesis nanopartikel bersifat ramah lingkungan, bersih, non toksik, murah, dan mudah. Biosintesis nanopartikel silika dari sekam padi belum optimum. Penelitian ini bertujuan melakukan optimasi biosintesis nanopartikel silika melalui penambahan waktu inkubasi. Fusarium oxysporum ditumbuhkan pada media PDA pH 6 dan PDL pH 4, suhu ruang, dan sistem aerasi 200 rpm. Biosintesis dilakukan dengan meresuspensi biomassa F. oxysporum dengan larutan sekam pada variasi waktu inkubasi 24, 48, 72, 96, dan 120 jam. Produk biosintesis dikarakterisasi menggunakan PSA, SEM, FTIR, dan XRD. Hasil yang diperoleh menunjukkan bahwa produk biosintesis pada inkubasi 96 jam sudah memiliki ukuran nanopartikel sekitar 46.3-93.1 nm (96%) dan diameter rata-rata 59.7 nm. Morfologi partikel berbentuk spherical (bulat) tetapi masih beraglomerasi dan memiliki struktur silika kristalin
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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.
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