Judul: Physico-Chemical Characteristic of Sediment in Teluk Kaping, Bali: It’s Correlation with Bacterial Composition and Abundance.
Abstrak: The objectives of this study were to determine the physico-chemical of the sediment in Teluk Kaping Bali., which is has closed topography and has been utilized for intensive Mari culture activities. Those activities influence the environmental condition. Samples (sediment) in this study came from 16 observation sites. Sediment has a stable characteristic. Its condition could be pointed by the physico-chemical characteristic and the bacterial composition and abundance. Physico-chemical characteristics of the sediment were analyzed using Correlation and Principal Component Analysis, whilst its impact to bacterial composition and abundance were determined using the Multiple Regression. Those analyses were using Minitab 2003 13.2 Version. The physical characteristics showed that the sediment were dominated by sand and clay fraction, meanwhile in the coast area there was also found silt fraction. The pH was alkaline (7.9-8.6). It also has reductive condition, with redox potential between -242.90 mV s/d -56.50 mV. The interstitial water (IW) was 28.85 – 60.49%. Total carbon was (C) 0.13 – 21.6%, nitrogen (N) 0.04 – 0.19%, and phosphor (P) 0.0004 – 0.003%. The C/N/P ratio has a high value, also the C/N ratio has a high value in the sediment, with high ratio variety. C/P ratio variety was higher than the C/N and N/P ratios. Identified bacteria from heterotrophic group, such as Enterobacter spp., Bacillus spp., and Pseudomonas sp., and nitrified bacteria (Nitrosomonas sp., Nitrosococcus sp., and Nitrobacter sp.) were dominantly found in the sediment. Meanwhile, there were also a small number of other identified bacteria from the Enterobacteriaceae group, such as Escherichia coli and Klebsiella sp. Bacillus spp. has the highest abundance, which is almost 60% of total identified bacteria abundance. Heterotrophic bacteria were more dominant than the nitrified bacteria in the sediment. This is related to the ability of the heterotrophic bacteria to utilyze different of nutritional sources, efficiently. It also has a broad environmental tolerancy. Statistical analyses pointed out that the physico-chemical charateristics has unsignificant correlation to the bacterial composition and abundance in Teluk Kaping sediment. This is caused by the characteristic of each bacterium that has an ability and special survival mechanism from limited nutrition and poor environmental condition.
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Judul: Diversity of Bacterial Community that Contribute in Nitrogen Cycle at Lake of Situ Sawangan-Bojongsari, West Java.
Abstrak: One of the problems in freshwater management is the declining of water quality due to pollution of nitrogen compound. Mechanisms of nitrogen transformation by indigenous bacteria in water body have been considered to solve this problem. Situ Sawangan-Bojongsari is the largest lake at Depok city, West Java. Antrophogenic activities on the lake have been accused to cause nitrogen pollution. Accordingly, the aim of this research is to investigate the abundance and diversity of bacterial community that contribute in N cycle as well as to study the profile of physical and chemical parameters that influence the bacterial community. Water and sediment samples were collected from three sampling station, each with three replicate. Water samples were collected from the surface of the water column (0 cm), secchi depth (110) and the bottom (230 cm). Sediment samples were collected by sediment core and divided to three section depth (0-2 cm, 2-5 cm, and 5-10 cm). Analysis of physical factors was fermormed at the time of sampling which included temperature, pH, and DO. Wheter analysis of chemical factors from water and pore water sediment covered some parameters: TN, TOM, DOM, TOC, N-NH3, N-NO3, dan N-NO2. Analysis of the bacterial abundance that contribute in N cycle was done using MPN method. The community structure of the bacteria was analyzed using DGGE method. Amplification product of nifH, amoA, and nosZ gene were targeted for DGGE analysis. The most abundance of nitrogen fixing bacteria was found at the sediment in the depth of 2-5 cm (4.43 log cell/mL) and the less abundance was found at the water coloumn in the depth of 0 cm (2.46 log cell/mL). The most abundance of ammonia oxidizing bacteria was found in the depth of 0 cm (270 cell/mL). The less abundance of the bacteria was found in the depth of 230 cm (73 cells/Ml). The most abundance of nitrite oxidizing bacteria was found at the water column in the depth of 0 cm (2.87 log cell/mL) and the less abundance of the bacteria was found in the depth of 230 cm. There was no ammonia and nitrite oxidizing bacteria found in the sediment. The most abundance of nitrate reducing bacteria (denitrification) was found at the sediment in the depth of 2-5 and 5-10 cm (6.04 log cell/mL) and the less abundance of the bacteria was found at the water column in the depth of 0 cm (1.32 log cell/mL). The most abundance of nitrate reducing bacteria (DNRA) was found at the sedimen in the depth of 5-10 cm (4.32 log cell/ml) and the less abundance of the bacteria was found at the water column in the depth of 0 and 110 cm (1.56 log cell/mL). The most abundance of amonifying bacteria was found at the sediment in the depth of 5-10 cm (4.43 log cell/mL) and the less abundance of the bacteria was found at the water column in the depth of 0 cm (1.86 cell/mL). A total of 11 unique bands of nifH gene generated after DGGE analysis. Six of eleven unique bands of the gene selected, sequenced and identified by searching
Keyword: DGGE, nifH, amoA, nosZ

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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