Judul: Aktivitas Ekstrak Tambelo (Bactronophorus Sp.) Dan Selulolitik Mikroorganisme Simbionnya
Abstrak: Tambelo merupakan moluska yang hidup di dalam kayu mangrove telah digunakan untuk tujuan pengobatan oleh masyarakat pesisir. Tujuan penelitian ini adalah menentukan aktivitas biologis yaitu aktivitas antioksidan, inhibitor - glukosidase, dan antibakteri, serta mendapatkan mikroorganisme simbion yang diisolasi dari tambelo, dan menentukan aktivitas selulolitik mikroorganisme simbion. Tambelo diekstrak menggunakan tiga pelarut yaitu metanol, etil asetat, dan heksana. Aktivitas antioksidan ekstrak diuji berdasarkan kemampuan ekstrak dalam mereduksi radikal bebas (DPPH) dengan menggunakan konsentrasi ekstrak 50, 100, 500, 1000, dan 5000 μg/mL. Aktivitas inhibisi -glukosidase ekstrak dengan konsentrasi ekstrak 25, 50, 100, 500, dan 1000 μg/mL. Aktivitas antibakteri ekstrak diukur menggunakan metode difusi agar dengan konsentrasi ekstrak 0.5, 1, dan 2 mg/sumur terhadap bakteri Escherichia coli dan Staphylococcus aureus. Mikroorganisme yang berasosiasi dengan tambelo diisolasi dari saluran pencernaannya. Isolat yang diperoleh diuji aktivitas selulolitik dengan media yang mengandung selulosa. Rendemen daging dan jeroan tambelo yang dihasilkan sebesar 93.98%. Kadar air, abu, lemak, dan protein masing-masing sebesar 73.93%, 1.24%, 0.47%, dan 6.22%. Rendemen ekstrak metanol sebesar 3.12% ± 0.62, etil asetat 0.68% ± 0.07, dan heksana 0.41% ± 0.13. Aktivitas antioksidan tertinggi pada ekstrak etil asetat dengan nilai IC50 sebesar 1072.19 μg/mL. Aktivitas inhibisi - glukosidase ekstrak menurun pada konsentrasi yang semakin tinggi. Aktivitas antibakteri tertinggi diperoleh pada ekstrak etil asetat dengan zona hambat sebesar 10.5 mm terhadap bakteri E. coli pada konsentrasi 2 mg/sumur. Ekstrak terpilih adalah ekstrak etil asetat yang mengandung flavonoid, tanin, saponin dan steroid. Ekstrak tersebut tergolong toksik dengan nilai LC50 sebesar 425.908 μg/mL. Mikroorganisme yang terisolasi terdiri dari 8 kapang dan 9 bakteri. Indeks selulolitik tertinggi ditunjukkan oleh isolat kapang TJ21 dengan indeks 4.53, serta isolat bakteri S3B sebesar 2.25.
Keyword: antibakteri, antioksidan, Bactronophorus sp., inhibitor -glukosidase, mikroorganisme simbion.

Judul: Chemical Composition and Identification of Antioxidant Compounds from the Extracts of Tambelo (Bactronophorus thoracites)
Abstrak: Tambelo (Teredinidae) is consumed freshly by local people in Papua without removing the digestive tracts. This study aimed to investigate the chemical composition of fresh tambelo, to conduct antioxidant and phytochemistry tests, and to identify the compound of active antioxidant obtained from selected fractionated extract. The research consisted of two stages. The first stage involved the analyses of proximate, fatty acid, amino acid and mineral. The second stage was the extraction of active materials by means of maceration. The maceration result was evaporated and partitioned with a solvent of n-hexane and ethyl acetate. Next, the extract underwent phytochemical and antioxidant tests (20, 40. 60, and 80 ppm) with DPPH method applying BHT and vitamin super ester C as the standard with a concentration of 4, 6, 8 and 10 ppm. Finally, the identification of fresh antioxidant compound was carried out using LC-MS. The composition of fresh tambelo divided into moisture 82,72±0,01%, protein 7,21±0,31%, fat 0,28±0,04%, ash 2,07±0,27%, and carbohydrate (by difference) 7,72±0,62%. The composition of dried tambelo was moisture 6,63±0,01%, protein 42,77±2,01%, fat 14,27±0,22%, ash 5,88±1,04%, carbohydrate (by difference) 30,45±2,83%. The protein of tambelo contained nine essential amino acids and eight non essensial amino acids. It had seven saturated fatty acids and eight unsaturated fatty acids. It contained calcium of 3532,46 ppm and phosfor of 2363,06 ppm. The highest antioxidant activity was found in the crude extract of ethyl acetate with IC50 of 15 ppm. The highest antioxidant activity obtained by column fractionation was the 9th fraction with IC50 of 8.87 ppm. Phytochemical test, described the crude extract of tambelo contained a group of alkaloid, flavonoid, steroid and triterpenoid. MarinLit database (Blunt and Blunt 2008), 9th fraction was similar to farnesic acid glyceride, sesquiterpenoic acid glyceride and labdane diterpenoid.
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Judul: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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