Judul: Pengembangan Membran Elektrode Optik Selulosa Triasetat untuk Deteksi Besi.
Abstrak: Besi merupakan logam berat yang dapat membahayakan kesehatan manusia. Penelitian ini bertujuan membuat membran elektrode optik (optode) dari selulosa triasetat yang mengandung reagen selektif terhadap ion Fe(III). Optode dipreparasi dengan melarutkan selulosa triasetat (CTA) dalam kloroform dan ditambahkan campuran asetofenon-asam oleat, alikuot 336, dan ion tiosianat. Kinerja optode dievaluasi berdasarkan rentang kerja, limit deteksi dan limit kuantitasi, presisi, akurasi, selektivitas, dan stabilitas. Kinerja terbaik optode terjadi pada rentang kerja 0.1-5 mg/L dengan koefisien determinasi 0.9951, limit deteksi 0.09 mg/L, dan limit kuantitasi 0.29 mg/L. Nilai akurasi rata-rata 99.80%, optode selektif untuk ion Fe(III) dari ion pengganggu Pb(II) dan Cr(VI), dan kompleks warna yang terbentuk stabil selama 11 hari. Dengan demikian, membran optode CTA dapat digunakan untuk deteksi besi dan hasilnya dapat diterima.
Keyword: besi, optode, selulosa triasetat, tiosianat

Judul: Cellulose Triacetate Membrane Based Optical Sensor (Optode) As Iron Detector in Water
Abstrak: Besi merupakan logam berat yang sering dijumpai sebagai pencemar peraian. Konsentrasi besi yang tinggi bersifat toksik bagi kesehatan manusia, sehingga perlu dipantau keberadaannya dalam air. Pendeteksian besi dalam air dilakukan dengan memanfaatkan sensor optik (optode). Penelitian bertujuan memfabrikasi optode berbasis membran selulosa triasetat dengan reagen selektif terhadap Fe (III). Optode difabrikasi dengan mencampurkan polimer selulosa triasetat, pemlastis (asam oleat dan asetofenon), alikuot-336, dan tiosianat sebagai reagen selektifnya. Kinerja membran diuji berdasarkan rentang kerja, linearitas, batas deteksi dan kuantitasi, presisi, serta akurasi. Kinerja membran menunjukkan respon yang linear pada rentang konsentrasi 0,1–4 mg/L dengan koefisien determinasi (R2) 0,9937, batas deteksi 0,0250 mg/L, batas kuantitasi 0,0757 mg/L, presisi keterulangan dengan simpangan baku relatif 3,31%, dan rerata akurasi 100,49%. Selektivitas optode baik terhadap ion pengganggu Cr(VI) dan Pb(II). Warna kompleks optode stabil sampai hari ke-10. Aplikasi pendeteksian besi dalam sampel air menunjukkan rerata konsentrasi sebesar 0,2541 mg/L dengan presisi dan akurasi yang baik.
Keyword: cellulose triacetate, iron, optode, thiocyanate, water

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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