Judul: Synthesis and In Vitro Test of Porous Hydroxyapatite-Chitosan with Sol Gel Method.
Abstrak: Hidroksiapatit (HAp) memiliki sifat biokompatibilitas yang baik dengan tulang karena memiliki kesamaan komposisi kimia dengan tulang. Salah satu metode sintesis HAp adalah metode sol gel. Metode sol gel dapat digunakan untuk menghasilkan kristal HAp yang baik. HAp berpori dibuat dari kalsium yang diperoleh dari cangkang telur dengan penambahan asam fosfat dan kitosan. Penelitian dilakukan dengan ragam volume larutan kitosan yang ditambahkan, yaitu 30, 40, 50, dan 60 mL. Analisis sampel dilakukan dengan menggunakan difraksi sinar-X (XRD), mikroskop elektron payaran (SEM), dan spektrofotometer serapan atom (AAS). Pencirian dengan XRD terhadap HAp-kitosan yang telah dikalsinasi menunjukkan tidak ada puncak kitosan, hanya terdapat puncak milik HAp. Pencirian dengan SEM menunjukkan bahwa penghilangan kitosan melalui kalsinasi menghasilkan HAp dengan pori berukuran mikro. Uji in vitro menunjukkan bahwa terjadi penurunan konsentrasi kalsium setelah 6 hari perendaman sampel dalam larutan simulated body fluid (SBF). Penurunan ini disebabkan oleh pengendapan ion kalsium pada permukaan HAp berpori untuk membentuk kristal apatit.
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Judul: Sintesis Hidroksiapatit dari Cangkang Keong Sawah (Bellamya javanica) dengan Metode Basah dan Modifikasi Pori dengan Kitosan
Abstrak: Hydroxyapatite (HAp) was synthesized using calcium originated from rice fields snail shell, that was reacted with phosphate obtained from diammonium hydrogen phosphate. The resulted ore was modified using chitosan. The HAp was prepared using wet method. Chitosan was used as porogen due to its bioactivity and biocompatibility properties. Sonication time in the synthesis was varied in 2, 4, and 6 hours. The longer the synthesis time, the higher the purity of the HAp. Pore modification was applied to HAp with the highest purity. Pore modifications were conducted by adding 4% and 6% chitosan. Scanning electron microscope identification showed no significant differencein pore sizes using 4% and 6% chitosan. Fourier transform infrared spectrum of HAp with 6% chitosan showed almost similar functional groups with that of the unporogened HAp. In vitro test of the porogened HAp revealed its bioactivity.
Keyword: wet method, rice field snail shell, in vitro test, hydroxyapatite, chitosan

Judul: Construction of Strongly Optimal Binary Linear Code with Minimum Distance 9 and 11
Abstrak: A binary linear code of length n over q F is a subspace of n q F . A code has three parameters that attached to it, namely length, dimension, and minimum distance. A code with length n, dimension k and minimum distance d is often called [n, k, d ]-code. Usually, when two parameters are given, then we want to find a code that has the best value for the last parameter. Based on Gilbert- Varshamov bound, if a [n, k, d ]-code exists and can not be expanded, we call it a strongly optimal code. In this paper, we construct strongly optimal code with minimum distance 9 and 11. In constructing the code, we created a theorem and algorithm based on Gilbert-Varshamov bound before we implement the algorithm to MAPLE programming language. Because of computational limitations, the program can only construct up to k = 10 for d = 9 and k = 12 for d = 11.
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