Judul: Selulosa Benzoat Berbasis Selulosa Mikrobial dan Aplikasinya sebagai Fase Diam Kromatografi Cair Kinerja Tinggi (KCKT)
Abstrak: Nata de coco is one of the alternative sources for the provision of microbial cellulose. This research aims to modify microcrystalline cellulose from microbial cellulose by esterification technique and subsequent esterification products are use as stationary phase in high performance liquid chromatography (HPLC). Microcrystalline cellulose was prepared by hydrolysis of dry nata de coco with a solution of HCl 4% for 4 hours. Esterification techniques performed by reacting benzoyl chloride and microcrystalline cellulose during 24 hours. Esterification products (cellulose benzoate) have a degree of benzoylation value is 2.84. Furthermore, cellulose benzoate used as the stationary phase in HPLC using a fluorescence detector for rhodamine b and erythrosine separation. The result showed that the average value of resolution was 1.150. Stationary phase obtained in this study was still not efficient for erythrosine and rhodamine b separation. It was seen from the high equivalent of theoretical plate value obtained is bigger than the theoretical value of the number plate.
Keyword: microcrystalline cellulose, microbial cellulose, HPLC, cellulose benzoate

Judul: Mikroselulosa Nata de Coco sebagai Bahan Baku Hydroxypropyl Methylcellulose (HPMC).
Abstrak: Selulosa merupakan polimer alam yang berpotensi sebagai agen enkapsulasi karena bersifat lembam dan tidak toksik. Nata de coco merupakan salah satu sumber selulosa dari fermentasi bakteri Acetobacter xylinum. Selulosa diperkecil ukurannya dengan menggunakan metode hidrolisis asam dan ultrasonikasi untuk menghasilkan mikroselulosa yang mudah terdispersi dalam air. Hidroxypropyl methylcellulose (HPMC) merupakan turunan selulosa yang digunakan sebagai kapsul pada industri farmasi. Penelitian bertujuan menyintesis dan mencirikan HPMC dari selulosa mikrobial. Ukuran mikroselulosa yang didapatkan dengan metode asam dan ultrasonikasi menggunakan scanning electron microscope (SEM) sebesar 0.161 μm. Pencirian HPMC menggunakan fourier transform infrared spectroscopy (FTIR) menunjukkan puncak serapan yang sama antara HPMC standar, HPMC selulosa komersial, HPMC selulosa nata de coco dan HPMC mikroselulosa nata de coco. Hasil pencirian dengan differential scanning calorimetry (DSC) menunjukkan HPMC mikroselulosa nata de coco memiliki kurva peleburan eksoterm dengan titik lebur pada 351.28 οC dan entalpi 92.42 g/J, yang berarti memiliki titik lebur yang tinggi sehingga tahan terhadap panas.
Keyword: hidroxypropyl methylcellulose, mikroselulosa, nata de coco, selulosa

Judul: Pengaruh vaksinasi terhadap dinamika populasi pada model SIR (Susceptible-Infected-Recovered)
Abstrak: SIR model can be used to model the spread of diseases in a closed population based on certain assumptions. In this research, the SIR model is formulated by including the factor of vaccination. As the result, the model has been shown to have two equilibrium points, i.e. disease free and endemic equilibrium. A simulation study is carried out to illustrate the model. The results show that some equilibrium points are asymptotically stable. Moreover, a minimum level of vaccination has been defined. For the vaccination level less than the minimum level, increase in the vaccination level results in decrease of the proportion of infected individuals in the corresponding equilibrium point. On the other hand, for the vaccination level greater than the minimum level, increase in the vaccination level results in decrease the proportion of susceptible individuals in the corresponding equilibrium point. Furthermore, when vaccination level is greater than the minimum level, it is found that the time needed for the disease to extinct is shorter.
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