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: Isolasi dan Karakterisasi Mikrokristal Selulosa Berbahan Dasar Sabut Kelapa (Cocos  nucifera)
Abstrak: Mikrokristal selulosa merupakan material dengan banyak keunggulan sehingga dapat diaplikasikan dalam berbagai bidang. Salah satu bahan potensial untuk memperoleh mikroselulosa adalah limbah sabut kelapa (Cocos nucifera) karena sumbernya melimpah dengan kandungan selulosa 43%. Mikroselulosa dari selulosa dapat diproduksi melalui hidrolisis asam. Percobaan ini bertujuan mengisolasi dan mencirikan mikrokristal selulosa dari sabut kelapa. Penelitian ini menghasilkan rendemen selulosa dan mikrokristal selulosa masing-masing 20% dan 62%. Karakterisasi mikrokristal selulosa menggunakan spektrometer inframerah transformasi Fourier menunjukkan gugus fungsi –OH, C–H, dan C–O– C. Karakterisasi menggunakan penganalisis ukuran partikel menunjukkan ukuran mikrokristal selulosa 0,15–0,97 µm dengan rerata ukuran 0,42 µm dan nilai indeks polidispersitas 0,0592. Difraktogram sinar-X menunjukkan puncak difraksi pada 2θ sebesar 15,7°; 22,6°; dan 34,6°. Indeks kristalinitas mikrokristal selulosa adalah 89,17%., Microcellulose is a material with various advantages that can be applied in several areas. One of the potential materials for obtaining microcellulose is coconut coir (Cocos nucifera) waste because the source is abundant, with a cellulose content of 43%. The microcellulose can be produced from cellulose through acid hydrolysis. This experiment aims to produce and characterize cellulose microcrystals from coconut husk. The yield of cellulose and cellulose microcrystals were 20% and 62%, respectively. Characterization of the cellulose using Fourier transform infrared showed –OH, C–H, and C–O–C functional groups. Characterization using particle size analyzer indicates the size of microcrystalline cellulose was 0.15–0.97 µm with an average size of 0.42 µm and polydispersity index of 0.0592. The XRD diffractogram showed diffraction peak at 2θ of 15.7°; 22.6°; and 34.6°. The crystallinity index of microcrystalline cellulose was 89.17%.
Keyword: cellulose, coconut fiber, microcrystalline cellulose

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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