Judul: Isolasi Selulosa Ampas Sagu dengan Delignifikasi Menggunakan Hidrogen Peroksida
Abstrak: Isolation of cellulose from sago waste has been successfully performed in this research. Through several steps, namely removal of extractive compounds, removal of starch, and removal of hemicellulose. The starch removal from free-extractive sample by extraction with water at 80 °C required a lot of water and time. By using HCl 3% at 80 °C, less time was needed. The yield of free-starch samples obtained from hot water extraction was 41.5%, higher than the product of HCl 3% extraction, which was 26.3%. Cellulose was also hydrolized with HCl 3%, in accordance with the appearance of C=O absorption in the fourier transform infrared (FTIR) spectrum. Lignin content after delignification with 0.75, 1, and 1.5% H2O2 were 22.2, 18.7, and 14.6% while the yield were 43.6, 41.4, and 39.4%, respectively. FTIR spectrum of cellulose isolated with starch removal method using water was more similar to the commercial cellulose than cellulose which starch removal method used HCl 3%.
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Judul: Kemurnian Selulosa Serabut Ampas Sagu pada Berbagai Perlakuan Isolasi
Abstrak: Sago waste fibers is wasted by sago starch industry and contain 42% cellulose. The cellulose was isolated to obtain the best isolate through various processes and treatments, including preparation with and without grinding, pulping in NaOH with and without heating in HCl, as well as delignification. Grinding and heating in HCl treatment were found to increase the alpha cellulose content. Heating treatment in HCl with and without grinding produced 79.96% and 74.70%, of alpha cellulose, respectively, higher than without heating in HCl that was 72.98% and 63.20%, respectively. Fourier transform infrared spectra of the isolates were not significantly different from a commercial cellulose showing characteristic by β-glycoside absorption at 894 cm-1. Heating in HCl with and without grinding also increased the crystallinity index by removing part of the amorphous region. The differential thermogram showed that the isolates started to lose the mass at around 98–102 °C and lost the maximum weight lost at around 352–377 oC.
Keyword: cellulose, isolation, sago

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model