Judul: Sifat Fisikokimia, Termal, dan Spektroskopi Selulosa Mikrokristalin Serabut Ampas Sagu
Abstrak: Microcrystalline cellulose (MCC) is a partially depolymerized from α-cellulose. MCC is generally used as a medicinal preparation. MCC isolates from sago waste fiber and commercial MCC (MCCK) were characterized based on physicochemical, thermal, and spectroscopic properties. MCC1 was isolated through hydrolysis, pulping, and bleaching stages while MCC2 was isolated by pulping, bleaching, and hydrolysis steps, respectively MCC1 and MCC2 yields were 13% and 6.5% with α-cellulose levels of 78.61% and 73.08%. Physicochemical properties results of all three MCCs were in accordance with MCC’s standard. MCC1 and MCCK had degree of polymerizations fulfilling MCC’s standard (􀵑���350) while for MCC2, the value was over 700. Infrared spectra of MCC1 and MCCK were also in accordance with MCC’s standard, whereas the MCC2 spectrum still showed the presence of lignin. Based on thermal analysis, MCC2 had the highest degradation temperature and degree of crystallinity, which were 396.26 °C and 66.4%, respectively, corresponding to the high lignin content. MCC1 had the largest surface area, enable to bind more active ingredient medicine.
Keyword: cellulose, microcrystalline, sago

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