Judul: Literature Review on Lyocell Fiber Production from Nata de Coco Microbial Cellulose Using Environmentally Friendly Solvents
Abstrak: Proses viskosa merupakan proses yang dominan dalam memproduksi serat selulosa. Namun, proses ini banyak menggunakan bahan-bahan kimia yang dapat mencemari lingkungan. Salah satu proses alternatif untuk memproduksi selulosa adalah proses liosel (lyocell), yaitu serat selulosa dihasilkan melalui pelarutan langsung selulosa menggunakan pelarut ramah lingkungan. Kajian pustaka terkait dengan pembuatan serat liosel dari selulosa mikrobial nata de coco hasil fermentasi oleh bakteri Acetobacter xylinum sebagai sumber selulosa menggunakan pelarut ramah lingkungan. Selulosa mikrobial nata de coco dicirikan menggunakan spektrofotometer inframerah transform Fourier, mikroskop elektron payaran, dan difraksi sinar-X. Hasilnya menunjukkan bahwa selulosa mikrobial nata de coco memiliki ciri yang sama dengan selulosa murni dan berpotensi digunakan sebagai bahan baku serat liosel. Pelarut ramah lingkungan yang dapat digunakan untuk menghasilkan serat liosel adalah N- metilmorfolina-N-oksida., The viscose process is the dominant process in producing cellulose fibers. However, this process uses a lot of chemicals that can pollute the environment. One alternative process for producing cellulose is the lyocell process, in which cellulose fibers are produced by direct dissolving of cellulose using environmentally friendly solvents. Literature review related to the manufacture of lyocell fiber from the microbial cellulose nata de coco fermented by the bacterium Acetobacter xylinum as a source of cellulose using environmentally friendly solvents. Nata de coco microbial cellulose was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The results showed that nata de coco microbial cellulose has the same characteristics as pure cellulose and has the potential to be used as raw material for lyocell fiber. An environmentally friendly solvent that can be used to produce lyocell fiber is N-methylmorpholine-N-oxide.
Keyword: environmentally friendly solvent, lyocell fiber, microbial cellulose, nata de coco

Judul: Kajian Penggunaan Selulosa Mikrobial Sebagai Bahan Baku Pembuatan kertas
Abstrak: Paper refers to thin mass of felted sheet separated from water suspension of prevalently cellulose-based pulp fiber on a fine screen, followed by sheet forming, compression, drying and finishing action. Paper and paper products are widely used as printing and writing media, packaging material and other varieties of functions. World consumption of paper steadily increases at 3,05 % per year, while in Indonesia the yearly consumption in the last five years (i.e 2002 – 2006) recorded an average increase at 2,8%. Consequently, this calls for intensive use of cellulose-based materials. In general, the raw material for pulp and paper comes from woods, due to their more secured continuity-supply and favorable properties or characteristic. Conversely, this situation can enchanc the rate of forest destruction (deforestation) from which the woods are obtained. Nowadays, deforestation rate tends to increase uncontrollably along with increasing-demand for woods and their derived products, including pulp and paper. Such alarming deforestation can exert negative impacts on the environment, among which is global warming. The global warming further will affect climate change radically and natural disasters (e.g. floods, erosion, storms, and hurricanes). The use of wood for pulp, paper, and other celullose based products reveals several weaknesses, among others, high energy consumption and catastrophic environmental pollution caused by the use of chemical substances for the delignification (lignin dissolution) process during wood pulping, which harmful to human beings and other living creatures. Another set back is the low productivity of wood for the supply of cellulose (i.e. polymer containing glucose units) compared to the cutting rotation of the tree growth to provide wood, which takes a long time and bring about concerns related to environmental issues. This unfavorable situation demand the seeking of other cellulose alternatives, which can expectedly substitute for or lessen the reliance on wood materials for pulp and paper manufacturing. One of the favorable alternatives is the microbial cellulose synthesized biologically from particular biomass materials potential as glucose source, using particular types of microorganisms (i.e. bacteria) among other Acetobacter species. The microbial cellulose afford remarkable advantage over the conventional wood derived sellulose, such as high level purity (free from lignin and hemicellulose), the easy isolation of the process, and exerting high cellulose crystallinity as well as its productivity. This entails an immense potency of raw material for microbial cellulose in an attempt to overcome the difficulty in procuring the conventional wood based cellulose materials for pulp and paper.
Keyword: 

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