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: Effect of EFB Elements on Pulp and Viscose as Raw Materials for Viscose Rayon Staples
Abstrak: Serat viskosa merupakan serat semi sintetis yang berasal dari proses regenerasi selulosa dengan dissolving pulp sebagai bahan baku. TKKS memiliki kandungan selulosa yang cukup tinggi sehingga dalam penelitian ini akan diolah sebagai dissolving pulp. Tujuan penelitian ini adalah mengetahui bagian TKKS terbaik yang dapat menghasilkan pulp dan viscose sesuai dengan standar. Penelitian ini juga bertujuan mengetahui waktu terbaik dalam proses aging dan konsentrasi CS2 yang dapat menghasilkan viscose. Proses pembuatan pulp menggunakan metode prahidrolisis kraft karena memiliki kelebihan dapat menghasilkan pulp dengan kemurnian tinggi. Dissolving pulp yang didapatkan selanjutnya diolah menjadi bahan baku pembuatan larutan viscose. Viscose merupakan larutan yang berasal dari pulp hasil aging kemudian diberikan CS2 membentuk selulosa xantat yang selanjutnya dilarutkan. Pengujian yang dilakukan berupa pengujian kimia bahan baku dan dissolving pulp, pengujian XRD, SEM-EDX, dan pengujian FTIR. Pada proses aging dilakukan variasi waktu dan pada proses xantasi konsentrasi CS2 divariasikan. Hasil penelitian menunjukkan TKKS stalk menghasilkan pulp terbaik yang sesuai dengan standar SNI. Pembuatan viscose dari kedua sampel menunjukkan bahwa pulp TKKS stalk menghasilkan viscose sesuai dengan standarisasi., In the cellulose regeneration process, the basic material for viscose fiber is dissolving pulp. OPEFB will be used as dissolving pulp because of its high cellulose content. This research aims to discover industry-standard OPEFB components for pulp and viscose production. Viscosity can also be produced by determining the ideal time of aging and the concentration of CS2 that produces it. The kraft prehydrolysis method is used in the pulp producing process because it produces high-purity pulp. Raw materials for viscose solution are made from the dissolving pulp. To make cellulose xanthate, aged pulp is mixed with CS2 to generate viscose, which is then dissolved in water. Raw materials and dissolving pulp are subjected to chemical testing, as well as XRD, SEM-EDX, and FTIR testing. In the viscose process, aging time and CS2 concentration are varied. In compliance with SNI criteria, OPEFB stalk pulp was found to provide the best pulp. Both samples showed OPEFB stalk pulp met viscose production standards.
Keyword: Cellulose, Dissolving Pulp, OPEFB, Viscose

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