Judul: Penggunaan Batang Jagung Dan Limbah Nata De Coco Sebagai Substitusi Serat Kayu Dalam Pembuatan Kertas
Abstrak: Tingginya permintaan kertas berdampak pada meningkatnya kebutuhan bahan baku pulp yang saat ini mengalami kelangkaan, sehingga perlu dicari bahan baku lain. Batang jagung dan limbah padat nata de coco dapat menjadi salah satu alternatifnya. Penelitian ini bertujuan mempelajari pengaruh proporsi pulp batang jagung dan pulp limbah padat nata de coco dan pengaruh penambahan aditif terhadap sifat fisik dan mekanik kertas. Parameter kertas yang diamati meliputi gramatur, kadar air, indeks tarik, daya regang, indeks sobek, ketahanan lipat, daya serap air, derajat putih dan opasitas cetak. Rendemen pulp batang jagung dan pulp limbah padat nata de coco yang dihasilkan berturut-turut sebesar 49.77% dan 60.67% (basis kering). Penambahan pulp limbah padat nata de coco berpengaruh terhadap semua parameter kertas dengan target gramatur 60 g/m2 maupun 120 g/m2. Perlakuan penambahan aditif hanya berpengaruh pada kertas dengan target gramatur 120 g/m2 pada parameter gramatur yang dihasilkan, daya regang, ketahanan lipat, derajat putih dan opasitas cetak, sedangkan pada target gramatur 60 g/m2, penambahan aditif hanya berpengaruh terhadap parameter kadar air, derajat putih dan opasitas cetak kertas. Sifat fisik dan mekanik kertas yang dihasilkan pada target gramatur 60 g/m2 yaitu gramatur 53.03-77.74 g/m2, kadar air 4.26-7.41%, indeks tarik 0.00815-0.02731 kNm/g, daya regang 2.09-3.59%, indeks sobek 0.43480-1.56643 mNm2/g, ketahanan lipat 3-43 lipatan ganda, daya serap air 221.9026-1213.8345 g/m2, derajat putih 30.30-47.82% dan opasitas cetak 52.71-96.28%. Sementara itu pada target gramatur 120 g/m2 sifat fisik dan mekanik kertas yang dihasilkan yaitu gramatur 107.2-144.09 g/m2, kadar air 4.66-7.91%, indeks tarik 0.01133-0.04516 kNm/g, daya regang 2.40-8.00%, indeks sobek 0.40900-0.90583 mNm2/g, ketahanan lipat 6-113 lipatan ganda, daya serap air 240.8668-2241.2341 g/m2, derajat putih 31.54-41.70%, dan opasitas cetak 49.55-99.80%. Sifat fisik dan mekanik kertas pada target gramatur 60 g/m2 berpeluang untuk memenuhi persyaratan mutu kertas cetak jenis A dan B.
Keyword: batang jagung, kertas, limbah, nata de coco, pulp

Judul: Penggunaan Selulosa TandanKosong Kelapa Sawit dan Selulosa Mikrobial dari Nata de Cassavasebagai Pensubstitusi Selulosa Kayu dalam Pembuatan Kertas
Abstrak: Nowadays, forest-extracted wood cellulose still predominantly serves as raw material for pulp and paper manufacture in Indonesia. Consequently, the deforestation rate has alarmingly increased 2% per year. Attempts are necessary to seek alternative cellulose sources that sound potentially available, among which are empty oil-palm fruit bunches (EOPFB) and microbial-cellulose, as synthesizedwith the aid of microorganisms from substrate containing glucose, fructose, sucrose, or other simple carbohydrates, such as juicy waste from tapioca processing (e.g. nata de cassava). In this research, pulp of nata de cassava‟s microbial cellulose was mixed with EOPFB pulp at various proportions (w/w), i.e. 100%+0%, 75%+25%, 50%+50%, 25%+75%, 0%+100%to be processed into pulp and paper. Grammage target made was 60 gr/m2 and 120 gr/m2. Prior to paper-sheet forming, additives were added to such mixture (i.e. 2% alum, 2.5% tapioca starch, and 5% kaolin). Sheet forming also made without additives (as control). The forming of each combination between mixture proportion, grammage target and additive/control-use was replicated 2 times, and the data examined comprised pulp/paper physical and strength properties. The data were analyzed using a completely randomized design with factorial pattern. The yields of microbial-cellulose pulp and of EOPFB pulp were consecutively (wet basis) 60,09% and 61,619%. Physical and strength properties of paper with grammage 60 gr/m2and 120gr/m2consecutively, i.e. water content (4,04-8,95% & 3,83- 9,01%), grammage (59,8-78,92gr/m2& 107,64-145,32 gr/m2), tensile index 0,0056-0,0424 & 0,01002-0.06499 kNm/g), tear index (4,04-8,22 & 4,55-7,72 mN m2/gr),folding endurance (3,5-108,5 & 4-397,5), Cobb60 (56,86-211,32 & 75,03- 398,12 g/m2 for the smooth surface; and 51,07-218,91 & 57,65-404,46 g/m2for the rough/lower surface), brightness (15,64-38,03% & 13,1-26,26%) and printing opacity (62,81-97,55% & 42,99-99,38%). Analysis on biomass conversion revealed that the manufacture of paper from the mixture (w/w) of nata de cassava‟s microbial cellulose (50%) and empty oil palm fruit bunch pulp (50%) through the expansion of each cultivating areas, both totaling 200 ha can substitute for 4.247.156forest-tree stands per year. With this tree-saving figure, it can afford the CO2absorption (uptake) from the air equal to approximately 594.601,85 tons of CO2 per year.
Keyword: carbon uptake, biomass conversion analysis, pulp/paper, empty oil-palm fruit bunch, nata de cassava, microbial cellulose

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