Judul: Analisis kestabilan titik tetap pada model penularan penyakit demam berdarah dengue
Abstrak: Penularan penyakit demam berdarah dengue telah meluas hampir ke seluruh dunia, terutama di perkotaan daerah tropis. Penularan penyakit tersebut terjadi melalui 2 cara yaitu secara vertikal (keturunan) dan mekanik (gigitan nyamuk). Pada tulisan ini yang akan dibahas hanya penularan seeara mekanik. Penularan penyakit ini dapat dijelaskan dalam suatu sistem. Dalam sistem tersebut terdapat lima kelas yakni manusia reotan (RM) • manusia terinfeksi (l N). manusia kebal (K M), nyamuk rentan (RN) dan nyamuk terinfeksi (/ N ). Esteva dan Vargas (1998) menyusun model penularan penyakit demam berdarah dengue yang melibatkan semua kelas di atas. Sistem persamaan diferensial yang diperoleh adaJah
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Judul: Analisis Kestabilan dan Kepekaan Parameter Model Penyebaran Penyakit Demam Berdarah Dengue Tipe SEIR
Abstrak: Demam Berdarah Dengue (DBD) merupakan suatu penyakit menular yang disebabkan oleh virus dengue. Penyakit ini ditularkan nyamuk Aedes Aegypti. Dalam tugas akhir ini populasi manusia dikelompokkan dalam empat kompartemen, yakni: rentan (S), terpapar (E), terinfeksi (I) dan sembuh (R). Sementara populasi nyamuk dikelompokkan dalam tiga kompartemen, yakni: rentan (S), terpapar (E) dan terinfeksi (I). Interaksi antar kompartemen dituliskan dalam suatu sistem persamaan diferensial. Model ini menghasilkan dua titik tetap, yaitu titik tetap tanpa penyakit dan titik tetap endemik. Analisis kestabilan bagi titik tetap tersebut ditentukan menggunakan kriteria Routh-Hurwitz. Berdasarkan hasil analisis diperoleh bahwa, jika , maka titik tetap endemik tidak stabil sementara titik tetap bebas penyakit stabil. Pada bagian akhir dilakukan analisis kepekaan parameter dengan menggunakan software Wolfram Mathematica, dan didapat bahwa parameter laju kematian nyamuk merupakan parameter yang paling peka.
Keyword: DHF, Parameter Sensitivity, Routh-Hurwitz, SEIR

Judul: Xylooligosaccharide production of corncobs as prebiotic candidate by high temperature heating and enzymatic hydrolysis.
Abstrak: Corncob waste is a rich xylan source that can be utilized as raw material for xylooligosaccharides (XOS) production. XOS is a potential prebiotic and has high economic value. Two corn varieties i.e. Bisi and Pioneer were first analyzed for its hemicellulose, cellulose and lignin contents and xylan yield to choose the corn variety to be studied. Process technology for XOS production was studied using available equipment such as oven. Xylooligosaccharide (XOS) from corncob was produced in two stages i.e. xylan extraction by heating at high temperatures in oven or autoclave as comparison, followed by enzymatic hydrolysis. Analysis of two corncob varieties showed that Pioneer variety contained higher hemicellulose content (34.98%) and xylan yield (18.32%) than Bisi variety (12.28% and 10.22%, respectively), therefore Pioneer variety was chosen as raw material for XOS production. Corncob particles were soaked in dilute acid (1 g/l H2SO4) for 12 h at 60 oC, filtered and washed with tap water and then heated in oven or autoclave. Before oven heating, The corncobs were added with water at various ratios (1:1 – 1:5) and then heated in oven at various temperature (130 oC, 140 oC, 150 oC for 0.5 h) and autoclave at 121oC for 0.5, 1, 1.5 and 2 h with one and two heating cycles. During heating, the total sugar and reducing sugar were increase, while the degree of polymerization was decrease. The results showed that heating in oven to extract the xylan was affected by the ratios of corncobs and aquadest and heating temperatures. Oven heating (130-150 oC) with optimum ratio of corncobs and aquadest (1:3) successfully increased the xylan content from 3.98% up to 18.21 – 19.46% while repeated heating cycle (two cycles) did not affect the xylan content. Heating the corncobs with aquadest (at the ratio of 1:3) in oven at 130 oC for 0.5 h produced 18.98% xylan and enzymatic conversion of the xylan by xylanase significantly increased the XOS content from 19.60% up to 44.06%. Heating the corncobs in autoclave (121 oC, 0.5 h) followed by enzymatic conversion produced higher XOS content (65.67%). The corncob XOS could stimulate the growth of Lactobacillus plantarum kik and Bifidobacterium longum ATCC 15707 by 1.2 until 1.7 unit log, indicating the prebiotic properties. Cookies prebiotic produced by addition of 5% (based on wheat flour) had higher hardness texture (1256 gf) than control without XOS (1067 gf).
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