Judul: Karakteristik Kimia Lignin Sepuluh Jenis Kayu.
Abstrak: Lignin is a chemical component of wood which was concerned in relation to pulping process. The content and reactivity of lignin affect the easiness of delignification in the pulping process. This research aimed to analyze the chemical characteristics of lignin in the ten wood species; which were expressed as total lignin, Klason lignin, acid-soluble lignin, and syringil/guiacyl ratio. Total lignin was defined as a sum of Klason and acid-soluble lignin. Lignin content varied widely between wood species. Klason lignin was 20.51-34.3% and acid-soluble lignin was 0.31-2.8%. Wood species having lower lignin content tend to have higher acid-soluble lignin and syringil/guaiacyl ratios. Consequently, there was clear and positive correlation between acid-soluble lignin and syringil/guaiacyl ratio (R2=0.92)
Keyword: acid soluble lignin, delignification, Klason lignin, monomers lignin, reactivity

Judul: Keragaman Kadar Lignin pada Jenis Kayu Daun Lebar.
Abstrak: Lignin merupakan komponen utama penyusun dinding sel kayu, kedua terbanyak setelah selulosa. Lignin terdapat diantara sel-sel yang berfungsi sebagai perekat untuk mengikat sel-sel bersama-sama, dan di dalam dinding sel yang seringkali berasosiasi dengan selulosa untuk memberikan ketegaran pada sel. Metode Klason merupakan prosedur standar yang umum digunakan untuk menentukan kadar lignin, yang menghasilkan informasi kadar lignin Klason dan lignin terlarut asam. Sifat reaktifitas lignin dapat diduga dari proporsi monomer penyusun lignin yang dinyatakan dalam nisbah siringil-guaiasil (nisbah S/G). Penelitian ini bertujuan untuk mengukur kadar lignin; lignin Klason (acid-insoluble lignin) dan lignin terlarut asam (acid-soluble lignin), pada jenis kayu daun lebar, dan korelasinya dengan nisbah siringil-guaiasil penyusun polimer lignin. Jenis kayu yang diteliti terdiri dari 14 jenis kayu daun lebar, dan sampel uji diambil dari dua posisi yang berbeda. Kadar lignin diukur dengan metode Klason. Kadar lignin terlarut asam diukur dari filtrat yang dihasilkan dalam penentuan lignin Klason menggunakan alat UV Visible Spectrophotometer SHIMADZU UV Pharma Spec. 1700 pada panjang gelombang 205 nm dengan koefisien absorbsi 110 Lg-1cm-1. Penentuan nisbah siringil-guaiasil diukur dengan menggunakan alat Pyrolisis Gas Chromatography Mass Spectrometry (Pyr-GC-MS). Hasil penelitian menunjukkan kadar lignin; kadar lignin Klason, lignin terlarut asam, dan lignin total dalam kayu berbeda antar jenis kayu dan posisi sampel. Kadar lignin bagian kayu dekat empulur cenderung lebih rendah dibanding bagian kayu gubal dekat kulit. Selain itu, terdapat kecenderungan dengan meningkatnya kadar lignin terlarut asam pada kayu diikuti menurunnya kadar lignin Klason. Korelasi positif terjadi antara kadar lignin terlarut asam dengan nisbah siringil-guaiasil, yaitu dengan meningkatnya kadar lignin terlarut asam diikuti oleh meningkatnya nisbah siringil-guaiasil. Oleh sebab itu, lignin terlarut asam dapat digunakan sebagai parameter penduga dalam kemudahan proses delignifikasi kayu pada proses pulping.
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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