Judul: Kadar Lignin dan Delignifikasi Empat Jenis Kayu Eukaliptus.
Abstrak: Lignin content and its reactivity are known as an important characteristics of wood in relation to the pulping process, because it will affect the process easiness and pulp quality. The aim of the research was to measure lignin content and delignification of four Eucalyptus woods, which is widely used as raw material in pulp industry. Lignin content was determined as Klason lignin, acid soluble lignin, and total lignin, whereas delignification was expressed as solubility lignin in alkaline cooking. The result show that Klason lignin of four Eucalyptus woods were 25.14-36.65% and acid soluble lignin were 2.07-2.44%. Alkaline cooking at 150 °C for 90 min obtained solubility of lignin 18.54-31.60%. The variety of acid soluble lignin of four Eucalyptus woods was not big different, therefore delignification was influenced by Klason lignin.
Keyword: acid soluble lignin, delignification, Eucalyptus, lignin solubility, Klason lignin

Judul: Keragaman Kadar Lignin pada Kayu Reaksi Apiapi dan Kelarutannya dalam Delignifikasi Alkali.
Abstrak: Reaction wood is a wood xylem formed as a respons of tree to external forces. Reaction wood has different chemical characteristics compared with normal wood. This research aimed to examine the variation of lignin contents at different positions in the reaction wood of Api-api (Avicennia sp.), and lignin solubility in alkali cooking. Klason lignin and acid-soluble lignin contents were determined using Klason method and UV-spectrophometry. Cooking experiment was carried out in 20% alkali solution at 150 C for 45 min. Klason lignin content varied between samples position was 15.03-20.8%, and acid-soluble lignin content was 3.06-4.29%. Wood samples derived from severest reaction wood part tend to have lowest Klason lignin content and highest acid-soluble lignin content. The lignin solubility of Api-api wood in the alkaline cooking at 150 C for 45 min was 46.13-54.47%. Although the statistical test was not significant, however, the lignin Avicennia sp. wood was relatively easy to be delignified in alkali cooking.
Keyword: Avicennia sp., reaction wood, klason lignin, acid-soluble lignin

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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