Judul: Penyamakan Khrom Kulit Ikan Kakap Putih (Lates calcalifer) Dikombinasi dengan Ekstrak Biji Pinang terhadap Karakteristik Fisik Kulit
Abstrak: Leather tanning is a process of converting of skin or hide protein into leather with adequate strength properties, resistance to various biological and physical agents, and capable of being used for a wide range of purposes. The use of vegetable tanning process leather tanning hasn't been much done. Vegetable materials used are derived from areca nut. This plant contains tannins which are the main substances in the process of leather tanning. The purpose of this research is to know the influence of the use of areca seed extract against physical quality Giant sea perch. Areca seed extracted using ethanol to get tanner tannins as an ingredient. The addition of areca seed extract affects physical properties of the skin. The physical properties are influenced, among others, thickness, elongation, tear strength, and sewing strength. Concentration of 10% gives the best effect for the four physical properties are analyzed.
Keyword: vegetable tanning, leather tanning, areca nut

Judul: Penyamakan Kulit Ikan Tuna (Thunnus sp.) Dengan Menggunakan Penyamakan Kombinasi Aldehida dan Nabati
Abstrak: The research of tuna’s leather tanning had been developed at laboratory scale with some type of tannages and not yet achieved optimum results. Therefore, further research is directed toward the combination of several types of tannage in order to obtain the optimum result. Combination tanning is a tanning process using two or more tannages in order to complete each other’s advantage and disadvantage. This research aimed to determine the effects of vegetable tannages (e.g. mimosa, gambier, and quebracho) and its concentrations (10%, 15%, and 20%) on the quality of leather produced using combination tanning. It also aimed to determine the best combination of treatments. Based on the result of this research, the type of vegetable tannages had a significant effect on increase of thickness, shrinkage temperature, tear strength, and elongation at break of the leathers. Concentration had no significant effect on physical properties of tanned leather. Interaction of two factors had no significant effect on physical properties of tanned leather. Combination tanning using 3% glutaraldehyde and 20% mimosa presented the best result. The physical properties of tanned leather resulted were 20.8% increase of thickness, shrinkage temperature of 88°C, tensile strength of 17.8 N/mm2, elongation of break of 41.4%, and tear strength of 54.59 N/mm². Organoleptic properties of the tanned leather were flexibility (fell or handle) in the scale of 6–7 and color of 7–8.
Keyword: tanned leather properties, vegetable tannages, glutaraldehyde, combination tanning, leather

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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