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 Kombinasi Penyamak Krom dan Nabati
Abstrak: Tanning is a way to change unstable rawhide (easily damaged by physical, chemical and biological effects) into a stable leather against those effects. Combination tanning method was a tanning process using two or more tannages in order to complete each other advantages and disadvantages to obtain leather with desired characteristics. Tanning using chrome would increase the flexibility, resistency of high temperature and tensile strength of leather. While vegetable tannage used in tanning gave an effect on physical quality on leather, including tensile strength, tear strength and other characteristics. The main purpose of this study were determined the effect of type and concentration of vegetable tannage on physical and organoleptic characteristics of skin tannage in the tanning process, to decide the best type and concentration of tannage for tanning, and to decide the characteristic of the leather. Tannages used were chrome with a concentration of 8% and vegetable tannages (mimosa, gambier, quebracho) with concentrations of 10%, 15% and 20%. The observed reponses in this study were thickness, shrinkage temperature, tensile strength, tear strength, elongation at break, and organoleptic characteristics. Based on the study, gambier with 20% concentration combined with 8% chrome produced the best quality of leather, highest increase thickness, tear strength of 84.76 N/mm, tensile strength of 22.68 N/mm2 and elongation at break of 57.38%. Organoleptic test showed that the colours produced by gambier looked more attractive, natural, finer texture, so that can be applied for material in sofa or jacket manufacture.
Keyword: vegetable, chrome, combination tanning, tuna’s skin

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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