Judul: Bioplastik komposit pati tapioka dan lilin lebah dengan tambahan natrium alginat sebagai pengemulsi
Abstrak: Bioplastic film made of tapioca starch and beeswax with addition of sodium alginate as emulsifier may be a potential alternative for biodegradable packing. The composition of tapioca starch-glycerol was fixed at 8:2. The sodium alginatebeeswax was added at various level, i.e. 19:6, 15:10, 12.5:12.5, 10:15, and 6:19. The films were analyzed for their tensile strength, density, water vapor permeability, morphology, and thermal properties. The film made of 6:19 sodium alginate and beeswax addition showed the lowest water vapor permeability, whereas the film with 19:6 sodium alginate and beeswax addition had the highest density and tensile strength, i.e. 1.5 g/mL and 4.1 MPa, respectively. The film had melting point and weight loss lower as compared to the 6:19 composition, therefore, these characteristic are not corresponding to the density due to in homogeneousity of the film. Morphology analysis showed the surface was rough and less homogeneous.
Keyword: tapioca starch., sodium alginate, glycerol, beeswax

Judul: Pencirian Edible Film Tepung Tapioka Terplastisasi Gliserol dengan Penambahan Natrium Alginat.
Abstrak: Edible film from glycerol plasticized tapioca starch with sodium alginate addition can be a potential alternative as biodegradable packing. In this experiment, glycerol was mixed into tapioca starch solution with tapioca starch-glycerol composition of 7:3 and 8:2. Sodium alginate solution was then added with concentration 0, 1, 2, and 3%. The edible film produced were tested for the density, mechanical properties, functional groups, morphology, and thermal properties. The edible film with 1% sodium alginate addition into 7:3 tapioca-glycerol composition, showed the highest tensile strength and elongation at break, 187.50 MPa and 95.62%, respectively. The edible film did not show new functional group formation, showing that the film was merely a physical mixture. The edible film’s surface was quite homogenous and formed needles-like pattern. Thermal analysis to the 8:2 and 7:3 tapioca starch-glycerol composition with 1% sodium alginate addition showed weight loss approximately 76.58 and 73.92%, respectively, with the glass transition temperature at 108.00 and 109.88 °C. The safe raw material used, and the results of analysis which fulfill led the standards provided evidence that edible film produced was safe for the body and was expected to be consumed after through the toxicity test.
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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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