Judul: Studi pemanfaatan gambir (Uncaria gambir Roxb.) dalam pembuatan cat alami
Abstrak: The main component of paints are binder, pigment, solvent and additive. Binder can be made from natural materials and also synthetic or polymeric materials. This study was conducted to observe the effect of weight ratio of casein to calcium oxide and concentration of gambier solution in the preparation of natural paint. The binder used in the manufacture of natural paints was casein mixed with calcium oxide (alkali). When casein was reacted with an alkali then casein will become more soluble in water and has adhesive properties. Use of gambier as dyes in the manufacture of natural paints was expected to increase the added value of gambier. Catechin and tannin as the substances contained in gambier will easily dissolve in water and can give brownish red colour.
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Judul: Studi pemanfaatan gambir (Uncaria gambir Roxb) dalam proses pewarnaan kain mori
Abstrak: Gambier is an extract of leaves and branches of gambier plant (Uncaria gambier Roxb). Gambier is one of Indonesia export commodities mostly produced in Sumatera island. Indonesia plays role as the world’s largest gambier exporter. In Indonesia, gambier utilized traditionally as leather tanning material, ingredient of traditional medicine, rust omission, etc. Chemical components of gambier mostly utilized are catechin and tannin. Technology of gambier processing that existed in Indonesia is still low in capacity, so the processing of gambier is mostly done traditionally. This kind of processing resulted on low quality and lack of economical value products of gambier. Therefore, development of processing method and wide utilization of Gambier in industry are needed to increase gambier added value. Tannin and catechin on gambier also can be utilized as colouring agent in textile industry to gain reddish brown colour on batik clothes that will be endure on intense sunlight exposure. Textile industries in Indonesia, especially batik industries, are now developing rapidly where the trend of batik clothes on every occasion is becoming common interest. On technological side, in general the batik industrialists have not done any development on their production sytem and method, so they could be more productive and produce uniformity of product quality. Utilization of natural colouring agent is also not becoming a consideration of most batik industrialists in the environmental issue that is now being widely concerned.
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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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