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 Tanin dari Gambir (Uncaria gambir Roxb) sebagai Produk Peluruh dan Pencegah Karat pada Logam
Abstrak: Gambier (Uncaria gambier (Hunt.) Roxb) is a genus of flowering plant species in Rubiaceae family. Part of the gambier utilized is the sap which is extracted and then to be dried. Indonesia is the world largest exporter of gambier in the form of raw material. Gambier has major components namely catechin and tannin. Tanin can be used as rust deactivator. High tannin content in gambier may be used as anti-corrosion material thought corrosion is a problem in the industry. The aims of this study were to add value of raw gambier and to obtain the best product formulas that can remove the rust and protect metal from rust (antirust). Preliminary study was conducted by tannin extraction from raw gambier of Lima Puluh Kota regency, measuring the purity level of tannin which was extracted and proxymat analysis of raw gambier and tannin powder. The main study conducted by creating rust remover and anti-rust solution using two-factors completely randomized design consisting of composition factor of tannins and phosphoric acid. Tannin level used in the solution were 2,5%, 3,33% and 4,17%, while level of phosphoric acid were 2,9%, 5,8% and 8,7%. After obtaining the best composition of phosphoric acid and tannin, then the study continued by making ethanol concentration as variable which were 10%, 13% and 16%. Analysis test of solution effectiveness were rust lost of weight analysis and metal appearance analysis, while for anti-corrosion solution, the analysis of metal appearance analysis and Fourier Transform Infrared (FTIR) were done. The tannin level obtained from the material used was 66,76%. Rusty iron soaked with rust converter formula successfully lost its rust content after six hours soaked. From lost weight analysis, it was known that the addition of tannin or phosphoric acid has a significant effect (α = 5 %) to decrease the weight of rust, but the interaction between tannin and phosphoric acid showed no significant results. The best concentration of tannin, phosphoric acid, and ethanol in the formula were 3,33%, 5,8% and 16% respectively. On the test with anti-rust effectiveness yielded that the metal plate was immersed in 3% NaCl for one day, had experienced corrosion while the previous metal plate coated with anti-rust solution had no corrosion on the surface. After one week, the metal plate was given a protective layer had corrosion in certain points, whereas the metal plate that was not given protective layer had corrosion on all over the surface. Results of Fourier Transform Infrared (FTIR) analysis on a rusty metal plate coated with anti-rust solution for one week showed the presence of tannin shown by several functional groups namely OH, CO, C = C aromatic, and C = O and the reaction between tannin and metals at a wavelength of 1625 cm-1. The present of tanin indicated that gambier tannin could react well with metal so it can be used as anti corrosive product
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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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