Judul: Material Biokeramik Berbasis Hidroksiapatit Tulang Ikan Tuna
Abstrak: Material of hydroxyapatite-based bioceramics have a new prospect in industrial electronics and microtechnology in future. Hydroxyapatite with natural raw material sources is a great potential, especially tuna fish bone waste utilization doesn’t done well. In addition, synthesis technology still not effective and also the characterization of these material has not been developed yet. This study aims to synthesize and determine the bioceramic material characteristics based on tuna fish bone-hydroxyapatite. Extraction method used in tuna fish bone hydroxyapatite is the high temperature heating (sintering). Through a sintering temperature of 700 °C produced bioceramic material based on tuna fish bone-hydroxyapatite with the highest yield of 65.61 ± 2.21% and white in colour. Through FTIR spectrophotometry testing, the functional group owned consist of̅ OH-, CO32-, and PO43-. The higher sintering temperature, would create the higher degree of crystallinity, whereas the SEM showed constituent particles measuring 0,050 μm up to 0,803 μm and resembles a hexagonal crystal form. The capacitance values decreased with increasing frequency given, with the highest value of 0.0061 nF, while the conductivity values increased with increasing frequency with the lowest value of 7.73 x 10-5 S/m.
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Judul: Modifikasi pori Hidroksiapatit dari Tulang Ikan Alu-alu (Sphyraena barracuda)
Abstrak: Hydroxyapatite (HAp) is an important material used in biomedical implants. Currently, porous HAp is widely explored. Large pores surface improve osteoconductivity and adsorption strength. Fish bone can be used as source of HAp since it has high level of calcium and phosphorus in the form of mineral apatite. Therefore, the objective of this study was to modify porous Hap from alu-alu (Sphyraena barracuda) fish bone with starch as the porogen. HAp was formed at temperature of 500, 750, 1000, 1250, 1300, and 1350 ºC. cConcentrations of starch used for porogen were 5, 10, 20, 40, and 60% w/w. X-ray diffraction pattern indicated that HAp was formed in the initial powder fish bone but it had low crystalinity and some impurities. HAp phases with good crystallinity were formed at temperatures of 750–1250 ºC. Electron microscope photographs showed pores with good uniformity was exhibited in the modification using fish bone material with starch concentration of 10%; the sizes were 2.38-3.28 μm.
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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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