Judul: Sintesis dan Pencirian Hidroksiapatit dari Cangkang Kerang Hijau dengan Metode Sol-Gel
Abstrak: Hydroxyapatite (HAp) is a major component of bones and teeth. HAp is widely used to repair, fill, extend, and reconstruct damaged bone tissue. In this research, HAp has been synthesized from green mussel shell by using sol-gel method. The controlled synthesis parameter was pH, and the variable being compared was heating temperature at 900 and 1100 oC. The HAp products were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrophotometer, and scanning electron microscope. The results showed that HAp was formed at alkaline pH. The XRD pattern showed that Hap was formed along with type A apatite carbonate, octacalcium phosphate, α- and β-tricalcium phosphate. The crystallinity was increased by raising the temperature and prolonging the heating time. The quality of HAp will get better with increasing crystallinity, and incrasing the temperature will raise the amount of HAp formed as well
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Judul: Sintesis Hidroksiapatit dari Cangkang Kerang Hijau dengan Metode Double Stirring Simultan
Abstrak: This research has been done on the syntthesis of hydroxyapatite using double stirring simultant method and stired with time and sintering temperatures variations. In this study the materials used as sources of calcium were green shellsand diammonium hydrogen phosphate as sources of phosphate. The synthesis results were characterizedusingX-ray Diffraction, Scanning Electron Microscope dan Particle Size Analizer. XRD characterizations resultedthat Hap was no longer 100% pure. Crystal size results varied between 10,50-26,65 nm. Precise lattice parameter was formed in almost all samples above 90%. The morphology using SEM resultedthat the crystallines formed particles, hence the PSA characterizationresulted greater suze than the size of crystalline using XRD. The higher the sintering temperature used, the larger the particle size formed, but the longer time used for stirring, the smaller the particles formed
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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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