Judul: Sintesis dan Karakterisasi Komposit Apatit-Kitosan dengan Metode In-situ dan Ex-situ.
Abstrak: Sintesis komposit apatit-kitosan dilakukan dengan teknik presipitasi secara in-situ dan ex-situ pada kondisi fisiologis tubuh manusia. Apatit-kitosan secara in-situ dihasilkan dari presipitasi Na2HPO4.2H2O dan kitosan yang diteteskan dengan CaCl2.2H2O. Pada proses ex-situ, kitosan diteteskan setelah proses presipitasi Na2HPO4.2H2O yang diteteskan dengan CaCl2.2H2O selesai dilakukan. Penambahan kitosan yang dilakukan diharapkan dapat meningkatkan kristanilitas dan kelenturan serta biokompatibilitas dari HAP sehingga dapat diaplikasikan untuk bidang medis terutama dalam implantasi tulang. Untuk mengetahui karakteristik komposit apatit-kitosan yang dihasilkan, dilakukan karakterisasi dengan XRD (X-Ray Diffraction), SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared), EDXA (Energy Dispersive X-Ray Analysis) dan uji mekanik. Hasil karakterisasi XRD pada sampel in-situ dan ex-situ memperlihatkan adanya puncak milik hidroksiapatit (HAp), Apatit Karbonat tipe A (AKA), Apatit Karbonat tipe B (AKB), Okta Kalsium Fosfat (OKF) dan kitosan. Hadirnya puncak milik apatit dan kitosan menandakan bahwa komposit apatit-kitosan berhasil terbentuk. Hasil XRD juga menunjukkan adanya penurunan derajat kristanilitas pada sampel komposit apatit-kitosan yang disebabkan karena kitosan bersifat lebih amorf dibandingkan apatit. Terbentuknya komposit apatit-kitosan juga diperkuat dengan hasil karakterisasi FTIR dan SEM. Pada FTIR, gugus fosfat (PO4), hidroksil (OH) dan karbonat (CO3) yang merupakan milik apatit muncul bersama dengan gugus fungsi milik kitosan yaitu NH2, C-H, dan amida. Pada karakterisasi SEM, terbentuknya komposit apatit-kitosan ditandai dengan morfologi sampel in-situ dan ex-situ yang berbentuk bongkahan yang menunjukkan bahwa kitosan telah berikatan dengan apatit. Kata kunci: apatit, kitosan, in-situ, ex-situ
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Judul: Sintesis Komposit Hidroksiapatit dengan Variasi 10-50% Kitosan
Abstrak: In medical cases, HAp/chitosan composite can be used as a synthetic implantation in bone. Addition of chitosan on HAp seems produce good composite. Chitosan can reduce the properties of brittle HAp. XRD characterization on all samples showed that pattern has formed apatite dominated by the peak of HAp. The peak of chitosan on the results of XRD was not visible. It is due to chitosan has spread all over the samples. On FTIR characterization, the appearance of phosphate group and hydroxyl group show that HAp was identified in samples, while chitosan was indicated by the appearance of a group of NH, CO and CH. The results of observations with an optic stereo microscope, samples morphology showed that HAp was well distributed in chitosan. Test results of shore A test showed the addition of chitosan on HAp proved able to eliminate brittle properties of HAp. A lot of chitosan in the samples will reduce the hardness of the composition of the HAp / chitosan
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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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