Judul: Karakterisasi Paduan Logam CoCrMo dengan Pelapisan TiN dan Hidroksiapatit Cangkang Keong Sawah (Bellamya javanica) Menggunakan Metode Elektroforesis Deposisi.
Abstrak: Hidroksiapatit (HAp) termasuk kelompok apatit yang paling banyak digunakan dibidang medis karena memiliki sifat biokompatibel dan osteokonduktif. Material ini telah diakui sebagai bahan pengganti tulang dan gigi karena memiliki kemiripan dari segi biologisnya untuk jaringan tulang keras manusia. Dalam penelitian ini HAp digunakan untuk melapisi paduan logam CoCrMo yang terlapisi TiN dalam implan tulang. Pelapisan HAp pada logam mengunakan metode elektroforesis deposisi selama 30 menit dan tegangan 120 Volt. Lapisan yang dihasilkan merata diseluruh permukaan logam dan tidak rapuh. Karakterisasi dilakukan dengan uji XRD hasil yang diperoleh selain HAp juga terdapat Apatit Karbonat Tipe A (AKA) dan Apatit Karbonat Tipe B (AKB). Uji korosi menggunakan perangkat potensiostat/galvanostat dalam media larutan infus menghasilkan kecepatan korosi sebesar 0.0134 mpy, hasil ini lebih baik dari standar Eropa sebesar 0.457 mpy.
Keyword: hidroksiapatit, paduan logam CoCrMo-TiN, elektoforesis deposisi

Judul: Hydroxyapatite coating on metal alloys CoCrMo-TiN with Sol-Gel method
Abstrak: Hidroksiapatit (HAp) disintesis dengan metode presipitasi-sonikasi menggunakan sumber kalsium dari serbuk cangkang keong sawah dan sumber fosforus dari (NH4)2HPO4. Kadar kalsium diukur menggunakan spektofotometer serapan atom sebesar 82.82%. Suhu diragamkan pada 600, 800, dan 1000 oC untuk menentukan suhu terbaik pelapisan. Suhu terbaik tersebut digunakan untuk melapiskan HAp pada paduan logam CoCrMo-TiN menggunakan metode sol-gel termodifikasi. Lapisan yang menempel pada paduan logam diidentifikasi dengan diffraksi sinar X (XRD) dan uji korosi. Hasil XRD menunjukkan sebagian besar permukaan paduan logam CoCrMo-TiN terlapisi oleh HAp. Selain HAp, terdapat fase lain seperti kalsium fosfat, apatit karbonat tipe A dan tipe B. Hasil uji korosi paling baik ditunjukkan pada paduan logam CoCrMo-TiN yang terlapisi HAp dengan laju korosi paling kecil, yaitu 0.0082 mpy., Hydroxyapatite is synthesized by precipitation-sonification using calcium from field snail shell powder phosphorus from (NH4)2HPO4. The calcium level measured by atomic absorption spectrophotometer was 82.82%. The temperatures were varied on 600, 800, and 1000 oC to determine the best temperature of the coating. The best temperature was used to superimpose the HAp on the CoCrMo-TiN metal alloy using the modified sol-gel method. The layer on the metal alloy was identified with x-ray diffraction (XRD) and corrosion test. The XRD result showed that most of the CoCrMo-TiN metal alloy surface was coated by HAp. Beside HAp, there were several other phases such as calcium phosphate, carbonate apatite type A and type B. The best result of the corrosion test was showed in CoCrMo-TiN metal alloy coated with HAp with the smallest corrosion rate 0.0082 mpy. Key words: hydroxyapatite, metal alloys CoCrMo-TiN, precipitation-sonification, sol-gel modified
Keyword: hidroksiapatit, paduan logam CoCrMo-TiN, presipitasi-sonikasi, sol-gel termodifikasi

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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