Judul: Hydroxyapatite Mineralization Characteristics Due to The Presence of Amino Acids Functionalized Gold Nanoparticles
Abstrak: Hydroxyapatite (HAP) is a well-known biomaterial used to aid in repairing bone and teeth. HAP was synthesized by using amino acid functionalized gold nano-particles. Solutions of KAuCl4 were reduced with borohydrate reducing agent, then added with amino acids, calcium chloride as a calcium source, and diammonium phosphate as a phosphate source. Hydroxyapatite conjugated with amino acid-functionalized gold nanoparticles (HAP-AA-AuNPs) were characterized using UV-vis spectrophotometer and SEM-EDS. The addition of amino acids leads to AuNPs aggregation as a result of modification on the particle surface. By adding calcium and phosphate source to the AA-AuNPs solution, the curve becomes more sloping and shifts. SEM-EDS results can be used to analyze sample morphology and determine the Ca/P ratio. The HAP-His-AuNPs sample has Ca/P ratio as 1.669 that is close to the theoretical of 1.67., Hidroksiapatit (HAP) merupakan biomaterial yang terkenal digunakan untuk membantu perbaikan tulang dan gigi. HAP disintesis dengan menggunakan nanopartikel emas terfungsionalisasi asam amino. Larutan KAuCl4 direduksi dengan reduktor borohidrat, kemudian ditambahkan asam amino, kalsium klorida sebagai sumber kalsium, dan diamonium fosfat sebagai sumber fosfat. Asam amino yang digunakan pada penelitian ini yaitu asam glutamat, glutamin, sisteina, dan histidin. Hidroksiapatit terkonjugasi nanopartikel emas yang terfungsionalisasi asam amino (HAP-AA-AuNPs) dikarakterisasi dengan menggunakan spektrofotometer UV-vis dan SEM-EDS. Penambahan asam amino membuat AuNPs mengalami agregasi sebagai akibat modifikasi permukaan partikel. Setelah penambahan sumber kalsium dan fosfat pada larutan AA-AuNPs, kurva menjadi lebih landai dan mengalami pergeseran. Hasil SEM-EDS dapat digunakan untuk menganalisis morfologi sampel dan mengetahui rasio Ca/P. Sampel HAP-His-AuNPs memiliki besar rasio Ca/P sama dengan 1.669 yakni mendekati dengan rasio secara teori yakni 1.67.
Keyword: Hydroxyapaite, HAP-AA-AuNPs, SEM- EDS, UV-vis spectrophotometer

Judul: Sintesis Hidroksiapatit Berbasis Cangkang Kerang Kepah (Polymesoda Erosa) Dengan Metode Presipitasi
Abstrak: Hidroksiapatit (HAp) adalah material sintetik yang dapat dijadikan implan ke dalam tubuh manusia. Sintesis HAp dilakukan dengan cara mereaksikan CaO dari cangkang kerang kepah dengan sumber fosfat (NH4)2HPO4 menggunakan metode presipitasi pada suhu sintering 900 oC selama 5 jam dan waktu kalsinasi selama 12 jam. Karakterisasi EDX menghasilkan output berupa grafik dan daftar unsur penyusun HAp. Setelah pengujian menggunakan AAS diketahui kadar kalsium cangkang kerang kepah sebesar 5% dari massa total. Berdasarkan hasil analisis XRD menunjukkan kemurnian dari sampel HAp sebesar 73%. Ketelitian parameter kisi a = b yaitu sebesar 99% dan parameter kisi c yaitu 99% serta persentase derajat kristalinitas sebesar 88%. Karakterisasi FTIR menghasilkan spektra serapan gugus PO4 3-, OH- dan CO3 2- yang merupakan penyusun dari HAp. Sementara uji SEM memperlihatkan morfologi dari sampel HAp.
Keyword: AAS, cangkang kerang kepah, hidroksiapatit, presipitasi, XRD

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.
Keyword: