Judul: Conversion of Borate-Based Bioglass to Hydroxyapatite in Phosphate Solution and Mixed of Phosphate and Carbonate Solution
Abstrak: Bioaktivitas material dengan sel merupakan salah satu parameter utama biokompatibilitas material yang berperan dalam regenerasi jaringan tulang baru. Biomaterial dengan luas permukaan yang besar mampu meningkatkan adhesi sel yang berperan dalam inisiasi regenerasi jaringan baru. Salah satu modifikasi untuk meningkatkan bioaktivitas material adalah pembuatan material dalam bentuk mikrosfer. Dalam penelitian ini dilakukan fabrikasi mikrosfer hidroksiapatit melalui konversi mikrosfer bioglass dalam larutan fosfat serta larutan campuran fosfat dan karbonat. Mikrosfer bioglass diperoleh melalui metode flame spray spheroidization dengan bahan baku dasar partikel bioglass berukuran 63 μm – 200 μm. Citra SEM menunjukkan bahwa mikrosfer bioglass berhasil difabrikasi dengan ukuran rata-rata 76,84 μm. Konversi mikrosfer bioglass dilakukan dengan variasi waktu pengamatan selama 14 hari. Hasil pola difraksi sinar-X menunjukkan bahwa mikrosfer kalsium fosfat untuk kedua larutan terbentuk pada hari ke-7 dan terdapat fasa apatit karbonat (CHA) pada hasil uji konversi dalam larutan campuran fosfat dan karbonat. Citra SEM pada hasil konversi menunjukkan bahwa ukuran mikrosfer kalsium fosfat memiliki rentang yang sama dengan ukuran mikrosfer bioglass sebelum uji konversi yaitu sebesar 73,59 μm – 90,83 μm. Hasil EDX menginformasikan bahwa mikrosfer kalsium fosfat memiliki rasio Ca/P yang mendekati literatur., The bioactivity of the material with cells is one of the main parameters for the biocompatibility of the material that plays a role in the regeneration of new bone tissue. Biomaterials with a large surface area are able to increase cell adhesion which plays a role in the initiation of new tissue regeneration. One of the modifications to increase the bioactivity of the material is the manufacture of the material in the form of microspheres. In this study, the fabrication of hydroxyapatite microspheres was carried out by converting bioglass microspheres in phosphate solution and a mixed solution of phosphate and carbonate. Bioglass microspheres were obtained through the flame spray spheroidization method with the basic raw material of bioglass particles measuring 63 μm – 200 μm. The SEM image shows that the bioglass microspheres were successfully fabricated with an average size of 76.84 μm. The conversion of bioglass microspheres was carried out by varying the observation time for 14 days. The results of the X-ray diffraction pattern showed that calcium phosphate microspheres for both solutions were formed on day 7 and there was an apatite carbonate (CHA) phase in the conversion test results in a mixed solution of phosphate and carbonate. The SEM image on the conversion results shows that the size of the calcium phosphate microspheres has the same range as the size of the bioglass microspheres before the conversion test, which is 73.59 μm – 90.83 μm. The EDX results inform that calcium phosphate microspheres have a Ca/P ratio close to the literature.
Keyword: Bone Graft, Carbonate Apatite, Flame Spray Spheroidization, SEM-EDX, XRD

Judul: Bioactivity examination for calcium phosphate-chitosan composites in simulated body fluid Pembimbing
Abstrak: Calcium phosphate-chitosan composites such of biomaterial that had biodegradable and bioactivity characteristics, therefore it potentially to make a biomaterial of bone substitution. This study aimed to synthesize calcium phosphate-chitosan composites and examine that composites had both of characteristics with in vitro evaluation by immersion in Simulated Body Fluid (SBF). Calcium phosphate was prepared by precipitation of Ca from eggshell which was dropped by ((NH4)2HPO4) at temperature 37oC. Molar ratio Ca and P was calculated approximately 0.3 M and 0.18 M for each volume 100 ml. Result of precipitation was precipitated 24 hours then was filtered. Precipitation results was dried at temperature 110oC for 5 hours then at 900oC for 5 hours to resulting hydroxyapatite (HAp) and at temperature 110oC for 5 hours to resulting carbonated apatite (AK). Calcium phosphate-chitosan composites was prepared by sonication method. Optimate composition of calcium phosphate-chitosan composites were 64% HAp, 16% AK, and 20% chitosan. Composition was sonicated for 3 hours untill homogen. Sonication results was dried in incubator at temperature 50ºC for 15 hours. In vitro by immersion in SBF was prepared by increasing consecutively KCl, NaCl, NaHCO3, MgSO4.7H2O, CaCl2, Tris+HCl, NaN3, and KH2PO4 then added aquabidest 100 ml. Composites was formed as a pellet then immersed in 50 ml SBF in petridish for 3 months and was observed for each week. Biodegradable characteristics results showed that there were alteration of weight-loss in composites. Bioactivity showed by X-Ray Diffraction (XRD), Fourrier Transform Infrared (FTIR), and Scanning Electron Microscophy (SEM). X-Ray Diffraction results showed that alteration phase mostly to HAp but there were fluctuative rate on crystallinity degree. FTIR spectra indicated that the longer the time of immersion, compositions for each chemical functions was decreased and it supported by SEM results that showed by the greater agglomerated particles and cavity in the longer time. Based on result, after in vitro evaluation by immersion in SBF indicated that calcium phosphate-chitosan composites had biodegradable and bioactivity characteristics it caused there were some interactions between composites and SBF.
Keyword: Composites, Calcv apatite, In vitro evaluation, Bogor Agricultural University

Judul: Gerak intertropical convergence zone di wilayah Indonesia
Abstrak: Intertropical Convergence Zone (ITCZ) merupakan salalı satu faktor yang mempengaruhi intensitas dan distribusi curah hujan di Indonesia. Pada umumnya daerah yang dilalui ITCZ memiliki curah hujan yang tinggi. Oleh sebab itu perlu diketahui posisi ITCZ setiap bulan. Dalam penelitian ini dikaji metode penentuan posisi ITCZ berdasarkan data Geostationery Meteorological Satellite serta pola gerak ITCZ tiap bulan. Penentuan posisi gerak ITCZ dilakukan dengan menggunakan persamaan regresi linear sederhana dan persamaan polinom orde dua/tiga. Dengan persamaan regresi linear sederhana dan polinom orde dua/tiga posisi ITCZ dapat ditentukan dengan ketepatan yang cukup baik. Posisi rata-rata ITCZ pada bulan Januari berada di belahan bumi selatan, sedangkan bulan April, Juli dan Oktober berada di belahan bumi utara. Dengan persamaan polinom orde dua/tiga pada bulan April, Juli dan Oktober posisi rata-rata ITCZ berada 2º lintang lebih ke utara dan pada bulan Januari berada 3º lintang lebih ke selatan dibandingkan dengan persamaan regresi linear sederhana. Untuk bulan Januari, April dan Juli penentuan posisi rata-rata ITCZ dengan persamaan polinom orde dua/tiga relatif lebih tepat, sedangkan dengan persamaan regresi linear sederhana terjadi penyimpangan yang cukup besar. Sebaliknya untuk bulan Oktober dengan persamaan regresi linear sederhana relatif lebih tepat. Secara umum pola gerak ITCZ tiap bulan (1994-1997) mengikuti gerak matahari. Pada bulan Desember-Februari ITCZ bergerak ke selatan ekuator, bulan Maret-Mei bergerak ke utara menuju ekuator, bulan Juni-Agustus bergerak lebih jauh ke utara dan bulan September-November kembali bergerak ke selatan. Posisi rata-rata ITCZ paling selatan pada 3° LS (bulan Maret), sedangkan posisi rata-rata ITCZ paling utara pada 14° LU (bulan Agustus). Penyimpangan posisi ITCZ dapat terjadi karena pengelompokan jenis awan yang kurang spesifik, juga dapat disebabkan oleh penyimpangan sirkulasi Walker dari keadaan normal. Luas zone ITCZ pada bulan Januari, April, Juli dan Oktober berubah-ubah baik dalam tahun yang sama maupun antar tahun (1994-1997).
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