Judul: The Influence of Ultrasonication and Stirring in Synthesis of Nanohydroxyapatite Based Chicken Eggshell
Abstrak: Hidroksiapatit pada tulang alami manusia berbentuk jarum yang mempunyai struktur nano, sehingga diperlukan hidroksiapatit yang sesuai dengan ukuran pada struktur tulang tersebut. Penelitian ini menggunakan tiga metode untuk menghasilkan nanohidroksiapatit yaitu sintesis hidroksiapatit dengan ultrasonikasi kalsium oksida terlebih dahulu, ultrasonikasi dilakukan pada saat presipitasi dan ultrasonikasi dilakukan setelah serbuk hidroksiapatit diperoleh. Hasil uji x-ray diffractometer dan particle size analyzer menunjukkan bahwa metode kedua merupakan metode yang optimum untuk menghasilkan nanohidroksiapatit. Metode ini menghasilkan fasa hidroksiapatit dan beberapa fasa lain seperti octacalcium phosphate dan tricalcium phosphate serta menghasilkan distribusi ukuran partikel paling kecil yaitu ±15 nm. Hasil uji x-ray diffractometer dan particle size analyzer pada metode pertama menunjukkan bahwa selain mayoritas fasa yang terbentuk adalah hidroksiapatit juga terdapat fasa lain berupa octacalcium phosphate dan tricalcium phosphate serta mempunyai distribusi ukuran partikel ±130 nm. Hasil uji x-ray diffractometer dan particle size analyzer pada metode ketiga menunjukkan mayoritas fasa yang terbentuk adalah hidroksiapatit disamping terdapat beberapa fasa lain berupa octacalcium phosphate dan tricalcium phosphate serta menghasilkan distribusi ukuran partikel ±150 nm.
Keyword: Bogor Agricultural University, Institut Pertanian Bogor, IPB, hydroxyapatite, PSA, ultrasonication, XRD, hidrosiapatit, pengadukan, bone groft

Judul: Pemanfaatan cangkang kerang darah dalam Sintesis Nanohidroksiapatit
Abstrak: Research on the synthesis and characterization of nanohydroxyapatite, by using the source of calcium from the shells of mussles blood has been conducted. This research used ultrasonic waves through ultrasonication and precipitation methods for the shyntesis. Nanohydroxyapatite obtained was based on two treatmens which were CaO powder ultrasonication and hydroxyapatite powder ultrasonication. Ultrasonication process aims to minimize the spread and average particel size by using cavitation effect of ultrasonic waves propagating in a liquid medium. Ultrasonication in this research was counducted in three variation of time which were 30, 60 and 120 minutes with three replications for each treatment. The results of XRD characterization showed that for HA from CaO ultrasonication, appeared other phases whice are TCP and OCP. The result of optimum time for ultrasonication was 60 minutes. This is because at the time of ultrasonication 30 and 120 minutes, the distribution and average particle size were very large.
Keyword: XRD, ultrasonication, PSA, Hydroxyapatite

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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