Judul: Synthesis of Hydroxyapatite Nanoparticle from Tutut (Bellamyâ Javanica) Shells by Using precipitation and Hydrothermal Method
Abstrak: Biomaterials as bone replacement is a bioceramics of calcium phosphate-based known as hydroxyapatite (HAp) (Ca10(PO4)6(OH)2). Hap have the similar composition and crystallography of bone . In this study, synthesis of HAp by using precipitation and hydrothermal methods have been performed by using tutut shells (Bellamya Javanica). HAp of precipitation product contained 100 wt% of hydroxyapatite phase with Ca/P ratio of 1.71. The result of functional group analysis also showed the presence of hydroxyapatite phase as indicated by–OH, –PO4, dan –CO3 groups. HAp of wet precipitation product had lattice parameter of a = b = 9.418 Å, c = 6.885 Å. HAp of hydrothermal product contained 94.55 wt% of hydroxyapatite phase and 5.45 wt% of calcium oxide phase with Ca/P ratio of 2.03. The functional group analysis result showed peaks of –OH, –PO4, dan –CO3 groups, indicated the presence of hydroxyapatite phase. In addition to the peaks, the characteristic peaks of Ca–O and Ca–OH bond were also appear. HAp of hydrothermal product had lattice parameter of a = b = 9.4163 Å, c = 6.8791 Å. The synthesis of HAp nanoparticle both using precipitation and hydrothermal method have yielded. The HAp particles shaped spherical-polygonal with an average size of diameter particles around 10-20 nm. Whereas that by hydrothermal method is nanorod with the particle size of 15–20 nm in diameter and 40–60 nm in length.
Keyword: hydroxyapatite (HAp), hydrothermal, nanoparticle, wet precipitation, crystal structure

Judul: Sintesis Hidroksiapatit Berbasis Limbah Cangkang Keong Sawah (Bellamya javanica) dan Modifikasi Pori Menggunakan Gelatin
Abstrak: Hydroxyapatite is a ceramic material with a structure and composition similar to bone. In this study, hidroxyapatite was synthesized using shell of rice field snail as basic ingredients as a source of calcium (Ca(OH)2) and (NH4)2HPO4 as a source of phosphate. Synthesis method used was the wet method. In the synthesis process, porogen in the form of gelatin was added to increase the pore size. Concentrations of the added gelatin, were 20% and 30%. X-Ray diffraction results showed that the HAp phase has been formed with a fairly high purity. The best pores size resulted from the 30% gelatin concentration, was 0.5-3.98 μm. Infrared spectrum showed that the porogened and nonporogened Hap indicated functional group of HAp constituent
Keyword: shell of rice field snail., pore modification, hydroxyapatite, gelatin

Judul: Variabilitas Transpor Arlindo Laut Flores dan Kaitannya dengan ENSO
Abstrak: Air Arlindo yang masuk ke Indonesia sebagian besarnya dilewatkan Laut Flores. Variasi volume transport Arlindo dipengaruhi oleh fenomena anomali iklim interannual seperti El Nino Southern Oscillation (ENSO). Hasil studi terdahulu menyimpulkan terjadinya La Nina meningkatan jumlah transport Arlindo, sedangkan El Nino melemahkan transport Arlindo. Untuk memahami lebih lanjut keterkaitan ENSO dengan variabilitas transport Arlindo dilakukanlah penelitian menggunakan data hasil model INDESO dan hasil observasi satelit dengan rentang waktu 2008 hingga 2015. Penelitian dilakukan di Laut Flores dengan mengkaji bagian barat (119.5oBT) dan bagian timur (123oBT) untuk melihat volume Arlindo yang masuk ke dan keluar dari Laut Flores. Analisis sirkulasi dilakukan dengan menghitung rataan komponen arus dan suhu permukaan laut secara tahunan dan pada rentang tahun ENSO untuk melihat pola sirkulasi perairan. Estimasi volume transpor dihitung dari transek di pintu barat dan pintu timur. Deret waktu volume transpor Arlindo Flores kemudian dianalisis variabilitasnya dengan analisis penapisan lolos-pita(band-pass filter) dan transformasi wavelet sinambung (Continous Wavelet Transform). Hasil penting studi ini menunjukkan bahwa sumber utama Arlindo Flores berasal dari pembelokan Arlindo Makassar dan Arlindo pintu timur Indonesia yang masuk melalui terusan Lifamatola. Kecepatan Arlindo Flores di lapisan tercampur menguat pada musim barat sebaliknya di lapisan termoklin Arlindo Flores menguat pada musim timur. Sumbu utama Arlindo Flores didominasi oleh komponen arus zonal serta mengalami intensifikasi dan bergerak menyusur bagian utara Kepulauan Nusa Tenggara. Fluktuasi Arlindo Flores pada skala-waktu interannual menunjukkan volume transport maksimum terjadi pada tahun La Nina (November 2008-Maret 2009), sedangkan volume transpor minimum terjadi pada tahun El Nino (November 2014-Desember 2015). Struktur menegak Arlindo lebih kuat di kedalaman antara permukaan sampai 400 m. Variabilitas Arlindo Flores menandakan adanya fluktuasi pada periode intraseasonal, semi-annual, dan annual. Fluktuasi Arlindo skala interannual muncul jelas dari hasil penapisan lolos-pita, dimana fluktuasinya terlihat signifikan di kedalaman termoklin.
Keyword: Arus Lintas Indonesia, Laut Flores, ENSO, INDESO model, variabilitas volume transpor