Judul: Synthesis and Characterization of Fluorapatite with pH Variations Based on Rice Fields Snail Shells Using the Precipitation Method
Abstrak: Kerusakan pada gigi biasanya membutuhkan pengganti berupa gigi buatan, yaitu implan gigi. Salah satu bahan utama pembuatan implan gigi adalah fluorapatit (FAp) yang dapat berasal dari limbah cangkang keong sawah sebagai prekursor berupa kalsium hidroksida pada sintesis FAp. Penelitian ini bertujuan menyintesis dan mengkarakterisasi FAp berbasis cangkang keong sawah dengan metode presipitasi menggunakan variasi pH. Metode penelitian ini dilakukan melalui tiga tahap, yaitu preparasi sampel cangkang keong sawah, sintesis FAp dengan tiga variasi pH berbeda (5, 7, dan 9) menggunakan metode presipitasi dan karakterisasi FAp dengan X-ray diffraction (XRD). Hasil karakterisasi terbaik dilanjutkan dengan fourier transform infrared (FTIR) dan scanning electron miroscope energy dispersive X-ray (SEM-EDX). Hasil penelitian menunjukkan bahwa dari tiga variasi pH, maka FAp dengan pH 9 memiliki hasil yang terbaik berdasarkan hasil XRD (kristalinitas, ukuran kristal, fase kristal) dan rendemen. FAp pH 9 terbukti memiliki gugus fungsi -OH, OH-F, dan -PO43- yang sesuai dengan analisis FTIR. FAp dengan pH 9 juga terbukti memiliki morfologi permukaan yang seperti gumpalan dan rasio molaritas Ca/P sebesar 3,59 dan P/F sebesar 5,83 dengan analisis SEM-EDX., Damage to the teeth usually requires replacement in the form of artificial teeth, namely dental implants. One of the main ingredients for making dental implants is fluorapatite (FAp) which can be derived from rice snail shell waste as a precursor in the form of calcium hydroxide in FAp synthesis. This study aims to synthesize and characterize FAp based on rice field snail shells with the precipitation method using variations in pH. This research method was carried out in three stages, namely preparation of rice snail shell samples, synthesis of FAp with three different pH variations (5, 7, and 9) using the precipitation method, and FAp characterization by X-ray diffraction (XRD). The best characterization results were followed by fourier transform infrared (FTIR) and scanning electron microscopy energy dispersive X-ray (SEM-EDX). The results showed that of the three variations of pH, FAp with pH 9 had the best results based on XRD results (crystallinity, crystal size, crystal phase) and yield. FAp pH 9 proved to have functional groups -OH, OH-F, and -PO43- which was by FTIR analysis. FAp with pH 9 was also shown to have a lump-like surface morphology and a Ca/P molarity ratio of 3,59 and P/F of 5,83 by SEM-EDX analysis.
Keyword: Dental Implant, Fluorapatite, Precipitation, Rice Fields Snail Shell

Judul: Variation of Sintering Temperature in the Synthesis of Fluorapatite Made from Snail Shells (Achatina fulica) Using the Sol-Gel Method
Abstrak: Karies gigi dapat menyebabkan gigi berlubang, keropos, bahkan patah. Perlu adanya penanganan terhadap karies gigi berupa pencabutan dan penggantian gigi alami dengan implan. Fluorapatit dapat digunakan sebagai bahan implan gigi. Fluorapatit dapat disintesis menggunakan bahan dasar cangkang bekicot. Cangkang bekicot memiliki kandungan kalsium karbonat sebesar 98%. Penelitian ini bertujuan mengidentifikasi karakteristik fluorapatit dan mengetahui pengaruh variasi suhu sintering pada sintesis fluorapatit berbahan cangkang bekicot dengan metode sol gel. Variasi suhu sintering yang digunakan, yaitu 700, 900, dan 1100 °C. Hasil penelitian menunjukkan fluorapatit yang disintering pada suhu 900 °C memiliki hasil terbaik. Fluorapatit 900 °C memiliki persentase kristalinitas tertinggi berdasarkan hasil spektrum XRD sebesar 83% dengan fase apatite pada sudut 31,8126°, ukuran kristal 79 nm, dan ukuran partikel 0,5 µm. Analisis FTIR pada fluorapatit 900 °C menunjukkan adanya gugus fungsi OH, OH-F, dan PO43-. Fluorapatit 900 °C menunjukkan morfologi seperti bunga karang dengan bunga berbentuk heksagonal dan rasio molaritas Ca/P sebesar 1,67., Dental caries can cause cavities, porous, and even broken teeth. There is a need for the treatment of dental caries in the form of extraction and replacement of natural teeth with implants. Fluorapatite can be used as a dental implant material. Fluorapatite can be synthesized from snail shells. A snail shell contains 98% calcium carbonate. This study aims to identify the characteristics of fluorapatite and determine the effect of variations in sintering temperature on the synthesis of fluorapatite made from snail shells using the sol-gel method. Variation of sintering temperature used is 700, 900, and 1100 °C. The results showed that fluorapatite synthesized with the sintering temperature of 900 °C had the highest crystallinity based on the results of the XRD spectrum of 83% with the apatite phase at an angle of 31,8126%, crystal size of 79 nm, and particle size of 0,5 µm. FTIR analysis on the sample showed the presence of OH, OH-F, and PO43- functional groups. The sample showed a spongy surface morphology with hexagonal-shaped flowers. A Ca/P molarity ratio of 1,67.
Keyword: cangkang bekicot, fluorapatit, implan gigi, kristalinitas, sol gel

Judul: Utilization of terra/MODIS L1B data for analysis of horizontal wind profile in the troposphere
Abstrak: This study was concerned with horizontal wind derived from data collected with the Moderate-resolution Imaging Spectroradiometer (MODIS) on board the NASA’s Earth Observation System (EOS)-Terra satellite. The aim of this study is to develop a method for the estimation of horizontal wind movement in the troposphere based on Navier-Stokes equation. The method was applied to a calibrated and geolocated Terra/MODIS L1B 1 km data set. The data inputs to estimate surface temperature are retrieved from TIR (Thermal Infrared) bands 31 (10.780 μm to 11.280 μm) and 32 (11.770 μm to 12.270 μm). The obtained surface temperatures were later used to approximate geopotential height on a constant-pressure surface by using the modified Poisson equation. The main assumptions used are the hydrostatic equilibrium, ideal gas law, constant lapse rate and constant acceleration of gravity. Based on the distribution of geopotential height, the pressure gradient force is measured by the gradient of geopotential on an isobaric coordinate to present the horizontal wind profile. For certain topographic areas especially in the mountain ranges, there was a disadvantage of using pressure as a vertical coordinate which lead to inaccuracy. In spite of that, Terra/MODIS L1B data with 1 km spatial resolution can be used to estimate the horizontal wind movement in the troposphere.
Keyword: