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: 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: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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