Judul: Hydroxyapatite Mineralization Characteristics Due to The Presence of Amino Acids Functionalized Gold Nanoparticles
Abstrak: Hydroxyapatite (HAP) is a well-known biomaterial used to aid in repairing bone and teeth. HAP was synthesized by using amino acid functionalized gold nano-particles. Solutions of KAuCl4 were reduced with borohydrate reducing agent, then added with amino acids, calcium chloride as a calcium source, and diammonium phosphate as a phosphate source. Hydroxyapatite conjugated with amino acid-functionalized gold nanoparticles (HAP-AA-AuNPs) were characterized using UV-vis spectrophotometer and SEM-EDS. The addition of amino acids leads to AuNPs aggregation as a result of modification on the particle surface. By adding calcium and phosphate source to the AA-AuNPs solution, the curve becomes more sloping and shifts. SEM-EDS results can be used to analyze sample morphology and determine the Ca/P ratio. The HAP-His-AuNPs sample has Ca/P ratio as 1.669 that is close to the theoretical of 1.67., Hidroksiapatit (HAP) merupakan biomaterial yang terkenal digunakan untuk membantu perbaikan tulang dan gigi. HAP disintesis dengan menggunakan nanopartikel emas terfungsionalisasi asam amino. Larutan KAuCl4 direduksi dengan reduktor borohidrat, kemudian ditambahkan asam amino, kalsium klorida sebagai sumber kalsium, dan diamonium fosfat sebagai sumber fosfat. Asam amino yang digunakan pada penelitian ini yaitu asam glutamat, glutamin, sisteina, dan histidin. Hidroksiapatit terkonjugasi nanopartikel emas yang terfungsionalisasi asam amino (HAP-AA-AuNPs) dikarakterisasi dengan menggunakan spektrofotometer UV-vis dan SEM-EDS. Penambahan asam amino membuat AuNPs mengalami agregasi sebagai akibat modifikasi permukaan partikel. Setelah penambahan sumber kalsium dan fosfat pada larutan AA-AuNPs, kurva menjadi lebih landai dan mengalami pergeseran. Hasil SEM-EDS dapat digunakan untuk menganalisis morfologi sampel dan mengetahui rasio Ca/P. Sampel HAP-His-AuNPs memiliki besar rasio Ca/P sama dengan 1.669 yakni mendekati dengan rasio secara teori yakni 1.67.
Keyword: Hydroxyapaite, HAP-AA-AuNPs, SEM- EDS, UV-vis spectrophotometer

Judul: Sintesis Hidroksiapatit Berbasis Cangkang Kerang Kepah (Polymesoda Erosa) Dengan Metode Presipitasi
Abstrak: Hidroksiapatit (HAp) adalah material sintetik yang dapat dijadikan implan ke dalam tubuh manusia. Sintesis HAp dilakukan dengan cara mereaksikan CaO dari cangkang kerang kepah dengan sumber fosfat (NH4)2HPO4 menggunakan metode presipitasi pada suhu sintering 900 oC selama 5 jam dan waktu kalsinasi selama 12 jam. Karakterisasi EDX menghasilkan output berupa grafik dan daftar unsur penyusun HAp. Setelah pengujian menggunakan AAS diketahui kadar kalsium cangkang kerang kepah sebesar 5% dari massa total. Berdasarkan hasil analisis XRD menunjukkan kemurnian dari sampel HAp sebesar 73%. Ketelitian parameter kisi a = b yaitu sebesar 99% dan parameter kisi c yaitu 99% serta persentase derajat kristalinitas sebesar 88%. Karakterisasi FTIR menghasilkan spektra serapan gugus PO4 3-, OH- dan CO3 2- yang merupakan penyusun dari HAp. Sementara uji SEM memperlihatkan morfologi dari sampel HAp.
Keyword: AAS, cangkang kerang kepah, hidroksiapatit, presipitasi, XRD

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.
Keyword: