Judul: Gelombang soliter internal pada lapisan atmosfiri yang memiliki perubahan kecepatan angin yang cepat
Abstrak: Gelombang internal adalah suatu gelombang yang terjadi di dalam suatu fluida. Gelombang ini muncul karena adanya perubahan rapat massa di setiap lapisan di dalam fluida. Salah satu gelombang internal yang ditemui di lappisan atmosfir adalah gelombang soliter internal, seperti yang terjadi pada fenomena "morning glory" di Australia. pada fenomena "Morning glory" terjadi penurunan tekanan hingga bebrapa milibar.
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Judul: Gelombang soliter internal pada lapisan atmosfir yang memiliki perubahan kecepatan angin yang cepat
Abstrak: Gelombang internal adalah suatu gelombang yang terjadi di dalam suatu fluida. Gelombang ini muncul karena adanya perubahan rapat massa di setiap lapisan di dalam fluida. Salah satu gelombang internal yang ditemui di lapisan atmosfir adalah gelombang soliter internal, seperti yang terjadi pada fenomena "Morning glory" di Australia. Pada fenomena "Morning glory" terjadi penurunan tekanan hingga beberapa millibar. Tulisan ini membahas perambatan gelombang soliter internal pada lapisan atmosfir. Lapisan atmosfir yang ditinjau memiliki suatu lapisan dimana kecepatan angin dan rapat massanya berubah secara cepat, sedangkan lapisan lainnya relatif konstan. Persamaan gerak gelombang diturunkan berdasarkan persamaan kekontinuan dan persamaan momentum. Sedangkan metode yang digunakan adalah metode asimtotik. Solusi persamaan gerak dimisalkan dalam bentuk gelombang berjalan, dan bentuknya berupa fungsi rasional. Sebagai contoh, diberikan suatu studi kasus dimana pada suatu lapisan kecepatan angin dan rapat massanya berupa fungsi linear, sedangkan lapisan lainnya konstan.
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Judul: Synthesis of Chicken Eggshells-Based β-Tricalcium Phosphate Bioceramics and Their Biocompatibility Test as A Tooth Filler
Abstrak: Preservation of alveolar bone following tooth extraction is an important step in dental practices before dental implant placement. This study reported synthesis of β-Tricalcium Phosphate (β-TCP) bioceramics and its biocompatibility test as a tooth filler to maintain the desired alveolar ridge dimension and stimulate the bone healing processes in the area of tooth loss. β-TCP bioceramics was resulted directly from precipitation of calcinated chicken eggshells as calcium source and phosphoric acid. The corresponding β-TCP was mixed with chitosan 2% to get β-TCP pellet for biocompatibility testing. Biocompatibility testing of β-TCP on lower incisor was performed in rabbits and sheep as animal model. In this study, the x-ray diffraction (XRD) profiles showed that 1000 oC calcinated chicken eggshells correspond to calcium oxide (CaO). There was also transformation phase of CaO into Ca(OH)2 observed after more than three months stored. The XRD profiles proved that obtained β-TCP bioceramics by precipitation has the same pattern with that of reference data base and commercial β-TCP. Fourier transform infrared (FTIR) spectra were completely consistent with the result of crystallization processes observed by XRD measurements. Moreover, the purity of the product shown by the atomic absorption spectroscopy (AAS) resulted in Ca/P ratio of 1.48 which was closed to that of standard β-TCP ceramics. The repeatable XRD peaks patterns and FTIR spectra obviously showed the sample reproducibility. Sheep’s alveolar socket that is filled with the corresponding β-TCP demonstrated the expected results. The x-ray radiograph of sheep’s jaw indicated no change on mesio-distal of the edentulous area. Moreover, the histological results were completely consistent with the x-ray radiograph and macroscopic result which is proved by the formation of new bone. In the contrary with sheep’s result, histological results showed no tooth growth on rabbit proved by the presence of lipid and collagen on the extraction site. This result did not correspond to the x-ray radiograph and macroscopic results that demonstrated the tooth growth and erupted tooth. It is clear that the corresponding β-TCP could minimize the bone loss and maintain the dimension of alveolar ridge.
Keyword: β-tricalcium phosphate, chicken eggshells, rabbit, sheep, tooth filler