Judul: Aplikasi Poli(asam laktat) sebagai Mikrosfer Pengungkung Obat Selekoksib
Abstrak: Mikrosfer polimer biodegradabel, poli(asam laktat) (PLA) berisi selekoksib dibuat dengan metode penguapan pelarut dalam air. Mikrosfer yang dihasilkan dari metode ini homogen dan selekoksib terdistribusi di dalam matriks polimer. Parameter yang diamati adalah ukuran mikrosfer, efisiensi pengungkungan dan lepasan obat selekoksib secara in vitro. Pengamatan morfologi mikrosfer menggunakan scan electron microscope dan kristalinitasnya dengan XRD. Mikrosfer berisi obat diinkubasi dalam bufer fosfat + 2% Tween-80 pH 7.4, diperoleh lepasan awal yang meletus pada dua jam pertama diikuti dengan lepasan yang tetap sampai waktu inkubasi 24 jam. Hasil penelitian ini memperlihatkan ada pengaruh ukuran mikrosfer berisi obat selekoksib pada lepasan awal dari matriks polimer. Obat yang lepas dari mikrosfer dengan kandungan obat yang rendah (1% w/w) dipengaruhi oleh ukuran partikel. Naiknya kandungan obat dalam mkirosfer mulai 1% b/b sampai 5% b/b secara nyata obat lebih cepat lepas dari mikrosfer. Kata kunci: poli(asam laktat), mikrosfer, selekoksib, metode penguapan pelarut.
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Judul: Degradasi in vitro mikrosfer polipaduan poli(asam laktat) dan poli (kaprolakton)
Abstrak: Poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) are examples of polymer that can be used as a matrix in drug delivery system because of its degradability property. Drug encapsulation system could be achieved by microspheres formation with emulsion method. The aim of this research was to examine in vitro degradation of microspheres obtained from PLA-PCL polyblend at pH 7.4. Several stages in the study consisted of PLA synthesis, mixing of PLA-PCL in polyblend, microspheres formation, shape and texture observation, and in vitro degradation test. Synthesis PLA produced a polymer with molecular weight 6064 g/mol. Microspheres were formed by emulsification with polyvinylalcohol (PVA) 1.5% (v/v) as an emulsifier. Physical texture of the microspheres was observed with stereomicroscope and scanning electron microscope (SEM). Degradation was analyzed weekly by measuring its molecular weight and viscosity using a digital viscometer, while its weight loss was measured using an analytical balance. The results showed that the composition of PLA microspheres: PCL (9:1) had degradation time faster than the others and it also affected morphological structure, viscosity, and weight of microsphere during degradation analysis. The higher the PLA composition the lower the viscosity value, therefore, the lower the molecular weight of microspheres. During degradation time, viscosity value and weight loss percentage decreased gradually. Kinetics of microsphere weight loss followed between zero and first order kinetic model.
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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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