Judul: Degradasi Poliblend Kopolimer Poli(Asam Laktat-co-Asam Glikolat) dan Poli(å-kaprolakton) secara In Vitro
Abstrak: Polimer telah banyak diaplikasikan dalam kehidupan manusia, salah satunya adalah untuk penyalut obat. Polimer sintetik seperti poli(asamlaktat) (PLA), poli(asamglikolat) (PGA), poli(å-kaprolakton) (PCL), poli(asam laktat-co-asam glikolat) (PLGA) merupakan jenis-jenis poliester yang banyak digunakan untuk penyalut obat. Para peneliti telah banyak yang melakukan penelitian tentang degradasi PLA, PGA, PCL, dan PLGA, tetapi belum ada yang melakukan penelitian tentang degradasi poliblend polimer ini, salah satunya adalah poliblend PLGA dan PCL. Poliblend dibuat empat komposisi, yaitu PLGA (90:10):PCL 3:1, PLGA(75:25):PCL 3:1, PLGA (90:10):PCL 5:1, dan PLGA (75:25):PCL 5:1. Degradasi dilakukan selama delapan minggu dengan menggunakan bufer fosfat pH 7.4 dan suhu inkubasi 37°C. Degradasi polimer diamati dengan adanya perubahan massa, viskositas intrinsik, dan bentuk permukaannya. Hasil penelitian menunjukkan bahwa komposisi PLGA (75:25):PCL 5:1 merupakan komposisi yang paling cepat terdegradasi dibandingkan dengan komposisi lainnya. Ini terlihat dari perubahan massa hingga 89.06% dan viskositas intrinsik hingga 20.13%.
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Judul: Pembuatan dan Pencirian Kopolimer Poli(asam laktat)-Poli(asam glikolat) Menggunakan Katalis Timah Oktoat
Abstrak: Polimer biodegradabel dan biokompatibel sintetik terus dikembangkan untuk mendapatkan sifat yang sesuai dengan kebutuhan. Polimer tersebut di antaranya adalah kopolimer poli(asam laktat)-poli(asam glikolat) (PLGA). PLGA merupakan polimer yang dapat diuraikan secara hayati. Kopolimer PLGA dapat disintesis melalui pembukaan cincin D,L laktida dan glikolida yang dikarakterisasi menggunakan Fourier transformed infrared (FTIR), X-ray Difraktion (XRD), dan viskositas intrinsik melalui viskometri. Hasil penelitian menunjukkan bahwa suhu pemanasan memiliki pengaruh terhadap PLGA yang dihasilkan. Viskositas intrinsik tertinggi pada PLGA didapatkan pada pemanasan dengan suhu 180 oC selama 23 jam dengan menggunakan katalis timah oktoat. Pola spektrum FTIR menunjukkan adanya gugus –OH ulur pada bilangan gelombang 3514.1 cm-1, vibrasi ulur C–H pada 2947.0 cm-1 dan 2997.2 cm-1, gugus karbonil (C=O) pada 1755.1 cm-1 dan (C-O) pada bilangan gelombang 1188.1 cm-1. Analisis kristalinitas menunjukkan bahwa PLGA bersifat amorf.
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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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