Judul: Biodegradasi struktur dan morfologi mikrosfer polilaktat
Abstrak: Penggunaan mikrosfer radioaktif merupakan metode alternatif untuk mengobati kanker hati. Teknologi ini sudah mulai diaplikasikan dengan bahan dasar mikrosfer terbuat dari kaca atau keramik, namun keduanya tidak dapat terdegradasi dalam tubuh. Karena itulah diperlukan alternatif bahan lain yang dapat terdegradasi dalam tubuh, salah satunya ialah dengan memanfaatkan polimer biodegradabel, seperti polilaktat (PLA). PLA mempunyai sifat biodegradabel dan biokompatibel sehingga cocok digunakan sebagai bahan dasar pembuatan mikrosfer. Akan tetapi belum banyak pihak terutama di Indonesia yang mempelajari proses biodegradasi dan perubahan yang terjadi selama mikrosfer PLA terdegradasi sehingga penelitian tentang pengaruh biodegradasi terhadap perubahan struktur dan morfologi mikrosfer PLA akan sangat bermanfaat. Mikrosfer PLA dibuat dengan mengemulsikan 10 ml larutan PLA 10% dalam kloroform dan 10 ml larutan polivinil alkohol (PVA) 5% dalam air menggunakan motor pengaduk berkecepatan 1000 rpm, kemudian mendispersikannya dalam 500 ml akuades. Proses biodegradasi dilakukan secara in vitro pada pH 7.4 dan suhu 37°C. Proses degradasi mikrosfer PLA diamati melalui gejala kerusakan pada permukaan mikrosfer, penurunan entalpi pelelehan, penurunan bobot molekul, berturut-turut menggunakan scanning electron microscope, differential scanning calorimetry, dan gel permeation chromatography. Proses degradasi mikrosfer PLA tampak nyata setelah inkubasi selama 4 minggu. Jadi, PLA memenuhi syarat sebagai bahan baku pembuatan mikrosfer untuk digunakan sebagai pengungkung. Waktu 1 bulan itu cukup untuk proses terapi menggunakan mikrosfer radiofarmaka. Proses degradasi PLA berjalan lambat, hal itu disebabkan karena PLA yang digunakan bersifat kristalin dan adanya gejala munculnya sejumlah mikrosfer baru dari mikrosfer besar yang telah terdegradasi
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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: Characteristic of Overshooting Top (OT) Based on  Himawari  8  Satellite  as  a  Convective  Cloud  Feature  that  Generates  Extreme Weather in the Java Island Region
Abstrak: Overshooting Top (OT) is a feature at the top of a convective cloud that is associated with extreme weather. Research on OT in tropical Indonesia is still very limited. The existence of geostationary satellites with wide area coverage and fast frequency observations is useful for observing the fast dynamics of the OT life cycle. Therefore, this study intends to analyze the relationship between OT and extreme weather, updraft and thermodynamic conditions of OT when extreme weather occurs, the best objective method for detecting OT in the day time and night time, and the spatiotemporal distribution of OT in the tropical region of Java Island during the 2018-2021 period. Based on visual analysis using visible channel and Himawari 8 sandwich products, 87% of extreme weather events in Java were accompanied by the appearance of OT. It indicates that the presence of the OT pattern is a convection cloud pattern or feature that is closely related to extreme weather events for the Java Island region. The existence of a time lag between the appearance of OT and extreme weather events on Java Island indicates that the OT of convection cloud can be used as a precursor or nowcasting for the appearance of extreme weather. Most of the convective cloud OT features during extreme weather events on Java Island have altitude that were only able to exceed the altitude of the equilibrium level and few were able to exceed the tropopause level of 9 km – 16 km. The difference in atmospheric conditions during extreme weather events on Java Island, which is in the tropics and subtropics, is a strong and unstable convective energy condition characterized by a larger CAPE, as well as unstable KI, LI, SI and TTI values. It is offset by kinematic factors in the form of a weak vertical wind shear (bulk wind shear 0-6 km) and a higher freezing point height. The difference between extreme weather events in the Java Island region and other tropical regions compared to subtropical regions is the strong updraft speed of convection clouds. The IRW Texture COMB algorithm based on the IRW-Texture Gradient modification and the COMB algorithm shows a significant increase in quality for detecting OT and non-OT pixels in Java. Rainy days with rainfall > 50 mm/day are very common in areas with an altitude of > 500 m. On the other hand, the level of convection activity which is indicated by the presence of OT and lightning is significantly reduced in this area. OT of convective clouds appear more frequently during the DJF season and less frequently during the JJA season. OT often appears during the day time and rarely at night time. Most OTs appear in the central part, away from the south and north coasts of Java Island during the day, while OTs that appear near the south and north coasts of Java Island can appear in the morning or afternoon.
Keyword: convective clouds, extreme weather, Overshooting Tops, Himawari 8 Satellite