Judul: Sintesis Biokomposit CHA/PVA/Alginat sebagai Biomaterial Substitusi Tulang.
Abstrak: Biomaterial merupakan material inert yang diimplan kedalam sistem makhluk hidup sebagai pengganti fungsi jaringan dan organ tubuh yang rusak. Di Indonesia, kebutuhan biomaterial substitusi tulang semakin meningkat seiring banyaknya kasus kerusakan tulang akibat meningkatnya jumlah kecelakaan kendaraan bermotor. Tingginya kasus kecelakaan yang terjadi meningkatkan permintaan material yang bisa memperbaiki tulang yang rusak. Apatit karbonat (CHA) merupakan material yang cukup menjanjikan dalam perkembangan material implan tulang karena memiliki sifat yang bioresorbable dan bioaktif. Dalam penelitian ini CHA dicampurkan dengan senyawa yang bersifat elastis yaitu polivinil alcohol (PVA) dan alginat. Polimer berfungsi sebagai matriks atau media tumbuh senyawa mineral yang membantu proses mineralisasi pada tulang sekaligus mengurangi sifat rapuh dari CHA. Biokomposit disintesis dalam bentuk scaffold karena dalam aplikasinya, biomaterial yang dibutuhkan para dokter ortopedi adalah dalam bentuk scaffold. Scaffold merupakan suatu struktur tiga dimensi yang digunakan sebagai media penyangga sementara untuk mendukung proses pertumbuhan dan pengembangan jaringan baru. Apatit karbonat disintesis dengan metode presipitasi bantuan iradiasi microwave. Sumber kalsium yang digunakan berasal dari limbah cangkang telur ayam yang mengandung lebih dari 95% CaCO3. Hasil XRD serbuk CHA menunjukkan munculnya fasa apatit karbonat pada sampel dengan nilai parameter kisi a dan c mendekati literatur JCPDS yaitu 9.626 Å dan 7.123 Å. Rasio Ca/P dari CHA yaitu 1.63. Hal ini akibat adanya substitusi ion karbonat pada gugus fosfat sehingga menghasilkan apatit non-stoikiometri. Scaffold CHA/PVA/Alginat berhasil disintesis menggunakan metode freeze drying. Hasil FTIR menunjukkan munculnya gugus fungsi hidroksil, fosfat, dan karbonat yang merupakan indikasi kehadiran CHA. Selain itu juga terdapat gugus ikatan C-O, C=C, C-H, dan C=O yang menandakan adanya kandungan PVA dan alginat. Scaffold yang dihasilkan bersifat lembut dan elastis seperti sponge. Morfologi sampel diamati menggunakan SEM dan berhasil menunjukkan terbentuknya pori pada komposit yang cukup untuk pertumbuhan osteoblas. Hasil uji mekanik pada sampel dengan variasi komposisi PVA menunjukkan bahwa semakin tinggi kandungan PVA, semakin meningkatkan nilai kuat tekan. Hasil XRD menunjukkan bahwa penambahan PVA dan alginat menurunkan ukuran kristalit dan derajat kristalinitas. Nilai porositas yang didapatkan dari hasil uji micro CT scan dibawah 50%. Hasil EDX menunjukkan bahwa komposit mengandung unsur-unsur diantaranya karbon, oksigen, fosfor, natrium, kalsium, dan unsur minor lainnya. Hasil perhitungan Ca/P didapatkan nilai rasio diatas 1.67. Scaffold ini menunjukkan potensi yang baik untuk dikembangkan menjadi bahan substitusi tulang.
Keyword: AlKata kunci: Alginat, biomaterial, microwave, polivinil alcohol, scaffoldginat, biomaterial, microwave, polivinil alcohol, scaffold

Judul: Synthesis and Characterization of HA-CHA/Collagen/Alginate and HA-CHA/Collagen/PVA/Alginate Composite  Scaffolds
Abstrak: Metode pencangkokan tulang yang sudah dikenal saat ini diantaranya yaitu autograft, allograft, dan xenograft. Meskipun metode tersebut terbukti dapat memperbaiki suatu jaringan tulang yang rusak, namun metode ini masih memiliki banyak keterbatasan yang dapat menyebabkan terhambatnya proses pengobatan. Salah satu upaya untuk mengatasi keterbatasan tersebut yaitu dengan dikembangkannya bone graft sintetis (scaffold). Fokus penelitian ini yaitu menyintesis scaffold komposit HA-CHA/Kolagen/Alginat dan HA CHA/Kolagen/PVA/Alginat menggunakan metode freeze-drying. Scaffold dibuat dengan memvariasikan komposisi komponen anorganik (HA, CHA) dan komponen organik (polimer) dengan rasio perbandingan anorganik:organik yaitu 25:75, 50:50, 75:25 dan HA:CHA masing-masing 100:0, 75:25, 50:50, 25:75, 0:100. Hasil sintesis kemudian dikarakterisasi menggunakan SEM-EDX, FTIR, dan XRD. Hasil SEM menunjukkan scaffold komposit HA-CHA/Kolagen/Alginat memiliki struktur morfologi cukup teratur dan pori-pori yang terbentuk tampak jelas, sedangkan scaffold komposit HA-CHA/Kolagen/PVA/Alginat memiliki struktur morfologi yang tidak teratur dan pori-pori tampak halus. Hasil pengujian EDX menunjukkan sebagian besar scaffold tersusun atas unsur karbon (C), oksigen (O), kalsium (Ca), dan fosfor (P). Hasil uji FTIR menunjukkan adanya keidentikan senyawa yang dihasilkan dan tidak terbentuk gugus fungsi baru. Hasil analisis XRD menunjukkan semakin besar kandungan organik dalam sampel akan memperkecil ukuran kristalit dan derajat kristalinitas dari scaffold., The methods of bone grafting that are known today are autograft, allograft, and xenograft. Although these method is proven to repair damaged bone tissue, but these techniques still have many limitations that can lead to inhibition of the treatment process. These limitations can be overcome by using a synthetic bone graft (scaffold). The focus of this study is synthesizing HA-CHA/Collagen/Alginate and HA-CHA/Collagen/PVA/Alginat composite scaffold using freeze-drying methods. Scaffold made by varying the composition between inorganic components (HA, CHA) and organic components (polymers) with inorganic:organic ratio is 25:75, 50:50, 75:25 and HA:CHA respectively 100:0, 75:25, 50:50, 25:75, 0:100. The synthesis results are characterized by SEM-EDX, FTIR, and XRD. The SEM results showed that the HA-CHA/Collagen/Alginate composite scaffold has a fairly regular morphological structure and the pores formed are clearly visible, while the HA-CHA/Collagen/PVA/Alginate composite scaffold has an irregular morphological structure and the pores look smooth. The EDX results test showed that most scaffolds are composed of the elements carbon (C), oxygen (O), calcium (Ca), and phosphorus (P). The results of the FTIR test showed the compounds produced are identical and do not form a new functional group. The results of XRD analysis showed that the greater organic content in the sample will reduce the size of the crystalline and crystallinity of the scaffold.
Keyword: Bone graft, composite scaffold, freeze-drying, inorganic-organic

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