Judul: Functionalization of Agar Processing Waste-Derived Nanocellulose with Silver Nanoparticles for Antibacterial Hydrogel Production
Abstrak: Limbah padat pengolahan agar ditransformasi menjadi nanoselulosa untuk diaplikasikan dalam berbagai bidang. Penelitian bertujuan mendapatkan nanofibril selulosa dari limbah padat pengolahan agar-agar, menentukan pengaruh fikosianin sebagai reducting agent dalam fungsionalisasi nanoselulosa dengan nanopartikel perak (CNF/AgNPs), menentukan aktivitas antibakteri dari hidrogel alginat yang diimobilisasi CNF/AgNPs. Nanofibril selulosa (CNF) telah berhasil diperoleh dengan perlakuan Hydated Deep Eutectic Solvent (choline chloride:oxalic acid) dengan diameter fiber dan nilai kristalinitas masing-masing sebesar 80,37±1,06 nm dan 85,66%. Nanofibril selulosa berhasil difungsionalisasikan dengan nanopartikel perak (AgNPs) menggunakan fikosianin sebagai reducting agent. Gugus fungsi aldehida (C=O) pada bilangan gelombang 1729 cm-1 dalam nanofibril selulosa berhasil berikatan dengan AgNPs. Hidrogel alginat yang diimobilisasi perlakuan CNF/AgNPs 20% memiliki aktivitas antibakteri tertinggi pada bakteri Gram negatif Pseudomonas aeruginosa, namun aktivitas antibakteri terhadap bakteri Gram positif Propionibacterium acne dan Staphylococcus aureus tidak berbeda nyata dengan perlakuan lainnya. Imobilisasi CNF/AgNPs pada hydrogel alginate memiliki potensi untuk diaplikasikan sebagai antibacterial wound dressing., Solid agar processing waste is transformed into nanocellulose for various applications. The research aim to obtain cellulose nanofibrils from solid agar processing waste, determine the influence of phycocyanin as a reducting agent in the functionalization of nanocellulose with silver nanoparticles (CNF/AgNPs), and assess the antibacterial activity of alginate hydrogel immobilized with CNF/AgNPs. Cellulose Nanofibrils (CNF) were successfully obtained through treatment with a Hydrated Deep Eutectic Solvent (chlorine chloride:oxalic acid), with fiber diameter and crystalinity index (CI) values of 80.37±1.06 nm and 85.66% respectively. Nanofibril cellulose was successfully functionalized with silver nanoparticles (AgNPs) using phycocyanin as a reducting agent. The aldehyde functional group (C=O) at the wavenumber of 1729 cm-1 in nanocellulose successfully bonded with AgNPs. Alginat hydrogel immobilized with 20% CNF/AgNPs treatment exhibited the highest antibacterial activity against Gram-negative bacterium Pseudomonas aeruginosa, while the antibacterial activities against Gram-positive Propionibacterium acne and Staphylococcus aureus did not significantly differ from other treatment. Immobilized of CNF/AgNPs in alginate hydrogel holds potential for application as an antibacterial wound dressing.
Keyword: DES, Fikosianin, Nanopartikel perak, Nanoselulosa, Rumput laut, Wound dressing

Judul: Nanokristalin Selulosa dari Limbah Padat Industri Agar-agar sebagai Filler pada Film Bionanokomposit Berbasis Polivinil Alkohol
Abstrak: Industri pengolahan agar-agar menghasilkan 65-70% limbah berserat padat yang mengandung selulosa tinggi. Tingginya kandungan selulosa, membuat limbah padat agar-agar berpotensi sebagai bahan baku dalam pembuatan nanokristalin selulosa (NCC). Nanokristalin selulosa dapat digunakan sebagai filler penguat polimer. Hidrolisis asam kuat H2SO4 40% (v/v) selama 1 jam dan ultrasonik (A=40%) selama 1 jam menghasilkan NCC dengan ukuran sebesar 458.7 nm, derajat putih 99.65%, dan derajat kristalinitas 50.97% dengan ukuran kristal sebesar 7.77 nm. Penambahan nanokristalin selulosa sebagai filler pada film bionanokomposit dapat meningkatkan karakteristik mekaniknya. Perlakuan yang diberikan pada film bionanokomposit yaitu penambahan konsentrasi NCC 3%, 5%, dan 8%. Film bionanokomposit dengan penambahan nanokristalin selulosa 3% dapat meningkatkan kuat tarik dan elongasi yang nilainya masingmasing 100.44 MPa dan 250 %, serta menurunkan laju transmisi uap air sebesar 0.43 ± 0.06 g s-1m-2.
Keyword: bionanocomposite filler, nanocrystalline cellulose, solid waste of agar

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