Judul: Peningkatan Fiksasi N2 oleh Bakteri setelah Penambahan Magnetit dan Kitosan‑Magnetit
Abstrak: Free‑living N2‑fixing bacteria are essential in the soil because they provide a source of nitrogen in the form of ammonium needed by plants to be used in building protein blocks. The fixation of free N2 needs to be increased by adding nanomaterials such as magnetite (Fe3O4), which has an active group and can be a source of nitrogenase enzyme cofactor. In this study, increased N2 fixation used N2‑fixing bacteria in Burks medium. This increase was determined by measuring NH3 levels using the Phenate method formed after Burks medium was treated with Fe3O4 and chitosan‑magnetite (CS‑Fe3O4). The study found that the number of bacteria can be well immobilized. The media treated with Fe3O4 and CS‑Fe3O4 increased ammonium levels by 15.40% and 75.54%, respectively., Bakteri pengikat N2 yang hidup bebas sangat penting keberadaannya di dalam tanah karena menyediakan sumber nitrogen dalam bentuk amonium yang diperlukan oleh tanaman yang akan digunakan dalam membangun blok protein. Fiksasi N2 bebas perlu ditingkatkan dengan penambahan nanomaterial seperti magnetit (Fe3O4), yang memiliki gugus aktif dan dapat menjadi sumber kofaktor enzim nitrogenase. Pada penelitian ini, peningkatan fiksasi N2 menggunakan bakteri pemfiksasi N2 dalam medium Burks. Peningkatan ditentukan dengan mengukur kadar NH3 menggunakan metode Phenate yang terbentuk setelah medium Burks diperlakukan dengan Fe3O4 dan kitosan-magnetit (CS‑Fe3O4). Penelitian ini menemukan bahwa jumlah bakteri dapat terimobilisasi dengan baik. Kadar amonium media dengan perlakuan Fe3O4 dan CS‑Fe3O4 meningkat, berturut‑turut sebesar 15.40% dan 75.54%.
Keyword: bacteria, chitosan, composite, Fe3O4, NH3‑N

Judul: Efektivitas fiksasi N2 dan oksidasi metan kultur campuran bakteri metanotrof asal sawah
Abstrak: Sebagian besar emisi CH4 di lahan sawah yang tergenang diproduksi oleh bakteri metanogen dan sebanyak 80 % dari CH4 tersebut dioksidasi oleh bakteri metanotrof. Selain kemampuan mengoksidasi metan, metanotrof juga memiliki kemampuan memfiksasi nitrogen. Empat isolat metanotrof dengan kemampuan fiksasi nitrogen (BGM 1, BGM 3, BGM 5, dan BGM 9) masing-masing dikombinasikan dengan isolat metanotrof yang memiliki aktivitas oksidasi metan tinggi (SKM 14) untuk mendapatkan formulasi metanotrof yang tinggi aktivitas fiksasi nitrogen dan oksidasi metan-nya. Kemampuan fiksasi nitrogen diukur dari kadar amonium yang diakumulasikan dalam medium pertumbuhannya dan aktivitas reduksi asetilen (ARA). Akumulasi amonium tertinggi dicapai oleh kultur BGM 1 untuk kultur tunggal (1,86 μM amonium), dan kultur BGM 3/BGM 9 untuk kultur kombinasi (4,905 μM amonium). Aktivitas nitrogenase tertinggi ditunjukkan oleh kombinasi BGM 1/SKM 14 (11,27 μmol/ml kultur/hari), sedangkan aktivitas oksidasi metan tertinggi dicapai oleh kultur campuran BGM 5/BGM 9 (18,20 ppm/ml kultur/hari).
Keyword: Metan, Bakteri metanotrof, ARA, Fiksasi nitrogen, Oksidasi metan, Bogor Agricultural University, Institut Pertanian Bogor, IPB

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