Judul: Simulasi Model Biosensor Berbasis Multi Enzim dengan Penambahan Faktor pH
Abstrak: Penelitian ini membahas mekanisme difusi reagen pada biosensor berbasis multi enzim. Model yang digunakan dibentuk dari persamaan difusi dengan faktor nonlinier Michaelis-Menten akibat reaksi kimia yang terjadi pada membran katalitik. Persamaan difusi tersebut direkonstruksi sehingga hanya mengandung besaran tak berdimensi dan diselesaikan menggunakan metode beda hingga eksplisit. Pada penelitian ini, faktor pH lingkungan dipertimbangkan dan dimasukan kedalam model biosensor berbasis multi enzim. Solusi numerik berupa mekanisme difusi dan keluaran fluks listrik diperoleh pada variasi pH lingkungan tertentu. Secara keseluruhan solusi numerik model tersebut menunjukkan bahwa pada pH yang tinggi laju difusi berlangsung lebih cepat dan keluaran fluks listrik lebih besar. Selain itu, pH lingkungan dapat mempengaruhi besar signifikansi dari kondisi parameter kimia yang berbeda seperti konstanta laju reaksi dan konstanta disosiasi asam-basa., This research discusses the mechanism of reagent diffusion in multi-enzyme-based biosensors. The model used is formed from the diffusion equation with the Michaelis-Menten nonlinear factor due to chemical reactions that occur in the catalytic membrane. The diffusion equation is reconstructed so that it only contains dimensionless quantities and being solved using the explicit finite difference method. In this study, environmental pH factors were considered and included in the multi-enzyme-based biosensor model. Numerical solutions in the form of diffusion mechanisms and electric flux outputs are obtained at some environmental pH variations. Overall, the numerical solution of the model shows that at high pH the diffusion rate is faster and the electric flux output is greater. In addition, the environmental pH can significantly affect the conditions of different chemical parameters such as the reaction rate constant and the acid-base dissociation constant.
Keyword: biosensor multi enzim, metode beda hingga, biosensor berbasis pH, kinetika enzimatik, multi-enzyme biosensor, finite difference method, pH based biosensor, enzyme kinetics

Judul: Simulation of Biosensor Multienzyme Based Model
Abstrak: Pengukuran zat oleh biosensor multi enzim didasarkan pada reaksi kimia antara zat dengan enzim sehingga menghasilkan produk dan elektron yang ditangkap oleh elektroda pada biosensor. Laju reaksi kimia tersebut dipandang sebagai persamaan diferensial parsial. Persamaan tersebut diubah menjadi persamaan tak berdimensi untuk mengurangi kemungkinan kesalahan pada dimensi yang digunakan. Persamaan tak berdimensi tersebut diselesaikan menggunakan metode finite difference dengan bantuan perangkat lunak Matlab. Hasil dari solusi tersebut menggambarkan perubahan nilai konsentrasi dari setiap reagen pada reaksi kimia tersebut. Adapun untuk melihat pengaruh dari variabel yang ada terhadap perubahan nilai konsentrasi dari setiap reagen dilakukan analisis variasi variabel terhadap perubahan nilai konsentrasi dari setiap reagen. Hasil penelitian menunjukkan bahwa setiap reagen yang diukur dipengaruhi oleh konstanta reaksi yang merupakan sifat dari setiap reagen. Hasil tersebut juga memberikan gambaran perlu adanya penyesuaian ketebalan membran agar mendapatkan hasil pengukuran yang akurat dan efisien. Model simulasi biosensor multi enzim ini diharapkan dapat dikembangkan kembali dengan menambahkan hasil pengukuran berupa arus listrik yang dihasilkan oleh biosensor. Pengembangan tersebut diharapkan dapat menghasilkan biosensor yang lebih akurat dan efisien., Measurement of substances by multi-enzyme biosensors is based on chemical reactions between substances and enzymes so that products and electrons are captured by the electrodes on the biosensor. The rate of the chemical reaction is viewed as a partial differential equation. The equation is converted into a dimensionless equation to reduce the possibility of errors in the dimensions used. The dimensionless equation is solved using the finite difference method with the help of Matlab software. The result of the solution describes the change in the concentration value of each reagent in the chemical reaction. Meanwhile, to see the effect of the existing variables on changes in the concentration value of each reagent, an analysis of the variation of variables was carried out on changes in the concentration value of each reagent. The results showed that each measured reagent is influenced by the reaction constant which is the nature of each reagent. These results also illustrate the need for membrane thickness adjustments in order to obtain accurate and efficient measurement results. This multi-enzyme biosensor simulation model is expected to be redeveloped by adding measurement results in the form of electric current generated by the biosensor. This development is expected to produce more accurate and efficient biosensors.
Keyword: biosensor multi enzim, metode finite difference, persamaan diferensial parsial, reaksi kimia, multi-enzyme biosensor, finite difference method, partial differential equation, chemical reaction

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