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: Lejeuneaceae Subfamily Ptychanthoideae (Hepaticae) in  West Java
Abstrak: Subfamily Ptychanthoideae of the family Lejeuneaceae (Hepaticae) in West Java is still poorly known. Publications on this subfamily are out of dated and written in the 19th or early of 20th century. The last taxonomic treatment of Ptychanthoideae of West Java was in 1933, many species names have changed since then. Studies on Ptychanthoideae of West Java are urgently needed. Studies on the Ptychanthoideae were based on the specimens collected from West Java. A total number of 361 of specimens deposited in the Herbarium Bogoriense (BO), Herbarium Biotrop (BIOT), Gottingen Herbarium (GOET) and Bangi Herbarium (UKMB) were examined, those are old and several recent specimens collected in West Java. Recent collections were made from Telaga Warna, Ciater, Gunung Halimun Salak National Park, Cibodas Botanical Garden, Bodogol Education Center and Conservation (Gunung Gede Pangrango National Park), University of Indonesia Campus Depok, including several collections from Banten Province. Twenty four species of Lejeuneaceae subfamily Ptychanthoideae are known from West Java, belonging to 8 genera namely Acrolejeunea (Spruce) Schiffn. (2 species), Archilejeunea (Spruce) Schiffn. (1 species), Lopholejeunea (Spruce) Schiffn. (10 species), Mastigolejeunea (Spruce) Schiffn. (3 species), Ptychanthus Nees (1 species), Schiffneriolejeunea Verd. (1 species), Spruceanthus Verd. (2 species) and Thysananthus Lindenb. (4 species). Two new records of Ptychanthoideae: Mastigolejeunea indica Steph. and Thysananthus minor Verdoorn are reported for Java. A determination key to the species is presented including their descriptions and illustrations.
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