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: Simulation of One Enzyme-Based Biosensor Model with the Addition of pH Factor
Abstrak: Model matematika pada biosensor berbasis satu enzim dengan penambahan pH didasarkan pada sistem persamaan difusi dan reaksi bergantung waktu yang menggambarkan mekanisme laju reaksi substrat dan produk yang sesuai dengan reaksi katalis Michaelis-Menten. Model tersebut dideskripsikan melalui bentuk persamaan diferensial parsial, lalu persamaan tersebut diubah dalam bentuk tak berdimensi dengan cara mereduksi parameter-parameter dari persamaan. Persamaan tersebut diselesaikan menggunakan metode beda hingga secara eksplisit dan perangkat lunak MATLAB. Hasil simulasi divalidasi melalui proses kekekalan massa pada reaksi substrat dan produk. Solusi numerik dari penelitian ini dapat menggambarkan konsentrasi substrat dan produk serta respons arus listrik di dalam lapisan enzimatik ketika ditambahkan pH. Perubahan nilai parameter-parameter dalam model dapat menyebabkan perubahan dalam proses laju difusi dan reaksi. Penambahan pH dalam simulasi ini mempercepat laju reaksi substrat-produk serta melihat lebih teliti puncak arus listrik yang dihasilkan pada saat biosensor bekerja. Model biosensor berbasis satu enzim dengan penambahan pH ini diharapkan dapat dikembangkan lebih lanjut dengan fokus pada jenis enzim dan analit yang spesifik. Nilai parameter-parameter yang digunakan dalam penelitian ini dapat disempurnakan melalui studi literatur ataupun eksperimen untuk lebih mengoptimalkan model ini., The mathematical model of a single enzyme-based biosensor with pH addition is based on a system of time-dependent diffusion and reaction equations that describe the mechanism of substrate and product reaction rates corresponding to the Michaelis-Menten catalyst reaction. The model is described through the form of partial differential equations, then the equations are converted into dimensionless form by reducing the parameters of the equations. The equation is solved using the explicit finite difference method and MATLAB software. The simulation results are validated through the mass conservation process in the substrate and product reactions. The numerical solution of this study can describe the substrate and product concentrations as well as the electric current response in the enzymatic layer when pH is added. Changes in the values of the parameters in the model can cause changes in the diffusion and reaction rate processes. The addition of pH in this simulation accelerates the substrate-product reaction rate and looks more closely at the peak of the generated electric current when the biosensor is working. This single enzyme-based biosensor model with pH addition is expected to be further developed with a focus on specific types of enzymes and analytes. The values of the parameters used in this research can be refined through literature studies or experiments to further optimize this model.
Keyword: biosensor, enzim, metode beda hingga, pH, biosensor, enzyme, finite difference method, pH

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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