Judul: Simulation of The Biosensor Model Based on One Enzyme with the Effect of Damköhler Number
Abstrak: Model matematika biosensor berbasis satu enzim dengan faktor bilangan Damköhler menggambarkan rasio antara laju difusi dan reaksi biosensor. Model ini melibatkan dua persamaan difusi dan reaksi waktu dengan mekanisme laju reaksi Michaelis-Menten. Persamaan diferensial parsial diubah menjadi bentuk tak berdimensi dengan parameter baru, dan diselesaikan menggunakan metode numerik beda hingga secara eksplisit, diprogram dengan Octave/Matlab. Hasil perhitungan numerik menunjukkan kekekalan massa antara substrat dan produk, membuktikan validitas solusi numerik model ini. Solusi numerik menggambarkan konsentrasi substrat dan produk dalam lapisan enzimatik serta respons arus biosensor. Perubahan parameter dapat mempengaruhi laju difusi dan reaksi. Model ini diharapkan dapat dikembangkan lebih lanjut untuk jenis enzim dan analit tertentu, serta nilai parameter divalidasi dengan data eksperimen untuk mengoptimalkan model biosensor., The mathematical model of a single-enzyme-based biosensor with the Damköhler number factor describes the ratio between diffusion rate and reaction rate in the biosensor. This model involves two time-dependent diffusion and reaction equations with the Michaelis-Menten reaction rate mechanism. The partial differential equations are transformed into a dimensionless form with new parameters and solved using the explicit finite difference numerical method, programmed in Octave/Matlab. The numerical results show mass conservation between substrate and product, validating the numerical solution of this model. The numerical solution depicts the concentration of substrate and product within the enzymatic layer and the current response generated by the biosensor. Changes in parameters can affect the diffusion and reaction rates. This model is expected to be further developed for specific types of enzymes and analytes, with parameter values validated against experimental data to optimize the biosensor model.
Keyword: enzim, biosensor, bilangan Damköhler, metode beda hingga, persamaan diferensial parsial

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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