Judul: Model mangsa-pemangsa-parasit dengan pemanenan sebagai control terhadap penyakit
Abstrak: Predator-prey interaction in presence of parasite can change the system stability in the population. This study aims to analyze the stability of predator-prey-parasite model with harvesting as a disease control measure and to study the effects of decreasing or increasing the harvesting process to the disease. Predator-prey-parasite with harvesting model is applied to a system with shrimp Penaeidae sp population as prey, Whitespot disease as disease, and blekok birds as predator in estuary waters. Mathematica software is used to carry out some numerical simulations. The results from this study show that harvesting can be used as a tool for controlling disease by choosing certain harvesting way.
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Judul: Analisis Kestabilan Model Mangsa-Pemangsa dengan Interferensi Antarpemangsa
Abstrak: In this study we reconstructed a predator-prey model of three animal species in a food chain, which consist of two species of predator and one species of prey (Feng et al. (2010)). From this model we investigated the effects of interference between predators based on the saturation and competition levels. In the stability analysis five equilibrium points obtained, in which two of them are unstable saddles. The effects of saturation and competition levels to population dynamics is shown by using numerical approach, where four conditions are considered. In the first condition, the saturation level of two predators is bigger than the competition level. In the second condition, the saturation level of two predators is lower than the competition level. In the third condition, the saturation level of predator I is bigger than its competition level, but saturation level of predator II is lower than its competition level. The fourth condition, the saturation level of predator I is lower than its competition level, but saturation level of predator II is bigger than its competition level. In general, the simulation results of the four conditions above, concluded that the saturation level of predator I and competition level of predator II effects the stability of populations, whereas saturation level of predator II and competition level of predator I did not effects the stability of populations.
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Judul: Spektrofotometri derivatif ultra violet untuk penentuan kadar kafein dalam minuman suplemen dan ekstrak teh
Abstrak: Metode spektrofotometri derivatif ultraviolet (SDUV) yang relatif murah, cepat, dan dapat dipercaya dikembangkan untuk analisis kuantitatif kafein dalam minuman suplemen dan teh tanpa pemisahan dari matriksnya. Hasil penentuan kadar kafein yang diperoleh dari metode SDUV dibandingkan dengan hasil kuantifikasi kafein dengan metode kromatografi cair kinerja tinggi (KCKT). Kuantifikasi kafein secara SDUV dilakukan berdasarkan pengukuran amplitudo puncak ke garis dasar pada panjang gelombang 274 nm untuk minuman suplemen dan 293 nm untuk teh. Hasil analisis kafein secara SDUV terhadap minuman suplemen dan teh menunjukkan kadar berturut-turut sebesar 335.99 ppm, dan untuk teh sebesar 1.91%. Hasil analisis kafein secara KCKT terhadap minuman suplemen dan teh menunjukkan kadar berturut-turut sebesar 333.91 ppm dan 1.74%. Analisis secara statistik dengan menggunakan uji t menunjukkan tidak adanya perbedaan yang nyata pada minuman suplemen, namun pada teh terdapat perbedaan yang nyata. Uji F dari kedua contoh tidak menunjukkan perbedaan yang nyata. Uji linearitas pada metode SDUV untuk minuman suplemen dan teh menghasilkan koefisien korelasi (r) masing-masing sebesar 0.9995 dan 0.9991 pada kisaran 2- 10 ppm. Nilai simpangan baku relatif untuk uji ketelitian pada minuman suplemen sebesar 1.26% dan teh sebesar 4.71%. Nilai perolehan kembali adalah 99.17-101.25% untuk minuman suplemen dan 99.50-106.75% untuk teh. Limit deteksi pada minuman suplemen sebesar 0.18 ppm dan pada teh sebesar 0.58 ppm. Nilai limit kuantisasi pada minuman suplemen sebesar 0.54 ppm dan pada teh sebesar 1.76 ppm.
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