Judul: Dinamika Sistem Mangsa-Pemangsa Fitoplankton-Zooplankton dengan Mangsa Fitoplankton yang Terinfeksi Virus
Abstrak: Dalam tulisan ini dipelajari model populasi fitoplankton sebagai mangsa yang terinfeksi virus dan zooplankton sebagai pemangsa dengan menggunakan respon fungsional dari Holling II. Model tersebut dianalisis sehingga diperoleh enam titik tetap. Berdasarkan nilai eigen dari hasil pelinearan tiga titik tetap pertama diperoleh empat kasus kestabilan yang berbeda. Dinamika model digambarkan dengan bantuan software Matematica 5.2. Secara keseluruhan dari setiap kasus yang diamati, kestabilan populasi fitoplankton terinfeksi bergantung pada penyebaran virus dan angka kematian dari fitoplankton yang terinfeksi. Jika laju penyebaran virus lebih besar dari angka kematian fitoplankton yang terinfeksi, maka populasi fitoplankton yang terinfeksi virus dapat bertahan hidup. Jika laju penyebaran virus lebih kecil dari angka kematian fitoplankton yang terinfeksi, populasi fitoplankton yang terinfeksi akan menuju kepunahan
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Judul: Pengaruh Infeksi Virus pada Phytoplankton dan Racun yang Dihasilkan Phytoplankton dalam Model Interaksi Phytoplankton-Zooplankton
Abstrak: Interaction of phytoplankton and zooplankton can be considered as a prey-predator interaction, where phytoplankton as prey and zooplankton as predator. This interaction is modeled into mathematical equations that was investigated by Gakkhar & Negi (2005). This model studied the effect of viral infection on phytoplanktons and the toxin produced by phytoplankton. In this model, phytoplanktons are divided into two groups, suspectible phytoplankton and infected phytoplankton. Hopf bifurcation describes the stability changes of population. The Hopf bifurcation occurs when the rate of viral infection and the toxin quantity produced by phytoplakton were changed. Both phytoplankton and zooplankton populations stable when the infection rate and toxin quantity are low. If the viral infection rate and toxin quantity increase then phytoplankton and zooplankton populations became unstable. If the viral infection rate and the toxin quantity relatively high then the zooplankton population would lead to extinction
Keyword: zooplankton, phytoplankton, toxin, viral infection, Hopf bifurcation

Judul: Development of ready-to-drink white tea shot.
Abstrak: White tea leaf has been shown to possess physiological activities and has catechin which is the most abundant antioxidant compound found. This study was conducted to develop white tea shot formulated with white tea extract (WTE), ascorbic acid (AA), and sucrose (SC) in order to get high stability of catechin in the product. The first part of the study was conducted to choose best formula of white tea shot. The amount of water was set at 50 ml while WTE was set at 0.4% water basis. AA and SC amount were varied at 0.02, 0.05, 0.10% for AA and 3.0 and 6.0% for SC. The formula chosen was consists of 50 ml water, 0.4 % WTE, 0.10% AA, and 6.0% of SC. The decision was based on the rating hedonic test and short time storage catechin stability analysis of six formulation which the chosen formula revealed the least catechin lost and acceptable overall product likeness. The study also revealed that addition of AA is significant to lower catechin loss (P<0.05) while addition of SC did not reveal any effect (P>0.05). Physical, chemical, and microbiological characteristic was also observed in this study.
Keyword: Catechin, product development, white tea