Judul: Analisis Kestabilan Model Mangsa- Pemangsa Michaelis-Menten dengan Pemanenan Tidak Konstan pada Populasi Pemangsa
Abstrak: Pada karya ilmiah ini dikembangkan sistem mangsa-pemangsa Michaelis- Menten dengan pemanenan tidak konstan pada populasi pemangsa. Parameter yang dipilih untuk melihat dinamika solusi pada sistem adalah koefisien penangkapan dan usaha luar dalam pemanenan yang berpengaruh terhadap kepunahan pemangsa. Dalam karya ilmiah ini ditunjukkan bahwa jika koefisien penangkapan diperbesar maka daerah pemilihan nilai awal kedua populasi yang menyebabkan kepunahan pemangsa akan semakin bertambah. Sedangkan jika besar usaha dalam pemanenan diperbesar maka daerah pemilihan nilai awal kedua populasi yang menyebabkan kepunahan pemangsa akan semakin berkurang. Dinamika populasi mangsa-pemangsa pada sistem ditunjukkan dengan adanya bifurkasi Hopf yang terlihat dari munculnya siklus limit akibat dari perubahan kestabilan yang ditunjukkan melalui simulasi.
Keyword: bifurkasi Hopf, Michaelis-Menten, limit cycle, mangsa-pemangsa, pemanenan

Judul: Analisis model mangsa pemangsa Michaelis-Menten dengan pemanenan pada populasi mangsa
Abstrak: In this manuscript, the dynamics of prey-predator model of Michaelis-Menten is discussed with harvesting on prey populations. Based on the analysis conducted, it was obtained four steady states with characteristics stable, saddle, unstable depending on the value of parameters used. A computer simulation was also carried out to show its dynamics by varying the parameter values. In order to prevent the extinction of the prey and predator, the harvesting level should be lower than maximum limit. The maximum limit of the harvesting level is a quarter of the prey population. If the harvesting level exceeds a quarter of the prey population, then the system has no steady state and both species will be extinct.
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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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