Judul: Abundance of Bleeding Frog (Leptophryne cruentata) at Cibodas, Tegallega, and Cisarua Resorts, Gunung Gede Pangrango National Park
Abstrak: Kodok merah (L. cruentata) merupakan salah satu jenis katak yang dianggap populasinya terus menurun selama 40 tahun terakhir. Monitoring kelimpahan dan kualitas habitat spesies ini harus terus dilakukan. Tujuan dari penelitian ini menduga kelimpahan dan mengidentifikasi mikrohabitat kodok merah serta katak jenis lainnya. Penelitian ini dilakukan di 6 lokasi di Taman Nasional Gunung Gede Pangrango pada Resort Cibodas, Tegallega, dan Cisarua dengan menggunakan metode perjumpaan langsung yang dikombinasikan dengan transek sampling. Kelimpahan paling tinggi kodok merah dijumpai di Curug Pariuk dengan kelimpahan per 100 m sebanyak 22,7 ± 23,6 ind/100 m. Kodok merah dapat hidup di sungai beraliran lambat dan deras. Salah satunya yaitu Curug Pariuk yang memiliki karakteristik curug berarus deras (50-100 cm/dtk), tutupan kanopi rapat (61-80%) sampai sangat rapat (81-100%), serta minim aktivitas manusia. Selain itu, kodok merah juga ditemukan di aliran sungai lambat seperti di Curug Ceret, Curug Cibeureum, Rawa Gayonggong, dan Sungai Jajaway. Selama penelitian berlangsung ditemukan 9 jenis katak yang menempati habitat yang sama dengan kodok merah., The population of bleeding toad (L. cruentata) is considered to continuously decline over the last 40 years. Therefor, monitoring the abundance and quality of the habitat of this species should be done regularly. The purpose of this study was to estimate abundance and identify the microhabitat of bleeding toads and other frogs. This research was conducted in 6 locations in Gunung Gede Pangrango National Park at Resorts Cibodas, Tegallega, and Cisarua using the visual encounter survey method combined with transect sampling. The highest abundance of bleeding toad (L. cruentata) was found in Pariuk waterfall with an abundance per 100 m of 22,7 ± 23,6 ind. Bleeding toads can live in slow and fast flowing rivers. One of them is Pariuk waterfall which has the characteristics of a waterfall with a fast current (50-100 cm/sec), dense canopy cover (61-80%) to very dense (81-100%), and minimal human activity. In addition, bleeding frogs are also found in slow river flows such as Ceret Waterfall, Cibeureum Waterfall, Rawa Gayonggong, and the Jajaway River. During the research, 9 species of frogs were found that occupy the same habitat as the bleeding toad.
Keyword: Kelimpahan, Kodok merah, mikrohabitat, Penurunan populasi

Judul: The Abundance of Hour-Glass Toad (Leptophryne borbonica Tschudi, 1838) at Bodogol Resort Gunung Gede Pangrango National Park
Abstrak: Leptophryne borbonica merupakan jenis amfibi yang bergantung pada aliran sungai, kondisi fisik sungai akan mempengaruhi kelimpahan dari L. borbonica. Monitoring populasi perlu dilakukan untuk mengetahui perbedaan kelimpahan antar waktu. Tujuan dari penelitian ini menduga kelimpahan L. borbonica dan komposisi jenis lainnya serta identifikasi penggunaan mikrohabitat L. borbonica di Resort Bodogol TN Gunung Gede Pangrango. Penelitian dilakukan di Sungai Cisuren dan Sungai Cikaweni menggunakan metode perjumpaan visual dikombinasikan dengan transek sampling. Penelitian ini memperoleh 12 jenis amfibi dari 5 famili berbeda. Leptophryne borbonica, Limnonectes kuhlii, Megophrys montana, dan Chalcorana chalconota merupakan 4 spesies dominan yang ditemukan di setiap lokasi pengamatan dengan nilai kelimpahan tertinggi. Rata-rata kelimpahan L. borbonica di Sungai Cisuren yaitu 18,70 ± 7,79 ind/100 m, di Sungai Cikaweni-1 rata-rata kelimpahan yaitu 0,80 ± 1,17 ind/100 m, dan di Sungai Cikaweni-2 rata-rata kelimpahan yaitu 0,20 ± 0,40 ind/100 m. Leptophryne borbonica dapat ditemukan di sungai kecil yang mengalir sepanjang tahun dengan kondisi air yang jernih, kecepatan arus sungai tergolong lambat hingga sedang, ditemukan pada substrat batu, dan ditemukan menempel di dedaunan sekitar sungai. Kata kunci: kelimpahan, kodok jam pasir, sungai
Keyword: Abundance, Hour-glass toad, Stream

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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