Judul: Keanekaragaman Herpetofauna di Areal Siberut Conservation Program (SCP), Pulau Siberut, Kepulauan Mentawai, Sumatera Barat
Abstrak: Based on WWF report (1980) in Siberut, reptiles and amphibians are the least species of vertebrates known in the island. Lack of data and information has become an obstacle in the effort to conserve herpetofauna. This study aims to determine the diversity of herpetofauna at several locations in the surrounding areas of Siberut Conservation Program (SCP), Siberut Island, Mentawai Islands, West Sumatra. The study was conducted on April-May 2007. Fourteen transects were established during survey. The observation was divided into 7 terrestrial paths consisted of T7-T16, Camp SCP, T7, T21, T14, T6 and T9 and 7 aquatic paths consisted of Pungut River, Panggasan River, River 19-15, River T10, Pool 7, and Simorara River, and 2nd Pungut River. Data were recorded by direct observation or Visual Encounter Survey (VES) (Heyer et al. 1994). Observation of terrestrial habitats was conducted using time search methods, while aquatic habitat was search on a- 400 m stream transect. Observations were carried out in the morning (08.00-11.00 am) and night (20.00-23.00 pm) for 3 consecutive days. The total number of herpetofauna found in the whole area of observation at Siberut Conservation Program (SCP) is 40 species, which include 26 species of reptiles and 14 species of amphibians. Most species found are those that inhabit lowlands area and mostly common. There are several species of herpetofauna that need more attention include Python reticulatus, Ophiophagus hannah and Varanus salvator. Compared to several other locations in Sumatra, the biodiversity of herpetofauna in SCP is relatively lower. However, the existence of SCP supported biodiversity which can be shown by the presence of herpetofauna such as Aphaniotis acustirostris and Limnonectes kuhlii. There are several species that have potential benefits for residents such as edible frogs in example Limnonectes blytii, L. paramacrodon and L. shompenorum. Therefore the presence of SCP in North Siberut hascontributed to the awareness of wildlife conservation to the local community.
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Judul: Keanekaragaman Reptil Berdasarkan Perbedaan Ketinggian di Sipirok, Kawasan Hutan Batang Toru, Provinsi Sumatra Utara
Abstrak: Kawasan Hutan Batang Toru merupakan salah satu hutan penting di Sumatra Utara. Penelitian ini menganalisis keanekaragaman reptil berdasarkan perbedaan ketinggian di Sipirok, Kawasan Hutan Batang Toru. Pengambilan data dilakukan pada Februari sampai April 2020, mulai dari ketinggian 400 sampai 1400 m dpl, dengan rentang ketinggian 200 meter menggunakan metode Visual Encounter Survey (VES) dan pemasangan jebakan lem. Tercatat 27 jenis reptil dan 107 individu dimana hanya 17 jenis (Sauria 8 jenis, Ophidia 9 jenis) dan 67 individu ditemukan di jalur pengamatan. Tiga jenis reptil masuk dalam Appendiks II CITES yaitu Varanus salvator, Naja sumatrana dan Ophiophagus hannah. Tidak terdapat jenis endemik yang ditemukan. Kelimpahan reptil mengikuti pola keanekaragaman jenis yaitu cenderung meningkat sampai rentang ketinggian 800 sampai 999 m dpl lalu menurun dengan meningkatnya ketinggian. Cyrtodactylus marmoratus merupakan satu-satunya jenis yang hidup menyebar di dataran rendah sampai tinggi. Terdapat kecenderungan penurunan keanekaragaman jenis dan kemerataan seiring peningkatan ketinggian. Nilai indeks kesamaan komunitas relatif rendah menunjukkan setiap ketinggian memiliki komunitas reptil berbeda.
Keyword: keanekaragaman reptil, ketinggian, ophidia, sauria

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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