Judul: Manipulasi alat untuk mendapatkan ganjaran makanan di lar gibbons (Hylobates lar)
Abstrak: Tool manipulation in Hylobates lar has not been well documented in Malaysia. The main aim of this study is to assess whether lar gibbons are capable of manipulating objects to obtain a food reward. We assessed whether lar gibbons can learn to pull on a rake-like object to gain a food reward without specific training. The main task that is to be observed is the pulling of a rake-like rod to obtain a food reward with a time limit of 60 minutes. All the gibbons managed to obtain the reward at least once throughout the five trials. The gibbons are seen using a trial-error approach which proved to be successful in obtaining the reward. Female gibbons were also observed to be more cautious in attending to a new task or object compared to male gibbons. This can be seen when female gibbons made more interactions with tools prior successful trial compared to the male gibbons., Manipulasi alat di Hylobates lar belum didokumentasikan dengan baik di Malaysia. Tujuan utama dari penelitian ini adalah untuk menilai apakah owa lar mampu memanipulasi objek untuk mendapatkan ganjaran makanan. Kami menilai apakah owa lar dapat belajar menarik benda seperti penggaruk untuk mendapatkan ganjaran makanan tanpa pelatihan khusus. Tugas utama yang harus diamati adalah menarik garu seperti garu untuk mendapatkan ganjaran makanan dengan batas waktu 60 menit. Semua owa berhasil mendapatkan ganjaran setidaknya sekali selama lima percobaan. Owa terlihat menggunakan pendekatan trial-error yang terbukti berhasil mendapatkan ganjaran. Owa betina juga diamati lebih berhati-hati dalam mengerjakan tugas atau objek baru dibandingkan dengan owa jantan. Hal ini terlihat ketika owa betina lebih banyak berinteraksi dengan alat sebelum percobaan berhasil dibandingkan dengan owa jantan.
Keyword: food reward, gibbon, Hylobates lar, tool manipulation, ganjaran makanan, Hylobates lar, manipulasi alat, owa

Judul: Aktivitas Makan dan Status Gizi Owa Jawa (Hylobates moloch) di Pusat Primata Schmutzer Taman Margasatwa Ragunan Jakarta
Abstrak: Hylobates moloch is endemic Indonesian primate which live in Java. The population of javan gibbon is declining because of the loss of feeds due to the degradation of habitats. This research aims to identify feeding activities, type of feeds, and nutrient status of javan gibbon (Hylobates moloch) in Schmutzer Primate Centre Ragunan Zoo Jakarta. Feeding activities observation was performed using focal animal sampling method which done in the same time with feed palatability. Feeds were given once a day which consist of fruits, vegetables, eggs, and bread. Highest feeding activities was recorded in the feeding given by zoo keeper. Biting and swallowing are the highest was shown Kecil (juvenile) feeding activities of first cage (22.00%). Highest feeding activity in second cage made by Rano (male) was chewing (21.43%) and in the third cage was carried out by Eneng (female) which were biting, chewing, and swallowing each 23.31%. Based on the palatability rank in the three cages, kumak (Lactuca indica) and banana (Musa paradisiaca) was categorized as the most favored feed. Based on the nutrient status, it was obtained that dry materials were consumed 683,83 to 1099,03 g/cage/day, protein consumption 13,13 to 19,37 g/cage/day, fat consumption 4,58 to 8,51 g/cage/day, and energy consumption from 594,64 to 1154,50 kal/cage/day.
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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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