Judul: pH Analysis of Tapanuli Orangutan Diet
Abstrak: Tapanuli orangutans are the newest and most endangered great ape species that have been known. Meanwhile, the pH values of Tapanuli orangutan diet is not available. Therefore, the aim of this study is to analysis the pH values of Tapanuli orangutan diet. The study was conducted from February to April 2019 at Camp Mayang, Batang Toru Research Station, North Sumatera. Next, foraging activity data were collected using focal animal sampling method. The pH values of diet sample were measured by MColorpHastTM as universal indicator of pH. SPSS 16.0 software was used in data processing. Data analysis was done with Shapiro-Wilk for normality test, while Kruskal-Wallis and Mann-Whitney for significant diferences test. In this study, five Tapanuli orangutans, two adolescent female and three adult female, have been followed. Fruits are their dominant food types. Camnosperma auriculatum fruits are their dominant diet during the observation. There is no significant differences between adolescent and adult female Tapanuli orangutans in the numbers of diet items at each pH values. On one hand, Tapanuli orangutan diets have pH values range between 3-7. On the other hand, Bornean and Sumatran orangutans prefer to eat fruits with range of pH values between 4-5.
Keyword: diet, food types, foraging activity, pH values, Tapanuli orangutans

Judul: Daily Activities and Food Selection Bornean Orangutan (Pongo pygmaeus) at Taru Jurug Animal Park, Surakarta City
Abstrak: Orangutan Kalimantan atau Bornean Orangutan (Pongo pygmaeus) merupakan satwa endemik yang hanya dapat dijumpai di Pulau Kalimantan dan tergolong ke dalam ordo Primata serta famili Hominidae. Pada umumnya, aktivitas harian yang biasa dilakukan orangutan diantaranya ialah makan, bergerak, istirahat, dan sosial. Orangutan sebagai satwa yang termasuk frugivor cenderung memiliki preferensi pakan pada buah. Penelitian ini bertujuan menganalisis aktivitas harian, preferensi pakan, serta palatabilitas pakan yang dikonsumsi orangutan kalimantan di Taman Satwa Taru Jurug, Kota Surakarta. Subjek yang diamati ialah dua individu orangutan berjenis kelamin betina dan jantan. Metode yang digunakan ialah focal animal sampling, penyajian pakan berupa cafetaria, penimbangan bobot konsumsi pakan. Hasil pengamatan menunjukkan bahwa lokomosi dan istirahat menjadi aktivitas yang dominan dilakukan oleh individu tori (♀) dan didi (♂). Apel, pear, pisang dan tempe rebus menjadi preferensi pakan dari kedua individu tersebut dengan bobot konsumsi pakan yang tidak berbeda signifikan berdasarkan perhitungan uji t terhadap jenis kelamin dengan jumlah bobot konsumsi pakan., Bornean Orangutan (Pongo pygmaeus) is an endemic animal that can only be found on the island of Borneo and belongs to the order Primate and family Hominidae. Orangutans' daily activities generally include eating, moving, resting, and social activity. Orangutans, as frugivores, tend to have a preference for food on fruit. This study aims to analyze the daily activities, feed preferences, and palatability of the feed consumed by the Bornean orangutan at Taru Jurug Animal Park, Surakarta City. The subjects observed were two male and female orangutans. The method used was focal animal sampling, serving food in the form of a cafeteria, and weighing feed consumption. The results showed that locomotion and resting were the dominant activities carried out by tori (♀) and didi (♂). Apples, pears, bananas, and boiled tempeh became the feed preferences of the two individuals with feed consumption weights that were not significantly different based on the calculation of the t-test for sex with the total weight of feed consumption.
Keyword: endemic, focal animal sampling, palatability, preference, Taru Jurug Animal Park

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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