Judul: Distribution and Density of Sympatric Agile Gibbon (Hylobates agilis) and Siamang (Symphalangus syndactylus) in Batang Toru Forest, North Sumatera.
Abstrak: Ungko (Hylobates agilis) dan siamang (Symphalangus syndactylus) termasuk keluarga Hylobatidae yang dapat dijumpai di Hutan Sumatera. Keduanya merupakan primata arboreal yang hidup dalam kelompok monogami dan memiliki banyak kemiripan termasuk kebutuhan hidup dan perilakunya. Keduanya memiliki banyak kemiripan dan dapat hidup dalam satu area yang sama (simpatrik), salah satunya di Kawasan Hutan Batang Toru (KHBT). Saat ini, keduanya terancam keberadaanya akibat perubahan dan degradasi hutan. Tujuan penelitian adalah untuk mengetahui dan mempelajari distribusi, kepadatan dan pemilihan waktu bersuara kedua spesies simpatrik. Metode pengumpulan data yang digunakan dalam penelitian adalah triangle count dan VES (Visual Encounter Survey). Triangle count dilakukan untuk mendapatkan kepadatan, distribusi dan pemilihan waktu panggil ungko dan siamang berdasarkan suara. Triangle count dilakukan pada 4 area dimana setiap area dilakukan survei 4-5 hari berturut-turut. VES dilakukan untuk mengetahui ukuran dan komposisi kelompok serta distribusi kedua spesies. Hasil pengamatan menunjukan ungko dan siamang tersebar hampir di seluruh area Stasiun Penelitian Yayasan Ekosistem Lestari-Sumatran Orangutan Conservation Program (YEL-SOCP). Walaupun terjadi tumpang tindih home range dan teritori antar spesies maupun antar kelompok, setiap kelompok ungko dan siamang tetap memiliki teritori yang dipertahankan. Keduanya dapat hidup simpatrik karena tidak berada pada relung ekologi yang sama. Kepadatan populasi ungko dan siamang di Stasiun Penelitian YEL-SOCP berturut-turut sebesar 5,12 kelompok/km2 dan 3,37 kelompok/ km2. KHBT yang berupa hutan pegunungan bawah dan hutan Dipterocarpaceae merupakan habitat yang baik bagi ungko. Ungko melakukan group call lebih awal dibandingkan siamang. Probabilitas group call ungko dan siamang stabil pada hari ke-4. KHBT memiliki biodiversitas yang tinggi untuk itu perlu dipertahankan untuk pelestarian plasma nutfah. Pengelolaan KHBT hendaknya memperhatikan keberadaan flora fauna di dalamnya. Ungko dan siamang memerlukan vegetasi dengan tajuk rapat dan kontinu, sehingga dalam pembuatan insfrastruktur seperti jalan dan bangunan tidak membuat habitatnya terpisah-pisah dan tetap menyisakan koridor yang menghubungkan antar hutan.
Keyword: 

Judul: Struktur dan Komposisi Jenis Vegetasi pada Habitat Ungko (Hylobates agilis F.Cuvier 1821) dan Siamang (Symphalangus syndactylus Gloger 1841) di Stasiun Penelitian Hutan Batang Toru Bagian Barat, Sumatera Utara
Abstrak: Gibbon (Hylobates agiliis) and siamang (Symphalangus syndactylus) are the two kinds of Hylobatidae species that inhabit a Sumatera’s forest. One of the Sumatera’s forest region, which was sympatrycally inhabited by the two kinds of Hylobatide, is Western Batang Toru Forest, North Sumatera Province. Gibbon and siamang are arboreal primates that lived exclusively at the forest canopies, and they are highly depended on their habitat’s vegetation condition. This research objectives were (1) to describe the structure, composition and diversity of the trees speciesat the gibbon and siamang habitat and (2) to identify a use of the vegetation by the gibbon and siamang in their habitat. There were three types of the forest in Western Batang Toru Forest namely transitory hill-montane forest formation (FHHM), peat forest formation (FHG) and upper Dipterocarpaceae forest formation (FHDA). All of the forest types in the gibbon and siamang’s habitat had high Shannon-Wiener’s diversity index (H’>3). Structure of that three forest types had an average density at 907 trees/ha with 80,89 m2 basal area value. Tree species with the highest frequency in the three habitat types were Anacardiaceae Campnosperma auriculatum (FHHM), Sapotaceae Madhuca laurifolia (FHG) and Ulmaceae Girroniera subequalis (FHDA). Hylobatidae habitat at Western Batang Toru Forest had a complete forest stratification level which were strata A, B, C and D. The highest space available on the gibbon and siamang habitat was strata C or 11-20 meter height above ground. Gibbon and siamang used mostly strata B and C at their habitat. It was related to the vegetation support for Hylobatidae movement and protection in their habitat, as well as food resources’s availability on those strata. Protection effort has to do to protect Western Batang Toru Forest ecosystem, because those forest region still get a threats and pressures from gold mining and logging area recently.
Keyword: 

Judul: Characterizations of low alloy steel sae 4422  plated with chromic acid (Cro3)
Abstrak: Characterizations of low alloy steel SAE 4422 plated with chromic acid (CrOrO3) was use Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), RD),Energy Dispersive Analysis of X-Ray (EDAX), Hardness Test and Roughness Test. Microstructures analysis exhibits cracks and grain boundaries microcracks as a characteristics of chrome metal found at plating metal. Perlite and Ferrite as grains of steel found at base metal with grain boundaries around it. Phase analysis of plating metal appropriate to chrome metal with lattice constant (a) is 2.559 Å and phase analysis of base metal appropriate to iron ferrite with lattice constant (a) is 3.318 Å. Both plating and base metal have cubic system. Chemical analysis of plating metal at surface section exhibits that cracks area have highest value of carbon element compare with grains and grains boundaries area. While chemical analysis of base metal at cross section exhibits that perlite have highest value of carbon element compare with ferrite and grain boundaries. The hardness value of plating metal at surface section and cross section are 753 and 637 VHN. While, the hardness value of base metal and interface area at cross section are 205 and 373 VHN. The roughness value at measurement points of chrome surface for as received sample are 0.445 μm. Observation used Optical Microscopy and Scanning Electron Microscopy exhibits surface irregularities combine to form surface texture of plating metal at surface section.
Keyword: