Judul: Sintesis dan Karakterisasi Barium Titanat dengan Modifikasi Metode LTDS (Low Temperature Direct Synthesis)
Abstrak: Barium titanat adalah material keramik yang telah dikenal luas pada pembuatan termistor, kapasitor keramik dielektrik, amplifier dielektrik, magnetik amplifier, dan kapasitor keping/multi keping. Pemanfaatan ini berhubungan dengan sifat ferroelektrik, piezoelektrik, dan konstanta dielektrik yang tinggi. Konstanta dielektrik keramik BaTiO3 berkisar antara 1000 – 12.000. Metode sintesis yang ada saat ini umumnya menghasilkan kristal BaTiO3 dengan distribusi ukuran yang besar dan homogenitas struktur yang rendah (campuran kubus dan tetragonal). Hal ini akan mengurangi sifat elektrik material
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Judul: Synthesis and Characterization of BaTiO3 from BaCl2 and TiCl4 by Hydrothermal Method
Abstrak: Seiring dengan kemajuan teknologi saat ini, peralatan elektronik semakin berkembang. Salah satu komponen penyusun peralatan elektronik adalah kapasitor. Salah satu bahan penyusun kapasitor, ialah barium titanat (BaTiO3). Penelitian ini bertujuan mensintesis dan mencirikan BaTiO3 dari campuran BaCl2 dan TiCl4 dengan mengamati perubahan suhu dan tahapan reaksi. Penelitian ini meliputi beberapa tahap, yaitu sintesis BaTiO3 dengan metode hidrotermal, perubahan tahapan reaksi, perubahan pH, dan membandingkan hasil sintesis menggunakan metode nonhidrotermal, serta pencirian dengan difraksi sinar-X (XRD). Berdasarkan hasil XRD, sintesis BaTiO3 menggunakan metode hidrotermal (T = 120-150 oC), perubahan tahapan reaksi, dan perubahan pH belum bisa menghasilkan BaTiO3 murni. Hal ini dapat dilihat dari rendahnya intensitas BaTiO3 yang terbentuk serta masih terdapatnya pengotor lain berupa TiO2, seperti pada metode nonhidrotermal (T = 600 oC).
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Judul: Phylogeography and Species Limits in the Papuan White Snake (Micropechis ikaheka) (Reptilia: Serpentes: Elapidae)
Abstrak: Papua white snake, Micropechis ikaheka, has been distingushed into two subspecies M.i. ikaheka and M.i. fasciatus. However, due to lack of data on their morphology, distribution and ecology, both subspecies often ignored in scintific discussions and refers only byas , Micropechis ikaheka. This study was designed to document the differences between M.i. ikaheka and M.i fasciatus by using scales characteristics and reproductive organ or hemipenes. The study also examine, zoogeography, habitat, diet and cannibalism of both subspecies to better understanding the the ecology of one of the most venomous snakes in the world. This study consists of three topics with method and also different in the size samples, respectively. The first study is the histology and microtopography of the skin were studied using paraffin method and Scanning Electron Microscope (SEM). The second is the hemipenis were examined by following Myers and Cadle (2003), and Zaher and Prudente (2003). The third is the abdominal surgery was carried out to document diet type and the investigate phenomenon of cannibalism in the snake. Specimens for this study came from the collection from Museum Zoologicum Bogoriense (MZB) and Universitas Negeri Papua’s Laboratory (LZU). The research result also indicated that the markers of skin and hemipenis described the same structure and microornamentation in all M. ikaheka groups being compared. Based specimens examined morphological descriptions do not s support the further differentiation in Micropechis. In short, two markers that used in this study could not sufficiently indicate the differences in the level of species and subspecies of M. ikaheka. The study, however, were able to delineate zoogeography and skin color patterns, which fall into four groups: M. i. ikaheka; M. i. fasciatus. M. i. ssp. “intermediate”; and M. i. ssp “black”. This study also revealed that color variations did not overlap in their geographic distribution. It is therefore, it suggested that environmental factors may contribute to the skin color variations. It also assumed that habitat discontinuous and biogeography factors may also cause the loss of the connection between the original populations (vicarians) or follow colonization events (dispersal). The examined of 22 stomach contents of M. ikaheka shows this species is carnivorous, and prey on vertebrates such as amphibians, fish, reptiles, and Mammals. These snakes are opportunistic predators since they prey on all that can be captured, but mainly reptiles (61.5%), followed by mammals and fish (both 15.4%), and amphibians (7.7%). Although categorized as terrestrial animal, the diet study showed that M. ikaheka snakes often go into the water to hunt for fish (the sample from Yapen island), including eel (the sample from Aru island). Based on prey items indentified, there is evidence that M. ikaheka is cannibal. At this time, there still no record on reason for cannibalism, but it is assumed that cannibalism was due to competition between populations and means to control population.
Keyword: geographic variation, white snake, papua