Judul: Gamma Ray Irradiation on UHMWPE and HDPE to Increase Tibial Tray Mechanical Properties
Abstrak: Ultrahigh molecular weight polyethylene (UHMWPE) is a polymer that is widely used in the manufacture of tibial tray, but it is very expensive. Therefore, high density polyethylene (HDPE) was developed for the manufacturing of tibial tray because the price is lower and has similar properties to UHMWPE. HDPE was made by two methods, namely hot pressing method and heating method, but UHMWPE wass made only by hot pressing method. Tibial tray film of HDPE and UHMWPE from both methods were irradiated with various doses of gamma rays 0, 100, 200, 300 and 500 kGy. The polymers were analyzed for surface microstructure, hardness , tensile strength, elongation at break percentage, and degree of crystallinity. The higher the dose of irradiation the higher the hardness and the degree of crystallinity, but not for the tensile strength and elongation at break percentage. Both polymers were not able to increase mechanical properties in those irradiation doses range because crosslink formation is inhibited by the presence of oxygen that causes chain scission. HDPE hardness enhancement by hot pressing method was close to
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Judul: Sifat Fisikokimia Biokomposit UHMWPE/HAp Pasca Iradiasi Berkas Elektron
Abstrak: Ultra-high molecular weight polyethylene (UHMWPE) often used for tibial tray as part of artificial knee joint. The selection of recycled UHMWPE as alternative for manufacturing tibial tray is due to its low cost compared to the pure UHMWPE of Sigma Aldrich. Therefore, the purpose this research is to evaluate physicochemical properties of UHMWPE-HAp biocomposites post electron beam irradiation. Biocomposite films were irradiated at doses of 0, 50, 100 and 150 kGy. The effect of additional HAp and irradiation on physicochemical properties were observed using various methods (tensile test, hardness test, X-ray diffraction, Fourier transform infrared spectroscopy, and differential calorimeter). The results showed that the recycled and the pure UHMWPE were similar in their properties. However, the addition of HAp and irradiation on the recycled UHMWPE, revealed higher hardness, crystallinity, and melting point, but lower elongation at break and maximum voltage as compared. FTIR results showed the formation of a new bond.
Keyword: UHMWPE, physicochemical properties, electron beam irradiation, HAp, biocomposites

Judul: Populasi dan Habitat Kakatua-Kecil Jambul-Kuning di Bentang Alam Mbeliling Bagian Barat, Kabupaten Manggarai Barat, Nusa Tenggara Timur
Abstrak: Cacatua sulphurea parvula or yellow-crested cockatoo were spread distributed at Sunda Kecil Archipelago, Nusa Tenggara, except at Sumba Island. This species amount in the nature is very small, caused by the illegal hunting and trading. The purpose of this research is to get the information about population and habitat of the cockatoo in Flores, especially at the western part of Mbeliling Landscape. Cocatoo census was conducted by look-down method at vantage points when cockatoo flew passed by. Habitat analysis was carried out with vegetation analysis. The census showed that there were two groups of cockatoo, consisted of 69 cockatoos in Tao hill and 15 cockatoos in Nggoer River. Flight pattern of each group ranged 0-100 meters above the sea level and crossed mangrove forest, savanna, monsoon forest and cultivation plant vegetation. The vegetation analysis resulted Ceiba petandra or silk-cotton tree as the tree that most used by cockatoo and had the highest TIV (Tree Importance Value), 47,48%. Cockatoo’s foods which observed were crown flower (Calotropis gigantea), and Moringa olifera. The population of Cockatoo which observed at western part of Mbeliling Landscape was estimated came from Rinca Island, Komodo National Park. It can be concluded that the location might be only used by rhe cockatoo came from Rinca Island as their daily exploration area for foraging.
Keyword: habitat., ecology, population, Flores, Cacatua sulphurea parvula