Judul: Release Pattern of Urea from Onggok-Polyacrylamide Copolymer Superabsorbent at Various Level of Crosslinking.
Abstrak: Rendahnya efisiensi penyerapan urea oleh tanaman akan menimbulkan kerusakan pada tanaman itu sendiri dan mencemari lingkungan. Polimer superabsorben (SAP) yang diperkaya urea digunakan dalam upaya peningkatan efisiensi penyerapan urea oleh tanaman. SAP disintesis dengan kopolimerisasi pencangkokan-penautan-silang akrilamida pada onggok (limbah padat singkong) dengan jumlah penaut-silang beragam (50, 75, dan 100 mg). Proses saponifikasi dilakukan untuk meningkatkan daya serap air SAP. Keberhasilan proses pencangkokan-penautan-silang ditunjukkan oleh spektrum inframerah transformasi Fourier. Pengayaan SAP yang diperoleh dengan urea dilakukan dengan cara merendamnya dalam larutan urea 1000 ppm dan diteliti laju pelepasan dalam air secara statis. Model matematika laju pelepasan urea, yang didasarkan pada model pertumbuhan logistik jenis hubungan eksponensial 2, dikembangkan untuk menggambarkan perubahan konsentrasi urea terhadap waktu. Laju pelepasan yang paling rendah sebesar 0.81 ppm/menit ditunjukkan oleh SAP dengan penaut-silang 100 mg. Pola laju pelepasan urea pada SAP yang semakin rendah mengindikasikan penyerapan urea oleh tanaman lebih efisien dibandingkan pemberian urea secara konvensional.
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Judul: Sintesis Superabsorben Onggok-Poliakrilat yang Diperkaya dengan Urea
Abstrak: Fertilizer-enriched superabsorbent polymer (SAP) could be used to help water savings, especially in dry areas, and improve the efficiency of fertilizer application compared with conventional method, stocking of fertilizer on the soil surface. In this research, several kinds of SAP were synthesized by grafting copolymerization of 40% neutralized acrylic acid with onggok (solid waste of tapioca factory) by using ammonium persulfate as initiator and by varying the amount of crosslinker N,N'-methylene-bis-acrylamide and urea added. Water absorption capacity of SAP before enrichment was 730.48 g/g with nitrogen content of 4.12%, and decreased after enriched by urea. For 0.025, 0.050, and 0.100 g of crosslinker, water absorption capacities were 293.38, 227.34, and 209.20 g/g and nitrogen contents were 17.99, 16.49, and 16.83%, respectively. Nitrogen release study of enriched SAP with 0.025 and 0.050 g of crosslinker showed nitrogen release of 6.29 and 7.35%, respectively while SAP with 0.100 g of crosslinker at the same time only released 23.92% of nitrogen. These results indicated that the amount of crosslinker greatly influenced the pattern of release of urea.
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Judul: Posisi Filogenetik Kura-Kura Carettochelys Insculpta  (Reptillia: Testudinata)
Abstrak: Carettochelys insculpta is an endemic freshwater turtle of southern Papua and northern Australia. Phylogenetic position of this turtle is remain unresolved until now. Most of the research conducted show close relationships of C. insculpta and members of Trionychidae family. However, some of the research show distance between C. insculpta and members of Trionychidae family. This research is conducted to analyze phylogenetic relationship between C. insculpta and other members of Testudinata using 12S rRNA, 16S rRNA, and both gene as markers. DNA samples were obtained from three different organisms of C. insculpta. Two species used as outgroups were Alligator mississippiensis and Iguana iguana. Phylogenetic analysis was carried out using Neighbor-Joining method with Felsenstein 1981 (F81) modeltest. A polytomy tree of Testudinata was produced by using 12S rRNA gene. However, analysis using 16S rRNA and both genes as markers confirmed that C. insculpta was located between the Chelonidae and the Trionychidae family.
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