Judul: Penyalutan Pupuk NPK dengan Poliakrilamida dan Parafin serta Sifat Pelepasan Haranya
Abstrak: Penggunaan pupuk yang tersalut dengan polimer bertujuan mengendalikan laju pelepasan hara agar dapat mengurangi kehilangan pupuk sekaligus meminimumkan pencemaran lingkungan. Pada penelitian ini, pupuk NPK disalut menggunakan polimer akrilamida sebagai penyalut lapis pertama. Polimer akrilamida dibuat dengan penaut-silang N,N'-metilena-bis-akrilamida 8.30%, inisiator benzoil peroksida 0.004%, dan kloroform sebagai pelarut. Sebagai penyalut lapis kedua digunakan parafin dengan kadar 5, 10, dan 15%. Pupuk NPK yang disalut dengan poliakrilamida dan parafin 15% memiliki sifat pelepasan hara (urea dan kalium) lebih lambat dibandingkan dengan kontrol (tanpa penyalutan) maupun dengan penyalutan poliakrilamida-parafin 5% dan 10%. Uji statik dalam medium air selalu menunjukkan laju pelepasan lebih cepat dibandingkan dengan uji dinamik dalam medium tanah. Meskipun semua pupuk NPK tersalut yang dipelajari menunjukkan pola pelepasan hara yang lebih lambat daripada pupuk tanpa penyalut, belum satu pun dari ketiga variasi konsentrasi parafin dapat dikategorikan sebagai pupuk slow release.
Keyword: Bogor Agricultural University, Institut Pertanian Bogor, IPB, Fertilizer, Nutrient release, Paraffin, Polyacrylamide, Slow release

Judul: Pelapisan Pupuk NPK dengan Poli(Asam Akrilat) Tertaut-Silang-N,N’-Metilena-bis-akrilamida dan Berbagai Konsentrasi Parafin
Abstrak: Coating of NPK fertilizer can increase the efficiency of fertilizing, fertilizer’s loss is reduced and environmental pollution is minimized. N,N’-Methylene-bis-acrylamide-crosslinked poly(acrylic acid) (MBA-PAA) and paraffin can be used as fertilizer coating. MBA-PAA layer was made from acrylic acid as monomer, benzoyl peroxide as initiator, N,N'-methylene-bis-acrylamide as cross linker, and chloroform as the polymerization medium. The second layer, paraffin was varied with the concentrations of 5%, 10%, and 15%. Release in static water media and leaching test in soil media were carried out. The results showed sigmoid patterns for urea release as well as leaching. Release and leaching test of NPK coated with MBA-PAA and paraffin 15% showed the slowest urea release curve. Urea release rate was determined by a mathematical approach y = ɑ(1 e (–bx)). The slowest rate of urea release and leaching were 0.21 and 0.32% per minute, respectively. The NPK fertilizer can be categorized as slow release fertilizer, but it cannot be regarded as controlled or measured release fertilizer yet
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Judul: Penggunaan Teorema Homeomorphy 2-Manifold dan Teorema Euler Poincare pada Torus 𝑇�� dan Simplicial Complex 𝐾��
Abstrak: Two dimensional topological spaces are said to be homeomorphic if they have the same topological invariant, where one of topological invariant used is an Euler characteristic. Homeomorphy 2-Manifold’s Theorem and Euler Poincare’s Theorem are used to distinguish two topological spaces. Homeomorphy 2-Manifold’s Theorem uses Euler characteristic to identify two dimensional topological spaces. Euler Poincare’s Theorem is an alternative way to find Euler characteristic with Betti number, which is topological invariant as well. The objective of this paper is to investigate the homeomorphism of torus 𝑇����� and simplicial complex 𝐾�����. Topological space torus and simplicial complex 𝐾����� have the same Euler characteristic, which is two. Based on Homeomorphy 2-Manifold’s Theorem topological space torus 𝑇����� and simplicial complex 𝐾����� is homeomorphic.
Keyword: simplicial, torus, Euler, homeomorphism, topology