Judul: Sumber dan Frekuensi Aplikasi Larutan Hara sebagai Pengganti AB Mix pada Budidaya Sayuran Daun secara Hidroponik
Abstrak: The objective of this research to determinate the frequency and source of nutrient applications on growth and yield of kangkong (Ipomoea sp.), caisin (Brassica juncea), and kale (Brassica oleraceae Var Acephala) in hydroponics. The experiment were arranged in a RCBD (Randomized Completely Block Design) with two factors, first factor source of nutrient (AB Mix, NPK 15:15:15, and NPK 12:14:12), and second factor is method of application (one time and two time) with four replication so there are 24 experimental units. The result show NPK 15:15:15 have similar effect with AB Mix in kangkong, caisin, and kale.With one time frequency application, the best fertilizer source is NPK 15:15:15, while with two time application the best fertilizer is AB Mix.
Keyword: nutrient solution., NPK 12:14:12, NPK 15:15:15

Judul: Sumber Hara sebagai Pengganti AB mix pada Budidaya Sayuran Daun Secara Hidroponik
Abstrak: Increasing in fertilizer price causing increasing in hydroponic system cost. The objective of the research is to find the best fertilizer that can replace AB mix by examining several sources of nutrients, such as NPK 15:15:15 and NPK 12:14:12by equalizing element N for hydroponic cultivation spinach (Amaranthus L.), pakchoy (Brassica rapa cv. pakchoy) and lettuce (Lactuca sativa L.) in hydroponic. The research was conducted in the Green House, Dramaga Field Unit, University Farm, IPB Dramaga Bogor from February to April 2013. The treatments (AB mix, NPK 15:15:15, NPK 12:14:12) were arranged in randomized completely blok design with 4 replications. Each commodities is separate experiments with 3 treatmens. The results showed that fertilizer treatments gave the highest yield in spinach plants, pakchoy and lettuce in the components yields an average weight/plant, total weight and weight of marketable yield, respectively at 21.65 g, 259.75 g, 235.75 g spinach, 46.06 g, 552.75 g, 465.75 g pakchoy and 25.93 g, 311.15 g lettuce. Based on these results NPK15:15:15 and NPK12:14:12 fertilizer can not replace AB mix as a source of plant nutrients in spinach, pakchoy and hydroponic lettuce.
Keyword: NPK 12:14:12, NPK 15:15:15, leafy vegetables, hydroponic, AB mix

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