Judul: Isolasi dan Karakterisasi Acidithiobacillus ferrooxidans dari Ekosistem Kawah Ratu Bogor serta Uji Degradasi Pirit
Abstrak: Acidithiobacillus ferrooxidans merupakan mikrob asidofilik kemolithoautotrof yang mendapatkan energi dari oksidasi besi dan sulfur. Kemampuannya dalam mengoksidasi besi dan sulfur menyebabkan Acidithiobacillus ferrooxidans sangat berpengaruh dalam proses pelarutan logam. Tujuan dari penelitian ini adalah untuk mendapatkan isolat Acidithiobacillus ferrooxidans dari ekosistem Kawah Ratu Bogor, mengetahui korelasi antara populasi Acidithiobacillus ferrooxidans terisolasi dengan karakteristik kimia dan biologi ekosistem Kawah Ratu Bogor, menyeleksi isolat unggul Acidithiobacillus ferrooxidans yang kemudian dikarakterisasi berdasarkan Bergey's Manual of Systematic Bacteriology dan menguji kemampuan masing-masing isolat unggul tersebut dalam mengoksidasi pirit melalui uji degradasi pirit. Metode yang digunakan dalam penelitian ini adalah isolasi, uji korelasi antara populasi Acidithiobacillus ferrooxidans dengan karakteristik kimia dan biologi ekosistem Kawah Ratu Bogor, karakterisasi Acidithiobacillus ferrooxidans berdasarkan Bergey's Manual of Systematic Bacteriology, dan uji degradasi pirit yang dilakukan dengan pengukuran sulfat, pH dan Eh. Hasil penelitian ini menunjukkan bahwa Acidithiobacillus ferrooxidans ditemukan sebanyak 48 % dari 25 sampel tanah dan air ekosistem Kawah Ratu Bogor, dengan rata-rata populasi 60 % dari total populasi bakteri. Populasi Acidithiobacillus ferrooxidans berkorelasi signifikan dengan karakteristik air Fe-terlarut (r = 0.711*) dan total populasi bakteri (r = -0.556*). Lima isolat unggul berdasarkan nilai optical density adalah isolat DSS-1, DSS-3, DSS-5, DSS-9, DSW-1, dan berdasarkan karakteritiknya terbukti merupakan spesies Acidithiobacillus ferrooxidans. Isolat DSS-1 merupakan isolat yang dapat menghasilkan ion sulfat tertinggi selama uji degradasi pirit
Keyword: Acidithiobacillus sp., oksidasi pirit, bioleaching, biooksidasi, metal sulfida

Judul: Isolasi dan uji aktivitas bakteri asidofil pengoksidasi besi dan sulfur dari ekosistem air hitam
Abstrak: Ekosistem air hitam merupakan salah satu ekosistem yang memiliki kondisi yang tidak normal/ekstrim. Salah satu kondisi tersebut adalah memiliki kemasaman yang tinggi (pH 3-4). Bakteri yang mampu tumbuh pada kondisi yang masam ini disebut bakteri asidofil. Aktivitas bakteri asidofil ini sangat kaitannya dalam kegiatan pelarutan logam dari bijih-bijih sulfida. Penelitian ini merupakan penelitian eksplorasi yang bertujuan: 1) mengisolasi bakteri asidofil dari ekosistem air hitam yang mampu mengoksidasi besi ferro (Fe II) dan sulfur, 2) melakukan pengujian aktivitas isolat terpilih terhadap pengoksidasian Fe (II) menjadi Fe (III) maupun aktivitasnya terhadap pelarutan logam sulfida pada kondisi ekstrim (pH rendah).
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Judul: The Construction of Greedy SVP LLL Algorithm
Abstrak: A lattice is a set of all integer linear combination of a set of linearly independent vectors in ℝ𝑛���. The independent vectors are called bases of lattice. Any lattice can be generated from many bases, and these bases have the same cardinality. In the lattice, the most fundamental and renowned problem is the Shortest Vector Problem (SVP). SVP is a tracking problem of the shortest nonzero vector in a lattice with equivalent bases. In two dimensions, SVP problem has resolved exactly by Gauss’ algorithm. When the lattice dimension is higher than two, A.K. Lenstra, H.W. Lenstra and L. Lovasz gave a LLL algorithm to compute approximation of nonzero shortest vector in the lattice. Reduced bases solution obtained from LLL algorithm still be an approximation and has polynomial running time of arbitrary dimension which large enough. In 1994, Schnoor and Euchner modified this LLL algorithm as a new variant which later was named deep insertion LLL algorithm. This algorithm is a modified version of the LLL algorithm to the terms of the exchange step to improve the accuracy of output of LLL reduced bases and applying it to the subset sum problem. The purpose of this research are: (1) Reconstruct the LLL algorithm and deep insertion LLL algorithm using a geometric approach. (2) Construct a greedy SVP LLL algorithm. (3) Implement the three algorithms in a symbolic programming language, and evaluate them experimentally. A bases ℬ=[𝐛���1,𝐛���2,…,𝐛���𝑛���] in ℝ𝑚��� is called reduced LLL with parameter 𝛿��� if satisfies: (a) |𝜇���𝑗���𝑖���|≤12, for every integer 𝑖���,𝑗��� with 1≤𝑖���<𝑗���<𝑛���. (b)𝛿���‖𝜋���𝑗���(𝐛���𝑗���)‖2≤‖𝜋���𝑗���(𝐛���𝑗���+1)‖2, for 𝑗���=1,2,…,𝑛���−1,where 𝛿��� is a reduced parameter of real numbers with 14<𝛿���<1. The first requirement is the reduced basis 𝛿��� must “nearly orthogonal” and in its computation case, this requirement can be reached out by using the Gram-Schmidt’s orthogonalization. While the second requirement is called exchange step, or used to called as Lovasz condition. By using both of these requirements, then they establish the LLL algorithm. Then, Schnoor and Euchner modify the LLL algorithm based on the requirements of the exchange step called the deep insertion LLL algorithm, where the exchange step is based on the comparison of the projected vector in orthogonal complement [𝐛���1,𝐛���2,…,𝐛���𝑘���−1]⊥ after j-th reduction. To construct greedy SVP LLL algorithm, the requirements of the exchange step is based on purely by comparing norm of lattice 𝐛���𝑗��� with norm lattice 𝐛���𝑖��� for 𝑖���=1,2,3…,𝑗���−1. The process of insertion reduced vector after the exchange step also has done greedily. Then, we calculate the number of arithmetic operation in greedy SVP LLL algorithm for further analysis. The result of our exprimentation for three algorithms on the certain matrix size shows that the running time of the three algorithms increases propotional to the size of the matrix. The result also shows that by using 𝛿���=34 for the LLL algorithm and the deep insertion LLL algorithm, and the greedy SVP LLL algorithm which is a new variant made by using no parameter of 𝛿���, outperform of the other of two previous algorithm in terms of speed with the same output.
Keyword: LLL algorithm, LLL deep insertion algorithm, greedy SVP LLL algorithm