Judul: Aktivitas Antioksidan Ekstrak Kulit Pohon Bakau Hitam (Rhizophora mucronata).
Abstrak: Kulit akar, kulit batang dan kulit ranting bakau hitam (Rhizophora mucronata) yang dikeringkan dengan sinar matahari secara langsung diduga masih memiliki aktivitas antioksidan. Pengujian aktivitas antioksidan dengan prinsip uji yang berbeda dapat dilakukan untuk membandingkan hasil nilai aktivitas antioksidan yang diperoleh yakni metode DPPH dan CUPRAC. Tujuan penelitian ini adalah menentukan senyawa aktif pada sampel kulit segar dan kering dan menentukan aktivitas antioksidan pada sampel kulit segar dan kering dengan metode DPPH dan CUPRAC. Proses esktraksi dilakukan secara maserasi selama 24 jam dengan pelarut etanol 70% perbandingan 1:3 (b/v). Sampel ekstrak kulit pohon bakau hitam dominan terdapat senyawa steroid dan flavonoid pada semua sampel kulit segar maupun kering. Hasil uji DPPH dengan aktivitas antioksidan tertinggi yaitu pada sampel ekstrak kulit akar segar (59.68 ± 0.36 μg/mL) dan pada uji CUPRAC yaitu pada sampel ekstrak kulit akar segar (95.45 ± 0.96 μmol asam askorbat/g). Aktivitas antioksidan cenderung menurun dengan adanya proses pengeringan dengan sinar matahari.
Keyword: antioksidan, DPPH, kulit akar bakau hitam, Rhizophora mucronata

Judul: Aktivitas Antioksidan Ekstrak Buah Bakau Hitam (Rhizophora mucronata) Hasil Pengeringan yang Berbeda.
Abstrak: Ekstrak buah bakau hitam (R. mucronata) bermanfaat sebagai sumber antioksidan alami. Aktivitas antioksidan diketahui mudah rusak apabila terpapar oleh sinar ultraviolet. Penelitian dilakukan untuk menentukan aktivitas antioksidan buah bakau hitam, serta menentukan pengaruh pengeringan terhadap senyawa bioaktif hasil pengeringan dengan sinar matahari langsung dan sinar matahari tidak langsung. Hasil pengeringan mempengaruhi rendemen ekstrak, total fenol dan aktivitas antioksidan ekstrak buah bakau hitam (R. mucronata). Pengeringan yang menghasilkan total fenol dan aktivitas antioksidan tertinggi terdapat pada ekstrak buah bakau hitam kering sinar matahari langsung. Nilai total fenol ekstrak buah bakau hitam kering sinar matahari langsung yaitu 1 714.61 mgGAE/g dengan rendemen 6.7%. Aktivitas antioksidan DPPH, ABTS, dan CUPRAC ekstrak buah bakau hitam kering sinar matahari langsung masing-masing 16.27 ppm; 17.63 ppm; dan 97.26 mg asam askorbat/g ekstrak. Aktivitas antioksidan yang dihasilkan pada penelitian termasuk kedalam kategori sangat kuat (IC50 <50).
Keyword: Antioksidan, pengeringan, Rhizophora mucronata, total fenol

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