Judul: Recordings On Sea Surface Temperature And Metals Pollution From Coral Reefs Sclerochronology
Abstrak: The aragonite skeleton of massive reef-building corals contain a record of the oceanic environment in which they grow. This proxy measurement is very important to understand past environmental condition due to the lack of instrumental records, and as basis how to manage it in the present and in the future. This research objectives are to find out the ability U/Ca ratio in showing SST fluctuations and to know metals fluctuation in the waters from corals sclerochronology. The robustness of U/Ca ratio was assessed by comparing it with local SST data set achieved by NOAA satellite due to period of 1983-2002. Porites stephensoni is used as samples, took from Seribu Islands – Jakarta, in specific Bokor Island, Tikus Island, and Tidung Island. Samples are analyzed with neutron activation analyses (NAA) to measure elements concentration, except for Pb and Cd we used atomic absorbance spectrometer (AAS). The U/Ca ratio show very weak correlation with yearly SST variations, with r2 = -0.23 (Tikus Island), r2 = -0.35 (Tidung Island), and r2 = -0.39 (Bokor Island). U/Ca ratio can not be used for showing SST variation at Seribu Islands waters. Sclerochronology show that metals pollution did happen, noticed by metal/Ca ratio that higher then its background value. Arsenic (As) is not naturally habits in corals skeleton, while the other metals (Sb, Pb, Cd, Co, Cr) seem naturally habit in it. Applying principal component analysis to all samples data set has resulted in categorizing them into one group. It show that those three island has similar water quality or they were influenced by the same water-mass. They have one general source for all the metals, except arsenic (As).
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Judul: Rekam Jejak Polutan pada Kerangka Kapur Karang Porites lutea di Pulau Tunda
Abstrak: Porites lutea is one of hard coral species which has sensitive respond to physical and chemical change of sea water. The line growth of Scleractinia’s skeleton has an ability to accumulate heavy metals continously as long as their life period. Therefore, it could be use as an enviromental changes indicator on long or short term period. This study aims is to assess trace pollutant record such as Pb, Sr, Cr and Zn which is accumulated in P. Lutea at windward and leeward Tunda Island. The sampling collection was conducted in coral core and analyzed by the outer circle of coral to determine the ages. Neutron Activation Analysis (NAA) was used to analyzes the heavy metals (Cr, Sr, Fe and Zn), while Atomic Absorption Spectrometer (AAS) was used analyze Pb. This research revealed metal concentration recorded in coral P. lutea skeleton in the windward location was started from 1940 to 2014 and in the leeward location started from 1969 to 2014, at which the metal concentrations increased. Cr concentration increased from 4.36 mgkg-1 to 11.77 mgkg-1, Fe concentration increased from 4.88 mgkg-1 to 47.70 mgkg-1, Zn concentration increased from 3.28 mgkg-1 to 15.59 mgkg-1, Pb concentration increased from 5.17 mgkg-1 to 17.66 mgkg-1. However, no increased of Sr concentration was observed, and it varied between 70.1-103.5 mgkg-1. It suggested that corals P. lutea can be used to evaluated changes at the environmental change from the past to the present at Tunda Island, to determining the concentration of pollutants recorded in the coral skeleton. The heavy metals concentration was increasing variation from year to years. The heavy metals concentration trend to increase towards percent years. This indicates that the region has contaminated due to possible anthropogenic activities from land.
Keyword: heavy metals, trace record in coral, P. lutea, Tunda Island

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf