Judul: IPB (Bogor Agricultural University)
Abstrak: Selected biomarkers, cholinesterase (ChE) and phagocytic activities from blue mussels, Mytilus edulis have been used to detect the effects of neuroimmunotoxicity of organophophate (OP) pesticide, dimethoate. The serial dilutions of dimethoate concentrations which were 0.00, 7.88, 15.75, 31.50 and 63.00 μg/l, showed dose-dependent effects on the ChE activity of blue mussels, Mytilus edulis after being exposed for 14 days. Statistical analysis showed that the significant effects of the pesticide on the ChE activity occurred at concentrations 31.50 and 63.00 μg/l (p <0.05). In contrast, the dose-dependent effects of dimethoate were not observed in the phagocytic activity of dimethoateexposed mussels. The suppression effects of dimethoate on phagocytic activity occurred significantly (p < 0.05) at two concentrations of dimethoate (7.88 and 15.75 μg/l), but stimulation effects significantly (p < 0.05) emerged at the following concentrations (31.35 and 63.00 μg/l). The reduction which occurred at the lowest concentrations along with the stimulation at the highest concentrations implied the occurrence of a U-shape hormetic response of the phagocytic activity under dimethoate exposure. The results suggested that two selected biomarkers, ChE and phagocytic activities were respectable tools to detect the effects of the pesticides when the dose-dependent and U-shape hormetic responses were taken into account in the laboratory scale study.
Keyword: organophosporus pesticide, feeding activity, backward multiple regression, siphoning activity

Judul: Pemanfaatan ganggang mikro sebagai bioindikator perairan yang tercemar
Abstrak: This study aimed to determine the sensitivity of some freshwater microalgae from Indonesia to the heavy metal contaminants (Hg, Cd, As and Pb) and pesticides. Result of the selection of ten isolates of microalgae grown in BG 11 medium obtained three strains which have the fastest growth rate: ICBB 9111, ICBB ICBB 9113 and 9114. Third is selected microalgae strains were identified as: Synechoccus sp. ICBB 9111 (originally there in Mt Salak, Bogor), Chlamydomonas sp. ICBB 9113 (paddy field of Ciomas - Bogor) and Chlorella vulgaris ICBB 9114 (origin Telaga Warna, Puncak, Bogor). To test the sensitivity of microalgae to heavy metals, three selected bacteria are grown in a medium containing heavy metals Cd, Hg, As and Pb at a concentration of 1.25 ppm, 2.50 ppm, 5.00 ppm and 10.00 ppm. Observation of the optical density (OD) performed on the first 30 minutes up to 96 hours. Based on visual observations obtained during this period that two strains of micro-algae growth stalled. Both strains of microalgae are Synechococcus sp. ICBB 9111 and Chlamydomonas sp. ICBB 9113. In contrast to Chlorella vulgaris ICBB 9114 still survive, especially in the medium containing metal ions Cd and Pb, whereas in medium containing Hg and As these strains are not able to survive. The next stage of research is the analysis of metal content, which is not absorbed by the micro algae biomass. From the analysis found that Hg and As are almost entirely absorbed by algae and micro-media content in each of the remaining <0.001 ppm and <0,002 ppm. Whereas for Cd and Pb only a small portion is absorbed by microalgae. Based on the results of the durability of each micro algae in media containing different heavy metals. ICBB Chlorella vulgaris strain 9114 has the durability and adaptability to heavy metals higher than the strain Chlamydomonas sp. ICBB 9113. While Synechococcus sp. ICBB 9111 had the highest sensitivity of all four metals tested. In addition to heavy metals tested, three strains were also tested sensitivity to the herbicide; isoprophylamine glyphosate and paraquat dichloride and insecticide ; buthylphenylmethylcarbamate (BPMC) and deltamethrin with variations of the following concentrations: 5ppm, 10ppm, 20ppm and 40ppm. Microalgae growth observations showed that all three strains are able to survive up to 24 hours in media containing pesticides tested. After 24 hours, the three began to show signs of decline. At the 96-hour observation of all micro algae die. The amount of pesticide concentrations ranged from 10-20ppm concentration which is critical to the durability and adaptability of microalgae. Of the overall treatment and observation can be drawn a conclusion that some micro algae have tolerance to pollutants (heavy metals or pesticides) that enter the aquatic environment. Adsorption capacity and adaptation of micro algae can be used as bio-indicators in monitoring and evaluation of marine environmental impacts of the heavy metal pollutants and pesticides.
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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